Wikipedia:Reference desk/Archives/Science/2011 August 29

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August 29

An atom of hydrogen

When an atom of hydrogen moves does the space between the nucleus and the electron shell move with the atom or is this space replaced by new space along the atom's path of motion? --DeeperQA (talk) 00:05, 29 August 2011 (UTC)

Your question doesn't make any sense. When the atom moves, it moves from one space to another space. You've been making odd suppositions like this for days. It appears your fundemental understanding of space is faulty; while this is common (the implications of Einsteinian relativity with regards to space are very non-intuitive), your problem appears to be that you are drawing wildly incorrect conclusions based on your misunderstanding. --Jayron32 00:32, 29 August 2011 (UTC)

It's not a meaningful question. How would you measure if it were "new" space or the "same" space? What would that even mean? Dragons flight (talk) 00:34, 29 August 2011 (UTC)

Yeah. Give us a break. We are just getting ready to sign up for our first class in college. Come back in about a year two years and a half and we will have all of the answers to your questions. --96.252.229.48 (talk) 00:42, 29 August 2011 (UTC)

It has nothing to with our understanding. He doesn't make any sense even to someone with advanced physics degrees (I don't, but prior comments by people that do make it clear that he makes no sense on any level). --Jayron32 01:33, 29 August 2011 (UTC)

Well, it makes sense to me, I regret to say. He thinks of space as a thing, like a sheet of paper. It's completely different from the way modern physics thinks of space, but I don't think it is all that unusual. Looie496 (talk) 01:46, 29 August 2011 (UTC)

He could think of space as a color or as a musical note, it wouldn't make it any more right. --Jayron32 02:31, 29 August 2011 (UTC)

-96.252... maybe I should wait a little longer than two and a half years. --DeeperQA (talk) 07:36, 29 August 2011 (UTC)

It's a good question because it addresses our concept of Space. The mainstream Big bang cosmology predicates space as the occupancy of local particle fields, hence the electron cloud carries its space with it when the atom moves and it remains the same old space. Alternatively if we postulate space as an all-pervading ether in which fields operate (an idea that Messrs. Michelson and Morley thought to disprove) then when an atom moves it acquires "new" space. Thank you for posing your question which has existential depth beyond the conceptual capabilities of less gifted editors who, I hasten to add, are not without usefulness. Cuddlyable3 (talk) 09:45, 29 August 2011 (UTC)

Talking of "old space" and "new space" requires the concept of absolute space which the theory of relativity threw out of the window. Ride on the back of that same atom and it won't move at all, so where's that "new space" supposed to come from? --Wrongfilter (talk) 09:56, 29 August 2011 (UTC)

The OP can't be riding on the hydrogen atom because then they would be asking about the rest of the Universe moving. But thank you for trying to reassure us that space in the Universe is now absolutely understood. Cuddlyable3 (talk) 10:20, 29 August 2011 (UTC)

That's not what I said. --Wrongfilter (talk) 10:27, 29 August 2011 (UTC)

The essential conceptual problem is that you are thinking of space as a substance, like a gas. Space is not a substance, as far as we know. It is sort of like asking, when you move a dot from one x,y coordinate to another x,y coordinate, does it take the coordinates with it or does it encounter new coordinates? Neither are really the right way of thinking about what the coordinate system really is — it is a means of assigning position, and nothing more. --Mr.98 (talk) 11:10, 29 August 2011 (UTC)

The OP is being criticized for assuming that space has some of the properties of substances or objects. That is not as absurd as you see it to be, since modern physics ascribes to "space" the ability to be deformed, and to [Metric expansion of space|expand]]. If it behaves in these ways like a substance, then it is not silly for someone to ask if behaves in other ways like a substance. Edison (talk) 23:55, 29 August 2011 (UTC)

Nice answer! 99.36.74.131 (talk) 00:01, 30 August 2011 (UTC)

@Edison and the OP: His misconceptions are certainly understandible. As I noted above, much of modern physics is very non-intuitive, and making mistakes are common. The problem with answering his question directly is that it makes some very wrong assumptions. The assumptions it makes are understandable (again, the fact that we can speak of space itself expanding, or of space deforming as GR predicts as the cause of gravity), but it doesn't make the wrong assumptions more right merely because they are understandbly wrong. The original question still has no sensible answer. --Jayron32 01:37, 30 August 2011 (UTC)

Is there any logical reason why physics has to be sensible ;-) AndyTheGrump (talk) 02:07, 30 August 2011 (UTC)

To pose a related question, when two black holes orbit one another, does space move with them? Or does space pull through each singularity and come out the event horizon as each hole moves through it? (This should be a much more absurd question to answer, yet...) Wnt (talk) 02:21, 30 August 2011 (UTC)

Neither. 'Space' is either just a mathematical/scientific construct used to explain our observations, or something we've invented to kid ourselves that we have a clue what is going on (and if you think there is a difference between the two explanations, you obviously don't understand the problem ;-). ) AndyTheGrump (talk) 02:31, 30 August 2011 (UTC)

