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July 25

Could a gull lift a cat in its beak?

See here. Sounds unlikely to me, taking into account that most housecats are heavier than most gulls and the wing-loading and compensation for nose-heaviness that would be necessary for such a feat of strength (in human terms, it would be a bit like piggybacking a person twice your weight, then trying to sprint at full speed - or possibly something more difficult than that). Considering that this was a rooftop-nesting gull in the UK, it would likely be a Herring Gull or a Lesser Black-backed Gull (with an outside chance of it being a Great Black-backed Gull). I've personally seen a gull grabbing an adult cat by the scruff of the neck and yanking it from a drainpipe as it tried to climb up and I've seen gulls fighting with cats and winning - but neither of these scenarios involve physically lifting the cat into the air. --Kurt Shaped Box (talk) 04:27, 25 July 2009 (UTC)

Are you asking for the airspeed of an unladen swallow gull? Seriously... It's not a question of where he grips it! It's a simple question of weight ratios! A five ounce bird could not carry a one pound coconut cat. --Jayron32 05:28, 25 July 2009 (UTC)

A lot of cats are more hair than flesh, so they're actually pretty light. And some gulls are pretty big, the ones at my adopted home of Vancouver are much bigger than the ones in Ontario (and they scr-r-ream like humans being murdered, early in the morning). Definitely a large gull could have a go at a small cat - but the weight ratio and nose-down problems would come into play, which I think explains the four-foot extent of the abduction attempt. The more interesting question for me is why a gull would decide to target a cat rather than, say, a discarded hot-dog bun. Maybe its eyesight is failing? Anyway, I'm definitely going to stop putting bread on my pets before letting them out! :) Franamax (talk) 06:00, 25 July 2009 (UTC)

For the gull to lift a cat it'd have to be dead. Getting the "neck grip" right isn't easy and I doubt a gull's beak is suitable. I would have thought it would also have to be a small cat, but then I found that those gulls carry off salmon in the 12 lb. range. So weight wise it might be possible. I'd agree with Framamax that the big question would be "why" and I'd rate such a necessity presenting itself as rather rare. 71.236.26.74 (talk) 21:46, 25 July 2009 (UTC)

If it really happened, it's pretty obvious to me that the gull was planning to kill the cat by flying up and dropping it from a great height. Gulls *really* don't like cats. I've heard of them killing rats and mice for food in that way (they apparently follow the prey down, then strike it beak-first, moments after it hits the ground). I read somewhere (and I *so* wish that I'd seen this myself!) that the gulls will sometimes go into a steep, full-speed dive with the prey in their mouths, then let go of the thing in a similar way to a Stuka dropping a bomb.

So, an approx 3-4lb gull can fly with a 12lb salmon? Really? I didn't know that - sounds amazing, if true... --Kurt Shaped Box (talk) 02:23, 26 July 2009 (UTC)

Reliable source needed for any bird carrying something weighing several times as much. And a cat dropped from a considerable height could survive. Edison (talk) 03:24, 26 July 2009 (UTC)

Indeed, 'extraordinary claims require extraordinary proof' and all that. I know that gulls are strong (if you've ever held one, you'll know how powerful the wings are) but I'd be astounded if they were strong enough to fly with 3x their own bodyweight (at least!) loaded at the front (they can't grip objects with their feet). As for the cat, I don't think it's fair to expect a gull to know that cats always land on their feet... --Kurt Shaped Box (talk) 04:13, 26 July 2009 (UTC)

At closer inspection the source that threw me off my common sense objection turned out to be a "fish story" in every respect of the phrase. Some fishermen apparently were trying to get rid of some presumed competition. A more reliable source says that Great Black-backed Gulls had never been reported to carry off anything heftier than an Eider duck. If those were anything like the ones described here is still pretty impressive,[1] but less than half the fishy tale. That would get us back to a rather small cat. If you'd ever tried to hold on to a cat that didn't want to be held you'd know that they are pretty good at wiggling out of being gripped. That makes the scenario of a conscious life cat being carried off rather impossible. It'd at least have to be stunned or unconscious.71.236.26.74 (talk) 07:09, 26 July 2009 (UTC)

Landing on the feet is NOT going to save the cat, if it's landing at terminal velocity, which I can't calculate off-hand, but can be 120 mph for skydivers, so it not likely to be very slow.

If the bird knows to, or accidentally does, pick up the cat by the scruff of the neck, the cat will dangle in a fairly helpless position, where it can't fight back or wriggle too much.

How much weight a bird can fly with would depend more on the size of its wings, less on its body-weight, as it is the wing-span which gives it the lift for flying. Migrating species often carry 50% more than their "normal" weight in pre-migration fat stores, albeit this weight is well distributed on their bodies, not dangling in a very un-aerodynamic manner from their beaks. - KoolerStill (talk) 14:11, 26 July 2009 (UTC)

Cat't don't typically land on their feet when falling that far. They land upright, but more spread out in a belly-flop formation to lower their terminal velocity. It sometimes works.[2] However, even when it does work, it looks like about 2/3 of them require immediate veterinary attention. (We can assume that the other third is really sore.) So I think that if I were a seagull I would consider this a suitable revenge against a cat who was being a jerk. APL (talk) 17:32, 26 July 2009 (UTC)

I'm having a bit of trouble envisioning how a gull is supposed to hold on to a cat by the scruff and take off. the former would put it's beak at an angle towards the cat's body. Hence it might work for dragging a cat off a pipe as Kurt seems to have observed. In this position I can't quite see how the gull could take off. There seem to be a lot more likely scenarios of what it could do, like throwing the cat or bashing it on to the ground to stun it. Carrying it off while it is still able to struggle and getting the neck grip to work with a beak in close to upright position is just a very unlikely scenario. 71.236.26.74 (talk) 21:08, 26 July 2009 (UTC)

Empirical evidence of a sort: Seagull flies off with cat in beak --Tagishsimon (talk) 09:04, 29 July 2009 (UTC)

HIV cure

why is a cure not yet found for HIV??What are the difficulties faced in finding the cure for HIV??whats so special about HIV?? —Preceding unsigned comment added by 117.193.139.242 (talk) 05:07, 25 July 2009 (UTC)

Mostly because HIV is a virus, and there are no "cures" for viruses. Antiviral drugs do not actually "cure" us of any viruses, merely slow them down so that our own immune systems can keep them contained. This is true of all viruses, not just HIV. Viruses have treatment, but no cures. Either your own immune system adapts to them, and you get better, or your immune system does not, and you die. Since HIV actually infects immune system cells directly, this creates a HUGE problem... --Jayron32 05:24, 25 July 2009 (UTC)

Me personally, I'd define "get better" as being "cured". Franamax (talk) 06:28, 25 July 2009 (UTC)

I think part of this is that HIV doesn't just destroy white cells, it actually uses the T-cells' CD4 receptor (which is the main receptor that they use to identify the virus in the first place) and / or the antigen-antibody complex to assist with binding to the white cells, then reproduces INSIDE those white cells -- so the body's natural immune response not only don't help at all, it actually just makes the infection that much worse. (Which is why I don't think a vaccine can ever work against the AIDS virus.) It might in principle be possible to cure someone with the AIDS virus by taking all the blood outside the body, radiating it to kill all the white cells, and filtering the blood through a nanofilter before returning it to the body -- followed by a complete bone-marrow transplant -- but the problem is, since you killed all the white cells, the patient will have to be confined to a sterile room for several weeks until his / her immune system creates new, clean white cells, cause if the patient gets even the slightest infection during those several weeks, he / she could easily die. FWiW 98.234.126.251 (talk) 05:29, 25 July 2009 (UTC)

I can't find any mention of this in the HIV article - but haven't there been a few tens of people who have completely recovered from HIV infection through means as yet unknown? Or was that all just ill-informed science by press conference stuff? --Kurt Shaped Box (talk) 05:50, 25 July 2009 (UTC)

Well, there's the Daily Mail [3]. I wouldn't exactly put that in the article though... However, I'm pretty sure that there are some tens of people who appear to be completely immune in the first place. Prostitutes in Uganda or something, if I recall. Franamax (talk) 06:28, 25 July 2009 (UTC)

Yes, the fact that the virus attacks the very immune system cells targeting it certainly makes things difficult. My understanding too is that the genius of this particular virus is the gp120 glycoproteins which "decorate" the proteins which effect entry of the virus into the cell. To "cure" something, or to make a vaccine against something, you need a target. But gp120 is highly variable, so it's difficult to target, and it hides the less variable proteins underneath that do the dirty work of infecting the T-cells. Any one successfully infecting HIV can produce a million new particles with variant gp120's, and only one of them has to work for the infection to continue.

And 98.234, your irradiation scheme might work except that HIV can cross the blood-brain barrier, so you'd have to remove and irradiate all the cells in the brain, which might not work so well. ;) And there may also be other undiscovered reservoirs of infection too. Franamax (talk) 06:28, 25 July 2009 (UTC)

I didn't know that it crosses the blood-brain barrier like methylmercury or something! (Ain't there so much new stuff to learn on Wikipedia?) I stand corrected regarding the radiation scheme. And BTW, Kurt Shaped Box, there haven't been "tens of people who completely recovered from HIV infection through means as yet unknown -- there was one man who completely recovered from the AIDS virus after being given a complete bone-marrow transplant (it's not yet clear if his recovery really is "complete" complete, as in NO viruses OR infected cells remaining in the body), but no other miraculous recoveries so far. That Daily Mail article is just plain wrong (well, what do you expect, they're just reporters...) 98.234.126.251 (talk) 08:01, 25 July 2009 (UTC)

This is only partically true... irradiation works similarly to chemotherapy in that it doesn't target specific tissues but is especially toxic to cells that are dividing quickly; this includes many cancers, but also the cells of the bone marrow, digestive tract and hair follicles. While irradiation would kill off a major HIV reservoir in the bone marrow, one major factor that keeps an irradiation approach from working is that HIV can also infect and replicate with macrophages, which don't divide, and therefore typically aren't killed off by irradiation. In addition, macrophages often migrate to and take up long-term (i.e., years) residence within many tissues, including the brain (where they're called microglia) but also many others (see the macrophage article for a short list). So in that respect HIV can cross the BBB, but only by being ferried across by a previously infected macrophage ([4]). HIV, however, can't actually productively infect any of the other cells in the brain though [5], so it's not the crossing of the BBB that keeps irradiation from working, it's the ability of macrophages to find a nice comfortable home, get a cat and a white picket fence, and live there for a looooong time. Another good thorough review: http://www.ncbi.nlm.nih.gov/pubmed/19486514. Cheers! – ClockworkSoul 19:34, 26 July 2009 (UTC)

Okay, fair enough. Thanks. --Kurt Shaped Box (talk) 02:46, 26 July 2009 (UTC)

wavelength distribution

Is there a similar diagram for wavelengths between .000002 and .000006 nanometers? -- Taxa (talk) 14:03, 25 July 2009 (UTC)

If my calculations are correct, those wavelengths correspond to temperatures in the region of 100 billion kelvin, which are associated with Type II supernovae. They emit light over pretty much the entire spectrum, so are easily visible from the Earth's surface. Gamma ray photons of those wavelengths have energies of about 0.6 GeV, which I don't think are quite strong enough to trigger showers of secondary particles when they hit the upper atmosphere (which is how really high energy gamma rays are detected), so they would probably be very difficult to detect from the surface (even if they could penetrate the atmosphere there would be so few of them that you would need an extremely large detector to stand a reasonable chance of one hitting it). You may find our article, Gamma-ray astronomy useful. If you explain why you are interested I might be able to give a more useful answer. --Tango (talk) 15:23, 25 July 2009 (UTC)

Within this range of wavelengths fits the radius and diameter of the electron. I'm curious how such a distribution of electromagnetic waves would look in this range whether produced in a laboratory or observed above the atmosphere. -- Taxa (talk) 15:58, 25 July 2009 (UTC)

Electrons don't really have a diameter, the classical electron radius (which I assume is what you are talking about) is a fairly meaningless concept. There is certainly no connection between electrons and photons of that wavelength. The closest you get to a connection between electrons an a certain wavelength is the de Broglie wavelength, which depends on the electron's speed. I'm not sure what the opacity of the atmosphere has to do distribution of wavelengths - the distribution will depend on what is emitting the radiation (if it is emitted above the atmosphere and detected beneath it then the opacity will be a factor, but it won't be the only factor). --Tango (talk) 16:32, 25 July 2009 (UTC)

I don't think you meant to say that the radius of an electron is smaller than .000002 or larger than .000006. Just in case let's change the wavelengths to between .000001 to .00001. nanometers. Also, lets replace the atmosphere with an electron and see whether there is any difference in the intensity for each wavelength between this range. You may be surprised. -- Taxa (talk) 22:06, 25 July 2009 (UTC)

I meant precisely what I said - electrons don't really have a diameter. In the standard model they are point particles. I don't know what you mean by replacing the atmosphere with an electron or what you want the intensity of. Your question makes no sense. This is a recurring pattern with your questions. Please learn a little more about the subjects that interest you before asking questions like this - your questions are often based on fundamental misunderstandings of the subject matter so cannot be answered. --Tango (talk) 01:34, 26 July 2009 (UTC)

Is this a request for us to perform original research? We don't do that. This self-published and typo-laden physics paper purports to investigate the earth-atmospheric and extraterrestrial absorption of high energy gamma-rays; maybe it can be a starting point for your investigations. The trouble is that not much experimental physics has been done with that range of gamma ray, because it's hard to make in the laborator (due to its very high energy). As such, characterizing the Earth's atmospheric absorption is difficult. I suspect there will be negligible absorption or attenuation, as such high energy waves don't interact with atomic-scale objects; but it sounds like you are proposing that somehow, they will interact with electrons. Take a look at scattering. At present, there are many types of known scattering observed in physics, but as far as I am aware, there is not experimental data for the wavelengths in question. Nimur (talk) 02:03, 26 July 2009 (UTC)

You might also be interested in terrestrial gamma-ray flashes, which until recently ( ~1994) were considered "spurious". They are now an active area of atmospheric and space-physics research. Nimur (talk) 02:05, 26 July 2009 (UTC)

Any charged primary above a few MeV is likely to interact in the atmosphere via pair production, which is the essential mechanism for a shower. The more energy, the larger the shower. Dragons flight (talk) 02:34, 26 July 2009 (UTC)

purpose of neutral wire in household supply

what is the purpose of neutral wire in the domestic electric supply? If the neutral one is provided for earthing then why an extra port is provided for earthing in three pins? —Preceding unsigned comment added by 203.197.117.165 (talk) 14:57, 25 July 2009 (UTC)

See Ground and neutral. It has a section on combining earth and neutral. --Tango (talk) 15:29, 25 July 2009 (UTC)

The neutral must carry the same current, but opposite in phase, to that carried by the hot or "phase" wire. If only one hot wire were connected to a device, and no neutral wire, no current would flow, no power would be drawn, and the device would not light up, heat up, move, or whatever its function is supposed to be. There would be an "open circuit," as surely as if the switch were turned off. The neutral wire is not there for earthing. The ground wire is the safety conductor, so that if a device shorts to the metal case, the current flows to earth on the ground wire and the fuse blows. The earth/ground wire should carry no current in normal operation. The neutral is essential to operation, and the earth/ground is a safety feature.Edison (talk) 03:21, 26 July 2009 (UTC)

Man With 'Two Brains'

I just watched a fascinating documentary about a man who had the two halves of his brain disconnected from each other and this answered some parts of an almost lifelong question I have had. Here is a hypothetical scenario: a person is laid on a track and a circular saw comes along and cuts him exactly in half from head to groin. Besides the obvious pain this person would be in (let's give him some strong painkillers first), what exactly would the two halves be feeling in the few minutes that it would take for the brains to shut down through lack of oxygen? I have thought about this ever since I heard that cutting a worm in half makes two separate worms. OK, it's more complicated with a person, because the two halves of the brain operate differently. Not only that, what would happen to consciousness? Would the person's brain favour the consciousness of one half or the other? Or both? --KageTora - (영호 (影虎)) (talk) 15:45, 25 July 2009 (UTC)

The brain has a tendency not to react well but to react fast to such shock. When people say a loved one died instantly in a crash what they really mean is that the brain shut down instantly. You are unconscious and in the case you have described unlikely to regain consciousness be fore your enter the next world. -- Taxa (talk) 16:07, 25 July 2009 (UTC)

Firstly, you don't get two worms, you get a dead worm in two halves. Occasionally the head end may survive, but what people usually see is just random muscle spasms for a short time after death. With a human being cut in half they would lose conciousness due to pain and blood loss extremely quickly (seconds, not minutes). There wouldn't be time for the two halves of the brain to have independent thought. When someone undergoes a corpus callosotomy it is done very carefully and cleanly. A circular saw would rip the head and brain to shreds. --Tango (talk) 16:08, 25 July 2009 (UTC)

Right, but what if a brain was separated into two halves and kept alive, although operating completely independantly from each other? My real question is where the consciousness would be - of course, it would be in both. But, how would that seem to a brain that originally had the two halves connected and now has two separated? --KageTora - (영호 (影虎)) (talk) 17:04, 25 July 2009 (UTC)

I think the only way you could keep it alive was if you separated them surgically with a corpus callosotomy. The resulting condition is called split-brain, that article will probably answer some of your questions. --Tango (talk) 17:18, 25 July 2009 (UTC)

There is not a clear scientific consensus on the presence or physical manifestation of consciousness in the brain. The OP's queries about "where" the consciousness would be provide an interesting thought-experiment (although the actual method proposed would result in near-instantaneous unconsciousness and death). We have a large number of articles related to consciousness. Some of the better ones, like neural correlates of consciousness, attempt to summarize current scientific understanding about the physiology of consciousness (e.g. where in the brain does it take place). Unfortunately, (as you will discover if you read through these articles), there is not much agreement on basic principles such as the definition (or even the existence) of consciousness, so it is hard to say in which parts of the brain it is residing. For a less biological and more philosophical overview, read mind-body dichotomy. Unfortunately a review of the results at Google Scholar shows a lot of philosophy and preciously little biology. This is a tough research area for real science. Nimur (talk) 02:11, 26 July 2009 (UTC)

Douglas Hofstadter's books discuss this stuff in an entertaining way. He likes he concept - the metaphor - of an anthill having consciousness as the result of the interactions of its individually mindless ants. 213.122.53.30 (talk) 17:16, 27 July 2009 (UTC)

Some of my questions are answered, but I still have one remaining one. What if (by some new method) we were able to keep the two halves alive? What would the person feel, now being two 'people'? This is really the crux of my question. --KageTora - (영호 (影虎)) (talk) 06:41, 26 July 2009 (UTC)

That experiment has never been done, so there are no suitable references to point you toward. The reference desk is not supposed to be the place for wild speculation about hypothetical stuff. Nimur (talk) 16:11, 26 July 2009 (UTC)

Well, the study has been partially done, in the split-brain patients studied by Sperry and others. The general outcome is that only one of the halves is capable of using language, and the language-using half is not aware that it only controls half of the body. The non-language-using half can often express itself to some degree by controlling behaviors such as hand movements, but can't understand or answer questions. (It should be noted though that these brains are not fully split -- there are subcortical connections that remain intact, and allow whole-body behaviors such as walking to be performed.) There have also been patients with massive strokes who to a large degree are left with only half a brain. Looie496 (talk) 17:33, 26 July 2009 (UTC)

You may be interested in a series of papers by Prof Donald Mackay of Keele about dialogue between the right and left half of almost split human brains (try google scholar). Also there is a very funny long poem written about this in 1910 by "APBS": The Amputee: A Forecast Circ AD 1970. There is a long medical history of a car/plane/tram crash then in the middle it goes "Now amputations Hitherto had left it fairly clear, and to causal observers it must obvious appear That it's easy to distinguish which is A the patient and, Which is B the part removed from him, an arm or leg or hand; But a singular dilemma now confronted Dr. P, He was really not quite certain which was A and which was B, For B or what he thought was B had horrified Perowne By indulging in a totally inexplicable groan..." The poem concludes "Some say A was first to die and some say it was B".

See the novel Peace on Earth by Stanislaw Lem. Mikmd (talk) —Preceding undated comment added 18:33, 29 July 2009 (UTC).

Viruses - what's the point?

What's the point of viruses? What's the point of inhabiting a body, killing it, and then dying when it dies? Why not be friendly with it and be a symbiotic bacteria or something? --KageTora - (영호 (影虎)) (talk) 15:49, 25 July 2009 (UTC)

Even in our own DNA are programs which cause death. For instance, the webbing between fingers and other extraneous materials and constructions which benefit us when they are gone. -- Taxa (talk) 16:02, 25 July 2009 (UTC)

True but irrelevant. --Tango (talk) 16:13, 25 July 2009 (UTC)

Most viruses don't kill their host. Take the common cold, for example - it's very mild and the only symptoms are ones that aid it in spreading (coughing and sneezing). Often when a virus is deadly it is because it has crossed over from a different species. It wouldn't kill members of that species, but does kill humans. It won't generally spread for long in humans before killing all its hosts and dying out. Consider Simian immunodeficiency virus, the version of HIV found in other primates. It doesn't do any harm to them, but when it crossed over into humans and became HIV it became deadly. HIV takes a long time to kill you, though, which is why it can spread so effectively. --Tango (talk) 16:13, 25 July 2009 (UTC)

No point. They just are. APL (talk) 16:17, 25 July 2009 (UTC)

Viruses don't have a motivation, or plan a strategy. What's important to think about is what mechanisms have led the virus to continuing to exist and spread. Viruses that fail in that disappear, and viruses that are successful continue on. The way that viruses reproduce is inherently destructive: they trick host cells into producing more viruses at the expense of the cells' normal functions. If that leads the host to eventually die, it's not necessarily a set back for the continuation of the virus if it has a means of spreading to other hosts in the mean time. However deadly viruses don't kill people out of malice, it's just a side-effect of the mechanism they use to effectively stay alive and reproduce. Rckrone (talk) 16:33, 25 July 2009 (UTC)

Exactly, but staying alive and reproducing are two different things. I'd love to be alive in a hundred years' time and with a bunch of kids to look after, but if having kids (through a host - not a nice way of putting it, but this is an analogy, remember) is going to kill me in a few weeks or months, I really wouldn't mind just getting along with the host and looking after each other. I think you see my point. --KageTora - (영호 (影虎)) (talk) 17:10, 25 July 2009 (UTC)

Your survival instinct is because you need to be alive to reproduce again or to look after your children. That doesn't really apply to a virus. Viruses reproduce exponentially, so the original virus still being alive is pretty much irrelevant to the rate the virus can continue to reproduce. --Tango (talk) 17:21, 25 July 2009 (UTC)

As others have mentioned, the virus doesn't care what happens to the host, as long as it's able to reproduce. Certain strategies diseases use to spread (diarrhea for rotavirus, uncontrolled bleeding for ebola, etc.) have very disastrous consequences for the host, but by the time the host dies, the virus has a new host. Your general inclinations are correct, though, that if the infection is too severe the virus may kill the host before it can spread, or reduce the host population to the point where spread is not sustainable. There is usually a tendency for diseases to moderate their lethality toward their native host over time - those viruses which can maintain themselves in a host without killing tend to produce more offspring over the long term than those which move quickly from host to host, leaving dead bodies in their wake. -- 128.104.112.87 (talk) 17:54, 25 July 2009 (UTC)

To add to what Tango said look through the article on Zoonosis, diseases which humans get from animals. Most of the diseases listed there kill us amazingly fast but their vectors are animals, not us. Killing humans really fast doesn't affect its ability to spread itself. They include Anthrax, Cholera (really infectious among us as well though), Hantavirus, Ebola, Marburg Virus, Plague.

Computeridiot34 (talk) 18:05, 25 July 2009 (UTC)

It's of note that cholera is not really that infectious from person-to-person, unless contaminated water supplies are shared. --98.217.14.211 (talk) 18:15, 25 July 2009 (UTC)

And anthrax is not contagious from person to person at all. 98.234.126.251 (talk) 01:07, 26 July 2009 (UTC)

Can we also point out that its not even clear if viruses are technically "alive" or not (see Life#Definitions, subsection on viruses). They aren't acting consciously. They're sort of ideal replicators — they are about one step up from raw DNA. It's like a bug in computer code that happens to perpetuate itself onward. --98.217.14.211 (talk) 18:13, 25 July 2009 (UTC)

That is purely a technicality. How we define life really doesn't make any difference to anything. --Tango (talk) 19:12, 25 July 2009 (UTC)

Except in that giving the virus itself too much autonomy in making its decisions is clearly wrong. --98.217.14.211 (talk) 02:52, 26 July 2009 (UTC)

KageTora also appears to be making a presupposition about self-preservation as an implicit goal for the virus. Self-preservation is present in most species because it has evolved and continues to enhance the capability to proliferate. As an intelligent creature, you can think about survival strategy and choose particular courses of action. However, most "lower forms" of life (and viruses, which are borderline "life") do not strategize. They simply "do". Viruses continue to exist on earth because their method of existence is conducive to reproduction and propagation. Though in some cases this results in catastrophic self-destruction, that is not something which precludes the virus from pursuing its natural course of action. In fact, the virus lacks the physical or biological capability to even be aware that its actions cause any environmental changes that might harm its future survival chances. You might find the articles about symbiosis, parasitism, and predation useful; many organisms participate in such biological coexistence relationships without any awareness that they are part of a multi-organism system. In some cases, this results in the eventual destruction of one or both organisms. Long-term sustainability is less relevant than the prior history here (as Rckrone mentioned). Nimur (talk) 02:21, 26 July 2009 (UTC)

Exactly my point. Viruses seem to have no stimulus whatsoever for self-preservation, but rather a goal for replication regardless of itself. That goes against everything that Darwin said. --KageTora - (영호 (影虎)) (talk) 02:45, 26 July 2009 (UTC)

Except it doesn't actually play out that way. In fact, they're a beautiful example of Darwinism at the extreme, to the point where you can represent their survival very precisely in an abstract way (which is a lot harder to do with, say, lions and tigers). On the one hand, if they killed everything they touched, they wouldn't survive to reproduce another generation. If they tip the "fatal" side too much that way, then they're definitely not going to be that prevalent. If they can get it just right, they thrive and thrive. Consider the common cold, most influenza, and other viruses we are rather familiar with because they don't actually kill most people who get them (any more). They come and go, spreading themselves through the population just fine. As for whether they kill the host organism, it's inadvertent in probably most cases (there are probably some viruses that benefit from death practices in being spread and wouldn't spread if the human was alive), in the same way that human biology starts to rapidly break down once we are past the age in which our health is vital to our reproductive success. --98.217.14.211 (talk) 02:52, 26 July 2009 (UTC)

The point of a virus is that it kills an unhealthy creature. Sickly creatures tend to go around making things unpleasant for more robust individuals, so for a virus to remove them from the ecosystem isn't a wholly bad outcome. Being that viruses are not strictly considered 'life', they don't need to have any higher goal. They just kill. They could perhaps be better considered to be an emergent, temporary aspect of a higher but very ill being, like vomit. What's the point of vomit? There's no point, it's just a disgusting product of a sickly animal. Vranak (talk) 17:27, 26 July 2009 (UTC)

I'm sorry, but that's unhelpful and incorrect. Viruses do more than simply kill; see mitochondrion#origin and Endosymbiotic theory for some interesting theories regarding how other viruses play the game. More generally, viruses are designed simply to reproduce; killing the host organism is only a problem if the virus has been unable to spread past the corpse. It's no different than people consuming corn or chickens - killing the organism during harvest is not the specific intent, but simply a result and a result we don't care about if we can move on to the next corn plant before we starve.

KageTora, you seem to be looking for purpose in nature. There isn't one. Our article on teleological argument is slated toward the religious aspect, but may still be helpful. Viruses don't get to chose their strategy and the one they have now seems to work just fine for them anyway. Matt Deres (talk) 16:21, 27 July 2009 (UTC)

What's the point of "life"? Richard Dawkins would say that it's to propagate DNA. Axl ¤ [Talk] 19:42, 30 July 2009 (UTC)

David Merrell's mouse experiments

where is our article on David Merrell's mouse experiments please? thx 82.234.207.120 (talk) 16:05, 25 July 2009 (UTC)

Try Hopping mouse. -- Taxa (talk) 16:15, 25 July 2009 (UTC)

What does that have to do with the question? --Tango (talk) 16:21, 25 July 2009 (UTC)

We don't seem to have an article. I've found this page via Google, though. I'm not sure it is notable enough to have a Wikipedia article - it is an experiment done by a high school student for a science fair. It got several awards, but I haven't found much independent news coverage or anything else that would make it notable. --Tango (talk) 16:21, 25 July 2009 (UTC)

Are you kidding? It sent shock waves through the UNIVERSE, no tto mention receiving acolade from the Navy and even CIA. It is the most notable thing I've read about in the past 3 weeks. 82.234.207.120 (talk) 16:28, 25 July 2009 (UTC)

thanks for that nice article. —Preceding unsigned comment added by 117.193.129.196 (talk) 19:20, 28 July 2009 (UTC)

If you can find several independent reliable sources about it, then by all means write an article. --Tango (talk) 16:35, 25 July 2009 (UTC)

If you are interested, there are a few articles here on Google News. It seems it did get some coverage, but I don't know if it was really enough to warrant an article. --Tango (talk) 16:40, 25 July 2009 (UTC)

Click "random article" on the bar at the left 20 times. Still feel that way? 82.234.207.120 (talk) 17:14, 25 July 2009 (UTC)

The ref desk isn't here to debate notability. I gave you some advice based on my extensive experience of Wikipedia, if you don't want to take it then write the article and see what happens. --Tango (talk) 17:23, 25 July 2009 (UTC)

I suspect the interest in the story is mostly about a 16 year old coming up with something interesting at a science fair. Would like to see proof of the CIA and Navy accolades. The story is more human interest than hard science (and it sounds like he left the music on while they navigated the mazes, which introduces a lot of question into the findings, in my opinion... I suspect that thumping hard rock music is going to disrupt a mouse's internal navigation a lot more than anything else). It also doesn't in any way actually show that hard rock is negative in humans (mouse models are not exact, especially cognitive models!!). Anyway... I don't see shock waves in the universe, personally. --98.217.14.211 (talk) 18:19, 25 July 2009 (UTC)

"Navy and CIA accolades" could mean that the recruiter who was present at the Science Fair commended the student. (Or it could mean national recognition and a scholarship). The article does not say. Usually, events that are notable enough to merit articles appear in several online and offline sources. If this research was worthy of followup work, eventually a paper would be published somewhere. That might constitute a reliable source, depending on who published it, whether it was peer-reviewed, etc. Nimur (talk) 02:27, 26 July 2009 (UTC)

rabbits and Hopping mouse

Are rabbits related to the Hopping mouse? -- Taxa (talk) 16:19, 25 July 2009 (UTC)

The mice are rodents, which are similar to rabbits (rabbits were once classed as rodents, but not now).83.100.250.79 (talk) 16:23, 25 July 2009 (UTC)

Not closely, no. Hopping mice are rodents, rabbits are lagomorphs. According to that article: "Though these mammals can resemble rodents (order Rodentia), and were classified as a superfamily in that order until the early twentieth century, they have since been considered a separate order. For a time it was common to consider the lagomorphs only distant relatives of the rodents, to whom they merely bore a superficial resemblance." --Tango (talk) 16:24, 25 July 2009 (UTC)

Muad'Dib, the hopping mouse! SGGH ^ping! 20:01, 25 July 2009 (UTC)

Maximum sustainable population

What is the best estimate of the maximum world population that would be environmentally sustainable? NeonMerlin 18:21, 25 July 2009 (UTC)

I don't think there are any particularly good estimates. Improvements in technology can increase agricultural yields and political issues can result in food not getting to where it is needed (or even not being grown in the first place). See Malthusian catastrophe for a discussion of the issue. --Tango (talk) 18:52, 25 July 2009 (UTC)

Considering what was done to people in the movie the Matrix people could be packed together to a degree that I care not to imagine considering the state of all the major cities today. -- Taxa (talk) 18:55, 25 July 2009 (UTC)

The Matrix is a load of nonsense. Humans don't generate energy, they use it. You can't pack people together like that without some kind of food source. --Tango (talk) 19:02, 25 July 2009 (UTC)

You need to define your terms, and you need to decide whether or not to permit technology that has not yet been invented. If we define "sustainable" as using only renewable resources, and you define "renewable" as coming from the sun, then we can compute an upper bound. The earths' diameter is 12,000KM, then the earth has a capture cross section of about 3/4 x 144 million Km^2, or very roughly 100 million million square meters. Each square meter is good for about one KW, and a resting human uses about 125W, so we have energy for 8 humans per square meter of capture cross section, or 800 million million humans. Now pick a technology "discount" based on your own assumptions: let's assume that an acceptable technoligy can practically operate at only one part in 800 "efficiency" in an environmentally sustainable manner. Then, we get one million million humans as an upper bound. Of course, by the time we have this level of technology, we will not need to remain on earth. -Arch dude (talk) 02:35, 26 July 2009 (UTC)

Does this take into account the costs of recycling air and waste products? NeonMerlin 04:28, 28 July 2009 (UTC)

I think so, yes. The energy required to photosynthesis CO2 and water into glucose and oxygen is the same (give or take some inefficiencies) are the energy released by respiring glucose and oxygen into CO2 and water. Ditto for all the other reactions going on in the human body. All you need to do is replace the energy lost as heat, and that is the 125W mentioned. There may be a little more lost by the plants, etc., but plants aren't warm blooded, so there isn't much. --Tango (talk) 20:25, 28 July 2009 (UTC)

Substance Dependence

What mechanism defines the "normal" amount of a particular neurotransmitter? Can this value be altered?—What prevents us from eliminating opiate tolerance, for example, and therefore allowing for an infinite amount of pleasure?

Alfonse Stompanato (talk) 18:55, 25 July 2009 (UTC)

"An infinite amount of pleasure" is an ill-defined concept. Increasing the dose of opiate will have adverse effects, though. Hypersensitivity and pleasure-response are not the only physical responses to opiates. Take a look at the adverse effects in our article. Respiratory depression can occur, which can lead to death, if doses are sufficiently high. Nimur (talk) 02:34, 26 July 2009 (UTC)

The mechanism is homeostasis. The amount of neurotransmitter could theoretically be extremely different in two people but the neurophysiology is near identical, because other factors are involved (number of receptors, receptor modification, enzyme number, et al). The problem at the moment is that agonists at the opioid receptor trigger signalling pathways associated with analgesia/euphoria/etc but also trigger signalling pathways associated with desensitization and tolerance. It may however be possible to trigger only the positive signalling pathways, but it's a relatively new discovery so don't expect any non-tolerant opioids on the market for at least 15 years. I strongly recommend reading these papers (in order):

Galandrin S, Oligny-Longpré G, Bouvier M. (2007). The evasive nature of drug efficacy: implications for drug discovery. Trends in Pharmacological Science. 28(8): 423–430.

Whistler JL, Chuang HH, Chu P, Jan LY, von Zastrow M. (1999). Functional dissociation of mu opioid receptor signaling and endocytosis: implications for the biology of opiate tolerance and addiction. Neuron. 23(4): 737–746.

Bosier B, Hermans E. (2007). Versatility of GPCR recognition by drugs: from biological implications to therapeutic relevance. Trends in Pharmacological Sciences. 28(8): 438-446.

The original question is the topic of a great deal of ongoing research, and the answers are still very unclear. The nature of pleasure in the brain is also still unclear in many respects. As Nimur says, eliminating opiate tolerance certainly wouldn't allow infinite pleasure -- opiates are mainly sedative and only secondarily rewarding. Eliminating dopamine tolerance in certain brain areas would be more effective, but there is probably more to the story. Looie496 (talk) 17:25, 26 July 2009 (UTC)

Thanks! I figured that this question might not have an answer yet—but I didn't necessarily know the reasons for this. —Preceding unsigned comment added by Alfonse Stompanato (talk • contribs) 18:14, 26 July 2009 (UTC)

Mysterious carpark bumps

Please help me identify the function of these mysterious objects found in the carpark of my local Tesco supermarket - context, closeup. Here is all I know about them: there is one in every parking bay, located on the midline of the bay about 1 metre from the end - roughly where the engine-block of a car would be if you were parking nose-in; the bumps have no identifying marks (no manufacturer, no patent number, no serial number, no "property-of" tag); the bumps are attached to the ground, but can be wiggled around - it's probably straightforward to prise them up with a couple of crowbars; there is no evidence of wires running to them; the bumps are made from a dense black plastic (not rubber) - it feels like they're just a shell over something; the carpark in question does not suffer from drainage issues; the bumps are approximately 100mm in diameter and are about 15mm high, with a tapered edge - they are too small to be effective as traffic calming measures; the carpark in question is close to the shopping area of town (and is used by non-tesco shoppers) so Tesco employs a man with a clipboard on Saturdays to police overstayers; the bumps are very robust (they can withstand frequently being driven over) and there is no indication that they have any mechanical aspect (I don't think they're mechanical switches of any kind); I've never seen a store employee or contractor cleaning, touching, or servicing them, and there is no signage suggestive of their purpose; I don't think they're caps for holes one would use to put in parking-prevention bollards - they're at the wrong end of the bays for that.

My guess is that they are related to parking control: that they house a magnetic car sensor and keep track of how long the car above them has been in that bay (resetting when a car leaves). If that's true, they must be battery powered and presumably have a short-range RF capability, so the clipboard-weilding parking man can interrogate them individually with some kind of handheld wand. If this is correct, I'm impressed that they can run a small computer, a magnetic sensor, and a two-way RF connection all off a battery, presumably for weeks or months on a charge. I doubt that having several hundred of such fancy devices would be cost effective in a carpark that is free.

