Wikipedia:Reference desk/Archives/Science/2009 April 30

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April 30

Envying the Chimps

You mean to tell me what with all of the lifting, the protein shakes, and the basically looking more badass—I will never be stronger than a CHIMP? How does this work? These things are eating berries and ants they poked out of mounds with twigs—and they certainly aren't going to the gym. Are their muscles simply more efficient?

I'm sorry, this is going to be a lot of questions—clearly chimpanzees have been on my mind lately.

Is there any downside to this demonic strength?

Why haven't humans evolved this kind of strength? Even with all of the intelligence and what have you, a human could still be a real lady's man with that kind of virility. Did humans and chimps evolve from a shared beastly ancestor—and humans just lost it? Or did we just never evolve it in the first place?

And—are apes unique in this respect? Or are humans just the weaklings of the animal kingdom? I've never noticed, say, a dog, having a surprising amount of strength (not that they're weak, but it doesn't seem like they are deceptively strong).

Alfonse Stompanato (talk) 00:04, 30 April 2009 (UTC)

In part, it's a matter of geometry - the shape of their bones and placement of muscles are different from ours. We have grace and dexterity plus endurance that a Chimp simply cannot match. We're simply engineered for a different job. SteveBaker (talk) 00:53, 30 April 2009 (UTC)

Interesting theory described here: http://www.sciencedaily.com/releases/2009/03/090330200829.htm, chimps are stronger partially because they lack fine control over their muscles. Truthforitsownsake (talk) 01:46, 30 April 2009 (UTC)

Perhaps because calories used for muscle could be better used for a large brain. A brain allows better development of tools and cooperative hunting, which is a much greater force multiplier than more muscle strength. Particularly when the strength becomes a moot point at some level. Domesticating plants and animals takes it to a whole other level.

You also ask about virility in comparison. That's always going to be a relative measure. In the past few generations, strength has been relatively unimportant, beyond a certain minimum. The fact that humans are less strong than chimps, gorillas, orangutans, etc. (but we are stronger than many other primates) suggests that for much of our evolution, other factors were more important than pure strength. This actually opens two questions that I don't know the answer to: 1) what's the average daily caloric intake of a chimp, and 2) are physically stronger chimps often the alphas, or is that a weak measure. An orangutan consumes between 4000 and 8000 calories a day (minus about a thousand to two-thousand for a female).

Maybe the real answer to why more men aren't more ripped is that 1) it's hard, and 2) it isn't as good at attracting women as one might assume. Shadowjams (talk) 05:57, 30 April 2009 (UTC)

Your body isn't fundumenltally incapable of making you look like a body-builder when you're actually a couch-potato. It just doesn't bother unless it thinks you need the extra muscle. — DanielLC 14:55, 30 April 2009 (UTC)

If you look at this image search for "hairless chimp" it's interesting to note that they're pretty buff, but not crazy ripped like a human bodybuilder. --Sean 14:46, 30 April 2009 (UTC)

That's true of strong humans too. I've see a picture (which I can't seem to find) comparing bodybuilders with olympic weightlifters. The latter just looked fat. — DanielLC 14:55, 30 April 2009 (UTC)

Smoothing capacitor advice

Can I ask for some kindly advice on smoothing capacitors, please. The scenario is, the ancient gas heating system in my house causes four seconds or so of nasty RFI, affecting my BBC Radio 4 listening pleasure, each time the (presumably) thermostat decides to switch the system on or off. Changing the whole system is out of the question, sadly. Do you think I have any realistic options in terms of suppressing the RFI? Is this a scenario amenable to smoothing capacitors or some other sort of RFI suppression? If so, is it possible that such smoothing could be done at the AC source to the unit, or is it more likely that it would have to be done local to the thermostat? thanks. --Tagishsimon (talk) 01:30, 30 April 2009 (UTC)

Have you determined where exactly the RFI originates? Does the furnace have a standing pilot or does it ignite the gas with an electric arc from a transformer? That would be a potent source of RFI. Is it a relay or contactor, which should not be creating RFI all that long. Is the RFI reaching your receiver through the electric supply lines or through the air? If you can herer it outside on a battery AM radio, it is likely through the air. There are ways to reduce if not eliminate RFI. Is an AM or FM station? The BBC Radio 4 article says they broadcast FM, AM and other modes, not to mention Internet streaming audio and satellite, which should be less affected by RFI. Capacitors and inductors of various sorts can be used as a filter to block the RFI from emanating from the source, or can be used to filter it from reaching a receiver. For FM (or AM) an external antenna might increase the signal strength and lessen the impact of the noise, as could re-orineting the antenna on the receiver (unless it is coming to the circuit through the mains). The BBC has RFI information at [1] and [2]. Note that if the BBC finds you are causing interference to neighbors, you may be compelled to get the source of interference fixed. Edison (talk) 02:47, 30 April 2009 (UTC)

The heating system is using A/C power - so nothing as simple as a capacitor is going to work. There are circuits you can buy to reduce power spikes coming from equipment like that - you very often find them sold by computer stores. If your radio is picking up the interference that way - then plug the radio into one of these gadgets and the problem should go away. However, as Edison points out - if this is radio interference - then it's a tougher problem. Sometimes you can screen out the interference by wrapping the source in some kind of shielding (see: Electromagnetic shielding, Faraday cage and mu metal depending on the frequency range). I've successfully shielded the motor on my freezer from producing RFI spikes (long story!) by wrapping it in a few layers of fine-meshed chicken wire and earthing that to the houses' earth wiring...but it's one of those 'black art' things - sometimes you get lucky - sometimes you don't. But the first step is definitely to try a battery powered radio and thereby discover whether this is a power supply spike or a radio-signal spike. SteveBaker (talk) 13:23, 30 April 2009 (UTC)

