Wikipedia:Reference desk/Archives/Science/2009 March 18

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March 18

Launching a satellite via balloon

I recently read a story of 4 teenage spaniards who were able to take a bunch of meteorological equipment and a camera 20 miles high. The pictures that were returned are stunning. A camera and meteorological equipment sounds very much like a satellite to me. If you add a couple of fireworks to the mix for a second stage, or whatever you guys can dream up...how difficult would it be for a bunch of teenagers to make a satellite orbit the Earth a few times? I mean really, is it that hard? Sappysap (talk) 01:36, 18 March 2009 (UTC)

Sadly, yes, it really is that hard. Balloons are relatively easy. You don't need any fuel - just a big enough envelope and a lot of suitable lightweight gas and you'll get up to "the edge of space" (whatever THAT means)...however, as soon as you run out of air - there is no more bouyancy and you can't go any higher no matter how clever you are. To get into low earth orbit means getting your rocket up to around 8 kilometers PER SECOND. 28,000 kilometers per hour. 17,000 miles per hour....that's pretty serious stuff. SteveBaker (talk) 01:49, 18 March 2009 (UTC)

That's not to say it's impossible to do, of course. Da Vinci Project was an X-Prize attempt. (They were not able to complete their space-craft.) However, I'm sure that their balloon would have been considerably larger than a weather balloon.

Here's another really cool balloon project that I read about recently. It's pretty awesome if you ask me. High Altitude Glider Project APL (talk) 12:50, 18 March 2009 (UTC)

For average teenagers, putting something into orbit is not feasible. If however, you took an exceptional group of teenagers, and adequately funded their project, it is possible, but how many teenagers do you know that would be able to maintain focus for long enough to build a suitable launch vehicle from scratch? 65.167.146.130 (talk) 13:26, 18 March 2009 (UTC)

And would they still be teenagers when they finished? APL (talk) 13:32, 18 March 2009 (UTC)

The term for this technique seems to be "Balloon Assisted Launch". And it would not be easy, and probably not within the grasp of hobbiests, but the airforce and other space agencies seem to be considering it seriously. APL (talk) 13:38, 18 March 2009 (UTC)

Yes, the current system of launching rockets from a stationary position, close to sea level, seems designed to waste as much fuel as possible. I suspect that as the era of cheap fuel ends, this practice may end, too. Launching from a balloon or piggyback on a large jet would reduce fuel and vehicle size requirements considerably. They could also launch from a mountaintop, with a great deal of momentum, if a launch tube was hollowed out of the mountain (or placed on the side of the mountain) and the rocket was accelerated using steam pressure, similar to the catapults on aircraft carriers. StuRat (talk) 16:38, 18 March 2009 (UTC)

The problem that most people don't understand is that getting into orbit isn't just about getting high enough - that is something a balloon with a simple rocket could probably manage. The problem is that to be in ORBIT - you need a horizontal speed of 8km/sec. The balloon doesn't really help you in that regard. In fact, if you got a rocket going at 8km/sec horizontally at sea level - barring air resistance, it would go into orbit. Really all that the balloon buys you is getting above enough atmosphere that your rocket motor's power can be devoted to getting up to that orbital speed. That's not an inconsiderable amount mind you...but you've still got to get that 8km/sec from somewhere - and that's hardly a science fair project! Launching from aircraft at high altitude HAS been done - Scaled Composites SpaceShipOne, for example. It didn't get into orbit either - same reason - it did get up high enough - but without that 8km/sec - it just came right back down again - as expected...but launching from a plane definitely helped. But recall that a pretty large plane (a 747 for example) can only just lift an empty space shuttle - and that's without a full fuel load, SRB's, payload and so forth. We'd need entirely bigger aircraft to launch the kinds of substantial loads we need for things like assembling space stations and trips to the moon. Rockoons (rockets launched from balloons) have also been tried. Problems in that case are to do with injecting the rocket into the DESIRED orbit rather than from just any old orbit from a spinning, drifting who-knows-what balloon. The idea of launching from a tube (whether in a mountain or whatever) has also been attempted...just before the first war against Iraq, Saddaam had started to build 'Project Babylon' - a gigantic gun that would have been able to propel a satellite into orbit (or shoot a nuclear weapon to any point on the globe). The US 'Project HARP' was a similar idea. So I guess that all of these things have been tried - one way or another. SteveBaker (talk) 01:39, 19 March 2009 (UTC)

I wonder which portion of a rocket's fuel is used to fight air resistance. Note that there's no fixed amount of air resistance to overcome to reach orbit, as a slower ascent would require less fuel to overcome air resistance. Hence the advantage of a balloon, which could rise at a much slower rate and cause less air resistance. StuRat (talk) 15:21, 19 March 2009 (UTC)

Well, we do launch rockets vertically - and not horizontally - and in fact we gradually transition from vertical flight to horizontal (well, perhaps "radial" to "tangential" is better here) - and I suspect that the reason for that is that taking off vertically gets you through the densest air resistance in the shortest distance. Ascending through the atmosphere relatively slowly - and then kicking it up a notch once you're out of the worst of the atmosphere is EXACTLY what modern multi-stage rockets do. The most intense g-forces in a shuttle flight are long after take-off. But in the absence of atmosphere - you'd climb vertically only enough to clear any nearby mountain ranges - then head off more or less tangentially. As your speed builds, you'd get higher. SteveBaker (talk) 19:52, 19 March 2009 (UTC)

Your "relatively slowly" is indeed relative, as a rocket takes minutes to clear the densest atmosphere, while a balloon could take hours, and encounter much less air resistance as a result. StuRat (talk) 04:42, 22 March 2009 (UTC)

Light can't be seen unless it's reflecting off of matter

Is this a fair statement to make? That light is invisible unless it's reflecting off of matter? ScienceApe (talk) 02:09, 18 March 2009 (UTC)

Only photons that strike a detector are detectable by it, so unless they enter the eye, the eye can't see them. Now I don't know about reflecting be required (you can see a lit light-bulb directly:), but somehow the light has to become directed towards the eye. DMacks (talk) 02:18, 18 March 2009 (UTC)

Sort of depends on what you mean by the verb see, or more precisely, what you intend by using a term as the direct object of that verb. It could be argued, if one wanted to be argumentative for the sake of it, that you can never see light at all, not in the sense that you can see, say, a desk. What you see would be the source of the light, or the thing illuminated by the light.

