Wikipedia:Reference desk/Archives/Science/2008 February 15

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February 15

Science

how to calculate head from the body radiation in given room temperature? —Preceding unsigned comment added by 123.201.38.52 (talk) 00:37, 15 February 2008 (UTC)

Can anyone understand this question? I can't even parse the grammar. Maybe it's about black body radiation? —Keenan Pepper 03:42, 15 February 2008 (UTC)

"Head" is the hydraulic equivalent of electromotive force. If you have a dam, the farther the water can descend to the turbine the greater the "head" and hence the more work it can do at a given flow rate. I can't even begin to relate that to black body temperature, except a higher temperature also implies more energy per photon, like more energy per cubic meter of water with greater head. No idea if this is related to the questioner's intent. Maybe they meant "heat" rather than "head." Edison (talk) 16:45, 15 February 2008 (UTC)

Maybe it's about how to calculate how much of a head your beer will have, given the temperature of the room you're in, and given how much heat is radiated from your body (especially your hand, via the mug) into the beer? Or how much body heat is radiated from your head, given the room temperature? MrRedact (talk) 17:08, 15 February 2008 (UTC)

I find the beer question more interesting, but we require more information. A stout with nitrogen injected will produce much more head than a lager, for example. This chart may be of use. However I rarely see beer served at room temperature although I hear they do that in the UK. I'd imagine the OP meant heat from black body radiation but my expertise relates more to beer. Mad031683 (talk) 17:59, 15 February 2008 (UTC)

(OR) My father, an electrical engineer, had a high regard for Lucas Electric's engineering staff, but rather less for their sales and management (they would promise buyers too much; forcing the engineering & manufacturing sides of the company to push technology, leading to nice kit which would fail early). He used to say that the English don't truly prefer warm beer, but they are forced to drink beer at room temperature because they have Lucas refrigerators. -SandyJax (talk) 19:56, 15 February 2008 (UTC)

Warm beer allows you to taste much more subtle flavours hotclaws 21:51, 21 February 2008 (UTC)

Japanese Monkey

I recently saw a monkey in Gifu Prefecture, Japan. It was up in the mountains (the Japanese Alps), sitting in the snow, eating some sort of plant (dead grass? I'm not quite sure). It was quite big, covered with light grey fur, and had a pink face. What species was it? And is it the same sort of monkey that I've heard bathes in hot springs? (there were hot springs near the place where I saw it). And while we're on it, how many species of monkey live in Japan?

202.124.215.123 (talk) 00:57, 15 February 2008 (UTC)Kagome

Try Macaque.--Stone (talk) 06:27, 15 February 2008 (UTC)

The Snow Monkey, one cool animal! (Japanese Macaque, Macaca fuscata).--Eriastrum (talk) 20:18, 16 February 2008 (UTC)

Energy

How efficient would the collision of two neutrons traveling at 100% 99% the speed of light in total conversion of mass to energy be compared to the total conversion of mass to energy in the colliding (at any speed) of a neutron and an antineutron? Zrs 12 (talk) 01:33, 15 February 2008 (UTC)

They can't travel at 100% the speed of light, as this would imply they have infinite energy. Someguy1221 (talk) 01:34, 15 February 2008 (UTC)

Hypothetically. Or would this mean when they collided that infinite energy would be released?--Zrs 12 (talk) 02:01, 15 February 2008 (UTC)

The "infinite" means that you get them to 100% of the speed of light you have to give them infinite energy. Since you can't do that, you can't get them that fast. Ariel. (talk) 02:53, 15 February 2008 (UTC)

This would mean they have infinite relativistic mass, which would mean infinite gravity. — Daniel 02:07, 15 February 2008 (UTC)

Yes, I know. Thats why I said hypothetically. Anyway, to avoid all of this, I will just change the question. Better? Zrs 12 (talk) 02:16, 15 February 2008 (UTC)

Are you sure you are asking the right question? mass to energy of two neutrons? None of the mass will be converted to energy. It will all stay as mass. A neutron can decay to a proton and electron, but that's it. It was no method of converting it's mass to energy. When they collide the energy (from velocity) will be converted to mass, and photons. If a neutron and antineutron collide then all the mass will be converted to energy, but lots of energy from velocity will also be converted to mass and photons, just like in the first situation. Ariel. (talk) 02:26, 15 February 2008 (UTC)

So colliding two neutrons at 99% the speed of light will not produce any energy at all? Zrs 12 (talk) 02:35, 15 February 2008 (UTC)

What do you mean by "produce"? The velocity of the particles is already energy. Ariel. (talk) 02:39, 15 February 2008 (UTC)

He knows that. Yes, colliding two neutrons will produce energy in the form of heat and other radiation. 64.236.121.129 (talk) 14:20, 15 February 2008 (UTC)

BTW mass and energy are the same thing, except that mass has quantum numbers. Since the only quantum numbers in your example come from the neutrons that's the only thing that matters, the speed is irrelevant. There is no "conversion" - they are both the same thing. The only thing that matters is what happens to the quantum number of the neutrons. If you get some particles emitted from the collision then you always emit them in pairs, one mass, and anti-mass. If you look at the entire system as a whole, it started as energy and they are still energy since the particles are opposites and cancel out. Perhaps you are wondering how many particles will be emitted from the two types of collisions? I'm pretty sure it's the same both ways. Ariel. (talk) 02:38, 15 February 2008 (UTC)

No. I knew ^^ that. I mean energy "produced" if you will as it is in a neuclear fission/fusion reaction. Zrs 12 (talk) 03:07, 15 February 2008 (UTC)

Um, OK. The energy produced in a nuclear reaction is due to the change in binding energy of the nucleus. That doesn't apply to two individual neutrons. Instead of keeping some energy as binding energy we release it. Like if you have a supply of stretched rubber bands. You can release the stretch and power stuff from it. But the energy in the rubber bands was already there, we just released it from inside the rubber band to outside. This doesn't apply to smashing neutrons. I still think you haven't asked the question you really intend. Why don't you write what idea you are thinking of, and I'll see if I can help you understand. Ariel. (talk) 03:17, 15 February 2008 (UTC)

No, this is the question I intended. Would the quarks in the neutron not have releasable binding energy? And on a completely different note: Why in the Schrodinger's Cat paradox can the cat not be considered an observer and collapse its own wavefunction? Maybe there is something I'm missing? Thanks, Zrs 12 (talk) 03:25, 15 February 2008 (UTC)

Excellent questions! To the first: to release binding energy you have to go to a lower binding energy state. In atoms the lowest is nickel and iron. You can't get any energy from them, because no matter which way you go (more protons or less) you need to add energy. Currently there is no known lower state for the quarks in a neutron to go to (except a proton and electron see neutron decay). But I should point out we don't know a lot about quarks. But I'm pretty sure a lower state doesn't exist, because if it did it would have shown up. But see the article on proton decay for a possible lower state for protons. To the second question: the cat is basically two cats, one dead, one alive, both at the same time. Each of them observes itself, but that doesn't affect the other. See Quantum immortality for a rather interesting possible effect. Ariel. (talk) 03:52, 15 February 2008 (UTC)

Thanks. So does this mean that we are all more than one person? Furthermore, in the Copenhagen interpretation why would the cat not be able to collapse its own wavefunction? I assume you were talking about the Many-worlds interpretation. Thanks, Zrs 12 (talk) 15:12, 15 February 2008 (UTC)

There's no reason to suppose it couldn't, but it really doesn't matter in this experiment. It makes no empirical difference when the wave function collapses, even from the cat's perspective. The only nonclassical event in the whole experiment is the decay of the radioactive atom. You can just as well suppose that the collapse happens right after the decay, long before the signal is even amplified. You can even suppose that the decay arises from classical chaos too. As an attempt to show what was new and strange about quantum mechanics, Schroedinger's cat was a complete failure. The double slit experiment is where it's at. -- BenRG (talk) 02:15, 16 February 2008 (UTC)

Agreed; what Schrodinger should have proposed was throwing cats at a wall until two of them cancelled out. Someguy1221 (talk) 03:34, 16 February 2008 (UTC)

Haha, yeah I would like to see two cats cancel out. The double slit experiment is easier to understand (at least to me) too. Ha, and this whole time I thought the whole cat thing was about when the wavefunction collapsed. Zrs 12 (talk) 17:28, 16 February 2008 (UTC)

Full-on beak-locked combat in gulls...?

