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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)

August 30

Negative matter

I remember Michio Kaku's book, Physics of the Impossible stated something along the lines of the statement that one could use matter with negative mass to hold the wormhole in the singularity of a black hole open for long enough to stabilise it for something to enter it. But since negative mass is supposed to be repelled by gravity, and nothing can escape a black hole, shouldn't the negative matter be unable to enter the black hole, as the hole's gravity will push the matter away infinitely? --Σ _{^talkcontribs} 00:04, 30 August 2011 (UTC)

Negative mass is such a fanciful concept that we can't answer questions about it. However, I'm going to say yes anyway. 99.36.74.131 (talk) 00:52, 30 August 2011 (UTC)

According to the equivalence principle, even negative mass would be gravitationally attracted to a black hole, but other than that you're basically right. There are mathematical theorems in general relativity that say that without exotic matter you can't make a traversable wormhole. That doesn't imply that with exotic matter you can make a traversable wormhole. There are a few other hurdles to be surmounted first, such as making sure the stuff goes where it needs to go and stays there. Realistically, none of this is possible. -- BenRG (talk) 01:26, 30 August 2011 (UTC)

Actually the negative mass is repelled from the black hole ... it's just that the repulsive force causes it to fall in. F=ma and all that. ;) Wnt (talk) 02:14, 30 August 2011 (UTC)

Indeed. The reason everything falls at the same rate, regardless of its mass (Galileo dropping cannonballs off the Leaning Tower of Pisa, and all that), is because the m's in F=GMm/r² and F=ma cancel. They still cancel if they are negative. --Tango (talk) 11:46, 30 August 2011 (UTC)

While we're on the subject, what is theorised to happen if you push such a thing? Surely it can't move right through your hand – or maybe it does? Grandiose (me,talk, contribs) 12:19, 30 August 2011 (UTC)

Surely when you push something the forces involved are electrical, not gravitational? Stanstaple (talk) 18:05, 30 August 2011 (UTC)

Exactly, so the force away from you would result in an acceleration towards you. The force on you (equal) would accelerate you back, but if you're more massive, then less, so... Grandiose (me, talk, contribs) 18:12, 30 August 2011 (UTC)

@BenRG What do you mean by impossible? All you have to do is get something that doesn't exist and stabilize in a intrinsically unstable configuration in a completely inaccessible position. Dauto (talk) 13:02, 30 August 2011 (UTC)

Why isn't there an X-Ray Structure of Bovine Serum Albumin?

Or any other structure of BSA for that matter? There isn't so much as a homology model out there. Seems odd, since it's so cheap you'd think someone would have given it a shot. It can't be because it's not interesting enough, or there wouldn't be so many structures of lysozyme (arguably one of the least interesting [and easiest to crystallize] things to ever have a structure solved). It can't be that hard to crystallize since there's a ton of deposited structures of Human Serum Albumin (HSA), and you'd think they'd be homologous. Anyone have a definitive answer? Or even some well sourced idle speculation? Thanks --Chemistry-grad-student (talk) 02:32, 30 August 2011 (UTC)

It has been done a number of times for human serum albumin but apparently isn't all that easy -- the only account I can find for bovine serum albumin is this thesis report from 2004. There are lots of other descriptions of the structure relying on simpler methods than crystallization. Looie496 (talk) 02:47, 30 August 2011 (UTC)

The 2004 paper describes considerable effort to get good crystals - the problem is likely, as the author says, the crystals don't diffract very well "probably due to three-dimensional flexibility in some flexible regions (such as N-terminus or C-terminus regions) of BSA that causes crystal lattices in these regions disordered." Bear in mind that albumin, as the major serum protein in a mammal, has a very special role, transporting hormones and drugs; it needs a certain special character about it, which apparently involves a certain amount of cussedness. While it's possible that the people who crystallized human albumin just did a really good job, it's also quite possible that the bovine form is just more flexible. Wnt (talk) 04:08, 30 August 2011 (UTC)

Thanks for the responses. I suppose there's no rule that homologs have to crystalize under the same or similar conditions or even have comparable dynamics. Was wondering if there was another obvious explanation (other than 'hard to crystalize'), I suppose not. Thanks again. (chemistry grad student) I(q) = User(q)·Talk(q) 00:56, 31 August 2011 (UTC)

Dizziness caused by a somersault

I was demonstrating an underwater somersault (forward roll), during which I suddenly felt an awfully strong dizziness and vertigo. That left me with a nauseous feeling for the rest of the day. As a child, I could do as many rolls as I pleased, one after the other. I never had any head injuries in the past. What could that be? Gil_mo (talk) 05:35, 30 August 2011 (UTC)

You should see your doctor for medical advice because there are many possible causes, but you might also wish to read our article on Balance disorder. Dbfirs 07:00, 30 August 2011 (UTC)

I don't consider dizziness during a somersault to be abnormal. On the contrary, those who can do gymnastics without becoming dizzy are abnormal, but in a good way. StuRat (talk) 07:15, 30 August 2011 (UTC)

Dizziness during a somersault doesn't sound abnormal at all. Nausea for the rest of the day, though, does. It's worth talking to a doctor. --Tango (talk) 11:49, 30 August 2011 (UTC)

Discuss Hypotension with your doctor. Cuddlyable3 (talk) 09:04, 30 August 2011 (UTC)

In a similar situation, I noticed that amusement park rides I used to enjoy in my youth now make me nauseous. Maybe it has something to do with age? Although somersaults under water have always given me a brief sense of vertigo, I don't notice any lasting effects even when I do them now. ~Amatulić (talk) 16:13, 30 August 2011 (UTC)

A quick google on "inner ear ageing" throws up many references around the increase of dizziness because of age-related changes to the balance mechanism. --TammyMoet (talk) 18:15, 30 August 2011 (UTC)

What injuries can be instantly healed?

The title's not exactly what I mean to say, but I couldn't think how to phrase it.

I write stories, and I like to injure my characters. However, I prefer injuries that can be instantly healed. For example, dislocated shoulders can be popped back into place and the character is right as rain (I know, not in real life, but its believable enough that Willing-suspension of disbelief discards it.)

Basically, I want injuries where the problem can solve itself using little to no 'medicine' or recovery time. So, not things like gunshot wounds or broken bones.

Can anyone think of anything? Remember that since it's fiction, you've got a bit of leeway regarding how incapacitating it would 'actually' be. ~~Ye Olde Luke — Preceding unsigned comment added by 70.179.55.4 (talk) 07:00, 30 August 2011 (UTC)

Well, simple bruises administered by blunt instruments will basically heal themselves over time (the no-medicine requirement), but it will not be instant - hours to days depending on severity and impact force. --Ouro (blah blah) 07:06, 30 August 2011 (UTC)

For a nice gross one, how about an eyeball popped out of it's socket, then popped back in ? Or maybe a tooth knocked out, then pushed back into place. StuRat (talk) 07:11, 30 August 2011 (UTC)

For truly sadistic inspiration see John and Lorena Bobbitt. Cuddlyable3 (talk) 09:01, 30 August 2011 (UTC)

Sorry, but that doesn't qualify as "instantly healed". 67.169.177.176 (talk) 05:36, 31 August 2011 (UTC)

A splinter, thorn, or other irritant that doesn't penetrate deeply could be most of the way fixed simply by removing whatever is causing the problem. Dragons flight (talk) 11:40, 30 August 2011 (UTC)

A fairly small cut that you can just apply pressure to for a few minutes and then put a plaster/band-aid or a dressing on and then leave alone could count. The injury is still there, but you can ignore it once it is dressed. If it's bad enough to need stitches then, if you don't get the medical treatment, you'll probably end up with a really nasty scar, but that might not be a problem depending on your story. There are also issues with infection, but you can just assume they get lucky and the wound isn't infected. --Tango (talk) 11:53, 30 August 2011 (UTC)

Getting the wind knocked out of you --Digrpat (talk) 13:18, 30 August 2011 (UTC)

About 90% of the injuries sustained on a soccer field, apparently. --TammyMoet (talk) 13:51, 30 August 2011 (UTC)

A minor electric shock. Googlemeister (talk) 13:57, 30 August 2011 (UTC)

A spinal misalignment that slips back into place, no longer impinging on the nerve ? StuRat (talk) 19:12, 30 August 2011 (UTC)

Not medical advice, and don't try this at home: Getting the wind knocked out of you as was mentioned above seems to fill the bill. A kick in the nuts is debilitating, and people seem to get over it, but it could certainly cause permanent damage to the reproductive system. "Nursemaid's elbow" occurs when someone lifts a small child by his arm, causing some kind of painful dislocation in the child's elbow. A pediatrician said it is pretty easy for a layperson to fix if the pe4rson is shown how by the doctor. (Once it happens, it is likely to recur). I've seen a football coach fix a dislocated finger. A martial arts teacher once said that men have had their testicles driven up into the abdomen by a kick and that they could sometimes be restored to their normal place without medical intervention. From personal experience, a "basket handle tear" in the knee can result in painful locking of the knee in a bent position when one puts pressure on the knee in certain ways, like standing up with the "trick knee" bent back under the front of the chair. Sometimes it can be "unstuck" in a short while. A "punch in the breadbasket" can somehow injure the diaphragm so it is hard to breathe, and this has typically corrected itself quickly. Any "charleyhorse," cramp or muscle spasm could be crippling for a short while: is there a way to induce one? Aren't there some martial arts pinches which cause paralysis of a limb for a bit? And don't forget the dread {Icecream headache]], an intense pain in the roof of the mouth which feels like a brain freeze, also typically self correcting in a short while. (Make the victim eat ice cream?) Eating a very hot pepper can cause intense pain, sweating, eyes watering for several minutes, as can pepper spray or tear gas. A Taser knocks a person down, and typically they get over it, though some die. Edison (talk) 20:38, 30 August 2011 (UTC)

Dr. Hibbert: "Worst case of brain freeze I've ever seen, get me 50 cc's of hot fudge, stat !" StuRat (talk) 21:51, 30 August 2011 (UTC)

Cracking your knuckles. ~AH1 ^(discuss!) 20:23, 31 August 2011 (UTC)

That's not really an injury. 67.169.177.176 (talk) 05:29, 1 September 2011 (UTC)

A whip or rope lashed around the neck,( perhaps while dangling from a balcony) which with great dexterity can be removed shortly prior to asphixiation etc. etc.190.56.115.105 (talk) 22:48, 31 August 2011 (UTC)

Seperatism...One foot tied to a ship, the other to the dock as the ship sails away. More dexterity, or perhaps weak roap.190.56.115.105 (talk) 22:56, 31 August 2011 (UTC)

I forgot ask. Can these misfortunes be purposely inflicted,, or must they be accidents?190.56.115.105 (talk) 23:00, 31 August 2011 (UTC)

Air embolism from diving or other causes, handled in a pressurized chamber. Wnt (talk) 23:18, 1 September 2011 (UTC)

Sound transmission and atmospheric pressure

So, there's no sound transmitted in a vacuum, or presumably in the near vacuum of space, while it transmits fine at both standard atmospheric pressures, and, AFAIK, at the reduced pressure atop Mount Everest. So:

1) At what pressure does it fail to transmit ?

2) Is it a sharp point or a gradual transition ?

3) Does the volume just decrease or is there a shift in frequency, too ? StuRat (talk) 08:16, 30 August 2011 (UTC)

1) Zero

2) Gradual

3) Volume decreases. Frequency is unchanged. Cuddlyable3 (talk) 08:58, 30 August 2011 (UTC)

In general, efficient sound transmission requires a wavelength that is much larger than the mean free path of the gas it is travelling through. Dragons flight (talk) 11:36, 30 August 2011 (UTC)

Are there any estimates on the mean free path of the smattering of molecules (1) on the moon and/or (2) in space? ←Baseball Bugs ^{What's up, Doc?} carrots→ 12:15, 30 August 2011 (UTC)

The article has a table of values at several orders of magnitude and the formula to calculate it at any arbitrary one you like. DMacks (talk) 14:42, 30 August 2011 (UTC)

Exactly why couldn't Jurassic Park happen?

This may sound like a crazy question, but precisely what park of the dinosaur cloning process from Jurassic Park is impossible? As far as I know, there really were dinosaurs. There really were mosquitoes. Some of those really were preserved in amber. That blood really could contain "Dino DNA". That DNA surely could really be cloned and implanted into an egg?

So basically, which of those is not true? Many thanks, Prokhorovka (talk) 10:55, 30 August 2011 (UTC)

To my surprise, this isn't discussed in the article Biological issues in Jurassic Park, which merely talks about inaccuracies in the representations of the dinosaurs. Well, one problem with resurrecting extinct species from DNA is the need for a suitable womb: it seems like it would be simpler for egg-laying species, but still doubtless very difficult to find a suitable surrogate. I suppose issues might include the yolk, the egg size, the temperature, and I don't know what else - perhaps something more fundamental than any of that. I also suspect the mosquitoes preserved in amber would not contain blood with DNA in it, since during formation amber is pressure cooked. Dinosaur#Soft_tissue_and_DNA says that we're not doing very well at finding any. Oh, and I found the section Jurassic_Park_(novel)#Biological_issues_and_accuracy, which is where the feasibility of getting the DNA is discussed.  Card Zero  (talk) 11:12, 30 August 2011 (UTC)

DNA at room temperature will break down spontaneously, even if you seal it away air tight. People can work with degraded DNA, but generally put a limit at 20-100 thousand years for getting any useful DNA under good conditions. Under absolutely ideal condition in very cold ice, you could perhaps reach one million years, but that's pretty much it. When you are talking about dinosaur age fossils, we simply don't expect there to be any DNA remaining. Maybe someone will come along and prove that wrong, but right now we don't know of any way to get dino DNA. Dragons flight (talk) 11:28, 30 August 2011 (UTC)

One of the big issues with the cloning as displayed in the film is the role that epigenetics plays. In nearly every example of cloning of multicellular organisms I can think of, the genetic material is hosted in a cell from the same, or very closely related, species; that is we take a cell and swap out the DNA for the DNA from a very closely related individual. For dinosaurs, the closest relatives (birds) are probably too distantly related for this to work effectively. --Jayron32 12:32, 30 August 2011 (UTC)

In principle, one might solve the host problem by bootstrapping. Use a currently-living animal (bird) as a host for a two-million-year-old extinct species' DNA; use that animal as a host for four-million-year-old exctinct species; and so forth. (This presumes a method to acquire, sequence, and synthesize suitable ancient DNA.) TenOfAllTrades(talk) 13:35, 30 August 2011 (UTC)

DNA is a very large molecule, and like most macromolecules, very unstable. It will eventually degrade even if only from background radiation. Estimates of eventual destruction of DNA like Dragon's Flight mentioned, is max 1 mya (thus definitely no dinosaurs, the last of which died out ~65 mya). Thus, claims of recovery of older DNA is sometimes viewed with suspicion, as they may be, in actuality, contamination of the samples with modern DNA or ancient microbial DNA. But who knows, there may be a way they actually survive that long through some unknown process. Endospores for example, are highly resistant, and may be enough protection. See example of 40-million year old DNA from an apparently still living bacterial spores recovered from a bee trapped in amber. Or claimed recoveries of 121 to 250 million (!) year old revived (!!!) spores of the archaean Halobacterium salinarum.

Anyway, in order to 'build' an organism you need the full DNA, and DNA even from specimens only a few thousand years old are usually only found in fragments or are not found at all. What DNA fragments that are recovered are like very complex blueprints with almost all of the pages missing, torn pages with no page numbers, ink stains, and written in a language we do not understand. Jurassic Park (at least the novel) had that premise. That only fragments were recovered, but were then somehow reconstructed by using DNA from extant animals to fill in the blanks. But gaps like that aren't really that easily filled, it must be sequenced, and there's the possibility that you could mix up DNA from two or more organisms from the samples if you're only getting fragments, and even just a minor mistake can mean one dead lizard with an arm growing out of its nose. And then yeah, there's the problem of actually implanting it in a viable egg and finding a surrogate mother.

We're probably centuries behind any technology like that, and even then, it's probably only feasible for recent extinctions in which we can recover intact DNA from. But I hope it's eventually possible. There are some research projects dedicated to this goal, particularly of the thylacine and mammoths. See Cloning#Cloning extinct and endangered species.

But we do retain ancient traces of our ancestors in our DNA. Unexpressed but still there, a sort of biological arsenal that manifests as vestigial traits (like gill slits in human embryos) or once in a while as (usually nonviable) mutations, specifically regressions(tails in human babies, scaly skin, etc.), but still important somewhat for adaptation and evolution. So... maybe we could go the other way around and reverse engineer birds? :P Though like Jayron said, birds are way too far down the ladder already.

But yeah, for dinosaurs... probably not ever. See Are Movies Science? Dinosaurs, Movies, and Reality from the University of California Museum of Paleontology -- Obsidi♠n Soul 13:33, 30 August 2011 (UTC)

So to summarise, it breaks down at the DNA stage since the amber would not in fact contain any or at best sufficient "Dino DNA". Even if this weren't true, going from cloned DNA to Dinosaur is fraught with difficulties. Thanks everyone, very interesting and comprehensive. Prokhorovka (talk) 19:14, 30 August 2011 (UTC)

In summary, too much frog DNA and your T-Rex croaks. ~AH1 ^(discuss!) 20:16, 31 August 2011 (UTC)

Errrrr

Sometimes when a person has to think for a period of time to produce an answer or continue a sentence, they make a noise like "errr", "errrm", "ummmm". Is this an innate or learned phenomenon? Does it vary between countries/cultures? Is there an article? --129.215.47.59 (talk) 15:04, 30 August 2011 (UTC)

Umm... Speech disfluency? Jebus989^✰ 15:11, 30 August 2011 (UTC)

And specifically see also Filler (linguistics), which discusses different fillers in different languages. They are considered by linguists to be meaningful parts of language — they mean, "I am still talking." I suspect (just guessing) that the use of them is innate, but the specific expression is certainly learned. --Mr.98 (talk) 15:28, 30 August 2011 (UTC)

Usage varies a lot between languages. I don't mean just the specific sounds. In Italian, if you quit making sound, other people will assume you've finished and start talking, even if you obviously haven't finished your thought or even sentence. So if you're not sure what to say next, you have to draw out the final vowel of the word you're on. Luckily, most Italian words do end in vowels. --Trovatore (talk) 18:04, 30 August 2011 (UTC)

If William ... SHATner were Italian, he'd never finish a ... SENTence. --Trovatore (talk) 19:00, 30 August 2011 (UTC)

See mental block and writer's block. Also this. ~AH1 ^(discuss!) 20:10, 31 August 2011 (UTC)

ET phone home ......... from L2?