Unless of course the light beam you're looking at is so intense that you can shine another light source on it and get a significant amount of scattering of light by light, which is a redlink that someone should really direct to the correct article. But in that case I'm not sure how long you'd live. --Trovatore (talk) 02:32, 18 March 2009 (UTC)

Until that happens, there's visibility of light through scattering at Light and the Tyndall effect. Julia Rossi (talk) 02:37, 18 March 2009 (UTC)

Well, no, that's different — you're still not "seeing" the light in the sense of detecting how it scatters other light. You're seeing the air or the dust or something. --Trovatore (talk) 02:39, 18 March 2009 (UTC)

Does Rayleigh scattering work that way? erm, still looks like matter particles in there though. :/ C'mon Trovatore, get that article blue-ing! Julia Rossi (talk) 02:40, 18 March 2009 (UTC)

Yeah - in both Rayleigh and Mie scattering (related but different things), the light is scattered off of something. SteveBaker (talk) 02:44, 18 March 2009 (UTC)

OK, so what about SOLBL? I would have assumed that the article must exist and I was just using the wrong search term. But searches like photon-photon scattering also come up blank. On the other hand a Google search for "scattering of light by light" gets lots of hits under that exact name and doesn't immediately suggest any synonyms. --Trovatore (talk) 02:54, 18 March 2009 (UTC)

Well, contrary to popular opinion - there are still a few things we don't have articles about. SteveBaker (talk) 04:49, 18 March 2009 (UTC)

There is no important difference between the light reflected from a surface and the light emitted from a surface...as far as the eye is concerned, it's all just light...so yeah - you can see light without it being reflected off of something...if your eye happens to be in the way. What I suspect our OP is wondering is if (for example) you were out in deep space - in a vacuum - with a big chunky laser beam shining a beam off into space just a foot in front of your face...would you be able to see the beam? And the answer there is no - because none of the light is reaching your eye - it's just shooting off into the distance. So in that sense, you can't see the light unless it's "reflected" (or perhaps "scattered" or "refracted") into your eyes. In all the action TV series when the good guy is breaking into the bank vault and all of the red security lasers are entirely visible...that's pretty much bogus. The light is somewhat scattered off of dust and such in the air - but even so, only the very brightest lasers actually light up the air as they travel through it. SteveBaker (talk) 02:44, 18 March 2009 (UTC)

I was making a linguistic point, not a physics one. As I said, a deliberately picky point, at that, not intended seriously. The point is that you say that you see the desk, not the light reflected from the desk. So "seeing" light, in that sense, is mostly impossible. Modulo SOLBL, which I'd still like to hear more about. --Trovatore (talk) 02:56, 18 March 2009 (UTC)

Yes - I suppose so. The problem here is that the linguistics pre-date the science by a considerable amount of time. As recently as when Newton was alive and trying to get a grip on what light is, there was still a common belief that somehow light came OUT of our eyes in order to see things. So it's not surprising that we talk about "seeing a desk" as a shorthand for "seeing light reflected from a desk". But it does go a little deeper than that. We can "see a desk" by virtue of it blocking light rather than reflecting it. If the sun is behind the object and all you can see is a sillhouette, you STILL talk about "seeing the object" rather than seeing by the lack of light behind it. We're also in a slightly odd position when we talk about seeing an object that's reflected in a mirror - when what we're really "seeing" is the mirror itself (by those standards). But when we talk about "seeing a desk" - we don't say "seeing the sun"...even though what we're really seeing is the sun reflected in the desk. So language is (as always) a mess - and we're better off defining our terms when it comes to proper scientific matters. SteveBaker (talk) 04:49, 18 March 2009 (UTC)

But light does come out of my — er, I mean, Superman's eyes. Yeah, that's the ticket. Because I'm not Superman, of course. Ha ha. Nope, not me. --Trovatore (talk) 07:54, 18 March 2009 (UTC)

It's true in POV-Ray, unless the light_source has a looks_like modifier. —Tamfang (talk) 21:16, 23 March 2009 (UTC)

Despite all the linguistic niceties the OP ask a prety simple question: "Is this a fair statement to make? That light is invisible unless it's reflecting off of matter?" to which there is no other reasonable answer then: No, that's not a fair statement, all light within the visible spectrum is visible as long as it reaches your eyes. That last requirement applys wheather the light has been reflected by a surface or not. Dauto (talk) 05:03, 18 March 2009 (UTC)

Probably you're trying to describe the fact that a "beam" of light can't be seen directly. But you're neglecting the case where light strikes your eye directly from the source. (ie: Look at the sun. (PS: Not for long.))

It'd be reasonably correct to say "Light is invisible unless it's reflecting off of matter or striking your eye directly.". APL (talk) 12:46, 18 March 2009 (UTC)

You could simplify further with "Light is invisible unless it enters your eye". Everything else is window dressing; your retina doesn't care what path the photon took to get there. TenOfAllTrades(talk) 13:37, 18 March 2009 (UTC)

technology

what are the roles of technology in growth of the economy.citing examples& applications —Preceding unsigned comment added by Solit (talk • contribs) 05:56, 18 March 2009 (UTC)

You might start with our articles on Technology and Economic growth. --Allen (talk) 06:56, 18 March 2009 (UTC)

We will not do your homework. Sorry. —Cyclonenim (talk · contribs · email) 11:42, 18 March 2009 (UTC)

How does it affect our lives to know why particles have mass

well i recently read that the Large Hadron Collider will also reveal through its experiments about WHY particles have mass? But what real use is this of to us? I mean there must be some big way in which this can be used but i fail to understand how?!?!?! Like technologically - how is it useful to figure out WHY a particle has mass? Wouldn't it be better to use all that time and money in using the LHC for some better useful experiment?Vineeth h (talk) 06:57, 18 March 2009 (UTC)

Thank you for signing this time but in future, please modify your original question if you make a mistake rather then posting again. I have removed the duplicate question Nil Einne (talk) 07:34, 18 March 2009 (UTC)

I don't know if this is what you're looking for, but here's one possible answer:

"The first question which you will ask and which I must try to answer is this, 'What is the use of climbing Mount Everest?' and my answer must at once be, 'It is no use.' There is not the slightest prospect of any gain whatsoever. Oh, we may learn a little about the behavior of the human body at high altitudes, and possibly medical men may turn our observation to some account for the purposes of aviation. But otherwise nothing will come of it. We shall not bring back a single bit of gold or silver, not a gem, nor any coal or iron. We shall not find a single foot of earth that can be planted with crops to raise food. It's no use.

So, if you cannot understand that there is something in man which responds to the challenge of this mountain and goes out to meet it, that the struggle is the struggle of life itself upward and forever upward, then you won't see why we go. What we get from this adventure is just sheer joy. And joy is, after all, the end of life. We do not live to eat and make money. We eat and make money to be able to enjoy life. That is what life means and what life is for."