I've asked several employees, but they didn't know (or have been sworn to secrecy by the carpark bump conspiracy). Does anyone have any idea what these might be, and who makes them? -- Finlay McWalter Talk 19:55, 25 July 2009 (UTC)

Perhaps parking related as you suggest? If not to time the car in and out then at least to tell when the car park is full. SGGH ^ping! 20:00, 25 July 2009 (UTC)

I should point out that there is no "car park full" sign, and no "spaces free" counter sign either, so I don't know what Tesco would do, in practice, with information about how full the lot was (other than internal statistics, which I'd doubt would justify the cost of sensors. And there is no barrier or ticket-machine at the carpark's entrance. -- Finlay McWalter Talk 20:05, 25 July 2009 (UTC)

There's plenty of material on parking space sensors from google, including a paper which shows the internals of one - much the same size as yours. However, per your narrative, it remains a mystery what tesco is doing with the information collected, if anything. Nice shoe, btw ;). --Tagishsimon (talk) 20:06, 25 July 2009 (UTC)

It seems apparent that Tesco has too much money for their own good. Vranak (talk) 20:08, 25 July 2009 (UTC)

I did also consider the possibility that they were passive reflectors, which could be used by a remote-camera system to count and time cars (if the reflector is obscured then there must be a car in the bay) - given the few cctv cameras around, this would have to be done by sensors atop lampstandards - but I don't think there are enough lampstandards for this, and these dull opaque bumps are the very opposite of reflective (I guess they're less reflective than cars, so maybe that's it). -- Finlay McWalter Talk 20:10, 25 July 2009 (UTC)

Meanwhile in SF, "The device, called a “bump,” is battery operated and intended to last for five and 10 years without service." - [6]. --Tagishsimon (talk) 20:22, 25 July 2009 (UTC)

If a camera/reflector system were being used, they would have to install quite a number of cameras or have them very high up since the car in the next space over could block more than a single bump. Dismas|^(talk) 20:27, 25 July 2009 (UTC)

The SF bumps are associated with revenue (I'd guess they'll cost at least $100 each, so they'd have to pay for themselves) whereas my Tesco bumps are in a free lot (and Tescos got to be as wealthy as Vranak says by not wasting money). And the SF bumps look pretty well grouted in - they'd have to be, to stop someone prising them up and making off with them (Berkeley had a vigilante problem a while ago, with someone cutting down dozens of meters to protest parking fees); Tesco's bumps don't seem that secure. Maybe I've misled everyone by suggesting the parking-management idea (which really doesn't seem cost-effective), and they're something much more passive and mundane. -- Finlay McWalter Talk 20:36, 25 July 2009 (UTC)

In the US at least, many shopping centers have free parking lots that are intended for the use of the shoppers, but are not supposed to be use by daily commuters. If a car is parked inthe early morning and is still there five hours later. The owne ofth lot can have it towed away. The bumps could monitor this.-Arch dude (talk) 21:12, 25 July 2009 (UTC)

They have a 2 hour maximum, and they can impose a civil fee (recoverable by court action) in England. But in general shops and shopping centres are rather reluctant to impose these fines (I think they do it for all-dayers, but not for people who stay just an hour longer) as it's a great way to annoy someone and lose their business forever. -- Finlay McWalter Talk 21:18, 25 July 2009 (UTC)

Google rulez! Looie496 (talk) 23:51, 25 July 2009 (UTC)

Awesome google-fu, Looie --Tagishsimon (talk) 23:55, 25 July 2009 (UTC)

Were you referring to Kidderminster, Finlay McWalter? --Rixxin (talk) 15:04, 26 July 2009 (UTC)

Good job on the Google-fu. As an aside in response to concerns about cost, I'll note that the scheme would work very nearly as well if only (say) 1 in 3 'bumps' were genuine and the rest indistinguishable dummies. The purpose is to discourage long-term or full-day parking that isn't related to visits to Tesco. If word got around that a) the bumps are tracking parking, and b) Tesco is issuing tickets or towing vehicles, then the fact that only a fraction of the bumps actually work is irrelevant. (Indeed, from Tesco's perspective the fractional coverage might actually be better — it would convey the message that tickets were being issued and parking rules enforced, while reducing somewhat the number of people who actually get mad about receiving a ticket personally. A similar effect could be achieved by issuing warning notices on first offences and by capping the number of tickets issued per day.) TenOfAllTrades(talk) 16:05, 26 July 2009 (UTC)

What happened to the US space VLBI program?

Looks like the Japanese did Space VLBI back in 1997: http://www.vsop.isas.jaxa.jp. If Moore's law was being followed, which in signal processing (as opposed to consumer goods) I believe it generally has been, we might have had a way to see the ozone spectrum characteristics of Earth-sized habitable exoplanets at 34 THz and below (9-10 micrometers) by now.[7]

However: http://web.archive.org/*/us-space-vlbi.jpl.nasa.gov/

Where did the US lose track and how can we get back on track? I don't want to know who was responsible (although I believe they should be held responsible if they can be identified) nearly as much as I want to know who can bring the thing out of mothballs.

Related research:

• Schneider, J. (2009) "Pathway Toward a Mid-Infrared Interferometer for the Direct Characterization of Exoplanets"
• Schneider et al (2009) "Search for Life on Exoplanets: Toward an International Institutional Coordination"
• Mugnier et al (2009) "Optimal method for exoplanet detection by angular differential imaging"

99.60.2.113 (talk) 19:59, 25 July 2009 (UTC)

I know a girl who's doing work with Cluster that one might call "VLBI"-like. That is an ESA satellite constellation, but the research is funded by the NSF (I think). I think there is also a new replacement small-satellite system (either IMAGE or THEMIS, both NASA missions; these have sensors which can also be used for VLBI-like work. The work that I am aware of is mostly using synthetic-aperture for terrestrial observation, though. I don't know if these satellites have useful science data for studying exoplanets. As far as the US "losing track", I agree that we're underfunding our space research; but you might want to look at this article. Space research is always lower-priority for government spending; and these days it is even lower priority than usual. Nimur (talk) 02:48, 26 July 2009 (UTC)

Also, I don't think any reliable economist or researcher has ever suggested that Moore's law even remotely applies to space research. An engineering professor explained Moore's law best during an ASIC class a while back. The "law" is only preserved because of an economic feedback loop, where profit is fed back into the engineering investment to double the performance. This produces more profitable products, so more profit can be fed back into the research. And as all engineers know, positive-feedback leads to exponential growth. Space research has no such profit-return path (or at least, not on the 18-month time-scales). Moore's law does not hold. Nimur (talk) 03:28, 26 July 2009 (UTC)

The necessary profit motive exists in, e.g., fiber optic communications bandwidth markets, which have been improving along with the continuing miniaturization of integrated circuit photolithography.

Why can't we use any two existing infrared space telescopes for VLBI? HowDoIUseUnifiedLogin? (talk) 06:58, 26 July 2009 (UTC)

We can, provided their data is sufficiently synchronous; but remember, our best timing accuracy is usually GPS time (depending on your circuitry, this can be anywhere from millisecond-accuracy to maybe nanoseconds with some phase locked loop filling in the subsampled time intervals. For interferometry, you need timing accuracy on the order of the wave period for the frequencies you are looking at; that makes VLBI very hard unless the equipment has been specifically designed to measure coherently. At lower frequencies, such as those EM waves suitable for electromagnetic surveys of the terrestrial and near-earth environment, VLBI is much easier. Optical surveying of exoplanets, though, is a whole different animal. Nimur (talk) 16:15, 26 July 2009 (UTC)

In fact, after searching yesterday and today, I could not find any real VLBI observations of exoplanets at optical wavelengths. Simulations abound - but this is because in MATLAB, any arbitrary timing coherence is possible. An actual satellite cluster must have synchronized clocks (or other wave coherency system) that is as accurate as the frequency of observation. This is not a "small detail", it is a major engineering obstacle that (at infrared wavelengths) pushes several orders of magnitude beyond the state of the art in clock coherency and accuracy. Nimur (talk) 16:18, 26 July 2009 (UTC)

Assuming that the timing and therefore the position information is poor, which I am not sure is a reasonable assumption given modern chip-scale atomic clocks, is there any reason that a brute force search for the matching phases isn't possible? It would seem that the features of the image including the spherical Bracewell-nulled star, possibly the elliptical interplanetary dust cloud emitting blackbody IR, and certainly the planets in question would all provide sufficiently discernible features for pattern recognition which would be distorted in a way that should be obvious to an algorithm when the phases aren't correctly matched. If brute force phase matching is possible, how about a binary search? 99.35.130.129 (talk) 17:26, 26 July 2009 (UTC)

It's not a matter of precision, it's a matter of accuracy. As you point out, we can make clocks that are precise to amazingly small time-intervals - but those clocks need to by synchronous across satellites which are tens of thousands of kilometers apart. That part has not made recent advances - as I said, GPS is our best bet, and it's about 1 ms accurate. It works great if you are doing low-frequency research. To be honest, I have no idea what "Bracewell nulling" is, this paper seems to mention it.

Bracewell, R.N, and MacPhie, R.H.. Icarus, vol 38, 1979: available here Nimur (talk) 18:05, 26 July 2009 (UTC)

Bracewell wrote in 1979, "... it is not clear whether technology or astrophysics will be limiting. It is conceivable that bulk motions of the stellar envelope ... could foil attempts to exhibit ...periodicity." This is the crux of the issue. Even in 2009 (thirty years later), we still have neither the technology nor the astrophysical understanding to be sure we are isolating the exoplanet via angular resolution; the interferometric approach suffers similar problems. Clearly this is an area that can benefit from further basic science research as well as technology improvement; the 1979 paper gives a great overview of the challenges and also has provides some formulae and some example numbers you can crunch for yourself, to determine the necessary engineering constraints for a given exoplanet size. In summary, "we aren't there yet."

Also, you seem to think that phase error "should be obvious to an algorithm when the phases aren't correctly matched" - but that is unfortunately not the case - phase noise. If you can think of such an algorithm which eliminates phase noise, and it actually works, then you'll have made a really solid contribution to interferometry, and signal processing in general! Nimur (talk) 18:29, 26 July 2009 (UTC)

The solution is independent of the time scale limiting initial phase matching accuracy. The interferometric image combination does not discard information, therefore it is a convolution. Expected star, background, and planetary images can be similarly convoluted to derive patterns, comparisons against which a search through the possible timing differences can be guided by to finish in O(log(N)) time. These convolved but information-rich patterns can be combined for comparison templates allowing an even faster phase match search.

There may be an even simpler algorithm. Please consider the phase vocoder used for pitch ("autotune") and time shifting. The total magnitude (or energy?) of changes it needs to make to match phases for resynthesis is proportional to how well the waveforms are matched. A calibration system at that level of sophistication could be tuned on a variety of wavelengths even if starting at 34 THz would be much harder. 99.35.130.129 (talk) 20:58, 26 July 2009 (UTC)

More related research:

• Pallé et al (11 June 2009) "Earth's transmission spectrum from lunar eclipse observations" Nature 459: 814-16
• Le Coroller et al (2004) "Tests with a Carlina-type hypertelescope prototype" Astronomy and Astrophysics 426: 721-8
• http://collab.digitaluniverse.net/wiki/Interferometry_from_Space - currently omits heteroscopic space VLBI
• Closure phase - a method of calibrating two VLBI telescopes with a third

99.35.130.129 (talk) 21:44, 26 July 2009 (UTC)

Why do buildings have foundations?

What is the reason for having foundations for buildings? Surely it does not make any difference if the weight of a building such as a house is supported on the surface of the ground or a few feet below? 89.243.185.143 (talk) 20:35, 25 July 2009 (UTC)

There are a number of reasons for considering sunken foundations, such as development of lateral capacity (i.e. preventing movement), penetration of soft near-surface layers, and penetration through near-surface layers likely to change volume due to frost heave or shrink-swell - see Shallow foundation. But there are above-ground foundation systems, such as concrete on grade, which are suitable for more temperate climates. See also Foundation (engineering) and Deep foundation. --Tagishsimon (talk) 20:53, 25 July 2009 (UTC)

Look at Foundation (engineering), Shallow foundation, Consolidation (soil) and Bearing capacity. Oh and read the Parable(?) of the man that built his house on sand, http://www.thisischurch.com/sermon/wiseman.htm ny156uk (talk)

Around here, the Frost line can be as much as 4 feet deep. So when the ground heaves (see frost heave), anything above it will move up. You don't want this happening under just part of your structure. Dismas|^(talk) 21:05, 25 July 2009 (UTC)

The simple answer is: buildings are expensive. While a house could be built for tens of thousands of dollars, many academic buildings are vastly more complex, and expensive the same way. At the same time, these buildings LAST. Many famous University buildings have been built more than a hundred years ago. So, when a foundation pays for a building, it is one of the longest-lasting charitable actions they can do, while at the same time there is a big financial need for support in building the buildings, which explains both the foundations' and the universities' / other bodies' eagerness to take on these kinds of projects. It's just basic economics, really. 82.234.207.120 (talk) 21:43, 25 July 2009 (UTC)

↑ cute.--70.107.76.121 (talk) 22:39, 25 July 2009 (UTC)

Does it help if the foundation rests on a solid rock..efeller? Nimur (talk) 18:50, 26 July 2009 (UTC)

The surface of the ground has several problems. In most places it consists of topsoil, full of organic matter that can decay or change. In areas prone to freezing the ground can expand and contract as it freezes, moving up and down. Even in areas where that isn't an issue, the ground will expand and contract according to its moisture content. You always want the material under a building to be essentially unchanging. Furthermore, the soil near the surface has almost always been disturbed by human activity, either building or agriculture and may not be consistent in nature, or may be insufficiently compacted. It is actually worse to have inconsistent bearing under a building than to have poor, but consistently poor bearing, as then different parts of the building will move in different directions, always a bad thing. With rain, freezing, topsoil and disturbance, even light foundations should be at least 18"/1/2 meter below grade, or have the soil cut out to that depth and replaced with a material of predictable characteristics. The better the bearing capacity of the material, the smaller the foundation may be.

It's worth noting that the skyline of Manhattan roughly parallels the availability of Manhattan schist at a depth convenient for the placement of skyscraper foundations. Where it's deeper, like in Greenwich Village, buildings are shorter in stature, as it's hard to spread the load of a tall building over a wide enough area in soil without resorting to pilings. Also, for a tall building, the foundation must resist the wind load or overturning moment, and even in a small building you don't want it tossed by the wind (think about trailers vs. tornadoes). Acroterion _(talk) 00:04, 26 July 2009 (UTC)

If a church is built on the rock it will stand, even when steeples are falling [8]. Edison (talk) 03:14, 26 July 2009 (UTC)

Surely it does not make any difference if the weight of a building such as a house is supported on the surface of the ground or a few feet below – actually, it makes a big difference. Try building something with sticks. You'll find that when they're stuck in the ground you can actually build a stable structure. Otherwise, things tend to fall over. Vranak (talk) 17:17, 26 July 2009 (UTC)

That's mostly an unrelated phenomenon. Sticks shoved in the dirt are stable due to the soil surrounding them holding them in place, that is mostly not the case for buildings. While having dirt around it sure doesn't hurt, the purpose of digging is simply to reach a stable level. Matt Deres (talk) 16:08, 28 July 2009 (UTC)

example of easy irrational problem?

I am looking for an example of an easy irrational problem or task, that is impossible for the deductive, rational left-brain (or a rigorous computer program etc) to solve or answer, but is so easy that EVERYONE who has both brain hemispheres can solve it, even the most rational, Asperger's-suffering mathematician on Earth. But where the solution MUST be done by their right brain.

Any ideas for what such a problem or task might be? (It's actually okay for me if a percentage of the rational people above mentioned fail at the task -- I am really looking for something almost all of them can do [but which is irrational, can't be done by the left brain].) Thanks! —Preceding unsigned comment added by 82.234.207.120 (talk) 21:49, 25 July 2009 (UTC)

Well, assuming the Church-Turing Thesis is true, and the brain is just a meat computer, there is no such problem. There are many problems that are very hard for computers using our current techniques, but which humans are very good at. Recognizing faces from minimal cues is one. Noisy image recognition is a related one. I would suspect music appreciation is similar - if a computer can recognize the Eroica as truly great music, I'd be surprised. --Stephan Schulz (talk) 22:24, 25 July 2009 (UTC)

Some experienced mathematicians are unable to complete the following series which is often solved easily by children:

3, 3, 5, 4, 4, 3, 5, 5, 4, 3, 6, ?

Cuddlyable3 (talk) 23:18, 25 July 2009 (UTC)

However, a computer with access to Google or the OEIS can also solve that easily, so it doesn't seem to be what the OP is after. Algebraist 23:22, 25 July 2009 (UTC)

Your conditions are so stringent that they probably make the problem impossible. For one thing, the standard left brain/right brain distinctions don't apply to everybody -- many left-handers have different lateralization. If you restrict yourself to people with the standard lateralization (i.e., ordinary right-handers), probably the most basic function that is highly right-hemisphere-dependent and not solvable by logic is recognizing people's faces. However, people with autism or Aspergers, and some other hyper-rational people (Isaac Asimov for example), are often impaired at this. Looie496 (talk) 23:36, 25 July 2009 (UTC)

Ho ho ho it looks like the problem I posed separated the left-brainers from the right-brainers. (Once you see it, it is a no-brainer.) To Algebraist I think we must distinguish between solving a problem and looking for someone else's solution. The GIGO principle suggests there is no irrational act that a computer might not do. Cuddlyable3 (talk) 23:42, 26 July 2009 (UTC)

For those of us really bad at spelling it does not become a "no-brainer" even after it's explained. It's not so much a puzzle as much as an exercise. It tests whether or not you've ever seen a puzzle of this sort before, and whether you have the patience to grind through common series until you find it. For me, I can't do these without writing down the words and counting the letters (Even so, how do you spell "eight"? I can never remember.), so I stopped after checking only two series.

It may have successfully identified me as a math centric person, but I'm not confident it worked the way you expected. I did at least correctly identify it as potentially being a count-the-letters puzzle.

(Incidentally, I was going to guess '6' because of the pairs of repeats in the series, So at the very least you're going to want to end the series on a different element.) APL (talk) 15:10, 27 July 2009 (UTC)

So ... what's the solution to the series? APL (talk) 19:32, 26 July 2009 (UTC)

Well, I have pretty serious Asperger's and I got it in about 10 seconds. The clue that made it easy was that the questioner didn't think I'd be able to solve it - which told me I shouldn't be looking at a numerical solution. However, smart people can think laterally too - so let me give you a clue: ONE,TWO,THREE,FOUR,FIVE,SIX,SEVEN,EIGHT,NINE,TEN,ELEVEN,...got it now? How about A,B,C,D,E,H,I,K,M,O...what's next? If you need to give me a problem I can't solve, have me talk about small British cars from the 1960's to an average person at a party. Challenge me to stop talking when the other person gets bored. I have no clue how to do that. Fortunately, people who know me well know that I'm also not in the slightest bit offended when I'm told that I've explained that enough already! SteveBaker (talk) 22:32, 26 July 2009 (UTC)

You probably wouldn't be far off if you just didn't start! --Tango (talk) 00:43, 27 July 2009 (UTC)

Ah. One of those. I tried the days of the week and the months of the year, couldn't make it fit so I tried a different tack. Are non-logical people (Esp, children) really so good at these? If so I must be pretty non-typical. Forget common series; I can't remember how many characters are in my name without seeing it written or counting on my fingers.

Not to make light of Asperger's at all, but I have to ask, for your party question, from the point of view of designing an algorithm, couldn't you get a rather close approximation by judging the interval between intelligent questions? APL (talk) 04:44, 27 July 2009 (UTC)

This series depends heavily on how you choose to visualize numbers. If you see the word "three" in your head upon seeing "3", the solution is easy to get. If you see 3 apples, 3 spheres, or the Arabic numeral "3" and have never visualized numbers any other way, it might take a while. --Bowlhover (talk) 06:16, 27 July 2009 (UTC)

no, the recognizing faces thing is totally a great example! It's "irrational". A mathematician would have nothing to say about what he's calculating or reasoning while he's doing that: literally nothing. You put them in front of a computer and tell them to write down their algorithm in pseudocode, they would say they're not following an algorithm, it's a nonsensical request. But you ask them to code approximately how they do their grocery shopping, they can lay down pseudocode before you've finished your sentence!!! So I like the example a lot. It's something "irrational" and yet all mathematicians can recognize SOMEONE. Can you give me more examples of this, of something "irrational" that all people, even mathematicians do? Also, the brain laterization thing isn't the crux of the request, but the "irrational" problem solving is!! Thanks. 82.234.207.120 (talk) 00:20, 26 July 2009 (UTC)

One simple problem of this type is to decide whether or not a sentence is funny. -Arch dude (talk) 02:12, 26 July 2009 (UTC)

Facial recognition can be performed algorithmically. See Facial recognition system. Maybe some mathematicians do not think about it in an algorithmic way, but clearly the problem can be set up, defined, and solved algorithmically. The accuracy is becoming very high, and in some professional-grade systems, beats human face-recognition error according to some metrics: "Computers outperform humans at recognizing faces in recent tests". Nimur (talk) 03:10, 26 July 2009 (UTC)

I'm not sure that a human being could consciously eyeball the measurements needed for a facial recognition algorithm. APL (talk) 04:44, 27 July 2009 (UTC)

How about just having a normal conversation? AI's still don't pass the Turing test. Robots with AI are also apparently very bad at soccer. Then of course there are those images of a word that you're supposed to type. Some of them have been broken, but in general it's a very hard problem. Check out the Artificial Intelligence page for for a more thorough description of the types of problems computers are comparatively very bad at. The original question wasn't really about computers per se, but I'm not sure how to tell if a problem is impossible with only the "left brain." Rckrone (talk) 06:06, 26 July 2009 (UTC)

Rckrone may be referring to CAPCHA . Cuddlyable3 (talk) 23:54, 26 July 2009 (UTC)

Oh yeah, I forgot that had a name. Also I did a really horrendous job of describing it. Rckrone (talk) 02:40, 27 July 2009 (UTC)

Certainly there are problems you can set up that a computer can't solve - but you'd be hard-pressed to find a human-solvable problem that a computer will never be able to solve (presuming it's given the same data and life-long learning that the human gets). Remember - people said that a computer would never be able to beat a grand master at chess - or that it would never be able to drive a car. It's dangerous to make these claims. But that's not what the questioner is asking. We're supposed to be finding problems that a highly logical brain can't solve - that more 'normal' people don't find difficult. SteveBaker (talk) 22:32, 26 July 2009 (UTC)

Well in that case I think Stephan Schulz has it right. There's no reason a sophisticated enough computer couldn't perfectly emulate a human brain. Rckrone (talk) 02:40, 27 July 2009 (UTC)

Hey! I may not always have it (I'm not Steve Baker), but if I have it, I always¹ have it right! --Stephan Schulz (talk) 11:29, 27 July 2009 (UTC)

¹ ...for sufficiently small values of always!

That isn't quite correctly stated. There is no conceivable computer that could perfectly emulate a grain of sand. A better way to put it is that there is no valid reason to think that the brain performs any useful function that couldn't be emulated by a computer. Looie496 (talk) 02:52, 27 July 2009 (UTC)

CAPTCHAs are designed to exploit the current gap between what humans can solve and what computers can solve. Ironically, they've been quite effective at driving research in these areas, research that continually proves each new CAPTCHA vulnerable to sophisticated machine learning methods. There will probably for a long time to come be tasks that humans perform better at than computers, but the gap continues to close. Dcoetzee 21:37, 27 July 2009 (UTC)

Which cow breed is this Swiss cow?

A swiss cow seen near Oeschinen Lake.

Hi, I took this photo of a cow in Switzerland a short while ago. I would like to know which breed it is such that I can update the file page description and categorize it properly. I guess it must be some breed of Bos taurus, but I am at a loss which one. Thanks in advance. --Slaunger (talk) 22:12, 25 July 2009 (UTC)

Montbeliarde Cattle? I'm not sure, I'm not an expert in that field :) . And it is Swiss, not Swizz. Actually, more like French ;). --Dr Dima (talk) 22:38, 25 July 2009 (UTC)

Sorry about the terrible spelling (which I've corrected now). I am not a native speaker nor speller... OK. I do not feel too sure when seeing the photos of that breed, and I think I would like a second opinion, but thanks of for your time. --Slaunger (talk) 22:52, 25 July 2009 (UTC)

I asked my wife, who works in the dairy industry, what breed it is and she doesn't know. She was able to definitively say that it's a beef breed though, as opposed to a dairy breed. Dismas|^(talk) 01:38, 26 July 2009 (UTC)

The English Wikipedia distinguishes between Simmental Cattle and Fleckvieh cattle which are treated as the synonyms by the German Wikipedia de:Fleckvieh. The Swiss are trying to establish "Swiss Fleckvieh" as a separate breed and are limiting the Red Holstein influence for that purpose. It's a dual purpose breed (beef and milk) like lots of the "older" breeds. Here's a picture for comparison,[9] looks pretty much like yours. 71.236.26.74 (talk) 03:34, 26 July 2009 (UTC)

Thanks for that thorough answer. I did have a look at the Simmentaler before asking but the photos does did not look quite right to me. --Slaunger (talk) 10:14, 26 July 2009 (UTC)

I don't think there is enough information in one photograph of a semi-recumbent animal to accurately identify the breed. Richard Avery (talk) 19:46, 26 July 2009 (UTC)

I understand your concern. I think I will conclude from this that "It is most likely a Swiss Flechvieh, could also be a Flechvieh, a Simmentaler or another dual purpose breed (beef and milk)." Finally, one of the Wikipedia articles points to a dedicated German Flechvieh site, which i have seen has a forum, where one can ask questions. I think I will also ask the question there, as they should know if any if it is a Flechvieh or not. Last, but not least, thanks for the help and feedback here. It is very much appreciated. --Slaunger (talk) 21:04, 26 July 2009 (UTC)

July 26

Cat bird owl?

There are so many hoaxes on the internet and on youtube, that I assume this is just pixel animation, but I was curious if it possibly wasn't what the hell is going on in this video where a startled owl stretches out into a cat-like resemblance? Like I said, I'm assuming it's fake until told otherwise, but it's pretty cool looking and there's something about that looked real enough that I thought I'd ask.--70.107.76.121 (talk) 00:24, 26 July 2009 (UTC)

Okay, now I really want to know just what's being said in these videos. Here's another; same owl type, totally bizarre stuff. Anyone speak Japanese?--70.107.76.121 (talk) 00:30, 26 July 2009 (UTC)

Some owls have large ears reminiscent of cats. There's no trickery in the first video; I couldn't spare 3:20 to view the second, but both appear to be about owl training. --Tagishsimon (talk) 02:10, 26 July 2009 (UTC)

I speak Japanese, and all it is saying in the second video is that the owls change shape according to what other owls appear in their vicinity. One changes shape to make it look bigger, signifying 'I am bigger than you' and the other changes shape to make itself look smaller, though the reason is not given. Also, the trainers are using both male and female owls for this experiment/show. --KageTora - (영호 (影虎)) (talk) 02:39, 26 July 2009 (UTC)

I definitely agree that the video is legit. It's a defensive response. The purpose might be to disrupt a potential predator's search image. Sifaka ^talk 05:15, 26 July 2009 (UTC)

Searching Japanese Wikipedia for アフリカオオコノハズク leads to Northern_White-faced_Owl although the English article doesn't mention its ability to change its shape like that. The Japanese article seems to have a bit more information but I don't know what it says. Rckrone (talk) 05:39, 26 July 2009 (UTC)

Am I the only person here who finds that transformation to be fairly unsettling - on a visceral level? --Kurt Shaped Box (talk) 07:14, 26 July 2009 (UTC)

If it's to deter predators, as suggested above, then that's probably the intention - ie to look like a bag of bones and sinew and not a very good meal.83.100.250.79 (talk) 08:51, 26 July 2009 (UTC)

Specifically, it's something about the way that the owl's face and eyes appear to change shape that trips off a feeling of 'wrongness' somewhere within me. --Kurt Shaped Box (talk) 09:10, 26 July 2009 (UTC)

It's all very simple. The owl has a face just like we do. It has muscles that change shape. The owl got scared (but not enough to fly away), so he shrunk away from the jack-in-the-box. The difference is, the owl is covered with feathers. Muscles retract, feathers go with it, and it's face changes shape significantly. If your face was covered in feathers it would be quite a sight when you got shocked, too. Vranak (talk) 17:15, 26 July 2009 (UTC)

Aye, birds' faces can be very expressive at times, despite being covered in feathers. I don't know if we could pull off 'curiosity' or 'anticipation' when similarly covered. A Budgerigar (for example) can. --Kurt Shaped Box (talk) 20:16, 26 July 2009 (UTC)

In the second video, the narrator said that it elongates its body to appear as a tree or branch. It squints its eyes so they are less visible. -- penubag  (talk) 09:08, 28 July 2009 (UTC)

Light energy

Light is frequencies of energy that the eye can see.Frequencies in the blue light field will create a magnetic field. Other levels will create cold temperatures. Who can help me prove this?

Light is not "frequencies of energy" - it is "frequencies of electromagnetic waves", usually referring to those frequencies we can see with the human eye. All light has both an electric field and a magnetic field because light is an electromagnetic wave. Light does not "create" a magnetic field. It is a wave phenomenon which includes a time-varying magnetic field. This has been proven many times by many different methods. See wave-particle duality for more on this topic. I am not sure what you mean by creating cold temperatures; do you mean laser cooling? Nimur (talk) 04:14, 26 July 2009 (UTC)

Your first phrase reminded me of St. Elmo's fire, but that works the other way round. The light is due to the electric field.71.236.26.74 (talk) 04:23, 26 July 2009 (UTC)

Is it common to imagine that puffins are bigger than they are?

I saw a puffin in real life not so long ago. I was surprised at how small it was. When you see them on wildlife shows on TV, they look much bigger. I was expecting something about the size of a medium sized penguin. --84.69.249.254 (talk) 07:29, 26 July 2009 (UTC)

On TV they are trying to show as much detail as possible, so they'll do close-ups. It's not uncommon to imagine stuff you haven't seen in real life as larger than it is. I still run into rivers that I only used to know from maps and am frequently underimpressed with the width of them. Very few held up to my idea of what a well known river should look like. As for animals, there's an anecdote about Malaria researchers showing a film about mosquitoes to some villagers in Africa and being told that there was no danger because the local mosquitoes never got as big as the one in the film. So apparently the effect isn't unheard of nor limited to puffins. 71.236.26.74 (talk) 08:07, 26 July 2009 (UTC)

Antarctic penguins suffer similar size-inflation. Television documentaries film the penguins via telephoto lenses, because they are not allowed to approach the birds (environmental and wildlife protection mandates are very strict in Antarctica - though how they are enforced is always a mystery to me). The result is a shot of birds against a barren, treeless ice landscape. With no measure of perspective, these birds appear huge - I always thought the Emperor Penguin would tower above an upright 6-foot human; but in fact the largest of them are only about four feet tall. But from these sorts of photos, how can you possibly tell? The only objects available for visual height reference are... other penguins. For all you know, those penguins could be twenty feet tall. Similar issues plagued the Apollo moon landers - without visual cues about height, it was very hard to tell pebbles from boulders; small holes from large holes; bumps from mountains; depressions from canyons. Human visual perception relies very heavily on the subtle peripheral clues to help judge perspective, distance, and size. Nimur (talk) 18:56, 26 July 2009 (UTC)

FWIW, when I was a kid, I used to think that the Emperor Penguin was about the same size as a human - a similar height to the extinct Anthropornis (I was just reading about that), I guess. I also imagined the Wandering Albatross as being man-sized, when stood up straight. --Kurt Shaped Box (talk) 12:55, 27 July 2009 (UTC)

The angle the photo is taken from gives a slight clue about size - a twenty foot tall penguin is likely to be photographed from below, any other angle implies it is smaller. (The horizon usually marks where human eye level is, on all objects in the photo, in flat terrain.) And I share the puffin experience - when I first saw one next to a person I was disillusioned and disappointed by its dinkiness. This anecdotal evidence doesn't really answer the question, though. 213.122.53.30 (talk) 18:13, 27 July 2009 (UTC)

Come to think of it, the lack of a horizon in puffin photos might be part of the problem. An image search produces lots of photos with blurry backgrounds, and any hint of a horizon is irregular and bumpy because that's the sort of place where puffins live. 213.122.53.30 (talk) 18:24, 27 July 2009 (UTC)

Name of tree?

What is the name of this tree? [10] I found lots of these [11] on the ground near it, what part of the tree was it? This tree is found in Auckland, New Zealand. thanks F (talk) 09:18, 26 July 2009 (UTC)

Liquidambar orientalis or Liquidambar styraciflua--Digrpat (talk) 13:21, 26 July 2009 (UTC)

thats a plane tree or plain tree (i dont know the spelling) but theres heaps of them in cambridge (new zealand)

Black Box

What are the components of a black box in the aeroplane??How is that it suffers very little damage and hence recovered fair enough???Also any idea of what kind of metal it is made up of??? —Preceding unsigned comment added by Gd iitm (talk • contribs) 14:46, 26 July 2009 (UTC)

Flight data recorders are located in the tail, so that the entire front of the aircraft will act as a “crush zone” that will reduce the shock that reaches the FDR. Modern FDRs are typically double wrapped in strong corrosion-resistant stainless steel or titanium. Red Act (talk) 14:59, 26 July 2009 (UTC)

IMHO, I don't think anyone other than Amelia Earhart ever referred to a Flight data recorder as an "FDR". (She was a big supporter of his, so that would explain it.)  ;-) 98.234.126.251 (talk) 23:28, 26 July 2009 (UTC)

They are also (typically) bright orange spheres - the name "black box" is singularly inappropriate! The sphere is a stronger shape than a box - and orange is a more visible color than black in a burned out wreckage! Actually, these devices are quite often damaged in a crash - but they are designed in such a way that the recording can still be recovered even when the damage is pretty serious. SteveBaker (talk) 22:08, 26 July 2009 (UTC)

Commercial airliners normally carry a flight data recorder in the tail and a cockpit voice recorder near the front. These units are orange painted rectangular boxes, similar in format to other modular equipment that is made for easy replacement. SteveBaker's notion of spherical units seems far fetched, but no more so than this movie dialogue:

King Marchand: Stick around, I might want to play some golf.

'Squash' Bernstein: Boss, it's snowing outside!

King Marchand: We'll use red balls. Victor Victoria (1982) Cuddlyable3 (talk) 22:43, 26 July 2009 (UTC)

You can find a picture of a data recorder and a voice recorder here: NTSB.gov. — QuantumEleven 08:57, 27 July 2009 (UTC)

They are called "black boxes" because they are sealed off from the outside world, so are a Black box in a computing/electronics sense, not by colour. The article includes several photos of aircraft ones of various ages. -KoolerStill (talk) 16:22, 27 July 2009 (UTC)

Black boxes was a generic name for all aircraft Line-replaceable units which were all painted black. It is just that the voice recorder and data recorder became better known to the general public as (one of the) black boxes although they were not painted black like the rest. MilborneOne (talk) 16:41, 27 July 2009 (UTC)

Relative velocity

Suppose imagine that you are driving the car down a beautiful country side.The trees nearby i.e.on the the either side of the road appear to go pretty fast while the mountains atleast a mile away from the road appear to pass by pretty slow.It is a common observation.But relative velocity doesnt talk about distance anywhere.In common high school problems of calculating the relative velocity, it just says "put the negative of your velocity on the object of observation and you get the velocity at which the object(can be tree or mountain) APPEARS to pass." But the following technique doesnt work in my case why?? —Preceding unsigned comment added by 117.193.128.83 (talk) 16:39, 26 July 2009 (UTC)

You are describing parallax. What you observe isn't actually the trees or mountains moving, it's the angle to them changing. The angle is a function of both speed and distance. --Tango (talk) 16:44, 26 July 2009 (UTC)

Think in terms of angular speed, which is what the eye perceives. --Bowlhover (talk) 18:11, 26 July 2009 (UTC)

See also visual perspective. As you well know, this pencil has a constant diameter; but looking at it, it appears to get smaller in the distance. This is the same effect which makes the apparent motion speed seem slower for the distant mountains. Nimur (talk) 19:00, 26 July 2009 (UTC)

More specifically - the effect of perspective is that the apparent size of an object is proportional to one over the distance. What this means is that when you halve the distance between you and some distant object, the size doubles. When a tree is (say) 100 meters away, you only have to drive 50 meters to make it appear to double in size. When it's 50 meters away, you only have to drive 25 meters for it to double in size - so that nearby tree seems to grow FAST! However, if you're looking at a house that's 10km away - you have to drive 5km for it to double in size - which means that it takes a couple of minutes to double in size. For a mountain that's 50km away - it could take you 15 minutes to drive the 25km it takes to make it double in size. SteveBaker (talk) 22:03, 26 July 2009 (UTC)

I think I havent worded my question properly.I didnt mean to ask about the size of the object growing.I am sticking to the concept of relative velocity alone.I meant you are driving and to the left or right of the car ,the trees etc APPEAR( this has a unique meaning) to pass by and I DIDNT ask about approaching a tree and hence its size growing. (APPEARS in caps because...consider this---u are in space and u observe some stone approaching you.But there u dont really know whether you are approacing the stone or the stone is approaching you or both approaching each other.This is because you have no references at all in space unlike earth where you have the sky,winds etc as references) so just by going by relative velocity,I still havent got a satisfactory answer.I seriously doubt if it is connected to angular velocity.Nimur your answer does give me a vague idea but I am not very clear about your answer. 203.199.213.67 (talk) 04:30, 27 July 2009 (UTC)

Also the visual perspective website tells only about the smaller size of the distant objective but nothing about the relative velocity as asked by the person above.203.199.213.67 (talk) 04:33, 27 July 2009 (UTC)

Lets get one concept straight. Say you look sideways at a far off mountain while driving a car forward at 40Km/hr, the mountain does indeed go backwards at 40Km/hr, with respect to us. There's no doubt about that. But it appears to go much slower than that because of its distance. Your car window has a certain size, lets call it say one meter. Lets say your eye can see through the window, but only within certain angles - you can't look at something right behind you or right in front of you using this window, as you're not turning your head around. Lets say you can see only around 30° to either side of the center of your window. Now, the whole thing becomes much simpler and easier to understand. Say you spot a tree some 10m away. Now, complete the triangle of your line of sights on either side using the 10m as the altitude of your triangle. Using trigonometry, you can figure out the length of the base of the triangle, which is the distance for which the tree will be visible. This turns out to be 5sqrt(3) meters. So if you're going forward at 40Km/hr, the tree whizzes past in 0.78 seconds. But if the tree is replaced by a mountain 10Km away, the same base of the triangle, which is nothing but the distance for which you see the mountain, turns out to be a thousand times greater, which means it will take 778 seconds, or over 10 minutes to go past. So you see, as the others explained, its nothing but perspective, it looks as if it is going much slower, as we realize the change only in angle, not in distance. I hope I was clear enough to understand. Rkr1991 ^{(Wanna chat?)} 05:47, 27 July 2009 (UTC)

Suppose that while you're in your car, a nearby house and a distant mountain both take up 20 degrees of your field of view. Your car moves 20 m and you completely passes the house, but 20 m is nothing compared to the mountain, so the mountain seems to have barely moved.

