Wikipedia:Reference desk/Archives/Science/2012 September 3

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September 3

For how long has Schroedinger's Cat been rotting?

So, I have set up the cat experiment with enough air, food and water to keep the cat alive for 10 days. Only then do I open the box. Given that he has neither been alive nor dead for 10 days, he certainly cannot have been rotting for 10 days. Indeed, he should still be warm, whether alive or dead. If he has rotted, who observed him ten days ago to kill him? I don't want arguments in response to this question, I want previously published considerations of it. Thanks for the help. μηδείς (talk) 00:10, 3 September 2012 (UTC)

The premise of the question is wrong. It's not that he's been neither alive nor dead, he's been both at once (supposedly). 86.177.105.185 (talk) 00:53, 3 September 2012 (UTC)

Yes, so he has been rotting or not for ten days? Or just since the box was opened? Maybe just rotting for five as a compromise? A published source which discusses this dilemma would be appreciated. μηδείς (talk) 00:57, 3 September 2012 (UTC)

The physical processes of rotting (if it occurs) will introduce all kinds of interference with the supposed superposition of dead/non-dead states, vaguely akin to opening the box. I appreciate that you want published sources, so please excuse my unsupported replies. 86.177.105.185 (talk) 01:07, 3 September 2012 (UTC)

Isn't the whole point of the cat thing that at the macro scale it IS a paradox? It doesn't make logical sense. So trying to infer other logical conclusions from it is kind of pointless. Vespine (talk) 01:39, 3 September 2012 (UTC)

It makes conceptual sense for the cat to be alive and dead at the same time if you believe that interpretation; however, in reality the cat is a big and vastly complicated thing, and once you start taking into account physical process and interactions such as rotting, breathing, eating, etc., the original concept of the thought experiment becomes overwhelmed with other factors not originally relevant. 86.177.105.185 (talk) 01:54, 3 September 2012 (UTC)

Inasmuch as the scenario makes sense at all, he has been rotting (or not) for ten days. More specifically, over a ten day period, |alive> + |dead> evolves to |alive for ten days> + |dead for ten days>. A quick search of the arXiv and Google Scholar failed to turn up any discussions of this, though. -- BenRG (talk) 01:42, 3 September 2012 (UTC)

I believe you're thinking about the cat too literally. It is a metaphor, and if you were to try it with an actual cat, you're not going to observe any particularly strange quantum effects. The problem with your question comes about with the addition of an additional variable (the rotting process) that really has no analogous feature in quantum physics, but the cat isn't a great analogy to begin with. (If the cat is alive, he damn well knows it, whether anyone on the outside of the box does or not.) If you were to forget about all the various problems inherent with the paradox and the question, though, I believe BenRG's answer is correct. Evanh2008 ^{(talk|contribs)} 02:12, 3 September 2012 (UTC)

My personal interpretation is the same as BenRG's, and is expanded as follows: The problem is that the thought experiment is indeed usually portrayed as literally true, yet a cat's being dead is not just a yes-or-no thing--death as variously defined is a moment that has a temporal location. If a cat is dead, it means it has been dead for a finite time. That raises the question of how long he's been dead before the door was opened to check. If he's rotten, it implies he did die, not when the door was opened, but when the atom did indeed decay ten days ago, before anyone measured it. If he has only just died when the door opens, then not observing an atom's decay would delay the cat's death by ten days. But we all know unobserved atoms decay regardless of whether they are observed. (And we can even add that the atom has to decay within a certain time frame as a condition.) One could, as BenRG seems to be doing, posit that opening the door now reaches back into time and kills the cat ten days ago. That's what I would guess is the orthodox position. But none of these answers quite seems to fit with what is supposed to be going on. I cannot imagine that this situation was never suggested before, so I am quite interested in knowing what the literature suggests. I cannot believe that physicists don't know the difference between a freshly dead and ten-day dead cat. 02:26, 3 September 2012 (UTC)

Before you open it, the contents of the (perfectly isolated) box is a mini-many deadly cat worlds. Count Iblis (talk) 02:59, 3 September 2012 (UTC)

Unless I have missed it, that article doesn't seem to answer the "when did the cat actually die?" question. Are we supposed to assume it didn't actually die at any specific time, and hence hasn't rotted? Or that it did die, if it died, ten days before anyone opened the box? This seems like such an obvious question to a biologist that I cannot believe ther is no mention of this question in the literature. μηδείς (talk) 03:13, 3 September 2012 (UTC)

The only way the "paradox" is in any way useful or logical is if you have a perfect box- that is, there is no way to tell if the cat is "rotten" since any information cannot escape the box. Asking about rotten cats implies you have not understood what the thought experiment is supposed to demonstrate. 70.162.10.166 (talk) 03:44, 3 September 2012 (UTC)