As seen in this video (and others on YouTube) - what exactly is this purpose behind this extreme aggression? This tug-o-war style squabbling is much more violent and intense than the typical inter-gull bitching, bickering and chasing for food and status you normally see. I've yet to hear a satisfactory explanation for what is a fairly uncommon behaviour (I've only seen it in real life a couple of times myself - and I watch gulls a lot). I've heard several suggestions (two equally-matched male birds fighting over a female, two male birds fighting over a particularly lucrative territory, or a female bird testing the strength of a male before deciding to pair up with him) but no-one I've ever asked seems to know for certain. Any ideas, folks? This one has been bugging me for a long time. --Kurt Shaped Box (talk) 01:39, 15 February 2008 (UTC)

Kurt, by now you are an expert on gulls. You should discuss this type of question with other experts, and then (citing the appropriate references) add the answer to the gull article. I do hope that you are by now in correspondence with other gull experts. -Arch dude (talk) 03:16, 15 February 2008 (UTC)

Haha, great answer. —Keenan Pepper 03:35, 15 February 2008 (UTC)

Where the heck is the Gull Ref Desk? There would be a load more interesting questions than they have in the dying "Entertainment" section. 206.252.74.48 (talk) 13:32, 15 February 2008 (UTC)

It was deleted. See this discussion for example. Algebraist 15:28, 15 February 2008 (UTC)

Ah, thanks for that. I knew it was mentioned at one point. I never get bored of Kurt's questions, because they are always valid and thought-provoking. As for this question: some individuals are more violent than others, that is all. This is true across the animal kingdom. I'm sure you've seen some meek seagulls, cowardly seagulls, and maybe even stupid seagulls, what is there to say there aren't psychopathic ones? —Preceding unsigned comment added by 206.252.74.48 (talk) 16:51, 15 February 2008 (UTC)

Thanks for that. It's certainly possible that it's just a case of two hot-tempered, particularly violent gulls clashing. Usually, a confrontation between gulls is a case of 'one bird attacks - the other immediately runs/flies away, with lots of noise made on both sides' - that happens all the time whenever gulls are in close proximity. Yes, what we are seeing could certainly be the end result of a bird refusing to back down in the face of another.

I've found it quite difficult to locate detailed/reliable information about gull social behaviour. It doesn't seem to be a particularly well-studied field. There are many 'gull experts' on the internet who know a lot about what different species of gull *look like*, gull migratory/nesting habits and gull physical biology - and many people who like to photograph gulls, then discuss their plumage patterns at length. If, OTOH you need to know about how gulls behave and communicate, then there are many contradictory accounts and personal theories from amateur birdwatchers to choose from - but little in the way of hard science backed by reliable sources. I have been unable to find out much about the 'pecking order' in gulls, for example - other than that "yes - they have one". Someone here did once recommend a book (quite an old book, IIRC) on this subject a couple of years ago, but I have been unable to re-find the thread in question and I cannot remember anything about the title or the name of the author (if it was you, please chime in - I'd be much obliged). --Kurt Shaped Box (talk) 00:53, 16 February 2008 (UTC)

No book, but i found this nice little piece on territorial behaviour in groups of chickens, gnats, gulls, cryptic moths, gulls, the purpose of fighting and spacing[1]. Attrition seems to be the name of the game. Julia Rossi (talk) 13:29, 16 February 2008 (UTC)

Kurt, have you read the classic book on gull behavior: The Herring Gull's World by Niko Tinbergen, published way back in 1953? Tinbergen was one of the founders of the whole field of animal behavior. His book is immensely readable and shows how clever Tinbergen was in making simple field experiments that answered many questions about gull behavior. In fact, I recommend reading any of his varied books. As to why gulls get into fights, one of the reasons is surely wrangling over the dominance hierarchy.----Eriastrum (talk) 20:10, 16 February 2008 (UTC)

I aren't able to see the video, but locking beaks together when fighting doesn't necessarily imply more violence. The locked gulls would then not be pecking or pulling feathers; and they could directly determine each others strength instead of bluffing.Polypipe Wrangler (talk) 21:05, 16 February 2008 (UTC)

That's certainly what they seem to be doing in this video. Of course, you probably won't be able to see it. The gulls in the first vid were being much more aggressive, however. --Kurt Shaped Box (talk) 23:01, 17 February 2008 (UTC)

Yes! That was the book! Thank you very much. Now (after looking on amazon.co.uk) I remember why I didn't buy it when someone last mentioned it. I *hate* paying silly money for out-of-print books - and I *hate* buying cheap out-of-print books that are stated as being 'slightly worn' without first being able to inspect them for myself (I've been burned before)... ;) I daresay that I will (eventually) get ahold of a copy... --Kurt Shaped Box (talk) 23:01, 17 February 2008 (UTC)

Black hole evaporation

When a black hole evaporates, what happens to its electric charge and angular velocity? — Daniel 02:04, 15 February 2008 (UTC)

The emitted particles have it. Look at it backward, instead of wondering what happens, nothing can happen unless electric charge, and angular velocity, and everything else is taken care of. If something prevented that, it won't evaporate in the first place. (BTW both black holes and evaporation thereof have never been seen, so it might not exist.) Ariel. (talk) 02:30, 15 February 2008 (UTC)

Aren't the emitted particles photons? They can't carry charge. — Daniel 03:36, 15 February 2008 (UTC)

You are the second person today who told me that blackholes emit photons (isn't that a contradiction it terms?). They don't, they emit a whole zoo of random particles, but not photons. They emit anything that has a matter/anti-matter pair. A photon is it's own anti particle and will not be emitted. Ariel. (talk) 03:43, 15 February 2008 (UTC)

They do emit a whole zoo of random particles, as you say, but I think photons are allowed to be in the mix. The whole "one particle of a virtual pair falls in, the other escapes" explanation is too simplistic to make this kind of prediction. Then again, the correct description of the process (quantum field theory on a curved space-time manifold) is way over my head, so you may be right. —Keenan Pepper 04:04, 15 February 2008 (UTC)

What makes you think that means they won't be emitted? A virtual particle pair can be made up of two photons and in fact photons would be a primary form of emission associated with an evaporating black hole. Dragons flight (talk) 06:43, 15 February 2008 (UTC)

Cool, that agrees with what little intuition I have about this. —Keenan Pepper 23:06, 15 February 2008 (UTC)

What exactly is a magnetic field?

All my life I have wondered, is it an OBJECT of some kind, or a process? Is it animal, vegetable or mineral? I’ve seen diagrams where it is stretched, warped, looped and tied up in knots; but what KIND of thing is it exactly? Can you spin it into a pair of pants? Can you heat or cool it? What would it look like under an atomic microscope? What the hell is it? No technical explanations please. This is just a general enquiry Myles325a (talk) 02:43, 15 February 2008 (UTC)

I'd say a magnetic field is an abstraction - it's something used to sum up or describe a physical property of different points in space. The property being described is magnetic field strength - i.e. the extent to which a moving electric charge etc would experience a force. The property is determined by whehther and how much stuff there is around that point which exerts a force on electric charges etc, and how far away they are.

