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Post by principled on Oct 24, 2011 18:17:09 GMT 1
During an interview this morning on Radio 4, prof Brian Cox said that QM should be taught in schools. I'm not convinced. I contest that Newtonian mechanics and conventional views of atomic structures are sufficient for almost all everyday situations and most technologies. If we could get those theorems across we'd really be making progress. What would QM bring to the secondary school party?
P
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Post by Progenitor A on Oct 24, 2011 18:32:44 GMT 1
During an interview this morning on Radio 4, prof Brian Cox said that QM should be taught in schools. I'm not convinced. I contest that Newtonian mechanics and conventional views of atomic structures are sufficient for almost all everyday situations and most technologies. If we could get those theorems across we'd really be making progress. What would QM bring to the secondary school party? P A healthy scepticism of self-confident dogmatic scientists like Hawking and Dawkins?
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Post by abacus9900 on Oct 24, 2011 19:59:26 GMT 1
Brian Cox seems a nice bloke but I tend to think he assumes other people will be as interested in something as obtuse as QM as him. I think you have to have a special interest in subjects like this which are highly theoretical and also very mathematical if you really want to get into them. I agree to some extent with principled in that traditional physics is enough as a starting point, at least for most people. QM can easily wonder into philosophy which may be good for mental exercise but leads nowhere in the end, as we have frequently seen in debates on this MB.
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Post by principled on Oct 24, 2011 20:56:11 GMT 1
Nay, You are obviously an optimist at heart! First you'd have to have a few lessons and a video to show the students who Einstein was, let alone Hawking! Abacus I agree with you. Not everyone is interested in science at any level, so if one starts talking about things that are counter-intuitive to mere mortals, one is likely to make all but the brightest students very sceptical about science in general. Prof Cox may find QM and physics quite straightforward, but he's talking from a slightly more elevated perspective than Mr/Miss Average student. P
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Post by marchesarosa on Nov 26, 2011 13:01:32 GMT 1
I just came across this on Lubos Motl's blog and thought you folks might be interested! The Fabric of the Cosmos: Quantum Leap
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Post by nickrr on Nov 26, 2011 18:33:29 GMT 1
Quantum mechanics is arguably the most successful theory in science but, as you say, it's completely counter-intuitive. I think that this is a useful lesson - it shows that human common sense is not necessarily a reliable tool for determining the reality of nature.
It also shows very clearly one of the basic principles of science - the facts are all that matter. If the facts say something is true, it doesn't matter whether we like it or not or whether it makes sense to us.
Whether this should be taught to all students is debatable but certainly anyone doing a science course at, say, A level, would benefit from these insights.
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Post by mak2 on Nov 28, 2011 15:43:52 GMT 1
The phrase "trying to run before you can walk" comes to mind. The average school pupil should certainly be made aware that there is more to physics than Newtonian mechanics but should be told to learn traditional science first and leave most of QM to be studied in higher education, if they are so inclined. There is a terrible tendency in education nowadays to teach the basics inadequately, missing out the more difficult bits, and then get on to an even more superficial treatment of the advanced stuff.
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Post by striker16 on Nov 28, 2011 17:48:36 GMT 1
What it seems to be saying is that at the quantum level, time and space do not exist, otherwise how could one particle influence another particle (which could be anywhere in the universe) instantaneously? The speed of light becomes irrelevant!
Maybe then, time and space are only a convenience at the macro level and really an illusion.
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Post by mak2 on Nov 29, 2011 10:38:39 GMT 1
Quantum mechanics is certainly very strange. I would not say that space and time do not exist, except in the sense that what exists is space-time, rather than separate space and time. The speed of light and space-time are relevant to most things but not, it seems, to the very special situations where there is quantum entanglement.