— George Leigh Mallory, 1922

For a rather different answer see this article. -- BenRG (talk) 13:00, 18 March 2009 (UTC)

It is the nature of basic research that we don't know beforehand what usefulness any discoveries that come up will have. Faraday was asked about what practical use could there possibily be for his researches on electricity. Turns out our modern society would not work at all without the knowlege of electricity. I would not expect any immediate practical aplications to come out of LHC's discoveries, but that's not why we do it. The purpose of the LHC is knowlege, nothing more. Dauto (talk) 15:13, 18 March 2009 (UTC)

You forgot Faraday's response: "What use is a new-born child?" Confusing Manifestation(Say hi!) 22:23, 18 March 2009 (UTC)

We don't know why. But then we didn't know why we needed to know about quantum theory either...yet the computer you are reading this email on right now wouldn't exist if we hadn't figured that out. Perhaps discovering the properties of the Higgs Boson will allow us to teleport objects - or maybe time travel will become possible - or perhaps we'll discover that an old coke can plus a discarded copy of the New York Post dated 13th January 1956 is all we need to fix up global warming. I very much doubt it'll be any of those thinge - but we don't know BECAUSE we don't know. What we DO know is that in almost every 'pointless' experiment of this kind, we've found something that eventually became useful - perhaps directly - perhaps indirectly. Hence doing this kind of thing - even though the cost is outrageous - is what keeps technology purring along. SteveBaker (talk) 22:32, 18 March 2009 (UTC)

Plus, it will strengthen the resolution between the ongoing conflicts in the unifying theories of the universe. It will give us a direction in the knowledge of how this universe came about. Higgs is a theoretical particle not having been detected so far, only predicted by theories. It will confirm whether or not those theories are right, whether or not we need another physical theory. I can't wait to see the resumption of the LHC experiment. - DSachan (talk) 22:40, 18 March 2009 (UTC)

Evolution

I posted this on the evolution talk page, and apparently Wikipedia isn't a forum so I'm posting it here:

"I know this has been posted a million and three times and is covered in the FAQ but I want to be absolutely sure, could I in good concious go on national television tomorrow and declare "Evolution is a fact"? The article "Evolutions as theory and fact" is too complicated and doesn't have a simple "if you look at in a general way then A, if you look at it this way then B". I get other pages on the web written by biologists and doctors saying that "Evolution is not a fact, but is likely to be true". Wikipedia keeps mentioning something like mathematical meaning and logical meaning and I just want some disambiguation- I know Wikipedia is not a forum, so just delete this is no-one is willing to answer, I just wanted to make sure. If someone could give me a good "phrase" I could say if I would be going on television to explain this (I'm not really going to be on a TV, just for the sake of an argument), i.e. in a concise and simple manner: "Simply put, if you look at it from a scientific viewpoint... but if you look at it from a logical viewpoint..."." --BiT (talk) 08:08, 18 March 2009 (UTC)

The reference desk isn't a forum either and sorry but I don't understand what you are asking. But evolution is a fact and a theory. You can confidentally go on to television tomorrow and declare it if you want. This is explained about as simply as possible in our article "First, the "fact of evolution" refers to the observed changes in populations of organisms over time, which are known to have occurred. Second, the "theory of evolution" refers to the modern evolutionary synthesis, which is the current scientific explanation of how these changes occur." There is also Evolution as theory and fact#Evolution compared with gravity which may or may not help. But if you want to be able to confidentally go on to national television and explain evolution then you really need to understand it. You can't confidentally go on to television and defend something without understanding it IMHO, there is no shortcut. If not you're liable to make similar mistakes in defending evolution to those creationists make when attacking evolution which helps nothing (and creationists are notorious for being very well prepared and picking at any little mistake). Our wikipedia articles are decent enough so start reading and come back if you have any specific questions Nil Einne (talk) 09:00, 18 March 2009 (UTC)

The OP mentioned going on television to ask how true the statement "Evolution is a fact" is, not because he actually plans to go on television. --Bowlhover (talk) 15:00, 18 March 2009 (UTC)

The OP said "I want to be absolutely sure, could I in good concious go on national television tomorrow and declare "Evolution is a fact"?" and "If someone could give me a good "phrase" I could say if I would be going on television to explain this (I'm not really going to be on a TV, just for the sake of an argument)". I'm not sure if I understand this but I think the OP is saying he/she wants sufficient understanding such that they can be confident enough that they could say it on television without fear of looking stupid (not because they actually plan on going on television but as an example of the depth they want although IMHO a better example would be being able to explain it to a conference of evolutionary biologist :-P). Perhaps my understanding is wrong but I don't believe your claim the OP wishes to go on television to ask how true the statement is is correct either. Nil Einne (talk) 19:36, 18 March 2009 (UTC)

Yes, you are absolutely correct. A conference of evolutionary biologists might have been a better way of putting it but I doubt I can teach them anything about biology :p --BiT (talk) 10:53, 19 March 2009 (UTC)

Sir David Attenborough recently went on the BBC and did exactly what you want to do. I suggest you go onto the BBC website and see if you can find the part relating to this: I suspect it's part of their Darwin season. --TammyMoet (talk) 09:53, 18 March 2009 (UTC)

Carl Sagan also said it on Cosmos. A Quest For Knowledge (talk) 17:00, 18 March 2009 (UTC)

That evolution has occurred is a fact, like gravity is a fact. How evolution occurs, like how gravity works, is a theory. --Scray (talk) 11:02, 18 March 2009 (UTC)

You might find Evidence of common descent useful. Zain Ebrahim (talk) 11:07, 18 March 2009 (UTC)

To put it another way, the word "evolution" has two different meanings which people routinely conflate. I don't think it's a good idea to say "evolution is a fact and a theory". It's a syllepsis or antanaclasis or some such thing. Better to say something like "there's a fact of evolution and a theory of evolution and they're different things". Better still would be not to use the phrase "theory of evolution", or for that matter "theory of gravity", since the theories explain a lot more than just evolution or gravity. There's a scene in Dirk Gently's Holistic Detective Agency in which Dirk mocks Newton's contribution to physics by releasing an object, watching it fall to the ground, and saying "someone was bound to notice sooner or later". Well of course that kind of gravity was known to the ancients; what Newton figured out was that a single force could explain both gravitation (i.e. things falling to earth) and the motions of the heavenly spheres. I don't know if that mistake was Dirk Gently's or Douglas Adams's, but either way it wouldn't have happened if we didn't use the term "theory of gravity". Darwin's theory didn't only explain evolution (i.e. the changes in organisms over time as seen in the fossil record), it also explained, for example, the existence of species (which, unlike evolution, was known to the ancients). You could call it "Darwin's theory of species". At least that would force the creationists to be more specific about what they're railing against. -- BenRG (talk) 12:38, 18 March 2009 (UTC)

First of all I don't know the difference between syllepsis and antanaclasis. I understand that evolution can be both a fact and a theory but what does the theory of evolution refer to, and what does the fact of evolution refer to? What parts of evolution aren't proven? --BiT (talk) 11:06, 19 March 2009 (UTC)

Personally, I avoid using the word "fact" in science, it causes no end of problems. Science is made up of theories. Some of those theories have so much evidence supporting them that the chance of them being wrong is minute - some people like to call those theories "facts", but really it's an arbitrary cutoff. There is no qualitative difference between a "theory" and a "fact". --Tango (talk) 14:19, 18 March 2009 (UTC)