• Lagrangian point

Currently several spacecrafts have been or are around the L2.

How do they phone home if the beautiful moon gets in the way?

Could they use long wave radio? Or do they need one or more communication satellites around the moon to relay the signal? -- Toytoy (talk) 15:13, 30 August 2011 (UTC)

Halo orbit--Aspro (talk) 15:29, 30 August 2011 (UTC)

Oops! My fault!

The moon could not block the spacecraft's view of earth if it is not exactly between the earth and the spacecraft. EVEN IF THE SPACECRAFT IS EXACTLY ON THE L2.

Even if the moon blocks the view, it is not large enough to fully block the whole earth. The earth and the spacecraft can still have visual contact.

The moon can only block the view of the earth if the spacecraft is within about 22000 km from the moon.

Earth ----- 60000 km -------> Moon --- 22000 km ---> Spacecraft -- Toytoy (talk) 15:32, 30 August 2011 (UTC)

(ec) The Moon's orbit is inclined to the plane of the Earth-Sun system (the ecliptic), which means that most of the time the Moon actually doesn't come between the Earth and L2 anyway—it passes above or below. Also, the satellites 'at' L2 (like WMAP) are actually usually in orbits around the L2 point, not stationary on it; the moon eclipsing such a satellite will be a rare occurrence, and could (in principle) be avoided entirely by careful tuning of the satellite's stationkeeping. Even if such temporary eclipses were unavoidable, most scientific satellites are capable of storing data on board for later transmission.

All that said, I've just looked at our articles on Lagrangian point and Moon, and noted that L2 is about 1.5 million km from Earth, while the Moon is just about 400,000 km from Earth; that puts the Moon 1.1 million km from L2, at its closest. The Moon's diameter is about 3000 km, so it actually doesn't cast a 'shadow' on Earth that's wide enough to completely obscure the L2 point; the Moon will only obscure a disc about 4000 km across as seen from L2. Since the Earth's diameter is about 12,000 km, there will always be spots on Earth that have a direct line of sight to L2, even when the Moon is in the worst possible place. TenOfAllTrades(talk) 15:42, 30 August 2011 (UTC)

Uh... The Op seems to believe that those spacecrafts are in the Earth-Moon L2 Lagrangian point. They are actually in the Sun-Earth L2 Lagrangian point. Dauto (talk) 16:10, 30 August 2011 (UTC)

In fact if you look at List of objects at Lagrangian points, only ARTEMIS is listed to ever have been in the Earth-Moon L2 point. Dauto (talk) 16:13, 30 August 2011 (UTC)

Evolution in animal thinking

From my understanding, humans had evolved from apes and primates. If this is the case, I have to questions.

1. If evolution from apes to proto-humans happened, why didn't all of the apes evolves into humans?
2. The process of this evolution also lead to evolution of our brains and how we think. If this is true, why don't other animals brains evolve to produce abstract thought?

Thanks! 64.229.155.210 (talk) 15:40, 30 August 2011 (UTC)

Q1 is the simplest: we didn't evolve from apes (at least not modern-day apes); we share a common ancestor. This ancestor more closely resembled a modern day "ape" than a modern human but the idea that half of all Gorillas suddenly became human, and the others were left scratching their heads and eating a banana is a common misconception. You can probably find more info at objections to evolution. For the details of why lineages diverge, see speciation. Jebus989^✰ 15:50, 30 August 2011 (UTC)

When told that the Spanish language evolved from Latin would you ask why in other regions Latin didn't evolve into Spanish? For instance, in the Italian peninsula Latin evolved into Italian which different from Spanish. Clearly the same way that one language can evolve into many languages over time, it is also to be expected that not all Apes should evolve into humans. Dauto (talk) 16:02, 30 August 2011 (UTC)

Well, while that may be the case, the only reason I asked is because wouldn't it be beneficial for all of our common ancestors to evolve into humans? While it wouldn't have been at first as humans haven't developed abstract thought thousands of years later, wouldn't evolution have it that the animals catch up to us? 64.229.155.210 (talk) 16:13, 30 August 2011 (UTC)

No, that's not how evolution works. Evolution is historic, just like the evolution of Spanish is historic, and cannot be replicated. Human evolution is one of a kind and will never happen again. Dauto (talk) 16:20, 30 August 2011 (UTC)

You have the misconception that evolution is a process of constant improvement. It isn't. Rather, it's a process of adaptation. If there is no environmental pressure for a population to evolve adaptations to give a survival advantage in that environment, then there is no need for the population to evolve. The thought development displayed by gorillas and dolphins, for example, is quite suited to their respective natural environments. ~Amatulić (talk) 16:33, 30 August 2011 (UTC)

Here's another way to think about this: if human beings kill off all species of primates other than themselves within the next 100 years or so (a not completely unrealistic possibility), will primates have all evolved into human beings? This highlights that when you say "evolved into" what you're really saying is "was outcompeted by." Homo sapiens sapiens (and its predecessor species) did out-compete most other large primates, as far as we know. Those that exist today are in niches that somehow were self-sufficient despite the fact that human beings took over in a major way. (And yet some species are highly endangered as a result of this competition, at the moment.) --Mr.98 (talk) 17:21, 30 August 2011 (UTC)

Since most other primates occupy arboreal niches (they live in trees), and we don't, we tend not to compete with each other. We more directly compete with large animals which live on the plains, and we've killed off many of those, such as the saber-toothed tiger and mammoth. StuRat (talk) 19:07, 30 August 2011 (UTC)

FWIW, we may have actually out-competed another sapient species. For a certain time period, modern Humans (Homo sapiens) and Neanderthals (Homo neanderthalensis) coexisted in Europe. Neanderthals went extinct, possibly out-competed or even directly decimated by interspecies warfare with Humans emerging from Africa. Though genetic studies have confirmed that a small percentage of Europeans and Asians still have traces of Neanderthal genes, also suggesting absorption to a certain degree as another possibility.-- Obsidi♠n Soul 19:25, 30 August 2011 (UTC)

The basic answer to the original question, I think, is that brain tissue requires a tremendous amount of energy to operate. Homo sapiens evolved in a region of the east African savannah where large amounts of rich food were available to animals with the lifestyle of our ancestors. For other species, the costs of very large brains, in terms of energy needs and the anatomical problems produced by large head size, appear to have exceeded the benefit. This is a speculative answer, of course, but I believe it follows the current mainstream line of thought. Looie496 (talk) 21:23, 30 August 2011 (UTC)

Few creationists find it objectionable that we're no longer bacteria. Imagine Reason (talk) 00:14, 31 August 2011 (UTC)

Standard model vs GR

Is the treatment of mass in the standard model of particle physics consistent with general relativity? If not, does it mean that only one model is right? --41.135.50.237 (talk) 17:58, 30 August 2011 (UTC)

It is not inconsistent. Dauto (talk) 18:26, 30 August 2011 (UTC)

The Dirac Equation expresses the wave function for a general relativistic particle. You should be pretty familiar with quantum mechanics before you try to understand the Dirac equation; it's somewhat complex. The relativistic compensations are expressed as the matrices α and β in our article's presentation; otherwise, as you undoubtedly instantly recognized, it's nothing more than the standard Schrodinger equation. Our article proceeds to translate the Dirac equation into a more generalized coordinate scheme; but this is not really useful for any practical purpose. I highly recommend the Shankar and the Griffiths' textbooks; they are more comprehensible than Dirac's original work. Nimur (talk) 22:00, 30 August 2011 (UTC)

Just making sure the information above is clear, the Dirac equation is used to describe relativistic particles that have spin 1/2. Particles with spins other than 1/2 are described by different equations. Dauto (talk) 17:21, 31 August 2011 (UTC)

Mammals physically capable of sticking their head up their bottom?

Do any mammals exist who are capable of sticking their head up their bottom, putting things as civily as is possible? My friend wants to know. Obviously it doesn't have to go all the way. My personal guess is that a duck billed platypus could at least touch their bottom with their beak, but I don't have one at hand to check (and I suspect even if I did it wouldn't cooperate, no matter how persuasive I was) Egg Centric 18:13, 30 August 2011 (UTC)

With or without assistance? 76.254.20.205 (talk) 18:28, 30 August 2011 (UTC)

You mean poppers? The animal would need to have a very small cranial-rectal ratio, so either a tiny head or a very broad rectum. It would need to have a great degree of control over the muscles in that region, or else it might suffocate or strangle itself, leaving a toroidal corpse. It would not necessarily require a long neck. Rabbits are capable of eating pellets directly from their own anuses, so that level of flexibility is not unheard of in mammals, even stocky, short-necked ones. Mammals' large skull size would make the feat difficult. (It is comparatively easy to imagine a ratite or reptile stuffing its smaller head into its relatively large cloaca.) The only insurmountable problem is ventilation. With the head completely enclosed, there would be no way for the animal to breathe. Of course, if you're assuming human assistance, and if you don't demand that the animal survive the procedure, then there's no problem at all. Any small mammal could, under heavy sedation, be forced into this configuration. I wouldn't be surprised if some taxidermist hadn't created such a specimen at some point, as a tacky novelty. LANTZY^TALK 19:25, 30 August 2011 (UTC)

I would expect heads to be much bigger than rectums, in all mammals. Perhaps an animal with a long, narrow snout, like an anteater, could jam that up there, if the motivation struck. StuRat (talk) 19:01, 30 August 2011 (UTC)

Ok so ignore the insertion issue...

Ignoring the head/rectum problem, what mammals can get their head down to their anus comfortably? Egg Centric 21:52, 30 August 2011 (UTC)

Let's see. Cats and dogs certainly can, and routinely do. And rabbits, as I mentioned. Probably most rodents can. It might be easier to come up with a list of mammals that almost certainly can't accomplish the feat: elephants, manatees, ungulates, hominids... LANTZY^TALK 22:42, 30 August 2011 (UTC)

I'm actually curious what the "head/rectum problem" is? lol... Vespine (talk) 23:54, 30 August 2011 (UTC)

Ok, I wrote that before reading the comments immediately above! Forget I asked, and in fact I wish I hadn't! lol Vespine (talk) 23:56, 30 August 2011 (UTC)

Could be that the OP was told he/she had his/her head up his/her ass. 67.169.177.176 (talk) 05:44, 31 August 2011 (UTC)

Helium ionization detector

Dear all, kindly note that,the article Helium ionization detector, the content is not correct. Most of the HIDs not using any radio active substances. This is with reference to VICI detectors. Please note that this is a nondestructive detector. Please update the article if i am correct... — Preceding unsigned comment added by 89.211.137.39 (talk) 18:22, 30 August 2011 (UTC)

Can you provide any reliable sources to prove that ? Also note that the article's talk page is the best place for such comments. StuRat (talk) 18:57, 30 August 2011 (UTC)

Chocolate bars

Moved from WP:HD#Chocolate bars. —Akrabbim^talk 18:59, 30 August 2011 (UTC)

On BBC News there is a title on EATING CHOCOLATE saying that for the hearth is good to eat one CHOCOLATE BAR a day but on WIKIPEDIA I could not find anywhere how much is the weight of one bar of chocolate, so please help me to understand, many thanks.- — Preceding unsigned comment added by 79.42.125.144 (talk) 16:51, 30 August 2011 (UTC)

Have you tried Wikipedia's Reference Desk? They specialize in knowledge questions and will try to answer just about any question in the universe (except how to use Wikipedia, since that is what this Help Desk is for). Just follow the link, select the relevant section, and ask away. I hope this helps. – ukexpat (talk) 17:00, 30 August 2011 (UTC)

(edit conflict)Wikipedia does not give medical advice, but if you look again at the BBC news item you will see that it gives a link to the BMJ report so you can read it for yourself. - David Biddulph (talk) 17:03, 30 August 2011 (UTC)

I have read many of the peer-reviewed journal articles on the topic. They are referring to the nasty bitter dark cocoa powder, not the candy you buy at the store. However, people WANT to hear that eating candy is healthy, so the news purposely implies that you should run out and stuff your head full of chocolate bars. Naturally, Wikipedia shouldn't repeat such misinformation. -- kainaw™ 17:16, 30 August 2011 (UTC)

Please continue this on the Reference Desk where it belongs. ---— Gadget850 (Ed) ^talk 18:08, 30 August 2011 (UTC)

Some people (like me) like the nasty bitter powdery stuff better than the candy. Dauto (talk) 19:12, 30 August 2011 (UTC)

I haven't read any of those, but I read the BBC article, which says they "compared the risk to the brain and heart in groups of people who reported eating low levels of chocolate, fewer than two bars per week, with those eating high levels - more than two bars per week." The word reported there (and the word bar) implies to me that in this study they are in fact talking about the delicious kind of chocolate, which people eat by choice, rather than recruiting test subjects and feeding them spoonfuls of cocoa powder. They go on from this to give what struck me as some very odd advice: although they apparently found eating chocolate to be (statistically) good for the heart, they didn't advise anybody to start eating it. I have to wonder whether they would have advised the same caution if they had made the same discovery about something foul-tasting and fat-free. It seems most unscientific. Presumably this is because those genetically predisposed to it would be more likely to get Type 2 diabetes if they started eating more sugary snacks: but why advise "those who do eat chocolate" to eat "small amounts on a regular basis"? Why not "large amounts on a regular basis", since that's where the study showed the benefit is?  Card Zero  (talk) 19:39, 30 August 2011 (UTC)

A chocolate bar can be healthy, in moderation, provided:

1) It doesn't contain any added trans-fats, like partially hydrogenated vegetable oils.

2) It contains a high cocao content, on the order of 75-85%. (Note that this means it won't be very sweet, since it can't be more than 15%-25% sugar, and cocao is bitter.)

If the bar isn't labelled for these items, don't eat it. StuRat (talk) 19:17, 30 August 2011 (UTC)

Thanks Dr. StuRat! We all appreciate your medical advice. --Mr.98 (talk) 20:07, 30 August 2011 (UTC)

You're welcome, but, of course, dietary recommendations are not medical advice. StuRat (talk) 20:08, 30 August 2011 (UTC)

Statements about what is healthy and strong statements about what one should or shouldn't eat are not medical advice? Seems to be riding an awfully fine line there, especially for someone who has not cited anything to back up their assertions. --Mr.98 (talk) 20:47, 30 August 2011 (UTC)

As you know, medical advice is that which seeks to diagnose and treat a specific medical condition. And whether one cite's sources is quite irrelevant to whether something is medical advice. If I don't cite sources on how to build a bicycle, does that make it medical advice ? StuRat (talk) 21:07, 30 August 2011 (UTC)

Surely you can't be telling me that obesity is not a medical condition (a medical condition whose primary treatment IS dietary). Googlemeister (talk) 12:53, 31 August 2011 (UTC)

First, there was no mention of obesity in this question. Secondly, I wouldn't consider obesity a medical condition as long as it still can be handled by diet alone, until it becomes morbid obesity of a degree requiring medical intervention, like gastric bypass surgery. And don't call me Shirley. :-) StuRat (talk) 02:57, 1 September 2011 (UTC)

Well if you don't cite sources, your instructions could result in anything, for all we know. Perhaps some abomination of a medical chocolate bicycle.  Card Zero  (talk) 21:32, 30 August 2011 (UTC)

It's a meta-analysis of seven studies:

Levels of chocolate consumption included the consumption of chocolate bars, chocolate drinks, and chocolate snacks (including confectionery, biscuits, desserts, nutritional supplements, and candy bars). All the studies reported chocolate consumption in a different manner: three categories (never, once a month to less than once a week, and once a week or more); two categories (less than once a week, once a week or more); four categories (never, less than once a month to less than once a week, once a week, and more than once a week); thirds of cacao intake; five categories (none, 1–3/month, 1–2/week, 3–6/week, and >1/day); fourths of chocolate consumption (ranging from 1.7 g/day to 7.5 g/day); and four categories (none, 1–3/month, 1–4/week, and >5/week). Considering the heterogeneity in reporting and measuring chocolate consumption, we decided to use the lowest and highest categories to measure the association of chocolate consumption with cardiometabolic disorders.

I'm not sure which of those "manners of reporting" the BBC picked up on when it said "more than two bars per week". I suspect they in fact were referring to one of the "how often do you eat chocolate products?" studies, rather than the one which specified (quite small) weights, and that's why the BBC didn't specify a size of a bar.  Card Zero  (talk) 20:11, 30 August 2011 (UTC)

I think the question was simply "how much does a chocolate bar weigh?" perhaps you could go to a store and read the wrapping.190.148.132.191 (talk) 23:50, 30 August 2011 (UTC)

Chocolate bars come in a wide variety of sizes. StuRat (talk) 05:53, 31 August 2011 (UTC)

I think these studies are still at the levels of correlations and vague assertions like "polyphenols are good for you" (an offshoot of the even vaguer and less well-founded belief that "antioxidants are good for you"). It's a happy finding that chocolate eaters seem to have some health advantages, but I don't think anyone has ruled out e.g. that people who can regularly afford chocolate have better health coverage, or have a less stressed attitude, or avoid potato chips, or any of a thousand explanations other than a longevity chemical in the chocolate. Wnt (talk) 00:19, 31 August 2011 (UTC)

In the US, at least, chocolate bars are quite inexpensive. StuRat (talk) 05:53, 31 August 2011 (UTC)

I'm adding a third thing you should look for in your chocolate bar:

3) It shouldn't contain milk products (that is, no milk chocolate). In addition to this meaning it would have less cacao, milk also seems to somehow cancel the anti-oxidant benefits. This also means you shouldn't consume the chocolate along with milk products. StuRat (talk) 05:56, 31 August 2011 (UTC)

And, to go along with your chocolate bar, I've broken off a little section of an article for you to digest: Types_of_chocolate#Dark_chocolate_health_benefits. StuRat (talk) 06:03, 31 August 2011 (UTC)

Stu, you haven't read the meta-analysis have you? Regardless of what you think the results should have been, it actually found that the benefit didn't specifically attach only to dark chocolate, or high cocoa solids, or chocolate taken without milk. This means that the benefit was probably not due to anti-oxidants (which are blocked by milk), or polyphenols. The effect was present for people who ate chocolate biscuits, or chocolate-covered toffee, or milk chocolate, or white chocolate. So it doesn't actually matter what weight of chocolate you ate, because it isn't really an effect from a dose of some substance. It seems to be a more fundamental benefit of regularly eating something nice which makes people feel happy and relaxed, regardless of the apparent health drawbacks of sugar and fat. If I were to step beyond the reported stuff, I would also say that regularly eating chocolatey things probably means you aren't dieting or worrying too much about food, which is healthier and less stressful. 86.163.211.187 (talk) 14:48, 31 August 2011 (UTC)

Yes, but I'm expanding beyond that article to describe how to best take advantage of all the benefits of chocolate, including the anti-oxidants. StuRat (talk) 03:03, 1 September 2011 (UTC)

Well, as described at Antioxidant, the idea of antioxidant supplements as some kind of cure-all is really not holding up - it never really had that much evidence supporting it beyond wishful thinking. Wnt (talk) 00:23, 4 September 2011 (UTC)

I remember reading somewhere that the beneficial cardiac effects of chocolate are due to stearic acid. 76.254.20.205 (talk) 19:08, 31 August 2011 (UTC)

Since women have longer life expectancy, could this simply be the case that women are more likely to eat chocolate regularly? Anonymous.translator (talk) 00:33, 1 September 2011 (UTC)

Self-reports are extremely inaccurate, and observational studies can usually only tell correlation, not causation. I wouldn't trust the results of this study at all. To me it was a waste of money and resources. Imagine Reason (talk) 03:35, 1 September 2011 (UTC)

I wouldn't call it a waste of time and money. You can't tell which way the train went by looking at the track. But you have a lot better odds of figuring out where the next one is headed if you know where the tracks are. Wnt (talk) 23:14, 1 September 2011 (UTC)

Io and Pulsars.

