Wikipedia:Reference desk/Archives/Science/2010 April 20

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April 20

ISI flight path during landing

Hey, I live in Japan and I'm interested in trying to spot one of the shuttles on their last flights, preferably before landing, and I have a couple questions. The landing trajectories (images) on the NASA site only generally show North America, is the flight path deviated from its regular orbit before it passes over North America? I guess this is the same question then: Does the shuttle enter the atmosphere over or near North America, or earlier? The shuttle sometimes orbits close to Japan, and I'm hoping that it might fly overhead on preparation for landing. Thanks! P.S. I'm relatively certain that Discovery wont be anywhere near Japan this time around, so I'm mainly trying to figure out how I might check for further missions. 219.102.220.42 (talk) 01:30, 20 April 2010 (UTC)

The website heavens-above tracks a bunch of satellites including ISS and the space shuttle missions, you can see the shuttle's current "path" in orbit by clicking the mission and then clicking on "orbit". It also predicts into the future but i'm not sure how reliably the STS missions can be predicted ahead. But sign up, it's free, and put in your lat and long and see what it comes up with. It's probably your best bet, unless NASA has something even more detailed online. Vespine (talk) 05:29, 20 April 2010 (UTC)

Those flightpaths are likely to be untrue as of this morning - there is a lot of cloud over Florida and they are looking at a later return to Earth - or a diversion to Edwards AFB in California. SteveBaker (talk) 13:11, 20 April 2010 (UTC)

You will not be able to see what I think you hope to see from Japan. It is possible that the Shuttle will overfly Japan during deorbit (today it passed several hundred miles east of Japan), but it will still be well above the atmosphere when it flies over. If the lighting conditions are right you may be able to see it during this time but it will look no different than any other Shuttle sighting, meaning it will look like a star rapidly crossing the sky. The trajectories for future missions are likely not published since they are difficult to predict far into the future.
This page has entry event information (including geographic coordinates) for today's Discovery landing, the landing was at KSC on orbit 238 (the third table). The deorbit burn occurred over the southern Indian Ocean, and lowered perigee so the Shuttle's orbit intersected the atmosphere at the proper time. This is the first deviation from the normal orbit, but doesn't change the ground track very much. Entry Interface (when the Shuttle crosses 400,000 feet altitude) occurred over the northern Pacific Ocean, this is the general area where the atmosphere becomes significant and one could consider 'entry' to begin. After this the ground track will deviate as the Shuttle navigates to the landing site. anonymous6494 22:03, 20 April 2010 (UTC)

knee posture?

What do you call the way the knee bends in the other direction in humans. Normally, the knee should bend forward when standing like a softer >. But in this case, the knee is depressed when standing so the profile of the leg is more like a < but not that extreme. I'm not seeking medical advice, just curious on what the symptom is called. --121.54.2.188 (talk) 01:48, 20 April 2010 (UTC)

Hyperextension of the knee. StuRat (talk) 02:03, 20 April 2010 (UTC)

Or "wonky knees" to use the medical term. DuncanHill (talk) 02:09, 20 April 2010 (UTC)

In my place, they call the knees "like that of a chicken".--121.54.2.188 (talk) 02:19, 20 April 2010 (UTC)

Which is a little weird, since chickens' knees bend the same way as ours do. 64.235.97.146 (talk) 16:56, 20 April 2010 (UTC)

See Hypermobility. -- Wavelength (talk) 02:10, 20 April 2010 (UTC)

Those who are knock-kneed may appear to have inward-bending knees also. George Reeves was somewhat knock-kneed, which I suppose was due to being cramped in that little rocket ship from Krypton while his bones were still soft. ←Baseball Bugs ^{What's up, Doc?} carrots→ 02:10, 20 April 2010 (UTC)

Yup it looks like those pictures but it is inward rather than sideward.--121.54.2.188 (talk) 02:19, 20 April 2010 (UTC)

word for a taxonomy guide

Many years ago I met someone who had written a book on how to identify bat species, in the form "If your bat has this feature, turn to page 23; otherwise turn to page 19." What is the word for such a key? —Tamfang (talk) 02:32, 20 April 2010 (UTC)

Single-access key. Intelligentsium 02:41, 20 April 2010 (UTC)

meditation

may i please know the most incredible power of 'meditation'? How long will it take for one doing regular meditation to achieve it? —Preceding unsigned comment added by 125.21.50.214 (talk) 04:51, 20 April 2010 (UTC)

Have you had a read of our article on Meditation? Maybe Nirvana might help a little too. My opinion is that meditation is an extremely subjective experience and as such you probably won't get very well defined answers for a question like this. Vespine (talk) 05:17, 20 April 2010 (UTC)

From the purely scientific point of view, meditation is nothing more than a state of intense focus, calm, and relaxation. This may enhance (or be enhanced by) physiological effects, such as a change in respiration and heart rate, and even neurochemical changes. This has been studied scientifically: for example, Physiological Effects of Transcendental Meditation (1970). Here's a perhaps more accessible article, "Meditation on Demand" from Scientific American. These results indicate that physiological changes occur almost instantly during the meditation period. If you're seeking philosophical or alternative viewpoints about meditation, you might find the humanities desk helpful to point you toward those sorts of resources. Nimur (talk) 06:50, 20 April 2010 (UTC)

See the article about Phala. Cuddlyable3 (talk) 07:51, 20 April 2010 (UTC)

I wonder how someone can be both intense and relaxed. ←Baseball Bugs ^{What's up, Doc?} carrots→ 07:57, 20 April 2010 (UTC)

For a deeper level of what meditation may produce, see gnosis. However one should be careful with this as it may reveal knowledge on areas that many people may not be comfortable with touching upon. ~AH1^(TCU) 00:37, 22 April 2010 (UTC)

pain receptors of preys

More often, a prey experiences excruciating pain while being hunted. Is that like their pain receptors are less sensitive (responsive) than ours? Because the 'hunting' occurs for quiet a long period down the evolution, i doubt if they are evolved in a way that they experience less pain than the others(nonetheless, it dies) - anandh, chennai —Preceding unsigned comment added by 125.21.50.214 (talk) 06:41, 20 April 2010 (UTC)

See the article Pain. Pain is an important part of animal life, vital to healthy survival.Cuddlyable3 (talk) 07:49, 20 April 2010 (UTC)

It's an unfortunate fact that the pain of being ripped to shreds by a predator is something that evolution can't remove. When an animal dies, it's genes cannot subsequently be passed to the next generation - so animals that (by some random evolutionary change) get a painless death have no evolutionary advantage whatever compared to those that die in the most painful way imaginable. In fact, the opposite might even be true. In a family of animals with similar genetics, if one animal screams horribly as it's ripped to shreds by a predator, the other animals in the group might be alerted to the presence of the predator - or might be much more careful to avoid that predator when they realize how nasty this experience might be. Groups of animals with a gene for extra pain at death might well out-perform other groups with a gene for less pain at death. Evolution is not a kind process. On the plus side, there might be an advantage to predators to be able to kill painlessly in order to avoid too much of a ruckus - and animals that use poison or who (like lions) grab their prey by the throat may be doing that to keep the prey quiet while they die. SteveBaker (talk) 13:10, 20 April 2010 (UTC)

One reason why the predators might want to kill the prey quietly is so that other animals (of their species or another) which would steal their kill don't find it right away. StuRat (talk) 13:23, 20 April 2010 (UTC)