While I have reservations about the seriousness of this question, no one else does, so I might as well through in my 2 cents. The problem with your above remark is that the cat is not a single particle, it is a whole bunch of them, this muddies up the whole affair, so let's try to simplify. Replace the cat with what we will call chemical X and instead of poison we have chemical Y. X and Y combine molecule for molecule to make a molecule of Z, for all X and Y to disappear and us to be left with just Z, it will take 10 days. Then, we can measure the amount of Z in the box to determine the length of time since the radioactive substance went off. So, what is the state inside the box before we look? In this case, the state is a super position of each possible count of Z molecules, the coefficients of which evolve in time so that higher numbers of Z are more likely at later times. The reason this question seems difficult is because "how long was the cat dead" is an entirely different question than "did the cat die", it's an entirely different Hilbert Space, looking at one in terms of the other confuses the issue and stretches the analogy past what it is meant to do. Phoenixia1177 (talk) 04:06, 3 September 2012 (UTC)

It died, if it did die, ten days before you opened the box. The whole situation is exactly the same as if you had a classical probabilistic distribution. If there's a 50% chance that the cat just died, ten days from now there will be a 50% chance that it died ten days ago. There is no interaction between the possible living cat and the possible dead cat. They are distinct possibilities that evolve independently. That's why in quantum mechanics if you start with |X> + |Y> and evolve it forward ten days, you always get |X after ten days> + |Y after ten days>. It's a manifestation of the probabilistic nature of the theory. Quantum mechanics is only different from classical probability if you later observe interference effects by doing something like a double-slit experiment. But that's not something you can do with cats, or any macroscopic system at room temperature. It's strictly more difficult than bringing the cat back to life.

You probably won't find a discussion of this in the literature because the part about the time evolution of |alive> + |dead> is too obvious to bear mentioning, and the rest is just cocktail-party philosophy. -- BenRG (talk) 04:12, 3 September 2012 (UTC)

I'm going to have to respectfully disagree with you. You're answer assumes we're talking about some event that happened, or didn't, but we aren't. If the poison goes off on day one, then in ten days the cat is ten days dead, if it goes off on day two then the cat is nine days dead, etc. A two day dead cat and a one day dead cat are not the same. That's the whole confusion, we aren't talking about if the poison went off, but when the poison went off (never being a possibility) For that reason, the cat must be a superposition of states from perfectly fine to ten days rotten and all in between. Really, we could dispense with the cat and just ask about the decay of the sample, which is a quantum problem, the cat serves no real purpose. [Also, as you point out, there is certainly know publication that would analyze this]Phoenixia1177 (talk) 06:40, 3 September 2012 (UTC)

I did assume that the poison is released (or not) at the beginning, which is what I think Medeis wanted. I also assumed that the cat wouldn't conk out for unrelated reasons later. If you want more realism you have to face the fact that these states make no sense anyway since you can't perfectly isolate a cat from its environment. -- BenRG (talk) 18:40, 3 September 2012 (UTC)

This is what you get when science nerds become famous. Talk about cats in boxes. Making other nerds think that's what science is, writing papers about quantum bomb detectors; "we can test a bomb without really testing it!" Why don't you show us with real bombs. Quantum eraser experiment, Delayed choice quantum eraser, Walborn et al. quantum eraser.. when I count the minimum number of detectors , polarizers, interferometers etc needed to perform these, I think a computer could simulate every conceivable thought experiment in a day. Maybe then they'd stop playing in their quantum sandbox and go do serious work. Like bridging the gap between their claim that "we have demonstrated in our experiment an interaction-free measurement with a figure of merit up to 1/2 i.e., half our measurements could be interaction-free", and the 2% detection rate, the dark counts, the convenient equalizing of detection rates by adjusting detector overbiases for "the purpose of this proof of principle" i.e., the actual results. There are complete libraries filled with new age mysticism, telekinesis, free energy and other crackpot ideas using quantum physics as support for their delusions. All these esoteric QM interpretations, just put them next to Aristotle's four causes, Heraclitus' "all things flow", the astrology of Tycho brahe and the philosopher's stone. </end of rant> Ssscienccce (talk) 15:09, 3 September 2012 (UTC)

Superposition does not come just like that, it came from the many worlds interpretation, and that came from back in time.

and If a particle falling apart,it should report the same world from the many worlds, and his time and his place is corelated to one world that you stabiliz on it . thanks water nosfim --81.218.91.170 (talk) 15:54, 3 September 2012 (UTC)

Look, Schrödinger's cat is stupid. Even Schrödinger thought so. It's famous because of the dead cat, not because of any merit as a thought experiment (much less a real experiment). The other experiments you mention are different. They're useful as illustrations of uniquely quantum effects, and they're experiments you can actually do and that could conceivably give results incompatible with quantum mechanics. Almost no one expects them to, since the quantum rules are too well tested at this point, but they're still better than Schrödinger's cat. -- BenRG (talk) 18:40, 3 September 2012 (UTC)

i got the honor to see "Cats" resurrected . Thanks water nosfim--81.218.91.170 (talk) 20:14, 3 September 2012 (UTC)