Around 1610 A.D it was noticed that the orbit of Io Around Jupiter changed in time depending on where the earth was around the Sun . I think I may be able to understand this , its a "time dilation" effect.

However I do not understand why Pulsars keep perfect time in relation to us moving around the Sun or indeed the galactic center. — Preceding unsigned comment added by 92.30.154.8 (talk) 23:30, 30 August 2011 (UTC)

I don't think it's a "time dilation" thing at all, it's a simple "speed of light" thing.. When the earth is closest to Jupiter (893 million km ), say (from earth) you observe IO crosses Jupiter at exactly 12:00 (hypothetically), when the earth is furthest away from Jupiter (964 million km ), you still expect Io to cross at exactly 12:00, but instead you observe it crosses at 12:03. This was puzzling until they worked out that light took an extra 3 minutes to cross the extra distance. As for pulsars, they weren't discovered until 1967, so i think speed of light was already figured into the observations as a matter of course, i don't think they're immune from the extra time it takes to reach the earth depending where we are in orbit around the sun, but there was nothing "surprising" about it by that stege. Vespine (talk) 23:46, 30 August 2011 (UTC)

In 1610 Jupiter's moon Io had only just been reported by Galileo. The modern value for its orbital period is 42.459 306 86 hours, see Io (moon), which resonates with the orbits of Europa and Ganymede, see Io (moon)#Orbit and rotation. What source claims an observation of a time dilation effect in 1610? Wikipedia has an article about Pulsars that cites a source for some pulsars having rates as regular as an atomic clock and describes studies of their regularity such as Pulsar timing array projects. Cuddlyable3 (talk) 00:04, 31 August 2011 (UTC)

See speed of light#Astronomical measurements. It describes quantitative measurement of the speed of light by observations of the periods of Jupiter's moons, but not until 1675 by Ole Christensen Rømer. (Actually we have a whole article Rømer's determination of the speed of light. But measuring it in 1675 is still quite impressive! Wnt (talk) 00:13, 31 August 2011 (UTC)

It's not a time dilation effect. It's a Doppler effect. Dauto (talk) 01:01, 31 August 2011 (UTC)

Not at all. The Doppler effect is caused by the relative velocity between two objects; the effect discussed here depends on their distance. It is strongest between those times when the distance between Earth and Io/Jupiter is maximum and minimum. At these times, the velocity is perpendicular to the line joining them, hence the Doppler effect is zero. In principle, the effect should be present in Pulsar data as a modulation of the arrival time of pulses; whether it matters for the measurements depends on the measurement method. Because pulsar periods are short, they can be measured over a short time span, hence there is no need to observe or predict pulse timing over the course of an entire year. In case it does matter, one would take it out of the raw data - scientific work uses reduced data where effects that are well known but unimportant to the scientific question are corrected for. --Wrongfilter (talk) 06:51, 31 August 2011 (UTC)

It is a Doppler effect. The Doppler effect shifts all frequencies equally—not just the frequency of the light but also the orbital frequency of the moons. When Earth is moving away from Jupiter the observed orbital period is longer, and that adds up to an overall delay of the eclipse times when Earth is farthest from Jupiter compared to when it's closest. There are other ways of looking at it, of course. The same thing happens to pulsar signals. -- BenRG (talk) 09:56, 31 August 2011 (UTC)

There is a Doppler effect due to Earth's motion about the Sun, but that was definitely unobservable in the 17th century. The orbital speed of the Earth is 30 km/s. That modulates the observed orbital period by a factor v/c = 0.0001. In Io's orbital period that is presumably unobservable even today; it may be in pulsar periods. The effect that Ole Romer observed is due to the fact that light from Io has to travel a further 2 AU when Jupiter is in conjunction with the Sun compared to when it is in opposition. That effect gives a difference of about 16 minutes, not in the period, to be precise, but in the phase of the orbit. --Wrongfilter (talk) 10:16, 31 August 2011 (UTC)

This shift in the phase is nothing more than the accumulation of the Doppler effect over a period of six months. It is a Doppler effect. Dauto (talk) 14:17, 31 August 2011 (UTC)

Ah, okay, now I see what you are talking about, thanks for the clarification. I was slightly worried and confused about having to distinguish between the phase and the period. So, the Doppler effect itself is unobservable, but its integrated effect is. The integration also explains the phase shift between Romer's observation and the instantaneous Doppler effect. There is an interesting parallel to the cosmological redshift, which can also be constructed as an integrated Doppler effect. --Wrongfilter (talk) 14:29, 31 August 2011 (UTC)

Hang on, is saying doppler effect the same as my 1st answer? I don't think "red shift" or anything "relative" has anything to do with what was described back then. Vespine (talk) 00:37, 1 September 2011 (UTC)

Yes, it is the same thing. The 17 minute delay is given by the integrated Doppler effect over six months. Dauto (talk) 13:09, 1 September 2011 (UTC)

Well, yes, the effect can be thought of as a generalised Doppler effect if you think of the rotation as a "wave", but this rather unusual interpretation was certainly not used centuries before Doppler was born and is not really helpful for a first understanding of the effect when the explanation of extra distance is so much simpler. Dbfirs 23:02, 1 September 2011 (UTC)

August 31

Superfluid

Is a superfluid a type of fluid or is it considered an entirely separate state of matter? Or is the difference decided by the definition of fluid that you subscribe to? Thanks. asyndeton talk 01:30, 31 August 2011 (UTC)

Does Superfluid answer any of your questions? --Jayron32 01:39, 31 August 2011 (UTC)

Fluid is not a state of matter. It is a set of states that includes gases, liquids, plasma, anything that flows. Dauto (talk) 02:19, 31 August 2011 (UTC)

Of course, the entire concept of "state of matter" is still a somewhat arbitrary (if very useful) classification scheme. How various states of matter may be classified and delineated isn't written in stone, and different models will have different schema to organize various states. --Jayron32 02:31, 31 August 2011 (UTC)

One small point Dauto. You missed out solids, which given certain scale/conditions can also be fluid.190.56.18.189 (talk) 12:30, 31 August 2011 (UTC)

Graphite is an example of a fluidic solid, if a shear stress is applied to the graphene sheets, they act as molecules in a liquid - they flow past one another, without seperating. This is why graphite is a lubricating agent. Plasmic Physics (talk) 12:59, 31 August 2011 (UTC)

Ice can also act as a fluid. Whoop whoop pull up ^{Bitching Betty | Averted crashes} 20:45, 31 August 2011 (UTC)

No, glaciers are an example of a rheid, i.e. a solid that deforms and flows when a very large shear stress is applied. A proper fluid is a substance that continues to flows even as the applied force approaches zero. Dragons flight (talk) 05:41, 1 September 2011 (UTC)

Different states of matter or different phases can be rigorously defined using the analytic properties of the free energy function. Two different thermodynamic states are in different phases if the analytic continuation of the free energy function in the neighborhood of one state to a neighborhood containing the other state does not yield the free energy function in that other state. Count Iblis (talk) 15:27, 31 August 2011 (UTC)

Translating into English what Count Iblis is saying: There are analytical ways to define (at least for most pure substances) differing states of matter by looking at the relationships between various components of the "free energy function", i.e. free energy, entropy, and enthalpy. Changes in state will result in changes of this relationship. That is rigorously true. But that doesn't work well in some types of matter which, like glass, which doesn't show clearly defined transitions from one state to another. --Jayron32 19:55, 31 August 2011 (UTC)

Exactness of astronomy in 1602

In the Kunyu Wanguo Quantu of 1602, I found a table of some orbital periods which amazed me with its precision, before the use of the telescope: For moon, earth (or sun, in the heliocentric view) and mars, the values lie within ±0.001% of the modern values. The worst, Saturn, is still within 0.2%. (See table at zh:Wikipedia:詢問處#1602年的「刻」). The 8th sphere, the "zodiacal heaven", is indicated as rotating with a period of 7000 years ("from west to east", just as all other spheres.) At first I thought that referred to the axial precession. But that was, according to our article, already known to be greater than 25000 years in Hipparchus' time. Was Matteo Ricci (or his sources) really that far off on that, or could he have meant something else? — Sebastian 08:14, 31 August 2011 (UTC)

I can't answer your main question, but yes, those sorts of measurements had been made extremely precisely by 1602, esp. by astronomers such as Tycho Brahe. His Uraniborg and Stjerneborg give a good idea of what the best astronomical instruments money could buy at that time. It was difficult and laborious observational work that required extremely good eyesight. I suspect (though I don't know this for a fact) that whatever measurements Ricci was using were derived from Brahe, whose work would have been well known, and well-regarded by Jesuits, by that point. (And despite their later backwards reputation, it probably should be recalled that the Catholic Church, and Jesuit order in particular, contained most of the best astronomers of the 16th and 17th centuries, and were certainly the largest patrons of astronomy at that time.) --Mr.98 (talk) 14:24, 31 August 2011 (UTC)

It's also the case that if one has even a single accurate observation from a very long time ago that can be accurately timed (say, an observation that a particular planet was in a given location during a particular solar eclipse), one can calculate the planet's orbital period to a very precise value (because effectively you have measured tens or hundreds of periods). {The poster formerly known as 87.81.230.195} 90.197.66.40 (talk) 16:50, 31 August 2011 (UTC)

Thank you for both your helpful and interesting replies, number guys! I too am impressed by the SJ's scientific patronage and scholarship. Just as an aside, it is fitting that they chose to translate "Catholicism" by 天主教 - "heaven-ruler-religion". Back to the subject of the forum; anyone has an idea what Brahe or the astronomers of his day could have meant by the 7000 year period? — Sebastian 18:28, 31 August 2011 (UTC)

According to Milankovitch cycles, "The combined effect of the two precessions leads to a 21,000-year period between the seasons and the orbit." There are four seasons and 21,000/4 = 7,000. However, that alone doesn't say much. ~AH1 ^(discuss!) 19:45, 31 August 2011 (UTC)

Could be something else in Earth's cycles, unless of course this 7,000 is an arbitrary number. ~AH1 ^(discuss!) 19:47, 31 August 2011 (UTC)

Chemistry XII Grade

Q1. Why is it so that all the Top elements in Group behave differently from its other family members in a periodic table? (OR) Why is it so that first element of each group shows different behaviour fro the rest of its group members?— Preceding unsigned comment added by 116.203.34.20 (talk) 10:38, 31 August 2011 (UTC)

Q1. Explain why is it so that first element of each group behave differently from its remaining members of the Group? — Preceding unsigned comment added by 116.203.34.20 (talk) 10:39, 31 August 2011 (UTC)

Q. What will be the structure of P2O5H2? — Preceding unsigned comment added by 116.203.34.20 (talk) 10:42, 31 August 2011 (UTC)

"If your question is homework, show that you have attempted an answer first, and we will try to help you past the stuck point. If you don't show an effort, you probably won't get help. The reference desk will not do your homework for you." Plasmic Physics (talk) 11:53, 31 August 2011 (UTC)

Wikipedia has an article about the Periodic table and it is also described in the Wikibook "General Chemistry". Cuddlyable3 (talk) 18:13, 31 August 2011 (UTC)

You can look in Phosphite for P₂O₅H₂^2- as a Pyrophosphite ion, but if there is no charge, I don't know what this is. Graeme Bartlett (talk) 10:47, 1 September 2011 (UTC)

You really should come back with what you know and don't know as the policy says. But in the interest of general chaos I'll mention that surprisingly to me, our article on hypervalent bonding seems to downplay the familiar old explanation that d-orbitals from the lower periods are involved in that process... Wnt (talk) 23:10, 1 September 2011 (UTC)

It isn't d-orbitals from the lower periods, it is d-orbitals from the same period. Phosphorus's hypervalency comes from hybridization of the 3s, 3p, and 3d orbitals on the valence level of the element. There are no lower d-orbitals; 3d is the smallest d orbital. --Jayron32 02:37, 2 September 2011 (UTC)

You might want to discuss that at the article, which seems to take a different view. When I said "lower periods" I meant S or Se rather than O, P rather than N and so on - sorry for any confusion. Wnt (talk) 09:20, 2 September 2011 (UTC)

zebras

Are zebras considered a game animal and hunted for their meat in Africa (by humans, not lions)? Googlemeister (talk) 14:54, 31 August 2011 (UTC)

If only there were an encyclopedia around. Zebra. --LarryMac | Talk 14:57, 31 August 2011 (UTC)

The rule of thumb is: If it's edible and legal (some times even if it's illegal) than someone in the world is eating it. Dauto (talk) 15:05, 31 August 2011 (UTC)

If your here in the UK you can easily try some. [3] - I think subjects about food should be banned from this Ref Desk as it encourages my to raid the fridge each time--Aspro (talk) 15:26, 31 August 2011 (UTC)

Regardless of any ethical issues, I don't think I could bring myself to buy anything from a site with such poor spelling: "biting of a mans arm"; "like Horse meat its sweater than Beef". *Shudder* AndrewWTaylor (talk) 17:02, 31 August 2011 (UTC)

What ethical issue? Dauto (talk) 18:51, 31 August 2011 (UTC)

Ethics aren't black and white. Googlemeister (talk) 19:22, 31 August 2011 (UTC)

Also, that comment smacks of discrimination against dyslexics.--Aspro (talk) 19:26, 31 August 2011 (UTC)

AndrewWTaylor does society a service by setting a standard that preserves the beauty of our precious English language and encourages the less literate among us to improve themselves. Cuddlyable3 (talk) 12:31, 1 September 2011 (UTC)

Dyslexia is a genetic attribute that confers talents that non-dyslexic people often lack (look up some of the more modern research into this). Do you expect the colour blind to learn how to see colours? Would you advocate plastic surgery for all those that don't meet your notions of beauty? All that comment does is show prejudice born out of ignorance. Indeed, society looses much talent when dyslexics get excluded from the education system. Hardly the sort of service that an any enlightened society should be proud of -don't ya think?. --Aspro (talk) 13:51, 1 September 2011 (UTC)--Aspro (talk) 13:51, 1 September 2011 (UTC)

I don't see the reference to dislexia in the statement, would anyone care to point it out? Plasmic Physics (talk) 22:17, 1 September 2011 (UTC)

A Person with dyslexia who publishes a web site is just as capable of hiring a proofreader as anyone else. thx1138 (talk) 16:42, 2 September 2011 (UTC)

Also consider Lady Meux who rode around London in a carriage hauled by a pair of zebra. Ok, maybe not relavent but quite interesting anyway. Alansplodge (talk) 00:36, 1 September 2011 (UTC)

There's mention of an extinct zebra subspecies. I wonder if anyone has discussed the possibility of cloning? ←Baseball Bugs ^{What's up, Doc?} carrots→ 12:38, 1 September 2011 (UTC)

The Quagga article mentions that they got the DNA for that in 1984, but the technology to do anything with it is not there yet for cloning it. Googlemeister (talk) 13:19, 1 September 2011 (UTC)

So at least it's on the table. I recall similar discussions about the wooly mammoth. I don't know if anything every came of that. ←Baseball Bugs ^{What's up, Doc?} carrots→ 14:11, 1 September 2011 (UTC)

Restoring a species that way is almost certainly possible but very certainly difficult. It's one thing to take an intact living nucleus and slip it into an egg cell and after 174 attempts you get a live sheep. It's another thing altogether to take scraps of DNA ten thousand base pairs long, splice them together perfectly into a fully known genome sequence without any errors or gaps anywhere (which still hasn't really been done even with humans AFAIK), then package that properly into authentic chromatin with histones and centromeres and telomeres and proper origins of replication and DNA methylation to suppress all the endogenous retroviruses from getting rambunctious, and who knows how many other special structures. I mean, it's a project that can and should be done, which even might become routine, but it's a moon shot, something that takes a lot of people working together perfectly doing things that have never been done before.

In practice, I suspect that a bastardized approach might be more likely to prevail in the foreseeable future - namely, identifying the crucial genetic differences that made a wooly mammoth or a quagga look distinctive, and splicing them in gene by gene until you have something that plausibly simulates those animals. But that's just a cosmetic operation and it shouldn't be confused with a genuine resurrection of the species. Still, doing that depends on the quality of palentological samples available (to see which genes were under positive selection or correlated with visible changes in the species' appearance), and the overall level of knowledge about what various genes (or their orthologues) do in related species. I'm not sure it will be that much easier. Wnt (talk) 23:01, 1 September 2011 (UTC)

potatoes, catalase, hydrogen peroxide...and an oven!

I had to do the ol' potato homogenate + hydrogen peroxide experiment in order to determine the rate of activity of catalase. My variable was heating the homogenate in an oven that was set to 80° C. Unfortunately, I didn't have a thermometer, so I left it in there for what seemed a good long time (about 15 or 20 minutes) for it to reach that temperature.

I don't know how standard this experiment is, but I had specimen tubes, sealed with rubber bungs, with thin tubes inside the bungs. When inverted the reaction causes liquid to drip from the narrow tubes.

I did four replicates with the heated potato and during any counting downtime I had the homogenate back in the oven to keep warm. The counts for my first replicate was in the teens. For each following replicate the mean count declined, until by the last replicate there were no drips, for 3 minutes out of 4.

