Wikipedia:Reference desk archive/Science/2006 June 26

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[edit] Evolutionary question

Why do lines have mains? What is their function, and why did they evolve? Mayor Westfall 05:22, 26 June 2006 (UTC)

Is this a question about lions and their manes?--Shantavira 06:29, 26 June 2006 (UTC)
No, electricity, surely. Electricity lines carry mains current. If they didn't, the TV wouldn't work. Older lines carried trains, but it was difficult getting them into the TV. Grutness...wha? 06:47, 26 June 2006 (UTC)
Yes what is the purpose of a lion's mane? Mayor Westfall 05:22, 26 June 2006 (UTC)
I'd guess that it's a secondary sex characteristic. GeeJo (t)⁄(c) • 15:14, 26 June 2006 (UTC)
yes, and I'd also guess that sexual selection is responsible for its evolution. - Nunh-huh 09:18, 4 July 2006 (UTC)
I think the mane also serves as protection for the throat when fighting. EdC 00:24, 27 June 2006 (UTC)
Clearly, lions' manes keep the seagulls away.

[edit] Does facial structure change during puberty?

A friend asked an excellent question...So good, I had no clue what the answer is:

"Can/will a person's face change structure during puberty? I mean, I know the rest of the body does, but no one's ever mentioned what happens to the structure of a person's face."

Now, nobody else I know could answer either. So I submit it here, in hopes someone can answer. -Penta 05:25, 26 June 2006 (UTC)

The bones certainly grow, along with the rest of the body. I can't say whether there is a noticeable change in the shape of the face though.  freshofftheufoΓΛĿЌ  05:40, 26 June 2006 (UTC)
Yes, the hormones (namely testosterone and estrogens) do affect the shape of the face during puberty. A boy's jaw broadens and a "ridge" of bone may develop above the eyes, to name a few. The male jaw also gets an overall more chiselled shape. A girl's face gets somewhat more rounded due to fat being distributed under the skin. –Mysid(t) 07:34, 26 June 2006 (UTC)
Actually, I think the male face continues changing long past puberty, till about the age of thirty.--Pharos 07:38, 26 June 2006 (UTC)

Here is a nice article. [1] Besides violence, the high-test. face (movie star) is also associated with chasing anything in a skirt before and after marriage. --Zeizmic 11:46, 26 June 2006 (UTC)

[edit] Mars Meteorites

How to meteorites that come from places like Mars and the Moon get 'dislodged' from these bodies, sent into space, so that they have a change of colliding with Earth? --Silex 09:02, 26 June 2006 (UTC)

Have you seen our article on Mars meteorites? They originate when a substantial body (a larger meteorite) hits Mars or the Moon, which sends rocks flying. Sometimes the rocks fly fast enough to escape the planet/moon's gravity and enter solar orbit. This is much more likely to occur on the moon and Mars than it is for Earth, because they have much lower escape velocities.-gadfium 09:16, 26 June 2006 (UTC)
Thanks a lot! I'd had a look on the meteorites page, but not the one you pointed too! Thanks. --Silex 11:08, 26 June 2006 (UTC)

[edit] Fire

How hot is fire? What temperature is a flame?

Please provide answers in degrees, celsius, where possible. :) Thanks.

  • That would depend on the situation. A flame's temperature is determined by the fuel that's being burnt, the surrounding temperature (is there any cooling?) and the amount of oxygen present. For example, you can't burn ice with a regular flame match or gas flame, but on Braniac they use an explosive that's so hot, it can make ice explode. - Mgm|(talk) 10:54, 26 June 2006 (UTC)
  • See Fire#Typical temperatures of fires and flames. Conscious 11:57, 26 June 2006 (UTC)

This is just silliness... Some of the temperatures on that page are in Fahrenheit, and some are in Celsius... I'ma have to sort that out.--Eh-Steve 23:32, 28 June 2006 (UTC)

[edit] Fermi's Hypothesis

I read the hypothesis and people's views to it. I'd like to raise a point and ask some questions:

1. What happens if aliens don't think like us? Or they don't see things as we do? What if they do not have the concept of communication, nor do they see the universe like we do? Always remember - everything we perceive to dictated by our senses.

2. If aliens do use radio communication technologies, what is the effective range of it?

3. What is the definition of an intelligent lifeform? Surely it can't be something based on us humans, can it?

This is more a discussion topic than a question. However, as far as point 1 goes, SETI researchers make the working assumption that they exist in the same universe as we do and are subject to the same physical laws. Furthermore, it seems a fair assumption that an intelligent species, by definition, would have some ability to communicate, even if their communication methods between each other are different to our own. They may well also see the universe differently, but the electromagnetic spectrum is the same for them as it is for us, and radio (and visible light) are two parts of the spectrum which are relatively well-suited for interstellar communication.
As far as the "range" of radio communication, that depends on the power of the signal and the sensitivity of the receiver. With current technology and a reasonably modest investment in antennas, it's possible to have point-to-point communications across the galaxy. A working assumption of SETI is that technological civilizations with interstellar communications capabilities are likely to be more advanced than us, seeing we have had such capabilities for only a few decades.
As to what an "intelligent" lifeform is, we don't have a good definition of what "intelligence" in the context of humans and computers is. I suspect the answer might be "we'll know it when we see it". --Robert Merkel 12:06, 26 June 2006 (UTC)
If an alien intelligence has a completely different means of communication, then SETI is wasting its time. I believe the SETI people have considered that risk, and decided to take the chance. Peter Grey 15:23, 26 June 2006 (UTC)
The work at SETI is not entirely wasted even if no intelligent life is ever found. The scientific advances in radio astronomy, cosmology, and electronics and computing are valuable endeavors for the progress of science. This helps justify the cost &mdash because even many of the researchers realize how improbable an actual extraterrestrial communiqué would be. Nimur 17:27, 26 June 2006 (UTC)