The bottom-line, regardless of Schrödinger's cat's merit or treatment, this definitive or indefinite cat has been discussed and elaborated on. I came across it plenty of times during the years I browsed the NCSU library stacks, but I found nothing regarding it of much consequence. Still, its entirely possible something similar to the OP's version can be found somewhere in that heap, along with the mostly incorrect QM interpretations that are nearly unfalsifiable. In recent years, the two most revealing experiments that I am aware of are the walking droplets [1] along with the successful measurement of individual particle paths and their stochastic interference pattern: described here and published here. The liquid analog entails some interesting particle-wave-like interactions, and although a similar medium, the aether, was once sought (and a form of it persists as a string-filled spacetime "mattress"), a medium is unessential. Modocc (talk) 20:32, 3 September 2012 (UTC)

Ok, maybe it's not the experiments themselves, but rather the way the are presented, either by the authors or by the media who report them. Take the article Quantum eraser experiment:

Because pairs of photons are entangled, giving one a diagonal polarization (rotating its plane of vibration 45 degrees) will cause a complementary polarization of its entangled pair member. So from this point on, the photons heading down toward the double slits will meet the two circular polarizers after having been rotated. And when photons enter either circular polarizer "half way off" from their original orientation, the result will be that on each sub-path half will be given one kind of circular polarization and half will receive the other polarization. The end result is that half the photons emerging from each circular polarizer will be "clockwise" and half will be "counter-clockwise." It will then be impossible to look at the polarization of a photon and know by which path it has come.

This seems a highly unlikely interpretation of the experiment. The Walborn paper itself isn't exactly an example of clarity, with ambiguous terms like "measuring the polarisation of the photon" or "destroying the information". The included data of coincidence counts and the detection time gives an indication of what is happening: there are large differences in total coincidence counts, the different setups "filter out" photons based on their polarization. But reading the article, one would assume that all photon pairs are detected and they change their behaviour in some magical way. Ssscienccce (talk) 15:14, 4 September 2012 (UTC)

Thing is, macroscopic objects behave classically because of a non-classical "weird" quantum effect, i.e. entanglement. The degrees of freedom of a macroscopic object get entangled with the environment, and that makes the object behave in an effectively classical way. So, if I detect purely classical behavior when looking at a macroscopic object, that is as much evidence for quantum mechanics as is doing some interference experiment using photons or measuring a violation of Bell's inequality. There is no alternative theory available that can explain classical behavior at the macro level, classical mechanics has already been falsified. Paradoxically, it would actually take an observation of a quantum effect on the macro scale where quantum theory predicts it shouldn't occur to falsify quantum mechanics.

Also, when one performs an interference experiment, this is also a probe of the validity of quantum mechanics for macroscopic systems. Take e.g. some interference experiment involving mirrors. Clearly, if the state of the mirrors would be affected by the photons bouncing off the mirrors, the interference pattern would be weakened, it would vanish if you could unambiguously tell which way the photon went using the state of the mirrors. So, you can intepret the fact that an interference pattern appears on the screen as experimental evidence that the momentum space wavefunction that describes the center of mass motion of the mirrors is a lot wider than the change in the photon momentum (in case you do the experiment with floating mirrors). Count Iblis (talk) 23:37, 3 September 2012 (UTC)

First the big world has same symmetry in time, then if easier for you, do first revelation of knowledge, and act in compliance . thanks water nosfim --81.218.91.170 (talk) 05:10, 4 September 2012 (UTC)

BenRG seems to have gotten the question right the way I meant it and Phoenix and IP70 are confusing an issue. The original condition is whether or not single radioactive atom with a 50% probability over a set initial "test" period decays, releasing a single photon. That photon is not entangled with anything. If it is detected druing the initial test period, a flask of poison is broken killing the cat.

Now, supposedly the cat is neither dead nor alive until you open the chamber to look. But what if you wait ten days to open the chamber? Would the cat have spent ten days rotting? If he was neither dead nor alive, did he rot over that period? If he rotted, was he not dead and rotting from the beginning regardless of our observation? Or did the rotting happen in some sort of instantaneous backwards time travel once the door was opened because of our observation? To push the absurdity, if he didn't rot, is this a way of preserving meat? The question is, how can the cat be in a state of superposition and rotting at the same time for ten days?

The instantaneous "he's dead and he's not dead until we observe him" description is plausible because we don't have to deal with the fact that dead cats rot over time. This development through time seems like an obvious objection to the theory that one has to wait for observation for the wave function to collapse. That is what surprises me, that no critic has asked what happens to the cat while it is in the state of superposition over time.