My question is: what is responsible for the reaction declining so much, over a period of only 20 minutes, with all other conditions the same?

I have two ideas: Was the homogenate not at 80° for the first replicate? Was it at a lower temperature that still allowed catalytic function, and then reach or get closer to 80° while it was waiting in the oven for the other replicates to finish? And obviously, the hotter it got, the less it worked on the hydrogen peroxide.

My other idea is that the homogenate was at 80° for all of the replicates, but that the loss of enzyme function was progressive the longer it was heated. Would this have been because more enzyme succumbed to the effect of temperature (enzyme quantity) or because the enzyme molecules themselves progressively broke down, having slowed down first (enzyme quality)?

What do you think? 82.71.20.194 (talk) 17:47, 31 August 2011 (UTC)

Probably the first; enzymes are very peculiar things, and even a small change in their structure can lead to a complete cessation of function. In otherwords, an individual enzyme molecule doesn't progress from "working real well" to "sorta working" to "not working at all", there is no quality continuum. The individual molecule gets broken, and just stops working, in most cases. So, I would guess that the decrease in activity would be due almost entirely to having a lower and lower concentration of working molecules. --Jayron32 19:50, 31 August 2011 (UTC)

Okay, that seems to make a lot of sense. Do you think that the homogenate was at 80° for each replicate, and that more enzymes succumbed to that heat the longer it was heated, or do you think that perhaps the temperature of the homogenate was still increasing as the experiment progressed through the replicates? I'd like to think that I got the basic thing right of heating my homogenate to 80° and pretty much keeping it there, but I have to admit it almost means that some of the catalase molecules had to be 'tougher' than others in order to have kept their structure for longer at the same temperature. Of course, it's not a case of reaching a certain low-ish temperature and bang, all the catalase collapses, so there would have to be some degree of progression...but I don't know how much. Hmmmm. 82.71.20.194 (talk) 20:10, 31 August 2011 (UTC)

It's tough to say. On the one hand, decomposition reactions probably have relatively simple first order kinetics, and are likely nearly instantaneous; i.e. when the molecule gets to a certain temperature, bonds break and the molecule denatures almost instantaneously. OTOH, if you are dealing with a potato in an oven which is right at the denaturation temperature, a potato is a pretty lousy conductor of heat, so you will probably have a temperature gradient, and it may take a long time for the catalase near the center of the potato to deactivate; which is why you see the time dependence in your experiment; i.e. even if it is 80 degrees on the outside of the potato, it takes some considerable time for the middle to get to 80. So, your idea that the initial potato mash (I assume that's what you mean by homogenate) wasn't all at 80 degrees, and the longer oven times only caused the heat to more evenly distribute. A possible way to test this would be to try two parallel experiments: one with the potato homogenate in a beaker, and one with the same amount spread out in a very thin layer, say on a petri dish. If the one in the beaker "lasts" longer, you know it is probably the heating time which having an effect, since the sample in the petri dish, with a larger surface area and being more "spread out" should reach the equilibrium temperature faster. --Jayron32 01:16, 1 September 2011 (UTC)

I'm not very clear on how you did the experiment - I assume you added the hydrogen peroxide after the period of heating so that it wasn't depleted before you measured the drips? In which case you should be able to measure denaturation as it happens (I assume that "homogenate" means you're not talking about lumps of potato and heating was fairly rapid and uniform). From a lab writeup like [4] I assume the potato catalase denatures at some fairly low temperature like you'd expect, so this seems quite plausible. Wnt (talk) 22:49, 1 September 2011 (UTC)

Name of the selenium analogue of greigite

How is the selenium analogue of greigite called? How are its the magnetic properties compared to greigite and magnetit?--79.119.214.150 (talk) 20:14, 31 August 2011 (UTC)

May be Ferroselite is what you're looking for? Dauto (talk) 20:42, 31 August 2011 (UTC)

If so, it is said to become magnetic when heated, while the monoselenide (FeSe) is ferromagnetic. Mikenorton (talk) 20:54, 31 August 2011 (UTC)

According to [5] Fe3Se4 is ferromagnetic below 314K. According to [6] there is a broad "FeSe" composition that doesn't adhere very precisely to stoichiometry, which perhaps explains why I didn't immediately come up with a different name for it than other somewhat different Fe/Se ratios. But this is not my field, just the outcome of a real quick search to try to goad the people who know into explaining this to us. ;) Wnt (talk) 09:16, 2 September 2011 (UTC)

Artificial gonads

Is it possible to create an artificial gonad in vitro using tissue engineering? Whoop whoop pull up ^{Bitching Betty | Averted crashes} 21:01, 31 August 2011 (UTC)

Possible "now" or possible "in principle"? I don't really have a very good reason for my answers but I'd say no and yes respectively. Vespine (talk) 22:09, 31 August 2011 (UTC)

How come? Whoop whoop pull up ^{Bitching Betty | Averted crashes} 23:00, 31 August 2011 (UTC)

Come on, throw us a bone, how come what? Vespine (talk) 00:06, 1 September 2011 (UTC)

Actually, come to think of it, I think my answer is for male gonads, I think female gonads would present extra challenges which might possibly preclude the possibility of engineering functional female gonads... Testicles are just sperm factories, if we've ALREADY engineered functional livers and pancreases I can't see why testicles couldn't eventually be engineered. But sorry, these ARE just guesses, I hope someone who actually KNOWS something about this subject can chime in. Vespine (talk) 00:14, 1 September 2011 (UTC)

You would need human tissue to start with. You'd need male tissue for testicles, since only men have Y chromosomes. You'd probably want female tissue for ovaries, as only females have two X chromosomes, but you could theoretically use male tissue, as men do have a single X chromosome (and mitochondrial DNA, which is normally only passed on from the mother). Now for the hard part, you need to find some way to convince whatever stem cells you got from the man or woman to start building the appropriate gonads. I imagine the proper supply of certain hormones is part of it, but there must be more to it than just this. And, of course, you also need to supply a suitable environment for those cells to develop and reproduce. So, theoretically, yes, but now, heck no.

Note that just removing a testicle of ovary from somebody (say a person who just died) and convincing it to continue to do what it does, would be considerably simpler. StuRat (talk) 03:13, 1 September 2011 (UTC)

The eggs are stored in the ovaries, if I recall correctly. That would put the recipient in the position of possibly becoming a surrogate to a long-dead biological mother. ←Baseball Bugs ^{What's up, Doc?} carrots→ 07:51, 1 September 2011 (UTC)

And neither testicles nor ovaries are simply gamete factories. Both produce important sex hormones (testicles produce testosterone + other androgens and ovaries produce estrogens and progesterone, plus possibly other hormones too.) And for either one you would also need to coax the cells into undergoing meiosis, which I think would probably be the tricky part (though as I have no real background in tissue engineering I have absolutely no idea whether any of my assumptions are in any way correct.) Whoop whoop pull up ^{Bitching Betty | Averted crashes} 20:23, 1 September 2011 (UTC)

Really big mosquito. Species?

I have make some photos of the really big mosquito - approximately 4 cm (1.5 in) in wing-spread. This monster live in Baden-Württemberg, Germany.

Could you please provide some piece of biological classification for this thing? (sorry for my english) - Ewigekrieg (talk) 21:02, 31 August 2011 (UTC)

A crane fly by the look of it, what we in the UK call a daddy longlegs - not a biting fly. Mikenorton (talk) 21:08, 31 August 2011 (UTC)

Yes, it isn't a mosquito, it is a crane fly. As for which of the 4200 or so known species, I'll leave this for someone else to say... AndyTheGrump (talk) 21:10, 31 August 2011 (UTC)

How did they figure out 4,200 species? They all look about alike. ←Baseball Bugs ^{What's up, Doc?} carrots→ 07:49, 1 September 2011 (UTC)

"about" is not good enough if you're a geek. Imagine all your baseball stats being "about". Richard Avery (talk) 14:11, 1 September 2011 (UTC)

They may be difficult to tell apart with the naked eye, but if you have access to a compact digital camera, I'd recommend taking a close-up - most such cameras can focus to within a few inches (a side-effect of the need for compactness) so you can get a decent macrophotograph without too much difficulty, and see some interesting details - using the flash often works best. The OP's photos are a little out of focus, but even so you can see the crane fly's halteres, which function as vibrating structure gyroscopes, and just about make out some of the details of its complex mouth parts. As always, Wikipedia commons obliges with a perfect image (taken with more expensive equipment - you won't get this close with a standard compact digital): AndyTheGrump (talk) 15:40, 1 September 2011 (UTC)

Citrobacter Nuclear Reactor

Would it be possible to grow Citrobacter on natural media to enrich the concentration of uranium and then use them as fuel for a moderated (RBMK or CANDU) nuclear reactor? Whoop whoop pull up ^{Bitching Betty | Averted crashes} 21:14, 31 August 2011 (UTC)

Only if the bacteria can differentiate between U-235 or U-238, which I find unlikely (keep in mind the isotopes are chemically identical). (Note that you wouldn't need to use the bacteria as fuel, and probably couldn't, since it wouldn't likely have the uranium in a chemically useful form — e.g. as an oxide or metal. If you could get something like that to absorb U-235, though, it would be rather basic chemistry to strip the uranium from the bacteria and convert it into metal or oxide or whatever you wanted it to be. The hard work is separating U-235 from U-238, not U from other stuff.) A more realistic (in the next 50 years or so) possibility along similar lines that I have read about is to use nanobots of some sort to do that sort of enriching (exact details not available, but presumably you could make them do very specific physical work to separate them out). The only way such an approach is an advantage to such an approach over current methods is if it is easier (technologically, politically) to make nanobots than it is to make reactors or centrifuges or laser enrichment or whatever, which isn't currently the case, but might be in a few decades. --Mr.98 (talk) 21:50, 31 August 2011 (UTC)

RBMKs and CANDUs don't need enrichment. They can run on natural uranium; check the relevant articles. And Citrobacter could make very-low-grade uranium deposits (less than 1/10 percent uranium) commercially viable. Whoop whoop pull up ^{Bitching Betty | Averted crashes} 22:05, 31 August 2011 (UTC)

Since you already seem convinced of the answer to your question, do you mind if I ask why you asked it? APL (talk) 02:20, 1 September 2011 (UTC)

Oh, I see what you are getting at. (Note that when you use phrases like "enrich the concentration of uranium," it sounds like you are talking about uranium enrichment unless you clarify.) I'm not sure what the advantage would be over just leaching out the uranium from the ore chemically. The problem with low quality ores is that you just need a lot of processing, an uneconomical amount. I find it unlikely that bacteria are going to change that — you'll still need to harvest the ore and the bacteria from the ore. That's got to be around the same level of effort as the normal mining/refining process. --Mr.98 (talk) 11:56, 1 September 2011 (UTC)

Why bother? In cost per kilowatt-hour, enriched uranium is already significantly cheaper than coal, oil, or gas. Fuel costs really aren't a limiting factor in the adoption of nuclear power, rather the costs are tied up with building and operating safe reactor facilities. Dragons flight (talk) 03:00, 1 September 2011 (UTC)

And with disposing of the spent fuel rods, etc. ←Baseball Bugs ^{What's up, Doc?} carrots→ 07:48, 1 September 2011 (UTC)

That's at the current level of demand. If there were to be an expansion of the use of nuclear power to the point that it could largely replace carbon-based fuels, demand would go way up. Could we fill it at the current, or any, cost?

I think it's worth thinking about. I know such an expansion is currently politically impossible because of the events in Japan. But the pressures that make it plausible aren't going to go away. --Trovatore (talk) 03:07, 1 September 2011 (UTC)

There is a practically infinite amount of uranium dissolved in sea water (more than humans would ever use, even if we replaced all power generation with nuclear). Extracting uranium from sea water is much more expensive than mining using current technology, but it isn't crazy expensive. If we had to get our uranium from sea water it would raise the cost of electricity 3-4 cents / kWh. That's a large enough increment that people would notice, but not so large as to be uneconomical. Full conversion to nuclear production is entirely possible with existing technology, but as you say, the political environment makes it an implausible option. Dragons flight (talk) 13:42, 1 September 2011 (UTC)

Two things: 1. breeders make this a lot easier, if you ignore the political problems; 2. low quality ores are only uneconomical because of current market conditions. If the demand went up, the price would go up, and they'd become economical again. I still don't see why bacteria are going to be helpful though. We have perfectly good methods of using low quality ores; the problem is that mining them is just expensive for what you get out of it. I don't see how the bacteria are supposed to change that (are you going to pump them in and pump them out again? I mean, how are you actually going to get the bacteria to the ore, and then get the bacteria out of the ore?). --Mr.98 (talk) 11:56, 1 September 2011 (UTC)

Increasing nuclear energy production means an increase in radioactive waste. Where should it be stored? ←Baseball Bugs ^{What's up, Doc?} carrots→ 14:10, 1 September 2011 (UTC)

New Jersey? Googlemeister (talk) 15:34, 1 September 2011 (UTC)

With breeder reactors you get a lot less of the long living radioactive waste. The remaining waste should be concentrated and be used as heat sources. The total volume then isn't large and because it is used it shouldn't be considered to be "waste" anymore. Count Iblis (talk) 15:45, 1 September 2011 (UTC)

The waste storage issue is a more of a political problem than a technical one. There are lots of pretty reasonable and rational solutions to the relatively limited spent fuel problem (the total volume of waste is pretty small compared to other types of hazardous waste). But that's a different question than the one being discussed here, I think. --Mr.98 (talk) 22:45, 1 September 2011 (UTC)

Sorry if this this comes across as selfish, but as long as it's not within my lungs [7] anywhere is fine. — Preceding unsigned comment added by Anonymous.translator (talk • contribs) 00:36, 2 September 2011 (UTC)

The problem is that politically in the US, the government wants to impose rules on nuclear waste storage so that the radiation has to be guarenteed to be below a set level for 1,000,000 years. Unfortunately, that kind of standard is completely unrealistic since our predictive methods for that kind of a time span is so incredibly vague. Googlemeister (talk) 13:22, 2 September 2011 (UTC)

I was trying to point out how unfair it is to harshly regularly certain types of radioactive wastes (to unachievable levels even) while imposing no restrictions on other types of radioactive wastes. Radioactive wastes resulting from fossil fuel burning has killed far more people than Chernobyl and yet it is still not regulated.Anonymous.translator (talk) 19:41, 2 September 2011 (UTC)

Can a person tell how close (feet wise or milage wise) certain coordinates are from each other; example, how far apart physically are Sueca from Cullera from Alzira?--Doug Coldwell ^talk 21:54, 31 August 2011 (UTC)

Yes; but calculating the shortest distance between two spherical coordinates is actually a little complicated; our article great circle derives the math for you. The entire science of geodesy formalizes this problem and deals with the practical details. You might also read about "the standard Geodetic Problem". (It's sort of a fancy, old-fashioned way of asking how far apart two cities are). Nimur (talk) 22:27, 31 August 2011 (UTC)

Another link: Vincenty's method, one of many "practical implementations" of the formula to calculate distance between cities. To be honest, nobody does this stuff nowadays - it's a little difficult and esoteric - ... most people just use a GIS software tool. The only people who really still do geodetic calculations are ... designers of GIS software tools. Nimur (talk) 22:55, 31 August 2011 (UTC)

Unless you want extraordinary precision, you can just use the scale on Google Maps. It appears to me that Alzira is about 11 km from Sueca and 15 km from Cullera and that Sueca and Cullera are about 6 km apart (all as the crow flies). Deor (talk) 23:12, 31 August 2011 (UTC)

Thanks Deor.--Doug Coldwell ^talk 11:10, 1 September 2011 (UTC)

Underice explosion

What would happen if an explosive was detonated under the ice on a frozen lake? Whoop whoop pull up ^{Bitching Betty | Averted crashes} 23:02, 31 August 2011 (UTC)

That dependends on the amount of explosive used, the thickness of the ice layer, and the depth underneath the ice layer. Plasmic Physics (talk) 23:52, 31 August 2011 (UTC)

I meant assuming an average ice thickness (around 6 inches?), an average-sized lake, and an explosive about the size of a few sticks of dynamite, detonated about ten to fifteen feet below the ice. Whoop whoop pull up ^{Bitching Betty | Averted crashes} 23:56, 31 August 2011 (UTC)

A pressure wave would deform the ice in an upward direction. It either would or would not break the ice. Probably. --Tagishsimon (talk) 00:03, 1 September 2011 (UTC)

As an aside, you'd prob'ly be better off using torpex instead of dynamite -- torpex is waterproof, while dynamite ain't. 67.169.177.176 (talk) 05:39, 1 September 2011 (UTC)

I said about the size of two sticks of dynamite, not to actually use two sticks of dynamite (ouch.) Whoop whoop pull up ^{Bitching Betty | Averted crashes} 20:26, 1 September 2011 (UTC)

On a much larger scale, subglacial volcanoes exist. ~AH1 ^(discuss!) 23:53, 2 September 2011 (UTC)

Energy Efficiency Calculations for Waste Heat Used in a Combined Heat and Power System

Inquiry: In determining the energy efficiency under Internal Revenue Code section 48(c)(3)(A)(iii), how is this done if the system is comprised solely of waste heat. Is it 100% efficient?

Facts: An existing industrial facility is currently venting its waste heat into the atmosphere. In a review of its efficiency standards, it has been proposed that the waste heat could be considerate to run both a turbine and other thermal applications without applying any additional fuel. As a part of the payback for this project is the investment tax credit for combined heat and power under section 48. The facility achieves both the 20% electrical and thermal standards, but we are unclear as to the calculation of efficiency when no additional fuel Cogenerationis involved. Kgordon016 (talk) 23:26, 31 August 2011 (UTC)

Welcome to the Wikipedia Reference Desk. Your question appears to be a homework question. I apologize if this is a misinterpretation, but it is our policy 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.--Jayron32 01:06, 1 September 2011 (UTC)

You misunderstood. The question based on the unclear statute as written by the EPA and comment by the DOE. No one in either organization has been able to address it either. I believe that someone in school could handle this, they would have a job. — Preceding unsigned comment added by Kgordon016 (talk • contribs) 00:49, 2 September 2011 (UTC)

Try searching through the Reference desk archives. ~AH1 ^(discuss!) 23:51, 2 September 2011 (UTC)

3066 McFadden

I was doing some vandalism removal, when I found this article. Being a huge Star Trek nerd, I was wondering if there was any relation of 3066 McFadden to Gates McFadden. Bluefist ^talk 23:34, 31 August 2011 (UTC)

As our McFadden (surname) article indicates, this is a common Scottish surname, so there is no particular reason to think that it would be, and given that it was apparently discovered (and presumably named) in 1984, [8] whereas Gates McFadden didn't appear in Star Trek until 1987, I can think you can safely rule this out. AndyTheGrump (talk) 01:31, 1 September 2011 (UTC)

According to NASA, it's named for this woman. Deor (talk) 01:45, 1 September 2011 (UTC)

And I've just discovered that we have a series of lists explaining the eponyms of asteroids. This question, for example, could have been answered by looking at Meanings of minor planet names: 3001–3500. Apparently, there are several Star Trek–related asteroid names, including 4659 Roddenberry, 9777 Enterprise, 68410 Nichols, and, indirectly, 2309 Mr. Spock. Deor (talk) 14:25, 1 September 2011 (UTC)

September 1

What would it look like inside of a gas giant like Jupiter?