[edit] How the hell!?

http://www.snopes.com/photos/people/pullapart.asp Someone explain plz. Mayor Westfall 12:32, 26 June 2006 (UTC)

I cant get it to show the video. how do you see it? Philc TECI 13:47, 26 June 2006 (UTC)
It works fine for me clicking on the link beneath the video frame. It appears to show a magician in a park getting two people to pull on a third person, who's lying down. The person then splits apart, and her torso chases after people. Quite scary, and the snopes article claims there is no digital trickery. Personally, I'mn not sure if I'd want the trick explained. 199 (talk) 14:27, 26 June 2006 (UTC)
It can also be seeen here. 199 (talk) 14:34, 26 June 2006 (UTC)

Reading the explanation, and just looking at the still, you can see certain geometrical oddities. Since this trick has been regularly done from the beginning of time, it is obvious that mrrpfl gaaggg (help I'm being attacked by rabbits coming out of hats!) --Zeizmic 15:04, 26 June 2006 (UTC) Template:Spoiler

First, open the clip in two browsers. Stop one film at around 1:04 and the other at 1:15 - i.e. just before&after the magician walks around the victim and places his hands on her stomach. Notice the woman holding the victim's hands has changed her position quite a lot. This is because there is a cut: the woman who walks to the bench and the one being pulled apart are different people. Yes, the audience is in on it.
The woman running around seemingly without her legs has a birth defect: she has very very short legs. The lower part on the bench is a mannequin. There is a separate zoomed in clip to show wiggling toes - notice the cut in the film. The toes belong to the normal-length woman who walks to the bench. Weregerbil 17:15, 26 June 2006 (UTC)
Just thought I'd tag it as a Spoiler... Nimur 17:24, 26 June 2006 (UTC)
But Snopes says, "The illusion he performs is not dependent upon video manipulation or digital trickery — it can be executed essentially as shown in the video clip." Doesn't careful omission of such a switcheroo qualify as video manipulation? Or are we to conclude that Snopes is bending the truth? Seahen 02:57, 30 June 2006 (UTC)
It could be executed without digital trickery, but it wasn't. The recipe for doing it without such cuts would begin, "first, take two midgets...." - Nunh-huh 09:26, 4 July 2006 (UTC)

[edit] Tired eyes

Why do my eyes feel so heavy and ache so much when I haven't slept enough the night before? What could help ease the achyness? Thanks, 199 (talk) 14:21, 26 June 2006 (UTC)

Read the sleep article while lying in bed. --Zeizmic 15:06, 26 June 2006 (UTC)
Wait, was that chiding me for not having read the article, or a suggestion for my second question? The article doesn't seem to have anything in it that answers why eyes feel sore when we are tired, and I didn't suggest I'm an insomniac, so I'm confused as to the point of that answer. 199 (talk) 15:30, 26 June 2006 (UTC)

The heaviness and aching you feel in your eyes is pobably due to a few things. First, the muscles around your eyes are not particularly strong, and they tire easily; thus as your body begins, at the end of the day, to tire, the weak eye muscles feel the most tired. The achyness is probably a byproduct of that exhaustion, but may also be due to dryness. People tend to blink less at night, and this can lead to dry eyes. You may find relief through rehydration (you can probably figure out how to do that yourself, I don't want to give medical advise over the internet), and a cold compress (they sell gel masks you can put in the refrigerator for just this). As always, if you think that you suffer from these things more than other people, or if you find that your symptoms get worse, call your doctor.Tuckerekcut 16:11, 26 June 2006 (UTC)

Thanks Tuckerekcut, for that explanation! Why are our eyes dryer at night? Aren't our eyelids closed, and aren't our eye's moving due to REM sleep? I don't know how I'd manage blinking while I'm asleep... Anyway, that's for those leads. 199 (talk) 16:26, 26 June 2006 (UTC)

The 'chiding' was for not getting enough sleep, and the article will tell you of the consequences. Tired eyes are just the tip of the iceberg for all the bad things that come with sleep deprivation. --Zeizmic 16:42, 26 June 2006 (UTC)

[edit] browser/URL

In email I receive WEB MD. When I open the WEB MD mail there are a number of URL's or browser lines to click on for more info. When I click on any URL nothing happens. The URL will not open to give me the info contained within. The little MSN flag in the upper right hand corner does not move. On other sites the URL's do open. I cannot find the answer to this. I have sent an email to web md but no response yet.

One possible explanation is that the emails use ActiveX or other scripting. These tools are often disallowed by your computer or browser's security settings. Do you have any more information on the problem? A workaround may be to copy/paste (maybe right-click and 'Copy Link Location') the URL into your browser manually. Nimur 17:20, 26 June 2006 (UTC)
Do you have a pop up blocker? It might be blocking the opening of a new window. User:Zoe|(talk) 02:54, 27 June 2006 (UTC)

[edit] Musky odor of certain woman

I am curious and have queried various search engines to no avail. Certain woman emit a pleasant musky odor and others do not. Is there a scientific explanation for this? Or is it a matter of hygiene, menstruation or hormones?