OP seems to be asking whether the space "inside" the outermost layer of the electron cloud and "outside" the nucleus is self-contained within the atom or constantly replaced, as if a membrane existed surrounding the atom. Unfortunately further incorrect questions arise such as those regarding how quickly this space is replaced relative to the atom's motion, and unless this space has some form of locatable quantum energy associated, it would be very difficult to make sense of quantifying whether this space is "orginally" inside or outside the atom, almost like asking about the rate of flow of spacetime. See fuzzy logic. ~AH1 ^(discuss!) 21:00, 31 August 2011 (UTC)

Dicarbon

Can two carbon atoms join by a quadruple covalent bond to form a C₂ molecule? Whoop whoop pull up ^{Bitching Betty | Averted crashes} 00:16, 29 August 2011 (UTC)

Yes, dicarbon exists, but no, it does not produce a quadruple bond. Molecular orbital theory predicts a double bond instead. See Diatomic carbon. --Jayron32 00:23, 29 August 2011 (UTC)

Hypervalent phosphorus

How come phosphorus, which has room for only three extra electrons in its electron orbitals, can bond with a double bond to an extra oxygen, making five bonds, in phosphate? And how can sulfur bind two extra oxygens, making SIX bonds, as opposed to its theoretical maximum of two, in sulfate? Whoop whoop pull up ^{Bitching Betty | Averted crashes} 01:03, 29 August 2011 (UTC)

See hypervalent molecule for some background. To put it simply, the valence level of phosphorus and sulfur is the third energy level (n=3). That energy level has availible s, p, and d orbitals (l = 0, 1, 2) availible for bonding. So, you can pack more than 8 electrons into that third energy level. Theoretically the maximum number of electrons you can put there would be 18, but geometry generally only allows a maximum of 12 or 14 (see Octahedral molecular geometry and Pentagonal bipyramid molecular geometry for some examples). --Jayron32 01:30, 29 August 2011 (UTC)

(edit conflict) Valence bonding theory as taught at your level is not completely "correct", it's just a good approximation that works for many cases (and even predicts many correct results even in some of them). You've now found cases where it doesn't for various reasons:) The phosphate article you linked even gives details and links in the "Chemical properties" section, to wit:

The phosphate ion is a hypervalent molecule (the phosphorus atom has 10 electrons in its valence shell).

And the sulfate article also discusses its situation, with an even more surprising (and ultimately comfortable to those who focus on octets and such) answer, in the "Structure and bonding" section. DMacks (talk) 01:34, 29 August 2011 (UTC)

Grácias. Whoop whoop pull up ^{Bitching Betty | Averted crashes} 01:49, 29 August 2011 (UTC)

Inland hurricane warnings

Why are hurricane/tropical storm warnings and watches only issued for coastal areas? Don't the inland areas also suffer damage from hurricanes and tropical storms? Whoop whoop pull up ^{Bitching Betty | Averted crashes} 01:57, 29 August 2011 (UTC)

The coastal areas are much more dangerous during a hurricane because of storm surge. 67.169.177.176 (talk) 02:00, 29 August 2011 (UTC)

Tropical Storm/hurricane warnings are issued for inland areas.Jason Rees (talk) 02:04, 29 August 2011 (UTC)

Thanks...! Whoop whoop pull up ^{Bitching Betty | Averted crashes} 02:15, 29 August 2011 (UTC)

Also, inland areas are much less susceptible because tropical cyclones dissipate very quickly over land; the mechanics of the warm core deteriorate rapidly. Irene was pretty unique going as far as Vermont and caused massive flooding, even though it was a tropical depression at that point. -- MacAddct1984 ^{(talk • contribs)} 04:07, 1 September 2011 (UTC)

AFAIK this had not happened since 1938. 67.169.177.176 (talk) 05:09, 1 September 2011 (UTC)

Actually, Irene was not so very unique -- see Great Atlantic Hurricane of 1944, Hurricane Carol, Hurricane Edna, Hurricane Hazel, Hurricane Connie, Hurricane Diane, Hurricane Donna, Hurricane Gloria, and Hurricane Bob, as well as the aforementioned 1938 New England Hurricane. 67.169.177.176 (talk) 05:17, 1 September 2011 (UTC)

How does the Esselstyn diet unblock blocked arteries?

On CNN in a documentary on heart disease, it was mentioned that the Esselstyn diet can not only prevent heart disease, but it can actually reverse it. Blocked coronary arteries become unblocked simply by sticking to the diet. But how can a blocked artery become unblocked without medical intervention? Count Iblis (talk) 02:36, 29 August 2011 (UTC)

(His diet, for those who are curious, is pure vegetarianism with minimal fat.) Bottom line: there is little scientific evidence that it works. There are some small-scale studies supporting his ideas, but the most extensive test of this type of regimen, reported in PMID 16467234, found no detectable reduction in cardiovascular disease. (He would probably say that the negative result comes from not fully implementing his program.) Looie496 (talk) 03:22, 29 August 2011 (UTC)

I believe the theory is that the arteries slowly clean themselves, so long as you stop adding to the mess. That is, fatty deposits eventually dissolve into the blood and are subsequently removed. If so, this would be similar to other limited abilities our bodies have to regenerate, like say when a small cut is completely healed. But, like the case with a cut; a large, heavily scarred area will never heal. StuRat (talk) 05:06, 29 August 2011 (UTC)