I would like to strongly caution the OP against anthropomorphizing the non-human animals. "Experiences excruciating pain" is an entirely human notion. Birds and mammals most likely can feel pain (as they exhibit both the behavior patterns consistent with it and neuro-chemical pathways that may account for it), but we cannot possibly know how they perceive it, or if they can grade it on a scale from one to ten. Other vertebrates may feel pain, but it is not certain. Cephalopods may or may not feel pain. There have been some work on the possibility that lobsters can feel pain, but I'm not sure if there is anything conclusive on that. A crayfish seems largely unphased by losing a leg, a human... significantly less so. Arthropods can certainly be trained using aversive stimuli, but it is not certain if any of those stimuli may be described as pain. Saying "an insect feels excruciating pain" is the same as to say "an insect has an immortal soul"; it is a personal belief, and does not belong in the scientific discussion until it is thoroughly tested. Does a single-cell organism with negative photo-taxis feel pain when exposed to light? Does your computer feel pain when it fails to boot? Its monotone beep certainly sounds like it's experiencing an excruciating pain... --Dr Dima (talk) 18:33, 20 April 2010 (UTC)

So, do you feel more comfortable to proceed on the assumption that non-human organisms don't feel pain until it's proven otherwise, or the assumption that they might feel pain until it's proven that they don't? Indeed, given that I can't know for certain that other humans perceive pain as I know I do, should I assume that you don't feel pain until you prove to me otherwise? A version of the Precautionary principle may be found attractive in such circumstances. Perhaps I should own up to a religious bias relating to such questions: we Wiccans regard ourselves as a part of nature, rather than divine appointees to a hegemony over it. (No personal spin on this intended, Dr Dima, but I think this is a profoundly important area of personal ethics.) 87.81.230.195 (talk) 01:34, 21 April 2010 (UTC)

I agree, but not on religious grounds. It seems far more reasonable to assume that the same mechanism exists in other animals to prevent them from being harmed than to presume there is a completely different, unknown mechanism. Of course, proof would overcome these initial assumptions, once it becomes available. StuRat (talk) 16:41, 21 April 2010 (UTC)

We have a (rather poor) article Pain in animals. It seems that most vertebrates can probably feel pain as we interpret it, but things are less certain for other phyla. In the UK, octopuses are regarded as "Honorary Vertabrates", meaning, for example, that anesthesia must be used when cutting them open. Buddy431 (talk) 19:59, 20 April 2010 (UTC)

Evolution, intelligent design, and irreducible complexity.

I'm not sure whether I'm wrong or right... can someone please affirm or correct me? The way I see it (and I've never been taught otherwise, I go to a Christian school, so feel free to refute me) is that inter-species evolution through natural selection doesn't make sense, because for new body parts to grow like a wing (for a crude example) loads more DNA information is required, and I don't see where that information would come from. Also, even if this was possible, Darwin states that the components of the wing would grow gradually, so until it was a fully working wing, it seems to me that it would just be a pointless deadweight, which would give the owner of the wing a disadvantage, therefore natural selection would remove it. Anyway, I'm just trying to gain a better understanding of the subject. Sullyj4 (talk) 07:38, 20 April 2010 (UTC)

Check the Wikipedia article Evolution of birds. Cuddlyable3 (talk) 07:45, 20 April 2010 (UTC)

Scientists are not suggesting that a completely new species appears suddenly (although that silly suggestion is often used by creationists in an attempt to ridicule and discredit the notion of evolution by natural selection.) The immediate ancestors were not creatures without wings - they were birds, perhaps with smaller wings and lighter body weight. At least one of those ancestor birds developed a very minor genetic modification, perhaps a slightly longer wing, that meant it was better equipped to survive and reproduce, and so gradually that genetic modification became part of the evolution of a species of modern bird. This species of modern bird might have taken 100,000 years to evolve from its ancestor species which is now extinct. The majority of animal and plant species that have ever lived are now extinct. I strongly recommend the book River Out of Eden by Richard Dawkins. Dolphin (t) 07:56, 20 April 2010 (UTC)

Please don't recommend Darwin's Rotteweiler as reading material. How about Carl Zimmer? —innotata 23:39, 20 April 2010 (UTC)

Why not? Dawkins is an excellent writer, he really knows his stuff, and his popular science texts are very accessible. In addition to River out of Eden, the new The Greatest Show on Earth: The Evidence for Evolution has also been reviewed quite favourably. --Stephan Schulz (talk) 00:03, 21 April 2010 (UTC)

The problem with Dawkins isn't his science, which is fine, it's his anger, which bleeds through every word he writes. It'd be fine if he kept to the facts of evolution. But he doesn't. He seethes with such bitterness that it is distracting to the point of making him lose his point to the proper audience. He does a better job of making people who already hate religion hate it more, and does a lousy job of providing a means for the religious to fit the truth of evolution into their worldview. --Jayron32 00:57, 21 April 2010 (UTC)

This is at least an over-generalization. I find no anger at all in The Ancestor's Tale, which is a beautifully crafted book, or in Unweaving the Rainbow. The Greatest Show is still in my stack... --Stephan Schulz (talk) 14:38, 21 April 2010 (UTC)

Writers shouldn't have to be responsible for making scientific theories fit with people's "worldview". If a well-established theory doesn't fit somebody's worldview, it's the worldview that needs to be changed, not the theory. --99.237.234.104 (talk) 02:45, 21 April 2010 (UTC)

For those on the pro-evolution, anti-religion side of the fence it is becoming clear that attempts at rational debate with the anti-evolution pro-religion groups has become essentially impossible. I suspect that Dawkins may have changed tactics toward providing better ammunition for his fellow pro-evolutionists rather than attempting to engage the opposition in debate directly. Reading his last two or three books - it's hard to imagine a pro-religion/anti-evolutionist getting much beyond the title - let alone the first chapter! Dawkins' early books were much calmer, quieter affairs - but they have been quoted out of context, mangled and downright lied about by the nastier ID/Creationist nutjobs. It must be very hard to write a comprehensible, readable book on these subjects when you have to consider how every word is going to be examined under a microscope and become a possible candidate for a mis-quote. FYI, Dawkins is said to be an avid Wikipedian - he is User:RichardDawkins but seems to edit using some other account to avoid obvious grief. SteveBaker (talk) 04:19, 21 April 2010 (UTC)

What of pro-evolution, pro-religion folks like myself? Are we supposed to be permanently trapped between the frontlines? 24.23.197.43 (talk) 22:00, 21 April 2010 (UTC)

You're missing out on a lot, then. The Selfish Gene and Dennett's Darwin's Dangerous Idea are a must-read. Imagine Reason (talk) 14:42, 21 April 2010 (UTC)

Neither am I suggesting that's what they suggest. What I mean is, what about before those 'birds, perhaps with smaller wings and lighter body weight.'? the wings must have come into the equation some time. Sullyj4 (talk) 08:47, 20 April 2010 (UTC)

The fossil record tells us a little about some of the creatures, now extinct, that have lived on Earth in past ages. Scientists don't know exactly how one species evolved into another because no-one was around at the time. It is serious scientific business to gather what evidence can be found, suggest plausible mechanisms that can account for what is observed, and allow other scientists to review the suggested explanation. (Scientific scepticism is both valued and important in the international scientific community.) So when scientists suggest how birds evolved from the ancestors it is an attempted explanation, not doctrine or dogma. Scientists don't actually know, but they are willing to make suggestions and allow other scientists to agree or disagree. Dolphin (t) 12:37, 20 April 2010 (UTC)

Where creationists get painted into a corner on this is their insistence that the earth is only 6,000 years old, which obviously isn't enough time for species creation to occur. Their usual complaint about evolutionists is that it requires huge amounts of time. That's the impasse, or one of them. ←Baseball Bugs ^{What's up, Doc?} carrots→ 08:03, 20 April 2010 (UTC)

Correction: young earth creationists Sullyj4 (talk) 08:47, 20 April 2010 (UTC)