Steve, I would really like to have a tour of your house someday. By the time that happens, you will probably have whipped up a gravity-field generator so you don't get dirty footprints in the hall! :) Franamax (talk) 20:03, 30 April 2009 (UTC)

So you've seen the dirty footprints on my ceiling then? :-) SteveBaker (talk) 00:01, 1 May 2009 (UTC)

Have a look at Problems Thermostats Can Cause to Television and Radio Reception on the Radiocommunications Agency's website. Appropriately, the URL begins "www.ofcom.org.uk/static". It says that thermostats are supposed to be fitted with suppression devices, but perhaps yours is too old to have one. You will find more useful stuff if you Google "boiler intereference suppressor". --Heron (talk) 17:40, 30 April 2009 (UTC)

Generally you need inductors not just capacitors. [3] points to some useful looking pages. 207.241.239.70 (talk) 15:16, 1 May 2009 (UTC)

Thanks for all of the above; I'll follow the links and your advice, and perhaps come back much later and tell you how I'm getting on. Much appreciated. --Tagishsimon (talk) 09:14, 5 May 2009 (UTC)

Bird fart

Is it true that birds can not fart or belch? If so, why is that? 69.69.75.22 (talk) 03:20, 30 April 2009 (UTC)

This depends on your definition of a fart and a burp. If you mean "expel gas from the anus", then a bird can (and does) fart. If you mean "make a loud fart noise from the anus", then a bird will not fart primarily because the bird's intestines are too short and the food passes through them too quick to get enough gas buildup to produce the expected fart noise. Basically, a bird expels a tiny bit of gas rather frequently instead of a lot of gas every now and then. As for burping, it depends on "allowing gas to escape from the stomach through the throat" or "making a burp noise". Birds do not have the biological structures to make a burp noise the same way that humans do. However, birds can (and do) vomit. When they vomit, excess gas is released. Because vomiting is something birds can do easily, they are able to release any excess gas with ease. Again, they are able to release a tiny bit of gas frequently instead of releasing a lot of built up gas every now and then. -- kainaw™ 03:33, 30 April 2009 (UTC)

So basically, they are dealing us 'silent' ones? I thought they were just being very, very polite!SteveBaker (talk) 13:12, 30 April 2009 (UTC)

I suspect this is related to one of the many urban legends regarding exploding birds. --98.217.14.211 (talk) 10:02, 30 April 2009 (UTC)

You really need some butt cheeks to get a good fart sound going. Birds just don't have them. --Sean 14:48, 30 April 2009 (UTC)

Volume of Ideal Gas at Absolute Zero

Hello. If the volume of an ideal gas at absolute zero is nothing, then shouldn't the matter occupy some space? I realize that absolute zero is an unattainable limit and that no known substance has a boiling point less than 0 K. However, I am looking forward to a theoretical answer. Thanks in advance. --Mayfare (talk) 05:23, 30 April 2009 (UTC)

Well, you've just given a totally convincing proof that no real gas can behave like an ideal gas all the way down to absolute zero. An ideal gas is simply an approximation of reality. Looie496 (talk) 05:42, 30 April 2009 (UTC)

And of course all gasses except (I think) helium are solids well before you get down to absolute zero...and of course the laws of thermodynamics don't allow us to actually reach absolute zero. Nature is very good at covering up zeroes and infinities in our equations! SteveBaker (talk) 13:11, 30 April 2009 (UTC)

It depends on the pressure, but I think all gasses are at least liquids before they get to the zero-point, the smallest possible temperature which is slightly above absolute zero. — DanielLC 14:44, 30 April 2009 (UTC)

As far as I know the zero point (ground state) is absolute zero by definition. It is a reachable state in principle in quantum mechanics because any (bound) system only has finitely many energy levels. It can take an insanely long time to reach the bottom (like 10¹⁰⁰⁰ years, to invent a number out of nowhere), but it's a finite time. It can also happen very quickly (like a lone hydrogen atom). I suppose the absolute-zero version of a gas would be a perfect Bose–Einstein condensate or fermionic condensate, not that I really know anything about this. -- BenRG (talk) 18:51, 1 May 2009 (UTC)

Everyone already jumped on this one, but to restate it: an "ideal gas" is a mathematical fiction. It is a heuristic idea based on the fact that "real gases" behave like "ideal gases" at most normal conditions. Only at very high pressures or very low temperatures do the difference start to show up. However, the assumptions one makes for an ideal gas are demonstratably false and even internally inconsistant. For example, the concept of an ideal gas assumes that individual molecules have zero volume. Even if a zero-volume particle was possible, how would it collide with other zero-volume particles? They would have no surfaces to bump, and yet Kinetic Molecular Theory demands that particles must collide and rebound off of each other. The concept of an ideal gas is useful because differences between the predicted behavior of an ideal gas, and the actual behavior of a real gas, are so small as to be practically unmeasurable under anything close to room conditions. See Van der Waals equation for the equation that applies to "real gases" as opposed to "ideal gases". --Jayron32.talk.contribs 03:56, 1 May 2009 (UTC)

The ideal gas model doesn't demand that gas particles bounce off of each other, in fact it assumes that they don't. It does demand that they bounce off the walls, though. I assume the original poster is thinking of PV = nRT. When T = 0 that reduces to PV = 0, but that doesn't mean V is zero, it means P is zero regardless of V. The reason for that is simple: the particles aren't moving, so they don't bounce off of anything, so there's no pressure. That's not correct in quantum mechanics, though, where a particle in a box still pushes on the walls even in its lowest energy state (because of the uncertainty principle). -- BenRG (talk) 18:51, 1 May 2009 (UTC)