The phenomenon you describe has everything to do with angular velocity. After all, the eye has no way of measuring actual velocity, so perceived speed corresponds to how quickly an object crosses your field of view (measured in degrees). If it zips by like nearby objects do, you think it's fast; if it takes ages to cross your field like a faraway house, you'd think it's slow. You might ask why evolution didn't wire the brain so that it can calculate actual speed from angular speed, but that's a question I'll have to leave for another ref desker. --Bowlhover (talk) 06:04, 27 July 2009 (UTC)

Because it can't be wired in! There's a shortage of input information, if the target is very far away. Even with stereo vision (two eyes), our depth estimation is still pretty poor (especially at far distances where the parallax of our eyes is negligible). To convert apparent angular motion into actual velocity, you also need a depth estimate. At close range (2 or 5 meters), we're pretty good at doing that. At long ranges (hundreds of meters and beyond), we're not getting actual depth information from our stereo vision (the parallax is beyond the range of our perception); we have to use other contextual clues to estimate depth, but these are unsuitably inaccurate. Nimur (talk) 15:37, 27 July 2009 (UTC)

My previous answer is still correct - but perhaps some more explanation is required. Our ability to perceive distance directly is by one of two mechanisms:

• by using the amount of distortion in the lens of the eye required to get a sharp focus.
• by using the amount by which our two eyes have to point inwards in order to form a single image. :The problem is that neither of those two techniques are sensitive enough to work beyond maybe 20 to 40 feet. Beyond that, we have to rely on the rate at which things change size as we move towards them (or they towards us). For very distant objects, (as I explained before) the size doesn't change rapidly enough for us to really notice that gradual increase - so it looks like far distant objects aren't moving at all...and we really can't tell how far away they are. For closer objects, the rate of size growth increases dramatically and it gets easier and easier to figure out how far away they are and how fast they are moving towards us (or us towards them). It really is all a matter of how the laws of perspective work. SteveBaker (talk) 18:24, 27 July 2009 (UTC)

If the nearby trees and the mountains a mile a way were really passing by, and you were standing still, the mountains would appear to move more slowly than the trees, because they are a mile away. Therefore they do indeed appear to pass at a speed equivalent to the negative of your velocity, when you are moving. That's what it would look like. 213.122.53.30 (talk) 19:02, 27 July 2009 (UTC)

Heh, I seem to have said that the mountains would appear to be moving more slowly than the trees, and also that they would both appear to be moving at the same speed. Oops. Both those things are true, though! Evidently "appear" has a flexible meaning. 213.122.53.30 (talk) 19:06, 27 July 2009 (UTC)

They do move at the same speed, but they don't appear to do so. That was the question. Rkr1991 ^{(Wanna chat?)} 10:06, 28 July 2009 (UTC)

Heart transplant: nerve connections

How does a transplanted heart connects to the brain?--Quest09 (talk) 19:49, 26 July 2009 (UTC)

Nerves severed in the tranplantation do grow back after a few years. However the patient does suffer from having no autonomic control prior to nerve regrowth, one of this is the increase firing rate of the SA node, with hemodynamic problems, hypertension, and arrhythmia also prevalent in postop patients. Sjschen (talk) 20:08, 26 July 2009 (UTC)

That means that the person won't need an artificial pacemaker? Can the new heart start firing by itself, perhaps after a small electrical shock?--Quest09 (talk) 15:53, 27 July 2009 (UTC)

Assuming nerve and muscle connections within the heart are all intact, the heart will beat spontaneously without external nerve connections. See Cardiac cycle#Regulation of the cardiac cycle. We don't have an article about suspended heart (or at least not a redirect to a related article), but one can remove a heart (I think it's most commonly done with frogs?), place it in an appropriate medium, plumb some vessels to it, and study the beating (and chemical effects on it) in vitro. DMacks (talk) 22:19, 27 July 2009 (UTC)

Elevator logic control

This question has been dual-posted at the Computer Desk, here. I am consolidating the answers from Science Desk to the post over there to avoid confusion and redundancy... Nimur (talk) 23:20, 26 July 2009 (UTC)

July 27

Chesty Coughs

When you have a chesty cought does it make any difference whether you cough up or swallow phlegm? Sometimes i'm too lazy to cough it up and just swallow it, assuming it will go into my stomach anyway, but i just wondered whether this was true or not? perhaps somebody could tell me. thanks! 140.247.249.83 (talk) 05:41, 27 July 2009 (UTC)

First let me tell you what phlegm is made up of.Then it is up to you to decide whether to swallow it or not.The respiratory and nasal passages are lined by mucous membranes.These are bronchial mucosa and nasal mucosa.They have epithelial tissue that secrete mucous.The main function of mucous is to trap the germs and bacteria that enter the respiratory passages.(another function is to keep the passages moist).So during fever there is surge in number of germs and hence the mucous production in the respiratory passages increase...the result of which you get chesty coughs.The components of phlegm are mucous,dead germs,proteins,lipids,immunoglobulins and many other inorganic ions that form the minor part of it.So best not to swallow it..because it may contain some live germs.Also the idea of swallowing dead germs may make you feel disgusted.So best eliminate it out of the body.Gd iitm (talk) 06:16, 27 July 2009 (UTC)

If you do, make sure you do it in a fashion that is not likely to infect other people, i.e. spit it into a tissue and dispose properly of the tissue. Don't just gob it on to the floor. This was illegal in some places!--TammyMoet (talk) 09:37, 27 July 2009 (UTC)

Whatever live germs you cough up will very likely be killed by your stomach acid. It's almost certainly harmless to swallow the phlegm. --Stephan Schulz (talk) 12:34, 27 July 2009 (UTC)

Gd iitm, that's a joke, right? Whatever live bacteria happen to be in your phlegm are going to be digested when you swallow them. Tempshill (talk) 15:53, 27 July 2009 (UTC)

nit: mucous is the adjective, mucus the noun. —Tamfang (talk) 22:38, 2 August 2009 (UTC)

99 % of bacteria get digested by HCl in the stomach.But doesnt the thought of swallowing 99% dead bacteria and 1% alive make u feel disgusted?? —Preceding unsigned comment added by 117.193.140.74 (talk) 05:48, 28 July 2009 (UTC)

I remember George Carlin once using a factoid in his routine that swallowing saliva is linked to cancer. I have to assume he didn't just invent this factoid, and that there was a real research paper on the subject. Also, traditional Chinese wisdom advises a person to spit rather than swallow. If you're too lethargic to get up and spit, perhaps improvise a spittoon. I used to do this. Expect people to complain. It's your life and your body though so don't worry too much, just be as discreet as humanely possible. Vranak (talk) 16:01, 27 July 2009 (UTC)

That's totally ridiculous! Saliva is crucial part of the digestive system - aside from lubricating the food, it contains an important enzyme that breaks down starch into sugars. (Try chewing a piece of dry, non-sweetened bread for longer than you really need to - and you can taste how it gradually becomes sweeter as the saliva turns the starches into sugar). Not swallowing the saliva is therefore impossible! SteveBaker (talk) 18:12, 27 July 2009 (UTC)

George Carlin was a comedian. He said a lot of very true things in his routine and, in a way, he's correct here too (or at least making the point) that living causes cancer. Vranak should have explicitly specified he was quoting a comedian, who was using the concept for rhetorical effect anyway. Matt Deres (talk) 19:04, 27 July 2009 (UTC)

Well regardless, I spit hundreds of times a day and I have never gotten sick since starting. Vranak (talk) 22:44, 27 July 2009 (UTC)

Now consider where the phlegm is going - into a handy bag full of hydrochloric acid. Best place for it. 213.122.53.30 (talk) 18:40, 27 July 2009 (UTC)

Indeed - put those (maybe) live bacteria outside your body and there is every chance that they'll get back in again through your nose and you'll have to fight them off all over again - or maybe they'll go on to infect someone else near and dear to you. Dumping the little buggers in vat of hot hydrochloric acid is a great solution to the problem! Heck, you'll even get some vitamins, protein and carbohydrates back from them - phlegm is practically a health food! (OK - I think I went too far!) SteveBaker (talk) 13:20, 28 July 2009 (UTC)

Yeah, I'd imagine most organisms don't end up possessing the ability to live in your stomach by accident. Germs tend to specialize—a cold virus won't find itself in your stomach and then just decide a vat of acid would be a good place to stay. So unless you happen to have cholera or something like that in your mucus for some reason, recycling might not be a bad idea. Alfonse Stompanato (talk) 21:17, 28 July 2009 (UTC)

I'm actually inclined to believe the opposite that spitting it is "better for you": http://www.davesdaily.com/bizarrenews/pickyournose_04-04.htm . Vespine (talk) 06:05, 30 July 2009 (UTC)

Common mistake

People make the common mistake of saying that their "weight" is xkg, rather it is the mass. I was reading the T-90 tank page and found that the weight is stated as 46.5 tonnes. Shouldn't it be mass? Thank you.--116.71.54.57 (talk) 07:17, 27 July 2009 (UTC)

Call me a descriptive linguist, but it seems unfair to call it a mistake when, in common usage, weight means mass. In engineering usage though, you're probably correct. AlmostReadytoFly (talk) 08:09, 27 July 2009 (UTC)

No it shouldn't be 'mass'. As AlmostReadyToFly notes - the term Weight (like a shockingly large number of terms in English) has more than one appropriate meaning (http://www.answers.com/weight) - it even referencs this in the opening section of the article. 194.221.133.226 (talk) 10:01, 27 July 2009 (UTC)

Weight means lots of things as the list on answers.com demonstrates but none of them is mass, which is the correct category for an object without a specified location. The weight of an object varies by several percent moving from pole to equator and the fact that it is locally equivalent to mass does not in my view suddenly make the error correct. --BozMo talk 10:59, 27 July 2009 (UTC)

Citation for the several percent? Aaadddaaammm (talk) 11:09, 27 July 2009 (UTC)

It's actually about half a percent. See Earth's gravity. Algebraist 11:25, 27 July 2009 (UTC)

Ok, half a percent at sea level and a bit more to the top of Kilimanjaro (the article isn't quite right but pretty close AFAICT). That's why the earth is oblate. --BozMo talk 12:43, 27 July 2009 (UTC)

Other way around: the strength of the gravitational field varies because the Earth is oblate. The Earth is oblate (primarily) because of its rotation. — Lomn 13:16, 27 July 2009 (UTC)

Nah. It is the rotation which makes the net weight less on the equator which makes things bulge. --BozMo talk 13:30, 27 July 2009 (UTC)

You are both kind of right. The rotation causes the bulge in the manner you describe, but gravity on the bulge is less because you are further away from the centre of the Earth (there is also a contribution from the rotation itself). --Tango (talk) 13:49, 27 July 2009 (UTC)

Weight isn't an 'incorrect' term - it has a perfectly simple, clear, valid meaning in physics and elsewhere - the only important things to understand is that (a) weight and mass are not the same thing - and (b) an object's weight will change depending on where you put it. Talking about the weight of a tank - which is pretty much only going to be trundling around on the surface of the earth - and highly unlikely to ever be driving around on the moon - is not at all unreasonable. Certainly there are small variations in the weights of objects depending on whether they are at the poles or the equator - parked on top of a mountain or near a magnetic anomaly caused by some particular flook of geology...but those differences are likely to be negligable compared to things like the amount of fuel and ammo the thing is carrying. So we should not be overly anal about our descriptions of things like that. Worse still, from an encyclopedic point of view, we are unlikely to be told either the mass of the tank or it's weight in Newtons. Since we're required to have references to back up what we write - it may actually be necessary to state the weight - and to give it in kilogrammes (with the implication that it's kilogrammes-force that we're really talking about). Most of our readers would have no clue what a Newton is anyway! There is utility in being useful, clear and understandable - and talking about the weight of a tank in kilo's is just fine. SteveBaker (talk) 18:06, 27 July 2009 (UTC)

Not to mention that almost no one knows their "mass". Scales, by definition of the way they work, measure weight, not mass. Besides, us stupid Americans still use pounds (scientists aside), which can describe both weight and mass.-RunningOnBrains^(talk) 18:31, 27 July 2009 (UTC)

The problem with allowing definition to become common usage and be divided by the lowest common denominator (warning: mathmo alert: things do not fall to their lowest common denominator in maths as the LCD of a list of numbers is larger than any of the numbers, they fall to their highest common factor or become divided by their lowest common denominator) is that education becomes nigh impossible. We make a lot of effort with kids when they are aged about 12 to understand the different between mass and force, speed and velocity etc just as we are careful in teaching kinds the difference between strength toughness etc. So commonplace poor usage should not be "just fine". --BozMo talk 18:38, 27 July 2009 (UTC)

If you consider "weight" to be short for "weight on earth", can you accept it as an accurate description of a quality of a tank? Words in context carry all kinds of subtextual meanings. Between the lines of the blankly-stated statistics of the tank we can read the assumption that people only very rarely care what it weighs on other planets. This may be a good thing. 81.131.54.159 (talk) 19:24, 27 July 2009 (UTC)

Accurate, just about. Optimal in terms of opportunity to be more educational, no. --BozMo talk 20:18, 27 July 2009 (UTC)

Like I say, missing an opportunity to educate readers into being engineers and physicists may be a good thing. The world also needs other kinds of people. 81.131.54.159 (talk) 20:25, 27 July 2009 (UTC)

That statement is so absurd, I don't know where to start. You're saying that we should take people who otherwise would be scientists and engineers and...not educate them? What "other kinds of people" did you have in mind? -RunningOnBrains^(talk) 20:34, 27 July 2009 (UTC)

Golfers, taxidermists, and so on, you know. People who quite rightly don't want to distinguish mass from weight. Maybe even some scientists, like botanists. It's desirable that they don't waste their attention on such matters, unless interested. I'm not sure why those people would be looking at the T-90 tank article, but it takes all kinds, is what I'm saying. 81.131.54.159 (talk) 20:52, 27 July 2009 (UTC)

It's also desirable that they don't get frustrated or irritated and go read Britannica. APL (talk) 00:50, 28 July 2009 (UTC)

Not everything has to be an opportunity for education. Stating the weight of a tank in Newtons will have precisely one consequence: Not one single person who actually wants to know the answer will actually understand it - and not one of them would bother to look up "Newton" to find out. Nobody wants to know the mass of the tank either...for any concievable practical purpose, the weight is the thing you need to know.

Just as scientists have to know not to use more precision in stating a result than is actually appropriate - just as we know that it's pointless to talk about having to go out and cut the Chloridoideae (when we are really going to mow the lawn) - we have to understand that there are times when a more approximate take on things like this is actually more appropriate than strictly adhering to the underlying physics. Nobody (and I mean NOBODY) gives a damn what the tank would hypothetically weigh on the moon. Nobody cares that the weight might be 'off' by a few percent because we weighed it at the equator rather than in the tropics. Our bathroom scales measure in pounds and kilos - every measurement of weight throughout all of society EXCEPT a very few physicists and other science nerds is in pounds or kilos. So what? So long as the people who need to know are aware that this "mistake" is made everywhere - we're OK. How many members of the public would understand if you said that you accelerate your car by putting your foot on the brake pedal? How many could tell you why 'velocity' is not the same thing as 'speed'? There is a place for rigor and a place for getting the message across in a comprehensible manner...and this falls firmly into the latter category.

Sure, we have a responsibility to educate people - but pissing them off by making these tiny pedantic statements does precisely the opposite - it completely alienates them. We need to teach them the scientific method - that homeopathic medicines are just water - that evolution is real - that the greenhouse effect is killing our planet - that you can't buy a herbal capsule that'll make "certain parts of your body" larger. Pick your battles - mass versus weight isn't one of them! SteveBaker (talk) 01:00, 28 July 2009 (UTC)

<deindent>
I'll second Steve's point that we should aim to teach the scientific method instead of fixating on scientific terminology. In fact, I would go further and say that a skill even more basic and indispensable that the scientific method is to learn to read and interpret statements in context, rather than try to parse them like automata. Fortunately, we humans are quite good at that! For engineers collaborating on a project, it is critical to get their units right; however, if a lay reader is actually confused by the statement that "tank x weighs y kgs", they have missed out on a basic cognitive and linguistic skill.
If one is talking to an elementary school kid about the T-90 talk, it is much better to tell her that the tank weighs as much as 700 grown men, than to talk about 46.5 tonnes or (worse) 460kN. On the other hand, if I am driving the tank across a bridge, I better know its weight (including that of the men, fuel and arms onboard) and the bridge's load-bearing capacity (along with the applicable margins). In short: context matters, and understanding that is more important that false precision and pedantry. Abecedare (talk) 01:48, 28 July 2009 (UTC)

I agree with the point of view expressed above by Steve and Abecedare. Context does matter. I am a physics teacher but I have no problem with the statement that a tank weighs 46.5 tonnes. I also have no problem with telling my kids to close the fridge to keep the cold from coming out. Some of my colleges pedantically state that the cold does not come out, and that we I should say that the heat is going in. I also have no problem with stating that the station is stationary while the train is moving, eventhough I know that movement is relative. Dauto (talk) 04:44, 28 July 2009 (UTC)

We obviously don't share a common perception of the kind of person who comes to Wikipedia for info on how much a tank weighs or what its mass is. If someone is relying on that to build a bridge they haven't read the disclaimer. The fact your scales aren't in Stone though is a give-away that you live in the land of loose language usage so the consistency I see. --BozMo talk 13:22, 28 July 2009 (UTC)

Is there some honest confusion that you are legitimately worried might occur? I am having a hard time imagining a scenario where a person, curious about the weight and/or mass of a tank would be confused by the articles as they stand.

I can see how this current system might confuse martians, but that works in our favor. It will lead them to believe that our Earth militaries are three times more powerful than they really are. p.s. This is the Reference Desk, changes to wikipedia policy go in the wp:Village Pump. APL (talk) 18:35, 28 July 2009 (UTC)

But the tank page says Weight: xkg. Any guy with a little knowledge of physics will tell you the problem is that weight and Kg are not same. It should be either Newtons, which would not help the average reader, or mass. I dont see where the problem is.--116.71.34.182 (talk) 16:47, 28 July 2009 (UTC)

The real issue here is that reliable sources and tank experts conventionally describe tanks in terms of their weight, not their mass. There appears to be no standardization to account for variation in weight in different locations, and consequently we have no access to the actual mass data for these tanks. Hence the question of which to describe is moot, because only the weight is known. Dcoetzee 19:48, 28 July 2009 (UTC)

There is no problem. We are only pointing out that the word weight can be used as a synonim for mass in coloquial language just as the words 'work' and 'field' have different coloquial meanings than the ones used by physicists. That's why context matters. There is no possibility of confusion since the units make clear wheather one is talking about mass or force. Dauto (talk) 20:08, 28 July 2009 (UTC)

But wouldnt a kid, assuming he is reading the page, be misguided and hence confused between what he learned in class and read here on wikipedia. I was just saying that here on wikipedia, with genius guys like Steve Baker, Runningonbrains (list goes on forever), such a mistake would be like 2+2=5.--116.71.34.182 (talk) 20:07, 28 July 2009 (UTC)

Kids also can learn that words have different meaning depending on the context. Dauto (talk) 20:11, 28 July 2009 (UTC)

Exactly. Training kids to be deliberately confused when someone tells them a weight in kilos is POINTLESS. By all means tell them that in formal scientific writing you have to be really careful not to make this faux pas - but that in normal usage, telling someone the mass or specifying the weight in Newtons is just as bad. If that's the hardest lesson a kid ever has to learn in science class, (s)he's doing pretty good! Words are just words - we can make them do whatever is convenient. Having that underlying understanding is important - but having a tolerance for the daily screwups of well meaning non-scientists is just as vital. SteveBaker (talk) 21:55, 28 July 2009 (UTC)

Knee surgery procedure

Hi,

I'm looking for the name of a operation. In it, the part of the femur where the patella ligament attaches is cut off, and moved to the side or down. I think it starts with an L, and I'm thinking something like "Lithuan". Any ideas? Aaadddaaammm (talk) 11:08, 27 July 2009 (UTC)

Lateral Release [12] Livewireo (talk) 15:29, 27 July 2009 (UTC)

Thanks for the reply, but that's not it. The ligament going down from the patella attaches to the tibia/femur (not sure which) at a certain point. In this operation, the bone is cut, and moved with the ligament still attached. —Preceding unsigned comment added by Aaadddaaammm (talk • contribs) 16:03, 27 July 2009 (UTC)

The only other thing I can think of would be patellar luxation which is pretty common in dogs (and people with ACL damage). It doesnt describe the procedure, but rather the diagnosis. Most knee surgeries can be performed with an arthroscopy without having to perform an open surgery. Livewireo (talk) 20:57, 27 July 2009 (UTC)

Not with an L but it sounds as though you're looking for Osteotomy or more precisely one subform of that. 71.236.26.74 (talk) 01:53, 28 July 2009 (UTC)

Automotive suspension

What are the necessary equations or formulas used for designing the automotive suspension and also to know its load carrying capacity? —Preceding unsigned comment added by 41.220.75.15 (talk) 13:37, 27 July 2009 (UTC)

Wikipedia has many articles about automobile suspension. An independent suspension for one wheel is a Dashpot that comprises a compression spring that can be treated by Hooke's law and a Shock absorber. Cuddlyable3 (talk) 15:16, 27 July 2009 (UTC)

Carrying capacity is generally estimated from materials strength. Because a suspension often has a complex geometry, simple equations are not very helpful, so Computer Aided Design and finite element analysis are used to compute the stresses. Nimur (talk) 15:28, 27 July 2009 (UTC)

The problem with Hooke's law is that it's only an approximation - and also there are many other constraints - the ability to set toe-in and camber angles for example. If there are formulae out there - they aren't simple! It would help us to know what exactly you're trying to do. Calculating the load carrying capacity for a particular vehicle is tricky - it's rarely possible to find out the spring stiffnesses and shock absorber parameters for any particular car. If you're trying to design a suspension to carry a particular load, then that's another matter - but you have lots of other constraints to consider. We need more information about what you're attempting to do. SteveBaker (talk) 17:51, 27 July 2009 (UTC)

Powering a guitar amplifier outside (in DRY conditions, of course)

Hey guys, little bit of a dillema for those good with technology to help me sort out.

Me and my friend are keen musicians, and when we're writing we often head out to a field somewhere (in bright, sunny weather, might I add, so the following need not be waterproof) to play. Usually this just consists of us heading out with our acoustic guitars and a pen and paper, so there's not much need for anything to power us. However, I'm now starting to considering taking a really small amplifier out with us so I can play a bit of electric guitar along with his acoustic. Something like this should do the trick nicely. It's advertised as a 15-watt amplifier, but the speaker is at least 20W so I presume I need something that can power 20W for a few hours.

Now here's the catch. I know I can just buy a simple petrol or diesel generator to power this and anything else I might need with it, but I don't fancy having to keep topping up with petrol everytime I want to out, even though it is only a semi-regular occurance. I was thinking that a solution might be using a solar power supply/generator. My problem is I'm having issues finding anything that would sufficiently power this amp for at least 2-3 hours. Does anyone have any ideas, or alternate solutions, to this issue?

Thanks in advance!

Regards, --—Cyclonenim | Chat  16:37, 27 July 2009 (UTC)

Your best bet is to get a battery-powered travel amplifier. Some of these operate on reasonable batteries (I think my Vox practice amp (one of these) can be powered off 8 D cells six C batteries, though I don't ever really bother). Solar power is going to be a lot of trouble (panels are fragile, heavy, and unreliable). The Vox DAs are not tubes, but I challenge you to tell the difference on a double-blind test! Nimur (talk) 16:45, 27 July 2009 (UTC)

Also, a note about power ratings - there is "power rating" and there is "actual power consumption." These two numbers are not necessarily at all correlated, thanks to the magic of marketing B.S. - and electrical power may have absolutely no meaningful bearing on acoustic power out. Your 15 watt amp has a 20-watt rated speaker, but that means that drawing more than 20 watts will damage it. The actual power consumption depends on a lot of things - steady-state current flow, and also the dynamic power (which will depend on how loudly you play). On some amps, static power draw is so high that there's no penalty to "battery life" if you crank the volume. On other amps, keeping the volume low will dramatically increase your play-time. The Voxes have a power level switch to hard-limit power to various wattages (at very slight expense to tone quality). Nimur (talk) 16:50, 27 July 2009 (UTC)

Heh, I can't believe I'd completely forgot about the possibility of using batteries. This should more than meet my needs. Thanks :) Regards, --—Cyclonenim | Chat  17:05, 27 July 2009 (UTC)

If you seriously want to use a proper power amp - get a car battery and a 12 volt 'inverter' (you can pick them up in most car accessory places). That will give you a regular 110volt power outlet that you can just plug your amp into. How long the battery will last depends on how much power the amp draws - but I think you should be OK for at least a couple of hours. Then you can recharge the battery with a regular car charger. SteveBaker (talk) 17:31, 27 July 2009 (UTC)

I am curious to hear how acoustic plus electric guitars plus a petrol or diesel generator would harmonise. The advertised 15W amplifier appears to be a single-tube Class A design that must consume continuously over 30W plus tube heater. The claim that the speaker can handle 20W says nothing about the amplifier power consumption, but is nice to know. As the OP realizes, a transistor amplifier/speaker combo running from batteries is a better choice for outdoor use. Most economical transister audio amplifiers are Class B designs that consume much less power that Class A. There are a couple of cautions:

• If you like to crank up the volume then valve amplifiers are almost indestructable while transistor amplifiers may be unforgivingly vulnerable and die expensively in a millisecond.
• SteveBaker dazzles us with the wonders of automotive technology but if you plan to run a 12VDC-->110VAC inverter from your own car battery then at the 110VAC output you can draw less than 0.9x 9% of the amp-hour capacity of the battery (and the real amp-hour capacity decreases from the day the battery was put in the car) and then your car won't start. Cuddlyable3 (talk) 22:42, 27 July 2009 (UTC)

According to (for example) [13], a typical car battery will produce 45 amp/hours...which means you can pull maybe 40 amps out of it safely - and if you do, it'll run down in an hour or so...but there is no way your guitar amplifier pulls 40 amps! Picking a guitar amp more or less at random: [14] says that a 2x30Watt Roland amplifier pulls 68 Watts at 110v (yes, I know - it's easy to get confused between audio watts and electrical watts - but these are honest-to-goodness 110volt electrical watts)...that's like one lightbulb... Watts=Volts x Amps - so you'll need about a half an amp of electricity if you have the amplifier turned up full. The inverter isn't anything like 100% efficient - so let's assume you need an entire amp to run your amp! That means you'll be able to play for several days before you have to recharge the car battery...and perhaps we'll quietly ignore Cuddlyable and you could forgo lugging a car battery around and just plugging the inverter into the aux outlet on your car. The aux outlet on my car has a fuse on it that'll blow if you try to pull more than about 2 amps - so if the fuse doesn't blow - the theory says that you're good for maybe 10 hours of hard outdoor rocking before the car won't start! However, your battery might be a crappy one that's about to fail anyway - so I'd want to start the car and run the engine for 10 minutes every few hours just to keep the battery topped up. SteveBaker (talk) 00:36, 28 July 2009 (UTC)

I've got a car, but I'll be honest I'm no good with them mechanically. Does running the engine actually recharge the battery, or does it just kind of keep it level? If it recharges it, I'm more than happy to use this idea of just using my car's battery to power the amp. Do inverters plug straight into the cigarette lighter? If so, I already have one which I can plug mains stuff into. Regards, --—Cyclonenim | Chat  13:19, 28 July 2009 (UTC)

A decent car alternator puts out 200 amps when the car engine is running at between 2000 and 3000 rpm. The battery holds around 45 amp-hours - so expect an utterly dead battery to recharge in about 15 minutes if the engine is revving. However, you're not going to get the battery that dead are you? (If you did, the car wouldn't start). So after a few hours of guitar playing, it's probably going to recharge in 10 minutes at idle - maybe 5 minutes at 2000 to 3000 RPM. The wheels don't have to be moving to recharge the battery - you can leave the car in neutral or park with the engine running and a brick on the gas pedal and that'll work just great. Don't rev the car much above ~3000 rpm because it'll probably overheat if it's not moving (if you do - keep an eye on the temperature gauge!). Some inverters plug into the 12v cigarette lighter socket - but those are somewhat limited on the amount of 110volt current they can produce because it'll blow the fuse in the car. The wires running to the cigarette lighter are usually rather flimsey and not meant to carry a lot of current. Not knowing what capacity of fuse your car has - I can't say whether that'll happen with the guitar amp or not...but my guess is not. The inverter I have can connect via the cigarette lighter outlet and produce 50 watts - which is a bit marginal for a large guitar amp - but more than enough for a practice amp. But my inverter also has another cable you can plug into the back that has heavy-duty cables and two big crocodile clips (just like the ones you find on jumper/booster cables). You can clip those directly onto the car battery (Red to '+', Black to '-'!) - thereby bypassing the fuses in the car and using the nice chunky wires. In that mode, it'll easily produce enough power to run a TV, my laptop and a table lamp for an hour or two when the power drops out during a storm. I have a couple of old truck batteries lying around at home that I keep charged for just that eventuality - truck batteries hold more amp-hours than car batteries. If you can find a cheap marine battery - you could do even better - but your needs are SMALL. SteveBaker (talk) 21:47, 28 July 2009 (UTC)

Just to clarify, if your amp actually draws 68 watts, then assuming a 12-volt battery your inverter-amp combo is going to draw almost 6 amps per hour (assuming the inverter is 100% efficienct), so you'll pull 40 amp-hours out of the battery in about 7 hours. (If I read Steve right, he seems to be assuming a 110-volt car battery.) 4.255.43.12 (talk) 02:01, 29 July 2009 (UTC)

What percentage of its charge does a battery recover during 10 minutes running time in a German retro copy of an undersized British box on wheels ? Cuddlyable3 (talk) 13:30, 28 July 2009 (UTC)

My experience is that you need to either rev the engine or actually drive the car at speed to get actual recharging. A ten minute tour will charge up the battery. Ten minutes idle won't do much. But I haven't done the car party thing much since the later engine management systems have come around. Cuddlyable, are you being mean? Didn't SB get his Mini miniaturized on the highway a few months ago? Or has he got a new one? Franamax (talk) 14:28, 28 July 2009 (UTC)

My wife and I now have two shiney red MINIs ("Captain Scarlet" and "Poppy" - one paid for by the insurance company in exchange for the cold, dead corpse of poor "Chubb-Chubb") - both 2009 models - and I have a rather fetching British Racing Green 1963 Mini called "Toad" (or, more often, "Towed").

But back to the question. Yes, the battery will recharge at idle - although it'll take longer than if the engine is revving a bit higher. However, it's totally unrelated to the wheels rotating - so you can put the car in neutral and place a brick onto the gas pedal and it'll charge the battery faster than idling it...the higher the revs, the faster the battery will recharge. The precise amount of time it takes to recharge the battery depends on the car - some have bigger alternators than others - some have bigger batteries than others - some use more current because they have computers and electronic dashboards and such. On my car, the battery would recharge faster by revving the engine when in neutral than if you drove it round the block a few times because the car has an electric power steering pump that consumes power whenever you turn the steering wheel. However, the battery will recharge pretty quickly in any eventuality...I would certainly just let it idle for 10 minutes every couple of hours. SteveBaker (talk) 21:12, 28 July 2009 (UTC)

How come it's supposed to be slightly difficult and time consuming to do then? Or is that only if the battery runs out entirely? Regards, --—Cyclonenim | Chat  22:46, 28 July 2009 (UTC)

I offer condolences on the loss of poor Chubb-Chubb, taken from you when his odometer was yet in its prime, in the certainty that he abides in the Great Wrecking Yard from which at the last toot-toot all good Minis shall be recycled. Amen. The OP wants to play music and not have to mess with fuel. If SteveBaker gets his way the OP will have to stop playing every few hours and rev up his car for a very uncertain time. I don't see any calculation of how long and how often that has to be. No one has mentioned the limitation of having to be joined by a cable to a car when one wants to play in a field somewhere. I think I last saw the brick-on-accelerator trick in a B-movie about a faked suicide. When the music stops and the OP's car won't start, Steve should offer to send the 46-year old Toad a-fetching home from that field two musicians, an inverter and a 110V mains powered amplifier (none operational). I don't wish to sound mean but a lead-acid car battery has a bad power-to-weight ratio for this application. It is optimised to deliver a brief huge starting current, which is no use here. I understand the enthusiasm to exploit someone else's car as a generating station but it is no improvement on Nimur's fitting recommendation. That was to use a battery-powered amplifier. With the money saved by not repeatedly driving a car to go nowhere and not buying an inverter, cable, connectors etc., buy instead NiCd cells that are lightweight and chargeable anywhere. It's not difficult to work out how long playing time they give, and the OP can play that time to the full and still get home before it rains.Cuddlyable3 (talk) 13:39, 29 July 2009 (UTC)

A final point - car batteries are not designed to be "deep-cycled" - that is, allowed to repeatedly discharge most or all of their capacity. They are instead designed to produce a lot of current for short periods for when the car starts. That's why car batteries typically list their "charge cranking amps". Deep-cycling conventional batteries repeatedly will drastically shorten their life. If you want to do this, you can buy deep-cycle batteries; they're used for things like powering electric motors for bass fishing boats.

XTraordinary stuff !!!

Can things which are against the laws of science such as levitation, mind reading, controlling ones mind exist ??? Also does the much hyped spoon bending due to pshycic powers exist???There are just claims but has anyone really witnessed it???gdsrinivas 17:02, 27 July 2009 (UTC) —Preceding unsigned comment added by Gd iitm (talk • contribs)

Everything you've mentioned there can be classified under pseudoscience in the sense that some people proclaim it's all real and true, when really there's absolutely no evidence in favour, and often evidence against, their plausibility. There's nothing about science which says these things won't be possible in the future with the advancement of civilization, but I suspect it's quite a way off and by no means available at the moment. Regards, --—Cyclonenim | Chat  17:07, 27 July 2009 (UTC)

There’s a $1,000,000 prize available to the first person who can show that any paranormal phenomenon like that is real. Although the prize has been available for 13 years now, it has yet to be collected. So either not a single person who can do paranormal stuff like that is bothering to take the time to collect their $1,000,000 for some inexplicable reason, or paranormal stuff like that doesn’t really exist. Red Act (talk) 17:15, 27 July 2009 (UTC)

If they could be shown conclusively to exist - they wouldn't be outside the laws of science because scientists would be revising the laws to include them. The reason they lie outside of those laws is because they don't exist - and have been shown to be fraudulant. Uri Geller (of spoon-bending fame) was conclusively (and very publically) shown to be a total fraud by James Randi in that famous 1973 episode of the Tonight show...and on at least two subsequent occasions. These days, it is REALLY safe to say that all of this paranormal stuff is junk. Treat paranormalists as you would a stage magician - by all means be amused by their capers - but keep a careful and skeptical eye out for the trickery that you KNOW is going on somehow, someway. SteveBaker (talk) 17:27, 27 July 2009 (UTC)

Steve "If they could be shown conclusively to exist - they wouldn't be outside the laws of science because scientists would be revising the laws to include them" is semi profound. We cannot really talk about "against science", just consistency of the scientific world. Of course Science is incredibly consistent (statistically at least) whenever we measure it and even many (?most) religious people regard "miracles=signs" as demonstrations of a wider narrative theme but not to be scientific inconsistencies. There is a little wrinkle there somewhere though. Extremely deep in the scientific assumptions are some dogmas about observation/decision/understanding (one step up from cognito ergo sum) and these include assumptions about the existence of an observer not interfering with whether laws apply. These kinds of dogmas like the assumption we are not a brain in a vat are things scientists to a degree take on trust; although we are completely right to do so they cannot really be completely ironed out. --BozMo talk 17:54, 27 July 2009 (UTC)

While we're taking all the wind out of your sales, it's worth noting that the scientific world has presented bountiful alternatives if you want to know about bizarre, freakish, yet totally true phenomena. I think that mind-altering parasites are, for example, waaaay more "xtraordinary" than some guy who claims he can bend a spoon (even if he could do it with his mind, it's still just a spoon, whoop-dee-doo). --98.217.14.211 (talk) 17:51, 27 July 2009 (UTC)

Scientists have not had a great track record of gracefully accepting as "science" things running contrary to their beliefs. From the early 19th century to the present, establishment science has denied many things that had good evidence: that stones can fall from the sky, evolution, germs as a cause of disease, relativity, and various forms of speech by animals (Washoe the chimpanzee, Alex the parrot) The deniers often go to their graves not accepting scientific revolutions, as described in "The structure of scientific revolutions" by Kuhn. "Science" eventually accepts the new paradigm, even if many working scientists do not. The pseudoscience phenomena mentioned above lack the robustness of the earlier things rejected as pseudoscience, in that they are not reproducible in the labs of skeptics., and a simpler and adequate explanation of a bent spoon is that it was bent by human hands and conjurer's skills, rather than by mysterious psychic abilities. Edison (talk) 19:42, 27 July 2009 (UTC)

In other words: none of the paranormal things the OP refers to have been shown to actually happen beyond reasonable doubt, but this don't mean that they fundamentally cannot happen, or cannot conceivably be scientifically proven and explained at some point in the future. The search for the truth is an ongoing process. 98.234.126.251 (talk) 23:29, 27 July 2009 (UTC)

No - it's more than that - the things our OP refers to have never, not even once, been successfully demonstrated in any kind of rigorous experiment. That's emphatically NOT because scientists don't want to do that. The very existence of the James Randi $1,000,000 prize proves that. If you can do one of these miraculous things - go and show James Randi and he'll give you A MILLION DOLLARS! Why is it that not one single person has done that? The pseudo-science nut-jobs claim that science is denying their abilities - and that's true, and it'll continue to be true unless someone with real, honest-to-goodness magical abilities comes forward, is tested and ISN'T shown to be a charlatan. So far, of the hundreds of people who've tried, every single one of them has proven to be a charlatan when the bright light of scientific testing is shone on them. There is a deep misunderstanding of what scientists are like...we love nothing more than to have some important law or theory overturned - that's the most exciting thing we can imagine - that's the thing that would open up more fruitful areas of study than anything else. But we've tried all of this stuff - we had people with decks of playing cards with circles, squares, triangles and waves on them, we did statistical studies on telepathy and god knows what else right through the 1960's and 70's...and it's all bullshit. Worse even than that is that most laypersons are happy to say "Wow! This guy can bend spoons with his mind!"...and kinda leave it at that. The bigger question is "Where does the energy come from to bend the spoon?" - if it comes from the guy's mind - then how come we can't detect any magnetic field, gravitational or radio waves, no light, no cosmic rays...what could possibly be transmitting that energy? The only answer could be some entirely new force that we have no inkling of whatever. But what are the odds that just one person can produce these forces - that we can't measure in ANY other way than by large chunks of metal being bent? How come nobody through all of history has ever come across any effect that's even remotely like this? How did the guy who bends the spoons learn to do it? If this one, single paranormal thing were true - pretty much all of science would have to be rewritten. What are the odds that all of the things we've successfully designed and built actually works - despite this massive hole in our understanding? It really does seem impossible for anything that major to have escaped our careful searching for a couple of hundred years. So that's what's on one side of the 'scales of truth'. What's on the other side? Well, we have the word of one person who claims to be able to do this - minus all of the professional magicians who claim to be able to reproduce the exact same demonstration using techniques which they openly admit are pure trickery. It hardly balances does it?