Do we have any idea of what it might look like? Is it possible for a man in a space suit to survive this? ScienceApe (talk) 03:09, 1 September 2011 (UTC)

Too dark to read :-) --Trovatore (talk) 03:15, 1 September 2011 (UTC)

Right, since the light from the Sun wouldn't penetrate very far through the thick atmosphere. If you had your own light source, the thick atmosphere would still quickly absorb it, but perhaps you could see a short distance. In that case, you'd see clouds of various colors, depending on where you happened to be, or perhaps oceans of various colors, depending on the chemical mix, if you were near the core. Of course, all of this assumes that you don't die instantly from the chemicals, winds/currents, and temperatures. I imagine something more like a bathysphere than a space-suit would be needed to withstand the extreme forces. StuRat (talk) 03:57, 1 September 2011 (UTC)

I'm pretty sure Jupiter is oozing ionizing radiation at a rate that would require some very protective environments. The effect of going even within a few hundred thousand miles of the planet unprotected would probably be acute radiation poisoning. --Jayron32 04:03, 1 September 2011 (UTC)

[9] See this link. It is artist Adolf Schaller's impression of the great red storm as viwed from within Jupiter, ignore the alien balloons. I would guess, that if you descended 1000 km into Jupiter, you would no longer see the sun, but the area should be continuely lit up by the perpertual lightning flashes. There should be a lack of proper statification between cloud layers such as that which exists higher up. It is not to say it doesn't exist, just that they aren't as clearly distinguishable. It should appear like a glowing fog that seems to extend indefinitely in all directions, don't forget the strong winds. Plasmic Physics (talk) 05:04, 1 September 2011 (UTC)

Actually, after the first 100 km or so (at a pressure of roughly 10 atmospheres) the Jovian atmosphere is expected to have warmed enough that none of the available materials condense any more. An observer who made it that far might essentially pass below the clouds and have a visibility extending for kilometers (assuming that they bring their own light source, or perhaps see via lightning). Dragons flight (talk) 05:28, 1 September 2011 (UTC)

At what depth would black body radiation from the core light up the surroundings? Plasmic Physics (talk) 12:00, 1 September 2011 (UTC)

I'm not sure exactly, but not too deep, I imagine. According to Jupiter#Internal structure, the temperature at the boundary of the metallic hydrogen is 10,000K and that's 78% of the way to the surface. Black body radiation becomes visible at about 1,000K, by 10,000K you are well into the ultraviolet. However, it's difficult to say how useful black body radiation would be to see by. Since everything around you would be roughly the same temperature, it would all glow the same colour. You might be able to make out objects by their brightness (consider an oven heated to 3000K - while the air is at 3000K and therefore is red hot, the density is so low that you hardly see it and what you actually see is the walls of the oven glowing red), but the extent to which you can see otherwise is the extent to which the objects aren't perfect black bodies. If we need objects to not be black bodies in order to see them (black bodies are, after all, black), then we can no longer approximate them as black bodies and it makes it difficult to work with. --Tango (talk) 18:41, 1 September 2011 (UTC)

AFAIK if the only major source of light was from black-body radiation, then the light would be coming with equal intensity from all directions (and with the same intensity from any object within visual range as from the background!), so you'd end up in pretty much the same situation as in a flat-light whiteout -- only this would be more of a redout/yellow-out, and would be even worse because (1) all the objects are glowing at the same intensity and color as the background, so are nearly invisible; and (2) the light itself would be bright enough to overwhelm the eyes, as in snow blindness. 67.169.177.176 (talk) 05:32, 2 September 2011 (UTC)

This may be a shot in the dark, but what if I change my question? At what depth would the brightness of the transmitted light from the core equal the intensity of sunlight above jupiter. It would be a complete guess since no one actually knows the internal properties of Jupiter with absolute certainty. Plasmic Physics (talk) 04:06, 3 September 2011 (UTC)

I recall a discussion of this topic a few years ago here. It should be possible to build a floating probe like a bathyscaphe, with a small pressure vessel for instruments and controls and a large buoyancy chamber which causes the craft to float at a desired altitude. Instruments could monitor pressure, temperature, wind speed, electromagnetic disturbances, composition of the atmosphere,and radiation. The buoyancy bag or chamber could have radiators to dissipate heat, prolonging the operating time. A rocket could be used to send a capsule to the upper atmosphere for data recovery, if radio propagation were impossible to an orbiting relay satellite. Edison (talk) 19:17, 1 September 2011 (UTC)

How would the radiators work? A radiator needs to be hotter than the ambient temperature in order to work. For something like a car, that's fine, since the heat in generated by the engine and the car is surrounded by cool air. Since it is the ambient temperature that is causing the craft to heat up, it can't get hotter than that. You would need some kind of heat pump connected to the radiator if you were going to get any cooling from it. --Tango (talk) 00:09, 2 September 2011 (UTC)

Yes, a working fluid could be used in a heat pump (or refrigerator). Alternatively, the evaporation of a fluid or sublimation of a solid could be used in a one-pass sacrificial way to keep an instrument capsule cool for a while to prolong the data collection capability. Such a more passive cooling system might offer a shorter operating life at a large saving of mass. The Russian Venera probes of the 1970's could operate for 50 minutes at 475C and 90 atmospheres, just buy prechilling and then using some sort of circulating fluid. The Galileo Jupiter atmosphere probe descended for about an hour and failed at 23 atmospheres and 153C. There is no surface, just a density gradient. If the Galileo probe could descend to a fairly dense area, couldn't a probe be made to float at some density level? Apparently that probe was able to get out a radio signal to an orbiter after considerable descent through the atmosphere, reducing the need for a rocket to rise to a higher level to transmit, though the lightning at some levels should produce considerable interference. From a level of atmospheric poor radio propagation or high interference, it might also be possible to release a buoy with a flotation bag which could rise to a higher level to transmit. Edison (talk) 20:28, 2 September 2011 (UTC)

The high pressure and temperature would likely overwhelm any spacecraft. ~AH1 ^(discuss!) 23:44, 2 September 2011 (UTC)

An idea for an arbitrary surface designation: the first encountered critical point - the first depth at which any of the components of the atmosphere is critical. Where is the first depth like this, and what component is it? I don't expect hydrogen to be the first component to be critical. Plasmic Physics (talk) 03:57, 3 September 2011 (UTC)

DNA polymers

Are there any standard techniques that create polymers of repeating sequences of DNA? I am having a hard time searching due to the fact that a DNA molecule is commonly referred to as a "polymer" of nucleotides, rather than of a specific sequence. 184.98.162.93 (talk) 03:19, 1 September 2011 (UTC)

There are natural processes that do this, see Repeated sequence (DNA) for some threads to follow. Much of it is junk DNA and doesn't appear to code for any known protein, but some may have other functions, such as telomeres. --Jayron32 03:24, 1 September 2011 (UTC)

I'm aware of that. I was specifically looking for laboratory techniques. 184.98.162.93 (talk) 03:27, 1 September 2011 (UTC)

Sure, if you synthesize a sequence ABBBBBC you can use PCR to make many of those, and if you have an enzyme which will convert ...BBB-C and A-BBB... to ...BBBBBB... (these are well understood but you or someone else will have to find a link as I'm pressed for time) then you just let that stew for as long as you need to make long strings of B. 216.239.45.21 (talk) 03:32, 1 September 2011 (UTC)

In concept making a repeated sequence is just a simple case of synthetic DNA. But in practice DNA that repeats precisely can cause special problems - "unclonable DNA"^[10][11], triple helix and other exotic structure formation, and all manner of improper annealing. For a common lab inadvertency, consider the typical 100 or 123 bp DNA ladder which, if heated by some overeager grad student trying to get it into solution, somehow transforms into what appears to be a single high molecular weight band. One wonders how the DNA figures out just how to anneal when there are anywhere from 1 to 30 identical sequences in each piece ... but somehow it figures out a remarkably sharp solution, at least, given that it is too high of a molecular weight for the gel and you probably don't have a useful standard to compare it to... Methods of multimerizing the insertion of restriction fragments into a plasmid exist; there's rolling circle replication; and as mentioned PCR methods can work, if properly done. (Note for example that misaligned annealing can allow extension of more repeats...) Still, this is one of those things that can turn truly terrible, depending on exactly what you're trying to accomplish. Wnt (talk) 09:07, 2 September 2011 (UTC)

genealogical research: Hepatic dropsy

One of my ancestors is listed as having died from hepatic dropsy after an illness of 4 months. Any suggestions as to a modern diagnostic term? Thanks in advance bcatt (talk) 06:34, 1 September 2011 (UTC)

Here is a list of archaic medical diagnoses, which are interesting in their own right. If you scroll down you will find a reference to "hepatic dropsy". It seems to be an accumulation of fluid dependant on liver disease. Richard Avery (talk) 07:08, 1 September 2011 (UTC)

(ec) Sounds like a euphemism for cirrhosis. Nimur (talk) 07:13, 1 September 2011 (UTC)

This may correspond to abdominal ascites, which is itself a symptom of liver disease such as cirrhosis. --TammyMoet (talk) 08:19, 1 September 2011 (UTC)

Thanks for all the helpful answers. bcatt (talk) 20:22, 1 September 2011 (UTC)

Multi-cylinder engine

why do indicated power in each cylinder of a multi cylinder engine vary? is it necessary for indicated power to be same in all the cylinders? what are the consequences if the indicated powers vary and dont vary in the cylinders of the same multi cylinder engine?? — Preceding unsigned comment added by Saritha2616 (talk • contribs) 07:43, 1 September 2011 (UTC)

"Include a meaningful title. Do not write "Question" or "Query", but write a few words that briefly tell the volunteers the subject of the question." Plasmic Physics (talk) 08:55, 1 September 2011 (UTC)

I added a meaningful title. Indicated power per individual cylinder is a theoretical value and I don't know of an engine where it is not by design the same for all cylinders. Different values could introduce imbalance leading to vibration and even crankshaft failure.

The horsepower of a four-stroke internal combustion engine is:

HP= MEP x CID x RPM/(33,000 x 12 x 2)

where

MEP = theoretical mean effective pressure acting on the piston top through its stroke. It is divided by the work of 1 hp (33,000 ft-lb)

CID = piston top area times crankshaft's stroke length, which is divided by 12 to convert the value to feet

RPM = revolutions per minute. which is divided by 2 because the cylinder fires every other revolution.

The actual powers delivered by the cylinders will vary with their conditions and are usually not identical. Source. Cuddlyable3 (talk) 09:44, 1 September 2011 (UTC)

Autumn is when? (Northern Hemisphere)

Why not just say it begins when the Autumnal Equinox is 23rd Sept 2011. They tell us that there is temperature lag and so it is 1st Sept 2011 due to meteorology. If there is a LAG due to weather why is it not in October then?... this makes no sense to me! — Preceding unsigned comment added by 92.30.154.8 (talk) 12:09, 1 September 2011 (UTC)

Meteorologists use the 1st of September, December, March and June as their season start points. However, folk tradition has them starting on the equinoxes and the solstices. ←Baseball Bugs ^{What's up, Doc?} carrots→ 12:16, 1 September 2011 (UTC)

The article Autumn notes the various starting dates for Autumn in different regions. Some cultures regard the autumnal equinox as mid-autumn and others define Autumn in whole months i.e. Sept/Oct/Nov in Northern hemisphere. Cuddlyable3 (talk) 12:20, 1 September 2011 (UTC)

Starting fall in October would be a larger lag than having it start in September but keep it in mind that both of them are lags. No lag would be if the Equinox coincided with the middle of the Fall season, not its beginning, so starting Fall at the equinox is already a lag of one and a half months. Dauto (talk) 12:55, 1 September 2011 (UTC)

Not really. Winter starts on about December 21 and ends on about March 20. And the midpoint, around Groundhog Day, is typically the coldest stretch of winter, at least in the American midwest. Likewise, late July and early August, the midpoint of summer, are typically the hottest days. ←Baseball Bugs ^{What's up, Doc?} carrots→ 14:08, 1 September 2011 (UTC)

Yes, the designations are decently aligned with the weather, by design. What Dauto means is that the weather and the season designations lag behind the Earth's orbit. The period of least direct sunlight is centered around the winter solstice, which is before the coldest time of year. Rckrone (talk) 16:11, 1 September 2011 (UTC)

The Midwest US I have experienced seems to short autumn and spring a bit to extend winter and summer. Typically around here, summer starts early June and ends mid September and Winter starts late November and ends in mid March. Googlemeister (talk) 14:26, 1 September 2011 (UTC)

These definitions are always a bit fuzzy around the edges, since cultural definitions vary so much, as do local weather conditions, and other issues. In the U.S. at least, the season are traditionally delineated by holidays or observances. Summer lasts from Memorial Day (last weekend in May) to Labor Day (First weekend in September), with autumn lasting until Thanksgiving (fourth Thursday in November), winter lasting until Spring Break (usually first weeks of March) and thus spring lasting until Memorial Day. --Jayron32 17:05, 1 September 2011 (UTC)

To clarify a bit:

1) First, let's start with the assumption that summer is to be the hottest season and winter the coldest, by which I mean we want to gather all the (contiguous) hottest days together and call them summer and all the (contiguous) coldest days and call them winter.

2) If there was no thermal lag, then the hottest day would also be the longest day (the summer solstice), and the shortest day (the winter solstice) would be the coldest day. Those would then be right in the middle of summer and winter, respectively.

3) However, to adjust for the thermal lag, those events actually mark the start of summer and winter, respectively. Astronomers did this because they still felt these astronomical events should play some roll in determining the season.

4) Meteorologists apparently thought that this was a bit of an over-adjustment, and moved the season starts back about 3 weeks to the start of those months. Of course, wanting to have an easy to remember point where each season starts instead of determining the exact time of the solstices and equinoxes also was a factor. StuRat (talk) 17:42, 1 September 2011 (UTC)

Astronomically (and calendarically) the equinoces and solstices are the starting points of the seasons. Meteorologically, the first days of March, June, September, and December are the starting points of the seasons. If the Earth had no atmosphere (and therefore no thermal lag,) the Earth's temperature would be greatest on the equinoces and solstices, much like StuRat said up there. Whoop whoop pull up ^{Bitching Betty | Averted crashes} 20:31, 1 September 2011 (UTC)

... so "astronomically" (as in most documents written by astronomers), the equinoxes and solstices are the mid-points of the seasons, not the start. Dbfirs 07:12, 2 September 2011 (UTC)

No. If there was no thermal lag, that would likely be the case, but, since there is, astronomers chose to have those events define the start of each season. StuRat (talk) 16:28, 2 September 2011 (UTC)

No atmosphere would certainly reduce the thermal lag, but oceans and the continents would still exhibit some thermal lag. StuRat (talk) 00:21, 2 September 2011 (UTC)

"Meteorologically" in Europe. In North America, I think meteorologists use the astronomical definition, because the lag is a bit longer here than in Europe. At least, if they don't, it's plausible that they could (in California, for example, the hottest month is not infrequently September). --Trovatore (talk) 20:39, 1 September 2011 (UTC)

California has gotten a bit slow since medical marijuana got legal there, hm...? --Jayron32 21:46, 1 September 2011 (UTC)

There is, of course, the Mid-Autumn Festival. ~AH1 ^(discuss!) 23:39, 2 September 2011 (UTC)

Calculate airline security

How are airline security statistics calculated? Accidents/km, Accidents/starts? Deaths/km, ... ? Quest09 (talk) 12:12, 1 September 2011 (UTC)

Many countries have a transport safety authority that collects this data. Cuddlyable3 (talk) 12:23, 1 September 2011 (UTC)

Air safety might be relevant at least as a starting point. Bus stop (talk) 12:38, 1 September 2011 (UTC)

Nice, but when they say: airline x is on the top 10 most secure airlines, how do they came to the conclusion? You have airlines like Qatar or Singapore Airlines, which fly many km for each start, and you have regional airlines, which start more and fly less km. What would be a fair comparison here? (provided the assumption that accidents happen mainly at start and landing). Quest09 (talk) 13:04, 1 September 2011 (UTC)

See Air_safety#Statistics — there are a few different metrics used, and they give different results. (Note also the bit at the end regarding the difference between what airline insurers use and what airline press releases use.) Air does pretty well when you are talking about the amount of time or the distances covered, obviously, but does much less well when you talk about deaths per trip (because the number of deaths per accident is very high, and the most dangerous parts of flying are the takeoffs and the landings, not the in-between time). --Mr.98 (talk) 13:53, 1 September 2011 (UTC)

It's interesting to look at the numbers per passenger-hour and compare them to the numbers per passenger-journey. The average air journey appears to be roughly 4 hours long; the average car trip is about 20 minutes. In other words, the duration of the average automobile trip – and, I suspect, of the vast majority of automobile trips – are substantially shorter than virtually all air journeys. TenOfAllTrades(talk) 14:13, 1 September 2011 (UTC)

And the time for flights gets even worse once you figure in all the extra time needed for a flight:

1) Drives to and from airports at both ends (these also should be considered in relative safety calculations).

2) Time to go through security (may involve waiting in line).

3) Time to check in and check luggage (may involve waiting in line).

4) Time to go from terminal to car and vice versa, which may involve waiting for, then taking a bus to move you between lot and terminal, or time to walk that distance.

5) Extra safety cushion time you need to allow. In some cases, we've been advised to arrive up to 3 hours before a scheduled departure.

6) Time to board and exit plane (including waiting for others to do so).

7) Time plane spends taxiing or waiting for clearance.

8) Time spent due to flight delays and cancellations (requiring rebooking).

9) Time spent reserving flight, especially if you want to compare prices.

