Wikipedia:Reference desk/Archives/Science/2008 March 9

From Wikipedia, the free encyclopedia

< Wikipedia:Reference desk | Archives | Science

Science desk
< March 8	<< Feb \| March \| Apr >>	March 10 >

Welcome to the Wikipedia Science Reference Desk Archives
The page you are currently viewing is an archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages.

[edit] March 9

[edit] Animal behaviour

I've read that chimpanzees are pretty violent and often rape and murder one another, and that dolphins kill for fun, although they kill big fish and not other dolphins. Humans are obviously prety violent what with our murdering and our warfaring, so my question is this: discounting territorial disputes, does propensity for violence increase with intelligence among animals? I mean with average species intelligence, not individual cases. And I mean 'senseless' violence rather than mating/food etc related. Thanks 81.96.160.6 (talk) 04:54, 9 March 2008 (UTC)

"Senseless" violence in animals is not really senseless. Just because we don't completely understand the motivation of the animals, does not mean that there is not good biological reasons for it. With regards to chimps that kill and rape, it may be a dominance behaviour, used to establish roles in society. I think its difficult to generalize but among mammals increasing intelligence is generally associated with less violence, since more intelligent animals tend to develop strategies of co-operation and exist in complex social structures. These tend to defuse aggression, rather than stimulate it. Male mice, for example, will robustly attack any other male mouse that happens to wander into his territory. When another guy comes into your house, (I expect) you don't attack him on sight. Rockpocket 09:12, 9 March 2008 (UTC)

If he comes in through the window, uninvited, I sure do. :-) StuRat (talk) 18:01, 9 March 2008 (UTC)

Hi. Remember that chimps have a ⅓ murder rate, meaning that one in three of all chimps become murdered at some point in their lives. Also, sometimes bottlenose dolphins will bully, attack, and kill Dall's porpoises. It may be hard to believe, but that "smile" of a dolphin is actually a threat. Occasionally but very rarely, dolphins might attack humans as well. Chimps are seven times stronger than humans. Humans ususally don't go on these "senseless" attacks because we are generally more civilized and have a code of laws. In fact, some consider the cimps' fighting and killing of monkeys a form of politics. Hope this helps. Thanks. ~A H 1^(TCU) 14:36, 9 March 2008 (UTC)

It could be argued that "murder" or the killing of your own species or of other species is part of human behaviour. There are people that train in wrestling and forms of martial arts - it seems to be part of human nature to be capable of this, and in an animal system where it's survival of the fittest and you need to dominate to find a mate, it's part of nature. Humans have similar behaviour - we have sports, and many people do fight (even mock fight) and try to dominate other people physically - of course even psychologically, verbally and sexually. Rfwoolf (talk) 18:50, 9 March 2008 (UTC)

But the mouse does have motivation: it's territorial. I'm not saying it's right, but I mean really killing for fun, like dolphins apparently do. Where there is really no gain. The chimps thing works: social gain is really an intelligence related thing so killing for that sort of maybe demonstrates a link. It just dosn't seem that many "stupid" animals go round getting their kicks from murder. 81.96.160.6 (talk) 19:41, 9 March 2008 (UTC)

I'm not sure killing is ever without purpose. If nothing else, it provides practice for a time in the future when killing might be necessary for survival. For example, a well-fed cat will still catch mice, even if it has no interest in eating them. They even let the mouse go, then capture it again and again, in order to sharpen their skills. In the case of humans, hunting may be an important survival skill in some situations, so the desire to hunt does have a purpose. The ability to hunt other humans can also be an important survival skill in war, but the ability to turn this aggression off when not needed is far more important in this case, as a person who hunts other people during peacetime will soon found himself hunted. StuRat (talk) 15:39, 12 March 2008 (UTC)

[edit] DNA sequencing

It seems that before a DNA sequence is sequenced, it is cloned into a plasmid for amplification in bacterial cells, then the plasmid is cut for sequencing. Why can't PCR be used to amplify the DNA for sequencing? ----Seans Potato Business 08:58, 9 March 2008 (UTC)

You can sequence a PCR product also. The problem, though, is that the thousands of amplicons may contain slightly difference sequences due to PCR error which can result in a messier read. Cloned sequences are more likely to be homogeneous. If you want to do something with the DNA after you determine the sequence then you clone it first (since you can't be sure which of the many PCR amplicons you have sequenced), but if you just want to determine what you have amplified, then you can sequence the PCR product without cloning it first. Rockpocket 09:16, 9 March 2008 (UTC)

Generally speaking, a plasmid is not cut before sequencing. In fact, invariably the plasmid is purified and left intact before sequencing with a primer. However, as stated above, one can always sequence a PCR product. And just as a note, PCR and sequencing are fairly similar. There is an extension reaction that needs to take place before the gel fluorescence is read by automated sequencer. Wisdom89 _{(_T / ^C)} 14:38, 9 March 2008 (UTC)

