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February 14

Lunar Eclipse

In science class, we were discussing the upcoming lunar eclipse and an interesting question came up. If one were on the moon during a lunar eclipse, what would happen? Would the moon be in a shadow? Or would it be brighter? Admittedly, this was assigned as an extra credit question, but I have tried searching online and have no idea. I had the idea that it would be darker on the moon, but I could find no information online to corroborate that. Oh, and please include sources, if possible! Thanks, FruitMart07 (talk) 01:44, 14 February 2008 (UTC)

You're thinking along the right lines, and if you continue you'll appreciate that it's going to look something like a solar eclipse seen from the earth. Both are eclipses of the sun. The difference is that the earth has a bigger diameter than the moon, and so one would not see a full corona, but might witness Baily's beads. And yes, it will be dark on the moon, in the same way as it is dark on the parts of the earth across which the solar eclipse passes. --Tagishsimon (talk) 02:04, 14 February 2008 (UTC)

But there's another big difference. Light passing through an atmosphere gets refracted and scattered. (The Earth's atmosphere scatters blue light more, so when you look through a great amount of it, like at the setting sun, you see red because that's what didn't scatter so much.) Now, in a solar eclipse, the light does not enter the Earth's atmosphere until it has gotten nearly all the way to Earth, so it doesn't have time to scatter much. The result is that in the umbra the light is almost totally blocked and it's almost like nighttime.

In a lunar eclipse, on the other hand, the light hits the Earth's atmosphere first and starts spreading out due to scattering, with the red light spreading least. It then travels roughly a quarter-million miles, still spreading out. The result is that some light scatters enough to fill the umbra, which is why during a lunar eclipse you can still see the Moon and it looks reddish. If the Earth isn't blocking all the light because some gets through the atmosphere, what would it look like if you looked at the Earth when it was in front of the Sun? --Anonymous, 02:53 UTC, February 14, 2008.

If you were on the Moon, watching the Earth eclipse the Sun, during totality, the Earth would probably appear as a black disk with a thin reddish ring around it. Other things to look for are stars and city lights. I don't know about the relative brightnesses of the ring, the lights, and the stars, so one or more might be too dim to be seen. --Carnildo (talk) 21:50, 14 February 2008 (UTC)

Thank you guys so much!! Everyone says this class is really hard, so I'm trying to rake up a lot of extra credit points... I concluded that there would be less light on the moon because the earth would be blocking much of the sunlight. It's a straight-forward conclusion, really, but I just needed to think it through. Thanks for all of the help! (Oops! Forgot to log in!!) FruitMart07 (talk) 00:07, 15 February 2008 (UTC)

Mercury Perihelion

OK, I've spent the past 2 hours reading and rereading everything on Mercury's orbit around the sun, and how it relates to relativity. So, I think I get it, but I would appreciate a nice laymen's explanation that details the major equations. Also, any links to failed theories that attempted to explain Mercury away would be appreciated. Thanks! Zidel333 (talk) 04:09, 14 February 2008 (UTC)

I don't know if this is what you're looking for, but I think the GR perihelion shift can be correctly understood in terms of the spatial curvature of the Schwarzschild metric, specifically the fact that the circumference of a circle centered at the sun is less than 2π times its "effective" radius. When you've completed what would be one Newtonian orbit, you've actually gone a bit farther than a full circle, so the orbit precesses forward. Let me work this out numerically and see what happens. We're ignoring t, and also θ since everything is in a plane, so we're left with $ds^{2}={\frac {r}{r-2m}}dr^{2}+r^{2}d\phi ^{2}$. As you probably know, this can be embedded in $\mathbb {R} ^{3}$ with cylindrical coordinates $(r,\phi ,z)$ by taking $r=r,\phi =\phi ,z={\sqrt {2m(r-2m)}}$. Supposing Mercury's orbit is roughly circular with a radius of R (which is not even close to true, but never mind), the only part of this embedded geometry that matters is the annular region at radius R. To first order this looks like an annular region of a cone with a slope given by $\left.{\frac {dz}{dr}}\right|_{r=R}={\sqrt {\frac {2m}{R-2m}}}$. If you slit open a cone along a line segment from the apex to the base, you can flatten it into a disc with a slice missing. The angle of the missing slice, as a fraction of a whole circle, is our predicted perihelion shift per orbit. For a cone slope of n, that fraction is $1-(1+n^{2})^{-{\frac {1}{2}}}\approx {\frac {1}{2}}n^{2}$, or in this case about ${\frac {m}{R}}$. Plugging in 1.5 km for m and Mercury's semi-major axis for R, that's about one part in 40,000,000, which is pretty close to the right answer of one part in 12,500,000. There might be a missing factor of two in there from the temporal curvature (the way there is with the bending of starlight) which would bring the prediction to one part in 20,000,000. Of course, Einstein didn't do anything like this; he used some form of linearized general relativity and worked out equations of motion, but I've forgotten the details and it's not as interesting.

I don't know anything about the history of other attempts to explain the anomalous precession, but I don't think it's hard to come up with modifications of Newtonian gravity which give the right result. What was exciting about the GR calculation was that it produced the right value without any new adjustable parameters. -- BenRG (talk) 21:47, 14 February 2008 (UTC)

Anthropology?

This is probably an anthropology question – if an Australian aboriginal man wears a red head band or a white headband in a ceremony, what particular role or status do these colours signify? Someone told me what the white one meant, but I forget (add: maybe it meant "elder") and I can't find it anywhere on google etc. Julia Rossi (talk) 06:37, 14 February 2008 (UTC)

Come on Jack, we're all waiting for you on this one, surely you've got some bonzer mates that can put you right. Richard Avery (talk) 13:35, 14 February 2008 (UTC)

To my shame, I have no indigenous friends. What I would say, though, is that the Australian indigenous peoples, while speaking with one voice on many matters, are ethnologically and culturally as diverse as the Incas, the Lapps and the Masai. It's not true, for example, that all or even the majority of tribes used boomerangs and didgeridoos, despite these having become symbols for indigenous people as a whole. Two tribes chosen at random would be much more likely than not to have spoken mutually unintelligible languages and to have widely different cultural practices. For a continent the size of Australia, it's not hard to see why this would be the case. The wearing of headbands and the significance of the colours is not something I can comment meaningfully on. Sorry. -- JackofOz (talk) 00:36, 15 February 2008 (UTC)

Sounds like he joined the Bondi Lifesaving Club Myles325a (talk) 02:13, 15 February 2008 (UTC)

Don't feel bad, Jack, Brendan Nelson hasn't got any indigenous friends either. Glad to see yu and Myles chimed in even though none of us are the wiser. Carmonozicarmoncarmon etc. ; )) Julia Rossi (talk) 08:32, 15 February 2008 (UTC)

BTW if it helps, it's a Northern Territory tribe like the Arrente (or pr: Arunta), so bit by bit maybe someone will know something. Julia Rossi (talk) 08:35, 15 February 2008 (UTC)

Colour

I can't remember whether an object that absorbs red light is red or an object that absorbs other light, but bounces back red is red. Which is it?KarateKid101 (talk) 09:51, 14 February 2008 (UTC)

Think about it carefully. If an object absorbs all light equally, it is black, because you don't see anything reflected. If an object reflects most light equally it is white (in white light), because you see all the light reflected from it. If an object absorbs red light you're not going to see red, but the other colours it does not absorb. For an object to be red, it needs to absorb most of the light that is not red hence what you see is the red light that it does not absorb but reflects. Nil Einne (talk) 10:05, 14 February 2008 (UTC)

Repeting things to help retrograde amnesia?

The article on retrograde amnesia is pretty clear, but I wonder about one thing. It says trying to force someone to remember can be too stressful, but what about repeating a past event without telling the person you are. (I asked in the discussion section, but this venue may be more appropriate.) I know TV often exaggerates things, but will repetition of a specific event help more than just surrounding with familiar things? For instance, in The Jeffersons, George repeated his first date with Louise - a comical disaster - to help her get her memory back. Other sitcoms have used the "familar things" approach, like an episode of Diff'rent Strokes (where it came back gradually, like normal) and the finale of Full House. But in the former, it could be aruged it was repeating a familiar event that triggered Mr. Drummond's memory of Arnold and Willis (threatening to ground them if they ran away), and in the latter, the Full House Chronology [[1]] describes in a footnote that it's implied an accidental repeating of an earlier experienced situation helped Michelle recover her memory. (Being in a strange place and looking for older sister Stephanie for comfort, like Michelle's first day of Kindergarten.) Or, would the "Full House" example be more an example of just using "familr things" to jog the memory, anyway, since it does seem to imply Michelle growing more comfortable with Stephanie first?Somebody or his brother (talk) 13:35, 14 February 2008 (UTC)

Matter to energy conversion using black holes

On the Mass–energy equivalence article, it says you can use black holes to convert matter to energy. What is the efficiency of this conversion? 64.236.121.129 (talk) 16:50, 14 February 2008 (UTC)

It's 100% efficient (which is why it's under the "perfect conversion" section!) The only problem is that it takes a while. (EhJJ)^TALK 18:15, 14 February 2008 (UTC)

Do you know this, or are you just assuming it's 100%? I seem to recall that another book I saw in the book store say that the conversion is 60 or 70% efficient. Can anyone confirm this? Also what does the energy manifest as? Just heat? Any neutrinos? 64.236.121.129 (talk) 18:20, 14 February 2008 (UTC)

You can toss anything you like into a black hole and the Hawking radiation will consist largely of electromagnetic radiation, but a hot enough black hole will also emit neutrinos, which are effectively lost energy, and possibly heavier particles as well (which could perhaps be tossed in again). And the electromagnetic radiation can't be converted into useful work with 100% efficiency in practice (I love the image of a miniature black hole being used to boil water which drives a steam turbine). So it does seem pretty dubious to claim that this is a 100% efficient conversion. I'm afraid I don't know the ratios of different particles emitted as a function of temperature.

Also, I should point out that theoretical black holes are able to attain such high efficiencies only by violating most conservation laws. The reason you can annihilate matter with antimatter producing "pure energy" (i.e. photons) is that the conserved quantum numbers attached to a particle and its antiparticle are negatives of each other, and the quantum numbers attached to a photon are all zero, so both sides of the interaction add to zero and the conservation laws are satisfied (except for spin and energy-momentum, which have to be considered separately). With a Hawking black hole you can turn ordinary baryonic matter into photons even though this grossly violates the conservation of baryon and lepton number. I'm not sure what would happen if real black holes actually respect these conservation laws, but you might get out pretty much what you put in, which would make the whole thing rather pointless. On the other hand the bill never comes due if the black hole never evaporates, and baryon and lepton number aren't exactly conserved in general even outside black holes, so maybe this is a non-issue. -- BenRG (talk) 19:39, 14 February 2008 (UTC)

I should note that matter + antimatter doesn't entirely result in photons. As much as 50% results in useless neutrinos. —Preceding unsigned comment added by 64.236.121.129 (talk) 21:04, 14 February 2008 (UTC)

The Position and Speed of Matter

I'm not a particle physicist but there is something I cannot get my head around. Documentaries I have seen state that it is not possible to plot the position and speed of a sub-atomic particle at the same time. But if you don't know where something is, how can you measure the speed it is travelling at. If I want to know how fast my cat is running up the stairs then surely I need to where the cat is in the first place and where it ends up with the time taken inbetween! —Preceding unsigned comment added by 82.21.54.17 (talk) 17:03, 14 February 2008 (UTC)

Simple explanation is that to measure the position of an object you have to interact with it in some way, and that interaction changes the object's momentum. Now measuring the speed and position of your cat by, say, bouncing a light ray off it is not going to change its momentum very much - but that is because your cat is a macroscopic object. No matter how carefully you try to make a measurement, or how sensitive your equipment is, there is an absolute lower limit on the precision with which you can simultaneously measure an object's position and momentum. This precision limit doesn't make a significant difference to your cat, but it is important for sub-atomic particles because of their small size and mass - see uncertainty principle for more details. (Yes, yes, I know this is an enormously simplified explanation, which glosses over several factors, but it will do for now) Gandalf61 (talk) 17:42, 14 February 2008 (UTC)

I think you have oversimplified what the documentary (should have) said. I have no way of knowing what they actually said. A better phrasing might be: "not possible to plot the position and speed of a sub-atomic particle to an arbitrary degree of precision at the same time." Gandalf61's comment follows from here. JohnAspinall (talk) 19:23, 14 February 2008 (UTC)

Gandalf, the uncertainty principle is distinct from the observer effect. It is possible to create two particles so finding the velocity of one will give you the velocity of the other and finding the position of one will give you the position of the other (I'm not certain how it works. It might be that they have the same position and velocity, but you make one after the other.) You can then measure the position of one and the velocity of the other. Anon, there are ways of finding the velocity of something without using two measurements of its position, such as the Doppler effect on a photon reflected from it. — Daniel 00:51, 15 February 2008 (UTC)

As I said, I do know that my explanation is enormously simplified, and glosses over several factors, one of which is the subtle distinction between uncertainty principle and observer effect. Yes, we could get into the whole topic of quantum entanglement. But I gave an explanation that I thought was appropriate for the questioner's level of knowledge. If you think you can give a better answer to the original question, then please have at it. Gandalf61 (talk) 10:34, 15 February 2008 (UTC)

This is a good question. I don't know how the speeds of quantum objects are measured in practice, actually. But it's not so strange for something to have a well-defined speed without having a well-defined position. Wind does, for example. The uncertainty principle shows up in the theory of classical waves, so there's a closer analogy there. The speed of a quantum particle corresponds to the frequency of a wave, and the location of a particle to, well, the location of a wave (in space or in time). You might know that you can tune one instrument against another by listening for beats between the frequencies. As the frequencies get closer the time between beats gets longer, which lets you know that you're tuning in the right direction. But to be sure that the frequencies were exactly the same you would have to wait forever. The frequency difference and beat time are related by an equation that looks like the uncertainty principle. This isn't a weakness of this tuning technique, it's a universal property of waves. A wave doesn't actually have a well-defined frequency unless it has a large extent in space or time. -- BenRG (talk) 13:43, 16 February 2008 (UTC)

War

Assuming that Nuclear Weapons were not used, who would be likely to win in the event of a war between the USA and Europe? —Preceding unsigned comment added by 195.188.208.251 (talk) 17:04, 14 February 2008 (UTC)

According to Military budget of the United States, the US spends 47% of the world military budget, so dollar for dollar, the US could take on approximately the rest of the world, let alone Europe (taking the premise of a unified Europe). Also, US military technology is generally recognized to be somewhat superior to that of other countries, so I'd speculate that each US dollar spent on defense is more potent then a European dollar. Europeans do outnumber Americans by a bit more than 2:1, but the population of Europe is also older. Overall, I'd bet on the USA. --Bmk (talk) 17:33, 14 February 2008 (UTC)

The Navy alone would be crushingly decisive. Our article claims that "The United States Navy is the largest in the world with a tonnage greater than that of the next 17 largest combined" and "the world's largest carrier fleet, with 11 carriers in service". Read the article Aircraft carriers and ponder what 11 of them could do. They'd get hurt; the Brits, French, and Swedes have good air forces, and the British subs would be troublesome. But not for long. Funny, isn't it, that throughout history madmen have been dreaming of conquering the world, and now sane men actually could but won't. --Milkbreath (talk) 17:52, 14 February 2008 (UTC)

Don't forget the individual units themselves. The M1 Abrams, the AH-64, and the A-10 are all pretty frightening. Let's also recall that the USA has remotely piloted stealth bombers and those fancy artillary units that makes safe zones that troops can find with GPS. Thank God they don't go and attack random countries. Oh wait, never mind. 206.252.74.48 (talk) 17:59, 14 February 2008 (UTC)