Surely I am not the first to raise this question? μηδείς (talk) 02:15, 7 September 2012 (UTC)

The cat is not "neither dead nor alive", it is both dead and alive (supposedly), until it is observed to be one or the other when the box is opened. If the superposition of dead/alive states could be maintained over ten days, then the cat would evolve as a superposition of "rotting cat" and "alive cat", and when the box was opened one or the other would be revealed. If the rotting cat was revealed then you would see a state that had been rotting for ten days. However, this is all impossible (even more so than the original thought experiment) because living and rotting cats are big and complicated objects, and the processes/interactions that they undergo will destroy the basis of the experiment. 86.146.104.131 (talk) 03:29, 7 September 2012 (UTC)

Sorry to the person above, I had the page up for a while before I clicked edit, I never saw your edit till I posted mine.Phoenixia1177 (talk) 03:39, 7 September 2012 (UTC)

Sorry for the initial confusion, I was assuming, since you mentioned time, that you were allowing the decay to happen at a later time if it didn't already occur. In the case you are discussing, the previous given answer that the cat will be in a superposition of the states |10 ten days rotted> and |10 days in box, but not poisoned> is the correct one. Ultimately, the various branches of the superposition all move forward in time. All introductory books on QM handle the question of how states evolve in time, some of these are approachable by someone with a little linear algebra experience and some calculus/basic physics courses (I'm not sure your background) Unfortunately, I'm not at home, so I don't have any recommendations at the moment. You can also look at our article on the Schrödinger Picture and the Schrödinger Equation and Hamiltonian(Quantum Mechanics), although I don't think any of them are overly helpful. You might also consider doing a google search of "Time Evolution in Quantum Mechanics", I'm sure some of the results should be of use.

As to the question of just how the cat ends up in either definite state, that is much thornier and I don't think it has a universal answer. However, it may help to look at things from a different perspective, namely that what we call definite states are the atypical. For an analogy, if you assume that the Earth is at the center of the solar system, you can still work out laws that predict the motion of the stars in the skies, however, these laws will not be elegant nor will they be intuitive. Similarly, looking at definite states as some special entitled things as opposed to just another superposition makes quantum mechanics seem far more mysterious. [Note: obviously there is a good reason to think about how definite states get entered and all that, I'm not advocating ignoring that, just looking at things from a different angle when useful.] Phoenixia1177 (talk) 03:38, 7 September 2012 (UTC)

I suspected the "both states keep evolving for ten days" answer would be given, since the "catmeat stasis" answer seems, to my intuition, to violate too many other laws. One of my undergrad majors was Bio, but I tested out of calculus, having gotten a 5 on AP Calculus in high school, so the furthest I went in math was series and summations, (and I mastered Springer Verlag's Chaos and Fractals when it came out) if that matters. What I really want at this point is some sort of source, preferably popular, Penrose is at my level, that discusses this specific issue, especially from a not unskeptical viewpoint. μηδείς (talk) 04:27, 7 September 2012 (UTC)

Objection to IP86. What does the fact that the cat is complex matter to the experiment? The decaying atom's photon is the simple causal agent. If that were a problem (and I am not saying it's not) wouldn't its complexity invalidate the original experiment without the 10 day delay as well? μηδείς (talk) 04:31, 7 September 2012 (UTC)

The complexity of the cat would matter if you were doing this as a real experiment, but we aren't and it doesn't. On to other matters, I, unfortunately, don't know much of the nontechnical literature on quantum stuff, so I doubt I'll be much help with that. Question: do you require a source to specifically talk about the cat or will anything on time evolution of super positioned states do? I ask because there is a book, I have the title at home, that should be readable (some math is required, though) that will discuss the concepts, but no cat- it is a philosophy meets QM book, it's interesting independent of any of this too, so that's a plus. If interested, I can get you the title.Phoenixia1177 (talk) 13:07, 7 September 2012 (UTC)

No, the cat was not important, the development over time is the issue. I will benefit from a book with clear prose that might use equations to illustrate. If the discussion is solely put forth in terms of math I'll probably get lost. But do give me the title and I'll look for it. μηδείς (talk) 16:29, 7 September 2012 (UTC)

For example, the equation at the top of the next thread below is above my pay grade. I know it has something to do with the (double?) integral of some sort of vector product. But I garner from the prose that the surface integral has to be zero presumably because otherwise you'd have a net polar magnetic "charge", in effect a magnetic monopole. μηδείς (talk) 16:37, 7 September 2012 (UTC)

The book I was thinking of is The Structure and Interpretation of Quantum Mechanics by R. I. G. Hughes, if you're feeling a little more mathematically inclined, you might try the first 7 or 8 chapters of Quantum Processes Systems, and Information by Benjamin Schumacher and Michael Westmoreland from Cambridge University Press.Phoenixia1177 (talk) 01:14, 8 September 2012 (UTC)

Is D necessarily zero?

