Wikipedia:Reference desk/Archives/Science/2006 November 3

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[edit] November 3

[edit] Chemistry

i need to know the name of the law that states that the mass of what you end with is the same as what you started with in a chemical reaction —The preceding unsigned comment was added by 71.96.48.6 (talk • contribs) .

I think conservation o"f mass is what you are looking for. --TeaDrinker 00:49, 3 November 2006 (UTC)

there is no "conservation of mass" law. the law is the "conservation of energy" which takes into consideration mass in the E=MC^2 equation. mass can be converted into energy (and vice versa) so the mass you end up with may not the same as what you started with.

[edit] Identificiation of a spider

Hi, can anyone tell me what species of spider these are? It was in the bathroom. I live in New Haven, Connecticut and I don't often see spiders this big around here. Image:SpiderOne.jpg Image:SpiderTwo.jpg Image:SpiderThree.jpg Thanks. SandBoxer 01:26, 3 November 2006 (UTC)

I would guess some sort of nursery web spider (pisauridae), maybe dolomedes, but how did you expect someone who knows american spiders to figure scale from a queen's coin of no visible denomination? How about we try again with a dime, nickel, quarter, or half dollar? alteripse 02:58, 3 November 2006 (UTC)

Well, it looks to be a British 5p, so just gotta figure out how many nickels that's worth to get a USAian physical scale. DMacks 03:08, 3 November 2006 (UTC)
We have an article on identifying spiders with some links that might be useful. Oddly, it doesn't mention bathroom spiders.--Shantavira 08:05, 3 November 2006 (UTC)
Hmm - my gut insticnt is to say that it's a 10p coin, but I've measured both for you anyway: 5p - 18mm (diameter), 10p - 24mm. (and now I've found our articles on them - sizes roughly correct). Martinp23 12:22, 3 November 2006 (UTC)
Coin may be Canadian (in which case the measurements are 18 mm or 22 mm). Rmhermen 14:34, 3 November 2006 (UTC)
There's a great website, http://www.whatsthatbug.com/ , where you can send in pictures of insects, spiders, and other creepy-crawlies for identification.--Shuttlebug 19:11, 4 November 2006 (UTC)

That is fairly obviously a Canadian quarter, almost exactly the same size as an American quarter. moink 00:53, 6 November 2006 (UTC)

[edit] Cable TV wiring methods

Not exactly science, but it is technology. Please tell me if I'm querying the wrong section.

I recently "upgraded" to digital cable, but the diagrams provided by the cable company and box manufacturer don't specify "bypass" methods, so that I have the option of viewing and recording the analog channels as I used to, or to view and record one digital channel. The suggested configuration (from a long time ago, when cable-ready VCRs were new), involves splitting the input cable signal between one feed going directly to an A/B switch, and the other going to the switch through the cable box. Unfortunately, none of my local stores has a coax (cable TV) A/B switch. Since my VCR has an aux video input, I'm thinking of still using the splitter, but, instead of having the "cable" output of the cable box going to an A/B switch, having the video output of the cable box going to the video input of the VCR. Any other ideas? Both the TV and VCR are "cable-ready", but not digital.

Full proposed configuration:

Cable input (from wall) -> splitter -> VCR coax in, and cable box coax in
cable box video out -> VCR video in
cable box coax out (unused)
VCR coax out -> TV coax in
VCR video out -> TV video in

Hence, perhaps I can use the VCR (effectively) as an A/B switch. I don't have all the cabling yet, but, if I understand this correctly, I can

  1. record any analog channel and watch any analog channel, by ignoring the feed entirely
  2. record a digital channel and watch any analog channel, by seting the VCR to record from line, and using the TV's tuner to process the coax input
  3. (optionally) record a digital channel and watch that digital channel, by setting both the TV and VCR to line input.