Interesting side note: Although the USA spends the most on its military, it is only third in military spending per capita (after Israel and Singapore). See this source. --Bmk (talk) 18:11, 14 February 2008 (UTC)

Also, the US has military bases in Germany, Italy, The Netherlands, Portugal, Spain, and Turkey (Well, alot of those are NATO bases, but there's American forces there) which gives them a strategic advantage. NATO bases would cause interesting problems, although I suppose that by the time it came to war NATO will have been dissolved. Also, we don't attack random countries, only countries with alot of oil, get it right. Mad031683 (talk) 18:21, 14 February 2008 (UTC)

Hi. Oh dear. Peak oil is going to be a big problem. Why is the US spending a trillion dollars fighting partially for oil that will proably run out in a few decades?!? Thanks. ~AH1^(TCU) 18:24, 14 February 2008 (UTC)

Ok, we attack countries that have oil at random. The paradox is the the vehicles used to invade the countries are mostly fueled by oil products - so soon we will fight for oil just to get oil in order to fight...for oil. 206.252.74.48 (talk) 19:28, 14 February 2008 (UTC)

Is this science? (rhetorical)87.102.114.215 (talk) 18:25, 14 February 2008 (UTC)

I don't think it is. It's also hypothetical. Not really appropriate.64.236.121.129 (talk) 18:29, 14 February 2008 (UTC)

Also it answers itself, if the supply is running out, its more worth fighting over it. Mad031683 (talk) 18:42, 14 February 2008 (UTC)

There are numerous forums where you can have this discussion to your hearts content. To get started go to YouTube and search for videos of the USS Enterprise, or M1A1 Abrahams, or whatever piece of military hardware helps you most. The enter the comments below the video and leave a message such as "USA ROKS, frenxch pussies can kiss my ass" or something similar.. Before long you will have lots of well wishers inviting you to their websites, as well as many heart warming replies from nice people around the world. Best of luck.87.102.114.215 (talk) 18:56, 14 February 2008 (UTC)

Ho ho - my web search turns up this "LOL i remember russian soldiers are forced to become prostitute by their officers according to UN LOL! " - given this information I think USA will win unless it catches AIDS from mexican woman first. Once again in peace and love to all of you.87.102.114.215 (talk) 19:11, 14 February 2008 (UTC)

I don't think the Europeans would keep those low military budgets if their existence was seriously challenged by a foreign power such as the USA. Whenever a country faces conflict, the portion of its GDP dedicated to military sky-rockets. Nowadays the US army is far stronger than those of the European Union countries combined, but the EU has a larger population and a slightly larger economy. Furthermore, Russia alone (if we let it join the European team) has a large army, something to keep in mind. To sum up, I guess that if the war began tomorrow, it would be a one-sided win for the US, but if we let the EU have 10 years for preparing itself, I wouldn't be that sure. --Taraborn (talk) 20:26, 14 February 2008 (UTC)

I don't think russia would make a big diference - once recruit was so badly beaten by his comrades he had to have his penis and testicles amputated.87.102.114.215 (talk) 21:11, 14 February 2008 (UTC)

Although if war began tomorrow the USA might have more difficulty extricating itself from the Middle East to deploy them elsewhere than various European powers. AlmostReadytoFly (talk) 23:38, 14 February 2008 (UTC)

ok that's enough isn't it. TRY SOMEWHERE ELSE.87.102.114.215 (talk) 00:35, 15 February 2008 (UTC)

Well, all the pointers say the US should win, but then Vietnam should have been a cake-walk, and you got your butt tanned big time there, and now you are getting second helpings in Iraq because the first lesson didn't sink in, so it just goes to show that "the bigger they are, the harder they fall". I think Monaco might be a safe bet. Myles325a (talk) 02:18, 15 February 2008 (UTC)

There are no winners in war...except for the ones who don't lose

Draw. The U.S. navy is far too strong for the Europeans to reach North America, but on the other hand, without nuclear weapons, the American army isn't big enough to conquer Europe, never mind the supply problems. After all, it's having trouble handling a single, mid-sized country. Clarityfiend (talk) 06:51, 15 February 2008 (UTC)

The Europeans kept low military budgets in the 1930s when they were menaced by Nazi Germany, such that the Germans were able to take over Czechoslovakia and other territory without any military oppisition from the powers such as Britain and France which had pledged to support its territorial integrity. What reason is there to believe they would arm themselves now to defend adequately against some threat from the U.S.? But as for invading, conquering and occupying Europe, I just can't see it happening, when after five years of occupation of Iraq the U.S. still finds it necessary to engage in large scale aerial bombing of Iraqi cities and cannot drive down a road without large IEDs being detonated. Edison (talk) 17:06, 15 February 2008 (UTC)

Ok, but the Iraqis didn't do anything to us. The average American wouldn't have known an Iraqi if he was waterboarding him back in 1980. Whereas the Europeans have been going out of their way to get on our last freakin' nerve ever since WWII, especially the French. I mean, look at it. The French hairdressers are on strike! How do you think that makes a red-blooded son of Uncle Sam feel? And that on top of pulling out of NATO. You just have to piss America off enough to swing public opinion in favor of the required total war mentality, and the population imbalance can be redressed pronto. Sorry, did I say all that out loud? --Milkbreath (talk) 17:17, 15 February 2008 (UTC)

You mean, all across France, with the hairdressers on strike, even as we speak, people are forced to tolerate ungroomed armpits? Ah, the humanity. - Zotz (talk) 00:44, 16 February 2008 (UTC)

Why have so many red-blooded sons of Uncle Sam forgotten that the USA owes its independence to France? Isn't the American Revolution taught in history classes in the US anymore? Pfly (talk) 07:05, 16 February 2008 (UTC)

Isn't the chronological order of the American and French Revolution taught elsewhere? It's not that Americans aren't cognizant of the help France provided by using America as a proxy in their conflict with England, it's that they've also learned the lessons in gratitude taught them by the French nation in the years since the last World War. - Zotz (talk) 07:15, 16 February 2008 (UTC)

For the record, no, the American Revolution is not really taught in any great detail. There is a wonderful mythological version which is quickly glossed over (OMG they taxed our TEA WTF!! and then we got the Constitution!), but nothing very serious and most high school students forget the salient points almost immediately after being tested on them. Most high school seniors today could not locate France on a map. Many probably could not locate Europe on a map. It is a pretty sad state of affairs. --98.217.18.109 (talk) 21:59, 17 February 2008 (UTC)

Of course you can't find Europe on a map, it's in orbit around Jupiter. 206.252.74.48 (talk) 17:39, 19 February 2008 (UTC)

Igniting gunpowder (smokeless powder)

If you were hit by free electrons (lightning bolt or something), while holding a rifle like an M-16. Would the gunpowder in the bullet shells ignite? 64.236.121.129 (talk) 18:28, 14 February 2008 (UTC)

Easily possible -- a lightning strike could certainly ignite gunpowder. Mythbusters did a segment on using a .22 cartridge as a fuse replacement and got it to fire (don't recall the current/voltage used, but far less energy than a lightning strike). It's hard to say anything definitively, though, as lightning does weird stuff. Would current pass through the rifle? Even if so, would the rifle's construction serve as a sufficient lightning rod? It'll likely vary from strike to strike. I'd put money on a strike on the rifle magazine causing the bullet to fire, though. — Lomn 18:40, 14 February 2008 (UTC)

Of note: M-16 shells do not use gunpowder. Also, the butt, handle, and barrel guards are plastic, not metal. The "handle" on top is not supposed to be used a handle. Still, it is possible for electricity to travel along the metal and, for some unknown reason, want to travel into the bolt mechanism and then, for some unknown reason, want to travel to the shell and ignite the propellant. It would make more sense for the electrons to travel along the outside of the rifle to the human and then to ground. -- kainaw™ 20:15, 14 February 2008 (UTC)

M-16 shells use smokeless powder I believe, which I mentioned in my topic. 64.236.121.129 (talk) 20:50, 14 February 2008 (UTC)

It appears that M-16s use WC844 ball powder, which is discussed as being distinct from smokeless powder in ways I don't really understand. I'd imagine it's a similar outcome in any event. — Lomn 21:25, 14 February 2008 (UTC)

What? I think it's just one of the (many) varieties of smokeless powder. Where do you see a suggestion otherwise? Friday (talk) 21:30, 14 February 2008 (UTC)

I was using this as a reference, but like I said, I didn't grok the details. It may well be a simple distinction in subtypes of smokeless powder. My confusion probably stems from reading all this with a "gunpowder=smokeless powder" mental filter, thus seeing Kainaw's comment as "M-16s don't use smokeless powder", which led to me trying to find out what they did use. Short version: my bad. — Lomn 22:01, 14 February 2008 (UTC)

It would be pretty surprising if any explosive used to propel bullets could not be ignited from an electrical spark. But the cartridge generally provides a metal shell completely surrounding the smokeless powder, gunpowder, etc. Certainly a full-fledged lightning discharge could ignite the rifle, the rifleman, and the cartridge, just from the high temperature. I have seen fairly large pieces of metal vaporized by lightning. Edison (talk) 16:59, 15 February 2008 (UTC)

Microwave radiation health effects - alternative questions

When possible health effects of microwave radiation is considered they usually look at the average energy concentration involved. What bothers me is that there is usually no mention that artificial sources of microwaves typically have lots of energy in a tiny band (relative to the frequency, not absolute). And microwave wavelengths are typically around the order of the size of humans, human organs or a human scull.

When during exposure a person does not move relative to the source of radiation such as when speaking on a cellphone held tightly against the ear, won't resonances occur (analogous to what happens when you sing in the shower) that push energy concentration in certain spots way above the average? If yes, is this taken into account with most studies and can we place a ceiling on the extent to which this effect can cause potentially dangerous hot spots?

Secondly, and perhaps this is still a controversial subject, I read about a possible HIV treatment that uses the resonant frequencies of the virus as a way to "shake them to death". I hope it's OK that I'm not mentioning the source because I really can't remember. They say the frequency is calculated at around 60GHz and that the proposed treatment won't affect normal cells which have a much lower resonant frequency.

Does anyone know in what sense this "resonance" is meant, because in order for 60GHz to resonate at that small scale I assume that there has to be some sort of wave that propagates much slower than the speed of light. And then, using this logic, roughly at what frequency DOES normal cells resonate and what would happen if they were exposed to EM radiation at this frequency? (What I'm asking is slightly different from the proposed treatment mentioned which instead proposes using a laser pulsing at that frequency).

41.241.187.40 (talk) 20:08, 14 February 2008 (UTC) Eon Zuurmond

• Yes, some spots of your hand/head will absorb more than others when you use a mobile phone. There's lots of people doing research and modelling in this and other areas, MTHR in the UK for example. I don't think they've found anything to worry about yet.
• I think the HIV destruction was by ultrasound not microwaves, so yes they will travel much slower. You'd have a job getting an HIV virus to absorb much microwave energy at 60 GHz anyway, you'd probably fry the surrounding cells first and end up killing the virus that way.
• I seem to remember that there were initially some worries about the TETRA system having a pulse repetition frequency of around 17 Hz which was close to the resonant frequency of a particular cell or reaction between cells. There's probably something about this in the Stewart Report if you want to look it up. JMiall₰ 20:21, 14 February 2008 (UTC)

can marijuana be consumed anally

and get high off of it —Preceding unsigned comment added by Boomgaylove (talk • contribs)

I would think not. The large intestine usually only absorbs liquids, so you can get drunk in this manner (one Darwin award winner died in this fashion), but not high off solid material. THC is not soluble in water either. Lastly, I highly discourage taking this path to get high, or any path. 206.252.74.48 (talk) 19:42, 14 February 2008 (UTC)

I believe the THC in marijuana undergoes a small chemical change when it is heated (decarboxylation?) which converts it to its psychoactive form. Supposedly injesting uncooked marijuana will not get you high. (This is according to a book by Ed Rosenthal). ike9898 (talk) 20:09, 14 February 2008 (UTC)

you reduce your credibility by saying "or any path". —Preceding unsigned comment added by 79.122.19.82 (talk) 20:56, 14 February 2008 (UTC)

What? I just vehemently oppose psychoactive drugs, and alcohol. My life has been the better for it. 206.252.74.48 (talk) 21:01, 14 February 2008 (UTC)

Someone who tells you marijuana can be consumed anally might just be blowing smoke up your ass. Edison (talk) 20:29, 15 February 2008 (UTC)

actually come to think of it, if you can make brownies, you can put them in your rectum, i think you could absorb it that way similar to a cotton rag with alcohol like puertorican youth do or a crystal meth enema like gay men Party and Play.Boomgaylove (talk) 05:32, 20 February 2008 (UTC)

crystal meth

how much does an ounce of crystal meth cost? —Preceding unsigned comment added by Boomgaylove (talk • contribs)

"In the U.S. illicit methamphetamine comes in a variety of forms, at an average price of $150 per gram for pure substance" from Methamphetamine#Production_and_distribution, and ounce is ~28g87.102.114.215 (talk) 21:38, 14 February 2008 (UTC)

Note that an ounce is a LOT. I would think (based on friends I used to have) that it would take a regular user maybe a week or two to go through just a gram. --140.247.11.3 (talk) 01:04, 15 February 2008 (UTC)

The typical price of an ounce might be less than implied by the stated price per gram, since larger amounts may be sold wholesale, to allow a markup for the risk and bother of selling it to all the crack heads and risking arrest. Law enforcement people love to show some huge shipment of confiscated drugs and announce its huge "street value." A far smaller sum would likely have changed hands had it reached the drug lord it was intended for. Edison (talk) 16:50, 15 February 2008 (UTC)

Dinosaur names

Why are dinosaur names written with a capital letter and in italics? I've seen this in both Spanish and English. --Taraborn (talk) 20:07, 14 February 2008 (UTC)

See binomial nomenclature. ike9898 (talk) 20:10, 14 February 2008 (UTC)

It's standard formatting and nomenclature - kinda like for bacteria, which is done in italics. Wisdom89 _{(T / ^C)} 20:11, 14 February 2008 (UTC)

Oh, kinda obvious. Thanks :) --Taraborn (talk) 20:27, 14 February 2008 (UTC)

Earthquake question

I'm working on a science project for an earthquake unit. I need to know of an earthquake that was measrured in the mercalli scale, where and when it happened. I need the answer before 5 'oclock eastern time. Please help me. QUICK! =0 —Preceding unsigned comment added by 72.221.113.46 (talk) 20:24, 14 February 2008 (UTC)

From what I can find, the Modified Mercalli Intensity Scale is still in use, this page shows the ratings for some areas of California after the 1989 Loma Prieta event. I haven't found any specific quakes using the original 1902 10-point version, but knowing it was in developed in 1902 might lead in the right direction. --LarryMac | Talk 21:11, 14 February 2008 (UTC)

Given the 1902 date, the 1906 San Francisco earthquake is an excellent contemporary example. — Lomn 21:22, 14 February 2008 (UTC)

Are we supposed to answer or honor obvious homework questions? Wisdom89 _{(T / ^C)} 21:39, 14 February 2008 (UTC)

We are allowed to help.. as much as we want to.87.102.114.215 (talk) 21:54, 14 February 2008 (UTC)

Yes and no. We're explicitly encouraged not to do someone's homework for them, but also encouraged to be helpful in assisting. I figure that "name a measured earthquake" is a pretty trivial homework question if that's the whole thing -- likely any major earthquake postdating the Mercalli system has been measured by it. Do you think I've crossed that line via the post above? — Lomn 21:57, 14 February 2008 (UTC)