The body keeps going by doing certain things... converting sucrose and fats to glucose and removing uric acid and carbon dioxide which requires energy it gets from consuming nutrients. Just from metabolism your body burns about 50 calories per hour. Consume less than this and your body starts consuming whatever it can find to use as fuel starting with sugars and when they run out from fats converted to sugar and then protein converted to sugar. Eventually your body will find those pieces of fat clinging to your arteries and realize they can be used for fuel. Goodbye globules of cholesterol your body needs fuel. --DeeperQA (talk) 05:21, 29 August 2011 (UTC)

In general, reversal of artery blockage may involve high-density lipoprotein as described in that article. Evidence for reversal tends to be a bit elusive, as we're generally speaking of trying to undo the effects of a lifetime of movement in the opposite direction with some simple, rapid intervention. In concept, a condition of homeostasis typically exists in biological processes, which are often reversible at the biochemical level - if a high fat diet is responsible for creating the blockage, then reversing that condition should allow the reverse process to occur to some extent. Though whether that extent is practically relevant is another question.

In specific, there are particular compounds and herbs thought to have some ability to clean out these deposits (most notably statins) or at least to promote HDL and reduce their formation.

As an aside, I should mention that I recently tried one such, a hawthorn supplement (labeled Crataegus oxyacantha), which has been suggested to have such effects (e.g. PMID 19885950). I felt a remarkable vasodilation effect from one 700 mg pill, which seemed to reduce the force needed for each heartbeat to something very small, and which had such a strong inhibitory effect on digestion that it was as if it reduced the ambient temperature by 10-15 F. For a short time I was pondering its use as an "herbal air conditioner"... Unfortunately after about 20 hours every artery constricted again, painfully - muscles I'd lightly exercised two days previously without note became sore, my eyes and gums were sore, all three branches of my cerebral arteries were sore, even my coronary arteries were sore (which never happens otherwise), all of which lasted for two days ... and my perturbed digestion had a miserable time getting back into sorts also. So while I think the herb is very interesting from a scientific point of view I'm not ready to recommend it! The aftereffects were somewhat comparable to getting the flu except without the respiratory symptoms. But for all I know that soreness might be crucial to how it works, and some people don't seem to notice such sensations. Wnt (talk) 05:41, 29 August 2011 (UTC)

If you ever repeat the experiment, I suggest a much lower dosage. StuRat (talk) 20:21, 29 August 2011 (UTC)

So, it's never too late to start to eat a healthy diet (although the Esselstyn diet doesn't look that healthy to me :) ). Count Iblis (talk) 15:43, 31 August 2011 (UTC)

Evolution

Is evolution falsifiable, if so, how?I mean there always seems to be a way to "fit in" evolution in biology, paleontology, etc.Don't get me wrong, I think evolution is a correct theory, but...is it falsifiable?--Irrational number (talk) 10:58, 29 August 2011 (UTC)

First, please explain what you mean when you say evolution, because that word is used in so many ways from "the observed change in biological life" to "a materialistic and atheistic world view". Sjö (talk) 11:02, 29 August 2011 (UTC)

Presumably they mean biological evolution by natural selection. --Mr.98 (talk) 11:07, 29 August 2011 (UTC)

It's been an openly debated question. See Objections_to_evolution#Unfalsifiability. Karl Popper, the philosopher of falsifiability, classified Darwinism as a "metaphysical research programme," not a scientific theory. But as a research programme, it could then lead to falsifiable scientific theories. But it's been a long debated question, in part because evolution has become such a huge supercategory for understanding so much of the natural world. --Mr.98 (talk) 11:06, 29 August 2011 (UTC)

Popper later changed his mind about that (at least, about whether it was testable: it's unclear whether he continued to think the term "metaphysical" applied). The quote is at Falsifiability#Evolution, and another part of the quote is in the article section you linked to - or see a long quote in fuller context here: [1]  Card Zero  (talk) 10:54, 30 August 2011 (UTC)

So it's partly unfalsifiable?I mean, a creationist may say "you believe in a theory that isn't falsifiable, so it's some kind of faith"...--Irrational number (talk) 11:21, 29 August 2011 (UTC)

Did you read the link I gave? That's not what it says. --Mr.98 (talk) 11:33, 29 August 2011 (UTC)

I finished it now, thanks!but generally, are people "blindly accepting science"?and how can a normal person be skeptical about scientific theories if he/she is not a scientist or is in the process of learning?should people other than scientists simply "accept" what scientists say, simply because they don't have time to research or something?--Irrational number (talk) 11:34, 29 August 2011 (UTC)

A person should be sceptical of theories, and that should motivate them to learn about them, because the only time the process of learning ends is when one is dead or lazy. Cuddlyable3 (talk) 11:54, 29 August 2011 (UTC)