Have I missed something? — Arthur Rubin | (talk) 01:42, 3 November 2006 (UTC)

Ah, yes, the locale. City is Brea, California, cable company is Adelphia changing to Time Warner Cable. — Arthur Rubin | (talk) 03:48, 3 November 2006 (UTC)
Chances are, you will get nothing but garbage on the VCR if you do what you suggest. Digital cable is a digital signal. It is possible (not probable) that the cable company sends the old analog signal as well as the digital signal. If that is the case, your digital box will give you digital channels and the VCR will give you the analog channels. However, it is more likely that the VCR will not have an analog input and provide nothing. So, the first issue is how the digital decoder is plugged into the TV. Obviously, the cable runs into the back. Then, do you run an analog cable out to the TV's cable/antenna in? Do you instead run a video line out and two audio lines out? If you are running an analog cable out, that can plug into the VCR like normal, looping out of the VCR to the TV. Since the digital box is doing the tuning, you cannot tune to different channels with the VCR - it must stay on channel 3 or 4 (whichever the digital box is set to). If you run video-audio lines out, those have to go into the VCR if it has input for them. Otherwise, you cannot record television. The benefit though is that you can run the antenna-out from the VCR to the TV and play tapes from it by switching the television from aux-in to antenna-in. All in all, your best bet is to pay the extra $10-15/month for a digital recorder addon from the cable company. --Kainaw (talk) 16:52, 3 November 2006 (UTC)
I already have the configuration above with all "cable box" input/output removed, and it works on the digital cable, but it (obviously) can't receive a high-numbered digital channel. (I haven't checked to see if the VCR's cable tuner can pick up the lower-numbered "digital" channels; the TV's cable "tuner" goes up to channel 125....) The "traditional" configuration for a cable box in the pre-cable-ready and pre-audio-video-cable days was:
coax in -> splitter -> cable box in, A/B switch
cable box coax out -> A/B switch
A/B switch -> VCR coax in
VCR coax out -> TV coax in
But no one makes coax A/B switches any more — at least the local stores don't keep them in stock. — Arthur Rubin | (talk) 17:40, 3 November 2006 (UTC)
Ask your cable company. I'm also in SoCal with TimeWarner-formerly-Adelphia. We have a splitter that was installed by the Adelphia cable guy. howcheng {chat} 18:26, 3 November 2006 (UTC)
From what I'm reading -- you don't actually *need* a switch(let alone an A/B A/V switch, although if that is what you are after -- Best Buy sells an RCA A/V Switch/RF Modulator for like $40 -- and I know of at least four Best Buy stores in Orange County (the one in Fullerton is probably the closest store to Brea)), because the devices themselves, including the digital cable box will do all of that.
From what I gather, you want to be able to watch analog cable on the TV while recording a digital program -- or record a digital program while watching that program
To do that, this is all you need:
$2 coaxial splitter (no need for a switch)
Run cable from wall into splitter
Connect one end of the splitter directly into the TV
Connect the other end into the Cable-In input on the Digital Cable Box
Run the A/V output from the cable box into the A/V input on the VCR
Run the A/V output from the VCR into the A/V input on the TV
Most of the time, you'll watch TV with whatever input number the VCR is connected through the TV (let's assume it is Video 1). You'll still use your Digital Cable remote, but can record manually from that input (video 1)
If you want to record digital cable, you will need to manually set the channel -- but the signal will be transfered to the VCR (you won't be able to do digital channel switching through the VCR).
While recording, if you want to watch something on analog cable, switch the input to "Analog or TV or whatever" -- you can use your regular television remote to change channels (since your TV is cable ready and all).
Done.

--Filmmakker 17:37, 5 November 2006 (UTC)

[edit] q = cp*delta t * m

why is it cp and not cv? why is pressure always assumed constant ?

Look up adiabatic process and isothermal process. I think they may mean something (to you not me)--Light current 02:23, 3 November 2006 (UTC)

Pressure is not "always" assumed constant, because there are important physical situations in which the pressure on a system is not constant. In these situations, the formula does not apply. If you consult your original source for that formula, you'll find that it is probably surrounded by text that describes what the formula means and the context in which it should be used. If you must memorize formulas in the physical sciences, make sure that you memorize these critical qualifications as well. Melchoir 15:14, 3 November 2006 (UTC)

[edit] The Harris-Benedict equations

In the article Basal metabolic rate

The original equations from Harris and Benedict are:

  • for men, 66.4730 + (13.7516 * w) + (5.0033 * s) − (6.7550 * a)
  • for women, 655.0955 + (9.5634 * w) + (1.8496 * s) − (4.6756 * a) >

where w = weight in kilograms, s = stature in centimeters, and a = age in years. (Harris J, Benedict F (1918). "A Biometric Study of Human Basal Metabolism.". Proc Natl Acad Sci U S A 4 (12): 370-3. PMID 16576330. )

What unit is the result of the equation? Watts? Calories per day? Pound force Furlongs per fortnight?

