Wikipedia:Reference desk archive/Science/May 2006

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See Wikipedia:Reference desk archive/Science/May 2006 part 2 for the archives of May 21 to May 31 2006.

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[edit] May 1

[edit] Animal survival in winter

How do animals obtain water in the winter when water sources are frozen.

Some hibernate; that's all I know. Melchoir 01:09, 1 May 2006 (UTC)

Although this is a very silly question for us Canadians, I actually found a quote: "Studies in Canada have shown some cows have gone 50 to 60 days with snow as the sole water source without any adverse effects." However, it quite uncomfortable to take a shower in snow. --Zeizmic 01:13, 1 May 2006 (UTC)

Cows shower? User:Zoe|(talk) 01:51, 1 May 2006 (UTC)
A cow shower is a brief or small area of precipitation that is heavier than "raining cats and dogs." For more information, see Raining animals. </official meteorologist opinion> EWS23 | (Leave me a message!) 02:23, 1 May 2006 (UTC)
It's quite a bit heavier than a baby shower. Grutness...wha? 06:41, 1 May 2006 (UTC)
Although I daresay some bridal showers might approach it in size. --Ginkgo100 19:46, 1 May 2006 (UTC)

[edit] Fullerene Formation

How are fullerene molecules formed? Is there a reaction mechanism process that creates hey!!!!!!!!!!!!!!!!! them or is it something else. I am particularly interested in buckminsterfullerene and its formation. Thankyou. Vollsa 01:05, 1 May 2006 (UTC)

I know nothing on this topic beyond fullerene purification. Isopropyl 01:48, 1 May 2006 (UTC)
Basically, you just zap graphite with lots of electricity (in a vacuum), which makes a messy mixture of all kinds of fullerenes and nanotubes. That's why the purification process is so important. —Keenan Pepper 02:09, 1 May 2006 (UTC)
You can actually make some fullerenes and nanotubes, as well as excessive amounts of graphite by building an arc furnace in your backyard. Something pretty unsafe to the common man, arc furnaces involve running large current and voltage values through a phantom loop. Get some firebrick, and big pieces of copper that are about in diameter to regular copper piping, hook up a generator and set the copper rods having a centimeter or so of space between them, and run the current through! I probably shouldn't have said that. I hope nobody dies. Extremely dangerous. But that's how you make nanotubes and fullerenes, at home! Its probably illegal too, because of the "touch-the-wrong-place-and-you-die-effect." -- Mac Davis] ⌇☢ ญƛ. 07:53, 1 May 2006 (UTC)
I have a friend who's banned from a nearby institution because of an "incident" involving nanotube generation and the apparent destruction of some lab equipment. He's been asked not to return, to use his words. Isopropyl 22:17, 1 May 2006 (UTC)
I also remember reading some article about using a Laser on a sheet of very pure, very clean graphite. Seem to recall it being in Japan. It might've been related to making C70 instead of C60 though, it was 4 years ago at least. SanderJK 23:32, 1 May 2006 (UTC)
Buckminsterfullerene occurs naturally in soot, although I'm not sure why. Ardric47 00:02, 3 May 2006 (UTC)
  • Basically because of the principle that if you throw enough bombs into enough piles of bricks, one of them will sooner or later form a house :). Basically they're formed at random at high enough temperatures, when you have enough carbon atoms whizzing around, most of them will link up and form graphite, but a few of them will become various kinds of fullurenes and nanotubes. So the rest is a matter of filtering them out (as mentioned above). There is currently no good, ordered way to synthesize them. But you can safely say it's only matter of time before someone finds a catalyst, since there's a huge amount of people working on this. --BluePlatypus 23:03, 6 May 2006 (UTC)

[edit] Mysterious line of skin

I dont now much but i am kind of concerned because i dont now what is wrong with me; my foreskin is retracted, but not past the head, and a line of skin runs from the base (on the underside) of my shaft to near the opening which connects the shaft to the skin. it is visible on the outside of the skin. Please help.

I am a virgin and a recent teen (i've been a teen for a couple years) --216.197.192.136 03:06, 1 May 2006 (UTC)

Sounds like your frenulum. I used to have one myself. Scared the shit outta me when it snapped. Howard Train 05:29, 1 May 2006 (UTC)

Doesn't that come with birth (the frenulum)? What do you mean you used to have one? AHHHHHHHH!! OMG WTF, the 4th time I read the above comment, I read that it snapped! Ahh! Owwwww. Owww!!

Anyway, to the question-poster: Does it stick out, three-dimensionally? How is it different from the surrounding? When did it appear? You're about 14-16? -- Mac Davis] ⌇☢ ญƛ. 07:58, 1 May 2006 (UTC)

If this is something you're worried about, may I suggest you talk to your doctor? There is no need to be embarassed about asking, doctors have seen all manners of things, and s/he will be able to help you if there is something wrong, or put your mind at rest if there isn't. Remember, we're not doctors :) — QuantumEleven 08:46, 1 May 2006 (UTC)
Seems that what you see is the penile raphe. The scrotum and foreskin are formed from tissue that in women would form the inner and outer labia. The ridge is where they have fused. Nothing unusual there, mate! Dr Zak 11:30, 1 May 2006 (UTC)

Yah it's '3D', it just connects from by where the scrotom connects to the shaft and goes to near the tip of my penis. So nothing is bad about it though? I can live happy with it? i think it is a frenulum...

Yah, i google image searched it and it's a frenulum....

[edit] Pictures?

Are there any pictures on frog anatomy...or any other type of science-related subjects? Mostly people I know tend to be visual. Thanks!

Did you try frog? I mean, it's got the full skeleton. Isopropyl 05:54, 1 May 2006 (UTC)

[edit] General Relativity

I know that mass and energy warps space-time but why?

Unknown. Possibly due to entirely theoretical gravitons. If you can understand it try quantum gravity. -- Mac Davis] ⌇☢ ญƛ. 07:44, 1 May 2006 (UTC)
See General relativity. – b_jonas 11:36, 1 May 2006 (UTC)
déjà vu. -lethe talk + 16:39, 1 May 2006 (UTC)
Fundamentally asking 'why' about physical laws is not helpful. Physical laws are descriptions of the way things are: asking why things are the way they are is the realm of metaphysics. DJ Clayworth 17:23, 2 May 2006 (UTC)

[edit] Naval Citrus Storage

How did the British Navy preserve lemons and limes that were used in preventing scurvy? A lemon may last several weeks if kept in ideal conditions, but it seems that the time between the fruit being plucked from the tree and the time it was delivered to the sailors would be a few months, or maybe even as long as half a year. The lime or lemon would have to be harvested, packaged, shipped, and stored before being finally served. Packing it in salt would just draw out all of the fruit's moisture. Does anyone have an answer?

--Sputnik

On a History Channel show, I remember that on one British naval exploration voyage to explore Canada, they used canned lemon juice, and had excessive amounts of it. But one of the downfalls of the mission leading to its death, was that the compounds in the lemon juice brokedown, and most of them ended up dying of scurvy. I seem to remember that they grew lemon and lime trees on the boat itself. -- Mac Davis] ⌇☢ ญƛ. 10:59, 1 May 2006 (UTC)
...which creates another question. "Exploring Canada" and "growing citrus fruit": They'd have had fun growing lemon trees if this was one of the Northwest Passage expeditions! How the hell did they get things to grow in those temperatures? Grutness...wha? 13:28, 1 May 2006 (UTC)

You can water them with snow. --Zeizmic 17:33, 1 May 2006 (UTC)

Ha, ha guys. I meant on trips to the Caribbean [for the growing trees on the boat part] you silly heads! -- Mac Davis] ⌇☢ ญƛ. 07:49, 2 May 2006 (UTC)

[edit] MSN Messenger 7.5 annoying login problem

When I try to login in MSN Messenger, sometimes (most times) the window about the unread messages in my e-mail account pops up but the rotating icon keeps rotating, impeding me from viewing my contacts. Has anyone else experienced this problem? Does anyone know how to solve it? Thanks.

That's because its a Microsoft product. Use Gaim to connect to MSN. --Chris 13:14, 1 May 2006 (UTC)
If you want to stick with MSN, go to Tools -> Options -> Alerts and Sounds and remove the checkmark beside "Display alerts when e-mail is received" Andrewjuren(talk) 15:46, 1 May 2006 (UTC)

[edit] Relativity

Relativity often emphasize that the laws of physics for everyone are the same no matter what speed they are travelling at. Why is that?

Did you try principle of relativity? Isopropyl 12:33, 1 May 2006 (UTC)

The laws of physics are the same all over our universe( and probably all others if there are any more ). irrespective of what speed you or the observed object is travelling relative to each other. They are this way because if they were not the laws would not be universal.

In other words the universe would break down and implode or flash into non-exixtence, because the physical laws in zones with common borders would not be compatible. Some may say that the laws could be different if there were volumes of space containing nothing between different areas or universes.

This is also impossible for at least two reasons. 1. there can be no areas where 'nothing' exists ( neither time nor space) for the obvious reason that if there is no space there is no separation and 2. If there was something called space between the two areas then such entity would have its own border regions which must by definition come up against the formerly mentioned regions and therefore be in contact.

As you can see the speed of objects or entities does not have any real meaning in this context because

1.Even if the two objects were travelling say in opposite directions at the speed of light ( as in fact photons often do ) each would be travelling AT the speed of light relative to the other. They must by definition respond to the same laws of physics because even though travelling at light speed they would have at some time have been in the same area.

2.If they are travelling at different speeds, say one is 'stationary' and one travelling at 180,000 k p sec. in the opposite direction, then what happens ? If the laws were not the same we could not 'see' each other, obviously because we would not be using the same laws. If we did 'see' each other we would have to conclude that we were subject to the same laws. If we swapped places and we were then on the object travelling at 180,000 kps what would happen ? We would perceive that the other object was travelling away from us at that incredible speed and that we were stationary ( if we did not have any other reference point which was within our sphere of observation )

You can also ask the questions: a) what happens when the two entities are travelling toward each other ? b) Which one is moving ?

--Antipodeite 13:37, 8 May 2006 (UTC)

[edit] Synaute

Is a synaute a real thing? zafiroblue05 | Talk 12:44, 1 May 2006 (UTC)

Very good question. it looks plausible, but (other than Wikipedia mirrors) gets virtually no google hits. I've sent it to Wikipedia:Articles for deletion where hopefully some people more in the know will be able to work out whether or not it's for real. Grutness...wha? 13:37, 1 May 2006 (UTC)
Yes, they are real things, only they are called cenotes.--Andrew c 20:49, 1 May 2006 (UTC)

i think people need to stop inveseting so much faith in the ridiculousness (sp?) of google. i could be mistaken but i believe it's filtered by republican war machines! but like i said i could be wrong....now off to macdonalds! PSYCH! peace -jms

Do you mean sign out ? That's a real thing !--Antipodeite 13:06, 8 May 2006 (UTC)

[edit] GSM v/s CDMA

in gsm technology, we have MSC codes(represented by first five digits of the 10 digit cellular number). what is the counterpart of this in the CDMA technology? is it diffrent in various parts of the world? if yes then , what is the trend in india?

dominic, new delhi.--210.210.24.146 12:55, 1 May 2006 (UTC)

I don't know whether we can help you on this highly technical question, but you might try our articles on GSM and CDMA. --Robert Merkel 01:49, 5 May 2006 (UTC)

[edit] Using a sextant instead of a GPS receiver!

Is it possible to use sextants or similar low-tech tools for Celestial_navigation in an activity like geocaching? The accuracy of many GPS receivers is about 3 metres. What would be the typical accuracy of using astronavigation techniques? Does it even come close to 3 or 10 metres or is it too fuzzy to use for geocaching? --Sonjaaa 13:19, 1 May 2006 (UTC)

I'm certainly no expert, but I'd be extremely surprised if you could get closer than a couple of kilometres to absolute accuracy with a sextant alone. In the days when they were the principal form of navigation, they were used (a) in the open sea, where absolute accuracy was not necessary, (b) close to or on land, in which case triangulation using major points of reference provided an important secondary tool and would be able to provide far greater accuracy. I certainly wouldn't think you could use astronavigation alone for geocaching, though a combination of it and triangulation from landmarks might get you fairly close. Grutness...wha? 13:46, 1 May 2006 (UTC)
While doing things the old way might be an interesting diversion for modern geocachers, the same problem faced polar explorers, particularly those hoping to be the first to either pole. A sextant is indeed much too crude, but celestial navigation is the only option - there's no maps (so no known landmarks against which to triangulate) and magnetic compasses are useless at such extreme latitudes (indeed, beyond the 80th parallel they're pointing in entirely the wrong way). Amundsen (at least, probably others) did use dead reckoning as a backup (a spiked wheel on one sled turned as it moved over the snow), but the irregularities and twistiness of the terrain make that only of moderate use. It's an interesting question to ask "who was the first person at a given pole" - how close does one have to be for it to count? Amundsen and Scott both took with them fairly bulky instruments (theodolites, I suppose) such to measure the precise location of the sun (remember also that they did their explorations in the antarctic summer, when the sun never sets, so there are no sunrise and sunset measurements to be had, and the stars are never visible). I imagine these were fitted with some form of tunable slit to allow the position of the sun to be precisely captured (when you get to the degree(sic) of accuracy needed, the apparent diameter of the sun will itself be an issue - so you'd need to measure the position of the left and right edges of the sun (hence the slit) and average the two). I believe (from my recollection of Roland Huntford's Last Place on Earth) that these observations (and the subsequent hour or so of calculations) were done only once per 24 hour period, except when they were very near the pole, when it was necessary to conduct them almost continually. Amundsen camped where he thought the pole was, but moved the following day (after extra detailed observations and calculations) showed it to be more than 1 km away. Even then, modern astronomers examining his logs and recalculating his position with more accurate tables think he was still about 1km off, and that two men in his party (when trekking from one camp to the other) probably came to about 300m of the actual geographical pole. And remember that Amundsen had a master's certificate and both Helmer Hanssen and Sverre Hassel mate's certificates, so a more experienced bunch of celestial navigators you'd not find. It's a remarkable feat of celestial navigation, but still too poor for geocaching, I think. -- Finlay McWalter | Talk 14:57, 1 May 2006 (UTC)
Even if the stars were not visible, I suppose the Moon would still have been visible some of the time, and it could have helped them slightly. – b_jonas 00:03, 2 May 2006 (UTC)

Torge, Wolfgang. Geodesy, 3rd Edition. mentions the accuracy of some observational instruments. For stationary observation the Danjon prism astrolabe achieved a precision of ±0.05". For field measurement, transportable instruments mentioned are: prism astrolabes, zenith cameras (±0.5" or better) and the universal instrument (a theodolite with attachments for astronomic observations, ±0.1" to ±0.3".) All these instruments require a very accurate integrated time source, synchronized with International Atomic Time. EricR 16:36, 1 May 2006 (UTC)

[edit] making map pictures for wikipedia?

I want to add an image of Leslieville to show the boundaries of the neighbourhood, can I use google maps or if not then what online mapping source can I legally use to make the image, showing all the streets and the boundaries?--Sonjaaa 14:34, 1 May 2006 (UTC)

No, you can't use google maps in wikipedia, either directly (by including the image) or indirectly (by tracing over a google map) - the maps are copyrighted by Google and its partners, and certainly aren't compatible with the GFDL. See Wikipedia:WikiProject Maps for links to resources for drawing your own map; suffice it to say that it's hard. -- Finlay McWalter | Talk 15:02, 1 May 2006 (UTC)
That's strange that tracing is not allowed (even from satellite view?). Does it mean that Google basically owns the shapes of streets in Toronto, for example?--Sonjaaa 15:33, 1 May 2006 (UTC)
No, you could go out into the street with surveying equipment and measure it yourself, and that would be perfectly legal. But maps are certainly copyright, as are photographs (and a tracing, as a derivative work, is still the copyright of whomever took the original photo/survey). It's questionable if you could really get caught tracing a google map, but remember that the map projection is specific to Google, and mapmakers are notorious for deliberately introducing small errors into maps to catch copyists. Now, there are PD satellite and aerial photos, so you could either use those or trace them. Things are particuarly nice for the US, because NASA World Wind will retrieve free USGS topographic maps, landsat photos, and (for major US cities) detailed aerial photography. All of that stuff is public domain, and can be used in Wikipedia directly or as the basis for composites, diagrams, maps, etc. But for Canada all worldwind will give you is the Landsat imagery, which (at 15m I think) is much too chunky for street-level stuff. Natural Resources Canada has some information here, but I don't know how detailed their stuff gets. Urgh, on checking their page even that is non-commercial-use only, which still means it can't be used on Wikipedia. -- Finlay McWalter | Talk 15:47, 1 May 2006 (UTC)

Ontario has digital base maps here [1] I just emailed them to check the public domain status, since I don't see anything on the web site. --Zeizmic 15:48, 1 May 2006 (UTC)

One thing that can be done is to compile an approximate map using GPS data. Image:London Underground Zone 1.svg is one such (the underground map of London), which was compiled by wikipedians with handheld GPS units and some software to bold the whole thing together. An impressive piece of work, but still a lot of work. -- Finlay McWalter | Talk 15:50, 1 May 2006 (UTC)
If i trace a map from Google..how will they know that i traced it?? Jayant,17 Years,India • contribs 16:07, 1 May 2006 (UTC)
As the recent Dan Brown copyright case shows, if a copyright case comes to court the creator of the contested content will be asked to prove they really created what they say they did. It's quite reasonable for a court, at some future point, to ask "where did this map come from?" Google (well, their suppliers) can show they made their map, because they have the original survey notes of the surveyors. If you traced a map or satellite photo, you can't produce such notes. "How", you might ask, "would Google or anyone else become so suspicious so as to sue in this manner?". Firstly, Google don't own most of their mapping data - they buy rights from regional mapping agencies - and for many regions, only one company (often a division or agency of the government) has actually done the on-the-ground survey. Say, for example, if someone uploaded a street map of a city in the UK. Bar a very few places, that original data has only ever been mapped by the Ordinance Survey - so the very fact that the map is fairly accurate is enough to make the OS's flesh-eating lawyers suspicious. And secondly, as I noted above, cartographers often put little errors into maps - if the error shows up in your map, it's strong evidence you copied the map. And don't for a moment imagine the satellite images Google shows haven't been montaged, adjusted, and potentially tweaked in just the same manner. Anyway, it's a very bad mindset for a Wikipedia contributor to be in when they're thinking "how can I sneak in copyvio stuff and get away with it?" -- Finlay McWalter | Talk 16:25, 1 May 2006 (UTC)
I wasn't thinking on those lines anyways.. was just wondering... Jayant,17 Years,India • contribs 17:08, 1 May 2006 (UTC)


Neat, I also found this: OpenStreetMap --Sonjaaa 18:21, 1 May 2006 (UTC)

Does it mean that I can't use Google earth pictures in my website, even if I don't make any money out of it ? Say I use a high resolution map of a city and lable the streets etc and display it so that it is helpful for others to find their way around ? If i really want to do it, can I get google's permission ? How do I get it ? --Wikicheng 18:26, 1 May 2006 (UTC)

I just got the standard answer back from the Ontario gov't: "These maps, and maps you make from them, are mine, mine only, and always mine!" There is no such thing as public domain in Canada, unless you are talking about a neato 1885 map of Ontario. --Zeizmic 18:51, 1 May 2006 (UTC)
Copyright is copyright: "I don't make any money out of it is" absolutely no legal defence. Imagine if you duplicated Disney's latest DVD and gave away copies. Would you make money? No. Would Disney sue you for every penny you owned, and a lot you didn't? Sure would. Similarly "being helpful" isn't a defence for copyright theft. Maps cost millions and millions of dollars to make, so the people who make them are every bit as keen as Disney to stop theft. Please stop looking for loopholes, you are doing yourself no favours! If you want to license content from Google, start by sending them an e-mail; but since Google in turn license their maps from other people they might not be able to sublicense to you. However, many parts of the world are covered by people who will allow limited use of their maps, in return, perhaps for a credit, or at least allow you to link to a small part of the map. For example, http://www.streetmap.co.uk/linkto.htm explains how to link to their maps of the UK, while http://www.ordnancesurvey.co.uk/oswebsite/getamap/ allows you to download up to 10 UK maps for use on your web site free (subject to terms and conditions including a particular form of credit with a link back to their site. Notinasnaid 18:58, 1 May 2006 (UTC)
Just let me note that you can read the exact Terms of Service for Google Maps – b_jonas 23:58, 1 May 2006 (UTC)

What about this?? http://geodepot.statcan.ca/Diss/2006Dissemination/Data/download_e.cfm Maybe we can use this data for a map of Toronto neighbourhoods? Do we have permission?--Sonjaaa 19:16, 1 May 2006 (UTC)

Does the web site give you permission? If you aren't sure, but it seems to, please post the URL of the information in doubt. Notinasnaid 20:04, 1 May 2006 (UTC)

Although this is depressing, throughout Canada, you will find the same thing. If you email them, you will get the 'crown' speech that I got. Only if they proudly splash 'public domain' on their web site (as the National Archives) are you in the clear. --Zeizmic 01:50, 2 May 2006 (UTC)

I don't find it depressing. I'd rather the Ordnance Survey made its money by commercial licensing of the results of its work, rather than pay more taxes so they can give it away. Notinasnaid 10:47, 2 May 2006 (UTC)
I thought I'd add a little more, since I've been reading the accounts of the Ordnance Survey. In 2004-5, it cost 105 million pounds to run the Ordnance Survey, but the total of government grants was 1 thousand pounds. All thanks to the wonder of copyright! By contrast, the United States Geological Survey (which admittedly does more than maps) has a government budget of $938 million. Notinasnaid 22:28, 2 May 2006 (UTC)

Let me assure that being a wikipedian I wasn't planning to misuse the google map. I just thought that it would be useful to setup a website which would allow people to navigate thru a city easily. Definitely not looking for loopholes ! My apologies if I sounded that way. Well... I may write to google and see what they say. Thanks for all the info and help --Wikicheng 12:08, 2 May 2006 (UTC)

[edit] Voltage Coversion with a small elecronic appliance

I live in the USA and am taking my USA Digital Canon Rebel XT to Europe this summer. Ordinarily I would take a voltage converter but the specs on the back of the battery charger say the "input" is 100V - 240V so I am thinking that other than the issue of incompatible prongs, I could theoretically use this charger without converting the voltage (just perhaps get an adapter so the USA prongs can fit into a European outlet). Doesanyone have any knowledge about the implications of the specs on the charger? Do you know anything about the Rebel's battery charger? (It is the CB-2LT charger).

You could just use a plug converter for the 50,000 different plugs in Europe. I would definitely use an external charger, since I hear they get power spikes when they change hamsters. --Zeizmic 15:18, 1 May 2006 (UTC)
Zeizmic is quite clearly a complete bell end. Let me re-phrase that for you;
You could just use a plug converter for the 3 different plugs in Europe. I would definitely use an external charger, since I hear they get power spikes when america declares war on another innocent country. Philc T+C 16:45, 1 May 2006 (UTC)
Thank you for standing up for us, PhilC :). Just to be sure, make sure that your charger also takes 50-60 Hz current (US is 60Hz, Europe is 50Hz). If it's 110V-220V it almost certainly will, but you want to make sure. As for plus, your best bet is one of those 'universal' adapter plugs they often sell at airports (although they're not always cheap). Alternatively, which country are you going to? Take a look at Electrical plugs: Most of Europe uses a type C, except for the UK and Ireland, which use a type G. In Italy and Switzerland you'll still find some type L sockets, but most hotels will have converters in stock so you can use a type C. Hope this helps! — QuantumEleven 13:06, 2 May 2006 (UTC)

[edit] Television set from USA to India

Hi i have a used Toshiba television set from 1997 which has only Closed Captioning and no fancy features. i plan to take it to India. i understand that the US has NTSC colour television system while India has the PAL colour television system. Is there a way that the television set would work in India? [++ Any specific knowledge of duty at Indian Customs would be welcome too ++]

Regards Babbu

See NTSC and PAL. As discussed here previously, if you try to watch a PAL program on an NTSC set, you will get a fuzzy gray image that rolls every few seconds. There are PAL-to-NTSC converters, but they cost far more than a new PAL television. All in all, you'd save a lot of money by leaving (or selling) the NTSC tv and buying a new PAL tv in India. --Kainaw (talk) 16:27, 1 May 2006 (UTC)
Worse, as India has 230V mains and the US 110V, it'll probably burst into flames as soon as you plug it in (so you can't use it even with a US DVD player, unless you wasted more money on an expensive voltage-transformer). Anyway, surely the cost of shipping would cost more than the price of a new TV in india. -- Finlay McWalter | Talk 16:33, 1 May 2006 (UTC)

Dear Kainaw and Finlay McWalter
Thank you very much for your prompt and informative replies and apt suggestions. i will certainly do as you say.
The shipping for the TV would cost over $300.
Regards, Babbu

[edit] Simple Carbohydrates in a Packet of Sugar

Hi there,

I was wondering how many carbs are in a packet of sugar. Or Even easier, how many grams of sugar are in a packet, because I have a carb count for 100 grams of sugar but I don't know by what to divide it.

Thanki

Why don't you look under the "nutritional information" of the packet and look. Looking at my bag of granulated sugar, per 100g of sugar = 100g carbohydrates; one serving (amount not specified) is 4g of carbohydrates. Kilo-Lima|(talk) 16:51, 1 May 2006 (UTC)
That would knda mean one serving is 4g of sugar -- is this some sort of trick question? Sugar is 100% carb; that's kinda the whole point. --jpgordon∇∆∇∆ 01:05, 2 May 2006 (UTC)

A restaurant packet of table sugar is typically 1 teaspoon of sucrose, equal to 4 g or 16 cal. Sucrose is 100% carbohydrate, readily digestible to about 50% glucose and 50% fructose. alteripse 05:15, 2 May 2006 (UTC)

[edit] Army pay for medical studies

I need to find information on army paying for my medical studies. I heard that the army pay for you university studies if you join the army for a short period. Does anyone know a good website to find information on this? I am looking for information for british universities.

Cheers

Please remember to sign all of your posts on talk pages. Typing four tildes after your comment ( ~~~~ ) will insert a signature showing your username and a date/time stamp, which is very helpful. Also, it might help if you said what army you mean (the British one?) Sandstein 19:49, 1 May 2006 (UTC)
  • I would recommend calling the army in question and asking. --Ginkgo100 19:53, 1 May 2006 (UTC)

Google is probably your best bet. I'd advise against speaking to recruiters as they're notorious for over-hyping military scholarship programs (at least that's the case here in the U.S.). Best, David Iberri (talk) 21:23, 1 May 2006 (UTC)

[edit] Stars n Universe

Since stars work out by Hydrogen fusion and at later stages Helium and then much heavier atoms as it begins to collapse, but where do atoms aobve the weight of iron come from, because only hydrogen was created in the big bang, so where do the heavier atoms come from since it becomes energy-wise unprofitable to fuse atomic nuclei beyond iron.

Also once a predominant amount of the nuclei have gone through whatever process is the answer to the question above, will stars cease to exist, or will there be fission stars, or what. Cheers Philc T+C 16:36, 1 May 2006 (UTC)

Q1: See nucleosynthesis and supernova nucleosynthesis.
Q2: See Ultimate fate of the universe. TenOfAllTrades(talk) 17:29, 1 May 2006 (UTC)
I couldn't really find anything about the fate of stars after large amounts of the matter in the universe make up atoms heavier than iron in Ultimate fate of the universe or wether fission stars are possible. Does anyone know the answer, or could point it out to me. Philc T+C 17:58, 1 May 2006 (UTC)
See uranium. It is a very plentiful material on Earth. It goes through natural fission on the Earth - enough to affect the core tempurature of Earth. So, if you define a "fission star" as something that floats around space and contains some material that goes through natural fission, then Earth is an example of a fission star. As for your assumption that Stars will eventually use up all the hydrogen in space, you are assuming that there is no source of hydrogen. Why can't there be fission going on all around space. There is certainly enough radioactivity to get things going. --Kainaw (talk) 18:17, 1 May 2006 (UTC)
I think he is thinking of a more intense and larger reaction going on than simple, small, localized reactions taking place on a tiny rock. That's a good question—the possibility of a fission star—I'd day no. Because in what I've read, I've never heard it mentioned. -- Mac Davis] ⌇☢ ญƛ. 20:51, 1 May 2006 (UTC)
I wouldn't of thought it was naturally possible after considering it for a while, for a star sized mass of such high concentrationns of heavy elements such as uranium to form. So although it is unlikely to ever occur, as a thought, would it be theoretically possible, and how would it differ from fusion stars (eg, nuclei created by fission tend to have huge half lives, whilst nuclei created by fusion have relativly minimal ones, so if it supernovad, would a fission star polute space or something) Philc T+C 17:56, 2 May 2006 (UTC)

As I understand it, the fuller cycle seems to be, and this is a laymans understanding only in outline:

  • Theres a huge amount of hydrogen in space. The mechanism for stellar formation and conversion for elements from fusion, from lighter to heavier, from hydrogen to to helium and up to around iron, is reasonably understood. After that point, usual stellar processes by means of atoms combining, cease to be net producers of energy and become net consumers, so heavier elements cannot form in that way.
  • As this happens, the star which has been burning hotter, cannot sustain its power output, and the immense pressures generated by this heat cannot counteract gravitational collapse. So (a sufficiently massive) star collapses somewhat, and sits there glowing as a dwarf star. Presumably it may become a nova for a time too.
  • A sufficiently large star has such a mass, that gravity itself can overcome the remaining pressures. The forces that prevent collapse above, are overcome, and the star may become a neutron star, or collapse and then explode as a supernova.
  • In this final collapse, forces other than nuclear fusion are at work, mostly driven by the immenses force of gravitational collapse. It is my understanding that this is the environment in which heavy elements beyond iron are formed and exploded out into the universe at large.
  • So in a nutshell, lighter elements are created by the fusion reaction of smaller atoms combining into more stable medium sized ones, and heavier atoms are created by gravitationally driven collapse. So ultimately, the energy given off by elements such as uranium, comes from gravitational energy which has been "used" to form unstable heavier elements that then in turn decay giving off energy themselves as they revert to more stable forms.

Hope this helps, and if it's roughly accurate add it to some appropriate article on creation of elements or stellar processes. As said, its my lay-understanding only, but I think its roughly ok as a broad non-technical answer. FT2 (Talk) 15:09, 2 May 2006 (UTC)

[edit] DNA synthesis techniques (also Protein synthesis)

Does there currently exist a technique which permits the synthesis (as opposed to the sequencing) of a specific desired strand of DNA or RNA of known sequence, presumably using its base nucleotides? If so, how does this work and what are the limitations of the technique? As this might be a lengthy answer, a very brief explanation and a reference for more data would be terrific.

(I am already familiar with PCR, and using and selecting an existing sequence/allele for amplification or expression in-vitro. I am curious about synthesizing very long strands or sequences which may not be found in nature.)

As a correlary, is there a simple, high-yield, automated process for protein synthesis from its amino acids? Especially for longer, more sophisticated proteins?

Thank you very much for your help. :)

--216.226.42.167 17:11, 1 May 2006 (UTC) Alaiyo

Do your own homework. And for that matter, I think the answer is no. We can splice, cut, alter, but not create DNA/RNA.--Frenchman113 on wheels! 17:23, 1 May 2006 (UTC)
My apologies.--Frenchman113 on wheels! 22:07, 2 May 2006 (UTC)
Don't bite the newcomers—his doesn't look like someone looking for us to do his homework; he's just looking for pointers. Worse, your answer is incorrect.
Short strands of DNA (up to a couple hundred of bases in length) are regularly synthesized for all kinds of purposes. These oligonucleotides (usually just called 'oligos') are often used as PCR primers. Google for 'DNA synthesizer' to find commercial equipment and information.
Since synthesizing really long strands of DNA artificially tends to be error-prone, you can sequentially stitch together shorter oligos using DNA ligases to build entire genes from scratch.
For proteins, a similar process can be used. (Different reagents and equipment, but similar concepts.) Protein synthesizers (again, Google for them for more info) can sequentially ligate amino acids to build an artificial protein. However, this works well only for relatively short sequences. 20 amino acid residues usually works fairly well; 30 is about the limit. Again, it is possible to ligate these chunks together, but it's more difficult than with DNA.
Trying to synthesize a larger protein in this way isn't – as far as I know – possible. Your synthesis and ligation yields get too low. Also, getting a large protein to fold properly usually requires chaperone proteins that won't be present in your system. TenOfAllTrades(talk) 17:52, 1 May 2006 (UTC)
Ten is correct. There is active debate in the synthetic biology community as to whether or not DNA synthesis should be regulated, as the sequences of many known human pathogens are available online. These include extremely infectious diseases that are otherwise difficult to acquire, such as smallpox or the previously extinct 1918 influenza virus. As the technology stands today, costs for synthesis hover at around one dollar per base pair, which is prohibitively expensive beyond a certain point. Worse yet, not every sequence can be successfully made (for a variety of reasons) which leads to enormous time sinks as orders come in, weeks are wasted trying to synthesize them, etc. Hope this helps! Isopropyl 22:01, 1 May 2006 (UTC)

Thank you to the both of you who offered me a nudge in the right direction. Yes, I am a newcomer, I am also a "she", and I had a brainstorm the other night on overcoming some of the protein synthesis challenges to which you alluded. DNA synthesis seemed like a reasonably obvious extension of the problem. Your leads (and admonition for caution in terms of safety/socio-economic implications) are very helpful. Have a terrific day!

[edit] Ingredients of "parfum"

Recently i purchased a deo which states under the ingredients list the following "alcohol denat" & "parfum". I read the comprehensive article with regard to "alcohol denat" in wikipedia site and all he ingredients used in making it, but was unable to find out the same with regard to "Parum" Please help me to get the ingredients used in making the same.

"Parfum" is French for "Perfume". It means "artificial scent". This is similar to food that lists "artificial flavors" in the ingredients. So, you won't find the specific ingredient used. --Kainaw (talk) 18:42, 1 May 2006 (UTC)


thanks for the reply, but a small clarification, i read in an article that there are two kinds of alcohol used in cosmetics and perfumes (1) alcohol denat (2) alcohol parfum. if parfum is french for perfume then what is alcohol parfum?. appreciate your views on this

"Alcohol perfume" is basically grain alcohol (190 proof). "Alchohol denat" is short for "denatured alcohol". A denatured alcohol is poisonous, which means that it falls outside of laws governing alcohol that you can drink. There are governmental laws and religious laws governing alcohol usage. By using denatured alcohol, perfumes get the benefit (the perfume evaporates faster) without the legal/religious hassles. --Kainaw (talk) 20:39, 1 May 2006 (UTC)
Denaturated alcohol is not actually poisonous, at least not more so than ordinary alcohol. It is just undrinkable, usually through adding Bitrex or some similar substance which tastes horrific even in trace amounts. Chemistry lab ethanol can be quite toxic though, in particular the "dry" kinds (with concentrations above the water azeotrope at 96%). Those often contain drying agents like Bromobenzene, which react with water. For use as a solvent in things like Grignard reactions when you absolutely do not want any water present. --BluePlatypus 22:55, 6 May 2006 (UTC)

[edit] magnetic north

If you travelled into space with a compass which way would it point once you'd left earths atmosphere??

It would still point along the magnetic field lines; see Earth's magnetic field and Magnetosphere for rough depictions. Melchoir 20:45, 1 May 2006 (UTC)
The Earth's magnetic field extends well past the atmosphere. Magnetosphere. However if you got far enough away from the Earth other planet's or the Sun's magnetic fields would be where you compass would point to. -- Mac Davis] ⌇☢ ญƛ. 20:47, 1 May 2006 (UTC)

[edit] BP suffix on medicines etc.

Why is it that some medicines have their name, for examples (this is made up) Magensium Hydrochoride BP. What does this stand for if anyone knows? Thank you

BP is short for benzoyl peroxide. --Kainaw (talk) 20:41, 1 May 2006 (UTC)

What is that exactly? Is it a preservative or just a solvent for the drug to be in a solution form? Thank you for the hasty reply.

On a medicine bottle, specifically following the name of the chemical, BP is short for British Pharmacopoeia. Notinasnaid 20:47, 1 May 2006 (UTC)
See benzoyl peroxide. It is a popular medicine for acne and teeth whitening. The initials "BP" commonly follow many acne medications to signify that benzoyl peroxide is the primary ingredient, such as Xerac BP. --Kainaw (talk) 23:24, 1 May 2006 (UTC)
Except I have medicines where it seems unlikely to signify an ingredient. For example, in the ingredients list it will say "Hydrocortisone BP 1% m/m Also contains white paraffin." In this case, Notinasaid's meaning seems much more likely, and seems to match the example. If I ever see it following the name of a tooth whitener or acne treatment however, I shall be sure to remember benzoyl peroxide. Skittle 01:39, 2 May 2006 (UTC)

BP does stand for British Pharmacopoeia. The comparable label in the US is USP, which stands for United States Pharmacopoeia and indicates that the product meets the specifications of the USP. This is normally used of older generic products (e.g., aspirin or Epsom salts) that you might consider "medicinal chemicals" rather than patented pharmaceuticals. alteripse 05:11, 2 May 2006 (UTC)

I've edited BP (disambiguation) to try and explain all this. Melchoir 05:34, 2 May 2006 (UTC)

[edit] Physics: Air friction in a hollow ball?

You have two balls perfectly next to each other on a perfectly smooth slope. Both balls are of exactly the same composition. When you roll the balls at the same time down the slope, they should both travel at exactly the same rate. Take the same situation, but this time make one of the balls hollow. Will the hollow ball be slower than the other because of friction from the air inside? Or for any other reason? Flea110 21:00, 1 May 2006 (UTC)

My guess is the 'friction' from the air inside would be minimal, the hollow ball would be lighter than the solid ball. Since it has the same surface area as the solid one it would be slower due to air friction of the air OUTSIDE.

Air resistance isn't really a factor here. Take a look at moment of inertia and see if you can figure it out. If not, we'll be happy to help you :) Isopropyl 21:34, 1 May 2006 (UTC)
Okay, so you're familiar with the concept of inertia, right? An object at rest tends to stay at rest. The moment of inertia is another way to measure inertia, only around an axis with rotation. You'll find (from list of moments of inertia) that hollow spheres have a greater mass moment than solid spheres, and thus have a harder time "getting the ball rolling", as it were. Your solid sphere will roll down the ramp faster. Isopropyl 22:10, 1 May 2006 (UTC)
True, for two spheres of the same mass but with the mass arranged differently within them. It occurs to me that Flea110 might be thinking about a case where the density of the material we're making the spheres out of is a constant, in which case it'll depend on how hollowed out it is. According to the back of my envelope, if the radius of the hollow region is more than 73.6% that of the total sphere then it'll have a lower moment of inertia than the solid sphere. --Bth 09:00, 2 May 2006 (UTC)
I did not believe Isopropyl at first either, but looking at the energy of the spheres at the top and bottom of the ramp: \frac{1}{2} mv^2 + \frac{1}{2} I \omega^2 = m g h If the angular mass is in the form kmr² and the translational velocity is related to the angular velocity by v=2πrω, then the mass and radius of the sphere cancel out. \frac{1}{2} v^2 (1 + \frac{k}{4 \pi ^2}) = gh EricR 15:58, 2 May 2006 (UTC)

[edit] Simple test for sugar?

Is there a simple test for the presence of sugar? I've been buying Nesquik made with Neutrisweet for years, but I bought some that has the appearance, texture, and disolving qualities of the sugared kind. I wrote tothe company about this, but they didn't understand what I was talking about. So is there a simple household test for the presence of sugar? Bubba73 (talk), 21:18, 1 May 2006 (UTC)

Why don't you try out the Sugar's chemistry for the chemistry of sugar. General Eisenhower 21:28, 1 May 2006 (UTC)
Not helpful. If you think a difference between the two types of nesquik include a reducing sugar such as fructose (look on the labels) you could test using Benedict's solution if you can get any. That article lists common sugars it detects. However, it's more likely you need a test for sucrose, and I can't remember or find one. I'll have another look. Meanwhile, just get clear and firm with Nestle. You bought a product labeled as sugar free, but you suspect it is the version with sugar. They may have a packing or labelling problem. Suggest you are diabetic :-) Skittle 22:58, 1 May 2006 (UTC)
I am, that's why I use the suger-free version. I think it is probably labelwd or packaged in error. I wrote back to them today. Bubba73 (talk), 23:09, 1 May 2006 (UTC)
Okay. If the difference in ingredients is sucrose, and you can get your hands on benedict's solution and fairly weak hydrochloric acid, then it should give a negative result to benedicts solution at first, but a positive result if it's been boiled with hydrochloric acid for a few minutes. However, since you are in America, there's a good chance that the sugary version is made using high fructose corn syrup, so it will test positive using Benedict's. If you buy some more sugar-free stuff, with a different batch number, and look at the label finding no reducing sugars, and test it with Benedict's and find it negative, then there you go. However, much better to complain effectively, send your sample and get reimbursed. In my experience, food companies (especially big ones like Nestle) will give you the benefit of the doubt quite quickly and try to sweeten you up with vouchers. They will also want to check your product so they know whether they need to issue a statement and a recall. Skittle 23:13, 1 May 2006 (UTC)
And you've probably already tried this, but you might get a faster response if you email them [2]. Good luck. Skittle 23:18, 1 May 2006 (UTC)
Actually not. I emailed them at first, and I got this reply on April 19: "Thank you for contacting Nestlé on the Internet. Questions and comments from our consumers are always welcome!... We reviewed your email and will be responding to your request via regular mail. You can look forward to receiving a written response from us within 7-10 business days.". Today I get the letter in the mail (and it was from the same person). Bubba73 (talk), 23:48, 1 May 2006 (UTC)

[edit] Identifying a flora or fungi from SE Arizona

I have uploaded a photo of what I thought was perhaps a mushroom of sorts. I have since looked through a catalog of fungi photos and saw none similar. The fellow in the photo felt smooth, cool, and mushroom-like to the touch. It grew near or in decaying organic material in the shade. Does anyone know what it is?

Thanks for your attention. This is a great service. I used a hyperlink rather than the Image: in brackets because I didn't know if it was acceptable to actually display an image on this page. Hope that is okay.


What am I?

--Bad carpet 21:45, 1 May 2006 (UTC)

I don't think it's a fungus, since they look like they have some sort of flowering apperatus at the top? I'm not sure. What I am sure about, though, is how to link to an image without displaying it. You'd use [[:Image:Unknown_SE_AZ_April_29_2006.jpg]] to produce Image:Unknown_SE_AZ_April_29_2006.jpg. Note the leading colon. Good luck with twenty questions! Isopropyl 21:50, 1 May 2006 (UTC)
  • I'm no botanist, but it looks like a match to me.--Ginkgo100 03:44, 2 May 2006 (UTC)
  • Props for the quick find :) Isopropyl 05:45, 2 May 2006 (UTC)

Gotta use the image for something: Conopholis. Melchoir 06:43, 2 May 2006 (UTC)

Looks like it to me. Thank you! --Bad carpet 16:17, 2 May 2006 (UTC)

  • Also, thanks for using the image. --Bad carpet 23:24, 2 May 2006 (UTC)
    • Well... thanks for providing it! Props all around, have a drink. Melchoir 23:35, 2 May 2006 (UTC)
      • In case anyone is curious, from the description, it was a saprophyte of some sort, and just did a Google image search for saprophyte. Luckily, there aren't all that many, and most don't look anything like the cancer-root. Wonder why it's called that? --jpgordon∇∆∇∆ 02:08, 3 May 2006 (UTC)
        • Perhaps because it is a root parasite (which accounts for the unusual color -- lack of chlorophyll). This site says they are invariably found among oak trees at least in Illinois (there were oaks in the area where the photo was taken.) Also curious is the common name of the family it apparently belongs to, "Broomrape." --Bad carpet 21:57, 3 May 2006 (UTC)

[edit] Trying to find old (1988-1992 range) DOS computer game.

Hi all. I'm trying to remember the name of a DOS - CGA computer game I played back somewhere around 1988 to 1992, I forget the exact name of it.

It was called something *like* Starflight I think, but I found that one on the underdogs, and it's not it. It was similar in that it was a space game. You had a crew of 5 (or is it 6?) on your ship, and you had skills such as tactics etc for each person to go up in. On occasion you would land on a planet and go inside a structure. Inside the structure you would see the action in front of you, but then overlaid on that would be a small HUD-type display with the walls and such in blue. Your 6 crewmembers would be behind you in blue circles on the HUD as well, and then unknowns would appear as red circles. You could get weapons like laser cutlass, some kind of mace, but also some projectile weapons. One of the worlds you landed on had (3?) large towers (like 500+ stories), which were all "populated", but you were only interested in one particular area of one of them. Anyways, that's most of what I can remember. If someone wants some more details, or has questions, post and I'll try to remember some more. Thanks in advance. Aaronw 22:50, 1 May 2006 (UTC)

[edit] May 2

[edit] Digital Video Recording Systems

on a digital cmara what is the Diffrence between the NTSC and the PAL video recording systems... is one better than the outher for taking videos?

Have you browsed the articles on NTSC and PAL? One thing you really need to take into consideration: if you record something in PAL, it won't play back properly on an NTSC-only VCR, and vice versa. If you're in the US (and I assume you are), NTSC is the standard and I'd say it's best you stick with that. Confusing Manifestation 04:17, 2 May 2006 (UTC)

[edit] Microevolution & Macroevolution

I've heard some Christians and creationists claim that microevolution and macroevolution are separate and distinct from each other.They claim that all examples of observed evolution are of microevolution and that 'small changes do not imply large changes'.They also claim that there is a genetic barrier stopping organisms from evolving so far as to cross the species border.Are those claims true?

There's a lot of information at Macroevolution. Melchoir 03:51, 2 May 2006 (UTC)

thx much

Long answer short: No. But reading the article is good.

[edit] Cockroaches surviving nuclear explosions?

Sorry if this is a kind of stupid question. Is it really true that cockroaches have survived nuclear explosions? I've heard people joke that cockroaches will be the only things still around after we all nuke each other to death, but I was wondering if that was really true. I already checked the page on cockroaches and several pages about nuclear weapons, and didn't find this information anywhere. I did see that they could survive high levels of radiation, but would they survive the amount of radiation in a nuclear bomb?

Thank you!

Not really... see the explanation at Great Moments in Science: Cockroaches & Radiation. Wikipedia really ought to address this, since it's so widespread; I'm surprised it's not in Snopes. Melchoir 04:50, 2 May 2006 (UTC)
Nice link, the picture of Conan the Bacterium is now stuck in my mind forever. SanderJK 08:53, 2 May 2006 (UTC)
Dr Karl is a really good reference for many of those odd-ball science things. He's like the Australian Mythbusters/Julius Sumner Miller. Actually, I got a newsletter from Sydney Uni today with a version of that very GMiS topic. Confusing Manifestation 09:49, 2 May 2006 (UTC)
I think scorpions can survive 10x more radiation that humans... not really really related to the nuclear/radiation, though. Kilo-Lima|(talk) 19:04, 2 May 2006 (UTC)

[edit] PSOC to Pic Basic

I am vary competent in basic and decent at C programming languages. A fellow robot enthusiast had suggested I switch to PSOC programmable system for my robotic uses.. had any one else had any experiences with PSOC?? is it worth the switch?? SumoBotMaker 04:40, 2 May 2006 (UTC)

I don't have any personal experiance with those chips but if they offer features you wan't that the pics don't and the programming hardware/software isn't too expensive (or you can borrow it off this friend) then i'd give it a go. It's always nice to expand your options. Plugwash 18:37, 9 May 2006 (UTC)

[edit] Recommend a chemistry text!

Hi all,

I'm looking for a good first-year-undergrad level chem textbook (or two, if it's impossible to get one that covers both organic and inorganic). My formal chemistry education goes up to A-level (about eight years ago), though I've done QM-of-the-hydrogen-atom what feels like a hundred times since. I'm looking to freshen up and slightly deepen my knowledge. Any recommendations? (Easily available in the UK is a bonus but not essential thanks to Amazon etc.) --Bth 07:51, 2 May 2006 (UTC)

I can recommend John McMurry Organic textbooks, if you get older editions (not that much difference) ago via amazon used they're quite cheap. (Though postage might be a killer) The books in general give a very good basis for organic chemistry. Unfortunately, it does not cover inorganic chemistry, i'm not sure what to recommend (I was taught inorganic using Shriver & Atkins, but that book is not so straightforward). SanderJK 08:50, 2 May 2006 (UTC)
Silberberg, ISBN 0072396814, is good for general chemistry. —Keenan Pepper 15:58, 2 May 2006 (UTC)
And there's a used paperback (Like New!) on Amazon UK for only £25 ... (or at least, there was). Thanks Keenan! --Bth 09:20, 3 May 2006 (UTC)

[edit] anthrax

can anthrax be used as a bioweapon?

Yes. See Anthrax#Biological warfare. In particular, the 2001 anthrax attacks used "weaponised" anthrax. --Bth 10:53, 2 May 2006 (UTC)

[edit] wierd skin problem

hello

i have a habit of chewing the skin near my nails.its like i cant think without chewing my skin.whats happening to me?

As per the disclaimer at the top of the page, you should speak to a medical professional if you're really worried about this. But nail biting (which this is considered a form of IIRC) isn't uncommon at all (the article contains both statistics on the prevalence and information on treatment).
Incidentally, this came up recently on the Miscellaneous RefDesk as to whether it counted as autocannibalism or not (it doesn't). --Bth 11:06, 2 May 2006 (UTC)
FWIW, I used to bite my nails and I'd bite the skin when I ran out of nails. Perhaps this is what you're doing? --Howard Train 03:56, 4 May 2006 (UTC)

[edit] Nuclear Fusion

Does all chemical reaction need an activation energy? If nuclear reactions need an activitation energy, what's the activitation energy for nuclear fusion? I mean what activates the hydrogen to collide and create and helium?

Nuclear fusion is not a chemical reaction, but a nuclear reaction. However, nuclear fusion does require a lot of heat to initiate. See nuclear fusion. -- Mac Davis] ⌇☢ ญƛ. 11:12, 2 May 2006 (UTC)
Yeah, nuclear fusion's the place to go, though I just want to correct another seeming misconception in the question: that "hydrogen" fuses to helium. Normal boring single-proton hydrogen doesn't fuse directly to form helium -- fusion experiments on Earth tend to use deuterium, tritium or helium 3 as fuel. In stars, the pp chain or CNO cycle are involved (in which some of the protons are converted to neutrons).
Just as an example, For a deuterium-tritium reaction the necessary energy is roughly 100 keV (about 1.6 x 10-14 J, tiny in everyday terms but huge compared to the equivalent for chemical reactions because the distances involved in nuclear reactions are so much smaller).
The energy needed can be provided by high temperatures and pressures (in stars and fusion bombs) or by various acceleration methods (in fusion experiments). --Bth 11:39, 2 May 2006 (UTC)

[edit] Physics

Coloumbs law gives us force of attraction between two particles(charged).Does that include their masses as well? How about if a massless particle (gravitron)were subjected to this postulate?

Coulomb's law is essentially analogous to Newton's law of universal gravitation, but it deals with the electromagnetic force, not gravitational force (see Force (physics)). It only takes into account charge-ness. Granted, the force on a massy particle will have a much bigger effect than that on a less-massy one, but that won't change the calculation of the force between the two particles. I don't believe that any massless particles have charges, but I may be wrong about that one. -- Plutor 11:29, 2 May 2006 (UTC)
I'm not sure what you mean by "bigger effect". For the same charge, you'd get a greater acceleration for a less massive particle, simply by F = ma. I can't remember any massless charged particles either (the W bosons are charged, but also massive), but since massless particles are constrained to move at lightspeed, you'd have to treat any interaction properly using QED. Which would be hard.
To go back to the other question: in general, you could get a correction for the gravitational force simply by adding together the Coulomb and Newton laws, but the correction would be tiny. Consider the fact that atoms are held together by electrical forces and are very small indeed -- gravity is so weak that an atom held together solely by gravity would have a size on about the same scale as the universe. Gravity dominates on large scales simply because on large enough scales the positive and negative charges cancel out, whereas gravity is always attractive. --Bth 11:46, 2 May 2006 (UTC)

[edit] Can nuclear power save the planet?

I live in the UK and here the debate about nuclear power seems to have entered a new era, with many people who would normally consider themselves "green" warming to the idea of nuclear, I suppose as a lesser of two evils. Meanwhile renewbles seem ever more remote as a possibility.

I would be interested to hear personal viewpoints on this from around the world. To phrase it as a question: Can nuclear power save the planet?

I'm in the UK and am fairly strongly pro-nuclear for the reasons you outline (incidentally, a leading proponent of this POV is James Lovelock, the Gaia hypothesis chap), though I have heard arguments that the extraction of nuclear fuel creates almost as much greenhouse emission as simple burning of an equivalent amount of fossil fuel, which would change the calculus.
I get very annoyed by many renewables advocates because so many of them who are pro in theory suddenly become anti in practice when someone wants to erect a wind farm within a sightline from their house. Terrible nimbyism. More general, the technology doesn't seem to quite be ready and AFAICS we need some sort of stopgap for another generation or so, either nuclear or carbon-sequestered fossil fuels. (From the security of supply POV, I'd choose nuclear.) Of course, the missing part of the equation is reducing the demand for power, at which we do an absolutely appalling job.
Having used your question to have a vent, I shall turn round and note that the reference desk isn't really for opinion polls. --Bth 11:38, 2 May 2006 (UTC)
When using "nuclear power" and "renewable power" in the same argument, keep in mind that nuclear power is a renewable power. Assuming that humans figure out how to fuse the nuclear waste back together, nuclear power will become twin fusion/fission reactors. Because fission reactions tend to create very nasty explosions right now, many refer to nuclear power as a non-renewable resource without adding the clarifier right now. Then, the smarter ones add that if it were possible to recombine all the pollution from a standard automobile, you'd get gasoline and it would be a renewable resource. The catch is that nobody is working to do that. Fission reactors are being worked on all over the world. --Kainaw (talk) 13:22, 2 May 2006 (UTC)
I don't beleive anyone is working on using nuclear waste as a fusion source - fusion power research concentrates on tritium and you would require more energy to reform the uranium than it would produce decaying, so you wouldn't gain any power by the process. And processes already exist to "make" gasoline - they are just not economically advantageous - see Alternative means of producing oil section of Petroleum. Rmhermen 13:45, 2 May 2006 (UTC)
(after edit conflict) Erm, Kainaw...? With all due respect, that's completely wrong. Fusing the products of uranium fission back together to create uranium must take more energy than was gained from the original split of uranium (by the second law of thermodynamics), so you would be using (far) more energy than you produce. The same goes for 'putting back together' all the pollution from an automobile (not to mention the difficulties in collecting it all!). What you are describing is a perpetuum mobile, they do not exist.
Nuclear energy is a definite non-renewable energy source, because once we have used all the uranium on Earth, there isn't any more. It could be argued that coal, oil and gas are ultra-long-term renewables, as they were formed by organic matter compressed at high temperatures for millions of years - so, if we wait long enough (the aforementioned millions of years) the supplies will replenish. But that's only a technicality - we don't have millions of years to wait, and in any case we're using them up hundreds of thousands of times faster than they are produced naturally. So they are effectively non-renewable. — QuantumEleven 13:51, 2 May 2006 (UTC)
If the question had been about "uranium power", I would not stated that it is renewable. However, the question was about "nuclear power". Waste from uranium fission plants is fusable. Therefore, it may be used is a fussion reactor. The waste from the fussion of uranium waste (which I never claimed would be uranium) will most likely be a viable fuel for a fission reaction. This cycle may be repeated until something unusable, such as radioactive carbon, is created. With the technology to rid ourselves of nuclear waste, we will certainly learn to create better reactors and have nuclear fusion/fission of common elements (how about water?). So, "nuclear power" is renewable. But, "uranium power" is not. --Kainaw (talk) 14:49, 2 May 2006 (UTC)
By law of conservation of energy the reverse of a process that releases energy recquires an equal amount of energy. You can only fuse atomes up to iron, and only break them down to iron, so in either way you can only end up with, at best iron. Which is not a viable fuel for any nuclear reactor. Philc T+C 20:50, 2 May 2006 (UTC)
That's not how it works, as far as I understand it. A uranium reactor uses uranium and splits it (fission), releasing energy. The resulting elements are (by definition) lighter than uranium, ie further up the periodic table. If these products are heavier than iron (which most of them are, if I remember my nuclear physics correctly), they may undergo fission again to produce some more energy, although you won't get much out of them - but you can not fuse them together again to produce uranium, because any fusion reaction which produces an element heavier than iron is endothermic. If you get some light elements in your fission waste, yes, these can be fused, but again only up to iron if you want an exothermic reaction - and fusing anything other than the first half a dozen elements in the periodic table is nearly futile, the amount of energy you get out of the reaction is minuscule.
You may have been thinking of nuclear reprocessing, where radioactive waste from nuclear reactors is processed to remove any unfissioned Uranium so it can be used again - but that's a whole different story, for obvious reasons. We have an article on the nuclear fuel cycle which explains everything in far greater detail. Facit: Nuclear power (all varieties) is non-renewable, because the reactions involved to regenerate the fuel used do not occur naturally on Earth (Uranium and other trans-iron elements are only formed in supernovae). So: non-renewable. — QuantumEleven
There is a lot of nuclear reprocessing going on, but that isn't what I was talking about. I was referring to fission of nuclear waste - more commonly referred to as "actinide-burning power plants". Actinide fusion has been done in the small-scale. The large-scale goal is to pair up an actinide fusion plant with each uranium fission plant. Also - please do not continue claiming that I stated "nuclear waste will be fused to make uranium". I never made any such claim. The comment about recombining gasoline is not mine. It should be clear that I was repeating comments from anti-nuclear power people that I do not believe. --Kainaw (talk) 17:21, 2 May 2006 (UTC)
That's still nonsense, sorry. Uranium is an actinide. There's a certain amount of "missing" nuclear binding energy that everything except iron has. This energy is negative, so by converting things to something which is closer (in an approximate sense) to iron, they get more negative energy and you get some energy out. But there's a single chart here; going down it gets you some energy (e.g., fissioning plutonium in a breeder reactor or fusing hydrogen in the sun), and if you like you can spend energy to go back up (which may be fissioning calcium or constructing gold from silver and germanium or so, although the latter may not be practically doable). There is literally no way to make any sort of useful "cycle" on the chart. Perhaps you can reburn the waste from one reaction -- perhaps even in the other direction, if you split big atoms into several small ones -- but it's still a one-way street, and it's entirely nonrenewable (on our time scales). --Tardis 18:51, 2 May 2006 (UTC)
You can believe it is nonsense. Since it isn't working yet, it may very well be nonsense. Just know what you are claiming is nonsense first by going to google and typing in "actinide fusion" to see what I am referring to. It is not fusing some nuclear waste to make some tasty uranium. --Kainaw (talk) 19:34, 2 May 2006 (UTC)
I did that search (without quotes, since with quotes gave results that seemed irrelevant) and saw that the proposal was to use the neutrons generated by power-producing fusion to break apart actinide atoms. This would release a little more energy, although perhaps not as much as building a more efficient reactor that didn't bother with it, and would clean up some nasty radioactive junk that has no other use. Some authors seem to think it could be used to generate plutonium from common 238U, which would be useful for more fission power production. So it's not a bad idea, but it has nothing to do with creating a "loop" of fission and fusion; there are actinides, and there is fusion, but the actinides are undergoing unsurprising fission and the hydrogen is undergoing unsurprising fusion. Hope that helps. --Tardis 22:07, 6 May 2006 (UTC)
I don't believe nuclear is a long run solution because just like petroleum, it's limited. Uranium and other minerals are not unlimited. However, I have to accept that it is a temporary measure and favorable vis-a-vis fossil fuel. Until renewables (minus dams) increase in efficiency and/or become relatively cheap/comparable to other source of energy, nuclear might be of help. There's an article about nuclear power in last April edition of National Geographic with comparison of carbon emission. IIRC in some other article some time ago in Nat'l Geo too, a cost comparison were made between all major source of nuclear, including solar and gangs vs nuclear, coal, crude.
All this however pertains to solving our energy crisis. I don't know about saving the world though. What do you mean by saving the world anyway? __earth (Talk) 13:52, 2 May 2006 (UTC)

Thanks to everyone who responded! I guess I was aware that I wasn't using the Desk as intended, but I couldn't help myself. Opinion-based questions seem to get extremely interesting and intelligent responses here (flattery will get you anywhere). Is there anywhere on Wikipedia where you can hold structured debates? I mean the articles tend to sketch both sides of an argument due to the NPOV policy without letting either side really vent, while Talk Pages tend to get hung up on details. Anyway, thanks again.

While I agree that questions like yours do generate interesting responses, I would have to say that Wikipedia is not the place for debates - it's an encyclopedia, and we try and write the best, most impartial and complete articles we can on a given subject. You could try Usenet, or one of the countless forums debating topical issues (I can't think of any on nuclear power offhand, but there have to be many, many out there).
But it was a fun topic to discuss :) — QuantumEleven 15:24, 2 May 2006 (UTC)
One point - while nuclear is non-renewable, the supply of potentially fissionable materials is pretty large (aside from breeder reactors, there is also the thorium fuel cycle; and thorium is available in massive quantities. Furthermore, increasing the price of uranium wouldn't affect the cost of nuclear power very much (because most of the cost is in building the plant itself). So much lower grade (and thus expensive to mine, but much more abundant) ores can be used; in the longer term even uranium extracted from seawater might become economically viable, and the supply of that is virtually unlimited. --Robert Merkel 15:32, 2 May 2006 (UTC)
Additionally if one factored in the amount of weapons-grade uranium which could be downblended for power production there is already quite a lot of uranium sitting around, out of the ground, with nowhere to go. If one allows reprocessing of plutonium fuel (done in some countries, banned in the US), then one could also get some more bang for the buck. In the end I don't think there will ever be a single technological solution to "save the planet," but ruling nuclear energy out of the possible ways to generate power is just foolish. There are hazards, there are limitations, there are issues, but the same is true with all forms of power generation, and is true in spades with coal and oil. --Fastfission 20:55, 2 May 2006 (UTC)

[edit] Evolution-oriented educational software

I'm wondering if anyone knows of any good software or games that focus on teaching evolution. Currently, the only title I know is SimLife. Anyone have any ideas? Thanks! — Asbestos | Talk (RFC) 16:07, 2 May 2006 (UTC)

  • Richard Dawkins used to have a software program which allowed you to simulate evolution, but I doubt it runs on any modern PCs. This page has some links regarding it and some other similar software, but most of the links are totally dead. SimEarth was another Sim game which had a lot to do with evolution (via ecology). I always thought Oregon Trail had some aspects of natural selection involved in it... --Fastfission 21:04, 2 May 2006 (UTC)
Well, there's E.V.O.: Search for Eden --Chapuisat 21:13, 2 May 2006 (UTC)

[edit] How do boats go

If someone is in a boat in the 1500s & the wind is blowing WEST, how can they go EAST, assuming there is no current?? Obviously they were able to, otherwise one would be at the mercy of the wind when sailing. 199.201.168.100 16:35, 2 May 2006 (UTC)

See sailing (there's a section on sailing upwind). TenOfAllTrades(talk) 16:39, 2 May 2006 (UTC)
Actually, if the wind is blowing straight west, it is impossible to travel straight east by windpower alone. Rather, a boat must keep zig-zagging accross the direction they want to travel in. Also, since you're speaking of the sixteenth century, I assume that you're asking about square rig sails. These do far worse when travelling upwind, although on warships one might see sails in many orientations, to try and sail in any direction. Typically, though, such ships make use of trade winds, which blow predictably, and so can be used to go where you want to go. — Asbestos | Talk (RFC) 17:08, 2 May 2006 (UTC)
The boat just zig zags going north east, then south east, repating this means you go east Philc T+C 21:15, 2 May 2006 (UTC)
I think the term for the zig zag sailing is tacking. --Ginkgo100 01:16, 3 May 2006 (UTC)
Yes, it is called 'tacking'

BigFatDave 12:06, 3 May 2006 (UTC)

[edit] Flowchart for the manufacture of DDT

Hello, I have been trying to get the flowchart for the manufacture of DDT(Dichlorodiphenyltrichloroethane)for sometime now but i've not been successful.Can anyone please help me out.I will be very greatful if anyone can get the diagram for me. Thanks.

Have you looked at our article DDT (which, I admit, does not contain instructions for it's manufacture). Why would you like to make this product? It is available in stores at >90% purity! Andrewjuren(talk) 19:36, 2 May 2006 (UTC)
My organic chemistry textbook (Hart-Craine-Hart, 9th ed.) says it's produced from chlorobenzene and trichloroacetaldehyde with an acid catalyst. No specific reaction conditions are mentioned, but sulphuric acid might make a good solvent. The acid protonates the aldehyde (and the intermediate secondary alcohol), activating it for electrophilic aromatic substitution of the chlorobenzene. Alternately, the reaction might be viewed as SN1 substitution of the activated carbonyl, with the chlorobenzene acting as a (weak) carbon nucleophile.
Consideration of possible alternate reactions suggests that the chlorobenzene, if possible, should probably be supplied in excess. Syntheses of the chlorobenzene and the trichloroacetaldehyde, where not directly available, are left as an exercise for the reader. (Can you tell I just had an org. chem. exam today?) —Ilmari Karonen (talk) 21:05, 9 May 2006 (UTC)

[edit] Krebs cycle

What are the names of the vitamins that play a significant role as coenzymes in the Krebs cycle?

See krebs cycle. (Wow! This is an encyclopedia, not just a message board!) --Kainaw (talk) 17:54, 2 May 2006 (UTC)

[edit] Energy

How many Joules of energy would be procured by a wire 1 metre away from a single iron dipole in a magnetic iron lattice (not counting other atoms in lattice) at 20oC (293.83K)? Thanks *Max* 20:43, 2 May 2006 (UTC).

I bet your textbook has an example that would help. -- SCZenz 21:44, 2 May 2006 (UTC)

This isn't homework! 69.17.182.114 18:32, 3 May 2006 (UTC) (Max)

[edit] Half-lifes

Acording to my Physics book all radioactive substances have a half life during which half of them decay. This means( according to my book) the substance should never decay entirly.

What happens then when 1/2 of the no. of atoms includes a decimal or is smaller than one? For example, 1,000,000,000 atoms with a half-life of 10 seconds. After 100 seconds this should decay to 975,562.5 atoms. Is this posible? If it continues (including Decimals) after 300 seconds (5 mins.) it will become 0.9313 atoms, Again is this Posible? I know an Atom can be broken into smaller particles but can it go like that?

Thanks.

The expected number of decaying particles calculated in this way is an average. Most of the time the actual number of particles to decay will be fairly close to the predicted value from the half-life, but if only a few are expected to decay the actual result will be very different. In the example where the expected value is 0.9313, probably the most likely number of atoms decayed in that time is 1, but in specific cases it may be that 0, 2, or more may decay. The actual number of atoms that have decayed must always be an integer. -- SCZenz 21:24, 2 May 2006 (UTC)
A good analogy to understand this principle is to imagine you have "radioactive coins". These coins are radioactive if they are tails up and not radioactive if they are heads up. So, you start with a bunch of coins that are all tails up. You flip them. About half of them will end up heads up (decayed) and half will land tails up (not decayed). The half-life of your radioactive coins is one flip. Now, on the next turn, you only flip the coins that are still tails up. Again, about half of those will decay. Once you reach a small number, you will realize that not exactly half of the coins will land heads up (especially if there are an odd number of coins) and that the result is entirely probablistic and not deterministic. To learn more, see our articles on Radioactive decay, Radiation, and the Poisson process (which shows the mathematical model of random radioactive decay). Andrewjuren(talk) 21:38, 2 May 2006 (UTC)
This reminds me of the impossibility of having the mythical 2.4 children. Sure, you could chop a kid in half, but that's not really the point. Melchoir 21:43, 2 May 2006 (UTC)
Well, but keep in mind that the number of atoms that have decayed, at a given point in time, is not necessarily well-defined, until you make an observation and collapse the wavefunction. Some atoms may be in a quantum superposition of decayed and non-decayed states. What exactly this means, or in what sense it corresponds to "reality", depends a lot on the interpretation of quantum mechanics. --Trovatore 22:05, 2 May 2006 (UTC)
The statistical interpretation of half-lives does not depend on this kind of argument. It is perfectly possible to measure and record exactly how many decays have occured, and the problem asked above is still valid. -- SCZenz 23:52, 2 May 2006 (UTC)
Well, the statistical interpretation does make the number of decayed particles approximately observable, when there are a lot. It's never exactly observable. Furthermore, the original poster asked about when there was one atom left, a state in which the statistical approximation does not hold, and Trovatore's comment is relevant. -lethe talk + 14:34, 3 May 2006 (UTC)
A famous thought experiment involving radioactive decay and quantum superpositions is Schrödinger's cat. —Ilmari Karonen (talk) 19:49, 9 May 2006 (UTC)

Only in a general sense, that half-life is a bit of a simplifaction. You can't have a partially decayed atom; wither it's one element or another. --Scienda 07:11, 3 May 2006 (UTC)

[edit] Chlorine

I was just wondering who discovered chlorine, and how it was discovered.


                                                                    Signed,
                                                                    Joe
  1. Try learning proper wiki formatting please. It's actually rather simple.
  2. There's a search button for a reason.
  3. Don't waste our time when you could look it up.--Frenchman113 on wheels! 22:06, 2 May 2006 (UTC)
  • uuuh, why is he on wheels?--TiNC 07:49, 3 May 2006 (UTC)
  • See Wikipedia:Long term abuse/Willy on Wheels. Going around saying things are "on wheels" is an injoke amongst some Wikipedians. --Bth 09:17, 3 May 2006 (UTC)

[edit] Flight

Would it be easier or more efficent for a plane to use a anamontronic wing-like aviation s ystem rather than using fixed wings? Would it be more fuel efficent if a giant plane were designed with big wings that moved similar to a giant hawk? And how would I go about getting a patent for this? Lord Westfall 22:32, 2 May 2006 (UTC)

Short answer; no. See Ornithopter. As to your patent question, see patent and prior art, but if you did hypothetically manage to come up with some new way to make an ornithopter's wing's flap, you could patent that. --Robert Merkel 22:42, 2 May 2006 (UTC)

[edit] Do those Pills work

I have a friend who wanted me to ask do those pills that claim to make your cock bigger actually work? My friend asked me, but I don't know what to tell him. So do those pills actually work? If so, which ones? My friend really wants to know. Lord Westfall 22:37, 2 May 2006 (UTC)

Yeah! I'm the one to tell you to look up Penis enlargement. And you have to tell us if you actually paid for those pills on the Internet. --Zeizmic 22:46, 2 May 2006 (UTC)
I was about to post that link. Instead, I will have to content myself with this: your friend, huh? Melchoir 22:48, 2 May 2006 (UTC)
To play counterpart to Melchoir: Why did your friend ask you? Did he suspect that you had needed to use a variety of these in the past? If so, why would he know that? --Tardis 22:51, 2 May 2006 (UTC)
Also read human penis size. The evidence that women actually prefer exceptionally large penises is pretty scanty. And, on the basis you were seriously asking, Melchoir and Tardis are having a bit of a giggle at your expense. Penis enlargement scams are one of the earliest forms of snake oil scam in existence. --Robert Merkel 22:55, 2 May 2006 (UTC)
Well my friend doesnt want to have an exceptionally large penis, he would be happy with 6-7 inches as opposed to the slightly below average size he may currently have. If those pills are a scam, what options does he have? Lord Westfall 23:10, 2 May 2006 (UTC)
You do know that 6-7 inches is about 0.5-1.5 inches over the average, right? You may also want to check out this link. - Mgm|(talk) 09:43, 3 May 2006 (UTC)
Nothing good. All enlargement techniques (various types of surgery, fat injection) result in a loss of penis function. --Serie 00:17, 3 May 2006 (UTC)
The organ between his ears, and how he uses it, will probably make a far greater difference to how enjoyable he and his sexual partner find their lovemaking is than the organ between his legs. Buying a sex manual or learning massage (for instance) would probably be a much better investment (and considerably cheaper)... --Robert Merkel 05:12, 3 May 2006 (UTC)
Note: The "pills to enlarge your penis" are not pills "to enlarge" your penis. That is what the commercials appear to be saying, but if you look at the fine print, they are herbal remedies for erectile dysfunction. You could rationalize that to mean that they enlarge the penis - but not in the way that most people would think. --Kainaw (talk) 12:54, 3 May 2006 (UTC)

Wiki is pretty much anonymous anyway, so no point in the old "my friend was wondering" explanation...we don't know who you are so why bother? Loomis51 01:39, 5 May 2006 (UTC)

[edit] Staphylococcal infections

Staphylococci (including S. aureus and S. epidermidis) are known to migrate along medical devices such as plastic intravenous catheters. However, I believe they lack a flagellum, pilus, or other appendage for movement. Do they migrate along the catheter simply by dividing? Thank you very much.

They cling and they roll: http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1082509 —Keenan Pepper 00:03, 3 May 2006 (UTC)

[edit] Smoking and cancer

Does anyone know what percentage of smokers actually develop some form of lung/throat/mouth cancer at some point in their lives? I'd be interested in seeing the statisics compared to the same kinds of cancer in non-smokers. I've had a look on the web but it's very difficult to wade through all the pro/anti-smoking propaganda. Anyone have a straight answer? Cheers. --Kurt Shaped Box 23:48, 2 May 2006 (UTC)

80-90% of all lung cancer patients are smokers. I'll try to do a rought estamate of the percentage. If 154,000 (estimated) patients were diagnosed with lung cancer in 2002, and about 85% of them were smokers (let's say), that means about 130,000 smokers worldwide were diagnosed with lung cancer. About 45 million adults just in the US smoked cigarettes in 2004 (I know the years don't match, but this is just an estimate). You should get the idea that a very small percentage (<1%) are actually diagnosed with lung cancer, but that doesn't include other illnesses, and is no excuse to smoke anyway! —Mets501talk 00:22, 3 May 2006 (UTC)
What is the percentage of Emphysema patients who are smokers? User:Zoe|(talk) 01:52, 3 May 2006 (UTC)
According to http://www.stats.org/record.jsp?type=news&ID=555 (not what I'd call authoritative, but the original sources seem somewhat elusive) 1 in 8 smokers ends up with lung cancer compared to less than 1% of non-smokers. These numbers presumably reflect data from the US. -- Rick Block (talk) 02:41, 3 May 2006 (UTC)

I'm not convinced the 154,000 diagnosed is a worldwide figure; it looks more like a country figure. 57.66.51.165 08:00, 3 May 2006 (UTC)

User:Mets501's number is the number diagnosed in a given year. Expand that to the lifetime of a smoker and you get a figure much closer to Rick's 1 in 8. Rmhermen 14:01, 3 May 2006 (UTC)

Thanks guys - I appreciate it... :) --Kurt Shaped Box 00:10, 4 May 2006 (UTC)

[edit] Taser noise

How come stun batons (tasers) make that clicking sound? —Keenan Pepper 23:52, 2 May 2006 (UTC)

Maybe the spark gap switching? [3] EricR 01:41, 3 May 2006 (UTC)

[edit] May 3

[edit] diluting acids 2

i have read over the answers to the previous question regarding this topic and realised that it was a pretty straight forward example and would like to rephrase it to more smaller quantities:

Q: What is the simplest way to dilute 1M Hydrochloric acid down to just 250ml of 0.1M Hydrochloric acid? are there any specific calculations that need to be carried out?

thanks in advance!

A: You need to find out how many moles of HCl you will need to have in 250ml of water in order to have a molarity of 0.1M. Remember, molarity is moles of solute over liters of solution. --Chris 00:48, 3 May 2006 (UTC)
Using
V_{undiluted}C_{undiluted}=V_{diluted}C_{diluted} \
we have
(\mathbf{x} \ L)(1.0 M) = (0.250 L)(0.1 M) \
where
\frac{(0.250 L)(0.1 M)}{(1.0 M)} = \mathbf{x} \ L
and x is liters of 1.0 M aqueous HCl in 0.250 liters of total solution. So your cocktail would be 0.025 L of 1.0 M aqueous HCl in 0.225 L of H2O. Isopropyl 01:34, 3 May 2006 (UTC)

[edit] Mystery Fish

This will probably seem less than mysterious to anyone with a vague knowledge of fish, but unfortunately there are lots and lots and lots and I don't know where to start looking, so... can anyone identify our little friend here so he can find some appropriate articles? Thanks :) Mystery fish (at the bottom) Yummifruitbat 02:24, 3 May 2006 (UTC)

Definitely a marine fish. My guesses would be something related to lionfish or rockfish, although to be quite honest I have no clue. Isopropyl 03:29, 3 May 2006 (UTC)
It's a goby of some sort. I can't name the species; there are quite a lot of them. --Ginkgo100 16:30, 3 May 2006 (UTC)
Thanks, Ginkgo100. I think this was a species from the Pacific coast of North America so I've spent a while googling for a likeness but haven't had much joy. I'll try emailing the aquarium. 'Goby' was right on the tip of my tongue/fingers but I couldn't quite get there and kept thinking of 'Dory' instead... when you replied a little lightbulb went on :)

[edit] Which side do you dress?

How much of the following is true:

A man's penis tends to hang to one side. With this in mind, tailors ask clients "which side do you dress". The majority of men "dress to the left".

I can't find it on Wikipedia, nor on Snopes. If it (or part of it) is true, what factors would influence it?

Thanks! --84.51.154.196 02:31, 3 May 2006 (UTC)

FWIW I've never had this question asked of me when I've purchased suits. Isopropyl 03:28, 3 May 2006 (UTC)
This would presumably be a cultural things. Maybe in some places (I've never heard of any) tailors ask for whatever reason. Maybe in other places tailors might face lawsuits. As for the actual right-left tendancy, if it isn't random then there's bound to be someone, especially on the Internet, who's researched it. Peter Grey 04:24, 3 May 2006 (UTC)
Most tailors cop a feel, or else they can tell very easily while they are down there hungrily studying your junk.

I recently read an article by a doctor, in response to a question from a reader that his penis was oriented towards the left. The doctor had mentioned that most of the men have this feature. He even mentioned that the crotch of the trousers are stitched sligtly to the left side to accomodate this. But I have never had a tailor ask me this neither did I find any left orientation in the ready-made trousers -- Wikicheng 06:14, 3 May 2006 (UTC)

This goes back to the days when men's trousers were a lot closer fitting than they are today. The crutch of the trousers would come right up tight against the scrotum, which needed to be positioned on one side or the other to avoid it being uncomfortably divided, with one testicle hanging left and the other right. It was more a scrotum problem than a penis problem. The penis would obviously go whichever side the scrotum went. Some men preferred the left side, some the right. Tailors would never be so rude as to assume which side the gentleman preferred his dangly bits to hang, but would always ask which side they "dressed". For a tailor's regular customers, this information would be noted the first time, and would be used when making future trousers. I have certainly had this question asked of me. It happens far less these days, mainly because trousers generally have a different shape and the problem is avoided, but also because a lot of guys would consider this a ludicrous invasion of privacy, and no shop wants its staff exposed to charges of inappropriate questions (or even sexual harassment). How times have changed. JackofOz 06:58, 3 May 2006 (UTC)

Strangely, a friend of mine was talkin about this "dress left/dress right" thing the other day, and wondering if it was the exact reverse of handedness (right-handed=dress left and v.v.) Neither of us was keen to conduct a survey, though. Grutness...wha? 07:40, 4 May 2006 (UTC) (r.h./d.l.)
Oh Grutness, you're unbelievably shy when it comes to legitimate scientific research. Live dangerously occasionally. :--) JackofOz 23:50, 5 May 2006 (UTC)

So is there a WP article about this? There seems to be enough information. It would be interesting.--Sonjaaa 13:34, 6 May 2006 (UTC)

[edit] Identifying trees

What's the easiest way to identify the exact species of various trees I spot in Toronto? Do I need to buy a field guide, and if so which one is best suited for my needs? Do I need to take pictures of the leaves or analyze the bark, or is there some sort of DNA test I need to do to figure out the exact species?--Sonjaaa 02:56, 3 May 2006 (UTC)

A little book, or a field guide is good. I can't think of the one I used when I was in Michigan though... Auto something... or something. He was a bird guy. -- Mac Davis] ⌇☢ ญƛ. 04:27, 3 May 2006 (UTC)
My old girlfriend used to use "Michigan Trees" by Barnes & Wagner. You're probably thinking of something by the Audubon Society. Isopropyl 07:03, 3 May 2006 (UTC)
Yes, why that is it. the Audubon Society Northeastern tree field guide or somewhat akin. -- Mac Davis] ⌇☢ ญƛ. 09:24, 3 May 2006 (UTC)


OK i ordered "Trees In Canada" by John Laird Farrar! :)--Sonjaaa 13:00, 3 May 2006 (UTC)

[edit] Electrostatics

Why electric field strength is greater than (force/charge)? thank you. s

Does Electric field help? Melchoir 07:11, 3 May 2006 (UTC)
I thought it was force over charge, although perhaps I am misremembering. — Knowledge Seeker দ 07:34, 3 May 2006 (UTC)
If you are talking experimental results, maybe you are underestimating force and overestimating charge somewhere. (E.g. your charge is leaking away somehow) --137.205.17.159 11:55, 3 May 2006 (UTC)

[edit] Solubility of Ethanol

I've learned in my Chem class that polar substances dissolve in polar solvents,eg NaOH dissolves in water.Non-polar substances do not dissove in polar solvents and vice-versa.Why does Ethanol(C2H5OH) dissolve in water? This is not a homework question.Just wondering. Thnx

Isn't it because ethanol is polar? Water should dissolve polar substances, in general. The hydroxyl group should make ethanol polar enough to dissolve in water. — Knowledge Seeker দ 08:13, 3 May 2006 (UTC)
Ethanol molecules form Hydrogen bonds with water.--Ring0 09:25, 3 May 2006 (UTC)
Ethanol is pissed off and wanted to screw everything up for chemistry students. -- Mac Davis] ⌇☢ ญƛ. 09:25, 3 May 2006 (UTC)
That dangling hydroxyl group has an acidic proton on it. Pretty much any time you see oxygen covalently bound to something, it's going to be a polar bond. Isopropyl 12:45, 3 May 2006 (UTC)
Right, some molecules have polar and non-polar portions of the molecule, Ethanol is one of these. Often it means these will dissolve in either kind of solvent.
Yes in general polar substances dissolve polar and non-polar with non-polar, but the reason why it happens at all is intermolecular forces. There are a few types of these forces, but the ones that are important for these examples are London dispersion forces, dipole-induced dipole forces, and hydrogen bonds. Think of CH3CH2OH as two parts, the hydrocarbon part (CH3CH2) and the hydroxyl group ( − OH). Between water and the hydrocarbon part there are are dipole-induced dipole forces and between water and the hydroxyl group there are hydrogen bonds. The water molecules are bonded together by the same hydrogen bonds while the ethanol molecules are bonded by hydrogen bonds(hydroxyl part) and London forces(hydrocarbon part). Since hygrogen bonds are strong and the hydrogen bonds between the water molecules and the polar (hydroxyl) part of the ethanol molecule have about the same strength the molecules attract each other about the same amount as the forces between two water molecules or two ethanol molecules. As such, they can easily be substituted for each other in bonds (and because of the shape of the molecules there are not many bonds being distrubed by this switch).
As it turns out ethanol is also miscible in hexane (C6H14). The hexane molecules are bonded together by London forces. Between hexane and ethanol the main forces are London forces between the hydrocarbon parts and dipole-induced dipole forces between the hydrooxyl group and hexane. Together these are about the same strength (in this case) as the H bonds between the ethanol molecules so the bonds are easily interchangable.
London forces generally increase with molar mass and more surface area. As the hydrocarbon chain grows to say hexanol (CH3(CH2)5OH) the London forces play a greater role. Now the forces between the hexanol molecules, largely dominated by London forces over the H bond interactions, is stronger than the H bond between water and the hydroxyl group of hexanol. There is also the issue that the hydrocarbon part of hexanol gets in the way of more H bonds between water molecules. As such, hexanol is not very soluble in water but still miscible in hexane.
If you go the other way and reduce the hydrocarbon chain to methanol (CH3OH) the opposite occurs. The methanol molecules have the same interactions with themselves, but the London forces are weaker. Thus, the London forces between it and hexane are also weaker and the H bonds between methanol and itself and the London forces between hexane and itself dominate and methanol is not very soluble in hexane. However, it is miscible in water. This is because the London forces between methanol molecules is tiny and the H bonds between methanol and methanol, water and water, and methanol and water are interchangable.
Basically, the greater the forces between two different molecules are in relation to the molecule's forces to itself determine how soluble something is. Generally, two polar substances or two non-polar substances will have greater intermolecular forces between each other than a polar and a non-polar so that is why most solvent-solute pairs are of the same polarity. Kotepho 14:30, 3 May 2006 (UTC)
The short answer is that where solubility is concerned, polarity doesn't have a strict binary yes/no effect. Polarity is a sort of continuum, running from ionic compounds that will dissociate into charged monatomic ions in solution (NaCl forms hydrated Na+ and Cl- in water, for instance) to covalently-bound molecules with a significant dipole moment (methanol or formaldehyde, say) to predominantly nonpolar molecules with some polar groups (long chain alcohols like n-octanol) to completely nonpolar species like carbon tetrachloride or cyclohexane. Solubility will depend on the difference in polarity — as well as a huge pile of other factors that influence the interactions between molecules. TenOfAllTrades(talk) 15:22, 3 May 2006 (UTC)

[edit] Fly-by-wire

Since solar flares are a threat to satellites are they not also a threat to fly-by-wire technology?

Incidentally, I just found a very interesting set of FAQs about aircraft safety here but the guy who runs it has just retired. --Shantavira 08:08, 3 May 2006 (UTC)

Yes. In principle, solar flares are a threat to any and all electronic technology, and plenty of non-fly-by-wire aircraft are more-or-less equally vulnerable to flares (say, when computers regulate the flow of fuel). However, in practice, aircraft fly under the primary protective layers of the atmosphere, so they're far less vulnerable to flares than satellites. — Lomn Talk 13:08, 3 May 2006 (UTC)
Also, most commercial aircraft have triple-redundant primary systems, so even if one computer is knocked out, there are two backups. — QuantumEleven 13:30, 3 May 2006 (UTC)
This is not as comforting as it seems, since, if one computer is knocked out by solar radiation, all three are likely to be. A problem also arose where an escape door blowing off knocked out the hydraulic tail controls, all three redundant systems went through the same place! 165.254.38.126 04:57, 4 May 2006 (UTC)

[edit] How do you improve the google rank of a Wikipedia article, e.g. Opus Dei

Hello fellow Wikipedians! I've been helping edit the article at Wikipedia. I've seen it rise in google rank over time. It is now ranked four, but as you know many Wikipedia articles rank number one. Thus, I also want to know if there are other techniques specific for Wikipedia to improve ranking. FYI, I've done my own search in Wikipedia and read Search engine optimization and other related articles.

Another issue. The pagerank of Wikipedia's Opus Dei article is 6/10 when I use the pagerank at the google toolbar. However, I found out that the Unofficial Homepage which has a google search rank of number two has a page rank of 5/10. This means it has a lower pagerank than Wikipedia's Opus Dei but it is still higher in the google search. Why could it be so?

Looking forward to some great insights on this. Maraming salamat po (thank you in tagalog! Cabanes 09:26, 3 May 2006 (UTC)

  • I think google rank is determined by the amount of people that link to it and the amount of places the article links to. Since spamming the article is out of the question, it might be helpful to ask people with relevant sites to link to Wikipedia. Where a page turns up in the search results not only depends on google rank but also on the meta tags of the site in question and the content of the page itself and the number of visitors. Wikipedia's results placement will improve on its own. - Mgm|(talk) 09:34, 3 May 2006 (UTC)
    • You have things a little backwards, I think. PageRank is determined by what pages link to the article, not the other way around. If the article links to too many pages with low PageRank, though, its own PageRank can be decreased as well (it is a way to penalize link farms). The easiest way to raise the article's PageRank is to link to it from a page which already has a high PageRank. (Easier said than done, but it can be done.) --Fastfission 20:50, 3 May 2006 (UTC)
    • May I ask why Google rank is important to you? Wikipedia is about writing the best possible articles on a subject - the better it is, the more people will link to it, and Google rank will come all by itself. But it's a secondary benefit and not the main reason for writing a good article - I would frown on blatant search engine optimisation at Wikipedia. — QuantumEleven 13:24, 3 May 2006 (UTC)
That's pretty mcuh how I feel. - 131.211.210.12 10:34, 4 May 2006 (UTC)
P.S. Do not try to create a Google rank article, PageRank exists (and is licensed by the guys). --DLL 20:10, 3 May 2006 (UTC)
I created it ;-P --Fastfission 01:12, 4 May 2006 (UTC)
Maraming salamat sa inyong lahat! (that's "thanks to all" in tagalog). Thanks, Fastfission, and congratulations on the article. I suppose when you said it can be done, it means requesting webmasters to put a link on Wikipedia?
Regarding Quantum's question, I completely agree with her/him that it's all about good writing, but I am also interested in countering the black propaganda done by the maker of the Unofficial Homepage who is a communist. I have nothing against him personally, but his ideas are propaganda and propaganda = misleading information. Wikipedia has more balance and more expert, trustworthy information. It would be great if more people get to read it. Thanks for all the help and whatever other help you can give. Salamat! Cabanes 01:53, 4 May 2006 (UTC)
On some level this is out of your hands. At least the official Opus Dei site is number one. But ultimately you're just going to have to trust people's critical thinking and source evaluation skills.
Yeah, I know. --Bth 09:36, 4 May 2006 (UTC)

[edit] First human to orbit earth

Who was the first human to orbit the Earth? Thank You in Advance. --Siddhant 10:36, 3 May 2006 (UTC)

That would be Soviet cosmonaut Yuri Gagarin aboard Vostok 1. --Bth 11:03, 3 May 2006 (UTC)
Indeed, although there are conspiracy theories claiming otherwise - Dammit 11:06, 3 May 2006 (UTC)
Have you ever wondered who makes all these conspiracy theories up, and whether they have some secret reason for doing so? I think that this should be investigated... Grutness...wha? 07:45, 4 May 2006 (UTC)

Of course it would be Gagarin. Sorry I wasted your time by asking such a silly question. Anyway thanks for the answer. --Siddhant 11:24, 3 May 2006 (UTC)

... although it is interesting to note that first non-stop aerial circumnavigation of the the Earth was completed as early as 1949 by the crew of the B-50 Superfortress Lucky Lady II. Gandalf61 12:04, 3 May 2006 (UTC)
Jean Michel Jarre has a song "Hey Gagarin" (Métamorphoses album) about Gararin orbiting Earth, with these cool lyrics: "I can fly, I fly like a sputnik, listen to the music spin, around the planet and lets, dance together".--JLdesAlpins 22:36, 3 May 2006 (UTC)
In any case, in case you're interested, the first true BITCH to orbit the earth would have to be the Russian Laika. But since she's a bona fide BITCH, you may not be interested. I, myself don't consider BITCHES like Laika to be human beings. But that's just me. You may want to call me a misogynist for saying that, but I think you'd be wrong. I may be letting my personal feelings to get in the way of an unbiased analysis, or maybe not. Loomis51 01:46, 5 May 2006 (UTC)

[edit] PVC protection

How can we protect workers who make PVC from the harmful effects of Vinyl chloride?

Replace the humans with robots. --Kainaw (talk) 12:43, 3 May 2006 (UTC)
I'd imagein all the usual methods (fume extraction, respirators, good equipment design, automation etc) can be used to reduce exposure to safe levels. Plugwash 00:48, 4 May 2006 (UTC)

[edit] Book about synthesizers

I've downloaded Chaosynth and its manual provides too little information about the physics of the sound and so. Can anyone recommend me an information source that speaks extensively about the subject? Thank you.

I don't suppose our article on synthesizers has some of the answers you're looking for? Take a look at some of the pages liked from that article, too. — QuantumEleven 13:03, 3 May 2006 (UTC)
How about a website about synthesizers? Sound On Sound magazine ran a very detailed series called Synth Secrets, and it's all up on their website at www.soundonsound.com , however I couldn't seem to find a good index to the series on their site, but there's a great one here: http://www.adp-gmbh.ch/csound/synth_secret.html --Noodhoog 15:55, 4 May 2006 (UTC)

[edit] Multiple choice!

Which of the following statements is true?

A. Electrons are negatively charged and are found in the nucleus of an atom.

B. Electrons are negatively charged and are found outside the nucleus.

C. Neutrons are positively charged and are found in the nucleus.

D. Protons are positively charged and are found outside the nucleus.

Please see the top of the page regarding not asking us your homework questions. Your textbook doubtless includes the answers but in case you haven't got it handy our articles on electron, neutron, proton, atomic nucleus and atom should tell you everything you need to know, and much more besides. --Bth 12:58, 3 May 2006 (UTC)
All are true in the right circumstances.
Apart from C, surely? (There you go, anon, a hint!) --Bth 14:09, 3 May 2006 (UTC)
Please read the following:-
1. Electrons revolve around the nucleus.
Some do, some don't. Electrons were thought to all revolve around the nucleus in older models of the atom. See atomic orbital and magnetic quantum number for a current view. (The latter because the magnetic quantum number is related to the electron's angular momentum, and whether it has non-zero angular momentum or not might be one reasonable intepretation of whether an electron "revolves" around the nucleus.)Chuck 17:35, 3 May 2006 (UTC)
2. Protons are positively charged.
3. Positive and negative charges repel each other.
This is just plain wrong. Chuck 17:35, 3 May 2006 (UTC)
4. Electrons are negatively charged.
5. I hope you got your answer.
6. Please do not ask homework questions again.--DIGIwarez 14:29, 3 May 2006 (UTC)
"Positive and negative charges repel each other" - this is a little awkwardly phrased; 'like' charges repel so two positively charged particles (or two negatively charged ones) will repel each other, but a positive particle will be attracted to a negative one. Yummifruitbat 16:06, 3 May 2006 (UTC)
Yes, very true. An exam question that I got a few days ago: "A covalent bond is a shared pair of electrons. Explain how this holds the atoms together." The answer is, of course: The positice nuclei are attracted to the negative electrons; which, overall, results in a neutral atom. This was actually in a prelim and this was a question that was in an actual Credit exam in 2001. Kilo-Lima|(talk) 18:57, 3 May 2006 (UTC)
I'm not sure what you mean by the above - a covalent bond results in a molecule with the two atoms sharing electrons in order to achieve full outer electron shells. This is not really relevant to the original question and I fear you may have misunderstood the exam question :( Yummifruitbat 22:21, 3 May 2006 (UTC)
I am extremely sorry. Positive and negative charges attract each other. Like charges repel each other. I am really sorry. The correct answer would be B. You are right Chuck. That was a small mistake I didn't notice it. Electrons in an atom always revolve around the nucleus. I think this question is about a simple atom not a covalent compound. Elctrons can be found freely but this is not about charge or radioactivity. It is a simple question on the structure of an atom. Negative charges can also be found inside the nucleus (β particles). But that is not important over here.--DIGIwarez 07:24, 4 May 2006 (UTC)
A negatively-charged beta particle is an electron. And D can also be true -- protons can be found outside the nucleus in many high-energy situations (though I suppose it can always be argued that they're hydrogen ions, though in such cases that's not a helpful way to look at them). The only one that's 100% always false is C, becauses neutrons simply aren't positively charged. --Bth 07:43, 4 May 2006 (UTC)
True, but the person who asked this question was probably not looking for all this. I think this is about the basic structure of an atom. We are making this too complicated.--DIGIwarez 07:53, 4 May 2006 (UTC)
Oh yeah, this is obviously a middle school level question with an obvious correct answer (not obvious enough that the questioner could get it, mind). However, you can't ask such a question to a bunch of people with more advanced knowledge without expecting them to caveat the hell out of it -- it's human nature. --Bth 09:33, 4 May 2006 (UTC)
As sad as it may seem, this could easily be from an american university general chemistry class--64.12.116.74 19:16, 4 May 2006 (UTC)
Can a proton be outside a nucleus, I don't think so as a proton defines a nuclei. A proton on its own with no electrons or neutrons, is not just a proton it is a hydrogen nuclei. So only A and B are possible. Philc T+C 21:43, 4 May 2006 (UTC)

[edit] RoHS Directive

In the Restriction of Hazardous Substances Directive page (2002/95/EC), paragraph 4 under "Details" states the maximum concentration of Hexavalent Chromium by weight of a homogeneous material is 0.1%. Where is that stated in the Directive? Thank you.