The field itself has no physical existence - it merely describes how much force you experience when you go near, say, an electromagnet (if you are a charged particle, that is). The force is caused by the magnet, and it is being experienced by you. When you are "outside" a field, that just means you are so far away from whatever is causing the magnetic force, that you don't experience it. --PalaceGuard008 (Talk) 03:39, 15 February 2008 (UTC)

But what is the argument that forces are less an abstraction than fields? As I discovered trying to research a question from last week, I can't find much in Wikipedia about the philosophy of forces. --Allen (talk) 05:27, 15 February 2008 (UTC)

The nature of science being to describe rather than explain, everything is an abstraction. Force is only formally explained in the fields that deal with the nature of the forces themselves: General relativity (or quantum gravity) for gravity, quantum electrodynamics for electric and magnetic force (essentially the same thing), and quantum chromodynamics for everything else. The best way to learn this without spending eight years learning advanced physics is just to accept that particles have interactions with eachother (explained in the above links, I presume, I don't actually feel like checking), these interactions are described by an equation involving a force, and a force field describes the force on a test particle at an arbitrary position in space. So then, neither the force nor the field really exist. They're just mathematically succinct ways of describing the nearly impossible to understand interactions between particles, for the benefit of everyone only cares what the end result is (which is just about everyone). Someguy1221 (talk) 05:37, 15 February 2008 (UTC)

• No, the nature of science is not to "describe rather than explain" as you put it. A scientific law is a description of observed phenomena, while a scientific theory is an explaination of observed phenomena. Theory is a big part of why we do science. 64.236.121.129 (talk) 14:15, 15 February 2008 (UTC)

This is getting a bit off topic, but, what exactly is the difference between explaining and describing?128.163.80.188 (talk) 18:44, 15 February 2008 (UTC)

A scientific theory is just a model used to consistently hosue mathematical descriptions for the purpose of predicting events. If you ever study the history of science, you'll notice the distinct prominence of explanation that prevailed in pre-Newtonian/Galilean physics, for example. The ancient theories of science (mostly Aristotelian), and notable later theories such as those of Descartes, endeavored to explain, well, why things do what they do. Why do solid objects fall to the ground? Why does smoke rise? These theorists came up with very detailed explanations, yet they themselves predicted nothing. Alternatively, a pioneer in modern science such as Newton produced a mathematical description of how objects interact, with the goal of predicting as yet undocumented systems of interaction. Of course there was always a larger theory behind it all (and Newton's was generally wrong). But then you get to the crux of the matter. Even though Newton's explanations were essentially always wrong, we still learn his equations to this day. And that's because his descriptions were very accurate. And for three hundred years since, theories have been overturned in favor of newer, better ones (ok, that mostly stopped once quantum was established, but plenty of physicists are still trying). The descriptions that these theories have produced have generally not been overturned (sometimes they're rendered useless or obsolete, however), and they are often not doubted even when their base theories are proven wrong. And this is all completely opposed to those earlier thoeries I mentioned, in which the descriptions stem from the explanation (and not the other way around). And so I feel quite justified in claiming that the purpose of science is to describe rather than explain. Although you can define those terms to force the validity of that statement to whatever you desire. Someguy1221 (talk) 20:08, 15 February 2008 (UTC)

Einstein in his book About Special and General Relativity Theory (I can't remember the title exactly, but it talked about the theories from a philosophical standpoint), called the gravitational and the magnetic field "something physically real". --Taraborn (talk) 07:00, 15 February 2008 (UTC)

Science is as much about explaining as it is about describing, if not more so. Unless you are a physicist who works at the very bottom of the hierarchy of abstractions, science is about describing observed phenomena and explaining apparently diverse phenomena as manifestations of a relatively small number of more fundamental phenomena. --71.162.242.55 (talk) 09:45, 15 February 2008 (UTC)

Now see my big comment above. Unless you don't care to see your science applied in your own lifetime, your only impetus to produce a novel explanation is to arive at a better description :-p Someguy1221 (talk) 20:22, 15 February 2008 (UTC)

Force is a concept that allows certain phenomena to be described succinctly. The phenomena described are real (as in actually observed), but their descriptions do not have to involve the concept of force. You can think of force as an accounting device for objects' tendencies to accelerate in certain situations. You can describe the gravitational attraction between two objects in terms of mass, acceleration, and the distance between the objects. You can also describe the attraction/repulsion between two charged particles in a similar manner. Now what if you have two objects that have both mass and electric charge? Do we need a whole new law to describe how they tend to accelerate? Fortunately the answer is no. The concept of force presupposes that the tendencies objects to accelerate as described by different "laws of physics", as we have formulated them, are combinable. The concept of force allows such combination to be done mathematically via vector summation. --71.162.242.55 (talk) 09:33, 15 February 2008 (UTC)--71.162.242.55 (talk) 09:33, 15 February 2008 (UTC)

Did somebody axe the pigeons? Julia Rossi (talk) 09:46, 15 February 2008 (UTC)

Ah, they on the other desk here{http://en.wikipedia.org/wiki/Wikipedia:Reference_desk/Humanities#What_exactly_is_a_magnetic_field.3F] —Preceding unsigned comment added by Julia Rossi (talk • contribs) 09:59, 15 February 2008 (UTC)

[I merged the duplicate threads; moved material is below.]

Well, I'm curious. In the documentary War of the Birds re their ability to navigate, pigeons were described as "seeing" the earths magnetic field to explain how they found their way home over say 250 miles (in those days) over a featureless ocean (oh, and in the dark). There's a bit here[2] in the homing pigeon article. Wondering, in what way is it visible? Julia Rossi (talk) 08:17, 15 February 2008 (UTC)

Well, we don't really see distant objects; we see light that of its own accord enters the pupils of our eyes, and infer the existence of distant objects from that. Static magnetic fields don't emit anything, so there's no way any animal could "see" distant magnetic field lines. I assume they're only aware of the direction of the field through their body, i.e. they have an internal compass. -- BenRG (talk) 11:53, 15 February 2008 (UTC)

The use of "see" here is a metaphor for "sense". It's a fairly common metaphor, do you see what I mean? JohnAspinall (talk) 15:57, 15 February 2008 (UTC)

I’ve thought about how we or other animals might feel other senses. I imagine it as a sort of feeling of mild pressure in the head. A sort of feeling whereby if the pigeon orients its head in line with a prevailing magnetic field, it experiences a sort of vaguely narcotic blocked out feeling of euphoria, like when you can finally stretch out after being cramped up for hours, or when you can finally get someone to scratch an itch on your back. Otoh, going in a direction ACROSS the lines, makes it feel jumpy and nervous, like someone was scratching fingernails across a blackboard. I should know. I was a passenger pigeon in a past life, and you bastards drove my people to extinction. Myles325a (talk) 23:13, 17 February 2008 (UTC)

A magnetic field is a stress in the luminiferous aether. I'm only half joking. As far as the Standard Model is concerned, everything in the world is a field, and the physics of the fundamental fields is close enough to the physics of vibrations and stresses in a solid. A static electric or magnetic field is a state of stress. If the field varies, you get sound waves that propagate though the solid; that's light. Ordinary matter is made of different kinds of vibrations in the field. Your body is a kind of soliton. -- BenRG (talk) 12:14, 15 February 2008 (UTC)