202.168.50.40 02:41, 3 November 2006 (UTC)

If you follow the footnote reference for those equations on that wiki page, you can read the primary-reference article in which those equations were originally published. DMacks 02:51, 3 November 2006 (UTC)

I looked at this at the bottom of the article:
And it does not say. All it says is
An analysis of the data of actual experimentation
on subjects at changing levels of nutrition shows that the changes
in metabolism are not proportional to those in body surface. Surface area
may not be looked upon as a determining factor in basal metabolism.
The closest prediction of the daily heat production of a subject can be
made by the use of the multiple regression equations,
For men, h = 66.4730 + 13.7516 w + 5.0033 s - 6.7550 a
For women, h = 655.0955 + 9.5634 w + 1.8496 s - 4.6756 a
where h = total heat production per 24 hours, w = weight in kilograms,
s = stature in centimeters, and a = age in years. These equations have
been tabulated for values of weight from 25.0 to 124.9 kgm., for stature from
151 to 200 cm., and for age from 21 to 70 years, so that the most probable
basal metabolism of an unknown subject may be easily determined.
Such tables should render service in clinical and other fields of applied
calorimetry. Their usefulness has been demonstrated in testing the typical
or atypical nature of series of metabolism measurements, in investigating
the differentiation of the sexes with respect to metabolic activity, of the
metabolism of athletes as compared with non-athletic individuals, an'd of
individuals suffering from disease.
The detailed measurements and statistical constants, with full discussions
of pertinent literature, are about to appear in Publication No. 279 of the
Carnegie Institution of Washington.

202.168.50.40 03:48, 3 November 2006 (UTC)

Well that does tell you it's [somethings] per day already. The first place the article uses the variable h is towards the bottom of page 371, and there it states: "h = total heat production in calories per 24 hours". DMacks 04:54, 3 November 2006 (UTC)

[edit] Gallium/gallinstan

What metals does Gallium not react with? Would these also not react with Gallinstan?

Gallium also attacks most other metals by diffusing into their metal lattice — another reason why it is important to keep gallium away from metal containers such as steel or aluminum. Gallium metal easily alloys with many metals, and was used in small quantities in the core of the first atomic bomb to help stabilize the plutonium crystal structure. --Light current 03:46, 3 November 2006 (UTC)

[edit] Krell

If the human race survives long enough, is it possible we could become like the Krell having (essentially) limitless energy and (highly ssuperior) knowledge (stored in WP of course)--Light current 03:17, 3 November 2006 (UTC)

This is kind of related to the idea of transhumanism and the related technological singularity. It has fans but has also been described as "Rapture of the nerds." --Robert Merkel 04:13, 3 November 2006 (UTC)
The Krell didn't have "limitless" energy and knowledge, just immense amounts. Any finite amount, no matter how huge is not "limitless." And they appear to have had a major hole in their knowledge of psychology. B00P 05:30, 3 November 2006 (UTC)
But of course, most of that knowledge would be in the form of poor articles about book/movie/televison/game characters ;-) Xcomradex 07:07, 3 November 2006 (UTC)
If we're attacked by the slimy, ten-tentacled Trivia monsters from the planet Boredom, we'll at least be well armed. Clarityfiend 17:00, 3 November 2006 (UTC)
Well, we haven't sterilized the planet with nukes yet. The next step in eliminating the Monsters from the Id ...is to convince people to stop electing them. --Wjbeaty 17:56, 3 November 2006 (UTC)

[edit] Dark colored cliffs in Great Britain?

Hello all!

I was wondering where one might find darkly colored cliffs in Great Britain. Specifically, rough/jagged black cliffs. Also, are there any small ports near these places? I'm working on a story for National Novel Writing Month, and currently have no basis in reality for my setting!

Any help would be much appreciated!

Russia Moore 04:45, 3 November 2006 (UTC)

How about these forboding cliffs? [1] They can be found near the fishing town of Hillswick on Shetland, Scotland. Rockpocket 06:38, 3 November 2006 (UTC)
The Stanage area has several miles of spectacular black rocky cliffs, but they are very much inland.--Shantavira 08:10, 3 November 2006 (UTC)
Alum Bay in Isle of Wight. --Light current 18:52, 3 November 2006 (UTC)
Fingal's Cave on Staffa? G N Frykman 10:15, 4 November 2006 (UTC)
When I visited Thurso in north east Scotland, they had large dark rock cliffs. I was rather appalled that you could stray three or four or five feet off the footpath (especially to the east of the town) and fall hundeds of feet to the hard rock below, without any railings, fences, or warning signs. Elsewhere in the town they had sudden drops of many feet again without any fences or warnings. Thurso is a port and on the railway, has a lot of tourists, so I expect there is a lot about it on the internet.