Suppose you have a sphere. Suppose $\int \int {\vec {D}}\cdot d{\vec {A}}=0$. Is D necessarily zero? Or, is there some symmetry condition that forces D=0? --130.56.91.41 (talk) 02:47, 3 September 2012 (UTC)

D is a vector field and dA is the area element, right? Then if the vector field points along the surface of the sphere at every point, the integral will be zero even though D is not zero anywhere. In fact, Maxwell's equations of electromagnetism say that the surface integral of the magnetic field is ALWAYS zero, across any surface, even though magnetic fields themselves are clearly not zero everywhere. --128.112.70.89 (talk) 03:51, 3 September 2012 (UTC)

If D points tangentially to the sphere at every point then it will have to be zero somewhere by the hairy ball theorem. But that's not really important here. Staecker (talk) 16:40, 3 September 2012 (UTC)

Several conditions related to this mathematical formulation are explained in our article on Green's theorem, Stoke's theorem, and the divergence theorem, and the articles linked from there. The math is very widely used, especially in the study of electromagnetic fields. Nimur (talk) 15:03, 3 September 2012 (UTC)

D is Electric displacement field--130.56.84.156 (talk) 04:39, 3 September 2012 (UTC)

Minimal food requirements

Suppose we want to send a small human, perhaps 10cm shorter and quite a bit lighter than the average woman, to Mars. It'll be a short 545-day trip, and the only requirement is that the astronaut is alive at the end. Being emaciated, insane, and suffering from osteoporosis are all OK, because no matter how cruel the conditions, there won't be a shortage of people (even small women) willing to go. What's the absolute minimum amount of food, in weight and volume, the astronaut would require? Does being in space change the food requirements from what they would be on Earth? --128.112.70.89 (talk) 03:48, 3 September 2012 (UTC)

Not sure about earth, but the minimum average calories a person needs to maintain their current health is about 1,800, per Food energy, but that is quite activity dependent. --Jayron32 03:55, 3 September 2012 (UTC)

But that's for an average person, not for a small woman or really small man. Also, an Earth-dweller needs to walk around, think, pump blood, drive, and eat, all under Earth gravity. I'm thinking that the astronaut could be confined to a small space or chained to prevent any physical activity. That would be a serious animal cruelty if done to any animal on Earth, but as I said, there's be no shortage of people willing to endure that to go to Mars. Finally, how much mass and volume does 1 calorie translate to, given the most compact possible storage? --128.112.70.89 (talk) 04:04, 3 September 2012 (UTC)

If you don't care about the health of the individual and just want to send them so you could say you did it, why not send an animal instead ? StuRat (talk) 04:26, 3 September 2012 (UTC)

I think the story you've made up as the premise is a bit too silly. Of course no sane person would want to endure 545 days of near starvation to get to Mars. What happens AFTER the 545 days? They stop eating all together? Obviously one of the 1st requirements for any planetary mission would be to provide enough food to keep a person healthy. I think saying it'll be someone who is "small" or "woman" won't play a significant enough part, I think far more important qualifications would be "smart" and "sane". Look at sailors in the days of discovery, they surely endured harsh conditions, probably surviving on minimal rations, but even wealth and fame weren't enough incentive to willingly starve yourself as part of the plan. CErtain people in the army also probably know quite a lot about "minimums" required to keep people alive and healthy. Besides, if you're taking thousands of kilos of fuel and cargo and spending billions on R+D, it's hard to not justufy a few extra kilos of food, especially if you dehydrate it and use recycled water, then maybe you could recycle food too by growing some of your own? It seems absurd that anyone going on that sort of mission would be expected to starve as part of the "price". As for calorie density, lard, butter and nuts are about as high density as you get. Not sure how long you could eat just those three before the mere sight or smell of them will make you vomit. Vespine (talk) 04:37, 3 September 2012 (UTC)

I agree that nobody is going to send people on a suicide mission to Mars. However, the idea of sending people of small stature and low basal metabolic rate is a good one, as long as they aren't so small as to suffer health problems as a result. It's not just their mass and the mass of the food to consider, it then requires more fuel to accelerate that mass, and more fuel to accelerate the mass of that additional fuel, etc. So, if we compare two people, one whose mass and the mass of the food they eat, water they drink, and air they consume is half of the other, then the mass of the ship could be half as much as well. It's all proportional (with some non-proportional effects in the case of launching through thick atmospheres, like the Earth, but hopefully a space launch or Moon launch would be used to go to Mars). StuRat (talk) 19:59, 4 September 2012 (UTC)

Taking 1400 kcal per day, high energy food of 5kcal per gram, you'd need 152kg for 545 days. Don't know if 5 kcal per gram is a good guess, proteines and carbohydrates are 4 per gram, fats 9. Ssscienccce (talk) 15:23, 3 September 2012 (UTC)

Yea, that's about right for calorie-dense foods. Cashews, for example, have about 5.5 kcal per gram: [2], while macadamia nuts are a bit over 7: [3]. StuRat (talk) 20:07, 4 September 2012 (UTC)

@Stu: Because the public doesn't regard animal spaceflight to be as important as human spaceflight. Tell me, who was the first animal in space? How many times have you heard that milestone celebrated? How about the first human?