Is that an English Comprehension homework question? And isn't the answer to the question contained within the first sentence? --Shantavira 16:13, 3 May 2006 (UTC)
That limit is not specified in the RoHS directive itself, it is in Commission decision 2005/618/EC, which ammends the annex to the RoHS directive to allow up to 0.1% by weight of the subtances covered by RoHS except cadmium which it limits to 0.01%. -- AJR | Talk 16:22, 3 May 2006 (UTC)

[edit] The Sims 2

How exactly do you get the helicopter to pick you up in The Sims 2, when you need to get to work? Thanks, Kilo-Lima|(talk) 18:48, 3 May 2006 (UTC)

Have you tried a game hint site like GameFAQs.com? You should be able to find the answer (and a lot more besides!) there. — QuantumEleven 07:51, 4 May 2006 (UTC)

[edit] brain size in dogs

do st bernards and chihuahuas have the same size brain since they are the same species? Or does brain size relate to the size of the dog? thanks

carol

Your guess ? --DLL 19:55, 3 May 2006 (UTC)
Generally body mass correlates with brain size (see brain to body mass ratio). Brain size does not correlate to "species" necessarily, especially with there is high variability in body size within a species (such as with dogs). --Fastfission 01:10, 4 May 2006 (UTC)

[edit] gas mantles (non radio active gas mantles)

does any body know what are the latest coleman non radio active gas mantles made of and what would be the appropriate composition and formula for making a durable ,strong ,bright white light gas mantle(non radi active ) and has there been further develoment in this particular area and by whom.

Wow, this attached encyclopia-thing always fails to amaze me! I typed in 'gas mantle' and I found out that your little Coleman is radioactive! but probably as much as smoking one ciggie. The problem is with mantle factories handling truckloads of thorium. Apparently, the substitutes don't work as well. --Zeizmic 20:18, 3 May 2006 (UTC)
Indeed; I'd be more worried about the health effects of the combustion byproducts generated while the lamp is still warming up—sooty things like polycyclic aromatic hydrocarbons, which are known carcinogens. (If you've been exposed to smoke from you campfire or barbecue, too, then you might as well give up now.) The exposure to radiation from the lamp mantle is negligible unless you're eating the darned things. TenOfAllTrades(talk) 20:37, 3 May 2006 (UTC)
Colman made mantles are nowadays made of yttrium, not thorium although other companies still make the thorium ones. [4] Rmhermen 00:52, 4 May 2006 (UTC)
Apparently they also contain a small amount of cerium [5] Rmhermen 00:55, 4 May 2006 (UTC)

[edit] Sequential times

Why no article on sequential times? 01:02:03 on 04/05/06, [6]?

Sequential times is now a redirect to sequential time. --Kainaw (talk) 19:59, 3 May 2006 (UTC)
Koolio! Thanx! I used the search, but nothing came up...
It also looks like some idiot is trying to delete the small article that there is - is there anything I can do to stop that?
He'll stop, don't worry. Monitor the article, and warn the jerk. -- Mac Davis] ⌇☢ ญƛ. 20:55, 3 May 2006 (UTC)
For the record, prods do not constitute jerky behavior. Melchoir 00:53, 4 May 2006 (UTC)
Stupid* ones do. 165.254.38.126 04:52, 4 May 2006 (UTC)
  • Where the 'proder' doesn't bother to research the article.

[edit] Computer science

WP offers a search bar with two buttons, Go and Search.

Firefox offers search engines but the WP one only ... searches. Does anyone know about a "Go" engine ? Thanks a lot. --DLL 20:06, 3 May 2006 (UTC)

When looking for seach bar options, pick "Wikipedia (en) - Instant" -Obli (Talk)? 20:31, 3 May 2006 (UTC)
Thanks! I never used the stupid search bar because it always went to a search result list. It was quicker to bookmark Wikipedia and use the page's search box. --Kainaw (talk) 23:14, 3 May 2006 (UTC)
Thanks, that's what I needed. --DLL 20:57, 4 May 2006 (UTC)

[edit] Warren Truss

hey i need information on the Warren Truss bridge design, thnk you, matt

I assume you mean truss bridge and not the Australian politician? Isopropyl 22:49, 3 May 2006 (UTC)

[edit] Bloody eye

This is NOT the place for medical consulting, I know that, but this is of no importance, and not exactly a thing I'm gonna see a doc about. I just noticed that on my right eye, there was a bit of pink discolouration. So I look closer in the mirror, and it looks like some veins that have blown or something. Nothing big, just a tiny bit of pink (no intense red) that's not noticable for anyone not looking closely, focusing on it. What could this be? More importantly, what could it be caused by? Although it's hard to describe it, I can clearly see that there are some veins there, so it's not some sort of spot that's flooded with blood. Thanks in advance! 213.161.189.107 22:24, 3 May 2006 (UTC) Henning.

There are blood vessels in the eye, and they can burst. Pressure, shock, randomness etc can cause this, and in moderate amounts it's normal and will disapear pretty quickly. See someone if it persists for more than a few days. 165.254.38.126 22:46, 3 May 2006 (UTC)
Sounds fine to me. If it hurts get help. -- Mac Davis] ⌇☢ ญƛ. 06:03, 4 May 2006 (UTC)

[edit] May 4

[edit] Illogical (to me, at least) gull behaviour...

I like to feed the gulls (herring gulls, lesser and greater black-backs around here). I get together a big pile of scraps and leave it out in the garden for them and watch them feeding through the window.

Invariably, as soon as one of the flock of gulls I've attracted descends and picks up a piece of food, the rest of them immediately get angry and give chase to that single bird across the sky in an attempt to rob it of its meal - completely ignoring the fact that there is about 2lbs of meat/cheese/bread/etc. just sitting there on the ground.

Why are gulls seemingly more intent on expending time and energy to deprive another gull of food when by simply cooperating and putting aside their squabbles for five minutes, they would all be able to gather round and eat plentifully from the pile? This doesn't make sense to me at all (actually, it seems like a very human mindset). :)

Quite often, while the rest of the gulls are flapping, bickering and screeching in the sky above, a single bird will land at the food and quietly and calmly eat its fill then leave before the others have given up the fighting and noticed. Thus, the 'jealous' majority miss out. Do you think that this is a sign that this particular gull is more intelligent than the rest?

As someone else, somewhere online once put it - a gull's mindset seems to be "Everything that's mine is mine. Everything that isn't mine is also mine". :)

--Kurt Shaped Box 00:38, 4 May 2006 (UTC)

Have you seen Finding Nemo? :-) Yummifruitbat 01:32, 4 May 2006 (UTC)
Heh. Yes I have - the characterization of the gulls was spot on, wasn't it? :) --Kurt Shaped Box 01:40, 4 May 2006 (UTC)

Three thoughts:

1) Perhaps having "excess food" is so out of their normal experience that they don't know a different behaviour would be beneficial in such cases. That is, they are going strictly by instinct, which developed based on food being scarce.

2) The fighting over food may also be a way of establishing dominance, which may also come into play during mating.

3) They might want to avoid landing for fear of predators, like dogs.

StuRat 01:56, 4 May 2006 (UTC)

Just wanted to remind ya'll that feeding the birds is generally discouraged if you wish to keep droppings off your aerially exposed surfaces. Isopropyl 04:02, 4 May 2006 (UTC)
Nah, just catch 'em, cork 'em, then let 'em go. :-) StuRat 17:57, 4 May 2006 (UTC)

[edit] Foreskin redux

This was asked further up the page a few days ago but no-one replied. Is a 'normal' foreskin supposed to retract fully behind the head of the penis when it's erect? Thanks. --84.71.80.239 00:44, 4 May 2006 (UTC)

When mine is pulled back the most it can go comfortably, mine doesn't go behind the head. It only reveals a little bit of it, but even then, just barely. But really, your question is too ambiguous. What does "normal" and "head" mean? Not that I'm an expert, but everyone's body is different. If I were you, I'd try not be overly concerned about what is "normal", and focus more on what's comfortable for you. --69.156.159.59 01:06, 4 May 2006 (UTC)
"Head" is pretty standard, and means the lumpy bit on the end that generally doesn't become really prominent (if I remember right) until somewhere during puberty. I hope it doesn't need to be pulled back much, since mine hardly does at all. No matter what state it's in, it always covers the entire head, with of course an opening of varying size, and pulling it back farther than that feels rather like pushing back my cuticle or giving blood: not pleasant, in a weirdly uncomfortable way. I can't imagine this ever causing me problems, and in fact I was amazed to find out it can work any other way short of circumcision. A word of advice, based on the conversation above: don't mess with it until it's actually a problem, and consider finding a second opinion. Doctors have been known, like everyone else, to talk out of their asses at times. Black Carrot 01:16, 4 May 2006 (UTC)
In the foreskin article, doesn't it say that "[a study] found that about 50% of young men had full coverage of the glans, [and] 42% had partial coverage"? Black Carrot 01:25, 4 May 2006 (UTC)
Have you read phimosis? I think it's only likely to be considered a problem if it can't be retracted fully even when flaccid,and even then opinions are divided about whether there are any serious implications. Yummifruitbat 01:30, 4 May 2006 (UTC)

[edit] Digg.com

Is [7] generally reliable? More specifically, what are your takes on [8] and [9]? Black Carrot 01:16, 4 May 2006 (UTC)

Digg is essentially just a collection of links to other sites, plus comments. The sites linked tend to be reasonably mainstream, though, rather than some sort of crackpot link collection. I would take essentially anonymous one-line comments on a website with a grain of salt. (Oh the irony!) As far as scitech goes, I'd put the collective intelligence of Slashdot ahead of Digg. The two stories you've linked seem like the classic "idea papers". Someone comes up with a novel idea, and the physics that might theoretically work; they write a paper because it's more fun than real research, the university promotes it because it's easier to get public attention than real research, and BBC prints it because it's cooler and more interesting than real research. So yes, they're theoretically correct. But moving from theory to practice may well be impossible. How long have there been blueprints for a space elevator, for instance? --ByeByeBaby 01:48, 4 May 2006 (UTC)
You'll like Digg. Kilo-Lima|(talk) 18:14, 4 May 2006 (UTC)

[edit] Do birds masturbate?

This is not an attempt at vandalism, so pls don't revert my question. :)

My (male) macaw likes to rub his butt area against his toys and perches and seems to get really excited when he does this. He goes faster and faster, hooking his tail under whatever he's humping before he stops and sits there panting with his feathers fluffed up. It looks to me like he's getting himself off and cumming. Is he? Do birds really masturbate? Should I try to stop him doing it?

I doubt you could stop him. Males of most species are remarkably persistent this way. :D
Console yourself with the thought that while your macaw is an onanist, unlike some birds he at least isn't a homosexual necrophiliac rapist: [10]. TenOfAllTrades(talk) 01:55, 4 May 2006 (UTC)
Dorothy Parker named her pet budgie Onan because he "spilled his seed". JackofOz 02:36, 4 May 2006 (UTC)
Sounds like the poor guy could do with some female company. If you don't want to buy a lady macaw perhaps a date could be arranged.--Shantavira 08:45, 4 May 2006 (UTC)
Raising parrot chicks is a major commitment and very time-consuming. Attempting to breed the bird without lots of knowledge and preparation is probably not a good idea. In other words, he should practice planned parrothood. --Ginkgo100 19:53, 5 May 2006 (UTC)

He probably is masturbating. Birds have no concept of 'sinful' or 'inappropriate' behaviour. It's a natural bodily function - I'd just let him get on with it. If you try and stop him (some bird owners squirt their pet in the face with cold water from a plant mister when they catch them wanking), he'll just get cranky and aggressive from the hormone buildup. --Kurt Shaped Box 17:54, 4 May 2006 (UTC)

Just to be sure here, it's not just male birds that are apt to that sort of behaviour. I once had a female parakeet who, on several occasions, would rather disturbingly raise her tail and develop a rather scary look on her face whenever I'd take her out of her cage. Needless to say it wasn't long before she laid an (unfertilized) egg. This happened several times. I actually tried to get her a male companion but she was so territorial that after a couple of weeks I found the male dead at the bottom of the cage. A clear case of ornicide. Oh well, at least I tried. Loomis51 01:31, 5 May 2006 (UTC)

[edit] Kiwi Birds

My daughter needs a source to interview for a report on kiwi birds. Any ideas of where to obtain a speciallized individual on kiwi birds? Dg2 02:54, 4 May 2006 (UTC) Thanks dg2

Try a university zoology department or a zoo. --Ginkgo100 03:27, 4 May 2006 (UTC)
If you can conduct the interview comfortably by email, then I'd suggest contacting the New Zealand Department of Conservation or the Kiwi Recovery Programme. There are more experts on kiwi there than anywhere else on earth. Grutness...wha? 07:53, 4 May 2006 (UTC)

[edit] Summer or Spring

Is it Summer or Spring when the North Pole is tilted toward the sun. -- Jesusfreak 03:47, 4 May 2006 (UTC)

The North Pole tilts furthest towards the sun at the June solstice. This occurs on June 21/22, early summer in the Northern hemisphere. -- Avenue 03:46, 4 May 2006 (UTC)

Thank you very much. -- Jesusfreak 03:47, 4 May 2006 (UTC)

In fact, the June solstice is the first day of summer. Consequently, the North Pole is tilted towards the sun (to varying degree) for the entirety of both Spring and Summer (and for none of Winter and Autumn), and the tilt is split evenly between the two. — Lomn Talk 13:26, 4 May 2006 (UTC)
Of course that's only in the northern hemisphere. Don't forget the Aussies! (And others like South Americans) For them, June 21/22 is the winter solstice. (You can thank me later, Jack!) Loomis51 02:21, 7 May 2006 (UTC)

[edit] Nitrogen

What color is a nitrogen flame?

Nitrogen is inert, and does not burn. -- Mac Davis] ⌇☢ ญƛ. 04:29, 4 May 2006 (UTC)
Nitrogen's atomic spectrum looks kind of golden yellow. [11] hyperphysics with pretty pictures of elements in spectral tubes. NOTE: spectral tubes are not flames, however both methods look at excited electrons. Nitrogen can't burn but we can shoot electrons at it and get the same results. Sifaka talk 04:58, 4 May 2006 (UTC)
Doesn't nitrogen "burn" during a lightning strike? (Though the colour of lightning isn't the colour of burning nitrogen.) --Bth 09:06, 4 May 2006 (UTC)
A quick look at nitric oxide supports that lightning indeed produces at least one of the nitrogen oxide compounds. (Here is where I go wildly speculative as my chemistry knowledge is zero:) Perhaps all reactions that produce nitrogen oxides are endothermic and thus not really burning which is defined as an exothermic reaction? Weregerbil 12:28, 4 May 2006 (UTC)
Reaction energy depends on entropy, which depends on temperature. A reaction which is endothermic at one temperature can be exothermic at another. For instance O2 + 1/2 N2 --> NO2 is endothermic at room temperature but exothermic at temperatures above ~190 C. --BluePlatypus 15:40, 4 May 2006 (UTC)
Mac Davis: Nitrogen does indeed burn at sufficient temperature, forming nitrogen oxides. NOx production is an environmental problem with any sufficently hot combustion using air as an oxidant. It's why we've got catalytic converters on cars. --BluePlatypus 15:31, 4 May 2006 (UTC)
Louise: Lightning occurs due to the ionisation of nigrogen, oxygen and other constituents in the atmosphere at the time, like an arc generated during welding.

[edit] Why does burning hair smell bad?

Hair has a lot of disulfide bonds (cystine I assume), and I assume it is liberated in the form of malodorous molecules, but is there a primary molecule or class of molecule (more specific than sulfides) that causes the stench? Sifaka talk 05:12, 4 May 2006 (UTC)

In my (extremely limited) experience, shoeing horses and cauterising wounds produces the same unpleasant smell. That suggests there's nothing specific to hair.Notinasnaid 09:22, 4 May 2006 (UTC)
That's because the same class of proteins - the keratins make up hair and epidermis. Someone else wrote already that they are rich in cysteine, a sulfur-containing aminoacid. Sulfur compounds smell bad, as a rule. Dr Zak 11:50, 4 May 2006 (UTC)
Why do we consider burning certain proteins a bad sensation ? 1) If it is our kin, there is a conservation thought, 2) if it is food (or foe), that indicates too much cooking. --DLL 21:03, 4 May 2006 (UTC)
All creatures find the smell burning creatures (particularly their own) disturbing, much in the same way that we don't like dead bodies, it has benefitted the human race through evolution to be scared of death, and generally burning human is closely associated with death. Philc T+C 21:31, 4 May 2006 (UTC)
Also, in general, gaseous sulfur compounds are poisonous in high concentrations, so it make sense that low concentrations stink: it encourages you to leave before you get killed. --Serie 21:34, 4 May 2006 (UTC)

[edit] Zero Gravity

Is it possible to achieve zero gravity on earth?

If by "zero gravity" you mean weightlessness, then yes: just go into freefall. Ways of acheiving this include being in an out-of-control lift (not recommended because of the crash landing at the other end), the early part of a parachute jump or flying a plane in a parabolic arc (see Vomit Comet, a name applied to any of several planes used for astronaut training -- one was also used for the weightless scenes in Apollo 13). Deep-sea diving provides a similar experience to weightlessness, because of the support provided by the water, and indeed much astronaut training takes place in huge tanks. --Bth 07:28, 4 May 2006 (UTC)
When you jump into the air and then fall back down, for about one second you're in zero-gravity. Try holding something like a ball in a cup (or a glass of water, if you don't mind getting wet) while you fall down. The ball will float inside the cup and it's really cool! Jonathan talk 17:20, 4 May 2006 (UTC)
If you were in zero gravity, you would not fall back down when you jumped, so your are in gravity, and if you are on earth that is 1G of gravity, you are however weightless, i.e. if you jump out of a plane and stand on some scales as you fall, you will register zero (discounting effects of air resistance). Philc T+C 15:40, 7 May 2006 (UTC)
Zero gravity can only be acheived outside the universe, or debatably at the centre of mass of the universe. Philc T+C 21:32, 4 May 2006 (UTC)

Continuing from Jonathan, even when you jump off from a small height (say from the top of a table or a small ladder (basically when you are experiencing a free fall), you are in zero gravity -- Wikicheng 23:57, 4 May 2006 (UTC)

Trampolines (especially the really big ones at the local gym) are brilliant for this kind of experiment - from the moment you take off to the moment you land, you are (barring a small component of air resistance) weightless. Although you may want to ask before doing Jonathan W's experiments... :) — QuantumEleven 06:55, 5 May 2006 (UTC)

[edit] Airplane Safety

Can diesel be used in a high compression ratio jet engine so as to enhance safety in case of a crash as diesel does not catch fire due to sparks and spillage?

What do you think they use as jet fuel? --Zeizmic 11:42, 4 May 2006 (UTC)
Diesel engines for airplanes exist, do check our article on aircraft engines and most especially aircraft diesel engines. In short, diesels do very well at running at medium power for extended times (operating consditions in aircraft); what prevents wide adoption is the small market combined with the extended certification process. Dr Zak 11:56, 4 May 2006 (UTC)
I believe a variant of Kerosene is used as jet fuel, because it does not burn as vigorously as gasoline.

[edit] Physics Question

According to the formula e=mc², it is possible to get a lot of energy from a very small amount of mass. Practically, we lose of a lot of energy in every machine. If we burn a lot of coal, a huge amount of it is wasted as ashes. Even in nuclear power plants, a lot of radioactive material is wasted as nuclear waste. Is there any(practical/theoretical)way to convert the whole of a substance into energy without wasting much?

Matter-antimatter reactions are pretty much the only candidate for total conversion of rest mass, though even that ends up with a substantial amount of the energy going into neutrinos. Very much a theoretical option, and even an arbitrarily advanced society would have trouble making antimatter without expending a vast amount of energy.
There is the possibility of collecting small amounts of antimatter (but enormous compared to what we can currently produce) in the magnetic fields of various bodies in the solar system. See [this Nasa Institute of Advanced Concepts study. However, the cost and complexity of such collection mean it's unlikely to be used as a domestic power supply; it'll almost certainly be used only where energy density is really important like spacecraft propulsion. --Robert Merkel 02:03, 5 May 2006 (UTC)
This is, famously, how the Starship Enterprise is supposed to achieve the power required to go faster than light. --Bth 08:59, 4 May 2006 (UTC)
In nuclear power plants, there is probably not as much waste as you think. Its a lot heavier, but by volume it is pretty small. (
Comparison of medium sized nuclear power plant's fuel consumption to a man, ~6 ft. tall.
Enlarge
Comparison of medium sized nuclear power plant's fuel consumption to a man, ~6 ft. tall.
Matter-antimatter reactions annihilate totally, releasing heat and light, with no waste matter (there is still waste, but only in energy form). It still takes a lot to generate that antimatter though. Nuclear fusion is probably the best way to go in the next few hundred years, supplemented by solar panels, if they are cheap and efficient enough. -- Mac Davis] ⌇☢ ญƛ. 09:05, 4 May 2006 (UTC)
I think the questioner is seeing all matter left over as possibly-energy-by-E=mc2 and thus views both ashes and nuclear waste as huge amounts of rest mass just sitting there going to waste.
In general, combustion releases energy from chemical bonds, which is absolutely tiny compared to rest mass (less than a millionth of one per cent), and both nuclear fission and fusion release nuclear binding energy, which is on the order of 0.1%. --Bth 09:19, 4 May 2006 (UTC)
I know about the small amount of enrgy which is released through combustion and also the nuclear binding energy which is released in fission and fusion reactions. I just wanted to know whether the total annihilation of matter and the subsequent release of energy is possible or not. The examples that I used in my question were probably not correct.
Thank you very much, but what about cold fusion? Is it really possible to make small scale fusion batteries?
See cold fusion. Short answer: no. --Bth 09:21, 4 May 2006 (UTC)

[edit] Copolymerization

How can polymerization be used to make PVC soft without using plasticers? Thanks in advance.

While this is just an educated guess (my schooling in polymers was limited) I'd say that using 2 different monomers with different spacial properties to polymerize randomly, you would end up with strains with random spacial properties, that are unable to neatly fit next to each other. And i do believe that the degree of order in a polymer is a strongly related to it's hardness. I've always seen it as the difference between the different in a bundle of Pick-up sticks lying neatly together, or it being a jumble. And this forces a jumble by bending sticks in different random places. SanderJK 10:37, 4 May 2006 (UTC)
Well, it depends on where you're starting from. If you've already got the PVC, there's not much that can be done by polymerisation (other than melting and mixing with another, softer, polymer) to make it softer. However, if you provide enough heat to raise the sample above its glass transition temperature, it'll become soft and flexible. If you're starting with the monomers, you can control the degree of polymerisation by a number of means, and this'll affect the physical properties of the polymer produced, including rigidity. Generally, the lower the molecular weight distribution, the softer the polymer. Unfortunately, Polyvinyl chloride is produced via an addition reaction rather than a condensation reaction, so I can't point you to the Carother's equation, but by adding another chemical capable of reacting with the vinyl chloride into the mixture, the average chain length should be decreased, and the polymer made softer. GeeJo (t)⁄(c) • 21:17, 4 May 2006 (UTC)

Anything you add to the PVC could be construed as a plasticezer because you are taking away from the purity of the end product. The best way to do this is to create a plastic that is more amorphous (non-crystaline) which will make the plastic more of a tangled mess of molecules thrown together in a ball rather than an ordered crystal which is much more rigid. The best way to do this is to heat the plastic past its melting point until it is in a near liquid form with a lowered viscocity. Mix it well then super cool it. This will shorten the chains as you have broken some of the intermolecular forces of the original plastic and it will take away from the crystalinity. However once you do this it will severely degrade the plastic.

True. Also, since the reaction forming PVC is based on a fre-radical chain, it's highly susceptible to temperature. So to add to my previous statement, provided you're starting with the vinyl chloride monomers, altering the reaction temperature (and keeping it regulated since the reaction is exothermic) is also a viable method of changing physical properties of the polymer. GeeJo (t)⁄(c) • 23:51, 5 May 2006 (UTC)

[edit] Converting pdf file to editable format

Hello, Is it possible to convert a pdf file (Adobe Reader 6.0) to a text format that I can edit. As it is currently Acrobat won't let me select anything to copy & paste it, when I try to save as text it saves a blank txt file & when I try to copy the file to the clipboard & paste it it doesn't paste anything. AllanHainey 09:47, 4 May 2006 (UTC)

If a PDF file is not protected and contains text, Adobe Reader will let you copy/paste the text into other applications. From this we can conclude that the PDF file you have does not contain text. It's most likely scanned pages, big pictures with no text at all. The only solution would be OCR (available in commercial Acrobat and other tools). Notinasnaid 09:53, 4 May 2006 (UTC)
A pdf file can be protected so that you are not allowed to select from it even though it is not password protected. So it is still text format and not a picture, but acrobate reader refuses to let you select from it. It is possible to convert a file like this to text using a pdf to text converter IF it ignores the select lock flag. Open source and freeware software is most likely to do so. Good luck. Stefan 10:15, 4 May 2006 (UTC)
This is indeed a possibility, but in such a case Reader would also refuse to save text. Since it allows you to save text, but saves nothing, I have to conclude there is no text. Notinasnaid 11:05, 4 May 2006 (UTC)

You can use a software called PDF to Word v1.6 to convert PDF files into RTF format. RTF files can be edited normally with a text editing software(MS word for example). This software is not free. You can get it at http://www.verypdf.com/pdf2word/index.html. This is not an advertisement, you can use any other software if you like.--DIGIwarez 10:06, 4 May 2006 (UTC)

But does this software do OCR? I can't see any mention of this on its web page. Without OCR, it's likely to produce a word file with a picture of a scanned page. Just like the picture in Reader, not editable text. Notinasnaid 10:06, 4 May 2006 (UTC)
No this is not an OCR. It works on a normal non-scanned PDF file. Please try it if you have any doubts. It's free for a limited amount of files. You should be able to edit the text portion quite easily.--DIGIwarez 10:27, 4 May 2006 (UTC)
So I think we have to assume that it won't help the original questioner? Since if it was a normal non-scanned PDF, they would have been able to copy/paste or save text? Notinasnaid 10:33, 4 May 2006 (UTC)
The questioner asked for a software with which he could convert a PDF file into a text file. The above software can do that. If it fails then an OCR software might be necessary.--DIGIwarez 10:41, 4 May 2006 (UTC)
Thanks, it looks like the pdf document is just scaned pages so I'll look into OCR, anyone know a good free OCR software? AllanHainey 12:12, 4 May 2006 (UTC)
GOCR is opensource and free. I've never used it however (I know the site because it was recommended to me once before on this very page). — Asbestos | Talk (RFC) 15:47, 4 May 2006 (UTC)
OCR is often pretty bad with PDFs. You'll probably do better to just print it out and then re-type it -- because you will probably have to go over and check every single word for OCR errors anyway. OCR is useful for searching documents, but it is not very good for replicating their exact text, in my experience with Adobe Acrobat's OCR functionality. --Fastfission 16:11, 4 May 2006 (UTC)

[edit] Radioactivity

If β-particles are negatively charged, how can they stay inside the nucleus?

They don't. They're emitted at high speed. But they start in the nucleus, hence all the hairsplitting in the previous question. (And note that being negatively charged shouldn't prevent them staying in the nucleus at all, as negative and positive charges attract one another; it's the high energy from their being created in a nucleon's decay that means they shoot off. What should surprise you is that the protons in the nucleus don't all repel each other, which is down to the strong nuclear force.) --Bth 10:07, 4 May 2006 (UTC)
By negatively charged particle I meant electron. I could not understand how electrons were produced inside a nucleus. Thanks for the answer
They are produced by means of beta decay: one neutron transforms into one proton, one electron and one anti-neutrino.--Ring0 15:21, 4 May 2006 (UTC)
Think of E=mc^2. Energy and mass, are kind of the same thing down at the particle physics level. -- Mac Davis] ⌇☢ ญƛ. 10:56, 4 May 2006 (UTC)
Yes, but how is it related to the question?

I think what you are trying to ask is how protons can stay in the nucleus together despite their mutual electrical repulsion due to their positive charges. The answer is that the nuclear force is a stronger attraction than their electrical repulsion, at that distance. StuRat 18:17, 4 May 2006 (UTC)

[edit] dieting

i recently heard that dieting DOES NOT reduce the amount of body fat.Then why do people recommend & follow it?

I suspect someone has played a prank on you (or is trying to sell you a snake oil dieting product of some sort). See dieting, in particular the section How the body gets rid of fat. 12:33, 4 May 2006 (UTC)
I'd say it depends on what the diet is. A diet of Big Macs and Cokes probably wont reduce the amount of body fat. GeeJo (t)⁄(c) • 20:58, 4 May 2006 (UTC)
I have seen someone lose weight with this kind of diet (Actually, it was Big Macs and beer). After three months of it, he had lost something like 20 pounds. If you can successfully force yourself to only eat one, it probably wouldn't be long before you get sick of it. - user:rasd

See http://home.howstuffworks.com/diet.htm for an excellent article on dieting --Wikicheng 00:12, 5 May 2006 (UTC)

[edit] milk

why does sugar mix well in hot milk than cold milk?

thanks!

Milk is mostly water. If you've ever tried to make lemonade or Kool-Aid before, you know that it is easier to mix the sugar in water if you use hot water and then refridgerate it. Of course, that takes a long time, so you have to suffer through that first warm glass with some ice cubes. --Kainaw (talk) 13:35, 4 May 2006 (UTC)
It takes energy to break apart the sugar molecules making up the crystals. By heating the milk, you increase the average temperature of the sugar/milk mixture farther above the activation energy of the solvation reaction, and so make it easier for the sugar to dissolve. GeeJo (t)⁄(c) • 20:57, 4 May 2006 (UTC)
The saturation point increases with temperature. Isopropyl 22:42, 4 May 2006 (UTC)

Simple Answer: Milk is made of molecules that whizz around, bumping into each other. Sugar is also made up of molecules, but they are 'holding on' to each other, making them solid instead of liquid like the milk. When a milk molecule hits a sugar molecule, if it's going fast enough and strongly enough it will break the sugar molecule off the lump of sugar and dissolve it in the milk. The warmer the milk is, the faster the milk molecules whizz, and the harder they hit the sugar molecules. Also, as they are moving faster, they hit the sugar molecules more often. This means they break sugar molecules off more often, dissolving the little lumps of sugar faster. Skittle 16:01, 5 May 2006 (UTC)

[edit] Disposal of nuclear waste/material

Hi again, a U.K. committee set up by the government to look into the best ways to dispose of nuclear waste/materials recently reported the best way would be to bury it deep underground. That got me thinking - what would happen to it if we got it into magma, like a volcano, but instead of just tipping it in Mt Etna we dug down & put it into a deep underground magma flow? Would it burn up, at least partially, solidify underground in the rock, shoot right back up & create a radioactive volcano where we dug or just turn the lava radioactive creating radioactive rocks/volcano lava sometime in the future? Also would it be possible to do this given the pressure/temperatures involved? AllanHainey 12:47, 4 May 2006 (UTC)

It can be "burned" in the correct circumstances. In a recent question, I referenced a process called "actinide fusion" - but the articles about it were too technical for me to read. Thanks to Philc for explaining it laymen's terms, I can now say that actinide fusion is, for the most part, burning up nuclear waste in a fusion reactor - rendering it harmless (non-radioactive). --Kainaw (talk) 13:30, 4 May 2006 (UTC)
There is, of course, no burning involved in "actinide fusion" - at least as that word is conventionally used and as the questioner appeared to use it. Dropping nuclear waste into magma will not change the waste into a non-radioactive substance. Rmhermen 16:37, 4 May 2006 (UTC)
Burning in this sense is used in a sort of slang physics way to mean a reaction that recquires activation energy, but then subsequently releases more energy, it also hot. This is an incorrent use of the term, however it is widely understood, and therefore regularly used. Philc T+C 18:17, 4 May 2006 (UTC)
I have heard it suggested the nuclear waste be reacted with silicates to make rock then dropped into a subduction zone. I have not read anything about the feasibility of this though.
At all of the places that we have access to the mantel, there is a high probability that it will come back up again relatively soon, for example hotspots, plate boundaries and volcanoes, these are likley to either spew magma onto the surrounding land, or leave it in rock form in the crust. So chucking radioactive waste, simply antognises the situation with already threatning magma now with radioactive waste. Philc T+C 18:17, 4 May 2006 (UTC)
  • The best way to dispose of nuclear waste is to bury it. (People seem to think that's bad because it's the same thing people have been saying for 40 years. But it's the other way around - It's still the best option after 40 years of heavy research in the field.) Anyway, to answer the question: You don't want to put it into a geologically active area because then it can escape. And the whole point of end-storage is that you don't want the radioactive materials to be dispersed. If we did, we might as well blow them out a smokestack. Also, nuclear waste is for the most part already solid. --BluePlatypus 15:23, 4 May 2006 (UTC)
    • As a caveate, one should bury it, but where and how to best bury it are still very contentious scientific and political debates. As for the waste itself, it depends on what sort of waste you are talking about. Reactor waste is solid but wastes generated by processing plants are often liquid. --Fastfission 16:15, 4 May 2006 (UTC)
It is dangerous to think that we can dispose of nuclear waste that will still be active thousands years after. In rich countries, you can pay for safety but you get a police state ; in poor countries, risks are greater and may come back to you if you go on feeding terrorism.
Cooking waste in clean nuclear plants is also risky, as costs are heavy, economic return uncertain, technology and security still immature. We use costly power (nuclear, oil) without seeing the true price. --DLL 21:13, 4 May 2006 (UTC)
Which is why a minor world war was fought on Talk:Nuclear power... ;-) — QuantumEleven 06:51, 5 May 2006 (UTC)
Note, however, that the Oklo reactor lasted intermittently on this planet for about 150,000 years, and now, 2 billion yars later, the waste from it has traveled remarkably little distance, despite geological fractures and the seepage of groundwater. (All this without, needless to say, any effort at all by human beings.) -Wiccan Quagga 07:27, 7 May 2006 (UTC)
Oklo may have lasted that long all that time ago, but the high intensity low half-life stuff is long gone now. What we make has to stay where we put it, and doing that properly means correct estimates of a larger number of quite disparate things: climate and hydrology of hte site, tectonic and hot spot activity at the site over say 100000 years, and so on. Otherwise, we might as well do what the Soviets are said to have done with quite a few submarine power plants, to wit, dumped 'em in the sea in the Arctic. 71.249.12.89 06:05, 11 May 2006 (UTC)

[edit] Heat Absorption from Light

Why does a black car absorb more heat than a white car when it becomes exposed to sunlight?Patchouli 14:08, 4 May 2006 (UTC)

Did you have the science class on visible light? (not everyone does, since science is considered a sin in many places) White things reflect all visible light. Black things absorb all visible light. Red things absorb all but red light. Blue things absorb all but blue light. The more light absorbed, the more heat the object will absorb. Now, if you want to get very technical, it is possible to reflect ultraviolet and infrared light while absorbing all visible light and avoid so much of the heating effect, but who'd waste their time doing that to a car? --Kainaw (talk) 15:06, 4 May 2006 (UTC)
Note that absorbing visible light warms a body up in exactly the same way as absorbing infrared or ultraviolet -- it's a common misconception to think that visible light doesn't warm up objects. All waves in the electromagnetic spectrum carry radiant energy, and absorbing this (which a black surface will do faster than a white surface) will warm an object up. Note also not to mix up cause and effect: It's not that an object reflects light because it is white, it is white because it reflects light. — Asbestos | Talk (RFC) 15:30, 4 May 2006 (UTC)

So we see the reflected color, and thus for a black object no light is reflected. Also, we don't see IR and UV light because they don't get reflected.Patchouli 17:45, 4 May 2006 (UTC)

We don't see IR and UV because our eyes can't detect them. Some other animals can see them, however. StuRat 18:06, 4 May 2006 (UTC)

Bees for instance can see the ultraviolet patterns on many flowers; you and I can not. -- Scienda 18:40, 4 May 2006 (UTC)

Keep in mind that "seeing" is only one sense. We "feel" infrared in large quantities as heat. Perhaps that is why our eyes never felt the need to see it. Also, I've read many articles that talk about a rather recent evolutionary jump that allowed humans to see blue. Before that, texts would describe grey skies and green oceans. Maybe we'll continue further along to ultraviolet. --Kainaw (talk) 18:53, 4 May 2006 (UTC)
I seem to recall that in an episode of QI, Stephen Fry brought up the fact that the ancient Greeks had no word for blue, instead calling it bronze. I very much doubt that an evolutionary jump could have affected every living person since the conception of the written word however, given the date of the most recent common ancestors ( GeeJo (t)⁄(c) • 20:53, 4 May 2006 (UTC)
I remember it from many stories. One I found interesting was a period where the king wore blue because most people saw it as greenish-gray, not blue. It was assumed that the upper class could see it as blue and it was used as a test. Of course, everyone claimed they could see it as blue even if the king purposely came out in a gray robe. Then, that article argued that this may have been the origin of the "king with no clothes" story. As for the evolutionary jump, it wasn't as much of a jump as it was a progression. To this day, blue-green blindness is common (though clearly a minority). It isn't really the inability to tell blue from green. It is an inability to see blue, so it looks green. --Kainaw (talk) 00:37, 5 May 2006 (UTC)
Maybe this is how blue blood came about to describe aristocrats.Patchouli 11:04, 5 May 2006 (UTC)


I'm sorry, but this is nonsense. 1) We don't feel infrared any more or less than we feel any other kind of radiation (IR not heat, read the darn articles). 2) Evolution has nothing to do with "feeling the need" to see different wavelengths. We just evolved to be receptive to one sub-set of wavelengths, birds and some other animals to other. 3) The idea that we had an evolutionary jump a few hundred years ago to see colors is rididculous, though having or not having a word for a color is a different matter.
See "Heat Transfer Mechanisms" in the heat article. Infrared is used to transfer heat and the human body senses infrared (and visible light) as heat. See evolution. An "evolutionary jump" doesn't happen overnight. It happens over many generations. Humans have been through many evolutionary jumps: gaining opposable thumbs, hips that allow us to walk upright, larger brains... Being able to see blue is an evolutionary jump that we are just getting to the end of. There are still many people who cannot see blue. It is nonsense to claim that people named every shade of every color on Earth with the exception of blue. --Kainaw (talk) 19:53, 6 May 2006 (UTC)
I must agree with Kainaw in some aspects; while of course we can perceive infrared as heat we perceive other electromagnetic radiation similarly. Eyes cannot feel a need to develop abilities, nor does evolution work like that. There would be many difficulties with an infrared-sensitive retina; ones that come to mind offhand are the infrared emitted by our own bodies (including our eyes), and the infrared-opaque nature of some components of our eyes. In addition, I must express strong skepticism regarding the proposed recent evolution of the ability to see blue; what precisely is meant by "an evolutionary jump that we are just getting to the end of"? Even if the ablility to see blue is a new mutation, it cannot affect an entire species in this manner; it will only affect its descendants. If this mutation truly arose after recorded history, then only the descendants of that person would have this ability. For example, if it began in Europe in modern times, for instance, then no African, Asians, or any others should possess this ability. In fact, the ability to see blue is quite old; most primates have two pigments, one for a bluish color and one for green/yellow, that diverged from each other some 500 million years ago. The cone commonly called "red" developed more recently, but was in a primate ancestor, not in humans. [12] has some information on this. — Knowledge Seeker দ 20:24, 6 May 2006 (UTC)
Plus, you can see a colour without naming it; Think of 'Robin red-breast' with its orange front. Seems like people just called orange things red in Britain until the orange was introduced. Skittle 15:33, 7 May 2006 (UTC)
IR is related to black body radiation, in that bodies at room tempuarture emit IR radiation. Therefore, IR camaras can be used to see people in the dark, and this is often referred to as "heat sensing" cameras. This then confuses people into thinking IR is heat, which is mistaken. Also, as KS shows above, it is impossible for any mutation in recorded history to have affected everyone on the planet, as not everyone on the planet can trace their history back to a single ancestor living in recorded history. [[edited by me to remove unecessary rudeness]] — Asbestos | Talk (RFC) 02:30, 8 May 2006 (UTC)
Nobody except you claimed any confusion about IR and heat. Where is your proof that humans do not have nerve cells that are excited by infrared light? That is the claim that was made. You just failed to read it in your eagerness to flame someone. Where is your proof that humans do not have a gene on chromosome 7 that was the last mutation involving human eyesight's ability to sense electromagnetic radiation? Nobody except you claimed it was a mutation that took place a few generations ago. I said that I read research papers that claimed it was still common for people to be unable to see blue in the earliest recorded history (about 5,000 years ago). But, you apparently failed to read it in your eagerness to flame someone. --Kainaw (talk) 02:52, 8 May 2006 (UTC)
I'm really sorry for the post above, as I mentioned on your talk page. I'm confused as to why we're on evolution, but in answer to your questions: people don't usually ask for negative proofs. You don't ask a scientist "where's your proof that we don't have nerve cells that sense [IR light/gamma rays/dark matter]", or "where is your proof that humans do not have a gene on chromosome 7 that affects [eye sight/ultra sonic hearing/etc]". Normally people expect positive proofs: e.g. a paper that shows we have a nerve cell that is affected by whatever it is. The fact that we sense heat by thermoception is undisputed, but no one is suggesting we have IR-sensing cells. Anyway, I'm really interested in the paper you read about not sensing blue. Do you have a citation I could look up? (PubMed finds nothing). I'm confused because, as KS mentioned, we know pretty much when the blue cone cell developed (c. 500 million years ago), but I wrote my undergraduate thesis in part on whether naming colors affects the perception of colors, so it's a topic I'm interested it. — Asbestos | Talk (RFC) 11:45, 8 May 2006 (UTC)
I replied on my talk page. What you said is correct. I have been plagued recently with accusations that I've said things that I haven't said. I was mainly just saying that our perception of the electromagnetic spectrum is not limited to our eyes, just as sound isn't limited to your ears when there is plenty of bass to rumble the floor. As for evolution, that is so long ago that is like another life. I really only remember the story I related. The rest of my memory is faulty. I know red/green evolved first in primates. I don't know if it is all primates, including monkeys and everything, or just the greater apes. Then, blue developed in early human ancestors. The research I as assisting (mainly by reading articles and highlighting parts the docs wanted) was in looking for a genetic cure for blue-green blindness. Since I can read Chinese, I would come in and have a stack of Chinese research papers on my desk. (Note to everyone: When someone says they can read Chinese, that means that they know the 300-500 common characters used in a Chinese newspaper or magazine, not the extra 1,000 scientific characters that are never used in common Chinese! I spent most of time with a Chinese dictionary.) I can tell you that the ability to see blue is on chromosome 7. A 'defect' in at least one gene (there was a dispute about some others) causes an inability to see blue. Then, I got off that stupid project and worked on one that used computers to detect if a song is "pleasing" or "not pleasing". I know, third-hand knowledge of a topic is rather useless, but that's all I had. --Kainaw (talk) 15:25, 8 May 2006 (UTC)

[edit] The speed of light vs. theory of relativity

Einstein says that it's impossible to go at the speed of light, because the closer you get to the speed of light, you become heavier, time goes slower, and you get flatter.

But Einstein also said that speed is relative. You can't measure your speed unless you compare it to something else. When you're going 100 km/hr on the highway, what's really happening is your car is moving 100 km/kr relative to the Earth. When you calculate that the Earth is moving 1500 km/hr when it rotates, what's really happening is the Earth is rotating 1500 km/hr relative to the Sun.

So how can you say that you're approaching the speed of light if speed is relative? Jonathan talk 15:20, 4 May 2006 (UTC)

The speed of light isn't relative. It is the same for all observers (see Michelson–Morley experiment). So, even if you had flied in a very fast spaceship, the light speed still would have been for you 300 000 km/s.--Ring0 15:49, 4 May 2006 (UTC)
The trick is that it's not that you are approaching the speed of light with respect to your own measurments of the speed of light -- your measurments of the speed of light never change, as you say. Rather, it's only using a third reference point that one can say that you're traveling at 90% speed of light. — Asbestos | Talk (RFC) 17:27, 4 May 2006 (UTC)
Yes, that's exactly what special relativity is about, solving that apparent

contradiction. – b_jonas 12:21, 6 May 2006 (UTC)

"Going the speed of light" doesn't have any physical meaning, just as dividing by zero has no mathematical meaning. Asking "I know you can't go the speed of light, but what would happen if you did?" is like asking "What would happen if you could cut a pizza into exactly zero slices?"

-User: Nightvid(unregistered)

Well, obviously light goes at the speed of light, but that's allowed (in fact required) because it's massless. I can cut a pizza into zero slices if there's no pizza to begin with! Melchoir 08:09, 8 May 2006 (UTC)

Oh, I get it now! Thanks. Jonathan talk 14:47, 8 May 2006 (UTC)

[edit] Mechanical collision

Give an example of a mechanical collision in which energy gets dissipated even in ideal circumstances, that is, where energy dissipation is unavoidable due to the law of conservation of momentum. —Masatran 15:26, 4 May 2006 (UTC)

Consider inelastic collision of, say, two plasticine balls. --Ring0 15:54, 4 May 2006 (UTC)
I am looking for an elastic collision. —Masatran 17:00, 4 May 2006 (UTC)
That can't happen in an elastic collision, so there aren't any examples. Conservation of momentum always holds. Conservation of kinetic energy does not. --HappyCamper 17:21, 4 May 2006 (UTC)
To User:HappyCamper: I think you mis-read my question. —Masatran 17:31, 4 May 2006 (UTC)
An elastic collision, by definition, conserves kinetic energy. Any collision where energy is converted to other forms is inelastic. TenOfAllTrades(talk) 17:36, 4 May 2006 (UTC)
There are two equations that together govern all collisions between two objects:
m1 * v1 + m2 * v2 = m1 * v3 + m2 * v4 (Conservation of momentum)
m_1 * v_1^2 + m_2 * v_2^2 = m_1 * v_3^2 + m_2 * v_4^2 + E(Conservation of energy)
For any collision, once you know all but two of the parameters (typically the two final velocities are unknown), you can determine everything else. What you seem to be looking for is a collision where the conservation of momentum formula forces "E" (the energy lost to inelasticity) in the conservation of energy formula to be non-zero. --Serie 22:04, 4 May 2006 (UTC)
I don't know an exact example, but I think the key is that the collision shouldn't be central (or head-on), that is, that the two bodies can't collide in an elastic way because then the force would have to act on a point where the two bodies don't touch. – b_jonas 12:15, 6 May 2006 (UTC)
Nothing in the law of momentum conservation prevents a collision from being elastic, regardless of whether the collision is head-on or not. A collision may be inelastic for other reasons, but not because of momentum conservation. Arbitrary username 17:43, 6 May 2006 (UTC)

[edit] Aluminum fluoride

Isn't the molecular formula for the ionic compound aluminium fluoride Al3+(F-)3? I done it in chemistry today and it apparently was correct. However, according to the PubChem article, [13], it is simply AlF3. Which is correct, mine or theirs? Thanks, Kilo-Lima|(talk) 16:45, 4 May 2006 (UTC)

These two formulas both reflect the fact that aluminium fluoride molecule consists of one aluminium atom and three fluorine atoms. The first formula shows additionally ions' charges. --Ring0 16:59, 4 May 2006 (UTC)
So, which one should really be included in the article? Kilo-Lima|(talk) 17:04, 4 May 2006 (UTC)
I would keep AlF3 and not use the ionic representation. The latter is implicit in the former if one knows that AlF3 is an ionic compound. But of course, an explanation in the article always helps. --HappyCamper 17:19, 4 May 2006 (UTC)
There is not normally any need to show the charges on the ions, as the compound AlF3 can only be formed from those ions. Most likely, the reason your chemistry teacher has asked you to show the charges is to illustrate that you understand what is happening. Yummifruitbat 17:24, 4 May 2006 (UTC)
  • The compound is only usually given as AlF3. Al3+ indicates that it is a free ion, which would usually mean that it is in solution. You do not write the redox state of ions in a compound, only for free ions. When you do need to give the redox state, it's done for the metal ion and in parenthesis. E.g. "Iron (II) oxide" is FeO and "Iron (III) oxide" is Fe2O3 --BluePlatypus 20:44, 4 May 2006 (UTC)
Also, the bonding is to some degree covalent in every molecule, so using Al3+(F-)3 as a formula would be using an idealised approximation. GeeJo (t)⁄(c) • 20:48, 4 May 2006 (UTC)
In fact, based on what I can find on the web, it seems AlF3 is more covalent than ionic, existing in its solid form as a polymer or network covalent macromolecule with three-center two-electron bonds. One simply does not normally get a 3+ charge on a single atom as would be required if AlF3 were mainly ionic. —Ilmari Karonen (talk) 22:34, 4 May 2006 (UTC)

[edit] Microscopic organism that looks like a tube

What is the name of the microscopic organism that looks like a tube, and moves by bending forward, placing its head(?) down, and bringing its feet(?) up; that is, it is upside-down(?) at every alternate step? —Masatran 18:00, 4 May 2006 (UTC)

You mean an organism than moves by rolling? Other than the tumbleweed I can't think of any offhand. But then, I'm not a biologist. GeeJo (t)⁄(c) • 20:45, 4 May 2006 (UTC)
I think he means it moves like a slinky. Black Carrot 00:19, 5 May 2006 (UTC)

Kinda like this?

 ___/    _____   _______   _____    \____
/       /                       \        \

A physics teacher told me about it. I don't know what it is, but it works because of the order the segments move in. If you thought about it in terms of physics without considering the solution it is in, it would seem like the creature would get nowhere, however it works becuase the fluid at this scale is very viscous. Whenever it makes a stroke, it either has the other segment streamline or out. When it makes a forward stroke, the other segment is stream line, whenever it makes a backward stroke, the other segment is down and provides drag which limits the amount of backwards motion. Looking at the picture above, it starts in the s shape. The stroke with the front segment pushes the creature backward a little, but the other segment is down limiting its backward motion. The next stroke pushes it forward, and since the creature is streamlined compred to where it was in the first position it has moved a little ahead. And no I don't know what it is called. I wish I could help more... Sifaka talk 04:18, 5 May 2006 (UTC)

It's called a hydra. --Heron 20:35, 6 May 2006 (UTC)
Those aren't the only small invertebrates to move that way - Temnocephalids do (we don't seem to have an article on them, but they're a type of flatworm, and part of class Turbellaria). Grutness...wha? 07:49, 8 May 2006 (UTC)

[edit] Headphones

I have three places for my headphones to plug into the computer: one on my DVD drive, CD drive and another near the bottom of the computer, where a bit of the computer "lifts up" and there are USB ports there, too. The only place I can plug the headphones into and hear sound is from the one in the bottom. When I plug it into the DVD or CD part, near the drive, no sound comes out of the headphones. Why is this? And can I route it to the CD drive? Thanks, Kilo-Lima|(talk) 18:38, 4 May 2006 (UTC)

The connection at the bottom is connected to your soundcard, while the ones on your DVD/CD drives are internal to the drives. Those two will only work when you're playing an audio cd in the respective drives, because that does not require processing by the soundcard. To answer your second question; I don't think it's possible to route the signal back to the drive. - Dammit 19:06, 4 May 2006 (UTC)

[edit] Contact in sports

Which is more likely scientifically? Making contact with a Roger Federer serve or a Roger Clemmons pitch?

Those situations are so different that the only scientific way to compare them is by experiment; that is, gathering historical statistics. Melchoir 19:18, 4 May 2006 (UTC)
The serve. Baseball pitches are contacted, generally speaking, about half the time. Federer does not generally have half his points via aces. — Lomn Talk 19:57, 4 May 2006 (UTC)
Depends on what matches you go to often. – b_jonas 12:01, 6 May 2006 (UTC)

[edit] Women more suceptible to cold?

I've frequently heard that women are, in general, more suceptible to cold than men. (That is, to feeling cold, not to freezing to death.) Is this true? If so, what are the reasons for it. Thanks. -- SCZenz 19:02, 4 May 2006 (UTC)

I have heard the opposite. Women have a layer of fat just under the skin which provides limited insulation.
Men have a layer of fat under the skin, too. Without it, every vein would be visible, as they are on some feet, which have very little fat.
Indeed they do, but women seem to feel the cold a lot more strongly than men, at least if the complaints by my mother and previous two girlfriends that "It's bloody freezing in here!" when the thermostat reads a fairly warm 24C have been anything to go by. I suppose it could be psychological, or have something to do with bad circulation or more sensitive skin, or it could just be that they feel more free to complain, while us macho men suffer in silence. Or it could be none of the above, and have a fairly simple explanation that I've not thought of. GeeJo (t)⁄(c) • 20:32, 4 May 2006 (UTC)
This is because women are whiners...
Put in a less technical sense, that is probably what it is. Although women produce more morphine in their body than men, they still have lower paint tolerances than men; men have a more machismo idea, that you're more manly if you can go through more pain. Women, have no such idea that they have to prove themselves like this. -- Mac Davis] ⌇☢ ญƛ. 21:13, 4 May 2006 (UTC)
I'm not sure that this is related to the production of morphine by the body. That generally only affects pain reception in the short term (minutes). Whereas after I spent a whole afternoon fairly comfortable in a T-shirt in a room heated to 24C, my last girlfriend walked in in a sleeved blouse and immediately said "Christ it's cold in here! Why don't you turn the heat up?" I'd say it's more likely to be a skin issue than an internal one. GeeJo (t)⁄(c) • 21:24, 4 May 2006 (UTC)
Responders to questions like this seem disturbingly eager to chalk apparent gender differences up to female inferiority! In my experience (no more scientific than the other anecdotes people are posting), most men whine more if it's too hot than women do. Although menopause in women switches it around. --Ginkgo100 20:07, 5 May 2006 (UTC)

I believe this is a simple surface area to volume ratio effect. That is, smaller objects lose their heat more rapidly than large objects. Women are typically smaller than men. Children and babies are even more susceptible to the cold, although their higher metabolic rate may compensate to some degrees. StuRat 23:29, 4 May 2006 (UTC)

I cant explain it, but my (male) hands are always warm, whereas girls hands i touch/hold are nearly always cold. am I alone in thinking this? --Ballchef 23:50, 4 May 2006 (UTC)

Nope you aren't alone. My hands are always cold. I agree with the surface to volume ratio idea and would also like to posit that muscle mass has something to do with it too. I have noticed the trend people with more muscle mass don't feel as cold as often. Men typically have greater muscle mass than women do Sifaka talk 04:03, 5 May 2006 (UTC)
Women react to temperature stress by concentrating heat in their core body mass more so than men. This adaptation is believed to exist to help protect the uterus (and any associated pregnancy) from the effects of cold; however, it means that everything else being equal a woman's extremities will tend to get colder than a man's. I also agree that surface area to volume effects probably play a role as well. Dragons flight 11:03, 5 May 2006 (UTC)
Which has the side-effect of making women better at making pastry, according to my cookery teacher. Cooler hands mean the fat doesn't melt as much when you're 'rubbing' the flour in. Skittle 16:10, 5 May 2006 (UTC)

Limiting blood flow to the extremities to preserve core body heat is not unique to women, men do this, too. However, if women are more often cold, due to their higher surface area to volume ratio, then this protection mechanism will be activated more often in them. Note that this shows they really are colder, it's not just a psychosomatic issue. StuRat 16:27, 5 May 2006 (UTC)

Another factor may be fat distribution. Slim men tend to have a rather even distribution of fat, while thin women tend to have fat concentrations in their breasts and butt. And, of course, evenly distributed fat provides for better thermal insulation. StuRat 16:34, 5 May 2006 (UTC)

I think it might also be that when a woman feels cold, it's more likely that he will complain about it or turn the thermostat higher, while a man – even though he feels cold the same way – is more likely to ignore that and just continue work or whatever he's doing. (Or am I thinking too much in a hacker way?) – b_jonas 11:59, 6 May 2006 (UTC)
I seem to remember that females have lower metabolic settings than men, by and large, and that will lead to colder extremities. The cube-square law difference seems to me to be too small to account for the observed behavior. And of course some of that observed bahavior is likely due to attention seekin, look at me! drama to which some females are prone, while the male equivalent is suually more about acting out in some way. Whatever, it's been my experience that they all have cold feet and hands. Most of the time. And all this despite the higher body fat percentage. 71.249.12.89 06:20, 11 May 2006 (UTC)

[edit] Boiling point or vapor pressure?

Which is more correct 'Distillation is a method of separation of substances based on differences in their boiling points.' or ' Distillation is a method of separation of substances based on differences in their vapor pressures.' -- ∞Dbroadwell 19:52, 4 May 2006 (UTC)

Offhand, and as a non-expert, I'd say they're both roughly correct, but the difference in vapor pressure is a bit more precise. In my understanding, what matters most is the difference in vapor pressures at the operating temperature of one's apparatus ; but realistically speaking, one probably designs an apparatus to take into account the entire phase diagrams of the substances. Melchoir 20:10, 4 May 2006 (UTC)
Both are just as correct, because vapor pressure and boiling point are not independent properties. Another way of saying it is that the seperation is due to the differences in Activity coefficient. (lousy article, though) --BluePlatypus 20:35, 4 May 2006 (UTC)
Perfect. -- ∞Dbroadwell 22:27, 4 May 2006 (UTC)
And if both are equally correct, we should use the simpler explanation, which is the difference in boiling points. That will make it easiest to understand by the widest possible audience. StuRat 23:21, 4 May 2006 (UTC)
Vapor pressure increases with temperature according to a standard formula (see Clausius-Clapeyron equation). The boiling point is the temperature at which vapor pressure equals the ambient pressure (because this is when you can get bubbles of gas forming within the liquid rather than just evaporation from the surface). A substance with a larger vapor pressure at a given temperature will also have a lower boiling point. Arbitrary username 14:54, 6 May 2006 (UTC)

[edit] Braking rocket vs. retrorocket

I've made a bunch of redlinks to braking rocket; there's already an article on retrorockets. I tend to gather that a "braking rocket" is fired during reentry and landing to oppose gravity and slow the fall, while a "retrorocket" is fired in orbit to lose angular momentum and allow a landing in the first place.

Is this accurate? Is there really a distinction in terminology and/or design between the two purposes, or am I just confused? Melchoir 20:24, 4 May 2006 (UTC)

Well, the term "retrorocket" generally refers to any rocket that provides thrust in the direction opposite to motion. I think "braking rocket" is just a less widely used synonym. — TheKMantalk 21:35, 4 May 2006 (UTC)
According to the last paragraph of Retrorocket, "[r]etrorockets are also used in landing spacecraft on other astronomical bodies, such as the Moon and Mars". This, admittedly brief, description matches the usage I'm familiar with, and Google seems to concur. I've therefore taken the liberty of turning your redlink into a redirect. —Ilmari Karonen (talk) 21:39, 4 May 2006 (UTC)

I see. Thanks! Melchoir 00:41, 5 May 2006 (UTC)

[edit] Aaargh! My eyes!

Howdy! Why is it that immediately after coming indoors after spending some time in bright sunlight, everything appears to have a fairly strong green tint to it, that disappears after 30-60 seconds? Is there a fairly humdrum reason, or could it be something to do with the multiple ophthalmic surgeries I had as a child to correct fairly strong strabismus (two on the right, one on the left)? GeeJo (t)⁄(c) • 20:25, 4 May 2006 (UTC)

I have no idea, but I don't know if it's green tint. I spent an entire day outside in the sun only, with lots of snow, and returned to my once so very familiar school building to find myself completely amazed at how different the colours were. Highly, highly freakish. So, might not have anything to do with such an operation.
It's because of the ability of the human eye/brain to compensate for light sources with different white points: clear-sky sunlight has a color temperature of around 5000K-6000K, while incandescent light bulbs have a color temperature around 2800K (a very "reddish" white), and fluorescent lights have a white point that's completely off the color temperature scale (typically, a bluish white). However, despite the differences in the light put out by these light sources, a white sheet of paper will still look white. That's your brain compensating. You're seeing green when you come indoors because the brain doesn't adjust instantly. --Serie 22:17, 4 May 2006 (UTC)

Another thought, are you wearing greenish tinted sunglasses when outside ? If so, those would block the green light and make everything appear less green. When you remove them, everything would then appear more green by comparison, until you got used to it. StuRat 23:15, 4 May 2006 (UTC)

That would be reddish-tinted glasses. Greenish-tinted glasses would make everything look more green by blocking red, and when you took them off everything would look more red. —Keenan Pepper 23:30, 4 May 2006 (UTC)
Well, if they reflect all green light, they would look green to others but reddish when looking through them. StuRat 16:38, 5 May 2006 (UTC)
I guess that's possible, but it would be really weird. I don't think I've ever seen a material quite like that. If you put it down on a table it would look green, but if you held it up to the light, so that the light was behind it, it would look red. —Keenan Pepper 01:09, 6 May 2006 (UTC)
Well, I have seen reflective sunglasses that look silver to others but like regular sunglasses when you look through them. StuRat 18:47, 6 May 2006 (UTC)
Keenan, you'd be interested in dichroic filter. kmccoy (talk) 05:01, 11 May 2006 (UTC)
The green-tint thing happens to me too. I always thought everything looked darker inside because your brain was trying to shift from lots of light outside to less light inside. Jonathan talk 01:59, 5 May 2006 (UTC)

It's not your brain that adjusts, it's the cells in your retina. --Username132 (talk) 20:14, 5 May 2006 (UTC)

Geejo, I'm going to tack a rider onto your question, because I have a question about tinting as well. Speaking of glass tint (someone brought it up! someone brought it up!), y'know that strip of blue...uh...stuff?...that's at the top of most windshields? What is that for? What's it called? It doesn't seem to do anything for glare...the windshield article doesn't mention it at all. Cernen Xanthine Katrena 14:12, 7 May 2006 (UTC)

It's supposed to prevent you from being blinded by the sunlight at dawn and dusk and getting in an accident. Putting the sun visor down, wearing sunglasses, and avoiding driving toward the sun at those times of day are far more effective, however. I haven't seen that blue strip as much on recent cars. StuRat 18:11, 9 May 2006 (UTC)

[edit] Name that bird

Outside my window in Charleston, SC, I see hawks circling a lot. They are rather large. The weird thing is that they are often chased and pecked at (in mid-air) by tiny black birds. The tiny black birds will pester the large hawks for a very long time. It makes no sense to me because the hawk is more than large enough to kill the tiny black birds with a single swipe of a talon. So, I wonder what kind of birds these little things are and why the hawks deal with them so patiently. Anyone have a guess? --Kainaw (talk) 20:26, 4 May 2006 (UTC)

  • could they be baby hawks?--64.12.116.74 21:18, 4 May 2006 (UTC)
Says this site "I see crows and other birds periodically chasing the hawks around our place." --DLL 21:32, 4 May 2006 (UTC)
The hawk is large enough to kill the smaller birds, but not fast enough. That larger size comes at a cost of increased momentum: by the time the hawk is in position to take a swing at the smaller bird, the smaller bird is long gone. This is why most birds of prey attack by diving: the higher speed means that the target doesn't have a chance to dodge. --Serie 22:20, 4 May 2006 (UTC)
I guess they are little crows (or the like). We have a lot of house finches (brown with black/beige stripes). I don't think it is them because the attacking birds are clearly black. I don't know why they attack though because there are more than enough bunnies for the hawks (and gators) to eat. Those things multiply like, well, like bunnies. --Kainaw (talk) 00:46, 5 May 2006 (UTC)
I'm not very familiar with US birds so I couldn't tell you what species your little black ones are, but their behaviour sounds a lot like mobbing (see the 'in animals' section). The smaller birds see the hawks as a threat to themselves or their eggs/chicks and will engage in seemingly suicidal bouts of aerial combat (often in groups) with the predators to try to chase them away. Yummifruitbat 02:28, 5 May 2006 (UTC)
It turns out that one of the doctors here is a bird expert. He pointed out that they are not just crows, they are fish crows. The differece is the smaller size, the paler beak, and the wings have a sharper point to them when it glides. According to him, they send one or two up to fend off hawks when they find a good stash of fish, shrimp, crabs... whatever. They take turns keeping the predators busy while they eat. They will also buzz-attack cats. Now, I pretty much know all of the birds around my house and office. I just have to figure out what type of woodpecker I have in my front yard. It has the head of a cardinal and the body of a bluejay. Since my yard if full of cardinals and bluejays, I joke that he is a half-breed. --Kainaw (talk) 14:46, 5 May 2006 (UTC)
I don't claim to be an expert on woodpeckers, but I figured I'd do a little searching on this. Your woodpecker sounds a lot like Woody Woodpecker to me. According to this site, Woody is a Red-headed woodpecker. This species shows up on the South Carolina Breeding Bird Atlas [14]. Here's another site with pictures: [15], and another that shows their range overlapping Charleston: [16] Is that your bird, or is it much more blue? EWS23 | (Leave me a message!) 17:04, 5 May 2006 (UTC)
"The head of a cardinal" makes it sound more like a Pileated woodpecker to me - this has the pointed crest on its head and the red area is restricted to the crest rather than the whole head. It is found year-round in South Carolina. Alternatively it could even be an Ivory-billed woodpecker, but if it is you're very lucky as they're thought likely to be extinct in North America. Edit: Apparently there have been sightings/possible audio evidence of the Ivory-billed in Arkansas in 2004/5. Yummifruitbat 17:24, 5 May 2006 (UTC)
The head of the red-headed woodpecker is correct. It even has the darkened area around the eyes like a cardinal. The reason I'm not sure if the guy in my yard is a red-headed woodpecker is because all the photos of them have black and white bodies. This one has a blue jay body. It is blue, gray, and white. It isn't a pileated one because it doesn't have such a prominent pointed crest - just a little point. I'm sure that some day he'll be out there while I have my camera. Normally, I come home and see him fly away when I pull in. --Kainaw (talk) 19:03, 5 May 2006 (UTC)
I got in touch with our local bird-expert doc again. He said that the only local bird with a red head and a blue-gray body is the red-breasted sapsucker (our article says they aren't in South Carolina - hmmm...). The picture on Wikipedia has a black and white body. Also, the one I see in my yard has a clear ring aound the neck where the cardinal head is joined to the bluejay body. So, it is probably a freak woodpecker with a blueish body or a freak sapsucker with a gray breast. --Kainaw (talk) 19:17, 5 May 2006 (UTC)
While I haven't seen any pictures indicating as much, the drawings of Woody Woodpecker seem to indicate that red-headed woodpeckers can take on at least a bluish tint to their body, if not a completely blue body. Then again, maybe that was just the artist ad libbing and making something that was more appealing to the eye. Either way, it would be nice if you could get a picture at some point. EWS23 | (Leave me a message!) 23:30, 5 May 2006 (UTC)
(getting a bit indented!) The National Geographic Field Guide to the Birds of North America, 4th Edition agrees that the Red-breasted sapsucker isn't found in SC. The distribution map shows it confined to the West coast, not venturing very far inland. Apparently, however, it frequently hybridizes with the Red-naped sapsucker which extends as far east as western Texas in winter. This species sometimes hybridizes with the Yellow-bellied sapsucker whose winter range includes South Carolina. The two former species were previously considered subspecies of the latter, so perhaps you're seeing some weird combination of all three! :) Yummifruitbat 03:16, 6 May 2006 (UTC)

[edit] Chemical Reactions

Do all chemical reactions recquire activation energy, or are there some that have none, and will decompose almost instantaneousley in normal conditions (or even extremely low temperature) lfor example possibly something like NeCa4 or NeC2, involving noble gases (I can't imagine those compunds are to hard to pull apart). If not, what is the bond with the lowest activation/bond energy. Thank you Philc T+C 20:56, 4 May 2006 (UTC)

All chemical reactions have an activation energy. This energy can, however, be below average room temperature and many reactions occur spontaneously at 20C. A chemical reaction with no activation energy would still take place at absolute zero and since there's no kinetic movement at that point, no such reaction exists. As for the lowest bond energy, I'd say the van der Waals bonds holding liquid helium-3 together. GeeJo (t)⁄(c) • 21:27, 4 May 2006 (UTC)
Well, first we have to define "chemical reactions" more precisely, because you could even claim that two electrons near each other flying apart (e^-_2\longrightarrow 2e^-) was a "reaction" that certainly required no input energy. There are certainly imaginable constructs of atoms with a positive potential energy and no containing energy barriers (meaning that they will fall apart spontaneously) like XeH20 or so. Indeed, probably the reasonable definition of "molecule" in the phrase "molecule with a bond energy of ..." is "an arrangement of atoms that requires energy to dissociate", guaranteeing that all bond energies are positive. Of course, there are synthesis reactions with 0 activation energy: consider Na++Cl- \longrightarrow NaCl. But that's not a bond energy at all. Anyway, it's certainly possible for the activation energy of a reaction (and/or the energy of a bond) to be \ll kT for many T (see Boltzmann's constant), so the reaction is usually spontaneous. But any reaction with a positive activation energy (including the analysis of all reasonable molecules) can be slowed arbitrarily (though never truly halted) by reducing the temperature sufficiently. At absolute zero, were it attainable, only the reactions with no activation energy at all (like the attraction of ions or the repulsion between random non-bonded atoms like the xenon-hydrogen nonsense) can proceed, and even then they raise the temperature back to something positive. Hope this helps. --Tardis 21:40, 4 May 2006 (UTC)
All chemical reactions have a reaction energy, which can be positive or negative. Isopropyl 22:38, 4 May 2006 (UTC)
Or zero. He's asking about the activation energy though, not the reaction energy. --BluePlatypus 00:15, 5 May 2006 (UTC)
All chemical reactions have an activation energy, which can be positive or negative. Isopropyl 02:35, 5 May 2006 (UTC)
Not all reactions necessarily have an activation energy and it is certainly never negative. If it was, the activated complex would be lower in energy than the reactant and/or product species. So it would be a stable or metastable state and the reactant and/or products would be unstable. So by any meaningful definition it can't be negative. --BluePlatypus 03:47, 5 May 2006 (UTC)
Ah, I see that your definition of reaction is one stable species to another; then you're right, of course. Isopropyl 03:53, 5 May 2006 (UTC)
Yes and no. It's all a matter of how you define "reaction", as mentioned above. Usually, a chemical reaction is the reaction from one stable species to another, where a stable species is by definition something which is at an energetic minimum. Since you're moving between two energetic minima, by the rules of calculus, there must be a local maximum of energy in-between. (potential-energy surfaces are continuous) So for a "reaction" to have a zero barrier, it must start from a state which is not an energetic minimum and thus not be a stable species to begin with (but possibly a metastable one). As was pointed out, the activation energy can be arbitrarily small though, including smaller than kT, which means it has no significance. But even at absolute zero you could, at least in theory have a spontaneous reaction, if the activation energy was comparable to the zero-point vibrational energy of the molecule. --BluePlatypus 00:15, 5 May 2006 (UTC)
As the Platypus says, the decay of excimers would be a reaction that doesn't require activation energy. When the excited state decays the molecule just comes apart. Dr Zak 01:13, 5 May 2006 (UTC)

[edit] Badgersex

I've heard badgers are the species which have sex for the longest time, can anyone verify/specify? Thanks in advance!

According to here badgers can go at it for up to 1.5 hours. Can't find verification that it is the longest among "big" animals. According to this page the longest (albeit not voluntarily) coitus occurs between some insects, for up to 60 hours. (I wonder if the good folks at Google ever read their server logs to see what people search for. "Badger intercourse"...) Weregerbil 10:23, 5 May 2006 (UTC)
I'm told there's a ticker at Google HQ showing some of the things people are searching for. As for how long various animals last, I've been hearing ads on the radio for some kind of impotence treatment that mentions some statistics. I'm pretty sure they mention that the mink lasts some large time, but I can't remember how long - a Google search suggests 8 hours. Confusing Manifestation 12:08, 5 May 2006 (UTC)
I believe I heard the mink was able to have an orgasm for eight hours, not counting the actual intercourse.

Please God, in my next life, let me be a mink! Loomis51 02:14, 7 May 2006 (UTC)

Oh, please. Humans can do it for longer if they try. You just mix a little foreplay every once in a while in with the actual...uh...dippity doo. Cernen Xanthine Katrena 14:07, 7 May 2006 (UTC)

[edit] Photons and EM interaction

Photon says "electromagnetic interaction is mediated by the exchange of virtual photons." Does that mean that there are constantly virtual photons exchanged between every pair of charged particles in the universe? If so, that is a lot of photons, and they last a long time. Bubba73 (talk), 23:10, 4 May 2006 (UTC)

Well, they're called "virtual" for a good reason. They're not actually real, they're just possibilities of photons, which taken together average out to explain the well-known force. —Keenan Pepper 23:58, 4 May 2006 (UTC)
You can think of it that way, but you can calculate the average rate of virtual photon exchange between two charged objects, and it is enormous. So yes, there are constantly photons exchanged between everything, and yes that is a lot of photons. -- SCZenz 00:10, 5 May 2006 (UTC)
Yes, but I thought that virtual photons could exist for only a short time. These must exist for billions of years, right? Bubba73 (talk), 00:14, 5 May 2006 (UTC)
For one thing, virtual photons can go faster (or slower) than the speed of light, so they don't necessarily take billions of years to travel between charged particles billions of light years apart. This is okay because they can't carry information. For anothing thing, it's not true that virtual photons can only exist for a short time. The only definite rule is that they can't be observed, or else they're not virtual anymore. —Keenan Pepper 03:56, 5 May 2006 (UTC)
Thanks, I didn't know that. I thought they could only exist for a short time because of Delta T in the uncertainty principle. Why can't they be observed? How does a particle detector know the difference between a virtual photon and a real one? (I hope this isn't a stupid question.) Bubba73 (talk), 03:40, 6 May 2006 (UTC)

[edit] salmonella

In Australia, we have a current affairs "news" show called Today Tonight. now, this show is notorious for bullshit, but i wanted to know more about it's report on salmonella. they reckon around 70% of cooked chicken availiable here has salmonella. This would infer that around %70 of australian chicken eaters would get salmonella related diseases right? of course I've never come across any thing worth believing that says our chicken is unsafe. The explanation given on Today Tonight is that our immune system will fight the salmonella, but if we keep eating the chicken eventually our system will give up. I always thought that if we fought something once sucessfully, we would become immune to it! The story focussed on a bloke who is now in a wheelchair because he ate too much chicken, but i thought salmonella just made you quite ill. I read the wikipedia article on salmonella which says "In March 2006, The New York Times reported that the US government said that 16.3% of all chickens were contaminated with salmonella". and i havent heard of huge worries in the states either.

Is this just more b/s from naomi "F..king" robson, or should i switch to beef?

Thanks --Ballchef 23:51, 4 May 2006 (UTC)

Beef? Haven't you heard of mad cow disease? Or is that just over here? Black Carrot 00:15, 5 May 2006 (UTC)
"Naomi Robson" and "mad cow" is a very pleasing juxtaposition. JackofOz 02:19, 5 May 2006 (UTC)

You always assume that the raw chicken is covered with nasty buggers, salmonella being very common. That is why the official 'cooked' temperature is much higher than beef. Well-cooked chicken has no bugs, and always use a neato very geeky electronic thermometer that beeps at you! --Zeizmic 02:16, 5 May 2006 (UTC)


Chicken is commonly contaminated with pathogenic salmonella and campylobacter species, as are chicken eggs. If you have ever visited a chicken farm and viewed first-hand the conditions under which poultry are raised, it should not be a surprise. Most of these disease-causing bacteria are effectively killed by thorough cooking. A good web site describing safe food practices is Safe Tables Our Priority (S.T.O.P.).--Mark Bornfeld DDS 03:19, 5 May 2006 (UTC)
You should always treat raw chicken as if it is covered in poison; this is a fundamental rule of working in a kitchen. This means considering everything (hands, surfaces, knives) that comes into contact with raw chicken as contaminated, until washed. Commercial kitchens may have separate colour coded knives, chopping boards etc.; in a domestic kitchen, it is considered very important to wash hands, knives etc. once contaminated. If you take the same knife to chop up salad, there is a good chance someone will get sick. Salmonella is only one of the nasties you might find on raw chicken. Cooking is considered to destroy all of the nasties. So, there may be a grain of truth in the article, which is a much as most press reports manage. (Raw eggs are a difficult area; some things like mayonnaise need raw eggs. In practice this means that commercial kitchens take pasteurised eggs, and domestic kitchens take a chance.) Notinasnaid 10:05, 5 May 2006 (UTC)
On the immunity assumption above. There are some things for which immunity is lifetime or at least very long. There are other things (tetanus, for instance) for which immunity wears off (in this case soem years). And there are some things for which there is no immunity retained after an infection encounter. I've never come across an explantion that seemed credible.
On the question of why everyone isn't infected with salmonella from having anything to do with chicken, well... We live in a sea bacteria and viruses. Few of them are pathogens for us, to be sure, but more than enough to be comforted are. So why aren't we always infected and mostly dead anyway. Several reasons are known. One is a community effect in which already present bacteria deter additional bacteria from becoming established. There is even some research about using this effect on chckens. If they are inoculated with a cocktail of benign organisms, then malicious ones are discouraged. And second, what we eat has to pass through a stomach which is actively maintained in a quite acid condition. Most organisms can't survive it. The low pH isn't really required for digestion and seems mostly to be a protective arrangement. 71.249.12.89 06:56, 11 May 2006 (UTC)

[edit] May 5

[edit] Speed of a 747 at 500 ft

My house lays just under the approach path of a major international airport. Watching the majestic 747-400s flying over my house on their final approach is a daily pass-time of mine. I just wonder: what is their airspeed at 500ft of altitude?--JLdesAlpins 00:24, 5 May 2006 (UTC)

Bear in mind that I'm not a pilot and this is all speculation, but 747s are probably going really slow at this point. When they're only 500 feet above ground, they're trying to trimming back speed so that when they touch down they're just about stalling. I forget how fast that is for a 747 but my guess is like 120 mph or so. Isopropyl 02:34, 5 May 2006 (UTC)
A bit of googling indicates a short approach speed of about 160-180 kts and a landing speed of about 150. Conversion of the landing speed gives 172.6 mph or 277.8 km/h. The approach speed at 500 ft should be pretty close to the landing strip I guess so the speed would be a bit above that too. - Dammit 07:32, 5 May 2006 (UTC)

[edit] Shoot and Unlock

An Hollywood's favorite: a guy shoots at a lock with a pistol and the lock shatters. Would a good quality lock break apart by being shot at in real life?--JLdesAlpins 00:30, 5 May 2006 (UTC)

No. Bullets are extremely fragile and locks are extremely sturdy. In the 70s (if not earlier) Master Lock ran commercials where they shot locks and showed that they still remained locked. --Kainaw (talk) 00:40, 5 May 2006 (UTC)
OK. I Googled and found this site where they were able to shoot a lock off using a 12 guage slug. That is similar to using a .50 cal (which will go through a tank's armor). So, I wouldn't consider that a normal "shoot a lock and it comes off" scenario. --Kainaw (talk) 00:43, 5 May 2006 (UTC)
Nice find. – b_jonas 11:51, 6 May 2006 (UTC)
Does the lock really shatter, or perhaps the hasp does? User:Zoe|(talk) 03:02, 6 May 2006 (UTC)
It is nearly impossible to shoot the hasp off. It is a curved surface. Ignoring the impossible rare scenario where the tip of the bullet strikes perfectly into the extremely thin smooth front edge of the hasp - the bullet is going to turn and move off to the side with the easy-to-pass-through air and away from the hard-to-pass-through hasp. In the examples on the site that I found, the goal was to break the locking mechanism inside the lock. On that site they did mention that it is possible to slowly widdle away at the hasp by shooting it over and over all day long. --Kainaw (talk) 19:31, 6 May 2006 (UTC)
I really hope you mean whittle away at it. To widdle away at a lock means something entirely different. DJ Clayworth 19:26, 10 May 2006 (UTC)
Well, it isn't that far off... a rifle is commonly used as a phallic symbol and the method described would be spraying it randomly over a long period of time. --Kainaw (talk) 20:27, 10 May 2006 (UTC)

[edit] Oil Production/Reserves

I'm sure this information is available on some wiki site(s), but I've tried, and I'm finding it difficult to find the precise site(s) to look for.

I would like to find out the top 10 Oil producing countries, in terms of barrels of oil per day produced, as well as the top 10 countries according to their potential production, i.e. the top 10 countries with the highest amount of petroleum reserves whether exploited or not, within their territories.

Some other pieces of information I'd be interested in would be:

1) At the current rate of consumption, approximately how long would it take to completely exhaust oil reserves (i.e. there'd be nothing left to pump) in such oil rich states as Saudi Arabia, Iraq and Iran in particular, and other states in the Middle East in general;

2) The degree to which Canada exploits its oil reserves, in relation to the degree to which these Middle Eastern countries exploit their oil reserves. (For example, if Saudi Arabia has 100x in oil reserves, and produces 1x per year, it's exploiting 1% of its oil reserves per year). What percentage of Canada's oil reserves are exploited each year? Thanks for the help. Loomis51 01:16, 5 May 2006 (UTC)

We don't know to precision how much oil is really down there, and you can bet that Saudi Arabia wouldn't say the found values. They would exaggerate them considerably if they did. Template:OPEC should help as a list
v • d • e
Organization of the Petroleum Exporting Countries (OPEC)

Algeria • Indonesia • Iran • Iraq • Kuwait • Libya • Nigeria • Qatar • Saudi Arabia • United Arab Emirates • Venezuela

-- Mac Davis] ⌇☢ ญƛ. 04:25, 5 May 2006 (UTC)

This is a difficult issue, and there is not much consensus on it. See our article on petroleum - in short, oil reserves are not like giant vats which have a set quantity in them. The oil is scattered throughout rock layers, and mixed to varying degrees with other substances. Current thinking is along the lines that, for the forseeable future, oil will almost never run out, just become ever more expensive (both in terms of money and energy needed) to extract, until we reach a point (barring, or even with, further advances in technology) where the energy/money needed to extract the oil becomes greater than the energy/money which would be gained by using the oil, at which point it no longer becomes viable to extract it (see the article for details on some ideas). At which point this will happen is extremely difficult to predict, but what can be safely assumed is that oil prices will continue to rise as global demand is rising, supply is barely keeping up, and the costs of extraction are rising also.
For the same reason, you can't tell "how large potential oil reserves are", so I'm afraid all your questions (save for the one about current production, where MacDavis has already pointed you) are unanswerable. — QuantumEleven 06:41, 5 May 2006 (UTC)
Top 10 oil producing countries in terms of barrels per day - this is likely to be hard to find as most frequently oil is measured in terms of oil reserves still in the ground (which, assuming its even pubicly available, is usually massively overestimated as OPEC assigns its production quotas on the basis of stated reserves) rather than daily production which is quite variable, not constant and depends on a number of factors.
Your question 1) is probably irrelevant as the current rate of production won't remain stable over time. It varies a lot now depending on capacity, demand & OPEC limits (though there is evidence that OPEC is pushing at the limits of its productive capacity). Once we get to the global oil production peak we'll be able to produce less each year (on average) - but demand will be higher than supply so attempts will be made to expand production by investing in new infrastructure/exploration, etc. This may lead to increased production in the short term (reducing the time before it is 'all' extracted) but over the longer term wouldn't make any difference. Incidentally it isn't possible to extract all the oil in any particular field, I believe due to geology about 70% is the maximum that can be extracted. The Saudis are currently, reportedly, pumping water into their Ghawar field inorder to squeeze every last drop they can out of it but they'll never take all the oil out, just all the recoverable oil which is what the reserves are based on. Technological advances could in theory increase the recoverable reserves but this is unlikely as over the past 30+ years so much money has been invested in oil extraction technology that they've advanced the capabilities of the technology about as far as it can go.
On point 2 there are a few problems, 1 - oil reserves are hard figures to be accurate on, as Quantumeleven says, even where they aren't purposefully overestimated by governments or oil companies (as Shell did with its Nigerian reserves). 2 - How do you define oil reserves, or even oil. A lot of attention is being paid to the Athabasca Oil Sands (which together with oil shale is, I think, a large proportion of Canadas oil reserves) however extracting oil from this source requires a lot of gas to be expended in the extraction process in the first place (0.4 million cubic feet of gas to produce 1 barrel of oil) and is only viable if the oil price remains high. Also as we exhaust this resource it'll take more gas to produce the same amount from oil sands until the point where it noone will bother as there won't be any money in it (or gas is running short too). AllanHainey 07:55, 5 May 2006 (UTC)
You may want to read Oil_reserves#Canada which gives some info on Canadian oil reserves, & the rest of the page for other countries oil reserves. AllanHainey 08:11, 5 May 2006 (UTC)

Thanks to all of you, the subject is obviously even more complex than I had originally thought. Loomis51 01:00, 6 May 2006 (UTC)

[edit] Thermal burns and metabolic acidosis

Can anyone tell me what causes metabolic acidosis in burn victims? Is it caused by the loss of bicarbonate during third spacing? Is it caused by inhalation poisoning such as cyanide? Or is it caused by hypermetabolism? What is the doctor looking for when he/she orders an immediate Arterial Blood Gas in trauma/emerg? What is he/she monitoring for when he/she orders ABGs later on in ICU or acute care? Thank you for your time! Student nurse in a current heated discussion with fellow student nurse.

I have no idea at all, but maybe our article acidosis might help? --HappyCamper 02:54, 5 May 2006 (UTC)

I understand acidosis and how it happens but not in the pathophysiology related to thermal burns.

I'm just thinking off my head so please take this with a grain of salt...but when someone is an acute burn victim, does that mean they lose a lot of body fluids? And when that happens, doesn't that shift the some sort of equilibrium in the bloodstream involving water, carbon dioxide, and bicarbonate ions? And doesn't hyperventilation do something too? I somehow don't think cyanide is involved...perhaps carbon monoxide if anything...I imagine that burn victims would be exposed to more CO gas simply because of partial combustion...from your local uninformed Wikipedian...Wait a bit longer, I know there's at least one Wikipedian out that who could probably help you... --HappyCamper 04:06, 5 May 2006 (UTC)
Yes! yes! yes! All that and a little bit more... that's exactly what fluid shift or third spacing is and that is my educated opinion of what happens... the fluid shifts out of the vascular and takes the bicarbonate with it... my colleague insists it's because of SNS response and the loss of the skin's ability to insulate causing the hypothalamus to increase the metabolic system into overdrive or "hypermetabolism". While I agree this may be a possible additional additive to metabolic acidosis - I disagreed that it was the reason that ABG's are drawn immediately in ER. The third possibility is toxins inhaled during the burn incidient causing carbon monoxide toxicty. However, I have found little research anywhere to support any of these theories or even if it's a combination of them. Burnsurgery.com mentions unexplained acidosis may be due to toxicity but no where can I find it explained. --StudentNurse 10:51, 5 May 2006
Are we talking about acute burn victims just arriving at the hospital? Well, I suppose most things in science are a mixture of reasons. There might be something predominant which is important. What I'm thinking is something like
H+ + HCO3- <-> H2O + CO2
See, I'm not so sure whether fluid loss in itself would cause the blood to become more acidic. Think of it this way: you have some vinegar (we'll pretend that's the blood). Now, you pour a little bit down the sink. The vinegar left in the jar is still just as acidic as it was before. The concentration (not the absolute amount) of acid ions needs to change in order for the pH to change. But let's assume your scenario. Lots of fluid loss. Don't really know if this happens, but say the body goes into shock. Let's make it even worse. The burn wound is diseased, causing the body to go into septic shock. Does *this* cause the the production of less bicarbonate ions? If so, then the equilibrium will shift to the left, making the blood more acidic. Now, I imagine the victim starts to hyperventilate to compensate. Breathing causes the CO2 on the right side of the equation to go away, shifting the equilibrium back. I would imagine this mechanism to be part of the sympathetic nervous system. I certainly don't want to be conscious of how I need to breathe in order to regulate my blood pH! Now, as for the Arterial Blood Gas stuff. My *guess* is that it is standard routine for acute burn victims - the rationale being "let's find out how our patient is doing so we can treat the appropriately". Maybe there are IV drugs you can add to help with the acidosis or something? When the patient is in an intensive care unit, I would hope that whatever medical intervention helped bring the blood pH back to normal. If it's not normal, then additional things need to be done (and thank goodness there are people who study this!) That's my guess. So yes, it's quite possible to see that both your friend and your perspective can be go together hand in hand. But you know, I think you're right to pinpoint the bicarbonate ions first. There isn't a reason for the hypothalamus to kick in unless something fundamental in the biochemistry changes. But, I'm a rather uninformed Wikipedian - and my bias is towards the chemistry, rather than the biology :o) Cheers! --HappyCamper 14:42, 5 May 2006 (UTC)
If you're still wondering: Its like any major injury, just more major: Burns leads to hypovolemia (intravascular fluid loss), leads to shock, leads to cellular hypoxia, leads to acidosis. Acidosis: related to extent of injury and duration. Recovery from acidosis indication of effective treatment. Pulmonary injury: due to burns upper airways and toxic gases lower down. Inability to breathe adequately and development of acute respiratory distress syndrome. Toxicity: HCN blocks aerobic cellular respiration, in the presence of normal oxygen tensions. CO causes inadequate oxygen delivery in presence of normal oxygen tensions and adequate hemoglobin. Both can cause acidosis, but cannot be diagnosed by routine ABGs (for CO: unless HbCO is routinely done). Later on (5 days+) hypermetabolism can caused increase CO2 production and respiratory failure (respiratory acidosis, not metabolic) if muscles are exhausted. Sepsis also a later cause for shock and metabolic acidosis. Acidosis as such, if severe, causes dysfunction of all the vital organs. --Seejyb 19:50, 7 May 2006 (UTC)

[edit] Second law of thermodynamics

we have seen each law has some or other exxeptions or failure so is there any thing in this world that does not follow 2nd law of thermodynamics. If any body elaborate on this i will be very thank full

sujay

The assumption that "every law has an exception" is not a good starting place for logical reasoning. As far as we know, everything follows the second law of thermodynamics. —Keenan Pepper 03:52, 5 May 2006 (UTC)
Well, even the second law doesn't describe quite everything. See the fluctuation theorem. It is absolutely beautiful. But read very carefully what it is really saying though. --HappyCamper 03:59, 5 May 2006 (UTC)
Don't listen to them. Wikipedia is lying here. It is possible to circumvent the second law of thermodynamics and gain energy from the vacuum. Someone even tried it, but they are silenced by the governments controlled by the global oil maffia, and the academic bigheads who don't like to be proved wrong didn't even allowed them to publish eir thesis. Now ey's alone and chased anywhere around the world and without material support he cannot build eir dream machine that would make infinite energy for free and change the whole world. :) – b_jonas 11:41, 6 May 2006 (UTC)
Myes, it worries me, there are people gullible enough to believe that. Mabye you should make it more clear you are being insincere Philc TECI 22:37, 8 May 2006 (UTC)
You can't hear it, but I'm giggling on the inside =) --mboverload 01:02, 12 May 2006 (UTC)
Sujay, the second law arises from probability and statistics. Take for example the reason why you can't get heat conduction going from a cold object to a hot one. Heat conduction happens by molecules transferring energy when they collide. Now you will get some of these collisions between molecules transferring energy from the cold object to the hot object, but you will get more of them transferring heat from the hot object to the cold one because for each collision that is the more likely outcome. If we're talking about hot and cold objects which are the size of everyday things, they will contain such a huge number of molecules that statistically you can be 99.99999999999...etc...% certain that the heat will go from the hot to the cold, even if you could in principle get an exception where it goes the other way. Arbitrary username 15:28, 6 May 2006 (UTC)
Exactly. It's hard to define what an exception to this law would be, because it states that matter tends to become more disordered. Of course, sometimes entropy decreases, but only on an extremely micro scale, and only completely randomly. But the law holds up extremely well: on any reasonable scale, for any reasonable amount of time, it always requires work to decrease disorder. --Leapfrog314 03:45, 12 May 2006 (UTC)
Well, keep in mind the actual premises of the Second law of thermodynamics: it strictly applies

only to an isolated system (i.e., one that exchanges neither mass nor energy with its surroundings). It is my understanding that the law is true without exceptions within that context. All examples given above (statistical collisions of molecules and local decrease in entropy) assume exchanges of mass or energy, so they are not examples of the application of the law, nor do they provide 'exceptions'. --Michel M Verstraete 20:44, 12 May 2006 (UTC)

[edit] Eating "Instant Krazy Glue"

Today, I accidentally got half a drop of super glue on my thumb and index finger, but fortunately pulled the fingers apart before the glue dried. I have the bad habit of biting pieces of skin off my fingers and then swallowing them, so that's what I did to the fingers which had a layer of dried glue on them.