Of course evolution is falsifiable, insofar as anything is falsifiable, given that you cannot make an infinite set of observations. One could observe that no living thing ever changed; that would have been a plausible observation. Actual observations confirm that living things change, however, so the theory has been confirmed, at least to the best of human observation (i.e. as well as I can confirm to myself that I positively exist). --Jayron32 12:34, 29 August 2011 (UTC)

Sjö is right, we need to clarify the meaning of "evolution". The word can be used to refer to the idea that random mutations happen and those that make an organism better at reproducing tend to prevail ("natural selection"). That isn't really a scientific theory, it's a simple logical deduction. As long as you accept the theories of genetics and sexual reproduction, then natural selection follows at once. Falsifiability doesn't come into it, it's a logical truism. The definition of "evolution" that causes problems is that of a theory regarding the origins of species. The claim "all life is descended from one simple organism (or a small number of them in some versions) and random mutations and natural selection have resulted in the variety of life we observe today" is the theory that needs debating. It could be falsified by the observation of an organism coming into being either without parents or with no (or very little) genetic similarity to its parents. --Tango (talk) 12:42, 29 August 2011 (UTC)

Everything is falsifiable, that is one of the main virtues of science. The freedom to change and adapt theories as new evidence are uncovered. The scientific method depends on skepticism for forward progress, after all. Like Tango pointed out, various hypotheses related to biological evolution has been disproven and changed and adapted throughout the years and the modern theory is quite different from Darwinist evolution. The specifics of evolution still have plenty of things to debate on.

However, the entire concept of biological evolution itself is not an isolated thing like creationists seem to think it is. Like almost everything in science, it's deeply enmeshed with different disciplines all supporting its basic truth. 'Disproving' evolution would mean disproving the basic tenets of several other applied sciences as well.

They'd have to disprove things like radioactive decay and the age of the Earth and the universe, in doing so they'd have to challenge the very technology that gave them the atomic bomb and nuclear reactors. Disprove basic stratigraphic truths we already know from baking layer cakes. Disprove the succession of lifeforms in the fossil record, possibly by finding a precambrian rabbit or a fossil of Fred Flintstone (LOL). Disprove heredity and the gradual shift of genetic material by coming up with a reason as to how we possibly managed to breed chihuahuas from wolves. Disprove that the sky and the sea are not firmaments and that the moon does not give off its own light. Etc. They'd have to disprove some of the very basic truths of the universe they'd already taken for granted but thought were not related to evolution at all. Not a very easy thing to do, hence the whining of 'unfalsifiability', as if it's the scientists' faults that everything meshes in so perfectly. But sure, if they managed to do all that, then yes, evolution can be falsified.

This is usually the point when creationists cross the threshold of denial to irrationality and outright insanity. In attempting to explain away evolution, they'll soon discover that they can't explain this or that away as false without affecting another aspect of science. They'll usually start inventing massive conspiracy theories like a staged moon landing, the New World Order implanting fossils, or scientists being part of an intellectual elite bent on taking over the world, etc.

As for blind acceptance, religions are wealthy and uberpowerful. They have all the time and resources they need to disprove it. But why don't they? No one is barred from doing experiments and results of previous studies are easily accessible and methodologies completely transparent (hence why it's "peer-reviewed").

And scientists are not clergy. They are not a special subset of privileged human beings whose word is divine unquestionable truth. As mentioned, anyone can do experiments. If you can find one that can prove or disprove something using scientific methodology, by sharing it, you yourself are already a scientist. Creationists accusing the general population of being blindly accepting of science is pretty hilarious when you stop and consider that in their beliefs, no one can question anything and you are actually forced to accept their truths blindly or become a heretic.-- Obsidi♠n Soul 13:17, 29 August 2011 (UTC)

Not everything is falsifiable. If that were true, then falsifiability wouldn't be a useful concept. The existence of an omnipotent god, for instance, isn't falsifiable. There is no observation you could conceivably make which would disprove the existence of an omnipotent god. For that reason, you won't see omnipotent gods appearing in scientific theories. --Tango (talk) 13:27, 29 August 2011 (UTC)

Oop. I meant scientific concepts obviously, it can not base theories and hypotheses on unfalsifiable premises, hence why everything in it has to be falsifiable in some way.-- Obsidi♠n Soul 13:34, 29 August 2011 (UTC)

That's not entirely true unless it is tautological. There are scientists who work on what they consider science but it may not be (yet) falsifiable. String theory is a famous example of this. Many-worlds interpretation is another. And so on. Saying, "well, that's not science, then," just gets around to the original question about whether evolution is falsifiable and thus science. --Mr.98 (talk) 14:33, 29 August 2011 (UTC)

I beg to disagree, the fact that they can work on it makes it apparent that they do think it is falsifiable. Whether it is actually falsifiable or not is a stickier question, and those who think it's not naturally do not consider them scientific. Not being familiar with them, I don't know if any of them have convincingly proven falsifiability yet though. Neither of that affects evolution, as it has numerous discrete statements that can be falsified unequivocally, some have, but most haven't. That contrasts sharply with creationism which can simply avoid its falsifiability by claiming that God created the universe as is - that is, with atoms already partially decayed etc. and ignoring evidence of absence by claiming a different interpretation of the original statements or by pushing the limits of "qualified investigation". They have an omniscient and omnipotent being as a premise after all, they can get away with anything.