By comparison, the other examples you gave were pretty minor.

• Not believing that rocks can fall out of the sky was an error - but when we finally figured out what it was, it hardly required us to change our ideas of how the universe worked at all. We already knew about comets - the idea that something like that could fall out of the sky wasn't really very profound. Not one existing law of nature had to be rewritten. Gravity, light, matter, energy, magnetism, mechanics, chemistry...all of those things were still 100% as they'd been described.
• Evolution filled a hole in our understanding - it didn't overturn ANY well respected existing scientific theory. It pissed off a whole load of religious people - but science simply didn't know how speciation came about - and this explanation filled a hole.
• Germs as a cause of disease - pretty much the same deal. We didn't really know how that stuff worked - this was a great explanation.
• Relativity - is actually the only one of your examples that is a REAL case where our current understanding was actually completely overturned...but it didn't come about because of an EFFECT that science was denying. We knew there was something odd about the nature of the speed of light and we'd been doing experiments for decades to try to understand why we couldn't detect a universal Luminiferous aether. When Einstein's explanation appeared, there was reasonable skepticism...but within months of the experiments that measured the displacement of stars during a solar eclipse, pretty much the entire scientific community changed direction and lined up behind the new theory.

SteveBaker (talk) 00:06, 28 July 2009 (UTC)

There are many cases where the leading lights of the scientific establishment (Lord Kelvin) proclaimed something was impossible a couple of years before someone demonstrated it, such as the "subdivision of the electric light," i.e. the invention of electric lights which culd furnish 16 candlepower or so to illuminate one room efficiently. There were doctors in the late 19th century who still practiced medicine, denying the "germ theory" of disease. Which scientists before evolution was written about acknowledged the "hole" that you say it filled? Wasn't heavier than air flight said to be impossible (Lord Kelvin)? The "leading scientists" denied radio waves and said it was "merely induction" when Preece and Thomas Edison ("etheric force") demonstrated wireless transmission of radio signals[15], until Hertz demonstrated the same phenomena with a mathematical basis in Maxwell's work. See [16] for some examples of the scientific establishment making asses of themselves. Edison (talk) 05:43, 28 July 2009 (UTC)

But almost all of your examples are not holes in fundamental scientific laws and theories - they are engineering matters. Sure, Kelvin believed that it was an impossible engineering problem to produce a 16 cd electric light - but I very much doubt he had basic theory proving that it was impossible. I very much doubt that we'll ever be able to send a living human to Alpha Centauri...but that doesn't mean that it's impossible. The laws of physics permit it - it's just an engineering problem that I don't believe we can overcome. Now, if I'm proven wrong, that's not great for my reputation - but it wouldn't in any way undermine the laws of physics. However, when I say that we'll never travel faster than the speed of light - that's a much more solid claim. We have laws of physics that guarantee that's true. In order to refute THAT claim, we'd have to rewrite huge swaths of solid physical laws and theories...it would be a major thing indeed if that were somehow to be found to be possible. Almost all major advances in science and technology are either exploiting well-known physical principles in a more extreme manner than previously expected (electric lights, heavier-than-air flight) - or they are filling in gaps in our scientific theories (evolution, radio waves, germ theory). Not one of the things you describe changed any pre-existing law or theory of nature...the number of times THAT has happened over the 150 to 200 years since we started following "the scientific method" you can count on the fingers of one hand...relativity is the only one I can think of right now...and that isn't something that affects 'normal' day to day life - it found an error in an existing law that only affects the most extreme condititions - it doesn't make any difference to how most simple day-to-day events are interpreted. To demonstrate relativity actually doing something requires some pretty extreme experimentation. In Einsteins' day - the only way to prove it was to measure the position of a star during a total solar eclipse! Levitation, mind reading, spoon-bending-with-the-force-of-thought are all things that would require us to rewrite fundamental laws/theories - in regions where they have been exceedingly well tested over 150 years. So the likelyhood that they are true is essentially zero. SteveBaker (talk) 13:11, 28 July 2009 (UTC)

When a scientist makes extraordinary claims, others often treat them with skepticism until irrefutable proof is presented. That attitude is perfectly fine, and doesn't mean every single theory that the scientific community doesn't believe in must be true. --Bowlhover (talk) 08:45, 28 July 2009 (UTC)

Agreed. "They said that about Einstein/Newton/Galileo too!" is a ridiculously common (perhaps *the* most common) pseudoscientist/crank rebuttal to sceptics. Doesn't make any sense whatsoever, if you think about it for a couple of minutes. Bonus points if they come out with something really fuckwitted, like "IT WAS BECAUSE OF PEOPLE LIKE THAT COPERNICUS WAS BURNED AT THE STAKE!" (and mean it). --Kurt Shaped Box (talk) 09:18, 28 July 2009 (UTC)

"...but they also laughed at Bozo the clown" is the standard retort. --Stephan Schulz (talk) 13:26, 28 July 2009 (UTC)

Edison, as a scientist my self I don't really give a crap what scientists "say". That is appealing to authority, as opposed to rational, free thinking which a scientist should be doing. Every scientist on the planet has an opinion on something, and that is fine as bias is hard-wired into us. As long as they don't show bias in their scientific method when conducting research, then I will respect their results. --Mark PEA (talk) 09:51, 28 July 2009 (UTC)

One way in which the scientific establishment mistakenly rejects new discoveries is by saying "Oh, this is just a rediscovery of such and such. Nothing new here." Pre-Hertz demonstrations of radio wave transmission and reception by Preece and Edison were dismissed as "mere induction." Radio might have been in general use several years earlier if the demonstrations had been accepted as a new phenomenon. Technicians and inventors often work years ahead of "scientists." If someone next month demonstrated some type of cold fusion, many would dismiss it without close analysis as a mere replication of the Pons-Fleischman experiment. Demonstrations of animal communication by Washoe (chimpanzee) and other chimps, or by Alex (parrot) are false dismissed as being a recreation of Clever Hans, the horse who just watched his master for cues, or as mere Operant conditioning. In the face of "irrefutable proof" scientists may redefine the terms. If science said that only humans use tools, and chimps are observed carrying around rocks to break open nuts, then rock use is defined out of being tool use, and it must be "make and use tools." If chimps are then seen fashioning sharpened sticks to spear bush babies in their hideyholes, the definition of tool use must be redefined again. Granted the "not invented here" attitude commonly applies to engineering devlopments or inventions. When Morse demonstrated he could instantly send telegraph messages between remote parts of the U.S. capitol building, politicians thought he was a madman, and said why not just send a messenger, instead of all that cumbersome apparatus, even though Morse had explained it was just as fast for extreme distances. When Chester Carlson demonstrated the Xerox it took many years to convince the business world that instant copying was useful to businesses. This was in 1948 ("They all laughed," by Ira Flatow, Harper Collins, 1992, chapter 11): "An interesting gadget, but no future." Tesla in 1898 demonstrated a radio steered torpedo, but no one could see the point of it, since they never had used one in a war. Another way in which mainstream science fails is by assuming something is impossible by analyzing it with the wrong model. The claims that electric lighting could not be "subdivided" were mathematically supported by leading physicists, but they assumed the light of 16 candlepower would be a grossly inefficient and impractical little bitty arc light, and did not allow for it being an incandescent light. We cannot send people to other star systems with rockets, so it is impossible. Physics says it would be easy if you could maintain a 1 G thrust the whole way, but we know of no present means of achieving that. A lab can also do an intentional nonreplication of some new phenomenon, to discredit the discoverer, and attribute the phenomenon to uncontrolled experimental confounds, thus delaying its general acceptance. Going way back to Newton writing that a prism could split sunlight into its spectral components, one of his competitors wrote that he could not replicate it, and that Newton probably just reflected the light off one face of the prism and the color was likely stained by dirt on the surface. The Edison effect, or one way flow of electricity from a filament to a charged plate, was denounced as just a stream of carbon particle breaking off the filament and carrying charge, delaying by years the "invention" of the vacuum tube diode and the advent of electronics. In the case of pooh-pooing by trivializing alternative explanations of a new discovery, the normal process of science should make things right over time, as others are able to replicate it or "reinvent" it, while carefully controlling the claimed confound. The cycle of "Discovery-alternative expl

Your examples are not scientific errors - they are errors of belief at the engineering level. Producing more and more of those example is very easy indeed - I could quote the guy who tried to solve the problems of determining one's latitude precisely in a sailing ship by killing a dog at exactly noon at the naval base and seeing when it's identical twin (which had been placed aboard ship) woke up and whined! But it doesn't help answer the OP's question in the slightest. Sure Tesla demonstrated a radio steered torpedo - but nobody previously said that science precluded that due to some fundamental law of nature. That the torpedo actually worked was a demonstration that Tesla had a better command of TECHNOLOGY than his detractors. But it didn't cause a single scientific law or theory to require modification in the slightest bit. If he'd found a way to power it with a perpetual motion machine - or control it via "thought waves" instead of radio - or make it travel faster than light...THEN he'd have produced a scientific breakthrough rather than a mere engineering marvel. That's not to detract from the cleverness Tesla provided - it's just that you're answering an entirely different question...one that I doubt anyone here is denying. Our OP is postulating things that - if true - would require a profound revisiting of most of what we think we know about how the universe works. A radio controlled torpedo is no more remarkable (in principle) than the next generation of iPhone...clever technology - but no new science whatever. SteveBaker (talk) 21:01, 28 July 2009 (UTC)

Mind reading, then is also just an engineering problem. Scientists already can determine an amazing variety of things about what someone is thinking by functional MRI. The denial of the possibility of subdivision of the electric light was not presented as an engineering statement but as a scientific one. I think you are making a false distinction between "science" and "engineering" (or technology). It would It should be a clearly disprovable assertion, or it is not science. The source should be a refereed scientific journal, a college level science textbook, or a distinguished scientist of the stature of Lord Kelvin, such as a Nobel laureate. I suspect that such listings are rare, because the writer would know he might be held up to ridicule if the stement were refuted. Examples might be like "Cold fusion is impossible," "Visits from or radio transmission from extraterrestrials are impossible." Would those be engineering or science statements? Edison (talk) 22:05, 28 July 2009 (UTC)

How did we get this far without a link to the relevant xkcd comic? — DanielLC 05:50, 29 July 2009 (UTC)

Just a thought to this thread; why do the FBI/Search and rescue Police force other Gov. people use so called psychic people who are blatantly fraudulent people! to help with the search for missing or dead people do any of these have results? if they dont why bring them in at all?????(there are many such cases were this has HELPED and documented -evidence yes/no); URI Geller just one and others have worked with many investigations and have provided vital clues for this exact purpose. Is that classed as evidence? if so case proved science wrong lets go home :) guessing science will say circumstantial not proved:) there for total fraud???? To dismiss these people as frauds when they are constantly used is seemingly strange>>>to say there is no evidence is down right daft due to the fact 1. people are found 2. killers caught 3. They keep being used ECT...does this go down the same road as pilots would not say they had seen a UFO as they would be ridiculed or it would affect there status as a pilot(many examples of this happening - again Evidence yes/no!!!! By saying something along the lines of prove you seen it and we give you 13,000,000 dollars but when you cant we say your a fraud??????? If i was in court for a crime and ten people say i did it case should be dismissed? as this is not evidence? So - the evidence is there; you just cant prove it scientificly yet to are understanding if it is indeed scientific. the other notion is that this is all a science i.e. brain wave manipulation will be discovered then it is know longer a psychic thing but a proven scientific method so the scientists were right all along. A difficult subject to discuss with science portal as they refute all knowledge other than scientific so no matter what you ask it will say fraud/not possible or scientific reasoning behind it. which could quite possibly be the caseChromagnum (talk) 10:23, 31 July 2009 (UTC)

You could provide further examples as evidence - Link between twins Evidence yes/no. Dog traverling across whole country to owners house evidence yes/no. Incidents like the Entity proven to have happened evidence yes/no. there are many many many cases that the science community happerly ignore in the name of science as they cannot explain them.

Maybe the TIGHAR team should hire a psychic to help them find that Electra 10-E! :-D 98.234.126.251 (talk) 05:16, 1 August 2009 (UTC)

There you go evidence of a typical answer pointed towards ridicule of anything other than the norm - Try next police mass murder investigation/missing person(or just use an old case file)... that uses psychic's if they help or helped in anyway have the Money reward given to the psychic and right a paper on it for the science communityChromagnum (talk) 07:13, 1 August 2009 (UTC)

That's very interesting -- can you give an actual example of an "old case file" of a missing person / murder investigation (BTW, TIGHAR's research surely qualifies as an "old case file" of a "missing person" search) where a psychic provided the vital clue that led to the case being solved? I'm downright intrigued by this question! :-D 98.234.126.251 (talk) 08:01, 1 August 2009 (UTC)

Resources for cultivated plant identification?

Hi all - I'm a Seattle resident looking to learn more about identifying plants, particularly flowering plants. I already found the National Audubon Society Field Guide to North American Wildflowers: Western Region and the Peterson Field Guide to Pacific States Wildflowers, but neither of these tells me anything about cultivated flowers. Most of the books I can find on cultivated plants are written for gardeners, which I am not. Any tips? Dcoetzee 18:29, 27 July 2009 (UTC)

Are you trying to source a plant for a situation or identify a plant you have found? --BozMo talk 18:45, 27 July 2009 (UTC)

I photograph plants in gardens and botanical gardens and I'd like to identify them (either at the time of photographing, or later based on the photograph). Sometimes they are labelled, but often they are not. I also have a personal interest in plant identification. Dcoetzee 20:17, 27 July 2009 (UTC)

Hi Derrick, I use a combination of two sites for identification of plants; one is the Wild About Britain identification forum and the other is the UBC (University of British Columbia) Botanical Garden forum. Between the two of them, I usually manage to get a definite genus and often a species match. Obviously, unless you plan to be travelling across the pond, the first link is no good to you, but the UBC forums are international and should hopefully be able to satisfy most of your needs. There is a good level of activity there, so it usually doesn't take too long to have queries answered. Hope that helps. Maedin\^talk 20:36, 27 July 2009 (UTC)

I realise I wouldn't have much trouble getting a hold of people who can help me identify things, but I really want to learn to identify things myself, so that I can make quick identifications in the field and help others identify things. These people must have learned somewhere, right? Dcoetzee 20:49, 27 July 2009 (UTC)

If you aren't going to undertake formal education or training, then I presume that most people learn by experience. Just by using the forums I have learned more about plants, hopefully in a manner that will stick with me. Other than that, I don't know what to suggest, apart from approaching a gardener or a botanist and requesting introductory lessons or guidance. You could also try to approach the families of plants in a logical manner and begin by studying overall characteristics, before narrowing down to genus or species. That would allow you to use your identification books more effectively. Maedin\^talk 20:57, 27 July 2009 (UTC)

I wouldn't mind formal education or training, I just don't know what background is pertinent. I'm pretty sure I need some basic anatomy and taxonomy, not so sure about genetics and genomics or cell biology or microbial plants. I'll be attending UC Berkeley but they don't appear to have specific classes in plant anatomy or identification (see plant biology classes). In any case I've mailed the department's advisor and I'll see if they can help with this. Dcoetzee 21:21, 27 July 2009 (UTC)

I think you are looking more for something like Botany and Horticulture. This link says Berkeley lumps that in with plant biology [17]. Maybe you could do something in the extracurricular area. This looks promising [18]. From your catalog the plant morphology classes have a different focus, but may still get you the information you seek C107 + C107L. This book is quite old, but may still be a good place to start. [19] There seem to be various versions about. [20] I'm not sure whether the online download is the same as the full 6 volume book. This seems to indicate only 3 of the 6 volumes can be downloaded if I'm reading it right [21]. See if your library has a copy for comparison. This site may also be a useful resource [22]. This is a lot to check, but may help [23] Hope this helps. 71.236.26.74 (talk) 01:21, 28 July 2009 (UTC)

Thank you for your help! Dcoetzee 19:57, 28 July 2009 (UTC)

A good first step is to learn the characteristics of at least the common plant families. You could start with a website like [24]. It is very satisfying to look at a plant and be able to tell, without looking anything up, what family it belongs to. The links at the bottom of that site are also useful - especially the bottom one on botanical Latin, try looking up some names that you see in plant labels in botanic gardens - they are a lot easier to remember if you know what they mean. Finally, if you get into some of the more technical literature some sort of glossary would be very useful, as the description of plants - phytography - is a whole new language. I'm sure good online ones exist but a quick and dirty google search only brought up books such as this one [25]. 84.12.138.49 (talk) 21:45, 29 July 2009 (UTC)

P.S. One book I just found seems just about perfect for what you want. It covers North temperate regions (I assume this includes Seattle), concentrates on flowering plants, and includes cultivated plants. —Preceding unsigned comment added by 84.12.138.49 (talk) 21:51, 29 July 2009 (UTC)

which vein is involved in echymosis over mastoid process in battles sign

which vein is involved in echymosis over mastoid process in battles sign —Preceding unsigned comment added by Ashupg (talk • contribs) 19:01, 27 July 2009 (UTC)

Is "echymosis" a typo of ecchymosis? Dogposter (talk) 20:55, 27 July 2009 (UTC)

We do have an article on Battle's sign, but it unfortunately doesn't say which vein is involved. Red Act (talk) 21:00, 27 July 2009 (UTC)

According to this, Battle’s sign results from the extravasation of blood along the path of the posterior auricular artery. Red Act (talk) 21:22, 27 July 2009 (UTC)

I have updated the Battle's sign article to include this information. Red Act (talk) 21:53, 27 July 2009 (UTC)

Butterfly effect - Changing the evolution of species with time travel

There have been lots of instances of the Butterfly effect in films and TV programmes (including the Simpsons) where somebody has travelled back in time, has killed some plant or animal, and has significantly changed the evolution of species. I wonder if there has been any serious scientific work done on the issue of how much impact the killing of a single individual can realistically have on the evolution of the species, and of other species. I would imagine that if all of the evironmental pressures remained the same, then the killing of an individual would actually have a minimal effect on the evolution of a species, because any mutation that individual had would no doubt be acquired my another individual soon enough - but soon, enough every individual would be slightly different. Perhaps treading on a rodent 100 million years ago might mean that Barack Obama would be Susan Stout instead, but would not make him a 20 foot lizard. But, has there been any serious research or publications that are relevant to this. Would really appreciate any help. Thanks Squashed Star (talk) 19:55, 27 July 2009 (UTC)

There are too many variables and hypotheticals to take into account. It might have no effect, it might have a large effect. Individuals sometimes don't matter, individuals sometimes do matter. I'm not sure there is any very scientific way to approach the question, given the magnitude of the uncertainties involved. --98.217.14.211 (talk) 20:14, 27 July 2009 (UTC)

It's not hard to imagine a situation in which killing an individual could have a significant impact. If the population in a region has been temporarily reduced to a level at which it can barely sustain itself, the death of an individual could have a dramatic effect. And just as an individual human touches many people in their lives, an animal modifies the behaviour of virtually every other animal it comes into contact with, and it's difficult to predict the long term effect of this. Dcoetzee 20:20, 27 July 2009 (UTC)

But if a population is big enough, and "real, text book evolution" is taking place, killing one individual should have no effect. That one that you kill can't be a special one, because evolution does not work by macro-mutants. The pressures are still the same so at least a similar solution should be found. Aaadddaaammm (talk) 20:48, 27 July 2009 (UTC)

Yeah, but consider this hypothetical scenario: you kill a prey animal which, if it had lived, would have distracted a group of predators from pursuing a harder-to-catch prey, who would have led the predator to its nest and caused its entire colony to be eradicated, which happens to be the only one remaining in the region. The point of the butterfly effect is that small things can lead to larger effects in a chain reaction. Dcoetzee 20:57, 27 July 2009 (UTC)

"If a population is big enough" is certainly a subset of the original question. However, there have been times in researchable history where populations dwindled to a few survivors only to roar back into prominence some time later. The most recent article was about wild cats in Africa, if I recall. In such a case, going back and "selecting against" one of the few surviving members could have a dramatic effect on the future size (or extinction) of the population. --66.195.232.121 (talk) 21:05, 27 July 2009 (UTC)

The main problem with research in this field is that, absent time travel devices, and absent access to parallel, almost-identical universes in which alternate events occur, there is no control available so we can compare what would have happened otherwise. Because of this, it's all speculation, so it's OK to stick with Homer Simpson. Tempshill (talk) 21:16, 27 July 2009 (UTC)

Jacques Hadamard just thinking aloud about the butterfly effect has had repercussions in literature, chaos theory and ripples of the event persist over a century later here in Wikipedia. The consequences of a hypothesis that travelling back in time is possible (if true) would be at least as great a perturbation to the way things are, and to actually do anything when one arrives in the past would cause an even greater upset. The OP's question, which I cannot answer, boils down to whether the upset would decay over time and whether the residual effect today would bother us. I think we could tolerate a US president named Susan. Cuddlyable3 (talk) 21:54, 27 July 2009 (UTC)

The very idea of 'time travel' is patently preposterous and denotes a serious misunderstanding of the nature of things. So anything predicated on 'travelling back through time' cannot be spoken of sensibly. Napoleon Dynamite got it right when the uncle tried to return to his high school days and just ended up electrocuting his testicles. Vranak (talk) 22:21, 27 July 2009 (UTC)

That's a rather rigid response. It's true that at our current level of scientific understanding and technology level we cannot conceive a realistic method of time travel, however that's not to say we couldn't at some point in the future do so. Exxolon (talk) 22:44, 27 July 2009 (UTC)

The trouble with that kind of thinking is that it prevents you from ruling out anything whatever - this makes doing science impossible. You'd be unable to do even the most mundane activities or come to the most basic conclusions without having to worry that some future development would utterly overturn it. We have to say that occam's razor says "NO!" to time travel until/unless some spectacular new science comes along. Meanwhile - the only rational and sane way to proceed is to make the strong assumption that it cannot exist. SteveBaker (talk) 23:29, 27 July 2009 (UTC)

Well, there are different levels of "ruling out". If someone walks up to you on the street and says he's from the future, doesn't have any 2009 money to make stock picks with, but if you'll give him yours he'll make you rich — yes, we can rule that out. On the other hand, if a respectable physicist wants to study a theory that might imply time travel in principle — if it looks vaguely plausible to other experts, fund it. You never know. --Trovatore (talk) 01:55, 29 July 2009 (UTC)

Certainly the butterfly effect exists. Changing any small thing today could potentially have a deep and profound effect on what happens in the future. That has nothing to do with time travel - it's more a function of Chaos theory. Chaotic systems (which many systems here on Earth are) can amplify small changes into big changes. Of course, there is no way to plan for that - and equally, no way to know whether some other small change wouldn't cancel out some of the effects of the first one. But there are plenty of cases in history where a very small change would have made a lot of difference. On 28 June 1914, three police officers got into the wrong car by mistake. Had they gotten into the right car - neither you nor I nor anyone else here would exist! Because...as a result of them getting into the wrong car, Archduke Franz Ferdinand didn't have sufficient protection in some parade or other - so he got assassinated - which started the first World War. Most of us are either 'baby-boomers' or descendants of baby boomers - the baby boom only happened because of soldiers returning from the second world war - which would undoubtedly have played out very differently if the first world war hadn't happened - our parents would have met different spouses - our genetic makeup would be different - and so would be that of Jimmy Wales - so no Wikipedia. It's pretty safe to say that everyone reading this thread would not exist...or at least not precisely as we are now. So three cops get into the RIGHT car - and all of us pop out of existance! But if three cops in a sleepy little village in (say) Argentina had gotten into a different car than they actually did - would the effect have been so profound? It's hard to say. Chaos theory says that the consequences could easily be just as severe - but it's really impossible to know specifically. I suspect that ANY change 100 years ago would produce effects that would be just as dramatic. SteveBaker (talk) 23:29, 27 July 2009 (UTC)

Sure, that's one extreme view of the butterfly effect. The other is that events take place more like a river flowing downstream. If you throw a rock into the water at 8:00AM rather than 9:00AM, the individual water molecules disrupted by your rock throwing will all be different; but the ripples look about the same, and from the viewpoint of a bystander along the river, it doesn't make a shade of difference. Anyway, to go back to the OP's question, you will notice that beyond this kind of speculation, nobody has cited any "serious scientific work" on the butterfly effect, let alone your related evolution question, which is what you had asked about. Tempshill (talk) 00:09, 28 July 2009 (UTC)

But who's a bystander in the History of Planet Earth? If cats instead of primates occupied our spot on the food-chain, I suppose the rest of the solar system would be pretty much the same. But it would make a big difference to the hypothetical time traveler returning from the Cretaceous to modern day after stepping on a butterfly. APL (talk) 00:45, 28 July 2009 (UTC)

@Tempshill: This is the RD - we don't have to cite serious scientific work - we have merely to link to appropriate articles - which in turn cite the serious scientific work. Hence, I linked to Chaos theory - which has 50+ references, 50 more citations in the scientific literature and about a dozen other useful web links for our OP to follow. Chaos theory is a solid mathematical field - it shows that the kinds of systems that have a sensitive dependence on initial conditions do not settle down after a small disturbance - instead, they magnify it. The mathematics also shows how to identify such chaotic systems - and indeed the entire field was discovered as a result of weather prediction studies in which it was discovered that the earth's weather conditions are indeed 'Chaotic' in the mathematical sense of the word.

If the weather were the only chaotic system on earth, we'd still have a situation where a tiny change sufficiently long ago would cause huge changes down the line...but it's not. Chaotic systems are everywhere. Our entire society is one gigantic chaos engine. One kid films himself playing with a toy light sabre in his garage - and a few weeks later, half the people on the planet have seen the video. Monty Python do one sketch that makes 'Watney's Red Barrel' beer seem un-cool, the company that makes it goes bust within a year - the entire British brewing industry flips over to "Real Ale" - pubs become more family friendly and the whole dynamic of how "guys" go off down to the pub leaving their wives behind is erased in just a few years. One guy comes up with the concept of a "wiki-wiki-web" and six years later almost all of human knowledge is encapsulated in one - millions of people rely on it.

Animal populations undergo boom/bust cycles for reasons that are far too obscure to ever decypher - because they are chaotic. Financial markets...chaos. Traffic speeds down a freeway...chaos. It's everywhere. If you look at the underlying mathematics - it's plain to see that the big picture is NOT one where these kinds of ripples 'die down' over time - they magnify enormously from small beginnings.

The problem is that we never really know what would have happened if any particular ripple hadn't started - all we know is that there are a tens of thousands of examples where the tiniest of nudges changed everything that followed.

SteveBaker (talk) 01:21, 28 July 2009 (UTC)

It seems unlikely that Barack Obama could become a murdered female caucasian graduate student in psychology, born long before he was, for whom a library was named: [26]. Edison (talk) 05:26, 28 July 2009 (UTC)

It's difficult to frame this question in a way that even makes sense. In order to say that some event had an effect you have to suppose that there was an alternative (if it had not happened then the future would have been different). But in order to attribute the whole future course of history to that fateful moment, you have to suppose that everything after that was a necessary consequence of what came before. That rarely makes sense. In the case of the "butterfly effect" you could argue that the butterfly had the choice to not flap its wings but the air didn't have any choice in how to respond (though I'm not sure I believe that—they're both quantum systems of similar complexity), but there are other butterflies, and other animals, and people, and how do you distribute the blame? It's not a linear system. And there's no way you can do that kind of thing in the case of an assassination. If the assassin could have not pulled the trigger then everyone else could have chosen to not react in the way that they did.

Also, though you can formalize what it means for a system to be chaotic, I don't think there was ever any mathematics or physics behind the butterfly effect specifically, i.e. the claimed influence of butterfly flight on weather patterns. The fact that the weather is hard to predict doesn't imply that it's unstable under perturbations of that particular form, and I'm not sure it actually is. -- BenRG (talk) 16:19, 28 July 2009 (UTC)

When I was a child I recall reading a short story at school about someone who went back in time and accidently trod on a butterfly. When they came back, the world had changed a lot. I read it long before the butterfly effect had become a common phrase. Perhaps that short story was its origin. Anyone know what short story it was? 78.146.235.174 (talk) 11:45, 31 July 2009 (UTC)

"A Sound of Thunder" by Ray Bradbury. 98.234.126.251 (talk) 05:18, 1 August 2009 (UTC)

What are these creatures/objects?

Hi, everyone, as I was uploading images of South Korea, especially Andong areas in the east southern part of Korean peninsula, I found them, but don't know what they are. Thus, the photo names are incorrectly named because of my ignorance, but I want to fix them. The photographer is a foreigner and inactive for a while, so I stumble here to seek a help from those who are knowledge of biology...If you could answer my questions, I would appreciate your input. Thanks.--Caspian blue 21:18, 27 July 2009 (UTC)

• 
  1. What is the name of the bug?
• 
  2. What function do these rocks have?
• 
  3. Mushroom?
• 
  4. Mushroom?
• 
  5. What mushroom species?
• 
  6. Bird nest?
• 
  7. What berry?
• 
  8. Pumpkin or gourd?

1. Probably a swallowtail butterfly larva. Check Old World Swallowtail which is found in Korea. Here is a taxonomy sheet with pictures which may be helpful [27] Sifaka ^talk 21:39, 27 July 2009 (UTC)

2. This is a kind of ancient burial called Dolmen. In Korea, they call it 고인돌. Elkellogg54 (talk) 21:46, 27 July 2009 (UTC)

also see Megalith#Asian_megaliths83.100.250.79 (talk) 23:54, 27 July 2009 (UTC)

3 Likely a mushroom (pretty sure it's not a lichen), probably the same species as #4. Sifaka ^talk 21:50, 27 July 2009 (UTC)

4 Definitely a mushroom of the bracket variety. These are going to be hard to identify by look and geographic location alone, but the family is probably Polyporaceae. Sifaka ^talk 21:50, 27 July 2009 (UTC)

Maybe Genus trametes [28]? Sjschen (talk) 18:52, 28 July 2009 (UTC)

5 I'm not sure it can be definitely IDed without a shot of the underside and a spore print. Those flecks on the cap make me think genus Amanita, but that's a real tenuous guess. Sifaka ^talk 22:05, 27 July 2009 (UTC)

6 Almost certainly a bird nest. No guesses yet as to what kind of bird. Sifaka ^talk 22:12, 27 July 2009 (UTC)

7 Maybe a cherry? Sifaka ^talk 22:12, 27 July 2009 (UTC)

I'm almost certain it's some kind of crabapple, if you look at the base of the fruit you'll see where the flower used to be. Sjschen (talk) 18:52, 28 July 2009 (UTC)

8 (Almost) definitely a pumpkin. FWiW 98.234.126.251 (talk) 23:09, 27 July 2009 (UTC)

But it really really looks like a gourd[29][30]. I'm also not sure pumpkins are grown on trellises? Sjschen (talk) 19:28, 28 July 2009 (UTC)

Thank you for the answers everyone. I really appreciate your help. --Caspian blue 03:31, 29 July 2009 (UTC)

day and night on gas giants

Do Saturn, Uranus, and Neptune have daytime or it is always nighttime? The differ between gas ginats and rocky planets is thye rotate faster on axis and the day/night is less than 18 hours. And they have so little sunlight penetrating through if they have a solid surface, then they would be always nighttime. —Preceding unsigned comment added by 69.228.145.50 (talk) 22:16, 27 July 2009 (UTC)

Daytime and nighttime isn't caused by penetration of light through the planet, as I guess you've noticed by observing our own planet. The speed of rotation doesn't effect the existence of daytime and nighttime, it only shortens or extends the respective durations of each. So yes, they would have a daytime (the side facing the sun) and a nighttime (the side being blocked by the other). I struggled reading your question, so if I misunderstood please do clarify. Regards, --—Cyclonenim | Chat  22:46, 27 July 2009 (UTC)

Well, there wouldn't be much light coming from the sun right down at the "surface" (to the extent that gas giants have something like a "surface" under all that metallic hydrogen and stuff)...but there would be some teeny-tiny number of photons making it down that deep - and there would be more of those on the side of the planet facing the sun than on the side pointing away from it - so technically, even down on the surface of the rocky core, there would be "day" and "night". But to human eyes, it would pretty much look black all the time. But higher up in the atmosphere day/night cycles are just like on earth. The question of how long day and night lasts is a little tricky since different parts of the atmosphere are rotating at different rates. SteveBaker (talk) 23:04, 27 July 2009 (UTC)

OKay, I got the point.--69.228.145.50 (talk) 23:42, 27 July 2009 (UTC)

Shotgun backfiring

What is the sequence of events involved in a semi-auto (not pump-action or double-barrel) shotgun backfiring? I know that the breech gets forced open somehow or other, but how exactly does it happen? Also, if a shotgun backfires, what kinds of eye/face injuries can you expect? Would those injuries be readily reparable by surgical means? (No, I'm not looking for medical advice, I need to know these things for a short story that I'm writing.) Thanks in advance! 98.234.126.251 (talk) 23:18, 27 July 2009 (UTC)

As far as the second part of your question goes, it's hard to say -- much depends on how close to your face the weapon is when it backfires, and how the backfire actually takes place. In a worst case scenario, you could undoubtedly be killed; people have ended up death from firing blanks, for example. You could definitely lose an eye or get badly scarred. Cosmetic surgery is pretty good, these days, so it's possible that the damage could be repaired, but it's impossible to generalize. It all depends on how the force from the backfire is directed, how close the shooter's face is to the backfire, what kind of a shell the shooter is firing, the model of the weapon, etc.

Suffice to say that you can get hurt really badly, but if you don't get hurt too badly, they can patch you up well enough to keep you from being horribly disfigured, even if there's a bit of scarring. -- Captain Disdain (talk) 09:08, 29 July 2009 (UTC)

Well, the problem is, although I'm pretty well versed in the mechanics of semi-automatic firearms, I don't really know the exact sequence of events that leads up to the breech being forced open, so I can't really say exactly how the backfire actually takes place, straight to the rear through the breech, or sideways through the ejection port. As for how close to the face, let's assume that the shooter has the shotgun braced against his shoulder but is using the point-and-shoot technique and is not using the sights to aim. The weapon in my scenario is a gas-operated, rotating-bolt semi-automatic hunting shotgun (say a Remington 1100 or similar), and the shell is a 3-inch, 12-gauge plastic-cased buckshot shell with, say, number-four shot. How dangerous would a backfire be in this scenario? Thanks! 98.234.126.251 (talk) 05:01, 30 July 2009 (UTC)

Honestly, it's impossible to say how dangerous it would be, especially as I'm not familiar enough with the weapon in question. In any case, you might as well be wondering something like, oh, "a guy fall off a motorcycle while doing 50 km/h, and he's not wearing a helmet, how badly is he going to get hurt?". And you can't answer that question, because a lot of it depends on how the guy falls down, whether he hits anything, etc. I mean, you can say he'll probably get hurt, but it's impossible to predict the exact result.

On a hunch, though, I'd say that the risk of injury in your situation would be considerable, but injuries like this aren't necessarily predictable -- it all depends on how much stuff there is flying through the air, how fast and at what angle it impacts with the shooter's face, what the exact position of the gun is at the moment of firing, etc. Let me put it this way: if a 12-gauge shotgun shell exploded next to my face, I'd expect to get pretty badly hurt. The gun itself is going to direct and shape that blast, though, so a lot of it depends on how it does that: if the blast is directed away from the face, there might not be any injury at all. Or maybe you're liable to lose an eye. I guess the only way to find out anything concrete would be to conduct a series of experiments where the weapon is forced to backfire, and see what kind of damage it does to things around them -- a ballistic gel dummy would be the classic "shooter" of choice for something like this, I guess. -- Captain Disdain (talk) 10:26, 31 July 2009 (UTC)

Ok, that's what I was hoping for. (For the record, I want my character to get hurt real bad, but not so bad that a good surgeon can't fix it.) I'll try to do some more research for the exact kinds of injuries to be expected. Thanks a lot, and clear skies to you! 98.234.126.251 (talk) 05:23, 1 August 2009 (UTC)

July 28

gaps

Is there a list of gaps in knowledge such as the first seconds of the big bang or in the trail of evolution, etc. -- Taxa (talk) 00:37, 28 July 2009 (UTC)

Yes. List of unsolved problems. --Tango (talk) 00:58, 28 July 2009 (UTC)

What pH ranges denature melanin?

It's probably an equilibrium reaction so pHs that would cause dynamic equilibriums of a few power of 10 percentages like 99/90/10/1/0.1% denatured etc. or a formula to find some values myself would be sufficient. Sagittarian Milky Way (talk) 00:46, 28 July 2009 (UTC)

By definition, denature reactions are not reversable, so it would not be an equilibrium situation. Denaturing destroys the Tertiary structure of the protein in such a way that it would be impossible to get it back by simply returning to prior conditions. You don't get a liquid egg back just by cooling it down! Otherwise, I don't have the answer to your main question, but I wanted to make sure you get the terminology right. --Jayron32 04:06, 28 July 2009 (UTC)

Our denaturation (biochemistry) article disagrees, noting (with examples) that the process may be reversible. However, still, I don't know the answer to the original question, except that it also may depend on how severely and reversibly you want to do it. DMacks (talk) 04:33, 28 July 2009 (UTC)

As DMacks notes, there are quite a few proteins which will spontaneously refold under appropriate conditions. (They're almost entirely all small, single-domain proteins, and even among that class they're not a majority — but there are definitely a few.) Perhaps a bit more important to this question, however, is that melanins are not proteins. They're small molecules derived from tyrosine, so the refolding issues associated with protein re/denaturation don't really apply here.

