Wikipedia:Reference desk/Archives/Science/2007 May 12

= May 12 =

extinction
extinction —The preceding unsigned comment was added by 70.51.217.228 (talk) 02:31, 12 May 2007 (UTC).
 * The likely fate of every species. Edison 03:09, 12 May 2007 (UTC)


 * Our own fate? A.Z. 04:50, 12 May 2007 (UTC)


 * Extinction (disambiguation) —The preceding unsigned comment was added by Nimur (talk • contribs) 06:29, 12 May 2007 (UTC).

sunlight
Does sunlight affect hair growth? 68.231.151.161 03:17, 12 May 2007 (UTC)


 * A 1991 article in the British Journal Of Dermatology studied "androgen-dependent" hair growth in bald men living in temperate climates. Androgen-dependent hair includes scalp hair and most body hair, but not eyelashes and eyebrows. The study suggested that androgen-dependent hair growth is faster during the spring and summer months and slower during the winter months in temperate regions. Although this study was conducted in men, the authours suggest the results may also apply to women, but not to children (who have an altered response to androgens). Rockpock  e  t  06:34, 12 May 2007 (UTC)
 * Children do not have an "altered response". They simply have no androgens. As soon as they get androgens, they grow androgenic hair too, at any age. alteripse 13:37, 12 May 2007 (UTC)

What's the verb that means 'to move by peristalsis'?
Peristalse? Peristalsise? Peristalsisticate?

Thanks,

Adambrowne666 03:29, 12 May 2007 (UTC)


 * I've heard peristalse, but I believe it's a rare enough formulation as to not actually appear in dictionaries. - Nunh-huh 03:42, 12 May 2007 (UTC)


 * The OED lists the noun, adjective, and adverbial forms, but no verb of peristalsis. I suppose I should ask you to use peristalse in a sentence, but I'm a little afraid what such a beast would look like.... . -- MarcoTolo 04:25, 12 May 2007 (UTC)


 * I thought it was just peristalate. -sis is kind of a suffix you know. [' Mac Δαvιs '] ❖ 05:18, 12 May 2007 (UTC)

like osmosiate and mitosiate, both of which also don't seem to exist. But really it doesn't matter as it still means the same whatever you write, it just might be difficult to understand.

Thanks all - I'll allow your suggestions to peristalse through the ideational guts of my brain and inspect what comes out the other end... Adambrowne666 22:25, 13 May 2007 (UTC)

A doctor I work for refers to it when referencing flow- "It appears to peristalse."

Peristalsis refers to the rhythmic contractions whereby material is propelled through a tube, commonly where food is propelled through the GI tract. At least within the institutional in which I work, "peristalse" is the commonly used verb to refer to the GI tract functioning properly; "The colon appears to be peristalsing properly," or "We are administering Relistor to allow the gut to peristalse while we continue to control his post-operative pain with opioids." I don't know if it's correct, but it's in the lexicon of my attendings. Jeffhall318 (talk) 16:02, 24 March 2010 (UTC)

Hair
Can hair products such as mousse or hairspray cause baldness for men?

Rockpock e  t  06:49, 12 May 2007 (UTC)
 * According to this site "hairspray, mousse or gel.. weaken the hair and dull its texture," but this site reports that "there is no hair care product that can cause direct hair loss". When asked what about hair colorings, hair spray or excessive washing leading to hair loss?, Marc Avram MD, a dermatologist replied "What you should be careful with -- you should be careful about using excessive chemicals, relaxants, hot combs. There are things that can burn the hair out and pull the hair out, but everyday shampooing, combing, blow-drying is not a problem."

Observing influences results?
Hello there,

I'm studying a BA in English and have an understanding of physics up to the level of your standard pop-science book such as A Brief History....

I remember reading somewhere that by observing a particle one must also influence the position of the particle. For example, to see something we must shine light on it, but the act of bombarding something with photons mens that by the time those photons return to us, the object has changed.