ALIENS

Ok i can all ready see people looking at the title and thinking OMG not again but bare with me...I would like to ask if we are looking for ET with boddies like [[4]] How do they think they will detect alien life? i understand the idea of looking for radio signals ECT...is there any thought on say how a non-carbon based life form may comunicate? what type of gas in the atmosphere would they give off meaning type of vegatation on a non carbon based world say if it was made of siliconm a common thought that i have heard of; what type of gas would it give off if burned do we look for the tell tail signs of these during the search or do we just look for the humanoid version of an Alien? —Preceding unsigned comment added by Chromagnum (talk • contribs) 09:02, 30 April 2009 (UTC) Chromagnum (talk) 09:03, 30 April 2009 (UTC)

Have you read the SETI article that you link to? It explains what they are looking for, what assumptions they are making. At the distances they are looking they cannot detect things like atmospheric gas on individual planets or anything like that. --98.217.14.211 (talk) 09:53, 30 April 2009 (UTC)

Actually, looking at the spectrum given off by a planet to see if there is oxygen in the atmosphere is something exoplanet hunters are either doing or planning to do in the near future (I'm not sure which). --Tango (talk) 10:01, 30 April 2009 (UTC)

Can they resolve extrasolar planets to that resolution? At the moment I have not seen any indication that they can, even with gas giants. --98.217.14.211 (talk) 10:08, 30 April 2009 (UTC)

You don't need any particularly high resolution to analyse a spectrum. The difficulty is getting the spectrum of the planet separate from the spectrum of the star, which is what they are currently working on. --Tango (talk) 10:22, 30 April 2009 (UTC)

There are just a few extrasolar planets that are sufficiently large, bright and far away from their parent star that we can image their light separately from the star and get their spectra directly...but those are few and far between - and they are such odd-ball planets that we're not likely to find life on them anyway. (No possibility of liquid water, etc). Fortunately, analysing the spectrum of a star is very easy - a routine matter for astronomers. So what they have to do is to watch how the star wobbles as the planet moves around it to figure out how fast the planet is moving and where it is in it's orbit - this is difficult - but we're getting the hang of it and we know the orbital periods of all 350 or so planets that we've found. Once you know that - you can (in principle) detect the subtle changes in the light reflected from the planet. When the planet is behind it's parent star, it's light is missing from the stars' spectrum. When the planet is in front of the star - its light is added to that of the star. By subtracting the spectrum when the planet is hidden from when it's in view you can theoretically eliminate the contribution of light from the star itself - so what you have left is just the spectrum of the planet. Then they can look for peaks or troughs in that spectrum to estimate the gasses present in the atmosphere. This is an exceedingly difficult thing to do - the amount of light from the planet is utterly dwarfed by that of the star - and not all extrasolar planets are 'eclipsed' by the star from our perspective (we could be looking the solar system from 'above' for example). So we can't do this for all extrasolar planets - and for those that are eclipsed, the measurements have to be taken over a long period of time and they have to be amazingly accurate - this may mean measuring the spectrum from the star for years in order to accumulate enough light to do this subtle calculation. For earthbound telescopes, where the light is first filtered by our own atmosphere, it would be easy to mistake changes in our atmosphere's absorption over time for changes from the star and its planets - and we'd end up merely measuring biologically active gasses in our own atmosphere changing from summer to winter or depending on the wind direction or whatever! Hence, we need big, expensive space telescopes to do this work. SteveBaker (talk) 12:12, 30 April 2009 (UTC)

I don't think the wobble method is much use for this. To get a noticeable wobble you need a large planet close in. For life you need a small planet far out. The transit method, detecting the drop in light from the star as the planet transits across is, is far more likely to find Earth-like planets (which is where we would expect to find human-like life, which is the only type of intelligent life we have any evidence to suggest exists). Subtracting the star's spectrum from itself at different points in the planet's orbit is certainly one way of getting the planet's spectrum. I believe another way is to use the Doppler effect - the planet is moving in relation to the star so its absorption lines will be shifted compared to those of the star. Since the radial (from the perspective of Earth) motion varies during the orbit, those lines will move around. If you see an oxygen line moving around in a star's spectrum, that's evidence for a planet with an oxygen atmosphere (especially if you already know there is a planet with that orbital period, which you presumably would otherwise you wouldn't be looking that closely at the star's spectrum). --Tango (talk) 14:20, 30 April 2009 (UTC)

So many questions! Let's take them one-by-one:

• Ok i can all ready see people looking at the title and thinking OMG not again - Actually, we RD folks secretly love these kinds of question. So much better than "How makes babby?".
• How do they think they will detect alien life? - Really there are three approaches:
  1. Hoping that the aliens are capable of detecting us from our feeble communications or the signature of advanced civilisation in our atmosphere (oxygen plus steeply rising CO2 levels for example) and sending us unmistakable narrow-beam communications (either laser or radio). Since our civilisation is fairly young - the aliens would have to be pretty close. We've only had the kind of advanced technological society that they might be able to detect for perhaps 200 years. So they'd have to live within 100 lightyears of us for our existence to have been noticed and for the message from the aliens to have reached us. There really aren't that many stars as close as 100 lightyears away. If only 10% of those have planets (which seems likely from extrasolar planet hunting) and only 10% of those are able to support life - it's pretty unlikely that we're going to be hearing from one of these civilisations for a few hundred years yet. However, in another 200 years - aliens as far as 200 light years away will have hopefully noticed us - and that would be 8 times as many potentially habitable worlds...so the longer we wait - the more likely someone will try to talk to us. But who knows? Perhaps there is this vast galactic civilisation - which (like on StarTrek) have rules that forbid them to talk to us until we try to talk to them? We aren't making much of an effort to do that right now.
  2. Imagining that the aliens have hugely powerful radio transmitters (much, MUCH more powerful than our own) and are broadcasting in all directions at once. Remember - if you took the most powerful radio transmitter humans have ever built - and put it on a planet orbitting the nearest star (just 4 lightyears away) - we'd be completely unable to detect it with the most sensitive radio telescopes we have. Since the strength of radio signals reduces as the square of the distance - at distances like 400 light years - we'd need the aliens to be broadcasting at more than 10,000 times the power of the best transmitter we can build! That's asking a lot. Recall how hard it is to measure the spectrum of light reflected from an extrasolar planet? Detecting their communications comes down to the same thing - we have to detect changes in the spectrum of all the electromagnetic radiation coming from their planet - against the background of this honking great star which is putting out billions of times as much. So for us to notice that - the amount of light their system is putting out has to be around the same as their entire planet reflects naturally. Put another way - if their 'transmitter' is able to produce that much energy - it would need a solar power station that covered their entire planet to make it work! This is a very hard thing to expect the aliens to do! Of course if they took the trouble to beam that energy directly at us - they'd need a lot less - but now were back to scenario (1) above - where they have to know where we are before they can talk to us.
  3. Hoping to detect their chemical 'signatures' in the atmosphere of extrasolar planets (see my preceeding answer).