Also note that some of the newer sequencing techniques don't require plasmid cloning. George Church's polony technique comes to mind, as do some of the nanopore sequencing techniques. Most of these aren't being used commercially yet, though.-- 128.104.112.85 (talk) 19:56, 11 March 2008 (UTC)

[edit] Energy

Which of these..(radiation, conduction, convection)...does heat from the sun reach the earth?? —Preceding unsigned comment added by Cassiesirevatarax (talk • contribs) 10:03, 9 March 2008 (UTC)

The answer is in the first sentence of the Sunlight article. --Heron (talk) 10:52, 9 March 2008 (UTC)

[edit] Firing on all pistons

What engines can be configured to fire on less than all pistons? ----Seans Potato Business 10:21, 9 March 2008 (UTC)

See Variable displacement and Active Fuel Management. --hydnjo talk 11:52, 9 March 2008 (UTC)

Your internal combustion engine can often work on less than the full number of cylinders, when a spark plug or lead goes bung. Graeme Bartlett (talk) 13:21, 9 March 2008 (UTC)

Would this be damaging to the engine? ----Seans Potato Business 22:28, 9 March 2008 (UTC)

No, but allowing an unburned fuel-air mixture to reach the catalytic converter will cause the converter to overheat and sometimes igniite fires in the surrounding materials. Backfires may also occur in the exhaust system and these can blow apart weak points.

Atlant (talk) 16:32, 10 March 2008 (UTC)

It's not generally a good thing efficiency-wise, because those cylinders are still getting dragged along for the ride while they're not providing useful power. Still, displacement on demand is being actively used and developed by Chrysler among others. Forced induction is a competing approach, from the other direction- this lets you have a small engine that "gets bigger" under load, rather than a big engine that gets smaller under light load. Friday (talk) 16:38, 10 March 2008 (UTC)

[edit] Which Australian native frog?

Which Australian native frog in the East coast region of NSW makes a sound like a piece of wood going clunk or "clock" against something? It's small and brown and turns up in metropolitan Sydney. Julia Rossi (talk) 10:32, 9 March 2008 (UTC)

Could it be the pobblebonk? Adambrowne666 (talk) 12:20, 9 March 2008 (UTC)

Thanks Adambrowne, pobblebonk gives the eastern banjo frog so I'm assuming when they say it sounds "like a plucked banjo string" means in an non-tuneful, "pock" way for percussive effect. Any banjo players confirm that? Julia Rossi (talk) 21:28, 9 March 2008 (UTC)

[edit] Quantum Mechanics: Operator and Eigenvalue

For a given wave function $ψ(x)$ of a particle at position $x$ , the momentum $p$ of the particle is the eigenvalue of (1)

$\hat{P}\psi(x)=p\psi(x)$		(1)

where

$\hat{P}=-i\hbar\frac{\partial}{\partial x}$		(2)

For example, if the wave function of a particle is

$\psi(x)=\exp\left(i\frac{p_0}{\hbar}x\right)=e^{i(p_0/\hbar)x}$		(3)

, the corresponding momentum $p$ will be

$-i\hbar\frac{\partial}{\partial x}e^{i(p_0/\hbar)x}=pe^{i(p_0/\hbar)x}$		(4)

$-i\hbar\cdot e^{i(p_0/\hbar)x}\cdot\left(i\frac{p_0}{\hbar}\right)=pe^{i(p_0/\hbar)x}$		(5)

$p_0e^{i(p_0/\hbar)x}=pe^{i(p_0/\hbar)x}$		(6)

$p = p 0$		(7)

Therefore, the momentum of the particle (3) is $p 0$ . But does it make sense to say the coordinate $x$ of the particle (3) is the eigenvalue of (8)? It seems that we will always get $x=\hat{X}$ if we replace (3), or any other wave function, into (8)!

$\hat{X}\psi(x)=x\psi(x)$		(8)

Justin545 (talk) 11:05, 9 March 2008 (UTC)

I think the problem you are running into here is Heisenbergs uncertainty principle which states that there is an unavoidable minimum uncertainty in the product of the momentum and position observables;

$\Delta x \Delta p \ge \frac{\hbar}{2}$

If you claim to know with certainty that the momentum of the particle is $p 0$ then the position must, of necessity, be completely indeterminate. There is a similar relationship between other pairs of observables, such as Energy and Time. SpinningSpark 13:17, 9 March 2008 (UTC)

