Wikipedia:Reference desk/Archives/Science/2007 April 7

= April 7 =

Primordial soup
I was reading through abiogenesis in my biology textbook and Wikipedia, but couldn't find any specific details on it. Are there any findings that substantiate such an environment?  bibliomaniac 1  5  01:06, 7 April 2007 (UTC)


 * The existence of life on Earth substantiates the concept that, at some point in the past, there must have been a specific set of conditions in which early lifeforms could spontaneously arise and evolve. − Twas Now ( talk • contribs • e-mail ) 04:34, 7 April 2007 (UTC)


 * Panspermia contests this, but there have been attempts to reproduce abiogensis directly. -Arch dude 04:56, 7 April 2007 (UTC)


 * However, if terrestrial life originated from an extraterrestrial source, there must have been a specific set of conditions in which early lifeforms could spontaneously arise and evolve. − Twas Now ( talk • contribs • e-mail ) 09:08, 7 April 2007 (UTC)


 * There have been experiments that take the kinds of non-biological things that would have been around in the early earth - added sparks to simulate lightning - and those experiments have produced basic amino acids - and those amino acids do spontaneously form short chains and such. The question for abiogenesis is whether it is possible - by pure chance - that such a chain could form something that could replicate itself - perhaps an RNA molecule.  That's all it takes - once you have thet, the well-understood processes of evolution gets us from there to animals and plants.  So the problem is: What is the probability of something like a short RNA strand forming spontaneously?  Bear in mind that this could have happened at any time over millions of years in any of the quadrillions of gallons of water in the oceans and in any of the molecules in each gallon of that water.  The number of opportunities for that to occur are truly astronomical - and it only had to happen ONCE in the entire history of the earth.  The event could be spectacularly rare.   Indeed, it must be fairly rare because we don't see new RNA-like molecules forming all the time in modern earth.  That being the case, it is not possible that a laboratory experiment could reproduce this event - you might well need an entire planet full of soupy amino-acid-laden water and to cook it for a hundred million years in order to make this happen.  We can only deduce that it did indeed happen...once.   There is some evidence that it may in fact have been so spectacularly rare that it did only happen once - if it had happened lots of times then I suspect we'd see multiple kinds of DNA in modern organisms that showed absolutely no common amino acid sequences whatever...we don't see that - so I strongly suspect that this was one single astronomically unlikely event. SteveBaker 16:10, 7 April 2007 (UTC)


 * The only thing is, what evidence do we have for such a soup? If such a concoction existed, why don't we find a nitrogen-rich layer of earth? Where in all the strata we have unearthed have we found remnants of such a world? Saying that because we are here, there has to have been spontaneous generation of living beings is a rather biased view. And how would only one single strand of RNA suffice to create what we have today, even if it overcame the odds? Infinite Monkey Theorem, it seems.  bibliomaniac 1  5  20:32, 7 April 2007 (UTC)
 * We have experiments that show that an amino acid 'soup' will arise when the mixture of gasses and water that we believe would have existed in pre-biotic times is stimulated with UV light and an occasional spark of electricity - the sun and lightning storms respectively. This shows that unless there is no reason whatever why the oceans of early earth would not have  had the necessary ingredients for the spontaneous formation or an RNA molecule at some time in the past.  Once the one single molecule existed, it would replicate until the oceans had a LOT of these peculiar molecules floating around in them.  Once that happens, the molecules are competing for resources (the free floating amino acids for example) and they are mutating (because RNA copying errors would be relatively frequent - and survival of the fittest would also be there - so evolution kicks in and the rest is really well known.  Why don't we find a "nitrogen rich layer"?  Well, because the land surface is a mess of shifting tectonic plates that slide over and under each other.  Whenever a plate goes under, it gets melted back into magma and mixed up...since the events we are talking about are so very old, not one scrap of the earths surface from those ancient times still exists for us to examine.  No firm records of that era can possible have survived.  We can only do experiments, calculate probabilities and produce believable mechanisms.  This is less than satisfying as solid proof goes - but it's the only explanation we have that doesn't rely on supernatural intervention - which we generally rule out using Occams Razor.  If there were a competing theory (which didn't require magic or whatever) then there would be a lot of interesting debate about it - but there really isn't.  The Panspermia hypothesis is (in a way) a competing theory - but even if life arrived on earth on a meteorite or something, it still had to start SOMEWHERE - and we're back to needing an abiogenesis mechanism to make that work. SteveBaker 07:16, 8 April 2007 (UTC)
 * Direct evidence? The answer is basically no.  Very, very few rocks survive for over 3 billion years, and those are so heavily metamorphosed that no complex organics would be expected to survive.  However, we can make a variety of arguments about the simple ingredients of that world.  We know for example that it had low oxygen and very high carbon dioxide (e.g. 1000 times modern).  We know there would have been much greater volcanic activity (providing a potentially interesting energy source).  We know liquid water was abundant (just as is it today).  Various simple organic precursors (e.g. methane, ammonium, hydrogen) would have been created naturally in that environment.  Work like the Miller-Urey experiment has shown that the synthesis of complex organic molecules and polypeptide chains is plausible (at least in small concentrations) from these raw ingredients.  With neither oxygen nor microbes to break them down, some of those organics should have persisted in the environment for a long time and this gives rise to the classical idea of an organic "soup".  Given the existence of complex life today, many scientists are willing to make the leap that somehow the accumulation of such organics eventually gave rise to cellular life, but we have very little evidence to show how this occured.  Some parts are fairly easily.  For example, lipids are easy to make and will spontaneously roll themselves into balls, effectively enclosing cell like spaces.  RNA (once generated) can both act as genetic material and catalyze reactions, in a way similar to how proteins function today, though proteins are more efficient.  In the presense of sufficient nuclei acids, RNA can also easily duplicate itself.  This has led to speculation that an "RNA world" might have existed in the early development of life.  Dragons flight 21:08, 7 April 2007 (UTC)


