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#41 |
Philosopher
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"I know my brain cannot tell me what to think." - Scorpion "Nebulous means Nebulous" - Adam Hills |
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#42 |
Penultimate Amazing
Join Date: Apr 2004
Posts: 11,055
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I know something about the no cloning theorem. It is not really relevant, because what we are talking about is not necessarily an exact copy of the book.
If I have the unburned copy of the book in front of me then I could produce a word for word copy of the book. If I have the remnants, ashes, light, heat etc, then there is no way even in principal ( as I understand it) that I could produce that word for word copy of the book. So that information - the words and the order they were in - was accessible when the book was unburned and thus represents information that is lost when the book is burned. |
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The non-theoretical character of metaphysics would not be in itself a defect; all arts have this non-theoretical character without thereby losing their high value for personal as well as for social life. The danger lies in the deceptive character of metaphysics; it gives the illusion of knowledge without actually giving any knowledge. This is the reason why we reject it. - Rudolf Carnap "Philosophy and Logical Syntax" |
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#43 |
Penultimate Amazing
Join Date: Apr 2004
Posts: 11,055
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Not really. I don't buy that the encyclopedia contains information about its eventual fate. An encyclopedia might be burned, rot away or be pulped. A burned encyclopedia might end up in all sorts of configurations of ashes light and heat.
OK, you might say that the information resides, not just in the encyclopedia, but also in a sufficiently large portion of its surrounding environment. But again, if you could, in principle, predict the eventual fate of the encyclopedia from information about the book (and enough of its surrounding environment) it would also imply that you could, in principle, get that information at an arbitrarily high precision. |
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The non-theoretical character of metaphysics would not be in itself a defect; all arts have this non-theoretical character without thereby losing their high value for personal as well as for social life. The danger lies in the deceptive character of metaphysics; it gives the illusion of knowledge without actually giving any knowledge. This is the reason why we reject it. - Rudolf Carnap "Philosophy and Logical Syntax" |
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#44 |
Penultimate Amazing
Join Date: Apr 2004
Posts: 11,055
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I don't think people here get what confuses me.
We have three statements: 1. It is possible in principle to do A 2. It is not possible, even in principle, to do B 3. In order to do A it is necessary to do B At least one of these statements must be wrong. |
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The non-theoretical character of metaphysics would not be in itself a defect; all arts have this non-theoretical character without thereby losing their high value for personal as well as for social life. The danger lies in the deceptive character of metaphysics; it gives the illusion of knowledge without actually giving any knowledge. This is the reason why we reject it. - Rudolf Carnap "Philosophy and Logical Syntax" |
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#45 |
Penultimate Amazing
Join Date: Apr 2004
Posts: 11,055
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Anyway, I think I understand better now. It is best to think of it in terms of a single particle in a single dimension.
If I have the quantum state of a single particle in one dimension and the expectation value for position then I could evolve it forward and get the quantum state at a future date with the expectation value of where the particle would be then. Then I could start with the future quantum state and evolve it backwards and get my original quantum state with the same expectation value. So Laplace's Demon doesn't need information about a particular momentum and position, rather he needs the quantum state - the probability distribution. Similarly, in order to get back to the encyclopedia Laplace's Demon would not need a particular state of ashes and light, but rather a probability distribution of all the ways that the ashes and light could be as a result of the encyclopedia burning. |
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The non-theoretical character of metaphysics would not be in itself a defect; all arts have this non-theoretical character without thereby losing their high value for personal as well as for social life. The danger lies in the deceptive character of metaphysics; it gives the illusion of knowledge without actually giving any knowledge. This is the reason why we reject it. - Rudolf Carnap "Philosophy and Logical Syntax" |
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#46 |
Penultimate Amazing
Join Date: Aug 2007
Posts: 39,678
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It's possible to have a fully-assembled jigsaw puzzle. It's possible to know it's fully assembled, even if the exact shape of all the puzzle pieces is somehow not known. It's also possible to have the same puzzle, disassembled, in any number of configurations of pieces. But even though you may not be able to reassemble it, the principle of conservation of information tells you that all the pieces are still there.
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#47 |
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#48 |
Penultimate Amazing
Join Date: Jun 2003
Posts: 44,866
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But we're talking about an exact copy of all the information in the book. The same math still applies.
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The difficulty is that the relevant information (the words) and the irrelevant information gets scrambled together when it burns. You can't pick out just the relevant information like you can when you read the book, you need ALL of it in order to untangle it. And it all exists, but you can't get it all. |
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"As long as it is admitted that the law may be diverted from its true purpose -- that it may violate property instead of protecting it -- then everyone will want to participate in making the law, either to protect himself against plunder or to use it for plunder. Political questions will always be prejudicial, dominant, and all-absorbing. There will be fighting at the door of the Legislative Palace, and the struggle within will be no less furious." - Bastiat, The Law |
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#49 |
Penultimate Amazing
Join Date: Apr 2004
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The non-theoretical character of metaphysics would not be in itself a defect; all arts have this non-theoretical character without thereby losing their high value for personal as well as for social life. The danger lies in the deceptive character of metaphysics; it gives the illusion of knowledge without actually giving any knowledge. This is the reason why we reject it. - Rudolf Carnap "Philosophy and Logical Syntax" |
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#50 |
Penultimate Amazing
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#51 |
Penultimate Amazing
Join Date: Apr 2004
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But so what?