Uncertainty principle aside, most wavefunctions are not eigenvectors of most Hermitian operators. In fact no proper (normalizable) wavefunction satisfies $\hat{P}\psi(x)=p\psi(x)$ for any p. An equation like $\hat{A}\psi=a\psi$ is not meant to be solved for a as a function of ψ, it's meant to be solved for ψ as a function of a. Most wave functions won't be in the solution set, but they'll be expressible as a sum of elements of the solution set. If you like you can think of Hermitian operators like $\hat{P}$ as an odd way of specifying an orthogonal basis with a real number attached to each basis vector. -- BenRG (talk) 15:50, 9 March 2008 (UTC)

It turns out what I did was just replace the solution, or the basis, (3) into (1) according to the reply. I also forgot the position of a particle is uncertain, it is good to recall Heisenberg's uncertainty principle. I just did some ridiculous generalization and thought that the operator $\hat{X}$ can be used as (8) which is similar to (1) :p But it seems the operator $\hat{X}$ is useless except it is only used to calculate the mean value $\langle\hat{X}\rangle=\int_{-\infty}^\infty\psi^*(x)\left[\hat{X}\psi(x)\right]dx$ - Justin545 (talk) 03:37, 10 March 2008 (UTC)

[edit] how do astronauts refer to spacesuits

The wiki space suit article is great, but I wonder if astronauts call them 'space suits' also, or use an abbreviation or colloqialism to refer to them. Can anyone enlighten me? Thanks Adambrowne666 (talk) 12:17, 9 March 2008 (UTC)

Normally, they'd just be space suits, although there are a number of different types, so astronauts probably just call them by their name - the Advance Crew Escape System Pressure Suit (commonly called the ACES) and the Extravehicular Mobility Unit (the EMU) are the two used on most American missions, for example. Russian space suits (Скафандр) are all named after types of bird: the Yastreb translates to "Hawk" for example. Laïka 16:12, 9 March 2008 (UTC)

Thanks, Laika - I like your space-themed name, btw. Adambrowne666 (talk) 22:48, 9 March 2008 (UTC)

[edit] Chemistry

Give an octahedral complex containing an optically active ligand? —Preceding unsigned comment added by Minmoy mld (talk • contribs)

Sounding like homework: so the complex may or may not be optically active, but the ligand is? Many of the biomolecules that incorperate a metal may be like this. cyanocobalamin is one example. Graeme Bartlett (talk) 13:18, 9 March 2008 (UTC)

[edit] A gamma ray burst extinction scenario

(Bolded questions) I have been reading up on the GRB articles for fun. Not so fun are the theories about some random GRB making us all extinct, in effect at least. My question is not about what is a good idea or not to help prevent the earth from taking damage, but if it is possible to build a kind of screen that could absorb the rays on earth's behalf, shielding earth, and most importantly what material would suffice? The disc, made of whatever we would harvest from other planets, would have a diameter a bit greater than that of earth. It's placed at a good distance from earth (in the hundreds of thousands, or millions of kilometers), and to make matters worse, would need to somehow follow earth's orbit around the sun. Assume of course, that we know exactly where the GRB is likely to come from (which isn't entirely unrealistic). Are there, for the sake of adding meat to this question, any serious discussions within scientific groups how to best protect earth against a GRB? 81.93.102.185 (talk) 13:17, 9 March 2008 (UTC)

The "screen" would probably need to be several metres thick to provide any useful protection. But let's suppose, for simplicity, we make a disk the same radius as the Earth but just 1 metre thick. This would require the same amount of matter as a sphere about 60 km in diameter - something about the same size as a small moon of Jupiter. Now remember that the hypothetical asteroid that may have wiped out the dinosaurs is estimated to have been only about 10 km in diameter. I think the risks caused by having such a massive object anywhere near the Earth's orbit would be much greater than the GRB risk that it was protecting us from. Gandalf61 (talk) 15:09, 9 March 2008 (UTC)

Hi. Well, it might be possible if you could somehow put the object in free-fall around the Earth. Now, an object that big would weigh roughly 5x10¹⁴ tons if I calculated correctly, so it would be pretty hard for it to get off the Earth in the first place, unless you assemble it in space, which would take decades and trillions of dollars for something that probably won't happen anytime soon anyway. Global warming is a much more immeinent risk. Also, if it were free-falling around the Earth, then you would have to know all the GRBs years in advance so that the disk could be positioned correctly. In reality, we probably wouldn't know about a GRB until the instant it hits us, because in order to detect it, we would need access to the radiation, unless you set up probes around the solar system, which might give us just a few hours' warning (or not, because for the time the signals from the probes would have gotten to us, the probe would have been destroyed and the GRB would ahve already hit us). This again would take decades and trillions of dollars. It's also pretty hard to tell when a particular part of the sky or star is about to go GRB, as when we see the star exploding, if it is releasing a GRB, it would have already hit us by the time we detect the light from the supernova. Also, if that disk hits Earth, its impact would be spread across the Earth, but can you imagine a metre-thick material crashing towards Earth at 15 km per second (9 miles per second) on every part of the half of the Earth? Sure, parts of it might burn up, but large fragments would still land all over the Earth, and there's another trillion dollars wasted. Besides, if an asteroid hits that disk? It's going to break if it's only a few meters' thick. Also, an average single gamma ray will be blocked by 10 km roughly of air, but with relativity and zillions of rays, anything can happen. It usually isn't a problem unless the ray is directly pointed at us or if a large supernova explodes very nearby. Hope this helps. Thanks. ~A H 1^(TCU) 15:44, 9 March 2008 (UTC)