And even those who might agree with the age of the earth still can't comprehend how species can evolve into other species. But that's because they can't really conceive of the endless trial-and-error that mother nature can make over billions of years. We barely comprehend a century or a millennium. Even a million years, a short time on the geoligic scale, is beyond our comprehension. One way to get a handle on it, though, would be to estimate the number of generations of a species that could occur in, say, a million years. That makes it a little more real. ←Baseball Bugs ^{What's up, Doc?} carrots→ 08:07, 20 April 2010 (UTC)

13.75 ±0.17 billion years is the currently estimated age of the universe yeah? Don't quote me on this, but I think someone might have done a probability equation and figured that it would take longer than this age for life to begin. Sullyj4 (talk) 08:47, 20 April 2010 (UTC)

There are many such equations put out by creationists. The problem is that they are all deeply flawed, in that they make unsupported assumptions about the first replicators, and in that they assume processes that are not random at all are random. We don't know how likely it is for live to evolve under the right circumstances. --Stephan Schulz (talk) 10:23, 20 April 2010 (UTC)

I don't find the creationist's estimates of the probability REMOTELY tenable. Let's look at what we have here: The basic building blocks for a self-replicating molecule are everywhere. We've done dozens and dozens of different experiments based around the chemistry, thermal conditions, radiation, etc of a dozens of possible "early earth" environments - all of them produce an abundance of complex organic molecules within a matter of days. From the far distant icy moons of Saturn and Jupiter, we detect organic molecules - we find them even in the horrible conditions on Venus and Mars - and in the interstellar gas clouds. So there is zero shortage of basic materials. The materials are chemically inclined for form long chains - they do it spontaneously. The question of how the "abiogenesis event" came about is then purely a matter of the odds of a randomly assembled string happening to be self-replicating. This is, without doubt, a rare event. But we know that almost every one of the 10¹² stars in our galaxy has a bunch of planets and moons. Let's say there are 10 places in each solar system where life could maybe form. There are 10¹¹ galaxies - so there are at least 10²³ places where life could have formed in our 'observable' universe - the entire universe is AT LEAST 10²⁶ times bigger (in diameter) - which is 10⁷⁸ times bigger in terms of volume - and hence probable number of galaxies! The anthropic principle says that the intelligent beings wondering how this happened have to be on whatever moon or planet it actually formed on - so it's not a coincidence that it happened to be on Earth. OK - well, how many chances were there for it to happen here on earth? If these chemical reactions were happening in the oceans (not necessarily the best current theory - but let's run with it to get a feel for the numbers) - then we might suppose that each drop of water might produce maybe a thousand new, random chain of amino acids every microsecond...that's probably a huge underestimate - but again, we can afford to be generous. How many drops of water are there in the world oceans? There are 360 million square kilometers of ocean with an average depth of 3.8km - so we're talking about a thousand million cubic kilometers of water (10⁹ km³) which is 10¹⁸ cubic meters. If a "drop" is 1mm x 1mm x 1mm then there are 10²⁷ drops of water. The oceans have been around for 4.4 billion years - which is about 10¹⁷ seconds. At one chemical reaction per drop of ocean per second per planet/moon in the entire universe, there have been 10¹⁵⁴ chances for a self replicating molecule to have formed at random. If we assume that some variation of our modern genetic code were required for that to happen, with A, G and T to choose from, 10¹⁵⁴ is something like 3³⁰⁰ - so the chances are good that every possible string of letters up to 300 characters long will likely have shown up completely at random. So is 300 base-pairs enough to make a self-replicating molecule? I think that's a definite "maybe". Researchers are still working on this part of the theory - but it's certainly not some kind of crazy long-shot that the abiogenesis event was sheer random luck. Once we have just one self-replicating molecule in the entire universe, evolution guarantees that we have life. SteveBaker (talk) 21:24, 20 April 2010 (UTC)

To gain a better understanding of the mainstream science position on such matters, I suggest you read our articles on irreducible complexity, evolution of the eye, evolution of flagella and entropy and life. But ultimately your conclusions will depend on your initial assumptions. If you start from the premise that the Biblical account of the creation of life is literally true, then there is no need for a mechanism such as evolution to explain the complexity of life on Earth as we see it now, so Occam's razor says it is an unnecessary encumberance. If you start from the premise that it should be possible to explain the complexity of life (and, indeed, other phenomena) without supernatural forces, then the modern theory of evolution is the only game in town. This is not because scientists have not considered alternatives - see the history of evolutionary thought; it is because it is the only scientific explanation that has stood up to rigorous examination. Gandalf61 (talk) 08:22, 20 April 2010 (UTC)

The "information" argument is bogus. Any random process is a source of information in the sense of information theory. Creationists and IDers redefine (using a very loose sense of "define") it to mean something very different (though I've yet to see an operational definition of, say, "specified complexity"), and then make unsupported claims about it. --Stephan Schulz (talk) 10:16, 20 April 2010 (UTC)

Wings are modified forelimbs, so the change required isn't too great; you just have to add some feathers (or webbing for bats) and some flight muscles. The feathers are also useful for keeping warm, so they can evolve without being effective for flight. Once you have wings, but no flight muscles, you can glide. Gliding is very useful in itself, so the feathers can evolve into wings without flight muscles being ready. The flight muscles (and lighter bones, etc.) can then evolve gradually making better and better gliders until eventually they are actually flying. It is often difficult to work out what the gradual steps were in any particular bit of evolution, but that doesn't mean they don't exist. We have worked out the steps for a very large number of features of modern species and there is every reason to believe will we eventually work out the steps for those features that are still a mystery to us. --Tango (talk) 11:55, 20 April 2010 (UTC)

• I'm not sure whether I'm wrong or right... can someone please affirm or correct me? - Well, science says you are wrong. There is zero doubt about that much!
• ...I've never been taught otherwise, I go to a Christian school, - That's a horrifying thing. It's one thing to teach evolution alongside creationism - and to let people make up their own minds, or at least understand the mainstream view - but to simply not teach it at all is terrible.
• that inter-species evolution through natural selection doesn't make sense, - The problem is that creationists typically claim that evolutionists say "Well one day there was a Dinosaur - then 'poof!' we have a genetic mutation and now there is a bird." - but that's absolutely NOT what evolution says. It's a very, VERY gradual process for such a complex change to come about.
• because for new body parts to grow like a wing (for a crude example) loads more DNA information is required, and I don't see where that information would come from. - It's like you took a bucket with 1000 six-sided dice in it. You shake up the bucket and dump it out - what are the odds of getting 1000 sixes? Just about zero! If you kept dumping out that bucket, it would probably take longer than the life of the universe to get 1000 sixes. However, if you're allowed to dump out the bucket, and keep all of the dice that show up with 6's - shaking up the ones that are left over and trying again - then after the first try you get about 160 sixes, you shake up the remaining 840 dice, do it again and you get 140 sixes, then 116 with 700 left - and so on. After about 35 rolls of the dice - you have all sixes. That's how evolution works. Each tiny change produced by a change in just a few base-pairs in the DNA molecule or just a couple of genes picked up from one parent versus the other make a tiny improvement to the animal or plant. With each generation, the population of animals adapts minutely towards a better fit to it's environment. After thousands or tens of thousands of generation, you get the animal you see today.

The actual answer to the question is this section here. You don't have to read this whole page.