 * There weren't microbes or oxygen to break them down, but keep in mind that there was no ozone layer to protect such substances from the UV rays of the sun. The Miller/Urey experiment is interesting, but a) only two percent of the resulting sludge was amino acids, b) only 2 amino acids were actually created, c) these compounds reacted with the other chemicals created, and d) they used a carefully controlled apparatus to create these compounds. As for "RNA world," the chances that one RNA molecule spontaneously generates is big enough, what are the chances that there are two identical ones?  bibliomaniac 1  5  01:29, 8 April 2007 (UTC)


 * I agree that the classic Miller/Urey experiment left something to be desired - but we don't know the exact conditions - and other experiments using other starting conditions produced quite different results. So it's peossible for four amino acids to have formed instead of two given a different value for some concentration or a different temperature or whatever...it's not a huge stretch of the imagination at least.  You don't need two RNA molecules to exist - a single strand is enough (see RNA virus for some examples of single-stranded RNA)- its complementary strand will form spontaneously from the first half - then they unzip and each half makes another complementary strand to match.  That part is OK - there is even some evidence for such simple "organisms" (iffy terminology!) still exist (see Nanobe for example).  The really, really unlikely part is that very first strand forming with exactly the right properties to replicate spontaneously with enough precision to make working duplicates over enough generations for evolution to cause it to survive more robustly.  But even at low concentrations, given the enormous volume of the earths oceans and the veast time-span during which it could happen - it's really not so very unlikely.  Suppose we estimate that there is a mole of reagent in every cubic meter of primordial soup and that 'candidate' reactions happen every millisecond or so...yeah there are lots of reasons why the numbers might be a lot lower than that - but stick with me for a moment.
 * The oceans contain 1.37x1018m3 according to 1 E+18 m³.
 * Avagadro's number (the number of molecules in a mole of reagent) is 6x1023.
 * A billion years is 3x1019 milliseconds.
 * So there could easily have been 2.4x1060(!) attempts at this happening before we got a result. That's an insanely large number!  If it only has to happen once - then the odds can be long indeed!   Furthermore - since we could have ended up being brought into existance on any planet during the entire life of the universe - the timeframe and volumes of reagents is MUCH more than that. SteveBaker 07:50, 8 April 2007 (UTC)

Monarch Butterflies
Do Monarch butterflies help to cross pollinate flowers and plants? IF they don't, which butterflies do? —The preceding unsigned comment was added by 67.186.153.196 (talk) 01:18, 7 April 2007 (UTC).
 * Yes, as do pretty much all butterflies ; simply said, if it goes from flower to flower, it carries pollen, if it goes to two flowers of the same species then it helps cross pollination. Pro bug catcher (talk • contribs). 02:19, 7 April 2007 (UTC)
 * I don't think it's accurate to say that pretty much all butterflies assist with pollination. I believe many butterflies don't feed in their adult/imago stage.  Monarch butterflies do, however. Matt Deres 02:48, 11 April 2007 (UTC)