Could it be a matter of perfume? Synthetic animal lipids probably would have a musky smell once esterified--152.163.100.74 18:42, 26 June 2006 (UTC)
I don't know about "musky", but you could prefer the odor of some women over others because they have a different immune system that you, which could mean that your potential children would have healthier genes. The only wikipedia reference I could find for this is here: Major_histocompatibility_complex#MHC_and_sexual_selection. 199 (talk) 18:55, 26 June 2006 (UTC)
I find that people simply have different odors. It's not a good or bad thing relative to them. For example, I don't really like the smell of most (natural) blondes whereas they are suppoed to be the pinnacle of beauty in American culture—I find them to smell a bit waxy. While perfume is so strongly discussed and marketed, I don't know why our own natural scents are not so much discussed. The above MHC reference is interesting. —Bradley 19:37, 26 June 2006 (UTC)
There are a lot of reasons for that. It's called bromhidrosis, or more simply, body odor. --Rentice 16:53, 4 July 2006 (UTC)
Oh, you said pleasant, not unpleasant. Sorry. --Rentice 16:53, 4 July 2006 (UTC)

[edit] Has anyone ever posted themselves in the mail?

I've just been listening to "The Gift" by The Velvet Underground. I know that the guy dies at the end of the song - but it has got me wondering. Has anyone ever got into a big box and mailed themselves somewhere else?

I don't see why it wouldn't be theoretically possible. All you'd need was a large enough crate to sit down in, some air holes, some food and water and a sealable receptacle for bodily wastes. Optional extras would include a radio, a flashlight and some magazines.

Anyone know? Would there be anything illegal about sending willing humans in the mail? It's got me all intrigued now... ;) --Kurt Shaped Box 18:27, 26 June 2006 (UTC)

Yup, some guy did, because he couldn't afford passenger air fares, and was caught as he got out, because the FedEx guy was still there. Sounded rubbish though, it was still about the same price overall including delivery etc. And he had to sit in a box for about a week, as it was moved about the appropriate depots. With his bodily waste and food in a confined space. Soory I cant find references. Philc TECI 18:34, 26 June 2006 (UTC)
I suppose that you could cut out on the food completely and take laxitives to clear out your bowels before you got in the box in order to minimise the solid wastes. Humans can go for three weeks without food and if you were just sat in a box for a week, it's not as if you'd be using much energy anyway (I suppose you could send yourself overnight delivery - if you guys have that in the US). The real bummer would be if the person at the other end wasn't there to sign for you and you were returned to the depot until they could be bothered to come down and pick you up... --Kurt Shaped Box 18:56, 26 June 2006 (UTC)
No offense ... but we're not a third world country. Of course we have overnight shipping in the United States. In fact, I do believe we pioneered it. So there. Hell, we're the only country who's even managed to do three-day shipment of live animals to the Moon. --Cyde↔Weys 19:06, 26 June 2006 (UTC)
Na, I wasn't trying to take the piss. The US is a big country - I wasn't sure whether it was feasible for the normal man to send something overnight from one end to the other... --Kurt Shaped Box 19:12, 26 June 2006 (UTC)
I am reminded of the time I visited Japan and a Japanese friend pointed out a 7-Eleven and explained, as if to a rube, "In Japan we have stores that never closes!" As for overnight shipping in the U.S., see FedEx, the original overnight courier, or at least the first in the U.S. --Ginkgo100 talk · contribs 20:16, 26 June 2006 (UTC)
  • Yes, if I remember correctly sending anything living is against the law (in the US and the Netherlands at least) and believe it or not, we have an article on Human mail :). - Mgm|(talk) 18:57, 26 June 2006 (UTC)
What about plants?Tuckerekcut 20:21, 26 June 2006 (UTC)
    • I do believe that living chicks (baby chickens) are mailed all the time. User:Zoe|(talk) 02:57, 27 June 2006 (UTC)
Goddamn. It seems that if someone has thought of it, then someone has already written a Wikipedia article on it. Whoa.
My father was a postman in the UK and he told me that they did occasionaly have to deliver living things. Off the top of my head, I can remember him mentioning that he once delivered a (well packaged and clearly marked) swarm of bees. I think there was a box of frogs and some exotic slugs at one point too. --Kurt Shaped Box 19:10, 26 June 2006 (UTC)
As I recall, the law against sending humans by post came about when someone put a stamp on a little girl to send her across the country by train. She wasn't boxed or anything, just had to ride in the mail car. Emmett5 22:22, 26 June 2006 (UTC)
LOL. I can just picture this - a girl with a stamp slapped on her fore-head, patiently sitting in the mail car.
Seriously, though, it's all just transportation. The box is only needed to hide the fact that it's a person who's being transported. Humans get transported just like mail items, it's just that they need some more comfort (although that is barely the case in airplanes). Of which some need more than others. Which is why there are often different classes. So why not make a super-low class for those who can't afford the normal fare? An empty train wagon could hold up to a tenfold of the capacity of a normal wagon with seats. Actually, that does exist, just not for larger distances - the metrorail. Add a water supply and you can go anywhere? What? Inhuman? Reminiscent of the transportation of Jews in WWII? How inhuman is it to deny poor people the right to transportation? Of course we could also eliminate poverty (could easily be done in western countries) or make transportation affordable for them. DirkvdM 08:05, 27 June 2006 (UTC)

[edit] Possible solution to rising sea levels (copied from Talk:Global warming)

I've just had an idea. Why not pump the rising water into any major depressions in uninhabited desert areas that could hold a lot of water, eg in Australia, the Sahara and America? This would stop flooding and the new seas could be used as fish farms and beach resorts could be set up around the edge. It might also be possible to introduce coral reefs to attract more tourists. Is this viable? Casper Claiborne 01:51, 25 June 2006 (UTC)