[edit] What is this?

http://www4.ncsu.edu/~stdidona/DCP_8386.jpg --Shanedidona 04:57, 3 November 2006 (UTC)

It is 1mm long by the way.

Sure looks like an unfed tick to me but chigger also come to mind. But then I'm not working the reference desk. Just trolling. Adaptron 06:16, 3 November 2006 (UTC)

It's neither a tick nor a chigger: both of these are arachnids. What you have is some kind of insect. I'm afraid it may be a bedbug nymph. Compare with this image of such a critter that has recently fed. – ClockworkSoul 06:49, 3 November 2006 (UTC)
Check out aphids.--Tbeatty 07:09, 3 November 2006 (UTC)
Or termites. --Dementios
I vote for cereal psocid, or book louse...--Mark Bornfeld DDS 13:13, 3 November 2006 (UTC)
Might we simply settle on insect that ought to be rendered extinct straightaway? Joe 04:00, 4 November 2006 (UTC)

[edit] Earthworm and grasshopper digestion times

Any help investigating these two statistics would be greatly appreciated. Thanks, anon.

In humans? Rockpocket 06:29, 3 November 2006 (UTC)
A quick search comes up with this which investigated a species of compost worm's gut retention time. From the abstract, it seems that they found digestion time is dependant on temperature, and possible other factors. Another article (Jeschke and Tollrian, 2005, Ethology 111, pp187—206) listed migratory grasshopper (Melanoplus sanguinipes) digestion time as 42044 minutes per gram of dry mass, carolina grasshopper (Dissosteira carolina) as 12818 min/g(dry) and undulate winged grasshopper (Circotettix undulatus) as 16011 min/g(dry). I did not read the whole article, just skimmed it to find the result. The article also pulled these results from other sources, so there may be problems with different methodologies. --TeaDrinker 06:34, 3 November 2006 (UTC)
Depends on the length of the worm. Depends how well you chew the grasshopper.--Shantavira 08:15, 3 November 2006 (UTC)

There are two possible interpretations of this question:

  • How long does it take earthworms and grasshoppers to digest their food ?
  • How long does it take humans to digest earthworms and grasshoppers ?

Please clarify which question you meant to ask. StuRat 17:07, 3 November 2006 (UTC)

[edit] Radiation

I was wondering how radiation could be reduced from nuclear style rockets such as the Salt Water Nuclear Rocket ? Thanks For Any Help 68.120.69.231 06:34, 3 November 2006 (UTC)

A nuclear salt-water rocket should be launched from orbit, such that the exhaust stream does not fall back into the Earth's atmosphere. Thus, the radiation released would be the same, but it would be released into space, not the atmosphere. Of course, even having that quantity of radioactive material in Earth orbit still poses a significant risk. StuRat 17:01, 3 November 2006 (UTC)

[edit] abortion

hey guys?need serious help.my chick got an abortion..shiz 18.two dayz after the abortion she was still feeling pain.took her bak to the doc n was told there was some blood in her uterus.she was cleaned again.now she hasnt yet had her periods.when are they suppose to resume? —Preceding unsigned comment added by [[User:{{{1}}}|{{{1}}}]] ([[User talk:{{{1}}}|talk]] • [[Special:Contributions/{{{1}}}|contribs]])

Go ask a doctor. --Tbeatty 08:41, 3 November 2006 (UTC)
Why give an answer if you don't have one and it's already at the top of the page? DirkvdM 08:55, 3 November 2006 (UTC)
Umm, because it's an urgent question and he should go to the doctor? That's the answer. "Go ask a doctor now" might have been better. Tbeatty 17:06, 3 November 2006 (UTC)
When was the D&C done. Can you give the date. And did she have regular periods before this (this means not abortion, but the present pregnancy !!!)  Doctor Bruno  13:49, 3 November 2006 (UTC)

Well, now that we have a real doctor on staff, we should change our boiler-plate at the top... --Zeizmic 15:13, 3 November 2006 (UTC)