Sadly, two out of the three of those possibilities assume that these are aliens that are much more scientifically advanced than us - and who are interested in talking to us. The third option is actually much more promising because it detects life rather than intelligence - and would allow us to send narrow-beam messages to them.

• ...is there any thought on say how a non-carbon based life form may comunicate? - Well, for starters, it's really not clear that sufficiently complex molecules can exist based around non-carbon chemistry. The nature of carbon is such that it makes much more complicated molecules than any other element. So it seems highly likely that all 'natural' life will have carbon chemistry. However, we could imagine a carbon-based culture such as ours inventing sophisticated robotics and artificial intelligence - then dying out leaving the computers in charge. That would result in a non-carbon civilisation. But there is no reason to assume that life based around other kinds of chemistry would be communicating any differently than we imagine. There are really only just so many things you can do. All communication over those distances needs to be with light or radio waves - and those waves have to be sufficiently different from 'natural' source that the recipient could find them. So what SETI are looking for is not a very specific kind of signal - but ANY signal that doesn't have the characteristics of a natural source.
• what type of gas in the atmosphere would they give off meaning type of vegatation on a non carbon based world say if it was made of silicon - As I said - I don't think non-carbon-based life is possible. However, a 'second generation' civilisation (life as in: computers/robots/AI) might exist in deep space - not on a planet at all - or it might exist somewhere like on our moon - where there is no atmosphere at all. So such a civilisation would be impossible to detect unless it WANTED to be detected. In that case, who knows what advanced technology it might use to change the atmosphere of a nearby 'junk planet' to say "LOOK! HERE WE ARE!" - but if they are doing it right - we'll know it when we see it.
• what type of gas would it give off if burned do we look for the tell tail signs of these during the search or do we just look for the humanoid version of an Alien? - For "Life as we know it", we can look for oxygen. Oxygen is a chemically reactive gas. Without plants around to make more of the stuff - it would pretty soon get used up by (for example) rusting iron or burning carbon to CO2. If we find oxygen out there - that's a pretty strong sign. There are other signature gasses to look for - methane for one - but we've found that in the Martian atmosphere - and so far, no little green men have appeared to issue traffic violations to our mar rovers. The problem is that one has to be skeptical - and there are always complicated explanations other than life for phenomena we see in planetary atmospheres.

What's difficult here is that there are three kinds of possibilities: "Life as we know it" - carbon-based, needing liquid water and oxygen - and with something like DNA so it can reproduce and evolve. "Life as we don't know it" - things like robotic civilisations or beings floating in the cloud layers of gas giants or based on weird chemistry. But there is also the possibility of "Life as we don't know it AND CAN'T IMAGINE IT" - since we can't (by definition) imagine it - we can't say anything meaningful about it - we just have to hope that we'll know it when we see it.

(And please - I love this kind of question!)

SteveBaker (talk) 12:47, 30 April 2009 (UTC)

Thanks Steve great answersChromagnum (talk) 05:32, 1 May 2009 (UTC)

Chemistry A-Level problem

Here is the question. Can anyone help me out with the answer and also give an explanation.

When dangerous chemicals are transported by road, vehicles must carry signs that indicate what measures should be taken in the even of a spillage of the chemical carried.

Which material must be used if there were a spillage of metallic sodium?

A. ethanol B. jets of water C. sand D. water spray —Preceding unsigned comment added by 123.49.43.236 (talk) 11:05, 30 April 2009 (UTC)

Please do your own homework.

Welcome to Wikipedia. Your question appears to be a homework question. I apologize if this is a misinterpretation, but it is our aim here not to do people's homework for them, but to merely aid them in doing it themselves. Letting someone else do your homework does not help you learn nearly as much as doing it yourself. Please attempt to solve the problem or answer the question yourself first. If you need help with a specific part of your homework, feel free to tell us where you are stuck and ask for help. If you need help grasping the concept of a problem, by all means let us know.