A magnetic field is a forcefield. Ofjects within the magnetic field will be attracted to the object producing it. The Earth has a magnetic field. You cannot touch or feel it. You cannot see it under a microscope (unless it was on paper and there were iron filling scattered about). You cannot weave it into pants. A magnet produces such a field. You cannot eat a magnetic field. It is not a object, but a field containing magnetic force. A magnetic object always has two poles. The poles will attract unlike poles and repel like poles. You cannot cut a magnet to isolate one pole. Was that simple enough? Hope this helps. Thanks. ~AH1^(TCU) 22:41, 15 February 2008 (UTC)

OP myles325a has sixpence left. Well, no, it doesn’t help at all. Look once again at your answer to my question ‘What is a magnetic field’ and you will see that it is a copybook example of circular reasoning, aka begging the question. It really tells one nothing at all to say “A magnetic field is a ‘force field’” unless you are prepared to say how that differs from one you plant potatoes in. And I know all the things you can’t do with it. To define a magnetic field as ‘It is not an object, but a field containing a magnetic force’ is just saying the same thing back the front. See follow up answers to yours which try to grapple with the problem. Myles325a (talk) 00:06, 20 February 2008 (UTC)

Dr Karl says watch out for Norberg[3] if you are a pigeon. Julia Rossi (talk) 13:39, 16 February 2008 (UTC)

OP myles325 responds. Oh guys, guys, please…settle down… Now see this is what always happens here You ask a simple question and request NON-TECHNICAL answers and you get whole dissertations on everything from the kitchen sink to relativity. Try to ENGAGE with where my head is at, why I am asking this question, and the GIST of the problem. GIST, get it? Now PalaceGuard8 (and I wonder if the other 7 work in the same palace) said that ‘magnetic field’ is ‘an abstraction’ but he doesn't tell me what he means by an ‘abstraction’. Is it like this? If I plotted the temperature of Sydney over one year on a graph with temperature as the Y axis and time (in days) as the X axis, I would get a sort of sine curve (due to higher temperatures in summer and lower ones in winter). This line on the graph is to me ‘an abstraction’. No such line exists in Nature but the line I have drawn from the data is a map of a real process. And consider the high tide line on a beach – on the sea side of the line, it is smooth, on the land side, there are pebbles and so on. But that line is not something laid down on the beach as an individual construction. It is only our perception of the two different states on either side of it that makes us see it as an individual thing. Now, is a magnetic field like the graph of example one, or the dividing line between forces of number two? Or is a ‘real thing’ in its own right? If the latter, is it an animal, vegetable or mineral? Myles325a (talk) 23:00, 17 February 2008 (UTC)

OK. When you have an electric current traveling through a loop, and you fire an electron past it, you'll notice the electron will follow a curved path, and only (assuming this sytem is isolated from the rest of the universe) if there is current in the loop. You can fire your electron along various trajectories and carefully monitor its path, which will tell you the force it feels at any position in space around this loop. You can also vary its speed to see how that varies the force as well. And when you are done, you'll be able to plot this neat looking field that happens to have the form of ampere's law. We call this an abstraction because you still have no idea what's actually going on. You've given yourself a powerful tool to predict how charged particles will move in the presence of an electric current, but you still have no idea what's literally influencing that motion. It's something that Maxwell's laws were simply never meant to explain (although people tried); it's just a predictive tool. You can consider it real in other senses, however. The field does not dissipate immediately upon the removal of current, and the field itself can carry energy through space (in the form of the potential to accelerate charged particles) long after the current generating it has been eliminated. And this would clearly imply that the magnetic force between a current and a charge cannot be simply explained by an interaction that is merely described by the magnetic field. There is obviously something that persists, something that moves with the field. But quite what is going on is only answered in quantum electrodynamics, which most people would rather not try to understand. So knowing all of this, it should be clear that a magnetic field (or any force field, really) is just a concise way of plotting how objects will interact at a distance, without telling you what's actually going in during the interaction. Someguy1221 (talk) 23:26, 17 February 2008 (UTC)

I don't think you realize how philosophical your question is. It makes me think of an anecdote I heard many years ago from one of my professors at Berkeley. He told it as a Feynman anecdote, but I don't know whether it's a real one. The story was that a non-scientist came to Feynman and asked almost exactly what you're asking now—for an explanation of electromagnetic fields in terms of familiar things. Feynman thought about it for a while before returning with (my professor said) the correct answer, which was that it can't be done. It can't be done because electromagnetic fields are the more fundamental thing. You can make animals, vegetables and minerals out of more fundamental stuff, but you can't make the more fundamental stuff out of animals, vegetables and minerals. So, that's my answer. Magnetic fields are real; animals, vegetables and minerals are abstractions. The world is not made of the stuff of familiar experience. My other answer (that magnetic fields are stresses in the luminiferous aether) still stands. That's not a vague analogy, by the way, but a precise mathematical correspondence. It might be too technical, though. (Certainly the articles are not very friendly.) -- BenRG (talk) 01:00, 19 February 2008 (UTC)

Opmyles325 here. Thanks Someguy1221 and BenRG. Between the two of you, you have taken the time and trouble to construct careful and meaningful answers to my query. My understanding of magnetic fields now is that they are like graphical depictions of wave-like events about which we know little, and can visualize less. When we do the maths about how these events operate and put them into graph format, we get lines and other visual effects, but these are prosthetic inferences (to coin a phrase) and should be recognized as such. Maybe it is anologous to seeing a weather map with its isobars and highs and lows. Those lines don’t exist either, but they map something which does. I think Someguy said something like that – I hope I’m not misrepresenting him too much.

And BenRG, I do understand the philosophical nature of my question – I have been interested in philosophy all my life. I take your point about ‘stresses’, but would only caution that the introduction of a term like that as a kind of synonym for ‘field’ runs the risk of merely calling the problem by another name, and leaving no one the wiser for it. Thus someone might object that saying that ‘magnetic fields are stresses in the luminiferous aether’ is like saying ‘sleeping pills work because they have a soporific quality’. I suppose the jist is that the field is a wave propogation through space, and thus an event and not an ‘object’. Btw, it only confuses a difficult issue further to state that magnetic fields ‘are real’ in counterposition to animals et al, which are ‘abstractions’. The properties of animals might well be contingent on more fundamental laws and processes, but that does not ipso facto make them ‘abstractions’. I understand ‘abstraction’ to mean something like World War 2, the Renaissance, heroism, and so on. But ‘animals’ certainly refer to particular concrete entities, not abstractions, except in the sense that ‘everything’ might be termed to be an abstraction ‘in the final analysis’. Finally, many writers on these boards keep maintaining that they can give no cogent answer to simple questions like mine without unleashing years of technical graduate physics. That’s tosh. If someone asked me what a cup of tea was, I would not feel compelled to give a detailed account of the thousands of chemicals involved, nor a long treatise on the beverage cultures of China, India, Sri Lanka and so on. This is a People’s Encyclopedia folks, let’s stop showing off our erudition and give short concise answers to questions which are appropriate to the learning of someone using a free general encyclopedia, and to the nature of their concerns. Myles325a (talk) 03:20, 19 February 2008 (UTC)

Dear OP Myles325, being nowhere near to unleashing years of technical graduate physics, the pigeons (who Know) and I, salute you. Julia Rossi (talk) 10:05, 19 February 2008 (UTC)

Coo… cooo… my magnetic field just turned into as Mobius strip… Polly want a cracker (oh hang on, wrong bird…)Myles325a (talk) 00:18, 20 February 2008 (UTC)

Is this thread too long yet? Nah, we're barely at the five page mark.