[edit] siddhis and the paranormal

what's the conclusion if any? do they exist? or ...what...--Cosmic girl 12:34, 3 November 2006 (UTC)

By definition, anything paranormal is "an observed phenomenon for which there seems to be no agreeable scientific explanation". So you'll just have to look at the evidence and decide for yourself.--Shantavira 13:45, 3 November 2006 (UTC)
Yes they exist. Today's science is yesterday's magic and today's magic is tomorrow's science
Today's science is yesterday's siddhi and today's siddhi is tomorrow's science  Doctor Bruno  13:50, 3 November 2006 (UTC)
Pulling a rabbit out of a hat is science? -- Consumed Crustacean (talk) 16:41, 3 November 2006 (UTC)

sweet...and dr. bruno, would you mind pointing the right direction for me to 'learn them' and test that for myself?.--Cosmic girl 14:06, 3 November 2006 (UTC)

I would argue that any which are actually testable can be easily disproven with a scientific test. For example, being able to fast indefinitely without starving has been disproven. StuRat 16:36, 3 November 2006 (UTC)
Seems like 8 of the 9 main siddhis would be trivially easy to test (Raise the dead. Turn lead into gold.). The only one that would be hard is Kanakdhara Siddhi (acquiring immense wealth - maybe we should ask Bill Gates about that one). Clarityfiend 16:43, 3 November 2006 (UTC)

hahhaaha!....yeah, totally...but it would be neat if they existed. :P --Cosmic girl 17:19, 3 November 2006 (UTC)

By "paranormal", do you mean ghosts and UFOs and the like? There's been no solid evidence for them, so it's better to assume that they don't exist than to assume that they do. --Bowlhover 17:22, 3 November 2006 (UTC)
To learn more of the siddhis, see the classic Patanjali's Yoga Sutras, section 3 (a quarter of the book). There are many English translations, such as How to Know God by Prabhavananda and C. Isherwood, or The Science of Yoga, Taimni. Or see many other works on yoga. Buddhagosa's Path of Purification, (early Buddhist work) I'm told has many exotic states listed. Then there are the "Six Yogas of Naropa", in the Indo-Tibetan tradition. There must be millions of yogis in India; how many have accomplished the siddhis? For a contemporary Western take on this, see The Future of the Body: Explorations Into the Further Evolution of Human Nature by Michael Murphy, follower of Sri Aurobindo, and co-founder of Esalen Institute --GangofOne 01:48, 4 November 2006 (UTC)
I guess mentioning TM-Sidhi Program (see Transcendental meditation) would be appropriate. For much money you will be taught to repeat lines from the sanskrit scriptures. Of millions of TMers, no one is levitating yet, just hopping. So I guess that tells you something. The only siddhi they have definitely accomplished is 'accumulation of great wealth'. --GangofOne 06:09, 6 November 2006 (UTC)

[edit] So, I quit smoking a few weeks ago...

So why am I now getting more (and more severe) coughs, colds and chest infections than I did when I smoked 40 cigs a day? --Kurt Shaped Box 15:49, 3 November 2006 (UTC)

From what I've read (mindful of the disclaimers lol), constituents of cigarette smoke anesthetise the lungs, preventing them from cleaning themselves. After you quit, they 'get bizzay' moving the junk up and out. Anchoress 16:11, 3 November 2006 (UTC)

Think of them as withdrawal symptoms, much like when an alcoholic stops drinking. StuRat 16:38, 3 November 2006 (UTC)

I've certainly been coughing up some interesting shades of green, brown, grey and red. --Kurt Shaped Box 17:00, 3 November 2006 (UTC)
Congrats on quitting! Some people have a really difficult time avoiding nicotine. Oh, and your dentist will love you for quitting. - Dozenist talk 17:47, 3 November 2006 (UTC)
Um, if you really are coughing up anything red you should see a doctor. You may have a lung infection or worse. --Cody.Pope 18:00, 3 November 2006 (UTC)
I have. It's because I've been hacking up so hard. As is life... --Kurt Shaped Box 18:54, 3 November 2006 (UTC)
You'll be coughing up tar for a few months, it is your lungs repairing themselves. Enjoy it, that's some disgusting stuff you are ejecting from your body :) --liquidGhoul 01:48, 4 November 2006 (UTC)
Although I have heard that your lungs take about 10 years to fully recover, but I doubt you'll be coughing for that long. I noticed a significant difference after a few weeks myself, but I wasn't that heavy of a smoker. --Wirbelwindヴィルヴェルヴィント (talk) 04:04, 4 November 2006 (UTC)
Months? Years? Awwww, nuts. How the hell am I supposed to stay quit for that long? I thought that the human body was this fantastic all singing, all dancing, self-healing machine? --Kurt Shaped Box 09:18, 4 November 2006 (UTC)
If you're not ready to abandon smoking forever, why quit in the first place? --Bowlhover 05:34, 5 November 2006 (UTC)