I think I ate around 0.02 mL of Instant Krazy Glue. After biting my fingers, I noticed this message on the glue container: "If swallowed, contact a Poison Control Centre or doctor immediately. Do not induce vomiting." I have two questions:

  1. What are the symptoms of swallowing large amounts of Instant Krazy Glue?
  2. Is swallowing 0.02 mL enough to cause noticeable effects? I would think not, unless the glue is a very strong poison (which I really don't think is the case). --Bowlhover 03:59, 5 May 2006 (UTC)
I think the Poison Control Centre (you know, the one that the label told you to call) would be able to answer you. - Nunh-huh 04:20, 5 May 2006 (UTC)
No, no harm has been done to you, don't worry. Cyanoacrylate (super glue) was even used by medics in the Vietnam war to glue wounds shut. -- Mac Davis] ⌇☢ ญƛ. 04:25, 5 May 2006 (UTC)
grr edit conflict.. Nope you are fine. I don't know what is in it and the website is completely useless, but a good rule of thumb is if kids can use it without adult supervision, it's not going to hurt. Sifaka talk 04:21, 5 May 2006 (UTC)
lol, I was just edit conflicted right before you. -- Mac Davis] ⌇☢ ญƛ. 04:31, 5 May 2006 (UTC)

Thanks everyone! --Bowlhover 02:36, 6 May 2006 (UTC)

[edit] pentium lga

what is lga stands for in pentium IV 2,66lga ???

Land Grid Array. -- Mac Davis] ⌇☢ ญƛ. 04:29, 5 May 2006 (UTC)

[edit] Is everything bendy?

For all of the materials we now know about, do all of them have some degree of 'bendy-ness'? (bendability?)

If we have a diamond a mile long, could we measure the amount we could bend it and the force needed to do so? --Kickstart70-T-C 06:18, 5 May 2006 (UTC)

Well, you can predict the amount of force at home! It would involve the shear modulus, which is finite even for diamond; the details depend on how far you bend it and the cross-sectional area. You can find the data here, if not on Wikipedia somewhere I haven't looked.
In other news, Shear modulus could use a table of typical values, if anyone's interested... Melchoir 06:23, 5 May 2006 (UTC)
Done! Isopropyl 07:07, 5 May 2006 (UTC)
.....I ... I am all-powerful! Behold my works, ye mighty, and despair!
(I mean, thanks) Melchoir 07:18, 5 May 2006 (UTC)

Thanks to both of you, much appreciated! --Kickstart70-T-C 16:33, 5 May 2006 (UTC)

Perfect rigidity is a violation of special relativity. It is no more possible to have perfectly rigid body than it is to travel faster than light. Therefore, yes, all materials are bendy. -lethe talk + 01:46, 6 May 2006 (UTC)

[edit] Mouse Trap cars

Does anybody know the best technique used to making a car from a mouse trap? there are heaps of websites on this topic but all are just trying to sell mouse trap car kits. so if anyone knows how to make one or if they know any good websites it would be very much apprecaited.

Thank you

Try here (simple model) or here (more advanced model). Gandalf61 09:27, 5 May 2006 (UTC)
Are you going for speed or distance? If it is distance, the ones that use the moustrap spring to wind up a clock spring tend to go the farthest at a very slow speed. --Kainaw (talk) 20:44, 5 May 2006 (UTC)

[edit] internet definition please

hello may i know the definition of internet and world wide web and their uses

thank you

See internet and world wide web. Dismas|(talk) 08:53, 5 May 2006 (UTC)
(darn you for getting there faster, Dismas! :)) The World Wide Web is one part of the Internet. We have excellent articles on both: Internet and World Wide Web. If you have any questions after reading the articles, you can come back here. — QuantumEleven 09:04, 5 May 2006 (UTC)

[edit] Menstrual cycles and the possibility of conception.

If my girlfriend and I had unprotected sex on the evening of March 6th/morning of March 7th, and her cycle started March 4th and apparently ended March 6th, is it possible that the aforementioned unprotected sex resulted in conception?

-Thanks, Jared

Less likely but certainly possible. See fertility awareness.-gadfium 09:30, 5 May 2006 (UTC)
If it did result in conception, and unless there were an early miscarriage, she would be in about her ninth week, and an over-the-counter pregnancy test would tell you for sure. --Ginkgo100 23:15, 5 May 2006 (UTC)

[edit] speed of light

what happens if one travels at the speed of light? I know its impossible but i want to know

You might find Faster-than-light of interest as well as special relativity. Dismas|(talk) 10:13, 5 May 2006 (UTC)
(Grr!!! Edit conflict!!!!) Your mass will keep increasing until it becomes infinity when you reach the speed of light. And you would stop moving because you would need infinite amount of energy to keep you at that speed. . But in short, we dont know what will happen because noone has ever travelled at the speed of light. I'd suggest you to read [this as it answers your question to a certain extent. Check back if you have anymore doubts. Jayant,17 Years,India • contribs 10:18, 5 May 2006 (UTC)
I'll modify an answer I gave at Talk:Speed of light. First of all, yes, it's impossible. That said, if you do accelerate to the speed of light, in your own reference frame, the very same instant you achieve that speed you will simultaneously slam into your ultimate destination, no matter how far away it is. If you like, this result is time dilation in the extreme; for every second that passes in someone else's reference frame, you experience 0 seconds. Since you can't pass time while cruising at the speed of light, you can't perform experiments or make observations, so in some sense, nothing happens. Melchoir 10:25, 5 May 2006 (UTC)
Pardon my ignorance/scepticism, Melchoir, but if it's impossible then ... it's impossible (even for all-powerful beings such as yourself). You could accelerate as arbitrarily close to the speed of light as you like, but you could never reach it. Therefore there would never be such an instant as you describe. Unless it wasn't really impossible after all. This sounds a bit like "You can never count to infinity, but if you could, the number would be <xxx>." JackofOz 10:51, 5 May 2006 (UTC)
You're right of course, but with some effort I could probably defend my interpretation. As in, draw a smooth, mostly timelike world line with a lightlike section included, parametrize it by proper time, and interpret that as someone's history of experiences. Sure, there are continuity problems, and it's kinematically forbidden for a massive particle to actually follow the path. But if you interpret the math liberally, what I said makes some kind of sense. Melchoir 11:04, 5 May 2006 (UTC)
Thank you. I would continue this Friday night frivolity, but I think it's kinematically forbidden. :--) JackofOz 11:14, 5 May 2006 (UTC)
I think it's perfectly reasonable to take your description of travelling along a lightlike path as simply what it's "like to be" a photon or other massless particle. I know some people don't like ascribing imaginary experiences to non-conscious POVs (to the point that many Wikipedia articles are less clear than they could be to avoid the issue), but I personally have less trouble imagining the perspective of something that cannot possibly be sentient than swallowing local portions of globally forbidden worldlines and what have you. --Bth 11:25, 5 May 2006 (UTC)
I think the best way to understand Melchoir's comments is as a limit. The correct description of what happens as you increase your speed becomes arbitrarily close to what Melchoir describes. The length of proper time to reach your destination becomes arbitrarily small, etc. -lethe talk + 01:44, 6 May 2006 (UTC)
See I am driving my car at the speed of light and I turn on my headlights. What do I see? and other questions from the Usenet Physics FAQ. – b_jonas 10:29, 5 May 2006 (UTC)
To be pedantic, it is possible to travel faster than the speed of light, just not in a vacuum. This is usually where someone brings up Cherenkov radiation. GeeJo (t)⁄(c) • 11:05, 5 May 2006 (UTC)
That confuses some people, though, due to the conflicting meanings of the speed of light. It isn't possible to travel faster than 186,000 mph (c, the speed of light in a vacuum), but it is possible to travel faster than the speed at which light travels through some materials. Even then, you might say that the "light" (photons) doesn't really travel any slower. - user:rasd
Yes, the Physics FAQ talks about whether Faster Than Light Travel or Communication Possible, but it seems that wasn't what the original question was. (Faster than light travel is impossible only because whenever anyone finds a way to do it, physicians redefine "faster than light" not to include that.) – b_jonas 10:58, 6 May 2006 (UTC)
No, it's just that all the 'exceptions' that get mentioned are pretty much useless. Sure, a shadow can "move" faster than light, but what's the point of something that can't pilot a ship across intergalactic space? Black Carrot 21:36, 12 May 2006 (UTC)

[edit] manufacture of lighting fittings

I would like to know how lighting fittings are manufactured. The process involved from sourcing the materials used to the final product. i would be grateful if the information could be broken down to specific lighting fittings. Also the what are the references of regular bulbs to low energy ones.

Incandescent light bulb Andrewjuren(talk) 08:58, 6 May 2006 (UTC)

[edit] Reflection

Why cant a plane mirror and a highly polished white surface produce reflection of the same kind?

Well, a white, shiny car is white. It has been painted white, and so it is only natural, indeed demanded, that it's most dominating reflection is white. This is because of pigments that WILL suck up light on certain frequencies, and reflect light on other frequencies. Thus, seeing yourself in the mirror image on a white car hood, you see yourself in shades of white, because all other colours are absorbed. A plane mirror is not coated with such pigments, unless artificially added, and reflects nearly all frequencies. I think most plane mirrors, when cleaned very well, can produce as much as 70-85% reflection. Thus, plane mirrors DO suck up some light, you just don't see it very well. 213.161.189.107 13:08, 5 May 2006 (UTC) Henning
Er, white light is made up of all (visible) frequencies ...
The difference between a mirror and a general white surface is smoothness. A smooth surface like a mirror will give specular reflection, but light hitting a rough surface will be scattered at different angles depending on which particular little part of the surface it hits -- diffuse reflection. --Bth 13:55, 5 May 2006 (UTC)
So basically, a highly polished white surface will no longer be white; it will reflect like a mirror if you polish away all the surface roughness. Neh? Skittle 16:26, 5 May 2006 (UTC)
I would think so. As long as it was highly polished. --Bth 17:50, 5 May 2006 (UTC)
If you ask someone what color a mirror is, don't they say "silver"? So, I think a highly polished silver car would have the effect of a mirror. --Kainaw (talk) 19:56, 5 May 2006 (UTC)
No, a white surface will never become a mirror no matter how long you polish it. The difference is that a shiny white surface has a transparent coating and then a microscopically rough white surface underneath. Some of the light reflects off the outer surface, forming the reflection, but most of the light passes through the transparent layer, is scattered off the white surface, and passes back out in a random direction. In a mirror, both outer and inner surfaces are microscopically smooth, so they both produce reflections. —Keenan Pepper 01:00, 6 May 2006 (UTC)
Yeah, I've always thought of mirrors as silver, and shiny silverness as mirror-like. Any color material can be made reflective, by reducing scattering of the light (polishing it), but anything reflected in it would appear really red/blue/whatever, like looking through a color filter. What exactly is the color silver, in terms of the additive spectrum? Black Carrot 22:19, 5 May 2006 (UTC)
A reflective red surface would look red (or "metallic red"), a reflective blue surface would look blue (or "metallic blue"), and a reflective white surface would look silver (or "metallic white"). True silver color is the same as white, as I understand; the difference is the degree of reflectiveness. --Ginkgo100 23:18, 5 May 2006 (UTC)
Silver is simply reflective/metallic gray. —Keenan Pepper 01:01, 6 May 2006 (UTC)

[edit] Butterflys

Last night (may 4th), I was in a play. Right before I heard my cue line I was feeling really nervous. I also had some "butterflys" in my stomach. What I was wondering was what are these called (the butterflys) and why do they feel like that. I already looked at the article anxiety but to no avail. I was just curious. THanks. schyler 11:53, 5 May 2006 (UTC)

I learned a new word today: Glossophobia --Zeizmic 11:56, 5 May 2006 (UTC)

While I also learned a new word, it didn't really answer my real question. What is the name for the butterflys, not the name that butterflys is a symptom of. Thanks though. schyler 12:16, 5 May 2006 (UTC)

It seems that butterflies (pedantic note: remember -y pluralises to -ies in most cases) is what it's called. Certainly, our Butterflies in the stomach article doesn't give an official name and even a rather worthy article on thePhysiology of the Stress Response doesn't use any other term (it explains it as a reduction of activity in the digestive system as a response to stress, if you're interested; on the other hand, this article claims it's the result of a second brain in the stomach. We report, you decide.) --Bth 12:34, 5 May 2006 (UTC)
Your stomach (and esophagus, small intestine, and colon) contains brain tissue. It functions like a normal brain, just small in comparison to the brain in your head. When you have a sudden fear, the brain in your head releases hormones to prepare the body to fight or flee. The sensors in the lower brain pick those up and charge up for action. The charging and discharging of all those sensors is what the brain in your head is picking up as butterflies. --Kainaw (talk) 12:53, 5 May 2006 (UTC)
Ahhhh, I made the mistake of skimming the top of that article and thinking it was a joke. (I still think it's a misleading use of "brain"; by that standard the spinal cord is a brain too.) --Bth 13:48, 5 May 2006 (UTC)
The spinal cord is not capable of making decisions and controlling parts of the body on its own. The brain tissue in the abdomen is. That is how a person with a completely severed spine is still able to have a functioning digestive system without input from the brain through nerves. Of course, the hormone communication between the brain and the rest of the body continues to function - but going in to that is just too technical for the question a bout butterflies. --Kainaw (talk) 14:27, 5 May 2006 (UTC)
D'you know, it'd never even occurred to me to think that there might be a problem with digestion for spinal cord patients -- very interesting.
But what about the other two parts of the autonomic nervous system -- the sympathetic and parasympathetic, both of which are based in the spinal cord? And of course reflex actions are responses to stimuli that don't involve the brain at all. --Bth 14:41, 5 May 2006 (UTC)
Automatic and reflex actions are controlled in the brain stem. You could argue that the brain stem is the top of the spinal cord. You could say it is the bottom of the brain. Either way, it is completely different in structure than the spinal cord. --Kainaw (talk) 14:55, 5 May 2006 (UTC)
Reflex arc claims "A reflex to a stimulus is almost simultaneous, as the reflex arc doesn't involve the brain at all." Does it need correcting? --Bth 16:03, 5 May 2006 (UTC)
That is the difference between a brain stem reflex (ie: burning your elbow and jerking your arm - which most reflexes are) and a reflex arc. There are many reflex arcs in the body and they do not all go through the spinal cord. For example, loud noise causes an acoustic reflex arc in the eardrum which constricts the stapedius muscle. A hiccup is a reflex arc but I don't remember the exact nerve that triggers the diaphram to contract. Regardless, it is a reflex arc. But, reflex arcs are controlled by neurons. They are hard-wired connections from a receptor (usually a nerve) to a reactor (usually a muscle). Trigger the nerve and the muscle contracts. So, because the spinal cord is a conduit for nerves, some of which traffic reflex arcs, does not put it anywhere near the classification of neuron formations in the digestive tract or brain. --Kainaw (talk) 17:01, 5 May 2006 (UTC)

Since I was dissed, I have to go back to the original question. I looked up stage fright and that led me to that fancy name. I always thought that butterflys (ies?) was the only symptom. What we have found out is that there is no Latin name for 'butterflys' alone, except 'weird reaction by your second brain - itis'. (Geez, I feel like ol' Noti!) --Zeizmic 17:35, 5 May 2006 (UTC)

Welcome to my world. I am a computer programmer working in a building full of doctors. I mention that I have a bump on my finger - a wart to any normal person. They spit out a bunch of weird latin words. Also, they ask for data reports on things like "hypercholesterolemia". What's that? High cholesterol to any normal person. If it wasn't for wikipedia, I'd never get by when asked for things like "nephropathy" or "gfr scores". On the flip-side, I got a shipment of 12 optical mice in. I sent out an email asking which doctors didn't have an optical mouse so they could be replaced. Most responded asking what an optical mouse is. --Kainaw (talk) 18:03, 5 May 2006 (UTC)

English not providing you with all the features you need? Don't dispair make it up. If you want a pseudo-Latinate word for that squirty feeling, try combining some of these funky elements:

lepidopter- : butterflies, moths duoden-, abdomino-, ventro-, ileum : various gutty bits

Unfortunately most of these are suffixes but I quite like ventrolepidopter and I would tell people about them if I did not have them. Bonus word of the day borborygamiphobia, fear that someone will hear your stomach rumbling. MeltBanana 16:05, 6 May 2006 (UTC)

[edit] Nuclear bombs in phase

I heard a nuclear bomb has an energy efficiency of about 3%. Would this be increased if we divided the bomb's mass over on ten (or hundred) smaller, identical bombs, and set them off so that the blast waves were in phase upon hitting the target? For some reason I don't think that's what energy efficiency truly means, so does anyone have a better word for what is actually increasing? Scientifically correct, that is. "Blast effect" sounds a bit too... Star Trekish, but if that's the word, I'll go along with it. I just need to use correct terms. Thanks! 213.161.189.107 13:31, 5 May 2006 (UTC) Hen

I think most people tend to quote payloads when talking about nuclear weapons. Isopropyl 13:56, 5 May 2006 (UTC)
I don't think it would be possible to make these mini bombs. There's a critical mass which needs to be taken into account I think. --HappyCamper 14:44, 5 May 2006 (UTC)
Don't nuclear warheads already consist of several mini-warheads that spread out - each one capable of hitting a separate target or surrounding and increasing damage on a single target? --Kainaw (talk) 14:57, 5 May 2006 (UTC)
MIRVs are one particular arrangement, whereby a missile has multiple warheads inside of it. --Fastfission 15:29, 5 May 2006 (UTC)
What you are basically arguing for is instead of having one 20 kt bomb, to instead have two hunded one ton bombs. That's obviously possible but completely defeats the entire purpose of nuclear weapons, which concentrate a large amount of energy in a very small amount of space (relatively speaking). There are, though, arrangements (again, see MIRV) where you can distribute the yields at bit — ten 300 kt bombs can do a lot more damage than one 3 Mt bomb, if they are arranged so that the borders of their blast zones are touching. See effects of nuclear explosions for more information about how increased yield results in much less damage efficiency because you are essentially increasing the volume of a very large sphere, rather than spreading out the damage along a single plane, if that makes sense. --Fastfission 15:29, 5 May 2006 (UTC)
In any case, nuclear weapons are more than destructive enough, "inefficient" or not. Extra destructive efficiency is hardly a priority; in fact, existing weapons, even, say, a 1 kiloton jobby that a first-time nuclear proliferator could construct out of reactor plutonium, are effectively too destructive to be of any use other than deterring other people from using nuclear weapons on you (or as a terrorist weapon).
What *would* be militarily useful would be a nuclear bomb that weighed 25kg, had the explosive potential of 10 or 100 tons of chemical explosive, didn't produce fallout, and whose lethal prompt radiation dose didn't extend beyond the blast radius (so everybody who would die from radiation effects is instead killed instantly by the blast). Thankfully, such a weapon doesn't appear to be possible, because the temptation to use it would be so strong I don't imagine the country that perfected the device would have been able to resist using it in their next conflict. --Robert Merkel 22:04, 7 May 2006 (UTC)
To address the "energy efficiency" question, that's something completely different than what you're asking about--it's not a question of what percentage of energy released is absorbed by the target, but rather what percentage of the theoretically possible yield is actually generated.
Nuclear weapons consist of a quantity of fissile material. You can mathematically calculate the energy which would be released if every single atom of the material underwent fission; but the actual energy released by a weapon is quite a bit less. It seems that the issue is that you have to have a minimum amount of material (the "critical mass") together to make an explosion, so a weapon has that much material, but normally kept in a configuration where it doesn't detonate--multiple pieces, or a hollow sphere, or something like that. When the weapon is set off, it pushes everything together so that a chain reaction becomes sustainable--but the energy of the explosion itself blows the material apart before the chain reaction is complete, and a significant portion of the material does not undergo fission.
In any case, it seems that the 3% figure you heard is too low for most weapons. The nuclear weapon article states "The efficiency of a fission weapon is the fraction of the fissile material that actually fissions. The maximum is ca. 25%. For Fat Man it was 14%, for Little Boy only 1.4%." Chuck 18:56, 8 May 2006 (UTC)

[edit] Extrusion of Polycarbonate

If polycarbonate is not dried before it is extruded, will the mechanical properties such as impact strength be degraded as it goes through the extrusion process. If so how large is this effect and would it be more cost effective to dry the material and extrude it or just extrude it without drying.

[edit] Censorware

The computers at my school (OS 9 iMacs) have all their internet traffic filtered at the server, so I need a method to bypass the filters? Basically, what I think I need is a proxy that does data encryption. Any suggestions?--Frenchman113 on wheels! 18:52, 5 May 2006 (UTC)

Certain sites are censored for a reason. --Chris 19:22, 5 May 2006 (UTC)
Yes, but sometimes you need to research marijuana for a reason. Is anyone gonna help or not?--Frenchman113 on wheels! 20:10, 5 May 2006 (UTC)
Do your homework and find a proxy. I've used "home13" in the past.Here7ic 20:45, 5 May 2006 (UTC)
Well, if you're really looking for marijuana info and not pr0n, you could try searching for it on Google, then clicking the cached link. That's always bypassed the blocks at my school. It doesn't give pictures, though, just text, with your search terms highlighted. Alternately, you could use [17], a proxy a friend of mine made that works reasonably well for most things. Black Carrot 21:42, 5 May 2006 (UTC)
"Certain sites are censored for a reason."
So this automatically makes it a good reason? --Bowlhover 04:33, 6 May 2006 (UTC)
Not necessarily, but it can be argued that since 1) the school is paying for the connection, and 2) it has intended it for (what it defines as) educational use, it has the right to filter content. This doesn't stop the user in question going elsewhere to access the sites s/he wants to access - at home, or in an internet cafe. — QuantumEleven 09:31, 6 May 2006 (UTC)
Why don't you talk to the school IT person? If you need to get past some filter and have a good reason, then they should be able to assist you. Otherwise, bypassing the firewall would be something that could get you into a whole heap of trouble (not just inappropriate content, but malware could slip by.) Andrewjuren(talk) 09:38, 6 May 2006 (UTC)
Well... because I'm looking for pr0n? Just kidding, I never thought of that.--Frenchman113 on wheels! 12:17, 6 May 2006 (UTC)
Sure you didn't. Did my suggestions work? If they did, and if you do decide to follow your instincts, I know another trick that might help: the Google image search is, as far as I know, pretty difficult to block. It is actually possible, in my school, to view thumbnails of hardcore porn, but not to look up the Nazi party (a real third party in America) for my AP Government report, without using a proxy. Black Carrot 16:15, 6 May 2006 (UTC)
BTW- Don't forget to set the image filter to "off". It's right below the search bar. Black Carrot 16:27, 6 May 2006 (UTC)
Personage: If you need to research mary jane, use Wikipedia, because we know almost everything about almost everything. And tell your friends to not vandalize it so you don't get banned from editing it at your school. Cernen Xanthine Katrena 14:02, 7 May 2006 (UTC)
  • If the school's censorware makes researching your homework impossible, maybe it's time to talk to the teacher who gave you that homework and have her talk to the school's IT personnel. You could also try researching using books. That would avoid all the internet censor stuff. - Mgm|(talk) 14:59, 7 May 2006 (UTC)
Argh, it's keyword based filtering! proxies aren't working on it!--Frenchman113 on wheels! 20:48, 9 May 2006 (UTC)

[edit] Water flow

I need to get a water flow of 100 liters/minute through a 12.5 mm nozzle. I will be pumping this from a 200 gallon tank at floor height through a short length of standard garden hose and out through the nozzle. I must pump this volume for a period of three minutes. I am trying to figure out what to use as a pump. I tried a standard sump pump that advertised a flow rate of 8600 gallons per hour but found my flow rate out the nozzle well short of the requirement I must meet. Do you have any suggestions? --12.19.235.34 18:58, 5 May 2006 (UTC)

When you're moving current no matter if its water or electricity, if you squeeze a large amount of it together then open it up in the direction it is going,it boosts the current. If you use a wider hose than a standard garden hose, more water will be putting pressure on your nozzle. This will increase the water pressure that is exiting your nozzle because the water has more space to move. Think of it as popping a paper bag. When you fill the bag with air it all wants out because there is too much pressure so it blows a hole in the bag. Your nozzle will act like the hole and release all the pressure. If that doesn't work you might need to consider a bigger nozzle.

Because you are looking for a short duration, you can go with a cheaper pump and a more expensive (sealed) tank. Pressurize the tank and then release the pressure through the nozzle. Then, it doesn't matter how fast the pressurizer pumps. The drawback is that you'll get a rather short period of steady pressure that dies off quickly. All in all, it is just like those super-soaker water guns. --Kainaw (talk) 19:37, 5 May 2006 (UTC)

I'm pretty sure you are talking fire-hose volumes here. Your sump pump could only do 2 gal/m or 8 L/m. City pressure at 40 psi might only get 12 L/m through a standard hose. You want another order of magnitude more than that. --Zeizmic 20:37, 5 May 2006 (UTC)

Pump are designed to deliver either a large volume of water at low pressure, a small volume of water at high pressure or some trade-off in between. When you purchase a pump it will often have a small table listing how many gallons per minute it will deliver at a certain pressure. You can estimate the pressure required at the nozzle to give you the required flow rate using the firefighters formula: gallons per minute = 29.7 x diameter in inches squared x square root of the pressure in pounds per square inch.

So you need around 14psi at the nozzle to flow 26.4gpm. That is if you are using a tapered smooth bore nozzle--if you are pumping directly out of a 1/2in pipe the pressure required will be slightly higher. You also need to take into account your "short length of standard garden hose". Trying to move 26.4gpm through a full 3/4in inside diameter hose you will have about 60psi friction loss per 100 feet of length[18]. Standard 3/4in or 5/8in garden hose will be even worse. You will need a pretty large centrifugal pump to push that amount of water through any length of small diameter hose like that. (Forgive all the non-metric units, i'm too lazy to convert them.) EricR 01:18, 6 May 2006 (UTC)

[edit] Electrical Grounding

I was wondering how it could be that a pole in the ground serves to conduct electricity to 'earth'. I mean, the concrete or soil or whatever it is that the pole is inserted into, isn't going to be electrically conductive is it? If I rectified mains electricity, and connected the negative terminal to a pole in concrete, wouldn't the pole just fill with enough electrons to eventually stop the current? --Username132 (talk) 19:49, 5 May 2006 (UTC)

You are correct. Just any old ground won't work. In 29 Palms CA, Kuwait, and Turkey, we had a hell of a time keeping ground grounded. We had to keep pouring water on it. In Turkey (since there were only 3 guys deployed), we made the ground post our pee hole. Water helps move electrons to the ground rod and keep a good supply of them ready for usage. --Kainaw (talk) 19:53, 5 May 2006 (UTC)
There's also some discussion at Ground (electricity), although it lacks the amusing anecdotes. Melchoir 20:37, 5 May 2006 (UTC)
Depending on the use, 'grounds' or poles in the ground, whatever you like to call them, are usually attached to the water piping that supplies the building which I think is copper, and anyway, grounds are generally their to serve as a better conductor than the alternative, eg you or furniture, therefore preventing fires, there use is not really to complete a circuit. Plugs generally have three prongs, the live, neutral and ground, the live and the neutral are the circuit, the ground is used if the appliance has a meatl outer casing, if through faulty wiring etc. this casing becomes live the ground/earth wire is a better conductor than you, so that should you touch the appliance you wont become the unlucky link to the earth. So however poor conductors the grounds are, as long as their better than the alternative, it doesn't matter. Philc T+C 21:47, 5 May 2006 (UTC)
And hopefully as soon as the live touches the earthed casing, it should trip the fuse or circuit breaker anyway. Typically this will require the earthing to take a number of amps, but if you have an RCD breaker then even a few tens of milliamps to earth should trip the breaker. Arbitrary username 18:23, 6 May 2006 (UTC)

[edit] Wikipedia on DVD-RW

How possible would it be to have wikipedia on a DVD-RW that was able to update itself when put into a DVD-RW drive on a computer with internet access? How long would it take to make such a thing happen if you knew how to program? When can I expect to see self-updating Wikipedia on DVD-RW? --Username132 (talk) 20:31, 5 May 2006 (UTC)

On a DVD-RW would technically be possible, but not advisable given the limited amount of times it can be rewritten. But if you really wanted it'd be a pretty easy task. In fact, it might be possible with hardly programming anything since the sourcecode to wikimedia is available and so is the database which holds the articles. Basically you could run a webserver with php support and a database engine from the DVD-RW and you're done. - Dammit 20:52, 5 May 2006 (UTC)
Note that, depending on what you want on your DVD, the amount of content on Wikipedia may be too big to fit on one disk. For instance, including all the images is an extra 76GB. Read all about it at Wikipedia:Database download. — QuantumEleven 09:27, 6 May 2006 (UTC)

[edit] Time consistancy theory??

What is the name of the space-time theory where all three time-periods (Past, Present, and Future) are all occuring at the same time? That is to say, as I sit typing this, I also sit thinking it up, and sit drinking my coke after submitting. Thanks! Here7ic 20:41, 5 May 2006 (UTC)

Well I don't suppose you're talking about Multiple World? If so, that wouldn't really be a fitting description. But then again it really doesn't sound like MW. I'll be waiting for a better answer, this sounds interesting. :)
I doubt there's a scientific answer. God is often said to exist outside of time, so a deity might experience all times at once. In the philosophy of space and time, an idea that resembles your question is called eternalism. See this and its subarticles for more. Melchoir 21:43, 5 May 2006 (UTC)
This is the Everett many-worlds_interpretation, or consciousness causes collapse that you are looking for, or maybe the Copenhagen interpretation. -- Mac Davis] ⌇☢ ญƛ. 00:38, 6 May 2006 (UTC)
You're definitely thinking of Time Cube. —Keenan Pepper 00:44, 6 May 2006 (UTC)
Ah, the time cube... Isopropyl 15:36, 6 May 2006 (UTC)
In special relativity, the time-ordering of events can depend on the reference frame that you're in, for events which occur far enough apart in space that you would have to travel faster than light to get from one to the other (known as a "space-like" interval). But the three events you describe are all in the same place (separated by "time-like" intervals), so the time-ordering is the same in all reference frames, and anything that says otherwise is probably sci-fi. See special relativity#Causality. Arbitrary username 15:43, 6 May 2006 (UTC)
I don't know if this is what you're getting at, but in a near-death experience, the past and present may become a single landscape of events. —Pengo 05:10, 10 May 2006 (UTC)

[edit] Nucleus and cytoplasm

This is probably a very simple question, but it occurred to me while doing some reading today. We know that one can remove the nucleus from one cell and replace the nucleus in another cell (somatic cell nuclear transfer) and it will (if you are lucky) develop normally. Does this work if the two cells are from different species? I imagine it would not work between animals and plants since their cells contain different organelles, but what about animals with high degrees of relatedness (i.e. a chimpanzee and a human)? Has anything like this been attempted (I assume not with humans, of course, but dog/wolf wouldn't surprise me if it had)? If not, should it work? --Fastfission 22:36, 5 May 2006 (UTC)

Note the last sentence in the somatic cell nuclear transfer article: "Not all of the donor cell's genetic information is transferred. DNA of organelles (mostly mitochondria) is left behind, with the resulting cells retaining those structures which originally belonged to the egg." I think this would be the main factor that determines if it will work cross species, the mitochondrial DNA would have to be compatible for it to be possible. I'm not a biologist though, so it's only a guess. - Dammit 23:57, 5 May 2006 (UTC)
That's a good question. I suspect not, but for very closely related species I can't be absolutely certain. I'll also note that SCNT is extremely traumatic for cells even when you're working in the same species.
Note that if it did work, the effect would 'wear off' as the host cell would start synthesizing proteins as specified by the transplanted nucleus. After a cell division or two you'd be hard-pressed to find any trace of the original host; all of the proteins present would be those specified by the transplanted nucleus' DNA.
The exception would be in the mitochondria, as mitochondria have their own DNA that's replicated and handled separately from the genomic DNA in the nucleus. In principle I suppose that you could have a human cell with chimpanzee mitochondria, say. To achieve that end result, it might be easier to transfer mitochondria than to swap nuclei, however. TenOfAllTrades(talk) 00:06, 6 May 2006 (UTC)
That's an interesting thought about it. I was reading about theories of cytoplasmic inheritance (which is surprisingly red-linked) which is what got me thinking about this. --Fastfission 00:36, 6 May 2006 (UTC)
It does work and it is already being experimented with to see if it can be a viable method of increasing the populations of endangered species. See somatic+cell+nuclear+transfer+interspecies. Dragons flight 02:30, 6 May 2006 (UTC)
It can work, and even if it does, it'll definitely have some problems associated with it. Isopropyl 04:39, 6 May 2006 (UTC)

[edit] Yellow ants

Are there such things as yellow ants? Sort of translucent like honey? --HappyCamper 22:40, 5 May 2006 (UTC)

Sure. They're called termites. GeeJo (t)⁄(c) • 23:45, 5 May 2006 (UTC)

[edit] May 6

[edit] Fear-induced incontinence

Though it seems to happen often enough in movies and is commonly used as an expression, is it plausible that a large segment of the human population would react to extreme fear by experiencing incontinence (either fecal or urinary). My understanding is that strong anxiety makes it dificult to urinate, so if anything, people who are scared should find it near impossible to urinate, and not the other way around (I assume the same rules apply to defecation). To be blunt, which is the more plausible outcome, being "scared shitless", or "shitting your pants"? --Aramգուտանգ 03:46, 6 May 2006 (UTC)

Funny how in "24", they never go to the bathroom... Anyway, strong anxiety can certainly take your mind off going to the loo, and this, I would say, is more likely than being scared so much that you actually piss yourself unintentionally. It sounds like a climbing ladder, and the first is more frequent than the other. I mean, you'd have to be REALLY scared, shock-scared, to immediately shit your pants. Either that, or go a long, long time in controlled anxiety.
What do you mean - in 24, they go to the bathroom the same time as we do - during the ads! -- Chuq 07:12, 7 May 2006 (UTC)
I couldn't say, but your last sentence is mistaken. Being "scared shitless" (which, incidentally, redirects to fight or flight response) means you no longer contain any, as it's all migrated downwards. Strong anxiety does make it difficult to pee in a public restroom (if that's what you mean), but my experience is that that's performance anxiety, and as such, stands in the way of action of any kind. Mortal terror, which is what it's supposed to be connected to, is rarely experienced in a bathroom outside of psycho-thrillers. I don't know how people really respond to extreme fear, having never seen it happen, but if it helps, the rationale I've heard for why it happens in animals (assuming it does) is that to run as quickly as possible, they have to lose as much excess weight as possible. Black Carrot 16:09, 6 May 2006 (UTC)

I'm guessing the defecation and urination fear response is a protection mechanism against predators. That is, once you do that, you no longer smell like food to the predator, so it might let you go. Our instincts might be sufficiently vague that any extreme fear causes this, however, not just predators. I recall a nice pick of a bungee jumper with an impressive brown streak up the back of his shirt (he was upside down, of course, when this happened). StuRat 22:01, 6 May 2006 (UTC)

I don't know for certain about extreme fear (though I have no reason to doubt that it's a real response), but severe trauma can definitely causes incontinence of both types. --Ginkgo100 23:04, 6 May 2006 (UTC)

Well, the losing weight and predator repulsion explanations make sense, but what I'm really wondering about is whether people actually piss/shit their pants when they're scared in real life. Since paruresis is caused by anxiety, it doesn't matter if it's anxiety caused by fear, or performance anxiety. Are there any documented cases of people experiencing incontinence when scared, where fear is the only cause for it, i.e. they haven't been holding it in for a long time, or they haven't found themselves suddenly to be in freefall. Also, is there a term for it that's better than "fear-induced incontinence", because this is a difficult subject to search for without key terms. --Aramգուտանգ 00:45, 7 May 2006 (UTC)

I can assert, through personal experience, that a person in imminent danger of drowning (surely, a situation involving real fear) can defecate involuntarily. It happened to my daughter, then 13, before I and my brother-in-law rescued her.G N Frykman 17:43, 8 May 2006 (UTC)

Interesting. When I was a kid and almost drowned (caught in rip tide), I found it very peaceful and no incontinence was involved. Apparently near death experiences vary widely. StuRat 17:07, 12 May 2006 (UTC)

I remember reading something that said something along the lines of when your body is experiencing extreme (performance, assumedly) anxiety, it does not want to bother with many less-important processes such as digestion, and so it simply voids the body so it can focus on immediate survival. Sounds very plausible to me. --T. S. Rice 03:28, 13 May 2006 (UTC)

[edit] The Neutral Wire.

The 3 wires that run to my house from the power lines are two hot and one neutral wire. The ground wires in my home electrical system are connected literaly to the earth via a ground rod which runs a certain number of feet into the ground. My questions refers to the neutral wire. When I plug a lamp into an outlet, the AC voltage moves back and forth 60 times per second, and electrons flow back and forth through my lightbulb giving up their energy as light and heat, and in turn this voltage is running through the neutral wire as well - does it run all the way back to the power station? Is it connected to a huge ground rod? Why can't I just use my ground as a 'neutral' wire? Aren't some neutral wires actually attached to the ground buss in the panel? (Not in Canada)

If anyone can help me understand this, I'd appreciate it.

CW

60.241.30.237 06:44, 6 May 2006 (UTC)

I wish I could give you a better answer, but I do know that the electrons in your wiring actually move very slowly, only a few meters per second and not nearly the speed of light as many people believe. Furthermore, although your ground at home may act okay as a neutral sink for electrons, I think that most houses don't have good enough ground to act as the "neutral" wire. Additionally, it would cause pretty nasty shock if you were to walk by it, not to mention potential radio noise. I would recommend reading our article on Electric power transmission, and related "See also" articles. Andrewjuren(talk) 08:48, 6 May 2006 (UTC)
Yes, it runs all the way back to the power station via the earth. There is so much mass of "earth" that it forms a very good conductor. Although you can connect an electrical circuit directly to earth, this is not a good idea as you need a very good, deep, solid connection. This is precisely what the supply company provides with their "neutral". I suggest you read our article on ground and neutral. --Shantavira 09:03, 6 May 2006 (UTC)
Yep, that's true, but just a point of note, that your power company probably provides three-phase electric power. Although each individual household will generally just be on one phase, the current that you (and others on the same phase as you) draw from the live cable approximately balances out with other households that are on the other phases, so the amount of current that actually has to run back down the neutral all the way to the power station is much less than you'd first think. Arbitrary username 15:52, 6 May 2006 (UTC)
The nuetral wire and live wire connect to the Generator, the earth wire is for safety. In the UK ans such countires, where laying vast amounts of power lines is not a problem, because the country is no that big, the current is not returned to the powerstation via the ground, which is done in some countries, it just goes back down the nuetral wire and completes the circuit. Philc T+C 09:18, 7 May 2006 (UTC)

[edit] Fat absorption

I've seen a few books and web sites out there that say that the humans cannot absorb more than 10 grams per hour of fat from the GI tract. Where does this come from, and what type of experiment (if any) was done to determine this? Experiments which I have undertaken on myself seem to suggest otherwise. -User: Nightvid(unregistered)

Well, it takes bile to break down fats into a form that can be absorbed, and this takes time, and, of course, bile. That rate doesn't seem all that slow to me; if food stays in the proper portion of your digestive system for a day, that's some 240 grams you can absorb each day. Since there are 9 calories per gram of fat, that makes 2160 calories per day from fat. That's plenty of calories per day, even if you don't eat any protein or carbs or consume any alcohol. I suppose any undigested fats which leaves the system would cause diarrhea, however. StuRat 21:50, 6 May 2006 (UTC)

[edit] Why is yawning contagious between different species?

I yawn, my parrot yawns. My parrot yawns, I yawn. I see a dog in the street yawning, I yawn. I yawn near my mother's cat, my mother's cat yawns.

etc.

Why can a yawn be transferred from species to species like this? I've read the yawn article and it mentions that it can be 'interspecific' in it's contagion but it doesn't explain why. Anyone know? Thanks.

This is from my shaky memory, so I can't guarantee 100% accuracy, but ISTR that t's a survival mechanism. Yawning is a way of increasing the oxygen uptake in the body. As such, it also aids alertness by increasing the oxygen getting to the brain. It makes sense that if one person/creature yawns then either (a) the oxygen level may have dropped slightly, or (b) there is some need for the person/creature to be alert. In both cases, it would be a good survival heuristic for other nearby people/creatures to also yawn. It's not a conscious decision to yawn in these instances; it's a natural response to the surroundings ("surroundings" in this case also including other nearby animals/people). As with other good survival heuristics, they tend to increase the chances of an individual's survival and... well, see evolution if you want to take that train any further. Grutness...wha? 13:34, 6 May 2006 (UTC)


There was an episode of Mythbusters about yawn contagion.--Sonjaaa 13:51, 6 May 2006 (UTC)

No, yawn says, "A long-standing hypothesis is that yawning is caused by an excess of carbon dioxide and lack of oxygen in the blood. The brain stem detects this and triggers the yawn reflex. The mouth stretches wide and the lungs inhale deeply, bringing oxygen into the lungs and hence to the bloodstream. It is almost certain however, that this hypothesis is not correct. One study..." Black Carrot 14:55, 6 May 2006 (UTC)
I can't even read this question without yawning. --Ginkgo100 23:07, 6 May 2006 (UTC)
When you end up thinking about yawning, you almost want to yawn. --Mac Davis 01:44, 7 May 2006 (UTC).

The consensus among people whos study this stuff seems to be that yawning really is contagious. A reasonable explanation, it seems to me, would be mirror neurons, neurons that respond to behaviors observed in others by performing exactly the same. (This explains why you wince also when another person steps on a thumbtack. However, the first Google result for "yawning contagoius" claims that a 2005 study using fMRIs found that the mirror neuron system was inactive when viewing videos of other people yawning. That would seem to indicate that some other system is at work, though probably still one that does depend on some degree of social and self-awareness as humans and chimps are the only species believed to exhibit contagoius yawning. If you want a slightly longer answer without having to wade through the scientific articles, you might want see this guy's blog. BTW, the result of that Mythbusters segment was "CONFIRMED," if you were wondering. -Wiccan Quagga 05:09, 7 May 2006 (UTC)

[edit] Immunity to self-produced toxins

Well, this may be a stupid question, but as the saying goes... How is it that animals who produce toxins are typically immune to them? I understand how, from an evolutionary POV, it's obviously beneficial for an animal not to be susceptible to its own species' toxins, but I was wondering how this is typically accomplished. How are scorpions who secrete neurotoxins not affected by them, for example? Do they have substances in their blood which break down the specific neurotoxin they use before it can harm them, or do they actually have a biological makeup which renders the neurotoxin ineffective? Are all animals who are broadly venomous to other species immune to their own toxins? 82.92.119.11 09:29, 6 May 2006 (UTC)

To answer your latter question, no. Your own example of the scorpions is a good example of that. On nature channels they often show two scorpions fighting, resulting in the death of one. Their protection against the venom is their exoskeleton. - Dammit 09:37, 6 May 2006 (UTC)
Our own scorpion article states "the belief that scorpions commit suicide by stinging themselves to death when surrounded by fire is of considerable antiquity and is often prevalent where these animals exist. It is nevertheless untrue, since the venom has no effect on the scorpion itself, nor on any member of the same species (unless the venom is injected directly into the scorpion's nerve ganglion)." This doesn't seem to imply the exoskeleton is what renders the venom ineffective, since otherwise the "same species" mention is peculiar. The article doesn't seem to be saying that the venom is ineffective because the stingers can't penetrate the exoskeleton (although it does say that if the toxin where to reach the ganglion directly somehow, it would be effective). Is the artticle wrong or simply misleading? 82.92.119.11 09:58, 6 May 2006 (UTC)
Hmm, I'm probably wrong then. It could be that the fights I saw on tv where different species (I recalled it from memory, havent actually seen one recently). - Dammit 11:23, 6 May 2006 (UTC)
I was just wondering.. What would happen if a King Cobra's venom was injected into another King Cobra? Jayant,17 Years,India • contribs 09:42, 6 May 2006 (UTC)
Well, shellfish are immune to shellfish poisoning because their sodium channels bind STX much weaker than most species. Same thing with TTX and the pufferfish. Dr Zak 14:23, 6 May 2006 (UTC)
I guess that it is quite common for poisonous animals to have better resitance against their own poison since that sounds to me like a quite obvious useful trait. ALso regular contact to the poison produced by the own body should produce antibodies. But that doesn't mean that all species are totally immune or even have better protection against the poison than animals in general. These are just my own guesses based on general knowledge about animals. Jeltz talk 16:22, 6 May 2006 (UTC)
Interesting. Apparently the cobra (and the mongoose) has its acetyl choline receptors at the neuromuscular junction "shielded" from the effect of the neurotoxin, by a genetically determined sugar complex overlying the binding sites. The normal ACh can "get through the holes" in this shield and still cause normal muscle contraction. The resistance that the elapids have to their own venom is thus not a function of their immune system as such. In contrast, the viperidae have circulating antibodies which neutralise their proteolytic venom, and their tissues lose their resistance in the absence of their serum. The pufferfish's immunity is based on the substitution of a single amino acid in the sodium channel protein. Japanese sushi chefs are trained and licensed to try to reduce the incidence of TTX poisoning, and they are required to eat the pufferfish dish that they have prepared as part of the exam. --Seejyb 20:53, 6 May 2006 (UTC)
So it appears that all mechanisms occur in practice: "active" immunity through antibodies and "passive" immunity by a change in regular makeup which renders the toxin ineffective. I'd also half expect some species to have no immunity to their own poison, but it would take an unusual set of circumstances for this not to be a huge drawback (as other members of your species would likely compete with you over territory/food/mates and casualties would be very high). 82.92.119.11 21:52, 6 May 2006 (UTC)
Actually some poisonous species fight among each other, and are vulnerable to each other's poisons. The difference is that the gland producing the venom is usually carefully contained within a thick layer of lipids so as not to have it escape to the bloodstream. However, when used against another organism, usually it is injected through fangs, which pierce skin, and any lipids, or similar protection on another species. If you were to pierce the venal glands of another species, that species may die. Of course, additional protections and immunities may protect that. Elle vécut heureuse à jamais (Be eudaimonic!) 23:55, 6 May 2006 (UTC)
Note the difference between venom and poison. Poison is distributed throughout, or in large areas of, an animal's body, whereas venom is produced, stored and delivered in a specific set of organs and not distributed in other tissues. A poisonous animal needs to be immune to its own poison, but not so for a venomous one. —Pengo 05:22, 10 May 2006 (UTC)

[edit] The Perfect Crime

Supposing you had to off a someone who happened to be an insulin-dependant diabetic, preferably without getting caught. What if you were able to remove the insulin from one bottle and replace it with a glucose solution, put the spare bottle in the microwave and then replaced them both where you found them. How long would it take for the glucose to have its effect, and would it be fully lethal? Obviously you'd need to dispose of the glucose-containing bottle, wash out the syringe, maybe take up some denatured insulin into the syringe and perhaps wipe the point of injection with some damp cottonwool to remove and traces of glucose. What would be left for forensics? They'd check his blood sugar and it'd be through the roof... would this look suspicious? How about if the glucose solution also contained some alcohol... would they check stomach contents? --Username132 (talk) 11:14, 6 May 2006 (UTC)

If you're gonna commit a crime, don't talk about it on a public website... I pray for the human race.--Frenchman113 on wheels! 12:14, 6 May 2006 (UTC)
Maybe you should stop trying to kill people and write scripts for CSI.--Sonjaaa 13:50, 6 May 2006 (UTC)
I think it is important to point out there is little or no forensic evidence in most cases (even murders). Life is not like CSI. --66.168.20.7 14:08, 6 May 2006 (UTC)
You were asking how long it would take for the glucose to take effect. Leaving aside the rather gruesome and distasteful nature of your post, if you do a first aid course you get to learn that hypoglycemia (caused by too much insulin and/or not enough food for the amount of physical exercise) can have a very rapid onset, but that hyperglycemia, although potentially just as serious, is a condition with slow onset over many days. Arbitrary username 15:59, 6 May 2006 (UTC)
I think a diabetic would probably notice very quickly if their insulin wasn't having an effect. And I don't think hyperglycemia would kill someone before they could get help. Besides, everyone knows the best way is to whack someone on the head with a frozen loaf of bread, thaw it, and feed it to your dog. --BluePlatypus 19:52, 6 May 2006 (UTC)
Sharpen a thick icicle and jam it hard into your victim's neck. Twist and pull. Throw icicle into a hot bath. Sorted. :) --Kurt Shaped Box 21:42, 6 May 2006 (UTC)
There would be blood in the drain. CSI would bring a shark to sniff it out. -- Mac Davis] ⌇☢ ญƛ. 02:56, 7 May 2006 (UTC)
Your idea doesnt come close to working for a variety of reasons. Removing the insulin and filling the bottle with glucose would be equivalent to delaying or skipping an insulin shot and then taking a sip of regular soda. Hardly a recipe for sudden death-- people with diabetes do this all the time. alteripse 22:10, 6 May 2006 (UTC)
  • And apart from what Alteripse mentioned, getting the syringe and insulin would almost certainly involve leaving trace evidence of some kind even if you were careful to get rid of foot- and fingerprints. If you've been on a crimescene, you always leave something behind. - Mgm|(talk) 14:16, 7 May 2006 (UTC)

[edit] Effect of wrong phasing (3-phase supply) connection to the UPS

I would like to know the effect of connecting the wrong phasing power supply to the UPS in the telecommunication base station. Explaination with diagram would be very helpful. Thank you

Perhaps you could improve your question; I don't understand your question and it doesn't seem as if anyone else has either. What is "the wrong phasing power supply" and which "telecommunications base station" are you referring to? Andrewjuren(talk) 07:09, 7 May 2006 (UTC)
Does our article on three-phase electric power answer your question? If you mess with three-phase supplies one danger is that you'll end up applying 415volts instead of 240volts. --Shantavira 07:25, 7 May 2006 (UTC)

I think his question was about wrong phase sequence. That is, what happens if one connects RBY to terminals marked RYB (R-R,B-Y,Y-B instead of R-R,B-B,Y-Y) of an UPS (doesn't matter were the UPS is used) -- Wikicheng 08:42, 8 May 2006 (UTC)

Yes, Wikicheng is correct-what is the effect if the supply connected to the UPS is in the wrong phase sequence RBY instead of RYB.

Depends entirely on the design of the UPS, In a simple offline or double conversion online type it would most likely make no difference. In types that work by adding to/subtracting from the voltage as it passes through it could well cause big problems if the UPS wasn't designed for the eventuality. If you are installing a UPS in a situation where phase reversal is a real possibility (e.g. a mobile unit in a country where sockets are often wired with wrong phase order) i'd strongly advise contacting the manufacturer first. Plugwash 20:54, 13 May 2006 (UTC)

[edit] Pearson Correlation

Would it be correct to say (as a general conclusion for relationships among correlations/ Pearson correlation) that if X is related to Y and Y is related do Z, that this necessarily means that X is related to Z? -- 4.155.249.93 17:04, 6 May 2006 (UTC)

No, correlation is not transitive. Consider f(x) = Sin(x), g(x) = Cos(x), and h(x) = Sin(x)+Cos(x). h(x) is partially correlated to both f and g, but f and g are uncorrelated to each other. Dragons flight 17:59, 6 May 2006 (UTC)
And you can easily extend this to a situation where f and g are actually partially anticorrelated, while h is still partially correlated to both f and g. Just consider f(x) = Sin(x), g(x) = Sin(x+2pi/3), h(x) = Sin(x+pi/3). Arbitrary username 18:04, 6 May 2006 (UTC)

[edit] modern communications technology

I would be interested in a recap or summary of the latest communications technology that includes such devices as the internet, telephone linkages, digital photography etc., and what these actually do in the real world. Thank you

Read these articles! internet, telephone, digital photography. Try using the little search box on the side to find other articles that interest you. Andrewjuren(talk) 01:34, 7 May 2006 (UTC)

[edit] confusion with Schrodinger's equation

Obviously, we all know that solutions to Schrodinger's equation is called wave functions. In convention, we call "a one-electron wave-function" a orbital. NOW, if orbital is essentially a mathematical description of the behavior of one electron, then why on every orbital we can have 2 electron filled up?

Thanks

Strictly speaking, you have to solve Schrodinger's equation for the system you have (e.g. an atom with multiple electrons). However, to an approximation you can use the solution of Schrodinger's equation for one electron (hydrogen atom) when considering the forms of the atomic orbitals in more complex atoms, provided that you take into account certain rules about how electrons behave. A key consideration is that electrons are so-called fermions, which means they obey the exclusion principle, that is the property that no two electrons can share the same set of quantum numbers. Each atomic orbital is described by a set of quantum numbers, but electrons have an additional quantum number, so-called spin quantum number, which for an electron can take two possible values (1/2 or -1/2). This means that a maximum of two electrons can share the same atomic orbital without violating the exclusion principle. Arbitrary username 17:53, 6 May 2006 (UTC)
You don't have to make the approximation of using hydrogen orbitals. - You still can describe the total wave-function in terms of single-electron orbitals. They're just different from the hydrogen ones (and can't be solved analytically). However: When you solve the Schrödinger equation for a two-or-more-electron system, you can't just solve the thing, because of the aformentioned exclusion principle. What this means is that the wave equation must also be antisymmetric with respect to the exchange of two electrons. Not just any solution is valid, in other words. Once you satisfy that condition, (for instance using a Slater determinant) then you can have two electrons with opposite spin in the same spatial orbital. Note that your resulting wavefunction is no longer a simple product of one-electron orbitals, but a rather large linear combination of them. But they're still one-electron orbitals. --BluePlatypus 19:29, 6 May 2006 (UTC)

[edit] Do people in comas dream?

I am curious about this. My guess is that they do. But it may depend, which is why I am asking. Thank you--ĶĩřβȳŤįɱéØ 18:40, 6 May 2006 (UTC)

We don't know. --Mac Davis 01:43, 7 May 2006 (UTC)
Somebody must know. Surely people who've come out of comas have been asked what they experienced, and whether or not they dreamed. JackofOz 02:25, 7 May 2006 (UTC)
If they say yes we have the answer, but if they say no we don't, because even during normal sleep people don't always remember their dreams. --Ginkgo100 03:01, 7 May 2006 (UTC)
That's fine. But all it takes is one ex-coma person to remember they were dreaming at some stage, and that proves it can happen. And surely coma patients have been monitored to detect evidence of REM. Is MacDavis saying no REM activity has ever been detected in a coma patient? JackofOz 03:12, 7 May 2006 (UTC)
I don't think that's true. What if the person has dreamt in a normal sleep just after he's come out of the coma? How would ey know? – b_jonas 13:00, 7 May 2006 (UTC)
So, no actual facts are available? Black Carrot 03:12, 8 May 2006 (UTC)
I think the real question is whether people in comas experience REM sleep, since it is during REM that we dream. Unfortunately, I don't know the answer to that question. --Ginkgo100 15:54, 8 May 2006 (UTC)

[edit] Helicopter and Car

A 5500kg helicopter accelerates upward at 0.50m/s² while lifting a 1200kg car. What is the lift force exerted by the air on the rotors? What is the tension in the cable that connects the car to the helicopter?

I drew my free body diagram and this is what I got for the two equations:

Helicopter

ΣFy = ma
 FA - FG1 - T2 = m1a

Car

 ΣFy = ma
 T1 - FG2 = m2a

FG1 being 9.81 x 5500, T2 being 0.5x 1200, T1 being 0.5 x 5500, FG2 being 0.5 x 1200

My problems lies here. I need something to cancel out so I can solve for FA or T, but nothing cancels out. T1 and FA are the same the force, and so are FG2 and T2, and I've tried going FA - FG (total) = m1a and FA - FG2 = m2a but I that didn't give me the right answer either. I think my problem may lie in the fact that I have acceleration as FA. I've noticed that in some questions that we have done that acceleration is sometimes FA, and sometimes isn't included at all on that side of the equation. Anyone know why? Now as I think about it I don't even know why I have a T1 and T2 and not just T... I am really unsure here. Thanks. C-c-c-c 19:34, 6 May 2006 (UTC)

Hi, I'll have a proper think about this and post again soon, but as a quick comment you should definitely just have a T (if we can neglect the mass of the cable itself) -- see Newton's third law. Arbitrary username 20:30, 6 May 2006 (UTC)
Maybe I should just clarify what I mean by appealing to Newton's third law here. I mean that the two tensions will also act on the cable. If we assume the cable is very light, then if there was any significant difference between T1 and T2 it would lead to a huge acceleration of the cable. Hence we can treat it that T1=T2. Arbitrary username 21:21, 6 May 2006 (UTC)

Okay, problem seems to be firstly that you've got these two different tensions, and then made some unfounded assumptions about what they should be equal to. Just set them both to T, and then solve for FA by adding the two equations:

FA - FG1 - FG2 = m1a + m2a

or as I'd prefer to write it,

FA = (m1 + m2)(a + g)

That gives you FA, which (no surprises) is enough to counteract gravity and provide the upward acceleration, for the combination of helicopter plus car.

Also you have

T = m2 (a + g)

In fact it's an important result that an upward acceleration and a gravitational field have an equivalent effect, so the a+g in the answers is no surprise.

I'll leave you to put the numbers in.

Arbitrary username 20:43, 6 May 2006 (UTC)

Thank you so much! I just have one more question related to this, you said that all you have to do is add the two equations and I was always told I should subtract them. Your method does give the right answer, so does it work either way? Also when you're subtracting, wouldn't it matter which order you put in your equations (eg. 2 - 5 = -3, 5-2 = 3). This gives you the same number, but negative, so could it just be giving it in the opposite direction? Thanks a lot again. C-c-c-c 20:53, 6 May 2006 (UTC)
Think about what you're doing when you "add" or "subtract" equations. You can do anything to the left side of an equation that is numerically equivalent to what you do to the right side. For example, adding terms to each side which are known to be equal because of another equation that you have. Or subtracting them. Which you actually do will depend on what terms you are trying to eliminate. Arbitrary username 21:21, 6 May 2006 (UTC)
Oh, I see now. I thought it was one either one or other, and there wasn't choice between adding or subtracting. Thanks a bunch. C-c-c-c 21:31, 6 May 2006 (UTC)

[edit] Identification of stars as distant suns

My question: when did we start "knowing" that the stars in the night skys are actually very distant stars? The star article itself is severely lacking in the cultural and historical prospect... Anyway after a bit of searching now I know there was this Nicholas of Cusa who proposed that stars are suns, though obviously he would not be able to "prove" his claim. However nowadays everyone regards this idea as a fact. So when and how people "prove" that stars are in fact suns very far away but not lamps embedded on the celestial sphere? Thanks! --Lorenzarius 19:48, 6 May 2006 (UTC)

The idea of extrasolar planets is more modern, but I believe Archimedes was able to prove that stars were distant objects, or even earlier, I think. It would be plausible for the Babylonians or the Egyptians to have known it. (Let me check a few articles). Simple trigonometry was used based on measuring the changes in distance over different positions. Naturally an extremely large distance would mean miniscule changes in perspective. Elle vécut heureuse à jamais (Be eudaimonic!) 22:32, 6 May 2006 (UTC)
Yup, with the method of parallex we would be able to notice minute movement against the stellar background of some very close stars. Ancient people would also know that the stars are more distant than the Moon, Jupiter, Saturn etc because they could observe the eclipse of stars by those solar system objects.
But perhaps let me rephrase my question: how did we know that the Sun is just one of the stars, and that the distant stars are the same thing as the Sun? --Lorenzarius 23:13, 6 May 2006 (UTC)
Actually the idea is fairly modern, with the invention of mass spectrometry did we "prove" that our sun was like other stars (or vice versa) - full of hydrogen, though differing in mass. The hypothesis was probably earlier, but it is my guess it wouldn't be more than 100-200 years before the mass spectrometer's invention, because the article at astronomy says that the idea that the sun was like other stars was fairly recent. Elle vécut heureuse à jamais (Be eudaimonic!) 23:15, 6 May 2006 (UTC)
Ordinary spectroscopy in the visual spectrum, not mass spectroscopy. Mass spectroscopy would require a sample. Which I think it's safe to say we don't have. --BluePlatypus 00:49, 7 May 2006 (UTC)
We didn't have a sample until the Genesis spacecraft. Dr Zak 01:24, 7 May 2006 (UTC)
It's spelled parallax. —Keenan Pepper 04:06, 7 May 2006 (UTC)

[edit] carbon dioxide

Is it considered a fact that the majority of trees over 30yrs of age produce more carbon dioxide than oxygen? 60.226.90.64 22:05, 6 May 2006 (UTC) JAG.

Hardly. If they did so, it meant they would consume more food than they were producing (photosynthesis), and would eventually run out of food. Besides, the aging of trees varies based on species, so I don't think the 30 year limit would be absolute. Elle vécut heureuse à jamais (Be eudaimonic!) 22:33, 6 May 2006 (UTC)
Well, it's true once they die and start decaying. Is that what you meant? --BluePlatypus 22:45, 6 May 2006 (UTC)
I think the petitioner wants to know more about photorespiration. Dr Zak 01:26, 7 May 2006 (UTC)

[edit] Nitrogen through breathing

The article "Breath" says that we inhale and exhale the same amounts of Nitrogen, about 78%. Obviously, at least to me, we're not absorbing it. Does this demand a natural defense mechanism, or is it rather the lack of anything for the nitrogen to bond to? (Mixed answers are thus fairly acceptable) THANKS! This is such an amazing resource, and that's just the articles on their own.

It is simply diffusion, or osmosis (sort of). There are little processes that consume nitrogen, so the nitrogen content in the bloodstream and the nitrogen breathed in is the same. There is exchange, but they are the same type of molecules, so the net diffusion rate is zero, though nitrogen molecules diffuse through the membrane of the air sacs at all times. Oxygen diffuses in because the oxygen content in breath is higher than that of the bloodstream (and is further attracted to haemoglobin), and carbon dioxide diffuses out because carbon dioxide content in the bloodstream is greater than that in the lungs. Nitrogen does get absorbed if the nitrogen content in the air is greater than that in the bloodstream...when you do deep water diving one risks getting decompression sickness too easily because the nitrogen has been pressurised and sudden retrieval upwards causes it to burst...then there's the opposite with nitrogen narcosis. Elle vécut heureuse à jamais (Be eudaimonic!) 23:51, 6 May 2006 (UTC)
Well, if there was something for it to bind to, we'd absorb it. I'm pretty sure that the body does not have anything which specifically binds nitrogen gas molecules as with O2 and hemoglobin. We don't have any use for it. Although there are bacteria which use nitrogen gas. (nitrification bacteria) As pointed out above, nitrogen gas (like all gasses, to different extents) does dissolve in water. Since the nitrogen dissolved in your body is in equillibrium with the nitrogen in air, you get the same amount going in and out. What happens in decompression sickness is that that equillibrium is disturbed, since more gas (again, like all) will dissolve into in your body at higher pressure. So if you suddenly drop the pressure, the nitrogen will evaporate into bubbles, which is very dangerous. It's the exact same thing that happens when you open a can of soda. Once the soda has gone flat, it's reached equillibrium with room pressure. So it's not about the concentration. Just the pressure. --BluePlatypus 01:00, 7 May 2006 (UTC)
The dinitrogen molecule is extermely inert in the absence of a catalyst. Only a few bacteria have evolved the ability to reduce nitrogen from the air to ammonia and use is in their metabolism. Wikipedia has an article on nitrogen fixation, unfortunately it's not very good at the moment.
At normal air pressures nitrogen is not an issue, but when breathing compressed air (as when SCUBA diving), the high partial pressure of nitrogen can lead to nitrogen narcosis and, if ascent is too fast, decompression sickness (the bends). (Actually, reading the article on DCS, looks like nitrogen alone is not to blame, if you want to quibble.) --Ginkgo100 03:19, 7 May 2006 (UTC)
Nitrogen goes into the lungs, is dissolved into the blood stream, body fluids and cells in proportion to it's partial pressure, However, even though the nitrogen molecules are floating about in all these fluids (everywhere - eye to big toe - at the same partial pressure) the body does not do anything with it, i.e. does not utilise it in any chemical reaction, nor does the body produce any N2 by any chemical process, nor does the N2 molecule take part in any unwanted chemical reactions (no defences needed). Therefore, at a constant pressure, the nitrogen that you breathe out is the same as what you breathe in - no nitrogen added or taken away or changed. Your conclusion, though mainly correct, is based on figures for dry gas. In reality the air you breathe out contains approximately 6% (approx 6 kPa) water vapour (at sea level and body temperature), so that the percentages given in the article are not true for the air coming out of your mouth or nose. I shall see if I can adapt the article, while still pointing out what you deduced. --Seejyb 23:32, 7 May 2006 (UTC)

[edit] May 7

[edit] Difference in Time

What is the difference in time during the existance of the universe as we know it today and since the Big Bang and anytime prior to the Big Bang? -- PCE 00:22, 7 May 2006 (UTC)

See Big Bang.-- Mac Davis] ⌇☢ ญƛ. 01:42, 7 May 2006 (UTC)
Age of the universe claims that the universe is about 13.7 billion years old. Before the Big Bang, time is believed to have not existed. Andrewjuren(talk) 01:44, 7 May 2006 (UTC)
Ahem, time is not known to have existed, not necessarily didn't exist. -- Mac Davis] ⌇☢ ญƛ. 02:48, 7 May 2006 (UTC)
There are many a misconceptions about the big bang caused by popularization. The big bang was not the so called, beginning of the universe/time. It was only a time period in which spacetime started to expand— for unknown reasons. Everything was still there before the big bang, the big bang was not a moment of creation either.-- Mac Davis] ⌇☢ ญƛ.
The Big Bang model goes to 10e-43 seconds. As far as most people are concerned, that's close enough to the beginning of the universe. I am fully aware that the stuff that happens before is "important", but to my knowledge there is no model which has general scientific consensus. So, I guess to correctly answer PCE's question: 13 billion years since the Big Bang and there were 10e-43 seconds before the Big bang. Andrewjuren(talk) 07:03, 7 May 2006 (UTC)
Sorry, I didn't mean to "condemn" your answer or anything, it was just fine, and you are right. But I do not agree with you impling that the big bang was the beginning of time and/or the universe. -- User:Mac_Davis (unlogged in) 11:40, 7 May 2006 (UTC)
Do you have a citation for that? The Stephen Hawking article seems to indicate that Hawking believes there was no "time before the big bang": "Asked in October 2005 to explain his assertion on the British daytime chat show Richard and Judy that the question, 'What came before the big bang?' was meaningless, he compared it to asking, 'What lies north of the north pole?'" Chuck 19:26, 8 May 2006 (UTC)
Also keep in mind that cosmologists and astrophysicists are still not 100% certain abut the origins of the universe. This, for example, gives a different interpretation to the events around the Big Bang. Grutness...wha? 07:45, 8 May 2006 (UTC)

[edit] Celestial Names

When a new celestial object is discovered, it is immediately given a specific name (at least in English...its name in other languages may be different). I understand that our planets have been named after Roman gods, but this goes back to antiquity. I also understand that certain planets' moons are named according to a theme, for example (forgive me for forgetting which one) one planet's moons are named after Shakespearian characters. But that is also an old tradition. (Also, it seems pretty anglo-centric...are those moons named differently in different languages? For example in Russian are they named after characters created by Russian authors?).

What I'm really getting at though is, say a comet is discovered, or a new extra-solar planet. What organization or body is it that seems to have the authority to define these objects' names? Loomis51 02:04, 7 May 2006 (UTC)

The International Astronomical Union is the sole authority recognized worldwide on Astronomical naming conventions. (Though the IAU doesn't really name all the new objects discovered, generally the discoverer would be able to propose a name for IAU's approval.) --Lorenzarius 03:59, 7 May 2006 (UTC)
See also planetary nomenclature. -Yummifruitbat 04:00, 7 May 2006 (UTC)

[edit] Queer Printing on New Bills

This is for Americans. Does anybody know what anti-counterfeiting purpose it serves to make our money pink? Black Carrot 02:57, 7 May 2006 (UTC)

Pink? Is there a new bill that I haven't seen yet? I know that the bills have blue and red threads in the paper that is used. These threads are in the paper so that you can tell that someone didn't just print a scan of the bill on normal paper. There is more info about Counterfeiting and Security printing. Dismas|(talk) 03:59, 7 May 2006 (UTC)
See [19]. I think it's not so much that it's pink, but rather that there are multiple colors, and a gradient of color on the reverse. Ardric47 04:01, 7 May 2006 (UTC)
I lost my answer in an edit conflict, sorry. I did say however, that when giving money for ransom, the police often put a dye bomb in the cash-bags, that explodes and magenta dye covers nearly all the bills. --Usre:Mac_Davis (unlogged in) 11:35, 7 May 2006 (UTC)
Yes, when I went to the states a few months ago, I was quite suprised to see pink money! Kilo-Lima|(talk) 12:44, 7 May 2006 (UTC)
-sings- All things just keep getting better... Yes, there's a new bill. It's like...yellow and pink and green and still has dead people on it. Cernen Xanthine Katrena 13:52, 7 May 2006 (UTC)

well, why not pink? who says green is the definitive colour for money? surely you don't think that people might think your gay if you pay with pink money, do you? that would just be tragic!

(this comment was added by someone who doesn't know how to sign their own name)

Who says? I fucking say! I don't care about the sexual orientation of my money, I just don't want it to be salmon pink! Green and black. Nothing shiny, nothing pastel, just green and black. That's all I ask. And I still don't know, how in God's name is the color supposed to protect us? Complexity I understand, watermarks I understand, UV sensitivity I understand, but why PINK? Black Carrot 03:08, 8 May 2006 (UTC)
If you don't care about the sexual orientation of your money, why did you introduce that very concept in the title the question "Queer Printing"? Seems you're not as entirely indifferent to it as you claim. JackofOz 03:25, 8 May 2006 (UTC)
Yeah, and watch your god damn mouth. ^_^ Cernen Xanthine Katrena 09:59, 8 May 2006 (UTC)
In serious answer to your question the choice of colours is almost certainly intended to make colour reproduction as difficult as possible. Research has shown that colour copiers and printers have more difficulty with the pinkish purplish colours than any others. Which is why you will see that many countries are introducing high-denomination bills looking very similar in colour. DJ Clayworth 18:26, 10 May 2006 (UTC)

[edit] Red-eye effect in photography

Does anybody know the technical term for the "red-eye" effect in photography? I thought that it began with "hemo-", but I might be totally wrong. Please, please, please, if anybody knows, I'd greatly appreciate it. (I doubt that I'll be able to sleep until I find out!)

Sorry, I don't know and there is no mention in the article: Red-eye effect. Andrewjuren(talk) 06:45, 7 May 2006 (UTC)
"Hemo-" means blood, so we are on the right track. However, the OED has no technical term for this effect. Interestingly, Googling for hemo and "red eye effect" suggests the word was in the Wikipedia article in an earlier edit, but I haven't been able to find it. Hope you got some sleep! --Shantavira 07:58, 7 May 2006 (UTC)

[edit] Intelligent Design

Many evolutionary scientists have criticized and refuted the arguments given for Intelligent Design.Well, how have Michael Behe,William Bemski, and other advocates of Intelligent Design reponded to these criticisms?

Have you tried looking at our article on Intelligent design and related articles listed under "See also"? Andrewjuren(talk) 06:48, 7 May 2006 (UTC)

[edit] Indian Almond

How the Indian Almond look like? Is it called 'chinabadam' in Bengali language?

Unfortunately, our article on Indian almond does not have a picture. There is a good description on this external site. Andrewjuren(talk) 07:23, 7 May 2006 (UTC)
I've found a free image; it'll be up in a minute. Melchoir 08:06, 7 May 2006 (UTC)
Image:Teca 001.jpg. For future image hunters, this is the second result if you Google for ("indian almond" usda). Melchoir 08:17, 7 May 2006 (UTC)

[edit] refractive index of sugar

does sugar have a refractive index?

It sure does! According to Sucrose, the refractive index of a sugar crystal is 1.5376. Melchoir 08:19, 7 May 2006 (UTC)
Also, if you look at refractometer you should probably find some stuff on the refractive index of different concentrations of sucrose solution, as that is the standard against which other concentrations are determined with these machines. Skittle 16:14, 7 May 2006 (UTC)
Sugar dissolved in water will also change the refractive index of the solution. And it will vary with concentration, so you can use that as a way to determine the sugar concentration with a refractometer (typically an Abbe refractometer to be precise). It's a good-old fashioned kind of chemical analysis instrument you don't see that often nowadays. --BluePlatypus 18:15, 7 May 2006 (UTC)
(Addendum: Apparently I'm not only old, but a bit blind too, since I somehow missed that Skittle had given essentially the same answer). --BluePlatypus 18:19, 7 May 2006 (UTC)
Hey, it's probably the chemical analysis intrument I see the most of. And Blue Platypus's answer was better. Brix scale if it helps Melchoir. Skittle 13:46, 8 May 2006 (UTC) (Hmm, seems to be red. Brix has some info, but not as practical as it could be)

[edit] Light

Is there an existing material that can travel faster than light?Does wikipedia have an article on it?i would love to check it out

--thanks

I think the closest we've got is Tachyon. Since tachyons have not been observed, I wouldn't call them existing materials, though. Melchoir 08:22, 7 May 2006 (UTC)
Keep in mind that going faster than light is equivalent to going back in time. See Introduction to special relativity for the details. —Keenan Pepper 08:34, 7 May 2006 (UTC)
It's probably not true that being a tachyon means traveling back in time (or FTL travel). Rather, it just means an odd dispersion relation until the stable vacuum is reached. -lethe talk + 09:45, 7 May 2006 (UTC)
Isn't there some law of physics relating to e=mc2 that says it is impossible to overtake light if you are slower than it, and go slower than it if you are faster than it. And also that objects that are faster than light cannot interact with objects slower than light? I' not actually sure, and I don't know where to look to verify this, so if anyone else who knows about this could so, it would probably help. But more to the point, if I am correct, there may be things going faster than light, but it is impossible for us to know. Philc T+C 09:30, 7 May 2006 (UTC)
I don't know about the interaction bit, but your first point is indeed echoed at Tachyon. Melchoir 09:36, 7 May 2006 (UTC)
Ah, yes, I found it at tachyon, if a Tachyon does exist, and travels faster than light, if we were able to interact with it it would violate causality, as loops in time could be created leading to plentiful paradoxes, therefore if they do exist, there is no way for us to know. Philc T+C 18:04, 7 May 2006 (UTC)
Cherenkov radiation might also be an interesting read if your question was not limited to the speed of light in a vacuum. It's also been mentioned above. - Dammit 10:22, 7 May 2006 (UTC)
A great answer is Is Faster Than Light Travel or Communication Possible? in Usenet Physics FAQ. We also have an article FTL. – b_jonas 12:50, 7 May 2006 (UTC)
Anyway, the short answer is that it isn't possible because physicists have once decided that it wasn't, and since that time they keep redefining FTL so that it would exclude any possible way of travelling faster than light so as to guard their self-pride. – b_jonas 12:55, 7 May 2006 (UTC)
Well, to be fair, the examples given in that article do seem pretty useless. Unless you can pilot a spaceship or send messages across the galaxy, what good is it? Black Carrot 02:59, 8 May 2006 (UTC)
Actually, recently Brian Greene gave a talk and he is the leading physicist in the field of quantum mechanics and string theory. He said, and I know cuz I was there, that if you have two quarks, and look at one and it's and UP quark, then according the the laws of physics the other must be a down quark. He said that this took place instantaniously, faster than light. I asked him 'What if you could affect the outcome of the quark? Wouldn't that cause for Faster-than light communication?' and he said 'Yes, if you could.'
That would be a case of quantum entanglement. The main problem is that affecting the outcome, based on curent models of quantum dynamics, is impossible. On the other hand, it does provide a neat means of creating a unique key for cryptographical purposes. Confusing Manifestation 13:26, 14 May 2006 (UTC)

This means that perhaps in the future the topic could lead to faster than light communications/information transport for teleportation. Turtleboyxtreme i do not know when.

[edit] detecting UV rays

i know that human eyes cannot detect UV rays.but is it possible to have any sorta eye surgery so that our eyes can spot UV rays without any damages?

No, we are not yet advanced enough that we can modify the cells on our retina in such a profound manner. — QuantumEleven 09:13, 7 May 2006 (UTC)
We can get Infra-red goggles, so If you are determined to see UV, im sure its possible to make some goggles that pick them up or something. Philc T+C 09:32, 7 May 2006 (UTC)
We would also have to alter our brain, to be able to register the new colors. -- Mac Davis] ⌇☢ ญƛ. Mac Davis 10:26, 7 May 2006 (UTC)
Infra-red is actually the opposite of UV, so i doubt that typical Night vision goggles would be much help. The trick to seeing UV rays is actually not hard, since they are energetic. Simply get a filter that only allows for UV rays to pass through, and then hit a material that will fluoresce properly, to convert the UV rays to normal light, and just watch them! This is how you 'see' things in a room lit up by only an ultraviolet bulb, visible light is supressed and only objects that fluoresce the light back to the visible range show up, like white socks, teeth, psychadelic posters, etc.
It is entirely possible, except it probably counts as damage: see Aphakia. Ardric47 20:05, 7 May 2006 (UTC)
There exists a device known as a starlight scope. I believe it uses ultraviolet from the stars at night to see.

Remember that UV radiation carries a lot of energy per photon; in fact, enough to be damaging to living tissues. Life as we know it today, above the ocean or soil surface, would not be possible without the ozone layer in the stratosphere that absorbs much of the UV coming from the Sun. By and large, there is relatively limited exposure to UV at sea level (just enough to tan...), but exposure does increase either with altitude or in regions located in the so-called ozone layer. --Michel M Verstraete 21:17, 12 May 2006 (UTC)

Some human children can see into the UV spectrum but eventually lose the acuity. Children can generally hear higher pitches than adults as well- call it ultrasound based on being above the arbitrary mark of pitches most adult humans can hear. --151.151.21.100 20:54, 2 August 2006 (UTC)BEN 8/2/06

[edit] Scientists investigating crashed spaceship

I'm writing a story that involves a crashed spaceship, among other things, and originally I just had SAS soldiers securing the site (plot device to get my characters there). It occurs to me that the government would also send scientists to investigate it. After all, that's what they do in movies and so on.

But exactly what kind of scientists would be sent? I can't imagine we have too many people lying around with a degree in extraterrestrial technology study.

Physicists, biologists and chemists I guess. - Dammit 10:24, 7 May 2006 (UTC)
NTSB with NASA-people, me'd think. 213.161.189.107 10:29, 7 May 2006 (UTC) Henning
Astrophyscists, engineers, nanotechnologists, & geologists (for examining the spaceship) biologists, bio- and astro- chemists, read Deception Point for more. For specific people, maybe you could add Michio Kaku and... that's all I got. Assuming its in the future. Don't forget Delta force, in case anything funny happens with the aliens. -- Mac Davis] ⌇☢ ญƛ. 10:33, 7 May 2006 (UTC)
Well, if SAS soldiers are being sent in, I'd presume that the crash doesnt take place in the United States, so I can't see a US-government task force being the first on the scene. GeeJo (t)⁄(c) • 11:47, 7 May 2006 (UTC)
Thanks. It does in fact take place in Australia, in the Snowy Mountains to be specific. I'm especially pleased you mentioned a nanotechnologist; nanotechnology plays a part later on in the story, and putting one in beforehand means I can set up an udnerstanding of it before the reader actually has to cope with it as part of the plot.
Stargate's universe has all sorts of people brought in to study strange things: Daniel Jackson is an archaeologist and linguist...Rodney McKay is an astrophysicist...and, yeah, take along a few guys with P90's just in case things get out of hand. Cernen Xanthine Katrena 13:34, 7 May 2006 (UTC)
Alot of stories send mathemiticians on trips to communicate with other life-forms, as it is the only common language we will have. Philc T+C 15:24, 7 May 2006 (UTC)
What makes you think our math would be even vaguely similar? And how do you use that as a language? Black Carrot 21:19, 7 May 2006 (UTC)
Maths is always the same, no matter where you go in the universe 2+2=4 F=ma and e=mc² so thats how its vaguely similar. addmitadly it cannot be used to communicate much, but it allows both species to gauge the others intelligence. However little you can get across, its better than just sitting there squeeling at each other in your respective languages at your respective frequencies. Philc TECI 21:45, 7 May 2006 (UTC)
Alright, let's assume we structure our quantitative views of the world more or less the same. Let's just say. How, then, are we supposed to communicate our understanding to the aliens without language? Cut up some squares and demonstrate the Pythagorean theorem? Black Carrot 02:42, 8 May 2006 (UTC)
The prime numbers are generally the best idea for a start. Then do the periodic table to demonstrate scientific understanding. --212.241.231.52 03:19, 8 May 2006 (UTC)
Even if you can only cut up squares and show each other pictures, all you have to do is show them a number square, and it would take seconds to grasp the ten based decimal system. There are only four basic functions, plus minus multiply and divide, so once weve got them acroos, you can discuss mathematics. However pointless it is there is no other way of communicating anything! ok! its better than nothing!!! Philc TECI 11:12, 8 May 2006 (UTC)
I hope the aliens aren't made of antimatter. That would be bad, eh?
They'd send expendable scientists. AllanHainey 15:33, 8 May 2006 (UTC)
It sounds like the scientists are secondary characters; in which case, in traditional science fiction, all of them are expendable. Black Carrot 23:10, 8 May 2006 (UTC)

[edit] Visible Spectra of Light

IN THE NAME OF HOOLA, there's edit conflict for a reason! Don't just delete my article like that! *hrm*... now. Humans see roughly from 400nm to 700nm waves (IIRC). First of all I would like to ask: If we could see from, say 300nm to 800nm, would we perceive the colours as the same, but "spread out", ie seen only a stretch? Then there is another, bit tougher question: Some animals are bound to have different spectra, what are the lowest and highest wavelengths that some animals can perceive in vision, that we know of? Manymanymanymany thankseses. :)

Sorry, it was me. Accident. The colors would not be the same at all! We would see completely new colors. Colors that we literally can't imagine. The lowest and highest are of the animal kingdom seen ultraviolet and infrared, although I am not sure of the wavelengths. --User:Mac_Davis (unlogged in) 11:31, 7 May 2006 (UTC)
Oh, thanks. Definitely not my intention to come off as cross, I should have placed a smilie in. ;) Thanks - it's the wavelengths that I'm interested in.

Who's Hoola and why don't we have an article on his/her worship? alteripse 16:28, 7 May 2006 (UTC)

Are you guys British or something? What does cross and hoola mean? -- Mac Davis] ⌇☢ ญƛ. 04:48, 8 May 2006 (UTC)
Cross: angry, annoyed [20]. Black Carrot 23:15, 8 May 2006 (UTC)

[edit] Traffic Lights

Okay, this'll probably get me banned from the reference desk. Let's pretend there's this traffic light at an intersection that never works properly, and despite the amount of protests and complaints to the state transportation (and whomever deals with transportation in the county, as well), nobody has come out to fix it. Let's also pretend that I'm fed up with said traffic light and wish to perform malicious action on said traffic light to force the DOT to come fix the damn thing. My question is, what would send a clear message and not allow me to be caught (hypothetically): a localized electromagnetic pulse (and how would one construct a device to do that)? A small explosive? It would, of course, be mounted on the control box. Cernen Xanthine Katrena 13:25, 7 May 2006 (UTC)

No hope, those things can take hurricanes. With our local paper, they have a daily article on the 'fixer', in which people complain about potholes and such. They are usually fixed the next day. --Zeizmic 13:38, 7 May 2006 (UTC)
Low-yield EMP bomb? :D
You could get one of those devices that ambulances and fire trucks use to change the lights for them while they are approaching it. Although, it's illegal for private citizens to own one... but you know... Dismas|(talk) 15:41, 7 May 2006 (UTC)
While traffic lights might not be susceptible to hurricanes, they do not survive lorry fires adjacent/right beneath them (there was one such incident in Wells a few years back). Alternately thermite might do the trick... Thryduulf 15:48, 7 May 2006 (UTC)
Well, it depends. If it doesn't have cameras attached (a lot of the ones around my house do, to catch people speeding), it gets alot easier. Wait for a time of day (or night) when there's nobody around, climb up on it, and smash one of the lights with a hammer. Or, cover it with paper; it'll still be disabled. As far as getting banned, people have asked about the mechanics of suicide in a padded room. Questions aren't a problem, as long as they're actual questions and not reformatted speeches. Black Carrot 21:10, 7 May 2006 (UTC)
If you are trying to create an emp grenade you have several options a capacitor bank (one about the size of a small house would do the trick), a specially construced tool which uses a spinning disk going very fast to cut through the field lines of magnets, so when the circuit is completed for a split second you will have mabye a Megamp of current (sorry can't find its name anywhere), or you can use a current going through a coil (an electromagnet) and use small explosives to collapse the coil very quickly, this will cause an incredible rise in current, and since its already a coil, voila emp. But all of this is pretty unpheasable for the task of dealing with trafficlights, mabye you should just tie them to your car and yank them over, or even easier, as someone suggested earlier i think, set off a large nuclear weapon in the upper atmosphere. ;-) Philc TECI 22:00, 7 May 2006 (UTC)


Perhaps you could do it the old-fashioned way? --Crucible Guardian 23:29, 7 May 2006 (UTC)

I considered suggesting that (in fact, I did suggest something like that), but there's the problem of reach. Black Carrot 23:38, 7 May 2006 (UTC)

Well. I don't think I could detonate a nuclear warhead (my insurance doesn't cover fallout from even accidental detonation of a nuclear device -- what a load of crap, hm?). And so much for the emp grenade. I could hit it with a sledgehammer, but there's a 7-11 right in front of it (which means that I can be caught...). It's not the lights I want to damage, it's the control box. They'll have to send a technician instead of just a repair crew, it'll be costly, and painful, for the county to do that. I was thinking of hitting it with the sh*tmobile...do you think a vehicle accident would take one of those puppies out? After reviewing a wikibook on thermite synthesis, I think I may have my answer, but the question is, is such a reaction simply incendiary or explosive? Cernen Xanthine Katrena 10:15, 8 May 2006 (UTC)

http://video.google.com/videosearch?q=thermite - mako 11:48, 8 May 2006 (UTC)

Yeah! Vandalism is the answer to real life problems as well as Wikipedia problems! --Ginkgo100 15:59, 8 May 2006 (UTC)

Yeah, it bloody pisses me off to when your neighbours accidentally set off their nuclear warhead, and then you have to ask them to cover the damages, because your insurance doesn't cover it! Philc TECI 22:32, 8 May 2006 (UTC)

I'd get three large stickers, one with "green" written on it in text (it doesn't matter what color), one with "orange" (or "yellow" if you wanna be nasty) and one with "red". Climb up the pole and stick them on each of the lamps, but not so much as to obscure the actual light, so that all the people that weren't colorblind wouldn't get confused.
You wouldn't cause enough damage to get into trouble, but your government would be enclined to set things straight, and there'd be a good chance they'd fix the other problems while they were at it.
Also, it helps if you live in one of those towns that has horizontal streetlights, like Montreal, which would make it even harder for the dumb colorblind people to tell which was which. freshgavinΓΛĿЌ 07:07, 10 May 2006 (UTC)

[edit] carbon in body

carbon isnt necessary for human survival,yes.But is it that carbon is needed atleast in little content in our bodies?or maybe i am wrong?If not,what are the diseases caused by deficiency of carbon?

--thanks!

I imagine starvation. Just about everything we consume has carbon in it. I don't know how the uptake of carbon works, if there is any.
  • Perhaps the questioner is referring to pure carbon as opposed to carbon compounds? --jpgordon∇∆∇∆ 15:04, 7 May 2006 (UTC)


--yes,as a matter-of-fact i was reffering to pure carbon and not carbon compounds.thanks!--the same person who asked the question:)

As in charcoal, graphite, diamonds or bucky balls? I don't think so :) -Obli (Talk)? 16:25, 7 May 2006 (UTC)

No, your body cannot do anything with pure carbon, however in cases of drug overdoses, paramedics often deposit activated carbon inside a patient's stomach to absorb the toxins --Crucible Guardian 23:25, 7 May 2006 (UTC)

I don't know if they still recommend it now, but 30 years ago, my dad was given charcoal tablets to try to deal with his upset stomach; same principle, I assume. --jpgordon∇∆∇∆ 23:43, 7 May 2006 (UTC)
There is also the idea to use fullenes to deleiver medicine [21]. --Chapuisat 20:08, 8 May 2006 (UTC)
Here's a link to the article on activated carbon, so that the person who wrote the original question can read about its huge surface area. Arbitrary username 15:45, 8 May 2006 (UTC)

[edit] Another computer problem

I have recently received a computer [for free] from my father’s company. He didn’t want it, so now it’s mine :P. I have a weird problem though: every time I turn it on, the computer asks me to log in with a username and password. FWIW, the computer runs on Windows 2000 Professional. I’ve tried to get around the login by going into safemode and whatnot, but it always ends up on the login screen. Even if I type in a legitimate username and password, I can’t get through, because the computer is making a vain attempt to connect to a server that no longer exists. My question is this: is there a way for me to disable the network login without being able to bypass the login or having boot disc for Windows 2000? Perhaps there is a way to get into DOS upon startup and disable networking…?--The ikiroid (talk)(Help Me Improve) 16:44, 7 May 2006 (UTC)

Wipe the hard disk and install Linux. --Trovatore 20:53, 7 May 2006 (UTC)
If you don't like Trovatore's suggestion (I may be a penguin fan, but it's not always the right solution) there should be seperate "Safe mode" and "Safe mode with networking" options. Also, at the login screen you should be able to select between logging in locally and using a network (domain) login - if you don't get a third box to select that beneth the username ansd password boxes then click "Options" and it should show up. Another possibility is that the recovery console may be installed - if it is then it will be shown as an option on the boot menu, you will need the local admin password to use it. -- AJR | Talk 23:04, 7 May 2006 (UTC)

With old corporate, networked PC's and laptops, the only answer is to go to Linux. First, for a corporation to give it away, it has to be really old! Second, the corporate IT-jocks have probably really done a number on it, for 'security'. I've had lots of success with those throw-aways and Linux. --Zeizmic 23:45, 7 May 2006 (UTC)

You'll get nowhere without admin priviledges, that is the way the system is designed, and it is quite good at it. If you cannot get these passwords (company may not want to reveal these), you can ask your dad to get the company IT person to add an admin account for you (he would have to take it in for this). Then all the logins and startups can be accessed and changed, using the new admin account. The simplest is really installing a system that you own - sounds like you are most comfortable with Windows, but that costs, whereas Linux is free, and the newer GUIs are relatively easy. If the system is running Windows 2000 it can't be too old. --Seejyb 11:20, 8 May 2006 (UTC)
Umm, well here's the other big twist: the company doesn't exist anymore. I guess I forgot to mention it's my dad's old company.--The ikiroid (talk)(Help Me Improve) 11:48, 8 May 2006 (UTC)

Then you are attacked by the proverbial helical inclined plane. --192.75.48.150 12:13, 8 May 2006 (UTC)

Try this[22] site to get access to admin account. With access to the disk the data can always be read, updated and changed, a computer is not that hard to break. Stefan 07:09, 9 May 2006 (UTC)
Will that work with Windows 2000? I don't need the data inside. BTW, I'm willing to format the hard drive to erase everything except Windows 2000.--The ikiroid (talk)(Help Me Improve) 01:28, 10 May 2006 (UTC)
Did you read the web page? Tested on: NT 3.51, NT 4 (all versions and SP), Windows 2000 (all versions), Windows XP (all versions, also SP2), Windows Server 2003 (at least Enterprise)., how can you format everything except windows 2000? and if you could, if you can not login it still does not help. If you are prepared to reinstall windows then just do that! Stefan 06:13, 10 May 2006 (UTC)

[edit] Diamonds: How many are consumed by the United States AND How many diamonds are extracted in the United States?

Diamonds: How many are consumed by the United States AND How many diamonds are extracted in the United States?

Thank you so much.

Are diamonds actually consumed? User:Zoe|(talk) 21:04, 7 May 2006 (UTC)
I dont know, its strange, consumers do something with them, the name suggest consumers consume, but to me atleast it implies ingestion... Philc TECI 22:02, 7 May 2006 (UTC)
I had 20 diamonds for breakfast today. Perhaps you want to consult our article on diamonds?--Frenchman113 on wheels! 20:51, 9 May 2006 (UTC)

[edit] History of Health Screening

My stepdaughter has been trying to find information on the history of Health Screening (as we are in the UK, I suppose with a UK bias) and has had little success. I too have tried and not really found anything. Could someone please point us in the right direction or give us some information. Many thanks. emjay----------

[edit] Fullerene

I had heard about fullerene, and learned a few thing about it, but never seen it until I saw the wiki article on it, where it shows the compound in crystalline form. I thought, how is fullerene bonded as a solid, was this at extremely low temperature, or is there a bond between the balls, or what, are they held together by Van der Waals, if that is possible. If they are, how can they stay together at high temperatures. Also the same question about buckminster fullerene, as that has Carcons with only 3 bonds, which would make inter molecular bonds possible (wouldn't it) so is that bonded differently? Philc T+C 18:46, 7 May 2006 (UTC)

Indeed, they are held together by VdW forces, and are therefore weak and soft as a solid. They sublimate at high temperatures. The carbons have more than three bonds, though - it's a conjugated system, so while it's possible for them to bond to other molecules, but that would break the aromaticity of the system, so they're not very happy to do so. --BluePlatypus 20:18, 7 May 2006 (UTC)

[edit] the gay gene

hi, now that its estabished that people are gay through nature rather than nuture, does anyone know whether there was definitive study that drew this conclusion or was it more a set of smaller ones that tended towards it? if anyone could direct me to them then that would be great. also, i would appreciate it if bigots wouldnt post their vitriol here... thanks! andrew

Biology and sexual orientation. -lethe talk + 19:40, 7 May 2006 (UTC)


There is almost certainly no single "gay gene". If homosexuality were a simple Mendelian trait, this would have been known for a long time. People with axes to grind on both sides like to describe homosexuality as though it were one single well-defined thing, but human beings are a bit more complicated than that. --Trovatore 19:42, 7 May 2006 (UTC)
"now that its estabished that people are gay through nature rather than nuture" - So, every single experiment peformed everywhere in the world by every scientist has proven that people are gay through nature, not nuture? Wow. That's news. I'm surprised to find it in the Wikipedia Reference Desk and not on CNN. Or... is this just another troll using a false assumption to pose a baited question? --Kainaw (talk) 22:39, 7 May 2006 (UTC)
WP:AGF. Arbitrary username 16:15, 8 May 2006 (UTC)

Homosexuality is most definatly not caused ONLY by genetics. Several studies on identical twins have been done that show that genetics probably plays a roll, but if genetics were 100% responsible for homosexuality, the percentage of twins that had the same sexual orientation would be 100, but it is not even close. It's more like 40-something. --Crucible Guardian 23:20, 7 May 2006 (UTC)

While I agree with you that it's certainly not 100%, 40% seems a little low. I haven't seen any recent statistics about sexual orientation (maybe someone could find some), but the most recent ones I remember seeing is that something like 10% of the population identify themselves as homosexual. (Note: I realize sexual orientation is much more complicated than a two-bin or even three-bin system, but I'm simplifying it for statistics sake.) Even if you up that to 20% of the population being homosexual or bisexual and 80% of the population being heterosexual, that would mean that if you pick two people at random, 64% of the time you would have two heterosexuals. So wouldn't 40% imply that twins are more different in their sexual orientation than two random people off the street? EWS23 | (Leave me a message!) 23:49, 7 May 2006 (UTC)
Not sure, but I think Andrew might have been thinking of this article - which, for the record, is still a long way from "establishing" that homosexuality arises from nature as opposed to nurture. -- Filliam H Muffman 03:48, 10 May 2006 (UTC)
It's worth noting that the binary distinction (hetrosexual vs homosexual) or even trinary (hetro, bi, and homo) is not granular enough. Alred Kinsey put people on a 0 to 6 spectrum (the so-called Kinsey scale), and found that found that 46% of people were bisexual, to varying degrees (see Kinsey_Reports#Sexual_orientation). Raul654 03:55, 10 May 2006 (UTC)

[edit] petroleum distillates

Are petroleum distillates absorbed through the skin? I'm having trouble finding out information. If they are absorbed, what is the effect on the body? KeeganB

The problem is that "petroleum distillates" is a huge group of products. Some are absorbed and some aren't. For example, some petroleum disillates are skin lotions - if they weren't absobed, they'd be useless. Other petroleum disillates are like a wax (such as the waxy coating on milk cartons). It isn't absorbed by the skin because it is too hard of a wax - if it wasn't it too would be useless. Of the literally thousands of products made by petroleum distillation, you need to specify which ones you are concerned about. Obviously, the effect of absorbtion would be different depending on the product. Skin lotion makes your skin softer. There are some aromatics that make your skin smell better (or at least different than the normal skin smell). --Kainaw (talk) 22:49, 7 May 2006 (UTC)

I'm talking about the kind in furniture polish. KeeganB

Oh, nevermind, I managed to find the MSDS. The answers is no. I'm such a fuck up. KeeganB

Hmmm... someone is calling themself a rude name and not me. I think I answered the question wrong. --Kainaw (talk) 00:04, 9 May 2006 (UTC)

[edit] May 8

[edit] Boy with 'no brain'

This post claims that someone with only 1 cubic mm of brain tissue functioned normally, and a search for the professor mentioned in the post reveals similar stories. Do you know if this has ever been published anywhere reputable, or is it just a spontaneously generated bit of wishful thinking?