The poster still has there report/essay to write - so no I don't think you've overstepped the line - you were very helpful in the case of an honest and straightforward request for info. Well done.87.102.114.215 (talk) 22:16, 14 February 2008 (UTC)

mixing chemicals

What cleaning chemical is produced when you mix salt, bi-carb of soda and vinager, I saw it used on the TV for cleaning drains 121.200.39.12 (talk) 22:12, 14 February 2008 (UTC)

The salt isn't part of the main reaction, but bicarb of soda (aka sodium bicarbonate) and plain vinegar (aka acetic acid) react to form sodium acetate, carbon dioxide gas and water. It's the reaction itself, in producing small bubbles of carbon dioxide, that does a lot of the cleaning work (it's like a gaseous exfoliation), although the individual chemicals have cleaning properties of their own, which is why it's such a multi-purpose cleaning method. Confusing Manifestation(Say hi!) 22:27, 14 February 2008 (UTC)

I suppose the salt introduces an abrasive providing it's not dissolved. Julia Rossi (talk) 23:45, 14 February 2008 (UTC)

The sodium chloride will dissolve in the aqueous portion of the vinegar which is only 3 % acetic acid. So it will probably not be abrasive. —Preceding unsigned comment added by 79.76.141.105 (talk) 00:36, 15 February 2008 (UTC)

That all depends on how much vinegar there is compared to the solids. Salt isn't infintely soluble, and it and the bicarb compete with each other in terms of solubility (common ion effect for sodium ions). Any excess would remain as a solid abrasive. Then later it could be rinsed away with excess water, so there's no solid residue to scrape out of ther drain. DMacks (talk) 20:25, 15 February 2008 (UTC)

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[2]. 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[3] 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[4] 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 ([5]) 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)

February 16

EMP and safe deposit boxes

(Note: I bumped this section down to February 15 even though it was initially posted on February 14 because I asked a whole bunch of new questions on February 15 and I wanted to make sure the questions were answered before this section ended up being archived and that people didn't overlook the section just because it was in an earlier day and assume that the questions had already all been answered.) —Lowellian (reply) 02:29, 17 February 2008 (UTC)

Would a typical bank safe deposit box form an adequate Faraday cage to protect electronic contents from an electromagnetic bomb? —Lowellian (reply) 00:02, 14 February 2008 (UTC)

Well I can't actually answer the question bear in mind your chance of getting access to your bank safe deposit box during the extreme chaos created by an electromagnetic bomb may be slim Nil Einne (talk) 06:54, 14 February 2008 (UTC)

Let's say it's electronics you want to get access to once the chaos calms down, so the question still stands, and I'd still like an answer if someone can give one. Also, your response did give me an idea for another question: would modern automobiles be able to start up after an EMP, or are they so dependent on electronics that they would be unable to do so? —Lowellian (reply) 12:50, 14 February 2008 (UTC)

A modern automobile would almost certainly toast after even a moderate EMP event. As it is, the police are learning to use devices that lay in the roadway and transfer an electrical transient to your car in order to stop you; this substitues (more safely) for the spike strips they now lay across the road to deflate all your tires.

A safe deposit box made of metal would probably provide pretty good protection against EMP. It all depends on how tightly the cover seals the box and how good and uniform is the electrical contact between the cover and the box; remember that a Faraday cage only works if the openings in it (including long, narrow slots!) are substantially shorter than the wavelength of the signal(s) you're trying to block.

Atlant (talk) 13:59, 14 February 2008 (UTC)

According to a recent documentary, you can make a car start after an EMP attack by replacing the solenoid. 206.252.74.48 (talk) 14:16, 14 February 2008 (UTC)

Very funny! Remember: after a nuclear attack, look for a car that predates any electronics fancier than an 8-track player.

Atlant (talk) 15:46, 14 February 2008 (UTC)

A safety deposit box generally is a thin metal box inside a thicker metal box inside a metal or reinforced concrete vault. This provides three levels of shielding against external electromagnetic fields, and should provide a respectable amount of shielding, but I have not seen figures on the strength of the hypothetical EMP so I could not attempt to calculate the field strength inside and compare it to the threshold for damage to electronics, magnetic media, etc. I'm surprised the folks who sell personal keychain radiation monitors [6] and iodine pills [7] do not advertise EMP safes for the home, perhaps welded from 1/2 inch ferrous metal. I expect that the avionics and communication equipment on military command planes and bombers are hardened to survive EMP, and they would not get off the ground if they had to be as solid as a safety deposit box installation. Edison (talk) 17:18, 15 February 2008 (UTC)

EMP-specific safes? Does that mean that ordinary metal home safes not secure against EMP? If not, then why not? —Lowellian (reply) 19:14, 15 February 2008 (UTC)

Many home safes seem to be plastic and concrete in large part, to deter theft and protect papers from fire. Older office safes are big steel boxes and it seems they would provide a great amount of shielding against external magnetic fields. I have seen nothing so far to convince me than a much thinner metal box would be inadequate. Edison (talk) 20:36, 15 February 2008 (UTC)

Another related question: websites I have seen about using aluminum foil or trash cans to construct Faraday cages usually recommend attaching a grounding wire to the makeshift cage. If, as suggested above, safe deposit boxes and metal safes without grounding wires may form adequate Faraday cages, why would the grounding wire be necessary on these makeshift cages? And does the grounding wire actually have to be stuck into the ground, as in the earth or soil? What if you can't leave the Faraday cage outside the house, then what do you do? (Besides sticking it in the soil of a houseplant vase? *wink* ) (Sorry for all these questions, but I don't know much about electrical physics.) —Lowellian (reply) 21:36, 15 February 2008 (UTC)

Whether a metal container is grounded or not should not affect its permeability to magnetic fields. Dissipating an electrical charge, such as from lightning is a different question. If current flowed through the container from a source to a ground connection, that might actually cause a magnetic field in the interior, if the current density was higher in one side of the container than in the other side. Aluminum foil would provide negligible magnetic shielding, but couod provide shielding against electric fields. I once used a coffee can as a Faraday cage to shield a large speaker magnet from causing distorted color in a TV picture tube. I have seen chicken wire used to provide a Faraday cage around a chamber where human subjects had electrophysiological recording of brain waves during perception experiments. No idea how either of these would fare against EMP. Edison (talk) 02:49, 17 February 2008 (UTC)

What about my general questions about grounding? How do you "ground" things inside the house without soil? —Lowellian (reply) 20:57, 18 February 2008 (UTC)

If the plumbing in your house is all-metal, you can ground something by wiring it to a cold-water pipe. --Carnildo (talk) 21:13, 18 February 2008 (UTC)

James Randy and Aliens

Anyone know if James Randy believes in Aliens? Malamockq (talk) 03:09, 16 February 2008 (UTC)

From his online bio] I get the idea that he does not believe that sentient technologically superior aliens have flown to earth in UFOs. I can't speculate on whether he thinks there is life, intelligent or not, elsewhere in the universe. Sifaka ^talk 03:50, 16 February 2008 (UTC)

Yea, the UFO thing is quite a bit different though. It's one thing if he thinks there might be life on other planets, it's another thing if they have actually visited us. Malamockq (talk) 21:51, 17 February 2008 (UTC)

You may want to see my somewhat OT comment here Talk:Unidentified flying object#What the hell is it going to take ... (please don't reply there tho) Nil Einne (talk) 17:26, 16 February 2008 (UTC)

Well, first, his name is James Randi, with an "i", not a "y". Secondly, to answer your question, it seems that he believes it's likely that there are other intelligent lifeforms out there in the universe, but that there is no good evidence so far that any aliens have ever visited Earth. For example, he has endorsed the SETI project in the past (see here). However, knowing Randi, he has probably never stated outright that he "believes in aliens" since he prefers solid objective evidence before making such a claim. -- HiEv 01:28, 18 February 2008 (UTC)

Probability speaking, it's far more improbable that Earth is the only planet in our universe to have life, than for life to exist on other planets. 64.236.121.129 (talk) 17:07, 20 February 2008 (UTC)

EMBRYOLOGY

Do you know some tacts to remember the steps of growth that ocurre in human embryo growth during the first 8 weeks? thanks —Preceding unsigned comment added by 201.220.222.140 (talk) 04:41, 16 February 2008 (UTC)

There aren't many tactics beyond just memorization. Embryology, Human embryo would help. Also search pubmed.org for reviews on human embryology. Wisdom89 _{(T / ^C)} 04:45, 16 February 2008 (UTC)

You can find some embryology mnemonics here. Personally I usually have more trouble remembering the mnemonics than I do the information they're supposed to help you remember. - Nunh-huh 04:47, 16 February 2008 (UTC)

I'm in Nunh-huh's camp and despise most mnemonics (although I hate "pneumonics" even more ;-). In approaching topics that appear to need rote memorization, I usually first try to understand terms, how structures got their names, etc. Some examples from embryology might be the origin of the term morula (a bunch of cells resembling a mulberry), why it's called the ultimobranchial body ("ultimo-", last; hence, "last of the branchial pouch derivatives"), etc. Works great for me, but your mileage may vary. --David Iberri (talk) 20:08, 16 February 2008 (UTC)

physics/water barometer

the height of water in a water barometer is measured from the open atmospheric pressure end vertically to the under side of the J tube.

the question is - If the lower u loop end of the J is elongated to about sixty feet, what differance will it make to the barometer?

M.Krishnapillai —Preceding unsigned comment added by 124.43.251.138 (talk) 06:59, 16 February 2008 (UTC)

I'm not certain if I understand your question, but I believe that extending the open side of a water barometer will make no difference. Perhaps our article on barometers may help. (EhJJ)^TALK 22:32, 16 February 2008 (UTC)

You will be measuring the pressure of the air from a different point, Although the extra weight of the air in the tube will largely compensate, the difference in air pressure inside the tube and outside could be due to different temperatures, or humidities, or due to wind, sound etc. Graeme Bartlett (talk) 03:33, 18 February 2008 (UTC)

Cowling nozzle?

Watching mythbusters today, when they tried to make a jet pack with 2 props and cowling, they didnt get enough lift. I would've thought that to get more lift, you could focus the air more by creating more of a nozzle effect, by narrowing the diamter after the prop instead of having it the same all the way down. Is there a technical reason why they couldnt do this? —Preceding unsigned comment added by 59.100.252.244 (talk) 12:53, 16 February 2008 (UTC)

How much elecricity does an solar panal of a sq mts produce.

Hello i am thinking of making a paper presentation on a way of producing power by concentrating mirrors and i want to know how they fare with solar panals .I would also like to know about there efficiency,cost etc.--Man manoj1990 (talk) 13:09, 16 February 2008 (UTC)

The article on Solar_radiation contains a number of estimates of how much solar energy arrives at the earth. The article on photovoltaics has a discussion of efficiency. JohnAspinall (talk) 04:54, 17 February 2008 (UTC)

Positive and negative load tests

G'day, RefDeskers. I'm stuck with something. I have come across the phrases positive load test and negative load test with reference to railway sleepers. I'm not seeking to learn the methodology of such tests, this is irrelevant - what interests me is the relevance of the terms positive and negative here. How do both of these tests differ and why the differentiation? If anyone has any ideas, I'd appreciate them. Thanks and cheers! --Ouro (blah blah) 13:42, 16 February 2008 (UTC)

Try this paper http://ro.uow.edu.au/cgi/viewcontent.cgi?article=1321&context=engpapers (look at figure 1) - can this be the answer. (the loads are 'moments' ie torque..)?77.86.8.83 (talk) 13:58, 16 February 2008 (UTC)

Makes me scratch my head, this diagram you pointed me to... could anyone briefly explain further? --Ouro (blah blah) 14:49, 16 February 2008 (UTC)

A railway sleeper somewhat works like a beam in a framed building structure. Such a beam is subjected to pressure (positive) in the top part and tension (negative) in the bottom part. In a typical reinforced beam the concrety bits cope with the pressure whilst the steel reinforcement takes up the tensile forces.

I assume that sleepers, being subjected to 2 point loads at the locus of the tracks, have similar characteristics of positively and negatively stressed parts, which have to be mathematically analysed to provide steel reinforcement in the zones of tensile forces. The article from the Wollongong University seems to indicate that significant tensile stress is measurable in the top part of the middle section of the sleeper.

There is a stack of suitable articles under the lemma structural analysis. Prost, --Cookatoo.ergo.ZooM (talk) 01:53, 17 February 2008 (UTC)

Goodness me. But thanks for youe explanation, ZooM! --Ouro (blah blah) 09:27, 17 February 2008 (UTC)

Deep space travel - Voyager and Pioneer

Are the Voyger and Pioneer space probes travelling particularly fast? That is, would it be hard, using exisiting, proven technology, to make a similar space probe travel ten times as fast as these probes? ike9898 (talk) 14:33, 16 February 2008 (UTC)

"Voyager 1 is departing the Solar System at a speed of 39,000 miles per hour. Voyager 2 is departing the Solar System at a speed of 35,000 miles per hour." http://www.spacetoday.org/SolSys/Voyagers20years.html

I have literally no idea about this stuff so couldn't say with any authority if faster speeds are possible but i suspect that the pace these things are travelling is not something that is controllable/could be changed in any meaningful way by modern technology design. ny156uk (talk) 14:38, 16 February 2008 (UTC)

Oh and Pioneer details on that page..." Accelerating to a speed of 82,000 mph, Pioneer 10 passed by Jupiter on December 3, 1973. so my assumption about speed is obviously wrong. (http://www.spacetoday.org/SolSys/ThePioneers.html) ny156uk (talk) 14:42, 16 February 2008 (UTC)

(ec) Well, let's see. Voyager I is travelling at 17,2 km/s relative to the Sun, Voyager II is supposed to be travelling 10% slower, so say about 15,5 km/s, and Pioneer 11 is travelling at 11,6 km/s, and Pioneer 10 is unfortunately unreachable. Now, say we increase tenfold the speed of Voyager II, giving ca. 150 km/s. As I read, one of the Helios probes reached around 70 km/s, a current record for a man-made object. Deep Impact reached velocities in the low twenties per second. So, we're not quite there yet actually, but ion thrusters promise certain advances. Also, keep in mind that probes tend to rely not only on engines for their speed, but also gravitational slingshots. Hope I helped a bit. --Ouro (blah blah) 14:48, 16 February 2008 (UTC)

Voyager can cross the galaxy in like 60 years or something x_X :D\=< (talk) 04:52, 19 February 2008 (UTC)

can we reabsorb water from the bladder?