• Also, even if this was possible, Darwin states that the components of the wing would grow gradually, so until it was a fully working wing, - Yes, but don't make the creationist mistake of then saying "What use is half a wing?" - because that's not what happens. Some species of dinosaur evolved slightly fluffy scales - those fluffy scales were good for keeping the dinosaur warm - the fluffy scales gradually changed into 'feathers' - not feathers good for flying - but fluffy feathers like a small chick might have. Then some variation of this dinosaur maybe found benefit to being able to climb trees to find food - some variation of that found it useful to be able to jump from one tree to the next - having longer feathers on the forelimbs made possible to glide a bit from one tree to the next - then holding those forelimbs out more horizontally made it able to jump further - then having stronger muscles, then longer feathers, then the ability to flap, then lighter bones, then...all the things you need to have something we'd call a "bird". Each stage of the way involved one more six being rolled on that bucket of 'genetic dice' - each beneficial 'six' was kept by the process of 'survival of the fittest' - each failed '1' roll resulted in a dead dinosaur that couldn't make it to that next tree - had to climb down and got eaten by a predator on the forest floor. Over a LOT of generations, dinosaurs change by a thousand intermediate species into something we'd call a "bird".

End of actual answer.

• it seems to me that it would just be a pointless deadweight, which would give the owner of the wing a disadvantage, therefore natural selection would remove it. - And that doubtless happened with some feature or other. Maybe some of the dinosaur-descendants evolved fluffy feathers on their back legs, that (for some reason of flight stability or whatever) turned out to be worse rather than better - and that species of dinosaur died out without leaving any descendents.

drop the hypothetical, four-winged dinosaurs actually existed! http://scienceblogs.com/notrocketscience/2008/10/microraptor_the_dinosaur_that_flew_like_a_biplane.php 83.134.175.147 (talk) 17:09, 20 April 2010 (UTC)

Why did the dinosaur cross the road? Because chickens hadn't evolved yet! :-D 24.23.197.43 (talk) 22:10, 21 April 2010 (UTC)

• Anyway, I'm just trying to gain a better understanding of the subject. - That's a good thing! Curiosity is a good trait! Use your brain - don't take everything you're told as true unless you can understand why. Your teachers are essentially telling you: "Birds appeared by magic." - that's not much of an explanation. Life would be very difficult if every difficult question were answered that way. "Why didn't you do your homework last night?"..."Magic!"..."Why did your car stop running? Did it run out of gas?"..."Nope - it was magic."..."How come there are birds?"..."Magic!". We can't run the world like that. When we have a good explanation for something, we should use that explanation - and there are few scientific principles as solid, clear, coherent, well-endowed-with-evidence as evolution.

SteveBaker (talk) 12:58, 20 April 2010 (UTC)

(Edit Conflict) To try to address a couple of Sullyj4's concerns as briefly as I can:

Organisms often wind up with surplus/duplicate DNA through such mechanisms as the duplication of single genes or entire Genome duplication: the latter has happened at least 4 times in our own (distant) genetic history and is very common in plants - most of our domestic serial crops are polyploidal hybrids of wild originals.

The resulting 'spare' copies of those genes can then be subject to mutations (thus creating new 'information') without affecting the organism by the loss of their original function, and those mutated genes can occasionally result in beneficial new characteristics, perhaps in a slightly different niche or environment than that which suited their carriers' ancestors better. (Most won't, and may well be disadvantageous, so organisms with them will generally not survive and pass on those disadvantageous genes - this is how "Evolution by Natural Selection" works: all the real 'duds' die and the few 'improvements' thrive better than the 'unimproved', either overall or in new niches, and are said to have been "selected".

While organs like wings or eyes are evolving in a species gradually over many, many generations, there is never a stage where (for the majority of the species) they are non-functioning encumbrances: if they were then - in line with the above and with your original supposition - their owners would survive less well and the genes for those versions would not be passed on. Every (rare) 'modification' that is retained (by successful reproduction) is in some way an 'improvement', while the (numerous) 'disimprovements' are not retained. This is not as obvious as it might be because we naturally tend to focus on the (few) successful mutations/improvements who went on to breed rather than the (many) unsuccessful ones that, at best, bred less often, and more often than not never even survived as far as hatching/birth.

It's tempting to look at the current version of an organ and think that a less-fully evolved version would have been 'useless' or at least inferior, but this is erroneous. At the time that version evolved by selection it was an improvement over what had gone before (or it wouldn't have been selected for and wouldn't have persisted) and was 'the best so far' (for that particular species). Consider birds' wings: originally they were (we think on the basis of what evidence we have, which is considerable) functioning arms, which had feathers for insulation and display; in some species (of what were then small dinosaurs) the feathers and also the bones and muscles of the arms and body (which were also being selected for or against by the environment), grew large enough to help (by aerodynamics) their owners to jump further, then glide (perhaps from trees) and finally fly, by which time the arms were wings and those dinosaurs were additionally what we call birds. Several 'lines' of those early birds developed for millions of years, but in the long run only one line, the Neornithes, survived (and diversified) to the present.

It's important to remember a few things.

First, the evolution of an organ or organism has no 'future target', it's only ever driven by adaptations to the current environment.

Second, it can (usually) only build on what is already there by a series of (generally minor) modifications that are then selected for and retained. The notion of "Irreducable Complexity" argues that there must have been some stages where 'the improvements were too radical/the organ is too complex' to have come about by this "tiny footsteps" process, but it's an argument invalidly proceeding backwards from a hoped-for conclusion (this couldn't have happened through E by NS so God did it) and no example has yet been identified where an evolutionary explanation has not been found (though IC proponents sometimes pretend it hasn't), though some have taken a few years to work out.

Third, the fossil record is, and always will be, very incomplete because fossilisation is a rare event requiring special conditions and there are large swathes of geography and time where the conditions were wrong or whose rocks have subsequently been destroyed by erosion. Consequently there is, and always will be, disagreements about how various fossil species are related to each other and to living ones, and new discoveries can cause revisions to established ideas. These however are fine details, which do not affect our understanding of Evolution (which is also supported by various other sciences, such as Genetics) as a whole, and certainly don't "disprove" it.

Sorry this wasn't as brief as I'd intended, but this is a large and complex subject that has taken many thousands of scientists over a century to bring to our current state of understanding, so it's hard to properly answer questions about it briefly. It's also fascinating, so I'd encourage you to continue pursuing it. 87.81.230.195 (talk) 13:00, 20 April 2010 (UTC)

"Evolution is cleverer than you are." Imagine Reason (talk) 13:13, 20 April 2010 (UTC)

....and I've never been taught otherwise, I go to a Christian school

Isn't there an inspection system for schools to see if the curriculum satisfies some minimal standards? Count Iblis (talk) 14:46, 20 April 2010 (UTC)

We don't know the country of origin of our OP - so we don't know what standards (if any) should be being enforced. SteveBaker (talk) 18:48, 21 April 2010 (UTC)

Many, if not most, changes, do not work. It is "back to the drawing board" time and time again, as concerns evolution, concerning most changes in organisms. Organisms have a behavioral dimension in addition to a physical dimension, especially concerning the higher order of biological entities. This can complicate our envisioning of the process of evolution. For instance, the rudiments of a "wing," at its moment of inception, can serve a different purpose entirely, than the purpose it may eventually serve. Bear in mind that evolution only has to provide some small advantage to one individual member of a species as concerns survival and reproduction, which is to say that evolution has no long-term plan whatsoever. The term evolution can be thought of as only retroactively applied. When looking back over a long period of time, it can be said that "evolution" has taken place. But each incremental change can be small indeed. Bus stop (talk) 15:00, 20 April 2010 (UTC)

One problem with the way the original poster has apparently been taught is that the conclusions he presents about evolution are not based on evidence, but inductive reasoning. See Problem of induction. We all know that the evolution over the millenia of the wing and of the eye were improbable — but we have the evidence of the fossil record that they did evolve; so here we are. Comet Tuttle (talk) 18:50, 20 April 2010 (UTC)

One question our OP might like to put to his/her "intelligent design" teachers is this: "Please explain the Recurrent laryngeal nerve in the giraffe." This is the most crazy piece of "intelligent design" you could imagine - it can really only be adequately explained by evolutionary theory. SteveBaker (talk) 21:36, 20 April 2010 (UTC)