I'd say avoid worrying about terminology altogether. Evolution is a model of the natural world, and just because of that, it's a theory. It also has a certain amount of evidence. Whether that amount of evidence is enough to make evolution a fact is up to the individual to decide. --Bowlhover (talk) 15:00, 18 March 2009 (UTC)

Just because evolution is a fact, does not mean that everything connected with it is a fact. There are modern legends such as our ancestors developing in a warm pool of slime, or that they crawled out of the sea. These ideas are not proven sufficiently to be called facts. Graeme Bartlett (talk) 20:57, 18 March 2009 (UTC)

Actually the origin of life has nothing to do with evolution. That would be abiogenesis. ScienceApe (talk) 02:04, 19 March 2009 (UTC)

• could I in good concious go on national television tomorrow and declare "Evolution is a fact"? - on National Television - yes, absolutely. In front of the Nobel Prize committee...maybe not. We have to be careful about the word "fact" in rigorous scientific debate. It is possible that everything we know and see comes out of a large computer called "The Matrix" and evolution is totally false. That's a certainly a possibility. Hence we can't say (with 100% scientific rigor) that ANYTHING AT ALL is a "fact". However, if you were to ask "Is it as likely that Evolution is true as Gravity is true" - then yes, evolution is true - and that's plenty good enough for ALL practical matters.
• The article "Evolutions as theory and fact" is too complicated and doesn't have a simple "if you look at in a general way then A, if you look at it this way then B". - Sorry about that. That IS a subject for the article's talk page.
• I get other pages on the web written by biologists and doctors saying that "Evolution is not a fact, but is likely to be true". - See my response to your first question. Evolution is as true as Gravity - neither are 100% certain. Evolution is at least as true as ANYTHING you know to be true - Gravitation, Quantum theory, Relativity, Thermodynamics, your home phone number. That's "good enough" for all but the most ridiculously hardened sceptics - and philosophers (who, as I have pointed out in the past - are a waste of quarks).
• Wikipedia keeps mentioning something like mathematical meaning and logical meaning and I just want some disambiguation...If someone could give me a good "phrase" I could say if I would be going on television to explain this... - Oh - you want a sound-bite! Why didn't you just say so?!

"Evolution is a scientific fact that is at least as solidly proven to be true as are (for example): Gravitation, Quantum theory, Relativity, Thermodynamics, Electromagnetism, The Big Bang, Atomic theory, The Germ Theory of Disease, Genetics and the scientific theory that "The Earth Is Not Flat" - HOWEVER, neither Evolution - nor ANY of those other things are quite as certain to be true as that 2+2=4 or that there are infinitely many prime numbers. For these mathematical truths are things that may be proven by the power of thought alone - where the other things require us to believe that the results of our experiments are meaningful when applied to the real world. It is just possible that none of our senses are to be trusted. If it should somehow turn out that we are living in a world of make-believe or that we live in a simulation of a real universe that's running (like "The Matrix") in a big computer someplace - then 2+2 still equals 4 - but we can't know that anything we've experienced is true. Since we have no way to prove that we aren't inside "The Matrix" - we can't regard Evolution - or any other scientific theory as "fact" to the same degree as we regard 2+2=4 as a "fact". In practical terms, we accept these other big scientific principles as "true" - and Evolution is right up there with the rest."

The trouble is that the 'nut jobs' who want the universe to be run by supernatural deities need to find any chink in the armor that is scientific proof that they possibly can. Hence, they are more than happy to corner some poor unsuspecting scientist and ask things that are (in essence) like asking: "Is Evolution as certain to be true as that there are an infinite number of prime numbers?" - and an honest, serious scientist has to say "No - it's not". The nut jobs then happily frolic off into TV-land and say "Scientists everywhere will tell you that Evolution isn't necessarily true" - without considering what exactly the scientist actually meant. So, should you happen to get onto national television - you should ON NO ACCOUNT say that evolution might not be true. You have to use a circumlocution such as "Evolution is as true as that I'm standing in front of you right now!" or "How sure are you that if I drop this brick that it'll fall to the floor? Well, that's how sure we are that evolution is true.".

SteveBaker (talk) 23:09, 18 March 2009 (UTC)

Ok I've got to give a standing ovation to SteveBaker, props to you. Bear with me while I respond:

• I wasn't really meaning in the sense of being so philosophical (I forgot which branch of philosophy says that it's possible that the world is a lie) that you don't believe anything at all, but other than that you explained it pretty well. I want to point out that I don't plan on holding lectures for the Nobel Prize committee, I'll just say thanks for the awards and leave. Of course we can't be 100% sure that evolution is correct, who knows, maybe some god made the world just as it is to fuck with evolutionary scientists and maybe all paleontologic evidence is just god fucking with us as some claim, maybe god made gravity seem like 'fact' just to make it stop working one time to see the reaction. Also I want to point out that evolution wouldn't have been any more false in the Matrix than it was in the 'real world' (if we assume that the real world was 'real' and not a part of another Matri system) as it was a replica of the world as it was around 2000 if I remember correctly, so if we assume that evolution is correct here it would have also been correct in the Matrix.
• True.
• I went through a phase where I tried to be as sceptical as I could, never assuming anything and staring every sentence with "it could be assumed in correlation with the environment that I detect that, in the terms of this world that I perceive to be true, that what you seem to say can be wrong" (a slight hyperbole). That didn't last long.
• No way! You aren't going to give me an actual soundbite?? Awesome. Ok, I get your point. Only things that are based on something that is predetermined to be true can be 100% true. We give that if we add two apples then we get four apples, then 2+2=4 is an absolute truth in the same way that "every man is a rapist, I am a man, therefore a rapist" if we assume that what I'm saying is true about every man being a rapist.

Thanks you so much for this, I agree with you an the 'nut jobs' and I decided to look this up after seeing a clip of Bill O'Reilley that just pissed me off. Now I know that I can declare that evolution is pretty much as proven as the common man cares. The problem is as Bertrand Russell pointed out that "...fools and fanatics are always so certain of themselves, but wiser people so full of doubts." Those are good points about what I should say instead saying "evolution isn't true" but rather giving people a quick point of reference like you've given me here (i.e. if you believe that we aren't really in the Matrix and that I'm here talking to you then yes, evolution is real). Of course wondering whether the world really exists when asking such questions is really nitpicking because that's not the point of topic. I also see that you use Linux and develop games? I like you --BiT (talk) 10:53, 19 March 2009 (UTC)

The philosophical viewpoint that you're thinking of is "solipsism". Axl ¤ [Talk] 11:11, 19 March 2009 (UTC)

OK - so now that we've established that our OP is indeed sane and NOT going to discuss anything like this in front of the Nobel Prize committee - we can stretch the point a little. I actually believe that Evolution is as true as 2+2=4 or that there are infinitely many primes. It is a mathematical truth that:

• in a system in which entities can replicate themselves to make subsequent 'generations'...and...
• the information about the construction of entity is contained within the entity itself and is copied into the 'next generation'...and...
• when that replication process has a small - but non-zero error rate...and...
• where small details of the construction of these entities can change the probability of them replicating...