Calling the problem by another name was my point. I wasn't trying to explain magnetic fields as stresses, I was just saying that they are stresses—that is, that you can think of them as stresses if you find that easier. I thought the concept of stress in a solid might be somewhat familiar to you, and since it's the closest thing to a magnetic field among objects of semi-familiar experience it seemed the most sensible answer to your question. One of the specific points I hoped the aether-stress analogy would clarify is that the magnetic field is not inherently wavelike, just as stress in a solid isn't. Waves are vibrations, and when a solid is under static stress it's not vibrating. You seem to have come away with the opposite impression. Teaching is hard. All of us in this thread (and most other threads, for that matter) are to some extent flailing around trying to guess all the unstated information about the questioner's educational background that we need to know to produce an answer that will be comprehensible to you. By the way, what is a cup of tea? You said you wouldn't talk about its chemical composition or its importance in various Asian cultures, but you didn't say what you would talk about, and I'd honestly like to know, because I have no conception whatsoever of what someone who asks "what is a cup of tea?" is really asking about.

Also, I can't let your "tosh" go unchallenged. Ultimately you do need to get an education in physics in order to understand physics, because that's what an education is. There's no royal road to spacetime geometry. You have to build up your knowledge gradually, starting with something that you kind of get but not really and working with it until you get it better, then moving on to something that depends on getting the last thing. You don't have to do that in an institution of higher learning; you can do it on your own, by working through textbooks and asking questions on forums like this; but you have to do it gradually. It's possible that magnetic fields are close to something you already understand and you just need a nudge in the right direction (and we haven't found the right nudge yet). But it seems more likely that the shortest path from what you now understand to an understanding of field theories is a pretty long path. Those people who said you'd need years of technical education were probably right. Everything takes time to learn, even something as simple as physics.

My comment about animals being abstractions was mainly a joke, but for what it's worth I do think that animals and World War II and heroism all exist in essentially the same way. That's just another way of saying I'm a materialist; if heroism exists as a concept, then ipso facto it has a material existence of the same kind as an animal's. I'm not sure what you mean by "concrete entities"; my best guess is that by a concrete entity you mean something made of atoms, but I don't consider that an interesting distinction to make. -- BenRG (talk) 02:06, 20 February 2008 (UTC)

OP myles325 makes a dash for the line. BenRG, there are two main ways a writer can confuse his audience; one is by employing technical jargon, and the second is by using terms which are archaic and of interest primarily to the antiquarian. And your utilization of luminiferous aether in a single term scores bulls-eyes in both quagmires. And the cherry on top is adding, - presumably as some kind of disclaimer - that you are "only half joking". Yes, what a gut-buster that was, I can assure you. Thanks for explaining it, much obliged. But could you please, for the short time that this will take, remove your hand from your knob and place it over your heart and tell us that it is absolutely necessary to invoke such a term to explain a layperson's query: "What is a magnetic Field?", and moreover affirm that not only is it necessary, but it must needs appear in the very first sentence purposing to provide said explanation? Because I (and there are many of my kidney) imagine you enjoy the notion that you are possess esoteric knowledge which is beyond the ken of mortal man, and instead of doing your unassuming best to shine clear light on the darkness, will rather do your best to pile obscurantism onto pedantry, while big-noting yourself and patronizing the humble seeker of truth. And that is the last thing a People's Encyclopedia needs - someone who is ever ready to tell those who dare peer into these pages that so arcane are these mysteries that no illumination can be afforded them but they should toil for years and years perusing dusty old tomes. And even then, only the most elect will be vouchsafed a glimpse of the truth. Tosh, I say again, and Double Tosh!

Of course I know the truth is rather more prosaic. In my reply to your post, I courteously thanked you for the time and effort you had given to formulating an answer, though I did bridle for a moment at your remark: ' I don't think you realize how philosophical your question is' having supposed that the language of my query might have revealed that I was not entirely unlettered. In the course of agreeing with your argument in general, I made some small dissent to a couple in particular. Even more grievously, the defendant (me) did cause the estimable Julia Rossi – about the only she-woman who hangs out around here – to smile and blow me a kiss, and thus was I condemned by your pride from the outset. Hoisting your considerable nose high in the air, you then advise me that I know not the nature of education, that I cannot follow the subtlety of your thought, that others of elevated station must ever 'flail their arms' in having to answer such questions from the unwashed masses, and so on and on, making me wonder finally as to why you would bother in the first instance to undertake this thankless pedagogy, so prodigious is your vanity and so miniscule your capacity for forbearance.

You profess not to know what to make of such a question as "What is a cup of tea?" for one cannot know to what purpose and from what vantage point the question is being asked. Rubbish! And so at odds with the very nature of an Encyclopedia. Are you like that hair-splitting egg-head who, upon being asked "How are you going?" replied: "Relative to what?" There is a tendency in Continental Philosophy (Leibniz in particular) to adopt a radically holistic approach to epistemology, holding that to understand the nature of any individual truth, you must understand the nature of all the prior truths that underpin it, and thus, as all the truths of the world are interconnected, one cannot understand a hard-boiled egg without knowing everything that God knows about the entire world. But in actual practice, as the pragmatic English masters discerned, one can get a perfectly serviceable synopsis of the truth that is adequate for the purposes for which it is required. Of course it is self-evident, and tediously self-evident, that a teacher must have some notion of a student's background. If Einstein were to ask: "What is time?" a savvy teacher might point him to a physics research library; if I were to so ask he might provide me with a few pars as a general introduction, and if someone from Yahoo Q and A asked, he might look at his wrist and offer: "Four thirty by my watch". But do you really maintain that you cannot know which is which? Teaching is more than a science, BenRG, it is an art, and a good teacher is foremost a good communicator, and a good communicator is someone who knows by intuition and empathy from where his questioner is coming. These are considerations you would do well to take on board. And I should tell you plainly, your writing style is often confused and ergo confusing. Try editing (and rewriting) your text via a word processor as I do – it makes all the difference.

In conclusion though, I should say that I understand by luminiferous aether the earlier theory that a pervasive field pervades the universe, providing the substrate through which light could 'wave', and subsequently retired after the famous Michelsen and Morley experiments and Einstein's Theory of Relativity (Special) appeared to render it superfluous. Now, there is a move amongst some physicists to rehabilitate some version of it, as the Holy Grail of Theory of Quantum Gravity appears to need a structure like that to explain in fine detail how it is that mass warps space-time. Of course this is simplistic and probably defective, but the task of expounding it in the round need not detain us here. I have, here and elsewhere in Wikipedia, spilled much virtual ink, arguing that WP editors should be clear that WP is not now, and never will be, and never should aim to be, a vessel which proposes to contain in some form, all extant knowledge about any topic. The world of specialist publications serves that purpose. WP can provide an invaluable service in adumbrating some general and useful knowledge on any topic, and pointing the user, via a decent bibliography, to repositories of advanced material, but little more than that. It is ironic that it has proved that amateurs writing for the lay public are far more inclined to bombast, pedantry, and pomposity than those experts who are paid to communicate. Scientific American and New Scientist would never print the self-serving and often impenetrable material one can find everywhere in WP, material that is not only opaque, but often syntactically and stylistically deficient. And you may "wave your arms" all the more, BenRg, but the unvarnished truth is that your writing is mediocre in the technical sense, and this is not helped by a tendency to patronize and insult your audience, and bog them down with largely extraneous and self-serving hocus-pocus. Myles325a (talk) 07:55, 21 February 2008 (UTC)

Um... wow. I haven't been flamed in something like a decade. I should have looked at your edit history before I got involved in this; had I seen stuff like this and this I probably would have skipped the thread. I assure you that most of the people you see as arrogant pretentious fools are just ordinary flawed people trying in their pathetic way to help other people, and often failing.