"Now, an object that big would weigh roughly 5x10¹⁴ tons if I calculated correctly," I don't think you calculated correctly. A cylinder 6378 km in radius, 1 m high, and with a mass of 5x10¹⁴ tons would have a density of only 3.9 g/cm^3. To block gamma radiation, the radiation needs to hit the atoms in the nuclei. Therefore, the nuclei have to be as large and heavy as possible. Lead is often used as a radiation shield for x-rays and gamma rays; its density is 11 g/cm^3, so the weight of the disk would then be 1.4x10¹⁵ tons. U-238 is much better, with a density of 19.1 g/cm^3; the disk would then be 2.4x10¹⁵ tons. --Bowlhover 04:38, 11 March 2008 (UTC)

To get to the end part of the question, no, there are no serious discussions in the scientific community to protect Earth from a GRB. As noted by the responses above, it's impossible short of some sort of Dyson sphere. However, there is one agreed-upon method to protect humanity from a GRB -- extrasolar colonization. — Lomn 17:45, 9 March 2008 (UTC)

Wouldn't a more realistic way to protect humanity be for us to live underground ? This would also have the advantage of providing protection from the far more likely scenario of a nuclear war. Environmentalists would be happy as underground living means less energy used for heating and A/C and the surface could be reclaimed and used exclusively for farms and nature. StuRat (talk) 17:56, 9 March 2008 (UTC)

Unless you can move the entire ecology (or at least a fully self-sustaining portion thereof) underground, the GRB is still going to fry life on the surface. — Lomn 22:07, 9 March 2008 (UTC)

Nuclear reactors could provide power almost indefinitely. Greenhouses could maintain plant life. Animals could be bred and slaughtered... -- 81.98.253.215 (talk) 22:35, 9 March 2008 (UTC)

Aren't you concerened about a mine shaft gap, though?

Atlant (talk) 16:36, 10 March 2008 (UTC)

Hi. How would extrasolar colonization help protect against GRBs? They are probably just as likely to hit that extrasolar planet as on Earth. Also if we were to create a dyson sphere then we would have become so technologicly advanced that we would have destroyed our own ecosystem and then we would have to colonise other planets. Thanks. ~A H 1^(TCU) 23:45, 9 March 2008 (UTC)

It's simply a matter of not having all one's eggs in one basket. You're entirely correct that any planet is vulnerable. — Lomn 18:24, 10 March 2008 (UTC)

How long does a GRB last? If less than a few hours, I'd submit that about half the Earth will be naturally shielded by miles of earth/Earth.

Atlant (talk) 16:37, 10 March 2008 (UTC)

As I understand it, it's not the immediate deaths from irradiation that make it an extinction threat, but the atmospheric changes it would cause. But there's not likely to be one close enough to us to matter anyway; as I recall it would have to be within about 500 light-years, and there just aren't any candidates within that sphere. There's more risk, I'd say, that we'll destroy our ozone layer ourselves. Minor planets, on the other hand, remain a genuine threat. --Trovatore (talk) 19:00, 10 March 2008 (UTC)

A gamma ray burst lasts seconds, not hours, and from the sources I have seen, a direct hit from a burst 8,000 light years away could cause changes in the atmosphere, but this is obviously theoretical. Jehochman ^Talk 19:19, 10 March 2008 (UTC)

[edit] Another birdsong?

Hi. This morning at around 8am (because of DST), I heard another birdsong. This time it was about -12C outside at sunrise, after a major snowstorm that dumped 25cm of snow and created 3 ft drifts. Anyway, it sounded like it was coming from a tree. First there were either one or two or three whistle-like notes, then six or seven flatter notes that sounded like a mix between a chirping bird's chirp, a pigeon's coot, and an owl's hoot. So for example: Whree? Whree? woo-woo-woo-woo-woo-woo-woo. The entire call lasted just over three seconds. It is sometimes repeated once every ten seconds maybe. I don't think it's an owl, and aren't owls nocturnal anyway? Any idea what it might be? I live in southern Ontario. Thanks. ~A H 1^(TCU) 14:27, 9 March 2008 (UTC)

Your description doesn't match exactly, but listen to the call of the mourning dove here and let us know if that's it. Most owls are nocturnal, but not all. --Milkbreath (talk) 14:47, 9 March 2008 (UTC)