THEN evolution must be true for that system.

As true as that 2+2=4 in fact because you can prove all of that from those basic requirements. So in ANY system in which those conditions prevail, evolution must actually happen.

So EVOLUTION (as a process) is as true as that 2+2=4. What is only as true as (say) the theory that the earth is not flat - is that evolution actually happens here on earth and explains everything we see around us. That's a teeny-tiny bit less true. But I could write a computer program that demonstrates evolution working using only arithmetic and logic. (This has in fact been done, many times). If I was sufficiently careful, bored and determined - I could run that program in my head instead of in some computer and the results would be the same (Church-Turing thesis and whatnot). So I could - in theory demonstrate an actual evolutionary system working in practice using only what's inside my head.

Hence we need a new sound-bite. Meh - write your own.

SteveBaker (talk) 19:32, 19 March 2009 (UTC)

With some credit to John Lynch (based on his ideas, but with my errors added on top of it), evolution can be viewed as an observation, but also a process and a mechanism.

• The "fact" of evolution is the observation that species change. Either direct observation (like the evolution of citrate metabolism in Richard Lenski's amazing experiment) or the observation of the fossil record. These changes are, in essence, observations, which is what we call facts.
• The process of evolution is the observation of how these changes occurred. This overlaps with the former, but adds sequences of events. Horse evolution is a classic example, but gene tree reconstruction is pretty powerful too. It's an inference based on observations. Not quite a "fact", but it's a very strong inference. There are multiple independent lines of evidence. It's about as close to a "fact" are you get in science.
• The mechanism of evolution is a theory. Actually a body of theories - some very solidly supported, some untested hypotheses. A good, solid body of science, but not something you'd be inclined to call a fact. Guettarda (talk) 15:36, 20 March 2009 (UTC)

Methanol again

Thanks for your suggestions in my previous question about methanol. I have a more basic question now. In a mixture of MeOH/water, do the 2 substances evaporate at different rates/temperatures, or does the mixture behave as a new "pure" liquid? I'm not talking about distillation, more like just the first step of distillation where the liquids are evaporated.

Hope that makes sense.

141.14.245.244 (talk) 09:21, 18 March 2009 (UTC)

You may find Vapor_pressure and Raoult's_law interesting --91.6.16.55 (talk) 11:17, 18 March 2009 (UTC)

And Vapor-Liquid_Equilibrium#Boiling_point_diagrams. --NorwegianBlue ^talk 20:01, 18 March 2009 (UTC)

Raoult's law (already mentioned) is the important bit here. Basically, the vapor pressure (which in an open container is essentially the rate of evaporation) of each component will depend both on the concentration of each component AND on the temperature of the mixture. Take the case of a 50/50 methanol/water mixture. At any given temperature, the methanol will evaporate faster, so initially, the mixture will become a lower proportion of methanol. However, as the methanol concentration decreases, it's rate of evaporation will ALSO decrease compared to that of the water; water's rate of evaporation is increasing at the same time since its proportion in the mixture is rising as well. Since we have two competing processes (the higher initial evaporative rate, which is decelerating due to lower concentrations later on), the mixture will arrive at an equilibrium at some point along the way. Basically, at any given temperature, there will be a characteristic equilibrium ratio of methanol-to-water that the entire system will settle into. As you increase temperature, that ratio will tend towards the "azotropic ratio" at the boiling point of the lower-boiling liquid, which for methanol/water would be 0/100 (per our earlier discussion)... --Jayron32.talk.contribs 03:41, 19 March 2009 (UTC)

learning languages

Hello Wikipedia,

I read last night that, should a human not have learnt a language by the age of 6, he loses the ability too. This, i cannot believe. Whats the theory behind it and how can there possibly be any evidence for it (its hopefully unethical to deprive a child of his development?!).. thanks81.140.37.58 (talk) 11:06, 18 March 2009 (UTC)

I don't know, but you don't have to deprive a child of language development to know that some people don't develop language skills. I suspect it's probably because by the age of 6, the language centers of your brain are fully developed and capable of learning language. If, by the age of 6, you have not achieved some form of language retention, there's probably a problem elsewhere that means you can't. All speculation. —Cyclonenim (talk · contribs · email) 11:36, 18 March 2009 (UTC)

There is some evidence (from feral children, for example) that a human who has not had the opportunity to learn any human language by around 6 will never be able to do so later - see Critical Period Hypothesis. 87.112.22.179 (talk) 11:38, 18 March 2009 (UTC)

Sure, it's unethical to deprieve a child of his critical period, and it's a general rule that everything unethical has already been done. --Bowlhover (talk) 14:45, 18 March 2009 (UTC)

You may also wish to consider posting on the languages desk, once this thread has been archived in a few days. (Posting in two places at once is considered rude.) The linguists who hang out there know a thing or two about language acquisition. BrainyBabe (talk) 15:56, 18 March 2009 (UTC)

Now for some thoughts on why this might be. Our brains are initially "like a blank slate", in that nothing beyond some basic instincts is actually hardwired. The rest all must be learned. As we get older, our brains are no longer as open to learning. This is because things we've already learned become permanently burned into our brains. Why ? So we don't forget critical things we've learned, like how to walk. Small children have the ability to learn rapidly, but at the cost of forgetting quickly and being unable to distinguish fantasy from reality.

Communication is similar, in that we learn a method of communication and then tend to use that all our life. We can learn new words, as that's just a small change, but learning a whole new language is a bit trickier. Many can only learn an additional language by relating it back to their original language. Thus, if they had no original language, they couldn't learn the new one. There are exceptions though, as some people can learn, and actually think in, a new language. StuRat (talk) 15:58, 18 March 2009 (UTC)

What do you mean by "the age of 6"? I believe the critical age for learning a language is the age of 6 months.--Mr.K. (talk) 16:12, 18 March 2009 (UTC)

What? Many children don't start speaking until they are one or two years old, so that's patently not true. Unless you're thinking of something different. —Cyclonenim (talk · contribs · email) 18:57, 18 March 2009 (UTC)

Just because they can't speak doesn't mean they can't learn the language. Learning which sounds have which meaning is the first step, and learning how to make those sounds with their mouths is the next step. StuRat (talk) 14:54, 19 March 2009 (UTC)

I meant, children must get exposure to language before the age of 6 months or they won't be able to learn any full-fledged language. Of course, empirically testing this assertions may be immoral, however, it has happened.--Mr.K. (talk) 16:59, 19 March 2009 (UTC)

Surgery complications and PT age

What "percentage" is there for possible complications with inguinal hernia repair for an otherwise healthy 40 year old, compared to an 83 year old with Atrial Fib on Wafarin (but otherwise healthy/normal weight etc).