Alcoholics Anonymous encourages people to think of themselves as alcoholics for the rest of their lives, so perhaps the same logic applies to "nicoholics". StuRat 07:07, 5 November 2006 (UTC)

I think it's a valid comparison. My mom quit smoking for years, twice, and then started again after one cigarette. She finally quit again, and admitted that she just can't take even one more puff. Anchoress 09:39, 5 November 2006 (UTC)

[edit] Bernoulli's principle

On Wikipedia's entry for Bernoulli's principle, it says, "It is named after the Dutch/Swiss mathematician/scientist Daniel Bernoulli, though it was previously understood by Leonhard Euler and others." I'd like to know what was previously understood by Euler and others (and who the others were, if possible), and what Bernoulli added. (I asked on the talk page for that article long ago, but no one responded.) Thanks muchJudahH 17:47, 3 November 2006 (UTC)

Bernoulli developed the basic tenet of kinetic theory: molecules are in motion. He also knew that flowing fluids exerted less pressure, but didn't connect the ideas logically. Meanwhile, Leonard Euler generalized a rate-of-change dependence of pressure and density on speed of flow. Due in no small part to Euler's empirical findings, Bernoulli then formulated his principle for liquids in modern form. Rockpocket 08:17, 4 November 2006 (UTC)

Thanks. Could you just clarify a bit more, please: You say that Bernoullil "also knew that flowing fluids exerted less pressure". Was this principle common knowledge back then (and Bernoulli's contribution was the equation for it, not the "principle" itself)? And was Euler's formula wrong, or incomplete in some way? (Qhat did Bernoulli add, in layman's terms?)JudahH 00:33, 5 November 2006 (UTC)

[edit] Electric Fences

Can somebody advise how much electricity does an Electric Fence use (in Kilowatt Hours over time) - I am thinking of installing one but worried about my electricity bill ! I would guess that it is minimal - only really using electricity through resistance in the circuit ? --Dr snoobab 18:14, 3 November 2006 (UTC)

The fences on the farms I worked on did not have continuous flow. They were like capacitors. They charged up and then, like any capacitor, they didn't use much electricity at all. When you touched it, it discharged and then had to use electricity to charge up again. --Kainaw (talk) 18:36, 3 November 2006 (UTC)
That doesn't sound quite right -- more likely the fence was simply intermittently active. I'm pretty sure if you could 'scope the electric fence, you'd see a pretty high frequency ac waveform on the fence for those moments its active.
In any case, I think electric fences are pretty low consumers of electric power; some of them are run from rechargeable car-type (or at least deep-cycle marine-type) batteries.
Atlant 19:15, 3 November 2006 (UTC)
Well, with the electric fences I've got, and I think this is typical of many, a pulse is sent through the fence "tape" and back to the generator thingummy (sorry...). Of course, there is a negligable loss of energy through this, affected by resistance, and this will, in part, determine some of the cost. Al of the energy in the pulse is only lost when someone/thing touches the tape (and so grounds the electricy, which travels to earth through the object). So, the number of shocks given is probably the most important part of the cost. As Atlant says above, most electric fences just run off a 12V car battery, which needs replacing every three to six months (or recharging). Really, after forking out for the tape and the generator (and battery), further cost is very low. Martinp23 19:24, 3 November 2006 (UTC)
See electric fence. The older ones did use AC. The newer ones use a capacitor. --Kainaw (talk) 19:31, 3 November 2006 (UTC)
Electric fences designed to carry potentially lethal currents can be used for anti-personnel purposes. *During World War I, the German occupant of Belgium closed off the border with neutral Netherlands using an electric fence. When the Dutch wanted to escape the evil liberals at home and side with the Germans threw many nuns on the fences to bridge it and marched over to Belgium. What???? Huh???? --Kurt Shaped Box 19:50, 3 November 2006 (UTC)
I fixed the apparent vandalism. Why didn't you, Kurt ? StuRat 20:26, 3 November 2006 (UTC)
I thought I had. My browser timed out after I stepped away from my machine. --Kurt Shaped Box 20:50, 3 November 2006 (UTC)

[edit] How to thicken bleach ?