The article you mention was certainly published in Science Magazine (1980, 210, 1232-1234) which is a reputable journal, your interpretation of the facts in the post that you link to are not accurate. Here is a better description of the article which discusses the thickness of the cerebral cortex (a PORTION of the brain) and not the volume of the brain as a whole. Still, the article raises many questions. -- C. S. Joiner (talk) 00:42, 8 May 2006 (UTC)
I looked up the article (citation above). While Science is a highly reputable journal, it's in the "Research News" section, which means it's not a research paper, nor is it subject to peer review. Anyway, Lorber is quoted as saying "we saw that instead of the normal 4.5-centimeter thickness of brain tissue between the ventricles and the cortical surface, there was just a thin layer of mantle measuring just a millimiter or so.". Later in the article, a neurosurgeon points out out the difficulty of interpreting brain scans ("Interpreting brain scans can be very tricky. There can be a great deal more brain tissue in the cranium than is immediately apparent"), and is quoted as saying "Lorber may be being rather overdramatic when he says that someone has 'virtually no brain'." And Lorber acknowledges as much, but still says that the brain must nevertheless be substantially smaller than normal. So as pointed out, it's only a particular portion of the brain that's being referred to there (and then as "a few millimiters" as opposed to 4.5 cm). And that should probably be taken with a grain of salt. The overall impression of Lorber seems to be that he's fairly well-respected but considered something of the kind of provocateur who likes to make big claims and challenge preconceptions. (other controversial ideas of his are mentioned) In other words, worth listenting to, but not trusting blindly. In any case the "One cubic millimeter" claim is certainly false. But the gist of the thing - that there's someone out there with high IQ and a substantially smaller brain than most, is probably true. The main point of debate seems to be (or have been at that time) what role the cerebral ventricles play. --BluePlatypus 01:08, 8 May 2006 (UTC)
And the cubic millimeter aspect refers to the thickness of a layer of cortex tissue, as I understand it, not a total volume of brain tissue. It is not a little cube of brain; it is a very squashed down and/or thin brain tissue. --Fastfission 01:59, 8 May 2006 (UTC)
There is no "cubic millimeter", that was a misreading. Black Carrot 02:35, 8 May 2006 (UTC)

[edit] Turkish Quadrupeds

Whatever happened to this story? Seems to have fizzled out. JianLi 00:56, 8 May 2006 (UTC)

What were you expecting? --BluePlatypus 01:39, 8 May 2006 (UTC)
Good question. I'm not sure exactly. The announcement that the whole thing has been a great fraud? Or, if not (since reputable news sources are carrying it), a conclusion regarding the cause of it?JianLi 02:52, 8 May 2006 (UTC)

it's really cool anyway

I remember watching that programme in the UK; it's a real shame for them. Kilo-Lima|(talk) 20:13, 8 May 2006 (UTC)
side note: i just read a story on them in Discover magazine. it was basically about how the media circus made a big deal out of nothing. -Jian

[edit] Pulse Jet

If a valveless pulsejet were to be built with a cruved pipe, with out a camber and increasing or decreasing pipes, would it still work? Patrick Kreidt

[edit] Medical Formulations

Why do most medications have HCl in their formulations?

Because they get absorbed faster your digestive system if they're a hydrochloride. --BluePlatypus 01:39, 8 May 2006 (UTC)
That's a rather bold statement. Surely you have some evidence to back that up? --Chris 03:20, 8 May 2006 (UTC)
What's bold about it? Note that I'm not saying everything gets absorbed faster as a hydrochloride. Nor did I say that it's the only reason hydrochlorides are used. If you expect a short, simple Reference Desk answer to a short, simple question to be an all-encompassing absolute truth of biochemistry, you're nuts. But no, I don't have any evidence of that. It's just what I was told in the (albeit introductory) class I took in pharmaceutical chemistry. Making something a hydrochloride salt can make it more water-soluble and faster to absorb in the digestive system. It seemed like a reasonable explanation to me then, and I assume that the people at the drug companies have the evidence to support it. I'm not exactly in the position to give a full review of all available litterature on pharmaceutical salts (and there seems to be a good amount of it), although I do feel pretty confident it doesn't contradict what I wrote. So what exactly do you think is wrong with that statement? --BluePlatypus 04:46, 8 May 2006 (UTC)
...Hydrochloride -- Mac Davis] ⌇☢ ญƛ. 04:46, 8 May 2006 (UTC)
Yeah, I just found that myself and was about to point it out. Hopefully it was written by someone with more direct experience than myself. At least it appears so from the details. --BluePlatypus 05:03, 8 May 2006 (UTC)
In general, most organic compounds such as pharmaceutical drugs are more soluble in water when they are in a charged (ionic) state rather than a neutral one. A large number of drugs contain nitrogen atoms than can be readily converted to ionic ammonium salts by the addition of an acid. The ammonium salts tend to have better bioavailability than the neutral compound because of their better solubility. There are many pharmaceutically acceptable acids that can be used to form the salts, but hydrochloric acid is common because it is a strong acid that will completely form the ammonium salt. And there is plenty hydrochloric acid in your digestive system already, so it is unlikely to cause problems. --Ed (Edgar181) 11:57, 8 May 2006 (UTC)

[edit] plant question

does co2 in a plant travel through xylem, phloem, or...?

You may be thinking of stoma; CO2 that enters there doesn't have to travel very far to get to the places where it's needed for photosynthesis. --AySz88^-^ 03:37, 8 May 2006 (UTC)

ok. the longer explanation follows. im taking the bio ap tomorrow, and my teacher gave us a take-home open-note (and internet, but not fellow student) test on the last section we'd need to know for the ap. one of the questions was: "If radioactive CO2 is supplied to a mature leaf of a plant, it is often possible to detect radioactivity in the young growing leaves of the shoot apex a few hours later. In which tissue did the radioactive compound(s) travel? a. phloem b. xylem c. stomata d. cortex e. pith"

I'm @$&# near positive it's not cortex or pith because that wouldn't make any sense and pith doesnt even really fit in the whole picture. i know the stomata accept the CO2 and transpire away water, so i was thinking the xylem would carry it, because it doesn't seem to me that the stomata, being small, single cells, could be the "tissue" (if they're considered tissue, which I think they're not)in which the compounds "travel." sorry i didn't elaborate earlier, and thanks for the help

The teacher is probably testing for some insight here: In the leaf, CO2 is incorporated into sugars via photosynthesis (hence the word supplied); how are sugars transported? --Seejyb 11:36, 8 May 2006 (UTC)
The C02 moves int through the stomata where it immediately enters a palisade cell, energey is used from a light source to combine the CO2 with H2O to make C6H12O6 (glycerol) this is then transported around the plant via the Phloem cells, the xylem cells are solely for carrying this up from the root, the phloem move in any direction. so CO2 travels through stomata only, the C (which would be the radioactive part of CO2 most likely) would then travels about the plant in sugars, which are in the Sap. Philc TECI 14:16, 8 May 2006 (UTC)
basically correct, but I'd like to point out that C6H12O6 is glucose, not glycerol. GeeJo (t)⁄(c) • 18:40, 8 May 2006 (UTC)
oops hehe, cheers for pointing that out ;) Philc TECI 22:30, 8 May 2006 (UTC)

thanks

[edit] very general physics

i am a highschool junior who has enjoyed science for years but has no particular affinity or interest in pursuing it heavily in college or as a job. so i signed up for the harder of two AP physics courses at my high school, which i'm supposed to take after learning calculus, when i haven't yet learned calculus (i'll be doing it concurrently), because the other course doesn't sound as interesting. i'm excited, but the course is supposed to be really tough, and i want to prepare as much as possible for it over the summer. any books anybody'd suggest i read to help me with understanding the physics (or calculus) basics? if i was just to try to learn physics basics on wikipedia, how should i go about doing that? they have a "where to start" section, but it didn't help much because i have no idea what i'm looking for. thanks so much to anyone who can help

Well.. I'd suggest working from a textbook. Wikipedia is (or tries to be) an encyclopedia, and as such isn't really that great for learning physics and math. (in my opinion) It's better to work from a textbook where the things build on eachother naturally, and where you can solve problems and make sure you understand things properly before moving on. Both are the kinds of subjects where if you skip ahead, you can miss some of the basics and have to pay for it later through lots of confusion. (I've been there plenty of times myself) On the other hand, if you've got a solid understanding of the basics, you can get pretty far on that alone. So I'd suggest seeing if you can get hold of the textbooks you're going to use, and start studying the first couple of chapters or so and build up a solid base. Or you could at least build up your existing skills and make sure that you're completely at home with the level of math and physics you're supposed to know so far. It's always easier to build on a solid base. --BluePlatypus 04:16, 8 May 2006 (UTC)
(Stop edit conflicting me! :p)
Coincidentally enough, I'm going to be taking this test tomorrow (and while I wrote this, my "tomorrow" became "today" >.< ).
Basically, I would comb over the Physics C Course Outline and concentrate on learning concepts. Personally, I needed a little extra effort to grasp concepts in rotation, like torque or angular momentum, and in electricity, like Gauss's law and voltage. (If, while you learn things, you encounter anything that you don't understand and/or is too mathy in Wikipedia, I would come back and ask here for help.) You'll probably also want to be familiar with concepts in calculus, like the meaning of taking a derivative (finding instantaneous rate of change) or an integral (adding up lots of small changes), and what the symbols mean (all the equations you need to know from calc are on the reference table). You might want to know just the concept of a surface integral - but you don't need to know how to do it - so you're not too confused when you see that symbol.
Our school actually takes Physics B and Physics C in sequence - two years in total - so you'll have to cover a lot of ground! (But B has some extra junk that C doesn't have, so that shortens things a bit.) Good luck! :) --AySz88^-^ 04:18, 8 May 2006 (UTC)

im taking the bio ap tomorrow. good luck too and thanks to both of you

(edit conflict again >.<) Oh, speaking of textbooks, there's a list from the folks at the College Board. Mine is the second one, "Physics for Scientists and Engineers". Don't just look at the first couple of chapters; that would be lethal with something with so many topics. I would look at the first few sections of each chapter, skipping the calculus-heavy parts.
Thanks, and good luck again! :) --AySz88^-^ 04:25, 8 May 2006 (UTC)

[edit] endocrine system

The chief cells of the the parathyroid glands produces a hormone that does what?

Homework? --BluePlatypus 04:02, 8 May 2006 (UTC)

parathyroid hormone (it's a wikipedia entry) - increases blood calcium levels, wheareas calcitonin (in the thyroid) decreases it

[edit] Faster Than Light

I've heard that light is the fastest thing in the world and nothing travels faster than it.But instead of saying that light is the fastest thing in the world, why don't we say that light is the thing that's known to be the fastest thing in the universe?I mean, what if there are things that travel faster than light, but it's just that they haven't been discovered?User:Bowei

  • Instead of "it is known to be the fastests thing in the universe" which implies we are absolutely certain there's nothing faster, I would say "light is the fastest known thing in the universe". By the way: Anything that travels faster would go against a few basic physical theories whose formulas include the constant c for the speed of light. We know it's the fastest because the mathematics say so. - 131.211.210.11 07:55, 8 May 2006 (UTC)
The Theory of Relativity, which has been extremely succesful thus far, says that some very weird things would happen if anything went faster than light. It makes accelerating through the speed of light impossible, since the energy required to even reach the speed of light would be infinite. Hypothetical particles that are always faster than light are called tachyons, and they present problems for causality, as you can read in the article. -- SCZenz 08:50, 8 May 2006 (UTC)
Interaction between things that are faster than light and slower than light would violate causality, and is therefore impossible, so if there is anything faster (eg. tachyons) they are effectively not in our universe, as they can in no way possibly effect anything in the known universe. Philc TECI 11:07, 8 May 2006 (UTC)
As I understand the theory of relativity it doesn't say that nothing can travel faster than the speed of light it says that nothing can accelerate to a speed faster than that of light. I don't know who but I've heard at least one reputable physisist has theorised about the possibility of traveling faster than light without accelerating beyond it. AllanHainey 15:39, 8 May 2006 (UTC)
Hmm, this is the third time I've brought up Cherenkov radiation in a discussion like this in a week. Maybe we ought to make a Reference Desk FAQ to save answering the same few questions over and over. GeeJo (t)⁄(c) • 18:37, 8 May 2006 (UTC)
You mean, like a resource where people can look up information that they might be interested in? A searchable database of the communal knowledge of contributers to answer their questions? Skittle 09:34, 9 May 2006 (UTC)
As if by magic, there already is one! :) — QuantumEleven 14:52, 9 May 2006 (UTC)
Who'd have thought people would act so quickly on my idea? : ) Skittle 15:15, 9 May 2006 (UTC)
I take objection to "We know it's the fastest because the mathematics say so". Please remember that both newtonion physics and relativity are simply equations that fitted the facts known at the time to the level of accuracy that could be measured at the time. All mathematics does is tell us that *IF* one thing is true another thing is also true. It CANNOT tell us outright that a statement about the real world is true. Einstein himself summed this up nicely with "As far as the laws of mathematics refer to reality, they are not certain; and as far as they are certain, they do not refer to reality." Plugwash 16:33, 9 May 2006 (UTC)
I am surprised that no one has yet mentioned the implications of Bell's Theorem, which can in many cases be interpreted to violate the local causality assumed in the EPR Paradox. Varied interpretations of this field are many, not least prominent among which is Jack Sarfatti's notions of superluminal travel. On the other hand the most favoured alternative to these considerations are the no-model option chosen by the Copenhagen Interpretation of Quantum Mechanics, and that has its own matters in the Problem of Measurement. So far, even for a maximal theory, Quantum Mechanics is still very much incomplete and one has to be prepared to delve into ever more esoteric speculations, not least because they are absolutely necessary. The problem really rests now upon the conceptions of causality in physics- we are struggling with the possiblity of having to give up the Principle of Local Causes after all. Yet if the Bell's Theorem is taken to be mathematically verified then this must fail, so the only alternative that became available is one that refuses the consider the matter by deeming it pointless- the Copenhagen Interpretation.
On the other hand if the other minor interpretations may be justifiable on some higher ground then superluminal possibilities may indeed be entertained. Or perhaps, like so many other human enigmas, it is simply one in which we will never solve, the beginning of a model which we look to only when other have collapsed or became too clouded.
Finally in another argument I would like to propose that there is a difference between "faster than the speed of light" to "exceeding the speed of light". In order to exceed one first must reach a certain standard, in this case the speed of light, which is a requirement that no bodies known to us may fulfil save the photon. However for a body that is already and always shall be travelling faster than the speed of light, matters may appear very different from a varied perspective. Luthinya 11:50, 15 May 2006 (UTC)

[edit] NGV.GAS

What is the NGV.gas?

Does NGV help? Weregerbil 09:34, 8 May 2006 (UTC)

[edit] a duck's quack

i have heard that a duck's quack does not echo.Is this true?If yes why?

A duck's quack WILL echo. The reason for why this is disputed is because the quack's sound "blends in" sort of with the echo. ALL air waves sent out will hit things in their way. Airwaves WILL bounce back (depending on material and composition), and though losing energy as they go along, WILL be heard as echoes.
A ducks quack diminishes at the same rate as an echo, so it is almost impossible to distinguish the two Philc TECI 11:04, 8 May 2006 (UTC)
This is a myth, and is very hard to differentiate after fairly scientific experimentation as well. -- Mac Davis] ⌇☢ ญƛ. 11:37, 8 May 2006 (UTC)
Look at the duck article where it links to snopes.com. The scientific experiment didn't seeem that hard to me. --KJ 11:54, 8 May 2006 (UTC)
  • The Mythbusters busted this myth. The quack had an echo, just a very faint one. - 131.211.210.16 07:59, 9 May 2006 (UTC)

[edit] Microwave data transmission

Just "suppose" I want to transmit 10 Mbit/sec of data across, say 30km of line of sight at microwave frequencies. First, what bandwidth of spectrum would I need? Secondly, what is the typical cost for receiver/transmitter/microwave dish/etc for the pair that are needed (one each end), excluding any masts and installation. Thank you.

I'm no expert in communications technology, but roughly speaking the bandwidth is going to be of similar order of magnitude as the data rate, and I guess probably a bit more to allow for some of the high-frequency components that you'll get in the sharp edges in your signal, so I guess maybe a few tens of MHz. Arbitrary username 16:10, 8 May 2006 (UTC)
I think it would be usually less than 10 MHz (strictly speaking, depending upon a modulation). I have seen 64QAM and 128QAM being used in radio relay links, in this case the bandwidth would be just about a few MHz. But, again, it strongly depends on modulation. --Ring0 22:25, 8 May 2006 (UTC)
The absoloute minimum needed comes down to signal to noise ratio (see shannon limit) and that comes down to distance and effective radiated power. In reality the bandwidth needed would be higher as no modulation scheme is perfect. Also i think you'd need quite a tall mast as microwave is largely line of sight. If you are seriously interested in this you need someone with practical experiance in whats availible. Plugwash 16:45, 9 May 2006 (UTC)

[edit] wierd!

hey 2 all!

In order to understand my question: Rotate your right foot in clockwise direction while sittin.Simultaneously draw the number 6 with your right hand in air.You will find that your foot has changed its direction!

Now my question: Why the hell does this happen?????

Because you rotate your foot. –Mysid 10:42, 8 May 2006 (UTC)
Welcome to Wikipedia, please talk smart next time. It is because your brain is getting mixed up basically. -- Mac Davis] ⌇☢ ญƛ. 11:36, 8 May 2006 (UTC)

Mac, please Don't bite the newcomers

Anonymous, this is because the brain is conditioned to do things in certain (easy) way. This applies to any new skill you learn (like playing piano, juggling the balls or rotating your parts in the way you discribed). You can overcome this by practicing the act slowly and repeatedly.--Wikicheng 11:54, 8 May 2006 (UTC)

Either I misunderstood the question or I'm a subconscious nitpicker, because it seemed so logical to me why a foot changes its direction while it's being rotated. –Mysid 12:04, 8 May 2006 (UTC)
Oh my goodness, that's cool! Mysid, the question was suggesting that your foot starts tracing a circle in the other direction, ie counter-clockwise. If you trace the circle clockwise and draw the six starting from the top, or trace the circle counter-clockwise and draw starting from the loop, I've found that it really does work (unless you're trying, in which case it's not too hard to do it correctly). It's much like patting your head and rubbing your body, in that it's hard if you're not expecting it, but easy to overcome. Anon, I have can't give a precise reason, but whatever it is, it's cool! — Asbestos | Talk (RFC) 12:11, 8 May 2006 (UTC)
Ah yes, the direction of rotation. :) Thanks and sorry. It really is weird... –Mysid 12:36, 8 May 2006 (UTC)
Yes the brain cannot concentrate on the two movements at once, which is where it asks the cerebellum and basal ganglia for help to automate part of the movements. This is called motor learning, and it takes practice. Some combinations of limb movements are learnt from a very young age, but when you think up a new one (such as writing, driving a car, or combining clockwise-foot and anticlockwise-hand movements) it takes some time for your brain and cerebellum to get it right. As suggested by Wikichen, if you try very slowly, maybe first just the foot movement, and gradually increase the pace, you will eventually manage to maintain your clockwise foot rotation while drawing what you want with your hand. Impress your friends and neighbours!--Seejyb 12:32, 8 May 2006 (UTC)
This trick is described on page 9 of the the classical book of our childhood: Grätzer József, SICC, Móra Ferenc könyvkiadó, Budapest, 1964. – b_jonas 18:15, 8 May 2006 (UTC)

Is it just me, or is this exactly like a question that was asked a really long time ago[23]? Black Carrot 23:28, 8 May 2006 (UTC)

Maybe the questioner meant, "Hey everyone, rotate your right foot a clockwise direction. Simultaneously, with your right hand, copy and past the same question you've already asked into Wikipedia. Get the same reponses. Why does this happen?" --Kainaw (talk) 23:58, 8 May 2006 (UTC)

[edit] science

who is the giant spagetti monster god

Chef Boy-R-Dee?
Flying spaghetti monster. Isopropyl 13:07, 8 May 2006 (UTC)

[edit] Collapse of Wave function

When we observe stuff the wave function collapses but why?

The dynamical evolution of the wavefunction requires that a state with definite value of some observable will eventually evolve into a state which is in a superposition of values (unless it's a stationary state). On the other hand, experience with measurement tells you that if you measure something to have a value, it definitely has that value. If you measure something twice in rapid succession, then you should see the same value twice. Therefore, measurement must change the wavefunction from a dispersed state (which is in a superposition state of different values) to a sharp state with a definite value of your observable. -lethe talk + 14:49, 8 May 2006 (UTC)
Not nessesarily, see þis. *Max* 21:45, 8 May 2006 (UTC)
That's just one of the popular interpretations of QM. There are also others that do better to avoid the Problem of Measurement. Luthinya 11:55, 15 May 2006 (UTC)

[edit] Dell Dimension and Pinnalce PCTV does not work properly together

I recently bought a new Dell Dimension 9150 and it works great, except for one problem: my TV tuner card (Pinnacle PCTV 310i DVB-T) is able to scan for channels, but no channels are ever found. I am quite sure that this is some kind of incompatibility between the PC and the card, because the card worked properly in my previous PC. Any suggestions on how to solve the problem? I have search the Internet, and it appears to a be quite common problem. Thanks in advance. --Andreas Rejbrand 15:27, 8 May 2006 (UTC)

If it is such a common problem, why are there no answers? Perhaps you should try asking a Dell tech support representativevs. That's what they are there for. You can find their main support page here. You can also chat with hardware support reps or visit the Dell forums. --Chris
Hardware Support Chat would be great, but I am not allowed to use it as I live outside the US (in Sweden), and I've already tried to ask the question in the Dell Forums. I thought that someone here might have encountered the same problem. --Andreas Rejbrand 16:01, 8 May 2006 (UTC)

[edit] Radioactivity at Chernobyl

The Prypiat, Ukraine article claims that it "will take up to 900 years to decay sufficiently to render the area safe" while the Chernobyl disaster article says "rendered land in a radius of hundreds of miles from the plant uninhabitable for at least 100 years." Both are unsourced and many similar unsourced claims appear on Google. Which is correct? How long will it take for the more contaminated areas (excluding the plant itself) to get back to about background levels? Cesium is the major radiation source and has a half life of 30 years, so in 900 years, only 1/10,000,000th of 1% would remain. The map in the disaster article shows the most contaminated areas at "greater than 40 curies per square kilometer" and the background radiation article says that average it is about 2.5 mSv, but there seems to be no way to compare those numbers. Rmhermen 15:42, 8 May 2006 (UTC)

It seems that the article on the radio-active isotope, Caesium-137, has a half-life of thirty years... Kilo-Lima|(talk) 20:20, 8 May 2006 (UTC)
Its quite hard to calculate. If all the radioactivity other than prior background was due to one element and that element decayed into a non radioactive element and didn't activate anything else then the time taken for radiation levels to drop to twice background (e.g. the point at which natural radiation would start dominating contaimination) would be (log2current/background)*half life (assuming current and background are in the same units). In reality the dominant isotope will change over the years and there are decay chains and activations of elements hit by radiation to consider. Unfortunately one of your figures is actual radiation and the other is a biological radiation effect figure so they aren't directly comparable. Plugwash 17:02, 9 May 2006 (UTC)

[edit] Reaction Types

Are ther eany types of chemical reactions that are not redox reactions? They teach about redox reactions as if they are special, but I can't think of any reactions that aren't redoxes. Maybe I'm not thinking hard enough?--Chris 15:37, 8 May 2006 (UTC)

If I am not mistaken, the
H + H → H2
reaction is not a redox reaction. --Andreas Rejbrand 16:06, 8 May 2006 (UTC)
There are plenty. (and more conventional than above) E.g., the classical textbook SN2:
CH3Br + OH- --> CH3OH + Br-. Indeed, all substitution and condensation reactions, among many others. --BluePlatypus 16:25, 8 May 2006 (UTC)

I Verify the above; while there may be some exceptions,substitution and condensation reactions are not redox reactions. --Craiglen 16:42, 8 May 2006 (UTC)

A variety of other types of reactions can be found at chemical reaction, or you can look at Category:Chemical reactions for many more examples. --Ed (Edgar181) 16:48, 8 May 2006 (UTC)

Acid-base reactions--usually studied in general chemistry classes before redox reactions--are not redox reactions. Chuck 19:42, 8 May 2006 (UTC)

[edit] Birds

Do all birds lay eggs? I seem to remember from my college orinthology course that there are some species of birds that do not lay eggs? I got $5 riding on this with a friend so if you can prove him wrong. Even if you have to stretch the "truth" a little, that'd be grrrreat.

Depending on how hard you're willing to bend the truth, male birds don't lay eggs :P -- Ferkelparade π 16:27, 8 May 2006 (UTC)
None of the readily available sources seem to cast doubt that all birds lay eggs. I seem to recall this debate in the past, and that there was a type of bird that essentially produced an egg but it hatched internally so the young exited the body without it... but i don't remember any of the sources for that so it may have been a delusion. There are a few sites that attest to egg laying as a critical feature of birds, and our article on birds has this to say: "Common characteristics of birds include... the laying of hard-shelled eggs". Hope this was the answer you were looking for! --Jmeden2000 18:12, 8 May 2006 (UTC)
Continuing to bend the truth, there's jail-bird, whirlybird, yardbird... --Shantavira 18:51, 8 May 2006 (UTC)
Maybe you are confusing birds with fish. I was always told that all fish laid eggs. Then, I found out that there is some type of fish called Molly (or something similar) that doesn't lay eggs. --Kainaw (talk) 23:59, 8 May 2006 (UTC)
Not all sharks lay eggs either. But again, that's fish not birds. Grutness...wha? 01:30, 9 May 2006 (UTC)
The term is "ovoviviparous", but a search for "ovoviviparous birds" gives me nothing. --KJ 00:24, 9 May 2006 (UTC)
Neither does "avian ovoviviparity". --KJ 00:29, 9 May 2006 (UTC)

Maybe there's a kind of bird that doesn't lay eggs, it just merely excretes them, or perhaps shoots them out at high velocity. freshgavinΓΛĿЌ 04:22, 9 May 2006 (UTC)

The article egg (biology) claims that "This is the reproductive way of many fish, amphibians and reptiles, all birds, the monotremes, and most insects and arachnids." However, I wonder if there exists some kind of "mule" bird that is sterile and thus cannot lay an egg. – b_jonas 17:13, 9 May 2006 (UTC)
If there was a bird that shot eggs out at high velocity, wouldn't they be liable to break, and therefore defeat the purpose of laying them? -- Filliam H Muffman 03:55, 10 May 2006 (UTC)
I imagine it would be a freak survival-of-the-fittest kind of thing, where the baby birds that learn to fly after "houdini-ing" out of the egg and before smacking into a wall survive, and those that doze off die before knowing that anything else ever existed. freshgavinΓΛĿЌ 06:55, 10 May 2006 (UTC)
That's a nature documentary I'd like to see. -- Filliam H Muffman 02:55, 11 May 2006 (UTC)
Lol – b_jonas 20:04, 11 May 2006 (UTC)

[edit] CT scan visuals?

Kind of a weird one here...the other day I went for a CT scan of my sinuses, and during the procedure I saw strange blue lines moving up and down my vision (eyes closed). Of course I was supposed to keep still, but the appearance of these startled me, and I wondered...if these are seen by many people, why don't they warn the patient? If they aren't seen by many people, what's different about me? --Kickstart70-T-C 17:21, 8 May 2006 (UTC)

See X-ray#Visibility to the Human Eye. —Ilmari Karonen (talk) 17:41, 8 May 2006 (UTC)
The scanner has a "targeting" line of light (usually red) which indicates to the operator what plane (transverse "cut") of the body is being scanned. As your head moved through the scanner, with sequential planes being scanned, the line of light moved down over your face. I agree about the need to tell the person being examined. I wonder though, why you experienced the light as blue - any chance of your having royal blood in your eyelids? --Seejyb 20:51, 8 May 2006 (UTC)
I'm pretty sure Ilmari Karonen has it...the lights weren't following a linear path (top to bottom or vice versa)...they were stripes of light that appeared in multiple lines at once. And now I can claim I can see x-rays :) --Kickstart70-T-C 05:55, 9 May 2006 (UTC)
Your experience asks for some looking into: Why blue light? Why the pattern not corresponding to external visible beams? As you say: Do more people experience this? If so, what do they describe? Maybe you can draw up a short questionnaire for persons having head scans at your local radiologists (to be answered afterwards!) - if you find others with similar experience, take it further. --Seejyb 07:42, 9 May 2006 (UTC)

[edit] Diesel-hybrid engines in cars?

Diesel engines have been hybridized with electric engines in trains, why haven't car manufactures spent money in putting the efficient diesel-hybrid engine technology into cars?

1. Wouldn't the diesel aspect gives cars the ability to be manufactured for biodiesel, therefore using a renewable resources?

2. diesel engines work on compression and therefore theoretically can last longer, right?

3. hybridizing this with an electric engine would create a relatively clean engine that runs on renewable resources, wouldn't this be a smarter alternative to today's engines?

Um, they are. :) Hybrid vehicle
Yeh they are, but it doesn't work, because all the energy used to move the huge battery discounts any saved by it being hybrid.... Philc TECI 22:21, 8 May 2006 (UTC)

[edit] Diesel Hybrid Engines

Why is it that car manufactures haven't built a car around a biodesiel-electric hybrid engine?

This type of engine (diesel-electric hybrid) has been used in trains for almost a centuary, it's efficient and robust, provides a lot of power (it drove trains) and it would use renewable resources...

-- Stewart Alexander --

Sweden is currently focusing heavily on biodiesel. This resource is rather renewable, and I don't think el-hybrids will be seen until a few years ahead, at least a decade. After all, you have to create a market for the normal car before you can sell hybrids.
Biodiesel is simply a fuel used in ordinary diesel engines - no new cars have to be developed to use it and Europe has a rather large market for diesel cars already, unlike the U.S. Rmhermen 20:02, 8 May 2006 (UTC)

A gas hybrid saves 20% in the city, and almost nothing on the highway (air resistance dominates). Current diesels already exceed that, but are dirty (I saw a brand new Jetta TDI belching!). New low-sulphur diesels should be much cleaner, so right now, a diesel hybrid doesn't make much sense. --Zeizmic 21:37, 8 May 2006 (UTC)

The diesel-electric Opel Astra should be coming out this year. The European diesels put out very little exhaust fumes. The car can apparently do 1-100 km/h in 8 seconds, and gets 60 mpg (claimed 25% better than diesel alone?). The advantage of hybrids is in short distances. See [hybridcars.com]. I personally like the idea of using butanol as a sustainable biofuel. --Seejyb 22:22, 8 May 2006 (UTC)
Hybrids cars don't work, they waste more energy than normal cars, as the battery adds so much weight to the car, scientists don't think hybrid cars will be worth the difference until a viable way of storing a lot of electricity in a small space is cracked, the current hopes lie in the hydrogen cell. Philc TECI 22:24, 8 May 2006 (UTC)
Phil, you're flat-out wrong. Hybrids are more fuel-efficient than normal cars in urban areas because a) they "recycle" some of the energy normally lost in heat when you put your foot on the brake into charging the batteries, and b) they don't waste fuel at idle in traffic; it's either used to recharge the battery or turned off. It doesn't work quite as well as the EPA mileage statistics would indicate, mind you, but it does work, and it does overcome the costs of the extra weight. The same principles also work fine with diesel engines as well.
One thing that needs to be appreciated with regards to diesel is that it's a much denser fuel than gasoline; a liter of diesel weighs about 15% more than petrol, contains about 18% more energy when burned, and releases about 18% more carbon dioxide. So, in terms of carbon emissions, the difference between diesel and gasoline is less than you might think by reading the raw fuel consumption figures.
Fuel cell vehicles will probably use most of the same tricks as hybrids to improve their efficiency, by the way; they will already have the electric motors so all they need is some batteries or supercapacitors to act as temporary storage. --Robert Merkel 23:47, 8 May 2006 (UTC)
"Hybrids are more fuel-efficient than normal cars in urban areas", I'll concede that, apologies, I should have specified. Though the battery weight is an issue, if you spend alot of time running solely off of the engine, and also I think you would be surprised how incredibly low the petrol consumption of a car in nuetral is, so when you stop in traffic, if you put it in neutral you'll save fuel. Also I dont know why they dont use the brakes to recharge the batteries in all cars, this isn't really something limmited to hybrids, although it is easier with them, already havein electric motors attached. Philc TECI 21:00, 9 May 2006 (UTC)

[edit] Visual Basic .NET

I need some help from someone good with Visual Basic.NET edition, as I learned to program in VB6, and I'm having a couple of problems with my .NET coursework project, and as usual trying to get a relevant answer out of MSDN is like trying to squeeze water from a stone.

You'll need to state what mechanism you're using to write the file. If it's something that's meant to "save" or serialize program data more-or-less automatically, there's probably a corresponding read function that will need, use, and strip the "s for you. --Tardis 17:39, 9 May 2006 (UTC)


Sorry, I've changed it a little today. I'm currently just using the PrintLine function to write the data to a .txt file:
PrintLine(1, txtIDNumber.Text, ",", txtSurname.Text, ",", txtForename.Text, ",")
I changed to that from WriteLine earlier, which was surrounding every individual string with quotes. PrintLine is not doing this. But the LineInput for reading text from the file seems to be placing quotes around the entire line feed:
"123, Smith, John"
Thats using the code (this is from my delete record sub):
Do While Not EOF(1)
    lineoftext = ""
    lineoftext = LineInput(1)
*   textarray = Split(lineoftext, ",")
    If textarray(0) <> txtIDNo.Text Then
        PrintLine(2, lineoftext(1))
    End If
Loop
All this does is read a line from the record (lineoftext = LineInput(1)), split the line into individual strings, and assign it all into an array (textarray). However, when I place a breakpoint at the * line, lineoftext's value is "123, Smith, John"
The If statement is getting confused as a result, as it is recieving the value "123 which of course does not match with 123.
Thanks for your help, CaptainVindaloo 19:31, 9 May 2006 (UTC)
Ok, got it all working now. CaptainVindaloo 18:11, 10 May 2006 (UTC)

[edit] Alternative life forms?

Is it possible that organisms could live with an element rather than carbon, i.e. silicon? Could it work hypothetically?


Thanks!

Ooh, we've got a lot of material on this question! See Alternative biochemistry and, for silicon, Silicon#Silicon-based life. Melchoir 19:56, 8 May 2006 (UTC)
[24] might also interest you. --Chapuisat 19:59, 8 May 2006 (UTC)

AHa, thanks for that :D

I recall being told that it is possible, but would recquire a radically different atmosphere, as C02, on which so much of the life on this planet depends on is a gas, however silicon dioxide, is sand, which is less easy to breathe. So hypothetically yeh, but then shouldn't everything in group IV be the same... Philc TECI 22:27, 8 May 2006 (UTC)
Unfortunately, the problems for silicon go a lot deeper than that; check out the articles. Melchoir 01:37, 9 May 2006 (UTC)
Isaac Asimov had a short writing on why carbon is the most suitable element for this form of life. I don't know its title. – b_jonas 16:14, 9 May 2006 (UTC)
If carbon is the only element that's able to form molecules neccessary for life, we could still ask whether it has to be the same molecules as we have, such as proteins built from the same 20 amino acids we have, and nucleic acids etc? If life would possibly exist based on different carbon-based molecules, I belive it would also be completely incompatible with ours, for example, we couldn't live on food made from such beings. – b_jonas 18:29, 9 May 2006 (UTC)

[edit] DSN in artic/antartica

i was thinking how much of an advantage/disadvanatges would there be to putting communication telescopes (like the deep space network) in the artic/anartica? i mean all the equipment will be kept cold easily, your a long way away from any man made sources of interfernce and u could in theory point the telescope in any direction, are there any other things i missed? and what problems are there?

Read Antarctica and find out why only penguins live there. --Zeizmic 21:33, 8 May 2006 (UTC)
Logistic problems and technocal problems with the dish aside, the ecliptic would be too close to the horizon. It is extremely expensive to shoot a spacecraft in an orbit inclined to the ecliptic, this has been done once and required a gravity assist from Jupiter. Besides, most spacecraft are shot to planets anyway. So for all practical purposes the antenna would be useless.

If you want a neutrino telescope that requires a mile of ice for detection, then Antarctica would be a good place to build it. Which is why our neutrino telescope is in Antarctica. -lethe talk + 03:29, 9 May 2006 (UTC)

[edit] IP Address

If I know someone's IP Adress how do I find out who it is? Someone insulted my friend and all I have is their IP Address. Þanks *Max* 21:25, 8 May 2006 (UTC)

You can't. So put away your ideas of keying their Rolls. --Zeizmic 21:31, 8 May 2006 (UTC)
(once again, Zeismic beats me to it) Usually it's impossible - IPs for private computers are assigned by the user's internet service provider (ISP), and some even use dynamic IPs (ie your IP changes every time you log on). At most you'll be able to get the name of the ISP, and maybe the town/city. It's different if the IP belongs to a website, in which case, you'll be able to get the name/company it's registered to. The tool you need is called a whois, I always use the one at DNSStuff.com, and it works pretty well. Try it, you may get lucky. — QuantumEleven 21:35, 8 May 2006 (UTC)
The ISP can technically trace that IP in their records. You're welcome to call and ask them to reveal the culprit, but unless you're the FBI you have nil chance. - Draeco 03:23, 9 May 2006 (UTC)
It's pretty much guaranteed that the person that insulted your friend knows your friend, and there's a very good chance that they are in close contact. Considering that the person managed to contact your friend via the internet, an easy first step would be to check the IP against people in your friend's instant messanger lists (if they use one/them). It's not possible for all programs, but in general there's hacks for things like ICQ (and I'm pretty sure messenger has one that works too) that will reveal their IP for you. Just don't do anything stupid with it. freshgavinΓΛĿЌ 04:17, 9 May 2006 (UTC)

[edit] HIV & blood transfusions

Do hospitals give people who already have HIV/AIDS blood from other HIV positive people? A Clown in the Dark 22:39, 8 May 2006 (UTC)

Doubt it as having aids, means you can't fight off any diseases, so someone with Aids probably also has just about every other disease they can get, so they would just be needlessly infecting already weak people with more viruses and illnesses. Philc TECI 22:45, 8 May 2006 (UTC)
No, hospitals don't intentionally give anyone HIV positive blood. HIV-positive people are asked not to donate blood, and any donated blood that tests positive for HIV is discarded. - Nunh-huh 23:00, 8 May 2006 (UTC)
To explain Nunh-huh's comment, the number of extra potential donors would be pretty small outside sub-Saharan Africa. Furthermore, as I understand it one person's HIV virus might not be the same as another person's - it might be resistant to a different set of antivirals - so infecting somebody who already has one batch of HIV with another might not be as harmless as you think. The very marginal benefits to the blood supply, which could only be given to a very small fraction of the population, wouldn't be worth the downsides. --Robert Merkel 23:34, 8 May 2006 (UTC)
Short answer: no. Longer answer: Robert Merkel is correct; there are a number of different strains of HIV. (Our article has the details.) This figure shows a 'tree' relating the different known strains of HIV; shorter branches link the more closely-related strains.
If you infect an individual with more than one strain of HIV, you can have (at least) two Bad Things happen. First, different strains may respond differently to a given patient's immune system and medications; trying to treat both virus strains is more difficult than finding drugs that control one strain. Second, the two viruses can swap genetic material – viruses are promiscuous little buggers – potentially resulting in a new strain that's nastier than either one by itself. This has obvious negative consequences for the patient; it also exposes the rest of society to (potentially) another more virulent and/or more drug-resistant strain.
There's also the consideration that collecting blood from HIV-positive donors would put the nurses and technicians involved in the collection, testing, transport, and delivery at additional risk. TenOfAllTrades(talk) 03:06, 9 May 2006 (UTC)

If I remember correctly, in And The Band Played On, it states that blood banks generally love lesbians, because they tend to have the cleanest blood (esbians almost never contract blood-born STDs). Raul654 03:10, 9 May 2006 (UTC)

[edit] May 9

[edit] Diesel-hybrid engines in any vehicle? Why not a quasiturbine-hybrid instead?

All the quasiturbine needs is an improved method of lubrication so that it will survive for more than 24 hours and according to its inventors its efficiency and capacity to use alternative fuels will be so high that the price of gasoline will plummet so low that there won't even be a reason for building gasoline pumps with meters. -- PCE 00:05, 9 May 2006 (UTC)

Sounds like a mild exaggeration, to say the least. According to the article and pistonless rotary engine, a functioning internal combustion version has not yet been demonstrated, and even if it were it sounds unlikely that it would offer such a revolutionary improvement in efficiency over the Wankel engine that people would abandon the 100-year-established internal combusion petrol/diesel engines en masse in its favour. What 'alternative fuels' would it run on that would warrant mothballing the massive petroleum industry? --Yummifruitbat 00:30, 9 May 2006 (UTC)
The inventor's web site (www.quasiturbine.com) claims that the quasi meets some 14 points that no other engine can (weight to power ratio, etc.) I think fuel types is one of them. The biggest fuel advantage is supposed to be its ability to be configured for photo detonation such that it can run extremely efficiently on hydrogen fuel but short of running on tar it is suppose to be able to hand even high viscosity oils - but most certainly 100% ethanol. -- PCE 00:41, 9 May 2006 (UTC)
I don't know what prompted this question, but you can't beat the Carnot cycle - the maximum possible efficiency is listed in the heat engine article. That gets you maybe a factor of two in basic efficiency over present-day piston engines, if I remember rightly. That doesn't go close to making oil too cheap to meter, particularly as what will happen is that most people would buy more powerful, heaver, and more accelerative cars to take advantage of the improved economy (see Jevon's paradox).
Furthermore, there have been all manner of alternative engine designs over the years, many resembling the quasiturbine. The Orbital engine was an example that was quite famous in Australia. None of them has been made to work much better than a piston engine. --Robert Merkel 08:03, 9 May 2006 (UTC)

[edit] Electrical generators - where do they get the magnets from?

Hi You must have a large coil of wires moving through a magnetic field, which could be normal magnets or produced from electromagnets. In large scale (power plant generators) - does each generator have a Huge magnet built in or do they have electromagnets? if the later is the case where did they get the electricity from in the first place - isn't this a case of catch22?

The electrical generator article says rotors can be powered by a separate turbine/engine. --KJ 01:33, 9 May 2006 (UTC)

If I remember correctly, to start with, they use the permanent magnets of low strength to generate some electricity. A part of this electricity is used to power the electromagnets, thereby increasing the magnetic field and hence the generated current. This goes on till a balance is reached. Please note that this is a kind of negative feedback and hence has to reach a atable state.-- Wikicheng 08:08, 9 May 2006 (UTC)

Also, this is why they price electricity differently if you buy it at low peak. As you can imagine, start-up of a large electric generator is a big deal, so it is better to keep it going as steadily as possible, continuously. This means that if you're going to produce enough power for people at peak times, you have to produce too much at other times even if nobody will buy it. Skittle 09:23, 9 May 2006 (UTC)

Its not the generator that can't increase and decrease power easilly (it can) its whatevers feeding it. IIRC nukes tend to be the hardest to ramp up and down the power on. Coal afaict isn't that hard but is so cheap its usually kept running anway. Gas turbines and hydroelectric dams are the best at varying power. The main reason electricity is cheaper at night is that comes from plants that are cheap to keep running (coal and nuclear) and moving demand to the night reduces the total installed capacity needed.
As for startup there are a number of catch 22's in starting a big plant without electricity. I belive they solve this with dedicated deisel generator units in certain plants to allow a cold start of the grid if absoloutely nessacery. Plugwash 17:09, 9 May 2006 (UTC)
Live and learn :-) Skittle 19:57, 9 May 2006 (UTC)
There's some interesting stuff about this sort of thing in Black start. --Saxsux 19:09, 10 May 2006 (UTC)
A minor aside—cold-starting a coal plant takes about a day, so utilities tend to fire them up when they will be running for at least a moderately-long time. Unfortunately, the highest-demand periods for most utilities are in the summer, when the smog from coal-fired generators is least welcome. Oil-fired boilers take a few hours to bring up; natural gas is used for peak capacity because it can be brought online in a few minutes. TenOfAllTrades(talk) 03:21, 16 May 2006 (UTC)

Typically I'd think its a permanent magnet. Likely a simple hard ferromagnet dug out of the Earth, it wouldn't be an electromagnet because if you think about it, if you could use the electromagnet to power a generator, then simply feeding the electricity back into the generator would produce more electricity -- violation of entropy and the conservation of energy. Soltans 23:07, 15 May 2006 (EST)

[edit] evolution

Greeting Wikipedia -

What is "ecosystem evolution" ? What evolutionary / game - theoritic mechanisms or principles apply ? What book describes the evolution of ecosystems ?

Thank you, Willie

I don't feel confident enough to answer your quesiton outright, but Paul A Selden's "Evolution of Fossil Ecosystems [25] is a recent work on the subject. You're going to find the best treatments in the area of paleontology, because the process is such a long one. - Draeco 03:16, 9 May 2006 (UTC)
"evolution of ecosystems" Try Into the Cool: Energy Flow, Thermodynamics , and Life Eric D. Schneider and Dorion Sagan, U Chicago Press, 2005, ISBN 022673936-8 and references therein. Like: Hutchinson The Ecological Theater and Evolutionary Play 1965. Key concept : Succession of dominance of different species. Ends up in "Climax community" and maximal use of energy flow through the system. see Ecological succession --GangofOne 00:14, 10 May 2006 (UTC)
Thanks for the advice.  - Willie

[edit] WiFi Going Insane

Hey. I'm currently on a 802.11g Wireless Network. My computer connects to a router that has a cable modem plugged into it. Every so often, my wireless network connection will still show 'connected', but all network traffic will stop working (including intranet file sharing, local apache servers, internet, etc.). The only way i can fix this is to 'repair' it in Windows (right-click on the icon in the tray and click 'repair'). What in the world is going on, and how can I fix this (and if I can't fix it easily, how can I get my internet working without having to click repair?). It's happening multiple times a day, and it's getting annoying. — Ilyanep (Talk) 01:58, 9 May 2006 (UTC)

  • What kind of router is it? Wireless routers are notorious for often going on the fritz and refusing to handle packets for no good reason whatsoever, so it would be worth checking if other users of the same model report a similar problem. --Fastfission 02:36, 9 May 2006 (UTC)
  • It happened with my current D-Link router, but it used to happen with my old Netgear 802.11b router as well (although much less frequently). Not sure on the model numbers for either. — Ilyanep (Talk) 02:59, 9 May 2006 (UTC)

Could be classic Windows Spyware Router Choke. --Zeizmic 11:48, 9 May 2006 (UTC)

This is an extremely common problem. I've always suspected it had to do with rotating the security keys. But, I haven't looked into it much because I get rid of all that. On the router, I look at the logs and I find the MAC for the laptop that I'm using. Then, I set up the router to use absolutely no key security. Instead, I tell it to only allow the MAC of the laptop I want to use (most routers let you add at least 16 MACs if you have more computers). Then, the problem goes away. --Kainaw (talk) 14:32, 9 May 2006 (UTC)
Another possible cause: have you checked your cable modem? Some models (my ADSL modem does this) occasionally update themselves while connected, and during this time, all connections stop for a time (one or two minutes), then come back on automatically. Just a thought. — QuantumEleven 14:36, 9 May 2006 (UTC)

Something similar used to happen with mine, before I upgraded to SP2. Theres an article about it here, with some possible workarounds. There might be some other useful stuff here as well. Hope it helps. CaptainVindaloo 16:56, 9 May 2006 (UTC)

"Then, I set up the router to use absolutely no key security. Instead, I tell it to only allow the MAC of the laptop"
right so all the attacker needs to do is sniff your mac and set it on his machine (not sure how well wi-fi will handle multiple instances of the same mac but if it doesn't handle it well he can always wait for you to turn your laptop off). Not that WEP is really that much better if the attacker has some time on his hands. Plugwash 17:17, 9 May 2006 (UTC)
If a hacker can detect your card's MAC and fake it on his card, he will have no trouble faking your keyset. --Kainaw (talk) 19:59, 9 May 2006 (UTC)

I use both a WEP key and 'only allow trusted MAC addresses'. Plus, I'm pretty sure it's not my modem since only repairing the wireless connection in windows seems to fix it (and the internet works on the other computers meanwhile). I'll check out the links that captainVindaloo posted shortly. They appear to be for pre-SP2 and I have SP2. Thanks for the help and let's hope it works. — Ilyanep (Talk) 20:30, 9 May 2006 (UTC)

Also, Spyware can do that? I'll run a scan but i don't think there was anything on my PC. — Ilyanep (Talk) 20:31, 9 May 2006 (UTC)

Have you tried turning off the WEP key? That is what I had to do to stop the constant connection failure in XP. --Kainaw (talk) 20:45, 9 May 2006 (UTC)
I'd really rather not :(. — Ilyanep (Talk) 21:26, 9 May 2006 (UTC)
I don't think you understand what I'm saying... Turn off the WEP key. If everything works great, then you know what the problem is. If you don't turn off the WEP key, you'll never know if it is the WEP key, DNS problems, bad cable, radar interference, positioning of the planets... Once you find out it is the WEP key, you can work on a solution for the problem.
As for the "security" of the WEP key - it should not be used to protect your computer. It protects your network. It keeps others from using your wireless network. Since your router is also a firewall, keeping computers off your network isn't only an issue of bandwidth, it is a security issue. If you don't have protection on your computer and you are depending on the router to protect it, you are begging for trouble. All in all, if you use your laptop in any public location (like a coffee shop), you have abandoned your router's firewall and you are open to attacks again. So, when it comes down to it, the WEP key is just there to protect your bandwidth. Obviously, your bandwidth isn't an issue because you are losing network connection on a regular basis, which is a classic problem with Windows XP wireless networking using WEP keys. --Kainaw (talk) 00:36, 10 May 2006 (UTC)
I understand about that, and that's why I run AV and firewall software (and the internet stops working in its absence as well, mind you). If it is the WEP key then what would I possibly do? Disable it? I don't know if I'd like my communications traveling unencrypted across my neighborhood. — Ilyanep (Talk) 01:16, 10 May 2006 (UTC)
If it turns out to be the WEP key, the problem (as it was explained to me) is: There are 4 rotating keys. Each lasts for a preset length of time (2 minutes or so). Windows XP connects fine with the first key. Then, it may fail when the key rotates, it may not. Two minutes later, it may fail on the next rotation, it may not. Eventually, it fails. There are multiple solutions. An obvious one didn't work for me: make all 4 keys the same. It still failed after the first or second rotation. Another one failed for me: increase the time for each key. I bumped it to to 10 minutes - so I could go 10 minutes before losing connection. Not a solution. The one that worked for me was disabling Windows wireless tools and only using the ones that came with my wireless card. But, most laptops come with wireless built-in now, so there's not special card drivers to use. However, I don't want you wasting your time going down that road if it turns out WEP is not the problem. That is why I suggest testing it. --Kainaw (talk) 01:24, 10 May 2006 (UTC)
We only use one WEP key anyways. But, I'll test it out later today. BTW, I use a desktop, but i don't believe that my wifi card came with software. — Ilyanep (Talk) 01:29, 10 May 2006 (UTC)

A couple of points here. WEP uses cryptography which was very poorly planned and as a result is easily breakable. It should therefore, be regarded more or less as a speed bump to attackers, not as a serious barrier to them. WPA (partial 802.11i) and WPA2 (more complete 802.11i) are MUCH better, but not available on all equipment, even with a firmware upgrade. If this is your plight, protest to your vendor... But, good quality crypto is the only possible way of defeating the security leak inherent in all broadcasting methods -- eavesdropping. Only if you force them ot cope with gibberish they can't convert ot something intelligible can anything going either direction be thought even remotely confidential.

Denial of service attacks are relatively easy to manage for 802.11 networks, most especially for Infrastructure mode (ie, when using an Access Point). These have nothing to do with cryptography (WEP, or 802.11i (partial or not)), but rather to do with the underlying management of the medium and with the realities of low power radio communications. Using 802.11a forces a penalty in range (roughly half that of the lower frequency 11b/g) but, by providing more, and less overlapping, channels, removes at least one of the possible denial of service attacks.

Wireless is not, though it can often be used as if, really securable. It remains vulnerable to many attacks, accidental and deliberate, even when observing best practices with high quality gear meeting all appropriate standards.

Wired connections (eg, Cat 5 10/100 Ethernet) with all its problems, has consderable advantages in terms of reduced downtime and invulnerability to many potential attack modes. And it's almost always faster.

Nonetheless, in the situation described, I agree that it seems to have been some oddity of Windows which caused this problem. Use Linux, one of the BDSs, or OS X, instead. There will be difficulties, largely due to lack of vendor support, but the advantages in less mystery in the problems encountered will be more than sufficient offset. And the software, and much of the applications (ie, a worthy equivalent of Office -- OpenOffice) are free. Both in liberty (they're open source) and as in beer (no cost). Avoiding licensing hell is alone worth almost any trouble, in my view. 71.249.12.89 13:29, 12 May 2006 (UTC)

From my experience with Windows, Windows handles WEP encryption very well. So do most recent Linux distros and even my Nintendo DS. WEP is more flawed than WPA, but only because it is a lot simpler, and this simplicity reduces problems.
We should look at what Windows is actually doing when it "repairs" the connection. IIRC, it disables the network adapter, clears the DNS cache, clears some other cache, re-enables the adapter and reconnects to the wireless network. This already seems to point to a possible problem related to the MAC filtering, as the router would detect a client reconnecting, which it identifies with its MAC address. Just a thought. Also, it might be worthwhile to narrow down the source of the problem by using a packet sniffer such as Ethereal. It is possible that you might not see any packets leaving your system, in which case the OS or related wireless hardware is at fault. If the packets are clearly leaving your system, then the router must be dropping the packets for no reason, and the router is at fault. Then again, Ethereal is a bit funny with some types of wireless cards, often not detecting any packets at any time ... but you are most likely fine. Try to find out in more detail how Windows repairs your NIC, you might find the problem there. -- Daverocks (talk) 12:29, 15 May 2006 (UTC)

[edit] Physics

The masses on a pulley are each initally 1.60m above the ground, and the massless frictionless pulley is 4.8 m above theg round. Mass 1, on the left side of the pulley, is 1.2kg, and mass 2 is 3.2 kg. What maximum height does the ligher object reach after the system is reached? don't think I even got the equations right....but here goes...


Σ F = ma
T - FG1 = m1a



Σ F = ma
T - FG2 = -m2a


Then I subtract my equations..

FG2 - FG1 = (m1 + m2)a
a = (3.2 x 9.81 - 1.2 x 9.81 ) / ( 1.2 + 3.2)

Then a is equal to:

a = 4.45 m/²

So next I solved for v2, just before m2 hits the ground

v2² = v1² + 2ad
v2² = 0 + 2(4.45)(1.6)
v2 = 3.77 m/s

Next I used 3.77m/s to solve for the distance that m1 is moving up, which is the original question

v2² = v1² + 2ad
d = (v2² - v1²) / 2a
d = (-3.77² - 0²) / 2(-4.45)
d = 1.6 m

That means that object moved 1.6m above the 1.6m, PLUS the 1.6 m that m2 moves. That's a total of 4.8m, but alas, that is not the answer (3.9m). If anyone could point show me what I've done wrong, thanks. C-c-c-c 03:25, 9 May 2006 (UTC)

What does "after the system is reached" mean? —Keenan Pepper 04:49, 9 May 2006 (UTC)
Sorry that should be "released". C-c-c-c 04:53, 9 May 2006 (UTC)
Are you sure you didn't leave something out of the question? I might be misunderstanding you completely but it doesn't seem valid to me. freshgavinΓΛĿЌ 06:08, 9 May 2006 (UTC)

Well it's a pulley system, and there are two masses. M1 is 1.2kg and M2 is 3.2kg. The moment after second or first mass is added on to the pulley, the heavier one falls down and lifts the lighter one. I'm supposed to calculate that distance. C-c-c-c 06:11, 9 May 2006 (UTC)

Yeah, I get that much. But the way the question is phrased it seems that the answer is simply 1.6, because the system will "release"? when the heavier weight hits the ground, 1.6 meters later. The smaller weight doesn't move twice that distance, it simply moves 1.6m in the opposite direction. freshgavinΓΛĿЌ 06:19, 9 May 2006 (UTC)
The system is already 1.6m above the ground. I really don't know, I didn't make the question up. The answer in the back is 3.9m for some reason. Any ideas? C-c-c-c 06:23, 9 May 2006 (UTC)
Ah, right. Then I guess we're back at the start, and I'm as confused as you are. freshgavinΓΛĿЌ 07:10, 9 May 2006 (UTC)

I'm guessing that by "maximum height" the problem means: after the large mass hits the ground, and the small mass rises through 3.2m, the rope will go slack and the small mass will free-fall until it returns back down to 3.2m (at which point the system will continue to oscillate until all the impacts between the big mass and the ground dissipate the energy). During that free-fall, what maximum height does the small mass reach? I wouldn't try to solve any equations of motion, or consider accelerations, forces, or tensions. Just apply energy conservation very carefully. Melchoir 07:30, 9 May 2006 (UTC)

I don't think it's that's complicated because I think this is just supposed to be as straight forward as possible. We haven't done energy conservation yet, this is all based on dynamics. So as the heavy block drops, it just stays there, and there's no dissipating energy. The rope is supposed is not supposed to sag. Am I on the right track with what I have so far? Do you know what I could do next? Thanks a lot. C-c-c-c 07:36, 9 May 2006 (UTC)
If the heavy block is to stay on the ground, then one second it's falling and the next second it's not; this is a loss of kinetic energy. And the rope really does have to go slack if the answer to this question is to be greater than 3.2m; the rope is geometrically incapable of pulling the small block any higher than that! There's only so far the poor thing will go.
As for what you have so far, I can't comment, because I don't understand your strategy. But I'm sure the correct answer will involve less work... Melchoir 07:45, 9 May 2006 (UTC)
Ah, yes, here we go:
1.6\mathrm{m}\left(2+\frac{3.2-1.2}{3.2+1.2}\right)=3.927\mathrm{m}.
That was energy conservation, but I'm sure there's another way to get there. Melchoir 08:03, 9 May 2006 (UTC)


Mhm alright. I'll check with my teacher. Thanks! C-c-c-c 08:16, 9 May 2006 (UTC)

Would this work?: The heavier mass is accelerating downwards for 1.6m. What is its velocity when it reaches the ground? (Aside: Would it be the same as a 2kg mass in free fall?) That downwards velocity would be the same as the upwards velocity of the mass on the other side of the pulley. Now you have a mass going upwards at a known velocity, being decelerated by gravity. How far does that 1.2kg mass go upwards before its velocity becomes zero, slowed down by gravity = maximum height reached?. I guess they are asking for that maximum height (remember the initial 1.6m). --Seejyb 08:28, 9 May 2006 (UTC)
You mean initial 3.2m, right? Melchoir 08:31, 9 May 2006 (UTC)
You're right, the way I stated it ignores the 1.6m acceleration phase, and the answer would be wrong if one did not include that too. --Seejyb 08:38, 9 May 2006 (UTC)

I was thinking too simply and I forgot that you'd be dealing with stuff like slack at that level! Melchoir's solution is obviously correct but it seems like you haven't been taught energy conservation yet, so you can think of it like this: You have the acceleration at the point the system releases (9.81m/s²), you have the velocity at release (3.77m/s up) and at max height (zero).

It's been so long since I've done math in an organized mannar so excuse me for my weird methods of deriving equations. Using the formula for acceleration you get:

\mathbf{\bar{9.81}} = {\mathbf{3.77} - \mathbf{0} \over t}

which gives you to 0.38 seconds.

\mathbf{velocity} = {\mathbf{d} \over t}, so find the average velocity, and calculate for d:
\mathbf{\bar{3.77 - 0} \over 2} = {\mathbf{d} \over 0.38}

and you get 0.72, which when added to the base 3.20 gives you the same answer (3.92) as Melchoir as well as the text book. I wonder if you understood that O o;;. freshgavinΓΛĿЌ 06:14, 10 May 2006 (UTC)

[edit] Physics II

Sorry to be a bother again, I just have quick question on solving problems without mass. A box is given a push so that it slides across the floor. How far will it go, given that the coefficient kinetic friction is 0.20 and the push imparts an initial speed of 3.0m/s? I have to figure out the acceleration, then I can use kinematics to get the distance.

So:

FA - Ff = ma
FA - μkFN = ma
FA - μkg = a
FA - 0.20(9.81) = a

I canceled out the masses but now I have two unknowns still. I don't know what to do with FA...I think I may be missing some critical information that I should know but can't seem to have pop up in my head. thanks. C-c-c-c 08:47, 9 May 2006 (UTC)

Admittedly, my physics is a bit rudimentary, but I'm pretty sure you can't cancel those masses out without also doing so with the FA term. I don't quite see how FA - Ff leads to mg, either, since this is dealing with movement on a plane and not freefall... —Zero Gravitas 08:55, 9 May 2006 (UTC)
It's "ma", I made a typo. That's how we dealt with questions that didn't give you a specific mass, you eventually had them cancel out and it wouldn't affect your answer. Not sure here though. C-c-c-c 09:00, 9 May 2006 (UTC)
What is FA supposed to be? Is there some force other than friction affecting the motion? Melchoir 09:04, 9 May 2006 (UTC)


FA is the force of the box being pushed C-c-c-c 09:05, 9 May 2006 (UTC)
During the time period we're interested in, that's zero. Melchoir 09:14, 9 May 2006 (UTC)
You don't need to know anything about how the box reached 3.0 m/s. The point is, it is released at 3.0m/s, then decelerates due to friction until it comes to rest. During deceleration, the only horizontal force on the box is the frictional force μN, where N is the normal force. And N must equal the box's weight, mg, since the floor is horizontal. So the box with (unknown) mass m is being decelerated by a force μmg ... Gandalf61 09:26, 9 May 2006 (UTC)


Oh, I see...it's not affecting it during the sliding... I didn't realiaze that,alright. Mhm yeah I get the acceleration then easily, and the distance too. Thank you Melchoir, and Gandalf61 and Zero Gravitas too. C-c-c-c 09:30, 9 May 2006 (UTC)

[edit] Name this tank

US tanks in the Solomon Islands during WWII

Can anybody tell me what kind of tank is pictured in this photo. Thanks.--Peta 04:41, 9 May 2006 (UTC)

It looks to my untrained eye like an M5 Stuart Raul654 04:48, 9 May 2006 (UTC)
Maybe a Sherman? Though now I'm not so convinced.... C-c-c-c 04:51, 9 May 2006 (UTC)
No, it's clearly not a sherman. The more I look at this pic the more I suspect it is a Stuart. Raul654 04:55, 9 May 2006 (UTC)
This page has an almost identically staged photo; it's got to be a Stuart. —Zero Gravitas 07:53, 9 May 2006 (UTC)
The document I got the image from just describes them as light tanks.--Peta 05:13, 9 May 2006 (UTC)
Stuart was a light tank, it looks like a Stuart to me, although maybe an early model.

[edit] Are autistic-savants child prodigies?

Are they? a.s.s can't survive on their own while c.p.s can. A.s. can't perform simple tasks like buying gum or estimating if things are expensive, etc.--Jondel 05:10, 9 May 2006 (UTC)

"A prodigy" is simply a person who has an exceptional talent or skill of some kind. That is, one and only one skill is enough. It depends what level of talent you consider prodigaeic, but the destinction between CPS and ASS doesn't apply. freshgavinΓΛĿЌ 06:05, 9 May 2006 (UTC)

[edit] What is this lizard looking thing?

I took these pics after finding the little guy in the ditch on the side of my road. He's about 2" long and orange with darkish spots. The road is in the Green Mountains of Vermont. I later found quite a few more of these things on the side of the road. Sorry the pics aren't better but I'm not that good of a cameraman. So, what is it? Dismas|(talk) 05:24, 9 May 2006 (UTC)

Maybe a salamander? I seem to remember some types of salamanders making occasional appearances in south-eastern Ontario when I was a kid, so they should be in your area as well. The spots are very common of salamanders too. freshgavinΓΛĿЌ 06:23, 9 May 2006 (UTC)
Or a gecko? --Shantavira 07:28, 9 May 2006 (UTC)
Definitely looks like a salamander to me, though I can't tell what species it is. — TheKMantalk 08:03, 9 May 2006 (UTC)
Thanks! We'll go with Salamander then. Dismas|(talk) 09:35, 9 May 2006 (UTC)

It is a newt! We have them at our diabetes camp farther south in the Appalachian mountains of Pennsylvania. A newt is an immature salamander still in the land-living stage. They eat small bugs. You can find them in the grass or leaves within a hundred yards or less of a swamp or wet area. They are about 2" long, move slowly and are easy to catch, not slimy. The dominant color of the Pennsylvania ones is a burnt or dusky orange, but they have two parallel rows of bright orange dots ringed with black running down their backs. Beautiful. When they get older the color changes (to black and white I think), they grow to maybe 5 or 6 inches, and they move back into the water and are rarely seen. alteripse 10:50, 9 May 2006 (UTC)

An Eastern Newt to be precise (Newts are in the family Salamandridae, so salamander is correct also). -Wiccan Quagga 14:16, 9 May 2006 (UTC)
Hey! Cool! Thanks, that's exactly what it is! Dismas|(talk) 20:49, 9 May 2006 (UTC)
It's also called a red eft. And eft is a cool word. Word.TheSPY 00:28, 10 May 2006 (UTC)

Cool. Never knew newts were salamanders. Not that I've ever thought hard about it before though! freshgavinΓΛĿЌ 06:16, 10 May 2006 (UTC)

[edit] how do they do it?

i've always been curious to learn how pros balance a basketball on their fingertips.just exactly how do they do it?

thanks a tonne

They spin it. With a little practice it's not that hard to get it going for a couple seconds. Keeping it going is harder. With the ball in your hand, spin it with your finger tips while tossing it up just a little. Then "catch" the ball on the tip of one of your fingers, usually the index finger works best, right on the axis of the spin. With a little balance, it will keep spinning on your finger tip. Dismas|(talk) 08:26, 9 May 2006 (UTC)

In fact, you can balance the ball even without spinning it (try it !). Spinning stabilises the ball due to gyroscopic effect and makes it easier (in theory). The tough part is to learn the art! Experts balance many other objects like plates too. -- Wikicheng 08:47, 9 May 2006 (UTC)

[edit] Titanic's exhaust pipes

Hi,

In the movie and in pictures of Titanic, the exhaust pipes of the ship seem to be not perfectly vertical but are tilted slightly. Is there a technical reason why it should be ? -- Wikicheng 09:11, 9 May 2006 (UTC)

I'm prety sure it was purely aesthetic. One of the funnels (as they're called) on the Titanic was even a dummy, because it looked better with four than with three. --BluePlatypus 10:15, 9 May 2006 (UTC)
Where was that funnel? Wouldn't be too beautiful with smoke coming out of only three, so it ought to be one of the central ones to cover up. :)
Actually it was the one in the back. Maybe they convinced people it was a spare,though according to our article it did serve as a vent. -Wiccan Quagga 14:08, 9 May 2006 (UTC)
Compare that with the picture at the top of RMS Titanic :-) Artistic license... Weregerbil 16:17, 9 May 2006 (UTC)
Were there any fires reported during the sinking? If so could smoke from them have gone up the rear chimney.
BluePlatypus is correct, the rake of the funnels was purely aesthetic. The fourth funnel in several four-funneled liners was a "dummy" again added for aesthetic reasons, but in Titanic, as the article says, this was not entirely without other function, but housed a ventilation shaft. To answer the question from an unsigned anon, the arrangement of the power plant of the ship (engines abaft the boilers) dictated that the three "real" funnels must be forward. As you can see in her plans, the exhaust flues from the boilers took up a great deal of space internally; there could be no question of avoiding locating the "real" funnels above the boilers. But this would put three funnels awkwardly far foward from the point of view of aesthetics, to the fourth was added to balance out her profile.---CH 10:33, 16 May 2006 (UTC)

[edit] Hypothetical engine questions

2 quick questions:

  1. Would it possible to make a diesel (i.e. compression ignition) Wankel engine? Judging from the article (under Advantages and Disadvantages), it seems the answer might be no.
  2. On a side note, what is the compression ratio of the Renesis engine? How is compression ratio defined for a rotary engine?
  3. Would it be possible to make a diesel engine that runs on petrol? Vice-versa, would it be possible to make a spark ignition engine that runs on diesel?
  4. For all of the above, what are the major disadvantages and/or reasons they would not work? (I'm assuming there must be something fundamentally disadvantageous/impossible about these concepts else we would probably have seen them by now.)

Zunaid 10:19, 9 May 2006 (UTC)

As for a diesel engine that runs on petrol, I think that even if it would be possible, it wouldn't make sense to actually mass-market one, as there's no other advantage of a diesel engine over a normal one other than that the fuel is much cheaper. – b_jonas 16:01, 9 May 2006 (UTC)
2) Compression ratio for a rotary engine would be defined as the ratio between the chamber volume when the fuel intake is cut off, and the minimum chamber volume.
3) A diesel engine that runs on petrol? Sure: see engine knock. The reduced compression ratio means that such an engine wouldn't be as efficient, and diesel fuel has handling advantages (such as reduced fumes) over petrol. It should also be possible to make a spark-ignition engine that runs on diesel, but you'd need some way to encourage the diesel fuel to vaporize (a fuel preheater, perhaps?). --Serie 21:12, 9 May 2006 (UTC)

[edit] Brain USE Percentage?

Hi, I was having a discussion with a few friends and was wondering if anyone had any reputable references in regards to how much of our brain we use. I've heard that we use only 1% of our brains ability. However I've also heard we only use a small percentage at any given time. Others have stated that we use 100% of our brain just that we do not use it all the time, and that with differnt tasks we use different parts of our brain but in the end every part of our brain we use.

The concept is widespread, but originated as marketing hype and is mostly perpetuated by people trying to sell you something you don't have a need for. Think about how silly the concept is by applying it to other organs.
  • At any given moment only 10% of your muscles are working. Get opisthotonus or spasticity so more of them are always contracting!
  • At any given moment only 10% of your retinal photoreceptors are firing: go stand in a nuclear explosion so that nearly 100% will fire!
Anyway, you get the idea. The concept is no more biologically meaningful than the slogan, "why not live life to the fullest", especially when used to market Armpit Kleener or somesuch. alteripse 10:41, 9 May 2006 (UTC)
See also The Ten-Percent Myth at snopes.com. –Mysid 11:05, 9 May 2006 (UTC)
I always thought this myth came from the fact that most of our brain cells are glial cells, not neurons, but snopes.com didn't mention that as a possible origin. --Ginkgo100 18:56, 9 May 2006 (UTC)

[edit] Name for a color / paint

Hi, I've been wondering about what could be the English name for the screaming colors usually used in highlighter pens and police vests. They are usually pink or yellowish green, but can also be orange (see Image:Helsinki fire truck H10.jpg), and often hurt the eyes on a clear day. In Finnish and apparently German they are called "neon colors" but I couldn't find anything similar in the English Wikipedia. –Mysid 11:13, 9 May 2006 (UTC)

A google search for "Neon Color" [26] results in approximately 132 000 pages. Perhaps, it is called "Neon colo(u)rs" in English as well? --Andreas Rejbrand 11:32, 9 May 2006 (UTC)
Yes, "neon colors", such as neon green, are commonly used in American English. --Ed (Edgar181) 11:38, 9 May 2006 (UTC)
Oh okay, thanks. (I found an article on fluorescence but it didn't really refer to the colors anywhere. Maybe there should be an article. :P) –Mysid 11:42, 9 May 2006 (UTC)

When the colors were first widely used in the US in the late 1960s, they were often called DayGlow or Day-Glo. alteripse 11:49, 9 May 2006 (UTC)

As far as their use in art is concerned, they're usually referred to as Fluorescent X, where X is the name of the particular colour (so there's fluorescent green, fluorescent yellow, fluorescent orange, etc). But the term day-glo is also widely heard (X-Ray Spex even had a punk rock song with it in the title :). "fluorescent orange" gets 340,000 google hits, for instance. Grutness...wha? 12:23, 9 May 2006 (UTC)
Quite often in the construction and factory trades in the U.S. the colors will be preceded by the word "safety". Safety yellow is often used to designate barriers and steps while vests and helmets are often safety orange. Dismas|(talk) 13:12, 9 May 2006 (UTC)
Y'mean like Safety orange? :) User:Zoe|(talk) 18:36, 9 May 2006 (UTC)
Sure, just go the easy route and provide a link. ;-) Dismas|(talk) 20:48, 9 May 2006 (UTC)

The jackets in these colours are (at least in the UK) called high visibility or hi (gh) vis. I've consequently heard the colours referred to as "high vis(ibility) yellow/orange". Thryduulf 01:01, 10 May 2006 (UTC)

Aren't they louminescent colours? (yes this is incorect use of the term, but it what I've heard) Philc TECI 18:10, 10 May 2006 (UTC)

[edit] Any idea what this flat head worm slug thing is?

I went to take the garbage out and since it rained last night there was a handful of earth worms on my drive way. To get a little good karma I started moving the worms into the grass to ensure the sun or my car doesn't kill them. It turns out one of them wasn't a night crawler though. It had the same body size as a medium sized worm, sticky with a slime trail like a slug, had a flat head it dabbed around and occasionally raised like a snake, and had two brown stripes down it's back. The girlfriend has the camera in her car so I can't take a picture of it. I've never seen one of these before. Anyone know what it could be or know of who I can ask about it?

I don't know much about invertebrates, but I've seen a flatworm on TV once that had some stripes. --KJ 13:25, 9 May 2006 (UTC)
This thing was only flat on it's head. The stripes were ligher brown on brown. I'm almost certian it was a slug becaused when I touched it it retracted itself.
Like this? --Kainaw (talk) 13:46, 9 May 2006 (UTC)
Nope. Tubular body, looked like a regular worm at first. Then I got close and it had a tiny flat shovel head. The head was not antenna like. Focus less on the strips and more on the head.
You mean like this? --Kainaw (talk) 13:53, 9 May 2006 (UTC)
The stripes are much darker and mine was skinnier but that looks like my mystery creature. It even says they are located in Florida. I should of mentioned I live there. Thanks a lot!
Far freaking out. I just saw one of these on a sidewalk in Virginia USA an hour or two after rain. It was much more slender and elongate than the species in this picture, and wholly earthworm-colored below the "neck." However, the gestalt of the head was exactly like in this species. It moved pretty pokey, with a sinusoidal snaking action. I googled flat head worm and here I am. Blows me away to see something so novel on the street after walking around Virginia for 25 years.

On a side note, these things eat earthworms by extending their esophagus-analogue into their prey. Disgusting! Isopropyl 02:09, 10 May 2006 (UTC)

[edit] Girls v/s boys

In most of the exams Girls outperform boys. Why is this so?

There isn't a straight answer to this. It's most likely a combination of:
    • Genetic factors. For example, girls and boys may have different brain structures that lead to proficiencies at different tasks. This issue is deeply controversial, and while most people agree it exists, there is alot of heated argument over how significant this effect is. (and whether it is moral to act according to this)
    • Social factors. Society expects different things of boys and girls - and among boys, for example, there may exist a general anti-academic sentiment that means boys work less hard in their studies. In many western societies, for example, there is a general perception of young males as lazy, and this sort of thing feeds back into the system and decreases individual motivation. Expectations can drive reality.

Of course, many people believe in the opposite - that boys outperform girls academically. Go figure. See also Sex and intelligence --Fangz 14:00, 9 May 2006 (UTC)

I think which gender performs best in exams correlates with ages, subject studied & also with race and social conditions (though frequently race is considered a proxy for social conditions). Certainly in the UK there are a range of statistics collected on this. Some research links are here and some statistics are included in here. This one also looks useful. AllanHainey 14:23, 9 May 2006 (UTC)
And type of exam of course. Skittle 15:05, 9 May 2006 (UTC)
My theory is that girls are better at memorizing things and recalling them than boys are. This is because boys are more analytical, they will tend to try to figure out if a thing makes sense before committing it to memory.
That's your well-considered opinion? Black Carrot 23:38, 9 May 2006 (UTC)
At the lower levels, girls tend to generally outperform boys, at higher levels boys outperform girls. Boys are better at specialization, and girls are better at generalization in education and academics. My own thinking. -- Mac Davis] ⌇☢ ญƛ. 04:42, 10 May 2006 (UTC)
Sorry, not that I disagree with you, but would you mind setting evidence to that opinion? It may cause some general interest. Luthinya 12:02, 15 May 2006 (UTC)
I agree with Mr. Mac Davis. Does that count as evidence? :P --Russoc4 18:35, 16 September 2006 (UTC)

[edit] Magnetic flux

A 50 turn coil has a sinusodial magnetic flux. Maximum rate of change of flux is 5Wb/s. Find the peak amplitude and RMS voltage.

I know induced voltage is e = dλ/dt, and λ = N.A.B, but I'm not sure where to go from there..?

Bwgames 12:37, 9 May 2006 (UTC)

See Faraday's law of induction for an explanation of your first equation (but note that \lambda\not\equiv\Phi). Note that the flux is a physical quantity independent of what you happen to do with it, so it can't possibly account for N's effect. See RMS for information on how to calculate the last bit. --Tardis 18:06, 9 May 2006 (UTC)

[edit] Hair

How does body hair know when to stop growing, and when to grow back? 87.194.20.253 15:52, 9 May 2006 (UTC)

This was asked very recently here. If you are the one who asked the question, please keep in mind that you must return to the Reference Desk to see the answers. --Kainaw (talk) 16:57, 9 May 2006 (UTC)

[edit] grain drying

i need relevant information about grain drying

I would start with food storage and harvest. --Ginkgo100 19:00, 9 May 2006 (UTC)

[edit] Brushless alternator

what about the brushless alternator voltage regulation?.I am a electrical engineering student.Its a portion on our syllabus.my question is again repeating,can you give any idea about the voltage regulation of brushless alternator?.I am engineering student in india.

                                       Thank you

what about the brushless alternator voltage regulation?.I am a electrical engineering student.Its a portion on our syllabus.my question is again repeating,can you give any idea about the voltage regulation of brushless alternator?. —The preceding unsigned comment was added by Chandykv (talk • contribs).

Aren't your lecturers meant to teach you the stuff thats on the sylabus?! Brushless presumablly means permanent magnet so you couldn't adjust the field strength. The only obvious approach would be to either use a tap changer or convert the voltage later with some kind of variable transformer or power electronics. Plugwash 18:27, 9 May 2006 (UTC)

[edit] Split up files

Because of a problem which is a long story, I need to send a large file to my home email address. The problem is my email services will not allow a file this size to be sent. This is an executable file so PKZIP will not shrink it much if at all. Is there a way to break the file up into parts and send each part seperately, then reconnect the parts on the receiving end?

You can break a file up into specified parts in WinRAR (and, I think, WinZIP). In WinRAR you'll have file.rar, file.r01, file.r02, and so on. You just put them all in one folder at the other end and open any of them and WinRAR does the rest. Sum0 20:29, 9 May 2006 (UTC)
Or, you can just split it and then add the pieces together by hand (careful about the metadata though).--Frenchman113 on wheels! 20:58, 9 May 2006 (UTC)
Google "file splitter" and you will find many freeware programs that would suit you. You do need a copy on your target machine to do the recombining. --Seejyb 21:02, 9 May 2006 (UTC)
PKZIP (or at least the old DOS versions) can split and rejoin files just fine. --Serie 21:22, 9 May 2006 (UTC)
I can recommend Chainsaw [27] It's freeware and you don't even need to install it on your target machine. Files can be up to 2GB. Slumgum | yap | stalk | 21:28, 9 May 2006 (UTC)
GMail accounts are free, allowing over 2GB of storage. Regarding compression of executables, I have just experimented with using WinZIP to compress to exe files and achieved over 50% on each, so I do not understand that portion of the question. --LarryMac 17:24, 10 May 2006 (UTC)
Unless the file is extremely sensitive (in which case, why are you sending it by e-mail?), you can try and send it through an online service such as Yousendit.com. I use them frequently for large files, and it works very well. — QuantumEleven 12:26, 11 May 2006 (UTC)

[edit] Notepad

When I press Ctrl + S in notepad while at the end of a line, the cursor jumps back several spaces - why?

When 'word wrap' is activated, and a long string such as "enteric/genital" wraps to the next line, and I decide to turn it into "enteric or genital", why does notepad ignore the fact that "enteric" will now fit on the line above? --Username132 (talk) 20:10, 9 May 2006 (UTC)

What OS is that? Ctrl+S is pretty much Windows standard Save As, my notepad does just that.
OS is WinXP. Notepad still saves, but at the same time I get the weird cursor jumping thing. --Username132 (talk) 20:51, 9 May 2006 (UTC)

As far as I know, both these things are bugs in notepad. They have been bugs since the earliest days of Windows 95. Why no one at Microsoft has bothered to fix it in 10 years is beyond me, but it's closed source so no one else can fix it. If it really bugs you you can use Wordpad (Which has its own host of bugs and problems, but has the above bugs fixed), or download another text editor. —Pengo 02:19, 10 May 2006 (UTC)

One workaround, if you're not operating with the window maximized, is just to change the width or height of the window by a pixel or two, which will cause it to recalculate the wrapping. —Zero Gravitas 02:29, 10 May 2006 (UTC)
If it really bothers you (I use Notepad a lot for offline e-mail writing, and this bug drives me nuts) there are several "Notepad replacement" programs out there which you might consider taking a look at, depending on what you want Notepad to do. Examples include Win32pad, BDV notepad, NotepadEx, Notepad2, and here's another list. Good luck! — QuantumEleven 07:56, 12 May 2006 (UTC)

[edit] Pigment in UV beads

What pigment(s) are used in ultraviolet-sensitive beads? The web sites I've checked don't indicate the identity of the color-changing material. Hyenaste [citation needed] 20:44, 9 May 2006 (UTC)

See photochromism --Seejyb 22:14, 9 May 2006 (UTC)
Ah, that's quite interesting. Thanks! Hyenaste [citation needed] 22:19, 9 May 2006 (UTC)

[edit] satelites

how accuratley are satelites tracked say if there in orbit around the moon or mars? and does the tracking relay on just radar based systems, or are other methods used? cheers Colsmeghead 21:06, 9 May 2006 (UTC)

I probably shouldn't answer because I really don't know, but I have a sneaking suspicion that using resources to actually track the paths of satellites is not a common practice. Their orbits are incredibly predictable (negligible friction and simple orbit patterns), and I don't see any reason why a simple mathematical extrapolation of the predicted orbit on a computer screen wouldn't suffice to pinpoint a satellite's current position.
In movies you often see the satellite paths swerving off course on computer screens and then blinking out as they break up in the atmosphere, but I doubt that would happen in real life as they're probably just simulations (of course... I don't really know that).
On the other hand, I imagine it's pretty easy to determine the position of the sattelite by triangulating it's signal, though would you really want to? freshgavinΓΛĿЌ 06:33, 10 May 2006 (UTC)
I don't think it would be that easy at all to triangulate the position of a satellite that is in orbit around another planet. The two sensors that were picking up a signal from the satellite would have such a small angular difference that the measurements would have to be extremely precise. I don't actually know if I'm right or not, it just seems implausible. Dismas|(talk) 10:35, 10 May 2006 (UTC)
Yes, I imagine you're right. I was thinking too short-range. freshgavinΓΛĿЌ 00:36, 11 May 2006 (UTC)

In general, a satellite's orbit can be determined by making a series of observations in some reference system: from a ground station on earth to the satellite, from the satellite to the ground station, or between satellites. A series of measurements of direction, range, or range-rate could be used to refine the orbital parameters.

A number of methods have been used to track earth-orbit satellites: photography to determine direction, electromagnetic signals such as lasers or radar–either impulse timing or phase comparison to measure range, and Doppler shift measurements to determine range-rate. Günter Seeber (2003). Satellite Geodesy, 2nd Edition.

For satellites orbiting other celestial bodies the most convienent method is most likely the Doppler method. Another technique that should probably be metioned is interferometry to determine direction. Very Long Baseline Interferometry is used to realize the reference systems in which measurements are made, and our VLBI article mentions that it was used to track the Huygens probe accurately enough to measure windspeed on Titan. EricR 12:32, 10 May 2006 (UTC)

The actual orbit of a satellite is actually NOT easy to predict with great accuracy. In fact, the US military is actively tracking all artificial satellites orbiting the Earth, and frequently updating the characteristics of all orbits. This information is provided to Space Agencies and other operators, who may actually activate small rocket engines on the platforms to adjust or correct the orbit on a regular basis. These orbital corrections are necessary because the Earth (or any celestial body, for that matter) is neither homogeneous nor symmetrical (even the center of mass of the Earth is moving as a result of ocean currents and wind systems), and because the orbit of each satellite results from the gravitational attraction of many (as in infinitely large) objects (mostly the Sun and the main planets, as far as the Solar System is concerned). Friction is often small, but never totally negligible either, and then there are other forces, such as the solar wind, impact from cosmic dust, etc. While each perturbation, by itself, may have a rather small impact, the cumulative effect of all these mechanisms over a long period of time does result in the 'degradation' of the orbit, hence the need to periodically apply corrections. Hope this helps. --Michel M Verstraete 21:57, 12 May 2006 (UTC)

Well that's an answer I can trust. Teaches me to assume so much! freshgavinΓΛĿЌ 02:11, 15 May 2006 (UTC)

[edit] May 10

[edit] Sensation of speed

Why does sensation of speed decrease with increased distance from the road/increased altitude? i.e. Why does 20mph in a go-kart feel so much faster than 20mph in a standard road car? I presume that it is the same reason why when you are on an aircraft coming into land it appears that you are going slower than any road traffic about until you are very close to the ground when you are suddenly aware of how fast you are truly going? Does this effect cause difficulties for pilots?

My initial vauge guess is that it is something to do with paralax, but I don't see how that would have any significant difference between being 20cm or a metre or 2 metres above the road? Thryduulf 00:53, 10 May 2006 (UTC)

If you are the passenger in a car, you can see why. Look out the window. Get a feel for how fast you are going. Then, look at the side of the road. Get a feel for how much faster you are going. Then, look down at the road right next to the car. See how much faster you are going. In a go-kart, you can easily see the road speeding by in your peripheral vision. In a car, you cannot see the road as easily because you are higher and the doors block much of your view. In an airplane, you can see even less of the ground below you. Also note that the body picks up on many other queues: wind, motor pitch/volume, acceleration force... --Kainaw (talk) 01:59, 10 May 2006 (UTC)
If you look straight down, the angular speed at which the ground passes through your field of vision is v / h, where v is your true velocity and h is your height above the ground. For other angles -- for example, if you're looking 20° below the horizon -- there's a slightly different formula that involves trigonometry, but it still scales like v / h. Well, clearly as h increases, this quantity decreases.
Rather than hinder pilots, it can actually help them land! Given that you're travelling at some roughly constant velocity, you can tell how high you are by watching features on the ground pass by. The faster they seem to be going, the lower you are. On the other hand, if there are no helpful features below, you can be in trouble; this is one reason why you don't want to try to land on glassy water. Just try Googling for (glassy water landing). Melchoir 02:06, 10 May 2006 (UTC)
The biggest difference I'm aware of between those things, other than what's already been mentioned, is the vibrations. Go-carts have almost no suspension, and planes don't even touch the ground most of the time. The more you feel every little change in the road, the faster it feels. Black Carrot 22:21, 10 May 2006 (UTC)

My dad owns a 40-foot steel sailboat. On days with very little wind, when we weren't in enough of a hurry to turn on the engine, he would put me in a lifejacket, tie a rope around my waist, and drop me off the stern. What felt like not moving at all while on deck was fast in the water. It just has to do with proximity to the reference point used to estimate your speed. moink 20:51, 12 May 2006 (UTC)

[edit] Shortest scientific name

I just came across the consonantless Ia io [28] (Great Evening Bat) and was wondering if this was the shortest binomial name there was, and if there was a place in wikipedia for such mindless trivia. —Pengo 02:31, 10 May 2006 (UTC)

Googling for 'shortest binomial name' seems to indicate that it is. As to Wikiappropriateness, why not? Once an article on the animal exists, there's no reason for it not to include that. —Zero Gravitas 04:49, 10 May 2006 (UTC)
Hey man, I'd say that's actually rather informative trivia. I'm sick of hearing DYKs like "Did you know that Jasper Weevuns' cat died in 1989?" that seem to serve no purpose other than to introduce the article. freshgavinΓΛĿЌ 06:40, 10 May 2006 (UTC)
It is the shortest binomial name recognized by the ICZN, and the Great Evening Bat now has an article. –Mysid(t) 08:20, 10 May 2006 (UTC)
Jasper Weevuns' cat died? - Nunh-huh 04:45, 11 May 2006 (UTC)

Nice work creating the article. Thanks Mysid, and everyone who researched it! —Pengo 13:10, 11 May 2006 (UTC)

As for mindless trivia, I've nominated it for the "Did You Know" section. Let's see. –Mysid(t) 19:25, 11 May 2006 (UTC)

[edit] Sense of Navigation

I know there are five main senses, but for the other senses that are not the five main senses would sense of navigation be considered a sense in some form or fashion?

That's a different use of the word sense. The "five senses" (actually more like six or seven if you include things like proprioception and kinesthesia) are the methods by which we receive information from the outside world. The "sense of navigation" is more like "common sense" or the "sense of proportion" in that it occurs completely within the mind, and in fact depends on the other senses. If you couldn't see, hear, touch, smell, taste, or feel where your limbs are, you would have no idea where you were or which way you were going, and your "sense of navigation" would be useless.
On the other hand, birds and some other animals navigate by magnetoception. Maybe that's what you're talking about? —Keenan Pepper 04:22, 10 May 2006 (UTC)
See senses for a list of all the senses. Also, hammerhead sharks navigate by magnetoception. -- Mac Davis] ⌇☢ ญƛ. 04:25, 10 May 2006 (UTC)
Neat! Got a source so we can add it to the article? —Keenan Pepper 04:43, 10 May 2006 (UTC)
[29], [30], [31], [32] for hammerheads. For trout [33]. Somebody else can add it to the articles: Hammerhead shark, trout, magnetoception, senses. Also, as a note, the hammerhead's magnetoception is different from its electroception. I think most sharks use electroception from their ampullae of Lorenzini. -- Mac Davis] ⌇☢ ญƛ. 07:24, 10 May 2006 (UTC)
You may be thinking of the act of navigating a geographical area using a sort of mental map. This is a cognitive ability, not a perceptual one (at least in humans). See cognitive map, although that article covers more abstract maps than strictly geographical ones. --Ginkgo100 19:41, 10 May 2006 (UTC)

[edit] Why an untied balloon flys foward

Hi. When a balloon, filled with regular air. Is inflated to a large size, not tied, and then released, it goes flying. This is common sense, however, I need to know the physics of it. What is the physical explanation for why it flys? I really need this question answered soon. Thanks Tobyk777 04:23, 10 May 2006 (UTC)

You mean, Hot-air balloon#Construction and theory of operation? Or a toy balloon the size of my head? Melchoir 04:35, 10 May 2006 (UTC)
I mean a toy balloon the size of your head. Basicaly, when you blow it up (with your mouth), then let go before you can tie it. Thanks Tobyk777 04:36, 10 May 2006 (UTC)
Hmm... maybe because breath is warm? Melchoir 04:38, 10 May 2006 (UTC)
Oh, before you can tie it! I missed that part... Melchoir 04:39, 10 May 2006 (UTC)
What exactly is your size in hats? I was guessing around 7 7/8[34] but am now revising that downward a bit. EricR 12:50, 10 May 2006 (UTC)
Okay, there's a short description at, woulldn't you know it, Balloon rocket. That article links to thrust, which is also good. Ultimately it's Newton's third law; the air being shot out the back of the balloon is balanced by a forward force on the balloon itself. Melchoir 04:42, 10 May 2006 (UTC)
It's Newton's third law in action! —Keenan Pepper 04:42, 10 May 2006 (UTC)
Thnaks the recomended pages told me everything I needed to know. Tobyk777 05:03, 10 May 2006 (UTC)

[edit] Hyacinth Macaw - taking for a walk?