Once urine is in the bladder, can the body reabsorb it if it needs it? Say, if you were dumped into the desert with a full bladder would you be better off to 'hold it' so your body could use it later? 216.77.239.212 (talk) 15:05, 16 February 2008 (UTC)

The bladder is unable to reabsorb urine. If the bladder was able to reabsorb what would be the purpose of the kidneys, how could the kidneys control the hydration of the body is the urine was reabsorbed. One of the problems of an enlarged prostate gland is the inability to pass urine at will. This causes a build up of pressure in the bladder which if unresolved will result in back pressure on the kidneys. If you are in the desert with a full bladder it would be more sensible to pass the urine into a container and possibly seek a method to distil the water out for reconsumption. I'm assuming a certain desperation here. Richard Avery (talk) 16:23, 16 February 2008 (UTC)

Stillsuits! --Ouro (blah blah) 16:53, 16 February 2008 (UTC)

However, some people have survived without water by peeing and then drinking their own urine, yes urine is drinkable but at least it is your own urine. Hope this helps. Thanks. ~AH1^(TCU) 17:27, 16 February 2008 (UTC)

Though there's only a limited amount of times that will work, of course, without an external water source. --98.217.18.109 (talk) 19:24, 16 February 2008 (UTC)

Maybe you should source this as from the little knowledge I have of extreme survival it is a bad idea to drink your own urine. On the impermeability of bladders, apparently there is a rise in cases of ruptured bladders in Europe that goes with the increase of the consumtion of beer and this especially for female drinkers as they have a smaller bladder. The scenario goes as follows: drink, to drunk to feel the need to pee, fall, rupture bladder. So if you drink beer, remember to pee! 200.127.59.151 (talk) 23:38, 16 February 2008 (UTC)

Drinking_urine#Survival APL (talk) 10:33, 17 February 2008 (UTC)

Seems unlikely 200.127, as drunk people with full bladders tend to just wet themselves. 79.66.116.27 (talk) 18:18, 17 February 2008 (UTC)

(unindent) thanks for this info, I wasn't really concerned about getting drunk and deserted in the desert. I did think though that the bladder membrane might be water permeable, which I think Richard answered, afaict. thanks Tim (talk) 00:23, 17 February 2008 (UTC)

A source is needed for the claim of females having smaller bladders. I have known females who could drink far more than males without needing to void urine. Edison (talk) 02:41, 17 February 2008 (UTC)

I don't know about smaller bladders but here is about overindulging [8]. 200.127.59.151 (talk) 18:48, 17 February 2008 (UTC)

toads and frogs can, however. Gzuckier (talk) 01:47, 21 February 2008 (UTC)!

Reverse engineering in baking

I've found a type of bun, sold commercially, that is heavenly. It's cinnamon- and apple-flavoured, and I would like to know how I may proceed to make these on my own. They are awfully expensive - £4 for 8x bitesize. Can one reversely engineer these and find the recipe? Thank you immensely. 81.93.102.185 (talk) 16:53, 16 February 2008 (UTC)

Are maybe ingredients listed on the packaging? --Ouro (blah blah) 17:21, 16 February 2008 (UTC)

Beyond apple, sugar, apple-and-cinnamon fillings (detailed description) and the next 20 ingredients and E-substances, it doesn't lend much of a hint. I am wondering if actual tests can be done on the bun to show its amount of e.g. flour, eggs, everything. 81.93.102.185 (talk) 17:39, 16 February 2008 (UTC)

I guess one could try to estimate the ingredients from the results, but it'd be way more costly than buying them every day fresh. Oh, but if you have the ingredients and e-substances you're not that bad off. --Ouro (blah blah) 17:46, 16 February 2008 (UTC)

The proportion of the most basic ingredients (flour, eggs, water, yeast) is reasonably fixed, and a simple Google search for a recipe will yield satisfactory results (different will mostly affect the texture and consistency more than the flavour). A lot of those other ingredients, particularly the E numbers, are there because it's a commercial product - they're stabilisers and preservatives that are needed because it needs to have a factory-to-you time of a week or more. That's the big difference between stuff you bake at home and baked goods you buy from the supermarket - the home baked stuff takes incredible for the first 12 hours or so, but very quickly deteriorates. I think you'll get nice results just baking a basic bun with the normal basic ingredients. You might find that it doesn't taste appley-enough; if so, try making a reduction from apple juice and using that in place of some of the water the recipe calls for. -- Finlay McWalter | Talk 17:52, 16 February 2008 (UTC)

A recipe is more than an ingredients list. I'm no expert on baking, but I believe that the heavenliness (or lack thereof) of baked goods is based at least as much on technique as on raw chemical composition. No amount of reverse engineering, or mass spectrometry (or whatever) is going to tell you how finely or coarsely the shortening was cut in, or how long the dough was kneaded, or how long it sat between kneadings, or at what rate various amounts of liquids (some of which, of course, evaporated later) were added. For that, you're either going to have to suborn an employee at the bakery, or do lots of experimenting yourself. —Steve Summit (talk) 19:43, 16 February 2008 (UTC)

If the dough and sweet mix are separated in swirls, then the sweet mix will almost certainly contain apple or (even nicer) pear concentrate. Also, using apple varieties suited to cooking helps. I used to bake these. Polypipe Wrangler (talk) 21:22, 16 February 2008 (UTC)

You could always ask the bakery for the recipe: they might not consider it a trade secret. Of course, even if they give it to you, it might turn out to require equipment you don't have at home. [And then there's this hazard. :-)] --Anonymous, 22:19 UTC, February 16, 2008.

You might wish to seek out Saigon cinnamon, since it has greater aroma than other varieties in the baking. One source listed in the article is [The Spice House]. The cinnamon is the essence of the baked good, and compared to premium freshly ground spice, the spices sold in little jars or tins in the grocery store are pale imitations. [User:Edison|Edison]] (talk) 02:34, 17 February 2008 (UTC)

Why do some people turn green when they get sick?

I have searched the internet on this subject and not seen anything of use. Recently my daughter (white, slightly olive coloured skin) was ill and she definitely had a greenish cast to her skin. Our family are curious to know what causes the green colour. She was feeling dizzy so may have had blood drain from her face to the part of her body that needed help. Why is the resulting hue green? —Preceding unsigned comment added by 124.197.36.202 (talk) 20:29, 16 February 2008 (UTC)

We discussed green skin on the Miscellaneous desk last month (here and also here), but I guess we didn't consider the illness angle much. —Steve Summit (talk) 21:53, 16 February 2008 (UTC)

This confirms your observation in a turn of phrase "looking green around the gills" meaning someone looks like they're about to be sick[9] and google came up with green bile in the erm, vomit, but nothing about the skin's appearance except that it can refer to someone looking pale before they er (excuse me...) Julia Rossi (talk) 11:56, 17 February 2008 (UTC)

FWIW I reckon it is just reduction in blood. If you reduce the red component from skin colours they often turn greenish. --BozMo talk 12:56, 17 February 2008 (UTC)

February 17

Carbonyl reduced to Hydroxyl

I understand that reduction is a gain of electrons and oxidation is a loss of electrons. But I don't understand how when a carbonyl is turned into a hydroxyl it was reduced. To me the number of electrons stayed the same in the functional group before and after. There were no gains or losses of electrons. Could someone explain this to me? 128.163.224.198 (talk) 00:29, 17 February 2008 (UTC)

It's a reference to the oxidation state of carbon, specificially. Whereas previously the oxygen-bound carbon (in the case of a ketone) was considered to have an oxidation state of +2, it now has an oxidation state of 0. Someguy1221 (talk) 00:34, 17 February 2008 (UTC)

If you're dealing with biochemical (aqueous) systems, here's another way to think about it: To start with, you have the carbonyl and an available pool of H⁺ ions from the water. In order to go from the carbonyl to the hydroxyl, you have to add two protons and two bonds (one each to both the carbon and the oxygen). To make the bonds, you need four electrons (two for each bond). Two electrons come from the C=O double bond that you "break" into a single bond, so you need to add in an additional two electrons for the second bond. -- 128.104.112.47 (talk) 19:13, 19 February 2008 (UTC)

Sleeping standing up

Are there humans who sleep standing up? I think that leaning on a corner it would be feasible at least.217.168.1.250 (talk) 00:58, 17 February 2008 (UTC)

It's not possible without an adequate means of support.The Updater would like to talk to you! 01:03, 17 February 2008 (UTC) —Preceding unsigned comment added by WikiHaquinator (talk • contribs)

If I can sleep sitting up, or sitting at my desk at work, I can probably sleep leaning against something. But unlike cattle, I do not believe humans can lock their knees and sleep while standing unsupported. Micronaps would occur if a person were sleep deprived long enough, but they would jerk as they started to fall. Edison (talk) 02:33, 17 February 2008 (UTC)

I could see it happening if someone had some sort of back problem that prevented him/her from laying down, with supports of course. Clarityfiend (talk) 04:56, 17 February 2008 (UTC)

Astronauts of course can sleep in any orientation, but in orbit there is no differential apparent force on a person distinct from that on the space craft, so there is no up/down. That said, astronauts do have preferences for which way in their sleeping bags they lie (head/feet up/down) but this is just preferences to which way the tethers and zips are orientated to them. Still it does look somewhat bizarre seeing one astronaut giving a video linkup tour of their living quarters, to then see one of there colleagues unzip from a sleeping bag in an opposite orientation. David Ruben ^Talk 13:28, 17 February 2008 (UTC)

Well, we would not stand unsupported, so we don't have to lock our knees. Imagine that you are on a corner facing it. You can lean your knees and lean your head on the corner. I'll try this at home and come back to you. 217.168.3.246 (talk) 20:35, 17 February 2008 (UTC)

(OR warning). It's possible to fall asleep standing up, but you tend to wake up fairly soon! A kind of semi-doze can be maintained for some time while clinging to one of those handle-strap things on a bus or train. And I've seen children soundly asleep clinging to a parent's leg or similar. And, of course, there are somnambulists who manage the whole upright thing quite well. Gwinva (talk) 22:01, 17 February 2008 (UTC)

Electron microscope staining

hey,

Is it possible to stain cells for observation under electron microscope? The Updater would like to talk to you! 01:02, 17 February 2008 (UTC)

It is not necessary to stain a cell for veiwing with an electron microscope. The cell must be coated with a thin layer of metal (Usually gold I think) to reflect the electrons so an image can be created. It may also be helpful to see electron microscope. --Zrs 12 (talk) 01:27, 17 February 2008 (UTC)

Variable Speed of Light

I was recently reading a scientific paper written by one of my teacher's uncles on his theory about light having a varying instead of constant speed. First, he set some units: $9.8m/s^{2}=1\,\!$, by Newton's equation $F=ma\,\!$ and defining $9.8m/s^{2}\,\!$ as the acceleration $m=F/g\,\!$. Also, defining gravity is $L/s^{2}\,\!$ in which $L=9.75m/s^{2}\,\!$. He then says therefore, $m={\frac {F}{1}}$ so $m=F\,\!$. Then he says Length is L, mass is F, t is time, and so $c={\frac {L}{t}}$. He says work is mass multiplied by Length and energy is the rate of performing work so Newtonian energy is $E={\frac {mL}{t}}$. He then says using the relativity equation $E=mc^{2}\,\!$ we need to define mass. Since Newtonian mass is ${\frac {Et}{L}}$ the relativity equation is as follows: $E=\left({\frac {Et}{L}}\right)\left({\frac {L}{t}}\right)^{2}$. He says when simplified this equation shows time is Length. My questions are:

• How did he get $c={\frac {L}{t}}$ (this appears to be just an assumption to me)
• Is there anything wrong with his logic? and,
• When I simplified the equation $E=\left({\frac {Et}{L}}\right)\left({\frac {L}{t}}\right)^{2}$ I distinguished between Einstenian and Newtonian energy and reformulated the equation to $E_{E}=\left({\frac {E_{n}t}{L}}\right)\left({\frac {L}{t}}\right)^{2}$ and when it was reduced I got ${\frac {E_{E}}{L}}={\frac {E_{n}}{t}}$ showing (it appears to me) that $L\neq {t}$ or at least $L=t\Leftrightarrow {E_{n}}=E_{E}$ for the fact that Einstenian and Newtonian energy are different. Who is correct? Does $L=t\,\!$ in fact?

Thanks, Zrs 12 (talk) 01:54, 17 February 2008 (UTC)

Showing ${\frac {E_{E}}{L}}={\frac {E_{n}}{t}}$ : ${\begin{aligned}E_{E}&=\left({\frac {E_{n}t}{L}}\right)\left({\frac {L}{t}}\right)^{2}\\&={\frac {E_{n}tL^{2}}{Lt^{2}}}\\&={\frac {E_{n}L^{2}}{Lt}}\\&={\frac {E_{n}L}{t}}\\\end{aligned}}$ ${\begin{aligned}\textstyle {therefore}\\\end{aligned}}$ ${\begin{aligned}{\frac {E_{E}}{L}}={\frac {E_{n}}{t}}\\\end{aligned}}$

Zrs 12 (talk) 05:14, 17 February 2008 (UTC)

ATTENTION: I accidentally put (L/t²). Now it's correct as (L/t)². Sorry. Zrs 12 (talk) 03:31, 17 February 2008 (UTC)

The theory starts out with gibberish, because if $9.8m/s^{2}=1\,\!$, then in dimensional analysis length equals time squared, which is nonsense. Edison (talk) 02:30, 17 February 2008 (UTC)

Anything else? (Remember, he is trying to prove that the speed of light is variable so maybe length does equal time squared?) Zrs 12 (talk) 02:56, 17 February 2008 (UTC)

Except that he didn't prove that length equals time squared, he just sort of declared it, and this seems to form the basis of the rest of the proof. Someguy1221 (talk) 03:19, 17 February 2008 (UTC)

Ok, thanks. What about the part where I showed $L=t\Leftrightarrow {E_{n}}=E_{E}$? Did I do this correctly or did he? In other words, did I reduce correctly? --Zrs 12 (talk) 03:24, 17 February 2008 (UTC)

The whole thing is basically gibberish. It's the mathematical trappings of high school physics without any of the physics. It's hard to know how to respond to your questions because you might as well be analyzing Star Trek technobabble. Have you correctly followed the procedure for realigning the tachyon compensators? Well, maybe, maybe not; only your teacher's uncle can say. -- BenRG (talk) 20:36, 17 February 2008 (UTC)

This is too physics heavy even for the likes of me ;) kidding. Seriously though, the only time the speed of light is not constant is when it passes through a medium, any medium that is not a vacuum. At least that's the extent of what I know regarding this. That's really all I can say about the above since it's mostly mathematical vomit. That's not a personal attack. It's just a really convoluted way to ask a question. Wisdom89 _{(T / ^C)} 20:58, 17 February 2008 (UTC)

Not to defend the uncle (I neither know nor care about the above), but 1. there are variable speed of light theories put forward by competent physicists, so dismissing that aspect of it a priori is a little presumptive, and 2. the simple manipulation of simple equations to reach unintuitive results has been done successfully before by none less than Einstein (the 1905 papers on special relativity are basically this—taking a few very well-known equations and trying to make them be compatible with each other in ways that hadn't been done before, specifically combining Galilean relativity with the axiom of a fixed speed of light in a vacuum, and the rest basically falls out from there), so that's not a great reason to dismiss it either. The original derivation of E=mc^2 does not use complicated physics at all; special relativity as a whole is extremely simple "high school" math (Einstein's emphasis was on axioms and concepts; he had to learn a lot of math before he could generalize the theory, however). However it is unlikely that one's uncle is going to do better than Einstein in that game, which would for me be a pretty strong a priori source of doubt, though it is no proof. --98.217.18.109 (talk) 21:40, 17 February 2008 (UTC)

The first warning sign that something dubious is going on is the use of $g$, the local gravitational acceleration at the surface of the earth, in a theory about light. Any theory about light has to account for the fact that light travels throughout space (i.e. we see stars). Why would the behavior of light throughout the universe depend on the local amount of gravity at the surface of the third planet orbiting an unremarkable G-class star, in the Orion arm of the Milky Way Galaxy? JohnAspinall (talk) 00:47, 18 February 2008 (UTC)

I kind of thought so. He had but 56 semester hours of math in college. Also, he is a chemical engineer, not a physicist, so it doesn't really suprise me that it seems to be "gibberish". Thank you all, Zrs 12 (talk) 00:33, 18 February 2008 (UTC)