Hi. No, that probably isn't it. The one I heard had more ooos and sounded less mournful. The first note I heard did not rise up so suddenly. The ooos I heard did not lower in pitch as they were sung, they stayed constant. Also, the one I heard was a bit higher in pitch, and there was often more than one starting note. By the way, I think I have heard that mourning dove song somewhere, and now I know why they call it the mourning dove. Thanks. ~A H 1^(TCU) 15:27, 9 March 2008 (UTC)

I don't think I know from personal knowledge what bird you've got there, but I'm trying to find it. The call of the saw-whet owl comes close. The northern pygmy-owl is diurnal and has a call like yours, except in the reverse order. A nocturnal bird will call in the daytime sometimes. --Milkbreath (talk) 16:19, 9 March 2008 (UTC)

Hi. Yesterday when I was outside, I heard about two dozen different bird calls. I actually heard an owl's call, and no this one did not sound like an owl. In fact, the whole thing resembled a chirp. I noticed the "woo" part actually sounded more like a "doo" or a "dchrew". Sometimes, there were as few as one or as many as eleven of these. I also saw some crows chasing a larger bird. There were many exotic calls, and I'm not going to ask for all of them. Ones like, "tchit-thcit-tsi-TCHEE!!!" and RDEW! RDEW! rd-RDEW!", "eeee! eeee! eee-ee!", a descending "oh-ree oh-ree oh-ree oh-ree oh-ree", a high-pitched squeal, and one that sounded like a shrill cry. I even heard one that sounded like a rattlous chirp, one that sounded like a baby crying, and one that sounded like wings flapping and chirpping at the same time for a dozen notes per half a second. I identified calls of crows, owls, seagulls, and geese. Possible sourses for some of the calls may or may not include: Red-Tailed Hawk, Northern Harrier, American Kestrel, Common Snipe, Greater Yellowlegs, Least Sandpiper, Herring Gull, Ring-Billed Gull, Bonaparte's Gull, Mourning Dove, Rock Dove, Eastern Screech-Owl, Long-Eared Owl, Great Horned Owl, Boreal Owl, Belted Kingfisher, Northern "Yellow-Shafted" Flicker, Red-Bellied Woodpecker, Downy Woodpecker, Hairy Woodpecker, Horned Lark, American Pipit, Black-Capped Chickadee, Red-Breasted Nuthatch, Brown Creeper, Winter Wren, Carolina Wren, Ruby-Throated Kinglet, Eastern Bluebird, American Robin, Northern Mockingbird, Blue Jay, American Crow, Northern Shrike, Cedar Waxwing, Yellow-Rumped Warbler, Northern Cardinal, Red Crossbill, White-Winged Crossbill, Eastern Towhee, Evening Grosbeak, Pine Siskin, Common Redpoll, House Finch, Purple Finch, Pine Grosbeak, White-Throated Sparrow, Field Sparrow, Swamp Sparrow, American Tree Sparrow, Fox Sparow, Song Sparrow, Dark-Eyed Junco, Snow Bunting, Lapland Longspur, Red-Winged Blackbird, European Starling, Eastern Meadowlark, Brown-Headed Cowbird, etc. Thanks. ~A H 1^(TCU) 15:07, 15 March 2008 (UTC)

[edit] Tortoise speeds

The common stereotype is that tortoises are slow animals. Form what I have observed from my german tortoise, this does not seem the case. For their size, ad the weight of their shell, the seem to have a relatively good speed. Does anyone have some outside input on this? —Preceding unsigned comment added by Gbgg89 (talk • contribs) 16:55, 9 March 2008 (UTC)

I would call tortoises slow, yes. Saying "for their size and weight of their shell they are fast" misses the point, in my opinion. That's like saying "may car is fast considering it's minuscule engine, poor gear ratios, and high mass". However, we can find other larger and armored animals which are much faster, like a rhino. I'd say the short legs are what slows tortoises down. Are tortoises fast enough to outrun any predators ? No, they must rely on their shell to protect them. Perhaps we should turn this around and conclude that they are slow because, due to their armor, they don't need to be fast to escape predators. StuRat (talk) 17:48, 9 March 2008 (UTC)

Ignoring WP:NOR, I would say the pet tortoise I have is not only slow because it cannot move quickly; it's also slow because it doesn't move much. It has an inactive life style and, except for eating, only very occasionally transports itself. --Bowlhover 04:52, 10 March 2008 (UTC)

[edit] How do astronauts swallow ?