What is this theory called? Does this mean that one can never take a 'fair' result? 139.184.30.18 10:00, 12 May 2007 (UTC)
 * You're thinking of the Heisenberg Uncertainty Principle, though "measuring influences results" is not really what it says, that's merely a popular misinterpretation. A more accurate way to describe "measuring influences results" is as an observer effect. :) - Nunh-huh 10:05, 12 May 2007 (UTC)


 * Absolutely spot-on advice. Thanks so much! My essay is going to be so much fun 139.184.30.17 14:59, 13 May 2007 (UTC)

Body Electricity
i held the cable to to my cale box and my other hand touched the cable circuit where i plug the cable into and when i touched it it zapped me and i held my fing on it but the zap was not that strong of course but the tv turned on?why is that? also when i just held the metal part of the cable while it was in the box the cable blacked out? could it be possible that my body can generate electricity or hold electricity without me getting shocked to death?could it be possible that the reason why the tv turns on and how it blacks out is becuase of my sub consciousness? becuase i go into my subconsious sometimes and my body cant move but i can see everything and i breathe automaticly? do i have super powers? im only a 12 year old kid and i wonder how is this possible? when my dad did it the tv didnt turn on or anything, it didnt even zap him? after the zapping my finger, the one that got zapped it was red on the tip of my finger?why?if i hold a lightbuld and touch the outlit will it kill me or will the light bulb turn on? -StaticJosh posted on 5/10/07 —The preceding unsigned comment was added by StaticJosh (talk • contribs) 10:15, 12 May 2007 (UTC).


 * I don't have an answer to your question, but am going to advise you not to mess with electricity. There are a number of variables which could cause a current to either kill you, or pass through you unharmed, and in many cases it can just appear to be luck whether or not you are seriously injured, so please do not risk it.  On the matter of the cable box/cable, I have done the same thing with an aerial cable and aerial input on a television, recieving a signal on the TV when connected up (however, I would not encourage anybody to do the same).  Appartely, a current passed through me, from the cable to the input port, seemingly bypassing any organs which could be severly damaged if struck by such electricty (or, the current was very low). Martinp23 10:58, 12 May 2007 (UTC)

Your body can't generate electricity but it can hold a charge. This static electricity results from normal activities, like walking in your socks on carpet. You can't detect a small electrical charge but a large electrical charge will make your hair stand on end. When handling electrical circuitry a spark can sometimes affect the circuitry. In your case it sounds like the spark affected the part of the circuit which turns on the TV. Sparks can also damage sensitive circuitry, so there is even a procedure using a grounding wire connected to the hand recommended for people who work with computer hardware. StuRat 15:18, 12 May 2007 (UTC)


 * Actually I believe both the brain and the heart generate a tiny electrical charge. Anchoress 21:38, 12 May 2007 (UTC)


 * That's true, in fact all nerves do. However, this charge is fully contained, and not sufficient to cause a spark that could affect electronic equipment, in any case. StuRat 05:06, 13 May 2007 (UTC)


 * See Electrostatic discharge —The preceding unsigned comment was added by 88.110.7.232 (talk) 01:15, 13 May 2007 (UTC).

Lupins in New Zealand
What species of lupin are most commonly found on roadsides, dunes, etc. in New Zealand? --superioridad (discusión) 10:15, 12 May 2007 (UTC)


 * Russell lupin (Lupinus polyphyllus), according to and  . Cheers, Dr_Dima.

Earth, Moon and Venus
The Moon occults the planets, like Venus, quite frequently. In case of such an event, and if we were observing Earth from Venus (obviously high above the clouds), I wonder what we would observe? A transit of the Moon? A very bright conjuction of the Earth and the Moon? Something else altogether? --(cubic[*]star(Talk(Email))) 10:20, 12 May 2007 (UTC)


 * Yes, assuming it was nighttime on your part of Venus, you would observe both. The Moon and the Earth would both be illuminated, and the disc of the Moon would pass in front of the Earth.--Shantavira 13:17, 12 May 2007 (UTC)