@Vespine: 545 days is the time for a round-trip, including 30 days of staying on Mars. A one-way trip takes 6 to 8 months unless you're willing to use a lot of fuel. The comparison with sailors is flawed because sailors needed to be competent at controlling their ship, while computers can land spacecraft on Mars just fine. Also, I never said that the astronaut had to be a starving wreck at the end, just that it's not a problem (so a safety margin is not required). --128.112.70.18 (talk) 15:15, 3 September 2012 (UTC)

Laika the space dog although the U.S. sent fruit flies suborbital much earlier. See animals in space. Rmhermen (talk) 22:45, 3 September 2012 (UTC)

Yes, I knew it was Laika, and also knew Yuri Gagarin was the first person in space. StuRat (talk) 19:52, 4 September 2012 (UTC)

Everyone of an age with good memory knows it was Laika. What is your point? If "Ozymandias the Maine Coon housecat" or "Maximilian the wire-haired dachsund" were sent on a one-way trip to Mars, do you imagine that no one would remember her or his name 50 years after? 98.220.239.210 (talk) 05:46, 5 September 2012 (UTC)

Yes, exceptionally old people know it was Laika, even though the first animals in space were technically fruit flies. 14 year olds like me, on the other hand, tend to know a lot about Gagarin and nothing about Laika, simply because it's not as memorable or significant an achievement. I'd also like to point out that the Apollo program was about landing a man on the moon--not flies, dogs, or cats, but a man. There's no reason that a new cold war, perhaps between China and the US, wouldn't be about landing a man on Mars.

Back to the question: as I (the OP) said, it's downright unethical to confine an animal to a tiny space and starve it for 500 days. That's not a problem with humans because a human can consent, and because humans already treat each other much more cruelly. Case in point: we euthanize animals suffering from terminal illness, but Christians have a problem with euthanizing humans in the same situation. --128.112.70.118 (talk) 02:36, 7 September 2012 (UTC)

Bauxite

What is "soundiferancic" in http://en.wikipedia.org/wiki/Bauxite?

It's under "Processing"

"Bauxite rocks are typically classified according to their intended commercial application: metallurgical, abrasive, cement, chemical, and refractory, cosmetic, electric, soundiferancic."

Thanks — Preceding unsigned comment added by 66.177.68.235 (talk) 04:26, 3 September 2012 (UTC)

I think it is a longstanding typographical error or something like that. A quick google search: [4] shows that the word exists only in the Wikipedia article on Bauxite and websites that directly copied the Wikipedia article. I'm not sure what it is trying to say, but I think you'd be safe removing the word entirely. It looks like gibberish. --Jayron32 04:36, 3 September 2012 (UTC)

It was part of a particularly nasty little vandalism edit by an anonymous editor in June (see [5]) that apparently nobody ever caught. It's a good thing that editor added the clearly nonsense word "soundiferancic," because the other things changed in that edit were not so obvious. I've reverted those changes. —Bkell (talk) 04:51, 3 September 2012 (UTC)

Good catch! --Jayron32 05:02, 3 September 2012 (UTC)

anatomy

is anatomy include in life science subject? i am a student of msc.(med.) anatomy .can i get some information about scope of anatomy? and can i give gate examination? — Preceding unsigned comment added by 117.224.24.237 (talk) 13:06, 3 September 2012 (UTC)

Anatomy can be classed as a life science according to our list. Does our article Anatomy help with your second question? If by "can I give gate examination" you're asking whether you can sit the Graduate Aptitude Test in Engineering, or use the results of that test for some purpose, you will need to discuss this with the university, college or examining board concerned. - Karenjc 14:35, 3 September 2012 (UTC)

Extinction

How often do they record that a species has gone extinct? Is there a place where they announce it every time when a species is recorded to have gone extinct? --Theurgist (talk) 15:24, 3 September 2012 (UTC)

This tool may not be precisely what you had in mind (and I hope others will make better suggestions), but you can search by many variables. For example, under "Assessment" you can choose "EX" (extinct) and one or more years (e.g. 2012) - that combination lists 138 new entries for extinct species in 2012. If they have a web service, you could conceivably automate the search and detect new entries. Perhaps registered users can get notifications - I have not registered. -- Scray (talk) 16:21, 3 September 2012 (UTC)

Which of these species has gone extinct, and which has merely moved on through evolution?