I would like to create a thick form of bleach suitable for cleaning shower grout. What would be best to add to bleach to have this effect ? Some possibilities I have handy are wheat flour, powdered sugar, or saw dust. StuRat 20:16, 3 November 2006 (UTC)

Polystyrene chippings? Or is that if you're trying to make explosives? --Kurt Shaped Box 20:51, 3 November 2006 (UTC)
Why don't you just buy some thick bleach? Anchoress 21:18, 3 November 2006 (UTC)
Domestos in UK is sold as the thickest bleach you can buy. I wont say how thick it is, but its thick!--Light current 22:03, 3 November 2006 (UTC)
If you're determined not to buy thick bleach, maybe soapflakes? Don't know how well soap would disolve in bleach tho. Vespine 01:30, 5 November 2006 (UTC)
Why not mix it with powdered bleach? Dina 23:56, 6 November 2006 (UTC)

The best thing is just to mix it with baking soda--cheap and effective. Scrub with brush.

[edit] Dayhoff matrix

Does anyone know which proteins were used to generate the original Dayhoff/PAM matrix? Thanks Aaadddaaammm 20:21, 3 November 2006 (UTC)

Dayhoff used reconstruction of ancestral states of 34 superfamilies, on 71 groups of closely related proteins for her PAM250 matrix (finding 1,572 changes). I expect the exact proteins are available in the primary reference (M.O. Dayhoff, ed., 1978, Atlas of Protein Sequence and Structure, Vol5), but one grouping was of the Immunoglobulin C-region domains. Rockpocket 07:52, 4 November 2006 (UTC)

[edit] waterspouts

If you were swimming around in the middle of the ocean and a waterspout came by... 1) Would it suck you up or pull you under 2) Would you be able to breathe in the mist of the waterspout or would it be so thick that you'd drown? Would you survive?--frothT C 21:04, 3 November 2006 (UTC)

They vary considerably in strength, but the typical water spout only pulls a water "mist" off the surface and into the funnel. I wouldn't think it would lift a person, but it might be hard to breathe while it was on top of you. If you were lifted up, I would think you would survive until dropped in the water, where the impact would likely kill you. StuRat 22:15, 3 November 2006 (UTC)
The waterspout article says that they are typically weaker then land based tornados. Since most tornados are not strong ehough to lift a human, (no matter how many flying cows and cars you've seen in hollywood portrayals of the events), ;) I don't think waterspouts would suck you out of the water. In a tornado, flying debris is your biggest risk, not actually beaing blown away. Vespine 01:28, 5 November 2006 (UTC)

[edit] What's so special about the ground?

In Jurassic Park, the kid gets shocked, but "not bad because he wasn't touching the ground" ... why is dry dusty dirt such a seemingly effective ground.. it's hardly electrically conductive. Is it possible to have electric potential with a non conductive object like the dirt? Or is low conductivity 0 volts by definition? I thought that was a special state, like what a tri-state buffer enters when it's not enabled --frothT C 21:12, 3 November 2006 (UTC)

The ground is usually quite moist just below the surface, so highly conductive. Even ground that appears to be dry still contains a surprising amount of water. StuRat 22:07, 3 November 2006 (UTC)
With a ground referenced source of voltage, you can (generally) avoid shock if you yourself are not grounded.--Light current 22:09, 3 November 2006 (UTC)
Ever wondered why something that takes electricity is called a ground? Vitriol 23:07, 3 November 2006 (UTC)
No why?--Light current 23:09, 3 November 2006 (UTC)
It's called ground (or earth, in Britspeak), because it's literally connected to the ground/earth. StuRat 23:20, 3 November 2006 (UTC)
Its a reference point. An infinite source or sink for electrons or positive charges but only when the system is connected to it!--Light current 23:25, 3 November 2006 (UTC)
If I understand the question correctly, he is asking why the ground is such a good, err, ground. If I remember my physics courses correctly, it is because the earth has such a huge capacity for charge. (Like) charges like to spread out as far as possible. Touching the ground will allow the charges to spread out throughout the earth below you. And since the earth is MUCH larger than you, you will have negligible amounts of charge left (practically infinite sink). But moving the charges creates the voltage and stuff that hurts. --Bennybp 23:27, 3 November 2006 (UTC)

That's also the reason squirrels jump from telephone pole to power line. If they didn't it would be power line + squirrel + telephone pole = zap. --AstoVidatu 21:36, 6 November 2006 (UTC)

[edit] The Human Tongue...