You want to build a pump that can transport billions of gallons of water to higher ground?--205.188.117.12 07:15, 25 June 2006 (UTC)
Well, appart from the unpredictable effects on the climate and the certain destruction of ecosystems, there is a slight problem with the magnitude of the task. A 1 cm increase in ocean level corresponds to about 3000 billion tons of water (if you are imperial: A 1 inch increase corresponds to 8000 billion tons) . A rather conservative estimate for sea level rise is 1 mm/year, so you need to move 300 billion tons of water per year. Portable high-performance pumps as used in New Orelans can move 900 tons per hour or slightly less than 8 million tons a year (assuming you can use them all-out all the time). If you just need to move water a small distance (so than one pump is sufficient), you need about 4000 pumps going all out all the time to compensate for a sea level rise of 1 mm/year. Less than I thought, more than is practical.--Stephan Schulz 08:04, 25 June 2006 (UTC)
4,000 pumps is nothing. Even if you would need 10 per pipe because the distance that's 40,000. At $100,000 each (wild guess) that's 4 billion dollars, which is a piddling little sum in a global context. There would also be some pipes to pay for. There would be electricity for the pumps to as well, and generating it could have bad environmental effects, but that could be cancelled out by raising the money from petrol taxes. And that's without taking the cost savings into account. The Italians are planning to spend € 3 billion on the MOSE project just to protect Venice. If there are even a hundred million people in zones that would be flooded, and you value property in those areas at just $100,000 per person, that is $10 trillion dollars, which is 2,500 times more than $4 billion. There would be some environmental damage, but there is going to be environmental damage from flooding, and my guess is the coastal ecosystems are more valuable than desert ecosystems overall. I don't see why it wouldn't work. Casper Claiborne 02:39, 26 June 2006 (UTC)
Umm....your guess is not wild enough. $100,000 will not buy you the truck it comes on. And even piddling little projects like the Three Gorges Dam cause concern about induced seismic activity (we need to fill 10 of these per year....every year for the forseeable future! Cost for this one dam is estimated at US$100 billion, at Chinese wages!) And then this amount of water will cause isostatic depression of the continental plate....--Stephan Schulz 06:54, 26 June 2006 (UTC)
Also, the water wouldn't stay there for long, it will evaporate.
So you keep on pumping. The Caspian Sea hasn't dried up yet. Casper Claiborne 02:39, 26 June 2006 (UTC)
That adds another dimension...you don't have to move the water once, but many times.--Stephan Schulz 06:54, 26 June 2006 (UTC)
There is something of an area problem. For every 0.5 m of sea level rise you'd have to cover an area the size of Australia and the Sahara combined to a depth of more than 10 meters. Even more assuming you still want parts of these places to be livable. There probably aren't nearly enough natural barriers to accomodate that much water so you've have to create some sort of super levee or dams around the regions you want to flood. At which point, one has to ask whether it makes more sense to build 1 m barriers around regions you want to protect or 15 m barriers around one region you want to flood... Dragons flight 03:09, 26 June 2006 (UTC)

Australia looked like this a long time ago  :) Count Iblis 14:48, 25 June 2006 (UTC)


You appear to have missed the point, water covering over the land is the problem of rising sea levels not the solution. If you think you can mearly pump the water away, you appear to have missed the massive implications of rising sea levels, since the earth is about 75% water, for every 25 cm rise in the sea, if you spread that equally over the entire landmass of the world that is 1metre, if you want to spread it over africa, its about 6 m, if you want to spread it over only the sahara thats probably about 60metres or so, so what are you going to hold it back with??? If you are just going to pump it despite the fact it will be evaporated and go back, you may as well just re-freeze the water and put it back at the poles, despite the fact it will melt. It's better to prevent the problem from ever happening really than trying to manage it. Philc TECI 19:24, 26 June 2006 (UTC)

I find this solution rather impractical, as well, but would suggest that partially diverting a river would be more efficient than actively pumping water from the ocean. If the Nile were partially diverted into the Sahara, for example, this could provide a nice freshwtaer lake, instead of a saltwater sea, and hopefully no energy would be required once the channel was constructed. If properly constructed, this channel could also limit flood damage caused by the river. StuRat 19:51, 26 June 2006 (UTC)

What's the point of pumping the water out if you're covering more land than the rising sea does? It just doesn't make sense. --mboverload@ 21:22, 26 June 2006 (UTC)

The point is to flood deserts and wasteland with water instead of valuable coastline covered with trillion dollar cities. Also, hopefully less area can be flooded by making the water deeper where it is sent. StuRat 23:41, 26 June 2006 (UTC)

Probably be cheaper to relocate the people. The huge water rise, we'll so glabaly 10metres, or in the sahara alone is 2.4 km deep of water, no dam or anything ever constructed could hold that back. Basically the water you could put on the sahare would make no difference. Philc TECI 00:02, 27 June 2006 (UTC)

What about electrolysis? --Username132 (talk) 00:16, 27 June 2006 (UTC)

I've actually had similar thoughts (i.e., the pumping of water into depressions) in the past. There are a few where it could definitely work, notably in inlamd Mali.Mauritania and along the Eritrea/Ethiopia border. In the latter case, a canal rather than a pump would do the trick. Directly, it wouldn't affect sea level enough to be worthwhile, but it could have serious advantages in other ways, such as changing local weather patterns enough to produce more rain. However, it would also change weather patterns in far broader ays that are impossible to predict. As to the cost, it would be prohibitive in the case of elevated depressions like in west Africa, but in the case of depressions currently below sea level a simple bore might be quite cost-effective. Unfortunately the vast majority of these areas around the world seem to be in political hot-spots. Grutness...wha? 03:35, 27 June 2006 (UTC)

Apart from the other problems, why not use the natural pump, the Sun? The Sun evaporates the water, pumping it into the atmosphere and dropping it on mountains, from where it goes to the sea through rivers. Just reroute the rivers to a reservoir and that water will not reach the sea. No pumps needed. Use what you have. DirkvdM 08:27, 27 June 2006 (UTC)

Good idea, I wish I'd thought of it...maybe 7 comments back ? :-) StuRat 15:47, 27 June 2006 (UTC)
Better luck next time, StuRat ;) --Username132 (talk) Image:United Kingdom Image:Netherlands 00:59, 3 July 2006 (UTC)