10) Time spent when switching planes, for non-direct flights, and also the additional time due to such flights not going straight toward the final destination.

For example, I used to regularly travel between Detroit and Toronto. Fortunately, there were direct flights, which took about 40 minutes, from tires off the runway to back on, versus a 4 hour drive. However, once all the other time was added in, I found it was quicker to drive. StuRat (talk) 17:58, 1 September 2011 (UTC)

irrelevant discussion of airplane flight time issues
The following discussion has been closed. Please do not modify it.
...which is totally irrelevant to the risk question. I mean, is there anyone here who doesn't know that air travel takes a lot of time? The reason it was brought up has to do with risk safety, but I can't see how your 10 point list above contributes to that discussion at all, unless I'm missing something. --Mr.98 (talk) 22:37, 1 September 2011 (UTC)

Yes, you're missing quite bit. I specifically mentioned that the risk from the drive to and from the airport should be figured in, but there are also risks in some of those other steps, like getting from the parking lot to the terminal and back. And, if you are comparing risk versus time spent, the issue does come up of whether you consider the time spent to be only when the plane is in the air or the entire time of the trip, from door to door. I'd argue that (total risk)/(total time spent) would be the best metric. StuRat (talk) 00:27, 2 September 2011 (UTC)

Stu's comment is most certainly not irrelevant (although appearing detailed and lengthy). Under discussion are the irrelevant parts of a trip that are included in the statistics in comparison with automobiles. Stu is reminding us that there are many irrelevant fragments to an airline flight that are included in the total hours upon which airline statistics are based. --DeeperQA (talk) 23:14, 1 September 2011 (UTC)

I would totally disagree with adding risk from the drive to and from the airport as part of the air travel risk since you are driving, not the airline. That would be equivalent to adding the risk of crossing the street to get to your car into the driving statistics. The two things are not really part of each other. You could live across the street from the airport if you wanted (at least at some airports) Googlemeister (talk) 13:16, 2 September 2011 (UTC)

If you try to determine the relative safety between driving directly to a destination, or flying, and fail to consider all of the risks involved with either, you will reach the wrong conclusion. And saying "you could move next to the airport" is also irrelevant. You could also buy an armored truck to make your drive safer. What matters is how things really are, not how they theoretically could be. As for considering the risk of walking across the street to get in your car (assuming your car is so parked), that would be appropriate, but, of course, you need to walk to your car whether driving directly or driving to the airport, so this cancels out when determining relative risks.

Your method reminds me of DNA analysis, where they say that 2 DNA samples match with only a 1 in a trillion (or some ridiculously large number) chance of them being wrong. What that is is the chance that two different people will have identical DNA at all the points checked. They completely neglect the much higher risk that the lab technician will screw up and test the same sample twice, say after being distracted by a phone call. StuRat (talk) 16:39, 2 September 2011 (UTC)

I too disagree. Factoring in the not-in-air time is irrelevant for airplane risk. Factoring in the time waiting for the baggage carosel or the switching between planes is also totally irrelevant. StuRat is complaining that airplanes are often quite time consuming despite their apparent speed. No one disputes this, but it is totally irrelevant for the question of safety statistics. Whether you spend 5 hours or 5 minutes waiting in the airport lobby for a layover does not have any effect on the safety of airplanes as a means of transportation, as I think should be completely obvious. Your time and means of going to and from the airport has nothing to do with airplane safety by itself; it is a completely separate variable. --Mr.98 (talk) 14:29, 2 September 2011 (UTC)

I don't think "risk per minute" is itself a very good metric, but, if you use it, you should use total risk over total time. If you don't do so, you could claim "there's X risk in a single hour-long flight, so if you fly 10 hour-long flights a day there would be 10X risk per day". However, when you consider that the one hour flight takes 4 hours overall, that would mean that 10 flights a day would take 40 hours a day, clearly an impossibility. Personally, I think "risk per mile (or km)" is the most useful measure of safety, but I would still include the total risk of the trip, from door to door, as the best method of deciding on the safest course of action. I would also use the straight-line distance you intend to travel (door to door), rather than counting extra miles you need to travel to make connecting flights or because the roads don't go directly where you want them to go. StuRat (talk) 16:55, 2 September 2011 (UTC)

As for when it would be appropriate to ignore total risk, and only focus on the risk of the flight itself, that would make sense for airline safety officials, assuming they have no authority to improve safety of passengers before they board and after they exit. However, the passengers aren't only concerned with their safety while on the plane, but for the entire trip, so, for them, the entire risk is relevant. StuRat (talk) 17:10, 2 September 2011 (UTC)

This is quite, quite silly. The time you spend on the ground is irrelevant. It does not have anything to do with the risk of flight. Calculating risks is not concerned with the practicality of multiplying the risks, it's concerned about comparing different outcomes. Comparing irrelevant metrics leads to irrelevant results. Think it through a bit. Risk per mile has its own obvious problems, which we've already discussed above. Each of the measures gives different results, as discussed above, and you really do have to take them all into consideration when comparing risks. You need not invent your reasoning on this from scratch, StuRat, as risk assessors have been discussing this for decades. --Mr.98 (talk) 21:51, 2 September 2011 (UTC)

I find it sometimes helps to view the extreme situation, in cases like this. Imagine the country is in a civil war, and the road to your destination is clear, but there are major battles around the airport. In such a case, would you still argue that the trip to and from the airport is irrelevant in calculating whether taking a plane or driving is safer ?

Reminds me of a real-life case. Last year, my Dad was in need of heart surgery. We asked what the risk was, and the surgeon gave us a rather low risk of death. Based on that, we decided to go ahead. He survived the surgery, but then died of a post-operative infection. We found out later, that the low number they gave us was only for death on the operating table, and that the total risk was much higher. We would have made a different decision had we been informed of the total risk entailed by the surgery. What's even worse, the doctor probably considers the surgery to have been a success, and will continue to recommend it, based on his faulty metric, even though a large portion of the patients die as a result of the surgery. StuRat (talk) 22:50, 2 September 2011 (UTC)

I live on one extreme side of a quite large city. The airport is way on the other side. Driving to the airport is quite a challenge. If I choose instead to drive to another big city where I can avoid that trip across town, I save a lot of hassles of all kinds. HiLo48 (talk) 03:05, 3 September 2011 (UTC)

Systolic vs. diastolic pressure as a severity indicator

For many years I heard that for people who have hypertension or are at risk of it, the blood pressure # that they should pay more attention to is the diastolic pressure. Recently on a TV program the voice-over said that the higher of the two numbers (i.e. the systolic pressure) is the one that people should be watching. Has there been a change in our understanding of the relative significance of the two numbers as a hypertension severity indicator? --173.49.82.36 (talk) 12:28, 1 September 2011 (UTC)

Both systolic and diastolic pressures should be controlled. Using the standards adopted by the American Society of Hypertension, adult blood pressure should be below 140/90 unless the person has diabetes or chronic kidney disease, then it should be below 130/80. To be below 140/90, systolic blood pressure must be below 140 and diastolic blood pressure must be below 90. In general, it is easier to lower systolic blood pressure with medication than it is to lower diastolic blood pressure. So, those with high diastolic and controlled systolic are in a particular risk group where more than simple medication may be necessary to control hypertension. But, millions of dollars are spent developing new medications to treat hypertension. So, the risk of high diastolic blood pressure is decreasing to the point that most hypertension specialists don't consider systolic or diastolic control to be any different. They just pick the medication that best treats the type of hypertension a patient has. -- kainaw™ 13:42, 1 September 2011 (UTC)

Is the difference between the two numbers significant? ~AH1 ^(discuss!) 23:34, 2 September 2011 (UTC)

medical student

is medical student takes admission for mehran university? if yes so, for which department? — Preceding unsigned comment added by 182.182.84.18 (talk) 15:41, 1 September 2011 (UTC)

Not the appropriate venue for asking, but try [12] -- MacAddct1984 ^{(talk • contribs)} 20:21, 1 September 2011 (UTC)

Co-occurring disorder(s)

Is it possible to have many different types of mental illnesses. And if it is possible, is it likely? If there is a Wikipedia article on what I'm asking, please point me in the right direction. Thanks. Lighthead ^þ 19:14, 1 September 2011 (UTC)

No a simple answer to this but generally having any one mental disorder doesn't bar an individual from having on other. However, a genetic disposition to having some disorders may protect someone from developing a disorder that is associated with some other set of genes. It also is unlikely to be the result of just one gene (for say schizophrenia) but a combination of several. Genes, it must be remembered, are normally protective, which is why they survive. Even the gene responsible for Huntington's disease is thought to have a protective effect against getting a particular physical condition (I forget which). Then there are disorders that are the result of bad experiences etc., and it possible to have several of those.--Aspro (talk) 19:58, 1 September 2011 (UTC)

But what makes me wonder is that the symptoms oftentimes overlap. It may sound funny, but it almost seems as if the whole field of psychology is a kind of pseudoscience. It seems to be a whole lot of guessing. Especially as relates to diagnosis. Lighthead ^þ 20:10, 1 September 2011 (UTC)

In most cases the DSM (the "bible" of diagnosis in the US) will describe a set of symptoms as a single condition of a mixed type, rather than as two superimposed conditions (for example, a schizoaffective disorder rather than a combination of schizophrenia and an affective disorder). But this is essentially arbitrary. Looie496 (talk) 21:26, 1 September 2011 (UTC)

I have both Asperger's and Tourette's syndromes. Plasmic Physics (talk) 00:20, 2 September 2011 (UTC)

That would have made for a FAR funnier Rain Man. I mean nothing personal by that, my intention is not to make light of your condition. Vespine (talk) 00:38, 2 September 2011 (UTC)

The entertainment industry has done a terrible job of stereotypeing Tourette's. Not everyone swears uncontrolably as in the Southpark episode. In fact, a large portion of us express non-verbal symptons. Plasmic Physics (talk) 01:01, 2 September 2011 (UTC)

That would be an example of coprolalia. ~AH1 ^(discuss!) 23:31, 2 September 2011 (UTC)

An individual may have many disorders simultaneously, as the disorders typically are not mutually exclusive, though this may increase comorbidity. However, the cause is rarely purely genetic, or even biological. ~AH1 ^(discuss!) 23:31, 2 September 2011 (UTC)

solar cells

Are their there solar cells which are more efficient in low light? --DeeperQA (talk) 22:47, 1 September 2011 (UTC)

Wait, solar cells posses other solar cells? Plasmic Physics (talk) 00:13, 2 September 2011 (UTC)

There is no correlation between luminous intensity and efficiency. A solar cell is as efficient in low light as it is in strong light. Assuming you are talking about an efficiency ratio. Plasmic Physics (talk) 00:53, 2 September 2011 (UTC)

Unfortunately, solar light includes infrared frequency and when concentrated increases the surface temperature of the surface it is absorbed by. I would imagine that at some point efficiency becomes less until the surface is so hot it melts at which point efficiency is zero. Some plants must have less light in order to do well and grow while other plants need more light. In either case the rate of growth is directly dependent on the amount of sunlight all other factors being the same. --DeeperQA (talk) 02:34, 2 September 2011 (UTC)

Plant life is not comparable in this context, it opperates and is affect in a completely different way. You could simply filter out infrared light, if your goal is maintain a low temperature. Plasmic Physics (talk) 03:33, 2 September 2011 (UTC)

But, of course, when visible light or UV is absorbed it also produces heat. StuRat (talk) 03:47, 2 September 2011 (UTC)

One method is to use mirrors to concentrate the low light onto the solar cells. Since mirrors are less expensive than solar cells, this can provide a cheaper alternative to covering the same area with solar cells. However, note that in full light, the excess heat might damage the solar cells. StuRat (talk) 03:54, 2 September 2011 (UTC)

I saw "floating" solar panels on tv a while ago. The water that the solar cells float on provides plenty of cooling allowing a configuration of mirrors to concentrate far more light onto them then they would normally tolerate. Vespine (talk) 04:58, 2 September 2011 (UTC)

See solar cell efficiency and fill factor. The materials of the photovoltaic cells may affect its absorptive capabilities, for example the usual silicon-based cells vs. organic ones. ~AH1 ^(discuss!) 23:27, 2 September 2011 (UTC)

September 2

Polythene molecules

Hi, I found this on a website:

"Linear polyethylene is pretty big, with molecular weight of 200,000 to 500,000, but it can be made even higher. Polyethylene with molecular weights of three to six million is called ultra-high molecular weight polyethylene, or UHMWPE. It can be used to make fibers which are so strong they are even better than Kevlar for bullet proof vests."

If each "unit" of the molecule, CH₂, has molecular weight 14, and the C-C bond length is 0.153 nm (which I found on another site), then 500,000-weight polythene molecules should be about 5 microns long, and 5,000,000-weight polythene molecules should be about 50 microns long. Have I done that calculation correctly?

Secondly, if polythene could be made with molecules say 30 cm long, then would the material be super-super-strong? Apart from possibly greater strength, would its appearance be substantially the same as that of ordinary polythene? 86.179.1.213 (talk) 00:56, 2 September 2011 (UTC)

No, it's incorrect. You have neglected the <CC bond angle, and treated the chain as straight, instead of a zig-zagging conformation. I don't have an answer for the second question. Plasmic Physics (talk) 01:06, 2 September 2011 (UTC)

We have articles covering the range of different polyethylene (note the spelling!) materials: Linear low-density polyethylene, High-density polyethylene, and Ultra-high-molecular-weight polyethylene. Interestingly, they discuss material properties and some discuss the origin of them, but none discuss the actual linear strength of individual polymer chains. The tensile strength of macroscopic fibers is in part because it's hard for separate polymer chains to slide past each other (so "longer leads to stronger") in addition to it being hard for a single chain to stretch (or even rip apart at exceptionally high forces). The chains in the materials commonly used aren't long enough to actually be gripping two ends of a single chain as your 30-cm example would allow. You're right that it might be even stronger strong because chain slippage (leading to fraying of the chains from each other) would not be relevant. I don't know if actual measurements have been made of simple polyethylene-chain linear strengths (approximated as elastic stretching a spring), but I assume they have because they have for some more complicated biopolymers (see Worm-like chain#Stretching Worm-like Chain Polymers—you can skip the math if you like). DMacks (talk) 07:52, 2 September 2011 (UTC)

"Polyethylene or polythene (IUPAC name polyethene or poly(methylene)) is the most widely used plastic..." This isn't a spelling issue: the words are in free variation. Polythene is more common in lay contexts, polyethylene in IUPAC compliant ones. I'm not the OP, I just wanted to note this is not a spelling issue. 86.164.62.111 (talk) 09:39, 2 September 2011 (UTC)

Interesting thanks! I've never seen that alt spelling used in any context (I've worked in recycling and science worlds in the US). DMacks (talk) 10:24, 2 September 2011 (UTC)

I think many Americans first encountered that spelling by way of Mr. Lennon. Deor (talk) 11:11, 2 September 2011 (UTC)

• (OP) Yes, "polythene" is the usual layperson's word in the UK. Here it says that the force needed to break a C-C bond is 1600 pN. So if we knew how many polythene molecules per cross-sectional area then we could work out the tensile strength of some super-polythene with 30 cm molecules. What would the (average) cross-sectional molecular separation be? Would it be slightly more than the C-C bond length? A lot more? Does anyone know? 86.177.107.255 (talk) 17:27, 2 September 2011 (UTC)

Using tidal power to generate electricity

I have a little fishing hut in south Louisiana. Its not much more than a single room with a bunk bed, a mini-refrigerator, a single light bulb, and one power outlet we use to charge the cell phone and operate an AM/FM radio for entertainment. So we use very little power, and currently rely on a propane generator. My question is, when the tide come in and out twice a day, it is a very powerful surge, to the point that an unsteady footing would result in a grown man falling over if he were to stand in the surge. Is there a way to harness this power? All my Internet searches have resulted explanations of commercial tidal-power generation...but nothing for a simple dwelling, or everyday use. Any ideas? Quinn ^{❀ BEAUTIFUL DAY} 03:05, 2 September 2011 (UTC)

It is possible, of course, but there are lots of drawbacks, like your generator getting various sea life encrusted on it, the whole apparatus washing away during a storm, needing enough batteries to "tide you over" between tides, etc. I picture a wheel with fins on it you could lower into the water when present and remove (to avoid encrustation) when absent, which would drive a small generator and charge a series of car batteries. You would then power the hut off those car batteries. You'd need an alternator to power an A/C outlet. StuRat (talk) 03:25, 2 September 2011 (UTC)

We have an article on pico hydro, which while not specifically addressing tidal power generation, may still be of interest. -- 223.207.148.174 (talk) 05:32, 2 September 2011 (UTC)

You are in a very exceptional situation, most dwellings would never have alocal access to tides, therefore, there is no commercial interest in developing something that could power you. You could invent your own device based on standard hydro-power mechanisms, though, something like sturat was describing. Let us know if you do and how much power you end up generating. --Lgriot (talk) 08:28, 2 September 2011 (UTC)

You'll also be continuing a venerable (pre-electric) tradition: see for example Eling Tide Mill. {The poster formerly known as 87.81.230.195} 90.197.66.179 (talk) 11:45, 2 September 2011 (UTC)

Supposing you can built and install this kind of equipment, the power you gonna get will be very small. Refering to Betz' law the energy of the tidal current is given by : $P_{\rm {max}}={\begin{matrix}{\frac {16}{27}}\cdot {\frac {1}{2}}\end{matrix}}\cdot \rho \cdot S\cdot v^{3}$ Suppose you can get all the kinetic energy with a 1 square meter equipement in a 0,5 m/s tidal current with no friction and a perfect generator, you could only get a electric power of 40W ! The fact is that tidal currents are very small in most areas, only few spots on the costs can reach interesting tidal current values worth installing power generation capacities.--Franssoua (talk) 14:10, 2 September 2011 (UTC)

I'm surprised nobody's realized that the OP is asking about the tide but (s)he probably mean to ask about wave power which is entirely another matter. 24.73.119.146 (talk) 19:12, 2 September 2011 (UTC)

I have to disagree: I think the details the OP gives show that he's clearly intending to ask about tidal power, not wave power. However, Quinn (aka David) will probably come back and clarify if you're right and the rest of us wrong. {The poster formerly known as 87.81.230.195} 90.200.79.225 (talk) 19:43, 2 September 2011 (UTC)

Nope, definitely not wave power. My hut is on a pretty narrow inlet of salt water, so it kind of funnels the tides in an out in a fast current. We go from about 3 ft of water to ~6 ft (I've never really measured) in a short amount of time (say, maybe-2 hours), depending on the tide...so you can imagine the "power" of the water flow. A few "neighbors" in similar situation have types of water wheels, but they don't seem to serve any purpose other than being conversation pieces. I am definitely not one to go invent something like this. And few other searches around the web seem to indicate that the tide change, though drastic, is not prolonged enough to generate anything other that a slight re-charge of batteries, and I might be better off doing something with solar panels, since the area is basically marsh, and there's pretty much no shade. Both technologies are still, unfortunately, pretty expensive for a fishing camp I inhabit, sporadically, maybe 3 weeks out of the year. 71.195.140.199 (talk) 00:39, 3 September 2011 (UTC)

Whoops, that was me above. Quinn ^{❀ BEAUTIFUL DAY} 00:41, 3 September 2011 (UTC)

Plug-in, portable solar panels might be best, then, since you could take them home with you and prop them up in a window to get some use out of them all the time. They would slightly reduce your home electric bill. About the shed, do you spend the night there ? If so, then there's the issue of how to run the mini-fridge overnight. You might want to continue to use propane then, since using solar for that would involve lots of batteries and bigger solar panels. Or you could just have it full of ice packs, to keep it somewhat cool overnight. Not appropriate for things like egg salad, but OK for soft drinks. StuRat (talk) 01:04, 3 September 2011 (UTC)

Yeah, I might stay there 4 nights at the most; but usually just for a weekend. We keep the beers/sodas/snacks in an ice chest...the mini-fridge is basically used for keeping the bait and the fish we catch cool until we're ready to leave, since you don't really want to combine dead fish/bait in the same place as your food/drinks. But the whole "free energy" thing is turning out to be one of those ideas that sounds great, but is simply not practical...especially for an old shed that'll probably get blown away in the next hurricane anyway. I like the portable solar panel idea, though, and may see about incorporating that, 'cause I'd have some uses for those around my home as well. Thanks everyone. Quinn ^☂THUNDER 02:16, 3 September 2011 (UTC)

Blood-vein, Mr. Schmidt and taxon authorities

My slowly ongoing project in fiwiki is to at least redlink all taxon authorities. However I drew a blank with Mr. Schmidt in Blood-vein (Timandra comae). Google tells me his first name starts with an A, but there my googling skills end. Any help on finding full names of taxon authorities in general is also appreciated, since I somehow feel that this isn't going to be the only tricky one I'm going to encounter. --Albval (talk) 05:25, 2 September 2011 (UTC)

His name was Anton Schmidt, and the title of the original paper was "Ein neue Timandra-Form aus Spanien” (A new form of Timandra from Spain) published in Internationale Entomologische Zeitschrift 25(6) (1931):57-59.