We're not allowed to give you the answers to homework questions - but we can give you ideas about where to look. In this case, it's pretty obvious: You can definitely find the answer in our article on sodium. SteveBaker (talk) 11:54, 30 April 2009 (UTC)

See also the article on metal fire (The question could be homework, but it could equally well be from a published past exam that doesn't come with an answer key.) --98.114.146.65 (talk) 12:27, 30 April 2009 (UTC)

I would say the same arguments for homework apply to self study of this sort. Note even if it's not a past exam it could be self study from an example question book or whatever Nil Einne (talk) 12:31, 30 April 2009 (UTC)

I would look up transportation of hazodous materials or HAZMAT start at this link [5] and expand your search Chromagnum (talk) 05:38, 1 May 2009 (UTC)

convergent evolution

How do we tell if a feature of a living creature is a violation of nested hierarchy predicted by common decent or from convergent evolution? —Preceding unsigned comment added by 121.241.167.100 (talk) 11:55, 30 April 2009 (UTC)

Imagine a creature with traits (and ideally, gene sequences) very similar to a wide variety of taxa. Provided you could rule out lateral gene transfer, a creature with some genes that are similar to those which evolved separately in different orders of mammals, for instance, would undermine an otherwise very well developed taxonomic tree rooted in evolution. The trick would be to show that each gene evolved subsequent to the divergence of the order. Suppose you found an animal with gene sequences from dogs, bats, and whales. If you could show that the common ancestor of each of these did not have the traits you found, but subsequent species from the various orders, you'd have shown our understanding of the evolution of mammals is very doubtful. This would be shown very well if you could examine neutral sequences (those not under selection) to rule out homoplasy as well.

There are many lines of evidence that point to evolution of which the tree is only one, but undermining such a tree would be enough to give anyone pause, perhaps enough to make people question evolution. Find such an animal and people will have to do some rethinking, to be sure. (You may be asking for a Popperian falsification, but those don't really exist anywhere in science, by the Duhem-Quine thesis; but through removal of supporting evidence, as described above, you can make something seem very unlikely.) --TeaDrinker (talk) 13:19, 30 April 2009 (UTC)

The ultimate way to tell is by looking at the genome. If a common feature results from common descent, the genes responsible for producing it are likely to be very similar. If it results from convergent evolution, they are likely to be quite different. There are other less certain approaches, but that's the ideal way to do it (short of tracing out the fully ancestry). Looie496 (talk) 15:39, 30 April 2009 (UTC)

Without genetics, it's really hard to tell in some cases. Consider eyes - for example. Eyes appear to have evolved quite independently in half a dozen different branches of the evolutionary tree. This is convergent evolution - vision is useful - and there are only just so many ways of capturing light and handing it off to the brain - but even so, the resulting eyes are fundamentally different from each other. However, you find differences even when divergent evolution is happening. The eyes of cats have slit-like pupils and dogs have circular pupils. Did cats and dogs evolve their eyes separately from each other? No...we can find fossil mammals that are the clear ancestors of both dogs and cats that clearly have eyeballs - so this must be divergent. But the common ancestors of (say) mammals and octupii or mammals and insects - were blind - so that must be convergent. You have to consider the whole organism and other features than the one you are looking specifically at. At the genetic level - one assumes that the genes for producing vision in octupii would be very different from those in cats and dogs - and we'd assume that the vision-related genes of cats and dogs would be almost identical. The odds of independent/convergent evolution of identical genes is a matter of statistics - it's very unlikely that convergence would produce identical genes since so many tiny variations on that gene work just as well. So if the same basic feature of two lifeforms have a totally different genetic basis - then we should assume convergence - if the genetic makeup is mostly identical - but with a few tiny differences - then divergence is more likely. SteveBaker (talk) 15:44, 30 April 2009 (UTC)

To give the context of my question, I asked it after I saw this [6] article. A post here [7] described it as "Chromosomal sex determination in the platypus discovered to be a combination of mammal and bird systems. The resemblance to birds is now more than just superficial."

First, I am not sure if that's what the article is saying, are they saying that platypus chromosomal sex determination is similar to birds or different from both mammals and birds?

Second, does either scenario pose a problem for nested hierarchy?

Lastly, you said "...This would be shown very well if you could examine neutral sequences (those not under selection) to rule out homoplasy as well"

I am not sure I understood that, could you clarify with an example? Say the platypus' chromosomal sex determination is similar to birds, how would one go about showing they evolved the trait independently? How would neutral sequences show this? —Preceding unsigned comment added by 121.241.167.100 (talk) 16:08, 30 April 2009 (UTC)

It is almost certainly convergent evolution. The only proof of that would be to show that the most recent common ancestor lacked the feature, which isn't possible. The reason it seems almost certain is that the evolutionary distance between bird and platypus is huge -- their lineages diverged around 350 million years ago. Basically, all four-legged land animals except amphibians date back to that same divergence point (the split between synapsids and diapsids) -- so if birds and platypus have a common feature, but other land animals lack it, it is very likely to arise from convergent evolution. Looie496 (talk) 16:23, 30 April 2009 (UTC)

With reference to the blog that you linked to, perhaps you could clarify the question you have in mind. What "feature" or "trait" are you referring to? Sex determination? You might find some explanation of your questions here (http://www.ncbi.nlm.nih.gov/pubmed/18983263). In any event, the paper that is referenced in the blog (and the discussion of its implications) are getting a bit dated (2006!!!). They've recently published the Platypus genome sequence (http://www.ncbi.nlm.nih.gov/pubmed/18464734), which in comparison to other species is beginning to shed some light on this fascinating critter!

In regard to your most recent questions, 1) Platypus sex-determination is more similar to birds (which use the ZZ-male/ZW-female system) than primates/rodents/marsupials (which use the XX-female/XY-male system). Not the same as birds, mind you -- the platypus has a really funky chain of small chromosomes that were called X1, X2, X3, X4, X5, and Y1, Y2, Y3, Y4, Y5. The unfortunate use of the same letters to designate the chromosomes doesn't mean that there's any DNA homology between the Platypus X and Y and the X and Y of placental mammals. 2) I don't really see a problem for "nested hierarchy" here. I'm certainly not an expert in the field, but the genome evidence seems to support that the lineage leading to the modern-day platypus diverged somewhere after the reptile/avian branch and before the marsupial/eutherian branch. --- Medical geneticist (talk) 18:13, 30 April 2009 (UTC)