Your mention of New Scientist just now in the context of this thread made something click for me. New Scientist is not a good place to learn physics. I think it was once a respectable magazine, but currently it's a disaster, at least in its physics reporting. It may be friendly, well written and well illustrated, but it's not real. Quantum computers don't do calculations in parallel universes. Spacetime isn't like a rubber sheet. String theory isn't a theory about vibrating strings. It's easy to picture, and it's wrong. It's meaningless pseudoknowledge. If you ever decided to learn string theory for real, this "knowledge" wouldn't help you in the slightest. If you wrote about the philosophy of string theory on the basis of this "knowledge" you'd make a fool of yourself. I don't think you want your understanding of physics to consist of a lot of lies and half-truths, but if you choose your sources on the basis of ease of reading, that's largely what you'll get. Real physics is harder.

(New Scientist is the worst of them, fortunately. Scientific American is better. John Baez recommends American Scientist, though the way he does so may sound pompous. QED by Richard Feynman is excellent in my opinion.)

I can't think of anything else to say that I didn't already say above, and I haven't changed my feelings about any of it. I'll respond to future substantive discussion (if you want me to) but not to future insults. -- BenRG (talk) 12:56, 22 February 2008 (UTC)

OP myles325a here. Is anybody else left in the all-night poker game, or is it just us? Ok, you’re on. May take a couple of days, though, I’m fighting on three other fronts, and I’ve got to retrieve the kitchen sink from where I last threw it. Myles325a (talk) 00:49, 23 February 2008 (UTC)

I wish I hadn't written that. It wasn't intended as a challenge. Ultimately I edit Wikipedia for fun, and I'm not enjoying this conversation any more. I think I would enjoy a similar debate with someone who had the same views as you, but not after your last reply. So I take back that offer; I'd rather just end this thread. I do (honestly) wish you success in learning physics, by whatever methods work for you. -- BenRG (talk) 12:58, 23 February 2008 (UTC)

science fair

hey, i need a science fair project with all the oooohhs and aaaaaaahhhhh if you know what i mean. i know the judges are suppose to judge on the other stuff but at this fair they don't. i need help bad! please help me! —Preceding unsigned comment added by 76.14.124.175 (talk) 06:37, 15 February 2008 (UTC)

A fission reactor would definitely illicit some sort of response (perhaps including a call to the police, or if you're in the US maybe DHS), though it may also result in an unpleasant demise if not executed properly. But more to the point: I think Do your own homework may apply here. -- Consumed Crustacean (talk) 06:50, 15 February 2008 (UTC)

That's "aargh!", not "aaahh". I don't think Do your own homework applies: s/he is going to, but just wants suggestions. Never having been to a science fair, I don't have any I'm afraid.AlmostReadytoFly (talk) 08:51, 15 February 2008 (UTC)

Regardless of your project, make sure you have pretty graphs and charts. Scientists fall for that stuff all the time! (EhJJ)^TALK 12:31, 15 February 2008 (UTC)

I seem to recall a story of a Boy Scout building a working fission reactor in a shed to earn an activity badge. And one of my mates built his own fusor, but it took him several months and a lot of money. You probably want something slightly simpler... the wub "?!" 12:36, 15 February 2008 (UTC)

The Boy Scout was David Hahn and he got in a lot of trouble with it. Also, that was very much pre-9/11. I wouldn't play with nuclear materials personally unless you'd like a visit from the FBI, the NRC, AND now Homeland Security. The worst part, though, is that on account of having exposed himself to that much radiation he is not allowed to do anything else with reactors for the rest of his life (or in more scientific terms, he has already maxed out his lifetime exposure rating)! --98.217.18.109 (talk) 20:37, 15 February 2008 (UTC)

How about a self built electric motor - with all the parts visible and with home wound coils etc... Is that too simple - what sort of level are you at eg age/class number?83.100.183.231 (talk) 14:19, 15 February 2008 (UTC)

If all you want is something fancy, wire up a bunch of lights to blink for no apparent reason. If you want to win the science fair, you must have a hypothesis. You must have an experiment which tests your hypothesis in a scientific, controlled way. You must use the results of those experiments to draw a conclusion about your hypothesis. Most people fail to realize that the purpose of the science fair is not to build something. It is to demonstrate a knowledge of the scientific process of hypothesis, experimentation, and conclusion. -- kainaw™ 14:25, 15 February 2008 (UTC)

I'm doing a project on the fluorescence of Induim Phosphide quantum dots. My teachers have said it will probably get some oohs and aahs. I ordered the stuff from Cenco Physics. It helps if you have access to a spectrometer for it but, it's not absolutely necessary. Hope this helps (I had trouble finding one too), Zrs 12 (talk) 15:17, 15 February 2008 (UTC)

I know a potential fair attender who is legally blind (20/800 - they can see but not real well, and glasses don't help) and I can appreciate the need to ask for ideas. I would be tempted to ask, myself, what can be done where he doens't have to see much - I'm thinking some sort of bridge, but would that be more engineering? You're right, having a hypothesis and being able to explain is crucial, but they do need to be able to design something, I think.

With baseball season upon us almost, I was thinking for this situation something that might intrigue you, as it's probably a bit advanced for 8th grade, which this student is. He's a huge baseball fan, and was thikning about a pitching machine that would release the ball at various speeds and manners, and explaining why balls curve, what makes a knuckleball doe what it does and the effects of even a little spin making it straight, etc. - if you have enough room, you might be able to do that.

But, with 8th grade, thta's a bit advanced, as I say.4.68.248.130 (talk) 18:01, 15 February 2008 (UTC)

How did he get the number of 20/800? As you can see with a question far above I asked how I could calculate my numbers, and came up with 20/14400, but my glasses bring me up to about 20/15. How can glasses not help with someone with much better eyesight than me? Are my numbers completely wrong? And just when I thought I solved this mystery...206.252.74.48 (talk) 19:24, 15 February 2008 (UTC)

You're assuming that he's nearsighted. He may have some other, more serious eye problem. APL (talk) 21:35, 15 February 2008 (UTC)

According to my simplistic calculation, if you can only recognize an optotype at 20 feet when a person of 20/20 vision can recognize it at 14400 ft, the optotype would have an angular magnitude of about 55°! That sounds really awful. Are you sure you did your calculation right? --71.162.242.55 (talk) 01:00, 16 February 2008 (UTC)

Most science fairs encourage you to actually use the scientific method, so simply building something neat usually doesn't get you many points, at the very least you'll need a pretense for building the neat thing. (For example, testing the durability of various building materials might give you an excellent excuse to build a trebuchet or a battering ram.) Projects involving insects are usually good crowd-pleasers. Maybe ants. APL (talk) 21:35, 15 February 2008 (UTC)

Check out this book. It may give you some ideas. --> http://www.gutenberg.org/ebooks/14664 (Get the PDF version. It's got pictures.) APL (talk) 01:53, 16 February 2008 (UTC)

after doing a lot of ooh and aah projects and not winning, i realized the way to win was to enter competitions which had nobody else entered. like everybody enters physics or chem or biology, nobody enters math. Gzuckier (talk) 01:45, 21 February 2008 (UTC)

RDI

What is the RDI of KJ for an 18 year old, 60 kg male? Thanks in advance.Cuban Cigar (talk) 10:05, 15 February 2008 (UTC)

According to Food_energy, it's 10,000KJ/day for a man. (I'm assuming your abbreviations are for Recommended Daily Intake and kilojoules.) AlmostReadytoFly (talk) 11:48, 15 February 2008 (UTC)