Unfortunately, I don't have a good answer for the original question; it's out of my field. From a bit of Googling, it appears that the extended structure of melanin is still something of an open question — apparently individual melanin molecules combine into larger complexes in vivo, but it is undecided whether these are small oligomers (tetramers), large networks, or some combination thereof. Moreover, it also appears that 'melanin' is actually a mixture of a number of chemically-related compounds, so any measurements of physico-chemical properties ought to be taken with a grain of salt. TenOfAllTrades(talk) 13:01, 28 July 2009 (UTC)

Super fast raster scan

An experiment I am conducting requires a display which updates at least fifty times the frame rate of a normal monitor, could I modify a CRT television to do this, or could LED's or lasers achieve this speed? If made a CRT with multiple beams could this do the trick? Also is their any way to electronically create a scanning transparent "hole" area that lets light through from ALL angles, equivalent to the mechanical Nipcow disc-could an LCD do this or is it more complicated? Trevor Loughlin (talk) 02:47, 28 July 2009 (UTC)

What possible purpose could there be? "Displays" are there for someone or something to see. No human or other earthly animal could derive more info from a display that refreshed that rapidly than from a more normal one. No, you could not "modify a CRT television to do this." You could spend a huge amount of money to have such a pointless device engineered from scratch. Edison (talk) 05:20, 28 July 2009 (UTC)

Come, now, his experiment might have some angle you haven't thought of. Maybe he wants to film a scene of himself singing a song, with a high-speed camera capturing this at 2000 fps, while this experimental monitor is in the background playing back a scene from Apocalypse Now at 2000 fps, so when it's played back as a 60 fps video, you're watching him react in really slow motion to Captain Willard dancing in front of the mirror. Or he's making a monitor for the benefit of houseflies. Tempshill (talk) 05:56, 28 July 2009 (UTC)

One could modify just the vertical timebase (and its synchronising) of a CRT TV monitor to run faster and deflect less. The flyback speed cannot easily be increased so one might get about 8 to 10 usable lines updated at, say, 1500 Hz. That is a very shallow "widescreen" raster. Phosphor decay time would limit the speed of updating a picture element from white to black. I don't see any use for an LCD on a Nipkow disk. There are shine-through LCD frame display panels for use on overhead projectors but their rasters are for standard data formats. Cuddlyable3 (talk) 10:17, 28 July 2009 (UTC)

This is one of those areas that I've personally researched. In a project I was working on, we needed a 180Hz refresh rate display system...just three times the speed of a typical computer display.

You really can't do that to a CRT. What you are attempting is a research project in it's own right. The project that tried to drive a CRT at 180Hz failed for all sorts of complicated reasons - we never got much more than 120Hz. Getting sufficiently powerful coils with the right inductance to run at three times the usual rate was "non-trivial". Your idea of putting 50 beams into one CRT in order to get around that problem (aside from being an exceedingly tricky problem for making the device and aligning all of those beams to the shadow-mask) wouldn't work because the persistance of the phosphors. When you hit the phosphor with an electron beam to make it glow, it takes around 1/150th second for the light from the phosphor to drop back to somewhere near zero - which really limits you to around 150 frames per second - nowhere near the 3,000 frames per second you're looking for!

LCD and plasma and LED and OLED displays all have the same problem. I don't think the tiny mirrors in a DLP projector could move that fast either...and that means that NONE of the 'conventional' display approaches used in consumer or even professional display products are going to come within a factor of 10 of what you claim to need.

I think you're going to need a laser display - but even then, it's an insanely difficult problem.

Scanning a laser display is typically done with mirrors that are moved around using piezo-electric crystals...but the momentum of the mirror and the force needed to accelerate it would be spectacular. That drives you to using a smaller, lighter mirror - but then the actuators that drive it have to be small - and you end up in a spiral of smaller mirror needing smaller actuators that have less power so you need an even smaller, lighter mirror...So I don't think you can move even a tiny mirror fast enough to do that.

Another approach is to aim the laser at a spinning cylinder with mirrors mounted onto it...let's say you make a 10 sided cylinder with mirrored facets...you'd have to machine it out of some very strong metal and polish it to make the mirrors. Point the laser at it and spin the cylinder and the laser will be reflected from one rotating facet after another. This will cause the laser to scan sideways 10 times for each revolution of the cylinder - just like the line-scan on a TV set. Use one cylinder for the horizontal line-scan and another spinning much more slowly for the vertical scan. The problem is that to get a 3000Hz refresh rate with 10 sided mirror cylinders, the vertical scan cylinder has to rotate at 300 revolutions per second and the horizonal one by 300 multiplied by the number of scanlines you need. If you have 500 scanlines - you need your line-scan cylinder to spin at 150,000 revolutions per second!! There isn't anything I could imagine that wouldn't disintegrate if you did that - and machining that cylinder to the precision needed to avoid vibrations would be a major engineering feat!

In the distant past, people scanned images using a tank of mercury and an acoustic stimulator that produced ripples in the liquid that travelled outwards. Aiming the laser at the liquid surface produced a scanning effect as the laser reflected off of each wave in turn. This works pretty well - although the scanning is very non-linear and you have to electronically pre-process your video stream to counteract that. In order to get 150,000 scanlines per second, you'd need to use a 150kHz audio source to make the ripples. I don't know what kind of quality of ripple you'd get if you did that (what's the speed of sound in mercury? That would determine the wavelength of the ripples.) That's maybe do-able. Then either some more complicated mirrors to get to a second mercury tank with 3kHz ripples - or (more conveniently) a 3000 revolutions per second spinning 10-sided mirror (which would still have to be insanely carefully machined and mounted to avoid it destroying itself...but not impossibly so. 3000 revs per second is 180,000 rpm - which is only 20 times faster than (say) a car engine spins...it's tough but just barely possible. You might even get a small piezo-electric actuator to vibrate a mirror at those kinds of speeds.

In order for the image to be bright enough - the laser would have to be a pretty powerful one - and of course if you want a color image, you need three of them.

The result is:

• Three dangerously bright lasers.
• A tank of poisonous mercury.
• A spinning death-trap.

Definitely a recipe for killing yourself if you don't know what you're doing!

From the relative naivity of your question - I doubt very much that you have the skills to come even within a factor of 10 of your goal. This is a multi-million dollar display research activity...and people who are about to launch into multi-million dollar display research activities don't usually start off by wondering if they can just adjust a TV!

I'm also puzzled by what you think you're going to drive this monster with? I can't think of any signal sources (like computer graphics cards, DVD players or anything else like that) which could provide a fast enough signal to drive this thing.

Perhaps you should tell us more about why you need it. I bet there is something else you could do that would work better.

SteveBaker (talk) 12:45, 28 July 2009 (UTC)

Just a small comment, but it is certainly possible to replace CRT phosphors with other materials that can reset much faster. I routinely work with fluorescent organic compounds with an excitation lifetime of a 100 ns or so. I suspect something similar is also achievable for LEDs. It would be an expensive custom job to create such a thing, but the engineering to create the screen strikes me as straightforward (provided money is no object). So, if you can get the rest of the control electronics to run at that speed I don't think designing an appropriate screen is really a limiting factor. Dragons flight (talk) 20:44, 28 July 2009 (UTC)

Quite a number of computer CRTs claim to support a refresh of 160Hz. You can get the comp to use this refresh as well. This is usually at rather low resolutions obviously (e.g. 640x480). Are these not really refreshing that fast? Nil Einne (talk) 01:48, 29 July 2009 (UTC)

Yeah - but they get pretty smeary at those rates. Looking at the screen with the naked eye - you really can't tell but for applications such as our OP evidently has in mind (see below), this smearing would result in a blurry image in the 3rd dimension. SteveBaker (talk) 02:50, 29 July 2009 (UTC)

If I recall correctly a half-silvered mirror will block (one polarisation of) light when charged (or carrying an electric current) - this could form the basis of a high speed light switch - since there are no moving parts. However it sounds like you'd need an array of these things - which as far as I know doesn't exist - eg you'd have to make it yourself - each array element would require an independent electrical supply - I'd guess you'd photlithography equipment at the least. 83.100.250.79 (talk) 14:00, 28 July 2009 (UTC)

If that was workable - we probably wouldn't be using DLP's to do that job...so probably those things don't switch as fast as you think they do. But DLP's are nowhere near fast enough...and really, neither is anything else that I can think of. Worse still - if you have a million pixels per frame and a 3,000 frames per second display - you need to feed it with with something like 75 Gigabits per second of data. That's extremely non-trivial...even if you manage to figure out a way to display it. SteveBaker (talk) 20:37, 28 July 2009 (UTC)

It's not the speed it's the heat that is a problem - a mirror reflects - these absorb the light. Why not check you understand first?83.100.250.79 (talk) 12:24, 29 July 2009 (UTC)

I am not giving much away, because it will result in a piece of consumer elecronics that no-one has a perfect version of even for use by large organisations. What if i had ONE spinning mirror for the horizontal scan and hundreds of individual lasers each with a light valve for the vertical "scan?" —Preceding unsigned comment added by Trevor Loughlin (talk • contribs) 15:00, 28 July 2009 (UTC)

As a point of interest, this user has invented a "retrocausal information transfer" device. He may actually be posting from the future. APL (talk) 15:26, 28 July 2009 (UTC)

As a second point of interest, are you trying to build a "swept volume" volumetric display? It sounds like it, but I don't see how those could ever become "consumer electronics". Hidden surface removal alone sinks it for most applications. APL (talk) 20:19, 28 July 2009 (UTC)

(ec) No - I bet I know exactly what he's planning to do. He wants to create a viewer-independent 3D display - probably by reflecting the 3000Hz image off of a moving screen or spinning the monitor or some such trick. However, there's no such thing as a free lunch - and the amount of information density required to do 3D in such a brute-force manner is HUGE. Getting this down to a price where a consumer could afford it is a major undertaking. If our OP had a hope in hell of doing that - he wouldn't be asking WP:RD/S whether it's possible to modify a TV set to do it! He'd be employing a bunch of professionals who already know the problems and have ideas for the answers. The trick for doing viewer-independent 3D is to take advantage of some of the natural constraints of the scenes you'll want to render. But we're not being told what it needs to do in enough detail to answer the question to speculate on that - and I'm not providing free consultancy in order that someone else can make a fortune! I charge $200 an hour for that (my email address is on my User: page)! Suffice to say that getting enough information into this thing will be a nightmare - and the cost of doing 3D in this way is pretty extreme. SteveBaker (talk) 20:30, 28 July 2009 (UTC)

Oh, I get it now. Not volumetric, but showing a different image to each degree of the circle around the volume. Even if you could work out the optics you'd need a monster of a computer to drive it. APL (talk) 04:30, 29 July 2009 (UTC)

The zoetrope shows a different scene to each viewer located around it. For sheer entertainment value, it provides hours and hours more fun than an average Hollywood movie. On the other hand, the back story and character development are generally rather shallow. Cuddlyable3 (talk) 20:57, 30 July 2009 (UTC)

Oh - this old thing again! [31] SteveBaker (talk) 20:43, 28 July 2009 (UTC)

Yes APL you have got it. You guys are not just nerds, you are smart. The high speed CRT or laser television image would create a circle with all the 3D pixels for each point of the image.For the hole,LCDs or alternatively a mechanical method capable of creating a scanning hole I have thought of(thousands of times better than the nipcow disk in terms of space to image size and definition) would provide the "hole" which would only have to scan at NORMAL television refresh rates. The speed requirements of the CRT/Laser screen behind it could be reduced by using multiple image circles with very little reduction in the viewing angle be for they interfered with each other.I admit the electronics for such a high data rate could be a slight problem. What about a programmable custom chip? Trevor Loughlin (talk) 14:26, 29 July 2009 (UTC)

That will be expensive and require an advanced engineering training. As much as I would like to encourage amateur hobbyists to engage in electronics design, let's be serious. A beginner will take one look at the HDL hierarchy or the ASIC netlist, and run away screaming in horror. But, don't let my dismal view on things dissuade you. Go ahead and download some free, free, opensource HDL and ASIC schematics from OpenCores Project Repository. You can buy starter kits for around two or three hundred dollars; but for the data rates I'm guessing you need, you may want to go for a high-end system. Funding should be no problem with all the casino earnings from the retrocausal information transfer device. Nimur (talk) 17:06, 29 July 2009 (UTC)

Chlorine

Chlorine used in swimming pools is harmless but chlorine gas used in the world wars was lethal. Why? Is the chlorine in swimming pools used in very low concentrations so that it is not harmful? Many thanks for any help. Chevymontecarlo (talk) 06:23, 28 July 2009 (UTC)

see Chlorination 71.236.26.74 (talk) 07:04, 28 July 2009 (UTC)

It's also very important to note that ions can be very different from their neutral atom counterparts. Sodium is a metal that likes to pretty much blow up when you throw it in water, and as you said, chlorine is a lethal gas; yet sodium chloride (Na⁺ Cl^-) is something we all need to live. -- Aeluwas (talk) 07:27, 28 July 2009 (UTC)

True but irrelevant, since chloride is not used in swimming pools while chlorine is. Algebraist 13:47, 28 July 2009 (UTC)

Hmm, I thought the chloride in swimming pools was mostly in the form of hypochlorite ions... but I've never owned a pool. ;) -- Aeluwas (talk) 14:10, 28 July 2009 (UTC)

Yes chlorine is in small concentrations, also it's dissovled (mostly) in the water, rather than as a breathable gas.83.100.250.79 (talk) 11:05, 28 July 2009 (UTC)

To rephrase the question for the OP; water in small volumes is required for life, but if I immerse you in a large volume of water, you would die! See the deal? Very few things are harmful at all amounts or healthy at all amounts. Some harmless things become harmful depending on the amount/concentration. Chlorine is no different in this regard. In small amounts, it kills bacteria, but not you. In larger amounts, it'll kill you too. Most disinfectants/antiseptics have the same basic properties. --Jayron32 13:11, 28 July 2009 (UTC)

But harmless the stuff in swimming pools is not. Just opening the packet before I add it to the dispenser is enough to bring tears to my eyes and make me cough. I have lots of bleach holes in my gardening trousers from premixing it. --BozMo talk 14:23, 28 July 2009 (UTC)

It's still a concentration issue...think about how small an amount from the packet has an effect, but then how much it gets diluted before you swim in it. The relative amounts in "Large amount, immediate and serious effects vs small amount, mild and weaker effects" depend on the intrinsic nature of the chemical you're using. Some are extremely potent or reactive, so even only a few grams is a "large amount" of that chemical and a "small amount" is measured in parts per million dilution. DMacks (talk) 15:26, 28 July 2009 (UTC)

Large pools often use bottled chlorine gas. Google "chlorine gas pool accident" to see some examples of what can go wrong. Rmhermen (talk) 16:55, 28 July 2009 (UTC)

I have heard the new trend is towards salt-water pool sterilization. Vranak (talk) 17:46, 28 July 2009 (UTC)

Virtually everything has several levels...

1. A no effect level (NOEL) - any dose below this has no effect
2. (for drugs)A therapeutic level - the amount of drug necessary to give the desired result
3. A toxic level - the amount to start causing unwanted effects
4. A fatal level - speaks for itself.

So for tiny amount of chlorine in water, then no effect. *Carefully* sniff some gas, and it will make your nose smart - or as one student did when I was at school, sniff too much and you fall over and go to A&E (don't have chemistry lessons like that any more...)  Ronhjones  ^(Talk) 20:02, 28 July 2009 (UTC)

Unsolved problems in astronomy

What is the significance of the asterisks in the Unsolved problems in astronomy article?--Shantavira|^{feed me} 07:41, 28 July 2009 (UTC)

Probably the same as in the Unsolved problems in physics article http://en.wikipedia.org/wiki/Unsolved_problems_in_physics .

** Problems marked with two stars are considered by a significant number of physicists to be resolved, though there is still significant debate about them.

*** Problems marked with three stars are considered by some physicists to be outside the purview of physics, more properly philosophical in nature.

**** The existence of problems marked with four stars is disputed.

You're probably right since User:Allen 124 who created this page [32] later removed some of the same problems from the physics page [33] (although they were restored, as they should have been) Nil Einne (talk) 00:04, 29 July 2009 (UTC)

code for jpg please..

I am using some matlab image processing codes in my experiment.unfortunately .. i found the standard code for bmp files only..can any one help me with ..the jpg version of this code..

err... on trying with the jpg version .. i got some .. problems .. with matrix dimensions.. kindly if someone could fix .it.

CODE: %This code would attempt to analyse the flame area and do the following %1. Frequency analysis of flame area %2. Frequency Analysis of fractal dimension of each static image %3. Correlation Dimension or Embedding dimension of area %-------------------------------------------------------------------------- image_thresh = 70; n_img = 1000;%Number of images in present sequence sampling_freq = 315;%Hz %-------------------------------------------------------------------------- %The starting string of the file name

string_start = 'vc';

%The file extension extension = '.bmp';

%3-D array for image import %pile = ones(256,256,n_img); intensity = zeros(n_img,1); for image_num = 1:n_img %loop counter variable image_num

   img = zeros(256,256);
   %IMAGE LOADING
   image_num_name = image_num - 1;
   image_processed = zeros(256,256);

aniket .. 59.93.135.1 (talk) —Preceding undated comment added 08:38, 28 July 2009 (UTC).

Well, that code is extremely incomplete, and doesn't really do anything that matters. But in any case this is the wrong place for your question, you'll have better luck at Wikipedia:Reference desk/Computing. Looie496 (talk) 15:56, 28 July 2009 (UTC)

When maths go horribly wrong

Okay, so I'm trying to calculate the relative abundance of the two nitrogen isotopes, knowing the mass of both isotopes and of nitrogen as a whole. Nevertheless, somewhere down the road the equation goes horribly wrong:

Step 1: X * 14,0035 + (1-X) * 15,0001 = 14,0067

Step 2: X + (1-X) * 15,0001 = 14,0067
                              -------
                              14,0035

Step 3: X + (1-X) * 15,001 = 1,000229

Step 4: X + (1-X) = 1,000229
                    --------
                     15,001

Step 5: X + 1 - X = 0,066681

Step 6: 1 = 0,066681

Can anyone please point out in which step I made the mistake? Thanks a lot! --Leptictidium (mt) 11:08, 28 July 2009 (UTC)

• Step two and step four both appear to be erroneous. Correct solution should be:

$140035X+(1-X)150001=140067\implies -9966X+150001=140067\implies X={\frac {4967}{4983}}$ Noodle snacks (talk) 11:17, 28 July 2009 (UTC)

Through which mathematical operation does $140035X+(1-X)150001=140067$ become $-9966X+150001=140067$? --Leptictidium (mt) 11:38, 28 July 2009 (UTC)

Take $140035X+(1-X)150001$

multiply out $(1-X)150001$ to become $150001-150001X$

which makes $140035X+150001-150001X$

which is $-9966X+150001$ -- Finlay McWalter Talk 11:46, 28 July 2009 (UTC)

You messed up between step 1 and step 2. Let's replace those constants with nice simple names so I don't have to type those L-O-N-G numbers all the time!

Step 1 is essentially:

  A = 14,0035
  B = 15,0001
  C = 14,0067
  X * A + (1-X)* B = C

In getting to step 2 you tried to divide though by A but screwed up. When you divide both sides of the equation by something - you have to divide EVERYTHING in the equation by that something:

  X*A   + (1-X)*B   = C
  X*A/A + (1-X)*B/A = C/A     -- Divide through by A
  X     + (1-X)*B/A = C/A     -- Cancel A/A

You missed out the A to the right of (1-X)*B! But that approach is ugly.

A better way to simplify would be to collect up the 'X' terms:

  X*A + (1-X)*B = C
  X*A + B - X*B = C    -- Multiplied out (1-X)*B
  X(A-B) + B    = C    -- Collected & factored out the X terms
  X(A-B)        = C-B  -- Subtract B from both sides
  X = (C-B)/(A-B)      -- Divide through by (A-B)
  X = (14,0067 - 15,0001) / (14,0035 - 15,0001)  -- Substitute A,B,C back into the equation
  X = 0,9967890828     -- Do the arithmetic.
  X = 0,99679          -- Round off to 5 decimal places.

QED SteveBaker (talk) 12:07, 28 July 2009 (UTC)

Vibrating parts of the body

Sometimes a few parts of the body vibrate involuntarily for a while and then get back to normal.Like say the right eyelid vibrating,left forearm parts vibrating etc.The nature of vibraion is only short lived. So what is the cause of such vibrations?? What do they indicate??117.193.146.232 (talk) 14:29, 28 July 2009 (UTC)

Some sort of spasm or tremor? DMacks (talk) 15:20, 28 July 2009 (UTC)

Ya kinda tremor ...short lived tremors. —Preceding unsigned comment added by 117.193.131.226 (talk) 17:36, 28 July 2009 (UTC)

These are commonly known as tics or "nervous twitches". The cause isn't really very well understood (many people show them when anxious) -- however there is a neurological disorder called Tourette's syndrome in which tics occur very frequently. Looie496 (talk) 15:49, 28 July 2009 (UTC)

Do not confuse tics which have neurological origin with twiches which are small muscles spasms. 71.203.58.148 (talk) 19:41, 28 July 2009 (UTC)

Looie i dont think tics as you mentioned above answers the question.As a further add on..I myself have experienced some vibrations or tremors you may say ,on my eyelids.It is something which you can feel. —Preceding unsigned comment added by 117.193.131.226 (talk) 17:49, 28 July 2009 (UTC)

I do want to note that Wikipedia can't give any medical advice which includes guessing why your eyelid might be vibrating. You can ask if there is anything else besides tics that might cause that sensation. Sifaka ^talk 17:53, 28 July 2009 (UTC)

Better yet, just go see your physician. Any number of things can cause twitches, including nervous disorders at the extreme end. On the other hand, it may be nothing, so get it checked out. Regards, --—Cyclonenim | Chat  18:31, 28 July 2009 (UTC)

The article you are looking for is Fasciculation. Small, rythmic contractions of an eyelid is a very common phenomenon - so common, in fact, that it has a name in Norwegian (leamus). This term is usually used about fasciculations of an eyelid, but can also be used about fasciculations of other muscles. This was one of the first hits on google.no (the site is well-reputed), and I'll translate the relevant part:

By definition, fasciculations are involuntary muscle contractions, that are sufficiently strong to be visible (or palpable) on your skin, but not strong enough to cause movement of the joint that the muscle controls. Fasciculation is a completely normal phenomenon, and only in exceptional cases a sign of disease. Most people experience fasciculations to a lesser or greater extent in periods of their life. When fasciculations are a sign of disease, they are always accompanied by other, more serious symptoms.

--NorwegianBlue ^talk 18:54, 28 July 2009 (UTC)

In my opinion, the last sentence is the one you need to pay most attention to. See your physician. Regards, --—Cyclonenim | Chat  18:55, 28 July 2009 (UTC)

killed while having sex

has anyone ever been killed while having sex? have they been killed bya third party? or by an accident? and is it more likely to happen in gay or straight sex? Questionabout"theman" adolf (talk) 14:40, 28 July 2009 (UTC)

I doubt there are statistics re: gay or straight in terms of death-while-sex, but certainly people have been killed while having sex both by third parties and by accidents. Why would you presume that it hadn't happened? That people were somehow immune from death by accident or murder while having sex? --98.217.14.211 (talk) 15:14, 28 July 2009 (UTC)

Do automobile, motorcycle and airplane crashes count? How about shootings by jealous spouses? Edison (talk) 15:21, 28 July 2009 (UTC)

There have probably been heart attacks. Or does auto-erotic asphyxiation count (see also Michael Hutchence)? AlmostReadytoFly (talk) 16:00, 28 July 2009 (UTC)

A few years ago, various magazines, including I think the UK's Bizzare, ran photos of a man killed by a falling rock while having sex with a chicken. (He was indulging his avian lust in a cranny in a cliff, and a piece of the cliff face immediately above him became loose.) 87.81.230.195 (talk) 16:04, 28 July 2009 (UTC)

Mostly all spermatozoids are killed when males have sex.--Quest09 (talk) 17:53, 28 July 2009 (UTC)

Millions of males a day die while having sex, see this. -- penubag  (talk) 20:09, 28 July 2009 (UTC)

Clearly the OP is asking about humans. Same goes for Quest09's response. --Sean 21:38, 28 July 2009 (UTC)

See Nelson_Rockefeller#Death if that counts. 70.90.174.101 (talk) 03:11, 29 July 2009 (UTC)

Heart attacks are fairly common during sex, but does dying of a heart attack count as "being killed?" Edison (talk) 18:43, 29 July 2009 (UTC)

How much does a ton of carbon cost at the Chicago Exchange?

I was planning on buying some carbon offsets, and was looking at the website liveneutral.org. Liveneutral buys carbon credits from the Chicago Climate Exchange, and doesn't do anything else, like reforestation. Liveneutral's price is a set $12/ton. How can I find out what those credits actually cost at the Chicago Climate Exchange? Their website is a little confusing...

Thanks! — Sam 63.138.152.238 (talk) 17:41, 28 July 2009 (UTC)

If I'm reading the chart right, it looks like it's trading at about $0.50 per metric ton. It looks like it peaked about a year ago at over $7 per metric ton. APL (talk) 18:23, 28 July 2009 (UTC)

That's what I figured as well. I'll have to write to them to see how they can explain charging $12/ton when all they appear to do is buy carbon credits. — Sam 63.138.152.155 (talk) 20:11, 28 July 2009 (UTC)

Gears

How does the gear system in clocks work??? —Preceding unsigned comment added by 117.193.131.226 (talk) 17:51, 28 July 2009 (UTC)

Well.. from minutes to hours there is a 60:1 step down gear, hopefully that doesn't need more explanation. If you are wondering about old wind up watches then the second counter mechanism is controlled by an Escapement.

There's more info at Wheel train (horology) which should give you all the answers you need.83.100.250.79 (talk) 18:05, 28 July 2009 (UTC)

I think the article you are looking for is Movement (clockwork) (which is oddly not linked from the clock article). — Sam 63.138.152.238 (talk) 18:06, 28 July 2009 (UTC)

It is now. Livewireo (talk) 20:11, 28 July 2009 (UTC)

What is it called when a swallowing attempts to pull down your own throat?

Caused by trying to swallow with too little "lube". Sagittarian Milky Way (talk) 18:23, 28 July 2009 (UTC)

"Getting something stuck in your throat". Couldn't find any specific medical term on wikipedia. 71.236.26.74 (talk) 06:00, 29 July 2009 (UTC)

Hot air

What's the effect called where hot air, or heated air, distorts light so it all seems blurry/wriggly? You can see it on hot days over long distances, or above a toaster (where I saw it this morning) for example. Regards, --—Cyclonenim | Chat  18:27, 28 July 2009 (UTC)

Heat shimmering/heat shimmer. [34]. - Nunh-huh 18:34, 28 July 2009 (UTC)

Caused by refraction of light in different densities of air at different temperatures. Sjschen (talk) 18:36, 28 July 2009 (UTC)

See also Schlieren photography. DMacks (talk) 18:41, 28 July 2009 (UTC)

The effect is refraction. See also mirage. Red Act (talk) 18:55, 28 July 2009 (UTC)

"Heat wave distortion" gets a few ghits too. Aaadddaaammm (talk) 19:22, 28 July 2009 (UTC)

The answer to your question is refraction of light.To get into more detail consider this.You have lit a bonfire.The air vertically above the bonfire is much hotter than the air surrounding the fire.Hotter the air, the lesser is its density.The air surrounding it is comparitively denser.Obviously the air nearer to you is very dense.Now the light has to travel through this range of varying densities of air and hence suffers a series of refractions which make the air to give it a quivering appearance.The densities of air also keep varying constantly which further add to the quivering effect.gdsrinivas 19:29, 28 July 2009 (UTC) —Preceding unsigned comment added by Gd iitm (talk • contribs)

The reason for the ripples is just turbulance in the air - much as smoke tends to curl and bend, so does the clear air that causes this shimmering. The difference between the refractive index of warm and cold air explains why the light coming through is distorted differently - and as the hot and cold air mix, you get this effect. SteveBaker (talk) 20:14, 28 July 2009 (UTC)

Turbulance? Hmm, I would say above your toaster it is very unlikely to be "turbulence" which I think is generally characterized by multiple length-scales of eddies? The formation of simple laminar and eddy flow as the buoyant laminar flow breaks up seems much more likely. But I couldn't be bothered to calculate a Reynolds number to check so I'll have to give SB the benefit of the doubt. And as Steve has said using the right technical term isn't the most important thing.... --BozMo talk 22:25, 28 July 2009 (UTC)

A quick look through my Fluid Dynamics library seems to indicate that twenty years ago (when all the books were written) the correct term for the flow above your toaster was laminal flow transitioning to an irregular "vortex street". Emphatically not turbulence. There you go then, that should change your whole perception of things. Unless I am out of date which is possible. --BozMo talk 22:40, 28 July 2009 (UTC)

Yeah - that's all true - but I don't see that same kind of shimmering over my toaster (at least, I just tried it with my toaster and it doesn't seem to generate anything like that). We're talking about much larger differences in temperature and much larger sources...I doubt that the airflow stays laminar under those kinds of situtaion. SteveBaker (talk) 02:33, 29 July 2009 (UTC)

My guess is actually that the "shimmer" is a coherent higher frequency eddy structure and that the distortion from the pure turbulence would be whiter in frequency terms. However both could exist in the same flow and I didn't do any serious stuff on flow since the early nineties. --BozMo talk 06:03, 29 July 2009 (UTC)

By the way are you a chemical engineer? In pipeflows people tend to talk about laminar or turbulent as though these were the only flow types but when talking of ddc buoyancy wakes jets etc they use a fuller range of flow regimes. --BozMo talk 06:14, 29 July 2009 (UTC)

Chains and Pulleys

Recently I paid a visit to a big construction site.There heavy objects were lifted,adjusted,shifted etc using a multiple groved hand operated pulley.This pulley had many grooves and had lengthy chains running through it.It wasn't a usual one.Also the chain was pulled effortlessly and had to be pulled long for a small movement.How does this work??? —Preceding unsigned comment added by 117.193.129.196 (talk) 19:47, 28 July 2009 (UTC)

To start - it sounds like a Block and tackle - this explains the easy of use and long pull.

They can also be used with chains -see http://www.h-lift.com/chainblock.htm

Potentially it may have been more complicated than block and tackle - some have ratchets to stop the thing falling.83.100.250.79 (talk) 19:55, 28 July 2009 (UTC)

Also there are chain lifting gears with continuous (looped) pulling chain with gears to give mechanical advantage plus ratchets.

—Preceding unsigned comment added by 83.100.250.79 (talk) 19:56, 28 July 2009 (UTC)

It's a simple matter of mechanical advantage. If you wrap a rope or chain around a pair of pulleys so that the rope goes up and down between them several times...let's say 6 times...then for every foot you pull on the rope, you've only moved the bottom pulley one sixth of that...two inches...that's because you had to shorten all six lengths of rope equally - and one foot of rope shared out six ways is two inches off of all of them. However, when you pull on that rope with a certain amount of tension - you are effectively pulling on all six lengths of rope at once - so the pulley at the bottom moves up with the force of six times the amount of tension. You are exchanging a big, gentle movement for a small powerful one...that's called "Mechanical advantage" - and it's the same principle as using a long lever - where you move one end of the lever gently through a large distance - and the other end moves through a much smaller distance - but is able to apply proportionately more power. Similar ideas explain how the hydraulics in your car brakes allow you to apply all of that force to slow the car down using a large (but fairly gentle) push on the brake pedal.

The grooves you see in the pulleys are there to stop the rope or chain from getting tangled up as it goes around and around them - pulleys that are designed for chains also have dimples in the pulley to allow the chain links to settle into them and reduce the tendancy to slip. SteveBaker (talk) 20:11, 28 July 2009 (UTC)

Birds vs. Insects

Why have insects (specifically ones possessing flight) failed to inhabit the ecological niche of birds (and vice versa)? What limits an insect's size that doesn't constrain a bird's?

Alfonse Stompanato (talk) 21:03, 28 July 2009 (UTC)

Having an exoskeleton and inefficient lungs limits the size of insects. - Nunh-huh 21:10, 28 July 2009 (UTC)

Our Meganeura (giant prehistoric "dragonflies") article says (with references):

Controversy has prevailed as to how insects of the Carboniferous period were able to grow so large. The way oxygen is diffused through the insect's body via its tracheal breathing system puts an upper limit on body size, which prehistoric insects seem to have well exceeded. It was originally proposed (Harlé & Harlé, 1911) that Meganeura was only able to fly because the atmosphere at that time contained more oxygen than the present 20%. This theory was dismissed by fellow scientists, but has found approval more recently through further study into the relationship between gigantism and oxygen availability. If this theory is correct, these insect giants would have been perilously susceptible to falling oxygen levels and certainly could not survive in our modern atmosphere.

However, more recent research indicates that insects really do breathe, with "rapid cycles of tracheal compression and expansion". If correct, then there is no need to postulate an atmosphere with higher oxygen partial pressure.

So I think the answer is "nobody knows". Insects don't have lungs, so that certainly places some limit, but not necessarily the limit that they're at now. --Sean 21:34, 28 July 2009 (UTC)

Well in a way they have - or rather one specific species has. The Humming-bird Hawk-moth seems to occupy the same niche in England and Europe that Humming birds do in the tropics. (I can't believe we don't have an article on Humming bird hawk moths - have I given the wrong name?) --TammyMoet (talk) 08:24, 29 July 2009 (UTC)

Macroglossum stellatarum. --Cookatoo.ergo.ZooM (talk) 10:09, 29 July 2009 (UTC)

Also fixed the link to the redirect above. --Stephan Schulz (talk) 11:24, 29 July 2009 (UTC)

Thank you! --TammyMoet (talk) 12:02, 29 July 2009 (UTC)

apparent size of celestial body?

How do astronomers measure the apparent size of a celestial body from Earth? Would it be in degrees of how much of the sky it covers? Or how many millimetres the object covers if a ruler is held out at a certain distance from the observer, or etc? Is there a term for this? Is it called "apparent size" or ? --69.165.137.164 (talk) 21:43, 28 July 2009 (UTC)

Our apparent size article would be a good place to start:) DMacks (talk) 21:48, 28 July 2009 (UTC)

"Angular subtense" or "angular diameter" is a term used to describe that which you ask about. Degrees, minutes, and seconds (or decimal fractions of a degree) could describe the apparent size. Edison (talk) 18:41, 29 July 2009 (UTC)

July 29

Is this true or made-up? Thanks.

"The concept that light appears to travel faster than the speed of light to an outside observer is known as super-luminous motion....If you have a charged particle moving close to the speed of light at angle 1/gamma (where gamma is the Lorentz factor) with respect the the observer. the particle can appear to be moving faster than the speed of light in the reference frame of the observer. However, the particle isn't actually moving faster than the speed of light. The speed of light is an Absolute. This effect is also known as relativistic beaming and is common in many Active Galactic Nuclei galaxies." [35] Imagine Reason (talk) 01:37, 29 July 2009 (UTC)

Well Relativistic beaming is real - our article is pretty clear and although it only has one reference, it's a good one. However, neither our article, nor it's reference talks about things appearing to move faster than the speed of light. Weird. SteveBaker (talk) 02:29, 29 July 2009 (UTC)

The speed of light may or may not be an absolute. There is a hypothetical particle knows as the tachyon which travels at superluminal speeds.CalamusFortis 03:08, 29 July 2009 (UTC)

That comment is super misleading. There is no reason to believe that the speed of light is not absolute, and every reason to believe it is. Sure it is always a possibility that our physics is wrong, but this question is asking a specific question about our current understanding of physics. It is not asking for wild ass speculation and ungrounded bullshitting. The question also has nothing to do with tachyons. APL (talk) 04:13, 29 July 2009 (UTC)

Indeed - there is a hypothetical space craft called "the starship enterprise" which travels at superluminal speeds too...and it's just about as real as tachyons. Just because we give something like that a name - doesn't bestow any additional legitimacy upon the hypothesis! SteveBaker (talk) 22:25, 29 July 2009 (UTC)

No, no particle can "appear" to travel faster than light. It's a cornerstone in relativity that all observers can agree on the laws of nature independent of how fast they'r travelling relative to each other. No observer should therefore observe a violation of the speed limit. Here's how I think it's meant to be interpreted:

Imagine that you'r shining a flashlight on a faraway wall. You move your flashlight a little and the point of light on the wall zips sideways. If the wall was further away, the point of light would move faster along the wall. Eventually, if the wall was far enough away, the point of light would move faster than the speed of light. However, no photons in the ray of light exceed the speed limit and it's impossible to transfer information at superluminal speed using the blob of light on the wall, as noone at the wall can affect its path or any other property. EverGreg (talk) 11:05, 29 July 2009 (UTC)

yes. I'm mentioning the light-ray because I'm guessing that's the effect in the relativistic beaming, though from what BenRG is saying, I'm not so sure anymore. :-) EverGreg (talk) 17:01, 29 July 2009 (UTC)

See also Faster-than-light#FTL phenomena. There are all sorts of cases where something can be made to exceed the speed of light relative to something else. The deal is, no information can travel at greater than the speed of light, so such actions are not useful. --Jayron32 11:15, 29 July 2009 (UTC)

See Cherenkov radiation. 98.234.126.251 (talk) 07:06, 30 July 2009 (UTC)

I think that quote is referring to the following fact: suppose you're at (0,0) and an object at (D,0) is moving with velocity v = (v_x, v_y), so after a time dt it's at (D + v_x dt, v_y dt). The light from (D,0) will reach you after a time of D/c and the light from (D + v_x dt, v_y dt) will reach you after a time of, to first order, dt + (D + v_x dt) / c = D/c + (1 + v_x/c) dt. The object's angular displacement over that time, meanwhile, is Δθ ≈ (v_y/D) dt. If you (wrongly!) approximate the object's tangential velocity as distance times angular displacement divided by time then you get D [(v_y/D) dt] / [(1 + v_x/c) dt] = v_y / (1 + v_x/c), which is off by a factor of 1 / (1 + v_x/c) and can exceed c. That's not surprising since the calculation is wrong (and would be wrong even in a Newtonian universe), but for some reason astronomers think it's interesting and call it "apparent transverse velocity" or some such. This doesn't agree with the paragraph's claim that the critical angle is 1/gamma, so it may be referring to a more sophisticated wrong calculation that gets a more sophisticated wrong answer. This "effect" is discussed briefly at Faster-than-light#Astronomical observations, which cites a paper that unfortunately doesn't seem to be available online. -- BenRG (talk) 16:08, 29 July 2009 (UTC)

That explains a lot. Thanks! Imagine Reason (talk) 00:10, 31 July 2009 (UTC)

Hypothetical math! ~~ Volume of water required for "the Great Flood" in Genesis?