Gravity seems to be an important factor in swallowing on Earth. I know I can't swallow when upside down and find it difficult when lying down. This is particularly true of difficult to swallow items like dry crackers. Related to this is the question of gastric reflux. This often happens to people while lying down, since they lose the gravity assist in keeping stomach acid in the stomach. Wouldn't this be even worse for astronauts, who always lack that assist while in orbit ? StuRat (talk) 18:08, 9 March 2008 (UTC)

Well, swallowing is largely due to peristalsis, which should be unaffected by orientation. In fact, in zero G, it ought to be easier to swallow than lying down or upside down in normal G, since you're not working against gravity, though harder than upright. -mattbuck (Talk) 18:25, 9 March 2008 (UTC)

That would explain how an astronaut's body would handle excretions too. Julia Rossi (talk) 21:35, 9 March 2008 (UTC)

You've brought this up before, and I'll say again that swallowing being completely independent of your orientation is one of the very first experiments I remember encountering in a children's science book. Gravity is not supposed to be a factor in anyone's swallowing. Skittle (talk) 19:15, 12 March 2008 (UTC)

[edit] Is it possible for someone of mixed race to be born transparent as a result? Why not?

Assuming the colors of his or her parents blend perfeclty, would it be possible to pick two such people that their son or daughter would (under the condition just specified) be born transparent as a result? Why or why not? I've tried to read our color article but it's a bit hard to take in all at once... —Preceding unsigned comment added by 79.122.37.156 (talk) 18:27, 9 March 2008 (UTC)

Not due to blood in the skin it would seem. Though this is based on a very rudimentary understanding of matters. Our article skin tone ny156uk (talk) 18:39, 9 March 2008 (UTC)

No. Skin cells are not transparent and in fact between people of different races they are almost identical with the main cause for difference in skin colour between these races being the saturation of melanin in ones skin, something dark skinned people have more of than white skinned people. Blood and other factors will always add colour to skin which is independent of race.PiTalk - Contribs 19:47, 9 March 2008 (UTC)

1. Colors of parents don't blend perfectly

2. Lighter skin is just an absence of melanin. There isn't a "transparent" option in skin, just a question of how much melanin. Total absence of melanin (see albinism) isn't transparent, it's just very very light.

3. You seem to be confusing additive color and subtractive color. Light is additive—it adds up to white; physical inks and dyes and melanin is substractive—it adds up to black. You can't mix white in a subtractive color system; white is the absence of color. --98.217.18.109 (talk) 19:46, 9 March 2008 (UTC)

When you look at a person's skin, the color you see is that person's phenotype. It's primarily determined genetically, but it's determined by a large number of genes (certainly more than six) which interact in complex ways. You can't determine exactly which genes (or alleles) a person has by looking at their skin. A child's skin color is determined by which alleles he inherits, and not by the skin color of his parents. It's not a matter of "blending" phenotypes, but of which alleles he inherits (at random) from his parents. There's no guarantee that the child's genes are those which have manifested in his parents. And there's no combination of genes that results in "transparency" in humans. - Nunh-huh 01:27, 10 March 2008 (UTC)

Of course some people claim to be transparent. With regard to skin, some animals are transparent, though I don't think we have an article about this.--Shantavira|^{feed me} 10:39, 10 March 2008 (UTC)

Tansparent animals are usually those that live in water. For things that live in air there is a big refractive index change from air to the flesh of the animal. Not only that but the skin on the surface is not completely smooth, and has air surrounding the dead cells. This results in light being scattered, and gives a white appearance. So if there is no colour in the skin, it will appear white. Light penetrating further in can be scattered by small organells etc, so that can give a bluish appearance. A human is so thick and full of light scattering, and coloured objects there is no way they will be transparent. Even the transparent animals are very small. Graeme Bartlett (talk) 22:36, 10 March 2008 (UTC)

[edit] Thermosynthesis & Radiosynthesis --

Definitions -

By these terms, I refer to processes similar to photosynthesis, but harnessing thermal or other radiative energy in the place of visible light.

Comment -

The natural origin of sucrose is living-plant photosynthesis, energized by visible light -- whereby (typically) sunlight, water and carbon dioxide (from the air) are reacted. I suspect that sucrose is an overall very efficient energy storage medium which is easily transported.

Question -

Does anyone know of any other radiant-energy process other than visible-light photosynthesis which can produce sucrose or some other simple, easy-to-handle hydrocarbon ? I suspect that such processes could possibly provide energy storage, transport and recovery mechanisms far superior to those based on hydrogen technology. 208.63.237.3 (talk) 18:45, 9 March 2008 (UTC) allenwoll

There are organisms that use chemosynthesis, but it is similar to photosynthesis as far as glucose creation is concerned. For storage, plants make polysaccharides, such as starch and pectin. Animals make glycogen and fat (a hydrocarbon). I'm not sure about your claim to a far superior mechanism, because burning oil is about as efficient as you can get using biological materials (as far as I know). The only problem is that this releases a lot of CO₂. Hydrogen fuel is an entirely different and efficient (albeit, slightly dangerous) way of storing energy. Generally speaking, if you're looking for high efficiency for storing and using energy, do not look at biological systems. They're good, but we already know of better. (EhJJ)^TALK 23:42, 9 March 2008 (UTC)

+++++++++++++++++++++++++++++++++++++++++++++

Regarding CO2 -- That is not an issue, since the manufacture of the sucrose used CO2 from the ait in the first place : no net change.