Ah, yes, the argument from poor design. I believe the standard ID responses are (a) God has inscrutable reasons for such peculiarities, which we mere humans cannot expect to understand and/or (b) God created these instances of less-than-optimal design to test the faith of believers and as traps for unbelievers. Gandalf61 (talk) 09:10, 21 April 2010 (UTC)

Please see http://www.mlbible.com/deuteronomy/32-4.htm. - Wavelength (talk) 15:55, 21 April 2010 (UTC)

Well, yes - exactly. "The Rock! His work is perfect, For all His ways are just; A God of faithfulness and without injustice, Righteous and upright is He." It's hard to imagine how the Recurrent laryngeal nerve is "perfect" in humans or most other mammals - but in the Giraffe, it's just crazy! The vocal chords in the larynx are controlled by two nerves coming from the brain. One goes straight to the larynx down your neck (as you might expect) - the other goes all the way down into your chest cavity - loops around an artery and comes back UP the neck to the larynx. This is a truly crappy piece of "design" - but make perfect sense if you look at all of the teeny-tiny steps that mammals have evolved through from fish onwards (our vocal chords are basically modified gill slits). But in the giraffe - this nerve goes about 20 to 30 feet out of it's way to get where it's going. The simple time delay introduced by that long trip down the neck to the chest and back up again means that the poor giraffes' brain can't coordinate 'instructions' to the left and right sides of the larynx accurately enough to make proper sounds. This is why giraffes are basically silent. The best they can do is a kind of gurgling "baaaa" sound. An intelligent designer would clearly have routed both nerves via the shortest route and allowed giraffes to sing as beautifully as you'd hope such graceful animals should! God hates giraffes. SteveBaker (talk) 19:05, 21 April 2010 (UTC)

I did a Google search for the heading of this section ("Evolution, intelligent design, and irreducible complexity."), and I found the following page.

• Irreducible Complexity is Evidence for Intelligent Design. -- Wavelength (talk) 22:02, 20 April 2010 (UTC)

That's a rather ancient document. The ID'ers have pretty much given up the 'bacterial flagellum' example since it was shot down so comprehensively in the Kitzmiller v. Dover Area School District trial. It's interesting that they always like to quote Darwin's statement: "If it could be demonstrated that any complex organ existed which could not possibly have been formed by numerous, successive, slight modifications, my theory would absolutely break down." - seemingly not realizing that one of the reasons that evolution is so compelling as a theory is that (as Darwin seems to be predicting), no such examples of irreducible complexity have ever been found. SteveBaker (talk) 04:35, 21 April 2010 (UTC)

I don't have much to add to the already excellent answers here, but I'd like to point out that there are organisms alive right now that possess what could be considered "half formed wings". See Flying squirrel and Gliding possum. On their own these do not constitute proof of evolution, and who knows if these animals will eventually adapt to have more fully formed wings, but I wanted to point out that a "missing link" between wing and no-wing doesn't have to be a "Dead weight" like the question-asker assumed. APL (talk) 01:37, 21 April 2010 (UTC)

There are also flightless birds eg ostrich, emu and all the New Zealand birds (eg kiwi). These birds have wings but they don't function as flight wings. It is a topic worthy of scientific research to determine whether these birds are descended from flighted birds that lost the ability to fly, or from birds that had evolved wings but not the ability to fly. Dolphin (t) 02:22, 21 April 2010 (UTC)

Struthioniformes (which includes Ostriches, Emus and Kiwis - but not, by any means, all flightless birds) seem to have appeared in the Cretaceous - which means that they were around at the same time as the last of the dinosaurs. They lack many features of modern birds. It's therefore entirely possible that they have always been flightless. However, the Tyto pollens (a kind of flightless owl) undoubtedly lost its' ability to fly after living for long enough in a predator-free island where flight simply wasn't useful to them. SteveBaker (talk) 03:58, 21 April 2010 (UTC)

For other examples of evolution in action, see the lungfishes, which are converting their swim-bladders to full lungs, and the mudskippers, which are converting their pectoral fins into fore-limbs. Of course, as their new niche is already occupied, this reduces the evolutionary benefits of their on-going adaptations. CS Miller (talk) 14:34, 22 April 2010 (UTC)

Oops, the lungfishes don't have a swim bladder; they are getting their lungs from another organ (one pair of gills?) CS Miller (talk) 20:49, 22 April 2010 (UTC)

Be very careful not to confuse "information" with "meaningful information". Take a look at [1].-Craig Pemberton 15:28, 21 April 2010 (UTC)

Sullyj4, for information about the formation of proteins from amino acids, see http://www.darwinismrefuted.com/molecular_biology_04.html. (The text says 1079 where evidently it was intended to say 10^79 or 10⁷⁹.) -- Wavelength (talk) 19:09, 21 April 2010 (UTC)

That's actually rather cool. If you follow my math (above) then you'll see that the number of times that 400 amino acid proteins have likely formed at random in the universe is at least 10¹⁵⁰ - so on that basis, the 'Darwinism Refuted' web site has handily pointed out that this "unlikely" event has probably happened 10⁷¹ times! Far from refuting the possibility - they've actually confirmed it! Ha! We win! SteveBaker (talk) 01:12, 22 April 2010 (UTC)

The last two sentences of the article on the web page to which I linked are important. -- Wavelength (talk) 19:46, 22 April 2010 (UTC)

Is volcanic ash worse for aircraft than other dust and sand?

I can remember several occasions in the UK when there was a liberal sprinkling of sand on cars etc, which was said to come from the Sahara[2]. Aircraft were not grounded or as far as I know diverted at that time. Now all aircraft are grounded, and there is hardly any reside on cars, maybe a very light dusting. Why should volcanic dust result in planes being grounded but desert dust not do so? -- Q Chris (talk) 07:56, 20 April 2010 (UTC)

Read the linked article and you'll see some of the problems peculiar to volcanic ash. ←Baseball Bugs ^{What's up, Doc?} carrots→ 08:00, 20 April 2010 (UTC)

... and these are particularly harmful volcanic particles because of rapid cooling of the magma in the ice-filled caldera. Dbfirs 08:54, 20 April 2010 (UTC)

Hmm. It depends on a lot of things, including critically the size and shape of the particles and melting points. Sand gives similar problems with forming glass in the back turbine blades of jet engines but it tends to happen at low altitude over the desert (there were warrantee issues with the Saudis on this 20 years ago). But the dynamics of the passage of particles in air between surfaces is reasonably complex: at some lengthscales they pass through the engine without getting near a surface (I think there is a Stokes number on that balance), at others they nearly touch and can bounce off an air layer if the shape is round enough (including if they are molten), at others they conventionally bounced without getting molten enough to stick at other regimes again they will stick only to already deposited particles (then they form "dendrites" I think they are called, a bit like soot webs). All in all it is difficult being sure whether or not a volcanic cloud is safe, which is the biggest problem, often the risks are small. --BozMo talk 09:18, 20 April 2010 (UTC)

Incidentally reading through the links it might be worth clarifying that jet engines are hot because the thermodynamic efficiency is greater at higher temperatures, (we don't explain it well). Clever people have designed jet engines so that at max output the gas temperature (which gives the efficency) flowing through the engine is significantly higher (hundreds of degrees) than the melting point of the solid turbine blades between which they are flowing in the engine. The turbine blades are kept cool by a slow bleed of cooler air out of perforations on the blade (which give it a tiny cool air jacket). I have an RB211 turbine blade lying around somewhere, I will try to dig it out to put up a photo. The problem is that the volcanic particles melt in the gas flow but then set when they hit the surfaces of the blades which are cooler. At worse they hit at the stagnation point at the front of one of the early sets of turbines and block the perforations which let the cooler air out. You can then get the front set of turbine blades over heating and melting which is not good. But this is seriously hard to model with confidence. --BozMo talk 09:32, 20 April 2010 (UTC)

Since we know that volcanic ash clouds can shut down jet engines (because it's happened on previous occasions), and since - due to the difficulties of researching such scenarios - we don't know nearly enough about what exact conditions will result in damage, we have to err on the side of caution.