Genesis 7:19 ~ 21 says that even the tallest mountains in the world were underwater. So, assuming that we need enough water to submerge Mt. Everest, just how much water do we need?

Bonus points for calculating the proportion of needed water against the world's current water volume! 95.172.239.38 (talk) 04:45, 29 July 2009 (UTC)

You only need enough water to submerge the "known world" to the writers at the time. That may have been as little as submerging Mount Sinai. 71.236.26.74 (talk) 05:46, 29 July 2009 (UTC)

Mean radius of the Earth is 6371.0 km and elevation of Mount Everest is 8.848 Km.

Approximate volume of water required to submerge the Mount Everest is = volume of sphere of elevation - volume of mean radius = 4/3*(6371+8.848)^3 - 4/3*PI(6371)^3 = 4521140066 km3

From this value, subtract volume of all mountains and land above mean radius. I guess 5 % of it. That gives us 4,295,083,063 km3

There is approximately 1,360,000,000 km3 water on earth.

Three times more water is required, approximately :) - manya (talk) 06:01, 29 July 2009 (UTC)

Apparently there is an entertaining book by someone called Bernard Ramm who tried to do all the flood maths and stuff on Polar bears getting back to the North Pole. James Barr reviews it in his book "Fundamentalism" but the review is short: "much good fun can be had reading Bernard Ramm". --BozMo talk 08:48, 29 July 2009 (UTC)

We don't know how tall the moutnains were at that time, that's the problem. Mount Sinai, as noted by 76., may have been as tall as any mountain was anywhere in the world. there could have been violent movements of the earth as well during that time. (And, I thought I read somewhere where Mt. Everest was getting higher., as the one continental shelf was pushing against another.) Some Christians believe that Pangea existed before the Flood.Somebody or his brother (talk) 13:52, 29 July 2009 (UTC)

Come on folks, Mount Ararat, which is mentioned in the flood story as the first land to emerge, is way higher than Mount Sinai. (Ararat is over 5000 meters, Sinai less than 2300.) Looie496 (talk) 16:19, 29 July 2009 (UTC)

If we introduce the extreme beliefs of some Christians that the continents have moved around dramatically around in the time humans have been on Earth, and that the heights of mountains changed dramatically in that span, then the volume calculation might as well set pi equal to three, since that is the value given by Kings 7:23, where a round font was said to be ten cubits across and thirty cubits around. Edison (talk) 18:31, 29 July 2009 (UTC)

You've touched on a small hobby-horse (hobby-pony?) of mine, Edison. If the figures of ten and thirty are considered to be not precise, but rounded to the nearest whole number, they're not incompatible with the correct value of pi. 87.81.230.195 (talk) 03:01, 30 July 2009 (UTC)

Clearly God manipulated the geological record to test our faith in the Bible and decide who should be saved! (More faith=more gullible=less worthy of immortality.) --99.237.234.104 (talk) 02:37, 30 July 2009 (UTC)

Oblation

While re-reading Kim Stanley Robinson's Red Mars, I encountered the unfamiliar term "oblation:" The sun was...small and round even though it was near setting; there wasn't enough atmosphere for oblation to enlarge and flatten it. I know what he means, but in trying to read about the actual science behind it, I can only find a religious meaning with Google, including our own oblation article. Does this phenomenon have another name, and how do I read more? - Draeco (talk) 04:59, 29 July 2009 (UTC)

From the context I would guess that what he meant is that the atmospheric refraction was insufficient to make the Sun look oblate (meaning here - looking like an ellipse rather than a circle) close to the horizon because the atmosphere was too thin to perceptibly refract the sunlight. --Dr Dima (talk) 05:39, 29 July 2009 (UTC)

We have nice examples of the atmospheric refraction distorting the apparent shape of the sun disk near the horizon in the green flash article. At any rate, the proper name of the phenomenon is "atmospheric refraction" :) . By the way, I wonder if KSR was really right about Mars atmosphere being too thin to do that. It's not just density, it's the density gradient that counts. And, Mars atmosphere being colder than ours, the gradient may be not too low... --Dr Dima (talk) 05:49, 29 July 2009 (UTC)

The speaker was very near the Martian north pole at that time, if that helps justify him. - Draeco (talk) 15:45, 29 July 2009 (UTC)

this is an image of Martian sunset taken by Mars Pathfinder. The colors are real. The color variation is due both to the light scattering on the dust and to the atmospheric refraction. Note that the Sun disk looks distorted (elongated vertically). So yes, Martian atmosphere can distort the apparent shape of the Sun near the horizon. --Dr Dima (talk) 16:18, 29 July 2009 (UTC)

On the other hand, the first part of the circumstance ("enough atmosphere for oblation to enlarge... it") smacks of the moon illusion. Additionally, our article there notes that flattening occurs in the vertical, not the horizontal. As such, I expect the vertical elongation in Dr Dima's image is a lens artifact or a squashed image, not a true representation. — Lomn 18:18, 29 July 2009 (UTC)

Note: the vertical distortion of the image may also be a function of the three exposures used to create the color image. Any motion of the sun between exposures would cause apparent vertical elongation when combined. — Lomn 18:29, 29 July 2009 (UTC)

Yes, Lomn, you may certainly be right about the vertical elongation being the artifact of the several exposures used to acquire the color image. Indeed, according to jpl.nasa.gov, the imager on Mars Pathfinder used a set of filters on both of its optical channels. That means that it required several consecutive exposures to take real-color images, pausing between exposures to rotate the filter wheels. However, I do not think that the atmospheric refraction always causes a vertical flattening; not even on Earth. Indeed, there is a well known "Etruscan vase" atmospheric effect where the apparent Moon disk is dramatically distorted and elongated vertically. So, lest we -God forbid!- dare bring the Original Research into this Temple of Wiki, we should probably leave the verdict on the question of whether the Martian atmospheric refraction is strong enough as "inconclusive". --Dr Dima (talk) 19:49, 29 July 2009 (UTC)

Lomn, how could elongation of the image due to movement between colour exposures occur without causing coloured edges on the sun? Cuddlyable3 (talk) 20:13, 30 July 2009 (UTC)

Conservation of energy

Let's say we have a collision between two atoms, where energy cannot dissapear in the form of internal kinetic energy or whatnot(let's pretend that, in this particular case, a photon isn't released). What theoretical argument justifies kinetic energy being conserved(in other words, how do we know that the work done on one atom = the negative work done on the other)?

If no energy is dissipated, the collision of fully elastic, i.e. in a frame of reference moving with the barycenter, both will have the same speed after the collision (but different directions). "Negative work" does not make sense here - "work" and energy are undirected scalars. Hence the kinetic energy before and after the collision will also be the same. --Stephan Schulz (talk) 08:25, 29 July 2009 (UTC)

Stephan, the question did not specify that you had to work on the reference frame of the center of mass. Negative work makes perfect sense on a different reference frame. Dauto (talk) 12:18, 29 July 2009 (UTC)

Conservation of energy is shown to hold empirically. Any physical theory is based on a set of axioms, which have to be accepted as true (hopefully because they match experimental evidence), and the rest of the theory is derived from there. Energy conservation I think is usually taken to be an axiom, but there are equivalent ones. Conservation_of_energy#Noether.27s_theorem mentions that time translational invariance of physics implies conservation of energy. Rckrone (talk) 15:45, 29 July 2009 (UTC)

To say that the reason the total kinetic energy remains constant is because energy is conserved, followed by saying that energy is conserved because it's an elastic collision, is circular logic. My question is, why is energy conserved in such a situation? And I would like to hear an explanation other than Noether's theorem, because conservation of energy was well understood before her time. I doubt a derivation using Newton's laws would be hard, and I have a rough sketch of what it would look like in my head (the atoms slow down because of the electric force bewteen them, hence energy is stored as potential energy, which should the push the atoms away with the same work), but the details are lacking.

And I wouldn't consider conservation of energy to be an axiom (at least not in classical theory), but rather Newton's laws to be the 'axioms', because from them, conservation of momentum and the like are able to be explained.

Let me turn your question around (and maybe let you clarify what you're really asking): where do you propose happens if energy is not conserved via work/change-in-velocity during the collision? Either the energy goes "somewhere else" (not into kinetic energy in the particles--conserved, but in some other variable in the system) or it disappears entirely (not conserved at all in the whole closed system). DMacks (talk) 19:30, 29 July 2009 (UTC)

Conservation of energy is not a consequence of Newton's laws. Rckrone (talk) 20:47, 29 July 2009 (UTC)

Are you sure? The interaction bewteen two bodies is mediated by the Coloumb force, and apparently (I remember reading this somewhere) because the Coloumb force can be represented as a gradient of a potential, energy is conserved.

Newton's laws alone only give you conservation of momentum. Coulomb's law together with Newton's laws does imply that energy is conserved when the only force is the electrostatic force. In other words, the electrostatic force as defined by Coulomb's law is a conservative force. (That article also goes into how you would go about proving whether a given force is conservative.) If you had a full description of all the fundamental forces, you could prove from that the conservation of energy generally. However, I don't think there's an accurate self-consistent theory like that right now, since quantum gravity is still a problem. Rckrone (talk) 03:40, 30 July 2009 (UTC)

The article says that a conservative force is one where the work done by it on an object does not depend on the path taken, only the change in position of the object...what I don't see is how this means that, in a hypothetical collision between two atoms, kinetic energy should be conserved.

You're right, you need a few more steps to show that things work out when both objects are accelerating. If you want to assume that only the electrostatic force is in play and that the objects can be approximated by point charges, then the Two-body problem article has what you need. Specifically, the displacement r between the particles follows the equation $\mu {\ddot {\mathbf {r} }}=\mathbf {F} (\mathbf {r} )$, and the total kinetic energy in the center of mass frame can be shown to be ${\frac {1}{2}}\mu {\dot {\mathbf {r} }}^{2}$ where μ is the reduced mass, so it behaves like the case of a single particle in a stationary electric field. Rckrone (talk) 17:28, 30 July 2009 (UTC)

Trees showing the undersides of their leaves before a summer storm

When I was a lil guy, I always heard that you could tell a summer storm was coming if the trees (especially silver maples and tuliptrees) showed the undersides of their leaves. I was thinking about this yesterday when driving home from a job:

1. at one point on the highway, I noted that many of the trees had upturned leaves
2. a few miles up the road, I went through part of a storm
3. past the storm, the leaves were turned up again, then after a few more miles they weren't

...so there's at least some anectdotal evidence from yesterday's commute :-).

I'm wondering though if this really does work, and if so, why? Is it something to do with an updraft? Buildup of electrical charge before a storm? --SB_Johnny | ^talk 09:32, 29 July 2009 (UTC)

We have an article on the weather stick. The web page that article uses as a reference says that the branch is responding to relative humidity.[36] Other web pages claim that it’s barometric pressure.[37] So far, I haven’t found a really reliable source that would give a definitive answer. Red Act (talk) 12:29, 29 July 2009 (UTC)

this link (can only access Google cached version for some reason) goes to a discussion among some university professors who conjecture that it has to do with a shift in winds. this link (warning .pdf!) concurs, saying that the leaves grow according to prevailing winds, and the approach of a storm, being a non-prevailing wind, will turn them over. Some jerk on the Internet (talk) 12:45, 29 July 2009 (UTC)

The experiment reported by this web site referenced by the weather stick article does make it look like it’s the relative humidity that’s affecting the stick. However, the experiment doesn’t control for other possible changes, such as barometric pressure, so it’s not quite conclusive. Red Act (talk) 12:54, 29 July 2009 (UTC)

So I'm getting from this that the "folklore" is true (leaves turned up do indeed mean rain coming), but it's not sure how or why it happens? Is there a name for the effect? Might be nice to start an article on it if there is.

Bummer that there doesn't seem to be any non-sales-oriented material around on the weather sticks. I'll look and see if maybe they're discussed in one of the Foxfire books. --SB_Johnny | ^talk 10:06, 30 July 2009 (UTC)

Erm... has anyone noticed that the answers given so far have nothing to do with trees? A weather stick is a dead branch, that is expected to expand/contract according to humidity. But a living tree is regulating the humidity in its branches, so that it is nearly independent from short-time fluctuations (like a storm). Did you notice that many light, loose things, e.g. tends, will preferentially show their underside before and in a storm? This is mainly an effect of wind. I would think that leaves, being very lightweight, react to the increased wind heralding a storm. Come on, everyone knows that a storm is coming when the wind starts to blow stronger and in gusts. I can't see anything special in the observation that wind turns leaves. Or did you really see the leaves standig still, in an upright position? Or were they "dancing in the wind"? --TheMaster17 (talk) 08:43, 31 July 2009 (UTC)

There’s more going on than just a branch expanding and contracting according to humidity. If that were the case, then a straight-ish branch isolated from the wind wouldn’t be expected to change its shape with variations in atmospheric conditions, due to symmetry. There’s also something more going on than just leaves blowing in the wind. I believe what’s going on is an example of hydronasty, which we unfortunately don’t have an article on, although we do have an article on nastic movement in general. My guess is that in some way the bottoms of the branches are more hydrophilic, and the tops of the branches are more hydrophobic, which causes the unequal swelling to bend the branches. I think the survival advantage of evolving hydronasty in this case is a matter of taking on a branch configuration that maximizes water making it down to the roots when it’s raining, and taking on a branch configuration that maximizes exposure of the leaves or needles to the sun when it’s not raining. Unfortunately, the first 50 Google hits on “hydronasty” don’t turn up a good web page about it, instead just turning up one-sentence definitions of the word, or listing it in a list of nastic movements. Red Act (talk) 10:09, 31 July 2009 (UTC)

It was clear to me that just contraction wouldn't bend the branch, but as branches are not symmetric (they work against gravity, which is really asymmetric), this is easily explained by the distribution of different types of fibres in the dead wood. But my point was: Is there really repositioning of leaves before a storm? Is there a reference available for this behaviour, which did account for wind and indeed did measure the position of the leaves? If it is hydronasty as suggested because of air humidity, how can the tree differentiate between an upcoming thunderstorm and a "normal" humid day? And I must say that I have never observed the phenomenon described in the OP's post, and I have been camping all my life, occasionally watching trees in thunderstorms. I have never read about this in any botany book (and I have studied biology at a university, with botany as one of my major subject). And what do you mean by "maximize the water making it to the roots"? All water comes to the ground (for examples as drops that travel over the leaves, finally dropping). Only a small amount of water sticks to the leaves as they have a hydrophobic surface of waxes, and as rain does seldom fall vertically in a storm, I cannot even see how a certain position would minimise the amount of droplets that remain on the leaves (which would probably anyway be blown of by the wind in a storm, which shakes the drops of the leaves). And as a remark, most trees don't depend on the water that falls just near their stem, they have a big system of roots, either collecting deep underground or in a wide area (or both). So in summary, I'm sceptical to the existence of the described movement, and even if it exists in certain plants that I'm unfamiliar with, I'm rejecting the explanations so far on scientific grounds. I think this question is really in a need of references. --TheMaster17 (talk) 13:26, 31 July 2009 (UTC)

It’s not surprising if you haven’t observed this behavior, since it doesn't occur with most species of trees, and since it’s not a motion that occurs fast enough that you’d notice it if you were to sit there and watch a tree for a couple minutes. As to the exact nature of how this behavior works, or what the survival advantages might be, or even if it’s even a survival advantage vs. just a side effect of other effects, I don’t claim to actually know the answers, which is why I identified my hypotheses with words like “my guess is” and “I think”. But some small branches of some kinds of trees do bend considerably within a short period of time due to atmospheric conditions even when isolated from the wind, as you can see in this video.[38] Or is what you are denying that this branch would exhibit this behavior if it was still attached to the tree it came from? Red Act (talk) 15:34, 31 July 2009 (UTC)

While not a paper in an academic journal, nor a scientific study, an article entitled "The Gardner's Weatherman" in the newsletter of the Muskegon County Master Gardner Association, published in cooperation with Michigan State University Extension, discusses the phenomenon:

All the previous plants [list of plants purported to predict weather changes] show a response to increasing

humidity in the atmosphere. As you will recall from previous discussions, the relative humidity usually rises before the onset of rainy weather. Since the internal water pressure of a plant is regulated by the evaporation rate balanced against the rate of water uptake from the soil, any change in the evaporation rate will also affect the internal water pressure. It is then easy to see that when a plant cannot get rid of excess water because of high humidity, the tissues will swell and change their shape, closing flower petals, and straightening stems. When the humidity falls after a storm passes, the plant can get rid of the excess water, and the flowers return to their normal condition.

Silver maple: the silver maple shows its undersides before a rain.... Trees: when the leaves of trees curl during a south wind, it will rain.

Here, the responses are not so easily apparent. The curling of the tree leaves may be due to increased tissue water pressure as above, but it may also be due to a strengthening wind caused by the pressure gradient of a deepening low pressure system approaching the area. Silver maple leaves showing their undersides is definitely due to a wind shift away from the prevailing wind. The tree gets “used” to the wind blowing from one direction, and when the wind shifts ahead of a storm, the leaves will flip onto their

backs, showing their undersides.

Many university horticultural websites describe silver maples' leaves readily turning in even slight winds. It's how the tree gets its common name. Some jerk on the Internet (talk) 17:40, 31 July 2009 (UTC)

Chlorhexidine

Chlorhexidine is widely used in medicine and dentistry as several % solution. What is chlorhexidine itself, is it solid or liquid? What is its appearance? Renaldas Kanarskas (talk) 10:50, 29 July 2009 (UTC)

Our article on Chlorhexidine has many external links to pages at other sites, such as in the infobox. According to this one: [39] from Chemspider, the melting point is 134 Celsius, which would make this a fairly low-melting solid in native state. --Jayron32 11:08, 29 July 2009 (UTC)

It's solid at room temperature. It's "white to pale yellow" in color.[40] Red Act (talk) 11:19, 29 July 2009 (UTC)

Thank you both! Renaldas Kanarskas (talk) 19:59, 29 July 2009 (UTC)

Charging an 18V battery for a drill

Hi all, I have two questions about charging up my cordless drill:

• I have an 18V battery for my Black&Decker drill. The drill came with a plug (wall wort and 5-6 mm jack) which, if you you have the battery inserted in the drill and the plug connected to the drill, you can charge the battery. The question is: I may or may not have lost the plug. I have one that has an output of 5.0V and 2.6 A with the right size jack, but am I right in thinking that this can't be the plug, because the transformer would need to supply at least 18V to charge the battery?
• Apart from this one plug (which has to go through the drill, making it annoying), why do all my power tool batteries need to be charged with some stupid expensive shoe like this or this? Why can't they just have a jack that lets them plug into the wall? Are they just trying to make me spend more money?

Thanks! — Sam 76.24.222.22 (talk) 12:25, 29 July 2009 (UTC)

I am not an electronics expert but I would have expected a much more powerful charger, I think that charger would take a long time to charge a battery of even only a few AH. As for the charging stations, the intention is to have 2 batteries, one on charge with the other in the tool for constant usage. 81.144.241.243 (talk) 13:01, 29 July 2009 (UTC)

See if it's not on this page [41]. If not you'll probably have to do a 2 step process here [42] First enter the model number of your cordless drill in the "need a manual" window (unless you are more organized than most and actually still have that) That will tell you what they call the wall wart/battery charger/power adapter /etc. and if you are lucky also a part no. Enter either the part no. or the description in the search window on top of the page (underneath the DeWalt logo). If that doesn't get you anywhere call their customer service [43] (USA 1-888-678-7278). Good luck. 71.236.26.74 (talk) 14:03, 29 July 2009 (UTC)

There does not appear to be standardization of voltage and plugs. The wall wart you have with a 5 volt output would not be able to recharge your 18 volt battery. It is a good practice to get a white paint marker, and write on each adapter what device it works with, because eventually they are bound to get separated. The adapters often just have the name of a factory in China on them and not the brand or model of device they are supposed to power or charge. Edison (talk)

High performance batteries and their chargers have specific voltage/current characteristic and charging time. They are designed together as a system and the manufacturer has to accept liability of overheating, explosion, chemical leakage or damage. This means it is to your advantage to have the charger and battery that the supplier guarantees for use together. It is inconceivable that any honourable company could dream of making a profit from your purchase. Cuddlyable3 (talk) 16:13, 29 July 2009 (UTC)

A "shoe" to hold the drill can be attached to the wall, and it harder to lose than wall warts. Many tools also have removable batteries, so one can be charged while the other is in use. I've even seen a boxed set of power tools that were cheaper because they shared the one battery pack. The "shoe" style connectors may also be stronger in some way than the tiny plugs on wall warts (something to do with resistance in the wires? all I know about electricity is to keep my fingers off it). - KoolerStill (talk) 09:24, 30 July 2009 (UTC)

Calcium Chloride in Damprid?

Is the calcium chloride in Damprid really just regular ole table salt that I can buy in the grocery store? If so, wouldn't it be cheaper for me to buy a bag of salt instead spending a lot of money buying the refills? --Reticuli88 (talk) 13:18, 29 July 2009 (UTC)

Sodium Chloride is "just regular ole table salt", more or less, but no that's not Calcium Chloride (which is nastier). On damp removers the reusable ones are Silica based but have lower capacity. There may be cheaper places to buy Calcium Chloride--BozMo talk 13:26, 29 July 2009 (UTC)

I think you can buy CaCl2 at a hardware store in large bags for use as ice melter. Coolotter88 (talk) 13:36, 29 July 2009 (UTC)

Bunsen Burners and Gas stoves

This has been puzzling me for long.Consider that you are lighting a gas stove or bunsen burner.When you light it,the gas gets ignited and undergoes combustion and hence it burns.The burning process takes place only outside the outlet.What is the mechanism that prevents the fire from spreading inside along the tube and into the gas cylinder and the final KABOOOOOM ???gdsrinivas 13:35, 29 July 2009 (UTC) —Preceding unsigned comment added by Gd iitm (talk • contribs)

probably because the gas pressure inside the pipe is higher than outside so the flames are blown outwards. also, there is no oxygen in the pipe to support combustion so the gas will extinguish any flame that manages to make it inside. Coolotter88 (talk) 13:38, 29 July 2009 (UTC)

In a bunsen burner,there is a hole at the bottom for mixing of air and gas.So it is a mixture of air and gas along the entire length of the bunsen burner.Now how do you explain it??gdsrinivas 13:43, 29 July 2009 (UTC) —Preceding unsigned comment added by Gd iitm (talk • contribs)

"Back burning" can occur in a bunsen burner. No flame shows and it smells bad. I think it can be provoked by throttling back the gas supply. It can be corrected by thumping the rubber supply pipe. Cuddlyable3 (talk) 13:48, 29 July 2009 (UTC)

yeah, probably the gas pressure pushes the flame outwards. When you light the bunsen burner, it's like a jet. Coolotter88 (talk) 13:52, 29 July 2009 (UTC)

There are two features here. Even in a tube of perfectly mixed methane and air, the speed at which a flame propagates into the mixture (the Flame speed) is limited (by memory about 5 cm a second I think) so if the flow speed exceeds this the flame will be being blown away not traveling down the tube. The flame only stays put on a bunsen burner because the double burner edge creates a recirculating eddy: try to light a straight tube of premixed air and you will fail. Gas stoves have similar design features. The second feature to stop this inadvertently happening at low nozzle speed is a Flame trap which is made of wound up nit-mesh: the flame cannot penetrate it because the heat loss to the metal fibres quenches the flame. However do not be fooled into thinking the gas emerges completely premixed; close inspection reveals a rich premixed inner flame (blue, the characteristic colour of Carbon Monoxide flames) and a CO rich diffusion flame outside it. Clever chap Bunsen. --BozMo talk 13:57, 29 July 2009 (UTC)

Your description of Back burning would indicate a cheap version of a Bunsen with no flame trap I guess. --BozMo talk 14:00, 29 July 2009 (UTC)

Or an old one! Most Bunsens don't easily do back burning anyway, but they certainly did when run on coal gas, as I remember well, when I started work. Not that we have Bunsen burners in the lab any more (sigh)  Ronhjones  ^(Talk) 19:14, 30 July 2009 (UTC)

Thats a nice question.But when I asked one of my friends he said it was one of the important concepts in fluid dynamics.Any info based on this???thanks117.193.144.206 (talk) 16:29, 29 July 2009 (UTC)

As an add on to the question why does the flame occur only exactly at the top of the bunsen burner opening???Why not it occur a few centimetres above the bunsen tube or a few centimetres inside the tube???117.193.144.206 (talk) 16:36, 29 July 2009 (UTC)

BozMo please explain this :The flame only stays put on a bunsen burner because the double burner edge creates a recirculating eddy.117.193.144.206 (talk) 16:38, 29 July 2009 (UTC)

I am not very good at explaining things. Flames are just reaction fronts which eat into flammable gas mixtures. To ignite the gas coming rapidly out of a pipe end you need an ignition source where the gas comes out (or with very fast turbulent flow ignition further downstream). Otherwise the flame will blow itself out. For a burner this could be a pilot light by the pipe end but if you can induce an eddy by the pipe end (a recirculating piece of flow) then the gas which is already burning keeps the flame going by reintroducing a piece of flame into the flow. This is the purpose of the double skin on a Bunsen. Unfortunately the Wikipedia article on Bunsen burners is not very good apparently because there isn't a very good reliable source on Bunsen's. However I have written a few peer reviewed papers on gas combustion [44] [45] and I do have some idea what I am talking about. --BozMo talk 19:42, 29 July 2009 (UTC)

If you understand flow dynamics I should add that a stagnation point is sometimes sufficient but not as stable and that just having a thick tube wall works at some flow rates. However if you get a pair of pliers and squeeze the two walls of a Bunsen together (so that you just have a circular pipe end) the flame will blow itself out. --BozMo talk 19:50, 29 July 2009 (UTC)

A really cool fact I heard which I think is relevant here, if you were in a pure methane atmosphere and had a burner connected to a bottle of oxygen, it would essentially behave the same way as the other way around here on earth. Vespine (talk) 05:03, 30 July 2009 (UTC)

Assuming the gas is leaving the 'tube' at room temperature, it has to be heated by the existing flame until it reaches 'flash point' or ignition temperature. For propane, that's 920-1020°F. While that's happening, the gas keeps moving. Twang (talk) 06:19, 30 July 2009 (UTC)

Yes, good way to look at it although technically ignition by gas inside a premixed cloud is not just by heat, but by a combination of heat and a load of free radicals from the ongoing combustion process (the radicals diffuse forward just as the heat does), which makes the temperature needed a little lower. --BozMo talk 06:45, 30 July 2009 (UTC)

Hey guys this question hasnt yet been answered..thought you didnt notice this " Thats a nice question.But when I asked one of my friends he said it was one of the important concepts in fluid dynamics.Any info based on this???As an add on to the question why does the flame occur only exactly at the top of the bunsen burner opening???Why not it occur a few centimetres above the bunsen tube or a few centimetres inside the tube???" —Preceding unsigned comment added by 117.193.137.0 (talk) 07:03, 30 July 2009 (UTC)

I think that the flame don't occur in the tube cause the gas flow blows it out of the tube faster than the flame front travels back into the tube (as BozMo said earlier). As for it not occurring above the tube, that's because the flow pattern recirculates part of the burning gas-air mixture back to the burner opening, so it ignites the rest of the mixture just as it comes out of the tube. FWiW 98.234.126.251 (talk) 07:20, 30 July 2009 (UTC)

By adjusting the fuel flow and air-holes, one can usually get the flame to partially "detach" from the rim of a bunsen burner, or even entirely "lift off" of it. If you have supplies higher than what the burner is designed to handle (perhaps mis-adjusted regulator or flow valve, or using a pressurized-air or oxygen source on a burner designed for simple air-holes), you can easily cause the flame to "blow out". Googling "bunsen burner" along with any of the other quoted terms I used can get you some fluid-dynamics and other studies related to these phenomena (and conversely, the conditions required for a stable flame). DMacks (talk) 07:27, 30 July 2009 (UTC)

Sorry I should add a strong warning not to try using pressurized oxygen as a source unless you really know what you are doing, he means a pressurized air source: changing to an oxygen cylinder or other oxygen increases the flame speed considerably and you may get something nasty happening (including conceivably gas detonation). As for the rest, I thought it was all answered. It is all determined by flow. Flow does tend to recirculate but not steadily and not necessarily at the right speed. A stable flame requires a stable re-feeding of burning gas into unburnt gas. The rest is all said...--BozMo talk 08:04, 30 July 2009 (UTC)

Concur on the safety issue. The ideas of flame detachment, burn-back, etc aren't limited to bunsen burners and others that use a simple inspirator/venturi-tube to get the oxidant. The same questions (and flame stability issues) apply to torches with compressed oxidant feeds (and are rated to handle them!). The oxidizer and fuel gases mix and then flow through a few inches of pipe before the tip where the flame is. DMacks (talk) 16:15, 30 July 2009 (UTC)

Volume to pressure ratio?

How can I know the volume of a gas, knowing the capacity of its container (50 L), the amount of moles (64,48) and the pressure (1,621,200 Pa), but not knowing the temperature? Thank you. --83.56.187.237 (talk) 19:58, 29 July 2009 (UTC)

You just defined the volume as 50 L. Temperature is the unknown, as you surmised, and can be calculated easily (assuming an ideal gas). — Lomn 20:02, 29 July 2009 (UTC)

Thank you, what a blunder! Therefore, what should I substitute for $R$ in the following state equation in order to determine the temperature?

$1,621,200\cdot 50=64,48\cdot R\cdot T\,\!$

--83.56.187.237 (talk) 20:20, 29 July 2009 (UTC)

R is the gas constant. Just make sure you use the right value for the units you're using. Rckrone (talk) 20:26, 29 July 2009 (UTC)

Precisely. I'm probably stupid, but I don't know which is the right value I should use. --83.56.187.237 (talk) 21:04, 29 July 2009 (UTC)

Well I'm not going to do your homework but you need to select the gas constant from the list that uses the same units as your problem. The closest one is in m3 Pa K−1 mol−1. Since you have your volume in L instead of cubic meters, you need to convert that 50L into cubic meters. Then you can use the R constant from the list at the article and it will work (because it's all in consistent units). TastyCakes (talk) 21:16, 29 July 2009 (UTC)

First I would recommend leaving the units in your equation. That makes everything much easier. It's not important that you choose R so that all the units cancel out right away. You can use unit conversion where necessary to get things into the form you need. So for example if you choose R = 8.314 472 m³ Pa K⁻¹ mol^-1, you'll be left with L on one side of the equation and m³ on the other, but we know that m³ = 1000 L. Any of the values for R on that page will work, but some will just require more unit conversions than others. Rckrone (talk) 21:44, 29 July 2009 (UTC)

Damps in coal mines

Reading Firedamp, I'm curious — using current technology, would it be possible/likely for coal mining companies to collect these gasses in mines and sell them for fuel? Nyttend (talk) 20:10, 29 July 2009 (UTC)

See Coalbed methane. That seems to be the general idea there. Rckrone (talk) 20:38, 29 July 2009 (UTC)

(EC)The concentration of methane in a coal mine might vary significantly over time and might be too low to run an internal combustion engine, but methane recovered from landfills also varies. Firedamp does not say what the methane concentration is as commonly found. It might be higher in rooms of abandoned mines than in working mines, so some mines might work better than others as possible sources. See Biogas. The solution with gas from landfills is to mix it with sufficient natural gas to properly run an engine such as a modified diesel to generate electricity, if the concentration is too low. The mix can be automatically adjusted as the concentration varies. Edison (talk) 20:40, 29 July 2009 (UTC)

Flufenamic acid

Our article on flufenamic acid, or fenamic acids in general, lists them as NSAIDs. However, I am not at all sure they inhibit COX. Do they? What flufenamic acid actually does is to block the Calcium-sensitive nonselective cationic current in neurons. What does that have to do with the anti-inflammatory action?! Any input is welcome. Thanks in advance, --Dr Dima (talk) 20:31, 29 July 2009 (UTC)

A Google Scholar for "flufenamic acid NSAIDs" gets a bunch of hits, including PMID 10866999 which seems to be relevant. Looie496 (talk) 23:06, 29 July 2009 (UTC)

Thanks Looie. So it does affect both COX expression and COX activity (as well as cation currents, Ca ion balance, and who knows what else...). It figures. Thanks. --Dr Dima (talk) 23:37, 29 July 2009 (UTC)

Dragons of Eden updates

Has Carl Sagan's The Dragons of Eden ever been updated since it was first published in 1977? NeonMerlin 21:02, 29 July 2009 (UTC)

It doesn't look like it. There was a paperback edition published in April of 1978 and a 'mass market' paperback in 1986 - but from what I can see of them in Google books and Amazon - they contain the same text as the 1977 version. Neither of them say anything about being revised - and there is only one author's copyright date. SteveBaker (talk) 21:31, 29 July 2009 (UTC)

Too bad - it's a great book, even though it's over 30 years old. — QuantumEleven 14:48, 30 July 2009 (UTC)

Eurasian plate

is Eurasian plate (western part) moving north or it is moving south in altitude. Eurasian is a large plate. The east plate is China, Japan, Phillipines, surrounding by Yellow Sea. Part of east half of Eurasian plate is moving southeast. Africa is suppose to collide with Europe, closing all the oceans nearby.--69.228.145.50 (talk) 21:19, 29 July 2009 (UTC)

I don't know if this source is valid. The Future Is Wild said Australia is moving north only, no showing of it moving south again. i'm confuse if Europe will be moivng north or south.--69.228.145.50 (talk) 21:07, 30 July 2009 (UTC)

I have watch The Future Is Wild in my classroom once, this is why I don't think Australia will ever move south again. This would help if you give me some suggestions.--69.228.145.50 (talk) 21:10, 30 July 2009 (UTC)

Help idenfying the following yard plants

The first is some kind of berry bush that has some kind of little (Chinese) red jack-o-lantern type fruit.

The second is uncut and thinned out (crab?) grass that when watered every day and cut every week grows very dense to make a lawn.

The third has fronds with very thin and tough stems.

All three are located in coastal mid Florida but no one here can identify the first two without the berries and the watered and cut grass roots.

No one here has a guess what the third one is either except that it might also be native to China. -- Taxa (talk) 23:21, 29 July 2009 (UTC)

For number 2, it looks like good-old, garden-variety fescue. It doesn't look like crabgrass, which is more "stalky" than "leafy". Most other lawn grasses in the southern U.S. are low-creeping grasses which don't grow bushy like this; such as Centipede grass, Bermuda grass, St. Augustine grass. I'm not sure which fescue variety it is, but based on your description and location, unless you are watering the heck out of it, it's probably not tall fescue which goes dormant during the dry summer months, but I would not rule that out. A few good thunderstorms and my tall fescue springs back to life. --Jayron32 04:45, 30 July 2009 (UTC)

You don't show the #1's fruit, but could it be Euonymus americanus aka "Hearts-a-bustin" aka "Strawberry bush" (not a real strawberry)? The give away would be the distinctive fruit, which look better in this google search, and the green stems. --Jayron32 04:50, 30 July 2009 (UTC)

Thanks for taking a shot... The grass has a seed bearing stalk that is about knee to waist high with only two branches like a sling shot. The fruit is completely round with a very sour taste unless you get one that's just dropped or is about to drop. They are kind of like little pumpkins only red and with soft skin and innards (when ripe). The ribs are much more pronounced than a pumpkin's. -- Taxa (talk) 06:41, 30 July 2009 (UTC)

Well, I guess I was wrong about the first one being hearts-a-bustin, but #2 still sounds like a fescue variety, of which there are hundreds. Fescue puts out small seeds on knee-high stalks with 2-3 branches lined with the seeds. I'm still going with fescue there. --Jayron32 18:27, 30 July 2009 (UTC)

The third one looks like Cyperus alternifolius.--Shantavira|^{feed me} 08:09, 30 July 2009 (UTC)

The third plant is a sort of Lady Palm, likely in the genus Rhapis.CalamusFortis 22:47, 31 July 2009 (UTC)

Drugs to make me smart

Can I get drugs to make me more intelligent to pass my exams? —Preceding unsigned comment added by 79.75.104.10 (talk) 23:31, 29 July 2009 (UTC)

Not really, no. There are many nootropic drugs, of various legal status, but none of them will really make a difference if you haven't studied for the exams. --Dr Dima (talk) 23:47, 29 July 2009 (UTC)

Sure they can. Try caffeine, preferably as coffee, which will also prevent dehydration. —Preceding unsigned comment added by 84.187.91.197 (talk • contribs) 00:12, 30 July 2009

I'm not sure if the OP is expecting to become somehow become more knowledgeable after eating the drug, as in the case where he/she doesn't study. Rather, I think the question is whether there are any drugs which will make your brain more active and sharper for a limited period of time, much like a steroid does to the body. Such a drug would be highly useful in a competitive exam, where speed and accuracy are essentially more important than knowledge. So I'm interested in knowing some answers, too. Rkr1991 ^{(Wanna chat?)} 00:59, 30 July 2009 (UTC)

There definitely are such drugs, amphetamine is the most widely used. Unfortunately it is illegal and highly addictive. Looie496 (talk) 01:21, 30 July 2009 (UTC)

In my experience, smart drugs seem to make me just smart enough to realise they're not having any effect. Adambrowne666 (talk) 01:38, 30 July 2009 (UTC)

If such drugs existed, were legal, and could be sold without a prescription - you can be 100% sure that you'd know it because you'd be bombarded with adverts for them every time you turned on the TV. Instead, the best we get are exceedingly dubious "food supplements" that can claim just about anything without any proof whatsoever because they fall through a convenient loophole in the law. I agree that caffeine is really the only one with any kind of a legitimate track record. It doesn't make you more intelligent though - it just ensures that you're awake. But even then, you have to be quite careful because if you take too much of the stuff, you'll become super-nervous and jittery - and that's just as bad as being half asleep! IN terms of not-legal-without-a-prescription, I've heard that some people take beta blockers because (as our article says) "Beta blockers protect against social anxiety: Improvement of physical symptoms has been demonstrated with beta-blockers such as propranolol; however, these effects are limited to the social anxiety experienced in performance situations. (example: an inexperienced symphony soloist)" - which can leave a person with exam anxiety feeling calm and relaxed. Not more intelligent - but perhaps calm enough to be able to better use the intelligence you already have. But these things can be dangerous - and taking them without a doctor's advice would be pretty amazingly stupid. SteveBaker (talk) 03:57, 30 July 2009 (UTC)

During the past 5 years or so there has been a large upsurge in the number of "smart drugs" that are sold in schools. The studies I have seen on these drugs say they range from ineffective to ineffective and dangerous. Even caffeine has debated impact on grades. While it would help you stay up the night before to study and help you stay aware during the exam itself, it lacks the ability to give you the mental agility provided by a good nights sleep. Using caffeine to stay up will not help with any exam that takes abstract thought, though could help with other types of exams. Anythingapplied (talk) 04:11, 30 July 2009 (UTC)

:::Polyjuice and then Steve could sit the exam for you (assuming he is cleverer than you for which no warranty is available under the Wikipedia Disclaimer). --BozMo talk 07:42, 30 July 2009 (UTC)

Would Modafinil help me be smarter in class and in my exams? —Preceding unsigned comment added by 79.75.68.48 (talk) 00:10, 31 July 2009 (UTC)

It might help a little if you've been crammin' all night long or if you've recently been sick with the swine flu (or if you're so high on crack that you can't think properly), but other than that, prob'ly not. It can also have some pretty bad side effects if you take it without a prescription. FWiW 98.234.126.251 (talk) 05:11, 31 July 2009 (UTC)

July 30

New word phenomenon?