Engineers of various sorts seem to be the ones behind a lot of this kind of speculation. Physics department around the country have "crank files" of people who write in to dispute or put forward various theories; engineers, in my experience in reading these files (which I have done on a few occasions), seem to go for this stuff the most. I imagine it has to do with their type of education—something that makes them feel quite technically competent but they actually lack a lot of the lower-level understanding that is superfluous for their profession. But that might be an exaggeration. --98.217.18.109 (talk) 02:49, 18 February 2008 (UTC)

Does your uncle happen to have some underlying reason to want the speed of light to be variable? Wanting to arrive at a desired result can certainly lead people to accept some tortured logic. --Sean 14:52, 18 February 2008 (UTC)

I haven't a clue. (He's my teacher's uncle) Anyway, this very well may be the case. However, in his memo on the subject, there was no indication of this. This could possibly be the case though. Zrs 12 (talk) 23:10, 18 February 2008 (UTC)

Speculative Science Question

I was watching a Twilight Zone episode,A Kind of a Stopwatch, the other day. In it, a man gains the ability to "stop time." Objects freeze in midair, people don't move, and none of it affects him. My question is this: If such a thing were possible, then wouldn't he die? Would he be able to breathe the "stopped" air molecules? Would he be able to walk through said molecules? —Preceding unsigned comment added by 192.136.22.4 (talk) 02:04, 17 February 2008 (UTC)

I can't believe I'm answering this......it's a narrative fiction, you're supposed to just accept the premise as a given, and not examine it too closely, lest you ruin the story. Nevertheless, as I recall it, the protagonist is able to move objects, even though the objects don't move under their own force. So he ought to be able to breathe, eat, move, etc. - Nunh-huh 02:11, 17 February 2008 (UTC)

Actually, if he has reset the velocities of all the air molecules to 0, there would no longer be any air pressure, and he would not be able to breathe. When you breathe in, you are simply expanding the volume of your lungs and permitting the air molecules to move into a new location. He would need to push the air into his mouth. — BRIAN0918 • 2008-02-17 16:15Z

Yeah just accept sci-fi. In Star Wars sound can be heard even though there is no medium through which sound waves can travel. Zrs 12 (talk) 02:15, 17 February 2008 (UTC)

Seen this before. There is an old (say 1970) Arthur C Clarke story where a jewel thief is given a device which stops everything more than a couple of metres away from him (or accelerates everything closer). That kind of works a bit. The story is interesting because it begs the question what would you do if you had all the time in the world. Crime? Revenge? Assasination? Sadly once you become a parent the only answer has to be "sleep". --BozMo talk 07:45, 17 February 2008 (UTC)

Except you'd still suffocate in your sleep since you'd basically be in a 2 metre bubble of air which would run out of oxygen :-P Nil Einne (talk) 18:53, 17 February 2008 (UTC)

When Isaac Asimov wrote the novelisation of Fantastic Voyage he addressed some of the basic physics which the screenwriters hadn't troubled with - for example (IIRC) when they're running out of air they tunnel into the lungs to get some, but in the book he actually had them shrink the air from the lungs. --ColinFine (talk) 21:31, 17 February 2008 (UTC)

Reading a more realistic sci-fi story some time ago, I've seen a solution for this kind of problem: the protagonist had to hold his breath while he was using his superpower. This way, the whole story was a bit more balanced, he could use his "power" only for around a minute. The power was to pass through matter and/or become invisible, but this "solution" can also be applied to the power of slowing down time. --V. Szabolcs (talk) 18:50, 18 February 2008 (UTC)

Use of Opiates in the treatment of psychiatric disorders in women!

Question is about medical/chemical applications re wife's treatment. This questioner is reminded: Do not request medical or legal advice. Any such questions may be removed. If you need medical or legal advice, do not ask it here. Ask a doctor, dentist, veterinarian, or lawyer instead. See your doctor. Julia Rossi (talk) 08:49, 17 February 2008 (UTC)

I'd like to add that if you do not agree with your wife's psychiatrist, you (as a couple) could consult a different psychiatrist. Generally, if you get a few "no, we don't do that" responses from several unrelated physicians, it's probably the best way to go (versus asking a bunch of non-medically trained, anonymous volunteers on the internet). Also, feel free to read our article on hydrocodone if you'd like to be an "educated patient", but use that information only to help you ask your doctor the right questions. (EhJJ)^TALK 21:16, 17 February 2008 (UTC)

absorption

Intensity of light decreases with the rise in concentration of the liquid through the light passes through: please explain this in detail.Jskirankumar (talk) 09:34, 17 February 2008 (UTC)

Beer's law. Someguy1221 (talk) 09:44, 17 February 2008 (UTC)

Photoreceptors

Hi all I am usure as to how a rod/cone cell become hyperpolarised. I know that when a photoreceptor such as a rod is resting K+ ions leak out of the inner segment and Na+ ions diffuse in through the outer segment. When a rod is stimulated the Na+ channels close but the Sodium/Potassium pump continues to pump Na+ ions out and K+ in. I'm not sure how this makes the charge go from -40mv to -70mv. Hope this makes sense and please correct me if anything I have written is wrong! —Preceding unsigned comment added by 172.207.224.229 (talk) 10:49, 17 February 2008 (UTC)

If I'm not mistaken, the channel lets 3 Na+ go out and then 2 K+ in. So in net total, +1 goes out of the cell, and the inside of the cell becomes more negative..206.240.25.247 (talk) 13:34, 17 February 2008 (UTC)

When rods are stimulated by photons, the signaling mechanism that is elicited activates cGMP phosphodiesterase which depletes and inacticates cGMP, stopping the depolarization due to sodium ions influx. Since the resting membrane of the cell is closer to the equilibrium potential of potassium, the cell hyperpolarizes. Wisdom89 _{(T / ^C)} 20:42, 17 February 2008 (UTC)

Why is there more static electricity in dry weather?

I wonder. 206.240.25.247 (talk) 13:30, 17 February 2008 (UTC)

I think the water vapour can bring the static electrictiy away. Visit me at Ftbhrygvn (Talk|Contribs|Log|Userboxes) 14:09, 17 February 2008 (UTC)

How does that work exactly? 206.240.25.247 (talk) 14:11, 17 February 2008 (UTC)

From reading several articles on electrostatic discharge, it seems that humidity tends to limit the electrostatic buildup because it makes surfaces slightly conductive, which provides a path for separated charge to recombine. (See [10] for a list of links on ESD. [11] contains animations of the process of tribocharging, in which surfaces of dissimilar materials become charged after contact, friction/pressure, and then separation. [12] explains the connection between humidity and "return current".) --71.175.22.137 (talk) 15:05, 17 February 2008 (UTC)

See the section "Simple experiments" in the Static electricity article. The preface notes that a humid atmosphere provides a conducting path for the rapid neutralization of static charge... --hydnjo talk 19:50, 17 February 2008 (UTC)

absortion1

why does the distance that the light travels through the material also effect the intensity of the light when the concentrator is constant? I shall be thankful for your convincingJskirankumar (talk) 16:45, 17 February 2008 (UTC) explanation

Assuming that the medium is homogeneous (i.e. uniform), you'd expect light to be attenuated by the same amount every time it travels through a unit distance in the medium. For concreteness, let's say

(intensity of emergent ray) = α × (intensity of the incident ray).

After traveling $L$ unit-length layers of the medium, you'd expect the emergent ray to have an intensity of

$\alpha ^{L}$ × (intensity of the incident ray).

--71.175.22.137 (talk) 17:38, 17 February 2008 (UTC)

If a helium filled airship wants to gain altitude...

How does it do this? Lift is determined by how much helium gas it has, so how can they make it fly higher, when they are already at a given altitude? Malamockq (talk) 20:21, 17 February 2008 (UTC)

The density of a gas can be decreased through heat - this would allow the craft to gain altitude. Wisdom89 _{(T / ^C)} 20:32, 17 February 2008 (UTC)

So similar mechanism to a hot air balloon then. Thanks. Malamockq (talk) 20:44, 17 February 2008 (UTC)

Yup, you got it. Wisdom89 _{(T / ^C)} 20:54, 17 February 2008 (UTC)

No, that's wrong. They couldn't burn anything inside the helium bag because anything they piped into the bag to burn, as well as its reaction products, would be heavier than helium and would weigh the ship down. Heating the outside of the bag is theoretically possible but it would be slow to act since the heat won't transfer efficiently to the mass of helium. And the remaining choice, an electric heater inside the bag, would require a heavy power source.

There are actually three solutions that were used in the heyday of airships (whether hydrogen- or helium-filled, doesn't matter).

The first and simplest is that when you take off, you carry something heavy on board as ballast, and when you want to make the airship lighter, you drop it. If you've seen pictures of hydrogen or helium passenger-carrying balloons, you'll note that the passenger gondola is typically ringed with sandbags. (You drop the sand, not the whole bag!) With an airship the preferred ballast is water for several reasons: it's cheap and widely available; it can be loaded with a pump and a hose; nobody will mind much if some of it lands on them; and it can be used to supply the onboard washbasins and recaptured (into a second set of ballast tanks) from the drains. The Graf Zeppelin, for example, carried about 12 tons of water ballast. (If they started to run low on ballast, this would be an emergency situation the same as running low on fuel, and they would land as soon as possible to replenish it.)

The second way is the same way that an airplane does it: by pointing the nose higher or by moving control surfaces in the tail. Of course, this only works when the engines are exerting enough force to keep the vehicle moving forward at sufficient speed.

• I slipped up here. The use of the tail control surfaces, as in an airplane, would be for the purpose of pointing the nose higher, not to provide increased lift directly (since it would be off-center). Pumping ballast toward the rear of the airship would be a second way to lift the nose. --Anon, 06:02 UTC, Feb. 19.

The third way is to burn some fuel, assuming that something like ordinary gasoline or diesel fuel is used. Of course, this is slow to act, but you have the burn the fuel anyway to keep moving. Now most airships have used a single type of fuel and no way to burn it except in the engines, so they had little control over this way of affecting their weight, but the Graf Zeppelin was an exception. It carried two types: Blau gas, which was a propane-based gas mixture about the same weight as air, and gasoline. If it was desired to make the airship gradually lighter, they would burn gasoline in the engines; if not, they would burn Blau gas.

Source: The Golden Age of the Great Passenger Airships: Graf Zeppelin & Hindenburg by Harold G. Dick with Douglas H. Robinson, 1985, Smithsonian Institution, ISBN 0-87474-364-8.

--Anonymous, 23:35 UTC, February 17, 2008.

Interesting, I had a feeling this was the case. For example, if the airship was filled with hydrogen, it wouldn't be very smart to try and heat it, considering it is flammable. Malamockq (talk) 02:37, 18 February 2008 (UTC)

It is possible to heat helium without igniting it. One doesn't have to use a direct flame or combustion. Just saying. Wisdom89 _{(T / ^C)} 09:38, 18 February 2008 (UTC)

I know that, but in airships they can also use hydrogen. Heating hydrogen to make it gain altitude prolly isn't a good idea, nor how they do it. Malamockq (talk) 16:39, 18 February 2008 (UTC)

Question : Why is it not possible to change the buoyancy of one of the gasbags by pumping the gas into and out of rigid tanks? APL (talk) 01:14, 19 February 2008 (UTC)

I think this has been discussed before, in an extreme form. If you could really do that, you wouldn't need any gas -- you'd just evacuate the tanks and off you go floating into the wild blue yonder. But no one knows how to make taks that rigid, without adding more weight than the weight of the gas. Your suggestion seems like a compromise somewhere in the middle -- my guess is it won't work either, for the same reason, but I haven't tried to run the numbers. --Trovatore (talk) 01:30, 19 February 2008 (UTC)

On second thought maybe I misread your question. I thought you wanted to make the gasbags themselves rigid. Maybe you're saying, when you want to lose altitude, pump some of the helium into a tank so that the bag partially deflates. I suppose that works in principle. Would probably use a lot of energy though, and it might be awkward to have the size of the bag change in flight. --Trovatore (talk) 02:47, 19 February 2008 (UTC)

Yes, that is what I was asking. I was not asking about the mythical Vacuum Blimp. I was asking about slightly deflating the gasbags without completely venting the hydrogen. Seems like depending on the type of airship, it wouldn't be that awkward to have the bag change in flight. Even if you completely deflated a gasbag on a Zepplin the envelope would presumably stay the same shape. APL (talk) 04:18, 19 February 2008 (UTC)

Well, I'm no airship engineer; I can't say whether there's some way the idea could be made to work (better than the alternatives). But I would note that there's still an uncomfortable tradeoff: If you make the tanks small, then in addition to having to make them very strong, you'll have to supply a lot of energy to compress the gas into them (integral of pressure wrt volume). Whereas, if you make them big, they'll be heavy, and you have

to lift them with the gas you're planning to put into them. --Trovatore (talk) 04:54, 19 February 2008 (UTC)

Sanity check: Either A) the gasbag is rigid (doesn't change size), in which it has a constant volume, and moving mass (with weight) between the gasbag and a similar rigid pressure tank doesn't change the total volume of the system, or total mass either, so there is no effect to overall bouyancy. Or, B) the gasbag is NOT rigid, meaning that as you pump gas into it, it expands to keep the same pressure as the outside air. Which means that as gasbag total mass increases, the total volume increases, too. Again, you don't gain anything.

The only way to gain something is to either change total airship volume, while keeping mass constant, or change total airship mass, while keeping volume constant. Note that hot air balloons do the latter - they heat the air, which expands out the bottom, making the whole balloon mass less while keeping the volume the same => it will rise. To descend, just let it cool off. The air will contract, and more are will come in the bottom, for more mass at the same volume.

The "right way" would certainly be to have rigid gasbags that we could pump down to a vacuum while they kept their size/shape, but that means a lot of structural strength, which, ahem, would make them too heavy to lift. -SandyJax (talk) 17:29, 19 February 2008 (UTC)

No, you missed a point in alternative (B): It's true that the weight of bag-plus-gas is increasing, but the weight of storage-tanks-plus-gas is decreasing by the same amount (not counting relativistic effects :-). So you do in fact gain buoyancy when you move gas from the rigid tanks into the inflatable bag, and decrease buoyancy when you move it the other way. Whether this is a good, or even feasible, design, is another question, but it does work in principle. --Trovatore (talk) 20:29, 19 February 2008 (UTC)

SandyJax, I think you misunderstood. I was suggesting changing the total displaced volume of the airship by inflating and deflating the gasbags while recapturing the gas in pressurized, rigid holding tanks for reuse, keeping mass constant. (total displaced volume should not be confused with total enclosed volume when talking about rigid frame ships like Zeppelins.) However, Trovatore has satisfied my curiosity by convincing me that my idea would require some pretty heavy equipment that would probably take up a pretty large percentage of the airship's carrying capacity. APL (talk) 05:38, 20 February 2008 (UTC)

Absolute frame of reference

According to the special theory of relativity there is no absolute frame of reference. But something bothers me. The kinetic energy of an object is 1/2 m v^2

For an object of 2 kg.

To get from 0 m/s to 1 m/s requires 1 joule of energy.

to get from 100 m/s to 101 m/s requires 201 joules of energy.

So why can you measure the amount of energy required to increase the velocity of the object by 1 m/s and thus calculate how fast the object is travelling on the absolute frame of reference (which special relative claims that it does not exists).