IE: <10% chance of complications for the 40 year old? >25% for the 83 year old due to having to stop Warfarin 4 days prior to surgery?

Is there a data bank that can provide this information?

Thanks Dave —Preceding unsigned comment added by 70.67.93.36 (talk) 13:56, 18 March 2009 (UTC)

The complication rate for any procedure varies depending on multiple factors, such as: age, sex, other health problems (which you already identified), as well as the location (the country, the hospital), there are also slight seasonal variations, and individual surgeons may have slightly differing complication rates for a given procedure. The other big variable is what type or types of complication you want to know about - since the rate of these also vary widely, and are also affected by everything else I mentioned. As far as I know, there's no one data bank for this, and if there was, I wouldnt rely too heavily on whatever it said because it'd necessarily have to average out all of those factors. If its a procedure you're contemplating having, discuss this with your surgeon. S/He will be aware of the local factors that affect risk and will be able to discuss them with you. Mattopaedia ^{Have a yarn} 05:29, 19 March 2009 (UTC)

Question about the knee

Im not seeking medical advise, i just want to know if a torn ACL can cause artrithis and in how much time? Thank you DST —Preceding unsigned comment added by DSTiamat (talk • contribs) 14:09, 18 March 2009 (UTC)

I don't think a torn anterior cruciate ligament can lead to arthritis, which is a disease affecting the joints, not ligaments or tendons. If you are concerned, however, please see a physician. —Cyclonenim (talk · contribs · email) 15:24, 18 March 2009 (UTC)

Our article Osteoarthritis#Two types? says "Some investigators believe that mechanical stress on joints underlies all osteoarthritis.." These researchers found a complete tear to be worse than a partial tear [1]. Maybe related or unrelated researchers have found that interrupted blood supply to the extracellular matrix of joints following surgery inhibited formation of cartilage when compared to methods where care was taken to preserve blood supply. Scarring (we don't seem to have a page on internal scarring) could be a factor here. 76.97.245.5 (talk) 16:33, 18 March 2009 (UTC)

From the Oxford Textbook of Orthopaedics and Trauma, pages 1207–1208: "Episodes of giving way may cause further injury to menisci and the articular surface. Reconstruction of the ACL has not been shown to prevent the development of osteoarthrosis. Reconstruction of the ACL may accelerate the development of osteoarthrosis." No timescale is indicated.

In paediatrics, page 2757: "Angus and Hall retrospectively studied ... the outcome of 27 children with arthroscopically documented ACL tears, 18 of which were partial tears. No activity restrictions were placed on the patients following diagnosis. At follow-up, 11 of 12 patients under the age of 14 were not satisfied because of functional knee instability. Most authors agree that functional instability, with associated damage to the menisci and articluar cartilage, will ensue in a patient with an ACL tear who returns to a high demand sport.... McCarroll et al. followed 38 patients with arthroscopically documented complete ACL tears for an average of 4.3 years following injury and found that 27 of the 38 patients treated nonoperatively developed subsequent symptomatic meniscal tears."

Axl ¤ [Talk] 18:43, 18 March 2009 (UTC)

Yes, a torn ACL can lead to OA. As for how long it takes- that depends on what you do with the knee. Lots of high impact, high demand activity generally equates with a faster rate of progression to OA (& a higher rate of re-injury), than low impact, low demand activity. Age also figures, as does sex, insofar as these factors are related to the types of activities one may be likely to undertake (for example a 20-something male football player may have a higher rate of progression than than a 50-something female who walks & swims a few times a week & has a sedentary job). Genetic susceptibility may also play a part. in other words: How long is a piece of string? Mattopaedia ^{Have a yarn} 05:38, 19 March 2009 (UTC)

Materials

Moved from Miscellaneous desk

I'm back! Based on facts ( and opinion, if you wish. Just make sure I know it's opinion.) which material do you think would work best for a windmill? Also based on how sturdy it is, how the weather effects it, cost, stuff like that. It can have drawbacks.

1. Titanium
2. Carbon Fiber
3. Magnesium

If you have any other suggestion, feel free to add. I'm just having trouble deciding on which to choose. <(^_^)> Pokegeek42 (talk) 22:27, 17 March 2009 (UTC)

Ah yes! Tensile strength! I think that might be important. <(^_^)> Pokegeek42 (talk) 22:32, 17 March 2009 (UTC)

For what parts of the windmill? The demand in the case of blades (for example) might be lightness or rigidity or tensile strength - but for the framework, extra weight might actually be beneficial and you'd perhaps be more interested in compressive loads. A lot depends on the design of your windmill too. SteveBaker (talk) 03:04, 18 March 2009 (UTC)

An interesting and somewhat relevant article: [2]. Bus stop (talk) 04:02, 18 March 2009 (UTC)

Maybe this should be on the science desk? That's where all the smart engineering types hang out. --JGGardiner (talk) 04:43, 18 March 2009 (UTC)

Carbon fiber would be pretty good as it's light and strong, except it's very expensive in the quantity that you'd want. Titanium is very strong, but heavy and therefore probably wouldn't be greatly affected by the wind. Magnesium, if pure, could be compared to Aluminum in terms of strength and weight, so it's probably the best option there. That's just in regards to the blades, though, because as Steve mentioned weight may well be beneficial to the framework of the windmill, in which case Titanium could be a good option (but also fairly expensive for large quantities). I'd have thought a steel structure would work better for that aspect. —Cyclonenim (talk ·contribs · email) 15:21, 18 March 2009 (UTC

I'd go with plastic for the blades (painted to protect against UV degradation) and steel for the frame (painted to prevent rust). The materials you named are rather expensive and probably only needed for the most extreme windmills. If looking at it in terms of amount of time until the windmill pays for itself, you'd want to keep the costs down as much as possible. The magnesium might also have the problem of burning when struck by lightning. The titanium is highly reflective, so you'd need to paint it to keep from blinding people from the Sun's reflection on the blades. Carbon fiber might be decent, but, again, is much more expensive than plastic. StuRat (talk) 15:39, 18 March 2009 (UTC)

You might be interested in Ceramic engineering. Glass-reinforced plastic and Biopolymer#Biopolymer as materials. 76.97.245.5 (talk) 15:41, 18 March 2009 (UTC)

Don't forget about galvanic corrosion if you use Mg. —Preceding unsigned comment added by 65.167.146.130 (talk) 20:14, 18 March 2009 (UTC)

Alrighty then. I've got enough to get started here. Thanks, guys! <(^_^)> Pokegeek42 (talk) 22:17, 18 March 2009 (UTC)