What are the products of the reaction of sodium with Sand

Hi, can anyone tell me what sodium produces on reaction with sand? I am so confused and I am skeptical whether they react at all.... —Preceding unsigned comment added by 123.49.43.236 (talk) 12:08, 30 April 2009 (UTC)

Okay so they may not react. What happens if you put water or ethanol on sodium? Will they react? How? Nil Einne (talk) 12:19, 30 April 2009 (UTC)

Sodium and water is a common high school lab experiment. There's a lot of youtube videos of it... I'll go find one. Vimescarrot (talk) 14:23, 30 April 2009 (UTC)

Here's one. 2Na + 2H₂O -> 2NaOH + H₂? I dunno, someone will tell you if that's right or not. GCSE Chemistry was a few years ago. Vimescarrot (talk) 14:27, 30 April 2009 (UTC)

P.S. In case it wasn't obvious, this wasn't a genuine question, rather I was posing the question to the OP to help get them thinking how they can answer the question Nil Einne (talk) 18:26, 30 April 2009 (UTC)

As I explained in my answer to your previous question - you can definititely find the answer to your original question in our article on Sodium. The article speaks very specifically about how water reacts with sodium (short answer: KABOOOOMMMM!!!!) and in the section called "Precautions" it tells you precisely the answer to your original question - if you understand a little chemistry already - then there is a strong clue in the very first introductory paragraph. If you are going to learn - you have to study by reading articles and finding the information from them. If we spoon-feed it to you, then you learn NOTHING and will not be as successful in life as you otherwise would. We're doing you a favor by not answering this one! SteveBaker (talk) 15:30, 30 April 2009 (UTC)

Sand usually consists of silicon dioxide (there might be other types, but these are rarer). If there is also air, sodium at first will burn, producing sodium oxide. If there is no air, but there is elevated temperatures, there might form sodium silicate and sodium silicide). Similar process (using magnesium instead of sodium), seems have been used to produce silicon or silane (by reacting silicide with acid). Also, sodium oxide will react with silicon dioxide (not sure about temperature requirements) producing sodium silicate. -Yyy (talk) 16:56, 1 May 2009 (UTC)

Photon

I want to know about the nature of Photon. —Preceding unsigned comment added by 117.98.13.180 (talk) 13:43, 30 April 2009 (UTC)

Try photon. —Akrabbim^talk 13:57, 30 April 2009 (UTC)

(EC) I want to know how come some people can't use the search box to the left which also has its special page here; or use Google, Live Search, Yahoo or whatever to find out article on photon probably taking less time then it takes to write out "I want to know about the nature of Photon". Guess neither of us will ever know... (edit: or perhaps I was wrong about your case) Nil Einne (talk) 13:58, 30 April 2009 (UTC)

Hey, that's a little unfair. I've been reading about photons all my adult life and I still don't understand their nature. --Sean 14:54, 30 April 2009 (UTC)

If you've been reading about photons all your life, you should be able to ask a more focused question by now. Looie496 (talk) 15:41, 30 April 2009 (UTC)

I didn't ask any question at all, which I agree lacks focus. --Sean 16:25, 30 April 2009 (UTC)

I mean, WTF?!?

But that's the point though isn't it? The question is unfocused and suggests either 1) The person has read all there is to know but is so hopelessly they don't know what to ask OR 2) The person hasn't read much, probably not even our article hence they asked so an unfocused question and our article is a good starting point, a starting point they could have more easily found themselves say if they knew how to search (hence I taught them how even if in not quite the most civil way). or perhaps 3) The person just has poor English or otherwise doesn't know that if they ask a generic question, they get a generic answer. I know which one I'm betting on... Nil Einne (talk) 18:21, 30 April 2009 (UTC)

It's so hard to catch up with one of them to ask! SteveBaker (talk) 15:23, 30 April 2009 (UTC)

Sadly, yes - RTFA. Check out our article: photon - if there is anything you don't understand, follow links until you find something that explains what you don't understand. If you have a more specific question, we'll try to answer it. SteveBaker (talk) 15:23, 30 April 2009 (UTC)

Karrick Process

I have read the articles for Karrick Process and also for pyrolisis. From what I can tell, the two are the same thing. Could someone perhaps explain to me how they are different? 65.121.141.34 (talk) 16:19, 30 April 2009 (UTC)

Sure. Pyrolysis is the general term for any decomposition via heating. The Karrick process is a specific pyrolysis reaction applied to coal. The concept of pyrolysis is a huge idea, and covers lots of chemical processes. The Karrick process is a specific application of a specific pyrolysis reaction. The difference is that one is a general class of chemical reactions and the other is a specific reaction. --Jayron32.talk.contribs 03:47, 1 May 2009 (UTC)

Central metal ions and EDTA

So I was wondering today about central metal ions and multidentate ligands, and EDTA comes to mind as a ligand which forms six bonds to its central metal ion. We studied in class about how it can displace unidentate ligands, but then I wondered, how could you displace a ligand which forms, say, six bonds to the central ion? Are there ways to strip EDTA off, say, an aluminum (III) ion? I'm studying at under university level, so forgive me if my idea isn't all that smart. It's bound to happen. Regards, --—Cyclonenim | Chat  19:30, 30 April 2009 (UTC)

My guess is that one could mess with the pH to protonate the EDTA^4- and return it to its acid form, and thus change its ability to form ligand bonds to the metal ions. Our article on EDTA notes that the ligand is the EDTA^4- form, and that the tetraprotonated form, H₄EDTA is not an effective ligand. So, it would seem to me if you added acid, you could remove the EDTA from its bonded metal ions, returning the metal to a free-ion form. Just speculation on my part however. --Jayron32.talk.contribs

Swine Flu

Is the swine flu that people get killing pigs too, or is it mutated into a mostly human disease? 65.121.141.34 (talk) 19:41, 30 April 2009 (UTC)