202.168.50.40 (talk) 21:39, 17 February 2008 (UTC)

To increase the momentum of an object in one direction, you must also increase the momentum of some other object in the other direction (conservation of momentum). You cannot directly observe the energy given to either one; you can only observe the energy given to both. And this energy doesn't vary by reference frame. This is true in classical mechanics too, so for simplicity I will not deal with relativity, and give an example in one-dimensional classical mechanics:

Suppose you have two masses $m_{1},m_{2}$ stuck together, moving at speed $v_{0}$. Then you have an explosion that imparts a momentum $p$ to both of them in opposite directions (let's say it accelerates $m_{2}$ in the positive direction and $m_{1}$ in the negative direction). Then $m_{2}$ will be traveling at speed $v_{0}+{\frac {p}{m_{2}}}$ and $m_{1}$ will be traveling at speed $v_{0}-{\frac {p}{m_{1}}}$. Now let's compute the difference in total kinetic energy of the objects before and after:

${\frac {1}{2}}m_{1}\left(v_{0}-{\frac {p}{m_{1}}}\right)^{2}+{\frac {1}{2}}m_{2}\left(v_{0}+{\frac {p}{m_{2}}}\right)^{2}-{\frac {1}{2}}m_{1}v_{0}^{2}-{\frac {1}{2}}m_{2}v_{0}^{2}$

$={\frac {1}{2}}\left(m_{1}v_{0}^{2}-2pv_{0}+{\frac {p^{2}}{m_{1}}}+m_{2}v_{0}^{2}+2pv_{0}+{\frac {p^{2}}{m_{2}}}-m_{1}v_{0}^{2}-m_{2}v_{0}^{2}\right)$

$={\frac {1}{2}}\left({\frac {p^{2}}{m_{1}}}+{\frac {p^{2}}{m_{2}}}\right)$

Notice that this increase in total kinetic energy is not dependent on the initial velocity $v_{0}$. --Spoon! (talk) 23:38, 17 February 2008 (UTC)

Pitch Drop experiment

The most famous version of the experiment was started in 1927 by Professor Thomas Parnell of the University of Queensland in Brisbane, Australia, to demonstrate to students that some substances that appear to be solid are in fact very-high-viscosity fluids. Parnell poured a sample of pitch into a sealed funnel and allowed it to settle for three years.

Considering how long it takes for pitch to flow. Exactly how long did it take for Prefessor Thomas Parnell to pour the pitch sample into the funnel? 202.168.50.40 (talk) 22:56, 17 February 2008 (UTC)

According to this, he heated the pitch before pouring it in - so I assume it didn't take that long. --Kurt Shaped Box (talk) 23:15, 17 February 2008 (UTC)

How clever! —Keenan Pepper 00:30, 18 February 2008 (UTC)

You've seen our article about the Pitch drop experiment, right?

Atlant (talk) 01:52, 18 February 2008 (UTC)

Sudden tics when drowsy?

Sometimes, especially in class, if I am leaning back and attempt to sleep, parts of my body will suddenly tense. This is really uncomfortable, and I'd very much like to sleep without this happening. Is there a good article on this muscle behaviour? 81.93.102.185 (talk) 23:18, 17 February 2008 (UTC)

Perhaps you might consider attempting to sleep somewhere else than in class? You probably want to read hypnic jerk and myoclonus, but if you want more than that, please see a doctor, because medical advice is not allowed here. --Anonymous, 23:47 UTC, February 17, 2008.

I doubt that this is a medical issue so I'll provide my insight and two cents. What you are experiencing are most likely hypnic jerks upon entering into stage one of non-REM sleep. Also, strange sensations when falling asleep might be a sign of sleep paralysis, which is completely benign. Wisdom89 _{(T / ^C)} 09:36, 18 February 2008 (UTC)

Who would win?

In a fight between a Predator and a Terminator, which would be more likely to win? --81.79.122.2 (talk) 23:40, 17 February 2008 (UTC)

Not only does this ask for speculation, it is not a science question. --Anon, 23:48 UTC, Feb. 17.

Sounds like a great idea for a movie proposal. And you get to decide! Someguy1221 (talk) 00:23, 18 February 2008 (UTC)

Predator by a mile - even though this isn't a legitimate science question. One blends into the environment and preys on a victim, while the other loafs around blindly. If you want to liken it to something in nature, how about a preying mantis verses a spider? Wisdom89 _{(T / ^C)} 00:27, 18 February 2008 (UTC)

But human Arnold beat a Predator so therefore clearly a robot Arnold must destroy a Predator. —Preceding unsigned comment added by Shniken1 (talk • contribs) 01:21, 18 February 2008 (UTC)

You do have to remember that a Predator, while probably of approx. equal strength and speed to a Terminator, is only slightly less vulnerable to gunfire/edged weapons/fists and feet than your average human. A Terminator can absorb significantly more damage and still keep coming. If the Predator cloaked, the Terminator would probably be able to calmly track its vague outline against the surroundings (and get a target lock) just fine. --Kurt Shaped Box (talk) 01:34, 18 February 2008 (UTC)

In the AVP movies, Preds usually wear bullet proof armor on their bodies. Does a pretty good job of deflecting bullets. Terminators are still more durable despite that though. Not nearly as agile though. Malamockq (talk) 02:42, 18 February 2008 (UTC)

The Predator might come out on top if he figured out what the humans obviously seem unable to when fighting Terminators - namely that plugging away at a cyborg's heavily-armoured head and torso is *very* ineffective and instead concentrated on shooting its spindly legs out from under it. Once crippled, the Pred could take his sweet time and concentrate plasmacaster fire on the Terminator from a distance, until he managed to damage something vital. --Kurt Shaped Box (talk) 16:35, 18 February 2008 (UTC)

See answer #4 here, and substitute the strings "Predator" and "Terminator" as appropriate. —Steve Summit (talk) 01:48, 18 February 2008 (UTC)

They are evenly matched. It's all up to the writers. That's what makes "vs." stories interesting. Pitting two evenly matched opponents against each other. Having Predator vs. Galactus, wouldn't make much sense for example. Malamockq (talk) 02:40, 18 February 2008 (UTC)

Despite the speculation comment, the opinions have come thick and fast :) In the latest Requiem AVP movie, the predator takes off his armour to experience an honourable fight to the death with his opponent, much like you see in the martial arts movies where the guy who has just disarmed the other guy, throws his sword away as well. So I suppose in the predator's mind, his opponent was a respected and worthy one. Sandman30s (talk) 12:26, 18 February 2008 (UTC)

Ten bucks on Terminator. Humanity shall prevail. --Ouro (blah blah) 13:02, 18 February 2008 (UTC)

Just ask Google [13] :P --V. Szabolcs (talk) 15:35, 18 February 2008 (UTC)

February 18

Tube guitar amplifier humming/rustling sound problem

Hello, perhaps this should be in miscellaneous but it deals with the internal components of an amplifier and speaker. Yesterday I purchased a Peavey Classic 30 guitar amp, a 30-watt all tube amp with one 12" speaker, 3 preamp tubes and 4 power tubes. It sounds fine except for a few quiet rattles: sometimes the amplifier makes a very low pitched crackly rustling sound that kind of sounds like the wind blowing. It is peculiar because it happens whether my guitar is plugged in or not, and it is at the same volume no matter what the volume of the amp is. I've turned it up very loud and I've turned the volume as low as possible and the volume of this little crackling hum has not changed at all. It's very quiet and I only hear it while playing quietly or not at all but while the amp is still on. Does this problem sound familiar to anyone, if so, does anybody know what causes it and, most importantly, how to fix it? NIRVANA2764 (talk) 02:11, 18 February 2008 (UTC)

Is it a bug or a feature? I thought it was little quirks like that that made tube amplifiers attractive in the first place... —Steve Summit (talk) 02:56, 18 February 2008 (UTC)

Try "tapping" the power tubes one at a time to see if any tube "responds" as sometimes a tube can become microphonic and generate unwanted background noise. Seems like a fine piece of equipment that you've gotten, have fun and good luck! --hydnjo talk 05:51, 18 February 2008 (UTC)

Googling suggests that the Classic 30 has a spring reverb: analog reverbs are always prone to hum (from transduction and interference). Does the hum persist if you take the reverb out of the circuit (assuming the amp has a "reverb on/off" button) as opposed to just turning the reverb knob down? Depending on its design, a spring reverb can sometimes act as an antenna, capturing unwanted RF interference from neighbouring devices. Try turning off everything electrical nearby (TVs, monitors, fans, AC units, and transformers in particular). If you can't be sure the reverb is off (as opposed to just dialled down) whack the amp (gently) - a whacked spring reverb makes a horrible noise like an explosion in a scrapyard. -- Finlay McWalter | Talk 15:23, 18 February 2008 (UTC)

I've never seen that sound so eloquently described! --hydnjo talk 15:39, 18 February 2008 (UTC)

I tend to agree with that as well. Especially since I've heard both that amp sound and an explosion in a scrapyard in real life. 206.252.74.48 (talk) 20:27, 18 February 2008 (UTC)

Hydnjo is right. I know that sound, too. There is a schematic diagram here. You have a transistor or two in there, you know. I would try freeze spray on Q2, being careful not to break a tube with it or electrocute myself (tube amps bite hard). You can pull tubes one at a time (unplugging the amp and letting it sit awhile between pullings) to narrow down the circuit the noise is coming from. Don't pull an output tube. Freeze capacitors one at a time and listen. It might be normal for this amp. --Milkbreath (talk) 16:56, 18 February 2008 (UTC)

Besides microphinics in tubes, the connection between the tube pins and the socket can be imperfect due to dirt or corrosion. With the power off, wiggling the tube in the socket or removing and replacing a few times may 'wipe" the contack and improve the noise level. Volume controls are another suspect. They can be cleaned with appropriate spray (power off)or replaced. Connects and things that plug into them are the third area where imperfect contactor frayed wiring can create noise. Edison (talk) 19:55, 18 February 2008 (UTC)

bug/insect identification

Can someone tell me which bug this is? http://farm3.static.flickr.com/2411/2272801999_ed19224b97_o.jpg It was about the size of a dime or a nickel. This is the underside: http://farm3.static.flickr.com/2119/2272814521_32f6c5f0b5_b.jpg Sorry for the blurriness. Thank you. --Rajah (talk) 04:08, 18 February 2008 (UTC)

Looks like a member of the Pentatomidae family. They're called shield bugs or stink bugs. This one might be the Brown marmorated stink bug, but many of the species in this family look similar. Sancho 05:51, 18 February 2008 (UTC)

Thanks! --Rajah (talk) 13:05, 18 February 2008 (UTC)

Volume of solution

Does the volume of water change when NaCl is added to it? What about solutions in general? Does the volume of solution change when solute is added to solvent? Kushal 13:06, 18 February 2008 (UTC)

In general, the volume of a solution changes when solute is added. That's why, for example, a molar solution is always prepared by putting the solute in the flask first, rather than starting off with a known volume of solvent and adding the solute. MrRedact (talk) 16:40, 18 February 2008 (UTC)

Yes, the volume of water changes when dissolving solutes as (in your example for instance) the NaCl displaces water molecules. Wisdom89 _{(T / ^C)} 18:49, 18 February 2008 (UTC)

By changing, I think you mean increase, it's important to realize that there some solutes which will decrease the volume of the solution. This is a particular chestnut of many physical chemistry courses. --Rajah (talk) 02:21, 19 February 2008 (UTC)

Sorry I can't find a reference, but I remember that it was either a solution of water and small amount of alcohol added or vice versa. In at least one of the cases, you can show that the volume of the solution decreases, because the solute and solvent are attracted to one another and pull the molecules closer together. --Rajah (talk) 02:50, 19 February 2008 (UTC)

And a followup point is that I would think, but am not sure, that if you can increase or decrease a solution volume by adding solute, then sometimes when you add a solute (or combination of solutes), the volume of the solution will remain the same. --Rajah (talk) 02:51, 19 February 2008 (UTC)

So, in no case involving a single solute and a single solvent does the solute just go in the intermolecular space of the solvent? I mean, if the solute were to go in the intermolecular space of the solvent, the volume would not change, would it? Kushal 17:57, 19 February 2008 (UTC)

It would be rare that the solute would be small enough and the spaces between the solvent molecules large enough and the interactions between the solute and solvent molecules be net-zero-effect. Things usually don't "just fit in and that's the whole story", but there could certainly be a net zero change in volume (balance of all interactions). Consider that if there's a (relatively) large space between solvent molecules, that means there's a strong (repulsive) force between them, so there's probably going to be a strong interaction (of uncertain direction) between those molecules and a solute molecule wedged between them. Cage-like molecules (cryptands, crown ethers, buckyballs) would be interesting exceptions: solute fits inside a single "solvent" cage, but it's perhaps rigid and so cannot change size/shape when the solute is present vs absent. Though it depends on how one defines "solvent" a bit. DMacks (talk) 19:28, 19 February 2008 (UTC)

I want an stream eletric generator to produce 80000 units of current annually

I want an stream eletric generator to produce 80000 units of current annually which is run by an cocentrated solar type stream producer.please help me. —Preceding unsigned comment added by 58.68.95.56 (talk) 14:16, 18 February 2008 (UTC)

Like - help you how? --hydnjo talk 14:40, 18 February 2008 (UTC)

Units of current annually? You might be able to phrase your question more clearly if you first study our articles on solar energy and Electrical Units.--Shantavira|^{feed me} 14:55, 18 February 2008 (UTC)

And SI electromagnetism units. --hydnjo talk 15:13, 18 February 2008 (UTC)

80,000 Amperes of current would require extraordinarily large conductors coming off the generator windings as well as in the windings. 80,000 kilowatt-hours per year would only require the generator to produce 9132 watts average (naturally it would have to produce much more than this during the hours the sun is shining). Before you issue bid specifications or begin construction, you should familiarize yourself with the units of measurement of electric power. Edison (talk) 19:51, 18 February 2008 (UTC)

See Russ Rowlett's pages on units of measurement: definition 6 for a "unit" is "in Britain, another name for the kilowatt hour, which was formerly called the Board of Trade unit." And by the way (to be picky) the man was Ampère but the unit is ampere without a capital letter. --Anonymous, 21:37 UTC, February 19, 2008.

claustrophobia

I am trying to find out if anxiety about being in a situation where escape might be difficult is also claustrophobia. eg being on an island or a large boat, not involving small enclosed spaces or panic attacks. thanks —Preceding unsigned comment added by 97.96.181.252 (talk) 15:38, 18 February 2008 (UTC)

I would have a look at the phobias article. Also, the DSM-IV is a good reference guide, which mentions anticipation of events. -- MacAddct  1984 ^{(talk &#149; contribs)} 16:28, 18 February 2008 (UTC)

The Merck Manual points out a website called The Phobia List, which lists hundreds of phobias. I tried searching for "escape" and several related terms, but no hits. Based on a Google search I did earlier, it does seem that claustrophobia includes the cases you mentioned (that is, any event in which one could not escape). Sorry, I'm not an expert. (EhJJ)^TALK 17:51, 18 February 2008 (UTC)

Also take a look at agoraphobia, maybe. --Ouro (blah blah) 19:04, 18 February 2008 (UTC)

inclined planes

If you put a sledge on a steep enough ramp, it'll slide down.. but where is the horizontal component coming from? Is it electromagnetic, from friction? If I had never seen something roll I don't think I'd ever have guessed a horizontal component would appear :D\=< (talk) 16:56, 18 February 2008 (UTC)

There are two forces on the sledge. There is gravity, and there is the force of the ramp pushing back on the sledge. Ignoring friction (for a moment, I'm just trying to keep it simple), the force of the ramp pushing back on the sledge is perpendicular to the surface. Which means, since the ramp is tilted, it has a horizontal component. JohnAspinall (talk) 17:05, 18 February 2008 (UTC)

There's a nice diagram at the inclined plane article. Sancho 17:13, 18 February 2008 (UTC)

Yes, the force is electromagnetic, at the molecular level. The molecules of the surface exhibit a net positive force against the molecules of the sledge -- static friction. Once the angle is sufficiently steep, gravity overcomes static friction and dynamic friction comes into play. -Arch dude (talk) 04:25, 20 February 2008 (UTC)

Blindness versus deafness

Have any scientific studies been done on the following questions and, if so, what did they conclude?