Umbilical cord
A developing fetus is connected to the mother via three blood vessels in the umbilical cord. My question is: whose are they? If you were to take tissue samples from the fetus and do genetic analysis, you'd obviously get fetus DNA. Presumably the placenta is the mother's tissue. But where does the baby start and the mother end? What is the interface like (gradual, discrete, etc.)? Thanks! --TotoBaggins 01:54, 7 April 2007 (UTC)


 * The umbilical cord develops from the embryonic allantois; it will have the baby's DNA. As you've correctly deduced, the placenta is indeed entirely Mom's.  The interface is at the chorion (on the fetal side) which forms chorionic villi that project into the decidua (mother's side); this is interface where nutrients and blood gases are exchanged in the placenta. TenOfAllTrades(talk) 02:56, 7 April 2007 (UTC)


 * Awesome answer; thanks! --TotoBaggins 03:28, 7 April 2007 (UTC)


 * No, the placenta is not entirely maternal; in fact, the functional placenta is almost entirely fetal, with a rather minor maternal component. The chorionic villi comprise the majority of the functional placenta. These villi are entirely fetal in origin, which is the rationale behind using chorionic villus sampling to screen the fetal genome. Maternal tissue only plays a role in support (the maternal decidua basalis is the supportive structure to which the fetal placental component attaches) and in placental circulation (the spiral arteries of the maternal endometrium penetrate the developing chorionic villi and bathe the fetal tissue in maternal blood). The interface between fetal and maternal components of the placenta is rather distinct: the decidua basalis (maternal) is separated from the chorionic villi by a cytotrophoblastic shell that is derived from fetal tissue (the trophoblast) and is several cells thick. Also, it is a common misconception that the allantois gives rise to the umbilical cord. True, the allantois begins as an evagination of the gut that extends into the body stalk (the umbilical cord anlage), but the umbilical cord itself is made mostly of extraembryonic mesoderm and Wharton's jelly. The allantois regresses into the embryo to give rise to the urinary bladder and median umbilical ligament. To answer the original question: the blood vessels of the umbilical cord are fetal, as TenOfAllTrades said. --David Iberri (talk) 22:14, 7 April 2007 (UTC)

Dinosaur age
How old could a dinosaur become? —The preceding unsigned comment was added by 62.78.246.132 (talk) 09:07, 7 April 2007 (UTC).


 * There were many different species of dinosaur, so this question is a little like asking "how old can a mammal become" - it all depends on whether you look at a shrew or a whale (note to experts - yes, I know that mammalia is a class and dinosauria is a superorder, so the analogy is not exact). Dinosaur lifespans probably covered a wide range, with the larger species having longer lifespans, as they would take more time to grow to maturity. This page] gives a range of "tens of years to hundreds of years", and makes some comparisions with the maximum lifespans of modern reptiles in captivity; whereas this page suggests a typical dinosaur lifespan of about 40 to 50 years, based on growth rings found in fossil teeth and bones. Gandalf61 11:12, 7 April 2007 (UTC)


 * Just to provide some additional info, this page lists the life spans of the huge Apatosaurus, Brachiosaurus, Diplodocus, and Supersaurus as roughly 100 years; smaller dinosaurs die sooner. This page says the life span is 75-300 years, though I doubt 300 years is accurate.  --Bowlhover 05:15, 8 April 2007 (UTC)

Turtles can reach a great age. cf Tortoise DDB 11:24, 7 April 2007 (UTC)


 * And of course it is widely believed that birds evolved from Dinosaurs - some species of parrot can live for 100 years in captivity. SteveBaker 16:00, 7 April 2007 (UTC)

WARTS
DEAR SIR, MY WIFE's DOCTOR HAS DETECTED WARTS ON HER VAGINA AND ANUS FOR WHICH SHE IS UNDER GOING THE TREATMENT. VAGINIAL WARTS AEE ALREADY FINISHED BUT STILL THEY ARE ON HER ANUS. I WOULD LIKE TO KNOW FROM WHERE DOES SHE CAUGHT THIS VIRUS AS I AND MY WIFE NEVER HAD SEX WITH ANYBODY ELSE AS SHE HAD IT ONLY WITH ME AND I ONLY WITH HER AND NOBODY ELSE AND STILL THERE IS A VIRUS. I WOULD LIKE TO SPECIFY THAT WE HAD ANAL, ORAL, AND VAGINIAL SEX.