A very good source for a lot of names is tierdoku.com. That's where I found his name:

http://tierdoku.com/index.php?title=Ampfer-Spanner

It includes full biographies for many of the most noted zoologists (but unfortunately not Anton Schmidt), but doesn't help much with less noted ones. The site is in German, though. Dominus Vobisdu (talk) 07:34, 2 September 2011 (UTC)

Many thanks! I can read (but not speak or write) German adequately, so the site helps my project a lot. --Albval (talk) 07:44, 2 September 2011 (UTC)

Are there any experts who can answer my question? (hand sanitizing)

It's been said that cleaning your hands with soap and water, or a hand sanitizer will eliminate most organisms that are not part of your normal body flora. I want to eliminate ALL of the organisms that are not a part of my normal body flora, not MOST. So I was wondering, is it possible to get rid of all the germs on my hands? If so, how can I do it? If not, why not?98.234.170.202 (talk) 06:40, 2 September 2011 (UTC)

It is possible to remove all bacteria, yeasts and whatnot from your hands, but then you'll be removing all of them. There is no way to differentiate between normal bacterial flora and "germs" when cleaning your hands. Not to mention some parts of your hands are removed as well (probably most of your epidermis, for example). --Albval (talk) 06:50, 2 September 2011 (UTC)

It's possible to remove all of them? How can I do that (and what's epidermis?)? 98.234.170.202 (talk) 06:55, 2 September 2011 (UTC)

I added to the title to make it useful. Epidermis is the outer layer of skin. I imagine submerging your hands in bleach might kill them all off. However, what you need to realize is that some bacteria are helpful. There was a problem, for example, when adult diapers were treated with a chemical (something hexaflouride, I think) which killed off all the bacteria. When you do this, other nasties which were controlled by the helpful bacteria then begin to grow. StuRat (talk) 07:02, 2 September 2011 (UTC)

And something that kills all of the bacteria will be (very) harmful to your hands as well, bleach and heat/fire being the most common answers. --Albval (talk) 07:14, 2 September 2011 (UTC)

"Normal" body flora includes plenty of bacteria of constantly varying extraction. The purpose of washing hands is to reduce the bacterial load, not eliminate it entirely. You absolutely can not eliminate all the germs on your hands without for example, surgical scrubbing followed by powerful antibiotic wash, but there is no reason you should want to unless you are touching a severely immunocompromised person; in which case wearing gloves is far easier. 76.254.20.205 (talk) 09:22, 2 September 2011 (UTC)

Even surgical scrubbing followed by a sterilizing wash won't eliminate all microorganisms -- there is, for example, no procedure that makes it acceptable for a surgeon to work without gloves. Looie496 (talk) 15:41, 2 September 2011 (UTC)

Killing off 99.9% of the harmful bacteria, for example, increases the likelihood of superbugs via disruptive selection. Each person's hands has a unique composition of bacteria, and the human body contains more bacteria than normal body cells. ~AH1 ^(discuss!) 23:17, 2 September 2011 (UTC)

Mold VS Mildew

I have been in the mold remediation business for over 11 years and performed these services around the world. During this time I have met and worked with several professionals within the industry and hence learned/aquired a great amount of knowledge. However I do not know the difference between mold and mildew. Here is why I'm asking this question. When the "Mold Frenzy" began hitting the USA in the mid 90's, most notibly the Ballard case in Texas and Brockovitch case in California, mold slowly became a dreaded "4-letter" word and hence the industry started to utilize the word Mildew instead. This supposedly was a way to calm any concerns or panics that our clients may of had because mildew was never associated with the terms "Black mold" or "Toxic mold". So, with that brief history is there a simple answer that may be given to the difference between mold and mildew. Such as "Mildew requires photosynthesis to grow" if this statement is correct? --CMjeter (talk) 08:03, 2 September 2011 (UTC)

Mildew is simply a term for unsightly molds that grow in damp places like bathrooms and basements and can damage walls, books, and other objects. Mildew is also used for certain fungal plant diseases. Dominus Vobisdu (talk) 08:22, 2 September 2011 (UTC)

In very humid climates mildew is different (and much more damaging to various natural textiles) than the sort of tile grout growth found in kitchens and bathrooms in more arid regions. 76.254.20.205 (talk) 18:22, 2 September 2011 (UTC)

You don't need a humid climate. Just a humid environment. For example, one of the worst cases of mildew I've seen was in sunny San Diego. A tenant had painted his whole apartment with cheap water-based paint and left for a few days, leaving the apartment shut up. There was a luxurious layer of mildew covering just about everything organic in the apartment when he got back. The carpets and upholstered furniture had to be discarded, and all clothing and bedding had to be washed. My friend and I were called in to repaint the apartment, which proved difficult and very costly. Every surface had to be scrubbed with bleach, scrubbed again with TSP, thoroughly dried, sealed, covered with a base coat, and painted with high-quality paint to give satifactory results.

The humid environment doesn't have to be all that big, either. The space under a sink or near an air vent can become humid enough to permit damaging mildew to grow. Dominus Vobisdu (talk) 02:29, 3 September 2011 (UTC)

scientific method

what are the tenets of the traditional scientific method? what is wrong with their account of science? — Preceding unsigned comment added by 41.204.186.18 (talk) 09:09, 2 September 2011 (UTC)

Have you read Scientific method? 76.254.20.205 (talk) 09:13, 2 September 2011 (UTC)

Properly the scientific method is a matter of philosophy rather than science, and as such it's not really one thing you can nail down but many related things. The hypothetico-deductive model is not really that different from the intuitive trial and error approach of the ancients. At the same time adding a control group is an important refinement, and further refinements (sometimes debatable) constantly emerge - double-blind studies, crossover studies and meta-analysis for example. When used properly, the scientific method is just a way of saying you've thought over how to do an experiment so that it proves what you think - but when improperly interpreted, you get people denouncing all the scientists of ancient times as being irrelevant because they didn't know Francis Bacon. Of course a certain amount of frustration at ancient authors is to be expected, because they didn't have monks copy out every result from a hundred experiments they did or heard of to see whether a given imported herb was useful for patients with a given disease. But I suspect often such work was done in one form or another, and I think it's unscientific, even cult-like, when people dismiss their results out of hand because "science wasn't invented yet". Wnt (talk) 09:32, 2 September 2011 (UTC)

The main problem with an account of science that relies upon a single scientific method is that no single such method exists, or has ever been used by scientists. Different scientists in different fields use different methodologies, and they are essentially never the method displayed in high school science fairs (form a question, propose a hypothesis, conduct the experiment, revise the hypothesis, publish the conclusion). Real life examples of scientists, past and present, show a lot more "messiness" in how they choose their problems of interests, how they attack them, how they filter over their data to figure out what is real and what is not, and so on. The belief in a unitary "scientific method" is a convenient falsehood that children are told to encourage them to think about knowledge in a systematic fashion, but it is not a reflection of the reality of scientific practice. (This in no way need disparage scientific practice, any more than disbelief of the stork disparages childbirth.) --Mr.98 (talk) 14:26, 2 September 2011 (UTC)

There are universal threads within the philosophy of science which one can distill out, however. Certain things like a) being organized in your thinking b) having goals in mind c) developing testable ideas d) developing reasonable experiments to test those ideas e) being skeptical f) universality and repeatability (i.e. anyone can do it, and the results should work always) g) a negative result is still a result, and probably several other concepts. What makes science work is that it is different than other ways of thinking, than other paradigms. --Jayron32 15:50, 2 September 2011 (UTC)

Unfortunately there's no really great way to distinguish a specifically scientific method (see demarcation problem), and much of what you've listed is only distinguishable long in hindsight (which makes it not so useful as a prescriptive and only problematically useful as a descriptive). So that doesn't really change things a whole lot, unfortunately. There's plenty of what all would consider to be "science", historically and presently, that doesn't fit into those criteria you've mentioned. --Mr.98 (talk) 21:42, 2 September 2011 (UTC)

I think observation, inductive reasoning, hypothesis and experiment (or in layman's terms, trial and error), are instinctive and ancient. Any plumber called to a home collects the data, forms a hypothesis, and tests it; if they lacked a scientific mindset, they would be very poor plumbers indeed. I don't know, but I suspect the plumbers in ancient Rome were just as scientific in their approach. I think that it is the small technical refinements that modern scientific method emerges - starting with the conscious use of a control group, which implies the planned decision to set up identical experimental groups and treat them differently. I think that any ancient herbalist knew to take a substance and give it to patients it's supposed to help and note down what happens - what's not so clear to me is whether they could find it in themselves, their ethics, and the tolerance of their patients to sacrifice the quality of care by giving half a treatment they believe to be less effective. I won't rule out that they did it, though, and in any case economic limitations probably caused such contrasts to occur whether they wanted them or not. Likewise meta-analysis implies a certain added level of sophistication, in which clinical studies are done with enough consistency and regularity (often perforce, due to the need to study people at many different hospitals) that people can actually tot up averages of the results of multiple studies and hope they really mean something. Wnt (talk) 22:20, 2 September 2011 (UTC)

They're not instinctive, they're not ancient. It wasn't anything like what Aristotle was doing, for one simple example. Consider that one of the major learned debates (Hobbes v. Boyle) in the 17th century was whether induction or deduction should be used to generate knowledge — it was essentially a debate about whether experimentation could create "real" philosophical knowledge. (The modern echo of this sort of discussion is the still relevant question for many people about whether scriptural knowledge or scientific knowledge should be believed.) Either one dilutes what "science" means to the point where every shaman and plumber is a scientist, or you have to assert that it's something much more recent... --Mr.98 (talk) 22:25, 2 September 2011 (UTC)

(edit conflict)There are many areas of disagreement among scientists, one of them being the hidden debate over the degree which materialism dominates the scientific method, and another over reductionism vs. holistic methods. Most of these controversies reflect differences between Scientific disciplines and patterns of thinking among specific scientists. Another matter of intense debate is when a new falsifiable hypothesis, theory or unrepeated observation is scruitinized using scientific skepticism, whether scientists attempt to explain a phenomenon using known parameters or completely explain away the phenomenon, under the line of extraordinary claims require extraordinary evidence. As a result, -isms in science are usually not falsifiable, any more than the usefulness of pattern recognition is falsifiable. Many tenets of scientific canon have a cultural background. Science undergoes various paradigm shifts, and interdisciplinary approaches to subjects are becoming more popular as the need for solutions to today's problems from various points of view is ever-increasing. Another area of disagreement is conforming to a generalist vs. specialist approach to science in today's world. See also scientism. ~AH1 ^(discuss!) 22:38, 2 September 2011 (UTC)

See logic, inductive logic and deductive logic. ~AH1 ^(discuss!) 22:38, 2 September 2011 (UTC)

Also take a look at meta-analysis, and one meta-analyst's essay: Why most published research findings are false (and this video). ~AH1 ^(discuss!) 22:41, 2 September 2011 (UTC)

Yet another issue is that in some fields including astrophysics and climatology, more than one reason (ie. more than one hypothesis) may explain the causes of an observed phenomenon or change. When factions of scientists want to reject all but one hypothesis, problems may occur in the form of incomplete explanation. ~AH1 ^(discuss!) 22:49, 2 September 2011 (UTC)

In the above mentioned fields, computer modelling is typically used over actual manipulations of the subject matter, for obvious reasons. The inherent chaoticity in some dynamical systems contributes to higher difficulty in testing hypotheses. ~AH1 ^(discuss!) 22:52, 2 September 2011 (UTC)

Caffeol

Is there a single unique compound called caffeol, or is it fairy dust? I find very few modern scholarly sources mentioning it in detail. If it does exist, what is its structure? Why has it vanished into obscurity? Plasmic Physics (talk) 10:19, 2 September 2011 (UTC)

After striking out in PubChem,^[13] I turned to Google, and found the blog of someone who had walked this road before. [14] He leads us to [15] which describes that caffeol is an aromatic distillate with many components, which is further modified by Maillard reaction during heating. It apparently is about 250 mg/kg of coffee, a pretty small amount. The book is pretty detailed, but even so I'm a bit puzzled how to define caffeol, because it's historical in nature and I'm not sure how many of the components are truly part of "caffeol" rather than simply "components of the coffee aroma". Wnt (talk) 15:29, 2 September 2011 (UTC)

Essential oils of any plant substance are usually dozens if not hundreds of different aromatic oils and esters, which is why artificial flavors -- which usually only have 1-3 synthetic components -- are usually distinguishable from the flavor they are supposed to represent. 76.254.20.205 (talk) 18:20, 2 September 2011 (UTC)

That is as far as what I got in Google, I searched PubChem, SpiderChem, ChEBI, MeSH, nothing. The closest thing I found on PubChem was a compounds containing the functional group called caffeoyl, which refers to 3-(3,4-dihydroxyphenyl)prop-2-enoyl. Plasmic Physics (talk) 22:13, 2 September 2011 (UTC)

Electromagnetic pump for ionic liquids

Can an electromagnetic pump be used to pump molten salts or ionic liquids as it is used for pumping liquid metals (without electrolytic effects)?--86.125.191.228 (talk) 10:49, 2 September 2011 (UTC)

Yes, these are sometimes used in nuclear reactors, but they aren't practical in (m)any other applications. 76.254.20.205 (talk) 18:14, 2 September 2011 (UTC)

Earthquakes

Why have there been so many large earthquakes the past few years? --76.211.88.37 (talk) 12:02, 2 September 2011 (UTC)

It's not obvious to me that there have been more large earthquakes in recent years than previously. There is more media coverage now. Increasing populations mean the more people are affected. It would be interesting to look at absolute figures for the earthquakes themselves. HiLo48 (talk) 12:08, 2 September 2011 (UTC)

This is a good place to get some numbers to play with. -- kainaw™ 12:58, 2 September 2011 (UTC)

I made 2 graphs to show how many eathquakes occur yearly in the past 40 years with Magnitude > 7 and Magnitude > 8. I let you make your own opinion whether there's more big earthquakes recently. I think a bit statistics would help but I'm not sure it would bring a clear answer since the data set is very small.--Franssoua (talk) 13:37, 2 September 2011 (UTC)

One should be cautious in interpreting plots such as those, as it's worth remembering that earthquakes often come in clusters (with foreshocks and aftershocks) in space and time. Consider, for example, the 2010 magnitude 7+ numbers. Out of 22 quakes listed, it seems apparent that the three quakes on July 23 – falling within a couple of hours and a few miles of one another – are part of the same event and probably would be covered in the media as one disaster, despite counting thrice. On the other hand, there were also strong quakes on 6 April and 9 May with epicenters about 200 km apart, off the coast of Indonesia. They were no doubt occurring on the same fault system and probably as part of the same gelogical event or process, but the two quakes would definitely have been on separate news cycles.) TenOfAllTrades(talk) 14:40, 2 September 2011 (UTC)

Three of the ten largest recorded earthquakes have occurred within the last 7 years (see Lists of earthquakes#Largest earthquakes by magnitude) -- that's a statistical anomaly for sure, but since it is post hoc, it is hard to assess it's significance. I have seen some discussion of it in the literature, but there are no definite conclusions. Looie496 (talk) 15:31, 2 September 2011 (UTC)

Note that large quakes in populated areas get far more coverage than in unpopulated areas. If a quake the size of the one in Japan had occurred in a sparsely populated area, with no video coverage of the event, it wouldn't have been a major news story, but at best a footnote on that day's news. So, the perception that there are more large quakes recently is probably due to them having occurred where they did.