The problem here is that people generally expect naive falsifiability, and expect that disproving a single discrete statement can utterly destroy any theory, and that is obviously not the usual case. Theories can adapt readily to fit into new discoveries without having to change its basic conclusions, that doesn't necessarily make them unfalsifiable as enough falsified key statements can result in its infeasibility to remain scientifically acceptable. -- Obsidi♠n Soul 15:49, 29 August 2011 (UTC)

I tend to agree with Popper, personally. Darwinian evolution as an overall worldview is so huge and malleable that it doesn't really amount to a theory. However it is supported by lots of more specific and tangible theories, and it is a worldview that on the whole does change with response to facts (Darwinism has changed a huge amount since Darwin's time) and there appear to be pretty good ways to tell truth from non-truth, which is the entire point of falsifiability. It does stand in stark contrast to Creationism in this respect, even if things are not always as airtight philosophically as pro-evolution folks would like it to be. You can see the contrast pretty strongly when you look at how Creationists and how scientists approach their theories: scientists want to know what happened and how it works; Creationists want to know how to fit new facts into their preexisting view of the world. Scientists get rewarded when they find something substantially different yet true; Creationists get rewarded when they find out that everything was more or less exactly as they wanted it to be from the beginning.

As for faith in science — science is more of an institution than a set of beliefs. So instead of thinking of the faith people have in it like the faith they have in the idea of Jesus or the New Testament or God, think of it like the faith that people have in their banks. You give your money to your bank. You have some confidence that they aren't going to blow it all on champagne. This isn't because you think they are infallible; it's because you know that in the past, they've mostly done a fair enough job, and that there are consequences if they misbehave. You also know that the entire industry of banking is not just one person or book or even place, but lots of independent people, regulators, police forces, and so on. You also know that there has been misbehavior in the past, and that you can't trust them blindly, but there is probably a level of trust you're willing to have. This trust might be buffeted by external institutions as well — for example, the fact that savings are often insured up to a certain value by the government. Still, your trust is always provisional on the results. If it turned out that the banking system was a total fraud, you'd probably withdraw your savings from them.

Science is similar enough, here. It is an international, often loosely organized institution for the production of reliable knowledge. When you have faith in the results "of science," what you're usually saying is that "the consensus amongst scientists in a given area of knowledge is high enough that what they say seems like the most probable preliminary conclusion about how nature really works." Notice how it's not about one person, and it's not about The Truth with capital letters. It might also be a statement that says, "I think scientists have a better idea of what is going on than anyone else," which is more a vote of confidence than a statement of faith. In any case, none of this is terribly blind. So while I would say sure, there is some faith involved, I would further clarify that it is a much more tentative thing, and of a very different nature, than the sort of faith that characterizes religious institutions. --Mr.98 (talk) 14:33, 29 August 2011 (UTC)

Hate to break it to you, but your bank analogy falls flat on its face when you consider the 1930s, and the recent banking situation that required massive government intervention. Googlemeister (talk) 15:15, 29 August 2011 (UTC)

The analogy was made with those sorts of interventions and systemic changes directly in mind. Science has not proceeded for the last 500 years without some major interventions in its institutional structure, its means of evaluating information (peer review didn't just pop up overnight or organically), or without problems of fraud. The analogy to the great collapse of the 1930s is the Sputnik crisis, when US policymakers decided their preexisting system of generating knowledge was unfocused and not large enough to meet their current needs, and instituted a massive set of funding changes, educational reforms, and so on. --Mr.98 (talk) 16:44, 29 August 2011 (UTC)

Evolution is definately falsifiable. If someone were to observe a human fossil in pre-cambrian rock, the theory of biological evolution would gbe thrown out of the window. Contrast this with creationism: A creationist rationalizes away genetic evidence by saying "The genes are there because God decided to put them there". Rabuve (talk) 16:08, 29 August 2011 (UTC)

I'm not a biologist, but as I understand things evolution is falsifiable because it makes useful predictions. If the predictions turn out to be false, then the theory that made those predictions evidently has some flaw. That's what scientific theories are for, after all—making useful predictions. Creationism is not falsifiable because it doesn't make any useful predictions. —Bkell (talk) 16:16, 29 August 2011 (UTC)

I think that the idea that life can evolve by natural selection is almost a philosophy (it actually started out as one - see Herbert Spencer); it may indeed be hard to falsify. But the idea that life did evolve represents a set of experimental results going back at least to Darwin. The experimental results could be easily falsified - even if a single bunny rabbit in the Cambrian strata were explained away as a geologic anomaly, we should bear in mind that certain alternate models predict that the Cambrian should be just chock full of bunnies from the day they overran the Garden of Eden, not to mention egrets and toads and all kinds of other such modernities.