INDENTED CONCRETIONS

The Tununk Shale Member of the Mancos Shale Formation in Emery County, Utah, contains many spherical “cannonball” concretions. In one unique area, about 1.5km x 200m, the familiar cannonballs are outnumbered by others, 10 to 30cm in diameter, in which the spherical shape is modified by one or more indentations, 1.5 to 5cm in diameter and 1.5 to 4cm deep. (Pix @ http://picasaweb.google.com/fossilcrete/ForWeb#slideshow/5314320039662488930) Opening the concretions reveals a septarian-like interior with one of the dark septaria connected to the indentation. One concretion, bisected along the axis of the indentation, contains an inclusion connected to the indentation which appears to have cell structure and possibly be biological in origin. Do similar indented concretions exist in other areas? What caused the indentations? What is the the cellular inclusion? BobPeyton (talk) 15:54, 18 March 2009 (UTC)

My first thought on looking at the inclusion was that it was a fossilised bone of some kind such as seen here [3]. Bones of marine vertebrates have been reported from the Tununk Shale [4] so I would go with that as at least a possibility. Many concretions have a fossil at the centre, presumed to have acted as a nucleus for the growth. Can't come up with a good reason for the indentation though. Mikenorton (talk) 16:40, 18 March 2009 (UTC)

Super conducting armor vs. Lightning

Lets say you have a tank with armor that's super conducting and has zero electrical resistance. You zap it with an electron particle beam or lighting over and over again. Is it true, that it will never take any damage? ScienceApe (talk) 15:55, 18 March 2009 (UTC)

This may be a very naive approach, but I'm imagining whether lightning rods would take any damage struck again and again. I imagine there is probably some small amount of damage not from the charge directly but indirectly—say, if it created pressure effects in the air or ignited or burned something very close to the rod? --140.247.254.34 (talk) 17:04, 18 March 2009 (UTC)

The resistance would cause the conductor to heat up, which a super-conductor would not. That heating would probably result in damage eventually. --Tango (talk) 19:41, 18 March 2009 (UTC)

Thinking out loud -- the superconductor is still going to accumulate charge even if it doesn't accumulate heat, right? And that charge will eventually have to do something. Pump in charge at a high enough rate and you're likely to overwhelm whatever mechanism deals with it -- discharge to ground melts the rock underneath you, spark jumps across to the interior of the tank, something. So, while your armor may be invulnerable, your tank likely isn't. — Lomn 20:12, 18 March 2009 (UTC)

At the point where the lightning hits the superconductor, there is a hot plasma, possibly several thousand degrees. This is quite likely to damage your superconductor. Graeme Bartlett (talk) 20:37, 18 March 2009 (UTC)

Superconductors lose their superconductivity when the current density gets too big. They are not magic or invulnerable. Edison (talk) 23:25, 18 March 2009 (UTC)

To expand on the point about hot plasma most superconductors need to kept at sub liquid helium temperatures. If they rise above these temperatures their conductivity is lost and the electronic energy they contain is released as heat. Its a very delicate process charging and handling super conducting magnets. It possible for NMR and MRI magnets loss their superconductivity if they are jarred or damaged. The loss of superconductivity is called a quenching, in an uncontrolled the coil rapidly heats spreading resistance through the coil which boils the coolants, liquid helium and liquid nitrogen. This can be very dangerous for researchers, patients, doctors since they can be frost bitten or suffocated by the boiling coolant. For these and the other reasons mentioned superconductors don't make good armor.--OMCV (talk) 03:47, 19 March 2009 (UTC)

Laser application

Re-glazing of bathroom ceramics is mostly done with acrylic based products. I find the results only marginally satisfactory. Would it be possible to use a laser to melt Ceramic glaze / Vitreous on to the existing tile/cast iron tub? (following appropriate prepping.) Would the thermal stress induced in the tile crack it? Could a suitable laser be constructed cheaply and portable enough to be a DIY or rental unit? 76.97.245.5 (talk) 16:48, 18 March 2009 (UTC)

A portable laser with enough power to melt ceramic is unlikely to be safe enough to use without specialist safety equipment. It is also likley that such a laser would need more power than a standard house could provide. Most industrial lasers, which would have the power you require run from a 3-phase supply with a high current rating. Most also have water coolers attached to extract the excess heat - lasers are not efficient at converting electricity into light beams. -- SGBailey (talk) 16:56, 18 March 2009 (UTC)

It would also take a long time, I would imagine - a laser is, by design, very concentrated and ceramic has very low thermal conductivity, so I would expect you would have to point the laser at every single point on the tile you want to reglaze. That would mean running the laser up and down the tile in very thin strips. --Tango (talk) 17:10, 18 March 2009 (UTC)

Good question. I used to use a iron bathroom sink as a forge, the glaze would get sticky when it got hot but the whole thing was fine when it cooled down. Whether or not you could heat only part of the iron and glaze is a question I would like to know the answer to also. 121.214.10.38 (talk) 03:06, 19 March 2009 (UTC)

@Tango one could construct a mirror/prism thingy to guide the beam (sort of like at a disco) that should be doable. This paper I found indicates it would still be too slow overall [5]. A focus area of 0.3 mm seems feasible. Staying with metric that would take 50 passes per 15 cm² tile. So one would have to be able to generate sufficient heat to take only of a fraction of a second per pass or you'd need an hour per tile. Bailey's answer indicates it wouldn't be feasible anyway. I had hoped, since one wouldn't need a specific wavelength nor narrow specs, a high power output laser would be possible. Too bad. Maybe something like a blow torch with an automated guidance system could work. That would be a lot more likely to set the house on fire, though. :-( Thanks for all the input. 76.97.245.5 (talk) 05:02, 19 March 2009 (UTC)

earliest/latest snow

I am looking for info on the earliest and latest recorded snowfalls for several cities including St Paul MN, Omaha NE, Des Moines IA, Chicago IL, and St Louis MO. Does anyone have a website or something to point me to?

Thanks 65.167.146.130 (talk) 20:54, 18 March 2009 (UTC)

Here's one for Chicago: [6] However, I think it's worth noting that as you move northward, you'll need to rigorously define "earliest" and "latest". What happens if it snows in June? — Lomn 21:23, 18 March 2009 (UTC)

Or July (1816, Year Without a Summer), or August (Alberta, Canada), for that matter? Also, do a few flakes on the outskirts of a city witnessed by a few people count as a snowfall event? ~AH1^(TCU) 22:21, 18 March 2009 (UTC)

And you can get hail even in the middle of summer in warm climates, frequently associated with tornadoes. StuRat (talk) 14:32, 19 March 2009 (UTC)

A city will usually have an official weather station (generally at the airport), run by an official weather service with rules on how to measure the weather, and it's what happens there that counts as the city's weather. --Carnildo (talk) 23:26, 18 March 2009 (UTC)

http://www.wunderground.com may be helpful for researching historical weather conditions in U.S. cities. --Jayron32.talk.contribs 05:10, 19 March 2009 (UTC)

Hail doesn't count as snow, not even close. I remember one occasion where soft hail (graupel) fell in the summer in Northern Ontario, and it was reported as 27C (80F) and snow, but actual snow doesn't fall at those temperatures. However, snow can sometimes fall at temperatures as high as 10C (50F) with low humidity and at high elevations, but the highest temperature I've seen snow at where I live (S. Ontario) was about 6C (43F), and the latest and earliest days I've seen snow here were in late May and mid-October. ~AH1^(TCU) 17:44, 19 March 2009 (UTC)

How to write on a photgraph

The instructions for a photo contest are 'label the back of the photograph with your name, phone number, etc. etc.'