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Post by striker16 on Nov 29, 2011 11:17:03 GMT 1
Quantum mechanics is certainly very strange. I would not say that space and time do not exist, except in the sense that what exists is space-time, rather than separate space and time. The speed of light and space-time are relevant to most things but not, it seems, to the very special situations where there is quantum entanglement. What entanglement shows is that there must be some level of reality where space and time isn't having any effect since one particle doesn't seem to be in separation from another. If measuring the spin of particle a causes an instant measurement (in effect) of particle b it's as if the universe is an unbroken whole and space and time, in terms of what we call 'spacetime', does not operate. Whatever it is that is making particle b react to measuring particle a doesn't seem to know about spacetime and doesn't find it a barrier. It's as if the two particles are still acting as one 'system' even though they are on opposite sides of the universe. The implication of this seems to be that someone on earth can affect reality in another part of the universe by simply making a measurement with two or more entangled particles! Incredible. No wonder Einstein didn't like the idea.
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Post by robinpike on Nov 29, 2011 13:30:57 GMT 1
Quantum mechanics is arguably the most successful theory in science but, as you say, it's completely counter-intuitive. I think that this is a useful lesson - it shows that human common sense is not necessarily a reliable tool for determining the reality of nature. It also shows very clearly one of the basic principles of science - the facts are all that matter. If the facts say something is true, it doesn't matter whether we like it or not or whether it makes sense to us. Whether this should be taught to all students is debatable but certainly anyone doing a science course at, say, A level, would benefit from these insights. I'm all for QM being taught to as many students as possible, for some of those students will undoubtably be smart enough to point out that QM is an interpretation of the facts - and not in itself a fact. And I am sure some of those students would also argue that QM is not a successful theory, for if it were, then we would be able to use it to model any atom / molecule of our choosing - but it cannot do that, can it!
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Post by striker16 on Nov 29, 2011 16:13:02 GMT 1
Robin, according to the video QM is one of the most successful theories in the history of science and has been tested again and again.
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Post by marchesarosa on Nov 29, 2011 17:52:52 GMT 1
Lubos Motl discusses QM including part of a lecture byRrichard Feynman and another by Alain Aspect motls.blogspot.com/2011/11/feynman-on-qm-in-1964.html#moreFeynman on QM in 1964 Whenever I want to mention Richard Feynman's attitude to the foundations of quantum mechanics, I typically point to this four-minute interview with an older Feynman. He says that physics at the fundamental quantum level is so fantastically different from anything we have seen before. There's still a school of thought that doesn't want to believe that those rules are fundamental and wants to find out some mundane things beneath all the phenomena. This effort is due to their deep prejudice, Feynman says, and they will be defeated because Nature's imagination is much greater than Man's. She will never let us relax. Decades later, those prejudiced people still haven't made any insight about Nature that would go in their preconceived direction but as the human population has dumbed down, it's also true that they have failed to be defeated. This anti-quantum stupidity is at least as alive as it was during Feynman's life. An 8-minute beginning of the lecture However, it's also interesting to listen to pretty much the same things that Feynman said in his 1964 Messenger Lectures at Cornell. The degree of constancy of his opinions is remarkable – and one could say that when it comes to topics that rapidly evolved during his later years, this constancy was too much of a good thing. If you want to see the whole lecture, open your Microsoft Internet Explorer (with Silverlight) and go to Bill Gates' Project Tuva in it. Or open the Tuva page in Chrome and click at the icon of the IE Multi Tab extension that you previously installed. Then click at Feynman's (not Gates') photograph and choose lecture 6, Probability and Uncertainty, the Quantum Mechanical View of Nature. In the beginning, he says that it shouldn't have been unexpected that the fundamental laws of Nature look ever more unintuitive. But the students in the room shouldn't try to "understand" what Feynman is saying in the sense of trying to create a model in terms of something they already know. There's nothing like that. They should appreciate Nature how She really is. And She's delightful and sexy and whoever doesn't see this sexiness is a physics faggot. The bulk of the lecture is dedicated to the double-slit experiment which knows about all the delightful aspects of the particles' quantum behavior. And indeed, it does. Around 50:00, he also explains the concept of "hidden-variable" theories and