I could be wrong but I don't think there's really enough information there to give a reasonable estimate. For starters, the height will be needed (a 2 metre guy will generally have a larger RDI then a 1.5 metre guy) and your level of daily activity (if you spend all your time at the computer your RDI will be lower then if you are a triathelete in training). Nil Einne (talk) 17:30, 16 February 2008 (UTC)

Hi. Yes, this male is around 1.55-1.6 m, and has low-to -moderate activity (Ie excercises regualarly for half an hour 2-3 times a week on average)220.237.156.78 (talk) 23:10, 16 February 2008 (UTC)

Wrist watches that read your heart rate

How does this watch ([4]) measure oxygen and energy consumption? Zain Ebrahim (talk) 14:16, 15 February 2008 (UTC)

I'm guessing that might be similar to Pulse Oximetry, which uses wavelengths of light absorbed by oxygenated and deoxygenated hemoglobin to determine oxygen saturation in the blood. Wisdom89 _{(T / ^C)} 19:30, 15 February 2008 (UTC)

Radiation Scope Thingy

I was going to reply to a question above with a reference to a device, I decided not to reply anyway, but I wanted to read about the device and completely forgot it's name. Searching all of Wikipedia and the internet has been fruitless. I am referring to a little scope that lets you see radiation from a small inbedded isotope. It was released as a novelty toy during the 1950s. I know the name ends in -scope, but I'm stumped as to the first part. I first heard about it on Wikipedia, so I know the article is here! 206.252.74.48 (talk) 14:43, 15 February 2008 (UTC)

Never mind, I found it, it's the Spinthariscope. 206.252.74.48 (talk) 14:55, 15 February 2008 (UTC)

You can buy them at http://unitednuclear.com, incidentally. --98.217.18.109 (talk) 20:38, 15 February 2008 (UTC)

A commerical Freeze Dryer used for making instant coffee

In you encyclopedia you have an artical on making Instant Coffee by freeze drying using a commerical freeze dryer. I would like to know as who manufactures this type of large commerical freezze dryer? —Preceding unsigned comment added by 70.240.79.154 (talk) 17:49, 15 February 2008 (UTC)

Google search result for "freeze drying equipment". --hydnjo talk 17:59, 15 February 2008 (UTC)

Nuclear bomb effects in space?

I am wondering about this because I am quite a fan of science fiction and space warfare in science fiction. My understanding of the effects of an nuclear bomb (be it conventional fission, "neutron," boosted fission, or thermonuclear) on Earth is that much of the damage is caused by the overpressure wave and thermal radiation (i.e. the 'shock-wave' and intense heat). In space, there is (virtually) no medium for an overpressure wave. Does this mean that a nuclear bomb will have less of an effect in space, or will more of its energy go into, say, thermal radiation? If it does, will the lack of convection (as I understand it, a nuclear bomb creates a very hot wind after the initial shock wave has passed) lessen the thermal effect of the bomb?

I am very familiar with the electromagnetic pulse and radiation effects so I don't need to know more about that.

Thanks! Zephyrus67 (talk) 18:32, 15 February 2008 (UTC)

NUUUKKKEESSS INNN SPAAACCCEEE! Um. With that out of the way, ... without an atmosphere, there is no blast effect. And without a way of conducting the heat, there is practically not thermal effect. However the radiation effects will be greatly enhanced if there is no atmosphere to stop or scatter it! This page has some great graphs illustrating the differences in effects. --98.217.18.109 (talk) 20:46, 15 February 2008 (UTC)

Yes, there is a blast, and there are thermal effects when you detonate a nuke in space. But it's less because the x-rays and other radiation isn't absorbed by an atomosphere. 64.236.121.129 (talk) 14:43, 19 February 2008 (UTC)

(edit conflict) I guess most people haven't had the experience of being near something that's extremely hot. I don't mean just really, really hot like a roaring wood fire, but astronomically hot. One time I was messing around with gunpowder, smokeless powder from a rifle round, and I set a little pile of it on fire with a match. It didn't blow up, not being confined, but my fingers got burned from the radiant heat. The temperature of the heat source makes a big difference. You know how on a clear day the sun actually sort of burns on your skin? Now imagine the sun was three or four time hotter, and you were only 20 miles away from it instead of 93 million. I don't understand our article on the effects of nuclear explosions. What it calls "blast" is caused by heat, the rapid expansion of material near the explosion when it is turned to gas from the heat. In space, the only material would be the bomb itself, which I imagine would turn into plasma and blow out in all directions as atomic particles. There would be no blast as such, but I can't see how the bomb would know to turn the blast energy into something else. It's all about the heat, which is the infrared portion of the electromagnetic radiation that emanates in all directions from the explosion. The hot wind you mention I guess is a firestorm. The wind is only hot because everything is on fire out a certain distance from the site of the explosion. --Milkbreath (talk) 21:03, 15 February 2008 (UTC)

"Blast" in the sense of that article is air pressure. It's what destroys most of the structures not immediately inside the fireball. The NASA link above disagrees with you about the thermal aspect—"Second, thermal radiation, as usually defined, also disappears. There is no longer any air for the blast wave to heat and much higher frequency radiation is emitted from the weapon itself." I'm imagining the difference here is that normally a lot of the actual heat from a nuclear explosion is caused by radiation scattering off of the atmosphere and releasing its energy that way—remember that most of the energy released in a fission reaction is kinetic energy, the speed of the neutrons and fission products. But maybe I'm misunderstanding something, but it seems that a lot of basic effects change when you are setting off a nuclear explosion in a vacuum. --98.217.18.109 (talk) 23:15, 15 February 2008 (UTC)

I'm in no position to argue with NASA, but if you follow the link to high altitude nuclear explosions provided by Sean down there, you'll find this: "Heat from the Bluegill Triple Prime shot, at an altitude of 50 kilometers (31 mi), was felt by personnel on the ground at Johnston Atoll, and this test caused retina burns to two personnel at ground zero who were not wearing their safety goggles." Bluegill Triple Prime was 410kt. The air is quite thin at that altitude, the top of the stratosphere. I'd like to know how an atom bomb knows whether there's air around it or not. --Milkbreath (talk) 02:53, 16 February 2008 (UTC)

If I were to guess, again, the heat was felt by people who were within an atmosphere. Lots of radiation comes out from the bomb, goes a far distance across the cold vacuum of space, and then heats up in the atmosphere. That'd be my guess. Again, I suspect the heat is caused by contact with the atmosphere, at least that's my reading of the NASA page. The bomb doesn't know if there's air around; the large amount of infrared radiation itself is probably caused by the scattering of high-energy particles in the atmosphere, is my guessing. --98.217.18.109 (talk) 14:38, 16 February 2008 (UTC)

Check out High altitude nuclear explosions and in particular the DOD report at the bottom of Starfish Prime. --Sean 21:14, 15 February 2008 (UTC)

I'm

Profound statement, that there. 81.93.102.185 (talk) 12:27, 16 February 2008 (UTC)

Ignore what I said above. Case of knowing a whole lot of stuff from years ago that is wrong. The situation is much more complex than I thought. And, 81.93.102.185, thanks. Just tell me to shut up next time, I can take it. --Milkbreath (talk) 15:35, 16 February 2008 (UTC)

Can humans hibernate?