THANKING YOU GAGAN


 * It depends on the type of warts. You would be best to seek advice from a medical professional&mdash;your family doctor, or at a walk-in clinic if you're too embarrassed. TenOfAllTrades(talk) 12:15, 7 April 2007 (UTC)


 * For what it's worth, we have an article HPV, the set of viruses that cause warts. Friday (talk) 17:54, 7 April 2007 (UTC)


 * Noting, of course, that there are other causes of genital warts and wart-like symptoms (some are listed in that article). See your doctor to be sure. TenOfAllTrades(talk) 18:12, 7 April 2007 (UTC)


 * It is not necessary to have had sex with someone in order to catch a sexually transmitted virus. As everyone says, it is better to ask your doctor or physician why the symptoms are still persisting and if it is normal for this to happen. That will put your mind at rest, as his/her answer will either be 'yes', in which case there is no problem, or 'no', in which case he/she will find another method of treatment. ScouseMouse - スカウサーUK! 23:11, 7 April 2007 (UTC)


 * Though in my experience most doctors will give you a condescending look, the "you can pretend if you want to but we all know what this means" sort of look. The "I don't actually know anything about you or your life but I'm going to presume that I do because I'm the one with the M.D., and this ain't no television show where doctors actually give a shit about ferreting out statistically unlikely causes." But maybe that's just my experience with doctors, which I admit is fairly infuriating. Statistical medicine works some of the time, but not all of the time, and when it fails it fails miserably. I wish more doctors seemed to care about that. Which is just a long way to say, you can ask your doctor for alternative possibilities, but don't expect them to really offer them up, or think they are necessary. They are going to tell you "they are spread by sex with people who have them" and no matter how much you inquire to the hypothetical that such might not have been the case, they'll just look at you like you're an idiot. --24.147.86.187 01:12, 8 April 2007 (UTC)
 * Two things occur to me. First, 99% of people "just can't imagine" where they got an STD, so if your doctor acts like she has heard it before and is a bit skeptical as to your amazement, and seems reluctant to engage in unprovable speculation about other alternatives, you shouldn't be surprised. Second, doctors being human beings, they often respond the way your attitude and signals tell them you expect them to respond. alteripse 17:34, 8 April 2007 (UTC)

Packing density
What is the packing density of grains with different regular shapes? E. g. how much air is in a bag of table salt? I'm quite sure that people have made mathematical models for these problems - is there a wikipedia article about the topic that I didn't find? Icek 13:45, 7 April 2007 (UTC)


 * Try crystal structure and lattice model (physics), for explanations at an atomic scale. For more mathematical explanations, some of which are not quite as applicable to this question, try some of the links listed at lattice. − Twas Now ( talk • contribs • e-mail ) 22:35, 7 April 2007 (UTC)


 * Interestingly "packing density" is a specific concept in crystallography (that's what I thought when I saw the title of this question), that uses a hard sphere atomic model to estimate how much "free space" exists in various crystal structures. Your example is a little trickier since, in practice, there's no way of knowing the exact size and shape of any grain of salt.  Solid NaCl arranges itself into an FCC lattice and will cleave along the major faces, leading to the rectangular prism shape of salt grains, but with the grains oriented in all manner of directions and coming in varying sizes, any model for the free space in a bag of salt would have to be statistical in nature.


 * That's a long-winded way of saying "I don't really know", but hopefully the crystallography links can give you some useful information. -- mattb


 * You might start at sphere packing and close-packing. —Steve Summit (talk) 23:59, 7 April 2007 (UTC) (Yes, I know you said "grains" and not "spheres", but it's a start.)