Are there particular types of labels that are good for this purpose? E.g., they won't damage the photo; they can be removed later if desired?

Thank you, Wanderer57 (talk) 21:24, 18 March 2009 (UTC)

Write on a piece of paper, sellotape that piece of paper to the back of the photo - should work fine. Alternatively use a soft-tip marker pen that doesn't smudge.

While I have no specific information, I suspect that the rules for a marker pen may be the same as for writing on CDs, i.e. use a "non-toxic" pen which doesn't deposit strong solvents in the ink which could soak through and damage the image surface on the other side. I use a Staedtler Lumicolor CD-R pen. Franamax (talk) 02:17, 19 March 2009 (UTC)

I think what you want is a grease pencil, a.k.a. wax or chinagraph pencil. The wax does not penetrate, so you can wipe it off later. --Scray (talk) 03:07, 19 March 2009 (UTC)

This must be a rather old-fashioned contest. I'd have expected it to say "label the CD containing your (digital) pics with your name, phone number, etc.". StuRat (talk) 14:29, 19 March 2009 (UTC)

If you do write on a paper photo, use a very hard surface under the photo to avoid putting an indentation into it which will be visible on the front. This could be a smooth shhet of class or metal. Graeme Bartlett (talk) 20:15, 19 March 2009 (UTC)

Thank you all for your inputs.

StuRat: You are correct, it is a very old-fashioned contest. Imagine looking at photographs on paper!

Wanderer57 (talk) 08:24, 20 March 2009 (UTC)

Speaking from professional publishing experience garnered in ye olde pre-digital age, it can be difficult to know if a felt tip will or will not bleed through and mar the picture (as per Franamax), or how little pressure might cause reproductible indentations/bumps (as per Graeme Bartlett), until you've already tried it (perhaps on a similar non-important picture). To be on the safe side, I'd suggest you write what you need to on a sticky-backed white address (or similar) label while it's still on its backing paper, and then stick the label on to the back of the photo(s). This method is always used by professional picture libraries on old prints, where the original negative may not be available. 87.81.230.195 (talk) 00:30, 21 March 2009 (UTC)

I agree. The stick-on label will also have the advantage of allowing me to swap the label on your pic with the label on my Xeroxed pic of my butt, allowing me to walk away with the grand prize. Then again, it would be just my luck that this is the year the judges finally understand my artistic vision.  :-) StuRat (talk) 17:25, 22 March 2009 (UTC)

Black hole thermodynamics and gravity

The zeroth law of black hole thermodynamics states that the surface gravity of a black hole is constant at a given temperature, right? Isn't this essentially proof of existence of a force carrier particle for gravity? I'm thinking that in standard thermodynamics, this applies because a change in temperature equates to a change in entropy, and we observe this by looking at the vibrational aspect of particles. Can this not be transfered over to black hole thermodynamics? I'm probably missing something big, so feel free to rip this idea to shreds. —Cyclonenim (talk · contribs · email) 21:50, 18 March 2009 (UTC)

I read somewhere that the only three laws of physics that probably aren't broken by black holes are gravitation, electromagnetism, and rotation. So, I'm not sure if the usual rules involving temperature apply properly in a black hole. However, it's probably still possible to predict the laws of physics as they apply to a black hole, and maybe some experiments such as those at the LHC will help improve our understanding, but I'll wait for someone with a more detailed answer as well. ~AH1^(TCU) 22:17, 18 March 2009 (UTC)

Perhaps you should better explain the point you are making and the reasoning behind it. It is not clear (at least to me) how you want to go from the zeroth law to the existence of a force carrier particle. Your idea about entropy seems to be going in the right direction but you did not develop it enough. Dauto (talk) 01:08, 19 March 2009 (UTC)

Surface "temperature" of a black hole is likely determined by events like Hawking radiation, and the rate of of "evaporation" due to Hawking radiation is mathematically proportional to the "size" and therefore surface gravity of the black hole. So if you measure the "temperature" of the black hole, what you are measuring is the kinetic energy of the particles lost via "evaporation". Our article on Hawking radiation covers this in exhaustive mathematical detail, but the basic principle is stated in the article more or less... --Jayron32.talk.contribs 03:26, 19 March 2009 (UTC)

My point was, in a completely speculative manner, that because the surface gravity of a black hole is proportional to the temperature, this seems remarkably similar to standard thermodynamics where the energy of a particle is given by its temperature (because of more vibration). —Cyclonenim (talk · contribs · email) 07:41, 19 March 2009 (UTC)

meteorite

Could this rock that was found in Ohio be a meteorite? It weighs 8.6 lbs.

• File:100 0537.jpg
• File:100 0541.jpg
• File:100 0542.jpg
• File:100 0545.jpg

I can't see the pictures.. is it just me? I'm not good enough at wiki to see where code may or may not be wrong. Can I get a second opinion? -Pete5x5 (talk) 01:37, 19 March 2009 (UTC)

Those images don't seem to exist either here or on Commons. I think you might need to put the "File:" prefix in front, but doesn't matter, 'cause I can't find them anyway... Franamax (talk) 01:54, 19 March 2009 (UTC)

I can't see it either. Dauto (talk) 01:47, 19 March 2009 (UTC)

Well, the <gallery> is incorrect - you need to put "Image:" or "File:" in front of each image - but I tried doing that and none of the images showed up. Then, the image uploader removes underscores from filenames - but doing that doesn't make them show up either. I suspect that the OP has not uploaded them successfully. SteveBaker (talk) 01:54, 19 March 2009 (UTC)

The trouble is not in your set. It's me. My next question is will a laptop still work after I throw it out the window? I will try to add the pictures when one the kids stops by. Please stay tuned.Curiouspatty45 (talk) 00:14, 20 March 2009 (UTC)

How does one teach a parrot to ride a tricycle?

Not a joke question. You can seriously buy small tricycles designed to be ridden by parrots online. How does that work then? If I bought one and showed it to my macaw, she'd probably just look at me as though to say "what do you expect me to do with THAT thing?". On the other hand, it might be a lot of fun for her, if I had the first idea about how I was supposed to teach her to pedal. Anyone know what I'm talking about here? --84.70.216.219 (talk) 23:15, 18 March 2009 (UTC)

See Operant conditioning and Shaping (psychology). Positive reinforcement is the key. Also be extremely patient, and do not continue a session when the bird does not want to play any more. You might start with basic bird training [7]. Edison (talk) 23:23, 18 March 2009 (UTC)