Those conditions will include things like extent, density and altitude. The current ash plume is very widespread, and high up, at normal cruising altitudes; the Saharan sand may have been less extensive (and so more avoidable), at different (lower?) densities, and different altitudes (some manifestly lower since it reached ground level). 87.81.230.195 (talk) 11:01, 20 April 2010 (UTC)

The tricky part of this is that even if the ingestion of volcanic ash doesn't cause the engine to fail catastrophically - it may cause horrible amounts of wear and bearing damage. The cost of this kind of incident could be very high even if passengers and crew are never aware of a problem during the flight. I'll mention the USGS advice I found yesterday about driving cars in volcanic ash situations - they recommend an oil change and a change of oil and air filters every 50 to 100 miles driven! Now translate that advice to a two million dollar jet engine! It wouldn't take much cumulative damage to the engines to make flying in such conditions unprofitable. SteveBaker (talk) 12:30, 20 April 2010 (UTC)

Russian EMP weapon used in Smolensk?

Various articles on the internet e.g. Kavkazcentre.com claim that Russia used EMP to down Polish plane near Smolensk. Could this be at all possible? And if so would it leave traces on the plane's instruments and/or the black boxes? This is my first try with Wikipedia and am not certain whether I am doing this right.220.253.193.132 (talk) 09:58, 20 April 2010 (UTC)

It would be too much of a risk for a government to do, as such a device would be readily detected. Space and Remote Sensing Sciences (ISR-2) .Its probably just another conspiracy theory. Much work has gone into protecting aircraft electronics from ordinary interference but damage from a Electromagnetic pulse would be apparent from the extent and nature of the fried and damaged components. Even capacitors would show puncture marks in their dielectric material due to the over voltage (OK, perhaps not in the mica's but in many of the common varieties).--Aspro (talk) 10:24, 20 April 2010 (UTC)

I don't think it's very likely, but the remote sensing you refer to only monitors nuclear EMPS—EMPs released by nuclear reactions (as a result of a nuclear bomb). A non-nuclear EMP device would probably not be detectable from space. --Mr.98 (talk) 14:56, 20 April 2010 (UTC)

? What are you gonging on about? Some 'two watt' animal tracking collars are quite successfully monitored by satellite (it's straight up). Filters can easily cope with the high noise to signal ratio picked up by EMP receivers. It ain't a weapon if it can't can't even reach into space. I've received five watt transmissions from the shuttle. --Aspro (talk) 00:30, 21 April 2010 (UTC)

Sorry, I find that pretty unlikely. The ISR-2 looks for nuclear-strength EMPs. It is not going to be looking for some smaller version. Whether a satellite theoretically could be scanning for such a thing, and constantly trying to filter out the signal from the noise, and whether or not a small EMP would actually be detectable through the atmosphere, I don't know (but I am doubtful—it is non-trivial to detect nuclear explosions from outer space, and conventional explosions EMPs are many orders of magnitude smaller, and you would have to discriminate from other, fairly similar phenomena, like lightning strikes... even unambiguously detecting atmospheric nuclear explosions from space is non-trivially difficult). But the ISR-2 ain't doing it, and I doubt anybody is (there are no great reason to be trying to detect them). --Mr.98 (talk) 18:04, 21 April 2010 (UTC)

The article Vela Incident I would say actual agues against your position – just think about what a properly functioning satellite can do – and not 30 years ago but now! Remote sensing devices don't “think” - they report. What sense would their be in making them partially deaf? Even meteoroid arrivals of magnitudes below a nuclear explosion are monitored. Analysis of Satellite Observations of Large Meteoroid Impacts. The sensors are not performance limited. The phase sifts within the signal can also give an estimate of distance to the source and its indicate its nature (i.e., lightning, EMP weapon, nuclear device etc.) Just because their full capabilities are not published in the popular journals isn't evidence that they use very primitive technology. --Aspro (talk) 23:25, 21 April 2010 (UTC)

You make them "deaf" because spending time, money, and resources on something that will go off every time lightning strikes is exceptionally wasteful. I see no reason to believe that they are (or could) discriminate for a small-scale EMP weapon (a device that not one military uses regularly, and one which poses little strategic importance), and would routinely do so on a global basis. I am unconvinced. It seems like a much larger assumption to me to guess that they are looking for such phenomena than to assume that they are not. Again, I don't think the Russians probably did it this way, but I doubt any US satellites would be searching for small EMP bursts on a regular basis. There would be better ways for the US to monitor Russian operations on such topics than constant satellite observation.

We could also break this down, Drake equation style. The probability is something like (chance that satellites can see this stuff) x (chance that satellites can distinguish from background) x (chance that they were looking at the right place at the right time) x (chance that even if they could and did look that the signal itself wouldn't have been distorted or confused by environmental factors). My guesses would be "maybe (unlikely)", "maybe (unlikely)", "no way", "maybe (unlikely)". --Mr.98 (talk) 01:39, 22 April 2010 (UTC)

It would be obvious from the 'black box' flight recorder - which is guaranteed to have been examined carefully. At the very least, the recording would have stopped abruptly long before the plane crashed - but there would be plenty of other signs of this having happened. This can't possibly have happened without the collusion of the authorities who examined the black box. The capabilities of EMP devices are greatly over-stated. We can be very sure this didn't happen as described - it's just another ridiculous conspiracy theory. SteveBaker (talk) 12:20, 20 April 2010 (UTC)

It would also fail to explain how the Russians convinced the pilot to attempt landing in thick fog after he was told by the control tower to divert to Moscow or Minsk. —Preceding unsigned comment added by 76.195.161.25 (talk) 13:09, 20 April 2010 (UTC)

The authorities that examined the black box? Wouldn't that be part of the investigation that Putin took personal control of? This conspiracy theory has as many flaws as any other conspiracy theory, but that isn't one of it! --Tango (talk) 23:42, 21 April 2010 (UTC)

Keep in mind that conspiracy theorists will throw out any sane explanations and focus on things that cannot be proven. Even when the theories are proven completely wrong, they will attempt to make those theories "fact" by spamming them all over the internet. -- kainaw™ 14:35, 20 April 2010 (UTC)

If my wife dies, how much time would I have to extract her eggs with which to produce children in-vitro?

I swear, if I find and marry the love of my life just to have her die before we have any children, even THAT will not stop us from having children!

So how long after her death would her eggs still be usable? How long can her eggs last in some kind of cryogenic freezer until they're ready to be fertilized through in-vitro methods?