Thank you for the answers, but I already knew about crystal lattices and sphere packing. I hoped someone would know something about statistical models of e. g. a heap of cube-shaped grains. Btw, I measured and weighed a sample of ascorbic acid (grain size roughly 0.1 mm) and arrived at a space filling fraction of 0.56. Icek 17:59, 8 April 2007 (UTC)
 * I know this is an active area of materials research. For clarification, Icek is talking about macroscopic packing of grains, not crystal-lattice structure of atoms/molecules.  I haven't yet found a specific article on Wikipedia, maybe we should create one.  Here's a MathWorld article on cubic close packing.  Nimur 21:01, 9 April 2007 (UTC)


 * This journal paper was published in AIP, and has a nice table of experimental, statistical data for various natural and man-made grains (such as "Nevada sand," "Daytona Beach sand," ASTM graded sand, and a few dozen others. You might need a subscription to view the article. Nimur 21:05, 9 April 2007 (UTC)


 * On a somewhat related note, is there a name for the phenomenon where smaller grains percolate down while larger ones percolate up? (I was noticing this in action while sorting a bowl of assorted Lego bricks yesterday.) —Steve Summit (talk) 01:01, 10 April 2007 (UTC)

Pen Lasers or 'Penned' Lasers
Those pen lasers, are they true "lasers" or are they just fancy, more sophisticated mini-flashlights?--JLdesAlpins 13:52, 7 April 2007 (UTC)


 * As it states in the article you linked "Most inexpensive laser pointers use a deep red laser diode [...]", so yes, they are actual lasers. --LarryMac 15:00, 7 April 2007 (UTC)


 * LarryMac, sorry if I don't always take what others write at face value and seek to doublecheck others' statements. This must be a scientific bug in me. One has to always be wary of marketing claims...--JLdesAlpins 15:20, 7 April 2007 (UTC)


 * See also our article on laser diodes. TenOfAllTrades(talk) 15:02, 7 April 2007 (UTC)

Sorry for hijacking the question, but I've always wondered: why does light from laser pens (...or in fact, lasers in general), reflect in all directions when hitting a boundary, such as a wall? Surely if all the laser's photons are heading in (ideally) exactly the same direction, the laws of reflection should make all the photons reflect through the same angle? Is it because the boundary is not a perfect reflector, and is atomically "bumpy"? Thanks, Icthyos 15:36, 7 April 2007 (UTC)


 * Yeah - when the laser reflects off almost any surface, the teeny-tiny bumps will scatter the light off in all directions - which is why you can see where the laser is pointing. It's no different from other kinds of light in that regard.  The light rays coming from the sun are very nearly parallel when they reach us - if all reflections were 'perfect' - it would be almost impossible for us to see anything! SteveBaker 15:58, 7 April 2007 (UTC)


 * The beam is coherent, but it has a non-zero cross-section. In fact, it has the cross-section of the laser, more or less. Therefore it is hitting a small area of the wall, not a point on the wall. Unless this small area is an optically flat mirror, different parts of the spot will affect the photons differently. For the same reason, you do not see your reflection in that same wall. -Arch dude 16:08, 7 April 2007 (UTC)


 * The beam has roughly the cross section of the exit point of the resonant cavity waveguide unless it is further shaped by optics (it often is). -- mattb


 * And with all the laser pointers I've used in the past, none of them are really that straight. The light all have an angle that you can clearly notice if you shine it far away when it's dark. The circle always increases. So with that imperfection built in, the light should also scatter slightly radially even with a perfect surface. --Wirbelwind ヴィルヴェルヴィント (talk) 17:43, 7 April 2007 (UTC)

Perpetual Motion Machine Idea
What is the fatal flaw with the following "pereptual motion machine"? A pendulum with a magnetic bob swings between two attractive magnets that are positioned near the top of each swing. However, the pendulum mechanism is also to attached to a kind of magnetic shield that is thrust between the bob and the attractive magnet towards the peak of its swing, thus cutting off the attractive force and allowing the magnet to fall. —The preceding unsigned comment was added by 76.211.141.7 (talk) 19:04, 7 April 2007 (UTC). Z


 * Well, one fatal flaw is that your innocent-sounding "some kind of magnetic shield" doesn't actually exist! If you could find a shield for magnetism (or, equivalently, a shield for gravitation) you could make quite a few very interesting devices!
 * More seriously, even if you did have a magnetic shield, how do you know that it wouldn't have some magnetic properties of its own? If thrusting the magnetic shield into the gap between two magnets also required force, it could (and almost certainly would) end up canceling out the gain you hoped to get from the device. —Steve Summit (talk) 20:17, 7 April 2007 (UTC)


 * If human intervention is needed, for example to insert the magnetic blocker, then it's not a pertual motion machine. But Steve:  the "magnetic blocker" could be another magnet with the same polarity as the bob.  --Bowlhover 04:07, 8 April 2007 (UTC)


 * A magnetic blocker like mu metal certainly does exist. DMacks 18:19, 9 April 2007 (UTC)


 * Bowlhover: I'm sure human intervention isn't needed; presumably some mechanism linked to the pendulum is supposed to shift the magnetic shields in and out. But in the case of "another magnet with the same polarity as the bob", I think that would always end up requiring extra force, and end up "canceling out the gain", as I said.