As it's summer here, I thought it would be quite nice to take my Hyacinth Macaw out for a walk with me in the sun sometime (or even just in the garden). He's fully flighted, so what would be the best way to keep him with me? A chain from his leg to my wrist, or one of those parrot harnesses you can buy on the internet? Anyone have any expierience with this? Thanks. --81.77.242.228 06:01, 10 May 2006 (UTC)

Personally I think it would be much better to return the bird to the wild where it could fly free. Alternatively you could give it to a bird sanctuary. Don't you think it is cruel and uneccessary to capture a free spirit like a bird ? That is my opinion.Antipodeite 11:31, 10 May 2006 (UTC)

Sunlight is good for parrots; kudos for trying to expose him to it. Animal rights activists' opinions aside, I would research the options. Above all, you want to choose a device that won't injure your bird if he startles and tries to take off. My birds' vet once mentioned she has seen injuries from bird harnesses, but that was several years ago and the design may have improved. I have also seen devices consisting of a leather loop on one end, a chain, and a quick link or snap link at the other end. The loop is for the human to hold, and the link is attached to the bird's leg band (this obviously wouldn't work for a bird without a leg band).
Oh, and in case there was any doubt, a bird sanctuary won't provide any better of a home than a dedicated parrot owner can provide. Releasing the bird to the wild would be cruel because a tamed and handfed parrot is very unlikely to survive. And unless the bird were released in its native habitat, if it does survive it can have severe repercussions on the local ecology. --Ginkgo100 17:08, 10 May 2006 (UTC)
There are lots of wild parrots in Southern California, I can't imagine they're native, but probably escaped or released, and they all look skinny, starved, and covered with mange. User:Zoe|(talk) 20:44, 10 May 2006 (UTC)
There are also The Wild Parrots of Telegraph Hill], San Francisco. --LarryMac 20:53, 10 May 2006 (UTC)

[edit] Mozilla Firefox Text-zooming

(Taken from Talk:Mozilla Firefox)

I use Firefox to browse Wikipedia and other websites. I often use the Control +/- function to make the text larger or smaller. For some websites this works really well because the lines of text stay the same width. For other sites though, the lines of text get wider and wider so that I have to scroll back and forth horizontally just to read them. On some sites, like Wikipedia, when I make the text larger it makes the lines get narrower and narrower.

So is there anything you can do with your Firefox settings or extensions to fix this problem, or is it just up to the webpage designers (including those who maintain the MediaWiki software) to code their pages better to fix this problem?

Any help with this would be much appreciated. I've got a small monitor, and I often need to make the text bigger so that myself and others can read it without being real close to the screen. Thanks!

You can change your Wikipedia skin so that nothing extra is on the left of the screen. With the default Monobook skin, the navigation, search, and toolbox links on the left need to grow when you zoom in. This will leave less space for the article. If you move those links somewhere else, then you'll get more screen space. --KJ 10:54, 10 May 2006 (UTC)

[edit] science

think of examples in your everyday life where the princlples of reaction rates are applied( temperature, disloving, or space) ~~

  • Do your own homework. If you need help with a specific part or concept of your homework, feel free to ask, but please do not post entire homework questions and expect us to give you the answers. Melchoir 08:18, 10 May 2006 (UTC)
Disloving may occur in an unhealthy relationship, for example. ––Mysid(t) 08:28, 10 May 2006 (UTC)
Yes, often including heated arguments, cold shoulders, and a need for more space. And overreactions. Melchoir 08:31, 10 May 2006 (UTC)
In many relationships there is a reverse coleration between space and heated arguments. -- Chris Q 08:51, 10 May 2006 (UTC)
I believe you mean "negative correlation". Black Carrot 22:09, 10 May 2006 (UTC)

The more objectionable a person's statements, the more quickly you react by disloving them. Grutness...wha? 06:55, 11 May 2006 (UTC)

[edit] Stars

I read the stars article, and there were a few things i didnt understand. Firstly, what the 'fuel' in the stars is. Secondly, when they die (im pretty sure this is when they run out of fuel). And thirdly, what size they need to form into black holes. Thanks. ````

If Star wasn't enough, you might want to try Stellar evolution and Black hole. Melchoir 10:31, 10 May 2006 (UTC)
Fuel of the star changes over time, mostly it is the fusion of hydrogen. --Mac Davis 11:11, 10 May 2006 (UTC)
By mostly, he means almost the entire life of the star, it changes to helium in the chain of events which leads to the collapse when it dies, then as it collapses anything gos. So i'd say about 99.99% of its life it is hydrogen. Philc TECI 18:20, 10 May 2006 (UTC)

[edit] Thyristor triggering

A gating current can latch a thyristor.But is it possible to latch a thyristor during the(90 -180)degree fall of input sinusoidal voltage? We know that a thyristor can be triggered by the +ve half rise(0deg to 90deg) of sinusoidal voltage,but a little gating current would latch it at a smaller potential than it would have.So is this triggering possible during the +ve half decrease(90deg - 180deg)?

[edit] Airplane

How were the planes that delivered the first atom bomb protected from electromagnetic pulse? Is it possible to protect ordinary devices from EMP weapons as well?

The Enola Gay and Bockscar had no EMP protection because EMP was discovered in 1962. The planes' electronics (what little there was, this was the era of cables and pulleys, not fly by wire and HUDs) used vacuum tubes, which are more resistant to EMP than today's fancy-smancy millivolt-spike-will-make-the-smoke-come-out transistors and microchips. Electromagnetic bomb suggests using a Faraday cage for protection. You won't be laughing at my tin foil hat when the EMP bombs start to fall, I tell you! Weregerbil 13:27, 10 May 2006 (UTC)
This was also a major plot element in Harry Turtledove's Worldwar series.
Whoops, that was me. --Ginkgo100 19:34, 10 May 2006 (UTC)
If you read the Electromagnetic pulse article, it addresses this directly:
It is important to note that many nuclear detonations have taken place using bombs dropped by aircraft. The aircraft that delivered the atomic weapons at Hiroshima and Nagasaki did not fall out of the sky due to damage to their electrical or electronic systems. This is simply because electrons (ejected from the air by gamma rays) are stopped quickly in normal (dense) air for bursts below 10 km, so they don't get a chance to be significantly deflected by the earth's magnetism (the deflection causes the powerful EMP seen in high altitude bursts), but it does point out the limited use of smaller burst altitudes for widespread EMP. If the B-29 planes had been within the intense nuclear radiation zone when the bombs exploded over Hiroshima and Nagasaki, then they would have suffered effects from the charge separation (radial) EMP. But this only occurs within the severe blast radius for detonations below about 10 km altitude.
--Fastfission 17:37, 10 May 2006 (UTC)

[edit] Melting Point

I wish know the melting point of Empirical formula : C8H12O5

Chemical Name: 1,4:3,6-dianhydro-2-acetyl-D-glicitol

or

2-acetyl isosorbide

Regards N Thanks

SciFinder says that it is reported as 78 °C in this patent: WO2003027119 A1 2003 --Ed (Edgar181) 14:35, 10 May 2006 (UTC)

[edit] Calcium Hypochlorite

Having found several tins, what is it used for. I am familiar with Sodium Hypochlorite which I use for sterilising beer bottles.

Sodium hypochlorite is commonly known as bleach. It's not unique to beer bottles. As for calcium hypochlorite Ca(ClO)2, its chemically very similar to NaClO, though, essentially has more chlorine, which is the active component of bleach. You can find more detailed information in the articles. --Chris 16:11, 10 May 2006 (UTC)

[edit] Colors --- this might proof im insane...

I was just wondering, when a baby named X belongs to a family named A, and a baby named Y belongs to a family named B, grow up at the same time. Lets say X sees a banana green, but his family A says a banana is yellow, and he sees a tomatoe blue and his family says the tomatoe is red! When he sees the sea red his family says the sea is blue! While the other baby sees a red banana and his family says its yellow and he sees a green tomatoe and his family says its red and he sees a yellow sea and his family says its blue... anyways the point is both babies will grow up, knowing all the colors, and knowing all their names but, they will be seeing somethin different! He sees a red banana but he calls it a yellow banana! he sees a red car and calls it a yellow car, and the other one will see the car blue but call it yellow too. I just want to know if anyone can proof that everyone sees the same colors...? it could have a simple answer i just want to know.

What you are talking about has nothing to do with colors; it has to do with the fact that language is semi-arbitrary. This is true but within limits. For example, someone who has been taught that the color of a banana is "red" will soon run up against the fact that in English the color of a banana is called "yellow", and everywhere they go people will identify it as such. So yes, they could learn arbitrary color names, but once they get out into the world in any capacity (even kindergarten) they will have it disciplined out of them pretty quick. There is some flexibility in this, of course, but language is generally not about one individual knowing words and correspondences, but communication between individuals with reliance on a common vocabulary. Meanings change, words get added, etc., and I don't know the dynamics of how that happens, but one individual who has been taught "incorrect" definitions is unlikely to have much effect by themselves. The colors of the banana, car, etc. themselves have to do with the wavelength of the light reflected off of them. There is some fairly compelling evidence that most human visual hardware perceives these wavelengths more or less the same way (focal colors correspond with the same wavelengths of light, cross-culturally), though how that translates into intuitive consciousness is a hard-to-define question and a rather nebulous research area, as I understand it. --Fastfission 17:34, 10 May 2006 (UTC)
This actually HAS something to do with colours, and I have thought about THE EXACT SAME THING!!! Quite simply, no one can "see" the same colours. Only you know what goes on in your head, and what you see. If I see purple what you see yellow*, that has only do to with chemical thingies. According to the laws of physics, however, there is a very steady, rule-following shift in visible light from the roundabout 400nm to 700nm wavelength (red to purple), so your brain shouldn't actually be complicated enough to be able to truly mix these up. If it was a question of chemistry alone, I would think that every person sees everything bit different, in fact some humans may see, say... light at 390nm, while others have lower limits at 410! Now, THAT is chemistry, and THAT is the only thing which may vary here. The true shift in colour is something limited by physics, so that you CAN'T misplace purple where once was green. At least I can't see how on earth that could be done. No, can't be done, I'm rather sure of it. :) * Of course this was hypothetical. It is very important to remember that "yellow light" in this case is not something which may vary, but is defined at a certain wavelength, as with all colours. 213.161.189.107 19:31, 10 May 2006 (UTC) Henning
I see this as a combination of the above two, plus some confusion with the original question. What you really seem to be asking is "what if X sees a banana as what outside observer O calls 'yellow' but Y sees a banana as what O calls 'red'?".
This situation can potentially happen, but it can't be observed. When asked, X Y and O all agree that bananas are "yellow", and will point to the same "yellow" on a color wheel, regardless of the precise way in which their brains individually process the notion of "yellow". — Lomn Talk 19:43, 10 May 2006 (UTC)
See Epistemology, Semantics, Semiotics. --BluePlatypus 19:45, 10 May 2006 (UTC)
Although the article has a somewhat strange style IMO, see also qualia. Ardric47 20:53, 10 May 2006 (UTC)
See also color blindness and tetrachromat for additional, unusual ways that people may perceive colors. TenOfAllTrades(talk) 20:19, 10 May 2006 (UTC)

[edit] Balance

I know humans have balance, but do animals with four legs have balance too?

A four-legged animal would fall over without balance - just not as easily as a two-legged animal. There are all kinds of activities that might shift the animal's center of gravity such that it would fall over if it couldn't sense the imbalance and correct it. --Ed (Edgar181) 20:20, 10 May 2006 (UTC)
Isn't the primary function of a tail a balancing aid? --Kainaw (talk) 20:21, 10 May 2006 (UTC)
All vertebrates (sea, air and land) have organs for equilibrium, used to balance. I wonder if ants know when they are upside down?
See collective nouns --Seejyb 21:41, 10 May 2006 (UTC)

[edit] Gender names

Hi: I notice that in english language male and fmales of diferent species have special names and also when they refer to a group and population have also different names e.g. hen - ruster bore - school - herd etc. How I can find a table or place that list all af those names without going species by species? Thaks MhE

Try List of gender names -- SGBailey 23:02, 10 May 2006 (UTC)
Our article on Collective nouns links to many lists you may find helpful. I'd treat that with caution, however, some of the lists are BJAODN in my view. --Howard Train 04:56, 11 May 2006 (UTC)

[edit] Xenotransplantation Affects Germ-line?

The article on xenotransplantation says "Disease transmission (xenozoonosis), and possible long-term effects of xenotransplantation on the human gene pool and permanent alteration to the genetic code of animals are a cause for concern." - how does it affect the gene pool? Unless it's testicle transplant, I don't see how the germ-line is affected? --Username132 (talk) 21:34, 10 May 2006 (UTC)

The germ line isn't affected. I've corrected the article. TenOfAllTrades(talk) 21:49, 10 May 2006 (UTC)

A past exam question was "Xenotransplantation will never solve the issue of the kidney tranplant waiting list. Discuss" - I'm wondering how this could be so? Is it because the engineered HLAs wouldn't please everybody all of the time... I mean what's the point in xenotransplantation if you still have to worry about finding a match? --Username132 (talk) 21:56, 10 May 2006 (UTC)

[edit] Numbered lists in Word

Anyone know how to make numbered lists in word where the numbers are genuine numbers and not a "magic field" using Word 2003 in XP?

I maintain a list of events and each month add any new ones at the bottom. I then want to be able to sort on (say) field 3 and have the numbers stay with the relevant line, so that i can later sort by field 1 and put them back in order. When I was using good old Word2, numbered lists just inserted text. Now it seems to do this magic stuff - including ignoring any numbers already there! Frustrated. -- SGBailey 21:40, 10 May 2006 (UTC)

Have you considered using Excel instead? It'll let you sort things however you want without mixing up the lines. --65.57.245.11 23:01, 10 May 2006 (UTC)
Yes, and I probably will convert. However I have only just upgraded from Word 2 to Word 2003 and the behaviour is very different so I'd like to know how to achieve to old behaviour. -- SGBailey 07:56, 11 May 2006 (UTC)
I'm no Word expert (Microsoft Word, that is; I like to think I'm coherent), but when it starts trying to do its magical formatting against my wishes, I hit CTRL+Z and hope for the best. --Ginkgo100 16:49, 11 May 2006 (UTC)
Tools > AutoCorrect > AutoFormat As You Type > Automatic numbered lists. -- Filliam H Muffman 22:33, 12 May 2006 (UTC)
That lets you manually enter lists - this is what I have to do now. What I was looking for was a way of using the "Format | Bullets and Numbering | Numbered Lists" magic to auto number a selection and then to "go away" and stop being "magic" - that is convert the resulting list into "text". If it was excel, I'd do a "copy" "paste special | Values" for a similar effect. The "magic" makes the numbers and tabs not part of the text that you have to work hard to get into and over which you have no control. Thanks though. -- SGBailey 21:57, 13 May 2006 (UTC)

[edit] Thioglycolic acid

After enduring an increasingly dreadful smell in the laboratory in which I teach for five days or so, I found that thioglycolates had been poured down a sink into an open trap below, rather like a sink in a cupboard, where they had presumably released thioglycolic acid into the laboratory all that time. I assume that the water in the trap must have been somewhat acidic. Does anybody have any similar experiences, and should I be concerned for my health?G N Frykman 22:07, 10 May 2006 (UTC)

  • This PDF file should help you along. If there's no respitory problems are rashes, you're probably fine, but it can't hurt to have yourself checked by a doctor anyway. - Mgm|(talk) 12:07, 11 May 2006 (UTC)
If it's still a problem, bleach will oxidize the thioglycolic acid to a non-volatile compound - this will reduce your exposure to breathing its fumes and will kill the smell too. --Ed (Edgar181) 12:25, 11 May 2006 (UTC)
Thanks for the helpful replies. I've now found that the experiment was being conducted with methyl thioglycolate, and what went into the trap was a filtrate. We poured litres of NaOH solution into the trap, and that seemed to get rid of the smell. I have not noticed any harmful effects, but this has become an H & S issue.G N Frykman 16:56, 11 May 2006 (UTC)

[edit] Pulse & Blood Pressure

In all the sources I've been able to find (a doctor via my sister's memory, Wikipedia, WebMD, some site off Google) except one (my dad), the ideal resting adult pulse is in the 60-100bpm range. Now, is this the "within this you're healthy" range, or the "outside this you're seriously messed up" range? Let's say I have a resting pulse of around 96 at 18 years of age. What's that mean? (BTW, to anyone who plans to say "ask a doctor", I'm already scheduled to get a physical in a few weeks, and all I'm asking is what the webdoctors' advice means. Eat me.) Black Carrot 22:17, 10 May 2006 (UTC)

Not a doctor, but being outside that range definitely sounds to me like you'd be pretty "messed up", or at the very least, "unhumanly". Athletes taking drugs to thicken their blood can often slow their heartbeat to less than 50bpm, but it's extremely irregular and can cause serious health problems if it isn't normalized for long periods of time. Having a fast heartbeat could be problematic depending on your body size/mass, but I'm willing to bet your heart beats so fast because you have a fast metabolism. My heart beats pretty fast too, although I haven't calculated in a while.
On the other hand, if you don't have a fast metabolism, and you are rather largely built, there could be a problem, and I'd advise you to go to a real (rather than a web-) doctor : ). freshgavinΓΛĿЌ 00:13, 11 May 2006 (UTC)
It's just an "outside this you're abnormal" range, If the heartrate is < 60, you have bradycardia, by definition. If it's higher than 100, you have tachycardia. You are in the normal range. There wwould be benign explanations, and serious explanations, if you fell outside this range, and you would need to see a doctor to determine which. The further you are outside this range the more likely that pathology, rather than normal variation, is the reason. Usually any significant arrhythmia produces symptoms rather than merely being noted when the pulse is taken. A resting pulse of 98 doesn't sound "seriously messed up", but your doctors visit should clarify that- Nunh-huh 00:27, 11 May 2006 (UTC)
Interesting. So, it's more towards the "within this you're fine range"? 'Cause I'm just on the edge of it. Also, you seem to be saying that certain other factors (metabolism, build) would shrink the range to something more specific. Do you know where I can find a table that lists that? Black Carrot 02:02, 11 May 2006 (UTC)
Incidentally, I'm fairly skinny (even though I don't excercize or diet), so I figure I've got a fairly high metabolism. Black Carrot 02:04, 11 May 2006 (UTC)
Yes, it's basically a "within this you're fine" range. There's no other well-established range based on other factors, but being in good athletic condition tends to lower the heart rate. - Nunh-huh 02:25, 11 May 2006 (UTC)
There's also a physical fitness component. The better your aerobic fitness, the slower your resting pulse. A high resting pulse could indicate a need for more aerobic exercise. --Ginkgo100 20:46, 11 May 2006 (UTC)

[edit] Color

I was thinking about this before and it just occured to me that I can ask the all knowing wikipedians if they have a usefull answer for me. What I was thinking of is the possibility that there are other colors in the world that humans aren't able to see and therefore because we don't live with those colors in our lives, they are also unimaginable colors.

I was thinking of this because I recently remembered that dogs can only see in shades of red, so maybe humans can only see in shades of blue red and yellow and mixtures of them. I talked to my dad about it, who isn't at all an expert, but he said that there are shades of those three base colors that we can't see, but what I'm talking about is major colors, not just shades. Anyhow I came to wikipedia trying to find an answer and got myself on the Pentachromat page. Now, you might say that my question is answered on that page, but I don't understand all that science blah blah blah.

So if anyone can give me an answer, that would be cool. Thanks a lot RENTAFOR LET? röck 00:01, 11 May 2006 (UTC)

Basically yes, there are animals that can see colors that we can't imagine. By "imagine" I mean we can't imagine what the color would look like, because, obviously, we can't see it, but we know pretty much exactly what color it is. Ultraviolet (the color after purple) can be seen by some animals, such as butterflies, and though the name would suggest it looks like purple, it doesn't, because if it did look like purple, it would be purple, and then we'd be able to see it. There is no way to imagine or describe how ultraviolet would actually look, it's unconcievable.
Some animals can apparently also sense infrared (the color before red) light, but I don't think they can actually see it, and instead feel it like heat or smell. They most certainly don't experience like the military does with their infrared sensors—as a colorful spectrum of all of the visible colors of the rainbow. freshgavinΓΛĿЌ 00:30, 11 May 2006 (UTC)
Are you sure they can't 'see' it in detail the way we can? BTW, you don't feel smell, you smell it (via chemical sensors), and infrared is an electromagnetic wave just like visible light, so I don't imagine the sensors could be much different. Infrared unfortunately doesn't say, and neither does a quick Google search. Other than that, ditto. Black Carrot 01:58, 11 May 2006 (UTC)
I meant to imply "feel it like heat" or "smell". I'm merely repeating what I've read in the past about infrared sensors, which seems to imply that the only animals that use it can't actually see it the way you would imagine they do. freshgavinΓΛĿЌ 04:30, 11 May 2006 (UTC)
Some people can see ultraviolet (see Aphakia). Ardric47 03:51, 11 May 2006 (UTC)

The short answer is yes; even limiting to the range of "visible light" (excluding ultraviolet, infrared, and so on), there are infinite colors we cannot see or imagine. Technically, though, since colors exist only in our heads, by definition I suppose there cannot be a color that no one can perceive. Color is complicated. An objective description of a color would need the intensity of each frequency, along the entire spectrum; that is, you could draw a curve of intensity vs. frequency (wavelength). Since (most) human eyes have three cones, we see in three color "dimensions". For each type of cone you can draw a curve showing how much it responds to different frequency light. (For instance, see the figure at the bottom of [35].) Therefore, we are trichromats. Dogs appear to be dichromats, as are humans who are "color blind". Every frequency of light stimulates the cones to different degrees; a mixture of frequencies as is normally present stimulates all three cones but to different amounts. Ultimately, the signal from the eye only carries three pieces of information: the red, blue, and green "channels". For a dichromat, two different colors (patterns of light intensity at different frequencies) may stimulate his 2 cones the same way, but would stimulate our third cone to different degrees, and so we could tell the two colors apart. Our televisions and computer screens only need three colors to produce the "full spectrum" of colors, but don't think that there is anything special about three. If someone (or an animal, or an alien), had a fourth cone with its own sensitivity pattern (say to yellow), two colors which look the same to us might look completely different. For instance, on my computer, purple is created with a mixture of red and blue; to a tetrachromat (or even a trichromat with different cone sensitivity patterns), the red/blue mixture might look different than a pure purple. There are three primary colors because we have three types of cones, not the other way around. Color is subjective; there is no guarantee that two different trichromats will see colors the same way. Colors exist inside our heads. It's tough to grasp some of these concepts—I still struggle with some of them—so feel free to ask me to clarify. Interestingly, for some further food for thought: there is evidence that some human females are weak tetrachromats since they have two X chromosomes and therefore two copies of the red cone gene (although they wouldn't be full tetrachromats for reasons I can explain if you're interested); so two colors which look the same to a trichromat like me might look different to a woman with such an ability. Finally, there's a fascinating article at [36] discussing the evolution of color vision in primates. The red cone is the most recent, and appears to have evolved probably to aid in selecting fruit against a background of foliage, or perhaps to select different types of leaves. I apologize for the long post; please ask me if I haven't been clear. — Knowledge Seeker দ 04:46, 11 May 2006 (UTC)

Can I have a question on this? Even though there are three kinds of cones in a human eye, there's yet another kind of photosensitive cell, the rod, with a different spectrum of sensitivity. Wouldn't this mean that it makes us "tetrachromats" to some amount? The writeup I've quoted below says that "Rods are sensitive to much lower intensities than cones, so they are essentially used in night vision: in day vision, their input is not used at all since it saturates, so the cones take over.", and wikipedia seconds this, but still, can't it give us some extra colors at dusk? (Is that why viewing sunset over a lake is so beautiful? Probably no, that's more due to the way it lights the sky and some rays are blocked by clouds.) – b_jonas 21:26, 11 May 2006 (UTC)
(Wow, we even have an article on Trichromatic color vision! – b_jonas 21:35, 11 May 2006 (UTC))
The rods provide a grayscale image (no color). If the cones fire enough to register a color, the brain simply ignores the rods. I programmer I used to know only had rods - no cones. He couldn't see a thing outside in the daytime, but could make out shadows if it wasn't too bright. He wasn't able to see any extra colors. In normal eyes, if the brain didn't ignore the rods when the cones fired, you'd just get brighter/darker shades of the colors you are seeing. --Kainaw (talk) 21:36, 11 May 2006 (UTC)
I'm affraid that doesn't make much sense to me. One type of cone by itself would provide grayscale vision with no colors as well. This doesn't expalain how rods are different. – b_jonas 12:59, 12 May 2006 (UTC)
Read this excellent article about Colors and Colorimetry. – b_jonas 21:12, 11 May 2006 (UTC)
Examples: many birds and insects (including pigeons and honeybees) can see ultraviolet light. Thomas Eisner and colleagues Cornell University built a UV video camera and walked around in places like Panama. They discovered that many flowers have striking patterns visible in UV which apparently help attract the attention of polinating insects. ---CH 10:44, 16 May 2006 (UTC)

[edit] May 11

[edit] Man vs. Bear

Who do you think would win in a no-holds-barred, to the death fight between a man highly-trained in martial arts, in top physical condition and a grizzly bear of approximately the same size - assuming that there were no outside variables whatsoever (just the man, the bear and a piece of perfectly flat ground)?

(I've just been thinking about an advert from a few years ago in the UK where a guy was fighting with a bear, Street Fighter II-style over a fish.) --Kurt Shaped Box 00:31, 11 May 2006 (UTC)

Two words: human sushi. - Nunh-huh 00:33, 11 May 2006 (UTC)
The human would know he was going to fight, plan and train specifically for the fight, and go into the fight ready to kill. The bear would just chilling like a bear until he realized he was in a life or death situation. Chances are, the bear would realize it too late. --Kainaw (talk) 01:04, 11 May 2006 (UTC)
I would say the human would lose. The bear, after all, has claws and the human only has hands. One good swipe from the bear would end it. --Think Fast 03:06, 11 May 2006 (UTC)
Maybe the bear is highly trained in martial arts too? If not then I would think the human's best strategy would be to use his highly trained body to run away - terribly fast.
On a more serious note, any martial art that relies on blocking blows from your opponent is going to be pretty much useless against a foe capable of ripping your arm off. DJ Clayworth 03:46, 11 May 2006 (UTC)

DJ Clayworth 03:45, 11 May 2006 (UTC)

Need not be. A highly trained martial artist can evade blows and attack when necessary and when opportunity is available. He can execute blows to sensitive parts of the opponent to inflict maximum damage. This is something like a kid who is a martial arts expert who can bring a bulky man down. This is a possibility. Hence I say that man v/s bear contest would be a 50% chance for each -- Wikicheng 06:20, 11 May 2006 (UTC)
I doubt even a highly trained martial artist would be able to "evade" a smashing blow from an animal the size of a small car, charging at the speed of a small car, with a reach of almost a meter on each side. And I'm assuming flat land here; our ninja isn't allowed to climb any trees, and it would be unfair to force the bear to run downhill. freshgavinΓΛĿЌ 06:35, 11 May 2006 (UTC)
You missed one small point in the question... the bear and the man are approximately the same size. So, this would be a baby bear, not a large one. --Kainaw (talk) 12:27, 11 May 2006 (UTC)
Yes, apparently I did. Well that just totally ruins it. A grizzly bear is a huge, formidable opponent. A young grizzly (without half the boldness of an adult) would be relatively harmless! freshgavinΓΛĿЌ 00:16, 12 May 2006 (UTC)

The bear would probably win, unless the human got extremely lucky (and was able to score a killing blow to the bear's skull or throat without first being mauled). A human - even one in top physical condition with extensive unarmed combat training - would have almost no defense against a bear's claws and teeth without the aid of some kind of weapon. Raul654 06:42, 11 May 2006 (UTC)

How old and strong would a 65-70kg grizzly be? --Seejyb 10:04, 11 May 2006 (UTC)
Hmmm, bear of man-size. I am no zoologist, but I estimate that a one-year-old grizzly would be about the size of a man. However, still stronger than a man, as well as faster (running speeds of about 50km/h), and with those pesky claws and teeth where one hit will slice you open. My money is still on the bear. — QuantumEleven 12:44, 11 May 2006 (UTC)
My guess is the bear would run off unless there was a reason to stay. Grizzlies are pretty tough, but most animals will not fight unless there is a reason. A female with cubs would be pretty aggressive, or a male fighting over mating rights. A hungry bear can be hard to manage also, but without that bears would tend to avoid people.
The martial artist might be able to sweep the bear off its feet; on the other hand, bear pressure points are likely a lot different from human. --Ginkgo100 20:51, 11 May 2006 (UTC)
I think the outcome of the fight would mostly depend on whether the bear is coward or used to fighting a lot. I've read up on bears in Brehm some time ago and it said that individual bears vary a lot: some live a completely herbivore life, and hide from humans if they meet; but some cannot find enough food where they live that way, so they take up hunting, and some even enjoy it so much that they even go near human towns and eventually get shot there. However, I don't really know how much of this applies to a grizzley. – b_jonas 21:11, 11 May 2006 (UTC)

I think if the human was smart he wouldn't take the bear on face-to-face. To do some kind of "honorable" martial arts style fight with a bear wouldn't be very smart, as the two most dangerous weapons the bear has (claws/arms and teeth) are situated in the front of the bear's body. I'd think the best strategy would be to keep the bear slightly disoriented by trying to run around a fair amount, and probably attacking it from behind, trying to make some kind of fatal blow to the head or neck. Those are my first impressions of the situation, at least. EWS23 | (Leave me a message!) 00:52, 12 May 2006 (UTC)

[edit] molecules

Hi, I need help with my prjoect. I need help on molecules and elements. What is the different stuff about them. There meaning/deffinition. What are they made up of.

I'd start with reading our articles on chemical element and molecule. Feel free to bring any questions back here. TenOfAllTrades(talk) 02:57, 11 May 2006 (UTC)
Though possibly too simple for your project, if you want a more basic, easy-to-understand definition, check out the simple.wiki pages on chemical element, atom, and molecule. freshgavinΓΛĿЌ 06:40, 11 May 2006 (UTC)

[edit] Gravitational time lens

As far as I know it's a silly, improbable theory that few people would put any proper thought into, but just for the sake of science...

Ignoring concerns with available technology (a big thing to ignore, I know) what problems might there be in using a massive object's gravitational field (for example, a supermassive black hole) to view the earth's light as it is bent around the supermassive object and back to the earth? I imagine half the problem would be finding such a source that would so accurately curve light so that the earth would be conveniently right within view, and the other half of the problem would be magnifying, filtering, and distorting the light to get an accurate picture out of it.

I know I'm talking about rediculously high resolution here (even within the earth's orbit, you're lucky to get a resolution less than a meter taking pictures of the surface), but since I'm assuming a time where problems with optical lenses have been done away with by much more complex technology is there any other reason why it wouldn't be possible to see the surface of the earth, light years ago? (Depending on the distance from the supermassive object.) freshgavinΓΛĿЌ 07:05, 11 May 2006 (UTC)

I am not an expert in this field, but my guess would be that, yes, in theory it would be possible. I know you said that technology does not play a role, but remember that you would be observing the equivalent of the Earth from twice the distance to the black hole, which would probably be on the order of several tens of thousands of light-years. Even given obscenely advanced technology, there are limits imposed by physics as to up to what degree of arc you can resolve objects (given by the wavelength of light), so your telescope for these trans-temporaral observations would need to be massive, possibly with the diameter of the Earth's orbit (rough estimate), no amount of technology is going to defeat that requirement. Not to mention that the Earth's image will be greatly swamped by the light of the nearby Sun. Also, light does very strange things in the presence of strong gravitational fields - I could imagine the image would get rather distorted, but I'm not enough of an expert to pronounce judgement on this.
However, if you can beat these obstacles, yes, I think that in theory it ought to be possible. — QuantumEleven 12:36, 11 May 2006 (UTC)
If you're writing a science fiction novel, you could always construct an array of telescopes to give you the necessary resolution. The Very Large Array demonstrates the principle using radio telescopes. By spacing out the telescopes they can simulate the resolution of a 36 km diameter instrument without having to build a 36 km wide dish. Similar principles are being implemented in some new and proposed optical telescopes. The technique is a lot more difficult since the wavelengths of visible light are much smaller, but it's the same concept. If you put a constellation of space telescopes into solar orbit, the maximum resolution of the combined instrument would be governed by the maximum distance between the furthest-separated telescopes. You could have an effective telescope the size of Earth's orbit.
A minor caveat to such a technique: you can only see half the Earth at a time, at most. The black hole will be below the horizon for half of the Earth's surface, so there won't be any photons to send back. If the black hole is over the equatorial sky, you'll see 12 hours of each day everywhere; if it's over a pole, you'll be able to see one hemisphere year 'round. TenOfAllTrades(talk) 15:18, 11 May 2006 (UTC)
I don't know the answer, but you may want to look at the Virtual Trips to Black Holes and Neutron Stars page. – b_jonas 20:22, 11 May 2006 (UTC)
Yeah, I imagined something like a VLA system orbiting the earth, probably a handful of independant systems simultaneously measuring other phenomenon in order to help clean up the image. I didn't really imagine angular resolution would be a problem; I figure intelligent sensors will overtake physical lenses in terms of accuracy and usefulness in the future. I always thought as a kid that it'd be so cool to be able to look into a telescope and see the top of the heads of historical figures, even prehistorical humans. Though I guess a much more realistic first step would be to manage some pictures of extra-solar planets first. freshgavinΓΛĿЌ 00:07, 12 May 2006 (UTC)
Not sure that I understand Freshgavin's question, but according to general relativity, light rays passing very near an ultracompact object such as a black hole can wind around several times before escaping. That means that in principle, if you were using your rocket engines to hover over a black hole, you'd see concentric annuli, containing multiple images of each star in the night sky, around a dark disk. This dark disk would be not the optical "image" of the event horizon (r = 2 m for a [[Schwarzschild metric|non-rotating black hole), but rather (sort of) the "image" of the photon sphere (r = 3 m for a non-rotating black hole). Distant obervers can and do observe "weak lensing": light rays bent slightly by a black hole, but not winding multiple times around the photon sphere. This might sound comparatively boring but in fact it is spectacular. However, gazing at a distant black hole would not be a practical way to examine the back of your own head, if that was the question!---CH 10:55, 16 May 2006 (UTC)

[edit] digestion

recently,i have undergone a lot of religious fastings which lasts for more than 8hours/day.In such a case,how come my body does'nt produce HCl and start digesting the walls of my stomach?

thank you

Your stomach is always producing HCl, whether you've eaten or not; see the article on gastric acid. There are things which can disrupt the system and cause, say, gastric ulcers, but as far as I can tell fasting isn't one of them. You may also be interested in Fasting#Physical effects of fasting. —Zero Gravitas 08:39, 11 May 2006 (UTC)
In the absence of food, your stomach produces less acid, but still enough that it would harm the stomach were it not for your stomach's protective lining. Some cells forming this lining produce a bicarbonate-rich mucus that coats the inner surface of the stomach and buffers the acid. --David Iberri (talk) 18:34, 11 May 2006 (UTC)
8 hours a day isn't very long to go without food for, you would be desperately unlucky to have any effects of this. Keeping in mind other animals (eg. Lion) eat once or twice every several days. Also remeber that the concentration of HCl in the stomach, to my knowledge is only 0.1mol/dm³. Philc TECI 22:20, 11 May 2006 (UTC)
True, eight hours isn't that long. But what do you mean "only 0.1 mol/dm³"? That much acid gives a pH of 1, which is pretty harsh. FWIW, gastric juices are closer to pH 2, which means the acid concentration is closer to 0.01 M, even lower than what you suggested. Still, this would be very harmful to the stomach if it didn't have its protective gastric mucosa. --David Iberri (talk) 02:26, 12 May 2006 (UTC)
Maybe but no acids would be great for you if they were in contact with you for your entire life, the only was on a scale of concentrations, not only acids, so on the grand scale of live the universe and everything, a conc of 0.01mol/dm³ isnt very large, given that pretty much everything is higher than that.... Philc TECI 17:46, 15 May 2006 (UTC)

[edit] light

what is the difference between color of light and color of pigment?

--thanks!

There is a lot of information in colour and articles linked therefrom. I think you are basically refering to colour mixing. Light adds its colours - eg a TV screen has red, green and blue dots which when all turned on appear as white. Pigments are filters and remove colours from light, so cyan, magenta and yellow pigments absorb light which isn't cyan, magenta or yellow. If the light passes through/ refelcts from all three pigments then all get absorbed and you are left with no light or black. -- SGBailey

[edit] stress-buster!

can stress actually lead to miscarriages in pregnant women?

There's been a good deal of research on the subject. See here for a good summary. GeeJo (t)⁄(c) • 09:30, 11 May 2006 (UTC)

[edit] pressure on human body

ok, i know this may sound something of an essay question, but its not, i'm a uni student and any kind of help would be great, even if its just what to search for as every obvious thing i have searched for has not come up with the answer i am looking for. what would be the effects of pressure on coordination in the human body? thanks skye

Once you reached a high enough air pressure, nitrogen narcosis would set in, reducing your coordination in the same manner as alcohol. The effects would increase in proportion to the pressure and time spent in the environment. GeeJo (t)⁄(c) • 09:24, 11 May 2006 (UTC)

[edit] Archiving

First, is there a RD:Wikipedia? I think that having it at the top of the RD page would be nice. Second, is there a proper way to archive talk pages? --Kainaw (talk) 12:43, 11 May 2006 (UTC)

Wouldn't that just be the Wikipedia:Help Desk? As for the second, doing a page move, rather than a cut-and-paste, preserves the edit history of a talk page. I think that's preferred. — Lomn Talk 12:54, 11 May 2006 (UTC)

thanks heaps

Thanks also! --Kainaw (talk) 13:24, 11 May 2006 (UTC)
I just found Wikipedia:How to archive a talk page. It didn't come up in the search. I think the Wikipedia search has been rather flaky recently. --Kainaw (talk) 13:58, 11 May 2006 (UTC)
Recently? It's been my experience that the search function here has always sucked. Better to use google. -lethe talk + 09:28, 12 May 2006 (UTC)

[edit] How to change Media player Icon

I've changed my default media player from windows to Jet Audio, but the Icon still remains as windows media player. How can I convert it to Jet Audio Icon? mp3 files are played via jet audio,.but its icon is media player !!

Are you talking about the icon displayed for individual MP3 files? If so, do the following:
1. Right-click an MP3 file icon, then click Open With.
2. If Jet Audio is shown in the Open With list, click it, or use Browse to find it
3. Tick the "Always use the selected program" check box.
4. Click OK.
If that's not what you need, please post again. Feel free to suitly emphazi. --LarryMac 15:52, 11 May 2006 (UTC)


  • 'I've already done the above steps. Mp3 files are played via JetAudio but Mp3 Icons are media player. need to change that to jetaudio icon.
Try: <Start> - <Settings> - <Control Panel> - <Folder Options> - <File Types> - select the registered file type - <Advanced> - in Edit File Type, select <Change Icon> and browse to your JetAudio directory to pick up the icon - click <OK>, etc. --Seejyb 21:59, 11 May 2006 (UTC)

[edit] physics-Light

Does the sparkling of a diamond and twinkling of stars have anything in commom?

thanks a lot

Nope. Diamonds (and other sparkling transparent substances) act as prisms. Stars twinkle as a result of atmospheric distortion (in principle, the same effect as wavy "heat lines" over a grill). — Lomn Talk 14:25, 11 May 2006 (UTC)
Well, I guess they both twinkle:) But seriously, other than that, not much. Also, in my opinion one of the major differences is that stars give off light while diamonds simply, as Lomn says, act as prisms. --Think Fast 01:15, 12 May 2006 (UTC)
Further thoughts on this question. Here is another difference between these two 'experiences': If the position of the light source, the diamond, and the eye are absolutely fixed, there is no 'sparkling'. The appearance of sparkling arises from the slightest motions of the diamond, that presumably offers a large number of faces and opportunities for internal pathways to the incoming light. On the other hand, the light output of a star may be actually quite constant, and if one looks at stars from, say, the Space Station, they do not twinkle. In this case, it is the result of the transmission of light through the atmosphere, itself subject to turbulence and thus density fluctuations, that gives the appearance of sparkling. --Michel M Verstraete 22:19, 12 May 2006 (UTC)

[edit] Mac vs PC advocacy - user interface

OK, I realise this is a minefield. I've read Apple evangelist, Operating system advocacy and others, and they don't really address my question, which is: what is it specifically about the user interface that Mac users find preferable to Windows? Do they think it's easier to find, copy, rename or delete files on a Mac, for example? To switch between open applications? Do they find the Mac's Dock easier to use than the PC's taskbar, and if so why? I'm not interested in issues such as speed, security, architecture, etc. Just these kind of user interface issues. As an example, someone once pointed out that the menu list across the top of the screen is easier to use on a Mac because it's right at the top of the screen, so you can slam the mouse up there and just hit it, whereas with Windows you have to point to it more carefully because there's that blue line across the top. That's the kind of comparison I'm interested in. And by the way, I'm a Mac user myself :) --Richardrj 14:00, 11 May 2006 (UTC)

Ooh. Hmm. Although I am mainly a Windows user, it's Mac OS that I truly love to use. I would say the best feature is Exposé, because it's such a time-saver - hit a key and all your windows show up in thumbnail size and you click on the one you want. Compare that to the slow process of alt-tabbing in Windows. Additionally everything... just works. That's the only way to describe it. I think it might be the way all programs integrate so smoothly with the shell so you always know what everything does - there's no nonstandard "Open file" dialogs. Oh, the "Open File" dialog is great because it shows the contents of a folder and its parent folder at the same time. And the Finder shows all the drives and important folders on the right at all times. Also, Documents go in Documents, Music goes in Music, and so on. Compare that to Windows, where things can get saved anywhere.
It's been said that the Mac's long-lamented lack of a second mouse button is actually a bonus, because stuff doesn't get hidden away in context menus. I don't know if that's true - I think it's just a hinderance really.
But that's my ramble over. Sum0 14:33, 11 May 2006 (UTC)
I pretty much have to agree with what Sum0 has said. Everything works so much better than on a PC, and it looks so much nicer too. All the little extras like the dock magnifying, the genie effect when you minimise windows, dock icons bouncing as they load or to notify you of stuff... they just make the experience so much more pleasant and enjoyable. To be hinest, it's undescribable. --Saxsux 19:17, 11 May 2006 (UTC)
The other awesome thing about Mac OS is the way that, if you want, the OS works like a toaster, or a TV, or a DVD player - it's an appliance, you don't need to worry about drivers or memory or paging or the "computery" bits. And yet unlike a toaster, you can "take the panels off" and underneath there's a proper, powerful Unix heart, which the technically minded can mess around with (I once met a Linux geek who, despite not being a Mac user, knew exactly what to type in the console). So it's fun to mess around with as a geek, but at the end of the day it still works. Unlike other OSes, which tend to break if you stick a spanner in. Sum0 22:09, 11 May 2006 (UTC)
I've concluded that OS X is very good at abstraction. Like Sum0 and Saxsux have pointed out, it looks very nice, things go in obvious places, etc.
But for me, for reasons I'm still figuring out, working with OS X gets annoying after a while. I should say that while I've never owned a modern Mac (and consider myself a PC partisan), I've used OS X, on and off, since the Public Beta, and I'm using a Mac right now (school computer lab). But I can certainly see the strengths of the OS X approach, and I recommend Macs to people other than myself. - mako 00:00, 12 May 2006 (UTC)
Exposé, the dock, Mac OS X, Unix underneath: these are all pretty new. But people have always loved Macs, and some people still yearn for Mac OS 9. So there must be other reasons than all the new gadgets people have been mentioning. (By the way, is there a trick with context menus? The Mac seems to have just as many, but because I don't have a right mouse button, I have to Alt+click. Having to use two hands doesn't seem an improvement, but I'm probably missing something). Notinasnaid 07:58, 15 May 2006 (UTC)
You can hold down the mouse button for a second or two to get the context menu. I don't have any experience with older versions of Mac OS, but if I had to guess I'd say it's because Mac OS is less technical than Windows. No messing about with drivers, no incompatibilities, etc. (Which does have its disadvantages - lack of upgrade potential, for example). Sum0 08:27, 15 May 2006 (UTC)

[edit] Great black-backed gull vs. Umbrella Cockatoo

This was a question that came up on rec.pets.birds a while ago (I found it interesting anyway). Umbrella Cockatoos have a reputation for being vicious, ill-tempered, quarrelsome and generally 'difficult' birds. If one of them was to go up against (arguably) the UK's most vicious, ill-tempered quarrelsome bird, the Great black-backed gull in a fight - which one do you think would win? Like with the man/bear Q. above, assume that there are no outside variables and neither bird was intimidated by the other's posturing, i.e. they both just got stuck in and the feathers started to fly - just a straight one-on-one fight until one of them couldn't fight any longer. --81.79.226.227 14:12, 11 May 2006 (UTC)

I hope you are not contemplating some kind of avian WWF! Like people, birds generally prefer to try to get their way by bluff or ritualized conflict (at most) rather than mortal combat. In nature, fights to the death between well matched contestants are fairly rare.---CH 11:01, 16 May 2006 (UTC)

[edit] Program For Text Translation from Arabic to English

Please I search for Program(software) to translate text from Arabic to English ?

Perhaps one of the links returned from this Google search would be useful. --LarryMac 15:45, 11 May 2006 (UTC)
There is a great site link title that will allow you to easily transilate for free once you get an account. --Welcometocarthage

[edit] autogeneic bone marrow transplants

What is the point in an autogeneic bone marrow transplant? Could you use this for leukemia, returning only the non-cancerous stem cells? --Username132 (talk) 16:15, 11 May 2006 (UTC)

One of the primary benefits is that autogenic transplants reduce the risk of graft-versus-host disease. Their use isn't limited to patients with leukemia; such transplants are likely to be considered in any disease that eliminates one's immune system. Regarding your second question, it is not currently possible to screen for and transplant only those stem cells that are non-cancerous. The major obstacle is that there is no way to determine with certainty whether a given cell is or will become cancerous. --David Iberri (talk) 18:14, 11 May 2006 (UTC)
Can you culture them and see which ones don't grow like cancer?
Also, the article says "Leukemia patients who develop graft versus host disease, particularly chronic GVHD, after an allogeneic transplant have a lower risk of their leukemia relapsing than those who do not develop any GVHD" but don't they also have a concomitantly higher risk of death by GVHD? --Username132 (talk) 20:10, 11 May 2006 (UTC)

[edit] Crystals form better if cooled slowly.

The bone marrow transplant article says "To cryopreserve HSC a preservative, DMSO, must be added and the cells must be cooled very slowly in a control rate freezer to prevent osmotic cellular injury during ice crystal formation." but I think slow freezing promotes crystal formation. --Username132 (talk) 16:30, 11 May 2006 (UTC)

DMSO, a very common cryoprotectant, acts to suppress the formation of ice crystals. Instead, it encourages vitrification of the water. By forming a glass rather than a crystalline solid, you avoid the mechanical damage due to pointy ice crystals.
Our article on cryopreservation gives a good outline of the considerations involved in freezing cells or tissues. TenOfAllTrades(talk) 19:17, 11 May 2006 (UTC)

In general, slow cooling leads to a small number of large crystals, while rapid cooling leads to many tiny crystals. However, based on the previous answers, this is not true in this particular case. StuRat 19:26, 11 May 2006 (UTC)

Rule of thumb: Slow Cooling: Less intracellular ice (good) but more osmotic imbalance (bad). Fast Cooling: More intracellular ice (bad) but less osmotic imbalance (good). So you find the best compromise:
For animal cells a constant controlled cooling rate of 1°C per min seems the best compromise, but the freezers are expensive, so techniques using mechanical freezers and different cryoprotectant strategies are being investigated for a usable cell survival rate at a lower cost. While a Good Survival may be 80%, a lower survival could be Clinically Usable. --Seejyb 22:16, 11 May 2006 (UTC)
As far as rocks go, the slower the cooling, the larger the crystals. --Think Fast 01:17, 12 May 2006 (UTC)

[edit] Ammonia

In the image on the right, what does the line going up with the two dots mean? Thanks, Kilo-Lima|(talk) 17:00, 11 May 2006 (UTC)

That's a lone pair of electrons. The line is optional (you may also encounter ammonia as :NH3). Presumably, the line helps illustrate the tetrahedral orientation of hydrogen atoms and lone pair around the central nitrogen. --David Iberri (talk) 17:14, 11 May 2006 (UTC)
It's not quite tetrahedral. The lone pair of electrons have a large enough density of charge to force the hydrogen atoms closer together. Tetrahedral would be 120 degrees but this according to the image is 107 or 102 - I think there might be a special name for this scenario but it's be three years since I completed that course... :( --Username132 (talk) 18:03, 11 May 2006 (UTC)
Just a minor correction: the angles in a tetrahedron (such as methane) are 109.5°. In ammonia it is 107° - a slight distortion. --Ed (Edgar181) 18:13, 11 May 2006 (UTC)
It's still considered tetrahedral despite the minor deviation from 109.5°. I don't believe the 120° bond angles you mention have anything to do with a tetrahedral geometry. Those angles would be common in other molecules such as the sp2-hybridized carbons in alkenes. --David Iberri (talk) 18:21, 11 May 2006 (UTC)
What I want to know is, since the hydrogens each have a partial positive charge, they should repel each other and the angle between them should be more than the 109.5°, not less. The lone pair of electrons at the top should have a partial negative charge and attract the hydrogens so the angle there should be less than 109.5°.
Read up on VSEPR theory. Your rationale is incorrect. First, the partial charge on the hydrogens is relative the nitrogen atom. Now, does the lone pair orbital have a negative charge relative the nitrogen atom? No. They belong to the nitrogen atom. --BluePlatypus 11:28, 12 May 2006 (UTC)
The lone pair is closer to the electrons making up the N-H bond than to the H-atom. Consequently the bondling electrons are repelled stronger than the hydrogen atom is attracted. Dr Zak 00:22, 14 May 2006 (UTC)

The correct term for the shape of the molecule is pyramidal. The electron pairs dominate the repulsions, and the tiny H atoms are insignificant in this respect. So the short, fat lone pair repels the longer, thinner bonding pairs (each with an H atom at the end) more than they repel each other, forcing the three bonding pairs slightly inwards to an angle of 107 degrees. The electron pairs can therefore be described as having a distorted tetrahedral geometry, but the molecule is pyramidal. X-ray data will not show up the lone pair - it is not part of the shape of the molecule itself.G N Frykman 21:26, 11 May 2006 (UTC)

The presence of lone pairs also explains why a water molecule is bent, and not linear like carbon dioxide, for example. Molecule shape gives an explanation in terms of electron orbitals. Gandalf61 08:33, 12 May 2006 (UTC)
One little thing I'd like to add is a little caveat: as a heuristic, you can pretend as if the lone pair is more repulsive than a typical bond. However, if you do ab initio calculations for the electron density, there really isn't a lobe where the lone pair is. For example, in water, there aren't those "rabbit ears" sticking out. --HappyCamper 00:58, 14 May 2006 (UTC)

[edit] flowchart for the manufacture of Dichlorodiphenyltrichloroethane,DDT

Hello,

 I will be very greatful if anyone could draw the flowchart for the manufacture of DDT for me.
                                    Thanks
                                  ----------
You may be interested in the answers from the last time you asked this question. --Kainaw (talk) 18:00, 11 May 2006 (UTC)

[edit] Internet data exchange

How much data is exchanged on the public Internet daily? 134.215.197.210 19:26, 11 May 2006 (UTC)

I doubt that there's any way to give anything aproaching a definitive answer to this question, but traffic stats from the London Internet Exchange show an average data rate of about 100Gbps[37] (which works out at approx 1PB per day) and that is only traffic going through LINX. -- AJR | Talk 00:03, 13 May 2006 (UTC)

[edit] Dodgy Bike Gears

On my old bike I'd change gear and it would always take ages for the chain to move across and I'd get a constant clickety sound. Even when it moved over, it would sometimes carry on clicketing like it wanted to be on another sprocket. Why?

Also, on dutch omafiets, the chain is usually covered by some fabric thing - what's that about?

If your shifter isn't aligned correctly, it tries to shift the chain near the gear you are selecting. Since it isn't put in the correct position, it just sort of clanks around between the gears. --Kainaw (talk) 20:26, 11 May 2006 (UTC)
I assume you're talking about an external derailleur shifting mechanism rather than an internally-geared hub. If this is the case, the alignment of the jockey pulley of the derailleur with the cogs on the freewheel may be innaccurate. This is especially the case with the "indexed shifting", where the shifter "clicks" into the gear position rather than being continuously hand-adjustable. The alignment can be modified by adjusting screws on the derailleur and/or barrel adjusters on the cable levers.
Another possibility is that your chain is worn, or "stretched." In this case, the effective pitch between the links has increased so that the chain links do not seat easily in the teeth of the chainring or rear cogs. Alternatively, your chainring and/or cogs are excessively worn. In any case, replacement of the worn part should help.--Mark Bornfeld DDS 20:52, 11 May 2006 (UTC)
Shifter cables tend to lengthen over time and with use, so a derailleur that was in adjustment is no longer in adjustment. There's a little knob called a "barrel adjuster" where the cable goes into the derailleur housing. By twisting it clockwise or counterclockwise, you can get it back into alignment. See this article on ehow.com for details. --Elkman - (talk) 20:54, 11 May 2006 (UTC)

[edit] Circular Motion

At what minimum speed must a roller coaster be traveling when upside down at the top of a cirlce if the passengers are not to fall out. Assume a radius of curvature of 9.6m.

I've done this about 5 different ways and gotten different answers each time. The example below is one I think may make the most sense....I don't have the answer to this problem so if someone could verify whether I got it right or not. Thanks.

\Sigma Fc = \frac{mv^2}{r}
FN + FG = \frac{mv^2}{r}
2mg = \frac{mv^2}{r}
2g = \frac{v^2}{r}
v = \sqrt {2gr}
v = 13.72

C-c-c-c 20:54, 11 May 2006 (UTC)

Almost. See circular motion; it's just
a = \frac{v^2}{r}
(where a = g in this instance; the rollercoaster can't be accelerating at 2g downward)
v = \sqrt {gr}
—Zero Gravitas 22:01, 11 May 2006 (UTC)
Haha that was one my "five" answers .... Thanks! C-c-c-c 22:10, 11 May 2006 (UTC)

[edit] car's sweet spot

i recently read in news scientist that there was a piece of US legislation that forced car companys to make there cars more effiecent at 55mph, ie the sweet spot where the cars runs the most effiecently, now is there a similar law in the UK and if so whats the speed? Colsmeghead 21:15, 11 May 2006 (UTC)

I've never heard of any such law. Searching the Library of Congress for anything with "55 mph" only turns up one bill: Fuel Economy Truth in Labeling Act. It notes that the EPA allows automakers to use a highway speed of 48mph when measuring "Highway MPG". It wants it increased to at least 55mph since most states allow speeds of least 65mph on highways. --Kainaw (talk) 00:54, 12 May 2006 (UTC)
There was also a law or regulation requiring that the speedometer have an emphasized marking (numbers larger or in a different color) for 55mph. --Serie 20:44, 12 May 2006 (UTC)
ok i made mistake its 27.5 miles per gallon (55mph was from soemthing esle in the article), done by presdient carter in 1975 and called the coporate average fuel effciency standardColsmeghead 22:46, 12 May 2006 (UTC)

[edit] Electrolysis of Water

I am seriously confused about some key elements in this process. First when water undergoes electrolysis then can the oxygen mix with the hydrogen without turning back into water and if it can why cant that gas be used in cars?

The oxygen and hydrogen can indeed mix together without reacting. In order to react there has to be a source of activation energy, such as a spark. There are many reasons why a hydrogen-oxygen mixture would be a bad fuel for cars. One is simply that oxygen is readily available in Earth's atmosphere, so it would be a waste of space to carry it along. Another is that it would be dangerously explosive, especially at the high pressure required to store it in a reasonable amount of space. Many people are working on designing hydrogen vehicles, but so far no one has conquered this problem of energy density. —Keenan Pepper 00:03, 12 May 2006 (UTC)
Oh, we are considering the problem, trust me - and, as you correctly pointed out, it's a bit of a pain in the backside! Hydrogen is so darn light that it either needs to be kept as a liquid (so you'd be driving around with a massive, insulated tank at about -250°C - oh boy!) or as some kind of molecular combination... it's a problem, and it's being worked on. I will be very curious as to the eventual solution to it...
Under compression Hydrogen can be a liuquid at room temperature. Like in the fuel chambers of rockets. Just for the record, the ice on hydrogen/oxygen powered rockets, is caused by the hydrogen boiling, and isnt because the rocket has been in some collossal fridge. Philc TECI 17:43, 12 May 2006 (UTC)
Erm - isn't it just because the insulation on the tanks isn't 100% perfect, and the outer skin of the rocket is cold enough that water vapour from the atmosphere freezes to it? I don't think I'd want to have any uncontrolled hydrogen boiloff in the middle of a rocket launch... — QuantumEleven 10:15, 13 May 2006 (UTC)
Yes, but thats my point, cold can't spread, as it doesn't exist, it is just the absence of heat, so heat has to be sucked, this energy sucked in by the liquid hydrogen gives a tiny amount of it the energy to boil (like possibly 0.1% of the contents) but the point is compressing a liquid to a level and then allowing to expand a bit (in this case as it is stroed, and then as it is pumped in) causes the ontainer to get very cold, like a deoderant can when you relieve some of the pressure by spraying some. Philc TECI 17:50, 15 May 2006 (UTC)
Also, liquid hydrogen has the para/ortho problem, which can lead to tank rupture.
And for the original question, to see what happens when hydrogen and oxygen get mixed together, see what happened to the Hindenburg. — QuantumEleven 07:44, 12 May 2006 (UTC)
On the other hand, liquid hydrogen and oxygen (which must be kept separate) make great rocket fuel. —Keenan Pepper 00:06, 12 May 2006 (UTC)
As far as I am aware hydrogen is not a resource in abundance on earth, the most viable way to get it would be from water, whivh then means hydrogen would only be viable as a way of storing energy, and not releasing it, as you need to initially split the H2 and O up to join them back together. Philc TECI 17:43, 12 May 2006 (UTC)
Nonetheless hydrogen is the most aboundant element in the universe. Luthinya 21:45, 16 May 2006 (UTC)

[edit] May 12

[edit] programmer/software engineer

what are the big differences between a software engineer and a computer programmer?--orphan frequently 03:21, 12 May 2006 (UTC)

About $15,000 a year. [38] - user:rasd

well, yes, i could have told you that, but i mean actual work wise.--orphan frequently 03:21, 12 May 2006 (UTC)

I suppose a software engineer might do more than just write programs, such as developing the specs, creating database tables, developing an implementation schedule, test plan, and rollout plan, etc. StuRat 03:30, 12 May 2006 (UTC)
Yeah, in general, software engineers do a lot more overall project work. It varies a lot, but you might think of it as a type of senior programming position. In larger projects, computer programmer becomes more the grunt work, whereas in smaller projects, "programmers" will do the exact same duties and will probably be paid similarly if not more than the software engineers. Seriously, though, the distinction is not always clear. When I did some undergrad study in computer science, the answer I gave you was more or less the same answer I got from two professors. Software engineer is (or at least was back then) a title that senior programmers gave themselves so they didn't look somehow inferior to other kinds of engineers. - user:rasd
A true software engineer is a licenced professional qualified to write software that involves risk to humans. Usually, however, it's just a fancy (and technically incorrect) name for a computer programmer, particularly one who designs software in addition to simply writing the actual code. Peter Grey 04:21, 16 May 2006 (UTC)
Where would that be the case? Neither our software engineering or Professional certification has any mention of that that licensing. Rmhermen 16:33, 16 May 2006 (UTC)
In Ontario, claiming to be any kind of engineer without the professional licence is illegal. But "software engineer" as a job title seems to be fairly common in places that allow informal meanings of 'engineer'. Peter Grey 02:11, 17 May 2006 (UTC)

haha, i have to come up with three careers for a project, anyone got another name, technical director maybe?--orphan frequently 04:06, 12 May 2006 (UTC)

[edit] Randomly generating the contents of a Javascript array

My knowledge of using arrays in Javascript is pretty weak. Basically, I want an easy way to fill out an array with, say, 10 numbers, from 0-9, in a "random" order. So a few possible options would be...

  • MyArray = Array(0,1,2,3,4,5,6,7,8,9);
  • MyArray = Array(7,0,4,5,9,6,8,2,1,3);
  • MyArray = Array(4,6,9,1,3,0,5,2,7,8);

Every number is used once. Now, just to add a little more complication, I'd like to be able to do this for n amount of digits (I did it for 10 up above, but it would be nice to be able to use the same function for 11, or 12, etc.). In every case I will be using the digits from 0-n, and will want each one to be used exactly once.

Is this a foolish desire? Is there an easy way to do it? You don't have to do all the work for me, but pointing me in the right direction would be fine. --Fastfission 05:29, 12 May 2006 (UTC)

I don't know JavaScript. But I would create an array of n+1 digits in the direct 0..n order. Then I'd apply the Knuth shuffle: move through the array from beginning, swapping the current element with a random one. That should give a random array with unique digits. Some pseudocode:
Declare MyArray of n+1 elements

For i = 0 to n
  MyArray(i) = i
Next

For i = 0 to n
  Temp = MyArray(i)
  RandomElem = int(random(n+1))
  MyArray(i) = MyArray(RandomElem)
  MyArray(RandomElem) = Temp
Next
Hope this helps. –Mysid(t) 05:47, 12 May 2006 (UTC)
I'll give that a shot. I'm not sure I 100% understand how it works at the moment but after I play with it for a bit it should make sense. --Fastfission 12:42, 12 May 2006 (UTC)
That works beautifully. Many thanks. --Fastfission 12:50, 12 May 2006 (UTC)
If (big if) I'm reading Shuffle right, Mysid's algorithm produces biased shuffles. You have to restrict the card drawn to the part of the pack not yet passed through (ie RandomElem >= i), or you end up with nn execution paths matching on to n! possible outcomes. Something along the lines of
                             RandomElem=i+int(random(n+1-i))
should work properly (I think). --193.38.88.6 15:49, 12 May 2006 (UTC)
You're correct! Great that you noticed. I seem to have skipped that part when reading. –Mysid(t) 16:55, 12 May 2006 (UTC)
The way I would implement it in JavaScript:
n = 10 // number of elements desired
r = 50 // random numbers can be from 0 to (r-1)
randarray = new Array(n);
i = 0 // temp counter
while (i < n) {
randarray[i] = Math.floor(Math.random()*r); // Math.random() produces pseudo-random number between 0 and 1
i++;
}
// randarray should now have random number elements.
Note that these "random" numbers are merely pseudorandomly generated ones. Apart from that, I tested it and it works fine. Enjoy. -- Daverocks (talk) 13:23, 15 May 2006 (UTC)
Erm, I'm not sure that's what Fastfission wants -- the array must include all digits between 0 and n-1 once only, but in a random order. I suppose you could sort the array and then assign the sorting indices back to the original place in the array that the number came from, but that'd be much more computationally expensive than the shuffle algorithm. --Bth 07:18, 16 May 2006 (UTC)
Oh, right! Sorry about that. Heh, you can use Mysid's algorithm then. :) -- Daverocks (talk) 08:37, 16 May 2006 (UTC)

[edit] silicon oil

is silicon oil bad for baby skin?

Nasty stuff, for industrial use only. See silicone, and this: [39] --Zeizmic 12:56, 12 May 2006 (UTC)

Baby no longer slippery? Maybe the first signs of rusk? What he (or she!) needs is oiling! But forget cheap silicone oils. Buy Baby oil. Babies just love it! Baby oil. Available at all good corner stores.

If you accidentally got silicon oil on a baby's skin, I would advise you to contact poison control just to be on the safe side. --Ginkgo100 19:33, 12 May 2006 (UTC)
You lot are chasing up spooks. Silicones are common and safe ingredients of many cosmetics. They do aid in softening skin. They are remarkably nonreactive. Allergies are virtually unknown. Not known to be carcinogenic. Silicone used in any body "oil" would be FDA tested and approved (as are those used in hair care products, cosmetic creams and pastes). If one is using industrial or home lubricating oils, the issue is different, but the problem is more with solvents and propellants than with the silicone compound itself. So don't use stuff not designed for human skin use, but those that are approved for skin use are safe for babies. Has anyone here ever had problems from accidentally getting lubricating silicone spray on their hands, not related to the propellant used? Why would plant oils be safer than silicone oils? You have probably given your baby silicone orally, without knowing it, as part of the treatment for "winds"--Seejyb 21:21, 12 May 2006 (UTC)
Peeve alert: Please distinguish between silicon and silicone. There's no such thing as "silicon oil", unless ordinary oil is "carbon oil". Silicon is a solid, metallic in appearance and to the touch (though not technically a metal). --Trovatore 21:25, 12 May 2006 (UTC)

[edit] global warming

has the world really been warming over the past 20-30 years?what are the consequences?

thank you

Yes, the average temperature on Earth has been steadily rising over most of the 20th century, and the scientific consensus is that this is caused by human activity. Our articles on global warming and climate change cover this very well. Note that I said average temperature has been increasing, this does not preclude some local cooling. The consequences of this will most likely be rising sea levels (as the polar caps melt, quite a few Pacific islands will probably disappear in the next 50-100 years), more violent weather (more storms, blizzards, hurricanes), longer and more intense periods of drought and flooding... I could go on. Our article on effects of global warming covers this quite nicely. — QuantumEleven 07:39, 12 May 2006 (UTC)
The scientific consensus is the reason for global warming is controversial. The political consensus is this is caused by human activity. The climate is too complex for us to understand without a lot of research, and the research is complicated even more by being infected with politics.
Just for the record: In addition to the excellent coverage within Wikipedia, you may want to consult the official reports of the Intergovernmental Panel on Climate Change (IPCC) which are available from http://www.ipcc.ch/. The full report is extensive and exhaustive, but there are 'Executive summaries'. Volume 2, in particular, deals with the expected impact of climate change. By the way, the Fourth Assessment Report is currently in preparation and should be released in 2007. --Michel M Verstraete 22:33, 12 May 2006 (UTC)

[edit] Electricity from Exercise Bike

People have said that you can ride an exercise bike that is properly equipped, and by doing so you can pour energy into the system and get reinbursed by the electric company. They even say that if you pour in more energy than you use, the electric company has to pay you money. Sounds cool, does anyone know how to go about doing it, if it is possible. Thanks, Chuck(척뉴넘) 07:54, 12 May 2006 (UTC)

This reminds of an episode of Catdog.. Jayant,17 Years,India • contribs 07:57, 12 May 2006 (UTC)
I am not sure about the electric company but you can definitely generate some electricity from the exercise bike. Basically the bike will have some mechanical device to introduce friction so as to make you do the work. In place of this friction device, you can put a dynamo. When you pedal the bike, the dynamo will generate electicity. This may not be sufficient to light up your home but you can possibly charge some batteries. Even if you tie up with the electric company, I don't think the reimbursement will be substantial, considering that you generate a very small amount of electricity -- Wikicheng 09:09, 12 May 2006 (UTC)
Ask your local power company if they offer net metering. There may be rules about it, such as what power production methods are allowed, you may need to promise to deliver at least a specific hour-wattage annually, you may need to pay (part) of the construction of necessary equipment, etc. Consult your local legislation and your power company. Weregerbil 10:49, 12 May 2006 (UTC)
This is from an article I recently used in a paper on global warming: "Got some solar power to sell, or are you finding you don't have enough to keep the lights on at home? GridPoint (www.gridpoint.com), an energy management appliance maker, is developing better ways to manage your homemade renewable energy. The company recently received a "Most Innovative Product" award from Green Builder Magazine for its battery-backup device for solar powered-homes, GridPoint Connect. The system plugs into your home's electrical system, balancing loads and protecting against power surges. GridPoint Connect also sells your unused juice back to the grid."--Chris 14:58, 12 May 2006 (UTC)
Depending on how athletic you are, you will probably only generate 80-120W of continuous power on your bike - that's enough to light one or two lightbulbs, and nowhere near enough to run a computer or a fridge, let alone a power-hog like an oven, hotplate or hair dryer. I doubt you will be able to make a significant dent in your electricity bill this way. But, it can't hurt to ask. — QuantumEleven 14:59, 12 May 2006 (UTC)
Let's see.. Running a marathon uses about 15 MJ. That's 4.1 kWh (if you could turn that all into electricity with 100% efficiency). Given a going rate of electricity of about 10 cents a kWh, that's almost half a dollar! Now subtract the cost of food it'll take you to sustain that kind of activity. --BluePlatypus 15:02, 12 May 2006 (UTC)
You'd be lcuky if you made enough electricty to work a fan and keep you cool. Philc TECI 17:36, 12 May 2006 (UTC)
I think the reason that some people think you can get a lot of electricity from a bike is because there are bikes set up so that as long as you keep peddling at a certain speed (or more), the television works. If you slow down, the television cuts off. If you don't know what is going on, you'd think the bike powered the TV. That is not the case at all. The bike powers a relay (an electrical switch) that controls the electicity going from the power outlet on the wall to the television. When the bike wheel moves, the switch closes and the TV turns on. When the bike stops, the switch opens and the television turns off. --Kainaw (talk) 17:40, 12 May 2006 (UTC)
Generally, unless you have a major waterfall in your back garden, or live in Sellafield, or have discovered cold fusion, the cost of generating the power would be greater than any possible returns. smurrayinchester(User), (Talk) 19:57, 12 May 2006 (UTC)
"you will probably only generate 80-120W of continuous power on your bike", so let's say 100W. If you ride for 10 hours, that's 1 kWh, which costs me 11 cents, according to my bill. That shows you what a great deal cheap energy is. Please help the good deal last as long as possible; please do not waste energy. So muscle power is tiny, compared to electricity use; that's not a practical way to go. "Generally, unless you have a major waterfall in your back garden, or live in Sellafield, or have discovered cold fusion, the cost of generating the power would be greater than any possible returns." WRONG. Wind and solar can feedback into the grid at high peak times. Case in point: http://www.solarwarrior.com/ 27kW system, feeds into the grid during the day, they get paid; grid charges electric cars at night, They pay NOTHING , net, for electricity , including NOTHING for their cars. (Other than capital costs, of course.) But their use of global oil for their cars is zero, their energy independence, total. Electric companies should be REQUIRED to offer net metering. --GangofOne 02:06, 13 May 2006 (UTC) Lower end systems: http://www.homepower.com/magazine/guerrilla.cfm --GangofOne 02:44, 13 May 2006 (UTC)

[edit] Astrophyton darwinium

"Astrophyton darwinium" (Gorgonocephalus sp.)
Enlarge
"Astrophyton darwinium" (Gorgonocephalus sp.)

What is the modern name of Astrophyton darwinium? Googling for the species name returns zero results (you get a few more on just the genus "Astrophyton"). The creature features prominantly on plate 70 in Ernst Haeckel's Kunstformen der Natur (1904) (see the Commons page for all the beautiful plates). The name is shown in the associated text [40] if you want to check it for typos, or if you can read German and want some clues. Note that Haeckel himself is the authority on the name. Any help appreciated. It's been bugging me for a while. (Note that Wikipedia's article on Astrophyton is for a genus of cacti, and not basket stars) —Pengo 07:56, 12 May 2006 (UTC)

...hello? —Pengo 00:59, 14 May 2006 (UTC)
Could it be in class/subclass euryalidae/euryalida ? Basket stars are a subset of brittle stars. Unfortunately, Wikipedia doesn't have much on them. But I think these pics match yours: [41] [42]. StuRat 04:39, 14 May 2006 (UTC)
Perhaps it's a gorgonocephalus verrucosus: [43] StuRat 05:03, 14 May 2006 (UTC)

[edit] Supernovae

Can I get a detailed explaination of observations accompanied with the Supernovae(like mag, and explaoination of types, naming etc.)? Contact : [email removed for spam prevention]

Did you try supernova? It's a bit short on exact details of the luminosities involved, but the rest of your question would seem to be covered there. --193.38.88.6 09:56, 12 May 2006 (UTC)


[edit] Supernovae

Can I get a detailed explaination of the observations accompanied with the finding of Supernovae (like the value "mag", and explaination of types of Supernovae, naming etc.)? Contact : <Email Removed>

Please do not post your e-mail address on a public forum. And you might wanna check out the Supernova article, if thats what you are searching for. Jayant,17 Years,India • contribs 09:38, 12 May 2006 (UTC)
Woops, I've just seen that this guy's repeating himself. Sorry. --193.38.88.6 09:56, 12 May 2006 (UTC)

[edit] Bomb

which of the following 3 bombs, kills only humans(living organism) but has little effect or damage on buildings & other properties? A. neutron bomb B. Hydrogen Bomb C. Atomic bomb --the preceeding unsigned comment was added by 196.200.102.42 at 10:32, 12 May 2006

A neutron bomb has been said to kill only humans but leave buildings intact. This seems to be disputed, though. See the article. (But the correct alternative is A.) –Mysid(t) 10:24, 12 May 2006 (UTC)
We cover hydrogen bombs and atomic bombs in the article on nuclear weapons. --Howard Train 10:31, 12 May 2006 (UTC)
Neutron bombs are designed to have lots of radiation (which kills living organisms) and relatively little blast/fire effects (wouldn't harm as many buildinging as "regular" fission or fusion weapons). --Fastfission 12:37, 12 May 2006 (UTC)
Neutron Bombs do have increased radiation, but I am not aware that they have a smaller blast than a standard fission bomb of the same size. Philc TECI 17:33, 12 May 2006 (UTC)
In the future, it's recommended you do your own homework. But thanks for asking. --Ginkgo100 19:37, 12 May 2006 (UTC)
For all of them, it depends on the size of the explosive and where it's detonated. Peter Grey 04:24, 16 May 2006 (UTC)

[edit] Frequency ramp generator?

I'm not sure if "frequency ramp generator" is the right term, but I need to build a circuit that produces a signal output whose frequency increases linearly as a function of time. Using a function generator and op-amps, transistors, timers etc, is there a simple way to build such a circuit? Thanks. -Wiccan Quagga 12:24, 12 May 2006 (UTC)

Why not take a simple VCO and connect it to the output of integrator on opamp (feeding constant voltage to this integrator)?--Ring0 13:30, 12 May 2006 (UTC)
I believe what you are looking for is a "sweep generator". Try Google. --68.238.243.228 01:11, 19 May 2006 (UTC)

[edit] Animals without dividing cells

I came across the following sentence: "If a constant killing radiation were endured, all living animals with dividing cells would die."

Logical follow-up: are there animals that do not have dividing cells? Are they short-lived? 194.151.6.67 12:41, 12 May 2006 (UTC)

Last I checked all cells divided. Luigi30
Actually, some cells (such are neurons) are too specialized to divide. They are the "end of the line," so to speak. --Ginkgo100 19:48, 12 May 2006 (UTC)

(Ταλκ το mε) 14:01, 12 May 2006 (UTC) Keith Richards --Zeizmic 14:21, 12 May 2006 (UTC)

They wrote it in that way to make the definition of radiation clearer. It would not be good enough to write "... all animals would die." It's just the style of writting the author chose to use. But you are right, all cells reproduce themselves by dividing. --Chris 14:55, 12 May 2006 (UTC)
I'm no biologist, but why would it be no good to write "...all animals would die"? Wouldn't that have been clearer, and avoided the questioner's confusion? --Richardrj 15:17, 12 May 2006 (UTC)
Perhaps the writer meant to specify the reason why animals die under radiation exposure – it disturbs their DNA replication, for instance, so that they can't divide normally. –Mysid(t) 16:52, 12 May 2006 (UTC)

Don't forget red blood cells. They have to be made in the bone marrow because they can't divide on their own. Jonathan talk 14:18, 15 May 2006 (UTC)

[edit] Real files to DVD?

Is it possible to burn Real Player video files (.rm) to DVD and watch them on TV through a DVD player? --Richardrj 14:59, 12 May 2006 (UTC)

Perhaps the only solution is to recode that files to a format supported by your DVD player (every player supports MPEG-2, for example).--Ring0 16:07, 12 May 2006 (UTC)

[edit] what is our physical universe

What's this about oval orbits? I mean, most people can visualise an object moving uniformly in a straight line, unless there is an external influence. Why is it that all orbits are not perfect circles? If an object is moving away from the point of gravitational infulence and there is no friction, (no friction in space, right?) it will tend towards the straight line. Surely the gravitational influence is weaker the further the object is aways from it? Why does it reach a plateau and return (and gain velocity)? I'm not sure the analogy of a rubber blanket, (gravity influencing from below), with balls rolling around a heavier ball makes sense here. What have I missed?

According to Newton's law of universal gravitation the energy of the planet in a star's gravitational field is:E=\frac{mv^2}{2}-G \frac{M m}{r}. This allows three types of movement: elliptic (when the planet lacks energy to go out from the gravitation potential well, that is, E<0), parabolic (when it has just enough energy and no more, that is, E=0) and hyperbolic (when it has more energy, E>0). It can be derived mathematically.--Ring0 16:04, 12 May 2006 (UTC)

Note that an ellipse is not the same as an oval. Ellipses, parabolas, and hyperbolas are conic sections, while an oval is a vague term that can mean many things. StuRat 16:52, 12 May 2006 (UTC)

While the equations prove to him that it's true, I don't think that's going to help him visualize why orbits don't all become circular. Instead of thinking about circular orbits, think of the way things fall back to earth. If you throw something up at an angle and let it drop down (lets pretend there's no air, and no friction), it follows a parabolic path, not a circular one. If you threw the object really far up, so far that on its decent back to the earth it would actually miss it (go over the edge, in a manner of speaking), the parabolic curve would continue around the earth and after a while it may end up in a regular elliptical orbit. Sure the farther the object is the weaker gravity is, but if the object is moving slower than the escape velocity at that point, it won't plane out into a straight line, and it will eventually fall back. In fact, it must be quite difficult to achieve a circular orbit naturally; the object must be travelling at a 90 degree angle to the circumference of the planet and at the exact speed to keep it stable at that height. freshgavinΓΛĿЌ 17:13, 12 May 2006 (UTC)

Since energy cannot be created or destroyed, a comet for example has two types of ebergu, kinetic energy (KE), and gravitatinal potential energy (GPE), as it falls towards a larger object, eg the sun, the GPE is converted into KE, the more KE it has, the faster it moves, and as it moves away KE is converted into GPE, once all of the energy is GPE, this is the furthest that the comet can go, and it starts to move back towards the sun in a round path, with the sun at one of the focuses. Philc TECI 17:26, 12 May 2006 (UTC)
That's cute, as in: "Ha, Romdyrom equation say, for Ebergu: r = nv3. That right Emhlish?" --Seejyb 23:27, 13 May 2006 (UTC)
Hehe, aww, sorry, that joke was a bit synical... mahwell, ok its energy. Philc TECI 18:53, 14 May 2006 (UTC)

Many thanks Guys. —The preceding unsigned comment was added by 82.24.122.46 (talk • contribs) 00:15, 13 May 2006 (UTC)

[edit] Water activity of food and storage at % ERH

Hi!

If a food stuff has a water activity of 0.70, then it would have an equilibrium relative humiditiy (ERH) of 70% (right?!). But to keep this constant, what ERH would it need to be stored under?

Thanks!

The equilibrium relative humidity ERH of the food is determined when it is made and packaged, it is a description of the indirect technique by which water activity (aw) of the food is measured. The aw and pH are used to predict the potential for bacterial or fungal growth in the food in it's original container / package form. The storage requirement is a separate issue, relating to temperature, moisture and light conditions of the environment, this is neither measured nor expressed in terms of ERH (the latter cannot be determined outside of a sealed container anyway). If food has a high aw, one would usually have to keep it refrigerated to reduce the available free water for bacteria to grow in, or include a preservative. So one does not store food "under an ERH of XYZ" - the aw is already specific to the food itself - but the aw (as derived from ERH) can give one an indication of what special storage conditions are required to help prevent spoilage, or of the expected safe storage period under specific conditions (see equation in water activity). The [FDA] publishes info on the variables affecting bacterial growth --Seejyb 23:41, 12 May 2006 (UTC)

[edit] psoriasis

does psoriasis spread to infants below 3 months of age. is it contagious. does it leave scars which is long lasting. can it be treated by medicine.

Try psoriasis and relax a little. I'm fairly sure it isn't contagious to anyone. Skittle 18:16, 12 May 2006 (UTC)

It is non-contagious, and is a challenge to treat. There are a number of treatments to relieve the symptoms, though. The condition is, according to the article, incurable and lifelong, so it's difficult to speak about leaving scars. Our article on psoriasis has more. –Mysid(t) 18:16, 12 May 2006 (UTC)
See the note at the top of this page. This is not the place for medical advice. Please, please, talk to a pediatrician and/or dermatologist if you're worried. That said, please note that Eczema (ordinary skin rashes), are quite common in babies and that the onset of psoriasis is usually around the age of 10 or later. Here are a few links on infantile eczema from a cursory Google search: [44] [45] --BluePlatypus 17:33, 13 May 2006 (UTC)

[edit] Video conferencing

Can video conferencing increase productivity in meetings? I'm looking for research or testamony.

I love video conferencing with my: juices --Mac Davis 22:00, 12 May 2006 (UTC)
Increase productivity relative to what ? If relative to flying people in from around the world for an in-person meeting, I would say, yes, definitely. If relative to plain old teleconferencing, then only if there is something visual worth seeing. If relative to not having the meeting at all, then that depends on the value of the meeting. Many meetings seem to be a waste of time and productivity, held only because it's on the schedule, not because anyone has anything of value to contribute. For example, my brother was once told to abandon a customer for an emergency meeting on increasing customer responsiveness, LOL. StuRat 22:15, 13 May 2006 (UTC)
Video conferencing is probably more productive than having geographically separated workers not communicating directly. I don't know that it's ever been researched, though. (It's interesting that industries that can't charge meetings to their customers (say, accounting) almost never have meetings.) Peter Grey 05:10, 17 May 2006 (UTC)
I think some meetings are productive, say if a team is working on a group project and needs to meet to figure out who will do which portions. Unfortunately, many meetings seem to be held for no real purpose, such as a work group composed of many people with unrelated job responsibilities meeting weekly. Such meetings tend to be a waste of time and resources. StuRat 06:25, 18 May 2006 (UTC)

[edit] What is on the other side of the world from me?

During a conversation with a friend, we were trying to figure out how you'd answer the topic question. I think you find out your current latitude and longitude; add/subtract 180 to/from the longitude and just flip the latitude north for south; then find out what's at those new co-ordinates. Do we have our algorithm right? --LarryMac 19:04, 12 May 2006 (UTC)

Is it true for the poles ? --DLL 19:09, 12 May 2006 (UTC)
What would you give as the (geographic) latitude and longitude for either of the poles?
Anyway, if our idea is correct, then if I were in my opposite place, I'd be drowning in the Indian Ocean off the SW point of Australia. (...waving to Jack ...) --LarryMac 19:16, 12 May 2006 (UTC)
Hey, Larry, how very thoughtful. I'm flattered that while you're drowning in a vast ocean about 3,000 kilometres away from me, you'd still find time to wave to me. If you survive, get in touch with the guys from Not Drowning, Waving. JackofOz 00:49, 13 May 2006 (UTC)
Very interesting; from where I am (near London), my antipode would be floating somewhere in the Pacific Ocean, some distance away from New Zealand, and close to the International Date Line. Maybe if I crossed the Greenwich Meridian, my antipode would thus cross the International Date Line and thus change a day... Andrew 15:57, 19 May 2006 (UTC)
You are correct. Change the latitude from north to south or vice versa; subtract the longitude from 180 and change it from east to west or vice versa. The point opposite you on Earth is called the antipodes (singular). Yes, this holds true for the poles. The north pole, for instance, is latitude 90° N (longitude is irrelevant/undefined); change to 90° S and you're at the south pole. Of course, this assumes the Earth is a perfect sphere or at least symmetric over the plane of the equator and rotationally symmetric around the axis (I think). http://www.antipodemap.com/ is a cool little page. — Knowledge Seeker দ 19:33, 12 May 2006 (UTC)
Excellent! That page is exactly what we were looking for. Thanks. --LarryMac 19:37, 12 May 2006 (UTC)
You'll notice from that page the surprising fact that there are very few antipodal points that are both on land. For the vast majority of the world's population, the answer to "What is on the other side of the world from me?" is "an ocean". The only overlap of continents, as shown in the Antipodes article, seems to be parts of Argentina and China. This makes me wonder: is this lack of antipodal continents a coincidence, or the result of some subtle effect of tides or continental drift or something? rspeer / ɹəədsɹ 19:45, 12 May 2006 (UTC)
I'd say it's a coincidence, as most of the Earth's surface happens to be water (which also might be a coincidence). –Mysid(t) 19:56, 12 May 2006 (UTC)
My friend who started all this happens to live in Hawaii, so he's in one of the few other places with a non-oceanic antipodes. --LarryMac 20:00, 12 May 2006 (UTC)
Mmmmh, there seems to be something odd in the Antipodes picture. Everybody in Italy know that New Zealand matches Italy on the other side, for position and shape. Cthulhu.mythos 09:26, 18 May 2006 (UTC)
Surprising how often "everybody" can be wrong. Although it's not too far from the truth really. -- Avenue 09:46, 18 May 2006 (UTC)
I found it very odd that when I went to the antipode map page, the default location was half a block from the hospital of my birth. moink 20:07, 12 May 2006 (UTC)
I actually don't think it's that much of a coincidence that the antipodes for most land locations is in the ocean. As Rspeer points out, most of the earth's surface is water, which decreases the likelihood that the antipodes will be on land. In addition, historically, the continents tend to cluster, repeatedly coming together in one or a couple large land masses before separating again. It wasn't that long ago that there was no Atlantic Ocean, after all, that Africa and South America were both part of Gondwanaland and North American and Europe were joined in Laurasia. The continents still tend to be clustered, which certainly helps in mapmaking. This beautiful map shows that the continents are still all practically joined, and in particular this image dramatically illustrates that the Pacific Ocean nearly covers an entire hemisphere. — Knowledge Seeker দ 20:36, 12 May 2006 (UTC)
From an antipodean perspective, this yields some interesting results for points on land.
  • New Zealand matches to substantial areas in both Spain and Portugal, whereas Australia’s only match is tiny Bermuda
    • A lot of New Zealand, but not all of it. I'd be swimming in the Bay of Biscay. Any hardy meteorologists at the weather station on Campbell Island would be directly opposite the southwestern coast of Ireland, the Chatham Islands rotate to Montpellier in southern France, and the Antipodes Islands themselves - the nearest land to the antipodean point of London - convert to Cherbourg in Normandy. And, of course, a small part of the Northland Peninsula is antipodean to Gibraltar. FWIW, the antipodean points of the capitals of Spain and New Zealand are close to Palmerston North and Valladolid respectively. Grutness...wha? 06:49, 13 May 2006 (UTC)
      • Fair enough, I was being a litle imprecise about NZ and Spain/Portugal, and totally missed the points in France, Ireland and Gibraltar (I blame the full moon). I'm glad you clarified the antipodean points of the NZ and Spanish capitals - antipodes claims that Wellington and Madrid are opposite each other, which didn't seem quite right to me. JackofOz 07:11, 13 May 2006 (UTC)
  • Is it true that no country has antipodal points in more than 4 other countries? Brazil maps to Philippines, Indonesia, Malaysia and Brunei; Peru maps to Laos, Vietnam, Cambodia and Thailand. Can anybody better this? JackofOz 01:50, 13 May 2006 (UTC)
I certainly couldn't. China maps to Chile, Argentina, and Bolivia, but no matter how hard I tried I couldn't get it to match Uruguay or Paraguay. EWS23 | (Leave me a message!) 02:15, 13 May 2006 (UTC)
Indonesia maps to Guyana, Brazil, Colombia, Ecuador, Venezuela, French Guiana, and Suriname is tricky but can be done. —Zero Gravitas 06:07, 13 May 2006 (UTC)
Ah, excellent. I hadn't considered non-contiguous countries. I also discovered that Argentina used to map to 5 countries, if you count Hong Kong and Macau as "countries" before they were reabsorbed into China. But it's down to 3 since 1999 (China, Mongolia and Russia). JackofOz 06:31, 13 May 2006 (UTC)
For a worldwide view of what's antipodal to what, see this map. The software used to produce it (GMT) is free, if you'd like to modify it somehow. Redrawing it with smaller cells reduces the visible edge effects, for instance. -- Avenue 12:41, 13 May 2006 (UTC)
Oops, I see there's a much better map showing the same thing in our Antipodes article, so my comment above is probably only useful if you actually want to generate such maps yourself. -- Avenue 12:48, 13 May 2006 (UTC)

[edit] Won't we run out of energy?

IF the universe is expanding constantly, but, according to the laws of thermodynamics energy cannot be created or destroyed, only converted tfrom one form to another, then won't the universe eventually "run out of energy" as such. For example, once the universe gets a whole lot bigger, the energy which exists currently will have to be shared amongst the huge, and still expanding universe, therfore the energy available to us will eventually become limited, thus meaning we need to search elsewhere in the universe for energy? no? Or that the possible systems nearer to the end of the universe than we are will have little energy thus collapse?

You are assuming that there are no voids of space empty of both mass and energy. --Kainaw (talk) 20:29, 12 May 2006 (UTC)
Could you clarify your question? It sounds like you believe that there is some sort of latent energy distribution throughout the universe. The major sources of energy available to us as humans on the planet Earth is limited to the natural resources of our planet and electromagnetic radiation from the sun. Also, I don't understand what you mean by the last sentence. Matter does not require a constant influx of energy in order to simply continue to exist. Isopropyl 20:30, 12 May 2006 (UTC)
See Big Bang, especially the section on the future. - Dammit 20:44, 12 May 2006 (UTC)
Mass can be converted into energy throug nuclear power, so as long as there is mass in the universe (that is not iron) there is energy in abundance. If there wasn't enough mass to provide enough energy, life would be long gone and out of the question, so if this ever does become a problem, we will long since be dead. Philc TECI 21:27, 12 May 2006 (UTC)
Also see ultimate fate of the universe. -- Filliam H Muffman 22:52, 12 May 2006 (UTC)

On a cosmological scale, there is no conservation of energy. As the universe expands, new energy is pumped in. We actually will eventually run out of free energy, but not just because the universe is expanding, rather because of the particulars of its rate of expansion. -lethe talk + 03:51, 13 May 2006 (UTC)

Erm - no, that's not correct. The total sum of energy + matter in the universe is constant (with the conversion factor E=mc²), energy is not "pumped in". What are might be referring to is the reduced entropy which means that energy is in a useable state (for instance, condensed into clumps of coal or oil). As per the article Muffman mentioned, if the universe keeps expanding forever (as it seems to be currently the case), then it will all end up as a lukewarm, mushy soup, and no further useful energy can be extracted from it.
However, the original poster need not worry about this too much - if this does happen, it will happen so many hundreds of billions of years into the future that it's way beyond what you can expect to influence you. Long before that happens, we need to worry about the sun dying (in about 5 billion years). — QuantumEleven 10:07, 13 May 2006 (UTC)
A lovely Luke-warm 2 degrees kelvin!! Philc TECI 17:58, 14 May 2006 (UTC)
Yeh there is most certainly is conservation of energy on a cosmological scale, more so than any other scale, as it is impossible for energy to leave the system. Philc TECI 18:25, 14 May 2006 (UTC)

You're talking about the heat death of the universe. It wont happen for a long long time after our sun burns out and swallows the Earth, but it's proposed that it will occur one day. —Pengo 11:06, 13 May 2006 (UTC)

[edit] Windows internet log

Hi everyone, need some quick help with this. Where exactly does Windows record all the websites you go to (is it .doc or .dat or what?), how, if possible, can I read the file, and is it possible to delete this without erasing all the data in the hard disk? Thanks a lot!