My son, who is three years of age has a sore on his tongue that is about 3/4 in. long by about 1/4 in. wide. He has not eaten anything out of the ordinary and , to my knowledge has not bitten his tongue, or eaten anything hot in the past few days. It is not too sore to touch, but he seems to have a problem with some foods. (spicy or with too much acid, which seems reasonable)My question is...is there a a cold or virus that would cause this to happen on the tongue? Jennifer Grandy

You would be wise to visit the doctor as we cannot answer medical questions here. Sorry!--Light current 22:04, 3 November 2006 (UTC)
Primary herpetic gingivostomatitis, caused by herpes simplex virus, could well cause tongue ulcers, but this would almost certainly be accompanied by other ulcers throughout the mouth as well as constitutional symptoms. Your best bet is to have the condition diagnosed by a dentist or physician.--Mark Bornfeld DDS 22:43, 3 November 2006 (UTC)
It also might be an aphthous ulcer (canker sore). howcheng {chat} 23:43, 3 November 2006 (UTC)

I would advice you to consult a paediatrician.  Doctor Bruno  13:57, 4 November 2006 (UTC)

[edit] Favourite quantum mechanics interpretation

What is your favourite quantum mechanics interpretation. Will we ever be able to figure out whats really going on ? 82.9.123.200 22:52, 3 November 2006 (UTC)

That is an extremely interseting question. Wait a mo.....--Light current 01:15, 4 November 2006 (UTC)

[edit] Genetic Engineering

It says in my book in bullet points that GE has increased yields of food. the first two bullet points said it has made plants resistant to diseases and ability to withstand damage. i thought those two bullet points tell how GE helps improve the production of our food. so when it says increase food yields does it mean in another kinda way? or that is just stupid why would it put increase food yields when it already tells you how in the first two bullet points.

It could be telling you that genetic engineering makes plants more resilient, so they don't die as often which increases yield.. not sure what you're asking --frothT C 22:57, 3 November 2006 (UTC)

"Increases food yield" could mean larger heads of grain, fruits, etc., are produced. But that's only one way to increase yield. Another is to reduce the amount of food lost to diseases, storm damage, etc. Thus, the total per acre/hectare is increased, either way. StuRat 23:14, 3 November 2006 (UTC)

[edit] Question on Special Relativity

Is the velocity of a photon from its own frame of refrence the speed of light or zero?

Speed of light, or the question is meaningless. You are asking what speed does the photon think its travelling at? Time stands still for the photon.--Light current 23:54, 3 November 2006 (UTC)
Light current's second statement is the technically correct one: the question doesn't really work. The problem is that the photon doesn't have an "own frame of reference." That's because relativity postulates that light moves at c in every frame, but what we mean by a particle's "own frame of reference" is that it's stationary in that frame. Logically, then, there's no such frame. -- SCZenz 00:31, 4 November 2006 (UTC)
Unfortunately, SCZenz's statement invites the consideration "How about postulating instead (and perhaps seemingly even more uniformly) that any photon, too, had an own reference frame in which it is stationary" as if it were a plain logical alternative; thus making relativity appear arbitrary.
More compelling should be first to review what in relativity is meant by "two particles (or in full generality, two observers) being stationary to each other", i.e. based on which measurement two participants could at least in principle agree on whether they belong together to the same frame, or not;
then noting that such agreement, at least in principle, requires the pair to exchange roundtrip signals (each stating signals, and observing the replies), while a photon doesn't exchange signals (but instead itself constitutes a signal, exchanged between charges);
and therefore concluding that a photon cannot belong with anyone (or any photon) else to the same frame.
Finally, with the definition of what in relativity is meant by a measure of distance between two particular members of the same frame (namely such that the participants agree on the value of distance between each other), and the resulting definition of speed, it follows as a consequence that the relativistic postulate is consistent and without logical alternative. Frank W ~@) R 23:29, 6 November 2006 (UTC)