You would see nothing but sulfuric acid clouds, if you were on the surface on Venus. However, if you were above the clouds, you wouldn't see much different from the normal star-like appearance of the Earth from Venus, if using the naked eye. You would need a telescope to distinguish between the Earth and Moon. StuRat 15:10, 12 May 2007 (UTC)
 * Much the same way you need to do the same in reverse. :) Since Venus also has moons, and is similar in size to Earth, I think it'd be pretty damned identical. Obviously you wouldn't have just a black dot moving in front of a full-lit earth, but under certain (lighting) circumstances I imagine one should be able to tell through use of a very good telescope. —The preceding unsigned comment was added by 81.93.102.185 (talk) 16:52, 12 May 2007 (UTC).
 * Er, I'm pretty sure Venus has no moons... 68.231.151.161 17:34, 12 May 2007 (UTC)
 * Correct (Venus) Tugbug 18:09, 12 May 2007 (UTC)
 * The earth is unusual amongst the planets - it's a relatively small planet - yet is has this gigantic moon - orbiting very close in. It would almost be correct to call the earth-moon system a "binary planet" (it's not because the center of rotation of the system lies beneath the surface of the earth...but it's close).  Hence an observer above the clouds on Venus would see a much more dramatic occultation of the Earth by the Moon than is the case with the tiny fly-specks that orbit other planets.  When there is a solar eclipse on Earth, the view from Venus ought to be pretty spectacular - especially if Venus were close-by at the time - because both the earth and the moon would be fully lit and the moon's shadow would be huge (by the standards of moon shadows on other planets).  But as previously pointed out - viewing conditions from the surface of Venus are far from ideal.  The view from Mars is going to be much worse because at closest approach, the earth and moon are presenting their dark sides to Mars - so not a whole lot to see there. SteveBaker 22:41, 13 May 2007 (UTC)

Coral reefs dissapeering from global warming
You guys are not doing homework for me-I need to know if there are any sites to retrieve information about coral reefs disapeering. I need specific data about how much coral is in the world and ocean temperatures over a number of years. This is not homework, I am doing a science project and need this data to do it. —The preceding unsigned comment was added by Kfswimmer17 (talk • contribs) 20:08, 12 May 2007 (UTC).


 * Coral bleaching might be a good starting point if you haven't looked at it already. --Allen 20:26, 12 May 2007 (UTC)

Lighning safety in houses
I have read at several websites that there is no danger from lightning strikes in a house. Why would a house (let's say a typical family home with brick walls and a slate roof) stop lightning bolts from entering it?


 * I think there's a reason people have been using lightning rods for the last 250 years or so. I'd like to see those websites.  Someguy1221 21:33, 12 May 2007 (UTC)


 * Here's a website that says you can be struck inside a house, especially if you're too close to a conductor . Speaking of which, I think I'd better shut off my computer and go inside now.  --Allen 21:35, 12 May 2007 (UTC)


 * There's lots of documentation for people being hit by lightning through windows (open and closed), as well as over telephone lines. Anchoress 21:37, 12 May 2007 (UTC)

So here is one of those documents (actually not a website): http://www.lightningsafety.noaa.gov/resources/Ltg%20Safety-Facts.pdf


 * That's a pretty sketchy document; I'm surprised NOAA is hosting it. (It's hard to take something seriously when it's Written With Every Word Capitalized.) —Steve Summit (talk) 22:11, 12 May 2007 (UTC)


 * My physics teacher once said that you can't be affected by lightning when in a closed hollow object (and away from the sides). That is why it is also safe to be in a closed car or an aeroplane during a storm (although the aeroplane could be affected in other ways by the lightning!). Regarding your house, the lightning would most likely strike the lightning conductor and dissipate into the ground. Or if it's like my house, strike the telephone wires and blow my modem and computer :) Perhaps someone would care to enlighten us with a scientific explanation of the 'hollow' theory? PS after e.c./ Closed window, Anchoress, really? (shudder) Sandman30s 21:44, 12 May 2007 (UTC)


 * Your physics teacher was talking about a closed hollow metal object. See Faraday cage. —Steve Summit (talk) 21:58, 12 May 2007 (UTC)


 * My personal house has a reinforced concrete roof, so I would bet that is pretty safe as it is a conducting grid covering the whole place. I once personally witnessed a ceramic roof being literally blown to pices by a lighting. The house subsequently burned down to the ground. Since then I am a little afraid of lighting, so that is why I ask this question. By the way, nobody was harmed in that incident. So were they just lucky?