Swine flu (the 2009 A/H1N1 virus) is new on the scene and information is sketchy right now. Viruses in general evolve to not kill their hosts, since they can't spread if their host is dead. The virus presumably is a mix of avian, porcine and human virus DNA (at least I think it's a DNA virus) and presumably can still be resident in pigs. Like any virus, some percentage of the infected population will die. Pigs don't get on planes though, so the spread through the pig population will be more limited. I've not seen anything to indicate massive pig die-offs, so yes, we're talking about a virus spread through human-human contact at the moment. Don't know if that helps! Franamax (talk) 20:39, 30 April 2009 (UTC)

The flu virus is a RNA virus. As far as we know pigs might even be completely immune to that virus. We don't know. Dauto (talk) 22:53, 30 April 2009 (UTC)

This page: [8] from the Centers for Disease Control and Prevention is a great resource about the flu. Also see here: [9] for updates. As with any event of this kind, there is a good deal of misinformation and personal opinion that may promote confusion. The CDC is a reliable source. Cheers, 10draftsdeep (talk) 21:03, 30 April 2009 (UTC)

The strain of "swine flu" that we humans are all worried about probably won't itself infect that many pigs, but don't be mistaken -- plenty of pigs are going to be affected by it. It is being reported that Egypt is slaughtering 300,000 pigs in a misguided attempt to prevent the outbreak. SO, you could say that more pigs have been killed by this outbreak than humans so far. --- Medical geneticist (talk) 21:30, 30 April 2009 (UTC)

The exact flu now appearing in humans has not been detected yet in swine; however; a very similar virus has been present in North America swine since 1998.[10] Rmhermen (talk) 23:11, 30 April 2009 (UTC)

And now it turns out that pigs can get it too.[11] Franamax (talk) 11:05, 3 May 2009 (UTC)

Type of coffee

What is the name of the coffee that is fed to some kind of animal (possibly cats?) in bean form and then brewed from the feces? --Retracted (talk) 21:37, 30 April 2009 (UTC)

Kopi Luwak. (Found by Googling for "fecal coffee".) It's actually fed to the civets in berry form, and the beans pass through undigested. Looie496 (talk) 21:53, 30 April 2009 (UTC)

Thanks alot. I've been trying to figure that out for a long time.--Retracted (talk) 22:07, 30 April 2009 (UTC)

I've heard it called civet coffee. 207.241.239.70 (talk) 15:19, 1 May 2009 (UTC)

why do Ferrel cells exist?

This really isn't clear to me from the article on atmospheric circulation. Why do Hadley cells stop around 30 degrees N (and S?) John Riemann Soong (talk) 22:02, 30 April 2009 (UTC)

What goes up must come down. Where else would you have it stop? The cell ends as soon as the air becomes cold enough (by radiation) that the atmosphere would become unstable if the cell didn't end there. There's nothing magical about 30 degrees or three cells. Jupiter as you can see, seem to have about half a dozen cells per hemisphere. Dauto (talk) 23:34, 30 April 2009 (UTC)

They way I learned it was this: Imagine an idealized earth, or any planet, that is spinning slowly enough that the coriolis effect is negligible, but enough that the equator is equally heated. Since the air at the equator is hot, and since hot air rises, it will rise. Air from more polar latitudes will circulate in, while air at the poles is cold and sinks and so has a higher pressure. So a surface flow of air from the poles to the equator is formed. In the upper atmosphere however the hot air that rose above the equator flows towards the poles where it sinks, thus forming two giant cells, one on each hemisphere. Adding the coriolis effect changes things however: breaking it up into multiple cells. Cells behave in some sense like gears, adjacent cells must rotate in opposite directions, so only certain numbers of cells are possible: 2 (as above), 6 (like earth), 10, 14 (like Jupiter I believe) etc... The number of cells that it breaks up into depends on the strength of the coriolis effect which depends on how fast the planet is rotating about its axis. Here are some articles which also explain this (about 3/4 down) : [12] : (the section "3-Cell Theory") [13]. Jkasd 06:29, 1 May 2009 (UTC)

Ooh, thanks! It makes so much sense now! Well, enough sense. I mean, I'm not seeing the equations go into this and physically I'd like a (non-obtuse) way to see how exactly the Coriolis force causes it to break up at such magic intervals.

I mean, 2,6,10,14 -- don't those remind you of the number of electrons that can fit into a subshell? Probably pure coincidence. I mean, I suppose the coincidence comes from the "discrete" part -- you can't have 3 and a half circulating cells and maybe there's some deeper mathematical significance somewhere (or not). John Riemann Soong (talk) 07:14, 1 May 2009 (UTC)

The sequence 2,6,10,14 is simply twice the odd numbers, so I suspect it will turn up in thousands of theories about all sorts of different things. To see why a number like 4 won't work here, try to put 4 cells on a planet, given that air will rise at the equator and sink at the poles. Jkasd 07:46, 1 May 2009 (UTC)

I guess my (actual) question is -- how does the Coriolis force cause a single cell to break up? Presumably, having a Coriolis force means you start to get longitudinal airstream velocity, but why does this cause convergence at the surface around the 30 N latitude, forming the Azores high and such? (Longitudinal airstreams ==> Divergence aloft?)