Regarding Storage & Transport -- A bag of sucrose looks pretty transportable and storable to me !! Starch is OK, too, but what would be the advantage ??

Regarding Biological SYSTEMS -- I wasn't considering LIVING systems, rather processes like what has become generally known as artificial photosynthesis.

Regarding Hydrogen -- The hydrogen storage/transport cycle is VERY inefficient at this time, as well as dangerous. So was that for acetylene at one time, but no more. But we are not there yet for hydrogen and may never get there, TBD.

"Know of better " -- What, then ??

+++++++++++++++++++++++++++++++++++++

. —Preceding unsigned comment added by 208.63.237.3 (talk) 00:03, 10 March 2008 (UTC)

Sucrose is not a hydrocarbon, but a carbohydrate (and the former would yield more energy per mass and per volume if burnt with oxygen, thus they are more efficient from a storage point of view; biological organisms also use fat, which are more efficient than carbohydrates but less efficient than hydrocarbons in this respect). As for other carbohydrate-producing processes, some fungi are suspected to use gamma radiation. Icek (talk) 03:51, 10 March 2008 (UTC)

++++++++++++++++++++++++++++++++++++++++

Thanks, Icek.

Let me rephrase -- I seek information on the potential existence of a process using thermal or other radiation to produce "optimum" chemical compounds from readily available, cheap and nominally non-toxic materials -- water, air (including carbon dioxide), etc -- "optimum" for energy storage and transport as well as for energy recovery. Such a process may or may not entail living organisms, but perhaps better not.

Whether the compound is a hydrocarbon, a carbohydrate or a fat -- or some other sort of compound altogether -- is, I think, irrelevant, except as to its potential performance toward the stated goal.

++++++++++++++++++++++++++++++++++++++++ . —Preceding unsigned comment added by 208.63.237.3 (talk) 05:09, 10 March 2008 (UTC)

Unfortunately, our article on thermosynthesis is just a single line. That said, there are some interesting hits if you Google search "thermosynthesis" [1], or take a look at PubMed. Unfortunately, I can't help you find industrial processes used for converting thermal energy directly in to chemical energy, as I only know of methods that involve an electrical energy intermediary step. Good luck! (EhJJ)^TALK 13:39, 10 March 2008 (UTC)

[edit] Query: Name of inedible string/fiber found in bananas?

I am a writer looking for the name of the inedible string/fiber that runs along the length of a banana (often left after the peel is removed).

I have been unable to find it anywhere.

Thanks in advance

Writerdog8 (talk) 20:34, 9 March 2008 (UTC)

I don't think any part of a banana is inedible? --BozMo talk 20:39, 9 March 2008 (UTC)

It seems to be part of the "pith" or inner rind inside the skin that takes a second stripping if you don't like it on the fruit. Julia Rossi (talk) 21:25, 9 March 2008 (UTC)

Its going to be equivalent to a leaf vein, or Vascular tissue, ie xylem and phloem. Graeme Bartlett (talk) 22:40, 10 March 2008 (UTC)

[edit] What plant are these people selling?

http://pics.livejournal.com/n0mad0/pic/0000gk7z --Sonjaaa (talk) 20:45, 9 March 2008 (UTC)

Russian "kale", perhaps? As here [2]. Julia Rossi (talk) 21:18, 9 March 2008 (UTC)

[edit] Lithium sunsets?

A co-workers claims to know why sunsets are pleasing to the eye. He claims that sunlight, when traveling through the large amounts of atmosphere (due to the sun's low angle relative to the horizon) somehow contains micro amounts of lithium that enter the eyes and makes the sunset watcher feel good. That sounds absolutely preposterous. Wouldn't landscapes then be encrusted with elemental lithium from the countless centuries of sunsets? Wouldn't particles of lithium be blocked by contact lenses, glasses, and sunglasses -- so only bare eyes could enjoy sunsets? --70.167.58.6 (talk) 22:26, 9 March 2008 (UTC)

You don't need to come with reasons why his idea is stupid. He needs to come up with ideas of why his idea isn't. Theresa Knott | The otter sank 22:28, 9 March 2008 (UTC)

Wiki doesn't have an article on everything, contrary to WP:WHAAOE: there's no article for chain yanking!