 * I'd say they were lucky, yes!
 * The point of the exercise is to be avoid being in or near the current path between cloud and ground, i.e. the path along which the lightning bolt travels.
 * If you're outside, and especially if you're standing on flat ground with nothing tall around you, it's all too easy to be on the path. So that's the last place you want to be.
 * If you're inside a Faraday cage, you're just about maximally safe.
 * The skin of a house is not (usually) made of continuous metal, so a house is not a perfect Faraday cage. However, the materials the house is made of are probably better conductors than air, so once lightning hits a house, it's likely to travel down through the walls, and not (say) jump back out of the ceiling, through the air above your head, and down through you.
 * If as it travels down through the walls of your house, the lightning finds any wires, it will of course preferentially travel through them. But small wires (especially telephone wires) can't carry the high currents of a lightning strike, so they're liable to catch fire or explode.  Also you obviously wouldn't want to be touching an appliance which is connected to a wire that finds itself carrying a lightning strike.  That's why you're advised to stay away from wires, telephones, and other appliances during a lightning storm.
 * If the lightning hits a tall and well-grounded metal object, such as a water tower or church steeple, everyone else is quite safe. If the lightning hits outdoor power lines, those will have lightning arresters which shunt the current to ground before it has a chance to travel along the wires and hurt anyone (or even damage very much equipment).  (Long-distance transmission lines have ground wires strung above the current-carrying wires, for even more protection.)  So if you're in a built-up area, I think you're probably quite safe.  In a rural area subject to thunderstorms, or if you happen to be in the tallest building around, you'd probably want to think about installing your own lightning rods. See the lightning rod article for more information. —Steve Summit (talk) 22:32, 12 May 2007 (UTC)


 * I believe in the US all telephone lines are protected at the point of input. In Malaysia this is not the case and modems and sometimes whole computers are killed by lightning. I haven't heard of human casulties or even injuries but I would say it's not imposible given the frequency of modems being killed. I once had an aerial on a hill to try and get better reception. Bad idea as it was struck by lightning and took out an aircon starter (the wire was touching the aircon), a LD player, a TV and a VCR (all interconnected devices). Nil Einne 10:53, 13 May 2007 (UTC)

Isotopes: the commercial uses of deuterium
How can deuterium be used to power nuclear reactors?--Daniel J. Keller22:49, 12 May 2007 (UTC)Harleydankeller


 * Deuterium is used in fusion reactors as fuel. I have never heard of any possible use for deuterium in fission reactors. All currently existing nuclear power plants are fission reactors. —The preceding unsigned comment was added by 84.187.19.133 (talk) 23:01, 12 May 2007 (UTC).


 * Deuterium is used in nuclear fusion reactors. See Deuterium. Deuterium oxide is called heavy water, and is used in fission reactors, ie standard nuclear power plants. See Heavy water. --h2g2bob (talk) 00:20, 13 May 2007 (UTC)


 * See our CANDU reactor article for a fission reactor that uses heavy water.


 * Atlant 01:12, 13 May 2007 (UTC)


 * The key point here is heavy water is not used as a 'fuel' source (i.e. to power the reactor) but is used as the moderator... Nil Einne 10:56, 13 May 2007 (UTC)

Deuterium is used in chemical analysis, particularly in Nuclear Magnetic Resonance spectroscopy. As the technique uses a magnet to alter the spins of hydrogen causing them to "flip" from one direction to the other. This generates a signal that can be interpreted. Deuterated solvents are needed, as they don't give a signal under a magnet, as it is a paired proton, allowing only the signal from the sample to be detected.

snowpack
How much snowpack has reduced in the past year and the current year? Coffsneeze 23:20, 12 May 2007 (UTC)


 * Where ? StuRat 04:59, 13 May 2007 (UTC)

Mother's Day questions

 * 1) Why do hen lay unfertilized eggs?
 * 2) Does a wild bird lay unfertilized eggs from time to time?
 * 3) Can we artificially fertilize a freshly laid egg?
 * 4) Can we artificially fertilize a refrigerated egg?
 * 5) Isn't it stupid for a chicken to lay an unfertilized egg if they are in the wild? I know today's chicken are selected by human but did their ancestors lay unfertilized eggs?

I think hens are strange mothers -- Toytoy 23:34, 12 May 2007 (UTC)

1) Because the rooster has been lax in his duties. :-) Actually, I'm assuming you mean "why lay an egg if no fertilization has occurred" ? I'm not sure, but human menstruation is similar (purging some material which would have been used to grow a baby, had fertilization occurred).

2) I imagine so, if the male bird is AWOL.

3) No, I believe it's too late.

4) No, I believe it's too late.