They are index.dat files, usually well hidden. See discussions and examples of tools you could use at, for instance [46], [47], [48] --Seejyb 22:13, 12 May 2006 (UTC)
From personal experience, clearing your browser history will erase the most detectable occurrences. To get rid of those in the address bar, in IE you can start up regedit and navigate to HKCU\Software\Microsoft\Internet Explorer\TypedURLs and erase all but the default value. If you don't know what I'm talking about, for God's sake don't do it. You will kill your computer, get the FBI knocking on your door and cause untold death and pillage if you mess up the registry. Howard Train 05:03, 13 May 2006 (UTC)
To clear your history, go to IE's options dialogue box and click on the "Clear History" button. In Mozilla Firefox, you can go to the options dialogue box, click the "Privacy" icon, and there should be options to clear your history etc. there. I agree though with Howard Train, don't touch the registry if you don't know what you're doing, and always back up the data first! Andrew 15:45, 19 May 2006 (UTC)

[edit] alcohol

when ever i go drinking i always end up yawning, nedding to wee alot during the night out and go for a number 2 alot the next day. are these all realted to alcohol comsuption, if so what causes if and is there any drinks which would have less of an effect

See Effects of alcohol on the body. --Serie 23:33, 12 May 2006 (UTC)
Yes, there are drinks which will have less of an effect: non-alcoholic ones. --Ginkgo100 04:52, 13 May 2006 (UTC)
Generally speaking, pure spirits (like vodka, gin, whisky, tequila, rum and brandy) create a more bearable morning after than beer, wine, sherry and the like. This is because distilled beverages have had most of the hangover-causing crap removed. As for the weeing, that's caused by your body trying to get rid of the alcohol (which is a poison) by flushing it out of your system with water. Which is why you end up dehydrated. Not sure why you're yawning or crapping so much, sorry. --Howard Train 05:09, 13 May 2006 (UTC)
Well, alcohol makes you tired, which, I guess, can explain yawning. – b_jonas 16:29, 13 May 2006 (UTC)

Plus, when you go out drinking, you consume alot more liquid than you normally would. You're just becoming aware of that fact from your frequent bathroom visits. Pretty simple actually. - R_Lee_E (talk, contribs) 05:51, 14 May 2006 (UTC)

Now for the real answer: Alcohol is a diuretic, which means that no matter how much of it you drink, it causes you to urinate more liquid than you're taking in. This explains both the constant "weeing" as well as the intense thirst the next day. Loomis51 11:30, 17 May 2006 (UTC)

[edit] alarm clock software

Is there any software I can run on my laptop, so that it emits a loud noise at a set time? Preferebly open source- googling didn't help me very much :( 138.237.165.140 23:03, 12 May 2006 (UTC)

What OS are you using? Most come built in with this sort of thing. 207.189.98.44 23:42, 12 May 2006 (UTC)
XP. Nevermind, I've found a program Borisblue

[edit] Extrasolar planets

Does anyone know if any extrasolar planets have been discovered in other galaxies? —The preceding unsigned comment was added by 205.157.110.11 (talk • contribs) 23:05, 12 May 2006 (UTC)

Almost certainly not. I don't know that it's even possible to pick out individual stars that far away, except when they supernova or something. (Can anyone confirm that?) --Trovatore 23:26, 12 May 2006 (UTC)
Cepheid variables, for example, can be spotted at over ten Mpc. -- Filliam H Muffman 00:26, 13 May 2006 (UTC)
Actually, we have! Wikipedia has a good article on this at Extrasolar planet. EWS23 | (Leave me a message!) 23:59, 12 May 2006 (UTC)
Sorry, I misread that. Other galaxies, I'd say not. As the Extrasolar planet article implies, it was hard enough until about a decade ago just to find other planets within our own galaxy. EWS23 | (Leave me a message!) 00:02, 13 May 2006 (UTC)
The Twin Quasar article mentions a suspected gravitational lensing event that would suggest a planet in a galaxy more than seven billion light years away! I have trouble buying it. Not that there'd be a planet there (I'd expect them in profusion) but that we could reliably detect any consequences of its existence here. But then I'm not an astronomer. --Trovatore 01:43, 13 May 2006 (UTC)
I'm 98% sure that we have not found any extrasolar planets in other galaxies - the distances are simply far faaaaar too great for our instruments (I am very skeptical of the note that Trovatore mentioned, and will probably delete it if I can't find anything else on it). — QuantumEleven 10:01, 13 May 2006 (UTC)
You can get an idea of how far away we are from looking at planets in other galaxies when you realize what a small percentage of science fiction is given to describing aliens from other galaxies. They're so unrealistically far away that it's much easier to concieve them coming from parallel dimensions and the like. freshgavinΓΛĿЌ 02:03, 15 May 2006 (UTC)

[edit] May 13

[edit] Physics of motion

When you throw a ball against a wall (for example), it has to travel half way, then half that distance and then half that distance again. If you carry on dividing the distances an infinite number of times, the ball will never hit the wall I would be most grateful if someone could help my poor animal brain conceptualise why this idea is wrong. It seems to me that balls DO hit walls (or don't they?). Many thanks and kind regards. Frecklemad

You are describing zeno's paradox. See our article for the solution. Raul654 00:36, 13 May 2006 (UTC)
It would be nice if the article put the solution closer to the description of the problem. In a very brief summary, each time you cut the distance in half, it takes half the time to travel that distance. As the distance to travel approaches 0 (no distance), the time required approaches 0 (no time). So, the distance to travel and the time required to travel it are both finite. --Kainaw (talk) 03:36, 13 May 2006 (UTC)

[edit] Tachyons vs. Special Relativity

The Special Theory of Relativity says that nothing, not even immaterial influences, disturbances, and signals can travel faster than light.But then, how come I've heard that there are subatomic particles in the world called tachyons which can travel faster than light? User:Bowei

Have you read the article tachyon, which has a lot of information about these theoretical particles? --Kainaw (talk) 03:32, 13 May 2006 (UTC)
Tachyons probably do not travel faster than light, despite what you may have heard. Rather, they indicate an instability of the vacuum, which grow exponentially towards a stable vacuum, at which point they become normal particles. The exponential growth is an aspect of their imaginary mass. -lethe talk + 03:48, 13 May 2006 (UTC)
Er, I thought the whole point of tachyons was that they could travel faster than c, though I am just an amateur and perhaps am completely off. As I understand it, tachyons are completely theoretical; there is no evidence to suggest they exist. I don't believe that special relativity per se forbids superluminal velocities, although matter cannot be accelerated to the speed of light. If tachyons exist, and if they can interact with ordinary matter, it will violate causality, which many people feel cannot be violated. The laws of physics do seem to conspire to prevent causality violations. Perhaps someone with more physics training can correct what I've written or expand on it. — Knowledge Seeker দ 05:29, 13 May 2006 (UTC)
Tachyons by their definition, travel faster than c. I'm not sure if Lethe's second and third sentences are right though. It would make sense, but sounds weird. -- Mac Davis] ⌇☢ ญƛ. 07:50, 13 May 2006 (UTC)
That's not the standard definition of tachyons. The standard definition is that it have negative mass squared. -lethe talk + 07:57, 13 May 2006 (UTC)
You're right. Special relativity does not itself forbid particles from going faster than light, though it does predict that such particles would have odd kinematics. But modern physics requires not only that all particles obey special relativity, but also that they be excitations of quantum fields. A field equation which obeys the dispersion relation dictated by special relativity for faster than light particles actually has a group velocity slower than light. So tachyons, from the point of view of modern theoretical physics, don't travel faster than light. Finally, you're right, tachyons (in either the particle sense or the field theory sense) have never been observed, and experiments have been done. Field-theoretic tachyons are a standard part of the Higgs mechanism, and while the Higgs boson has also not been observed experimentally, people are pretty confident that it will be (FWIW). -lethe talk + 07:54, 13 May 2006 (UTC)
Higgs Boson experiments will be run at the Large Hadron Collider, sometime in or after 2007. Half related, thought I'd share.

[edit] Swimming the Atlantic

I have been trying to Google to find out if anyone has swam across the Atlantic. All I find are pages and pages of some fool at Opera who said he was going to do it and didn't. I'm sure someone has swam the Atlantic - I remember seeing a documentary of a woman swimming in a cage (to keep the jellyfish away). Is that a false memory or did she actually do it? If so, who was she (and where did she swim from/to)? --Kainaw (talk) 03:50, 13 May 2006 (UTC)

I don't think it was the Atlantic...how long with the trip last? It would probably be unhealthy to be in the water for so long. Anyway, I believe there was a woman, possibly of this name, who swam across Lake Ontario, which I think is a lake in Canada. http://soloswims.com/roach.htm --HappyCamper 03:52, 13 May 2006 (UTC)
Susie Maroney swam 197 km (122 miles) from Mexico to Cuba, the longest distance ever swum without flippers in open sea. JackofOz 06:24, 13 May 2006 (UTC)
This individual walked across the Atlantic. Surely that counts for something? --Chris 04:56, 13 May 2006 (UTC)
[49] Short article on swimming across oceans and other big waterways. Feel free to make an article about it. - Dammit 05:37, 13 May 2006 (UTC)

HappyCamper speaks of "Lake Ontario, which I think is a lake in Canada". Kind of hope that's a joke. If not, or for anyone who doesn't know, Lake Ontario is partly in Canada, and partly in the United States. --Trovatore 20:12, 13 May 2006 (UTC)

Why would you hope it was a joke? Getting it 50% right seems pretty good to me. OK, its a big lake but I've (sadly) known people who weren't aware that Canada was the big lump "on top of America". -- SGBailey 22:05, 13 May 2006 (UTC)
(Lol) Why would you think that half-right is an acceptable standard of accuracy from a Reference Desk? :--)
The way I read it, Happy Camper didn't just say that he wasn't sure what country Lake Ontario belongs to, but that he's only vaguely aware of its existence at all. As it's not just "a lake", but part of probably the best known group of lakes in the world, I refuse to believe it wasn't a joke. I have much more faith in the level of general knowledge of Ref Desk Regulars than that. JackofOz 00:10, 14 May 2006 (UTC)
Yes, it was a joke. I thought it was obvious enough? Anyway, I promise, I won't do it again :o) --HappyCamper 01:20, 14 May 2006 (UTC)
There is also a city of Ontario in California (pop 158,000), along with smaller cities in Oregon and New York and a county in New york, too, so I suppose a person might possibly think the lake was in one of those places. StuRat 11:28, 14 May 2006 (UTC)
Using that logic, it would be very possible for someone to assume Canada was somewhere in New France, Maine, Minnesota, Sydney, or even London. I am reminded of Rick Mercer's brilliant Talking to Americans skits. freshgavinΓΛĿЌ 01:49, 15 May 2006 (UTC)
Nice try, StuRat, but that was drawing a particularly long bow, even for you. We were talking about extremely large bodies of water, weren't we? :--), lol, etc JackofOz 02:16, 15 May 2006 (UTC)
I don't know...what qualifies as a large body of water to someone from Ontario, Oregon, which has an average annual rainfall of ~10.5 inches (26.5 cm)? The local pond?:o) EWS23 | (Leave me a message!) 02:44, 15 May 2006 (UTC)
Oh, come on! The relevance of this line of argument to the original question is very rapidly diminishing. I know you're a mad scientist, EWS23, but even mad scientists have their limits. The question was about swimming the Atlantic Ocean, for godssake. Happy Camper mentioned Lake Ontario by way of it being a very sizeable and world-famous body of water. Swimming the local pond in Ontario, Oregon would probably not even get a mention in the "Ontario Daily Bugle". :--) JackofOz 03:07, 15 May 2006 (UTC)
Yes, and I, being from Michigan, the Great Lakes State, know the names and locations of all 5. However, I don't expect that everybody else in the world would know that. Someone from Australia who visited Los Angeles and noticed the large suburb named Ontario might assume there was a lake somewhere nearby called Lake Ontario. Also note that the lake could be quite small in area if they swam the length of a long, narrow lake (such as a fjord/loch). StuRat 01:45, 16 May 2006 (UTC)
But is there a lake near Ontario (Los Angeles) called Lake Ontario? And if there is, is it so large that it could have any relevance to the question about swimming a body of water the size of the Atlantic Ocean? And if so, why doesn't it appear on any maps? And is there a Lake Ontario somewhere else that's long and thin? As a scientist, you wouldn't normally give a tinker's cuss about assumptions but would stick to the evidence, so why are you trying on this occasion to accommodate assumptions that as far I can see (a) haven't even made by anybody, and (b) would have no basis in truth even if they were made? You also seem to be trying to squeeze out the last vestiges of the point of Happy Camper's joke, which is surely cruel and unusual, and belies everything I understand about the great American sense of humour (of which you are usually a fine exponent). Unless (a) there really is a Lake Ontario somewhere other than the Great Lakes, and (b) that other Lake Ontario really does have a length comparable to the famous one, I don't see what you're on about. And if you come back with some smart riposte, I'll sic Benoit Lecomte on to you. :--) JackofOz 02:47, 16 May 2006 (UTC)
You seem to be the one dragging this discussion on. My pt was only that someone might think Lake Ontario was somewhere else, and I'm done beating this dead horse, and hope you are, too. StuRat 05:19, 17 May 2006 (UTC)
Since when was it relevant? And while we're on the relevance issue, it's called the Argus Observer, and they don't seem to have any good articles about people swimming. freshgavinΓΛĿЌ 04:56, 15 May 2006 (UTC)
However, they do have a nice picture of "a large water feature" in someone's garden. [50] :o) EWS23 | (Leave me a message!) 05:05, 15 May 2006 (UTC)
Let's celebrate for Benoit Lecomte - the first person to swim across the Atlantic! --HappyCamper 19:13, 15 May 2006 (UTC)
Well, there you go. It kinda brings a whole new meaning to the words "Search first. It's quicker, because you can find the answer in our online encyclopedia instead of waiting for a volunteer to respond", doesn't it. We should all hang our heads in shame. :--) JackofOz 02:49, 16 May 2006 (UTC)

If you ask me, I have no trouble believing that HappyCamper was only vaguely aware of a "Lake Ontario", and even less vaguely aware that it was (partially) in Canada.

The point is that Lake Ontario is a big lake - Wikipedia claims 14th largest in the world - and crossing it was close to the limits of human endurance. Peter Grey 02:17, 17 May 2006 (UTC)

Reminds me of a story I heard. Some high school in Missouri was entertaining the thought of teaching foreign languages to their students. The idea was shot down. The parents were adamant: If English was good enough for Jesus, it's good enough for us! Loomis51 04:07, 16 May 2006 (UTC)

[edit] "Backward Walking"

Dear Madams / Sir,

I find no article on "backward walking" in the Wikipedia, do you think some experts can contribute to writing an article on this issue?

Thank you very much for your kind attention.

Cheung-shing YEH

The best place for this request would be here. If the topic is likely to produce an interesting and notable article, someone should write it.
Someone? Who?
Michael Jackson?
Exactly. The chances of there being someone out there with a burning desire to write your article for you are fairly slim, so I'd recommend that you just write it yourself. Consult the pages on your first article and the links on that page for advice. If other Wikipedians like the subject matter, they will probably be bold enough to expand and improve upon it, given time. Good luck! --Howard Train 05:31, 13 May 2006 (UTC)
You probably won't be able to write much in a Backward walking article— you probably should write about a paragraph or less in the gait article. -- Mac Davis] ⌇☢ ญƛ. 07:48, 13 May 2006 (UTC)

[edit] Radiation resistance

I basically have 2 questions:

  1. What other animals are are very resistant to radiation like cockroaches? (I wanna see if there's a pattern, like just insects, etc..)
  2. What exactly makes them so resistant to radiation? The article on cockroaches doesn't mention this at all. - Dammit 07:10, 13 May 2006 (UTC)
Cockroaches are not particularly radiation-resistant by insect standards. See Wikipedia:Reference_desk_archive/Science/May_2006#Cockroaches surviving nuclear explosions?. We should probably add an explanation about this in the cockroach article. --Robert Merkel 07:27, 13 May 2006 (UTC)
Scorpions are thought to be resistant to radiation. See the scorpion article in Wikipedia, in particular the section about nuclear radiation (2/3 down the page). --Michel M Verstraete 11:18, 13 May 2006 (UTC)
A factor that favors insects is their large number of offspring. If the coachroach population is reduced by 99% due to radiation, the remaining 1% which are more resistant to radiation can rapidly replace the original population with a more radiation resistant strain. If 99% of the human population was destroyed, however, it would take centuries for the population to recover to present levels. StuRat 03:34, 14 May 2006 (UTC)
I was searching for the same kind of info a while back (for ants), and it is definitely not well documented on the net. The "causes" end up as "the general opinion seems to be"! However, there is
  1. a correlation between radiation sensitivity and the relative mass of DNA in a cell, i.e. more DNA per unit of cell mass = more sensitive, and conversely.
  2. a difference in cellular DNA repair mechanisms - if the work on Deinococcus radiodurans is anything to go by, then this is likely to be related to a factor such as selection for survival in a very dry environment, with intra-cellular dessication, and only incidentally to radiation injury.
  3. differences in the handling of intracellular free radicals - mice can be bred to be more or less radiosensitive, according to the activity of enzymes systems inactivating these radicals. I did not find any such info relating to insects.

--Seejyb 10:19, 14 May 2006 (UTC)

[edit] sun & moon

When we see or look from the earth to the sun & moon, is it in every 15 years, 17 years or 19 years their visual movement meets at the same date & day?

Erm... are you referring to a solar eclipse, when the sun and moon appear to occupy the same bit of sky (as seen from the Earth), and the moon blocks out the light from the sun? They do follow a pattern, but it is far more complex than that - it depends on the orbital mechanics between the sun, earth and moon, but these can now be routinely predicted decades in advance (you just need to calculate at which point in the future the moon will be in the correct position.) The section on eclipse prediction should answer a lot of your questions on this. Also, don't forget that a solar eclipse only occurs over a very small part of the Earth's surface, so while (on average) there could be a total eclipse somewhere on Earth every two years, at any given location, fifty or more years could pass between eclipses. — QuantumEleven 09:55, 13 May 2006 (UTC)
Are you thinking about the Saros cycle perhaps? After 18 years 11 and 1/3 days the Sun and Moon return approximately to the same place in the sky. Dr Zak 00:18, 14 May 2006 (UTC)
This sounds like a multiple choice question, although I don't understand what "visual movement" means. freshgavinΓΛĿЌ 01:37, 15 May 2006 (UTC)

For multiple choice questions, when in doubt, choose "C". I'd therefore guess that the answer is 19 years although I too have no idea what the question means. Loomis51 11:25, 17 May 2006 (UTC)

[edit] Pedialyte formula

I was recently told the World Health Organization has published a formula for people to mix up a homemade version of Pedialyte to help replace fluids and electrolytes for babies, especially when the babies have been having diarrhea. Can you tell me what that formula is?

Most I can find so far is "An ORS containing sodium 60 mmol/l, glucose 90 mmol/l, potassium 20 mmol/l, and citrate 10 mmol/l with an low osmolality of 240 mmol/l is safe and effective for the prevention and treatment of dehydration in European children with acute gastroenteritis" from [51] You're probably better buying a packet of ready-made stuff, if you can. Skittle 15:29, 13 May 2006 (UTC)
The version I heard had just water, salt, and table sugar, as those other ingredients are unavailable to most of the world's poor. See this link for a video of the Oral Rehydration Solution: [[52]] StuRat 21:30, 13 May 2006 (UTC)
An encyclopedia is a wonderful thing, see Oral rehydration therapy. -- Rick Block (talk) 21:46, 13 May 2006 (UTC)

The caveat about recipes for ORS is that studies have shown that a large proportion of ostensibly literate mothers in developed countries cannot follow a simple recipe so that concentrations are within 20% of intended. The premeasured envelopes are not foolproof but safer. alteripse 02:49, 14 May 2006 (UTC)

[edit] blackholes and light

If blackholes exert an attractive force on light, what effect do they have on the speed? Thanks guys.

-Timothy

None; it's an axiom of relativity theory that light always travels at a constant speed: c, the speed of light. Instead, light falling into a gravity well picks up energy that appears as an increase in frequency rather than a change in speed. (See gravitational redshift for a discussion of the parallel phenomenon—a loss of energy associated with light climbing out of a gravity well.) TenOfAllTrades(talk) 16:00, 13 May 2006 (UTC)
That idea that TenOfAllTrades quotes, that the speed of light is the same in every frame, is valid only in inertial frames, i.e. only in the absence of gravity. -lethe talk + 18:15, 13 May 2006 (UTC)
I'm pretty sure that the invariance of the speed of light holds true under all frames, not just inertial ones—it works under general relativity, and not just special. The speed of light is constant for all observers, not just non-accelerating ones. TenOfAllTrades(talk) 21:57, 13 May 2006 (UTC)
I'm pretty sure that you're mistaken. Light travels along geodesics. This means that the wordline of a photon satisfies ∇v = 0. In flat spacetime, this means that the velocity is constant. In nonflat spacetime, or in any coordinates with nonvanishing Christoffel symbols, this means that the velocity may not be constant in local coordinates. You can also see this from Maxwell's equations. In flat spacetime, they read ∂2A = 0, which is the wave equation for a wave travelling at c. In curved spacetime, this equation picks up a term proportional to the curvature.
No, you're simply not correct in saying that the invariance of the speed of light is an axiom of general relativity. And a black hole does have an effect on the speed of light. -lethe talk + 06:36, 14 May 2006 (UTC)
Just to be picky, it should be pointed out that, in this thread, every time someone says "the speed of light" they really mean the speed of light in a vacuum. The speed of light in any material is defined to be C divided by the index of refraction (where a vacuum has an index of refraction of 1) and for all but a few extremely odd materials, the index of refraction is greather than 1. Raul654 22:01, 13 May 2006 (UTC)
I wish there were a name for c other than the speed of light, so we could do away with this proviso. It doesn't even mean "the speed of light in a vacuum". It really means "the speed that light would travel at in a perfect vacuum if its mass is exactly zero". The easiest way around this is to simply call that number c, which is what I (and I think a lot of people) do. -lethe talk + 06:41, 14 May 2006 (UTC)
Er, Lethe and TenOfAllTrades, I commend you both to frame fields. Then see Shapiro time delay effect and contemplate why this does not contradict the principle that light always has speed one in any frame at the tangent space to any event. This frame can be drawn from any frame field on any Lorentzian manifold. In a phrase: local versus global. HTH (you two, not the original inquirer).
Original inquirer: all quibbles aside, it is best if you remember the idea that a radar pulse always travels at speed c (in a vacuum), as measured in some small region, but the path taken by this pulse can be bent in a gravitational field, so that over very large regions, two radar pulses emitted at the same time at A might take different paths from to B and might arrive at different times.---CH 11:19, 16 May 2006 (UTC)

[edit] Reverse SHA-1 Digest

Is there an easy way to reverse engineer a SHA-1 digest in Java? I am trying to construct the info_hash for the bittorrent protocol but what I'm creating doesn't match what I see when I open the torrent file in Azureus. Thus, I would like to see what string is being hashed so that I know what I should be hashing. For the record, I'm hashing the entire [d6:length...e] bit after "info", which I've been told is the correct way. Remy Suen 15:17, 13 May 2006 (UTC)

If you are trying to compute SHA-1 of something google for examples on how to use the SHA function that comes with Java. E.g. here. Weregerbil 15:55, 13 May 2006 (UTC)
Well, I know how to compute the SHA-1 digest, I'm trying to figure out how to reverse it to get the original data. -- Remy Suen 16:57, 13 May 2006 (UTC)
You can't. Such a hash function produces 160 bits from however many bits you feed it; I'm assuming that's a lot more than 160. That means there are lots of inputs that produce the same output. It should be infeasible even to find a single input that produces a given output; if it's possible to find such an input with any reasonable amount of computing power, then the hash is not secure. --Trovatore 17:01, 13 May 2006 (UTC)
Yeah, I kind of expected there to be not be a way of reversing the process since it is an encryption algorithm. Ah well, I guess I'll continue poking around my code and reading over the specifications to try and figure out what is wrong. Thanks all. -- Remy Suen 17:13, 13 May 2006 (UTC)
A cryptographic hash function is different from encryption. Hash functions are like a complicated modulo operation. If you know that X mod 10 = 7 it is impossible to tell what X is — 7, 17, 27, 37, ... There are an infinite number of files that produce the same hash checksum. Weregerbil 19:08, 13 May 2006 (UTC)
I see, that clears things up, thanks for the correction and clarification, the modulo example makes perfect sense. -- 19:20, 13 May 2006 (UTC)
If you can't figure it out I'd suggest asking in the Java forums, probably in the "Java Programming" section. Weregerbil 19:12, 13 May 2006 (UTC)
I'll probably just ask designers of existing BitTorrent implementations to figure out why my hash is wrong, thanks though. -- Remy Suen 19:20, 13 May 2006 (UTC)

[edit] Leaving a notebook on overnight?

Servers are always left on overnight, and many people leave their desktops on too. Are notebooks different enough that this practice should be discouraged or not performed at all outright? Remy Suen 15:17, 13 May 2006 (UTC)

It depends. If you keep your notebook in a bag or some sort of carrying device, then it should not be left on for long periods of time, as inside these devices proper ventilation is almost non-existent and the notebook can easily overheat, possibly causing damage to the hardware. However, if you leave it on a table, desk, etc. or any place where air can freely circulate around the fans and ventilation slots, a notebook can be left on all night. I, for one, leave mine on at all times, even while running Distributed Computing. But I usually keep mine on my desk and rarely move it, as such I have never had an overheat problem. Hope this answers your question. -- yaninass2 | talk 16:53, 13 May 2006 (UTC)
Yeah, all I do is leave it on my desk and go to sleep, so it's not like I leave it on in my bookbag or anything. Thanks! -- Remy Suen 17:02, 13 May 2006 (UTC)
You should consider removing the battery from your computer. LiIon batteries deteriorate over time, a process that is sped up by heat. Store them at 15°C (59°F) and at 40 percent charge [53]. Also, you might want to check that your hard drive is fully spun down and not accessed while you aren't using the computer. Since laptops aren't expected to be on all the time, laptop hard drives have shorter lifetimes than typical desktop variants. Finally, if you are running an old OS or programs with bad [Garbage_collection_(computer_science)|garbage collection] you will want to restart your system periodically to clean up scattered files and clear the memory. --Swift 04:38, 14 May 2006 (UTC)
Hm, very interesting. I usually leave it on because I'd like to complete or make some progress on a download. Thank you for your information, I'll keep the battery bit in mind and also give my computer's hard drive a rest on a regular basis. --Remy Suen 20:04, 14 May 2006 (UTC)
It may not be too useful but if you want to be really nice to your laptop, I suggest putting something underneath it to elevate it a centimeter or so from the desk surface (even a couple pencils would work). If you've ever used your laptop on your... lap, you would know that even though the fans are running properly the under surface is not exactly cool. Older laptops can get quite hot after extended use. There's probably no danger of overheating, but after a year or so, extended periods of less-than-optimal heat can cause the innards of your laptop to start showing problems (such as sudden crashing and memory errors) earlier than they would if you hadn't used it so much. freshgavinΓΛĿЌ 01:33, 15 May 2006 (UTC)
The lifting-the-laptop idea is definately good. Increasing the efficiency of the fans will reduce the amount of time they are spinning. The bearings will eventually wear and well before they die (which will probably not be before the laptop gets replaced) they will become noisy :-(. Another heat-caused annoyance is that various stickers have started to become loose, including one of the nubbins that keeps the laptop off the table/lap ... --Swift 22:24, 15 May 2006 (UTC)

[edit] Who is M. Theiler

I collect autographs. I have a letter from the Rockefeller Foundation dated Nov. 4,1953 thanking a lady for wanting this autograph as an outstanding citizen, it is signed M. Theiler. Who is M. Theiler, and what did he contribute perhaps to science or humanity? Thank you, Linda

Any information would be greately appreciated especially on his biography.Thanks
I typed Theiler into the search box at the left of this page and found one Max Theiler. I don't know if he is the Theiler you are looking for but he won the Nobel Prize in 1951 so the date makes sense. Weregerbil 15:58, 13 May 2006 (UTC)

[edit] Wikipedia on a DVD ?

Hello,is someone ( or maybe Wikemedia itself) planning to releases DVD's of wikipedia? If not, then why not....because it would be a good idea to promote it this way also!

Half of the essence of Wikipedia is that it updates, frequently. Bad articles are changed, important things are added, corrections made over the whole floor. If one was to release Wikipedia on commercial DVD, one would have to make such an ironic warning as that WikiMedia can't be held responsible for there being flawed articles, with perhaps downright misleading content. Still, it IS feasible, and has been discussed here before.
Legally that would not be a problem. All encyclopedias have disclaimers in them saying they are not responsible for incorrect or misleading content (see Wikipedia:Non-Wikipedia disclaimers). The online one has this disclaimer as well (Wikipedia:General disclaimer).--Fastfission 19:20, 13 May 2006 (UTC)

There are people working on this, but it's a tough job to really police everything that will go on a "fixed" version. See Wikipedia:Version 1.0 Editorial Team. --Fastfission 19:18, 13 May 2006 (UTC)

The Germans were faster and released a DVD in Spring 2005. de:Wikipedia:Wikipedia-Distribution. Dr Zak 22:43, 13 May 2006 (UTC)
Just as a note, depending on what is put on the DVD, it could end up being a lot of DVDs - for instance, all the articles and their histories amounts to 40GB (or 1.2GB for just current versions). All the images are 76GB. — QuantumEleven 09:19, 14 May 2006 (UTC)
Just curious. When you say that all the pictures are 76 GB - is that all the pictures used in Wikipedia (from Wikipedia and Commons) or just all the pictures stored on Wikipedia? Rmhermen 01:34, 15 May 2006 (UTC)

[edit] How to transform a regular telephone handset into a mobile phone handsfree kit

How can I transform a regular telephone handset (such as this -> Image:Phone handset.jpeg) into a mobile phone "handsfree" kit (of course it would not free one of your hands, but you get the point), connectable through a 2.5mm subminiature jack. Perhaps this is not so relevant, but the handset uses a regular RJ11 jack, with four cables (Black, White, Green, Blue) and I intend to connect the 2.5mm jack into a LG mobile phone. Afonso Silva 20:25, 13 May 2006 (UTC)

With difficultly, probablly the easiest way would be to buy a cheap handsfree kit, cut the ends off and wire it into the microphone and speaker units in the handset. this however assumes that the parts are similar enough for it to work and that you can actually get the handset open. Plugwash 21:02, 13 May 2006 (UTC)
I wanted to buy a jack and solder (is this verb correct?) it to the wires that come from the handset. Of the four cables, two should be ground and the remaining two are for "speaking or listening" (S/L). The Jack has a ground and it will need to be stereo, in order to connect both channels, am I correct? If I am, I just need to find what wires carry each signal (S/L) in the handset and in the phone. This is just like you proposed, but buying a jack would be cheaper. I also don't know if the voltage produced by the mobile phone is able to make a regular handset work. Afonso Silva 21:28, 13 May 2006 (UTC)
You could just buy one. I saw one shown as a "cool new gadget" on telly, but I don't know who and where sells it.
Slumgum | yap | stalk | 22:27, 13 May 2006 (UTC)
That's where I got my ideia, from an online shop of stuff like that. If I had imagination to create things like that I'd be rich. I can't afford it, Portuguese young people aren't properly among Forbes 400, so, I decided to do my own cool gadget. What do you say about the voltage? Afonso Silva 22:52, 13 May 2006 (UTC)
Your idea will work. [This page] gives th whole process, pictures of colours of wires to be soldered and all. --Seejyb 00:20, 14 May 2006 (UTC)

Thanks people! And thanks Seejyb for the website, it seems that my ideia was correct, hehe! I'll have a thing like that, so cool! Cheers! Afonso Silva 11:02, 14 May 2006 (UTC)

Haha, ThinkGeek has one you can buy for 30 bucks. I want it! freshgavinΓΛĿЌ 01:08, 15 May 2006 (UTC)

[edit] May 14

[edit] Find the Time period

If a body attached to one end of spring executing simple harmonic motion(SHM) on friction less horizontal surface then how to derive the formula of time period T of this body--86.62.206.4 03:20, 14 May 2006 (UTC)

SHM, eh? It's years since I had to think about that. I count myself lucky. Our article on Simple harmonic motion contains the very formula you need. --Howard Train 03:55, 14 May 2006 (UTC)

Thats good article but "how to drive the equation of time period i.e T=2π--"will u explain this only--86.62.206.4 04:29, 14 May 2006 (UTC)

You need to solve a second order Ordinary differential equation. The ODE you get from
F(x)=ma=m\frac{d^2}{dt^2}x
So, care to share what sparked your interest? --Swift 04:57, 14 May 2006 (UTC)
I'm not exactly sure I understand your question (and I'm unsure of the differential equation answer given above), in part because your assumption is that T = 2π, which isn't the case (in fact, T is measured in units of time, while 2π is in radians, so they cannot be equivalent). Nevertheless, it sounds like you might be asking where the 2π comes from in the equation
\omega = \frac{2 \pi}{T}
The answer has to do with the definition of angular velocity, ω, which is the number of radians/degrees traversed per unit time:
\omega = \frac{\Delta \theta}{\Delta t}
The task is to find a Δθ and Δt that correspond to one another. Since we're interested in having the period (T) in the equation, let Δt = T. Now what is Δθ when Δt = T? In other words, how many degrees are traversed in one period? By definition, one period is the time it takes to complete a single cycle/revolution.
(To easily visualize this, imagine an object starting at point A along the border of a circle, traveling at a uniform velocity around the circle's circumference, until it returns to point A. The object has completed one cycle, and the time it took is (by definition) equal to the period, hence Δt = T.)
Now we know how long it took to complete one cycle, but how many degrees has the object traveled? The object traversed the entire circumference of the circle, so this question is the same as asking how many degrees are in a circle. 360° sounds about right, and if we convert to radians, we get 2π. So when Δt = T, we have Δθ = 2π. Inserting this back into the second equation from above, you have
\omega = \frac{\Delta \theta}{\Delta t} = \frac{2 \pi}{T}
I hope that helps. If not, maybe you could ask a more specific question? --David Iberri (talk) 23:39, 15 May 2006 (UTC)
86.62.206.4 was asking how to derive the equation for the period. This is easily done by solving the differential equation above (setting f(x) to the force that acts on the body). In the case of the SHO, the solution is a simple trigonometric function (sin or cos) as a function of time with a time constant that yields the period T.
As for the "how to drive the equation of time period i.e T=2π--": Note the last two dashes, I took them to mean "etc." (as in, I'm not in the mood to write out "\frac{1}{T}").--Swift 11:44, 18 May 2006 (UTC)

[edit] Blocking banner ads

Since these tend to come in standardized sizes, 468x60 for one, wouldn't it be really easy to block them all by instructing a browser to not load all images of those specific dimensions? I dimly remember a program called Webwasher which offered this function, but most web browsers and popup blockers do not. Is there any reason why this option isn't as widespread as it should be? -- 61.6.59.73 05:27, 14 May 2006 (UTC)

Have you tried AdAware with Mozilla Firefox? -- Mac Davis] ⌇☢ ญƛ. 06:49, 14 May 2006 (UTC)
Yes, I have. Actually... what I'm really curious is why more browsers don't include this functionality when they already have built-in popup/image blockers. It doesn't seem like it would be a hard thing to add. ----
Maybe it has something to do with money and the relations between web advertisers and browser vendors (or The Vendor). I remember seeing a personal firewall that was able to block images based on their dimensions, and also GIF animations, other JavaScript things etc. but I can't find it now. Opera, at least, can be instructed to block images and other files matching a certain mask (such as http://ads.*/*). –Mysid(t) 09:31, 14 May 2006 (UTC)

If you took that approach the ad vendors could react by just varying the size slightly, say to 467x60. Thus you would be fighting a moving target. StuRat 11:09, 14 May 2006 (UTC)

This is doable with user style sheets (they work -- at least -- on both Mozilla Firefox and Opera. Since the ads are often stored on specific hosts, an alternative is to not display any content from specific hosts. Firefox has a right-click option that works on this. I've read that this can also be done on Linux by listing these hosts in a specific file (can't remember where exactly as I've never actually used this). --Swift 06:02, 15 May 2006 (UTC)
Couldn't you then make the browser reject any images within a range, say, of certain dimensions ±5 pixels?. Or reject all images of aspect ratio 7.8:1 ±5%, etc., since banners almost always come in high aspect ratio shapes. Anyway, thanks for all your responses. :) ----

[edit] Density-

You are provided with 10 small identical pellets with each of mass about 0.5g and volume about 0.8 centimetre cube. Describe an experiment how you will determine the density of each pellet as accurately as possible.

IBM used a very similiar question as part of their application process, with one difference - you had to figure out a *non-destructive* test - e.g, you couldn't cut them open. There are about three different tests I can think of that will work, but you really should do your own homework. Raul654 05:39, 14 May 2006 (UTC)
Also, for the record, as you have described it, it's a trick question. If they all have the same mass and volume, then the *average* density is the same for all 10. Raul654 05:41, 14 May 2006 (UTC)
I think the point of saying the mass and volume of each is about those values means that the values are guidelines to show you what methods may work. On the other hand, if they are really identical, then the best method would indeed be to find the total mass and volume and use that to find the density of the 10 pellets together (which of course should be the same as the density of each pellet). Confusing Manifestation 07:07, 14 May 2006 (UTC)
:) It's no use suggesting that the questioner do their own homework and then providing the answers. --Hughcharlesparker 16:59, 14 May 2006 (UTC)
I think I'm missing something. It seems like the best way would be to measure each one's weight using whatever available tool is most precise, then measure each one's volume (perhaps using water displacement), and divide. What better way is the applicant supposed to come up with? Black Carrot 23:06, 14 May 2006 (UTC)
I assume the question is asking you to figure it out without directly weighing them. freshgavinΓΛĿЌ 01:04, 15 May 2006 (UTC)

[edit] Turbine

How does the supercruise function work in a jet engine?

Supercruise isn't a function as you describe it, nothing special has to be done for it to be enabled. It's achieved by having engines which deliver a lot of power without enabling the afterburner. This is achieved by a more efficient design, and a bigger engine in general. - Dammit 06:41, 14 May 2006 (UTC)
And the point of supercruise is that afterburners are terribly fuel-inefficient. In general, a bigger engine operating without afterburner will use a lot less fuel than a smaller one using an afterburner to produce the same power. Therefore, even if the F-22 doesn't necessarily have a higher top speed than an F-15 or Su-27 (it may or may not, the people in a position to know have been very vague on the matter), the older aircraft will only be able to keep up for a very short period before it runs out of fuel and has to head back to base. --Robert Merkel 12:00, 14 May 2006 (UTC)

[edit] Gulls on the roof...

Here we go - yet another bird question... :)

It's been really hot and sunny here recently and I have noticed that my local gulls have been hanging around on the flat rooftops nearby soaking up the rays. There is one particular factory roof that I pass every day that is made of sheet metal (aluminium?) and painted black. From my basic understanding of high-school physics, dark objects basically absorb the sun's light energy and radiate it as heat, right? So, after a few hours of continuous direct sunshine, a black rooftop would become incredibly hot to the touch, right?

If this is the case, then how is it that the gulls are able to perch on the roof for extended periods of time without showing any apparent discomfort? Some of the birds were even sat down, napping and didn't seem bothered by the heat rising up from beneath them in the slightest (in fact, they looked pretty content with life). As an experiment, I placed my hand upon a black car nearby and timed how long I could hold it there - it wasn't long and my palm was red raw afterwards (it was a *very* hot day).

How on earth do the gulls avoid burning the skin on their feet and general heatstroke? The obvious answer would seem to be that 'gulls are physically tougher than humans' - but can anyone be more specific? --Kurt Shaped Box 07:19, 14 May 2006 (UTC)

One possibility is that they've been on the roof since it was dark and thus they blocked the sunlight and didn't allow that spot on the roof under them too get hot. Also, certain places on the roof may be cooled by water pipes which run under them, etc., and the gulls might be experts at finding those cool spots. StuRat 11:03, 14 May 2006 (UTC)
If the area they were sitting on was that hot, one could say that their sitting down on their feathers is like your being able to hold on to an styrofoam cup containing boiling water. Standing is more difficult; if the birds do not have a thickish dead insulating layer under their toes, then they are likely to be standing on their nails, so that the live parts are kept off the metal. This is the explanation given in an archived article from 1946 [54], which mentions birds perching on the plates of a hot coal stove, presumably by balancing on their nails. --Seejyb 18:04, 14 May 2006 (UTC)
Has anyone here actually handled a seagull? Their feet and legs are not covered in what we would indentify as 'skin'. It's more like horn - thick, cool to the touch, hard and rough. I don't know what the scientific name for the stuff is but it's a lot more noticable on those seagulls with yellow legs (the hard coating stops and regular skin starts where the feathers begin). It looks like armor plating in a way - I don't reckon that they could feel much through it at all. I doubt that they stand on their nails, as they only have tiny claws.

[edit] Gulls - part deux

Another couple of gull-related questions that have been bugging me for ages (I like gulls, what can I say?)...

1. It's an oft-quoted 'fact' that gulls can drink salt water with no ill effects. I watch gulls a lot and I have never seen them do this (they like to drink from puddles of fresh water). I can understand that they might *prefer* fresh water and drink it over salt, if available - but if they can drink it, what mechanism do they use to remove the excess salt from their bodies? Gulls do not have the tubenose desalination systems of fulmars and albatrosses.

2. Can gulls unhinge their lower jaws like certain snakes do when swallowing large items of food? This is an argument that has been on a slow boil on a mailing list I'm on for the last couple of weeks now. They can certainly open their mouths *very* wide but photographic evidence is inconclusive.

Thanks for your help, guys. :) --Kurt Shaped Box 07:37, 14 May 2006 (UTC)

As I understand this, tubenose refers to the shape of the beak, not to a physiological function as such. As far as I know from helping my daughter with a task entitled "How Seabirds Survive Perpetual Drought", the gulls also have saline organs in their noses somewhere. I can't find a description in Wikipedia. The article she used as basic reference was:
Hmm,I forgot to sign my note above... anyway, your observations set me to thinking.
According to this site on [seabird osteology], "The upper mandible is connected to the forehead with a flexible but bony 'hinge'. This hinge and the loose connection of the quadratums and pterygoids form a flexible construction enabling the upper jaw to move up and down to a certain extent. The lower jaw is built out of two pairs of partly fused bones and is even more flexible. These features enable the seabird to open its mouth extremely wide to provide a passage to large preys which are swallowed in one piece. Pelicans are the most extreme in this respect.".
The term unhinged would have to be defined, before any judgement could be made as to whether the jaw movement qualifies as an "unhinging". Is there a joint that can be unhinged, or is the lower jaw suspended by ligaments and muscles, with possibly a bursa in between? Compare the movement movements of say a human scapula on the chest wall, where there is no joint at all, simply a muscular attachment.
Incidentally, on the osteology page you will see the place where those salt glands are hidden: The "Fossa glandula nasalis: A depression that contains the nasal or salt gland in most seabirds" appears to be located on the sides of the frontal bones of the bird's skull, just medial to the eyes. --Seejyb 19:03, 14 May 2006 (UTC)

[edit] On death and decay

Why is it that humans decompose only after death? Why can't the fungi, bacteria, etc. attack and decompose you when you're alive?

You can thank your immune system for that. - Nunh-huh 09:11, 14 May 2006 (UTC)
(After edit conflict) They do, at least they try to. But the living human body regenerates its cells continuously and removes dead ones. The body also fights back by e.g. immunoglobulins and T cells – see immune system. –Mysid(t) 09:15, 14 May 2006 (UTC)
Great, thanks!
However, your extremities can die if, for example, they freeze. See gangrene (disturbing image warning). --Shantavira 13:41, 14 May 2006 (UTC)
If you are researching something, do not underestimate the contribution of the nervous system in protecting you from being eaten alive. In the absence of normal sensation, which would warn one to take some healing or preventative action, body parts can be extensively damaged, in spite of an active immune system. --Seejyb 19:37, 14 May 2006 (UTC)
They can decompose you, and you die from it. There are diseases which are exactly that. Peter Grey 16:23, 16 May 2006 (UTC)

For the record, decomposition does not require bacteria, fungi, 'etc. When someone dies, the lack of oxygen replacement in the blood stream means that muscles cannot "reset" actin-myosin binding, and thus the person enters what we call rigor mortis. A person comes out of rigor mortis about 24 hours later when those bindings disintegrate (for reasons I am not aware of off the top of my head). But again, none of this requires any action by bacteria/fungi. Raul654 19:42, 14 May 2006 (UTC)

[edit] whats this?

what is the meaning of the word "symmetrical monodisperse architecture"?i tried searching in wikipedia but couldnt find the meaning.any help would be appreciated.

thanks

The IUPAC site gives definitions. The word "uniform" seems to be preferred over "monodisperse". I see monodisperse is still a tag, maybe you can write something there after your research. --Seejyb 10:37, 14 May 2006 (UTC)
and just to be picky, it's not a word - it's a phrase. Grutness...wha? 06:57, 15 May 2006 (UTC)

[edit] longest river

is the nile river still the longest river until now? If not, which is? Thanks. Carlrichard 10:25, 14 May 2006 (UTC)

According to the first sentence in Nile, yes it is. AlbinoMonkey (Talk) 10:31, 14 May 2006 (UTC)
"Until now" ? Did we just get a new longest river ? LOL StuRat 10:53, 14 May 2006 (UTC)
Perhaps he is asking if a longer river ever existed, like 100 million years ago, or something. Afonso Silva 11:05, 14 May 2006 (UTC)
In that case I would expect longer rivers existed back when there was the supercontinent of Pangea and earlier supercontinents. StuRat 11:34, 14 May 2006 (UTC)
The definition of "longest" is an issue. See the discussion at List of rivers by length. --Shantavira 13:46, 14 May 2006 (UTC)
Thanks Shantavira. A site about the Amazon (I can't find it now) also mentioned that Congo-Amazon combination, which may have existed before Africa and South America separated. I have not seen reports of archeological evidence for this. --Seejyb 14:03, 14 May 2006 (UTC)
The question may also be referring to the fact that the location of the true source of the Nile has recently been discovered to be at a different point to previously thought. But that would simply mean a longer path from source to sea, so if it was alreadly listed as longest it wouldn't now only be second longest. Grutness...wha? 06:59, 15 May 2006 (UTC)
You guys are giving the questioner waaaaay too much credit here. Loomis51 03:47, 16 May 2006 (UTC)

[edit] light

why is the convex lens a diverging mirror ? why do the rays of light donot converge in it?

This may be language problem. However, here goes:
  1. If a convex surface were transparent,
    1. we'd call it a lens (specifically, an optical lens, ideally 100% transmission of light, with no reflection) and, for a glass lens in air,
    2. it would have the effect of converging incident light.
  2. If a convex surface were reflective,
    1. we'd call it a mirror, and
    2. it would have the effect of diverging the incident light.
  3. Why this happens is best understood by making drawings of the two devices, and drawing for yourself the path of light rays, using pencil, paper, retractor and ruler, applying the laws of refraction and reflection. Information on these constructions can be found if you search for the terms "mirror image formation" and "lens image formation" on the web. The Physics Classroom is a site that is useful.
  4. In practice, glass in air transmits some of the incident light, and reflects some of it, so that such a lens ends up being both a convex transparent lens and a convex reflecting mirror, at the same time.
  5. Since the focusing or bending of light can be brought about by means other than optical lenses, these other devices, which includes mirrors, have come to be called "lenses", meaning that they have the same effect as optical lenses (but not necessarily in the same direction!). This may be why you are experiencing confusion. --Seejyb 13:21, 14 May 2006 (UTC)

[edit] Physics:Pasek

What's this. I'm not sure of the spelling but I think it should be a measuring unit.And it should be connected to gravity somehow.

Try parsec. It's related to gravity in the fact that gravity is only really significant in cosmological terms, which is what parsec is a useful measurement of distance in. Confusing Manifestation 13:19, 14 May 2006 (UTC)
[Possible nitpic and OT] Except gravity is significant on smaller scales, say, distance from earth to sun: ca. 5×10-6pc. Opposite to saying that gravity is only significant in cosmology, one could say that cosmology is only significant in gravity. I know .. lousy sentence .. bear with me: On cosmological scales (such as parsecs) the only interaction that has any significance is the gravitational one. Sorry ConMan, if that was what you were referring to. I hope you don't mind me clearing it up.--Swift 22:42, 15 May 2006 (UTC)

[edit] Breeds vs. Races

Are breeds in domesticated animals analogous to races in humans? I suspect that because a breed is characterized by a higher level of inbreeding, and races are poorly defined, they aren't. JianLi 14:23, 14 May 2006 (UTC)

All analogies have correspondences and non-correspondences unless they are identities. The validity is usually determined by the context and purpose of the analogy, which you have not provided. Therefore the correct answer is "yes and no". You are welcome. alteripse 14:25, 14 May 2006 (UTC)

Hm...I mean "are they similar in terms of intra-group genetic variability and inter-group genetic overlap."JianLi 14:42, 14 May 2006 (UTC)

Much better question. Much harder too. I think there are some analogous features. Both animal breeds and human races are usually identified by the distinctively recognizable association of a relatively small number of aspects of external body appearance. I am guessing that breeds of dogs or cats differ in a relatively small number of genes that mainly affect timing and duration of action of various body part genes (evo devo) and I suspect these genes play little part in human racial differences, which depend more on the statistical association by geography of minor polymorphisms of genes for aspects of skin and hair development. Note that "purebred" is a socially-defined term with respect to animals and requires pedigree information. Analogous concepts with respect to humans are also purely socially defined and have little biological meaning except as a statement that the last 2-3 generations of your ancestors originated from the same small geographical area. alteripse 15:06, 14 May 2006 (UTC)

I think it also depends on at what level races or breeds are defined. The main "races" of humans are so large in comparison to the whole population that it's easy to be "pure" Asian or white or black, even though there is a large amount of intermixing within each group among the various sub-groups. And all races have undergone basically the same selective pressures, while artificial selection for animal breeds is much more varied, depending on the whims of the humans who create the breeds.JianLi 15:13, 14 May 2006 (UTC)

The so-called "purebred" dog breeds tend to represent a very high level of inbreeding, so probably show a low level of genetic variation. I would draw a rough analogy to the royal families of Europe that – at least until recently – represented a fairly small population that didn't interbreed much with outsiders (at least, not officially). With both purebred dogs and royal families, one tended to see a much higher incidence of certain genetic disorders.

Drawing a general conclusion about much larger populations of humans (or dogs, for that matter) is much riskier. Human groups that originated with a small number of founders tend to be more genetically uniform, though again this depends on the degree of interbreeding that has taken place with outside groups. For instance, some research suggests that half of all Ashkenazi Jews originated from as few as four women, based on studies of mitochondrial DNA. TenOfAllTrades(talk) 15:24, 14 May 2006 (UTC)

[edit] brady's reagent

I was working in the laboratory and accidentally got some stains of brady's reagent on my lab coat. Please how do I get it off?

Bleach? Just a guess. –Mysid(t) 19:31, 14 May 2006 (UTC)
Why try? That's what a lab coat is for. The dirtier it gets the more authentic a chemist you are! Rmhermen 01:23, 15 May 2006 (UTC)

[edit] Why cant there be any other Alien Species in the universe see my question details....?

I mean i wanna Ask why can't there be any alien species in this universe... Tell me-----

  1. Cant there be any, be any planet having same conditions as earth?
  2. It is not necessary that a living thing requires oxygen to live?.. we all want oxygen to live but There can be an alien species in universe that requires nitrogen or carbon or sulphur or any other gas to live it can be hazardous to us but beneficial to them...?
  3. There can be some organisms in this universe that just dont have any effect of conditions on them. They can live by any type of things . Don't solely need a particular gas to live.....

By the above asked questions i believe that you all must be convinced that such can happen. We humans need Oxygen but Oxygen is not the sole need for some other race, right! So, there can be an existence of Aliens very well...

And mind you if any Alien species do visits us we need be very very cautioned becuz. if these species is able to visit any other planet by help of spaceships then they are really more than 500 years advanced than us.... They are a type of biggest threat to us and may b having instant destruction weapons to end us!......

Enrico Fermi thought about this. See Fermi paradox. Dr Zak 15:27, 14 May 2006 (UTC)
(after edit conflict) It is by no means regarded as a truism that there are no alien species, indeed it is hotly debated. There may well be planets similar to Earth, though the only planets outside the solar system we can see using current methods are huge ones many times the size of Jupiter. The articles Extraterrestrial life, extrasolar planet, Fermi paradox and Drake equation may be useful to you.
You don't have to look for alien species to find examples of lifeforms that do not breath oxygen, as plants get energy through photosynthesis (though they also use oxygen for cellular respiration). Anaerobic bacteria do not require oxygen. Oldelpaso 15:49, 14 May 2006 (UTC)
I reformatted your question a bit. Black Carrot 22:57, 14 May 2006 (UTC)
Also check out the FA, Planetary habitability. freshgavinΓΛĿЌ 00:44, 15 May 2006 (UTC)
There's a famous quotation by someone like Arthur C. Clarke that goes something like "It would be an astonishing thing if there was life elsewhere in the universe - but it would be far, far more astonishing if there wasn't." Also, your initial statements reveal one flaw that makes life even more likely than you've postulated - why does it need to be the sort of life that can thrive on an Earth-like planet? Even on Earth there are species which live in an amazing range of different ecological niches. There's no reason why a life form couldn't exist, for example, in the clouds of a gas-giant, or deep beneath the surface of a small rocky planet with minimal atmosphere. It might be a case of "it's life Jim, but not as we know it!", but that wouldn't stop it being life. Grutness...wha? 11:38, 15 May 2006 (UTC)
To quote Calvin, "the surest sign that there is intelligent life elsewhere in the universe is that none of it has tried to contact us yet." :) — QuantumEleven 12:14, 16 May 2006 (UTC)

[edit] blood test

my Dr. has told me I have a very high CED count on a blood test he has done. He said it has to do w/ inflamation, and this is what is causing my pain. He is trying to find a Rumatolagest who will accept Gateway INS. I have no idea what any of this means. I know I have arthritis of the spine. What is CED count in blood? What does all this mean? Thank you, David C. Shoenfelt

I believe your doctor means the "sed" rate, or Erythrocyte sedimentation rate. - Cybergoth 16:16, 14 May 2006 (UTC)
True, and he's looking for a rheumatologist. While you're waiting you may want to look at the symptoms of rheumatoid arthritis or ankylosing spondylitis to see if they sound familiar. A rheumatologist will take a careful history of your symptoms, and possibly perform some x-rays and blood tests before deciding on a diagnosis. - Nunh-huh 22:07, 14 May 2006 (UTC)

[edit] Volcano erupting in Asia

What is the name of the volcano erupting in Asia? I would prefer it if someone would paste this section on my my talk page to make it easier for me to find, but I also have this page on my watchlist. Thanks. Robot569 15:56, 14 May 2006 (UTC)

You're probably thinking of Mount Merapi, Central Java, although it wouldn't surprise me if there were more than one. HenryFlower 15:59, 14 May 2006 (UTC)

[edit] The discovery of a photographic fixing agent... how exactly? [Problem now solved.]

Back at school the other week we were talking about photography and fixing agents and such in Chemistry, and I stated to the teacher that I had heard, from some TV program or another, that the first fixing agent was discovered by accident, so to speak. An unsuccessful photograper/scientist (in the sense that his photographs kept on developing and eventually were all black) had been mixing around chemicals trying to find a fixing agent. Being unsuccessful one day, he decided to quick working and placed his bottles of chemicals and a picture or two in a cupboard. The next morning he found that a bottle had fallen over during the night, spilt a substance onto a picture, and voila! he had a fixing agent. My chemistry teacher was quite intrigued, and asked me, just out of interest, to research the story. I went on to Wikipedia, and because I didn't know the name of the particular scientist or photographer, found it extremely hard extracting the information. Does anyone know who the person was, and the exact details? Is the story even true? Many thanks --Zooba 16:09, 14 May 2006 (UTC)

Starting at Photography you might just read the articles about the people involved in the early development of photography and do some google searches. In general, it is the nature of research to not know for certain whether you'll actually find something you might be looking for. I'll give you a hint - as far as I can tell, this anecdote is not in the English Wikipedia but it's out there somewhere. -- Rick Block (talk) 16:46, 14 May 2006 (UTC)
It's presumable true. The scientist was the painter Loius-Jacques-Mandé Daguerre, but he has discovered the first photographic developer, mercury this way, not fixing. He has later found a fixing agent too. See also Photography#History of photography.
I'm reading this from the following interesting book: Greguss Ferenc, Élhetetlen feltalálók, halhatatlan találmányok (2nd ed., Móra Ferenc Kiadó, Budapest, 1986), vol. 1., p. 199. – b_jonas 16:59, 14 May 2006 (UTC)
Aha! Found the following from a biography of his (@ http://www.bookrags.com/biography-louis-jacque-mande-daguerre-woi/index.html):
Though Niepce died in l833, Daguerre continued the work they had begun, experimenting with copper plates and silver iodide, which he discovered was light-sensitive. Quite by accident he then discovered that mercury vapor could develop images. Daguerre had placed a silver iodide plate in a cabinet containing various chemicals, later discovering a clear picture on the plate; by process of elimination he determined that the miracle he had been seeking was wrought by mercury vapor from a broken thermometer.
Thanks for the help - I didn't realise it was a developer, rather than a fixing agent. Thanks for all the help, I'll close the discussion now (as in state that I no longer need help). --Zooba 17:07, 14 May 2006 (UTC)

[edit] External HDD troubles

I have a bit of a problem here. I have an external Hard Drive of my own creation. It's a normal Seagate 80GB in an aluminum enclosure, which I purchased. I connect it by USB 2.0 to my computer. Recently it has been moody and refused to turn on sometimes. That problem seemed to work itself out and now it turns on fine. The problem comes when I plug it into the USB port on my computer. Windows knows I plugged something in, as it makes the device found sound and the icon appears in the task bar. When I go to My Computer it is not there and any program that can access a disc drive crashes when it looks for devices. The only way I can think to fix it would be a reformat, which I would rather not do. Any suggestions would be appreciated. -- yaninass2 | talk 17:55, 14 May 2006 (UTC)

Do you think the problem is OS-linked? Is it possible for you to access a *nix box to try reading it? Isopropyl 18:07, 14 May 2006 (UTC)

Apparently it is Windows fault. I popped in my trusty Knoppix DVD and the External worked fine. I just assumed it was a hardware problem. Now to find a way to write to the External from Knoppix, since it doesn't seem to want to. -- yaninass2 | talk 18:37, 14 May 2006 (UTC)

That might be because the disk contains an NTFS filesystem. Wait for Knoppix major version 5, and then you may be able to write it. Alternately, reformat it to some other type of filesystem. – b_jonas 18:47, 14 May 2006 (UTC)

The External drive is in FAT32 already, as I use it with my home Linux box. The permissions are probably wrong, but I don't have much experience with permissions in Linux and even less in KDE. -- yaninass2 | talk 18:55, 14 May 2006 (UTC)

You can use chown to change ownership. It's probably a problem with how you mounted it; you should check /etc/fstab. Isopropyl 18:59, 14 May 2006 (UTC)
what does Device Manager says about attached devices? --Seejyb 19:55, 14 May 2006 (UTC)

If I have the drive plugged in, the System Properties will not even open, let alone Device Manager. If I open Device Manager and then plug the drive in, it shows up as a USB Mass Storage Device. If I try to open its properties, Explorer freezes until I disconnect the drive. It gets better and better. -- yaninass2 | talk 20:07, 14 May 2006 (UTC)

Oops. I'd see if my external hardware does the same on another machine. And whether the USB socket works properly with other devices - a different cable and something like a scanner (as opposed to a mouse) to test it. Attempting Windows re-engineering without checking the hardware seems like a potential disaster. If it works on other machines, but not mine, then removing all references to it seems the only alternative. This may entail removing hard drive drivers, usb drivers et al, and one still has no guarantee that it would work. Am i right in assuming the "hard drive of my own creation" means you had a USB2 Seagate 80G External drive which you encased yourself? If so, you seem to be right in assuming that an up to date Windows should pick it up first time, and assign the right driver. --Seejyb 22:05, 14 May 2006 (UTC)

My entire purpose for using the external is so that I can save all my important data to it before I reformat my main Hard Drive. This Windows installation has logarithmically declined in usefulness and stability. The problem seems to run deeper than just the External HDD and I need a reformat and reinstall but I would like to save my stuff. The hardware is apparently fine, as it all works in Knoppix. "Hard drive of my own creation" means I took a normal 80GB EIDE Seagate Hard Drive and put it in an aluminum enclosure with USB2.0 functionality which I purchased. Thanks for all your help so far. It is much appreciated. -- yaninass2 | talk 23:41, 14 May 2006 (UTC)

[edit] Does earth have "voltage"?

Voltage is AFAIK, simplified, the difference in energy levels between bodies. Can one claim that earth's body has a certain level of voltage? Perhaps by comparing it to other bodies in space? Thanks in advance, hope this isn't too far from reality. 213.161.190.228 09:59, 15 May 2006 (UTC) Henning

The voltage difference between the earth and the clouds can get quite high during an electrical storm. Thousands or millions of volts, I forget exactly, but it's a lot. -lethe talk + 21:36, 14 May 2006 (UTC)
As you say, voltage is not an attribute of a single point entity as such, it is a difference between two points. Do you then mean something like: earth is at +5v relative to the moon? The concept is unknown to me, but someone may have theorised on such an idea. --Seejyb 22:19, 14 May 2006 (UTC)
The ground is often defined at a 0-volt level for some applications. --AySz88^-^ 22:22, 14 May 2006 (UTC)
In AP Physics, we were taught to set the 0-point for things like that at infinite distance if no better option presented itself. Black Carrot 22:53, 14 May 2006 (UTC)
The voltage between the Earth and the Moon is a definable quantity, although calculating it might be tricky. Each has a certain charge, dependent on their excess of protons or electrons; and the capacitance of the Earth-Moon system can be calculated by modelling them as two spherical conductors separated by 3.8*10^8m of (near-)vacuum. Divide charge differential by capacitance to get voltage. EdC 23:56, 14 May 2006 (UTC)
My question partly springs from thinking about the Apollo lunar landers. Wouldn't they be carrying an Earth Voltage, and wouldn't this be capable of destroying their electrical equipment (if being grounded, which I suppose they weren't because of rubber materials used to soften the impact). Many thankseses for the answers already here. :) 213.161.190.228 09:58, 15 May 2006 (UTC) Henning
Wouldn't solar radiation, which is ionized too, equalize the difference and set Apollo and Luna (no atmosphere) to the same level ? --DLL 19:34, 15 May 2006 (UTC)
IIRC, the ground contact probes that dangled below the landing pads of the landers doubled as grounding rods, to equalize any voltage difference between the lander and the Moon. --Serie 00:11, 16 May 2006 (UTC)

[edit] Obsessive-compulsive disorder

I'm pretty sure I have OCD.

Everytime I go out with friends, I keep checking my pocket each minute to make sure the cell phone is there.

When I lose my pen, I look for it under the couch, and I don't find it. Then I get up, go look under the couch again, and I don't find it. So I repeat 2 more times, thinking that it will suddenly reappear. But of course it doesn't.

What do you guys think? OCD or not? Thank you.

I doubt it, maybe somewhat irrational fear or anxiety, looking for something in the same place if you fail to find it in other logical locations is also relatively normal, and since you posted this question, you may have a touch of hypochondria. Philc TECI 21:43, 14 May 2006 (UTC)
There are ways to learn to control this, but to my knowledge they demand of the subject that s/he actively try to counter the crave to look under the couch and etc.
Since s/he said s/he was expecting it to re-appear there counters the normal symptoms of OCD, which are generally that they only perform the action to satisfy the craving, and not because they believe that it will benefit them in anyway, or that something may have changed. Philc TECI 21:48, 14 May 2006 (UTC)
Think of yourself as existing somewhere on a spectrum of human behaviour. People vary in their "obsessiveness" or "compulsiveness", both relative to others, and from time to time within their own life. If your thoughts and actions disturb your life, detract from your enjoyment and quality of life, then you may feel that you have a "Disorder", in which case you may feel inclined to ask a professional opinion. If still unsure, ask some persons who know you if they think it disturbs your life - the internet is surely not a wise place to obtain such opinions.. If these things don't disturb your life, then why bother about diagnosing yourself? --Seejyb 22:33, 14 May 2006 (UTC)
Do you need to do these behaviours even when you don't want to? Would you become very uncomfortable if you were prevented from checking your phone or the pen? If not, you probably don't have OCD. —Pengo 04:34, 15 May 2006 (UTC)
But of course our standard advice is to: See a doctor. I also have the same problem, but that's more likely a holdover from when my parents always use to be worried that someone would steal their phone(s) and waste all our minutes... --M1ss1ontomars2k4 | T | C | @ 05:30, 20 May 2006 (UTC)

[edit] Nutritious shampoos

Do the vitamins and provitamins in shampoos actually do your hair any good? Don't they just get washed down the drain when you rinse? User:Zoe|(talk) 21:38, 14 May 2006 (UTC)

Well, half answering the question: To my knowledge, provitamins cannot be taken up by hair, at least not efficiently (dun take my word for it). I've heard much about "Provitamin B5" in this context, but as the talk-page of B5's article Pantothenic acid gives an impression of, there's not much factual evidence out in the public, at least not that I can see, that documents any actual effects. In whatever case, nutritious shampoos DO have an effect, as one can clearly see a difference between non-treated showered hair and treated. Exactly what effect, I don't have a clue, and I don't think the people behind the commercials have much of a clue either!
I couldn't say, but one thing I'm pretty sure of is that not everything gets rinsed off. So, that could be one of the things that's made to stick. Black Carrot 22:51, 14 May 2006 (UTC)
Look, hair is dead. It doesn't need any "nutrition". Conceivably the vitamins could work their way into your scalp, though, where they might have some physiological effect. Or, their physical/chemical properties could do something to your hair, independently of their status as "vitamins". --Trovatore 22:55, 14 May 2006 (UTC)
Yup, hair is dead, and can't be remade. So what can shampoos do? Clean out muck (old oil, dust, broken hair and dead scalp cells). May contain salts (e.g. selenium sufide) that alter scalp micro-organisms. Add oil and increase moisture content, improving elasticity and softening dry ends. Add light-reflecting particles to give better shine. Add polymers that temporarily bind in weaker areas to prevent breaks and temporarily bind split ends (until the polymers fall out). Anything else needs to get to the living cells in the hair follicles under the skin surface. Vitamins usually get there via the blood stream. Pro-vitamins - whatever that is supposed to mean - are surely undefined nonsense, with no scientific evidence to support the advertising claims. Gentle hair care - e.g. mild shampoo (with a nice parfum), low heat, gentle brushing, a neutral hydrating oil, no dyes, bleaches or other reactive chemicals such as perms and straighteners - is old-fashioned but remains good advice. Think about it, if something really worked well, it would take over the market. --Seejyb 23:54, 14 May 2006 (UTC)
Well, "provitamin" actually means a substance which is not a vitamin but which can be metabolically converted to one. But such a conversion requires living cells: you can bet hair isn't doing any conversion. - Nunh-huh 01:23, 15 May 2006 (UTC)
The 'provitamin' talk is nonsense, like the guys in star trek talking about the photontransmuter overload. But. Just because the hair is dead, doesn't mean that stuff you smear on it doesn't stick, and might give it (temporarily) qualities that you want. Try some, and, if you like what it does to your hair, stick with it. For great justice. 05:00, 17 May 2006 (UTC)

[edit] poop

Why does it have peanuts? A Clown in the Dark 21:47, 14 May 2006 (UTC)

Probably because you recently ate some. GeeJo (t)⁄(c) • 21:53, 14 May 2006 (UTC)
I blame time dilation. 213.161.189.107 21:57, 14 May 2006 (UTC) Henning
You might find some useful information in our article on human feces. I couldn't face reading it myself. (Disturbing image warning.) --Shantavira 07:38, 15 May 2006 (UTC)

[edit] babies in vomit?

Why is there always babies in your vomit, even when you haven't been eating babies? Many people have told me (urban legend?) that what look like pieces of infant are actually chunks of stomach lining. Anyone have an educated answer?

I really doubt stomach lining would be it. But then again, I didn't know vomit had babies in them. Are they a typical part of the American diet? --HappyCamper 02:50, 15 May 2006 (UTC)
I've only seen babies in vomit after eating carrots. The article on vomit might be helpful. And I can't believe I'm writing about this. --Ginkgo100 03:12, 15 May 2006 (UTC)
I can't find a source for it at the moment, but I read somewhere recently that certain types of fats congeal in the stomach as small orange blobs resembling baby pieces. --Canley 03:52, 15 May 2006 (UTC)
This question reminds me of a truly charming scene in the 1971 movie The Devils. A nun's vomit was examined to discover evidence of witchcraft, and they picked thru the bits and noted the presence of infants. JackofOz 06:38, 15 May 2006 (UTC)
Ugh. My mind flashes back to Catch-22 and stewed tomatoes. User:Zoe|(talk) 16:18, 15 May 2006 (UTC)
I actually think that it is a slight bit of stomach lining. Kilo-Lima|(talk) 18:04, 15 May 2006 (UTC)
Sheesh. No, there is not normally any stomache lining in vomit. Nor are there always carrots in vomit. It's just food that's been stained by bile. --BluePlatypus 23:48, 15 May 2006 (UTC)

There are two types of vomit: if it comes back from the stomach directly, it will not be having bile and the yellow discouloration is the color of the stomach juice... but if the vomit comes from the intestine, and this usually happens, then, yes it contains bile; as bile doesn't get poured on ingested food exept in intestine...... and for the carrot pieces, there are not so, it is just the remnants of the yet not fully digested food.

[edit] In conferences or competitions

What does it mean to have a " poster presentation" or " paper presentation" ? Thanks in advance 23:47, 14 May 2006 (UTC)23:47, 14 May 2006 (UTC)23:47, 14 May 2006 (UTC)23:47, 14 May 2006 (UTC)

A poster presentation is when you lay out your project or information on a poster board, all words and illustrations. People walk up to the posters and read your writing and see your illustrations. You sometimes have a time when you are expected to be near your poster, to answer questions. The poster usually remains displayed for the duration of the meeting / occasion. To read or present a paper means you give a talk to an audience - live. This may or may not include illustrations, and you are usually expected to answer questions from the audience, as well as to provide a written summary, but it's all over in the 20-40 minutes. --Seejyb 00:19, 15 May 2006 (UTC)

[edit] Coffea fruit

Do the raw berries of the coffea plant contain caffeine? What do they taste like? Can you make juice out of them? —Keenan Pepper 00:01, 15 May 2006 (UTC)

According to the article on Caffiene, it is found in the beans and leaves of the plant. No word on the taste. --Howard Train 16:01, 15 May 2006 (UTC)
The plant is of the same family as jasmine. If we roast the beans, the taste is acceptable (but does this operation produce caffeine ?). I suggest it is not tasty when raw. --DLL 19:29, 15 May 2006 (UTC)
Really? Wikipedia says Coffea and Jasmine aren't even in the same order. —Keenan Pepper 01:19, 16 May 2006 (UTC)
This article from the BBC says that scientists have discovered the gene that makes caffeine, and speculates that genetic engineering could produce a coffee plant that doesn't contain caffeine. I seem to remember something about caffeine being a natural defense against insect predators and the like, but I haven't looked for a reference. --Elkman - (talk) 09:15, 16 May 2006 (UTC)
They've already used genetic engineering to produce a decaf coffee plant (though some rare species produced decaf already - just not as efficiently). AllanHainey 10:08, 16 May 2006 (UTC)
Sorry for the Jessamine gag. My coffee vendor machine says so! They are both in the Magnoliopsids class, and class is very large (mammals, for instance, is a class). --DLL 21:10, 19 May 2006 (UTC)

[edit] May 15

[edit] Perfect banking

If a curve with a radius of 70m is pefectly banked for a car traveling 60km/h, what must be the coefficient of static friction for a car not to skid when traveling at 90km/h?

I don't know what they mean by "perfectly banked", is this the maximum speed with which there is sufficent friction force? Another possibilty? How would you go by doing this problem? Any thoughts? Thanks. C-c-c-c 04:17, 15 May 2006 (UTC)

I agree that this problem is worded confusingly. If the road is banked, your answer would have an undefined theta component, because your coefficient of static friction depends on the normal force which in turn depends on the angle of banking. A request for clarification may be in order. -D. Wu 05:47, 15 May 2006 (UTC)
Ordinarily, in order to drive a car around a circle, its tires must exert a frictional force against the road in order to provide a centripetal acceleration. However, if the road is "perfectly banked" for a given speed (meaning the surface is at some angle which you must calculate), no friction is necessary; the same normal force that supports the car against gravity has a horizontal component that exactly equals to centripetal force. Instead of a car with a steering wheel, the same circular path would be followed by a greased hockey puck.
Since the centripetal force depends on speed, if you drive at a different speed, you need friction again to maintain the circular path. By balancing forces, you can calculate the frictional force required and therefore the minimum necessary coefficient of static friction. Melchoir 08:11, 15 May 2006 (UTC)
I found the PDF of the book from which this question comes, if anyone cares (Section V.4 - More Banked Curves). --193.38.88.6 08:53, 15 May 2006 (UTC)
By "perfectly banked", it is referring to the angle at which cetrifugal force of the vehicle going around the turn is forced "downward" at a 90° angle with the ground. For example, in a cloverleaf exit ramp on a U.S. interstate, there is a sign that tells you the speed at which an average car will appear to have no outward force because it will be directed directly downward onto the tires.
Now, going with the question, assume the car has mass M and is travelling in an arc at 60km/h. You can calculate the centrifugal force. Now, what tilt on the road is required so that gravity puts the exact same forve in the opposite direction. that is the "perfectly banked" angle. Now, gravity remains constant. Increase the speed to 90km/h and the centrifugal force changes. Subtract (vector-wise) the force of gravity and you get the force between the tires and the pavement. You need at least that much static friction between the tires and pavement or the car will skid. --Kainaw (talk) 18:43, 15 May 2006 (UTC)

[edit] Where can I get various data in Access format?

I would like to have a fiddle around with a database (in Access format), but I don't have any data. So, are there any databases available online? Preference would be to those related to human-related (ie health, psychology etc). Thanks! 153.111.60.15 04:21, 15 May 2006 (UTC)

Aside from the Northwind databse that ships with Access, I found a number of samples here, but most samples seem to be corporate-oriented. This page has a sample database of Canadian provincial data, but it's a pretty primitive database. --ByeByeBaby 05:09, 15 May 2006 (UTC)
You can create yourself any kind of data and visually create links between pertinent elements of those lists of data (tables). You have to keep in mind lawlike principles of databases such as 1) No redundancy 2) Always integrity 3) A database must protect its own existence, as long as such protection does not conflict with the First or Second Law (this one from Asimov's.) --DLL 19:24, 15 May 2006 (UTC)

[edit] How does the blood type system work? Is there an error on the entry?

Hi, sorry to bug you guys...I'm not sure how to report an error on a page, so I'm using this feature...I guess it's kind of a question.

Anyways, I was looking at the entry for "blood charts". I am no expert in this area, and actually often have trouble remembering how the whole blood type thing works. So I was looking at the two charts for Donors/Recepients...and the two charts contradict each other completely.

So, I'm wondering what it is for AB blood types: Are you able to donate to anyone, or can you only receive from anyone?

Thanks!

There are three factors - A, B, and rhesus. You cannot put a transfuse someone with a factor their blood does not posses (or you'll cause massive clotting and kill the patient), but you can tranfuse someone with blood that lacks the factors their blood has. That's why someone who has no factors (O negative) can donate blood to anyone, and someone who has all factors (AB positive) can take blood from anyone. I hope that clears it up. Raul654 05:32, 15 May 2006 (UTC)
An AB patient produces red blood cells with the A and B antigen and no antibodies for the A and B antigen. Therefore, the AB patient is a universal recipient of red blood cells, because he has no A or B antibodies. However, the AB patient can only receive plasma from another AB patient. Since antibodies reside in the plasma, transfusing an AB patient with plasma from a non-AB patient will introduce A or B antibodies into the recipient that will in turn recognize and bind to the A and B antigens on the red blood cells, causing the incompatibility.
So, both charts are right. AB is a universal recipient for red blood cells, but a universal donor for plasma (b/c there are no A/B antibodies). Note that I didn't talk about the Rhesus factor, but the reasoning's the same. -D. Wu 05:54, 15 May 2006 (UTC)
Which two charts? —Pengo 07:56, 15 May 2006 (UTC)

[edit] https

If someone intercepts a https transmission, without cracking the encryption, can they figure out:

  • which website you were visiting
  • which page on the site you were looking at
  • the GET and POST values? Thanks WP 08:48, 15 May 2006 (UTC)
Certainly the web site (except for certain multi-host systems). The destination IP address, which identifies the website, has to be in clear text, otherwise your request wouldn't be able to reach the site. Notinasnaid 09:47, 15 May 2006 (UTC)
The destination (and source) IP address is in the cleartext, partly because it is on a different layer (see OSI model) which is not encrypted. The page you were viewing on the site is not recoverable from the traffic, neither are the GET and POST data. –Mysid(t) 12:28, 15 May 2006 (UTC)
Please correct me if I am wrong: There may sometimes be a way to make an educated guess about the page you are fetching by looking at the length of the reply you get, and as your browser immediately makes additional requests for embedded elements (style sheets, images) the number and sizes of those. Browser-side caching and keepalive connections makes such analysis harder though. Weregerbil 16:15, 15 May 2006 (UTC)
Keep in mind that encryption forces all transferred data to specific-sized blocks. So, data transfers of different items may be forced to be the same size during the transfer. --Kainaw (talk) 17:26, 15 May 2006 (UTC)
(Warning: non-expert talking, take with a grain of salt:) That would depend on whether you have a block cipher or a stream cipher, wouldn't it? And with a block cipher the size of the block affects things; e.g. a 64-byte block cipher rounds data size up to a 64-byte boundary so it would still be easy to tell apart a 1000-byte and a 1500-byte page or image. Weregerbil 21:47, 15 May 2006 (UTC)

[edit] Green leaves as opposed to Black ones?

Why are leaves not black? For all the awe that advanced photosynthesis inspires, it seems counter-intuitive for leaves of plantlife to be any color other than black. Why are they reflecting away that valuable green light? --Demonesque 10:36, 15 May 2006 (UTC)

It might seem a paradox, the green pigment Chlorophyll is the primary light-sucker on a plant, along with Carotenes and Xanthophylls. It seems to me like an unavoidable sideeffect. Do remember that just because the pigment reflects visible green light, it might be much more efficient than realistic alternatives; even if a leaf was black, it would only tell us that the visible light spectrum light was efficiently captured, not the more energyrich light that we can't see, Infrared. Henning 10:49, 15 May 2006 (UTC)
Ah. Yes, I didn't consider the invisible light spectrum -- do plans gather energy from the infrared spectrum as well? Thank you for your answer. :) --Demonesque 12:06, 15 May 2006 (UTC)
Short: Yes. Light is light is energy, plants gather all the energy that isn't reflected, as do all bodies (well if the light doesn't pass right through them, of course, which happens quite often. Just consider a thin leaf being subject to bright visible-spectrum light. One side will be brightly lit, the other not quite as brightly. Same happens with light in all spectrums, to lesser and greater extents depending on blahblahbblah. See Ultraviolet and Infrared for details. —The preceding unsigned comment was added by 213.161.189.107 (talk • contribs) 13:16, 15 May 2006 (UTC)
Well, it depends on what you mean by "gather energy". They "gather energy" from infrared light in the sense that, when you shine it on them, they get warmer. That's not the same as saying they can use it to make glucose; I doubt they can, at least I doubt they can use anything very far into the infrared. The chlorophyll article shows the absorbtion spectrum for chlorophyll b falling off almost to zero by about 700 nm, and chlorophyll α doesn't even get that far. --Trovatore 16:30, 15 May 2006 (UTC)
I think this is a fascinating question, and unfortunately don't have an answer. I can speculate some possible reasons, though: Perhaps there are no good pigments to absorb in the green range, or perhaps they are just difficult to evolve. Perhaps when an additional variant pigment evolves, its cost is so high that the plant is at a selection disadvantage and does not reproduce enough for the pigment to become very different. Perhaps the energy cost to make enough pigments to absorb all visible light would not outweigh the benefit of the increase in energy provided. Or perhaps plants just never got around to it. — Knowledge Seeker দ 17:12, 15 May 2006 (UTC)
Plants use red and blue light for photosynthesis, and thus reflect the green, which they can't (or don't) use. I believe there's different pigments or capturing thingies for both red and blue, perhaps with more than one type for red. Why they can't use green, I don't know. I believe they use quite a range of red light though, and some might be in the infrared, but i'm not sure. There are also some purple plants. How they fit in I'm not sure. I should probably look stuff up before replying, but I wont. —Pengo 05:19, 16 May 2006 (UTC)
Because they weren't painted by Henry Ford#The Model T. More seriously, though, there are other pigments in leaves as well. Think of leaves on trees that change colors in autumn. When photosynthesis stops, pigments like anthocyanin are more readily visible. --Elkman - (talk) 09:26, 16 May 2006 (UTC)
Black leaves? That would be ugly I think. – b_jonas 18:56, 16 May 2006 (UTC)
If you thought the woods were dark and scary with regular chlorophyll... Peter Grey 02:21, 17 May 2006 (UTC)
"The woods are lovely dark and deep, But I have promises to keep ....." JackofOz 09:09, 17 May 2006 (UTC)

[edit] Immortality

Are there certain kinds of bacteria or viruses that are immortal?

thank you!

gracy,13

No, all organisms on Earth are mortal. Some of them are tough, though, and some bacteria can stay alive in very unfavorable conditions for very long periods as so-called dormant spores, after which they can continue living. –Mysid(t) 12:47, 15 May 2006 (UTC)

This article uses the phrase 'effectively immortal'. [55]. You could also use the phrase 'philosophically immortal' to describe bacteria which constantly split, so that they never actually 'die'. They may split so much, however, that no molecule from the original still exists, but what the hey.. --Zeizmic 12:53, 15 May 2006 (UTC)

There are some plants that are nearly immortal. While they could be killed (making them mortal), they have not been killed and have continued living as a single plant for thousands of years. A quick google turned up this one. However, I was actually looking for one in or around Yucca Valley that was found to be older. --Kainaw (talk) 13:50, 15 May 2006 (UTC)
I would consider bacteria and viruses to be immortal in the sense of "no natural cause of death", like the Elves in Tolkien's Middle-earth. Obviously, they are not immortal in the Tuck Everlasting–cannot–be–killed sense. — Knowledge Seeker দ 17:03, 15 May 2006 (UTC)
Viruses can live forever, so in that sense they are immortal, however keeping in mind, they have no life functions recquired to keep them alive, as all they are is a piece of DNA. So it is debatable wether they were ever alive. Philc TECI 17:28, 15 May 2006 (UTC)
Viruses are a bit more than just DNA (or RNA) and have protein coats (you could also say humans are just DNA with protein coats just the same), but I won't split hairs or go off topic futher. —Pengo 05:23, 16 May 2006 (UTC)


I agree with life and Philc. Consider: a virus particle is isolated from all potentially damaging forces, as well as host cells, and observed for a million years. What is seen? It stays just the way it is - not dividing, growing, moving or ageing in any way. What would one call that? Immortal? Hmmm, it would have lasted a long time, but how could the observer tell it was alive? And if it weren't alive it can't be termed immortal. Maybe a virus is never recognisably alive in the first place; maybe we only recognise such things as alive by the fact that they break up (die) and in so doing make more of themselves. --Seejyb 23:53, 16 May 2006 (UTC)
Most things don't die when they reproduce. And inability to die isn't why viruses are considered nonliving. See Virus Black Carrot 18:07, 20 May 2006 (UTC)
I didn't say that was the reason. Philc TECI 17:16, 21 May 2006 (UTC)

[edit] physics

Use Newton´s laws how to acheived terminal speed to free falling objects?

Perhaps by reading your textbook and notes from class. Perhaps you can start by telling us what you have Newton's laws down as, and we can go from there? Skittle 16:46, 15 May 2006 (UTC)
Every force has an equal and opposite reciprocal force. Terminal velocity of an object in freefall is where the downward force of the object's mass is equal to the opposite force of air resistance. CaptainVindaloo 16:55, 15 May 2006 (UTC)
Newton's laws by themselves are insuffecient to determine the terminal velocity. Terminal velocity is achieved when the force of drag due to air resistance (which is a function of velocity, the shape of the object, the density of the air, 'etc) is equal to the force of gravity. Raul654 17:12, 15 May 2006 (UTC)
Try this;
Force due to Air Resistance = Pressure (Nm-2) X Area of object (facing the force)
And;
Downward Force = Mass of Object X Acceleration of Gravity (9.81ms-2)
Terminal velocity is where these two are equal (resultant force = 0). CaptainVindaloo 17:55, 15 May 2006 (UTC)
That's a pretty big oversimplification and poor way of stating drag. I mean, yes, it's true, but how are you going to get that pressure? It's not atmospheric pressure by a long shot, it's a dynamic pressure. I suggest you look at the drag article. We have some pretty good empirical models for, e.g. spheres. If you know the Reynolds number and Mach number you can look up the coefficient of drag. So terminal velocity V such that: \frac{1}{2} C_D \rho V^2 S= mg where I am refusing to define the terms in order that you do at least some of your own homework. moink 21:23, 15 May 2006 (UTC)

Or, let's try and look at it from the point of view of Newton's laws. I was hoping to talk you through it, so you could do it yourself. At terminal velocity, the object isn't accelerating any more; it is at a constant velocity. I think it's the first law that tells us what being at a constant velocity means as regards the forces on the object. Look at that and have a think. Then come back here, say something, and we'll keep going. Skittle 18:05, 15 May 2006 (UTC)

[edit] Psychological disorder of computer-leave-oners

I was recently thinking about my habit of leaving my home computer running 24/7. It serves no purpose really, especially since it only takes about 45 seconds to completely boot up, and it's not doing anything terribly important when I'm not using it. Still, I feel an urge to leave it on all the time, to the point that I get uncomfortable if I know it's not running.

Afaik, the only real benefit of leaving a computer on is in preventing thermal creep which can cause premature failure, but I end up buying myself a new computer every 9-12 months anyway so it's not like i'm worried about that. Am I too attached to my computer, and is this some sort of way of anthropomorphizing it by keeping it 'alive' all the time? I must not be the only one who acts this way, are there support groups available? --Jmeden2000 16:05, 15 May 2006 (UTC)

Hehe:
mark@Akki:~$ uptime
13:14:24 up 55 days, 3:38, 4 users, load average: 0.00, 0.02, 0.00
Raul654 17:13, 15 May 2006 (UTC)
Don't claim it isn't doing anything important. Spammers like it when you leave your computer on 24/7 because they get more use out of it. --Kainaw (talk) 17:22, 15 May 2006 (UTC)
Assuming you've taken the necessary steps to make sure your computer isn't being used as a spam zombie, you might want to have it do something important by becoming part of one of the many Grid computing projects, such as Folding@home or one of the others listed at Protein folding. Or if you like little green men, you could try SETI@Home. --LarryMac 18:23, 15 May 2006 (UTC)
If you buy yourself new hardware every 9-12 months then, no, you are not too attached to your computer. ;-). LarryMac's suggestions are good for your peace of mind (I'd go with protein folding rather than SETI -- not only does it have a guaranteed outcome, it will do humanity much more good than knowing that there is someone out there whom we can return a call to in 60 generations).--Swift 23:44, 15 May 2006 (UTC)

There are 8766 hours in a year. Let's say your computer, excluding monitor, uses 200 watts=0.2 kilowatt.

  • 0.2 kilowatt * 8766 hours = 1753.2 kilowatthours (per year)

My electric bill says I'm paying $0.11430 / Kwh, (check yours).

  • So 1753.2 kwh * $0.11430 / Kwh = $200.39 (per year)

(That's a numerical coincidence that the watts is numerically equal to dollars /per year, in my case) Let's say you use your computer 8 hours every day, ie 1/3 time. So every year you send 2/3 * $200 = $133 to the electric company FOR NO BENEFIT. In ten years, that's $1330. Let's say you own a computer for 60 years out of your life, that's $7980 over a life that you send to electric company, (not counting lost interest) FOR NOTHING. Back to yearly basis, using 1752 kwh / per year, 24-7. Let's say there are 50 million computers in use daily. ( probably on the low side, just a guess), 1752 kwatt hour *50e6 = 8.76e+13 watt hour (per year) A typical nuclear power plant, or other, is 1 gigawatt, say, so in a year it produces 1 Gwatt * 8766 hours = 8.766e+12 watt hour (per year) Therefore it takes 10 powerplants of the gigawatt capacity to power those 50 million computers. If they are used 1/3 of the time but ON all the time, that's 6.3 power plants running continuously FOR NOTHING. (except to waste resources and environmental degradation.) I started with a computer using 200 watts. Some of the latest overclocked, high end ones have 500 watt power supply, multiply above by 2.5. Plus monitor, if big CRT, left on, add 1000 watts, or whatever. Factor of 5. etc. Did that cure you? --GangofOne 03:04, 16 May 2006 (UTC)

Oh, no, not even close ;-) I have a kill-a-watt meter that I use to sum energy usage for my various devices. The computer and monitor when loaded (playing a system intensive game) draws 260 to 300 watts, whereas the pc by itself idle is 60 to 75. Still, I realize that there would be a cost savings by turning it off for the 18-20 hours i'm not using it, but it doesn't nearly outweigh my urge to leave the thing on. And you want to talk about waste, what I do at home is NOTHING compared to where I work, I am talking drop in the ocean here, we waste a LOT LOT LOT of power (we *are* in the power business but thats here nor there). --Jmeden2000 20:33, 16 May 2006 (UTC)
What do you pay per kilowatthour? GangofOne 20:55, 16 May 2006 (UTC)
12c per kwh, give or take. I fully realize the potential to save cost here, but i could also save a lot of money by only showering once every other day, altho i'm not likely to start up that any time soon either... --Jmeden2000 00:46, 17 May 2006 (UTC)
  • Washing is good for your hygiene. Leaving your computer on only gives hackers more chances to get in and serves no purpose. I don't see why saving money by turning the computer off when you don't use it could ever be a bad thing. I don't think the shower comparison works. - Mgm|(talk) 10:56, 18 May 2006 (UTC)
If you don't leave the computer on, how do you guys get your daily backups done? Notinasnaid 11:00, 18 May 2006 (UTC)
It works because he was arguing a *cost* benefit. It's debatable that showering every day vs every other has any hygenic benefit beyond the superficial. The direction of my question was to probe the possibility that my condition is psychologically common, but it doesn't seem like anyone has answered supporting this. I am so alooooone! --Jmeden2000 13:41, 19 May 2006 (UTC)
I think I recognize the feeling, and if I do, don't feel bad. For me, it's never become attached to leaving the computer on, but it has shown up in other things. Leaving the door open, for instance. It starts out that, for whatever reason, you feel a bit more comfortable with something one way and a bit less so with it another. In this case, it was because my dad used to get seriously pissed off whenever we "wasted air conditioning". As you tend to go with this feeling, it's strengthened. If you happen to notice its existence, especially if you're not really familiar with it and don't know what started it, it'll tend to become even stronger, probably for the same reason that sports superstitions start - it feels like something will go wrong if you don't follow your gut. The only way to get rid of it is to simply ignore it. As you turn off your computer whenever you're not using it, and it turns out that it doesn't actually feel half bad to do so, the compulsion to leave it on will go away. Black Carrot 18:21, 20 May 2006 (UTC)

[edit] Human Evolution

What are the expected next changes through evolution for man? Are there any that are slowly happening now? Are there any predictions for the future changes?