Atlant (talk) 16:40, 10 March 2008 (UTC)

More concerningly - we have no article on floor buffers (or at least that I could find)! --Kurt Shaped Box (talk) 00:17, 12 March 2008 (UTC)

How can sunlight contain lithium? Sunlight are photons and lithium are atoms. 122.107.151.153 (talk) 23:35, 9 March 2008 (UTC)

There is water on the exterior of the eyes, and when lithium comes into contact with it, it forms lithium hydroxide, hydrogen, and energy in the form of heat (an exothermic reaction). I don't know how lithium in the eyes would feel, and nor do I want to. Lithium hydroxide is highly caustic and the temperatures are hot enough to burn.

There won't be buildup of lithium on the ground, though, because any contact with water will cause it to immediately become lithium hydroxide and hydrogen. The hydrogen would escape to the very outer limits of the atmosphere, but does anyone know what will happen to the LiOH?

As for reasons why your friend's theory is ridiculous:

(1) Lithium cannot pass through the atmosphere without reacting with the oxygen and forming lithium oxide.

(2) How can the lithium pass through the atmosphere almost horizontally without falling due to gravity or stopping due to air resistance? What is propelling them?

(3) Why is it that the lithium only exists when the Sun is low on the horizon, and not when it's high in the sky? Ask your friend to explain this.

(4) Sunsets do not look any different through optical aid (your reason).

(5) Your friend was probably ascertaining your guillibility. --Bowlhover 01:04, 10 March 2008 (UTC)

According to him, the sunlight doesn't contain lithium, but carries/propels the lithium that's formed by some reaction between sunlight and low angle atmosphere. I guess these particles are being wisked into my eye carried on beams of sunlight. SO... just why are sunsets pleasant to look at? --70.167.58.6 (talk) 03:41, 10 March 2008 (UTC)

I'm guessing because they're beautiful. 206.252.74.48 (talk) 12:51, 10 March 2008 (UTC)

There has to be some kind of psycho-social theory regarding why so many distinct cultures all find a sunset aesthetically pleasing. It seems counter to the general notion of sun worship, as the sun is leaving for a while. This topic could probably result in several academic publications, if I were a student in the humanities - "Sociocomparative aspects of the aesthetic appeal of solar activity," "Anticipation of diurnal solar rearrival as a cultural indicator of Freudian delayed pleasure-principle," etc. Nimur (talk) 16:09, 11 March 2008 (UTC)

Cute titles but those read like science or social science papers. Real humanities papers are of the format "Something witty (bonus points if you make it a variation of "A Tale of Two Cities" or some other bad Dickensian pun): Something more specific, but not scientific sounding." --98.217.18.109 (talk) 23:57, 11 March 2008 (UTC)

Does your friend have any alternative medicine products based upon his theories in the pipeline, as a matter of interest? --Kurt Shaped Box (talk) 00:15, 12 March 2008 (UTC)

I wouldn't want to see him down his elemental lithium tablets with a glass of water. bibliomaniac 1 5 00:20, 12 March 2008 (UTC)

Oh, but I would. It's surprisingly how exothermic the reaction is and how caustic LiOH is, especially when both are sensed with the tongue. --Bowlhover 15:34, 12 March 2008 (UTC)

[edit] This week's meteor

Hi. I saw on the news that an astronomer reported that a meteor this week may have landed in Georgian Bay near Parry Sound, Ontario. Do we have either an article, a mention in an existing article, or a Wikinews article on this? Should this be mentioned somewhere perhaps in the meteorite article? Thanks. ~A H 1^(TCU) 23:36, 9 March 2008 (UTC)

Well, I suppose it might warrant a mention, but meteorite impacts aren't really that rare, it's just we don't tend to notice them. -mattbuck (Talk) 01:06, 10 March 2008 (UTC)

I don't think this meteor is notable enough to be mentioned in meteorite. There is nothing extremely unique about this specific rock; it hasn't even been recovered yet. Many much more significant meteorites exist, such as ALH84001, suspected of containing Martian life, and the Kaidun meteorite, which could have come from Mars' moon Phobos. --Bowlhover 05:28, 10 March 2008 (UTC)

[edit] Hawking radiation emission rate inversely proportional to black hole mass - why?

The rate of Hawking radiation emission increases as the mass of the black hole decreases([[3]], second paragraph), what I don't understand is that if the emission method ([[4]]) is related to zero-point energy particles appearing and one half of the pair being captured, why is it that when the surface area of the event horizon would be greater for a larger black hole the Hawking radiation doesn't increase? To my lay understanding the probability of the particle capture would increase. 86.5.95.29 (talk) 23:51, 9 March 2008 (UTC)

Well, regardless of black hole size the ambient temperature goes to infinity as you approach the event horizon. The usual Hawking temperature is the limit at large distances. So I guess you could say that a larger hole emits less radiation because more of it gets pulled back in, although I don't know if that's a correct picture. -- BenRG (talk) 00:35, 10 March 2008 (UTC)