Now, both proving evolution and falsifying it gets more difficult the more precise you want to be. For example, suppose we assume that for the past billions years flying saucers have abducted organisms every few millennia and flown them back and forth between carefully chosen cognate points on Earth and some world with similar geographic conditions. Could we rule that out? I doubt it. And yet, that would mean that many of our models of biogeography had been forced to try to explain occasional movements that didn't really happen (i.e. between cognate points on the other planet that were easier to get between than the corresponding Earth map). Or the way in which certain species became popular - like flowers and bunny rabbits - might reflect alien aesthetic preferences rather than symbiotic communication and sexual selection. So we should recognize the amount of falsifiability is indeed somewhat practically limited, and possibly that has damaged our understanding of the world. Wnt (talk) 17:55, 29 August 2011 (UTC)

If aliens did shunt organisms back and forth, they apparently changed enough in the interim for them to be different when they were reintroduced, in which case they still evolved, they just didn't migrate as we thought they did. If the aliens were introducing successively complex organisms they built from ground up in trickles, it would also then be unable to explain devolution, vestigiality, and evolutionary deadends. There are too many variables to consider that the only real way for it to be plausible is if the aliens were omniscient, omnipotent, and patient enough to carefully engineer each organism (and fossils besides) as to give the impression of evolutionary history (a la Scientology). Then that's basically an unfalsifiable premise, a massive conspiracy theory much like creationism or ID itself. Either way such aliens would obviously be batshit crazy, LOL, and I guess this is where Occam's razor applies. FWIW though, I do think panspermia is a valid hypothesis.-- Obsidi♠n Soul 18:56, 29 August 2011 (UTC)

Yes. If survival of the fittest were not accompanied in aggregate by natural selection of advantageous traits, then evolution would be falsified. 76.254.20.205 (talk) 20:01, 29 August 2011 (UTC)

Most scientific theories are based partly on axioms and paradigms, which usually change as they are improved or discarded, thus evolving (oops!). However, public opinion on prevailing theories is not always based on scientific evidence or arguments and may have a socio-philosophical basis. ~AH1 ^(discuss!) 20:34, 31 August 2011 (UTC)

Are there any land-dwelling chordates with other than zero, two or four legs?

Heading says it all. 69.243.220.115 (talk) 15:27, 29 August 2011 (UTC)

Do tails with Prehensility count as a fifth appendage? Googlemeister (talk) 15:41, 29 August 2011 (UTC)

Also mutants and amputees? :P Otherwise no, I guess. -- Obsidi♠n Soul 16:04, 29 August 2011 (UTC)

Several examples on Pandora.190.56.115.192 (talk) 21:24, 29 August 2011 (UTC)

LOL, Avatar? Also check out Discovery Channel's Alien Planet.-- Obsidi♠n Soul 21:29, 29 August 2011 (UTC)

Ha, Avatar's what prompted the question. Alien Planet sounds like just the kind of fictional documentary I'd find entertaining to watch. I'll have to see if my library has it. 69.243.220.115 (talk) 23:33, 29 August 2011 (UTC)

The relevant articles are Body plan and Tetrapod. Vespine (talk) 01:31, 30 August 2011 (UTC)

Silver coating that makes tarnish removable without polish.

So, I had one of the few moments where something amazes me. I picked up my silver kiddush cup that I bought a year ago, and was annoyed by how tarnished it looked. I saw a mark of untarnished area near the rim where my thumb had been and then rubbed a bit more on a tarnished spot and saw that the tarnish came right off (the thing that amazed me). I then took a tissue and proceeded to rub the remaining tarnish off until it was good as new. I remembered that the lady had given the cup a special treatment before I bought it that would allow someone to do this. What is this treatment exactly? By this treatment, I mean one for silver that allows you to easily remove tarnish without the use of any srt of polish. Apologies if there is something about silvers that I am completely ignorant of and this is a stupid question. Sir William Matthew Flinders Petrie | Say Shalom! 16:05, 29 August 2011 (UTC)

I suspect that something different than you think is going on here. Actual tarnish is oxidized silver, and is probably not that easy to remove. I bet there was some kind of clear lacquer on the silver, which prevented tarnishing by keeping the silver away from the oxygen in the air, and what you thought was tarnish was actually just soot (are candles used nearby ?). Note that there is likely soot in other places, too, but that it's more visible on what would otherwise be a shiny bit of silver. If you don't use candles, then soot could come from smokers, cooking (even if electric), or general air pollution. StuRat (talk) 18:38, 29 August 2011 (UTC)

Silver does not readily oxidize in oxygen in the air. Silver tarnish is silver sulfide, which comes about by reaction with trace amounts of sulfides in the air, usually hydrogen sulfide. See tarnish and Silver#Compounds for more. --Jayron32 18:44, 29 August 2011 (UTC)

OK, thanks for that correction. The rest of my comments still stand, however. StuRat (talk) 18:47, 29 August 2011 (UTC)

Nope, the times it has been around candles, said candles have been far away from it and lit for only a short time. Besides, I know the difference in appearance. We have a few older silver pieces that were tarnished and required heavy polishing with polish (fun except for the fumes) and it was basically the same sort of uneven discolouration. It spends most of its time in the living room and no one dares smoke in the apartment. This was most definitely tarnish, hence my amazement at it simply coming off on my thumb. It needed a bit of pressure, granted, but it still came off without the use of any sort of polish or polishing cloth. Sir William Matthew Flinders Petrie | Say Shalom! 22:29, 29 August 2011 (UTC)