[edit] Thunderstorm

Right now there is a raging thunderstorm over my house that is so loud it would make Popeye cringe in fear. I am currently using my computer in the top floor of my house. Is this unsafe? Russian F 18:57, 26 June 2006 (UTC)

A friend of mine's computer was destroyed when his telephone line was struck by lightning a few years ago. Okay, there's probably no way of saying for *definite* that it was the lightning that caused it - but the facts are that he was browsing the internet during a thunderstorm, there was a lightning flash, swiftly followed by his machine catching fire... --Kurt Shaped Box 19:04, 26 June 2006 (UTC)
If you have a lightning rod on the side of your house, then you are perfectly safe. If not, then there is some risk. StuRat 19:34, 26 June 2006 (UTC)
Not really. The lightning can strike a phone line or a power cable miles/kilometers away and still cause a voltage spike bad enough to fry unprotected circuits. This is particularly likely in neighborhoods that still have overhead phone lines — I've personally had an ADSL router die valiantly while defending my computer from a power surge. A surge protector may help, but it should be noted that after a cheap surge protector has absorbed one major spike, it's probably no longer able to absorb another. So get a good surge protector that has an indicator light, make sure all the wires going into the computer are protected, and pull the plugs (all of them!) during a thunderstorm anyway just to be sure. —Ilmari Karonen (talk) 21:11, 26 June 2006 (UTC)
I believe they were asking about risk to their own safety, not risk to the computer. While voltage spikes can come through either the power line or phone line that could damage a device, I find it unlikely that they could electrocute a computer user sitting in front of the computer. That is, unless the lightning strikes the house directly, which won't happen if it's equiped with a lightning rod. StuRat 23:31, 26 June 2006 (UTC)
And as suggested above, the damage can come through a modem/network port as well as the power connection. I had an internal modem and PCI slot get fried by a lightning strike several years ago (the rest of the system survived). — Lomn | Talk 22:57, 26 June 2006 (UTC)

[edit] Spotted humans

Image:Male chest.jpg

Some people, especially caucasians, will have a variety of little (few mm) dark circles/patches scattered across their skin. Some examples can be made out in this photo, though it is not great quality (best I could find). My question is what are these patches called? Why do they occur? And are there any selection forces (e.g. aesthetic choice or biological utility) that act to encourage/discourage their prevlance in the population. Dragons flight 19:16, 26 June 2006 (UTC)

They're just flat moles aren't they? I have a few of them myself and I've never really thought much about them. --Kurt Shaped Box 19:19, 26 June 2006 (UTC)

Is this site for Q&A or for T&A ? :-) StuRat 19:38, 26 June 2006 (UTC)

Little dark colored circles across their skin? you mean freckles? :-)64.12.116.74 20:14, 26 June 2006 (UTC)
They are just one of a number of types of birthmark. Different birthmarks have different prevalences in various ethnic groups. --Ginkgo100 talk · contribs 20:23, 26 June 2006 (UTC)

You need to get out and spend more time with the White Man and you would know these things, hehe =D --mboverload@ 21:19, 26 June 2006 (UTC)

They might be Skin tags. User:Zoe|(talk) 03:00, 27 June 2006 (UTC)

[edit] Methylated spirits?

Is there any way of extracting the methyl alcohol, purple coloring and foul tasting/smelling stuff from methylated spirits at home in order to leave only the ethanol behind? --84.65.143.250 19:23, 26 June 2006 (UTC)

make a distillation device, the boiling temperatures are very close though so it has to be well made. ~Peter
Why do you want to make pure ethanol from methylated spirits? If you are trying to avoid local laws regarding the purchase of alcoholic beverages, there are easier ways. --Ginkgo100 talk · contribs 20:27, 26 June 2006 (UTC)
Depends on what's in it. Some types of additives can be removed by solvent extraction, but that won't work for methanol. For that, careful distillation is indeed probably the only simple way, and it's very error prone. Also, unlike most ethanol additives which taste awful but are mostly harmless, methanol is tasteless but poisonous. Like Ginkgo100 says, I wouldn't bother. —Ilmari Karonen (talk) 20:59, 26 June 2006 (UTC)

[edit] Rapid strep test

How much more accurate is the rapid strep throat test than the 24/48 hour culture test? Looking for percentages of false negatives/false positives.

Thanks, ~Peter

A Google search for "rapid strep test accuracy" turned up this article as the top result. --Ginkgo100 talk · contribs 03:31, 27 June 2006 (UTC)

Thanks! I really need to work on my googling skills. ~Peter

[edit] HIV Transmission

Is the table of the right in HIV#Transmission saying that I can have vaginal sex with no protective devices with a prostitute who tells me she has HIV and I will have a 0.05% chance of getting HIV? I feel like I'm reading this wrong but if now then that's...really low.