5) It does seem inefficient, yes. I don't quite understand it myself.

StuRat 04:55, 13 May 2007 (UTC)


 * Note that chickens has been domesticated for many thousands of years. A "wild" chicken is perhaps more properly called a "feral" chicken.  Could they survive without humans or apart from human created environments? I'm not sure. They have certainly evolved (via selective breeding or otherwise) to be what we humans want them to be. It should be no surprise they act in rather unnatural ways. 07:31, 13 May 2007 (UTC)


 * To answer question 5. No, I don't think it's stupid to lay unfertilized eggs. Think of it this way. If you have a clutch of 5 eggs, 2 of which are unfertilized. Then you'd have a 40% percent chance that a predator would take an unfertilized egg from the the clutch. This assumes of course that the predator takes one egg and not more. So maybe in a sense the unfertilized egg can be a decoy for the fertilized ones. This of course is just the babbeling of someone who has very little knowledge of chickens. But it does strnagely make sense to my laymans ears. PvT 12:06, 13 May 2007 (UTC)


 * In this case, you may lay 5 fertilized eggs as well. Sperms are cheap, aren't they? They also could lay decoy eggs without much nutrients or simplay eggs filled with bird droppings. -- Toytoy 14:33, 13 May 2007 (UTC)

As a lover of chickens with a hungover sense of rhetoric;

a. a domesticated chicken has been bred to produce masses of eggs - hundreds a year - regardless of fertilisation; in the wild birds usually produce eggs only 'on demand'. how long it took to breed them to the way they are now i am unsure of, i lost my chicken book a while ago.

b. a modern-day chicken is no toy poodle. two of mine escaped one night and the following morning a huge pile of feathers was sighted in the meadow: classic fox leftovers. naturally my parents and i assumed the poor buggers were both dead.

two weeks later one of them turns up, all casual, and helps herself to the feed as if nothing had happened. she'd been living in the woods for all that time, presumably finding safety from foxes and badgers using her limited flight, and a natural scavenger instinct to feed herself. we called her 'hero chicken' from then on.

incidentally (which is a poor way to start a punchline i know) the next week she was mauled by a customer's dog. what this story tells us about the domestication of animals i am unsure. as i said, hungover. thanks lovely people.


 * So even if you are chicken, you can still run wild and outfox your enemies, but you'll end up dogged by trouble in the end ? StuRat 21:54, 13 May 2007 (UTC)
 * I have seen a very few domesticated hens (probably Plymouth Rock) who could fly like a bird over any fence and to the top of the tallest tree. Edison 23:15, 13 May 2007 (UTC)
 * LIke a bird? No foolin? &mdash;Tamfang 23:27, 15 May 2007 (UTC)

Cats
Our article on felines states there's 41 species. Do you know where I can find a comprehensive list including both common names, and more importantly, scientific names of all 41 species? Surprisingly, neither a quick Google or Wikipedia search turns up anything useful. 209.53.180.107 23:59, 12 May 2007 (UTC)


 * Um, in the article you link to it lists 41 species with both common and scientific names. Here. --TotoBaggins 00:58, 13 May 2007 (UTC)

Dogs
Our article on canines says the domestic dog is either classified as a seperate species C. familiaris or a subspecies of Gray Wolf, C. lupus familiaris. Why does our Dog article list it as a subspecies of wolf? Is that the more widely accepted view? Can domestic dogs successfully interbreed with gray wolves? 209.53.180.107 23:59, 12 May 2007 (UTC)
 * I remember reading somewhere that all wolves and domestic dogs belong to one species: Canis lupus, with the possible exception of red wolves, which are hyprids of wolves and coyotes (or decendants of those hybrids). Which raises yet another curiosity to me, why the heck are wolves and coyotes different species if they interbreed. Adam2288  T  C  00:11, 13 May 2007 (UTC)
 * Good question, Adam; see Species problem. --Allen 02:58, 13 May 2007 (UTC)


 * Oh, and domestic dogs can successfully interbreed with grey wolves (assuming there is no physical problem for that particular breed of dog). So the man at the rare-breeds centre told me anyway. I seem to remember them being in vogue as expensive pets not so long ago. More dangerous than dogs or wolves, if I recall, since they didn't fear people. Skittle 21:09, 13 May 2007 (UTC)