demonstrates that this is not a possible description of Nature. The reason is simple: if it were in principle possible to predict in advance whether the electron would be observed in the slit #1 or slit #2 (assuming that the photon trackers are added), then it would inevitably imply that the experiment in the absence of photon trackers has to produce the N1+N2 dull juxtaposition on the screen instead of the nice N12 interference pattern. You don't need any idealized experiments with qubits; the double-slit experiment is enough to falsify all such fundamentally misguided theories. The probabilistic character of the predictions seems to be Nature's intrinsic property; it is not due to the lack of knowledge of the internal wheels and gears. As someone said, Nature Herself doesn't know which way it will go. Deliciously enough, near 52:10, Feynman mentions that a (pompous) philosopher once said (in a deep authoritarian voice) that it is necessary for the processes in science to produce the same results from the same conditions. Well, they don't, Feynman responds. ;-) He even constructs a thought experiment in which the World War III (something important) depends on this quantum random outcome. No amount of science can settle it, anyway. The future of the world is unpredictable. Science isn't about obeying arbitrary philosophical preconditions; it depends on the ability to do experiments, on honesty in reporting them and on intelligence in interpreting them. However, it must be a non-dogmatic kind of intelligence that is not sure ahead of time what the results should be. Finite bias is OK because a finite amount of accumulated evidence will ultimately push a biased person to give up and accept the truth. ;-) The debunking of various influential pseudoscientific hypotheses such as the hidden-variable theories should become a standard part of the QM and other courses, I think. Throughout 47 years after Feynman's Messenger Lectures, the public has made no positive progress in understanding the basic framework of modern physics. Quite on the contrary. Alain Aspect, the well-known boss of an Atom Optiques institute in France, gave a 55-minute talk at the Israel's Technion in August 2011. It focuses on the wave-particle duality, petty much the same topic as Feynman's lecture above. Aspect reviewed the history of light as particles and waves. Then he discussed experiments with individual photons; Feynman was the only one who immediately told him what would happen in the experiments, Aspect recalls. Finally, we learn about Wheeler's delayed choice experiments. motls.blogspot.com/2010/11/delayed-choice-quantum-eraser.html Bohr's complementarity principle is shown in action.
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Post by robinpike on Nov 30, 2011 14:14:48 GMT 1
Robin, according to the video QM is one of the most successful theories in the history of science and has been tested again and again. The problem is that QM theory has two parts (as do most theories): it predicts an outcome; and it gives an explanation as to how that outcome came about. It is that second bit that I disagree with. For example, in the two slit experiment, rather than the light (or electrons etc) having 'quantum behaviour', a more likely explanation would be that the atoms in the material of the barrier affect the path of the light... Take away some of that material to make a second slit, and the influence on the light by the atoms overall changes. Place a detector next to one of the slits to determine the path of the light, and the influence on the light by the atoms overall in the detector and in the barrier changes.
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Post by striker16 on Nov 30, 2011 15:18:33 GMT 1
Robin, according to the video QM is one of the most successful theories in the history of science and has been tested again and again. The problem is that QM theory has two parts (as do most theories): it predicts an outcome; and it gives an explanation as to how that outcome came about. It is that second bit that I disagree with. For example, in the two slit experiment, rather than the light (or electrons etc) having 'quantum behaviour', a more likely explanation would be that the atoms in the material of the barrier affect the path of the light... Take away some of that material to make a second slit, and the influence on the light by the atoms overall changes. Place a detector next to one of the slits to determine the path of the light, and the influence on the light by the atoms overall in the detector and in the barrier changes. How do you explain the interference pattern at the photosensitive plate behind the slits? This shows that the photon or whatever, was travelling as a wave and in many places at once, passing through both slits simultaneously, not as a single particle. I'm still a bit confused, however. If, by interacting with the environment, a particle in a number of probabilistic locations at the same time 'collapses' to just one specific position how come that when the barrier is met (not the slits) the photon does not collapse but carries on as a wave through the slits to reach the plate beyond the double slits? Surely a collision with the solid part of the double slit screen will constitute a 'measurement.' What have I misunderstood?
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