Also, how much would it cost in the US? Which country would I have to fly to in order to find the same treatment for a far lower cost? --Let Us Update Wikipedia: Dusty Articles 10:27, 20 April 2010 (UTC)

You can get rough idea about what's involved here. Oocyte cryopreservation, & In vitro fertilisation.This article mentions that the eggs are harvested from 'live' donors because hormone treatment is given in the run up of the operation, to release the mature eggs. Ethics committees might/will also feel they just have to get involved for a donation from a dead donor. So you might have to persuade your wife to die in somewhere like China and to have the hormone treatment and egg retrieval done first. --Aspro (talk) 10:44, 20 April 2010 (UTC)

I think if you have the wife's consent, then many countries would allow it. Since it is apparently impossible (or, at least, very difficult) to get ova from a dead woman, you would have to do it in advance "just in case" and you can get the wife to sign something consenting to them being used after her death. --Tango (talk) 12:01, 20 April 2010 (UTC)

I agree - if you have your wife's consent - do it while she's still healthy. If you don't have her consent then you shouldn't do it at all - and in any case, you'd probably find it very hard to find a reputable medical facility who would do it after her death. SteveBaker (talk) 12:15, 20 April 2010 (UTC)

Indeed. In the absence of fertility treatment, only one or two ova mature in each menstrual cycle (see oogenesis), and we don't (AFAIK) have the ability to bring immature ova to maturity outside of the human body, so harvesting ova from your dead hypothetical wife is very unlikely to be successful. Gandalf61 (talk) 13:01, 20 April 2010 (UTC)

The fact that it's very unlikely to be successful and therefore no one is going to try may make this a moot point but I'm not convinced ethically you wouldn't be able to convince a facility to try if it were possible. Why would they treat this so much different then Posthumous sperm retrieval which while not allowed in some places (like France), is allowed in others like the UK (with written consent) and the US (where there's no law so it's up to the facility, I don't know how they handle it but it's unlikely any would do it without consent but some may use e.g. something like the Israeli system of implied consent where they allow it if you can present enough evidence to convince them your partner would have wanted it)? (I presume most people know this, it's a common theme on TV.)

Edit: Actually enough people seem to think there's enough chance it may be possible in the future that there are refs discussing the ethics ref 1, ref 2 (brief mention at the end about the need for a surrogate and how that could affect the ethics), ref 3 (brief mention of it as a future possibility), ref 4 (says 'In addition to the research potential of donated human ovarian tissues, actual clinical utility for assisted reproduction may be close to being possible'), ref 5 (mentions it as the next logical step), ref 6, & ref 7 (not sure if it has anything relevant, couldn't read the full text)

Nil Einne (talk) 16:47, 20 April 2010 (UTC)

deleted youtube vids

is there a site where i can watch deleted youtube vids the vid i wanna watch is

http://www.youtube.com/watch?v=ZzIfeo1L04Q&feature=related —Preceding unsigned comment added by Jonny12350 (talk • contribs) 13:44, 20 April 2010 (UTC)

I tried http://www.youtube.com/v/ZzIfeo1L04Q it didn't work, but I did see the title and initial photo. The old websites that let you watch deleted videos essentially created the same URL, back when youtube didn't delete videos right away. It doesn't work anymore. Ariel. (talk) 18:37, 20 April 2010 (UTC)

In this case, it says it was removed by the user who uploaded it. Apparently ax9426 (http://74.125.153.132/search?q=cache:9cMaio82KY8J:www.youtube.com/watch%3Fv%3D3j1BEss6MRc+%22chemical+spill+in+downtown+st+louis%22+ax9426&cd=1&hl=en&ct=clnk&gl=nz&client=firefox-a). You could try contacting them Nil Einne (talk) 21:40, 20 April 2010 (UTC)

is there a way to find who the user was that uploaded it? —Preceding unsigned comment added by Jonny12350 (talk • contribs) 22:59, 20 April 2010 (UTC)

Silver nitrate

What is the formula of Silver (I) nitrate (V)? Is it Ag (NO3) or smth. else? Thanks. —Preceding unsigned comment added by Atacamadesert12 (talk • contribs) 15:24, 20 April 2010 (UTC)

Yes: the silver ion has a charge of +1, and the nitrate a charge of -1, so the ratio of the two is one to one. Typically, this would be written AgNO₃. Buddy432 (talk) 15:46, 20 April 2010 (UTC)

As you might have anticipated, we have an article on silver nitrate.

Ben (talk) 16:36, 20 April 2010 (UTC)

eggs

why is it that a egg is stronger on its long side than the short side —Preceding unsigned comment added by 41.18.200.49 (talk) 18:12, 20 April 2010 (UTC)

The reason is that on the long side, the pressure is spread out over a larger area, so a specific place takes less pressure. On the short side, the pressure is applied on a small area, so it cracks more easily. Hope this helps, --The High Fin Sperm Whale 18:36, 20 April 2010 (UTC)

The pointier side is more of an arch, which is a strong structure for the reasons THFSW mentioned. --Sean 18:41, 20 April 2010 (UTC)

That explanation aint right. In fact, the pointier end will expose a smaller area leading to higher pressure. That's the oposite of what THFSW said. Dauto (talk) 19:55, 20 April 2010 (UTC)

The question aint right either (unless I am misunderstanding?) Dbfirs 20:08, 20 April 2010 (UTC)

I'm with Dbfirs here. Eggs seem pretty strong end-to-end but are easy to crush/crack sideways. DMacks (talk) 20:10, 20 April 2010 (UTC)

Eggshell is like concrete - it's very strong in compression but very weak in shear. When you push on the pointy end of the egg, the force vector may be resolved into two components - one parallel to the shell surface (which is a compression force) and one at right angles (which is a shear force). Assuming you aren't stabbing the egg with a pin (which is equally easy everywhere) but rather with a more distributed, blunt force, most of the force at the pointy end of the egg ends up being parallel to the surface and very little is at right angles. When you hit the side of the egg, the reverse is the case. Hence the egg is stronger where the curvature is sharper (ie end-to-end) than it is side-to-side where the curvature is less. The principle of the arch is somewhat similar - and it works because stone and concrete and other common building materials share the same good-in-compression characteristics of eggshell. SteveBaker (talk) 20:21, 20 April 2010 (UTC)

Thanks for that. I've always found the "spreads the pressure over a greater area" to be nonsense, but never thought about asking it. Certainly clears that up! Vimescarrot (talk) 21:58, 20 April 2010 (UTC)

--87.114.87.107 (talk) 23:13, 20 April 2010 (UTC)

Is it cold in here, or is it just me?

What is the relation of core body temperature to thermal sensation/thermal comfort? For example, could a difference in core body temperature explain why one person feels uncomfortably chilly while the person sitting right next to him (dressed the same) thinks the temperature is lovely? I'm not talking about extremes of heat or cold (either ambient or endogenous), but humans within the normal range of core body temperatures in an environment in the room-temperature range (20-25 degrees Celsius, 68-77 degrees Fahrenheit). 71.104.119.240 (talk) 20:28, 20 April 2010 (UTC)

Yes, body temperature effects how one feels the surrounding temperature. A sick person with fever will feel cold. Hunger, hormonal levels, medications, anemia, etc. will also have effect. Personally, when I ride a car with other people, opening the windows is often an issue between fellow passengers. --88.242.252.205 (talk) 22:20, 20 April 2010 (UTC)

It is more likely to be correlated to the fitness of their vascular system. Having cold showers at public school ensures that vasoconstriction becomes very adapt at avoiding heat loss. Some medical conditions such as ME have been found to have an mild elevated base temperature – but I'm presuming you mean: otherwise healthy people. A poor diet preventing the liver from utilising the body's fat reserves can also cause a person to feel cold. Also, drugs like chlorpromazine, which the Nazi's experimented with in their concentration camps, in the hope that it could save their pilots dying from exposer when they parachuted down into the cold North Sea. This drug makes people appear, not to notice the cold. They don't scream out, with the pain of becoming hypothermic.--Aspro (talk) 22:36, 20 April 2010 (UTC)

I think even tiny changes in core body temp, like a tenth of a degree, are enough to make you feel either hot or cold. StuRat (talk) 22:38, 20 April 2010 (UTC)

Yes, a very good point. Yet deviations greater than that don't seem to register in some situations. Feeling cold because one is four fifths the way up K2 'verses' feeling the cold because one is suffering from what ever King David suffered from. Quote: Kings 1:2 King David was now very old, and no matter how many blankets covered him, he could not keep warm. Kings 1:2 So his servants said to him, "Let them seek a young virgin for my lord the king, and let her attend the king and become his nurse; and let her lie in your bosom, that my lord the king may keep warm." [3]