• Which is "worse" or "harder" ... which is "better" or "easier" ... to be blind or to be deaf?

• Which is "easier" ... which is "harder" ... to be born blind ... or to have sight and then subsequently lose it?

• Which is "easier" ... which is "harder" ... to be born deaf ... or to have hearing and then subsequently lose it?

For lack of better words, I use the terms easier / harder / better / worse to generically mean ... the ease/difficulty a person has adjusting, getting by, everyday living, accomodating, adapting, etc., in a world today where most people are not deaf or blind ... physically, mentally, socially, psychologically, etc. Thanks. (Joseph A. Spadaro (talk) 17:33, 18 February 2008 (UTC))

I doubt the first question is even a matter of studies- its' obviously far harder to be blind than the be deaf :D\=< (talk) 18:19, 18 February 2008 (UTC)

Well, I don't know. There is a story (which I haven't tracked down but is referred to here) that Helen Keller would have preferred to have her hearing back instead of her sight if she could have only one: "... because when you lose your sight, you lose things. When you lose your hearing, you lose people." Also, "The problems of deafness are deeper and more complex, if not more important, than those of blindness. ... Deafness is a much worse misfortune. For it means the loss of the most vital stimulus – the sound of the voice that brings language, sets thoughts astir and keeps us in the intellectual company of man." Of course, this was before the internet and texting. --Milkbreath (talk) 19:11, 18 February 2008 (UTC)

Also the phrase "tis better to have loved and lost then to have never loved at all" may provide answer to the second query. Although similarly so could the lines "if i hadn't seen such riches I could live with being poor" from James Sit Down...I guess it depends on an individual's perspective. I recall reading a story about a man who had been blind from birth, was getting rather old and was gardening with his wife, helping to turn over the soil when his eyes focussed and he saw for the first time - bold yellow flowers. The most beautiful thing, the flower he had loved that his wife had described on many occasions was the first clear vision of his life. A nice story I always thought, but i'm not sure if vision can just 'return' like that? ny156uk (talk) 18:50, 18 February 2008 (UTC)

My impression from the recent Gallaudet University presidential succession controversy is that if you don't learn sign language as a mother tongue, you may have trouble integrating fully with other deaf people, just as an adult who goes to a foreign land might never overcome the language barrier. --Sean 19:16, 18 February 2008 (UTC)

Considering that 80-90% of the average person's sensory information comes from sight, it's probably more difficult to be blind than deaf. —Lowellian (reply) 20:59, 18 February 2008 (UTC)

There are ranges of degree for both deafness and blindness. Total deafness is, as I understand, quite rare. Also, if we are talking about being born or becoming deaf or blind at an early age, then for most of history and to the present in parts of the world, deafness is far worse. See Prelingual deafness and History of the deaf -- until surprisingly recently in history being prelingual deaf (total or profoundly deaf), meant never learning language and never acquiring symbolic thought. This is far far worse a fate than being blind in any form. But as I said, profound prelingual deafness is rare compared to most kinds of hearing impairment. Still, since the question didn't specify I thought I would point out this example in which being deaf is worse than being blind, no contest. A book that explores this particular topic in some detail is "Seeing Voices" by Oliver Sacks. Pfly (talk) 04:38, 19 February 2008 (UTC)

If you never even develop symbolic thought that's not such a bad fate.. it might be pretty confusing but you don't know what's going on or that you can't think properly. Same as those quotes above, you wouldn't know or care what you're missing. Also it reminds me of the Futurama episode where the professor gives a martian monkey superintelligence and it's smart enough to see that knowing things sucks and it was happier in the jungle, so it takes off its brainwave hat and returns to the wild as a stupid monkey :D\=< (talk) 05:04, 19 February 2008 (UTC)

For humans there is no wild to return to. Not having language does not mean you not want to be among other humans, to have social feelings and emotions, etc. If your needs were taken care of by kind loving people, then perhaps it would not be so bad. The norm, however, for most of history, was isolation, abuse, scorn, and such like. Pfly (talk) 00:17, 20 February 2008 (UTC)

Non-foaming shampoo on first wash, explosion of foam second wash.

Can someone explain what's going on here? When I wash my hair in morning, the first shampoo does not foam up at all. But after rinsing and applying a second dose of shampoo, my hair explodes with lather. --70.167.58.2 (talk) 17:35, 18 February 2008 (UTC)

Lather, rinse, repeat... ;-) hydnjo talk 17:55, 18 February 2008 (UTC)

I'm not 100% sure, but I guess it's caused by saturation. The first time you apply shampoo it will mostly solve in the water and attach too the fat in your hair, but the second time most of the fat is already washed off and the water already saturized, preventing the extra shampoo from solving and thus creating foam. - Dammit (talk) 18:00, 18 February 2008 (UTC)

For this reason, i usually first take a smaller amount of shampoo and do a quick scrub and rinse through all my hair to get the bulk of the oil out, then I take a little more and have a longer and more satisfying leathering scrub. Vespine (talk) 00:36, 19 February 2008 (UTC)

Hair oils. The oils prevent it from lathering up the first time, but after they are washed away, then a nice foam can arise. bibliomaniac15 00:51, 19 February 2008 (UTC)

Note also that lather is affected by the hardness of the water. If there is a lot of Ca2+ in your water supply it may not be as easy to form a lather, obviously unless you go somewhere else with softer water you won't notice this though.

Shniken1 (talk) 02:25, 19 February 2008 (UTC)

Fundamentally, oil neutralizes soap or detergent. In the first case, most of the soap/detergent is neutralized, but it removes all of the oil from your hair. On the next application, no oil remains, so all of the soap or detergent is un-neutralized and is available to form bubbles. -Arch dude (talk) 04:15, 20 February 2008 (UTC)

Newtonian Physics

I'd like to start a space program with an objective of sending a manned expedition to Mars. The major caveat of the expedition is that I wouldn't want any of my planners or engineers to use General Relativity. I'd like the entire mission to run on the assumption that Newtonian physics is the physics of the universe. Will my crew be safe?Sappysap (talk) 18:44, 18 February 2008 (UTC)

Since I assume you're actually a world leader starting such a program and not just a student doing homework or something, I'll give you a very practical answer. Putting people on Mars is an enormous undertaking that will require the best engineers in the world. These are pragmatic and careful people who will simply refuse to be involved in such folly as to risk lives, billions of dollars, and their own reputations on something like running a space program on long-discredited science. Sorry, George. --Sean 19:27, 18 February 2008 (UTC)

Isn't space travel mostly Newtonion Physics these days? What does relativity have anything to do with launching a rocket, slingshoting it near another body of mass, and then landing on Mars? 206.252.74.48 (talk) 20:24, 18 February 2008 (UTC)

Well, or more to the point: would any of the speeds, forces, etc. that they would be experiencing come to the point where Newtonian physics wasn't a good enough approximation? GR generally only becomes a significant factor when you are talking about very high gravities, very high densities, very fast speeds. I'm not sure if anything involved in a Mars landing using modern technology would require relativistic effects to be factored in; the Newtonian might be good enough. --98.217.18.109 (talk) 20:51, 18 February 2008 (UTC)

Or not! I'd factor in anything that I knew about even if it only affected the margins. --hydnjo talk 21:13, 18 February 2008 (UTC)

Hydnjo's comment is well stated. Newtonian physics provide a very good approximation of actual orbital mechanics for present space travel. However, when you're talking about billion-dollar programs, it's sheer hubris to ignore a better approximation. Risk management is a very important part of space exploration, and excessive approximation is bad risk management. — Lomn 21:43, 18 February 2008 (UTC)

You should probably avoid anything that takes precise timing measurements on radio signals like a GPS does, and also design your computer systems so that they can gracefully handle any minor discrepancies in time-keeping. (Especially compared to ground-based clocks.) 72.10.110.107 (talk) 22:05, 18 February 2008 (UTC)

I disagree. Timing is everything! --hydnjo talk 23:37, 18 February 2008 (UTC)

Incorrect textbook?

My textbook on geography states:

“ If Earth did not rotate on its axis - creating day and night - only the half facing the Sun would receive solar energy. ... The half of the planet facing away from the Sun would always be dark and cold. ”

I agreed with this statement until the word always; if the Earth did not rotate, at least at some point, the other side would be exposed to the Sun's energy within the year. Is this correct? --~~MusicalConnoisseur~~ Got Classical? 19:30, 18 February 2008 (UTC)

I agree with your assessment of their wording. They may have been trying to describe tidal locking. --Sean 19:50, 18 February 2008 (UTC)

Yes, but nowhere in that paragraph does it mention tidal locking (though that idea did enter my mind). Its topic is a totally hypothetical situation - if the Earth did not rotate, period, unlike the moon. --~~MusicalConnoisseur~~ Got Classical? 20:13, 18 February 2008 (UTC)

Well, the side of the Earth that is not facing the sun is dark and cold(er). Nobody said that side ever stayed over the same geographic location. —Preceding unsigned comment added by 206.252.74.48 (talk) 20:55, 18 February 2008 (UTC)

Yeah, I agree. As it reads, there's nothing wrong with the statement in the textbook, since it doesn't specify that the side facing away from the sun is always the same part of the Earth. —Lowellian (reply) 21:01, 18 February 2008 (UTC)

It's a textbook. They get things wrong. Don't hold them to the same standards as Wikipedia. Considering some of the anti-Wikipedia articles linked to in the In the News section of the Wikipedia Signpost (not necessarily today), no one else does. — Daniel 21:14, 18 February 2008 (UTC)

It's a classic frame-of-reference question, isn't it? When we say that an orbiting body "doesn't rotate", do we mean that it always keeps the same face towards the body it's orbiting, or that it always keeps the same face towards 0° longitude in the "fixed" frame of the body it's orbiting?

Supposedly there was an ancient Greek philosopher whose lifelong, quixotic quest was to find students who had not been "brainwashed" otherwise by his peers, and teach them that the moon does not rotate as it revolves around the earth... —Steve Summit (talk) 23:09, 18 February 2008 (UTC)

A rotating reference frame is non-inertial. From any inertial frame, a body with a tidal lock is rotating. — Daniel 00:30, 20 February 2008 (UTC)

Is it physically possible...

To die from the loss of the will to live?

Assuming that the person doesn't commit suicide, eats properly, sleeps properly, does not OD on medicine, and is perfectly healthy in every way...

could it happen?

Thanks!

❦ECH3LON❦ 23:41, 18 February 2008 (UTC)

I doubt that anyone would respond by saying "that's impossible". --hydnjo talk 23:49, 18 February 2008 (UTC)

I think most normal people would not have the ability to will themselves to death, or in this cases unwill themselves from life. There are many people, for example in jail that wish they could will themselves to death, but they still usually have to resort to more physical measures. Don't hear too many cases of death by lack of will to live. On the otherhand, it seems quite common with old couples that seem to keep them selves going, but once one dies the other soon follows, seemingly having "lost the will to live".. Vespine (talk) 00:32, 19 February 2008 (UTC)

...But, similar to the idea of hypocondriacs and the Nocebo effect, if it is possible to have a disease that is self-procured, then surely, isn't it possible to have that same "illness" kill someone? I'm not sure if this complicates the question though. ❦ECH3LON❦ 02:30, 19 February 2008 (UTC)

Of course, everyone has many diseases at any given time, which are wiped out by our immune system before they become noticeable. So, all that's necessary to die from disease is to suppress your immune system to the point where the diseases win the battle. I'm not sure if this is possible, but it might serve an evolutionary purpose, if individuals which no longer contributed to the survival of the group were to have killed themselves in this way, thus enhancing the chance that others in the group carrying their genes would survive. StuRat (talk) 09:38, 19 February 2008 (UTC)

Kurdaitcha might be of some interest. In these cases, the person doesn't just decide of their own volition to give up the will to live, it's externally imposed; but the effect is the same. We need a better article (or any article) on Pointing the bone, so I can't say how widespread this practice was or, indeed, if it's still practised at all. -- JackofOz (talk) 23:31, 19 February 2008 (UTC)

So...It's like the horror story 'The Candidate by Henry Slesar in which the main character is told of a way to kill people by using wishes, or willpower, and then later die of "Natural Causes"?

That's interesting...❦ECH3LON❦ 00:46, 20 February 2008 (UTC)

February 19

About time dilation and planet habitation

I've been wondering about the effects of time dilation on planets orbiting at different velocities around a star. My question is this: if Planet A is orbiting around its star at say twice the velocity of Planet B, does time pass slower on Planet A in relation to B? Also, if you're sitting stationary in a solar system, does time pass slower on an orbiting planet in relation to you? There's probably some weird gravitational dilation that I'm not taking into account here, but I'm really aching to find out the answer to this, so any help will be greatly appreciated. --Closedmouth (talk) 04:10, 19 February 2008 (UTC)

Yes to both, but not significantly. See the Lorentz factor for the underlying math. — Lomn 05:08, 19 February 2008 (UTC)

The question doesn't really provide sufficient information to say for sure that time passes more slowly on the surface of planet A. Besides the orbital speeds of the planets, you also need to take into account the rotational speeds of the planets as of where the observers are, as well as differences in gravitational time dilation between the two planets. MrRedact (talk) 07:32, 19 February 2008 (UTC)

Orbiting objects are always accelerating. Accelerating things are not really in the realm of special relativity. General relativity has Gravitational time dilation, which indeed says that time in lower gravitational potential (closer to the star) runs slower. --131.215.220.112 (talk) 12:09, 19 February 2008 (UTC)

The time dilation effect would most likely be insignificant. All objects that are traveling at different speeds experience the phenomenon, but it goes unnoticed. A good example is a traveler on a jet airliner. They experience a minute and insignificant time dilation with respect to observes on the ground. Wisdom89 _{(T / ^C)} 18:37, 19 February 2008 (UTC)

The above statement that "accelerating things are not really in the realm of special relativity" is overly general. This is a common misconception about special relativity vs. general relativity.

Special relativity works just fine for dealing with rapidly moving, accelerating objects in the absence of gravity, such as a charged particle in the presence of an electromagnetic field, or a spaceship that's not near an astronomical body, that's accelerating due to thrust from its engines. For example, see Hyperbolic motion (relativity), which deals with an accelerating object, but only uses special relativity.