Among other things, I think I have read that our jaws are becoming smaller, while still accommodating as many teeth as before. This causes a need for bracers and etc.
There are some sites listed at Human evolution#External links that you may find useful. — Knowledge Seeker দ 16:56, 15 May 2006 (UTC)
No evolution can occur in humans anymore, evolution depends on natural selection. This means that the weakest have to die, there is no process anymore which gives any increased liklehood to a stronger human breeding than a weaker human. Human evolution can only occur in the most undeveloped LEDC's in the world, where they death rate is still so high, and civilisation so undeveloped, that natural selection can still take place. Only one attempt has ever been made to rectify this, and it didn't go down to well, the Nazis and their selective breeding program to create a Master race, where the marrige of an Aryan and an Untermensch was forbidden. Naturally, this isn't right, but as a down side, expect no human evolution. Philc TECI 17:36, 15 May 2006 (UTC)
I quite disagree with Phil's assessment. Certainly evolution may be expected to proceed more slowly now that we control our environment so much. But there are still genetic factors that contribute to mortality—we might expect to see genes for resistance to HIV become more prevalent, for instance. Furthermore, it is not death per se but reproductive fitness that is relevant. If an allele causes its carrier to be slightly more fit—reproducing more, or earlier, or somehow providing an advantage to its offspring—we can expect over time for that allele to become more prevalent. — Knowledge Seeker দ 18:06, 15 May 2006 (UTC)
I mostly agree with Philc, only slightly agreeing with Knowledge Seeker. Humans do not pick mates based on genetic well-being. No matter the quantity or severity of genetic defects, humans find ways to breed. Any suggestion that people with genetic defects should not be allowed to breed brings up criticism and images of Nazi Germany. However, a genetic disorder that causes infertility or kills quickly in childhood is one that human evolution can still handle. --Kainaw (talk) 18:22, 15 May 2006 (UTC)
It isn't about not letting people with genetic 'defects' breed as you put it, it's about certain genes producing differences in people that affect whether other people want to breed with them, and how well they breed. For example, someone with genes that give them a tendency to be smelly, fat and obnoxious, for whatever reason, is going to have a harder time finding a mate than someone with more helpful genes in this area. A woman who hits her fertility peak later in life than normal, and stays healthily fertile for longer, will have a reproductive advantage in the current environment in the developed world, where people are putting off reproduction until later. It isn't eugenics, it's adapting to a different environment. But yes, slower with fewer people dying. Skittle 18:27, 15 May 2006 (UTC)
Kainaw, it's not that humans pick their mates based on genetic well-being, it's that genetic well-being is defined in part by how humans pick their mates. Any trait that causes increased mating, more offspring, and so on will tend to become more predominant. It could be that people are less likely to mate with someone with HIV (perhaps because the person is dead). Someone with altered fat metabolism or appetite mechanisms might be more likely to pass on genes both because of improved mate selection as well as cardiovascular fitness. Skittle is correct. A trait doesn't have to cause death for selection to take place; it simply must alter reproductive fitness, even to a tiny disagree. — Knowledge Seeker দ 18:39, 15 May 2006 (UTC)
My point is that for evolution to work, a segment of the population must have fewer children each generation. The only population that I know of that continually has less children is the highly educated one. More education = less children. Less education = more children. But, even that has exceptions and it isn't proven to be based on genetics. From a genetic standpoint, there is no segment of the population that makes it past childhood and into adulthood and does not breed. Therefore, all genes have the same probability of being passed on. Of course, I noted the exceptions that genetically cause infertility or childhood death. --Kainaw (talk) 18:49, 15 May 2006 (UTC)

I am astonished that intelligent people can even consider the proposition that "evolution isn't happening anymore". All it takes for evolution is (a) multiple versions of genes, and (b) some versions of some genes being associated with being more or less successful at reproducing than other versions. If you dont think both are still happening, please retake biology 101 and restrict your opinions to things you know about. I realize this sounds harsh, but good grief, people, it's hard to be polite about this degree of silly ignorance! alteripse 18:42, 15 May 2006 (UTC)

Claiming that Evolution is hindered by the promiscuity of humans is not the same as claiming "evolution isn't happening anymore". If you take nearly any claim to an extreme, the claim becomes silly. If I said that kids like candy, would you claim that it is silly to claim that every single person under the age of 13 absolutely loves candy? Of course not, that would be silly. Evolution is a topic that appears on the RD weekly. So, some extreme views get mentioned. That doesn't mean that the person really means the extreme point. They have just defended a more relaxed view so much that it is now written in an extreme view. --Kainaw (talk) 19:05, 15 May 2006 (UTC)
In response to Alterprise, natural variation (changing of genes) is very different from natural selection (those with weaker genes dyeing), and that this is on Human evolution, and not evolution in wild enviroments, where admittadly, natural selection can still occur. My main problem with Human evolution, is that a large amount of the things that effect your liklehood to breed eg sociability, wealth, charm, charisma, knowledge, social standing and class, are completely irrelavant from your genes, and quite a few are gained through life. So basically, not only do I think genes are relatively in comparison to other factors irellavent to reproduction, but also that alot of the factors are gained well after birth. Another point is that modern medicine keeps even those with the most horrific genetic dissabilities alive, and then they can go on to live perfectly normal lives, which usually entails reproduction, for natural selection to occur, these people have to die, however, this is agreeably morally wrong. Philc TECI 19:29, 15 May 2006 (UTC)
As Knowledge Seeker said above, evolution doesn't necessary require death, just some change in the reproductive fitness of an individual. Small genetic disadvantages can be slowly phased out without there being any kind of mortality issue, simply that individuals with that gene systematically reproduce less than individuals without that gene. While I agree that evolution among humans has certainly slowed due to reproduction being determined by many more factors than genetics, I think there can be little doubt that at least small changes will continue among humans, whether we're aware of them or not. EWS23 | (Leave me a message!) 19:41, 15 May 2006 (UTC)
I believe that Kainaw and Phil are confusing mortality with reproductive fitness, which is understandable, since it is how evolution is usually presented. Kainaw writes "From a genetic standpoint, there is no segment of the population that makes it past childhood and into adulthood and does not breed. Therefore, all genes have the same probability of being passed on." This is not accurate; organisms may breed to varying extents. As noted above, different characteristics may cause one human to be more likely to breed, or breed more often, or even to provide an advantage to his child later on (for instance, having parents that survive longer may help children survive and be successful themselves). Philc is correct in noting that cultural aspects control a number of mating factors; however, it it may not be accurate to assert that tehey "are completely irrelevant from [one's] genes"; furthermore, that there are other factors involved in selecting a mate or in breeding does not negate the impact of natural selection on inheritable traits; evolution will continue, albeit slowly. Philc also correctly notes that modern medicine has indeed lessened the impact of evolution on removing many deleterious genes, though those affected may have fewer children. Finally, one cannot ignore the effects of sexual selection. For instance, a woman who tends to choose mates by whatever criteria (wealth, career success) that may cause a family to be successful will be more likely to pass on her genes; the same goes for men of course. Having the un-selected organism die or fail to breed is the extreme case; much of evolution has worked in degrees. Successive generation have evolved not necessarily because other organisms were dying or being killed or not reproducing, but becuase there were some who were just a little better at reproducing, who could perhaps obtain just a bit more food so that one in a thousand, or a million, would produce one additional offspring. Average over a few million years and the result is evident. Evolution is slow—I'm not suggesting any X-Men–style changes in a generation—but make no mistake, it will continue. — Knowledge Seeker দ 19:43, 15 May 2006 (UTC)
I think I may be misunderstanding your point, as if I have understood it is quite flawed, in modern society surely advantages involved with reproduction would not come out until a mate has been selected, and nowadays mates are not generally selected until the subject is in their twenties to thirties, so regardless of how early a male becomes ready to reproduce, he still has little chance of reproducing until he is much older. If I have misunderstood your point it would help if you could provide some examples of these advantages you speak of. Philc TECI 19:51, 15 May 2006 (UTC)
I'm afraid I'm not understanding your question, but I agree that there are many people who do not have children until their third or fourth decade. — Knowledge Seeker দ 20:26, 15 May 2006 (UTC)
My point is that when choosing a partner, people are not aware of their potential partners sexual capabilities. And also that however early someone matures and is ready to have children, they do not until they ar married in general. Philc TECI 20:46, 15 May 2006 (UTC)
I'm not sure what precisely you mean by sexual capabilities, but potential partners don't have to be aware of anything at all—indeed, for most organisms today and of course throughout history, there is no awareness of differing qualities and their potential benefits. I'm not sure how many humans are married prior to having children, but I'm not sure it's relevant, either. — Knowledge Seeker দ 20:51, 15 May 2006 (UTC)
I was reffering to whatever you were referring to when you spoke of Humans that would evolve to be a little bit better at reproducing, I didn't understand what you meant, can you specify. Philc TECI 21:47, 15 May 2006 (UTC)
I will invite you to continue this discussion on our talk pages; if you find any information indicating that human evolution has ceased of course please post it here. — Knowledge Seeker দ 08:01, 16 May 2006 (UTC)

Sorry, but both of you are still making arguments that show you still fail to understand how simple the definition of evolution is: all it takes is a pool of genetic variation and a source of new variations, and differences in reproductive success of those gene variations. The population then undergoes changes in the varieties of genes expressed in living organisms. Everything else you are trying to load into it are arbitrary exclusions and special cases that show you dont grasp the basic concept, which is breathtakingly simple and powerful, and which operates in a thousand ways in the human population. alteripse 00:43, 16 May 2006 (UTC)

Alteripse, you are repeatadley reffering to mutation, and not evolution, which also recquires natural selection, something which I don't believe exists in the enviroment humans have created for themselves anymore. Philc TECI 17:50, 16 May 2006 (UTC)

To answer the original question, I would expect that, to go along with smaller jaws, wisdom teeth will slowly evolve out of existence (I don't have any, but maybe that's due to my total lack of wisdom). The elimination of the appendix may also occur eventually. While not many people die from impacted wisdom teeth or appendicitis, there are some, and certainly more than those who die from lacking wisdom teeth or an appendix, so I would expect these obsolete body parts to slowly evolve away. StuRat 04:02, 16 May 2006 (UTC)

Future human evolution depends on what selective pressures will be exerted on the human population in the future. Today we can overcome environmental factors (and even certain congenital disorders) at low cost to ourselves, so science can effectively eliminate a selective pressure faster than human could adapt to it, but then again global warming or a pandemic could set civilization back. Peter Grey 04:47, 16 May 2006 (UTC)

I imagine the areas we will (or are) evolve most quickly would be (in no particular order): the brain (e.g. see the controversial Flynn effect), the immune system (shaped e.g. by HIV, malaria, and other diseases), the liver (its the organ with the second largest amount of DNA dedicated to it, second to the brain. We're also producing lots of new toxins). As for more interesting morphological changes, I imagine our backs will develop new structures, as spines are pretty crappy for upright beings as they are (they seem much better suited to fish and quadrapeds to me) —Pengo 09:32, 16 May 2006 (UTC)

I picture a "properly designed spine" moving the spinal cord out of the spine and into something more like a notochord (a tough flexible tube) inboard from the spine. A tough, flexible, solid elastic column could then be placed inside the spine to keep it straight and eliminate the possibility of pinched nerves from misaligned discs. The problem is, I don't see an evolutionary path that would lead to this improved design. StuRat 05:48, 17 May 2006 (UTC)

And, Yes of course we're still evolving. Even in the most "modern" societies evolution still occurs. Someone who gets sick just for a couple of weeks due to a genetic "disorder"—and is unable to woo a mate or look after offspring—is going to pass on less DNA than someone without the disorder, that is on average, when we talk about a thousand generations, which is the type of timespan we use in evolution talk. No one has to be killed (or fail to "survive") for natural selection to occur. —Pengo 09:32, 16 May 2006 (UTC)

A woman is unlikely to have a child after two weeks, so the guy who was ill has hardly missed out, also seeing as once someone has picked a life partner they stay with them, the other guy still has the rest of his life to catch up, which is very likely if you ignore any outside factors. Philc TECI 21:45, 16 May 2006 (UTC)
Yes, it's unlikely to make much difference. And that was my point. As long as it is making some difference, over many generations the negative effect of the gene is multiplied and selected against. —Pengo 02:15, 17 May 2006 (UTC)

Lots of junk speculation and misunderstanding of evolution in these paragraphs. For example, the business about smaller jaws, larger heads, and less hair was speculation from the 1950s based on popular ideas of aliens that still gets repeated-- there was never any science behind it. Those of you who think conscious mate selection is a big factor are missing the enormously bigger factors-- the societies with sizeable numbers of people who think like that have very low birth rates and the selection pressure exerted by that type of process is minimal. Think of humans like any other population: where is the most reproduction occurring? Perhaps the most obvious near future evolutionary trend will be a reduction in the number of people with light white skin. Another will be selection for resistance to AIDS, at least in the african population, analogous to the selection for tuberculosis resistance in the European. Finally, to illustrate how futile this whole discussion is, how reproductively successful are those who write encyclopedias and argue about evolution? alteripse 16:14, 16 May 2006 (UTC)

Why what possible reproductive advantage does having darker skin have in a modern society? Maybe its a genetic advantage, but people don't look for those it a potential life partner, they have other things they look for. Philc TECI 21:48, 16 May 2006 (UTC)
He's implying that in the future, probably due to something related to climate change, people with extremely light skin will develop cancers at a higher rate and die off before making many offspring. Which is possible, but of course that doesn't take into account the bolstering sun-protection industry which will allow such humans to succeed like the others in our UV-filled posthuman future. ;-) --Fastfission 01:20, 17 May 2006 (UTC)
I took his argument to be that whites, being wealthier and better educated than the average world citizen, have a lower reproductive rate, so will ultimately reduce in population relative to the rest of the world. I disagree, however, as overpopulation in other societies will lead to higher death rates from starvation, war, and genocide (such as in Rwanda and Sudan), which are due in large part to population pressure in areas with scarce resources. Thus, their higher birth rate causes a correspondingly higher death rate. StuRat 05:35, 17 May 2006 (UTC)
Poorer people have a higher death rate. And people can have treatment to survive cancer. So it all evens out. Philc TECI 08:52, 18 May 2006 (UTC)
By this sophisticated statistical argument, a homeless kid has an equal chance of being a wealthy adult as does a child of a millionaire: the child of a millionaire will probably get some advantages but a kid who lives on the street has a better chance of picking up lost change on the sidewalk. If you can find even a single factor that would provide an advantage in the opposite direction, it all evens out, doesnt it Phil? alteripse 19:12, 18 May 2006 (UTC)

Phil still doesnt understand reproductive advantage and is trying to cram it into an unnecessarily small box. It means producing more offspring in the real world, nothing more complicated. People with darker skins greatly outnumber people with lighter skins and are reproducing at much higher rates, so the disparity grows each decade. Furthermore, intermarriage produces darker skins than pale white, not lighter, and the opportunities for intermarriage are rising not falling. Despite war, famine, etc, in Africa and South Asia I suspect the average human skin tone in 100 generations will be darker than the current average. Isolation and diferential selection pressures in different continents probably led to the marked color distinction to begin with, and will probably turn out to be a relatively temporary distinction in the long run (assuming the human race has a long run). Don't twist this into something I am not saying, or a complaint, just a prediction based on trends that seem quite unlikely to reverse (barring separation of the continents, reduction of travel, complete reversal of birth rates and socioeconomic status, etc). I doubt an average twenty human beings in 10,000 years will have as wide a variety of skin tones as we can current round up for an American TV commercial (unless we implant color genes or chameleon genes-- in which case green might be as likely as pale pink). alteripse 16:36, 17 May 2006 (UTC)

The increased birth rate is in LEDCs, it is just coincidence that most of these are mainly populated coloured people, see Demographic transition model, most LEDCs are currently in stage two, where the government has through medical care managed to drastically reduce the death rate, however large sectors of the population remain uneducated and continue having large amounts of children, it will require many years, but eventually the birth rate will drop too. So being coloured is not a reproductive advantage, however being uneducate, having no access to contraception, and having children with the belief about half of them can be expected to die (when now thanks to medical care most of them won't) could possibly be argued as a reproductive advantage, however this would not lead to evolution, as it is just a random array of people, who are not all uniformly better at something, or have some advantage that can be passed on. Philc TECI 21:16, 17 May 2006 (UTC)
And "coincidence" is what evolutionary science calls "contingency": it just happened to turn out this way even though one can imagine another course of events. And you still don't grasp that reproductive success is reproductive success: you don't get to say "that doesn't count as reproductive advantage if people with certain characteristics have more progeny than people with different characteristics". And you most certainly don't get to say that deliberate choices dont count as evolution! If gradual change in the mix of genes and characteristics in a population occurs because of differential reproduction rates, it is evolution. Take a course or read a book on this please. alteripse 19:05, 18 May 2006 (UTC)
How is this evolution, this is just an increased birth rate in a certain sector the the worlds population and demographic, soon it will pass, and there are no genes to last a show the advantage they had, this is just a variation, they happen all the time, populations are not static, if a rabit population increases slightly, there is no reason to expect rabbits to over populate the world by a million years time, these things even out. Which is my point, I agree with you on some aspects of reproductive success, though I disagree on a few examples or specific cases, but I feel that almost all things that lead to reproductive success in the modern world are completely unrelated to genes by so much that evolution cannot occur as the traits will not be passed on. Philc TECI 21:43, 19 May 2006 (UTC)
One last time: Evolution is a change in the distribution frequency of genes in a population that occurs because of differential reproductive success of the organisms passing on those genes. Period. That is all. You have tried to impose irrelevant distinctions because of human choice and activity, because of "coincidence", because you confused reproductive advantage with mortality, because you dont understand the difference between mutation and polymorphism, and because of an astonishing inability to distinguish large magnitude effects (like population birth rates) from small ones (like medical care of a rare disease). If you someday have learned more about it and review this exchange you will cringe; if you never learn enough to change your current opinions nothing I can say will make sense to you. I apologize if I have offended you, and I am sorry to have perseverated on this but so much stupid education policy, social policy, and even religious doctrine is based on misunderstanding of evolution that I couldn't let it pass without protest. People who wouldn't think of arguing about the molecular biology of DNA or the mechanics of a satellite orbit with someone who knows more about it will apparently defend their misunderstandings of this topic to the death. But I will stop. alteripse 23:32, 19 May 2006 (UTC)
The distibution of genes at best fluctuates, to a minor degree, there are no major changes as all the factors which give a reproductive advantage are unrelated to genes. Philc TECI 11:59, 21 May 2006 (UTC)

[edit] Java: Converting Strings to Arrays

Hello. I have an array of strings. I need to order this array alphabetically. I really have no idea how to do this, but maybe I've headed in the right direction: can anyone tell me how to extract the strings and convert them, especially the first letter of each, into an array of chars? Any help would be grealy appreciated. Thank you. --Chris 18:52, 15 May 2006 (UTC)

Use the Arrays class (http://java.sun.com/j2se/1.5.0/docs/api/java/util/Arrays.html see the API). It has a sort function: Arrays.sort(your_array); --Kainaw (talk) 19:01, 15 May 2006 (UTC)
Hey thanks for that. My friend helped me a little too, so I got it down. :) --Chris 19:15, 15 May 2006 (UTC)
If you need to keep that set of Strings always sorted, you'll want a TreeSet. --AySz88^-^ 04:53, 16 May 2006 (UTC)

[edit] Fruit

Why does fruit rot?

Try reading our article on decomposition. --Chris 19:15, 15 May 2006 (UTC)

[edit] What is this called?

What is it called when an animal can change it's sexuality when it's in an environment with only one type of sexuality so that it can breed.

Thanks

--86.134.85.23 20:21, 15 May 2006 (UTC)

Hermaphrodites, such as snails, can do that. -- Mac Davis] ⌇☢ ญƛ. 21:00, 15 May 2006 (UTC)
To be more precise, those that are always both sexes are called "simultaneous hermaphrodites" and those that change between male and female are called "sequential hermaphrodites". --Kainaw (talk) 21:19, 15 May 2006 (UTC)
If you want to be even more specific, sequential hermaphrodites may be further classified as protogynous (starting as female and then possibly changing into a male) or protandrous (starting as male and then possibly changing into a female). Clownfish are a popular example of the latter. --David Iberri (talk) 21:38, 15 May 2006 (UTC)

[edit] hearing of a sperm whale

what is the lowest and highest frequencies that a sperm whale can hear, i've checked the sperm whale section but can't find anything on hearing. Thanks

--86.134.85.23 20:37, 15 May 2006 (UTC)

The whale song article has some info on the hearing range of other types of whale. Maybe you could download a sperm whale song and look at the frequencies present in the file, (provided the compression hasn't chopped anything significant out) I would guess that sperm whales could hear most of the noises that they produce themselves. JMiall 23:22, 15 May 2006 (UTC)

Considering humans can hear sounds in the range of 20Hz to 20,000Hz, whereas they can usually only produce sounds withing the range of 85Hz to 255Hz (these are very bad figures, but they serve my point), I would assume sperm whales can hear a large range of sounds that they are unable to produce. freshgavinΓΛĿЌ 06:07, 17 May 2006 (UTC)

[edit] Bird Droppings. Not from the rear but from the mouth.

I have just finished a new concrete driveway and since spring I cannot keep it clean. Everyday i come home from work it is completely covered with what seems to be bird droppings. However, after cleaning the driveway off so my children can play on it, I sat and observed. These birds are flying overhead with what looks like a little white ball in their mouth. They glide over the driveway and drop it, splattering it all over my driveway. What is this that they are carrying and dropping on my driveway?

Thank you for taking the time to look for this answer. I have been all over and noone can give me an answer.

Brian Wardlow [email removed for privacy]

weird. Some kind of fruit?? -- Mac Davis] ⌇☢ ญƛ. 21:02, 15 May 2006 (UTC)

What kind of bird is it? What's your geographic location, and what sort of food is available around there that they might be carrying? Not that I personally would know the answer even if I knew that stuff, but someone else might. --Trovatore 21:10, 15 May 2006 (UTC)

Are these finches? Finches (as well as many other birds) clean their nests. They take the poop, roll it up into white balls, and then carry it away in their beaks and drop it elsewhere. Normally, they drop it in water - but they are easily confused by any reflective material on the ground (especially shiny cars). --Kainaw (talk) 21:21, 15 May 2006 (UTC)
Perhaps his driveway is marble? Or blue? freshgavinΓΛĿЌ 05:54, 17 May 2006 (UTC)
Remarkably, Wikipedia doesn't have an article on bird pellets, nor any mention in pellet of this important behaviour. Birds including owls, hawks and herons will spit up what they couldn't digest. If these "droppings" are fairly firm, and contain things like bones, then they are probably pellets. You can tell a lot about the bird and its diet from them, if you like that sort of thing, and there is a market for owl pellets. There is a little on this in owl. Notinasnaid 21:27, 15 May 2006 (UTC)

[edit] May 16

[edit] Making Hydrogen

Will combining lye, amuminum foil, and water produce Hydrogen?Zoobtoob 20:41, 23 May 2006 (UTC)


[edit] Faster than light physics

Recently, the Toronto Star (Canada) had an article stating that just after the point of the Big Bang, in a trillion trillionth of a second the universe expanded to roughly the point where it now is. Given that Einstein stated that nothing can go faster than the speed of light, how is it possible for the universe to expand at a rathe that would have to be faster than the speed of light?

The nifty thing is that while no matter or energy can travel faster than light in its local frame of reference, there is nothing stopping that frame of reference (ie the geometry of space-time) to travel that fast. It actually provides a (very theoretical) means of super-fast space travel, if you can somehow cause the space around you to warp in just the right way. Confusing Manifestation 01:06, 16 May 2006 (UTC)
Hmm, that's a weird way of saying it, but I think you're right. Few people realize that, in relativity, the amount of distance you can cover in a certain amount of your own proper time is only limited by the acceleration you can produce (and survive). You could travel to the opposite edge of the galaxy in ten or twenty years of your own time if you had a rocket that could provide a constant acceleration of one g. Of course, the people back on Earth will see you always go slower than c, so from their point of view you won't get there for billions of years. See Twin paradox and The Relativistic Rocket. —Keenan Pepper 03:25, 16 May 2006 (UTC)
You'll want to check out our article on cosmic inflation for more details. TenOfAllTrades(talk) 03:24, 16 May 2006 (UTC)
For the first question, see Cosmic inflation (short answer, it doesn't travel through space, space doesn't exist yet.) For travel , see Alcubierre drive. --GangofOne 03:28, 16 May 2006 (UTC)

Also Popular Science, http://www.popsci.com/popsci/aviationspace/d1e527098dcda010vgnvcm1000004eecbccdrcrd.html

What actually happened is that space between all the things in the universe increased (was created) at a rate faster than the speed of light, the things themselves did not move per se.

The cosmic inflation article is pretty thick with science, and it's hard to find any easy-to-understand analogies so I'll lay out this one (extremely general):
Imagine the universe as a spiderweb and at each of the points where the strands meet, there is some matter. At the beginning, the spiderweb was infinitely small, and suddenly the spiderweb expanded to about the size it is now. Since the matter never moved from its original position on the web (the fabric of space), it didn't have any problems obeying relativity and the speed of light. Essentially the only thing that changed (moved would be inappropriate) is the extent of the fabric of space. freshgavinΓΛĿЌ 05:52, 17 May 2006 (UTC)

[edit] cc in Automobiles

When a car has a spec like "1488 cc", what does that mean? J. Finkelstein 03:41, 16 May 2006 (UTC)

Cubic centimeter Raul654 03:42, 16 May 2006 (UTC)
Note that it's the same as 1.488 liters, which might be rounded to 1.5 L. StuRat 03:46, 16 May 2006 (UTC)
Yeah, but what specifically is that? Is that the size of the engine, how much empty space is in there? J. Finkelstein 03:48, 16 May 2006 (UTC)
It's the Engine displacement. -- Rick Block (talk) 04:14, 16 May 2006 (UTC)
Thanks. J. Finkelstein 04:18, 16 May 2006 (UTC)

[edit] Owl identification

Mystery owl
Enlarge
Mystery owl

I spotted the owl in this picture a few days back, and I can't figure out what it is. It's a largish owl -- I'd guess it's standing about a foot to a foot and a half tall in the picture, with a three-foot wingspan. It was in an area of mixed pine forest, fields, and wetlands, about fifteen miles outside of Spokane. Any ideas on what it is? --Carnildo 04:25, 16 May 2006 (UTC)

I suggest you ask user:Jimfbleak - he's our resident bird expert. Raul654 05:03, 16 May 2006 (UTC)
To my eye, that looks so fake its funny. But it may be some kind of owl.. -- Mac Davis] ⌇☢ ญƛ. 06:45, 16 May 2006 (UTC)
For sure, it's an owl. Not a Barn owl, not a Spotted or Barred owl... maybe an immature Short-Eared Owl? ---CH 11:47, 16 May 2006 (UTC)
That looks like a cuddly toy! Kilo-Lima|(talk) 19:03, 16 May 2006 (UTC)
I know, seriously. --M1ss1ontomars2k4 | T | C | @ 00:00, 19 May 2006 (UTC)
I'm also interested in which species it is, as we seem to have a photo of three owls of the same species on our fridge. —Pengo 01:37, 18 May 2006 (UTC)

To me it looks like a young eagle owl of some kind. Don't know what country you're in. Definitely a young owl.

[edit] non Volatile memory

Could you tell me how does ddrsdram is non-volatile in construction as ram's are volatile in nature?

I thought DDR SDRAM was volatile... See Non-volatile memory. —Keenan Pepper 05:00, 16 May 2006 (UTC)

If I remember correctly, all transistor-based memory is inherently leaky (and thus violatile). Raul654 05:02, 16 May 2006 (UTC)

I think you are mixing up SRAM and SDRAM. DRAM requires continuous refresh because the bits are stored in capacitors that continously discharge while in SRAM the cells consist of four transistors. Dr Zak 14:25, 16 May 2006 (UTC)
And BTW, for future reference the "D" in ram usually stands for "dynamic", meaning that it must be...er...dynamically refreshed. So it's volatile. --M1ss1ontomars2k4 | T | C | @ 23:56, 18 May 2006 (UTC)

[edit] vaned diffuser design in centrifugal compressor

sir/madam, i'm chandan a project trainee in hindustan aeronautical limited, bangalore.i'm in need of detais of vaned diffuser design in centrifugal compressors, please do the needfull. thank you.

I suggest you ask your boss, or consult an aeronautical textbook in your local library. — QuantumEleven 11:53, 16 May 2006 (UTC)

[edit] Solar Radiation (and wind) averages for Newcastle, NSW, Australia

I need to calculate some things for a project but I need some accurate measurements for Solar radiation and average wind speeds for Newcastle, NSW.

If any of you can help, that would be great. The solar radiation levels I need in the form kWh/m²/d in monthly or daily averages if possible.

Thanks Wayne

This site has monthly and yearly insolation data for Sydney and Brisbane. Perhaps you could take an intermediate value. Rmhermen 16:19, 16 May 2006 (UTC)

[edit] Compression

We know that air is compressible,water is not.Then how is the concept of pressure applicable to water?In case of air,it can be pressurised in a cylinder by a piston,but not water.. —The preceding unsigned comment was added by 210.212.194.215 (talk • contribs) 09:56, 16 May 2006 UTC.

IIRC, water can still be compressed, just not as easily as air. Dismas|(talk) 10:05, 16 May 2006 (UTC)
Perhaps you should think of it in a different way. If I squeeze a plastic bottle of water, I cannot compress it. But I am excerting force on the bottle, which means the water must excert a force on the inside of the bottle. The water is definately under pressure, as is evidenced by the fact that a tiny hole in the bottle would now cause the water to squirt out. Squeezing harder will increase the pressure, and will casue the water to squirt harder. -- Ec5618 10:13, 16 May 2006 (UTC)
As far as I know, being compressible is a property only found in gases. - Dammit 12:40, 16 May 2006 (UTC)
See this article: Physics of Water and scroll down to Water's Compressibility. –Mysid(t) 12:45, 16 May 2006 (UTC)
Being compressible is a property of fluids in general, surely? But liquids are generally far less compressible than gases because their molecules are closer together. If this were not the case, we wouldn't have to specify 'incompressible' for certain calculations.Skittle 12:51, 16 May 2006 (UTC)
That's negliable (sp?).
And to asker:You should see pressure (of air and water) not as compressibility but as force exerted by an amount of air/water. You can imagine that on the bottom of the ocean there's a whole lot of weight pressing on the subject. - Dammit 12:56, 16 May 2006 (UTC)
Water is compressible, but to a degree that's not apparent under everyday circumstances. While the figure that the website linked above cites looks to be about right, it should be noted that water compressibility has nothing to do with brake failure when brake fluid is contaminated with water. Brake failure caused by gross water contamination results from 1) corrosion of metal brake components and 2) reduced boiling point of brake fluid when mixed with water. (Brakes get very hot in operation—hot enough to boil contaminated brake fluid. Suddenly, you don't have nearly-incompressible brake fluid, but rather highly-compressible gas pushing on your brakes.) TenOfAllTrades(talk) 14:13, 16 May 2006 (UTC)
Water does not compress to any appreciable degree. However, although a change in volume might be too small to detect, water under pressure (force per unit area) has an energy density (energy per unit volume) equal to the pressure. Peter Grey 14:41, 16 May 2006 (UTC)
The fluid statics page would probably help with this question. Pressure is defined as the force normal to a surface. If you were to place a block of wood inside a piston and apply a downward force, the block of wood (at rest) would apply pressure to the top and bottom of the cylinder, but not to the sides. If the piston contains a fluid then, according to Pascal's Law, the fluid at rest will exert an equal pressure normal to any contacting surface. The fluid exerts equal pressure on the sides of the cylinder (and any other surface) not because it is compressible, but because it cannot resist a shear stress (see fluid).
When there is a compressible fluid (such as a gas) inside the piston–then you need to exert the downward force through a distance; decreasing the volume and performing mechanical work before the fluid comes to rest. EricR 16:10, 16 May 2006 (UTC)
Water is compressible just like gas. The difference is that the compression, at the usual pressures we deal with, are so small that we cannot easily detect the change. It takes very large pressures to make small differences in volume. So in practice the approximation is made that water is incompressible.
For some scientific work that is not good enough. The compressibility of water is 4.59 x 10^-4 / MPa. At the pressures generated in the fluid column inside a laboratory ultracentrifuge (>30MPa), the density (mass/volume) can increase by > 1% in the solvent column. This means that incorrect determinations of sedimentation coeffiecients can be made, if the compression (increase in density) is not taken into reckoning. Which means you can incorrectly identify molecules. That is Not a Good Thing.
Also, if water were really incompressible, so that all of the water in the sea were equally dense, the seas would be about 30m higher, with loss of 5 million square km of land. --Seejyb 21:41, 16 May 2006 (UTC)
O yes, references: [56] and [57] --Seejyb 21:48, 16 May 2006 (UTC)
"A property of fluids in general". Men are compressible too. See Tax. --DLL 18:06, 17 May 2006 (UTC)
Basically, gases are much more compressible than liquids because the molecules in a gas start out much further apart on average, so it's easier to compress. However, in a liquid the molecules are already pretty close together. So it's harder to compress. --M1ss1ontomars2k4 | T | C | @ 23:58, 18 May 2006 (UTC)

[edit] Neural network

How do non-living neural networks that can continously learn and adapt like their living counterparts work?Ex:- logic gates are fixed and perform a fixed boolean function,they cant change the boolean function by themselves to suit the environment. —The preceding unsigned comment was added by 210.212.194.215 (talk • contribs) 10:00, 16 May 2006 UTC.

A neural network can't be composed solely of fixed gates, some switches are required. Computers are also typically used, rather than hardwired electronics. StuRat 04:39, 17 May 2006 (UTC)
Use the search box on the left hand side of the top of this page. Search for "neural network". I've just checked, and it takes you straight to your answer. --Hughcharlesparker 10:15, 16 May 2006 (UTC)
Neural networks are designed with a large number of parameters; the behaviour changes whenever the parameters are adjusted and the calibration of the parameters represents learning. Often they can be adjusted automatically by a feed back algorithm. Peter Grey 14:45, 16 May 2006 (UTC)

Well i would like to know with an simple illustration how does the feedback change its main function...

The main function is the calculation it performs on the input, and outputs as a single signal. The main function changes whenever anything within the network does. Backpropagation (not feedback) changes the calculations within the net, so changes its function. Black Carrot 02:10, 23 May 2006 (UTC)

[edit] Test for determining the best way you learn

You know how there is different ways of learning (visual, auditory, kinesthetic etc) is there a set of questions or a app online to determine your domonent form of learning?

See learning styles, and particularly the criticisms section, for why this stuff is controversial. (My personal stance is that the practical effects of its use are good, but the "theory" behind them is pseudoscience that goes way beyond the available evidence and runs the risk, like so many personality tests, of assuming that people can only do things their "natural" way).
If you're desperate to tick some boxes on a web form, google for "learning styles" -- there's plenty of stuff out there. However, some of it wants you to pay before it will tell you what pigeon hole you should force yourself into it, which to me is emblematic of the movement's snake-oil-salesman nature. --Bth 12:54, 16 May 2006 (UTC)
Is the article definitive, because my learning style doesn't match any of those things... Philc TECI 21:52, 16 May 2006 (UTC)
It'd definitely an area of on-going research, so it probably isn't 100% conclusive (as if any field of science is). freshgavinΓΛĿЌ 05:37, 17 May 2006 (UTC)

[edit] Ibuprofen

Why is Ibuprofen always pink in colour ? In all dosage form?

Tulsi A Shulka - 3rd year pharmacy student at Mumbai, India

The ibuprofen I have at home (USA, from the CVS/Pharmacy drug store chain), is a small white caplet. --LarryMac 14:18, 16 May 2006 (UTC)
I'm assuming they mean the liquid stuff. The likely answer is something to do with branding and making the product appeal to customers, though i'm not so sure if that's a good idea. -Benbread 16:57, 16 May 2006 (UTC)
Brand identity. As you know, ibuprofen powder is white, as is the solution in alcohol. Manufacturers of generics try to let the consumer feel that their product is in all respects as close as dammit to the original - I have seen the consumer trials they used locally to determine this for a beta-blocker. Specifically, it has nothing to do with regulations or the chemical properties of the drug. Interestingly, the non-presciption (Over-The-Counter) form in my country is an off-white tablet, while the prescription form (same strenght, same manufacturer, different name, different schedule!) is that typical bright pink. --Seejyb 19:23, 16 May 2006 (UTC)

[edit] how the scientists discovered that earth is spherical?

how the scientists discovered that earth is spherical?

Well, a really big hint was the fact that the earth's shadow (as it appears against the moon) is round, which is why the moon appears as a crescent most nights. It was already well known (from observing the motion of stars) that earth rotated on its axis. The only thing that is round when it rotates is a sphere. Raul654 15:12, 16 May 2006 (UTC)
The fact that the moon appears as a crescent on most nights has nothing to do with the shape of the earth. It has all to do with the relative position of the sun shining on the moon. I'd suggest you completely ignore the first post. Loomis51 11:19, 17 May 2006 (UTC)


See Flat earth and Eratosthenes. Rmhermen 16:00, 16 May 2006 (UTC)
Um, isn't the Earth's shadow shown on the moon only during a lunar eclipse? Notinasnaid 16:15, 16 May 2006 (UTC)
There is the undocumented and likely European-created false claim that Columbus knew the Earth must be round because ships sink over the horizon instead of just getting smaller. It is far more likely that formulas for explaining the movement of the other planets only worked with a round Earth. --Kainaw (talk) 16:37, 16 May 2006 (UTC)
Columbus wasn't a visionary who believed the world was round contrary to popular belief that he would sail off the edge. Educated people at that time accepted the world was spherical, based on work done by the Greeks. Columbus just disagreed about the diameter of the Earth; in fact he was wrong. Notinasnaid 16:40, 16 May 2006 (UTC)
Didn't some Italian quite a while back do an experiment with a pendulam, and over a very long period of time the swinging proved that the world was round or something, and Also that the ancient greeks using sun dials at very different locations measured the tiny difference in the shadow and proved that the earth was round as well. I'm not sure about these, and I can't find the articles to back me up sorry. Philc TECI 18:11, 16 May 2006 (UTC)
You're probably thinking of a Foucault pendulum. While such a pendulum will demonstrate that the Earth rotates, Foucault didn't perform his demonstration until the nineteenth century: well after the Earth's shape and rotation were firmly established. TenOfAllTrades(talk) 18:17, 16 May 2006 (UTC)
Vincenzo Viviani, although the Frenchie is the more famous one. The Greek chap was Eratosthenes. HenryFlower 18:19, 16 May 2006 (UTC)

The earliest experiment to determine that the Earth was round and find it's approximate diameter was to note the difference on the angle of shadows from a fixed length pole observed at noon at two points along a north-south axis on the Earth. Observing the difference of angles and knowing the distance, it's then just a bit of geometry and trig to find the Earth's diameter. "Noon", incidentally, meant when the Sun was at it's highest point (when shadows were shortest), prior to adoption of time zones (which mess up everything). This experiment was done by an ancient Greek, Eratosthenes. StuRat 03:38, 17 May 2006 (UTC)

It's Eratosthenes, as mentioned above. Noon still does mean when the sun's at its zenith, more-or-less—equalizing the time zone shouldn't change it by more than 7.5 degrees or so. Now Daylight Saving Time; that will definitely ruin your day. — Knowledge Seeker দ 03:44, 17 May 2006 (UTC)
Well, time zones can put you off by up to half an hour at the two edges, and more than that in the case of oversized time zones (like the Eastern Time Zone in the US). Daylight Savings Time can then throw you off by another hour, so you could end up off by close to two hours, in some cases. StuRat 05:03, 17 May 2006 (UTC)
Im am going to have a quick look but i think the first person to find the earth was round was an Egyptian that on the solstice or equinox he could look into a well in his city and see to the bottom, but in a different city you couldn't. Using a pacer (they actually had people who would walk from one place to another to measure it) and some very simple trig, he figured out that not only the earth was round, but also the diameter. This information was forgotten and then relearned many years later. (I just remembered the book its from so I'll repost this more accuratley later) Zoobtoob 20:25, 23 May 2006 (UTC)

[edit] Canting water gives weird horizon?

Wow, bad title. Anyway! I read somewhere, I can't remember where, about some kind of physical phenomena. To prove it, there was a picture of a rectangle-shaped box of plastic filled with water, seen from the side. Apart from at the sides, due to tension, the horizon of the box was flat, as one would assume. However, in the next picture, the box had been tilted slightly, and the horizon was broken off near the middle, so that the water on the higher elevation was above! Like... |_ _ _ _ ,.--------| Any help would be wicked! Henning 16:32, 16 May 2006 (UTC)

I'm not sure what you're asking ... are you talking about a meniscus? --Ginkgo100 20:21, 16 May 2006 (UTC)
Maybe refraction?... —Keenan Pepper 22:26, 16 May 2006 (UTC)
Have you considered rereading your messages before you post them? If I understand you (big if), you're saying that there was a tub of water, with the water nice and flat; next, there was a tilted tub of water, with the water forming two more or less flat surfaces and a step between. The only thing I can think of, assuming it's really water you're thinking of, that there wasn't any foul play with Photoshop, and that there wasn't a cleverly hidden barrier between the two sides, is that they tilted it fast enough to form a wave and took the picture at just the right moment. What physical phenomenon this demonstrates I can't imagine. Black Carrot 02:32, 17 May 2006 (UTC)
If the water is moving qute fast, you can get an effect known as a standing wave where the flow suddenly changes from laminar to turbulent. The depth of the water increases at this point, and can look a bit like you describe.--Shantavira 07:12, 17 May 2006 (UTC)
Erm ... Shantavira, you might want to read through the article on standing waves that you linked to. They have little to do with laminar/turbulent flow. Standing waves can even exist in non-fluid wave carriers such as the string of an instrument or a spring. --Swift 11:54, 18 May 2006 (UTC)
@Black Carrot: Yes, you understood perfectly, and it made equally little sense to me. Whether or not the cube was tilted at a speed didn't seem to be of any importance, as the cube in the second picture was held tilted by some box put under one end, implying there water-horizon kept its... skew, despite the tilting motion coming to an end. I look forward to having access to the library of my school on Monday, to investigate further. Henning 15:09, 20 May 2006 (UTC)

[edit] Candles

Whats the proper way to maintain a cande? Particularly one thats incased in glass. Should I scrape the sides if theres its only burning in the middle? Should I dump out the hot wax? etc.?

Don't dump the hot wax out of the candle (unless you want it for something). This is the fuel, what makes the candle burn. Any wax you remove will shorten the time for burning. Most candles need no maintenance: all of the wax eventually melts and turns into fuel. However, trimming the wick if it gets too long can help: see candle. The main thing with candles is to make sure they can't be knocked over. Notinasnaid 18:14, 16 May 2006 (UTC)
I'd start with safety: does the candle look like it's burning with a nice even flame? If it is, I wouldn't mess with it. I wouldn't go playing with hot wax. Certainly don't pour wax down the drain or you'll get a clog (sorry if this is too obvious...) If the flame gets too big then maybe trim the wick. Other than safety, do what looks good! If there are thick sides so you don't get the light you want then try cutting them after the wax has cooled down. If you find you have a high maintenance candle buy another kind the next time. A good candle maker will have taken care of everything for you: good wick material, good wax, right candle thickness so it burns just right. Weregerbil 18:18, 16 May 2006 (UTC)
I don't know exactly what kind of glass you are talking about, but with candles which sit on glass pedestles it is important to make sure they don't burn all the way down, or the glass will burst. --Fastfission 01:11, 17 May 2006 (UTC)
Wow, a candle holder that shatters if exposed to candle temperatures, that's pathetic. Why not make a flammable or explosive candle holder, while they're at it ? StuRat 03:27, 17 May 2006 (UTC)
Whether it's pathetic or not, I agree with Fastfission - some candle holders will crack (I haven't had one explode on me yet, but several cracked ones) when exposed to too much local heating. It makes sense - a small part of the glass is subjected to a high temperature (about a hundred degrees C or so, I would guess), while the rest is at ambient. The glass expands locally, and since glass is brittle, it may crack or shatter. Just be careful. — QuantumEleven 09:08, 17 May 2006 (UTC)

[edit] Food pyramid

What exact quantity of food do they mean when they say 4 portions?

In the United States, there is a required USDA label on packaged foods that is required to clearly define what a portion is. It is different for each product. --Kainaw (talk) 19:47, 16 May 2006 (UTC)
Isn't a portion a serving? -- Mac Davis] ⌇☢ ญƛ. 21:11, 16 May 2006 (UTC)
This comprehensive USDA document, written for educators, defines portions. --Seejyb 01:19, 17 May 2006 (UTC)

[edit] Airport X-Ray Exposure

I have tried without much success to find an answer to this question. I've asked a number of people, including doctors and physicists.

Everyone knows that we run our personal carry-on belongings through x-ray devices which are said to be quite benign. My concern is with prescription medications, some of which contain organic substances. My situation is unusual in that I fly a lot, usually twice a week. So I am running these items through that x-ray device at least twice a week, sometimes more. I'm not worried about the radiation, but about possible damage to organic compounds.

Are there any studies about the cumulative effect on organic compounds of this type of exposure to radiation? Natuarlly I am just a little skeptical about swallowing drugs that might have been altered slightly due to this type of exposure. Lately, I have taken to cramming them in my pants pockets so that they are only exposed to the metal detectors, but this is not an optimal solution. ------------- 148.165.17.120 20:08, 16 May 2006 (UTC) Thanks, Far Too Frequent Flyer

This is a suggestion, not an answer, but maybe it's helpful: put the pills (in bottles, or out of them) in a metal box. You may get your bag searched because of the opaque square on the x-ray, but they're probably not going to x-ray them again just out of spite. --Tardis 20:29, 16 May 2006 (UTC)
It's a good question. A lot of drugs are sterilized in their packaging by radiation, so those drugs have been tested to not form any toxic products from the effect of radiation. But for the rest, it's quite possible. However, I wouldn't say it's probable; The intensity of X-ray scanner radiation is very low (less radiation), the density of drugs is also low (less radiation absorbed) and the amount of active substance in drugs is also very small. So I think it's very improbable that any amount of the drug would be affected (if it is affected) in quantities significant enough to cause any adverse effects should the product be toxic (another if). Or you could follow Tardis' suggestion. --BluePlatypus 20:45, 16 May 2006 (UTC)
I don't think the X-rays will hurt your pills. There is enough mass in the pills for them not to be significantly affected. -- Mac Davis] ⌇☢ ญƛ. 21:13, 16 May 2006 (UTC)
In case you're wondering, the reason living people should avoid X-rays and other ionizing radiation is that damage to DNA can cause errors in replication that can multiply and cause cancer. Your pills aren't made of living cells, so there's no way the tiny amount of damage can spread. —Keenan Pepper 22:24, 16 May 2006 (UTC)
I would not worry about this myself, but there is a very simple way for YOU to

find out if YOUR pills absorb THESE particular X-Rays: Next time you fly, put your medicines in one of the little trays provided by airport security, and place that separately from all your other possessions. Then make sure to get through the metal detector BEFORE your little tray comes through the X-Ray machine, and watch the screen of the operator. If you can't see your pills on the screen, they have not absorbed any radiation at all and no damage could possibly have taken place. In fact, it would even be better to remove your pills from any container or packaging, as the latter may well absorb more than the pills themselves. Once you find out, you may want to report your findings to all of us... Hope this helps you find peace with this issue. --Michel M Verstraete 22:38, 16 May 2006 (UTC)

Just because they're not visible on the screen does not mean they haven't absorbed "any radiation at all", it just means that they haven't absorbed enough to make a visual difference depending on the settings and sensitivity of that machine. --BluePlatypus 22:49, 16 May 2006 (UTC)
The FDA says: "The radiation dose typically received by objects scanned . . . is 1 millirad or less. The average dose rate from background radiation is 360 millirad per year. The minimum dose used in food irradiation for food preservation or destruction of parasites or pathogens is 30,000 rad." That 360 millirad is what you and your pills are getting every year just by being on earth, 1 mrad per day. So if you think that a mrad will affect your pills, subtract 1 day from the expiry date for every pass through the machine, while realising that expiry dates are very conservative. Also: the 30,000 rad used for food sterilisation, 30,000,000 times the radiation from the luggage scanner, does not adversely affect the food value. There is practically zero chance that your pills will become dangerous from being scanned, or about as much chance as if you kept them in the cupboard at home. Keenan's point about cancer is important, there is no (as in zero) chance that you can pick up any sort of radiation injury or illness from the pills. --Seejyb 23:01, 16 May 2006 (UTC)
Going with the 1 millirad dose, your drugs are going to be quite safe. 1 millirad is equivalent to a deposited energy of 10 microjoules per kilogram of material. You're just not going to be able to do significant amounts of chemistry with that tiny amount of energy.
Ionizing radiation only kills living things because DNA is so exquisitely sensitive to damage—and to kill human cells you need more than a hundred thousand times the dose your pills get. To drive appreciable amounts of chemistry – that is, enough to bring about chemical changes in perhaps a hundredth of one percent of the molecules in your pill – you'd probably need another couple of orders of magnitude beyond that.
So, briefly, your pills have nothing to fear from the airport x-ray machines. It would probably be cruel of me to observe that your radiation exposure is increased just by flying. Being above much of the Earth's sheltering atmosphere will increase your radiation exposure by anywhere from 0.3 to 0.8 millirad per hour [58], depending on the solar cycle and your altitude. TenOfAllTrades(talk) 04:10, 17 May 2006 (UTC)
Wow, only 1 millirad. That's almost nothing. -- Mac Davis] ⌇☢ ญƛ. 07:32, 17 May 2006 (UTC)
Airport scanners are very very low radiation indeed. Mainly to avoid them damageing photographic film! Hospital x-rays at least conventional film based ones are a LOT STRONGER! Plugwash 16:51, 23 May 2006 (UTC)

[edit] Flat Discs and Long Sausage dogs

A human being becomes shorter in the course of a day, due to compression of the intervertebral discs. This is associated with dehydration of these discs. Now: a Daschund, sleeping all curled up through the night, compresses the intervertebral discs. While walking in the course of a day, the hanging body, curving convexly downwards and supported only at the shoulder and pelvis, could conceivably cause a distraction force between the vertebral bodies, "thickening" the discs. Does a Daschund grow longer by day, or "sag" more? --Seejyb 22:05, 16 May 2006 (UTC)

The difference in height of a human during the day is very small, to the point that you could argue that the minute shrinkage is due to something all-together unrelated to the spine (your hair got oily during the day and flattened to your scalp more). The difference in each disc would be a tiny fraction of the overall shrinkage. So, in something as small as a daschund, it is very unlikely you'd notice any thickening or shrinking of the discs throughout the day. --Kainaw (talk) 23:15, 16 May 2006 (UTC)
Actually, a study on diurnal variation in intervertebral disc height mentions that "the observed normal diurnal loss of height has been shown to be 17.00mm". Another site mentions that "[s]tudies show that the average young adult shrinks about 2 centimeters during daily activities" and that "Scientists estimate that astronauts gain three times as much height in space". --Swift 12:19, 18 May 2006 (UTC)
I imagine muscles would also play a major role. As you tire towards the end of the day, your muscles may not hold your back and shoulders as straight as they would be when you are fully rested. freshgavinΓΛĿЌ 05:27, 17 May 2006 (UTC)

[edit] Feeding the gulls - how much is too much?

(I posted this on usenet yesterday but no-one has responded yet. Thought that I'd try asking the nice folks here... :) )

I threw out a big pile of bread and ham for the gulls this afternoon. 'My' great black-backs came down and proceeded to chow down - carefully picking out all the pieces of chopped ham and leaving the bread untouched.

I'm certain that because I feed them several pounds of food (I have a deal with the local butcher for off-cuts, which I cook up for them, plus they get anything edible that I don't manage to get through) on a daily basis, they have realized that they can afford to be picky.

Serious question time. I've noticed that my four 'regulars' (one hand-raised by me as a baby and three others that have come to somewhat trust me) have started looking fat. They're getting very 'wide' and stocky-looking and you can see the ridge down the middle of their chests with the meat bulging on either side - in other words, they're getting to be right oven-stuffers.

I enjoy watching the gulls at close quarters but I don't want to make them lazy and unfit by overfeeding them, or make them too reliant on a human for food - do you think that I should stop feeding them completely? Is it a bad thing for a gull to be overweight? Will they actually come to rely on me completely for food and decide not to bother looking elsewhere if I continue? On the other hand, they're probably laying/raising chicks now and I don't want to do anything that could result in the neglect/death of the youngsters.

I'm a bit worried about them now. Don't laugh - I've grown quite attached to these birds now, especially the one I raised pretty much from the egg (she's grown into a huge, strong, magnificent bird now and has raised several clutches of her own chicks - yet, she's never completely forgotten me and for the last ten years has returned to nest on the rooftops near my house and hang around my garden).

Any advice would be appreciated, guys. :) --Kurt Shaped Box 23:06, 16 May 2006 (UTC)

From my stock of useless information: The falcon can suffer from gout if fed too much meat (I think that's the culprit). If you can make something of this then maybe the info was not that useless :) --Seejyb 00:43, 17 May 2006 (UTC)
Gout is caused by excess consumption of rich organ meats. StuRat 03:11, 17 May 2006 (UTC)
Hmmmm. I didn't know that. I thought that falcons ate nothing but meat?
As for the gulls, I'm more worried about them suffering from heart problems because they are overweight - I think I've been 'killing them with kindness'. It's kinda spiralled out of control recently - the more I feed them, the more they come to me and stand there begging for food, so the more I feed them. I get the distinct impression that they just eat their fill, go off somewhere to let it settle, have a nap for a couple of hours, then come back for more. --Kurt Shaped Box 01:34, 17 May 2006 (UTC)
I think it's a very bad idea to feed any wild animals, for the reasons you listed, such as them growing dependent on you for food and losing their natural survival skills. Their chicks, for example, are probably only taught to go to your backyard pile when they are hungry, and not shown any other way to find food. Eventually this will also lead to an overpopulation of gulls. That is, there will be more gulls than could survive on the natural sources of food in that area alone. This may have already happened. Wild animals can also develop a sense of "entitlement" and become aggressive if they don't get the food they feel they "deserve" (their is an obvious analogy to a welfare state here, don't you think ?). However, now that they are dependent and perhaps have an overpopulation, the issue comes up as to how to get them off their addiction to easy food. You could have them go "cold turkey", but there would likely be a major die off that way. Assuming you don't want this to happen, I suggest you slowly taper off with a goal of eventually getting down to nothing. You will likely see a lot more fighting over food, and a few of the those less able to compete may still die, but the majority should hopefully survive this way. So, to summarize, you now seem to realize that you were "killing them with kindness", but it may be too late to avoid it now. One question, don't your neighbors object to all the squawking and pooping gulls you attract ? StuRat 03:04, 17 May 2006 (UTC)
I doubt that there'll be a 'major die off', as it's only really four gulls that frequent my garden for food. I have grown to recognise them by their behaviour towards me (one of them is completely unmistakable as, like I say - I've known her since she was a little fluffy chick, she still acts like a baby gull around me and she'll take food from my hand, which is how this thing started, with me 'looking out for her'. The other three turned up later and are the only ones that will allow me to stand anywhere near them) - they're also the only *really* flabby ones. They don't let the rest anywhere near for the most part. TBH, they're beginning to take advantage of by better nature - as soon as it starts to get light, they're stood near my back door, whining and begging. Thanks for the tips, anyway - I'm going to take your advice.
The neighbours don't seem to mind, btw - it's a serious 'gull area' around here. They nest all over the rooftops and a lot of people feed them - just not to the extent that these four are getting pampered. --Kurt Shaped Box 06:32, 17 May 2006 (UTC)
One other negative effect of feeding them is that they may lose their natural fear of humans. This could leave them as vulnerable as the now extinct dodo bird. StuRat 03:11, 17 May 2006 (UTC)
Somehow, I just can't imagine gulls ever completely losing their fear of people - they're way too smart for that. They have as much contact with humans as the street pigeons around here, yet they are always very suspicious of us. Three out of the four will hang back when I go into the garden but they won't let me get any closer than about 12' away. The fourth ('my' gull) will vanish immediately if she sees anyone else besides me watching her and will not approach me unless I'm alone. I'm pretty sure that she thinks I'm her mother or something - or at least knows that I've always been good to her. She definitely recognises me, as she'll sometimes approach me when I'm on the other side of town and start clucking and flicking her head, begging for food. --Kurt Shaped Box 06:32, 17 May 2006 (UTC)
On the falcon getting gout from too much meat: yes, they may eat only meat, but in the wild a balance is reached, because it probably won't bother to hunt when it has eaten enough. People who keep hawks to fly them for hunting or display will start the day by weighing their bird. As little as half an ounce (14g) of weight difference will decide whether the bird does what it is required to do, or whether it will just go and sit in a tree until it is hungry again. People who keep birds of prey just to look at may not be so precise, and could easily overfeed; if they do not feed entire animals (skin bone and all) the hawk can also suffer from dietary deficiencies. Notinasnaid 09:16, 17 May 2006 (UTC)

[edit] Suspended Animation in Fish

I recall tales of fish found frozen solid in ice, that become "alive" when thawed. I cannot find estimates of how long the creatures have been in suspended animation. Where would I look for information on this? Thanks --Seejyb 23:20, 16 May 2006 (UTC) Think or thwim

Since the cellular damage is mostly done during the freezing process, not while frozen, the length of time wouldn't particularly matter if the fish is truly frozen. However, if the fish possesses something equivalent to antifreeze, it may remain unfrozen even though contained in ice. In this case, it is in more of a deep hibernation state, and the time it can survive in such a state is limited. Perhaps someone else can enlighten you to the actual time limits observed. StuRat 02:48, 17 May 2006 (UTC)
It's possible to freeze some organisms solid. These creatures secrete cryoprotectant compounds (often glycerol or glucose) that act as vitrifying agents — that is, they allow water to freeze in a glasslike state by disrupting the formation of large, destructive crystals. I don't know of any fish that freeze solid, though a number of reptiles and amphibians can do the trick.
Fish employ antifreeze proteins (and antifreeze glycoproteins) that act to depress the freezing point in their tissues by a degree or two. Since the salt water in the sea never gets any colder than that without itself freezing, the fish are protected. TenOfAllTrades(talk) 04:28, 17 May 2006 (UTC)
I am not familiar with frozen-then-thawed fish, but lungfish can be dessicated-then-rehydrated -- that is, a dried-out lungfish can be revived even after a long time. --Ginkgo100 03:31, 17 May 2006 (UTC)
Protection from dessication usually involves the secretion of the sugar trehalose. Our article gives a pretty good explanation of how it prevents drying damage to cells. TenOfAllTrades(talk) 04:28, 17 May 2006 (UTC)
But then the question is: Do the fish still remember who they are when they thaw out? freshgavinΓΛĿЌ 05:16, 17 May 2006 (UTC)
If I remember correctly, a fish has no long term memory (ala, the movie memento). Raul654 06:10, 17 May 2006 (UTC)
And if I remember correctly, fish don't even know who they are. freshgavinΓΛĿЌ 06:56, 19 May 2006 (UTC)
Interesting. If lungfish are resistant to dessication, one can predict that they could be resistant to radiation. True? --Seejyb 07:25, 17 May 2006 (UTC)
You're thinking of a different mechanism, that of say, Deinococcus radiodurans. Fish are resistant to dessication by means of trehalose secretion, while microorganisms tend to be resistant due to the prescence of certain metals — notably manganese. The latter also offers radiation protection, while the former does not. GeeJo (t)⁄(c) • 07:40, 17 May 2006 (UTC)

[edit] May 17

[edit] Weather QA

I've been currently requesting more articles on weather instruments and the study of meteorology, however, I cannot find a couple of detailed answers to my questions. Maybe you can be of some help to me:

  1. Weather is the sum of what five variables?
  2. What units is air pressure measured in?
  3. When the air has reached the ______ temperature, humidity is 100%.

—The preceding unsigned comment was added by 207.69.137.13 (talk • contribs).

While the latter two questions are answered in millibars, and dew point, the first one seems like a question based from a textbook, and is quite subjective. Titoxd(?!? - help us) 02:02, 17 May 2006 (UTC)
Millibars (or the equivalent hectopascals) is certainly what's always used in professional meteorology, though if you're watching television in the United States you may still hear the antiquated inches of mercury. EWS23 | (Leave me a message!) 02:09, 17 May 2006 (UTC)
Can you at least paraphrase your homework questions? —Pengo 02:04, 17 May 2006 (UTC)
  1. Weather is the sum of what five variables? W , e , at , h, er
  2. What units is air pressure measured in? Pascal
  3. When the air has reached the ______ temperature, humidity is 100%. 100 degrees Celsuis.

If you are mathematically-inclined, you may want to visit the page on primitive equations. Your second question has been adequately answered. However, your last question is meaningless because an air parcel can be saturated at any given temperature (at least within the "usual" temperature range normally experienced at or near the Earth's surface) by adding more water vapor into it. If the water content of the air is fixed, and the relative humidity (a particular water vapor measure implied by the units you are using) is less than 100%, you will have to cool the air sample to raise its relative humidity until you reach the Saturation vapor pressure. --Michel M Verstraete 20:42, 17 May 2006 (UTC)

[edit] 802.11 Wireless

In what way does an 802.11 wireless repeater work? I suspect that doesn't make much sense on it's own, so: in my case I'm talking about an unwired box (specifically the Linksys WAP54G) configured act as a "wireless repeater" to another box (the same model) which is plugged into a wired network and acts as an access point. Does the repeater box act literally as if it's an extra aerial on the access point (which would be lovely), or is there a delay associated with the relay of the signal? What's the effect on performance? By performance I mean how does a client near to the access point perform compared with a client near to the repeater? I know the best answer to all wireless questions is "give up and plug some wires in" but unfortunately that's not an option here. Thanks a million. --87.194.20.253 05:45, 17 May 2006 (UTC)

I had to install several wireless repeaters (thick granite walls). What actually happens may be complicated, but you can just think of a repeater as a box that listens for wireless traffic, and when it gets some, repeats it. This way a transmission can reach an access point that is too far from the original for getting there directly. I found it awkward to set up with the model I have: each repeater has to list the Mac addresses of everyone it is willing to repeat for. I had performance problems until I made sure each repeater ONLY listed those that it could reach (I need a daisy chain of the things and the first one couldn't reach the last). Finally stable, the performance is adequate, mostly, for a couple of networked MP3 players in a distant part of the house. Notinasnaid 08:07, 17 May 2006 (UTC)

Thanks for this. Do you know what the behaviour of a client that can "see" both the original access point and a repeater would be like? Does it choose who to receive / transmit from? Thanks again. --87.194.20.253 17:05, 17 May 2006 (UTC)

[edit] Alkali Metals

When reacting an alkali metal with Fluorine, Lithium has the greatest difference in electric potential and therefore will create the largest explosion, but when reacting the alkali metals with water, why is Lithium the least spectacular? Is it true that Cesium will have the strongest explosion? --Chris 06:44, 17 May 2006 (UTC)

Surely that would be Francium (if you could get ahold of a big enough chunk)? :)
That was always a common question in my chemistry lessons at school - "What would happen if you were to lob a piece of Francium in a tank of water?" One of my teachers told us that when he was in research, he once took the opportunity to drop a large piece of Rubidium into water 'to fulfill his scientific curiosity', (i.e. because he wanted to see it go 'boom'). Apprently, it exploded immediately, the tank shattered, the equally-curious onlookers got showered with glass and he got shouted at and ordered to pay for the damage. I guess that Caesium would destroy the worktop too (so, will anyone fess up to performing a caesium/water experiment? I'd like to know what happened, if only to satisfy my 'scientific curiosity')... :)
Sorry I can't be of more help with your question - it just reminded me of that story... :) --Kurt Shaped Box 07:06, 17 May 2006 (UTC)


That doesn't answer my question, and according to this video, cesium is too dangerous to be shown. :/ --Chris 07:14, 17 May 2006 (UTC)
It seems they said Francium is too dangerous, not Cesium, which is the second.... experiment. GOD, Brainiac is so brilliant. It might be worth to add, Francium is rare. I mean rare. The second most rare on the planet. At any time there is perhaps about a pound of it, divided on earth's crust. So, if we ever DO get a hold of a reasonable amount of it, Brainiac MUST HAVE SOME!!! God, can you IMAGINE the bang? If I was a science teacher, THIS is what I would do to make my students interested! Henning 09:01, 17 May 2006 (UTC)
Lithium has the most negative electrode potential because its smaller ionisation energy is cancelled out due to its smaller radius and correspondingly massive hydration enthalpy. With the reaction with water the main factor would be low ionisation enthalpy, and caesium wins hands down. There do exist video clips of this reaction, and I believe it to be quite impressive. I doubt whether the teacher dropped a "large piece of rubidium" into water unless he stole it, or was unrealistically rich - for a teacher, that is...G N Frykman 16:58, 17 May 2006 (UTC)
I guess that the guy could've been telling us all a tall tale but he claimed that he did it while he was working in some research lab or other many, many years ago... --Kurt Shaped Box 21:01, 17 May 2006 (UTC)
It is because of the increased amounts of electrons as you go down the period, the outer electron of the alkaline metals (the one that is removed in the reaction) is further and further from the atom nucleus, and so is held with less energy, and is therefore given up far more readily, allowing the reaction to take place with use of far less energy, leaving more for the boom. I think thats right. Philc TECI 21:08, 17 May 2006 (UTC)

[edit] Italics in Word

I have a Micro$oft Word file with _italic_ expressions represented by _underscores,_ like that. Is there some way of converting these to proper italics? I can think of several ways to do this outside Word (e.g. editing the rtf file with a text editor), but is it possible within Word?--Shantavira 07:55, 17 May 2006 (UTC)

Yes. Go to the Format menu; select AutoFormat. Check the Options to ensure that "*Bold* and _italic_ with real formatting" is checked (and that anything else you don't want changed is unchecked; choose OK. Then select either AutoFormat now or Autoformat and review each change, click OK, and voila! — Knowledge Seeker দ 08:02, 17 May 2006 (UTC)
Easy when you know how, eh? Thanks muchly.--Shantavira 08:47, 17 May 2006 (UTC)

[edit] Appropriate Source Technology Hand book.

Hi I am trying to find a copy of this book it was produced by the W.H.O. it was a hand book on low tech machinery for developing countries our local library had a copy but someone cut the section on solar heating out of it , then someone fell in love and took what was left of the book. It had pedal powered saws and pumps , also covered methane producing digesters for small scale production. Thank you Vince Collis (vincefish.)

I have never heard of the WHO book (it does publish the PATH series, but that relates to health matters in our 3rd world mostly), but I used The Field Guide of Appropriate Technology (Authors B Hazeltine & C Bull; Academic Press; 1st edition November 15, 2002; ISBN: 0123351855) from our local library as a source for a project , and was amazed and intrigued by the possibilities. I plan to buy a copy when I can. There is a very comprehensive source for finding more specific publications on the net, called The Appropriate Technology Sourcebook By Ken Darrow and Mike Saxenian. There is little that you won't find there. --Seejyb 21:49, 17 May 2006 (UTC)

[edit] Paper Project

For a school project I need to find out how to build a paper tower out of a manilla folder. It can be held only with glue and has to at least hold 100 lbs.

Are you sure you mean 100 lb? That's 45 kg. I can't imagine a paper tower hold so much. (What does the height has to be? Couldn't you just lay a single sheet of paper on the floor and call it a tower?) – b_jonas 11:05, 17 May 2006 (UTC)
You'd be surprised. I once saw what looked like a flimsy trusswork made out of toothpicks, weighing less than an ounce, hold 50 pounds. --Serie 20:24, 17 May 2006 (UTC)

You could probably make a 2 inch high honeycomb structure that would hold a spread weight of 100 pounds. If the tower needs to be a certain height, and a narrow aspect ratio, then it looks very, very difficult. --Zeizmic 13:03, 17 May 2006 (UTC)

It's impossible to build a paper towel out of a manila folder. Ohanian 13:08, 17 May 2006 (UTC)

I think it's about a paper tower, not a paper towel. :--) JackofOz 02:35, 18 May 2006 (UTC)
What you want to do is make rolls, a tube is the shape that can withstand the most force. You then place theses tubes next to eachother (and glue em together). Depending on the amount of folders you can use you can make it strong enough go hold anything. (And yes, I know this is similar to the honeycomb answer) - Dammit 14:29, 17 May 2006 (UTC)
If you could roll enough solid tubes, you could go from there. --Seejyb 14:19, 17 May 2006 (UTC)

I once constructed a working table (capable of holding my 75kg weight) out of corrugated cardboard. It's close to the tube idea, but uses triangular cross-sectioned lengths, guled together into a honeycomb-like pattern (six equilateral triangles into a hexagon, tower made of seven hexagons in 2-3-2 formation, so 42 triangular prism shapes in total). Grutness...wha? 01:42, 18 May 2006 (UTC)

Now, in a properly designed competition, there's usually a weight limit, or a materials limit, or both. Without that, what's to stop you from "holding" two pieces of folder about a foot apart with a block of hardened glue? Black Carrot 02:30, 18 May 2006 (UTC)

It has to be 4inces high and 4 inches in diameter

See this and try to get hold of the video - BBC built a 4-5 metre paper tower that a person could stand on top of... Ojw 19:44, 18 May 2006 (UTC)

[edit] iron removal hydrocloric acid

Dear sir, I have used this sie for first time. I am working with organization involved in galvanizing. I want to ask you how to remove iron from hydrochloric acid solution. Our seq. is Acid Degreaser, Hydrochloric acid, Water Rinse, Flux, Hot plate, Galvanize.

Can You please tell me how shall I remove iron from Hydrochloric Acid Solution.

Can Hydrogen peroxide treatment be used. I have found that using H2O2 give iron Oxide Precipitates which is very minute not easily pas out of the filtering media ( filter paper # 40) What i can use to filter the same.

Make the solution alkaline, either with ammonia or with sodium hydroxide solution. The vast majority of the iron, whether 2+ or 3+, will then precipitate out, and can be filtered off as normal.G N Frykman 16:47, 17 May 2006 (UTC)

[edit] Physics Question

Besides expanding, what else happens to a piece of wood in an oxygen-free room at 10000 degrees celsius? (Answer question on my Talk page ) Anonymous_anonymous_Have a Nice Day 13:13, 17 May 2006 (UTC)

At high enough temperature the bonds will break and the components of wood would float around in oxygen free air. Ohanian 13:40, 17 May 2006 (UTC)

Most of the organic compounds would be decomposed (but not combusted) to form simpler compounds. The process is called pyrolysis. See also thermolysis and dry distillation. --Ed (Edgar181) 17:10, 17 May 2006 (UTC)
At 10,000°C, would there be any sort of compound molecules left? And pressure would have to be consided in here somewhere. If the wood were suddenly introduced, and had enough mass, wouldn't the "room" possibly explode? --Seejyb 22:23, 17 May 2006 (UTC)
There's gonna be nothing left intact. Ten thousand degrees is hotter than the surface of most stars—the Sun's surface is less than six thousand degrees. Not only will the material be atomized, a good fraction of its constituent atoms will be ionized. You're going to get a plasma. In principle, the pressure in your container will increase when you add additional material; the stuff will behave like a gas in that regard. (Of course, you will also have to add heat; the pressure will drop as the room 'air' gets cooled by the addition of your wood.) TenOfAllTrades(talk) 03:08, 18 May 2006 (UTC)
Thanks Anonymous_anonymous_Have a Nice Day 16:35, 19 May 2006 (UTC)

[edit] staccato speech and breathlessness

My cousin is suffering from staccato speech and breathlessness. Is this a recognised medical condition, if so what is the cause and is there a recognised treatment

Please note at the top where it says "If requesting medical, dental, or legal advice, please consider asking a doctor, dentist, or lawyer instead." However you might want to look at the article on stuttering. --LarryMac 14:44, 17 May 2006 (UTC)

[edit] spear thrower

did a leather thong stone throwing sling serve as a spear thrower thanks

It would be difficult to use a sling shot as an atlatl. alteripse 16:24, 17 May 2006 (UTC)

While a leather thong designed for stone throwing would be useless as a spear thrower, there is some evidence of spear throwing techniques that did involve seperate, purpose-designed leather thongs. This article has one reference, and I seem to remember that someone -- maybe ancient javeliners? used leather thongs as a grip/tension device. --ByeByeBaby 06:49, 18 May 2006 (UTC)

[edit] Base units

write down the seven base units of "system international"(SI) with their unit and symbol?--86.62.237.139 16:41, 17 May 2006 (UTC)

Please do your own homework. However, you may be interested in reading our article on SI. EWS23 | (Leave me a message!) 16:44, 17 May 2006 (UTC)

Actually, this does sound like homework. It doesn't look good having us do your work in this way, and trying to palm old schoolwork off onto us isn't recommended. A lot of this info will be in any old text or almanac; don't come here with it. Keep this page for its proper uses. Grutness...wha? 01:57, 18 May 2006 (UTC) (Da Vinci code? Feh!)

[edit] Listing Species in Wikipedia

In Wikispecies you can list the species in a particular genus by the abbreviated format: G. species1, G. species2, etc. How do you do that in wikipedia?

please give us an example. I tried Canis (dogs, coyotes, wolfes) and the lists are not what you tell about. --DLL 17:31, 17 May 2006 (UTC)
Looks like he was answered on the Help Desk - looking for how to pipe links. Confusing Manifestation 06:13, 18 May 2006 (UTC)

[edit] How To Use CYM To Make Blck

My printer is a Canon i320 and the black ink has run out. Is there any way I can trick it into using the three colours to make black? My old Epson had either color or black, and if it had a colour cartridge it would *make* black. -Username132 (talk) 17:34, 17 May 2006 (UTC)

From the Canon FAQ: "When printing in grayscale or on special paper, although printing appears in black and white, the color black may be created using the three (cyan, magenta, and yellow) color inks." (emphasis added). Maybe you can go into the printer settings and tell it to print grayscale? On my Canon S300, that is just a checkbox on the properties page. --LarryMac 17:49, 17 May 2006 (UTC)
I think that setting does the opposte > turns everythng from using colour ink to using black ink. --Username132 (talk) 19:57, 17 May 2006 (UTC)
But did you try it? --LarryMac 20:01, 17 May 2006 (UTC)
I tried it. It didn't work. --Username132 (talk) 14:51, 20 May 2006 (UTC)
Usually it is CMYK, with the K being black. I was just looking at my own ink jet's black print yesterday. It looked like it printed all the colors. It was a grey.
C+M+Y mixed gives black. The reason why you've usually got a seperate black is that the three colors must be well-balanced to create a good black. This is all explained at CMYK. --BluePlatypus 23:34, 17 May 2006 (UTC)

In printing, one reason for K is you need to reduce the total amount of ink. Too much ink simply takes too long to dry. If you don't know exactly how much is too much, 270% is the rule of thumb (e.g. 90% C + 90% M + 90% Y + 0% K). Too much ink can lead to trouble. Good paper and slower printing may allow you to exceed this limit.

Let's say you want to print a rich black square on paper (spot color). If you only print 100% K on paper, this black square would usually be too thin to cover the paper. You need some CMY to make the 100% K even darker. Maybe you can try 56% C + 56% M + 56% Y + 100% K (total ink density = 268%).

You can also obtain a tinted black by adding a color to black. For example, 100% C + 0% M + 0% Y + 100% K gives you a very "cold" black.

It's good to use over-100% blacks. But misregistration can be a serious problem when you add colors to K. If you use C + M + Y to substitute black, you usually get an ugly muddy dark brown instead because inks are far from perfect. And a slight error in ink control would give you a tinted black.

If you know how to tweak Adobe Photoshop or similar software, you can control the amount of black to be generated by RGB to CMYK conversion. If you want to print using CMY only, just let it generate no black at all. -- Toytoy 00:07, 18 May 2006 (UTC)

Well I want to print out PDFs - how do I control the inks used for that? -Username132 (talk) 14:42, 18 May 2006 (UTC)

[edit] sound energy travelling through a vacuum

why can you not hear sound coming from something inside a vacuum?thanks --86.134.85.23 18:21, 17 May 2006 (UTC)

Sound is a compression wave - a travelling wave of compressed and rarefacted matter (usually air, although sound can travel through liquids and solids too). However, in a vacuum, there's no matter to carry the sound, so it cannot exist in a vacuum. Raul654 18:24, 17 May 2006 (UTC)
The same reason you cannot have a wave in the ocean without any water. (Note to pedants: yes, I know, but if I defined all the terms it would be confusing) Skittle 22:16, 17 May 2006 (UTC)

[edit] Universe = lab?

is it acyually possible that the world, our universe ect. is just some kind of scietific experiment made in a lab by some kind of special race or something like that, thanks --86.134.85.23 18:35, 17 May 2006 (UTC)

Yes, see The Matrix and The Hitchhiker's Guide to the Galaxy. But personally I don't think there's any point in believing in things like that, even if it was true. It doesn't lead me anywhere and I could spend the time better by living in this world. –Mysid(t) 19:20, 17 May 2006 (UTC)
See Forever Free (great book, the ending was *THE BIGGEST* letdown in all of literary history). Raul654 19:28, 17 May 2006 (UTC)
I think there were also numerous short stories on this (many probably by Philip K Dick), but one stuck in my mind. Probably by Arthur C Clark, but I forget. Anyway, it had a very bright scientist work out that not only were we some big experiment, but there was a sort of poisoned line marking the limits of how far we were supposed to go, like putting a line of antibacterial agent round a bacterial culture to make sure it doesn't spread. This led to him constantly, involuntarily, attempting to suicide. Fun. Anyway, it is perfectly possible. However, it would be very hard to prove or do anything about so you're just going to have to keep living as if it weren't true (the same advice I'd give regarding the world not being real or us not really having free will because we always do what we'll always do) until you receive some evidence to the contrary. Otherwise, madness beckons. Skittle 22:12, 17 May 2006 (UTC)
Asimov, actually. Though I can't remember the name of the story. EdC 22:37, 17 May 2006 (UTC)
You're probably thinking of the The Last Question, but that's not so much an experiment. Raul654 22:38, 17 May 2006 (UTC)
No, "The Last Question", while an excellent story, is different. I can't remember the title of this story, though the (fictional) scientist's name was Ralson, if I remember correctly. — Knowledge Seeker দ 22:42, 17 May 2006 (UTC)
Aha! Searching for "asimov ralson" reveals the title: "Breeds There a Man...?" — Knowledge Seeker দ 22:45, 17 May 2006 (UTC)
Excellent. Good work people. I'd wondered about Asimov, but didn't think it was quite 'him'. Skittle 13:17, 18 May 2006 (UTC)
There's also Send Her Victorious, by Brian Aldiss (it's in the collection "Intangibles, Inc.", IIRC. In this one the earth has been created as an experiment by a being known as "Queen Victoria"! Grutness...wha? 06:36, 18 May 2006 (UTC)
On a philosophical note (well, it's a philosophical question): Yes, it may be all one big lab. But can we know if it's a lab or not? And can we know if that lab is not actually just a lab inside a bigger lab? And so on. At this point I'd invoke Occam's Razor; Don't multiply the number of universes needlessly. :) --BluePlatypus 23:32, 17 May 2006 (UTC)
But how many are neccessary? Anyway, see: Edward Fredkin ,Digital physics, Digital philosophy ,Digitalism,

http://www.wired.com/wired/archive/10.12/holytech.html God is the Machine, Simulated reality, http://www.simulation-argument.com/ Are You Living In a Computer Simulation? The Simulation Argument Nick Bostrom ---GangofOne 02:59, 18 May 2006 (UTC)

I hate to be the one who brings up religion in a science board, but.... If you're Christian, God made the world for our spirits to come and learn the things we need to know. So, by that definition, the earth is not an experiment, but rather a test for our spirits. If you're Christian, that is. I can't be sure about other religions.

--Welcometocarthage

What kind of test is it when you already know the outcome? omnipotence, omniscience and omnipresence seem to render that kind of thing moot. If you fail, sie must have put you in circumstances where sie knew you would. Or maybe sie doesn't know and it is all an experiment. Skittle 21:20, 18 May 2006 (UTC)

[edit] Concentration of an HCl solution

I've got a new bottle of concentrated HCl, and I'd like to know the concentration. I know that concentrated HCl is normally about 12M, but I'd like to know the concentration a little more accurately. I looked up the certificate of analysis from the manufacterer and found that this batch is 37.1% (w/w) and has a density 23.0 degrees Baume (equivalent to specific gravity of 1.1885). Anyone know how to use one of these facts to determine molarity? (This isn't a homework question!) ike9898 20:00, 17 May 2006 (UTC)

OK, I think I found the solution ( [59] ). The formula is 10 * concentration [in terms of % w/w] * specific gravity, all divided by molecular weight of the solute. In my case this came out to be 12.093M. Let me know if you think this is incorrect. ike9898 20:28, 17 May 2006 (UTC)
Yes, we could tell that wasn't a homework question - you answered it yourself. --Hughcharlesparker 23:18, 17 May 2006 (UTC)
If we assume that the manufacturer's CofA is accurate to ±1 unit in the last digit of each measurement, you only get three significant figures for your concentration: 12.1±0.1 M. If you need more precision than that, you can get a good measure of concentration by titrating against a basic solution of known concentration. TenOfAllTrades(talk) 00:07, 18 May 2006 (UTC)
Good point, thank you. ike9898 13:40, 18 May 2006 (UTC)

[edit] Mukade

I'm trying to find the genus and species designation for the mukade, a type of poisonous centipede native to Japan. I've been unsuccessful on Google so far. Can anyone help? Thanks, — BrianSmithson 20:19, 17 May 2006 (UTC)

It probably doesn't help that "mukade" is the Japanese word for centipedes in general and not any specific species; the article at ja: is definitely general in scope, and interwikied to other general centipede articles. I'm having trouble finding reference to any centipede species peculiar to Japan, actually... —Zero Gravitas 21:29, 17 May 2006 (UTC)
You might try Wikipedia:WikiProject Japan. -- Rick Block (talk) 01:49, 18 May 2006 (UTC)
I bet it's just an instance of Westerners adopting a local word for something they don't have at home (giant centipedes). Though I'll be clobbered by the Japanophiles if I dared delete mukade. This image gives the name Scolopendra subspinipes mutilans for one species. Is this probably the same species? This may be the monster that scares the Westerners and which they have dubbed "mukade". — BrianSmithson 03:25, 18 May 2006 (UTC)
I'm willing to bet it was just an uninformed Westerner trying to make another article using Japanese words. The most common types of mukade here are poisonous (possibly the one from the picture, I've never seen one before), and many Japanese people believe that centipedes (mukade) are in general poisonous, so I'd be willing to bet that it's just a misunderstanding. Unfortunately nobody seems to know what the poisonous ones are called though. freshgavinΓΛĿЌ 04:28, 18 May 2006 (UTC)
I'll move this to WP:JAPAN, but I think the centipede pictures I linked to are of the Chinese red head: [60]. — BrianSmithson 12:41, 18 May 2006 (UTC)

[edit] A practical way to make azeotripic mixture of HCl and water

I want to make an azeotropic mixture of HCl and water from concentrated HCl. I suppose I can do this simply by diluting the HCl to the concentration of the azeotropic mixture (which I think is 6.102M). But I am wondering if there is a practical laboratory method to be more accurate. I was thinking that I could, for example, make up a 6M soln, and boil it in the fume hood. I suppose eventually enough water would boil off and the solution would be exactly the azeotropic concentration. No? I suppose I could monitor the temperature to know when I had reached that point. What would happen to the concentration if I made the starting concentration greater than that of the azeotropic mixture and then boiled?

(Again, this isn't a homework question...) ike9898 21:09, 17 May 2006 (UTC)

The azeotrope is about 20% (Equillibrium diagram [61]), concentrated HCl has a higher concentration than that, which is why it gives off HCl fumes. (Put a container of ammonia next to it and see the NH4Cl fog form from the vapours (alliteration not intended)). So boiling concentrated HCl would give off ammonia in far greater concentration than water, until its concentration has dropped to the azeotrope at 20% (or thereabouts). I don't see how monitoring the temperature would be a good way to do this. Monitoring the concentration would be the most obvious thing to do. (The definition of azeotrope is that, at that point the vapour and solution have the same concentrations - so the concentration stops changing once you reach the azeotrope.) --BluePlatypus 23:25, 17 May 2006 (UTC)
Monitoring T seems less laborious than monitoring conc. ike9898 13:44, 18 May 2006 (UTC)
Sticking an electrode into the solution isn't terribly laborious. --BluePlatypus 21:35, 18 May 2006 (UTC)
Do you think a garden-variety pH electrode can measure such a low pH accurately? (I calculate a pH of -0.76) ike9898 14:05, 20 May 2006 (UTC)
Glass electrodes don't give correct values for extremely low pH values ("acid error"). However, I don't think that's a problem since you're not really interested in the exact value of the pH, only that it is invariant. --BluePlatypus 06:09, 22 May 2006 (UTC)
Yep, since the HCl-water system forms a positive azeotrope (temperature maximum) you could just boil until your mixture reaches a constant maximum temperature. (About 108°C at one atmosphere of pressure). Of course, unless you collect and condense the vapour, you're potentially wasting a fair bit of perfectly good HCl. TenOfAllTrades(talk) 00:19, 18 May 2006 (UTC)

[edit] Well deary, let me tell you, my Jimmy and his mates marched London Bridge to bits..

When a platoon of soldiers approaches a bridge they "break step" and no longer march as though on parade because a march in unison could resonate with the bridge and cause it to collapse. Makes sense for the wooden structure over which farmer Brown drives his cows to pasture, but are there well-known world bridges where this could be reasonably possible (for use as an illustration in a talk, not for field testing!)? How would one go about calculating this? Could one give a high school student such a project? Would he/she have to approach a University Civil Engineering dept and do high-tech computer simulations, or is it simpler than that? --Seejyb 21:55, 17 May 2006 (UTC)

Well, the Millennium Bridge, or 'Wobbly Bridge', in London had this problem. So much so that shortly after opening, they had to close it to add dampeners and support structures. There was feedback from the slight wobble each person caused, leading other people to walk in step with them which increased the wobble. Skittle 22:04, 17 May 2006 (UTC)

The textbook example of resonance destroying a large structure is Tacoma Narrows Bridge, though the resonance was caused by the wind rather than traffic. GeeJo (t)⁄(c) • 22:51, 17 May 2006 (UTC)
List of bridge disasters mentions a bridge in Angers that was brought down by marching soldiers in 1850, killing 226; there's no WP article on the disaster but it's mentioned in an article here as well as this PDF. —Zero Gravitas 23:23, 17 May 2006 (UTC)
The millennium bridge did not suffer from this problem. Rather it had a slight sway and people swayed (unknownly) and caused it to sway even more. Mike (T C) 00:42, 18 May 2006 (UTC)
Yes, but that wouldn't have been a problem if the bridge hadn't had a resonant frequency near the frequency of human walking. — QuantumEleven 09:24, 18 May 2006 (UTC)
Even if there are no examples of large bridges that would realistically collapse from the resonation of a march, it makes sense as a maneuver because putting any stress on a bridge can cause slight weakening of the cables or supports, and in war-time you may be crossing structurally weakened bridges that, despite appearances, are on the very edge of collapse. freshgavinΓΛĿЌ 04:18, 18 May 2006 (UTC)
I'm pretty sure that the harmonics involved are pretty intense, and that it would be a heck of a project for a high school student to tackle. I believe that until fairly recently, wind-tunnel testing was the primary way of finding resonances, which tells me that the maths are too hard for professional state-of-the-art as of, say, 1970. For what it's worth, I did four structural engineering courses in university (the minimum possible in Civil engineering!) and we never even came close to harmonics. The Mythbusters did a show on this (season 1, episode 12) and I remember they had a lot of challenges in doing it. I don't think you could do anything more than a really simplified waving-a-jump-rope type demonstration at the high school level. --ByeByeBaby 06:42, 18 May 2006 (UTC)
Starting from just a design or drawing of the bridge, calculating the harmonics is brutally hard - it involves finite element analysis, which takes teams of engineers working with powerful computers. I too took civil engineering courses at university, and even though we discussed the principle, we never got anywhere near modelling anything as complicated as a bridge. For a high school student, I would think that they could do some research on historial bridge problems/collapses (we've already listed a few here), but actually modelling the harmonics of one would be way beyond them. — QuantumEleven 09:24, 18 May 2006 (UTC)
If your students are as creative as the Myth Busters they may have a chance. This clip shows their test model. --Bad carpet 10:38, 18 May 2006 (UTC)

There is a famous single case of a bridge collapsing due to resonance from soldiers crossing it in step, probably the Angers bridge mentioned above. This was before resonance of structures was fully understood or analyzable. It was that disaster that created the procedure of breaking step over a bridge. Note that the Tacoma Narrows Bridge collapsed not due to structural resonance, but due to aeroelastic flutter, which is resonance of a complete structure-airflow system. This is the part that is tested in wind tunnels, though we can model it pretty well these days with good rules of thumb and sophisticated computer analysis. The mathematics of resonance are not all that complicated for a simple system, once you know linear algebra, particularly eigenvalue problems, but I think it's still beyond the abilities of a high-school student. moink 20:48, 19 May 2006 (UTC)

[edit] prostate

what is the best treatment for enlarged prostate.? i have problem starting flow after ive been abed for fewhours. no problem during yhe day

thanks frank

  • You should probably see a doctor. But barring that, I've heard that if one wants to do this "naturally", that saw palmetto is often used to treat this. I heard from a reasonably reliable source that it is one of the few "natural" cures which has gotten some successful results in clinical trials, and we seem to have a JAMA citation in our article on the subject which confirms this. --Fastfission 22:47, 17 May 2006 (UTC)
More recent studies suggest saw palmetto is no better than placebo. [62]. JAMA's a rag! <g> - Nunh-huh 21:20, 19 May 2006 (UTC)

[edit] Mark X mine?

In Vannevar Bush's 1970 autobiography, he refers to a British WWII development which he calls the "Mark X mine", which was a mine which, from his description, used sound detection as a way of "homing in" on submarines when lobbed at them as a depth charge. I've Googled around a bit and found nothing like this out there. He describes it as: "The Mark X mine was a self-propelled target-seeking torpedo. Dropped in the swirl where a submarine had just submerged, it would listen to the sound of the submarine's propellers and steer itself to run into the submarine with fatal results." Any clue what this was actually called? --Fastfission 22:45, 17 May 2006 (UTC)

This page might be helpful. -- Rick Block (talk) 03:06, 18 May 2006 (UTC)
I had seen that one, but saw nothing which sounded like what he described on it. --Fastfission 13:37, 19 May 2006 (UTC)

[edit] May 18

[edit] average time of sunrise and sunset

On average, what time does the sun rise and set? I don't think it matters because it is an average, but my latitude is approx 35 north. Thanks. 152.163.100.74 01:07, 18 May 2006 (UTC)

Maybe this utility would help? --Chris 01:19, 18 May 2006 (UTC)
On average, it should be 6 a.m. / 6 p.m., as far as I can tell (daylight saving time and time zones nonwithstanding). — Knowledge Seeker দ 06:55, 18 May 2006 (UTC)
If you average it over the entire year and assume that your clocks are set to local solar time (which is rarely the same as the standard time in your time zone), then, yes. But even assuming this, at 35°N, the variation over the course of the seasons is considerable (several hours either way). The link given by Chris seems pretty good. — QuantumEleven 09:16, 18 May 2006 (UTC)
Also, the 6-to-6 average is a bit off because sunrise and sunset are measured from the first and last moment any part of the sun is visible, not when the center of the sun is visible. Consequently, days always average slightly longer than nights. — Lomn Talk 13:57, 18 May 2006 (UTC)
It's also very much off because daylight saving time is used in more than half of the year (this might not apply to your part of the world of course) so it's more like 6:30 and 18:30. But that's only if you live on exactly the central latitude longitude for your timezone, for example, E15° for CET/CEST; otherwise you have to subtract four minutes per every degree you are more to the east from that latitude longitude.
See the book Öveges József, Játékos fizikai kísérletek (Nemzeti Tankönyvkiadó, Budapest, 1995) – b_jonas 15:35, 18 May 2006 (UTC)
Nem mindenki beszél magyarul.. :) --BluePlatypus 20:08, 18 May 2006 (UTC)

[edit] combustion

what product is formed if incomplete combustion occurs in a car engine? —The preceding unsigned comment was added by 142.165.111.39 (talk • contribs) .

Many different substances — that's part of the problem. If it were just one substance we could focus all our resources on eliminating that one thing. You're probably looking for carbon monoxide but there's also nitrogen oxides and polycyclic aromatic hydrocarbons. —Keenan Pepper 02:18, 18 May 2006 (UTC)
Homework question I believe. Standard Grade Chemistry or something. Tsk tsk. The SG answer would be "Carbon Monoxide and oxides of nitrogen" however.

What, then, would the SG pundits consider to be the nitrogen oxide which represents complete combustion? Nitrogen dioxide only? I would have thought that the correct answer to this homework question would be simply "CO". Further questions might lead to why there are also oxides of nitrogen in the exhaust gas.G N Frykman 17:39, 18 May 2006 (UTC)

I'm doing GCSE chemistry, and we get told CO and NOX. Philc TECI 17:52, 18 May 2006 (UTC)
Ditto. But if your fuel sucks, you might get other stuff in there too, like sulfur oxides. --M1ss1ontomars2k4 | T | C | @ 23:54, 18 May 2006 (UTC)


I was merely giving the answer which I was taught, and is accepted in Scotland by the exam board. We were only taught "carbon monoxide and oxides of nitrogen". It doesnt specify which ones exactly. But the question doesnt ask what ALL the products are, just to name some. And as many go beyond the scope of Standard Grade/GCSE chemistry, I believe the given answer is suitable.

[edit] Why can birds sit on powerlines?

Why can birds sit on powerlines? -- Mac Davis] ⌇☢ ญƛ. 04:42, 18 May 2006 (UTC)

There is no voltage, i.e. potential difference, between the bird's legs; thus, no current passes through it. If it would touch another powerline or the ground at the same time, bad things would happen. –Mysid(t) 04:56, 18 May 2006 (UTC)
Because powerlines are normally insulated --Fuhghettaboutit 06:07, 18 May 2006 (UTC)
Power-lines are bare, but anyone can sit on one as long as they don't complete an electrical circuit with another power-line or with a supporting pylon or earth. Passerines like to sit on power-lines because it is their nature to perch. --Shantavira 07:03, 18 May 2006 (UTC)

Power line electrocution is a killer for the big raptors. See this: [63] Power companies put a lot of effort into reducing the carnage. --Zeizmic 12:23, 18 May 2006 (UTC)

Can you explain why they would kill raptors but not other birds?ike9898 13:36, 18 May 2006 (UTC)
It's a matter of size: larger birds are more likely to contact different wires, or wire+pole, or wire+tree, or whatever other lethal combination. — Lomn Talk 13:55, 18 May 2006 (UTC)
Large birds are likely to develop more potential difference across their bodies when in the strong electric field around a high voltage power line. This is why maintenance men working on live OH 275kV etc lines wear equipotential conducting suits (so the electric field cant cause curernts to pass thro their bodies. Anyway, any birds you do see on the supergrid lines are usually sitting on the ground wire (the top one) Thats propbably cos they can feel the field if they fly any closer to the live conductors. 8-)--Light current 14:18, 23 May 2006 (UTC)
When a bird sits on a power-line, it is not grounded, as electricity rushes to the ground. If the bird happened to spread its wings and hit the pole, well, you'd have a fried bird. What I don't understand is, aren't power lines really, really hot? Can't electricity burn you?
If power lines were really, really hot, it would be a terrible waste of electricity. Some power is lost, but it depends on the resistance of the wire used which is kept low enough to reduce power loss to acceptable amounts, and the very high voltages also reduce power loss for particularly long wires. The power loss is a trade off between voltage/safety issues/cost of wires/extra weight of wires (requiring more support)/other things I've overlooked. Notinasnaid 19:12, 18 May 2006 (UTC)


Power lines are warm, from electrical resistance. They don't get very hot, though, because the hotter a wire is, the higher the resistance, leading to runaway heating and the wire catching fire.
Yes, electricity can burn you, but only if it's flowing through your body. For a bird sitting on a power line, there's nowhere for the electricity to go, so it doesn't fry the bird. --Serie 19:17, 18 May 2006 (UTC)
Not quite true. See my post above about electric fields--Light current 14:20, 23 May 2006 (UTC)

Ooh! I have a variant on this question. For trains that run on electrified rails, such as on the London Underground, there is a live rail. I travel on parts that are overground and so I see pigeons perching on these rails all the time. I often think that they must come close to electrocuting themselves (surely they would only need to briefly touch the ground while perching on the rail?), and ditto for the rats scurrying around on the underground parts of the system. But I've never seen this happen. Maybe it's this thing about the rails only being electrified in the area before and after a train, or is there another reason? Carcharoth 21:15, 18 May 2006 (UTC)

Ah. Following the link through electrified, I eventually found Railway electrification and the bits about the Third Rail and London Underground's Fourth Rail. Which is helping - but science-orientated explanations would be great. Carcharoth 21:23, 18 May 2006 (UTC)
And you'll notice that birds don't sit on the super high-power lines that span across more rural areas (the ones that make the loud buzzing sound). There is probably enough stray current to cause some damage, or at least prickle their feathers when they get close. freshgavinΓΛĿЌ 06:43, 19 May 2006 (UTC)
It's actually because high tesnion power lines dont actually have the electricity inside the wire, the voltage is so high, it forms a field around the wire. That is also why the insulators are so big.