For what it's worth, I very rarely use any form of silver polish, saving it for dirty or severely tarnished items. I find that most household cloths will remove the discolouration that silver items accrue over time, provided you don't let it get too bad. --TammyMoet (talk) 08:26, 30 August 2011 (UTC)

Vasodilating food

Besides hot peppers which I believe are vasodilating, are there any other foods with such a property? Vasodilation lists ethonol, but that raises blood pressure, which makes me think it has vasoconstrictive properties. Googlemeister (talk) 18:33, 29 August 2011 (UTC)

This paper seems to indicate that Allyl isothiocyanate, an active flavor compound in mustard and wasabi and horseradish, as well as Diallyl disulfide, an active flavor compound in allium like garlic, onion, and shallots, have vasodilatory properties. Like capsaisin (the active flavor compound in chili peppers) they act on TRPA1 channels, which probably lends itself to vasodilation. Look for other foods which activate these channels, and you'll probably find similar reactions. --Jayron32 18:41, 29 August 2011 (UTC)

X-ray photography

How does X-ray photography work? When I was at the dentist's for tooth X-rays, they had me put a small object in my mouth, which they called the film, and then shot an X-ray emitting device at it through my teeth. But from what I understand about photography, getting the image to proper focus requires diffracting the light through a small hole, otherwise the image will be blurry. I tried this myself by looking through the viewfinder of my DSLR without a lens attached, and could only see a vague gray cloud. Isn't it the same thing with X-rays? Does the X-ray emitting device shoot the X-rays in very straight lines, in contrast to the Sun or lamps, which shoot light all over the place? JIP | Talk 18:42, 29 August 2011 (UTC)

Rather than comparing an x-ray photograph with a normal light photograph, it's better to compare it with a shadowgraph, which records variations in the degree of opacity in the object. The film (or often a detector hooked up to a computer these days) is positioned just behind the teeth and records just the received intensity of the x-rays, which are affected by the material properties of the teeth, including any holes and previous fillings. Mikenorton (talk) 18:54, 29 August 2011 (UTC)

Are images like this one shot in the same way? The image looks so sharp that I imagine that either the rays must have been diffracted or been very straight all along. Do X-rays work differently from visible light? I don't know very much about the physics behind all this, but aren't X-rays photons with shorter wavelength than visible light? JIP | Talk 19:12, 29 August 2011 (UTC)

The image is crisp because the xrays are coming from a single source, and a single direction. If the room was full of xrays, then the image would be blurry, but then you'd also have other problems. --Goodbye Galaxy (talk) 19:28, 29 August 2011 (UTC)

So it's like I imagined, the X-rays are very straight all along? JIP | Talk 19:35, 29 August 2011 (UTC)

No, that's not it. It would be the same if it was regular old visible light (disregarding the fact that visible light wouldn't penetrate your skin). The major difference is there's visible light everywhere, muddling things up! In a dark room you can place objects on photographic paper, shine a direct beam of light on it, and the objects will leave a clear and crisp image on the paper, because there's no other light sources. --Goodbye Galaxy (talk) 20:02, 29 August 2011 (UTC)

Is there a branch of (light) photography which does this ? It doesn't seem like it would be very good for pictures of people, since being in a dark room then getting a single point source of bright light would be even more blinding than a regular flash. However, it might produce better pictures of objects, where you have 100% control of the light source. (Perhaps they could use a color for ambient light which the film or digital camera doesn't detect, so the photographer wouldn't be stumbling around in the dark.) StuRat (talk) 20:18, 29 August 2011 (UTC)

Just pointing out again that in X-rays we're talking about transmitted radiation not reflected. Mikenorton (talk) 20:25, 29 August 2011 (UTC)

Well, the problem is that unless the object is transparent, you'll only get a silhouette. In high school I did the process I mentioned above with transparent chess pieces for some interesting results. I also feel compelled to add that the film/paper must be basically touching the object in question (in your mouth, touching your teeth, for instance). The further away it is, the blurrier the image will be. --Goodbye Galaxy (talk) 20:31, 29 August 2011 (UTC)

Not a problem for any translucent object in a shadowgraph or teeth in an X-ray. X-rays do use a point source, with a controlled amount of spread so the object does not need to actually be touching the film/detector - or an x-ray of your gut after a barium meal wouldn't be much use. Mikenorton (talk) 20:38, 29 August 2011 (UTC)

Sounds like it would work best with flat, transparent objects, like panes of stained glass. Also, since pretty much everything is transparent if sliced thinly enough, this technique might work well for taking pictures of laboratory slides. StuRat (talk) 20:34, 29 August 2011 (UTC)

It isn't that x-rays are somehow 'straighter' than other types of photons (including visible light); it's the geometry of the source, teeth, and film. Go outside on a sunny day and look at the shadow you cast on the ground. It's not perfectly sharp, though some detail remains visible; what causes that lack of sharpness?