I don't really know much more than I've already explained, this all just all from my memory of a meteorology class I took once. The second article I linked to explains how the coriolis effect breaks up the cell. I think that the reason the cells break at 30 and 60 degrees is simply because that gives each cell equal spans of latitude, but I'm not sure. Jkasd 07:46, 1 May 2009 (UTC)

I also note that while the Hadley cells definitely exist, my textbook tells me the Ferrel cells and the polar cells were more like idealisations. However, Wikipedia tells me the Polar cells and Hadley cells are more "real" while the Ferrel cells are just idealisations. Which is it? (Idealisation disrupted ==> because of presence of continents when the models assume 100% ocean?) John Riemann Soong (talk) 07:19, 1 May 2009 (UTC)

This whole explanation is just an idealization, but so is pretty much every explanation for anything, I'm sure the continents will alter it, and besides atmospheric circulation is largely chaotic. I tired to find some mathematical formula for this somewhere but the best I could find were the two articles I linked too. (Admittedly I didn't try very hard) I have no idea which cell is the most like the idealization, but I would suspect the Hadley cell and the Polar cell since the Ferrell cell is mostly the result of forming a "gear" in between the other two cells.

Hopefully this helps Jkasd 07:46, 1 May 2009 (UTC)

Elements that have no application?

Are there any elements that we don't have an application for? It seems pretty much every element ever discovered can be used in some way I suppose. Just was curious. 69.69.75.22 (talk) 22:54, 30 April 2009 (UTC)

A bunch of them are too rare or too unstable to do much except be studied themselves. Which leads to "studying elements to learn about how to make them, what their structure is, how stable they are" as the major application. DMacks (talk) 23:47, 30 April 2009 (UTC)

There's an old Time/Life poster (maybe taken from their Matter book?, definitely a few decades old now!) in my department with a picture of every element that had been isolated. Or in one or two cases, just lab notebook data for the "only made a few atoms for a few microseconds" ones. There's also a quick sentence or two about uses, or at least potentially interesting properties. There's often an "Applications" section in the article about an element. I know some chemists keep a periodic table on which they check off each element they have personally used, separated by "at all in life" vs "as part of a science experiment" (yeah, we're usually the life of a party:). My latter one is over half-checked. DMacks (talk) 00:15, 1 May 2009 (UTC)

(e/c) Thanks for the question, it's always fascinated me! I'm not aware of any element that human ingenuity hasn't found a use for somewhere. Hopefully others can point out what I'm missing. Beryllium is quite toxic, but even it has some uses, as in emeralds. I'd love to see an answer, it's one of the the subjects that ever drew me to Wikipedia. :) Franamax (talk) 00:01, 1 May 2009 (UTC)

Beryllium is has a number of nuclear properties that make it very important for a lot of applications. It is a great neutron source (hit it with alpha particles and it gives you neutrons), and is a great neutron reflector, and as such is used in nuclear weapons for these two purposes. --98.217.14.211 (talk) 01:29, 1 May 2009 (UTC)

Looking through the periodic table, the lightest one I found with no described applications other than research is Protactinium. Looie496 (talk) 16:34, 1 May 2009 (UTC)

For many of the artificially created, high atomic number, very short-lived elements, their only function to date has been to provide intellectual stimulation for nuclear scientists and scholars, and income for textbook publishers, journal publishers, and physics teachers. Of course the same could have been said for several newly discovered elements in the early 1800's which are in everyday use today. "No application" today may turn to "must have it" tomorrow. Edison (talk) 18:42, 1 May 2009 (UTC)

Wikipedia has articles on each element, and all ofthe 111 articles are linked to from the Periodic table article. Each "element" article has a "use" section of some sort when the element has a use. You will need to decide whether or not to count the "use" of an element as part of a compound: some elements are almost never found in nature in elemental form. As stated above, many elements have no long-lived isotopes. Of the 111 elements, only 92 were known before about 1930. The periodic table in a high-school chemistry text from 1930 has 92 elements. -Arch dude (talk) 23:57, 1 May 2009 (UTC)

Are household bleach or disinfectant effective at killing viruses on hard surfaces?

Their articles mostly mention their anti-bacterial properties - not the same thing. I'm wondering if its worth paying far more for some fancy brand-name spray, instead of using just bleach or disinfectant diluted half and half with water. Would bleach or disinfectant be equally effective? 78.149.130.97 (talk) 22:56, 30 April 2009 (UTC)

Bleach and similar oxidizing agents are generally effective at destroying most viruses. Other types of disinfectants will vary in effectiveness depending on their method of action. Some common antimicrobial approaches, such as alcohol, tend to be relatively ineffective against viruses. It is also worth noting that soapy water followed by a thorough wipe with a dry cloth will generally remove, but not necessarily destroy, most viruses deposited on most hard surfaces via casual contact. Dragons flight (talk) 23:19, 30 April 2009 (UTC)

If we are talking about influenza in particular (and isn't everyone these days?) then I would note that according to the CDC it can be inactivated by alcohol. See here for a discussion of influenza cleaning methods. Dragons flight (talk) 23:29, 30 April 2009 (UTC)

The advice from that American government site is to "use a chlorine bleach solution made by adding 1 tablespoon of bleach to a quart (4 cups) of water" (with an American quart being 32 fluid ounces). This seems a very weak solution. Is American household bleach more concentrated than British household bleach? The label on my bottle of British household bleach says it contains "less than 5% chlorine based bleaching agent" and the rest must be water. 89.241.144.80 (talk)

I believe that standard "bleach" in the US is only 3% actual bleach. However, it's a very powerful chemical, even at that level of dilution, as anyone who has ever gotten any on their hands or clothes knows. So, diluting it further may be wise, especially since bleach fumes can be toxic in an enclosed area.

Two things I've noticed are how important time and air is with bleach. If I spray it on the toilet bowl, the vertical surfaces don't get cleaned, because the bleach runs right off. Also, under the waterline, where the bleach remains, but without much air, it doesn't work all that well. Right at the waterline it does a good job. So, making the bleach into a paste or foam seems quite important to get it to adhere to a surface long enough to do it's job, especially for vertical surfaces. StuRat (talk) 14:11, 1 May 2009 (UTC)