Thanks, ~Peter

All I know is that STD transfer rates are bullshited to young teens in the schools in the United States. They make it sound like you're going to get an STD no matter what - even using a condom. Ah, those crazy christian fundies =D running our country--mboverload@ 21:17, 26 June 2006 (UTC)
I took a look at the original source for the Wikipedia table [2] (See table 1 near the end), although that's taken from a journal which isn't available to me online. I expected a higher infection rate, but it does seem to be a reputable figure.-gadfium 22:05, 26 June 2006 (UTC)
Yeah, but each time it increases the chances by a megaload, I'm not sure how much, really need a statistician or someone from the Mathematics Desk to tell us the increase per time. Emmett5 22:19, 26 June 2006 (UTC)
Each time you have sex with an HIV-infected person you have the same chances of getting HIV. However, when you put those together you have a larger chance of getting it. You still retain the same chances per incident. See Gambler's fallacy--mboverload@ 23:15, 26 June 2006 (UTC)
Technically, the chance might go down a bit each time, since you might already have it from a previous contact. StuRat 23:47, 26 June 2006 (UTC)
I'm not sure what you mean =D --mboverload@ 04:27, 27 June 2006 (UTC)
You can't get a disease you already have. In other words, if you're already screwed, who cares? DirkvdM 08:46, 27 June 2006 (UTC)
Yeah, low chance, but high risk. You decide.
Apart from that, does it have to be a prostitute? I guess that any woman who is willing to have sex with you without a condom is more likely to have some STD. So prostitutes are probably your best bet. Though that may depend on where you're from - what the social/legal status of prostitution there is and consequently how safe the practise is (ie whether prostitutes insist on the use of a condom). DirkvdM 08:46, 27 June 2006 (UTC)
it's gotta be a prostitute cause I ain't getting any from anywhere else. All I'm saying is, I like those odds. I have a greater chance of dying on the spot than I do of getting the HIV . ~Peter

[edit] Gull vs. Fulmar

Sorry guys, this one is stuck in my head now.

If a gull (say a herring gull for the sake of argument) and a fulmar were to have a fight (no-holds-barred, neither backing down, fight ends when one of them hits the deck and can't carry on, etc.) - which one do you think would win? --Kurt Shaped Box 19:42, 26 June 2006 (UTC)

Kurt, I think you need some shock therapy to destroy that part of your brain that's fixated on seagulls. Either that or we need to add a new Reference Desk for Seagull questions. :-) StuRat 19:55, 26 June 2006 (UTC)
Yeah, sorry - I'll knock it off. I've got some nesting nearby and I can't stop watching them going about their lawful business. I think they're fascinating birds... --Kurt Shaped Box 21:39, 26 June 2006 (UTC)
I'd guess whichever one first got its beak on the other one's skull. I don't know about fulmars, having never seen any, but I know herring gulls do attack and kill other gulls nesting nearby, so there's a good chance such fights do happen. Presumably one could observe them and calculate the odds, but I'm not aware of anyone having done so. If I had to bet, I'd put my money on the herring gull; if nothing else, it's bigger. —Ilmari Karonen (talk) 20:41, 26 June 2006 (UTC)

What about a munchkin an Oompa-Loompa and one of the seven dwarves? Who do you reckon would come out on top? Theresa Knott | Taste the Korn 21:37, 26 June 2006 (UTC)

  • With their pick axes, I would say one of the seven dwarfs (cut the Tolkien spelling), but perhaps the Oompa-Loompa has a surprised under his sleeve... - Mgm|(talk) 08:09, 27 June 2006 (UTC)

Aladin vs. Timone and Pumba... who'd win? --Eh-Steve 23:00, 28 June 2006 (UTC)

[edit] Jammed Thumb

I recently jammed my thumb playing football. What are the most apporpriate steps to take? How do I know if it is okay?

Stop playing in goal? --Dweller 20:18, 26 June 2006 (UTC)
From an ex-goalie: Keep your hands open. I jammed and broke many fingers until I finally trained myself to keep my hands open. It was so often that I had a rotatable finger splint and I just taped my fingers together myself instead of going to the doctor. --Kainaw (talk) 20:35, 26 June 2006 (UTC)

Has it not occurred to the two of you that the poster may be talking about American or Canadian football? (...especially interesting from a Chiefs fan...)

Has it not occurred to you that outside the US and Canada 'football' usually means association football, and occasionally rugby or aussie rules? DirkvdM 10:02, 27 June 2006 (UTC)
Regardless of Football/Soccer - my advice was to keep your hands open. All of my hand injuries happened when my hands were partially closed and I hit the ground, the ball, another player, the goalpost, my own head... --Kainaw (talk) 21:26, 26 June 2006 (UTC)

If it is still bothering you, go to the doctor to check for broken bones or damaged nerves.Tuckerekcut 20:57, 26 June 2006 (UTC)

Why has it taken all of you so long to finally just tell the questioner to see a doctor? Loomis 21:59, 26 June 2006 (UTC)
  • No idea, but if he read the instructions on top of the page to begin with, he would've known that was the best thing to do. - Mgm|(talk) 08:07, 27 June 2006 (UTC)

Have you noticed that most people do not answer the question given by the asker. They either give an unhelpful answer or think that the quetion is being asked because of school homework. The truth is, they have no idea what to say, and assume that most people are trying to get homework answers. If the latter is true. SO WHAT!!!!!!!!!!. You are only giving a little help.

No, I haven't noticed anything like that. Are you doing a survey for sociology homework? --Kainaw (talk) 19:08, 27 June 2006 (UTC)
I believe I answered the question in the most appropriate possible way. "[T]he most apporpriate steps [sic] to take" is to see a doctor immediately, before any further damage is done. Loomis 01:55, 28 June 2006 (UTC)

[edit] Lightbulb

How many scientists does it take to change a lightbulb? --Dweller 20:30, 26 June 2006 (UTC)

It depends on what you want the lightbulb changed into. --Kainaw (talk) 20:37, 26 June 2006 (UTC)
I expect none: they'd have a grad student take care of it. Unless the scientist is funded by the NSF, in which case about a dozen scientists from the advisory board would be on hand to supervise and they'd come back in a month to check on the progress. 128.197.81.181 20:39, 26 June 2006 (UTC)
This question has been posted on all reference desks ( except /M). --hydnjo talk 20:54, 26 June 2006 (UTC)

The scientist in charge over the situation would first consider if this is worth reporting to the media. After this he or she would consult other scientists and take head leadership over the light bulb problem. The board would contact the Directorate for Engineering's Reorganization at the NSF and apply in the International Research and Education in Engineering program for funds. At this point numerous journal articles would be produced by the board. In the end the lightbulb would either be destroyed or passed on for another more important situation. If a grad student took care of the problem, he or she would not receive any credit, but this is also a possibility.