A few months back, I stumbled upon a wikipedia article that explained a phenomenon about when people learn new words (i.e. 'perfunctory') and over the course of the next few days, they see that word more often (i.e. in a book, a newspaper article, billboard on the highway.) What is this effect or phenomenon called? 24.148.59.37 (talk) 02:32, 30 July 2009 (UTC)

It sounds like a form of confirmation bias. Or at least related to it. --Jayron32 04:33, 30 July 2009 (UTC)

It's called Baader-Meinhof phenomenon. --Gwern (contribs) 09:57 30 July 2009 (GMT)

It's not just with new words, either. I remember when I was a kid, when my dad got a new car, suddenly the streets seemed to be full of the same model. It might not even be a cognitive bias, it could just be that since the word is new, it is forefront in your consciousness and seeing it easily reminds you that you just learned it. Over time it falls back to the "just another word" status of everything else in your vocabulary, and seeing it does not trigger the "hey that's that new word" thought. Maelin (Talk | Contribs) 04:39, 30 July 2009 (UTC)

Arnold Zwicky, who blogs at Language Log, has coined (or at least promoted) the term "frequency illusion", which I think is pretty good.--Rallette (talk) 05:19, 30 July 2009 (UTC)

Novel information is kept briefly in short-term memory where it is readily revitalised by chance repetition, then it fades into long-term memory where a trivial recognition is a mundane event. Cuddlyable3 (talk) 19:27, 30 July 2009 (UTC)

Attention is affected by the demand characteristics of the situation. Someone in a book (Sorry, don't recall the author) wrote that he had promised to get a helicopter for the arrival of someone at a charitable event. Thereafter, he seemed to see helicopters wherever he went: arriving, departing, or being transported on a truck. The "Ziegarnik Effect " which I only half remember, comes to mind. A waiter remembers an order in detail, but only until it is served at the table. If you are told that Mr. Colvin will be your new boss, then you seem to hear the name Colvin several times a day. It becomes salient in a way it was not previously. There may be a lexical priming effect, which makes any occurrence of a salient word very noticeable. Edison (talk) 02:01, 31 July 2009 (UTC)

Spider identification

Is this spider found in mid-Missouri an orb spider? Just wondering if I should shoo it off the porch or invite it to stay a while. -- kainaw™ 02:37, 30 July 2009 (UTC)

Yeah, looks like an orb-weaver alright. With these guys, no matter what you do they'll still have your porch for themselves :) . Usually, they would spin a new web every day, you know. --Dr Dima (talk) 05:38, 30 July 2009 (UTC)

Mortality rate relating to refusing blood and/or medical procedure on religious grounds?

I imagine there would be such a statistic but I'm struggling to find it as it's a bit specific. How many people die as a result of refusing to be given blood in a medical emergency for religious reasons? Specifically when doctors believe there was a reasonable chance that blood would have saved them. But less specific any statistic regarding refusal of medical procedure would be helpful. This is not homework or medical advice. Vespine (talk) 04:51, 30 July 2009 (UTC)

A Wikipedia article cites from the May 22, 1994 issue of the Jehovah's Witness magazine Awake, p. 2: "In former times thousands of youths died for putting God first. They are still doing it, only today the drama is played out in hospitals and courtrooms, with blood transfusions the issue." The statistic you seek is unlikely to be given by a reliable medical source because of the legal, technical and ethical issues of the controversy. Cuddlyable3 (talk) 19:16, 30 July 2009 (UTC)

This article is helpful. "Although there are no officially published statistics, it is estimated that about 1,000 Jehovah Witnesses die each year through abstaining from blood transfusions". Axl ¤ [Talk] 20:03, 30 July 2009 (UTC)

Did human muscles mutate to become weaker than those of apes and other animals?

I read recently that human muscles are intrinsically much weaker than those of a chimp, one of whom would have no problem in overpowering a human. The idea was that a mutation during the evolution of humans made such a mutation beneficial, which sounds very odd. But then I thought that perhaps the weaker musculature allows for finer motor control. Apes are great at swinging and leaping around trees, but could they do ballet moves, or juggle balls, or handwrite? And when the technology becomes sophisticated enough, could we opt to reinstitute the more powerful muscle variants, and breed humans who make Arnie look like a wimp. Myles325a (talk) 06:57, 30 July 2009 (UTC)

I think it is natural that we are much weaker than Apes or Chimps, because our survival is not dependent on our strength. This means we naturally get more and more weaker with time due to cross breeding, as weak people survive almost just as well as strong people, much like how that recent study which told women are getting more beautiful over time... With all the medicines available, I think I can safely say that we humans will get more and more weaker over time. Our parts evolve according to our needs, and hence we have hands which can write rather than swing trees with. I'm pretty sure some research is going on in the area to use technology to make us physically stronger, along with scientific research about genes, but I'll leave that bit for others... Rkr1991 ^{(Wanna chat?)} 07:08, 30 July 2009 (UTC)

OP Myles back. I don't know about "get more weaker and weaker", but our grammar appears to be getting worser and worser. Also, the last ape I saw swinging trees was King Kong. Myles325a (talk) 23:58, 30 July 2009 (UTC)

It may be an adaptation for Persistence hunting, very few animals do that and extra muscle would use up a lot of energy. Dmcq (talk) 08:35, 30 July 2009 (UTC)

"[E]volutionary biologist Alan Walker, a professor at Penn State University" came up the the same hypothesis about fine muscle control[46], with the difference being more motor neurons in the spinal cord in humans. AlmostReadytoFly (talk) 08:55, 30 July 2009 (UTC)

A hypothesis that I doubt. Any inhibition would be to stop us hurting our joints I'd have thought. Which is part of the same overall business about why are we being weaker. Anyway he can go ahead and try testing it - that's always good and might turn up something. Dmcq (talk) 10:12, 30 July 2009 (UTC)

Rkr1991,you have told that animal organs evolve according to their needs.It is not so.It is like this- some individuals of the same species develop some mutations which give them a upper hand in survival and competition among the individuals of the same species.They survive better than the other members and the their traits are passed down to their offsprings.Thus we observe evolution.Infact Lamarck also told "organs evolve according to their needs"(the giraffe neck stuff) but was clearly disproven by weismann's 21 time rat's tail cutting experiment.gdsrinivas 15:45, 30 July 2009 (UTC) —Preceding unsigned comment added by Gd iitm (talk • contribs)

OP Myles back. As a Jew, Weismann need not have not have cut off rat's tails. He need only have noted that 3000 years of circumcising Jewish boys has not led to males being born already cut. Myles325a (talk) 23:58, 30 July 2009 (UTC)

(At gdsrinivas) How is the cutting of a rat's tail beneficial for it, to be passed on ? And according to your argument, how exactly did humans develop hands which could write rather than those like the apes' or the chimps' ? Surely, a mutation of this sort wouldn't have helped better in their survival, at the time they were living in caves ? Please explain this. Rkr1991 ^{(Wanna chat?)} 07:44, 31 July 2009 (UTC)

As an argument against the extra nerves and control idea have a look at Elephant#Trunk. Lots of nerves don't make them weak. Dmcq (talk) 07:53, 31 July 2009 (UTC)

Eating packing peanuts

Someone on IRC brought up the subject of the om-nom-nommable packing peanuts (fex the starch ones) last night. Now I wouldn't exactly go nomming these as sustenance, but if you were starving to death would these do anything for you? And are they made of pure starch, or is there some sort of additive/filler? One time I was incredibly hungry/bored and ate about six, I didn't get sick or anything, but is this even remotely a good idea? ZS 08:03, 30 July 2009 (UTC)

I was once told they're Cheesy Wotsits without the flavouring and colouring! --TammyMoet (talk) 08:40, 30 July 2009 (UTC)

I seem to recall a previous discussion here on this, but can't be bothered looking in the archives. Anyway, the result I recall was that they are likely to contain rodenticides, insecticides or repellants to prevent them being omnomnommed by bugs or rodents in transit. As a rule, don't eat stuff that isn't food. --203.202.43.54 (talk) 08:58, 30 July 2009 (UTC)

According to this manufacturer's site [47] the starch peanuts won't attract bugs or rodents because "the sugars and any food value" has been removed in processing. Since "any food value" is a rather vague term it makes that source a lot less reliable. Researchers found in this study [48] that bacteria don't grow quite as well in it. Most sources say starch packing peanuts dissolve in water. Except in Raleigh they didn't [49]. Your saliva contains Amylase which, if the experiment suggested here [50] works converts the starch in the peanuts to sugar. This patent for making them [51] mentions on page 4, line 23 that manufacturers may use additives in starch packing peanuts. This patent identifies such additives as dyes, processing aids and anti static products [52] Given that ordinary foodstuff also sometimes contains questionable ingredients you may be o.k. to nibble some packaging occasionally. You can't sue the manufacturer if this turns out to be overly optimistic, though. (Definitely don't eat any pink ones. Those are the ones with antistatic additives.) Gwen may be happy to learn that at least one source on the web [53] thought they were safe for ferrets if they didn't eat too many.:-) 71.236.26.74 (talk) 19:37, 30 July 2009 (UTC)

There are people who consider it their moral duty to eat these peanuts when they're done with them. See [54]. I have no idea how serious these people are. Dcoetzee 04:08, 31 July 2009 (UTC)

Are there really 32 AA batteries hidden inside a 6V lantern battery?

See this youtube video. Is this truth or hoax? There are a few more vids on Youtube of people opening up lantern batteries, finding something completely different inside and claiming that the AA batteries claim is a hoax. But there are loads of different brands of lantern battery on the market, so could it be that batteries made by different companies have different contents? --84.70.227.184 (talk) 09:50, 30 July 2009 (UTC)

Snopes says it's a hoax, which is a good start. There's a pretty obvious cut in the video just before the contents are visible, suggesting the small batteries were added then. AndrewWTaylor (talk) 11:04, 30 July 2009 (UTC)

Usually there are four F cells inside. F cells are like D cells except an inch or so longer. Some brands just have four D cells plus some empty space. There are holders you can get that let you use your own D cells, which is cheaper. 70.90.174.101 (talk) 11:07, 30 July 2009 (UTC)

FWIW, an A23 battery can be peeled open to reveal 8 usable 1.5V button cells. Also, some 9V (i.e. 'square') batteries contain six AAAA batteries. Any others that people know of? --Kurt Shaped Box (talk) 12:04, 30 July 2009 (UTC)

32 AA batteries would be 48V not 6V. It would be horribly inefficient to make 6v batteries this way -- Mad031683 (talk) 18:26, 30 July 2009 (UTC)

Not necessarily. It depends on the way they are connected. Kotiwalo (talk) 18:28, 30 July 2009 (UTC)

The battery in the hoax video above is a “Heavy Duty Powercell”, which is sold by Walgreen’s. In this video, you can see the exact same brand of 6V battery, opened up to show the 4 F cells inside. Note that the hoax video contains “cuts”, which makes it easy for the hoax producers to remove the real contents of the battery, and replace it with the 32 AA cells. In contrast, the real video shows the entire disassembly process, with no cuts. Also, in the hoax video, you can see that the top of the battery does not contain any metallic contacts that the top layer of AA batteries would make contact with, so those batteries can’t be a part of a real circuit. Red Act (talk) 18:41, 30 July 2009 (UTC)

The thing is that an individual 'cell' can only produce 1.5 volts. So to make a 6v or 12v battery - you need 4 or 8 cells wired in series. If you want higher capacity (more amp-hours), then it makes more sense to use bigger cells than to wire a bunch of little cells in parallel. Also, there is a problem with wiring 'dry cell' batteries in parallel: Because the manufacturing tolerences of these individual cells aren't precise, it's likely that some of the cells will start to run down before the others. When the voltage drops on one cell that's wired in parallel with another - there is a net voltage difference that will cause current to flow from the cell that still has power into the one that's failing. Since these are not rechargeable, that current has to go someplace - and what it does is to turn into heat. Net result is that if you tried to make a LARGE 6v battery from 32 AA's, you'd need four sets of 8 cells - with each group wired in parallel and the four groups hooked up in series to get up to 6 volts. Then as one cell started to run down, all seven of the other AA's would start to drive current into it and that one weaker cell would overheat very rapidly - and probably even explode. This is NOT a good thing! Hence, they don't do that. Using 4 F-cells works fine because all four can be wired in series to get up to 6volts without any need to wire them in parallel. SteveBaker (talk) 00:47, 31 July 2009 (UTC)

I agree with Steve. 1.5 volt cells in parallel is asking for trouble. Make your cells large enough for the current demand, then place enough in series for the voltage requirement. Then there will be no current out of each cell when the external circuit is open. Edison (talk) 01:52, 31 July 2009 (UTC)

Waking up on falling

So I've noticed that when I take a ferret out of its cage when it is sound asleep, and I carry it around or breath on its nose, it takes a good half minute or so before they're really awake - which is reasonable enough. But if I were to take the same ferret and toss it in the air and catch it, it seems to wake up instantly halfway up.

Which makes me wonder: would the same thing happen for a human who is suddenly falling? If it would, then perhaps the best alarm clock would be a bed hoisted by ropes, which fell at the set time! Is this the passing vagary of a demented mind, or a possibly cool project to try out sometime? --Gwern (contribs) 09:55 30 July 2009 (GMT)

I'm glad I'm not one of your ferrets. Don't toss them in the air to wake them. That's not nice. Theresa Knott | token threats 10:36, 30 July 2009 (UTC)

A lesson is learned but the damage is irreversible! But seriously, now that I know this about ferrets I rather want to know about humans as well. --Gwern (contribs) 10:55 30 July 2009 (GMT)

Finding that your house is on fire will also wake you up immediately. Or seeing your bed surrounded by gunmen. Or getting thrown into a pool. Lova Falk (talk) 10:56, 30 July 2009 (UTC)

Sure, but all three of those are a bit hard to arrange cheaply & easy, and one might get used to the gunmen. Falling could probably be arranged with some rope and tinkering, and I don't think one would easily get used to it. --Gwern (contribs) 11:02 30 July 2009 (GMT)

It must be possible to get used to falling. Astronauts experience a constant sensation of falling, but they're able to sleep with no problem. APL (talk) 13:15, 30 July 2009 (UTC)

That's true, but they are "falling" even as they are falling (sorry) asleep, so it doesn't wake them up. A sudden fall I would think would be hard to get used to, since you have been stationary for some time before the bed drops you. —Akrabbim^talk 16:43, 30 July 2009 (UTC)

That's a good point; they may not sleep well, but they do sleep. But I doubt you could get used just by a few seconds a day - otherwise rollercoaster fans would quickly be bored by any free fall! --Gwern (contribs) 16:55 30 July 2009 (GMT)

Of course, it would probably vary by the person, and how routinely tired they are when waking up. I have accidentally trained myself to reflexively turn off a very obnoxious alarm clock without ever waking up. Now I use my cell-phone alarm across the room that forces me to get out of bed to turn it off. For me, falling would probably wake me up, but I would very easily fall back to sleep considering I would still be comfortably in bed after the fall. After falling asleep again a few times, I think it would get to the point where I would just not wake up, like with my first alarm.

That is just me, so it would probably work pretty well who don't have trouble getting out of bed but don't get woken up by just a loud noise. —Akrabbim^talk 17:15, 30 July 2009 (UTC)

What would get both you and your ferrets going would probably be a Fight-or-flight response and the adrenaline that is released in the process. If one could really train one's body to ignore the fact it is falling it might be dangerous because you would fail to wake up sufficiently to figure out whether you were heading for fluffy pillows, a bramble bush or solid concrete. 71.236.26.74 (talk) 17:34, 30 July 2009 (UTC)

I have personal experience with falling while asleep. When I was a kid, I had the top bunk of a bunk bed. I fell out several times and I didn't actually wake up until after I hit the floor. Admittedly I wasn't in the air long, but I don't remember the sensation of falling, only the jolt and the pain from hitting the floor. I also recall a news story about someone who sleepwalked and fell from a building but never woke up even after hitting the ground. Until I can find it though, I am skeptical. Sifaka ^talk 17:40, 30 July 2009 (UTC)

My alarm clock goes with me wherever I travel, it fits in a small bag and works in any guestroom. Please explain how a contraption of ropes and pulleys that generates a local earthquake is better than my alarm clock. Cuddlyable3 (talk) 18:39, 30 July 2009 (UTC)

In this context "best" obviously means "most likely to wake you up." APL (talk) 20:25, 30 July 2009 (UTC)

What APL said, and I'd note that there are groups for whom regular alarm clocks don't work, period. For example, one such group I belong to would be the hard of hearing. We generally use vibrating alarm clocks; mine works reasonably well, but still takes me a while to wake up.

Also, half the justification for this project is that it's geeky and weird! (One would think Wikipedians would be sympathetic to that impulse.) --Gwern (contribs) 07:09 31 July 2009 (GMT)

Sifaka, what are the chances of someone waking up after falling off the building? Unless it was a rather short building, this might make it quite likely that they didn't wake up. Nyttend (talk) 21:49, 30 July 2009 (UTC)

Found the story! "A German teenager accidentally climbed out of a fourth-floor window and fell 10 meters to the ground where he kept on sleeping, albeit with a broken arm and leg." Sifaka ^talk 01:28, 31 July 2009 (UTC)

Global stress meter

A couple of years ago I read an article about something like global stress meter technology. According to the article the meter consists of about a hundred devices scattered around the globe. The devices continuously log the people's mood variations of the surrounding area, and the results are combined to form a graph. The article had a picture of one of the graphs, showing a clear peak at September 2001. The magazine I read this from is rather reliable, although not specialized in scientific content. Now I ask you, is this real, and if it is, how on earth does it work? Kotiwalo (talk) 10:05, 30 July 2009 (UTC)

One way to measure “global stress” in the sense that you mean the term is with a series of surveys, such as the International Business Owner Surveys.[55] Another form of “global stress” really is measured with physical devices, namely the stress field of the Earth’s crust.[56] But there is no physical device for measuring the amount of emotional stress felt by a large group of people in the vicinity of the device. Red Act (talk) 13:19, 30 July 2009 (UTC)

I never heard of such a thing but I don't think it would be too difficult to build something like that. A microphone and a compuer to tell if peoples voices were losing the high frequencies for instance and just stick it in a shopping centre. Or I believe some people are now trying to detect people who are stressed at airports by using a camera and analysing their movements - that sort of thing probably could be used much more reliably for overall stress in a crowd. The other possibility I can think of is it is some sort of development of the Scientology scam with E-meters. Dmcq (talk) 14:17, 30 July 2009 (UTC)

Then there's http://www.moodyornot.com which, admittedly, is very self-selective! Tonywalton ^Talk 14:24, 30 July 2009 (UTC)

Thanks for answers, everyone. No, they were (according to the article) small devices, about a hundred of which were produced, that could detect anxiety and tension and other varieties of mental activity on the local area. These devices were scattered over the world to provide the most accurate possible global mood. But it doesn't seem feasible to me either. The graph that was shown on the article could have been made without any input from such devices, everyone knows that global stress should leap when something disturbing happens. Unless someone recognizes this as something real, I am satisfied. Thank you for your answers. Kotiwalo (talk) 14:31, 30 July 2009 (UTC)

Global Consciousness Project.--Shantavira|^{feed me} 14:44, 30 July 2009 (UTC)

In case it isn’t obvious, the Global Consciousness Project is solidly within the realm of pseudoscience. The devices that project uses are just random number generators, and don’t actually measure people’s mood variations. Red Act (talk) 15:22, 30 July 2009 (UTC)

Actually I think it had something to do with the RNG. I'm going to check the article. Thanks! Kotiwalo (talk) 10:21, 31 July 2009 (UTC)

That's it! That's the thing I was looking for. But I still wonder whether it's real. I guess we can't know. Kotiwalo (talk) 10:23, 31 July 2009 (UTC)

Stock markets give an index of mood. A global index-of-indicies (of which at least one exists although I dont remember the details) would give a global mood index. 78.144.197.8 (talk) 17:07, 30 July 2009 (UTC)

The stock market measures mood - but mixed up with a lot of other variables. I don't think you could call that reliable. This thing is a hoax...there is no way to do what they claim. Even asking people how they feel is unreliable. SteveBaker (talk) 00:39, 31 July 2009 (UTC)

I thought of stock market myself, but it is a special type of mood I suppose. Kotiwalo (talk) 10:21, 31 July 2009 (UTC)

With modern internet and social network websites providing plentiful information, I wonder why the designers chose to feed "random" input into this worldwide sensor grid? Actual data can be fed in and processed, if they seek a real result. The presupposition that a random number generator would be influenced by "mood" is totally preposterous - if any such mechanism were discovered, I think we would conclude that the random number generator was defective, and that it was actually a predictable, controllable system that was receiving input of some form. I'm curious what proposed mechanism exists to couple the random number electronics with "mood" - again, if such a mechanism exists, it should be nonrandom and repeatable. This project is very pseudoscientific. Nimur (talk) 15:50, 31 July 2009 (UTC)

The reason the designers aren’t using real data is because the designers have no interest at all in developing a global mood index. The whole point of the “experiment” is to try to prove that “psychic energy” or whatever can affect hardware random number generators.

I personally don’t have any problem in principle with people doing a science experiment to test whether some phenomenon exists, even if there is no known mechanism by which the phenomenon could occur according to currently accepted scientific theory. Indeed, that description would describe the circumstances under which the Geiger–Marsden experiment was performed. In that experiment, there was no good reason to test for large-angle deflections of the beam, based on the then-accepted plum pudding model of the atom. What makes the Global Consciousness Project pseudoscientific bullshit is the methodology used, not the subject matter.

It would be possible for the Global Consciousness Project to do an actual, valid science experiment to test if global mood can affect random number generators, requiring essentially no more time or money than what those people have already invested. For example, they could hypothesize before the experiment that there will be a correlation between the moodyornot.com percentile on a given day, and the average values of the numbers created with those random number generators on that day. After making that hypothesis, they would then gather data for a predetermined large number of days, and then test for a correlation, using all the data they collected.

Unfortunately, the GCP people have chosen to avoid a reasonable scientific methodology like that, and instead retrospectively cherry-pick little bits of their data at carefully chosen times, based on their subjective ideas of what the global mood should be in specific instances that they’ve chosen, in such a way that it will make what they’re trying to prove look valid. The project suffers from a severe case of selection bias, making their “results” completely meaningless. Red Act (talk) 17:52, 31 July 2009 (UTC)

Perpetual motion from electrolysis of water under high pressure?

I have come to the conclusion that the electrolysis of water under high pressure must take more energy than for water under low pressure, since if water in a very deep lake (lets say five miles deep) was converted into hydrogen and oxygen at the same efficiency as normal pressure, this could fill a float with a cable (or drive a turbine) to generate electricity on its rise to the surface, the water could be recycled and further energy gained by using the hydrogen and oxygen in a fuel cell -though this would be less then the energy used in electrolysis, but combined with the "flotation generator" energy, would provide more than enough to repeat the cycle. Unless this really is a scheme for perpetual motion, which I doubt,what would actually happen? —Preceding unsigned comment added by Trevor Loughlin (talk • contribs) 10:21, 30 July 2009 (UTC)

Pressure doesn't really have anything to do with it. You could have a pressurised champer that only allowed in water at normal pressure. I think you will find that the answer is because of heat. What you are saying would eventually make the water cooler and cooler and more and more energy would be needed for electrolysis.--58.111.132.76 (talk) 12:23, 30 July 2009 (UTC)

What I would expect is that the standard electrochemical potential would increase as the water pressure increases since hydrogen and oxygen at pressure are at higher energy than when they are at low pressure. This would offset the extra energy obtainable from the gases being at depth.

However if it doesn't do this, the maybe it could form a perpetual motion machine. However the variation of electrochemical potential is well known (there are well known equations describing it as well), and I wouldn't expect any net energy gain.83.100.250.79 (talk) 13:22, 30 July 2009 (UTC)

Only an experiment could prove or disprove this - an experiment measuring the voltage required for electrolysis at different depths.83.100.250.79 (talk) 13:25, 30 July 2009 (UTC)

See this. It is estimated that there is 5% reduction in power needed for electrolysis of water under high pressure. That is, of course, an estimate. Any actual implementation will likely be less efficient due to numerous other factors. -- kainaw™ 13:51, 30 July 2009 (UTC)

Although it's been published I'd tend to ignore that in relevence to the original question-- (actually it doesn't really seem to have anything to do with the original question..)

The process can be split into two steps:

H+ + e- >>> 1/2 H2 (absorbed on electrode) no real volume change - chemical potential independent of pressure

and

 H2 (absorbed on electrode) >>> H2 (gas free under pressure) increase in volume therefore increase in energy(work) required as pressure increases

The same applies for the production of oxygen.

The usually accepted view is the the increased pressure will increase the energy required for elecrolysis - offsetting any extratable amount to make both equal. That's just one of the standard thermodynamic principles - ie that energy can't be made from nothing.

I can't think of a reason why this would change in this example - so I think it wouldn't be a perpetual motion machine. If it does turn out to be different then that would require a lot of explaining. The second equation above is the reason why mor energy is required for electrolysis at higher pressures. (edited once)83.100.250.79 (talk) 14:30, 30 July 2009 (UTC)

Casimir effect-flotation in a vacuum?

Could the low energy cavity between two fixed Casimir plates lead to both plates floating upwards even in a vacuum if made of a very light metal such as lithium? Would the low energy be equivalent to a lightweight gas balloon under normal atmospheric pressure, or for that matter the proposed "vacuum balloon" under normal pressure? Could such a small force be measured if it existed?Trevor Loughlin (talk) 10:29, 30 July 2009 (UTC)

Wouldn't the Casimir effect push the plates outward from each other, and not 'up' or 'down'? --Gwern (contribs) 10:38 30 July 2009 (GMT)

Normally, but the plates would be fixed in place to prevent this. I just wondered if a "more then vacuum" would float like a balloon in a normal vacuum. Probably a silly question since it compares energy density to gas density, no doubt entirely different. —Preceding unsigned comment added by Trevor Loughlin (talk • contribs) 11:09, 30 July 2009 (UTC)

Well, if the plates are fixed, then nothing will happen. If you put yourself between two walls fastened together, and push outwards, the walls will go nowhere if they're really 'fixed'. The net force would be negative. And consider the symmetry: if we have the 2 parallel plates - || - that we need, which direction would they hypothetically go? There ought to be a unique direction, but that's rather asymmetrical.

A 'v' shape might work, but I think what would happen is the forces in the wider part would cancel the forces in the narrow part, although it'd take a physics guy to say exactly what happens there. If a 'v' shape could work that way, it seems suspiciously like perpetual motion... --Gwern (contribs) 11:30 30 July 2009 (GMT)

Read Newton's laws of motion#Newton's third law: law of reciprocal actions to see why that's not possible. Dauto (talk) 15:14, 30 July 2009 (UTC)

ammonium stearate??? Ammonium distrate

In the TV series 24 episode 5, Jack Bauer "flushes" people out of their safe room, by creating a poisonous gas with the help of ammonium and something else he found in the kitchen. Does anybody know which substances he mixed and what was the name of the poisonous mixture (ammonium stearate???) Does anybody know what substances he mixed in order to create "ammonium distrate"? Lova Falk (talk) 10:49, 30 July 2009 (UTC)

Ammonium Stearate is a compound, I don't know what else "distrate" could be, but "distrate" is not a chemical term.

Mixing any ammonium compound including ammonium stearate with an alkali (base) produces ammonia which woul force most people out of a room.83.100.250.79 (talk) 13:13, 30 July 2009 (UTC)

According to this "Distrate" appears to be a pesticide containing alkyl dimethylbenzyl ammonium chloride and alkyl dimethylethylbenzyl ammonium chloride. This is listed as acutely toxic, carcinogenic, a developmental toxin and an endocrine disruptor. Probably not something you'd find in the average kitchen. sometimes used as a disinfectant. Please do not try mixing things with things at home - remember, 24 is fictional! Tonywalton ^Talk 14:37, 30 July 2009 (UTC)

Actually the listing you gave says it's effects are not known with certainty, except that it is poisonous to aquatic life.

(edited twice due to error) However mixing this with an alkai (eg sodium carbonate or sodium hydroxide) would not do anything under these conditions

It's basically a strong detergent.83.100.250.79 (talk) 14:51, 30 July 2009 (UTC)

Here's a list of things that contain the same compound(s) [57]

There's a risk assesment here [58] (long article!) - There doesn't seem to be any such reaction that could clear out a room - probably just "hollywood chemistry" aka 'bull' ...83.100.250.79 (talk) 15:01, 30 July 2009 (UTC)

I can't see any reaction that would work.83.100.250.79 (talk) 15:05, 30 July 2009 (UTC)

The makers of TV shows often are very "creative" when the characters are making bombs or poisons. This is simply to protect the viewers. It is very possible that either the mixture doesn't work at all or is much less effective than portrayed. Sometimes the explosive materials are not revealed at all. Kotiwalo (talk) 15:15, 30 July 2009 (UTC)

No need to make it easy. One of my children read a chemistry textbook and then went off an mixed up something from chemicals round the house that produced a poisonous gas and I had to open the doors and windows to get rid of it. Good understanding of the chemistry but not much sense. Dmcq (talk) 20:12, 30 July 2009 (UTC)

Sorry about that. Luckily in this case what jack bauer did doesn't seem to work. It's actually surprising how difficult it is to mix up something toxic in the home - despite the wide variety of chemicals in the garage, and kitchen.. There's actually a way to make hydrazine in the home very easily. (not telling) - and bleach should probably be banned...83.100.250.79 (talk) 20:49, 30 July 2009 (UTC) I spent most of my years from 12 to 20 trying to do just the same... probably a common story.83.100.250.79 (talk) 20:50, 30 July 2009 (UTC)

If you want to drive people out of a room using common household chemicals, simply mix ammonia and clorine bleach. This releases clorine gas in dangerous quantities, and clorine gas is really irritating to eyes and lungs even in small quantities. DO NOT TRY THIS, even in small amounts, as an experiment, except in a well-equiped laboratory under an exhaust hood. Unfortunately, quite a few people do this "experiment" by accident every year, usually by using first ammonia and then bleach, or vice versa, while trying to remove stains from a toilet bowl. -Arch dude (talk) 23:49, 30 July 2009 (UTC)

"Phase shifts" in brain and IQ

What exactly is going on during the "phase shift" described in the article here? http://www.newscientist.com/article/mg20227141.200-disorderly-genius-how-chaos-drives-the-brain.html?full=true It seems very important as an extra 1 millisecond is said to give a 20 point increase in IQ. 78.149.172.96 (talk) 11:52, 30 July 2009 (UTC)

It sounds like a bad analogy to complexity theory with handwavey, inaccurate terminology. There have been numerous attempts to describe the brain or the mind as a "chaotic" system in the past, but they range from "stretches of terminology" to "wild speculation and making stuff up." Nimur (talk) 15:09, 30 July 2009 (UTC)

The article describes research into how ideas, and hence intelligence, arises in the brain. The model and terms used are similar to the engineering of a regenerative radio receiver where forming an idea is analogous to tuning in to a particular transmission frequency out of many. The idea is that there are two energy states in the brain: 1) an incoherent or chaotic state where energy is dissipated at random comparably to thermal noise in a radio, and 2) a particular thought gains critical mass (or in the terms of the NS article triggers a sand avalanche). The latter event is proposed to correspond to a particular frequency and phase of resonance in neurological activity. The significance of one frequency and phase is that it is a unique focus for accumulating energy. Random energies at other frequencies and even at the same frequency but a different phase do not contribute to the resonance. They represent chaotic thoughts that become imperceptible as the significant resonance takes hold. These speculations suppose that there is a mechanism in the brain for collecting energy at a unique frequency and phase, with some correlation to intelligence, which the researchers report having detected. The significance of "an extra millisecond" could be that longer time taken to integrate a frequency achieves better elimination of noise. Compare that with a chess player taking extra time to decide a difficult move.

However while this frequency-selective model lends itself to pretty simulations on video the reported data is not convincing. Only 17 children were tested for EEG activity and IQ. Their IQ spread is not stated. 1 millisecond may correspond to a large or an insignificant phase change depending on the frequency concerned. I am doubtful when I read that 1 ms longer in one brain state increases IQ and 1 ms shorter in the other brain state increases it by a different amount. Cuddlyable3 (talk) 17:51, 30 July 2009 (UTC)

The abstract linked to says "The electroencephalogram (EEG) was recorded from 19 scalp locations from 378 subjects ranging in age from 5 years to 17.6 years." So the journalist or someone had made a mistake - it was 378 children, not 17. 78.146.235.174 (talk) 10:58, 31 July 2009 (UTC)

I was thinking that the "phase" was something like the phases of water (solid, liquid, gas) or phase of regular or chaotic rather than a phase in the electronic sense. I recall the AI technique of Simulated annealing. The phase shift could be when a lot of things are thrown together at random, some of which catch on as new ideas. The longer this random phase, the more random throwing together of things, the more of the problem-space is searched. Tell me if you disagree. 78.146.235.174 (talk) 10:47, 31 July 2009 (UTC)

In the context of brainwave frequency measured in Hz it looks like phase must mean phase angle, especially when the terminology is "phase shift" not "phase change". We read "..the brain often synchronises large groups of neurons to fire at the same frequency, a process called 'phase-locking'." Simulated annealing can regularise crystal structures but is not AFAIK an established technique for artificial intelligence. Cuddlyable3 (talk) 23:05, 31 July 2009 (UTC)

Saddle joints

Hi everyone I'm having trouble understanding how a saddle joint works. I understand the diagrams I have seen showing a concave surface sitting in a convex surface; but I just can't see in my mind how this works in the carpometacarpal joint of the thumb. I've looked at the external links listed in the 'saddle joint' article and I even have a copy of Gray's anatomy right next to me but I just don't 'get' it. The article on saddle joints states that the saddle joints are capable of flexion and extension, abduction and adduction and circumduction. Perhaps I don't understand because I don't know what flexion/extension or abduction/adduction of the thumb looks like. One other thing about saddle joints that I don't get is that I can move my thumb up, down, left and right and can spin it round in a circle (which I believe is circumduction). These are all things that a ball and socket joint can also do. The article on saddle joints says that they have no axial rotation, which I believe a ball and socket joint does have. What would be different about our thumbs if they had axial rotation? Basically what I'm asking is what would be different about our thumbs if a ball and socket joint held them in place instead of a saddle joint? Hope this makes sense; as you can probably tell I'm rather confused about saddle joints. Thanks in advance to anyone who helps. RichYPE (talk) 18:47, 30 July 2009 (UTC)

If you had a ball and socket thumb you'd be able to twist your thumb (around it's length - like a door knob turns)

The saddle joint moves like a universal joint (a bit less flexible) (but not attached to something that can rotate) - are you familiar with those?83.100.250.79 (talk) 19:18, 30 July 2009 (UTC)

Compare this image http://www.heumann.org/body.of.knowledge/a8/rdts45.gif with that a universal joint - can you see how if one end turns the other end must also turn. - With a ball and socket joint the other end doesn't turn... (did that help - or just more confused ?!?

Also looking at the image again - note that the two surfaces are the same - imagine how they can move against one another, and how far they can move. The thumb joint will be less simple - but it is 'the same'83.100.250.79 (talk) 19:23, 30 July 2009 (UTC)

Practical problem - something light and compact to stand on

What could I use to stand on that will raise me about two feet in the air? The criteria are that it must be light enough and compact enough to be carried by hand on public transport for some time, and that there is not enough time to do major woodworking for example. It can lean against a wall like a ladder while I am standing on it, although a ladder itself would be too big. I only need to stand on it for about a minute. I would prefer something that's cheap enough to dispose of after I've used it. 78.144.197.8 (talk) 19:27, 30 July 2009 (UTC)

A plastic rubbish bin / trash can should do the trick, depending on your weight, of course. --Cookatoo.ergo.ZooM (talk) 19:37, 30 July 2009 (UTC)

It would be rather an ordeal to take a wheelie bin with me on public transport. A chair would be too big too. 78.144.197.8 (talk) 19:39, 30 July 2009 (UTC)

See if you can find s.th. like this [59] Try your local home improvement box or a store for supplies for the elderly, a kitchen store might also carry s.th. similar. 71.236.26.74 (talk) 19:48, 30 July 2009 (UTC)

That would be ideal if I had one already, but I'd rather not pay a lot just for one use for less than a minute. I've been thinking that perhaps I could strengthen a cardboard box somehow, which could be folded flat to carry. Other design possibilities would be three pieces of wood to form a thin "A" shape, or two sheets of something in an "X" shape with another sheet on top to stand on. I'm still looking. 78.144.197.8 (talk) 20:20, 30 July 2009 (UTC)

I was thinking the same. You probably need two cardboard boxes - one to be the shell, the second the reenforcement. Cut up the second so you have diagonal bits which will fit into the first, with each diagonal cut with a half-width cut half way down. That way they slot together to make an X shape, which will brace the shell box. This, including the shell box, can be collapsed and folded during transit (a roll of parcel tape will help reassembly, but shouldn't be necessary). If further support is required, more sheets of the donor box cut with slits at either (horizontal) edge, so they can be looped around and slotted into themselves, forming tube(ish) structures - put these tubes in between the arms of the X both to hold weight and to prevent it from folding sideways. -- Finlay McWalter • Talk 20:26, 30 July 2009 (UTC)

Finlay is on the right track. Go to your local wines&spirits store, and get three empty booze boxes. They are heavyweight (usually "triple-wall") corrugated cardboard, and usually have the interlocking cardboard pieces called an "egg crate" inside, to keep the bottles from rubbing on each other during shipping.