It's only when dealing with a curved space-time, i.e., when dealing with gravity, that you need to use general relativity. This particular problem does indeed require general relativity, but that's because gravity is involved, not just because acceleration is involved. MrRedact (talk) 00:22, 20 February 2008 (UTC)

Aircraft carrier design

Current US aircraft carrier design features two runways, one for launches and one for landings. Would it be possible to put the launch deck below the landing deck to dramatically reduce the length of a carrier ? One potential problem with this would be ventilation, as the jet engines on the planes burn large quantities of oxygen and put out large quantities of exhaust. Perhaps this could be dealt with by having open sides and ends on the launch deck (with steel columns supporting the landing deck, of course), massive exhaust fans, maximizing the use of catapults, and only going to full jet engine thrust at the final moment of launch (I visualize the launch sequence being fully automated, with no pilot interaction until the plane is airborne). Besides the smaller size, other advantages of such a setup might be the ability to launch in harsher weather conditions and less reduction of launch capability due to bombs dropped on the deck from above. Does this approach seem feasible ? StuRat (talk) 09:30, 19 February 2008 (UTC)

My first thoughts are:

• Airplanes and concrete runways tend to be heavy
• Runways tend not to work so well with steel supports sticking out of them

:D\=< (talk) 11:42, 19 February 2008 (UTC)

The additional launch decks ("second flying-off decks") are actually mentioned in the aircraft carrier article, in the aircraft carrier#Hurricane bow section. The article makes it sound like a bad idea, but provides no explanation. I would think that the main problem with such a configuration would be that the planes are taking off too close to the water. An increased threat of flooding would also be a concern. Besides, the carrier size is not crucially dependent on the takeoff strip size. It may well be (I am not sure) that the area and volume requirements on hangars and depots are more important for carrier design; in that case, placing launch deck below the landing deck is counterproductive. Cheers, --Dr Dima (talk) 11:41, 19 February 2008 (UTC)

Takeoff height and hangar volume are easily solved -- build the second deck higher. I expect, though, that Froth has hit on the problem -- how do you support the upper deck without interfering with flight ops? Topside, aircraft wings can overhang as needed, which an interior flight deck wouldn't permit. On that alone, you're losing a great deal of usable area.

Additionally, the angled-deck design isn't simply one of "two runways". It's perhaps more important as "runway plus storage". The angle allows for safe execution of landings, with the allowance for an aborted landing attempt where the plane returns to full power, with other aircraft stowed forward on the usual launch area. There they can be refuelled, rearmed, and otherwise quickly maintained without introducing the additional bottleneck of the aircraft elevator. — Lomn 14:48, 19 February 2008 (UTC)

American vs British style aircraft carrier

Are, I wonder, flight decks the way of the future in any form? The current crop of aircraft carriers under construction now are probably the last that will feature full complement of human-operated aircraft. The next generation will surely have drone fighters (and probably fighter-bombers and attack/bomber aircraft). It's not clear how this will affect shipboard operations (and it'll probably be another generation before they fully figure that out). It's quite possible that launch systems for drone fighters might move to a rocket-cartridge system (like that used for naval TLAMs now, leaving the flight deck only for recovery and (for those navies that operate them) for other aircraft like tankers and ELINT aircraft. For a carrier that only hosts small agile hardy fighters (which can take the high forces associated with rocket-launches and "giant butterfly net" landings) it's quite possible the flightdeck will shrink or maybe even disappear altogether. -- Finlay McWalter | Talk 15:13, 19 February 2008 (UTC)

It all depends on what type of plane you want on the carrier. The British carriers are already much smaller (see figure to right for a comparison) since they use the Sea Harrier. David D. (Talk) 15:27, 19 February 2008 (UTC)

This is kind of a misleading statement. You seem to be insinuating that the British carrier is better. It isn't. It's a lot worse in fact. Bigger aircraft carriers, hold more aircraft, and thus can project more power. 64.236.121.129 (talk) 19:33, 19 February 2008 (UTC)

The converted cruisers: Glorious, Courageous, and Furious all had small, auxiliary flight decks below the main deck over the forecastle which could launch Fairey Flycatcher fighters. They were too small to operate the aircraft of the '30s and '40's and were converted to gun decks during later refits.—eric 16:38, 19 February 2008 (UTC)

Thanks for all the info so far. As for the issue of the steel columns interfering with flight ops, in a fully automated system the pillars could be only slightly farther apart than the widest wingspan, since the pilot doesn't need to navigate between them. If this didn't provide sufficient support for the upper flight deck (recovery deck), then arches could be used between the columns (this might require increasing the height a bit, though). As for reducing usable area, aircraft wings could still extend out over the edge of the carrier, between the columns. It would also be helpful if a system were used where the planes could be moved sideways to quickly get them onto the runway from a storage slot on the side. StuRat (talk) 18:34, 19 February 2008 (UTC)

The "usable area" point I wanted to make was one of launching. Note, for instance, that a Nimitz carrier's two forward catapults are set far enough to the sides that the wings overhang. Putting the catapults on a lower deck would likely force launch ops to a single catapult (I concur that otherwise you can trim the clearance margins). — Lomn 19:33, 19 February 2008 (UTC)

On an other note, see past dreams of grandeur with Project Habakkuk. 200.127.59.151 (talk) 22:38, 19 February 2008 (UTC)

...which inspired the 'mili-habbakuk' as a unit for measuring impracticability.—eric 23:04, 19 February 2008 (UTC)

The Hall Voltage in Ionic Fluids

I've derived a formula to find the Hall voltage of a flowing ionic fluid:
$V_{H}={\frac {-IB/d}{ne}}.$

Current = charge passing through area cross section per second $I=vAne$
Where the ions in solution have charge -1, are traveling at velocity v through area A, and there are n ions per unit volume.
Substituting, $V_{H}={\frac {-vAneB}{ned}}$
$V_{H}=-vwB$
where w is the width of container.
Is this correct - the voltage depends only on the velocity, width of container and field strength? Why doesn't concentration of ionic solution make any difference?
In practice, does it make any difference with different ionic solutions / concentrations (due to grouping of ions/mobility), if so how will concentration affect voltage?
Also, I need to setup a strong magnetic field - does it matter if the field is not uniform and how can I arrange electromagnets to give a uniform field over about 0.2m²?
Does the choice of electrodes matter? Thanks --90.241.222.228 (talk) 10:12, 19 February 2008 (UTC)

I'm assuming this is a followup to a previous question about the Hall effect. Your question, "Why doesn't concentration of ionic solution make any difference?" is a good one. Remember this voltage was derived on the basis of an equilibrium between Lorentz force (from the magnetic field) and electric force (from the charge buildup). The concentration of ions will affect how fast you approach the equilibrium, but once the equilibrium is there, the net sideways force on any new moving charge is zero, regardless of how many other moving charges are around it.

I am not any sort of expert on Hall sensors, but I would guess that small variations in the magnetic field would be balanced by small variations in the charge buildup, and the resulting equilibrium would be "near" the equilibrium of a perfectly uniform field, making your answer "near" the real values. None the less, a nice uniform field can only help you. The classical way to get a fairly uniform magnetic field is to use a Helmholtz pair. JohnAspinall (talk) 16:05, 19 February 2008 (UTC)

Thanks. Is there any way of predicting how changing concentration will affect how fast equilibrium is reached? Can you suggest any other area to investigate other than changing concentration / ions in solution / speed / field strength? —Preceding unsigned comment added by 90.241.222.228 (talk) 21:08, 19 February 2008 (UTC)

Supermagnet

A strange question just popped into my head. What if someone, with incredible technology or magic (basically the same thing) developed a monopole electromagnet with incredible strength? I had a similar discussion with a friend a while ago and she said that a strong enough magnet could tear electrons away from all the atoms in its range. Would this make such a silly device applicable as a superweapon? What horrifying effects would such a device have on matter, if any? 206.252.74.48 (talk) 17:17, 19 February 2008 (UTC)

I'm sure I've read a science fiction story about a scientist that invented a monopole magnet and submitted a paper about it, and then suddenly found himself being shadowed by agents from at least one government. I'm sorry that I don't remember the title or author. APL (talk) 17:35, 19 February 2008 (UTC)

At a given point in space, the magnetic field produced by a magnetic monopole would no different from the field produced by a dipole or any other distribution of "magnetic charge". The difference is in the global geometry of the field, not the quality of the field itself. So the effects of an incredibly strong monopole magnet on materials would be the same as those of an incredibly strong (but otherwise ordinary) dipole magnet. —Keenan Pepper 18:09, 19 February 2008 (UTC)

That is a good point, so just ignore the monopole part with this question. I want to know what the effects would be. 206.252.74.48 (talk) 18:28, 19 February 2008 (UTC)

Except that a monopole field would be felt over much longer distances. — Laura Scudder ☎ 20:13, 19 February 2008 (UTC)

Right, that's the only relevant difference in this context: a monopole field falls off as the inverse square of the distance rather than the inverse cube. —Keenan Pepper 04:25, 20 February 2008 (UTC)

When my foot falls asleep

I know that when my feet "fall asleep", it's because there's not enough circulation to it. One question, though: when that happens, what causes the "tingly" feeling, as if I'm being poked by little pins or having little electrical shocks? Nyttend (talk) 21:29, 19 February 2008 (UTC)

It's not just that you're cutting off the circulation to the cells and tissue of the limb, but also you're physically preventing nerve impulses from entering the CNS and vice versa. This causes the neurons/nerves to fire erratically after the pressure is released. Wisdom89 _{(T / ^C)} 21:35, 19 February 2008 (UTC)

MATERIALS/CHARATERISTICS (Homework?)

LOOK,GUYS sorry I used the f word. When,I last posted this question but that`s a testament to How I much I need it answered. Just,tell Me The Measurements and Charateristics of a balloon going across a room. —Preceding unsigned comment added by Yeats30 (talk • contribs) 23:56, 19 February 2008 (UTC)

Homework much?Zrs 12 (talk) 00:21, 20 February 2008 (UTC)

Perhaps you could rephrase your question? Something like:

I deeply regret posting previous homework questions under false pretence and undertaking plagiarism in using these responses to dishonestly complete my homework. I promise not to do it again. Furthermore, I will not get upset with you, the Wikipedia Reference Desk volunteers, if you are not willing to aid me in continuing the aforementioned. Nevertheless, I request your assistance in understanding the concept of how to measure and characterize a balloon crossing a room. Sincerely, The "Physics Magazine" Guy

Honestly, we'd like to help you. We just don't want to get yelled at for not being willing to help you cheat. (EhJJ)^TALK 01:07, 20 February 2008 (UTC)

I like the way you phrased that EhJJ. Furthermore, I agree. Zrs 12 (talk) 01:18, 20 February 2008 (UTC)

I don't care if this might be a homework problem, I'm willing to help you anyway. The most important measurements and characteristics of a balloon going across a room are as follows:

1) Since the balloon is (usually) a prolate spheroid, it's important to consider the balloon's various radii of curvature, which will generally be on the order of 4 diopters.

2) The balloon's modulus of elasticity, assuming a rubber balloon, would be in the range of 0.01 to 0.1 GPa, if there were only a small strain. However, due to the balloon’s relatively large stress, the nonlinearity of the balloon material's stress-strain curve must be taken into consideration. Therefore, you’ll need to use the strain tensor for large deformations, which is $\varepsilon _{ij}={1 \over 2}({g_{ij}-g_{ij}^{(0)}})$

3) Since the balloon is in motion across the room, it will undergo a relativistic length contraction. The amount of this effect is given by the formula $L'={\frac {L}{\gamma }}=L\,{\sqrt {1-v^{2}/c^{2}}}$

4) It's important to take into consideration the balloon's de Broglie wavelength, so that interference effects can be computed as the balloon travels down various hallways and through windows and doorways. The balloon's de Broglie wavelength is given by $\lambda ={\frac {h}{p}}={\frac {h}{\gamma mv}}={\frac {h}{mv}}{\sqrt {1-{\frac {v^{2}}{c^{2}}}}}$

I hope this was helpful. MrRedact (talk) 01:32, 20 February 2008 (UTC)

Oh! I thought of another very important characteristic of a balloon going across a room: the balloon’s relative static permittivity. I don’t know how such an important measurement could have slipped my mind; you’d have a heck of a hard time trying to figure out the balloon's capacitance without it! According to our article, the relative static permittivity of rubber is about 7. MrRedact (talk) 01:59, 20 February 2008 (UTC)

Would time dialation not be an important factor as well? Zrs 12 (talk) 02:18, 20 February 2008 (UTC)

Don't forget isotopic analysis. Any helium 3 that may happen to be in the balloon will contribute more to buoyancy than your regular helium 4 will. --Anon, 02:50 UTC, February 20/08.

Not true...the He-3 nuclei weigh less than He-4, but that's because there are fewer particles in those nuclei. They're lighter but also smaller and you can thus fit more into a given balloon volume. On average the gas still weighs the same per volume. That's a simple result of the ideal gas law: constant density of a gas regardless of what gas it is. DMacks (talk) 03:00, 20 February 2008 (UTC)

Are they really smaller? Yes, the nuclei are slightly smaller, but the nucleus is orders of magnitude smaller than the atom anyway. AlmostReadytoFly (talk) 08:47, 20 February 2008 (UTC)

...Besides which, the ideal gas law assumes pointlike atoms.AlmostReadytoFly (talk) 09:13, 20 February 2008 (UTC)

Also, there may by oxygen, nitrogen, etc. Furthermore, there will constantly be helium passing through the balloon into the atmosphere due to the pressure inside; there may even be some quantum tunneling (although probably not much).Zrs 12 (talk) 02:54, 20 February 2008 (UTC)

You guys are neglecting impulse and delta-v. The balloon is operating as a rocket, but in an atmosphere. IF he balloon were released in a vaccuum, we could neglect many of the effects mentioned above. However, assuming a vaccum will have important consequences for the delta-v. -Arch dude (talk) 03:58, 20 February 2008 (UTC)

Fuel efficiency of a Hot Air Balloon (and other questions)

If one would travel with a Hot Air Balloon from Texas to Florida, how would the fuel efficiency compare to a typical passenger airliner or personal jet? How safe is Ballooning compared to other forms of air travel? Malamockq (talk) 23:59, 19 February 2008 (UTC)

Hot air balloons are only safe when used under some rather specific conditions, like slow, steady winds and relatively flat ground (or water) which is clear of trees, buildings, and other obstructions. When used by a trained balloonist in airspace clear of aircraft, under those conditions, balloons can be fairly safe for short distances. Note, however, that balloons only go where the prevailing winds blow them, which makes them quite useless for general transportation. As for fuel economy, it's probably better than aircraft when measured on a per hour per passenger basis, but worse when measured per mile per passenger. StuRat (talk) 07:49, 20 February 2008 (UTC)

February 20

what would you call a small mountain range

Like Potrero Hills specifically, this is regarding a dispute on the wording of navegation disambiguation tag at the top of the similarly named neighborhood Potrero Hill, San Francisco, California. It's sloppy to say for the potrero hills see potrero hills, but one user believes that it should not state, the minor mountain range see potero hills, because they don't count as a minor mountain range, so is there some other term which could be found mutually agreeable. hill range? minor range?Boomgaylove (talk) 04:39, 20 February 2008 (UTC)

Here's a topo map of the feature.—eric 05:25, 20 February 2008 (UTC)

scratch that, those Potrero Hills are about 30 miles away, southeast of Fairfield.—eric 06:14, 20 February 2008 (UTC)

You mean this? Certainly the word moutain does not spring to mind if that is where you are talking about. I would have thought range would be used to describe huge area. For the disambigution why not just say See Potrero Hills for East Bay Regional Park? David D. (Talk) 05:42, 20 February 2008 (UTC)

I see the disambiguation at Potrero Hill, San Francisco, California currently reads For the Potrero Hills in Richmond, California, see Potrero Hills. What's wrong with that? David D. (Talk) 05:48, 20 February 2008 (UTC)

Does the human brain have limits?

Does the human brain have "limits"? Is there only "so far" that it can go? For example, is it humanly possible, say, for a person to memorize an entire phone book? Or, are there some things just impossible / out of range for the human brain? Thanks. (Joseph A. Spadaro (talk) 07:11, 20 February 2008 (UTC))

Try photographic memory. This article led me to Ben Pridmore who holds the official world record for memorizing the order of a randomly shuffled 52-card deck in 26.28 seconds. Not exactly the phone book but pretty impressive. David D. (Talk) 07:23, 20 February 2008 (UTC)