 * DMacks: Oh! I'd never heard of that stuff!  So why wouldn't it work here?  Does it, too, end up requiring substantial force to thrust into an existing magnetic field, before it can start blocking it? —Steve Summit (talk) 00:24, 10 April 2007 (UTC)


 * Yes, inserting anything requires work, and you can't easily see whether this work is going to exceed the pendulum's work output or not. Also about Mu metal:  it's 75% nickel and 15% steel, so the bob will attract it.  --Bowlhover 02:44, 12 April 2007 (UTC)


 * What about air resistance? This would have to be done in a vacuum, would it not? - Wo o  ty   Woot?   contribs  04:08, 8 April 2007 (UTC)


 * No, the idea is to use the magnetic force to overcome air resistance and friction. --Bowlhover 05:03, 8 April 2007 (UTC)


 * The interesting and important thing about perpetual motion machines is that they quite simply cannot exist because of that boring old first law or thermodynamics. In the end it's a big waste of everyone's time to debumk each and every wild-assed idea for one.  The reason it won't work is that the universe won't let it.  Precise details of why are unimportant. SteveBaker 07:03, 8 April 2007 (UTC)


 * Except that the precise details are precisely what we were asked for ... there was no suggestion that the thing ought to work. Steve Summit thought the question was worth answering.  If you think it's a waste of time, then I suggest picking a different question to answer.  --Anonymous, April 9, 2007, 02:57 (UTC).


 * Thanks for sticking up for me, whoever you are, but in all honesty, I very nearly replied as SteveBaker did! If we have faith in conservation of energy and the three laws (er, make that the three laws), it's true, we don't have to think too hard about these claims; as soon as we hear the words "perpetual motion" we can reflexively say, "Pish-tosh!  Won't work!  Next question."


 * ...except of course that faith is what those other systems of thought depend on. If challenged, we're supposed to be able to explain these scientific beliefs of ours rationally, without handwaving or appeals to authority.  (Not that I'm trying to lecture anybody.  I'm sure other Steve, and anyone else who cares enough about science to be answering here, understands this.)
 * Invoking a well established scientific law is not handwaving or appeals to authority - any more than claiming that the magnet will attract the pendulum in the first place is handwaving or an appeal to authority! How do you know that the magnet will attract it? You only know because you are appealing to a scientific law relating to magnetism that (in all likelyhood) you don't understand!  You may be thinking of claiming that you've seen lots of magnets attract lots of pendulums - but that's no more valid than me claiming I've seen lots of perpetual motion machines that don't work.  You cannot possibly expect every single scientific argument to go all the way back to primary evidence...there always comes a point where you have to say "We know this to be true".  It's not an act of blind faith because we know that if called upon to do so, we could look back at the original mathematics and experiments that caused science to adopt those laws.  It's "trust" - but it's not "faith". SteveBaker 02:19, 10 April 2007 (UTC)
 * We're not in disagreement. When I said "we're supposed to be able to", I didn't mean we had to do it from memory, or every time a bad-faith skeptic insists. (This is about to get even more speculative & opinionated, so I've moved the rest to your talk page.) —Steve Summit (talk) 00:23, 11 April 2007 (UTC)