That said, seismic activity can cluster together. A large quake in one place moves the crust of the Earth slightly, causing other misalignments which cause other quakes, etc., within hours, days, or weeks. StuRat (talk) 15:35, 2 September 2011 (UTC)

A 9.0 earthquake would be a big news story no matter where it occurred -- because of its high likelihood of producing a destructive tsunami if nothing else. Of course a 9.0 in, say, Vanuatu, would not draw the same attention as a 9.0 in Japan, but it would still draw attention. Looie496 (talk) 16:25, 2 September 2011 (UTC)

I don't believe such a quake, in the middle of a continent, would have any chance of triggering a tsunami. StuRat (talk) 22:36, 2 September 2011 (UTC)

Also from the list it's not clear it's a 'statistical anomaly for sure'. If we take out all the ones from before ~1900 i.e. as our article notes, the ones which are estimates so their position in the list is unclear as they before the widespread distribution of seismometers, we find that 6 of the top 10 happened in 1960, 1964, 1952, 1965, 1950, 1957. You can put these in various combinations including 3 in a 5-6 year period and another 3 in a 7-8 year period; 6 in a 15-16 year period; 4 in a 8-9 year period and 2 in a 2-3 year period. (Although if you expand it to top 11 you get another for your past 7 years, I'm not sure if it makes sense to restrict it to the top 10 in that fashion anyway since the moment magnitude appears to be the same.) To be fair, 3 of those were in Alaska (although I haven't looked how close they are) and 2 of those less then a year apart so they may have been related, but it still shows the fallacy of calling a statistical anomaly from such limited statistics and without actually looking at the rest of the statistics. P.S. Noticed that our article on the 1960 quake says "This 2010 Chile earthquake may be related or consequential to the 1960 tremor.[17]" Nil Einne (talk) 17:54, 2 September 2011 (UTC)

I am fairly convinced that, due to a number of factors, there is a systematic reporting/detection bias that makes it seem as if extreme natural phenomena of all kinds are increasingly frequent. 86.177.107.255 (talk) 20:31, 2 September 2011 (UTC)

This is a question that the USGS is often asked, their response is here and further statistics can be found here. Mikenorton (talk) 21:54, 2 September 2011 (UTC)

Some geologists speculate that we are currently in an active earthquake cycle, as well as a high volcanic activity cycle. Also, some studies, though not all, have found that large earthquakes often trigger smaller earthquakes several thousand kilometers away that cannot be considered aftershocks. Some zones experience very large earthquakes (M8 and 9) on irregular intervals, such as the Cascadia subduction zone. ~AH1 ^(discuss!) 22:06, 2 September 2011 (UTC)

The same is also true of the Sunda megathrust, which has had three great earthquakes in the period 2004 to 2007, but a long gap before that. There were three relatively closely spaced magnitude 8+ events in 1797, 1833 and 1861 in a previous cycle. Mikenorton (talk) 22:16, 2 September 2011 (UTC)

Could this be a sign that a big mantle plume is approaching the crust and a flood basalt event is imminent? Count Iblis (talk) 23:48, 2 September 2011 (UTC)

Don't mantle plumes typically take place over hotspots, such as Iceland, Hawaii or Yellowstone? What about Large igneous provinces? ~AH1 ^(discuss!) 00:18, 3 September 2011 (UTC)

climate change

The economics of climate change includes issues to do with; Human Behavior, Economic Development and Negative Nxternalities. discuss these aspects of climate change problem, and give a brief example of how poor countries loose out as a result? how best can one answer the question,i seem to have limited information--Soft tembo (talk) 15:00, 2 September 2011 (UTC)

This looks like a homework question, and the Reference Desk will not do your homework for you. Weren't you given ideas about what to read to answer it? Have you read our Climate change article? Looie496 (talk) 15:21, 2 September 2011 (UTC)

We also have an externality article. —Akrabbim^talk 15:26, 2 September 2011 (UTC)

The Climate change mitigation article might also be helpful. Rckrone (talk) 15:32, 2 September 2011 (UTC)

Some other suggested articles to glance over include economics of climate change, economics of climate change mitigation, peace and conflict studies, politics of climate change, Stern Report, geoengineering, climate change, industry and society, climate change and agriculture, climate change and poverty, and environmental migrant. ~AH1 ^(discuss!) 22:01, 2 September 2011 (UTC)

At what point in the big bang did particles come into existence?

I've been reading the article "Timeline of the big bang," but it seems a little vague. Were they there immediately? (Certainly they were around by the electroweak epoch... but earlier?) --Goodbye Galaxy (talk) 15:23, 2 September 2011 (UTC)

I'm really not being trite, but what is a "particle"? Its all a matter of perspective, and at the scales you are talking about, it isn't really clear that such concepts are necessarily understood in the same way we experience the world with our senses. --Jayron32 15:39, 2 September 2011 (UTC)

Somewhat simplified answer: before the quark epoch the universe is so hot that frequent energetic interactions, high density of virtual particles and continual creation and decay of exotic heavy particles make the questions of particle existence and identity somewhat moot. Once we get into the quark epoch the universe is filled with a quark-gluon plasma of quarks, neutrinos and electrons and their antiparticles, so we can reasonably say that these particles exist at that point, although many are still being annihilated in particle/antiparticle interactions. Once we get into the hadron epoch quarks become confined within hadrons (protons and neutrons, plus their heavier cousins, which eventually decay). Neutrons combine with protons into stable atomic nuclei (helium, lithium and beryllium nuclei) during the first few minutes after the Big Bang. Stable atoms don't form for another 380,000 years. Gandalf61 (talk) 16:00, 2 September 2011 (UTC)

What exactly do you mean by "heavy exotic particles?" Stuff that's not one of these guys? --Goodbye Galaxy (talk) 16:54, 2 September 2011 (UTC)

I still think of anything other than a proton, electron, neutron, or photon as "exotic." The last time I saw a muon was more than six months ago (and all I really saw was a digital readout indicating a large current due to the electrons the muon produced). I have never seen a quark; I have to accept indirect evidence of their existence. If that's not weird enough to be called "exotic," I don't know what is... Nimur (talk) 17:40, 2 September 2011 (UTC)

Quarks are not considered exotic matter any more. Exotic would be anything beyond the standard model. 24.73.119.146 (talk) 18:18, 2 September 2011 (UTC)

In inflationary cosmology, the inflationary era is the earliest state about which anything is known. It's basically a vacuum with a nonzero cosmological constant and a few stray particles (just like the future of our universe according to ΛCDM cosmology, except that the cosmological constant is much larger in inflation). At the end of inflation you suddenly get a hot particle soup by a process called reheating. But until electroweak symmetry breaking (the beginning of the quark epoch) concepts like "photon" and "electron" and "quark" don't really make sense. All particles are exotic. -- BenRG (talk) 03:06, 3 September 2011 (UTC)

Eyes going in different directions

As seen here, it looks like Oprah's eyes go in slightly different directions. What's the name for that? 20.137.18.50 (talk) 16:02, 2 September 2011 (UTC)

Strabismus. —Akrabbim^talk 16:05, 2 September 2011 (UTC)

Of course, not all photographs prove a person has the actual condition. ~AH1 ^(discuss!) 21:56, 2 September 2011 (UTC)

Exactly. The ability to turn the eyes horizontally towards or away from each-other is not only normal but necessary for proper binocular viewing of, respectively, close-by or far-away objects. See Vergence. --Dr Dima (talk) 01:17, 3 September 2011 (UTC)

I couldn't see anything wrong with her eyes in the picture. Dauto (talk) 01:40, 3 September 2011 (UTC)

That's probably because there isn't anything wrong with her eyes in the picture. She is looking into the distance and not at the camera; this may seem like exotropia but probably isn't. --Dr Dima (talk) 02:51, 3 September 2011 (UTC)

SAXS q range?

According to the lede of the Small-angle X-ray scattering article "SAXS is capable of delivering structural information of macromolecules between 5 and 25 nm, of repeat distances in partially ordered systems of up to 150 nm". I'm far from an expert but I thought that most modern synchrotron SAXS beamlines were capable of accessing a much larger q range than that? The website of this beamline at APS seems to imply that they can get to a Dmax of over 500nm with a particular detector configuration. Is it because APS is a 3rd generation light source and the primary reference is the 1982 Glatter and Kratky text (I'm far from an expert but at that time 2nd generation light sources were still state of the art?). I'm only beginning to dive into small-angle scattering, so am unsure if I'm missing something obvious or if the article simply needs to be updated. Thanks. I(q) = User(q)·Talk(q) 16:32, 2 September 2011 (UTC)

Follow up: or is it just that this type of setup is formally considered USAXS (Ultra-Small-Angle X-Ray Scattering)? Thanks again. I(q) = User(q)·Talk(q) 16:36, 2 September 2011 (UTC)

Sound in space

A star breaks the sound barrier in space?

Some guy I encountered on the internet made the claim that the fact that there's no sound in space is a misconception and that if the sound is loud enough, it can be transmitted through the tiny particles floating in the vacuum. In other words, if the sound is loud enough, you can hear it. Is he full of shit? ScienceApe (talk) 21:35, 2 September 2011 (UTC)

First of all, it all depends on the mode of transmission. Human speech requires air to be present in the lungs, which is an impossibility when a person is exposed to a pure vacuum, since the blood would boil along with other nasty effects. However, if electrical sensors are used to detect subtle vibrations, then the signal is transmitted in the person, then communication may be possible. When discussing other sounds, such as a drum set, sound waves would likely not transmit in a vacuum, but a person listening to a drum on the Moon by pressing his/her ear to the lunar soil may detect seismic vibrations. In higher levels of atmosphere such as the mesosphere (the level of space shuttles), air particles are indeed present, yet I'm uncertain about sound transmission. You may find speed of sound interesting. ~AH1 ^(discuss!) 21:54, 2 September 2011 (UTC)

I've added an interesting picture of Mira above, making a sort of bow wave ahead of it as it passes through the interstellar medium. I suppose that as that wave approaches you, you feel fluctuations in the pressure of the ever so tenuous interstellar gas, which can be considered as a type of sound. The turbulence in its wake probably has some "sonic" aspect to it also. I don't know if this is a true shock wave created by moving faster than sound ... sort of looks like one though. Of course, all these "sounds" are ever so slow and faint, not meant for human ears. I should also note that because atoms in outer space are often ionized, "sound" has a strongly electrical/radio frequency component to it as the ions repel one another - see e.g. [16] for the Cassini Jupiter flyby's detection of ion-acoustic waves which are in low radio frequencies but also represent the compression and expansion of the gas of charged particles. Wnt (talk) 22:07, 2 September 2011 (UTC)

Here is a paper that discusses the possible physics of sound waves in a vacuum, although it is pretty technical. I think this may be the sort of thing the OP's friend was talking about. Looie496 (talk) 22:31, 2 September 2011 (UTC)

They just can't hear you scream. Clarityfiend (talk) 22:41, 2 September 2011 (UTC)

speed of sound

why does sound travel faster in warm air than in cold air? — Preceding unsigned comment added by 175.110.242.217 (talk) 23:27, 2 September 2011 (UTC)

The formula for the speed, IIRC, is 331.4 m/s + 0.606(T°C). ~AH1 ^(discuss!) 00:04, 3 September 2011 (UTC)

Why: According to speed of sound, a lower density allows the sound waves to travel more readily and thus at a vaster speed, and warmer air generally has less density. The fact that warmer particles vibrate and move around faster may also allow the motion transfer of a sound wave to propagate faster. ~AH1 ^(discuss!) 00:11, 3 September 2011 (UTC)

Imagine making a wave in a bathtub full of water. Now imagine doing so in a tub full of honey. You'd expect the thicker fluid to make slower waves, right ? StuRat (talk) 01:09, 3 September 2011 (UTC)

Honey has a high viscosity which is unrelated to the question asked so that analogy doesn't seem to be very helpful. Dauto (talk) 01:37, 3 September 2011 (UTC)

September 3

Oxygen and cancer

Hi. I read somewhere that when normal cells are starved of oxygen, their metabolism changes to glycolysis through the Warburg effect and the normal self-destruct mechanism based on mitochondria stops, thus making these cells cancerous. Does this mean that any oxygen starvation of tissues, for example through ischemia or mountain sickness, automatically increases the risk of cancer? Finally, does sleep deprivation reduce the amount of oxygen to organs and various parts of the human body? Thanks. ~AH1 ^(discuss!) 00:15, 3 September 2011 (UTC)

Ruptured star

Is it possible for a star to sort of "pop" and expel its contents through the rupture via its own gravity (kind of like a balloon bursting when you squeeze it)? Whoop whoop pull up ^{Bitching Betty | Averted crashes} 00:19, 3 September 2011 (UTC)

Nova,Supernova, and Hypernova are the known ways stars can "pop". Dauto (talk) 00:24, 3 September 2011 (UTC)

Also see Polar jet and Coronal mass ejection and Gamma-ray burst for different phenomena which may meet what the OP is talking about... --Jayron32 00:29, 3 September 2011 (UTC)

The question implies that a star has some "membrane" keeping it intact. Usually, the opposing forces of gravity (keeping the star from exploding) and internal pressures (keeping it from swallowing itself) keep the star in equillibrium. Sometimes in core collapse events, the star will start to implode, superheat and reach an outward pressure exceeding the gravitational force, and thus shedding its layers in a way somewhat similar to a balloon popping. It is the internal gravity, not an external membrane, that keeps the star together. Although the transition from a red giant star (similar to the Sun in late stages) to a white dwarf is commonly described as the star "shedding its outer layers", it in other words explodes. The presence of heavy elements such as carbon and oxygen in high amounts causes the star's pressures to exceed its gravity, ejecting its atmosphere. ~AH1 ^(discuss!) 00:31, 3 September 2011 (UTC)

Rotor and propeller vs. cylinder

Why are rotors and propellers used instead of a cylinder, which could compress the water or air? What makes those solutions more efficient than the latter? Quest09 (talk) 00:25, 3 September 2011 (UTC)

Water isn't compressable. --Jayron32 00:29, 3 September 2011 (UTC)

You mean it's difficult to compress, right? Anyway, you can push it with a cylinder, and make a vehicle move forward. Quest09 (talk) 00:36, 3 September 2011 (UTC)

No, it is essentially uncompressable. The atoms are already at essentially maximum density, you can't actually push them any closer together. --Jayron32 01:10, 3 September 2011 (UTC)

Of course what Jayron means is that you can't push them much closer together at any reasonable pressure. Water does have a bulk modulus; it will compress a little bit. And if you use truly extreme pressures, it will compress a lot (it's not anywhere close to electron degenerate matter, much less neutron degenerate matter). --Trovatore (talk) 01:14, 3 September 2011 (UTC)

Yes, true, but for the application of what the OP is looking for, we can treat water as uncompressable. The reason things like jet engines and turbo chargers and superchargers work in air is because air is very compressible; essentially you get a direct relationship between decreased volume and increased pressure (Boyle's law). Water doesn't work that way. Yeah, it is in a very small way, compressible in the sense that with some massive pressures, you can get minute changes in volume, but not in ways that make it anything like an effective means of propulsion akin to a jet engine or something like that. For the purpose of this application, you can assume it as essentially uncompressable (to a first approximation). --Jayron32 01:29, 3 September 2011 (UTC)

Used for what? ~AH1 ^(discuss!) 00:31, 3 September 2011 (UTC)

They are used for moving a vehicle forward. Quest09 (talk) 00:36, 3 September 2011 (UTC)

So your idea is to compress water in a cylinder, then release it out the back to propel a Ski-doo-type vehicle forward ? It wouldn't work very well. As was said, water isn't very compressible. Then there's the problem of this method providing a putt-putt motion instead of smooth movement. StuRat (talk) 01:17, 3 September 2011 (UTC)

Could someone explain how a cylinder would be used for propulsion? Are we talking about something like a turbine? Dismas|^(talk) 01:42, 3 September 2011 (UTC)

I think he's thinking along the lines of a Hydraulic cylinder, but I'm not sure how such a device could make an efficient propulsion system... --Jayron32 01:45, 3 September 2011 (UTC)

Now, if you make it a pneumatic cylinder, and use it to launch a projectile, then that sounds more practical. I believe some children's toys work like that, and it might be practical for other applications, like launching unmanned airplanes. StuRat (talk) 01:53, 3 September 2011 (UTC)

Well yes, but then we're back to air again, but the OP is interested in water propulsion. There are water-based "jet" engines, like the Pump-jet, but these don't rely on compression; they are basically just encased propellers which are optimized for higher RPMs and more directionality, and with a constricted output, akin to putting your thumb over the garden hose. Still not proper "compression", but they do provide thrust by pressurized water. --Jayron32 04:00, 3 September 2011 (UTC)

Jupiter sized object crashing into Sun

Hi, suppose an object about 1/1000 the mass of the Sun came from interstellar space and hit a bullseye with the Sun at 200miles/sec?Would there be brief fusion at sun's surface? Would the sun be changed drastically in some way? Would life on Earth be destroyed? What if we tweaked the mass and velocity of the object up and down?...It seems to me tha if impact of a comet or asteroid with Earth is probable enough to be at least a minor worry nowadays, an impact on the sun with a larger object could be a minor possibility, if not a worry. 200miles/sec seems reasonable, since Earth revolves around sun at 18miles/sec, and object is supposed to go straight toward sun from a long way--no need for it to have a closely comparable velocity.Thanks24.7.28.186 (talk) 03:47, 3 September 2011 (UTC)

You mean aside from completely throwing the earth out of its orbit before it ever got to the sun? --Jayron32 04:01, 3 September 2011 (UTC)

If it came from the other side, I don't think it would affect the Earth's orbit very much. Of course, I'm not sure how much it would take....

In response to the OP's final sentence, though, that's really not true. The kinetic energy of an object in a circular orbit is half the energy it needs to escape, which means escape velocity is only square-root-of-two times larger. If the Sun pulls an object in from infinity, it hits at the escape velocity, so around 25 mi/sec if the OP's numbers are correct.

Of course if it doesn't get its velocity by falling into the Sun, but simply because it was already going fast, then there's no special limit. But then the odds against it hitting the Sun are large; if it's a little bit off, it just makes a hyperbolic path past the Sun and heads back into interstellar space. --Trovatore (talk) 04:07, 3 September 2011 (UTC)

Whoops, now that I think about it, that's the escape velocity from the Sun at the radius of the Earth's orbit. The escape velocity at the surface of the Sun would be a lot larger. About 15 times as large if my calculations and quick googling are right. So could be on the order of 350 to 400 mi/sec. --Trovatore (talk) 04:11, 3 September 2011 (UTC)

Sure the object could come in while the Eath is on the other side, or more generally from out of the ecliptic entirely. How much time would an oject that fast to meaningfully perturb Earth's orbit?...I think most comets that get in close must be going very fast at that point...Are the odds of a hefty object hitting the sun, in a 10 million year span, say, really so small? Thanks again.24.7.28.186 (talk) 04:20, 3 September 2011 (UTC)