Congratulations, scientists! You have by far the most developed sense of humour in my totally subjective and unscientific experiment. --Dweller 23:38, 26 June 2006 (UTC)
P.S. Someone explain to User:Hyndnjo. Thanks. --Dweller 23:38, 26 June 2006 (UTC)
You forgot the first step - the scientists would first have to check if the lightbulb has not already been changed by someone else. DirkvdM 10:06, 27 June 2006 (UTC)
Add another scientist to perform the control experiment of not changing the lightbulb. --Heron 18:03, 27 June 2006 (UTC)
The same one? :) DirkvdM 06:24, 28 June 2006 (UTC)
Q: How many lightbulb jokes does it take to get hydnjo into vandal patrol mode?
A: One *blush*, only one! --hydnjo talk 13:28, 29 June 2006 (UTC)

[edit] Unknown tiny animals

Hi all, one of these days, I was sitting on a bench at park near my home, when my friend's dog showed up with his nose dirty. To clean it up I took some leaves from a nearby tree. That's when I picked up a couple leaves that were stuck together somehow. With little strength needed I pulled the leaves apart and found that it was glued by some kind of web-like tissue, probably made by an insect to create a shelter for itself between the leaves.

Looking closer I noticed this strange looking ...er, thing. Like an alongated black ball with many white er... things coming out of it. Then I saw that there was another one like it only smaller in size hiding behind the white cobweb-like stuff. I saw some debris around it, but couldn't make out anything else.

So, I took the leaf home and took a few close-up pictures. I own a fine camera that allows me to take pics at about 4 cm (<2in) from the subject, and at 6Mpx I could magnify it. To my amazement, there were several other small animals around the thing that caught my attention, somewhat large black things, some really small white ones, another type was light green and dark green. And a large skin coloured ball in the middle!

Well, does anyone have any idea of what these things might be?? I've been looking at the pictures for weeks. The only biologist I know will come to my house probably sometime this week or the next and I'll show it to him, but he is more into water animals, so I don't think he'll be able to help much.

You can even see the white spots on the leaf where the cobweb-like stuff is fixated. This picture has been cropped, and I have some other pics where the black things can be better seen.

Thanks all.--VdSV9•♫ 21:01, 26 June 2006 (UTC)

Wow, cool pic ! You must have an impressive camera. It looks like there is a whole universe on the back of that leaf. StuRat 23:20, 26 June 2006 (UTC)
I was thinking the same thing. I keep checking back to see if anyone has named the little black thing yet. A co-worker and I suspect it's some sort of caterpillar, but that's mostly a guess. Around these parts there are a ton of gypsy moth caterpillars making their little cocoons, so it might make sense that that little guy had wrapped himself in a cocoon between those two leaves. I'd actually like to see more of these close-ups just to see what other creatures are hiding there. :) 65.96.221.107 00:32, 27 June 2006 (UTC)
The black caterpillars look to me like Doratifera Casta. I had to look up the scientific name for the "Black Slug". I then googled for images using the scientific name and they look similar, but not identical. You can google for images and see what you think. --Kainaw (talk) 00:34, 27 June 2006 (UTC)
Urgh. That spiky thing is horrible - makes me shudder just to look at it. I'm not exactly sure why (maybe that's another question for the desk) but there's something menacing about it that makes me feel very uneasy deep down. In fact, if I was confronted by it, I'd probably feel the urge to either a) run away or b) destroy it. --Kurt Shaped Box 00:41, 27 June 2006 (UTC)
The good old fight or flight. Just that the fight would be bit uneven in this case.
The black one in the foreground, although a bit blurry, looks a bit like a tick. And the green ones are, of course, aphids DirkvdM 10:14, 27 June 2006 (UTC)

Yeah, I thought it might be a tick also, let me find one where it can be seen better, here, crop it, upload it. there you go.

Now, the cobweb-like stuff, what is it called and who spun it?] The other Doratifera casta I found on google images are much large than "mine". They are 25 mm catterpillars and have 8 mm pupas, while mine is ~2 mm and has a <1 mm pupa! Maybe they're different species? Well, that day I took it to my friend's house and after about an hour most of them had left the leaf and some ants were walking over it, my guess is that the ants might have taken away the catterpillar (hmm, protein...). Next time I'll bring it home and see if it pupates. :D VdSV9•♫ 13:52, 27 June 2006 (UTC)

And as for StuRat's comments, the camera is nice, but not at all that impressive. If you go to the image page, besides from getting a large version of the image, go all the way down and you'll se a METADATA box with all the info pertaining the camera and stuff. VdSV9•♫

The real question is, who would win in a fight: an army of spikey beasties, or a gull? --Ginkgo100 talk · contribs 16:33, 27 June 2006 (UTC)

Depends on whether they're allowed to exceed the speed of light. Melchoir 18:19, 27 June 2006 (UTC)

All I can say of relevance is that those little green ones are indeed aphids. I've seen them before. Funny little creatures, they seem to be the "cows" of the insect kingdom. Each year a colony of ants attacks my apple tree, and brings their aphids there to graze. Apparently the relationship between ants (or possibly other insects) and aphids is like the relationship between humans and cows. The aphids "graze" on my apple tree, and in doing so apparently produce some sort of sticky liquid that the ants love. The ants then take this liquid, and guide their "herd" of aphids to greener pastures. Loomis 01:48, 28 June 2006 (UTC)