 * Also, figuring out where the energy goes (or doesn't come from) in a putative perpetual motion machine is often a good exercise, to keeps one's energy conservation skills finely honed. (Me, I still can't figure out where the energy comes from when water lifts itself up a tube by capillary action, which'd be a dandy way to make a perpetually-flowing waterfall, if only you could get the capillary action lifing the water fast enough to build up some momentum to push it over and past some lip at the tip of the tube... :-) )
 * —Steve Summit (talk) 00:12, 10 April 2007 (UTC)
 * Capillary action - like magnetism and gravity - exerts a force. But there is a lot of misunderstanding about the difference between exerting a force and doing work. These misunderstandings are at the heart of a lot of perpetual motion machine proposals.  Work is force moved through a distance.  When your fridge magnet defies gravity by exerting a force against the metal door it's not doing work - it's just sitting there.  If you misunderstand the difference between exerting a force and doing work, it appears that magnets are mysterious devices with some infinite supply of energy just waiting to be tapped...this promise of infinite power attracts crank pseudo-science like...well...like a magnet.  Same deal with capillary action - the water is clinging to the side of the glass - but once it's there, it's not expending any energy to stay there.  Now - certainly the liquid does move in order to take up that shape - so if you lower a glass rod very gently onto the surface of some water, the water will crawl up against gravity to form the meniscus.  This looks like the water is generating some kind of energy in order to propel that small amount of liquid upwards against gravity.  What we're missing is that the meniscus forms because it's a LOWER energy state than if the water surface was horizontal.  So the water flowing uphill to form the meniscus is LOSING energy - just as a rock loses energy when you drop it or a fridge magnet is in a lower energy state when it's stuck to the refrigerator than it would be if it was a quarter inch away from the door.  So just as there is no mysterious 'magnetic energy' - there is no mysterious capilliary action energy. If you really want to boil your brains - figure out how supercooled liquid helium can flow right up out of a container and down the sides! SteveBaker 02:19, 10 April 2007 (UTC)
 * I didn't realize capillary action could be thought of in the same way as magnetism and gravity! Thanks for that.
 * You're absolutely right about the confusion between force, work, and energy. What's particularly amusing/ironic/pathetic/disgusting is when some new quack du jour produces Yet Another alleged perpetual motion machine based around permanent magnets, and a well-intentioned critic pipes up to say that it can't work -- because the magnets will only last for a finite time before their "magnetic energy" is "all used up".  Sigh.
 * (Also, thanks for the offer, but no thanks, I am not gonna boil my brain trying to think about liquid helium. I already know that liquid helium is PFM. :-) ) —Steve Summit (talk) 00:23, 11 April 2007 (UTC)


 * I don't think so. It would be really awesome to find one. [' Mαc Δαvιs '] ( How's my driving? ) ❖ 02:47, 9 April 2007 (UTC)


 * Now this is the guy that Steve Baker's comment should be addressed to, not the original poster. --Anonymous, April 9, 2007, 02:57 (UTC).


 * I thought it was the second law that prevented that from ocurring? Tito xd (?!? - cool stuff) 03:01, 9 April 2007 (UTC)


 * Point. "First law: you can't win.  Second law: you can't break even.  Third law: you can't quit the game."  As to perpetual motion machines, which one applies depends on whether you're talking about the kind generates energy output or the kind that just keeps running forever.  --Anon, April 9, 05:45 (UTC).
 * And from a practical perspective, even the kind that that people imagine "don't generate any output energy" are still generating heat in any moving parts in overcoming friction, tidal gravitational forces, air resistance or photon pressure - so both first and second laws apply in essentially every case. SteveBaker 23:23, 9 April 2007 (UTC)


 * Steve, I disagree completely with your suggestion that "it's a big waste of everyone's time to debumk each and every wild-assed idea for one [PMM]." Newton's laws are like any other laws based on physical evidence: they are completely vulnerable to a contrary piece of evidence.  Further, I find it highly objectionable to support a scientific point using an appeal to tradition. Matt Deres 03:07, 11 April 2007 (UTC)


 * Well, no, not quite. Newton's laws are "vulnerable to a contrary piece of evidence" only in a very abstract, philosophical sense.  Realistically, at macroscopic scales and in this Universe, those laws are rock-solid; a contrary piece of evidence is just not going to be found.


 * The reason to spend any time "debunking" a putative perpetual motion machine -- a practice which I have been supporting and SteveBaker has been discouraging -- is not any kind of "due diligence"; it's not to admit the possibility that the inventor of the machine might have succeeded.  On that point, the burden of proof is definitely on the inventor.


 * No, the primary reason to spend any time debunking or explaining is merely to educate any impressionable children or other credulous observers who might be standing around. Secondary reasons are to keep in practice, and to remind any incredulous observers (i.e. those who might accuse us of taking science on faith) that we can explain any of our scientific truths, all the way back to first principles if necessary, any time we want to.