I hate to hitch a ride on this person's question, but could lack/excess of sleep also cause one to feel hot or cold? I find that oftentimes if I fail to get more than a couple hours sleep, I feel cold the majority of the following day in what would normally be a comfortable room temperature. Ks0stm ^(T•C•G) 22:45, 20 April 2010 (UTC)

I second your suggestion, Ka0stm. being domestically solitary and currently unemployed, I tend to abuse my diurnal rhythms, and not infrequently notice periods of subjective temperature swings that have no obvious environmental cause. 87.81.230.195 (talk) 01:14, 21 April 2010 (UTC)

I #3 this suggestion -- when I used to work the graveyard shift at the refinery, I'd get chilled all the way through to my bones by quitting time, and then no matter how warm the morning was, I just couldn't seem to get any warmer. FWiW 24.23.197.43 (talk) 22:19, 21 April 2010 (UTC)

I'd think that acclimatisation would be the main factor to look at as 'thermal comfort' is somewhat subjective. If you've ever been on holiday somewhere hotter that where you live you'll know that it feels cold when you get back home, but your core body temperature will be the same, it's your perception of the temperature that has changed. I'd be interested to see some studies though, I know that I as a recovering alcoholic felt very cold when i first gave up booze (the liver generates heat while processing alcohol in case anybody doesn't know) so I can see that a tiny increase/decrease in core body temp can make a huge difference. —Preceding unsigned comment added by 87.114.87.107 (talk) 23:12, 20 April 2010 (UTC) edit.. i forgot my tildes

Alcohol may be metabolised as fuel but it is also a vacodilator. In other words, warm blood flows to the skin, giving the delusion of warmth. This is why a stiff brandy from a St. Bernard to warm one cockles on the mountain pass can prove fatal.--Aspro (talk) 23:31, 20 April 2010 (UTC)

Thank you for the your interesting observations and the points you've raised. My interest in this subject comes from an observation of my own: I'm often cold in the morning, and my family teases me for being all bundled up, but at night, even though the air temperature is probably cooler, people ask me why I'm not wearing a sweater! I have a circadian rhythm abnormality (probably, as Aspro knows, originating in the suprachiasmatic nucleus) which causes me to be wide-awake at night and sleepy in the morning - and from what I've learned of circadian rhythms, that means my core body temperature is highest during the time of day when most people's core body temperatures are dropping, and I'm at my low ebb when everyone around me is warming up. Could this explain the difference in our thermal comfort levels at different times of the day? It isn't that I don't perceive the night air as being cold; it just doesn't generally bother me and often I think it feels good. Could this be because I'm at my warmest? And am I more susceptible to feeling chilly in the morning because I'm not so warm on the inside? 71.104.119.240 (talk) 04:24, 21 April 2010 (UTC)

From what I remember reading, typically peoples temperatures are lowest in the early morning and highest in the evening. The image below shows this, along with other normal "human clock" events. Along these lines, it is quite possible that your lowest/highest temperatures are a few hours later than most peoples if your circadian rhythm is offset a few hours later than most peoples. Ks0stm ^(T•C•G) 14:46, 21 April 2010 (UTC)

And would that account for the difference in the way other people and I often perceive the comfortableness of the ambient air temperature? 71.104.119.240 (talk) 19:02, 21 April 2010 (UTC)

Some other factors which affect how warm you feel:

1) Weight. Larger people feel hotter because they have more "insulation" and lower surface-to-volume ratio.

2) Level of activity. Someone watching TV may feel cooler than someone doing housework in the same room (at least until they dump boiling water on the one watching TV).

3) Emotional state. If you are highly agitated, you may literally feel "hot". StuRat (talk) 15:25, 22 April 2010 (UTC)

of the following, which informs the innate sense of rhythm

is it:

1. One's breathing pattern (breaths per minute)
2. One's pulse (heartbeats per minute)
3. One's gait (steps per minute while walking etc)

Specifically, which of these would be likely to "match up" with someone singing a song with a set tempo. I am inclined towards #3, because I see people moving back and forth rhythmically to keep their rhythm (pianists, saxophonists, etc), and also it is my impression that marches are played in a tempo informed by a brisk marching gait. However the other possibilities (or something else) seem just as likely to me. Thank you. —Preceding unsigned comment added by 84.153.182.163 (talk) 20:51, 20 April 2010 (UTC)

(I fixed your formatting.) I would answer none of the above. #3 is an effect not a cause. The source of rhythm is innate, and not dependent on something external. So people walk in rhythm because they have a sense of rhythm not the other way around. #1 is regulated entirely differently and is not under conscious control, or even awareness. #2 does not actually have a set rhythm but rather responds to the need for oxygen on a breath by breath basis. Bands sometimes need to synchronize one to the other, so walking is visible and easy to follow, so they may agree to sync to it. But that's different from what the source of the rhythm is. PS. I hope I understood your question. Ariel. (talk) 09:05, 21 April 2010 (UTC)

Agree with the above, although I will say that in my experience songs that have a beat that matches my walking pace (most notably Technologic) I find inherently likable (although that's probably just because I don't like the slow down that necessarily accompanies most other songs). I think more than anything a certain beat is just easier to sway/bang heads to. There's a limit on how fast and how far you can move in a period of time, and since humans are all roughly the same size and strength, the same movements end up being roughly as comfortable amongst each other. ~ Amory (u • t • c)

Causes for human genitalia variation range?

From both real life experience and watching lots and lots of adult films, I can conclude that the structure of the penis is pretty darn consistent from man to man. Sure, some are longer than others, perhaps some are thicker, but there's none of the variation seen in female genitalia - specifically the labia majora and labia minora - the latter of which comes in all sorts of shapes, sizes, and lengths. Another indicator of the wide range of configurations is that it is possible for women to undergo plastic surgery to adjust the appearance of their labia to suit personal preference, cultural norms, etc. In terms of human development, what are the differences between the genders that create relatively standardized male genitalia and such wide variation in that of females? Is it hormonal? 61.189.63.145 (talk) 22:09, 20 April 2010 (UTC)

Just wagering a guess, but the structure of the penis is probably rather uniform because of the evolutionary purposes it has. It has two specific purposes: urination and penetration of the vagina. If it came in "a variety of shapes and sizes", I'm guessing it would lose efficiency at preforming one or both of these tasks. (For example, a micropenis would have a much harder time penetrating a female than would an average sized penis.) Ks0stm ^(T•C•G) 22:51, 20 April 2010 (UTC)

For a truly equivalent comparison, you would have to compare the penis to the clitoris, which develops in the female fetus from the same tissue that develops into the penis in a male. And although I may not have the OP's experience examining genitalia, it's safe to say that there's not a lot of variety among clitorides either apart from some variation in size (excluding Linda Lovelace, of course). Beyond that, Ks0stm is right - there's a lot more possibility for variety in structures that don't have a precisely defined and crucial function in ensuring the survival of the individual or the species. Hair, for example comes in many colors, thicknesses, and textures and can be fixed into an almost endless variety of styles, but one healthy heart looks pretty much the same as any other healthy heart. 71.104.119.240 (talk) 04:00, 21 April 2010 (UTC)

Keep in mind that porn is not a representative sample of human variation. To compare variation in the labia with that in the male, the homologous structure of interest would be the scrotum. Some men are "high and tight" while others hang looser. 24.227.222.8 (talk) 21:50, 21 April 2010 (UTC)

Labioplasty is the answer to one of the questions in there.. I recently saw a show about the topic reporting that the practice is very much on the rise. The concern is that even young girls in their early 20s are undergoing the procedure because they think something is "wrong" with them, when in reality there's nothing wrong with them unless you compare them to photoshopped playboy bunnies and porn stars, which is not a healthy comparison, for women or men. Vespine (talk) 04:29, 22 April 2010 (UTC)