Carefully chosen, you should be able to get two that stack on each other quite nicely. Use the third one as a step to get up on the stack of two. Good luck! --DaHorsesMouth (talk) 22:42, 30 July 2009 (UTC)

How about a pair of stilts? SteveBaker (talk) 00:34, 31 July 2009 (UTC)

Have you seen the film Tommy? Check out the character played by Elton John. 87.81.230.195 (talk) 00:40, 31 July 2009 (UTC)

And now for the real question: what are you going to be doing for a minute that needs you to be two feet taller? (If you are going to be lifting something heavy or firing a weapon, for example, you might have to consider strength of materials and their stability. This is not just idle curiousity, but most of it is.) // BL \\ (talk) 01:12, 31 July 2009 (UTC)

For being seen while making an address to the public, a Soapbox is classic. Edison (talk) 01:47, 31 July 2009 (UTC)

Wow, all these baroque solutions. All you need is a folding two-step ladder, which you can buy at any decent home supply store. Looie496 (talk) 03:53, 31 July 2009 (UTC)

Apart from a folding two step ladder being not compact, not light, not cheap, and not disposable. Didnt you even read the title? 78.146.235.174 (talk) 11:08, 31 July 2009 (UTC)

A folding chair would work just as well. 98.234.126.251 (talk) 05:25, 31 July 2009 (UTC)

Ah, but the OP said they didn't want to buy a set of steps for such a brief use. I assume they couldn't borrow one from a friend or neighbour? AlmostReadytoFly (talk) 08:09, 31 July 2009 (UTC)

A soapbox would be more traditional. SteveBaker (talk) 13:41, 31 July 2009 (UTC)

Would it cause an echo ...echo....echo? Edison (talk) 15:10, 31 July 2009 (UTC)

For a women to lose weight after pregnancy

How long does this takr women to lose most of extra weight after when a baby is born. Average woen is still overweight over even 5 month after the baby is born. Like a english teacher at school, she got her baby in late January, and the teacher temporaily on intermission absence shows up every week in June, and her face is now as wide as a honeydew melon, and I made girls upset by criticizing the teacher by her weight. Until how long after the baby will average women lose extra weight. 9 month?--69.228.145.50 (talk) 21:19, 30 July 2009 (UTC)

I'm not sure where you live, but where I live, openly criticizing any woman for being overweight, especially when other women can hear you, is considered extremely rude and socially just unacceptable. And if it's after a pregnancy, then your comments are way out of bounds. (At least, where I live they are.) The speed of weight loss is highly variable and depends on hormone levels and whether she is breastfeeding, as well as the usual factors of exercise and diet. Trying to slam back to the previous weight could be harmful to both the mother and child. So, knock off making comments like that. Tempshill (talk) 21:37, 30 July 2009 (UTC)

A very wide face can sometimes be moon face, which can have a variety of causes, some of which are very serious. I suggest you apologize to your teacher and make some efforts at becoming a more compassionate human being. --Sean 14:11, 31 July 2009 (UTC)

homemade radiation treatment of food without cooking

Can a low-power dose of defrosting microwave radiation prolong the life of refrigerated (non-frozen) meats or milk without significantly affecting taste quality? If this is not so, is there any type of radiation treatment that would kill bacteria without cooking the food? Are there plasmid-attacking agents that would be harmful to bacterial DNA but not harm human cells once in the digestive tract? John Riemann Soong (talk) 22:01, 30 July 2009 (UTC)

The thing with Food irradiation is it uses ionising radiation to damage the bacteria. Microwaves are not ionising radiation, so I doubt they'd do more than slightly warm the food. Looking at the doses used, they're pretty high (kiloGrays), so I don't think you could do it at home. AlmostReadytoFly (talk) 22:14, 30 July 2009 (UTC)

As AlmostReady just said, you need ionizing radiation (X-ray or gamma) and not microwave radiation to sterilize food. And, moreover, you need extremely high doses of ionizing radiation. To be precise, you need doses high enough to damage every living cell, every bacterium or spore, in the food product to be preserved. And the radiation doses required to do so are astonishingly high, orders of magnitude higher than those sufficient to kill a human. Some bacteria - notably Deinococcus radiodurans and some others mentioned in D. radiodurans article - are especially good at surviving irradiation. --Dr Dima (talk) 22:27, 30 July 2009 (UTC)

Now, on the second part of your question, there are certainly ways to preserve food without actually cooking it. Preserving food with salt is very common. Fermentation is another way of preserving food, by actually using some (normally harmless) bacteria to produce chemicals that kill or inhibit growth of other microorganisms. We have an entire article devoted to Food preservation. There are also antimicrobial chemicals defined as food preservatives, which may be what you are looking for. --Dr Dima (talk) 22:44, 30 July 2009 (UTC)

Actually I'm looking at preserving milk and fresh meat ... yeah I use vinegar and pickling techniques but I'm just looking if there's anything to extend the life of refrigerated (non-frozen) stuff. John Riemann Soong (talk) 04:31, 31 July 2009 (UTC)

Ultraviolet light is used to purify water. It acts by ionizing (irradiating) the DNA of organisms in the water. Ultraviolet light can also be used for food processing. Axl ¤ [Talk] 23:44, 30 July 2009 (UTC)

For preserves and juices they sometimes use high pressure, but "at least 10 MPa" [60] is probably way above what zoning regulation and code would let you have at home. 71.236.26.74 (talk) 23:54, 30 July 2009 (UTC)

And of course for UV to work, the thing you're trying to preserve has to be transparent to UV light (which isn't always the same thing as "transparent"!)...so for most things, you'll only kill the bacteria on the surface. SteveBaker (talk) 00:19, 31 July 2009 (UTC)

What about delaying effects? Like giving it extra storage life for a few more days, etc. John Riemann Soong (talk) 05:02, 31 July 2009 (UTC)

It's hard to believe that you mentioned milk and no one brought up pasteurization yet. Dragons flight (talk) 05:11, 31 July 2009 (UTC)

I assume homemade pasteurisation is difficult? And what about repeated pasteurisation? John Riemann Soong (talk) 05:16, 31 July 2009 (UTC)

Actually, you can get a similar effect (though not as good as commercial methods), by microwaving milk just long enough to get it to ~70 C and then removing it quickly and placing it in a cold water bath to rapidly cool it back down. It's a trial and error thing though because if the milk boils (100 C) you will have ruined the taste/composition. The time required will depend on the volume of milk and the intensity of your microwave. Also, any pasteurization process will still have some effect on the taste, whether the difference if important to you is a matter of personal taste I suppose. Dragons flight (talk) 05:31, 31 July 2009 (UTC)

And for meat, you can try salting it or cold-smoking it. Also, pasteurizing temperature is 80 C, not 70 C as Dragonsflight said. 98.234.126.251 (talk) 05:35, 31 July 2009 (UTC)

The USDA standard is 72 C. It varies a bit by country. Dragons flight (talk) 05:38, 31 July 2009 (UTC)

I really don't think we should be recommending using a microwave to pasteurize milk (or anything else for that matter). The heating is far too uneven. In order to get the entire container of milk to the desired temperature and keep it there for long enough to kill the bacteria, some parts of the milk will be getting up towards the temperature that it'll start to 'cook' and taste funny - while other parts are either not hot enough - or don't get hot enough for long enough. You need a much more controllable heat - and you need to keep the liquid stirring so that it doesn't develop hot spots or retain cooler areas in which bacteria can survive. If you don't kill all of the bacteria - then the ones that escaped will recolonize the parts of the milk that you sucessfully pasteurized. This happens rather quickly - and then you'll be back to square one. SteveBaker (talk) 13:27, 31 July 2009 (UTC)

The most delicious way to preserve meat is to make a confit. --Sean 14:11, 31 July 2009 (UTC)

July 31

Grated Puffin

What does it taste like please. Jermy clarksson said he had some —Preceding unsigned comment added by 79.75.68.48 (talk) 00:17, 31 July 2009 (UTC)

Puffins are fatty aquatic birds. The fatty aquatic bird most often eaten is duck. Therefore, all others tend to be compared to how similar they are to duck. So, to someone who hasn't had puffin, you'd say "It is almost just like duck." -- kainaw™ 00:53, 31 July 2009 (UTC)

I was under the understanding that sea-birds taste fishy - in contrast to freshwater birds. This biased search seems to confirm that : http://www.google.co.uk/search?hl=en&q=puffin+fishy+taste&meta=&aq=f&oq= 83.100.250.79 (talk) 06:28, 31 July 2009 (UTC)

Two heat transfer questions

1. Assuming a constant internal temperature, how rapidly does a wall-mounted room air conditioner lose its ability to cool the room (or, at least, lose efficiency) as the outside temperature rises? By way of example, suppose the room is at 27 degrees C, the air conditioner is continuously attempting to cool the room to 25 C, and the outside temperature starts at 32 C and rises to 37 C. I'm not using the numbers to try to get someone to cough up a formula; I'm just using them to illustrate what I'm trying to get at.

2. When cooking a grilled cheese sandwich on a frying pan which is atop a gas stove, I imagine a smaller pan will transfer heat into the sandwich faster, assuming the pan surface is heated more or less evenly by the gas flame. If it's as I expect, does a pan with half the surface area heat the sandwich twice as quickly? Tempshill (talk) 02:30, 31 July 2009 (UTC)

1. You would need to measure the temperature of the condenser at the outside of the air conditioner. Its ability to transfer heat to the outside is a function of the differential temperature between the condenser and the ambient air; as the difference becomes smaller the rate of cooling decreases. There is a formula somewhere, but I lack the engineering background to dig it up. Someone else I am sure will.
2. Actually, it depends on how you cook the sandwich. Once the pan is "at temperature", it is mainly acting to transfer the energy directly from the flame to the food. Metal, being a good thermal conductor with a low specific heat will basically pass the energy quickly and efficiently from the flame to the sandwich. Placing a cold sandwich will sap some of the heat from the pan, and the amount of energy that is lost is a function of the mass of the pan. A heavier pan will lose less of its energy to the cold sandwich, so a heavier pan will cook a sandwich faster assuming that both pans are "preheated". If you are starting with a cold pan and a cold sandwich, then the lighter pan will heat up faster, and thus start cooking the sandwich faster. So it depends on your methodology. --Jayron32 03:25, 31 July 2009 (UTC)

As a first approximation to question 1 - the rate of heat flow is proportional to the temperature difference (see Heat transfer), however as mentioned above ^^ this is the temperature difference between the outside air, and the temperature of the 'radiator' on the outside of the air conditioner (which is by default always hotter than the temperature inside the air conditioned room). However the temperature the radiator reaches will depend on the outside temperature. maybe someone else will be able to finish the answer.83.100.250.79 (talk) 06:24, 31 July 2009 (UTC)

Retain Martian water using deuterium!!??

Woke up with this BRILLIANT{??} idea! Heard that Mars and other planets significantly lighter than Earth gradually lose their water as it evaporates into space. What about flooding Martian plains with "heavy water". This means the H in H2O are the deuterium or tritium isotypes, and heavier than ordinary water, while being chemically exactly the same. Would this tactic permit Mars to retain water better? All you would have to do is find a vast reservoir of this kind of water. Btw, if a person only drank heavy water, and ate foods that had been irrigated with this water, how much heavier would they be than persons who only drank normal water? Myles325a (talk) 02:52, 31 July 2009 (UTC)

Yes. All you would have to do is find an ocean of heavy water, which sounds simple until you consider that the natural abundance of deuterium is 0.015%, so there are no such vast reservoirs. – ClockworkSoul 02:56, 31 July 2009 (UTC)

I don't know if heavy water evaporates more slowly and acts as vapor differently than regular water, but our heavy water article does say that mammals die when about half their body water has been replaced with heavy water. It goes into some detail about the death rate of other life forms. Everybody dies except for bacteria. Tempshill (talk) 03:04, 31 July 2009 (UTC)

Heavy water has a slightly higher boiling point. With care (and huge amounts of time and energy) one can use distillation to separate (or at least enrich) a mixed sample. But there are other, more efficient ways of doing it than direct fractional distillation. DMacks (talk) 05:32, 31 July 2009 (UTC)

Which leads to an answer to the first part of the question - no - heavy water is so similar to normal water that it would be lost (almost) just as fast.83.100.250.79 (talk) 06:17, 31 July 2009 (UTC)

Also, to answer your last question: this site cites Review of Physiological Chemistry, 16th ed. in stating the hydrogen composes 10% of the human body by weight. Since deuterium has 1.998 times the mass of hydrogen, if all hydrogen in the an ecosystem was replaced by deuterium, and our biochemistry was sufficiently altered so we don't, you know, die... our mass would be increased by a total of about 10%. – ClockworkSoul 03:26, 31 July 2009 (UTC)

Do artificial sweeteners taste like sugar to non-human species?

Do artificial sweeteners only fool human taste buds, or do they taste like sugar to other species too? If the latter, do they taste like sugar to all animals? Do insects confuse artificial sweeteners with the real thing? —Preceding unsigned comment added by 98.114.146.177 (talk) 03:27, 31 July 2009 (UTC)

They don't even fool human taste buds. Just about anyone can tell the difference between real sugar and any artificial sweetener. Merely because both are sweet, doesn't mean that they taste identical. --Jayron32 03:32, 31 July 2009 (UTC)

I think this is a legitimate question. Say for example, you make a big mound of artificial sweetener right next to an anthill. Will the ants collect it and take it back to the nest? Or will they say "screw that, that stuff isn't food"? Dcoetzee 04:15, 31 July 2009 (UTC)

Oh, it is a perfectly legitimate question; I did not address whether or not animals would eat artificial sweetener or not; however the premise that it "fools" humans, except those that willfully allow themselves to be fooled, is incorrect. Artificial sweeteners are readily recognizable as not-sugar by anybody. Again, not that there's anything wrong with that, but it doesn't mean that they are indistinguishable from sugar by humans. --Jayron32 04:22, 31 July 2009 (UTC)

I left a half-empty bag of popcorn out overnight, and because I leave the windows open, I now have a trail of ants marching across my floor. I removed the bag earlier, but they are still here (and I don't want to spray and kill them). So I have just poured a small mound of Sweet 'n' Low (saccharin) next to their trail. Surprisingly enough, about a dozen ants have actually stopped at the mound, but I don't know why. They don't all respond to it like thye would if it were a pile of real sugar, though. HYENASTE 06:23, 31 July 2009 (UTC)

Insects - at least some of them - have pyranose receptors and furanose receptors; so anything that elicits response from either one will presumably taste to the insect as a corresponding type of sugar. --Dr Dima (talk) 06:39, 31 July 2009 (UTC)

What's this about fooling taste buds? Sweet reception works by combining different chemical effects. Try http://en.wikipedia.org/wiki/Sweetness#Historical_theories_of_sweetness."Simply put, they proposed that to be sweet, a compound must contain a hydrogen bond donor (AH) and a Lewis base (B) separated by about 0.3 nanometres. According to this theory, the AH-B unit of a sweetener binds with a corresponding AH-B unit on the biological sweetness receptor to produce the sensation of sweetness." + a third nonpolar London force binding site. If you look at table sugar, sucrose, sure enough, you get a hydrogen bond donor (the OH groups), a weak Lewis base region (the ether oxygens with their lone pairs) and some nonpolar regions. And then there are more elaborate theories based on the study of the sweet receptor with 5 more regions or something, but that's the basic idea.

The thing though, is that I also guess that the sweet receptors also send inhibitory signals to bitter receptors -- or the sugar molecules in themselves activate bitter-inhibiting receptors at the same time they are exciting sweet reception. This would be in order to suppress the sugar's OH groups binding to the receptors that give alcohols their bitter taste; some sweeteners inhibit less effectively or trigger receptions that normal table sugar wouldn't. (At sufficiently high concentrations the bitter receptors will be inhibited again -- have you tried eating pure sugar, or lived near a sugar factory? At sufficiently high concentrations even sugar becomes bitter.) But the basic motif of the sweet receptor I would think be conserved. John Riemann Soong (talk) 07:08, 31 July 2009 (UTC)

Rats prefer saccharin to sucralose. Indeed they really don't like sucralose. The black blow fly Phormia regina likes glycyrrhizin. Axl ¤ [Talk] 09:05, 31 July 2009 (UTC)

What do hummingbirds think of artificial sweeteners, as a matter of interest? It's reasonably common for people to troll bird forums/newsgroups with suggestions that people put Nutrasweet and similar in their hummer feeders, deliberately feigning ignorance of the lack of nutritional value in the stuff... --Kurt Shaped Box (talk) 09:11, 31 July 2009 (UTC)

It's a common legend that hummingbirds will drink nutrasweet (or other zero-calorie sweeteners) to the point of starving themselves if it's more easily available than real sugar. I'm not sure that I've ever seen a good confirmation or debunking of this legend. (Usually would-be debunkers miss the point and repeatedly insist that nutrasweet isn't toxic!) I'd be interested to know the answer to this question, but I'm not eager to run the experiment myself. APL (talk) 14:17, 31 July 2009 (UTC)

Hummingbirds are not interested in artificial sweeteners. Axl ¤ [Talk] 18:18, 31 July 2009 (UTC)

Cool. Thanks. One less thing to wonder about. APL (talk) 18:39, 31 July 2009 (UTC)

how are scientists able to see something that is billions of light years away

On July 11, 2007, using the 10 metre Keck II telescope on Mauna Kea, Richard Ellis of the California Institute of Technology at Pasadena and his team found six star forming galaxies about 13.2 billion light years away

How is this possible. If it takes Light 13.2 billion light years to reach, which is an insane distance, how in the hell can we see these objects. Ivtv (talk) 03:31, 31 July 2009 (UTC)

We're seeing the light that these objects emitted 13.2 billion years ago which is just now reaching us. That's why looking at far away objects is also useful for figuring out what the early stages of the universe were like. There's also the concern that the farther away something is, the lower the intensity of the light is that reaches us and the smaller the objects appear, which is why we need extremely sensitive detection devices (very large and powerful telescopes) to see these things. Rckrone (talk) 03:47, 31 July 2009 (UTC)

Because galaxies are huge. Imagine every second you have ever driven in the past say, 15 years, passing by in 1 second and maintaining that speed for 1000 years and still have gone only 1% of the size of a galaxy. The telescope is a million times the area of your pupils combined and accumulates the picture over hours. Sagittarian Milky Way (talk) 04:28, 31 July 2009 (UTC)

Be sure to see Size of the observable universe and Distance measures (cosmology) for an explanation of why a comoving distance can have a value in light-years that exceeds the age of the universe. -- Coneslayer (talk) 15:30, 31 July 2009 (UTC), who used to have an office across the hall from Richard Ellis

Did the Apollo lunar missions have a contingency plan for damaged space suit during EVA?

Did they have a plan for dealing with a torn/punctured/leaking space suit during EVA? Would something like duct tape be able to stop a small leak from a space suit? —Preceding unsigned comment added by 98.114.146.177 (talk) 03:54, 31 July 2009 (UTC)

Whatever will stop a leak in the base of a 3 story aquarium will hold back the vacuum. Sagittarian Milky Way (talk) 04:40, 31 July 2009 (UTC)

It's much less than that. Spacesuits are kept at a pressure only about 1/3 that of the atmosphere at sea level. Dragons flight (talk) 05:01, 31 July 2009 (UTC)

Oh right, inconstant volume issues caused by and making it harder to bend the joints. Sagittarian Milky Way (talk) 05:27, 31 July 2009 (UTC)

This doucument on Page 2-79 shows a mantenaince kit for lunar spacesuits with fiberglass repair tape. Whether the suits could be repaired while being worn I don't know. 75.41.110.200 (talk) 06:11, 31 July 2009 (UTC)

For a very serious leak, this might have been deployed. --Sean 14:11, 31 July 2009 (UTC)

Hmmm. Interesting seed for an Alternate History novel. 87.194.161.147 (talk) 14:21, 31 July 2009 (UTC)

Oh, the annoyance of snippet view in Google Book search. A glove was the most llikely spor for a puncture, because they handled core drills and other tools. The following suggests that for a glove puncture on more recent (Russian?) suits, a cuff in the arm could be inflated to prevent a fatal loss of oxygen in the suit and helmet, perhaps giving time to get inside: "Walking to Olympus: an EVA chronology‎ - Page 71.by David S. F. Portree, Robert C. Treviño, United States National Aeronautics and Space Administration. History Office - 1997 -"The suit was sized for specific cosmonauts by pulling or releasing cables and pulleys in the arms and legs. • In the event of glove puncture, a forearm cuff..." Another snippet, from "Protecting the Space Shuttle from Meteoroids and Orbital Debris‎ - Page 17 , NASA, 1997, refers to time a small puncture could be survived: "... a 30 minute supply of oxygen in case of a 4 mm puncture in the space suit" On an EVA at the ISS, an astronaut noted that a cut had gone through several layers of the glove, but had not penetrated the pressure layer, so he ended the EVA early. Edison (talk) 14:58, 31 July 2009 (UTC)

If we aren't limiting ourselves to lunar suits, there has been one documented puncture: on STS- 37. See Talk:Extra-vehicular activity#What really happened on STS-37. 75.41.110.200 (talk) 17:39, 31 July 2009 (UTC)

Name of body groove?

Is there a name for the groove that male athletes have? It starts from both hips comes forward diagonally down toward the groin area. A groove between the upper thigh and the lower abdomen. It's kind of hard to describe without a photo. --68.102.170.184 (talk) 06:53, 31 July 2009 (UTC)

Inguinal ligament. Tempshill (talk) 06:59, 31 July 2009 (UTC)

I think a bit more correctly, or pedantically if you will, the surface feature is the inguinal groove, which marks the path along which the inguinal ligament runs. - Nunh-huh 09:28, 31 July 2009 (UTC)

Colloquially, this is sometimes called the Apollo's belt. That article also refers to the "iliac furrow", which turns out to be a redirect to Apollo's belt. --LarryMac | Talk 15:48, 31 July 2009 (UTC)

Why do attractive parents have more daughters?

Hi guys. Here's an article from telegraph.co.uk. I understand the first bit of that article about how "attractive genes" are selected for. But I don't get the following three sentences near the end:

A study in 2006 by scientists at the London School of Economics found that good-looking parents were far more likely to conceive daughters.

He suggested this was because of differing "evolutionary strategies" that each sex has adopted to survive, and which had been subtly programmed into their DNA.

Mr Kanazawa said: "Physical attractiveness is a highly heritable trait, which disproportionately increases the reproductive success of daughters much more than that of sons.

If attractiveness increases the reproductive success of daughters more than sons, surely all this means is that those daughters of attractive parents will have more children than their brothers. I don't see why a gene causing attractiveness would also cause one to have more daughters. Please help. TIA! Zain Ebrahim (talk) 07:52, 31 July 2009 (UTC)

Every child is an investment for the parents, with the pay-off being further offspring. For females, their reproductive success depends on attractiveness. For males, it depends on other factors (smarts, I would hope ;-). So if you are attractive, you can make sons that have an average number of offspring, or daughters, that have a larger number of offspring. The second strategy is better, and natural selection will hence favor that combination of traits (attractive+propensity for daughters) over the other 3 combinations. --Stephan Schulz (talk) 09:16, 31 July 2009 (UTC)

I get it now. Thank you, Stephan. Zain Ebrahim (talk) 10:00, 31 July 2009 (UTC)

Not to mention, although we don't seem to have an article on it, organisms can change the average gender of their offspring (for example, reptile eggs can assume gender based on temperature; and there are more indirect genetic examples) or more directly by infanticide; they would want to do this because by Fisher's law the ESS for sex ratio is 1:1 - if there's a temporary deviation then there're arbitrage opportunities. (If there're only a few females, then female offspring are a win; if there's a shortage of males, obviously you might want to have male kids.) --Gwern (contribs) 10:34 31 July 2009 (GMT)

I'm very bothered by the phrase "scientists at the London School of Economics"...what is a reputable scientist doing at an economics school? SteveBaker (talk) 13:13, 31 July 2009 (UTC)

Slumming? 87.194.161.147 (talk) 14:18, 31 July 2009 (UTC)

A look at London School of Economics might be enlightening. There's economics and economics... --Stephan Schulz (talk) 14:31, 31 July 2009 (UTC)

Water for both nuclear coolant and hot coffee?

Would it be possible for a nuclear power plant to do part of its cooling with potable water, remove that water before it went well above 100C, and use it to provide hot beverages or showers for staff? NeonMerlin 08:23, 31 July 2009 (UTC)

well, maybe? :-) Withouth checking our reactor articles, I believe that they need heavy water in the reactor core, but that this water is used to heat ordinary water. This ordinary water drives a turbine and the "smoke" rising from nuclear powerplants are in fact the steam escaping. Nuclear powerplants then emit a lot of warm water to nearby rivers. So much that there's actually regulations in some countries to stop them from damaging the river from it. I would think that you could build a comfortable outdoor pool around this warm water, though I don't know what the typical temperature is. EverGreg (talk) 09:01, 31 July 2009 (UTC)

A related concept is greywater. --Gwern (contribs) 10:08 31 July 2009 (GMT)

It seems a fair bit safer to let it heat way above 100 degrees, and use the hot pipes to heat up some water that has not been in touch with the reactor core. It is also cheaper to get clean potable water only for the coffees, not the whole operation, which is often done with ordinary river water.-KoolerStill (talk) 11:17, 31 July 2009 (UTC)

A more closely related concept is Combined heat and power, although it's more common to do this with small power stations built in residential areas. The water/steam coming out of the generator turbines is already used to preheat the water going into the reactor, it may be practicable to heat water for "domestic" use in this way. If you had a turbine trip, you might lose "domestic" water heating though. Taking water out of the steam generator part-way through wouldn't be allowed, because it would make the system needlessly complex and more prone to failure.

EverGreg, many or possibly most reactors don't use heavy water in the reactor. Candu does, but many other reactors use normal water, or carbon dioxide, or other fluids. Temperature limit is covered in the USA by the Clean Water Act, and as an aside, I've known people go swimming downstream of Beznau Nuclear Power Plant in Switzerland to enjoy the warm water. AlmostReadytoFly (talk) 11:20, 31 July 2009 (UTC)

In a serendipitous coincidence, I see that Beznau Nuclear Power Plant provides District heating (i.e. hot water) to 20,000 homes. AlmostReadytoFly (talk) 11:28, 31 July 2009 (UTC)

Reuse of the waste heat from a power plant (for applications like heating) is cogeneration ("combined heat and power"). It's perfectly possible to heat whole districts of towns near powerplants (and this is done in Russia, for example), but the district has to be close to the plant for this to be efficient, and generally (even in Russia) people don't live that close to nuclear plants. You probably wouldn't want to drink the light-water secondary coolant, as it'll likely be contaminated with lubricants and maybe solvents left over from manufacturing (and if you're not heating the secondary coolant to boiling point, and staying at low-ish pressure, then you'd be drinking warm river water, which also isn't safe). There's no reason you couldn't pass the secondary coolant through a heat exchanger to heat regular treated potable water, although it's questionable if there are enough people in the plant to make it worth while (I can't see there's that much call for showering in a nuclear power plant, it's a fairly clean place). Now there is talk about small, sealed-unit, plug-and-play reactors being used in places like Alaska, so there may be more utility(sic) to CHP there than elsewhere (although the additional complexity of running and maintaining the district heating pipe system may again thwart real efficiencies). -- Finlay McWalter • Talk 11:38, 31 July 2009 (UTC)

A course of drugs that can be taken before conception to reduce the risk of fetal abnormalities?

I'm not asking for medical advice, I'm asking for this is bullshit/not bullshit.

I live in China, the land of Chinese medicine... today I was talking to a former coworker and she informed me she was going to start trying for a baby at the end of the year. She further informed me that she would begin a 3 month course of pre-pregnancy drugs in October that ensures (or improves the chances) that your baby will be healthy.

I called bullshit on anything other than vitamins and a balanced diet, but she not only insisted it was legit, she insisted that it was "xi yao" (Western medicine -- as opposed to some random animal's foot, or some fungus from a back alley dumpster).

I am highly skeptical, but I defer to the collective wisdom of the reference desk.

Note that this woman is only 26 and has nothing wrong with her - we're not talking about fertility treatments for women who have proven difficulty conceiving.

Also note that China is notorious for prescribing anything for everything in order to inflate hospital bills...

61.189.63.167 (talk) 11:13, 31 July 2009 (UTC)

Sounds like folic acid#Human reproduction -- Finlay McWalter • Talk 11:23, 31 July 2009 (UTC)

That's a vitamin, though, which he accepted as a viable/non-bullshit way of improving the baby's health. (As should anyone!) -- Aeluwas (talk) 14:24, 31 July 2009 (UTC)

I'm sceptical too. I can't see how it would work. The man taking drugs before conception to improve the quality of sperm might make sense as a way to reduce the chance of chromosomal abnormalities, for example (I don't know of any such drugs, but I can't see why they couldn't exist). That wouldn't work for women though since the ova are all made before (or maybe shortly after) birth, so if they are faulty it is too late to do anything. Other than good nutrition and making sure you are in good health, I can't see how what you do before conception can have any effect on birth defects. --Tango (talk) 18:43, 31 July 2009 (UTC)

Identification of an NZ tree

I frequently visited the Wairarapa in my childhood days and would always see trees like this in little clumps by the side of the road, but was never sure exactly what kind of tree they were. For some reason I always got the impression that they weren't endemic to NZ. Is anyone able to help? AustralianMelodrama (talk) 11:46, 31 July 2009 (UTC)

looks like a juniper --Digrpat (talk) 20:33, 31 July 2009 (UTC)

Not hungry in the morning

What is that condition called when you are not at all hungry when you first wake up? As if you will puke even if you swallow water? Some of my friends wake up hungry and can't wait to eat while I feel like my stomach cannot deal with processing anything (maybe a few sips of coffee). It almost feels like heartburn but not really. I have been like this all my life. --Reticuli88 (talk) 14:34, 31 July 2009 (UTC)

Asking us to name your condition sounds like a request for diagnosis; and we cannot give medical advice (even if your condition is mild, you are still asking for a diagnosis). See our medical disclaimer. Nimur (talk) 15:35, 31 July 2009 (UTC)

I doubt it has a name. I think it's just something with the biological clock. Some people are hungrier when they get up, some aren't. You say that yourself when you say "some of your friends" are like this, implying some aren't. It's just like some people are "morning people" and some aren't; some function well, all bright and bushy tailed, int he morning, some don't.

As an aside, if you have a doctor but because of some autism spectrum disorder can't verbalize things well, write what you just wrote down and give it to them. (Something that should probably be inaour medical disclaimer as a suggestion. Because I have experience in that area, I wouldn't be surprised if there are at least a few people with that who come on here because they want to be able to tell the doctor "I think I have 'x', rather than verbalizing their symptoms and engaging in a discussion. Writing your symptoms down is the best way to go there, not asking random strangers to say something that might be wrong and might lead a doctor downt he wrong path.)209.244.30.221 (talk) 15:56, 31 July 2009 (UTC)

Hey! How did you know I have Asperger's? --Reticuli88 (talk) 17:41, 31 July 2009 (UTC)

It's called morning sickness, heh heh (sorry). No, it's more commonly called "morning anorexia", and there are lots of possible causes, including nighttime overeating or alcoholism -- but some people are just that way all the time with no apparent health impacts. Looie496 (talk) 17:03, 31 July 2009 (UTC)

I saw this artcle: Night eating syndrome --Reticuli88 (talk) 17:57, 31 July 2009 (UTC)

In weight loss programs some members, when told to start the day with a healthy breakfast, reply that they never eat breakfast. The trainer may point out they in fact they ate supper at 7 pm then breakfast at 11 pm while bingeing in front of the TV set: crunchy snacks, ice cream, cookies, extra helpings of supper leftovers. After 8 hours of inactivity during the night, that could explain the lack of appetite at breakfast. Edison (talk) 18:45, 31 July 2009 (UTC)

DST Boston Mass 1964

Was there a Daylight Saving Time for Boston, Mass in 1964? If yes, please include dates. Thank You —Preceding unsigned comment added by 99.253.158.214 (talk) 16:22, 31 July 2009 (UTC)

Accoriding to our article on History of time in the United States, the federal government did not institute DST from 1945-1966, though it says that many states and localities did have their own versions. It does not, however, specifically mention Boston. There are some sources in our article, specifically book sources, which may give you more information and places to research. --Jayron32 17:17, 31 July 2009 (UTC)

neurons

what organism has the fewest known number of neurons —Preceding unsigned comment added by 76.119.246.167 (talk) 16:31, 31 July 2009 (UTC)

Hmm, interesting question. My best guess would be the hydra, a microscopic coelentrate. It has probably less than 100, but counting is tricky, because there is evidence that in hydras the neuron phenotype is plastic -- that is, cells can switch between functioning as neurons and functioning in other ways. The lowest actual count I know is for the roundworm C. elegans, which in the hermaphrodite form has exactly 302 neurons. Looie496 (talk) 16:54, 31 July 2009 (UTC)

Exactly 302 neurons sounds very suspicious. I just checked the source cited for that line, Collective dynamics of 'small-world' networks. There is no mention whatsoever of "302 neurons" in the full article (not even for an individual specimen), let alone that this is valid for all C. elegans. It seems strange for that kind of consistency across all individuals of C. elegans - can anybody find a source which explores this in more detailed? In the mean-time, I tagged the statistic as unverified in our article. Nimur (talk) 19:51, 31 July 2009 (UTC)

Apparently I can buy the neural circuitry schematic on 5.25" floppy - AYs Neuroanatomy of C Elegans for Computation - to verify... Nimur (talk) 19:56, 31 July 2009 (UTC)

Does zero count? Because most organisms are unicellular and so have no neurons at all. --Sean 17:49, 31 July 2009 (UTC)

Vaccines

I recently had to make a presentation for Biology about Genetic Engineering and recombinant DNA. In it, I mentioned that vaccines can have either dead or inactive viruses, and the teacher corrected me by saying that they only have "dead" viruses. I recently looked it up on Wikipedia, and found that they can be of both types. Can somebody please explain this to me? —Preceding unsigned comment added by 190.95.97.35 (talk) 16:38, 31 July 2009 (UTC)

There are many different ways of making viral vaccines, and if you read our article on Vaccine, especially the "types" section, you will find there are all sorts of vaccine types, from completely dead to inactivated to fully living and functional. Indeed, the very first vaccine from Edward Jenner contained fully functioning cow pox viruses, which as a less deadly cousin of small pox, worked quite well as a vaccine (the name vaccine even comes from the latin for cow, vacca). Not that Jenner even knew what a virus was in the 1770's, but it still is true that there are a wide variety of ways a vaccine is made. If you teacher insists that there are not, they are mistaken. Don't look to this as an opportunity to "show them up"... Just be silently content with the knowledge that you are right. If you wish, you can direct your teacher to, say, any introductory High School Biology textbook written in the past 50 years, which will explain the way different methods of vaccination work. --Jayron32 17:12, 31 July 2009 (UTC)

As a teacher myself, I believe very strongly that students should feel free to correct teachers when they are wrong. You shouldn't do it in a way that is offensive or that obstructs the flow of a lesson, but when your own understanding conflicts with that of a teacher, it helps everybody to make that clear. Not all teachers react well to being corrected, but the good ones do. Looie496 (talk) 18:09, 31 July 2009 (UTC)

The majority of viral vaccines are live attenuated versions. The Salk polio vaccine, some influenza vaccines, and Hepatitis B vaccine are notable exceptions.

• Salk polio vaccine: inactivated (killed)
• Sabin polio vaccine: live attenuated
• Influenza vaccine TIV: inactivated
• Influenza LAIV: live attenuated
• MMR vaccine (measles, mumps & rubella): live attenuated x 3
• Rubella vaccine: live attenuated
• Hepatitis B vaccine: non-living protein
• Yellow fever vaccine: live attenuated

Axl ¤ [Talk] 17:57, 31 July 2009 (UTC)

I have a followup question: What do we mean by "dead" and "killed" and "live" in the context of a virus anyway? They are basically non-living things - so are we talking about preventing them from inserting themselves into our cells so they don't get replicated? What is the distinction between "inactivated" and "dead" anyway? What exactly are we doing to them that's different in the two cases? I understand that our immune system can be trained to recognise little bits of a virus - and that this is enough to result in the real virus being recognised too...so clearly chopping up into little bits is one kind of "dead". SteveBaker (talk) 18:09, 31 July 2009 (UTC)

"Dead/killed" in this context means that the material previously contained viable virions (complete virus particles), capable of infection and reproduction. This material has been treated, usually chemically, to render the virions non-viable, incapable of replication. There is no distinction between "dead" and "inactivated". Axl ¤ [Talk] 18:49, 31 July 2009 (UTC)

Well, that's what I thought - in which case our OP and the teacher are both right (or is that both wrong?)...anyway, they agree. SteveBaker (talk) 19:35, 31 July 2009 (UTC)

However, in the context of vaccines, "inactive" could also mean "attenuated" rather than completely dead; the student's point was that there are multiple ways to make a vaccine, and the teacher seemed to (incorrectly) state that there was only one... --Jayron32 19:48, 31 July 2009 (UTC)

Steve: both the original questioner and the teacher are wrong. Jayron32: I suggest you read the articles "Inactivated vaccine" and "Attenuated vaccine". Axl ¤ [Talk] 20:17, 31 July 2009 (UTC)

F-104 engine

I was looking at some pictures on a blog and noticed that on a particular F-104 Starfighter, there was something on the tail. Here is a link. Could it be a JATO? --Blue387 (talk) 20:51, 31 July 2009 (UTC)

No not a JATO this was a special test NF-104A, according to http://www.airliners.net/photo/USA---Air/USA---Air/1055869 One of three NF-104As constructed. These aircraft had 6,000 lbs thrust Rocketdyne AR2-3 rocket engines installed at the base of the vertical fin to enable them to climb to over 100,000 feet. Lot more information at Lockheed NF-104A. MilborneOne (talk) 21:22, 31 July 2009 (UTC)

There's an Lockheed NF-104A article. -- Finlay McWalter • Talk 21:29, 31 July 2009 (UTC)

What proportion of people with flu have swine flu?

Now in the UK for example. 89.243.180.82 (talk) 21:31, 31 July 2009 (UTC)

great-grandfather

So you have a maternal grandfather, and a paternal grandfather (2). But how do you distinguish between your four great-grandfathers? —Preceding unsigned comment added by 86.162.105.200 (talk) 21:50, 31 July 2009 (UTC)

I would just say "My mother's maternal grandfather" vs. "My mother's paternal grandfather" vs. My father's maternal grandfather" etc. etc. --Jayron32 22:26, 31 July 2009 (UTC)