For the purpose of comparing geometries in this example, the sun is comparable to the 'x-ray source', the ground is our 'film', and you are the 'tooth'. Ideally, you'd have a perfectly sharp outline of your body on the ground—each spot on the ground would either see the sun (be lit) or not see the sun (be in dark shadow). This would happen if the Sun were a point source, but it's not. The Sun has some width to it; it's about half a degree across in the sky, which means that around the edge of your shadow there are portions of the ground which can see only a part of the Sun past your body. It's this width of the Sun that is the major contributor to your shadow not being perfectly sharp.

The other thing you may notice is if you put yourself (your hand, say) close to the flat surface of the ground, the shadow gets sharper; it becomes (nearly) perfectly sharp if your hand is in contact with the surface. The distance across the surface of the ground (or film) you need to travel to go from complete shadow to complete illumination gets smaller the closer the object being imaged is. Photographers from the pre-digital era will be familiar with contact prints, which made sharp images (even using diffuse light sources) because the negatives were placed in direct contact with the photographic paper.

So, going back to x-rays, why is the image so sharp? First, the effective width of the source is quite small—the spot from which the x-rays emerge from the machine is quite limited. Second, the film (in the little cardboard/plastic cassette that goes in your mouth) is placed in nearly direct contact with the teeth; this sharpens up the image quite a bit further. Both of these factors contribute to producing an adequately sharp image. TenOfAllTrades(talk) 22:47, 29 August 2011 (UTC)

JIP, see contrast medium and the inset “Contrast media” at http://science.howstuffworks.com/x-ray2.htm.

—Wavelength (talk) 23:37, 29 August 2011 (UTC)

Rabid skunk

Can a rabid skunk pass on their rabies if they spray someone? The Mark of the Beast (talk) 19:31, 29 August 2011 (UTC)

No. Rabies virus is present in nerve tissue and saliva, and is usually transmitted by bites, but can also be transmitted during butchering or handling if the victim is cut or has an open wound. It cannot penetrate intact skin, and is not present in skunk spray. [[2]]. Dominus Vobisdu (talk) 19:54, 29 August 2011 (UTC)

Agreed per PMID 11973559. 76.254.20.205 (talk) 19:58, 29 August 2011 (UTC)

Thank you. The Mark of the Beast (talk) 05:05, 30 August 2011 (UTC)

Stem cell compatibility

A question came up during a conversation with a friend. Can stem cell treatments work on people with odd chromosome count, such as people with Klinefelter's syndrome. I'm pretty sure the cells must have human DNA. But would the donor of the stem cells also have to have the same chromosome configuration? ~Amatulić (talk) 23:52, 29 August 2011 (UTC)

If they depend on genes in the missing or duplicated chromosomes it might cause complications, as would rejection by the host's immune system, but I have no idea whether that would typically be a problem. You might want to review PMID 8590864 and PMID 19229047 for hints, but I doubt either source will address the question directly. A citation search on the first or both might help get the answer, if it is even known yet. I suspect it is known by now. 99.36.74.131 (talk) 23:59, 29 August 2011 (UTC)

Hmm, thanks. I found one (PMID 10222629) where a Klinefelter's patient took stem cells from a Klinefelter's donor. Another (PMID 7724525) describes how the offspring of female chimeras implanted with embryonic stem cells may have XXY chromosomes similar to Kleinfelter's syndrome. Another (PMID 18331539) describes a successful stem cell transplant using a Kleifelter's donor. Lots of related stuff, but so far nothing that directly answers the question. ~Amatulić (talk) 00:15, 30 August 2011 (UTC)

Well ask the corresponding author whose email address is listed on PMID 18331539. Dr. Balci is likely to either know the answer or quickly recommend someone who does if he or she doesn't. 99.36.74.131 (talk) 00:55, 30 August 2011 (UTC)

I have done so, and waiting for a reply. Thanks. ~Amatulić (talk) 16:08, 30 August 2011 (UTC)

Sterling engine charger?

I would like to use a sterling engine and heat differential source to recharge One Laptop Per Child and USB devices. What is the most economical solution? Is there anything off the shelf in sterling power generation? 99.36.74.131 (talk) 23:54, 29 August 2011 (UTC)

I'd think you'd do better with a solar panel with a long cord, as that has no moving parts, so is more reliable. Also, the hot parts in a Stirling engine might be dangerous to children, and then there's the danger from the fire itself, and the expense of the fuel, to be considered. StuRat (talk) 00:16, 30 August 2011 (UTC)

This is for indoor night time use. There's a source of cold water and a gas furnace, but no open fire. 99.36.74.131 (talk) 00:50, 30 August 2011 (UTC)

With a battery you don't need to charge at the same time you use the appliance. In fact, with some configurations, it's not possible to do so. So, charging the laptop during the day and using it at night would be perfectly appropriate. The long cord is so the solar panel can be outside (or in a window) while the laptop is inside. StuRat (talk) 07:19, 30 August 2011 (UTC)

Here is an off-the-shelf toy sterling engine demonstrator. Cuddlyable3 (talk) 09:16, 30 August 2011 (UTC)

Here is a video and a paper from 1994. 64.134.229.117 (talk) 01:03, 31 August 2011 (UTC)