Yeah, that's basically their shit (or is it piss in this case because it's s fluid?). They bore into the plant, suck out the sugar-rich fluids, over-eat themselves (maybe the ants stimulate them to do this) and 'shit' it out, which the ants then suck up. DirkvdM 06:29, 28 June 2006 (UTC)

Making progress. Aphids are interesting, it did help out a little having a featured aphid article in portuguese. So maybe those ants were not after the catterpillar after all, but after the tiny little green ones. What was I thinking? "hmm protein..." ants are not that atracted to protein. Well, if I ever find out more about these guys I'll let you know. --VdSV9•♫ 11:08, 28 June 2006 (UTC)

[edit] Grandpaternity testing

How accurate is DNA grandpaternity testing? Specifically, assume that for purposes of custody it is desired to prove that individual A is the grandfather of individual B, and DNA samples of each individual are available but not of any other family members. First, could the grandparental relationship be distinguished from other 25% relationships like half-brothers or uncle-nephew? Second, assuming that you rule out uncle-nephew etc. a priori, so that all you are really looking for is whether or not there is a 25% genetic relationship, can modern testing establish this to a greater-than-99.9% confidence level, just like standard paternity testing where the mother is available? Third, does it make a difference whether the individual is alleged to be the paternal grandfather or maternal grandfather? This question was originally asked by someone on the Humanities desk: Wikipedia:Reference desk/Humanities#will grand father's dna and grand son's dna match?. --Mathew5000 21:09, 26 June 2006 (UTC)

Also, somebody responded in the humanities desk that there is a (.5)^23 probability that a male individual received no DNA from his maternal grandfather (that's approximately 1 in 8-million). This seems to be based on the idea that for each chromosome, you have a .5 probability of inheriting the entire chromosome from your mother (although then wouldn't the probability be (.25)^23 ?). Is there any validity at all to this line of reasoning? --Mathew5000 21:22, 26 June 2006 (UTC)

That was my reponse. Since we have 46 chromosomes, and the mother would always get EXACTLY 23 from the grandfather, the only remaining question is which portion of these 23 chromosomes are passed down from the mother to the grandson. There is a 50% chance that each will be passed down, which leads to (0.5)^23 chance that none of the 23 chromosomes will be passed down. If mutations and gene transfer are included in the calcs, that makes it more likely that none of the chromosomes in the grandson are exactly the same as in the grandfather. This also assumes that the grandfather doesn't have any genes in common with any of the other grandparents, which may not be the case, especially in isolated communities. In this was the case, it would be less likely that the grandfather would be completely genetically unrelated to the grandson, since the grandson might also inherit a chromosome which matches his grandfather's from some other source. So, given our assumptions, a maternal grandfather may vary from 0% to 50% of chromosomes in common with the grandson, while a paternal grandparent would be guaranteed to have at least the Y-chromosome in common with a grandson. Regarding distinguishing between half-brothers, uncle-nephew, and grandparent relationships, the only thing that could be done genetically is to establish that they have different Y-chromosomes. Assuming no mutations, this would mean they can't have a relationship where they are descended from a common male ancestor down a fully male line. Beyond that, there is no way to distinguish between these relationships genetically without testing other relatives. StuRat 22:59, 26 June 2006 (UTC)
The odds of zero inheritance are actually quite a bit lower, due to homologous recombination. Two matching chromosomes can swap material back and forth during meiosis (the process by which gametes are formed).
A paternal grandfather can be identified essentially conclusively by comparing the grandparent and grandchild's Y chromosomes. The Y chromosome must be inherited from the father, who had to get it from his father; except for a very small number of mutations, the grandchild and grandfather's Y chromosomes should be identical. With a maternal grandfather, there's no such easy comparison. (A similar technique can be used to trace chains of female descendents; children inherit essentially all of their mitochondrial DNA from their mothers, again allowing a direct comparison up the chain.) TenOfAllTrades(talk) 21:39, 26 June 2006 (UTC)
Certainly a negative result on a Y-chromosome test would prove that A is not the paternal grandfather of B. However, what would a positive result tell you? Only that A might be the paternal grandfather of B, but they might simply have a common ancestor eight generations back on the paternal line (so that they are merely distant cousins). Right? Or can DNA analysts reliably distinguish eight generations of Y-chromosome mutation from two generations of Y-chromosome mutation? --Mathew5000 21:57, 26 June 2006 (UTC)
Oops—you're right, of course. Combined with other markers, though, it might be a pretty reliable positive test. I don't know how rapid and uniform the genetic drift is in the Y chromosome is from generation to generation; I suspect it's not a good enough measure to nail down the father-versus-cousin question, but I'd love to hear some comments from experts. For that matter, we don't know if the suspected father had a brother.... TenOfAllTrades(talk) 22:29, 26 June 2006 (UTC)

[edit] vaccinations

i had a coulpe of jabs today and after the second one i felt dizzy abd the nurse said that was just due to a drop in blood pressure, does anyone now why i would have a sudden drop in blood pressure after an injection? also i heard peolpes veins collaspe aftre they inject themsleves to often again why does this happen?--Colsmeghead 21:12, 26 June 2006 (UTC)

It's usually a vasovagal reaction - Cybergoth 21:41, 26 June 2006 (UTC)
And the answer to the other part of your question is that repeated injection or needling of a vein causes scarring and contracture. alteripse 15:54, 27 June 2006 (UTC)

[edit] Weight of US Quarters

How much does five (5) dollars of US quarters weigh?

One US quarter weighs 5.67 G. 20 US quarters would then weigh 113.4 G. 128.197.81.181 22:29, 26 June 2006 (UTC)
Search first. It's quicker. See quarter. --Shantavira 07:56, 27 June 2006 (UTC)
Of course, if they're dirty or oxidized, that could add a lot of weight. —Keenan Pepper 22:54, 27 June 2006 (UTC)