The question will also depend on what you mean by extinction. Homo erectus is extinct, but we are descendants of theirs, so they did not all die without progeny that are still living. This PBS website suggests the average mammal species exists for one million years, with ten million as about the maximum: http://www.pbs.org/wgbh/evolution/library/03/2/l_032_04.html On that basis almost all species that have ever existed are extinct. μηδείς (talk) 19:38, 3 September 2012 (UTC)

No, I don't mean million-year-long evolution; I mean reports that critically endangered or extinct in the wild species have gone extinct due to the death of the last known organism. --Theurgist (talk) 05:31, 4 September 2012 (UTC)

Gone extinct? this seems an odd expression, maybe it is because I have gone old that I find it difficult to accept. (with thanks to Lynne Fotheringham). Either species go or they become extinct. Richard Avery (talk) 07:16, 4 September 2012 (UTC)

I think the nearest thing to an "official announcement" of extinction will be found in the IUCN Red List that Scray linked to above. Gandalf61 (talk) 08:56, 4 September 2012 (UTC)

Even then, how would we treat the "extinction" of Homo erectus? Erectus colonized Africa and Eurasia. See human evolution. A subpopulation in Africa evolved into Homo sapiens. As it spread out of Africa, prexisting populations of Erectus in Asia dwindled, and went extinct. (This is the out-of-Africa theory, which not all people accept, but it is an example of a mechanism no one doubts exists.) Eventually there were very small pockets of Homo erectus, rare, and distinct from modern humans. So, did they actually go extinct? Or were they replaced by their own offspring? There are on the order of some 27 or so species in the clade Hominina which makes up all human ancestors more recent than our common ancestor with the chimpanzees. Are 26 of those species extinct? Or are only the ones that didn't evolve into us extinct? When a lineage goes extinct, as in the pterosaurs, the ammonites, and the trilobites, then the lineage is extinct. But are the dinosaurs extinct? It is not a clearcut distinction, and rigourous definitions are necessary.μηδείς (talk) 17:32, 4 September 2012 (UTC)

Speciation is very difficult to define (it is based on whether different parts of a population can reproduce together, but that is rarely a simple yes/no thing) and we draw quite arbitrary lines between species. Once you have an arbitrary line, it is fairly easy to define extinction, but it does depend heavily on where you draw that line. --Tango (talk) 11:24, 5 September 2012 (UTC)

Darold Treffert speculative claims regading genetic memory

I refer to this article, the last 3 or 4 paragraphs. Anyone has any insight or comments? Such claims call for some sort of response. Zarnivop (talk) 17:57, 3 September 2012 (UTC)

I don't think you will find many scientists who take that idea seriously. The argument is similar to the one Plato gave in his dialog Meno, where Socrates asks a slave a series of questions that purport to reveal inborn knowledge. There is of course a large amount of information encoded in the genome, but not many people would say it is likely that it takes such an explicit form. Looie496 (talk) 19:02, 3 September 2012 (UTC)

Well, it's science. Such claims can be verified. I find it unrealistic as it is, go accept that some 2Gb are enough to code a human being. To go further and require the poor 2Gb to contain "genetic memory" turns unrealistic to plain miraculous. Zarnivop (talk) 19:16, 3 September 2012 (UTC)

Both answers above seem more skeptical than they need be. There is no reason to discard offhand the possibility that some of our abilities are innate. This is not a new idea. See Nature versus nurture. Dauto (talk) 00:57, 4 September 2012 (UTC)

I didn't mean to deny that some of our abilities are innate: if nothing else, our ability to learn must be innate, or we could never even get started. I meant to deny that the ability to play the piano or to do fancy mathematics are innate. Looie496 (talk) 03:07, 4 September 2012 (UTC)

There are 4 different things that might be called "genetic memory", in humans:

1) One is covered under Genetic memory (biology)#In animals, dealing with immunity to disease, but this type is not passed on to the next generation.

2) A second is instinct, which has been known about for a very long time. This could seem like passed down memories, in some cases, as in you possibly being terrified by snakes along with previous generations, but the reality is that this tendency was passed down to all the generations because those who lacked this trait died out from encounters with venomous serpents. The origin of such traits is just mutations, not memories, but such mutations are selected for and thus passed down preferentially.

3) Epigenetics is the third, where the genes are changed in one generation, and passed down to others, as a result of experiences in that first generation. I believe periods of starvation are one such experience which changes the epigenetic code.

4) However, actually being able to recall what happened to a previous generation seems to be pure fantasy. See genetic memory (psychology). StuRat (talk) 03:00, 4 September 2012 (UTC)

Treffert claims clearly relate to #4 in your list, hence the strong skepticism. Zarnivop (talk) 05:50, 4 September 2012 (UTC)

There's also the idea of Memory RNA, based on experiments with "trained" flatworms being ground-up and fed to other worms who apparently showed the same learned behaviour. The work was done by James V. McConnell, who became a target of the Unabomber. Stress related proteins seem a more plausible explanation for the findings.