Can humans hibernate? Are there any "how to" guides floating about on the interweb? Weasly (talk) 18:19, 15 February 2008 (UTC)

See human hibernation. Algebraist 18:44, 15 February 2008 (UTC)

No go there, looks like you'll have to put up with Christmas like the rest of us. Richard Avery (talk) 16:40, 16 February 2008 (UTC)

Poison through the ear

In William Shakespeare's Hamlet, Claudius murdered King Hamlet by pouring poison in his ears. How is this possible? If I had some liquid poured into my ears, I think I would wake up immediately, and shake the liquid out. Is there some pathway that the ears provide that allow the poison to act so quickly that this it would be impossible to respond to? Sancho 18:35, 15 February 2008 (UTC)

Maybe King Hamlet is a more sound sleeper than you? There are times when I've slept through people shaking me, they had to slap me to wake me up. Mad031683 (talk) 18:42, 15 February 2008 (UTC)

I got the impression that it may have made Claudius wake up but poison began acting immediately such that he couldn't tell anyone before he died. This would explain how his ghost knew how it had happened. — Ƶ§œš¹ _{[aɪm ˈfɻɛ̃ⁿdˡi]} 18:51, 15 February 2008 (UTC)

I always thought it was really quite a weird way to do it. My thinking is that he wanted him poisoned while sleeping, so that rules out something he ate, and he didn't want something that appeared to be obvious foul play (no poisoned knives and swords), and in Shakespeare's time that doesn't leave a lot of options (there weren't hypodermic needles for quite a long while later). But it's still weird. I guess if it were me I'd have gone with spider bite, but that shows how much I know. --98.217.18.109 (talk) 20:49, 15 February 2008 (UTC)

I think one theory is that it's supposed to be somewhat symbolic or foreshadowing or something like that -- it parallels the poison that the ghost of Hamlet's father pours in Hamlet's ear, metaphorically, regarding Hamlet's mother, which ultimately leads to Hamlet's undoing as he tries to avenge his Oedipal outrage. --Trovatore (talk) 20:59, 15 February 2008 (UTC)

Hmm, yeah, that actually sounds pretty plausible. Poison in the ear is a great metaphor for dangerous knowledge, etc., even if it sounds like a lousy way to actually kill someone. --98.217.18.109 (talk) 23:08, 15 February 2008 (UTC)

Could smothering with the pillow have been easily detected back in that era? 206.252.74.48 (talk) 21:00, 15 February 2008 (UTC)

Any liquid (Water, hydrogen peroxide etc..) that is placed in the ear, pretty much just sits there. I'm not sure how much absorption there actually would be, if any. My guess is that it was symbolic, or for dramatic affect. Wisdom89 _{(T / ^C)} 21:28, 15 February 2008 (UTC)

Presumably if the poison was bound to a skin-penetrating substance like DMSO, then it could be absorbed into the bloodstream from the ear canal as much as from the exterior skin. But I don't think any substances like that were known before modern chemistry. --Anonymous, 00:33 UTC, February 16, 2008.

Indeed, and I doubt it was meant to be interpreted literally, and the audiences would have known not to do so. Re the question of metaphorical poison vs. actual poison, this is quite enlightening:

• In his advice to Reynaldo, Polonius explicitly develops one of the themes of Hamlet, the idea that words can be used to bend and alter the truth. He explains to Reynaldo how to ask leading questions of Laertes’ acquaintances and how to phrase questions in a way that will seem inoffensive. As with Claudius, who manipulated the royal court with his speech in Act I, scene ii, words become a tool for influencing the minds of others and controlling their perception of the truth. Remember that Claudius killed King Hamlet by pouring poison into his ear. Shakespeare continually illustrates that words can function as poison in the ear as well. As the ghost says in Act I, scene v, Claudius has poisoned “the whole ear of Denmark” with his words (I.v.36). The running imagery of ears and hearing serves as an important symbol of the power of words to manipulate the truth.

I think there's something in that for all of us. -- JackofOz (talk) 00:55, 16 February 2008 (UTC)

That's a very nice metaphor I had missed. I like this answer. Sancho 22:09, 16 February 2008 (UTC)

I guess another angle on this is that back in the 14th/15th century anatomical knowledge was not as refined as it is today and it may well been thought that the ear connected with the throat and it would be possible to administer poison thus. But having said that I go along with what Jack says, so much of Shakespeare is symbolic it would be reasonable to expect this to be. Richard Avery (talk) 16:37, 16 February 2008 (UTC)

If the king were severely allergic to bee venom he might well die of anaphalactic shock. Alcohol drinkers often are very difficult to rouse from sleep.Polypipe Wrangler (talk) 21:15, 16 February 2008 (UTC)

Anyway, Shakespeare was never one to let facts get in the way of a good story. Gwinva (talk) 21:43, 17 February 2008 (UTC)

WTH?

You don't even list the large planet Beetlegeuse in Wikipedia. Am i out of my mind? Who's running the show there?  :) —Preceding unsigned comment added by 64.237.99.46 (talk) 21:02, 15 February 2008 (UTC)

It's spelled Betelgeuse, and it's a star, not a planet. --Trovatore (talk) 21:06, 15 February 2008 (UTC)

Well, you can 'run the show' if you want to. That's one of the neat features of Wikipedia everybody is 'running the show'. But please don't get angry with those that are 'running the show' because you spelt Betelgeuse wrongly. Richard Avery (talk) 16:30, 16 February 2008 (UTC)

what he is trying to say is: why is there no spellchecker on the wikipedia search box like there is on google!

The spellchecker is disabled due to performance issues. If you don't know how to spell a word, you can often find its article very easily by Google searching for "<your guess on the spelling> + wikipedia." Someguy1221 (talk) 23:48, 16 February 2008 (UTC)

visual acuity conversions

Hi. Please convert 0.5, 1.0, and 1.5 to the 20/x way of measuring visual acuity, as well as how many arcminutes each can resolve. This is not a homework question. Also, eyeglasses such as 100, 200, 500 degs, etc, equal how many of 20/x for the visual observer eyes? How many is that for arcminutes? Or are the degrees for nearsighted only? What is the decimal way of measuring known as? How can I convert these numbers, is there a formula or online calculator or something? I realise there are similar questions above, but I would like a clarification of these numbers. Let's say someone can see 5 arcminutes resolution naked. How much resolution with 10x binoculars, for example, or does it depend on the aperture rather than magnification? Does it depend on the Dawes or Raleigh limit as well? Also, a rather unrelated question, is the cloth used to clean glasses called lens cloth? Thanks. ~AH1^(TCU) 22:34, 15 February 2008 (UTC)

I'll answer a couple of your questions (I don't know the answer to all of them). I believe the decimal specification of 'visual acuity' is a specification, in dioptres, of the correcting lens required (please note that this may be wrong). As for resolution in 10x binoculars, this will vary depending on the quality of the binoculars – the quality of the glass (or plastic, if it's a particularly cheap-and-cheerful pair) and its coating, the number of elements and their arrangement, and the like. The 10x merely specifies (as I'm sure you know), the magnification they offer. These are (some of) the reasons that prices for camera lenses (and so, presumably, also binoculars) vary from the low hundreds to many thousands of pounds. Angus Lepper^{(T, C, D)} 01:44, 16 February 2008 (UTC)

I'm not an eyecare professional, but I think your answer about visual acuity is incorrect. Dioptre is a unit for the power of lenses, not a measure of visual acuity. In my non-expert's understanding, the "degrees" figures in the OP's question refer to the powers of corrective lenses. In the case of corrective lenses prescribed for myopia, a prescription informally referred to as "200" actually refers a lens of -2.0 dioptres power. Visual acuity, as I understand it, is an operationally defined performance measure. It's about what a subject is able to "do" under standard test conditions—not what kind of corrective lenses the subject needs. You can have separate visual acuity measures for corrected and uncorrected vision. --71.162.242.55 (talk) 03:00, 16 February 2008 (UTC)

That's quite possible, hence my original disclaimer! Apologies if it is incorrect. Angus Lepper^{(T, C, D)} 21:32, 16 February 2008 (UTC)