 * The trap SteveBaker doesn't want to fall into -- and I don't, either -- is to be forced to repeat known truths ad nauseam in a futile attempt to cajole the whims of unthinking skeptics. If someone says, "I've invented a magical new device that puts out more energy than it takes in, and I won't tell you exactly how it works, but unless you can prove to my satisfaction specifically why it doesn't work, I get to claim it does", we get to say, "No, sorry, bucko, if you can't understand our rigorous and long-since-published general explanation of why no machine like yours can ever work, that's your problem.  If we're feeling nice we might show you one of 17 equally well-known specific reasons why yours doesn't.  But we don't actually owe you anything unless you will condescend to submit your device to a demonstration, under conditions we specify, of its alleged ability to put out more energy than it takes in."


 * Similarly, if someone says, "Evolution is no more a fact than creation is, you can believe it if you want, or appeal to authority, but your faith in the books you read it it in or the people who wrote those books is no different than our faith in creation and the book we read it in", we get to say, "No, sorry, I'm not going to get into that pissing match with you; there is a difference between our fact-based theories and your beliefs, and if you'll try honestly to listen to how the scientific method really works I'll be glad to explain it to you, but if your mind is closed, or if you're going to trot out tedious old 'gotchas' trying to 'prove' based on one piece of contradictory or difficult evidence that all of evolution and science is wrong, or come up with a bunch of pseudoscientific 'proofs' claiming to support your myths and other beliefs, then I'm sorry, I've got better things to do." —Steve Summit (talk) 04:26, 11 April 2007 (UTC)

Where do birds get their blood cells from?
I was wondering if the bones of birds are hollow, how do they produce red bloodcells and B-cells? Do they have another organ dedicated to this task or can their bones still produce blood cells even though they are hollow?PvT 19:49, 7 April 2007 (UTC)


 * The bones of birds aren't hollow; they just have a bunch of air pockets in them. There's still enough marrow to generate blood cells.  bibliomaniac 1  5  20:33, 7 April 2007 (UTC)


 * Thanks for the answer PvT 20:38, 7 April 2007 (UTC)
 * There are other hematopoietic organs involved as well. See also Bursa of Fabricius (the "B" in "B-cell"). --David Iberri (talk) 21:43, 7 April 2007 (UTC)

Voice power
Does being a fat person help in any way to have a powerfull voice? If yes how does it work?Bastard Soap 22:54, 7 April 2007 (UTC)


 * Well, it would depend on what you mean by 'fat'. Having large, strong lungs, backed up by large, strong stomach muscles would certainly help if you needed a strong voice, but just being clinically overweight would not really help at all. Pavarotti is certainly a large man, but then, so is Forrest Whittaker. ScouseMouse - スカウサーUK! 23:04, 7 April 2007 (UTC)
 * There is an article in the register about "Why are opera singers fat?" it discusses some of the theories but not in much depth. http://www.theregister.co.uk/2006/06/23/the_odd_body_opera_singers/ —The preceding unsigned comment was added by Sifaka (talk • contribs) 00:25, 8 April 2007 (UTC).
 * The article about Maria Callas reports on theories relating her voice decline to weight decline. --Lambiam Talk  00:43, 8 April 2007 (UTC)


 * I've never accepted those theories about her. Despite the stereotypical image of opera singers, the vast majority of them are not fat, and don't need to be.  A strong voice comes from good voice training, admittedly helped by naturally solid physical attributes, but obesity as a necessity is a myth.  I suspect the reason many earlier opera singers were overweight was because they typically commanded much higher salaries than other mortals, and could afford more food.  Singing for a whole evening is a very physically strenuous activity, so having a good meal after the performance would be natural, and if this is followed by going more-or-less straight to bed and having little or no exercise other than for the voice, it would tend to produce obesity.  JackofOz 06:19, 8 April 2007 (UTC)

gluconeogenesis/glycolysis regulation
PFK-1 regulation: insulin activates PFK-2; increasing F2,6BP formation while also inhibiting FBPase-1 activity. Increased F2,6BP activates PFK-1. My question is does [F2,6BP] inhibit FBPase-1 (directly- not through decreased insulin)?
 * Not an expert, but I want to help. Fructose 2,6-bisphosphatase doesn't seem to help. Try this I found on pub med. http://www.pubmedcentral.nih.gov/picrender.fcgi?artid=45462&blobtype=pdf The two proteins in question were crystallized together. (they seem to gave good R values) This means it is a direct interaction. They also seem to discuss how the inhibition may work, but I only gave the article a cursory look. Sifaka   talk  00:23, 8 April 2007 (UTC)