Treffert mentions memory of the "rules" of maths and music. I have no problem accepting that these are in part genetically encoded, change the frequencies of the notes used in a piece of music to random values and it will sound awful, even to a baby, we perceive certain frequency ratios as pleasant and I doubt this is simply based on experience. As for maths, clearly our brains have the capacity to perform maths, and the rules of maths are not some arbitrary conventions that we can change at will, so it's not impossible that evolution has "favoured brain structures implementing these rules", so to speak. But I wouldn't call it memory, it is something we are born with. Ssscienccce (talk) 16:12, 4 September 2012 (UTC)

Yes, I'd call it instinct. Basic counting, addition, subtraction, and perhaps multiplication and division may be instinctive in humans, since counting the number of lobes on the leaves on a plant, knowing if everyone is present, dividing food up evenly, etc., were important survival skills. Higher math is not. StuRat (talk) 19:45, 4 September 2012 (UTC)

Assassin's Creed uses "genetic memory" as a cute plot device to explain video-game rules, but it's not science. Human DNA actually holds only 3 x 10⁹ base pairs of information - i.e. 6 gigabytes. For people who download videos off the Internet that's not really a lot of storage space! And there's a reason - all genetic memory, whatever it is, has to fit in one tiny little sperm and one relatively small egg (0.12 mm = 0.0000017 cc) - the adult brain (about 1200 cc) has 700,000,000 times more space to hold information. Wnt (talk) 23:47, 4 September 2012 (UTC)

Principle of relativity

The (special) principle of relativity says that the laws of physics take the same form in any two inertial reference frames.

Can this principle be (slightly) generalized to say that the laws of physics take the same form in any two reference frames (possibly non-inertial) provided they move relative to one another at a constant velocity?

My gut feeling says that it's true, but a) I can't find a way to justify it, and b) I know that two observers that move relative to one another at a constant velocity in one reference frame might be accelerating relative to one another in another reference frame. This gives me some doubts... 65.92.7.148 (talk) 22:15, 3 September 2012 (UTC)

You may find the topics of Lorentz covariance and Noether's theorem to be of interest. Also General relativity and the Equivalence principle. All of those topics deal with the laws of physics as they apply to different frames of reference. --Jayron32 22:19, 3 September 2012 (UTC)

The generalization is certainly true. Your statement (b) is not true. Any combination of linear transformations gives a net result that is a linear transformation. Looie496 (talk) 22:24, 3 September 2012 (UTC)

But linear transformations keep you in inertial reference frames. What if you go from an inertial frame to a non-inertial one? 65.92.7.148 (talk) 23:08, 3 September 2012 (UTC)

Yes, you are right, if non inertial frames are considered, than two objects might be accelerating with respect to each other (that is the second derivative with respect to time of the distance between them is not zero) in on frame, while not accelerating with respect to each other in another frame.Dauto (talk) 00:08, 4 September 2012 (UTC)

To answer the OP, yes the laws of physics take the same form in any frame (whether its inertial or not) within General Relativity. Dauto (talk) 00:08, 4 September 2012 (UTC)

What if we restrict ourselves to just special relativity? 65.92.7.148 (talk) 01:04, 4 September 2012 (UTC)

I'm not sure I understand the question, but consider the following analogy: you can do Euclidean geometry using Cartesian x, y coordinates, and write down various equations expressing that a particular shape is a square, or whatever. If you pick a different Cartesian coordinate system x', y', those equations will be the same, except with ' after each x or y. You can say "the laws of Euclidean geometry take the same form in any Cartesian coordinate system", which is another way of saying that Euclidean geometry isn't affected by rotation or translation (since the Cartesian coordinate systems are related by rotation and translation). On the other hand if you pick some other wonky coordinate system p, q (it could be bipolar coordinates or something), the equations will look different, but they will look the same as if you'd used a wonky coordinate system p', q' which is related to p, q by rotation and translation. This isn't a generalization, it's just a consequence of what we already knew: Euclidean geometry isn't affected by rotation or translation. But the formulas for p' and q' in terms of p and q aren't going to be the same as the formulas for x' and y' in terms of x and y, so in that sense the relationship between the coordinate systems isn't the same. -- BenRG (talk) 02:15, 4 September 2012 (UTC)

If two reference frames are moving at constant velocity with respect to each other, they must have the same acceleration at all times. That's because the integral of a2-a1 can only be constant if a2-a1 is 0. So your question is really "if frame A is accelerating at 5 m/s^2, and frame B is accelerating at 5 m/s^2, do the same laws of physics apply in both?" The answer is trivially "yes", because what's going to differentiate the two frames? --128.112.70.118 (talk) 02:49, 7 September 2012 (UTC)