For the bird to get electrocuted, the current has to enter from one part of the body (a leg) and come out of another (another leg or the wing etc). But these two legs are 'shorted' by the conducting wire and hence, the potential difference between the points where the bird holds the wire is (nearly) zero. The current flowing thru the bird's body is in the inverse ratio of the resistances of the bird's body and the conducting wire and hardly any current flows thru the bird's body. Even if a human is to hang on to one live electric wire, negligible current would flow thru his body and nothing would happen to him. But the momeent and other part of the body touches the other wires or any path to the ground, a considerable current would flow and cause death or injury. Many birds die when they sit on one wire and peck on other wire, or when they spread their wings. -- Wikicheng 07:25, 19 May 2006 (UTC)

There's another effect. A bird is a capacitor, and there's alternate current in the wire. So the bird is charging and discharging repeatedly, and it leads to a current flowing throug its body, even if the bird is touching the wire with only one leg. Apparently it's so small that the bird isn't harmed (the corresponding resistance is R = 1/ωC; ω is 50-60 Hz, C is about 10 pF for a 10-cm bird, it gives R ~ 1 GΩ and I ~ 10 µA for a 10-kV line; IIRC a human can feel a current of about 1 mA, don't know about birds). Conscious 11:34, 19 May 2006 (UTC)
I would say that a bird makes a very poor (low Q) capacitor since its body resistace will be a few hundred ohms and the main current thro its body will be in phase with the voltage. THats what'll kill it-- not capacitive current!--Light current 14:24, 23 May 2006 (UTC)
But the voltage between bird's legs is much smaller than the voltage between the bird and the grounds. Conscious 06:22, 24 May 2006 (UTC)

[edit] Sleep

Moved from misc. 61.25.248.86 06:37, 18 May 2006 (UTC)
In high school, I used to sleep through half of my classes, but so did everyone else, so I didn't really care. After I breezed through that, I ended up sleeping a lot in University too. That was a little more problematic, and no matter how hard I faught to pay attention during lectures, a lot of the time I just couldn't keep my eyes open, and I eventually just started sleeping in a lot and going to later classes. Even now, while working, I feel incredibly tired in the morning, though I'm almost always standing up so I don't really get a chance to close my eyes (thank god).
I may be returning to school sometime soon, and I want to work a little harder this time, but I don't know how I can get over my sleepiness.
I've never really been that susceptible to agents like nicotine, THC, and caffeine, so although I recently started taking coffee in the mornings (I don't even like it) I don't really feel the effects of it. For some reason, drinking coffee or coke at night prevents me from falling asleep, though.
I generally get enough sleep (8-10 hours on working days) but it doesn't really seem to matter because I go through the whole day yawning and rubbing my eyes anyways. I am not any lazier than most people, but I know that working out in the morning will wake me up (I've tried it). My problem with that is that I don't understand why I have to resort to something so extreme (waking up before 5am!) when most people here don't seem to have any problems, even when having only slept 6 hours. Is there some kind of perpetual sleepiness condition that I might have? Anything that can help? 61.25.248.86 03:33, 18 May 2006 (UTC)

Sleep and Fatigue might link to something of use, but it's a long shot. Wikipedia is not really geared towards providing practical advice. Howard Train 05:21, 18 May 2006 (UTC)
I was posting under the impression that it might be some sort of known medical condition that could be treated. 61.25.248.86 06:35, 18 May 2006 (UTC)
You could try moving West a few time zones. The effect probably would only last for a few days though.-gadfium 06:50, 18 May 2006 (UTC)
In that case, your best bet is to have a visit with your physician. He will know best if it's some sort of medical condition or what kind of treaments might work. — Knowledge Seeker দ 06:53, 18 May 2006 (UTC)
Perhaps the quality of your rest is poor. Sleep apnea is one common condition it may be worth asking your doctor about. --Bad carpet 10:27, 18 May 2006 (UTC)

Insist that your doctor sends you to a sleep clinic. Apparently, many doctors still don't do this for sleep disorders. There are about a dozen possibilities (types of disorders), each with a different treatment. --Zeizmic 12:26, 18 May 2006 (UTC)

Maybe you need to sleep more, like go to sleep before 22:00 atleast, as I'm guessing you don't. And also, you said drinking caffine drinks at night seems to keep you awake, well as a bit of a no brainer, don't do that anymore. You can always try pep up pills of some sort. Philc TECI 17:50, 18 May 2006 (UTC)
I strongly agree with others who suggest you visit a physician specializing in sleep disorders, since your extreme sleepiness is unusual for sleeping up to 10 hours a night. However, you might also try ginseng in the meantime. Many products containing this herb have a very low potency; your best bet is to try to find a concentrated form and make a tea of it. --Ginkgo100 18:47, 18 May 2006 (UTC)
You could try something physical like a 5k run to start the day or something, that keeps me wide awake for ages. Philc TECI 19:54, 18 May 2006 (UTC)
Rust never sleeps. --DLL 20:55, 18 May 2006 (UTC)
What? Philc TECI 18:40, 19 May 2006 (UTC)
Actually, I did move west... 13 hours west in fact. I didn't sleep at all the first day and it didn't help at all : 8! Also for that reason just "going to visit my physician" isn't really that easy. I don't trust the doctors here (they tend to overprescribe medicine in huge quantities and charge you hell for it too), and I don't have a physician anyways. I'd like to handle it by myself (I'm that kind of guy ... like I broke my fist on a wall and I just stuck it out).
I'm pretty sure the quality of my sleep is poor, I've always been a little bit of an insomniac. When I don't have work my sleeping pattern gradually shifts later and later until I end up sleeping after the sun rises, and it takes a lot of concious effort (and lying awake in my bed for hours) for me to keep my patterns from shifting.
If I sleep more, it keeps me from flat out falling asleep, but I never really stop yawning, and if I'm sitting down I always migrate to more sleep-like positions. Lately I've been waking up at 6am for work, and I find it quite easy to sleep at 10pm. It feels like I'm going into a much better, deeper sleep, but I can never seem to get the hang of waking up so early, and I always end up twice as awake in the evening as I was during the rest of the day. I kind of consider myself the ultimate anti-morning person. : 8.
I'm pretty sure taking a 5km run in the morning would work, but can you honestly say that you'd be able to do that 6 days a week, before 6am? I know that it might be the only solution for me though. 61.25.248.86 06:19, 19 May 2006 (UTC)
I'm not a doctor... Do you drink vitamins? ellol
Personally I would suggest exercise of almost any sort, at any time during the day (doesn't have to be the morning). One gets better quality sleep when they've been physically active during the day. Try biking to places you need to go to closer than 5 miles away rather than driving or taking the bus. - McCart42 02:27, 24 May 2006 (UTC)

[edit] PDF files to WORD files.

Hello, just recently i donwloaded lots of ebookz, most of them in pdf format. I found that reading from pdf files is really uninteresting. The way the pages scroll down, and everything else works is too uncomfortable for me to enjoy the reading. So is there any softwares avaliable for converting pdf files to word (".doc") files. Or alternatively, is there any way to copy all the text and images from a pdf files, as it is, to a word file? I tried to copy, but both cannot be copied simultaneously. So is there a solution for me? Thank You.

See Converting PDF files to Microsoft Word files. -- Mac Davis] ⌇☢ ญƛ. 09:00, 18 May 2006 (UTC)
This kind of conversion is only possible in certain circumstances and is generally not meant to happen. If a PDF was created from text (and has the proper permissions) you can select the text and copy it into Word, but you'll have to copy the pictures manually. If they were made by scanning in the text, you're completely out of luck.
Short answer: you can't.
Also, I don't understand what you mean by "uncomfortable to read" - you know that Adobe Acrobat reader (which I presume you're using) has options on how it should treat scrolling (for instance, by page, continuously...). Try playing around with these options instead, and try zooming in/out to make the text a comfortable size for reading. — QuantumEleven 09:11, 18 May 2006 (UTC)
Some people just don't like to read lengthy things on the computer screen. And if it is more than 10 pages you just gotta print it out! -- Mac Davis] ⌇☢ ญƛ. 11:40, 18 May 2006 (UTC)
That question recurs periodically. --DLL 20:53, 18 May 2006 (UTC)
If you have a later version of microsoft office, you can print to the Microsoft Office Document Imaging something something. Then, you can use the program to OCR the text back into msword. In theory, at any rate. --M1ss1ontomars2k4 | T | C | @ 23:51, 18 May 2006 (UTC)
Your problem isn't just Acrobat. I hardly think reading a word document would be much more enjoyable. If you refuse to print them out you could always buy an e-book type utility, many/most of which support Acrobat files, but if you had the money to buy one of those you probably wouldn't mind printing them out in the first place. freshgavinΓΛĿЌ 06:36, 19 May 2006 (UTC)

I mention (purely hypothetically, of course) that open-source PDF readers are easily available, such as xpdf. You could, hypothetically, get the source code, and comment out the places where it won't let you do things (such as print the file) based on permissions. I looked at the code once (hypothetically) and it appeared fairly trivial to find these code snippets and circumvent them. Of course if you're in the United States there's that pesky DMCA—I think the prescribed penalty is breaking on the wheel. --Trovatore 16:26, 23 May 2006 (UTC)

[edit] "92% water"

I want to know how much water is in the flesh of a watermelon. Searching the wikipedia article and Google I see the figure 92% over and over again, but no where seems to say if this figure includes the rind and seeds or not. I'd like to know how much of a watermelon is water, excluding the rind and seeds. (This is to settle a bet) —Pengo 10:27, 18 May 2006 (UTC)

Is that 92% by volume or 92% by weight? Ohanian 11:10, 18 May 2006 (UTC)

Would have to be by weight; watermelon is much too airy to be 92% volume water. — Lomn Talk 13:53, 18 May 2006 (UTC)
If you're betting on it, then I'd suggest you take a watermelon and come up with a way to measure it by yourselves. By googling it seems that different percentages are mentioned, depending on the site and watermelon in question (typically 90–97%). No site mentions if the number is for the whole fruit or the flesh only, though. One site says that "The flesh of this succulent fruit is over 90 percent water" (italics by me), so if you trust them, at least it is over 90. –Mysid(t) 15:29, 18 May 2006 (UTC)
One could puree a known mass of rindless, pipless watermelon flesh, boil it, and gently heat till dry. Assuming there is not a significant mass of other volatile compound boiling off, weighing the dry stuff would give you your own answer. -Seejyb 19:52, 18 May 2006 (UTC)

[edit] NBME Question bank - STEP1 USMLE

NBME Question bank - STEP1 USMLE hi, i am lookin for question bank series book, that is used to prepare for step 1 USMLE exam. Can any one let me the latest edition details along with the author name. If referenced to publications then can u please let me know the publisher name.

thanks.

[edit] Fish flatuence?

This might seem like a crazy question, but does anyone know whether fish produce flatuence or not?--Bjwebb (talk) 18:25, 18 May 2006 (UTC)

Google for "fish fart" and you'll quickly find this. --Kainaw (talk) 18:54, 18 May 2006 (UTC)

[edit] Hummingbird Nest

Last week a hummingbird built a nest in my backyard and laid a single egg. The next day it was gone. My questions: How rare is it for hummingbird to lay a single egg rather than two? Can a mother pick up an egg and carry it away after she has laid it?

It's possible something sinister happened to the nest. An adult hummingbird would have no way of moving the nest nor the egg. Mortality in baby birds is very high. --Ginkgo100 03:50, 19 May 2006 (UTC)
Carry an egg? Would that be an African or a European hummingbird? ;-) --Swift 05:10, 19 May 2006 (UTC)

[edit] Garden soil safety

I've just moved into my current house, and I would like to be sure that the vegetables I am planting in the back yard will be safe for my family to eat.

Plants grow very nicely in the soil, and it is full of earthworms and other small animals. My concern comes from the fact that when I dig, I find a certain amount of old trash, and pieces of glass, brick, and concrete, and that the neighborhood, Hampden, Baltimore, Maryland, was once the home of many old industrial sites.

I have also seen among the red earthworms a few bright yellow ones, looking not unlike the worm shown in this Nature article, "Don't eat yellow worms". The article suggests that this coloration may be a sign of high levels of arsenic or copper.

What is a sensible level of caution on this question? Is there a way to find out the history of a particular piece of land? All the soil testing services I have found are for pH, nutrients, or parasites; is there an easy way to have the soil tested for contaminants or toxicity?

Thank you; 128.220.220.95 18:59, 18 May 2006 (UTC)

This could be a community-wide ecological issue, not just your personal gardening problem. Plants, insects, birds could all be affected. I would contact my local university for advice (e.g. http://www.umbc.edu/biosci/ UBMC). Maybe they would see this as an opportunity for research, more than just pointing you in the right direction. --Seejyb 20:54, 18 May 2006 (UTC)

For city gardens, it might be best to do 'planter gardening' or raised beds. See a gardening book on this. That way you are assured of fresh, safe organic material. --Zeizmic 23:43, 18 May 2006 (UTC)

You could try contacting your local council or environment agency to see if they have any information on the safety/composition/pollution levels of the soil nearby. AllanHainey 13:54, 22 May 2006 (UTC)

[edit] Technology: Developement

Here's a question for all you tech people out there. If human developement is continuously improving computers, palm pilots, and everything else, why is it we are still stuck in an age where we rely on the most costly almost 80year old technology of four wheels on the ground? shouldnt we be in a more economical way of hovering either only a couple inches off the ground or couple miles above the ground and in a safe way. I know movies are just movies, but we should still be at an age where we move past prehistoric wheels?

And a question linking to the top: Why is it that oil and gas are still the dominant source of fuel in the world? Souldn't we be in an age of alternative fuels, to almost electrical technology that can allow us to constantly reuse and recharge? Thank you for your imput. --134.29.205.119 19:00, 18 May 2006 (UTC)

Infrastructure for production, storage and distribution of a new fuel system would be very expensive to install. Think about it: you would have to get rid of every gasoline/diesel/propane station and replace it with whatever, a hydrogen tank center or something. The fuel companies would hate that. And they would lose all their institutional knowledge. A changeover period of some years, maybe a decade, would be necessary. Do you remember when leaded fuel was outlawed in the 80s? That was a big deal for many people. This would be much more challenging. Refineries, fuel companies and governments have vested interests in retaining the current fossil fuel power method. However, cars become more fuel-efficient all the time, so every year our supply of fossil fuels will actually last longer. Vehicles also pollute in decreasing amounts with every new model. Now, if you want to become an elected legislator, and take your ideas to government, you can. There you will encounter stiff resistance in the form of lobbyists, other politicians, and just plain regular folks who downright don't like change. Change happens slowly. That's why laws like the Clean Air Act are important, because they force manufacturers to steadily improve their products. Eventually a target can be set that is impossible for an internal combustion engine to achieve, and then you will get your hovercars. But the executive has to take the plunge on that, and at present they aren't; they are actually moving back from it.--24.80.70.174 19:15, 18 May 2006 (UTC)

It is true that many things are getting more efficient, but see Jevons' Paradox --WhiteDragon 18:42, 25 May 2006 (UTC)
Why do you say "most costly"? Doesn't it seem like a hovercar (a HOVER...CAR) would be unimaginably more expensive than something very basic that's been streamlined and perfected over about a century? Also, there's the basic problems with floating in the first place. Anti-gravity has been studied for quite a while, and the closest we've gotten is the age-old trick of holding two magnets together. Maglev trains are good that way, except that they only float a little bit, and never leave their pre-defined tracks. Mass transit is, like all other things that start with "mass", rather more economical that individual transportation if everyone's going in the same direction, so it's got that going for it as well, but I don't think it's quite the answer you're looking for. There have also been efforts to combine cars with tiny airplanes, in fact Popular Science has an article on exactly that this month, but have you ever been to an air traffic control tower? I have. It's hectic as it is. Can you imagine putting the same retards (the same tens of millions of retards, compared to the relatively few commercial jets in the air) that get into fender benders on residential roads into planes that go five times as fast, a few hundred feet above the ground? It'd be chaos. Really, apart from the fact that it's in many cases impractical and unpopular to make such major changes, there's very little reason for it in the first place. Wheels are awesome. Engines are practical. And what could be cooler than combining effectively frictionless objects (wheels don't rub the ground, do they?) with a powerfully explosive liquid and a few tons of metal? It's just a shame we're running out of the second one. Black Carrot 22:19, 18 May 2006 (UTC)
About the hypothetical control tower operators you mentioned...it is, at least, an interesting thought of a realistic concept for skilled labour positions... -Tim Rhymeless (Er...let's shimmy) 03:47, 19 May 2006 (UTC)
In the 1970s, New Zealand supported many vehicles running on Compressed natural gas, with a substantial proportion of petrol stations installing the tanks for vehicles to refuel. It was probably Government subsidised, but it seemed to work rather well. It was much cheaper than petrol, but vehicles had somewhat less power. I ran a CNG-powered car for some years. Liquified petroleum gas was also available as a vehicle fuel, but less popular, as it was more expensive than CNG (still cheaper than petrol, and without the powerloss of CNG). When petrol prices declined in the mid 1980s, these alternative fuel systems largely disappeared in New Zealand, but I understand they're still in use in Argentina and Chile.-gadfium 08:53, 19 May 2006 (UTC)
It all comes down to a cost and benefit analysis. I spent several hours today making notes using a pencil on a piece of paper. Pencils are several hundreds of years old, paper several thousands. Why do I still use such 'primitive' technology? Why don't I use a laser pen on a smart pad which inputs my writing directly into a computer? Because the cost of doing it would be greater than the benefit I get out of doing it - very little, in fact, as the same information is written down either way, but the laser pen, smart pad and PC are vastly more expensive than by HB pencil and sheet of paper.
It works the same way with most of the examples you mentioned. Why don't we have flying cars? Because at our present technological level, the benefit we would get from flying cars (faster journeys) is far outweighed by the costs. A flying car would be far more expensive than a regular car (a jet aircraft engine, which is what we'd probably use, easily costs several tens of millions of dollars). The fuel consumption would be enormous (so, more cost, not to mention the environmental damage from the exhaust). The risk to the occupants is far greater (not just in terms of collision (as Black Carrot rightly points out), but if the engine fails, you tend to fall out of the sky and end up as a splotch on the landscape). With conventional cars, boy racers and their roaring machines are at least confined to the roads, with flying cars, you could well having them buzz your house at ten meters above you at 3am. I could go on... I think you get the idea.
Rather than private flying transport it's worked out that, for economic and safety reasons, airliners have been more successful than private planes. That said, there is finally a bit of action in what was the moribund private aviation market, centred around two areas; at the very low end amongst homebuilts, ultralights and the closely related light sport aircraft category. Further up, the prospective very light jet aircraft might put the "air taxi" within economic reach of a lot more people. So over the next few decades, while we may not have the flying car, private or small-scale charter flying may become a lot more popular assuming that safety and environmental issues don't shut it down again (particularly in the case of the VLJs, which chew quite a lot of fuel per passenger). --Robert Merkel 14:28, 19 May 2006 (UTC)
The bottom line: just because something is 'old' doesn't mean it shouldn't be used.
And to answer your second question, our article on future energy development should go some way towards explaining why all forms of energy production have their advantages and disadvantages. — QuantumEleven 08:57, 19 May 2006 (UTC)

[edit] Diaphragm (obscure science meanings)

I recently expanded the diaphragm disambiguation page, but some of the terms seem to lack articles, and some other terms need someone to explain them properly. Does anyone here know enough to expand on the battery use of the word diaphragm, or the more general anatomical term found in organisms other than humans (such as bryozoans and gasteromycetes). Also, I am now confused about how diaphragm relates to septa and septa (biology). Can anyone clarify the different meanings of these terms? There seems to be a fair bit of overlap.

Oh, and I know it is not science, but if anyone knows enough about engineering and architecture to explain diaphragm wall, that would be great as well! Carcharoth 20:22, 18 May 2006 (UTC)

It takes the place of the salt bridge that is used in the Galvanic cell. Hope this clears things up. --M1ss1ontomars2k4 | T | C | @ 23:47, 18 May 2006 (UTC)
That has helped. Thanks. Have a look at diaphragm and see if what I wrote was clear enough, at least for now. Unfortunately, there is confusion at the relevant articles:

So hopefully someone will clear that up! THanks again. Carcharoth 01:49, 19 May 2006 (UTC)

[edit] Micrognathism

Does anyone know where I can find a photo, or at least a diagram showing micrognathism in humans? I've been having a bit of trouble finding anything readily online. -Tim Rhymeless (Er...let's shimmy) 21:38, 18 May 2006 (UTC)

I'm not sure what types of pictures you're looking for; if you're looking for more anatomical pictures or just pics of people with the syndrome. Anyhoo, I googled 'Micrognathism pictures' and found this site, a plastic surgery site it seems, with before/after pics. I suspect if I looked further I'd find more, the search returned a lot of sites that hadn't been anywhere near the top of the google results for just 'micrognathism'. You might have even better luck googling 'micrognathism "plastic surgery"' or 'micrognathism "cosmetic surgery"' because those sites usually have galleries of before/after photos.--Anchoress 22:47, 18 May 2006 (UTC)

[edit] Mosquito size

What is the size of the biggest mosquito ever? I killed one today, and want to be sure it was not the biggest available model. --Roundedge 21:43, 18 May 2006 (UTC)

"Size varies but is rarely greater than 15 mm (0.6 inch)" Mosquito. --Halcatalyst 15:43, 19 May 2006 (UTC)
Was it possibly a crane fly instead? Melchoir 23:04, 19 May 2006 (UTC)

[edit] Heart Regeneration

I have open on my lap this month's (that is to say, June's, because ever magazine I've ever received fell through a wormhole on the way) issue of Popular Science, and I'm looking at rather a curious article. It's centered around some of the most recent work of Hydra Biosciences, a company apparently dedicated to the dream of effective regeneration of dead and damaged tissue. My question is, what do you think of this? Does it sound like something we can look forward to in twenty years, or someone just trying to get attention? Black Carrot 21:55, 18 May 2006 (UTC)

For what it's worth, PopSci really is filled with pop-sci. According to today's technology, what the article discusses may be feasible in the future, which is much unlike cold fusion. Cold fusion, thermodynamically, doesn't make much sense. At least this does. --M1ss1ontomars2k4 | T | C | @ 23:44, 18 May 2006 (UTC)

[edit] speed of light

ok, so my perental told me when you approach the speed of light time slows down. i dont understand how or why. i got the following idea: first since time is an arbitrary concept agreed upon by human(i would like to know what exactly time is if im wrong, please) say speed wasnt measured int distance/time but, oh banannas for example. so the speed oflight would be say 300 banannas, 0 banannas being completely still. as an object increases banannas time begins to slow down; so at 150 banannas "time" is twice as long(for what though? the observer or the object?) so if at 1 bananna the object traveled 6 feet at 150 banannas 1 minute would become to, but the object is still goin at 150 banannas, so now it travels 12 feetin a "minute" because it has twice as much time to travel at the same speed. pretty much i would greatly appreciate someone telling me why is it impossible to reach the speed of light, the questions in the parenthese and wats wrong with my example --69.140.210.163 22:05, 18 May 2006 (UTC)Artem

My understanding is that as an object accelerates towards C, it's mass increases, and thus the amount of energy required to accelerate increases towards infinity. In other words, it would take an infinite amount of energy to accelerate to C. Raul654 22:07, 18 May 2006 (UTC)
Sorry to intrude, but you mean "its", not "it's". --M1ss1ontomars2k4 | T | C | @ 23:42, 18 May 2006 (UTC)

Let's try by analogy.

as you approach the speed of light, the rate of passage of time slows down.
as you reduce the clock rate of CPU, the rate of computation slows down.
but you will not noticed that the rate of time slows down.
but a computer program will not notice that the rate of computation slows down.
Unless you observe an external stationary processes (like your friend on earth).
Unless the computer program references an external real time clock.

The reason time slows down is because all (chemical/nuclear) reactions slows down as light "slows down".


Ohanian 22:18, 18 May 2006 (UTC)

For what it's worth, we do have an article on Special Relativity, which is the theory you're talking about. Black Carrot 22:33, 18 May 2006 (UTC)


can someone please clarify:

what causes the mass to increase? thanks again --69.140.210.163 23:28, 18 May 2006 (UTC)

Yeah, actually I need help on this too. --M1ss1ontomars2k4 | T | C | @ 23:42, 18 May 2006 (UTC)
Question: what causes mass to increase as an object approaches the speed of light?

Answer: Now assume that you are applying a constant force on an object.

  Remember that F = M * A

  You can rewrite that as   F = M * dV / dt

  Re write as  M = F * dt / dv  

  So what you have is Mass is Force times rate of change of time per velocity. 
  Now listen carefully. As an object approaches the speed of light, 
  it takes longer (more time) and longer to gain an extra/additional velocity 
  (say an additional 1 meter per second). 

  So dt / dv becomes larger and larger. 

  Therefore the Mass is getting larger and larger.

Ohanian 08:03, 19 May 2006 (UTC)

Unfortunately, the monkeys eat the bananas, and "banana time" ceases to exist. You should have tried apples instead. Carcharoth 00:47, 19 May 2006 (UTC)

According to the special relativity article, "Mass and momentum - when gaining momentum the apparent mass of an object increases as well as the energy (giving the famous E=mc2 equation.)" In other words, just as the relationship between time and distance warps at extremely high speed, so does the relationship between mass and energy. Black Carrot 01:59, 19 May 2006 (UTC)
Just to complicate things a little, light can apparently now travel [backwards], faster than the speed of light.--Shantavira 08:09, 19 May 2006 (UTC)

[edit] Sea urchins

how many teeth do sea urchins have.

I haven't checked yet, but does sea urchin help? --HappyCamper 23:57, 18 May 2006 (UTC)
You didn't want to guess five? :-) Carcharoth 00:42, 19 May 2006 (UTC)
Those teeth form an Aristotle's Lantern. But do not play discordianist theories here. --DLL 19:30, 19 May 2006 (UTC)

[edit] May 19

[edit] Does dioxygenyl act like a normal ion?

Can dioxgenyl (O2+) bond with say, chlorine, to form something like O2Cl?

Try Chlorine dioxide. Whether or not dioxygenyl is actually present as one of the intermediate steps in the chemical reaction is not clear. The reaction mixture shown is a strongly acidic solution, but I have no idea what the intermediate steps would be. Carcharoth 01:26, 19 May 2006 (UTC)
My guess is that the chlorine is positive. What I'm really asking is, do radicals essentially act like ions?

I seem to remember that this ion was vital in the discovery of inert gas compounds. See xenon. G N Frykman 18:18, 19 May 2006 (UTC)

[edit] Formula

In the kinetic theory of gases what is the formula of P?--82.148.105.112 03:40, 19 May 2006 (UTC)

P is pressure, force divided by area. See [64]. alteripse 04:10, 19 May 2006 (UTC)

So "what is this formula tells us about <1/2mv²> in the kinetic theory of gases or other formula similar to it"

Sorry, the question as asked is uninintelligible. Please restate in English and one of us may try to answer. alteripse 10:35, 19 May 2006 (UTC)

See our article kinetic theory, it contains the formula. Conscious 11:18, 19 May 2006 (UTC)

[edit] Still unanswered..NBME Question bank - STEP1 USMLE

hi,

NBME Question bank - STEP1 USMLE hi, i am lookin for question bank series book, that is used to prepare for step 1 USMLE exam. Can any one let me the latest edition details along with the author name. If it can be referenced to publications then can u please let me know the publisher name.

thanks.

Do not post the same question on multiple Reference desk pages, and be patient. If it is here, someone is bound to look at it. Google turns up a few pages, perhaps start from there? --Ouro 06:27, 19 May 2006 (UTC)

[edit] plants & water

Since recently, we have a Venus Flytrap and a Sarracenia in our home. Following wiki-instructions from the Venus Flytrap article, I am watering them only with distilled water, and happily they seem to be doing very well (touch wood). Yesterday my partner went shopping and mistakedly brought back a bottle of deionized water instead of distilled water. Can I also use this to water them or not? Thanks for info. --JoelAbend

Yes. See deionized water. --Shantavira 08:14, 19 May 2006 (UTC)
Just a slight caution. Deionized water can become fairly acidic when stored by absorbing CO2 from the air (I can't remember the exact process). Anyways, this sometimes causes problems with very sensitive equipment when deionized water is used. It probably isn't a concern for your plant, unless they are very sensitve to slight pH changes. --Chapuisat 14:01, 19 May 2006 (UTC)
Actually, I believe Venus Flytraps prefer acidic water, so if anything it would be an advantage. --Ginkgo100 19:45, 19 May 2006 (UTC)

[edit] center of mass of the Universe?

do we have a discussion of the "consensual" inertial frame of reference of the Universe somewhere, defined, I suppose, by the distribution of background radiation, and (possibly) by the center of mass of the Universe (which I realize may lie outside the Universe for geometrical reasons)? Are there any practical effects tied to the existence of such a de-facto preferred inertial system? Can we measure our speed relative to it? dab (ᛏ) 09:08, 19 May 2006 (UTC)

Yes, there's only one frame of reference where MBR has no dipole component. But if we assume that the Universe is homogenous on the large scale, its centre of mass if nowhere (or anywhere, if you like). Conscious 11:16, 19 May 2006 (UTC)
Surely the centre of mass of the universe would be where all of the unvierses gravity pulling on you is perfectly balanced, so that you never move. Philc TECI 18:46, 19 May 2006 (UTC)
The usual definition of "center of mass" is problematic if the universe is infinite, which it appears to be. -- SCZenz 00:20, 20 May 2006 (UTC)
The Universe is not infintely big. Philc TECI 17:22, 21 May 2006 (UTC)
precisely, and what can we say about the frame of reference where there is no dipole component? Is there a discussion of this somewhere on WP? What is our speed relative to it? dab (ᛏ) 20:19, 19 May 2006 (UTC)
380 km/s, according to Cosmic microwave background radiation. Melchoir 23:07, 19 May 2006 (UTC)
This is an area of disagreement within the physics community, though one with little practical impact. See Mach's principle for one side of the argument: that a local inertial reference frame is determined by the distribution of all matter in the universe. Another way of interpreting it is that Newton's second law is a definition rather than a law: that is, an inertial reference frame is one in which the second law holds. moink 20:28, 19 May 2006 (UTC)
"Disagreement" is the wrong word. There are certain issues where taking one philisophical perspective is most helpful for some problems, and another is helpful for others. -- SCZenz 00:20, 20 May 2006 (UTC)
You may also want to look at Philosophy_of_space_and_time#Absolutism_vs._relationalism moink 20:32, 19 May 2006 (UTC)

[edit] Fish out of water?

Can a fish out of water see? The refractive index of water is about 1.33 and air is about 0. That means the image shall form in front of the retina and the fish shall suffer from myopia.

How does an amphibian animal deal with this problem? -- Toytoy 09:59, 19 May 2006 (UTC)

The refractive index of air is about 1, not 0. Arbitrary username 20:42, 19 May 2006 (UTC)
I don't know about you, but I can see under water. HenryFlower 10:15, 19 May 2006 (UTC)
Perhaps you mean to ask, "can a fish out of water pass an eye exam?" Which of course introduces a myriad of other problems. You are correct when you say that the eye's function in water vs in air is dramatically different and there are none (that I am aware of) that are suited well for both. I have heard of animals that posess a sub-eyelid that acts as a sort of contact lens to adjust the eye to underwater vision. I thought it was the Penguin, but a skim of that article doesn't turn up any clues. --Jmeden2000 14:31, 19 May 2006 (UTC)
The unique divided eyes of anablepidae, or 'four-eyed fishes', can see above and below the water line at the same time. Femto 14:56, 19 May 2006 (UTC)
The feature I mentioned is a Nictitating membrane, but it doesn't seem like many would suggest it functions to improve vision, but more as protection for the cornea.
"How does an amphibian animal deal with this problem?" You might be interested in this famous paper: "What the Frog's Eye Tells the Frog's Brain". Lettvin, JY, Maturana, HR, McCulloch, WS, & Pitts, WH (1959) Proceedings of the IRE, Vol. 47, No. 11 online --GangofOne 22:53, 19 May 2006 (UTC)
A flying fish has a flat cornea, so that in air it does not focus light. A normal convex cornea of course does not do this under water - nor does the flat one. Many fish focus by moving their spherical lens forwards and backwards. What do amphibians do? Dunno. Most of human focus occurs at the air/cornea interface, so that the lens does not have much to do. --Seejyb 22:03, 20 May 2006 (UTC)

[edit] a drop from 3.5 km

if I jump of a plain at a height of 3.5 km. with how many speed do i fall down?

Just one at a time. Cthulhu.mythos 10:49, 19 May 2006 (UTC)
As an alternative, you might have a look at Air resistance before doing your homework. Cthulhu.mythos 10:50, 19 May 2006 (UTC)
Or read terminal velocity. Conscious 11:07, 19 May 2006 (UTC)
The question looks very much like a homework problem. As stated, there is not enough information in the question to provide an accurate answer. For example, the drag coefficient of your body, which depends on its geometry, is not known. Maybe the question makes a simplifying assumption that air resistance has little or no effect. If that's the case, the question reduces to one of energy conversion (from gravitational potential energy to kinetic energy). --68.238.243.228 12:47, 19 May 2006 (UTC)
Jumping from a Plain at a height of 3.5 km would be quite a feat! Even the Great Plains are great only for their horizontal dimension, vertically they are quite uninteresting.
A giant was drunk enough to fall his entire height which was 2.17479917 miles. Did it hurt ? Ex-plain and give the proper calculations. --DLL 19:25, 19 May 2006 (UTC)
Make it so that the answer is terminal velocity of the object. -- Mac Davis] ⌇☢ ญƛ. 07:20, 20 May 2006 (UTC)
Very roughly -- something about 60m/s (Here speed's limited with air resistance. Would you fall from height of 1km, 3 km or 8km, your speed would be about 60m/s. Conversely, if you'll fall from heights of about 5 m or 30 m, your velocity will be nearly the same as if there were no air). However, air resistance wouldn't allow you to remain alive after such fall... ellol 01:27, 23 May 2006 (UTC)

[edit] microeconomics-pricing in a competitive market

In a competitive market, the firm's price equals the minimum average total cost (ATC)How? If the marginal revenue is greater than the marginal cost, profit will increase, and vice versa. So if the MR is greater than the MC in a competitive market, why is the profit maximising level when they are equal? Dont you need the marginal revenue to be bigger than the marginal cost in order to make profit? —The preceding unsigned comment was added by 192.115.60.109 (talk • contribs) 08:21, 19 May 2006.

Congratulations on taking an entry-level economics course! You will not find a lot of success here in getting people to do very basic assignments. Our minds cloud over at the horrible memory of when we actually did our own homework, long ago. --Zeizmic 13:37, 19 May 2006 (UTC)
This is easiest to explain with calculus, but I'll refrain because I don't know if you know calculus, so here it goes: Profit equals revenue minus cost. The quantity of output at which the difference between revenue and cost is GREATEST (i.e. greatest profit) is the quantity at which marginal revenue and marginal cost are equal (if you know calculus, marginal revenue is the first derivative, or the slope, of the graph of revenue versus quantity output, and marginal cost is the slope of the graph of cost versus quantity output. Keep in mind that MARGINAL REVENUE DOES NOT EQUAL REVENUE, and the same for cost, because they are different things). J. Finkelstein 16:31, 19 May 2006 (UTC)
And take a look at the graphs at the article Profit maximization. J. Finkelstein 16:37, 19 May 2006 (UTC)

There, some people are very nice and have helped you with your homework (a little bit). In general, companies hate this, and whine about Commodification in their business. --Zeizmic 17:17, 19 May 2006 (UTC)

[edit] It's Sheep We're Up Against: keeping mutton as a lawnmower

Hi all,

I'm currently inquiring into the legality of this with town council, but it may be okay, so I figured I'd do some preliminary research: how much lawn would I need to have ... actually, let me broaden the question: what are the practical considerations when looking into having a sheep as an outdoor pet to act as a lawnmower during the summer months, and having it slaughtered in the fall for winter mutton? I have a double lot, which means about 1200 feet of grazing area. Breaking this down into sub-questions: How much land is necessary to sustain a single sheep? Are sheep okay solo, or do they get bored/depressed/weird if they don't have companionship? What are the medical requirements of having a sheep... cost for a vet visit, etc.? How much does a full-grown sheep weigh? I have a very large outdoor shed that's practically unused, so the plan would be to buy a little sheep, convert the shed into a barn area, fence in the whole property, and let the sheep live and graze all summer; in the fall, pay a slaughterhouse to "convert" it into meat. Is this a practical idea, or a fool's paradise? --MattShepherd 17:17, 19 May 2006 (UTC)

Ah, I grew up with the creatures. In my country, in moderate climate, as a very rough basic start for ordinary range meat sheep, 1 per 15000 to 22000 sq ft. That is, you should then not need additional feed. But type of grass/pasture, rotation and watering etc modifies that greatly. Farmers in the area could help you there. If you wish to keep the sheep on your lawn only, you are going to have to become a grass farmer, with maybe two paddocks, or accept that you would need to buy feed, and let the sheep keep the lawn closely cropped as a sort of fresh delicacy. For adult sheep you are looking at weights of 90kg to 180kg (200 to 400lb), unless you go for miniatures.
A sheep is ok solo, but you are going to become her/his friend. But then, of the small breed sheep like Southdowns you could put two on your grazing. I'd get a small breed, plan on feeding, but wouldn't plan on eating it! Like I wouldn't eat my dog or pet pig. It just gets that way. At the house that myself and a few friends rented while students, we had the bright idea of obtaining two ducks for snail control, and eventually a Christmas meal. Well, when that meal came out of the oven, no-one had an appetite, while a passing beggar had a windfall.
The vet issue stumps me, one obviously can't buy farmer-size bottles of medication as one would for 1000 sheep, so you would probably be taking your friend in to the vet's twice a year, and getting yourself a book on the signs of sheep well-being and illness. All in all, I think it would be a rewarding undertaking, and a wonderful learning experience. The best place to look for advice is from a local farmer, especially if your vet can recommend one. If you then buy one of his sheep, you may be able to return it if your undertaking turns out to be non-sustainable. --Seejyb 21:31, 19 May 2006 (UTC)
I'm no expert on sheep but I recently took a small night course on raising them. It was offered through the local university as an extended learning sort of thing where just anyone could sign up for the course whether they were students at the time or not. Course the university is well known for its agriculture studies, so if you live near MIT or some other mainly tech/business school, you may not have the same luck in finding such a course. But you could look into that and maybe learn more than you ever thought you'd learn about sheep in just a few nights. Dismas|(talk) 01:24, 20 May 2006 (UTC)

How much land is necessary to sustain a single sheep? I once had a pet sheep that operated quite nicely on a 1/8 acre section (that's about 20 x 25 m). It all depends on the type of land you've got though, since this affects the stocking rate. Are sheep okay solo, or do they get bored/depressed/weird if they don't have companionship? Sheep are weird even with companions. They do get a bit bored, but as long as they've got something to keep them interested (my one seemed to like the odd old cardboard box). They also appreciate human comany every now and again, so going out to pet it is recommended. In other words, treat it like a pet, not like a lawn mower. How much does a full-grown sheep weigh? they can be lifted if you're strong, but they are fairly heavy, especially when they have a full fleece. At an estimate I'd say 100 lb (45 kg). You've got an apt name, BTW! :) Grutness...wha? 05:30, 20 May 2006 (UTC)

Also keep in mind that there will be lots of sheep dropping on your lawn, which can be unpleasant when you want to use it for recreational purposes (i.e. lazily lying around in the sun). You will also have to shear the sheep from time to time, as common sheep have been bred to grow a thick fleece. There may still be other races without the excessive buildup, though. --212.202.184.238 14:43, 20 May 2006 (UTC)
Those would be hair sheep breeds. Rmhermen 20:20, 21 May 2006 (UTC)
Thanks for all the replies. I took some initiative and contacted a sheep farmer in the 'States, and she confirms most of the above. I have not, however, heard back from Town Hall. I suspect that nobody has ever actually banned livestock within town limits and they're frantically passing laws in Council even as we speak. --MattShepherd 12:47, 25 May 2006 (UTC)

[edit] I was playing with it and it fell off? a little help

I was rubbing it the other day and for no reason at all it just fell off? I didn't think i was rubbing it that hard, will it be ok? I heard from a couple of my friends that it's perfectly normal, and that it's supposed to fall off? even that it's able to grow back. I kind of miss it, and wish it hadn't fallen off, will I be less of a person for going through life without it? Will not having it affect my masculinity at all? will i not want to eat meat anymore? how long does it take to grow back? can it be reattached? or is the area too sensitive for that kind of surgury? I mean I have extras, and from now on I'll never rub it so hard again. But still, I liked the one I had--Question asker 18:05, 19 May 2006 (UTC)

Dude, some of us are trying to ask serious questions about using sheep to mow our lawns here. I hear your style of dazzling wit is in high demand over at SomethingAwful, though. Go spread your genius there! --MattShepherd 18:21, 19 May 2006 (UTC)
I understand this is most likely to happen with really small ones.
IANAMD. Do not fret so much, it is quite normal at age 7 (however, if yours now fell out a bit early, there is still a good chance you may grow up normal) A new one will grow out, called an "adult" one. And this may continue for a few years still, eventually culminating in so-called "wisdom". But that needn't worry you now, if this was just a front one, you're still miles away from the wisdom stage. Until all the "adults" have grown out, you may have a problem with mastication. --Seejyb 22:15, 19 May 2006 (UTC).

[edit] Why is Foam White

I searched online, however was unable to locate any references. I was standing on my balcony overlooking the Thames and it is a muddy river with constant boat traffic. My question is this... why is the foam so incredibly white, both at the bow and stern? --Djymz 18:27, 19 May 2006 (UTC)

Some ideas... Foam isn't a good food for bacteria, mold, fungus - so none of that will flourish on the foam. Foam left in the sun bleaches easily. Foam is fragile, so the dirty outside is easy to chip off and expose the clean inside. --Kainaw (talk) 18:35, 19 May 2006 (UTC)
I think the questioner was refering to foamy water caused by a boat, not foam like styrofoam. --Chapuisat 18:47, 19 May 2006 (UTC)
And to try to suggest an answer, foamy water is full of tiny bubbles and this changes it from fairly transparent very reflective because the surface of these bubbles reflect the light. See Whitewater --Chapuisat 18:52, 19 May 2006 (UTC)
A soap bubble has colors because the light reflects off the inside and outside surfaces and interferes with itself constructively or destructively depending on its wavelength. Foam is many tiny bubbles oriented randomly, so the colors average out to make white light. Put another way, a ray of light that hits the foam is scattered in a random direction which doesn't correlate with its wavelength because the bubbles have random thicknesses. —Keenan Pepper 05:57, 20 May 2006 (UTC)
Perhaps foam is white for the same reason that clouds are white? Mist is white too. -- Mac Davis] ⌇☢ ญƛ. 07:19, 20 May 2006 (UTC)
Sounds right. The eye is too far away from the bubbles or the clouds to notice the individual colors, so we can only see the combined light. freshgavinΓΛĿЌ 13:11, 20 May 2006 (UTC)


Not quite - clouds and mist are white due to Mie scattering of incident white light, if you shine red light on foam, it appears red. The reason for white foam with very small bubbles is the same. Why foam with larger bubbles is also white is different however. Incident white light is reflected at random from the spherical(ish) surfaces of the bubbles, and eventually, some of the light is reflected back towards you.--Eh-Steve 15:28, 25 May 2006 (UTC)

[edit] Advances in computer science

What would a programming language have to do to be truly new? I mean to truly do something which no other language had done before? Is this limited by what computer chips themselves can do? What I'm getting at is that it seems to me that comparisons between languages are comparisons between how they do things and how easily they do things (as well as things like which paradigm(s) they allow / encourage, what type system they use etc etc), not between what they actually can do.

Thanks --87.194.20.253 18:51, 19 May 2006 (UTC)

You may want to take a look at the series of articles: Theory of computation, Computability theory (computer science), Computational complexity theory, and Turing machine. EricR 19:05, 19 May 2006 (UTC)
I imagine a language where you could just tell the computer what you want to do, and it would figure out how to do it. For example, if you told it to solve the quadratic equation:
ax^2+bx+c=0\,
using the quadratic formula:
x = \frac{-b \pm \sqrt {b^2-4ac}}{2a}
it would then ask the user for values a, b, and c, and handle the cases of no solution, one solution, two solutions, and imaginary solutions, without the programmer having to specifically code for each of those cases. It would also know how to avoid the potential division by zero error and print out the results automatically. StuRat 19:30, 19 May 2006 (UTC)
If you take Mathematica or Maple as "programming languages", then they can do this sort of thing, even though they're not very new. --Borbrav 20:47, 19 May 2006 (UTC)
"What would a programming language have to do to be truly new?" That's like asking What would a piece of art have to be like to be truly new? If we knew ahead of time, it wouldn't be truly new. Let your mind explode, and then write it; we're waiting. --GangofOne 22:33, 19 May 2006 (UTC)

"Is this limited by what computer chips themselves can do?" - No! Any mathematical question can be reformulated and programmed into a Turing complete programming language, almost by defition. Programming language development today centers around "productivity" - sure, you can write anything C/C++, but do you really want to spend all that time coding it in C/C++ when you can do it in {Java/Python/Perl/Ruby/etc} in a fraction the time? More specifically, programming for parallel computers (multi-processor, or multi-core machines) is *HARD* and the software tool simply don't exist (I should know this very well since I'm doing my PhD in parallel computing). Raul654 22:40, 19 May 2006 (UTC)

I consider quantum programming languages to be new, but they aren't going to run natively anytime soon. Melchoir 22:58, 19 May 2006 (UTC)

New doesn't always imply "good" or "beneficial". I think the better aim is to create something useful, not something new for newness sake. Dysprosia 02:14, 21 May 2006 (UTC)

[edit] LPG vs petrol

hi, everything i've read about LPG tells me that for running cars LPG is more economical, less polluting and is generally better for cars than petrol. in these days of global warming and i guess, "energy security" ( as i understand it, which i may not, gas, at least in Europe, comes from Russia) why don't governments promote it more heavily? at least in fuel-taxed societies, if the government increased taxes to pay for converting peoples cars, surely it would cut carbon emmissions over night? basically, i guess i'm actually asking, are there any cons to LPG that i don't know about? thanks 87.194.20.253 18:58, 19 May 2006 (UTC)

It still comes from russia, and it still burns to form carbon compounds. Due to the explosive nature of the fuel, containers have to be very thick and sturdy, in order to cut out all risk of a puncture. Philc TECI 19:08, 19 May 2006 (UTC)
LPG is currently cheaper, but it is supply and demand; less people want the product, so it is cheaper. If enough people want it, the price will go up and match other energy sources. The hope of early adopters is that it will stay unpopular long enough for them to profit. Notinasnaid 19:12, 19 May 2006 (UTC)
It's not just about price, it's also about freedom. In the USA about 25 years ago I know that gas stations were forbidden to sell LPG by their franchise owner. IE if they offered LPG they couldn't buy gasoline from them. (It would undercut the gasoline business.) There weren't many LPG cars, but some. Some people converted their trucks and so forth. But here we have a case where a "free market" is subverted by the resource owners to maximize profit, not to maximize consumer demand. If LPG had been commonly available over the recent decades, other benefits would have included less dependence on the usual gang of foreign sources, that we are now fighting over, plus whatever hybrid technical delevopment that may have occurred, plus more choice for the individual. --GangofOne 22:27, 19 May 2006 (UTC)
There are also other disadvantages. Most cars are not originally sold as LPG, and if you make convert a car to LPG the gas tank will occupy much space from the trunk. Also, LPG is currently available at fewer gas stations than petrol, at least here. – b_jonas 09:28, 20 May 2006 (UTC)
And because of the danger of explosions (as mentioned by PhilC), many underground car parks, ferrys etc either ban or restrict LPG-powered vehicles. Check the laws in your area about this. — QuantumEleven 11:51, 22 May 2006 (UTC)
Around here (Rio de Janeiro) there is a lot of converted natural gas vehicles (which can run on both natural gas and gasoline, so there's no problem if there's no station nearby), because the natural gas is much cheaper than both gasoline and alcohol. While it's not LPG, it's a similar situation. --cesarb 12:29, 22 May 2006 (UTC)

[edit] getting a head start

hi, all the chat about evolution got me thinking (in a lateral sort of way), it's widely assumed (at least by me) that bi-lingual children, regardless of what languages they speak , are better at learning new languages than monolingual children becuase their concept of language is more refined from an earlier age (e.g. a french/english child would have an easier time learning arabic say, than someone from a monolingual background). is this the same for any other subject areas? if i teach my child long division at the age of three, will he go on to find nuclear science a walk in the park? or how about if i get him started on shakespeare, will he then go on to have mastery of the english language beyond his years? if not, what is it that makes language so special and, if so, aren't we shooting ourselves in the foot by starting school at the ripe old age of 5?87.194.20.253 19:14, 19 May 2006 (UTC)

Teaching as much as possible early on has advantages, but if you overdo it and make the child hate school and learning, this strategy may backfire completely. Learning a language as a way to communicate with friends or family members who speak that language doesn't seem like work, so isn't as likely to cause a backlash from the child. StuRat 19:23, 19 May 2006 (UTC)
It isn't facts that helps. For example, my white trash brother-in-law tried to impress me because his son at age 5 could count to ten using the names of the Nascar drivers in place of the actual numbers. However, he couldn't count to ten with actual numbers. So, knowing the Nascar drivers by number order isn't going to help him in any way in the future. However, if he had learned the foundation of how numbers relate to one another, how the basic math operators work with those numbers, and then how everything in the world relates to numbers... he would have a good headstart when all the other kids are still memorizing their addition tables. I have found over and over that it is the foundation of basic knowledge that sets the "smart" kids apart from the rest. In high school, I was dumbfounded when a classmate tried to tell me tha a tree was an insect because it wasn't an animal. Her foundation of separating plants from animals was never formed so she was destined to fail just about any biology class. --Kainaw (talk) 20:23, 19 May 2006 (UTC)
If you read Feynman's various memoirs you find that he doesn't mention his father drilling him on physics facts, but rather nature walks he took where he and his father discussed why various plants and animals did what they did. I believe he even mentions how a childhood friend scoffed at him because he didn't know the names of any of the local birds. Feynman points out that although his friend knew all their names, he didn't actually know anything else about them. Anyways, further anecdotal evidence that developing reasoning capabilities as a child is more important than learning sets of facts. — Laura Scudder ☎ 21:09, 19 May 2006 (UTC)
Read to the kid. All book knowledge comes through having language skills. Makes it clear that books are important. But only interesting ones--don't force it. Even better than books is actually DOING something. But early SCHOOL is a killer. One to one learning about relevant concepts, that seems the thing. (But what do I know?) --GangofOne 22:13, 19 May 2006 (UTC)
No. Cognitive development needs time to run its course. A three-year-old will never understand long division on any level, and atempting to teach it would be, as the educators say, "developmentally inappropriate". You could do serious harm by pushing such things too soon. As for why language develops sooner than abstract thought, well, that's a research question. Melchoir 22:52, 19 May 2006 (UTC)
That's not true, when you hold back abstract concepts from young children, all you do is teach them that understanding isn't as important as structure and memorization. There's no practical reason that you couldn't teach biophysical chemistry to a 3 year old, other than that such a child will be teased mercilessly every second of their life from their first day of elementry school all the way through grad school--71.249.0.202 23:20, 19 May 2006 (UTC)
Three-year-olds can't even understand that when you take ten marbles, toss them in the air, and let them settle, you still have ten marbles. Not even if you do it in front of their faces a hundred times; they'll just become distressed. Biophysical chemistry?! Forget it. And if by some perverse miracle you got a three-year-old to be able to pantomime long division, that would be memorization, because there's no way the poor child understands what's going on. Melchoir 23:32, 19 May 2006 (UTC)
Honestly, most students seem to lose interest in what they're doing by the time they're in thier late teens anyway, that's why 90% of the people in, let's say, a biophysical chemistry lecture, are sitting there with their eyes glazed over nodding their heads alot. Say what you want, but I think the 3 year old is more likely to show interest in it--71.249.0.202 23:38, 19 May 2006 (UTC)
Oh, absolutely, they'll show interest if you present the material in an age-appropriate fashion. I'm not sure what that is... they might have the motor skills by that time to manipulate ball-and-stick models, but they'd also try to eat them. Maybe they'd be amused by some safe chemical reaction that changes color? Melchoir 23:50, 19 May 2006 (UTC)
This all seems to presuppose that a 3 or 4 year old can't be a formal operational thinker, I can't really see why this would be the case, assuming you gave a toddler a crash course in calculus, matrix algebra, simple hermitian operators, and a little bit of inorganic chemistry, you could get through most of that before the child is even in 1st grade, assuming you started the instant they were capable of abstract reasoning, of course that child would probably have a nervous breakdown before it ever entered its teens--71.249.0.202 00:18, 20 May 2006 (UTC)
How absurd. Do you have experimental evidence of concrete operational 3 or 4 year olds that you're holding back from the scientific community? Melchoir 02:46, 20 May 2006 (UTC)
I don't see why no 3-year-old would ever be able to perfrm long-division. It's possible that they would have to record it in a special way, as they might have difficulty with the motor skills required to write it, but it's really a few simple operations repeated over and over. I think it could be done. Getting them to understand why they're doing what they are doing might be harder, but probably achievable. I was always annoyed with people who said children couldn't learn certain types of maths and things until a set age. For example, they refused to introduce us to negative numbers for ages, as apparently children can't understand them until a certain age. However I, along with a few others, was happily using them from the age of about 6, ever since we heard people talking about them. Multiplying and dividing with them was harder, because nobody would tell us properly about them for ages. The main problem I had as a child wasn't the inability to understand certain types of thing, but a lack of built-up experience that left me guessing what 'soda water' and 'rouge' might be in the experiments I read about. Without a knowledge of times tables, I couldn't perform harder maths quickly. I'm not sayig children should be intensively taught these rote-learning things, just that it always felt like the main difference between ages. Skittle 12:23, 20 May 2006 (UTC)
Yes, and no. It's quite possible to be ready for negative numbers at the age of six, assuming more basic operations and properties (like the commutative property of addition, and addition itself in the first place) are already understood. I have a pet peeve of my own in that area: people I trusted in math areas have been telling me for my entire life that division by zero is, plain and simple, impossible. In fact, it's meaningless. And yet, for two years now, I've been using limit notation to do exactly that without fear or hesitation. I could have learned at least the basics of limit manipulation, in fact, right after learning Algebra in middle school. However, there quite simply are limits to what the brain can handle at very, very early ages, like 3 years. It's not just motor operations, it's mental operations as well. I don't know whether long division is one of the things most 3-year-old couldn't handle, but I wouldn't be surprised if it was. Black Carrot 18:54, 20 May 2006 (UTC)
What about teaching them the game of go? The rules are pretty simple to grasp. --Username132 (talk) 13:15, 25 May 2006 (UTC)

[edit] do neutrinos have mass?

elaborate please--71.249.0.202 20:55, 19 May 2006 (UTC)

See neutrino. — Laura Scudder ☎ 21:00, 19 May 2006 (UTC)
See title ^ I was hoping for more of a discussion though--71.249.0.202 21:02, 19 May 2006 (UTC)
I just thought that the article discussed it more thoroughly than we could. — Laura Scudder ☎ 21:10, 19 May 2006 (UTC)
Ok, let's try something more philosophical, a neutrino has angular momentum, which classically implies mass... but doesn't have to--71.249.0.202 23:27, 19 May 2006 (UTC)
Photons have angular momentum but no mass. -- SCZenz 23:37, 19 May 2006 (UTC)
That's why I said classically, not quantum mechanically, and I still seem to be failing at actually starting an interesting discussion about fermions--71.249.0.202 23:40, 19 May 2006 (UTC)

This isn't a discussion board. It turns into one, sometimes, but a good question usually helps jump-start things. Yes, neutrinos have mass. This is observed due to neutrino oscillations, and the Seesaw mechanism may be involved. What else would you like to know? -- SCZenz 00:16, 20 May 2006 (UTC)

Is this homework? ?_? --KJ 01:22, 20 May 2006 (UTC)
What sort of homework would that be?--4.236.165.94 02:15, 20 May 2006 (UTC)
Debate? --KJ
Hahah. Neutrinos have mass. Period. Ooops I just put three periods. :P That was an excessively lame joke... -- Mac Davis] ⌇☢ ญƛ. 07:17, 20 May 2006 (UTC)

Yes, but they don't take Communion. --MattShepherd 12:49, 25 May 2006 (UTC)

[edit] Time

I've looked in time and not found anything relating to the question "Is time continuous or is it formed of discrete quanta". Any pointers to anything discussing this? -- SGBailey 21:33, 19 May 2006 (UTC)

I can't offer anything but I really want to know what the possible interpretations (I won't say answers) are too. Could I extend the question to cover matter and space too? Sorry to butt in without anything to offer but I think the whole thing's really interesting - you know, whether the concept of discrete quanta as you put it has any basis in reality or not. The way I see it, possible interpretations would have great potential bearing on the philosophy of science and maths - we go around counting things all day but are there really any things that would justify the abstraction? Thanks. --87.194.20.253 21:39, 19 May 2006 (UTC)
Time is continuous, the only things that are discrete are the things you can count. Like apples. yum yum. Philc TECI 22:00, 19 May 2006 (UTC)
Says who? You would be equally able to state that matter is continuous, not discrete, but then someone discovered atoms. I doubt we could (ever?) count discrete time - if such is - as it is probably quantised at some tiny level like 10^-30 second. -- SGBailey 22:06, 19 May 2006 (UTC)
Isn't time, more specifically the second, defined in the precise terms of the harmonics of a cesium atom? Last I heard, cesium is a discrete unit, and since you're measuring the emmesions of said atom, you're measuring a photon, a discrete quanta if I've ever seen one--71.249.0.202 22:42, 19 May 2006 (UTC)
No, Our unit of time is defined that way, but that says nothing about the nature of time. The metre used to be defined as the length of a rod in Paris - that says nothing abiout the existance or otherwise of atoms. -- SGBailey 23:15, 19 May 2006 (UTC)
Well that's the problem, time isn't something you can measure directly or otherwise, you can only measure a process that's supposed to occur over the course of time, but that's a bit of a circular definition--71.249.0.202 23:23, 19 May 2006 (UTC)
I didn't say matter was continuous I said apples where, if you have two apples, even if you count to a million decimal places, you still have two apples or to be precise, 2.00000000000000000.... Philc TECI 07:44, 20 May 2006 (UTC)
Most of what I've heard is that we wouldn't be able to measure units of time smaller than the Planck time, so we wouldn't be able to distinguish continuous time from discrete time of that quanta. There's also a Planck length. — Laura Scudder ☎ 22:13, 19 May 2006 (UTC)
I 'kind-of' like the concept of quantised time - it suggests that, in combination with quantised space, we could live in a giant 4-D array - The Matrix like. (I'm not saying this is how things are...) -- SGBailey 23:15, 19 May 2006 (UTC)
To answer the original question, you may like to read this discussion between philosophers and physicists on physicsforums [65]. -- Mac Davis] ⌇☢ ญƛ. 07:12, 20 May 2006 (UTC)
Yes, there is considerable speculation that space and time may be quantized at a tiny subatomic level. I don't have the issue with me, but a recent issue of Scientific American] had an article discussing this. I would not be surprise were it to be so. Perhaps there is nothing continuous in nature, nothing analog—the universe really may be digital. — Knowledge Seeker দ 08:09, 22 May 2006 (UTC)

[edit] roving a sheave block

I have 3 pulley blocks: 1x single, 1x dbl, 1x triple. The multiple blocks are sheaved side by side. What is the correct way to rove (run the rope through) the blocks to avoid them twisting? I am seeking a mechanical advantage of 6:1 for lifting. PS - The single pulley will be the tail out as it has a ratchet. Regards -JAG.


[edit] Soda losing fizz!

This has annoyed me for quite some time now, so I am going to ask here. A friend of mine says that leaving a bottle of soda without the cap on will not reduce the amount of fizz in the bottle faster than if one was to screw/unscrew the cap every time one needed to refill. Have there been any studies on soda losing fizz? It is an economical issue, actually. Today I was going to the store with some bottles, and found that there was half a gallon in total of unfizzy soda left in the "empty" bottles. You CAN'T drink unfizzy soda, it's like torture of some kind. The only good thing about soda losing fizz is that it becomes something to clean the pipes with, albeit not very efficiently. Henning 22:46, 19 May 2006 (UTC)

Your friend is mistaken. While the bottle of soda is under pressure, carbon dioxide gas – the 'fizz' – is forced to remain dissolved in the soda. (The pressure in the bottle actually comes from a small amount of the dissolved carbon dioxide accumulating in the headspace of the bottle between the top of the liquid and the cap.) When you open the cap, that carbon dioxide (CO2) gas escapes, and fresh CO2 is free to come out of solution. That CO2 will continue to come out as bubbles as long as the soda is open to the air.
Putting the cap back on the bottle allows CO2 gas to build up in the bottle once again. Once it reaches a sufficiently high pressure, it will hold the remaining CO2 in solution in the soda and preserve your remaining 'fizz'. The more times you open and close the soda, the less CO2 will remain—but it's still better than just letting the CO2 escape continuously. TenOfAllTrades(talk) 00:37, 20 May 2006 (UTC)
Also (and this is one of my great pet peeves) do *not* squeeze the bottle when you put the cap on. If you do, the CO2 in the soda will escape and re-fill the half-crushed bottle, thus causing the soda to go even more flat. Raul654 00:52, 20 May 2006 (UTC)
Ah, great! Thanks to both :) I will now venture forth in life with good knowledge of flattening soda. Henning 10:51, 20 May 2006 (UTC)
Unless the bottle is going to be shaken, in which case squeezing the bottle will minimise the ratteling which causes faster release of the fizz. The squeezing also makes sense if the bottle will be forced to keep that shape. I was taught the squeezing trick on a hiking trip where a squeezed bottle was then tied to the rucksack with a strap -- which makes it both easy to access and saves the fizz. --Swift 00:24, 21 May 2006 (UTC)

[edit] May 20

[edit] What phase of matter is a Frosty?

I need something to reply to that "soquid" nonsense. Is it a gel or an emulsion or what? —Keenan Pepper 01:34, 20 May 2006 (UTC)

Seems to me it's a liquid, with a high viscosity. -- Filliam H Muffman 02:28, 20 May 2006 (UTC)
The definition of a solid is that it retains it's shape whereas a liquid takes the shape of the container it is in. Even if refrigerated, a frosty will take the shape of its container (albeit slowly - as Muffman said, indicative of high viscosity). Thus, it is a liquid. Raul654 02:31, 20 May 2006 (UTC)
Don't be ridiculous. The Frosty is either: A) solid ice crystals in liquid flavoring or B) liquid flavoring in a solid...er...thing. I vote for "A", which would make it a sol, like paint. Not "sol" as in the other name for the sun, but "sol" as a colloid with solids mixed into a liquid. --M1ss1ontomars2k4 | T | C | @ 05:25, 20 May 2006 (UTC)
Sand will take the shape of the container it's in, but I don't see any claims that sand is a liquid. Notinasnaid 08:00, 20 May 2006 (UTC)
A single grain of sand is solid and will not take the shape of its container. For the same reason, a single steel ball-bearing is solid, but a ton of them poured into a swimming poll will take the shape of the pool. Raul654 08:04, 20 May 2006 (UTC)
I don't think that's relevant about sand not being a liquid. I think it isn't a liquid because even though it will take the shape of the container, that's only the bottom surface of the sand. The top surface might not be flat, but can form a cone or any shape that isn't too steep. As an analogy, put a large pile of chlotes (to be ironed) into a basket, and push it down somewhat. They will take the shape of the basket, that is, there won't be large gaps between the wall of the basket and the chlotes, but the top surface of the chlotes won't be flat. On the other hand, the surface of a liquid will always become flat and horizontal. – b_jonas 20:04, 21 May 2006 (UTC)
So, to demonstrate that a frosty is a liquid, you would have to first demonstrate that it is a single solid object rather than a collection of them. It seems easier to explain that the frosty is a loosely bound collection of solids (with some liquids acting as a binder). Notinasnaid 08:07, 20 May 2006 (UTC)
Guys, don't be silly. Everybody knows its a colloid—it is composed of more than one state of matter, and cannot be said to be any one phase. It is composed of crystals of different shapes, sizes, and constipates, bubbles, and liquids (from the melted crystals), suspended in a liquid. Asking what state of matter is a frosty is comparable to asking what state of matter is a pizza, without offense, you know. -- Mac Davis] ⌇☢ ญƛ. 07:04, 20 May 2006 (UTC)
Yeah, colloid, that sounds right. Much better than "soquid" anyway. —Keenan Pepper 08:21, 20 May 2006 (UTC)
I thought it was an interesting commericial. Boy are frosties good. The local Wendy's's frosty machine is broken :( -- Mac Davis] ⌇☢ ญƛ. 08:46, 20 May 2006 (UTC)
Are you certain it's a colloid? If you've seen the add, it seems like the ice crystals at least are way, way to big to fit within the range mentioned in that article, and it certainly isn't at all comparable to mayonaise and fog. Black Carrot 19:02, 20 May 2006 (UTC)
A good frosty doesn't have ice crystals big enough to see or feel. It's as smooth as mayonnaise. —Keenan Pepper 20:05, 20 May 2006 (UTC)
What would it be if it did? Black Carrot 21:59, 20 May 2006 (UTC)
It would probably still be colloid because no matter how big the crystals are, there's a good amount of water and syrup sticking them all together. freshgavinΓΛĿЌ 11:33, 23 May 2006 (UTC)


Its an OIW (oil in water emulsion), and due to the solid state of the milk fat, a colloid. Technically its also a foam because it contains air bubbles. The "water" of the OIW is actually a mixture of water, ice, sugar, and (possibly) whatever else is in a frosty (otherwise they're dissolved in the fat). --Eh-Steve
See? See? I told you it was a colloid! A sol is a kind of colloid!--M1ss1ontomars2k4 (T | C | @) 04:49, 27 May 2006 (UTC)

Hey, check out the article now...according to it, it's a "Bingham plastic"? JianLi 20:25, 26 May 2006 (UTC)

Not anymore. I removed it for now, since it doesn't make much sense. We can discuss it on the talk page. --M1ss1ontomars2k4 (T | C | @) 04:49, 27 May 2006 (UTC)

[edit] Domestication question

Okay, I've actually gotten into a discussion about this with some people and I want to ask it here: Do you think it would be possible to domesticate a giraffe? I mean, obviously it would be an outdoor animal --but I think they might be quite fun as pets or at the least an alternative farm animal like ostriches. Same for sea otters, although I don't think they'd be as easy to take care of (and I have no interest in eating them) --sure you could place them in a pool but the chlorine would probably not mix well --would they require a base amount of salinity? They're sooo cute! Okay, the first question is serious, not the one about otters. The latter just rock. -- Bobak 02:10, 20 May 2006 (UTC)

  • Far as I can tell, river otters can be domesticated (see Ring of Bright Water if you want some lessons as to why you might not want to make a pet of one), but not sea otters -- you'd need something of an ocean, a lifetime supply of abalones, and one hell of a lot of kelp! Dunno about giraffes, but I did find a picture of someone named Jimbo riding one. I think the giraffe was stuffed, though. --jpgordon∇∆∇∆ 02:32, 20 May 2006 (UTC)
  • Otters can be tame if they grow up in captivity. This is different from domestication, as they have not been bred to be this way, they're just raised by humans and are less wild. For example, at Wellington Zoo they have a small-clawed otter which is highly "domestic" as he was raised by humans (he was the runt of the litter and wouldn't have survived otherwise), meanwhile his brother has very different behaviour, having been raised by his mother, and he doesn't respond to humans the same way.
Back to the main question. Yes, I'm sure giraffes could be domesticated over many generations just like horses (a not too distant relative) have been. As for keeping them as pets, I'm sure you already could, if you had the space, just like zoos do. —Pengo 03:29, 20 May 2006 (UTC)
Do zoos count as really large backyards, the zookeepers the "owners" of sorts", and the animals "pets"? OK that was weird question, but I'd like to know what others think. --M1ss1ontomars2k4 | T | C | @ 05:22, 20 May 2006 (UTC)
In a word, no. People generally keep pets for companionship or for a practical function (such as cats to control rodent populations). Zoos keep animals for conservation, education, and entertainment, but not for companionship for the keepers (who are paid staff) or for a practical function. Also, almost all zoo animals are not domesticated. In other words, even if they are tame, they are still genetically wild animals identical to their relatives not in captivity. Truly domesticated animals such as dogs and livestock are different from their wild relatives, usually to the point they are considered different species. --Ginkgo100 21:12, 20 May 2006 (UTC)
There are giraffe preserves in which giraffes are more-or-less tamed/domesticated/conditioned to be used to humans. The most famous is probably "Giraffe Manor", founded by Betty Leslie-Melville, the Giraffe Lady, near Nairobi in the 1970s to preserve the Rothschild Giraffe. The giraffes poke their headsd through the second-story windows to "have breakfast" with the guests there. - Nunh-huh 05:39, 20 May 2006 (UTC)

Wow! Thanks for all the feedback. I really thought otters weren't going to work, but I guess they could too. Just reading the Wikipedia synopsis of Ring of Bright Water was depressing... I think I'll pass on it (sounds like the Old Yeller of otter movies). I remember seeing otters similar to the small-clawed otters at the Osaka Aquarium Kaiyukan (they were small and freshwater), I guess those would be possible. I guess I'll have to be a millionaire some day to raise them, though. As for giraffes, thanks for all the suggestions as well. Thanks for the reference to the Giraffe Lady, very interesting stuff! -- Bobak 19:26, 20 May 2006 (UTC)

Jared Diamond has some theories on the un-domesticatibility of most animals. See Guns, Germs and Steel. Rmhermen 20:11, 21 May 2006 (UTC)
As Pengo says Domestication of wild animals is different from taming them, compared to the former the latter is relatively easy. It is unlikely that there are any wild species which are now capable of domestication but haven't already been at least partially domesticated. AllanHainey 14:28, 22 May 2006 (UTC)

[edit] Viruses, etc

what is the difference between bacteriophages, viruses and retroviruses —The preceding unsigned comment was added by 211.28.236.104 (talk • contribs).

Answers taken from the opening paragraph of the articles:

bacteriophages
A bacteriophage is a virus that infects bacteria.
viruses
A virus is a submicroscopic parasitic particle that infects cells in biological organisms.
retroviruses
A retrovirus is a virus which has a genome consisting of two RNA molecules, which may or may not be identical. It relies on the enzyme reverse transcriptase to perform the reverse transcription of its genome from RNA into DNA, which can then be integrated into the host's genome with an integrase enzyme.

—Pengo 03:22, 20 May 2006 (UTC)

Note that bacteriophages and retroviruses are all kinds of viruses. --M1ss1ontomars2k4 | T | C | @ 05:18, 20 May 2006 (UTC)

[edit] The Speed of Time

I've heard of a saying in physics that "time travels at the speed of light".What does it mean by that?

In Einsteinian physics, it is impossible for information (i.e. causal influence) to travel faster than the speed of light. Time and causal influence are closely related concepts; events that are causally connected (i.e. one is in the other's future time cone) are said to have a timelike separation. Thus causal influence -- "time" -- expands through space at the speed of light. -- EdC 06:51, 20 May 2006 (UTC)
The speed of time can only be said as going at one second per second. 1s/s. One second elapses each second. This is, of course quite silly, because speed is change in position over time. Time is not a physical concrete thing, and cannot change in position. -- Mac Davis] ⌇☢ ญƛ. 07:01, 20 May 2006 (UTC)
I beg to differ. Claiming that something travels doesn't necessarily imply it's a concrete matter-based substance; forces (like gravity) travel without manifesting physically. If you drive your warp-drive mustang to the convenience store, you're going to send out ripples in space-time at the speed of light, which is unfortunate because to travel as fast as they do in the TV show you're going to need to be sending out ripples quite a bit faster. freshgavinΓΛĿЌ 12:51, 20 May 2006 (UTC)
Of course it doesn't have to be concrete matter-based substance. Supersonic cracks in glass?--— <tt>[[User:Mac_Davis/Esperanza|<font color="green">'''The'''</font></tt> '''[[User:Mac Davis|<span style="font-family:Times;color:navy;cursor:crosshair;"><em><font color=#006600>Mac Davis</font></em></span>]]]''' [[User talk:Mac Davis|ญƛ.]]]] 00:21, 17 September 2006 (UTC)

[edit] Cockroaches

Are cockroaches known to cannibalise within their species or other species? -Tim Rhymeless (Er...let's shimmy) 06:29, 20 May 2006 (UTC)

How would a cockroach cannibalise anything that isn't a cockroach? Just being picky... Howard Train 06:19, 21 May 2006 (UTC)
Yes. I thought this was mentioned in the cockroach article, but it's apparently not. Do a google search for "cockroach cannibalism" and dozens of references turn up. While we're talking cockroaches, I'd never thought I'd feel sympathy for the things but this is the most evil thing I've ever heard of. If I didn't know better you'd almost count it as evidence for a malevolent deity...--Robert Merkel 08:18, 20 May 2006 (UTC)
Or as evidence towards creationism. How the hell do you evolve skills like that?? freshgavinΓΛĿЌ 12:38, 20 May 2006 (UTC)
Feel sympathy do you? Well that's your empathy talking. Cockroaches don't even feel pain. Sure, I'd be bad if it happened to you, but you have feelings and can think. -- Mac Davis] ⌇☢ ญƛ. 08:44, 20 May 2006 (UTC)
What makes you say they don't feel pain? I can't imagine a scientific test for this. —Pengo 09:09, 20 May 2006 (UTC)
Moral values are not absolute concepts, thus a discussion about what is evil and what is not, simply referring to "mystically produced" empathic feelings is absurd by definition. When it applies to the behaviour of animals it's even more ridiculous. This seems to be the cause of powerful predators (whatever methods they use) seen as evil and a possible cause for moral vegetarianism and veganism. --GTubio 10:45, 20 May 2006 (UTC)

This is not at all disimilar to what the homo-sapien females do to their male counterparts. 12.183.203.184 17:31, 27 May 2006 (UTC)

[edit] Trouble with DRM

I've recently bought an Aigo A208-1G MP3 player. It is supposed to support DRM 9, but I downloaded the sample track from tesco but it wouldn't play - on my computer it made windows media player crash and on my mp3 it doesn't appear in the list of music (this is what happens to non-music files). Do you think it is the file, or my system that is the problem? Is there anywhere I can download a different drm 9 test from?--Bjwebb (talk) 10:49, 20 May 2006 (UTC)

Oh, I've just realised, it does appear in the list on my MP3 player, it just doesn't play - it skips to the next song.

I've managed to fix the problem by reinstalling media player and using it to transfer the file to my mp3, along with the license.--Bjwebb (talk) 13:10, 20 May 2006 (UTC)

[edit] Ratiocination in Evolution

On 19 May 2006, Rush Limbaugh said, "If the closest relatives of humans are chimpanzees, then why do they still exist?"

What is the best argument to counter such a query? I am very much baffled in light of the fact that humans and chimpanzees have inhabited the same regions throughout history.Patchouli 10:54, 20 May 2006 (UTC)

Unless we eradicate all other living things from the earth, we'll always have a closest relative. But in the case of the chimpanzees and other great apes, it's important to remember we didn't evolve from them, but instead share a common ancestor. Somewhere we split up, and both continued to evolve from that point on, taking on their own niche, with it's own habitat and food sources. How much those overlapped in the past i won't dare to guess. While the DNA match is high, humans and chimps really are quite different animals in many ways. SanderJK 11:27, 20 May 2006 (UTC)
I wasn't aware that there was any proof of human involvement in the disappearance of our other close ancestors. By that I mean that I don't believe we have proven homo sapiens caused the downfall of any of its close relatives, and so I don't see why anyone would assume that they would do the same to chimpanzees. freshgavinΓΛĿЌ 11:33, 20 May 2006 (UTC)
As the chimpanzee article says; Biologists believe that the two species of chimpanzees are the closest *living* evolutionary relatives to humans. So, by definition, they still exist, and Limbaugh's question is a circular argument. The fossil record shows other species (both within and outside of genus homo) that were much closer in evolutionary terms to homo sapiens than chimpanzees, but they are now extinct - an example is Australopithecus. Gandalf61 11:41, 20 May 2006 (UTC)

Simply put, chimpanzees are our relatives, not our ancestors. They are better described as our distant cousins than as our grandparents. —Pengo 13:42, 20 May 2006 (UTC)

  • Thank you.Patchouli 19:36, 20 May 2006 (UTC)
I'm not sure I understand the argument either. There's no reason to think someone's ancestor automatically can't coexist with their decendants. --BluePlatypus 22:19, 20 May 2006 (UTC)
If cakes are made out of eggs, why do we still have eggs? Skittle 22:51, 20 May 2006 (UTC)
good analogy.Patchouli 11:37, 21 May 2006 (UTC)
Because cakes cant have sex to make baby cakes, eggs don't grow into cakes, cakes did not evolve from eggs, eggs are essential to making every single cake, not just one initial master caker. Poor analogy, on so many levels. Philc TECI 17:07, 21 May 2006 (UTC)
But it wasn't meant to be an analogy for the entire process of evolution; that would clearly be stupid. The purpose of an analogy is to take an aspect and simplify it to be more easily understood, not to be accurate. It was merely making the point that not all 'monkeys', 'chimpanzees', or whatever form the silly slogan is taking today evolved into humans. Of course, we all know that the argument is flawed on so many levels. Humans did not evolve from monkeys or modern apes, etc. But even if you make the assumption that they mean 'non-human primates' in general when they say 'monkeys'/'apes'/'chimpanzees', the cake analogy explains in an instinctive manner that just because something comes from something else, doesn't mean all the original thing has gone. If cakes evolved from eggs, it wouldn't be an analogy at all. I don't know what you expected :-\ And I don't know why it's orange. Skittle 22:03, 21 May 2006 (UTC)
  • I arbitrarily chose orange to make it stand out. I think it is an analogy because it is simplification to ease comprehension which need not be accurate in every facet.Patchouli 23:52, 21 May 2006 (UTC)
But as pointed out, it's a false analogy, and even if Rush understands it he still would have not been informed that he's been caught deliberately mischaracterizing evolution. The takeaway lesson for someone who asks such a question should be "I don't know enough about evolution to talk about it in public, I'd better read something so I don't embarrass myself again like that in the future". We're not dealing with someone who has a habit of letting facts get in the way of his opinions..... - Nunh-huh 04:46, 22 May 2006 (UTC)
  • I think Rush Limbaugh was knowingly and purposely using the query to mischaracterize evolution; he bent the facts in the Terry Shiavo case.Patchouli 13:29, 22 May 2006 (UTC)
Of course he was. You could easily fill a book with all the mischaracterizations, misleading statements, factual errors, self-contradictions and outright lies Rush has spouted over the years. Several such books have even been written. On the other hand, Rush isn't in the business of pursuading people through rational arguments, weighing pros and cons against each other from a premise to reach a conclusion. Rush is in the business of entertaining his listeners by reaffirming their existing views with amusing rhetoric and personality. He's quite brilliant at that. --BluePlatypus 06:35, 24 May 2006 (UTC)

If my closest relative is my brother, why does he still exist? Gdr 12:42, 24 May 2006 (UTC)

XBOX 360s evolved from the original XBOX. Why do they still exist? 12.183.203.184 17:27, 27 May 2006 (UTC)

[edit] Fears of a protein famine

I remember reading about this in the 1980s (and our Quorn article mentions it too) - apparently the "big thinkers" decided in the 1950s that the world was headed for a global shortage of dietary protein (presumbaly due to some kind of cow shortage). Motivated by this, lots of folks tried producing protein from novel sources. I remember reading about some large organisation trying to produce protein by growing something (bacteria?) in an unwanted heavy fraction of mineral oil, only to be thwarted by the excessive levels of uric acid found in DNA and RNA (a problem solved by the makers of Quorn). Do we have an article about this supposed protein shortage, and about those novel alternative sources projects? It'd be a fascinating read. -- Finlay McWalter | Talk 13:39, 20 May 2006 (UTC)

Oh, I did find this (PDF). -- Finlay McWalter | Talk 13:42, 20 May 2006 (UTC)
"Unable To Deliver Document. Sorry. We are currently unable to deliver your document. The delivery URL has expired" Could you provide a reference to the paper you found? Cheers! Dr Zak 00:43, 21 May 2006 (UTC)

[edit] Global Warming

What percentage of global warmingis caused by polution from transport?

I think our article on Global warming has some information on the percentage increases in carbon dioxide gas emissions in recent times. It's a comprehensive article, so you may find the information in there that you want. -- Daverocks (talk) 14:32, 20 May 2006 (UTC)

[edit] #wikipedia-science plug

I've recently kicked off a science related chat room, which readers and writers on the Science reference desk may be interested in:

#wikipedia-science on freenode.net.

Come along and ask a question or join the discussion on #wikipedia-science. All welcome. —Pengo 13:59, 20 May 2006 (UTC) </plug>

I've always wanted one of these. Some of the discussions on this ref desk are great and it would be much enhanced as a live chat :) -- Daverocks (talk) 14:16, 20 May 2006 (UTC)
I tried to follow the link, but it didn't work. Is there something special I have to do? Black Carrot 21:59, 20 May 2006 (UTC)
Yes, the link points to an IRC channel. Since following the link didn't work, your browser doesn't understand what to do with a URI that begins with irc://. You will need to open the channel in your IRC client (see: List of IRC clients), direct your broser to send all IRC protocols to the client or get a broser that has an internal IRC client (Opera does). --Swift 00:41, 21 May 2006 (UTC)

[edit] SDS-PAGE electrophoresis

I analyze protein solutions with an electrophoresis system from Amersham called "PhastGel" (I've heard other people refer to them as 'mini-gels'). I'm not a molecular biologist and I just use this system because it is what was already available in my lab.

I never see 'real' molecular biologists use this type of system for electrophoresis. I'm pretty sure that this simple-to-use system has some weaknesses, but I don't know what they are. Basically I want to get an idea of what I am sacrificing by using this type of system, versus the type of system used by more sophisticated workers. ike9898 14:21, 20 May 2006 (UTC)

This article, http://www.pubmedcentral.gov/picrender.fcgi?artid=175959&blobtype=pdf lists some disadvantages on the PhastGel system. Mike (T C) 15:50, 20 May 2006 (UTC)

[edit] Number of moles?

I need to determine the number of moles I used in a titration.

The gfm of NaOH is 40, and I used 38mL of it. Do I take 40 times 38...?

Please help! Thanks in advance!

You need to know the concentration (or "molarity") of the NaOH solution. The molar mass and the volume are not enough information. —Keenan Pepper 19:47, 20 May 2006 (UTC)
It is a .25M solution of NaOH.
That means each liter of the solution contains 0.25 moles of NaOH. You know how many liters you used, so you can easily figure out how many moles that is. —Keenan Pepper 22:10, 20 May 2006 (UTC)

[edit] Old radio "Bands"

I've checked the articel here on radio spectrum but can't seem to find an explanation for this: I found an old radio (vacuum tubes, etc) with different "bands" marked on the tuning dial (Weather, Foreign, Police and AM), but except for the "AM" dial (Which is written the same as it is now), I can't figure out what the other bands frequencies are, given their markings of things like "6.5" for the foreign on. Anyone with old radio info know what these bands corresponded to? Thanx. 68.39.174.238 19:11, 20 May 2006 (UTC)

They are most likely shortwave bands. The "6.5" is probably in MHz. Dysprosia 02:12, 21 May 2006 (UTC)

Have a look at [66]. If that doesn't give you all the information you wanted to know about shortwave receivers...--G N Frykman 19:55, 21 May 2006 (UTC)

[edit] Radio+Bath=???

This is partly inspired by the discussion above involving birds and power lines. I've heard all my life, from very reliable sources, that if you drop an electrical appliance into a bathtub while it's plugged in, and someone's in the tub, they'll be killed or seriously injured. How? Tap water is (if I'm not mistaken) almost infinitely less resistant of current than the human body, so according to my physics class, almost no current should pass through them. Besides, it would have to travel quite a bit out of its way to even reach them, if I'm understanding the circuit correctly: (one wire->resistant appliance of some kind->other wire) becomes (one wire->barely resistant water right next to it->other wire). Black Carrot 19:21, 20 May 2006 (UTC)

Pure water is a pretty good insulator. Salt water, and water with other kinds of impurities in it, is a pretty good conductor. Tap water tends to have impurities in it, many of which decompose into ions: see hard water. Also, person + water = somewhat salty water. moink 19:49, 20 May 2006 (UTC)
I'm not sure I buy that. There's still no reason a significant current would flow through you instead of the radio. —Keenan Pepper 20:03, 20 May 2006 (UTC)
I'm aware distilled water (which is expensive to get in sufficient quantities to fill a bathtub on a regular basis) doesn't conduct at all well. I'm also aware, from my AP Chemistry class, that it's the free-floating ions in the water that carry the actual current, by moving away from one wire and towards the other. That's why I figured it ("it" being the tap water, which is certain to be quite conductive in this sense) would be carrying the current in the first place. BTW, since you mention it, I can't help doubting that even the most foully sweaty person could possibly make a tubful of water strongly conductive on their own. It starts out that way. Black Carrot 21:02, 20 May 2006 (UTC)
Surely from the point where the live wire enters the water it can go two directions, or split and follow both: 1. back through the neutral wire to earth, or 2. through the large mass of water and human to earth. Which way it goes, and the split of the current depends on the relative resistance of the parallel paths. That depends surely on what is dissolved in the water, the temperature of the water, the connection between the bath and ground, and the resistance of the neutral return wire. Since people do get electrocuted this way, conditions favouring conduction through the water do occur, and it would be a brave or foolish person who trusts his life on the purity of his tap water, and adequately low resistence in the neutral return wire. Wet skin has a much lower resistance than dry skin. --Seejyb 22:57, 20 May 2006 (UTC)
From AP Chem, I learned that DI water doesn't do anything, but even the slightest trace of ions (like in tap water) will conduct electricity. --M1ss1ontomars2k4 (T | C | @) 04:01, 25 May 2006 (UTC)

When I first saw this post I thought, "That sounds like something the MythBusters should test," and then I wondered if they already had. Sure enough, here it is. (It was confirmed, for those of you who don't want to follow the wikilink.) EWS23 | (Leave me a message!) 07:11, 21 May 2006 (UTC)

[edit] Equation Balancing?

Can someone explain to me how to balance this equation in a double replacement reaction?

NaOH + C6H8O7 = ?

It depends on the structure of the organic reactant, but one of the products is probably water. Balance it by making the number of atoms of each element the same on either side. —Keenan Pepper 19:39, 20 May 2006 (UTC)
So would it be NaOH + C6H8O7 = C6OH + NaH8O7? I haven't started on the numbers yet but is that being correctly replaced so far?
No, because C6H8O7 isn't an ionic compound of C6 and H8O7. It's citric acid, so it'll give up three hydrogen ions and leave a citrate. —Zero Gravitas 21:09, 20 May 2006 (UTC)
So it'd be more like NaOH + C6H8O7 = H3OH + C6H5O7 something like that?
Be careful, you can't just eliminate the sodium. A hydroxide ion would bond with one hydrogen to form water. The sodium cations would bond with the citrate to give sodium citrate, so the unbalanced equation is:
NaOH + C6H8O7 = Na3C6H5O7 + H2O
The rest is just stoichiometry. A balanced equation doesn't necessarily have to start with one of each reactant... —Zero Gravitas 21:53, 20 May 2006 (UTC)
So the balanced equation is 3NaOH + C6H8O7 = Na3C6H5O7 + 3H2O
Is that right?
Yep, looks right to me. —Zero Gravitas 04:04, 21 May 2006 (UTC)

[edit] Specific heat of Hydrogen Plasma

I read that the specific heat of hyprogen gas goes up with temperature. When it gets hot enough for the hydrogen to change into plasma does this tren in rising specific heat continue, or is there a whole diferent ball park estimate for a "relitivly" low temperature plasma specific heat. I think I read some thing about the specific heat changing due to the diassosation of H2 into H1 so maybe this levels off, no?

This is a really good question and I'm surprised no one has answered it yet. I know it has to do with the number of degrees of freedom, which should be higher for the plasma than for the monatomic gas (I think...), but I can't say how that will affect the specific heat. I haven't even taken thermodynamics yet! Could someone knowledgeable please answer this question? —Keenan Pepper 19:14, 22 May 2006 (UTC)
I don't know about \partial c/\partial T (the "trend"), but the specific heat for the plasma should be higher than for the gas because there's more particles to heat (the dissociated hydrogen, then later (hotter) the protons and electrons separately, although the plasma will not in general be completely ionized). If this is the only effect, then the specific heat would increase forever as the last little bits of the gas ionized. But there are probably other factors eventually. --Tardis 21:20, 22 May 2006 (UTC)

[edit] CD-RWs

How do rewriteable CDs work? I assume that recordable ones simply laser away the unwanted material, leaving behind the correct sequence of pits and bumps. But rewriteable ones must be able to create bumps also. How do they do this? Daniel (‽) 19:28, 20 May 2006 (UTC)

The article CD-RW says how they work. What in particular do you want explained? —Keenan Pepper 19:34, 20 May 2006 (UTC)
Actually, neither CD-Rs or CD-RWs work by burning away material. It's all dye. --WhiteDragon 20:11, 25 May 2006 (UTC)

[edit] volcanos

i may not know excalty what causes volcanos to erupt. but i understand that the pressure builds up to a a point where it cant be contained anymore. so heers my idea, why not manulay release the pressure every so often so the pressure cant build up to a destructive point. ie by say drilling into the volcano away from populated areas?--Colsmeghead 21:19, 20 May 2006 (UTC)

Well, there are a few reasons for why not. First, you would have to drill DEEP. The further away from populated areas you want the vent, the deeper. Imagine the lava/magma/whatever the heck inside the earth's crust, a few kilometers down or so (see volcano for that, I don't remember the distance. It only rises in a rather steep "/\" depending on where you are. That means, it isn't realistic at all to even start thinking about drilling. Drilling is also not a good idea because if you want to drill far down and close to the magma, it gets hot. If it gets hot, things can be dangerous, and your tools could very well melt away. In most cases, I think it's much more economic and realistic to just move people out of the way, ALTERNATIVELY creating lava shafts and routes, leading any eruption away from populated areas. Then there are those cities that are very close to big ones (see Vesuvio). It's a good idea, but in the end it can't be done with today's technology. Henning 23:18, 20 May 2006 (UTC)
well i didnt mean down into the earth but rather into the mountianside--Colsmeghead 10:27, 21 May 2006 (UTC)
Let's imagine that there is no magma in a volcano until it begins to erupt, only cold lava, ashes, &c. Magma people live very deep. --DLL 17:39, 21 May 2006 (UTC)
Every volcano lies somewhere between two extremes. At one end are volcanos whose magma is very fluid (e.g. Hawaii); it easily flows out the top and rolls down the sides. The only real danger with that kind of volcano is being right in the path of the lava, and since it doesn't move very fast, this is rarely a problem. The other extreme are volcanos with magma that is very viscous and solidifies as soon as it reaches air. This means that wherever it reaches the surface the magma freezes and creates a plug that prevents more magma from flowing. However, the magma behind it keeps trying to move forward dispite this obstruction. This causes pressure behind it to build and eventually the blockage ruptures and the volcano erupts in a large explosion. This is the kind of volcano that tends to be very destructive. You couldn't effectively release this pressure by drilling because as soon as you got past one obstruction you'd find that the magma behind it would solidify and create a new obstruction. In practice, the only way for large quantities of material to get out of a volcano like this is for it to be moving so quickly that it doesn't have time to solidify; in other words, such volcanos require explosive eruptions to dissipate magma. The difference between these two kinds of volcanos is based primarily on the chemical composition of their magmas, so there isn't much you can do with an explosive volcano to make it tamer. Dragons flight 18:26, 21 May 2006 (UTC)
Even though we can't do it, this seems to be a popular science fiction idea. You might have read The Little Prince by Antoine de Saint-Exupéry, in which the Little Prince explains how he cleans his volcanos every day so that they burn with a steady flame, but that the volcanos on the earth are too large to do this. Another novel is A Földrengések Szigete by Fehér Klára, in which the heroes actually drill a hole in a mountain to avoid a great catastrophe. (Sorry for any spoilers.) – b_jonas 19:30, 21 May 2006 (UTC)

[edit] botany:physiology of bacteria

the study of bacteria bacteriology --Seejyb 23:06, 20 May 2006 (UTC)


[edit] NaHCO3, water and an acid

One of the oldest ones from science class. NaHCO3 in water turns into Na+ and HCO3-. Add an acid, and the HCO3 reacts with the H+ in the acid. AFAIK, pH means percent of Hydrogen ions, ie H+. The question is simple: Will the reaction become more violent the higher pH my acid has? Henning 23:11, 20 May 2006 (UTC)

Yes. —Keenan Pepper 00:38, 21 May 2006 (UTC)
Nit: pH isn't the percent of hydrogen ions, it's -log [H+]. --David Iberri (talk) 03:35, 21 May 2006 (UTC)

You've both fallen for a very old trick. The reaction will become more violent the lower the pH. And I do believe that the "p" of pH originated from the German for percentage. G N Frykman 08:51, 21 May 2006 (UTC)

No it did not. See pH. --Heron 09:26, 21 May 2006 (UTC)
Now I am utterly confused. The acid becomes more alkaline the higher the pH. I have seen alkaline metals react with water, and they seem to react violently enough. So untill Frykman gives reason to his claim, I'm going to go with the answer that Keenan was the first to give. :) Thanks! Henning 10:51, 21 May 2006 (UTC)

In the reaction between sodium hydrogencarbonate and a dilute acid, the sodium ions do absolutely nothing. It bears no relation to the reaction between alkali metals and water. The more H+ ions there are per unit volume, the faster will be the reaction between them and the hydrogencarbonate ions (giving carbon dioxide and water). The pH scale is slightly odd in that the lower the number, the greater the concentration of H+ ions. I said that you had fallen for an old trick - in many exams, the question is asked - which has a higher pH, a strong acid or a weak acid? And the answer is the weak acid. In a similar way, a weak alkali has a lower pH than a strong alkali. To summarise - a low pH indicates lots of H+ ions which will give a fast reaction with sodium hydrogencarbonate. G N Frykman 11:38, 21 May 2006 (UTC)

Thanks, that does make a bit of sense. So, a pH of 6 indicates a WEAK acid, a pH of 2 is a STRONG(er) acid? Similar, a pH of 8 is a WEAK alkali, a pH of 12 is a STRONG(er) alkali? A WEAK alkali interacts more violently with the H+ than a strong alkali, and a STRONG acid interacts more violently than both a weak acid, a weak alkali and a strong alkali? Henning 16:16, 21 May 2006 (UTC)
In determining whether an acid is strong or weak, it's more important to look at pKa than pH in solution (pKa is constant for a given acid, while pH varies depending on the acid's concentration). Clarifying your first statement, an acid whose pKa is 2 is stronger than an acid whose pKa is 6. pKb is a similar dissociation constant used to indicate the strength of bases: a base whose pKb is 8 is stronger than a base whose pKb is 12. --David Iberri (talk) 17:17, 21 May 2006 (UTC)

Spot on, Henning! But you're not likely to notice much difference comparing the reactions of a strong acid and a weak acid just in the basic neutralisation reaction (acid + base) except that weak acids produce a marginally smaller temperature rise. Where it does become obvious is in the reactions of acids in which a gas is given off, and they are: acid + metal (eg magnesium); acid + carbonate (eg calcium carbonate) and the one you started with, acid + hydrogencarbonate. In all of these the speed of fizzing is dramatically slower with weaker acids, such as ethanoic acid, compared with the typical strong acid, hydrochloric acid. David Iberri - I was trying to keep it simple. Direct comparisons of pH can be made as long as the acids are of equal concentration. G N Frykman 17:25, 21 May 2006 (UTC)

IANAC (Chemist). Referring to the original question: I thought the rate of a reaction depends on the activity of both substances, in this case H+ and HCO3-. In other words, I'd expect the rate to be limited by either the amount of HCO3- or the amount of H+. Decreasing the pH (increasing the H+ activity) would normally increase the reaction rate, until the reaction goes as fast as the HCO3- concentration allows. Then increasing the H+ beyond that (decreasing the pH) would not give a more violent reaction. Or am I wrong, does the concentration of NaHCO3 not influence the rate?
What "p" stands for: the pH article gives a number of "explanations", but as I read the original paper, Sörenson didn't state precisely why he chose "P", except that he wrote "10¯P". See the extract from S.P.L. Enzyme Studies II. The Measurement and Meaning of Hydrogen Ion Concentration in Enzymatic Processes. Biochemische Zeitschrift, 21, 131-200 (1909): "The value of the hydrogen ion concentration will accordingly be expressed by the hydrogen ion based on the normality factor of the solution used, and this factor will have the form of a negative power of 10. . . . CP . . means the number of gram atoms of hydrogen ions per liter, is less than 1 in all cases treated in this paper and can thus be placed equal to 10¯P. For the number P, I have chosen the name "hydrogen ion exponent" and the written expression PH." It would be strange if Sörenson would choose "P" to refer to a percentage, when he is writing about the negative of a Power (German: Potenz) to the base 10 of a number. --Seejyb 17:50, 21 May 2006 (UTC)
I think this reaction is first-order in both H+ and HCO3-, which means the rate is proportional to the product of their concentrations, so the rate wouldn't be limited by either one. That's a total guess though. P.S. Sorry for not reading the question through the first time. Obviously the reaction is stronger with stronger acid, which corresponds to lower pH. =P —Keenan Pepper 19:09, 22 May 2006 (UTC)
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