I am not doubting that all the pieces of the burned book are still there, I am doubting that their prior arrangement could, in principle, be retrieved from the remains because that would imply that we could, in principle, access information about the remains to an arbitratily high precision. Sent from my Moto C using Tapatalk |
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The non-theoretical character of metaphysics would not be in itself a defect; all arts have this non-theoretical character without thereby losing their high value for personal as well as for social life. The danger lies in the deceptive character of metaphysics; it gives the illusion of knowledge without actually giving any knowledge. This is the reason why we reject it. - Rudolf Carnap "Philosophy and Logical Syntax" |
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#52 |
Penultimate Amazing
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#53 |
Penultimate Amazing
Join Date: Apr 2004
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The non-theoretical character of metaphysics would not be in itself a defect; all arts have this non-theoretical character without thereby losing their high value for personal as well as for social life. The danger lies in the deceptive character of metaphysics; it gives the illusion of knowledge without actually giving any knowledge. This is the reason why we reject it. - Rudolf Carnap "Philosophy and Logical Syntax" |
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#54 |
Penultimate Amazing
Join Date: Apr 2004
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We are talking about a claim often made by physicists that if you burned a book " if you were able to capture every bit of light and ash that emerged from the fire, in principle you could exactly reconstruct everything that went into it, even the print on the book pages."
For the purposes of the current discussion we only need to know if you can reconstruct any information that you could have observed when the book was intact. Something we couldn't observe in principle when the book was intact is beside the point. Some information like "What this encyclopedia says Albert Einstein's birthday is" is something that we can easily observe when the encyclopedia is intact. After it is burned, it is not so easy. But physicists say that it is, in principle, still possible to reconstruct what this encyclopedia says Albert Einstein's birthday is even after it is burned. I say that this appears to contradict the Heisenberg Uncertainty Principle, ie that if you could, in principle, get back that data from the remains it would imply that you could, in principle, get at information about the remains like momentum and position to an arbitrarily high precision. But, as I understand it, it is not even in principle possible to know the position and momentum of a particle to an arbitrarily high precision. |
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The non-theoretical character of metaphysics would not be in itself a defect; all arts have this non-theoretical character without thereby losing their high value for personal as well as for social life. The danger lies in the deceptive character of metaphysics; it gives the illusion of knowledge without actually giving any knowledge. This is the reason why we reject it. - Rudolf Carnap "Philosophy and Logical Syntax" |
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#55 |
Penultimate Amazing
Join Date: Apr 2004
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The non-theoretical character of metaphysics would not be in itself a defect; all arts have this non-theoretical character without thereby losing their high value for personal as well as for social life. The danger lies in the deceptive character of metaphysics; it gives the illusion of knowledge without actually giving any knowledge. This is the reason why we reject it. - Rudolf Carnap "Philosophy and Logical Syntax" |
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#56 |
Penultimate Amazing
Join Date: Apr 2004
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Again:
Originally Posted by Robin
B="Access information about a physical state to an arbitrarily high precision" So I am unclear on anyone's position on this which means I am still at the question I asked in my OP. Is it "There is no contradiction between those statements"? Or is it "Yes there is a contradiction between those statement, one or more is wrong"? If the latter case then which statement is wrong? |
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The non-theoretical character of metaphysics would not be in itself a defect; all arts have this non-theoretical character without thereby losing their high value for personal as well as for social life. The danger lies in the deceptive character of metaphysics; it gives the illusion of knowledge without actually giving any knowledge. This is the reason why we reject it. - Rudolf Carnap "Philosophy and Logical Syntax" |
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#57 |
Penultimate Amazing
Join Date: Apr 2004
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OK, lets get this clear. Here is the statement from Sean Carroll again that I referenced in the OP:
Originally Posted by Sean Carroll
Then what principle is he referencing here, if any? |
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The non-theoretical character of metaphysics would not be in itself a defect; all arts have this non-theoretical character without thereby losing their high value for personal as well as for social life. The danger lies in the deceptive character of metaphysics; it gives the illusion of knowledge without actually giving any knowledge. This is the reason why we reject it. - Rudolf Carnap "Philosophy and Logical Syntax" |
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#58 |
Penultimate Amazing
Join Date: Jan 2003
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A fool thinks himself to be wise, but a wise man knows himself to be a fool. William Shakespeare |
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#59 |
Penultimate Amazing
Join Date: Jun 2003
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Note the conditional. If that condition isn't satisfied, then nothing else follows.
Quote:
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"As long as it is admitted that the law may be diverted from its true purpose -- that it may violate property instead of protecting it -- then everyone will want to participate in making the law, either to protect himself against plunder or to use it for plunder. Political questions will always be prejudicial, dominant, and all-absorbing. There will be fighting at the door of the Legislative Palace, and the struggle within will be no less furious." - Bastiat, The Law |
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#60 |
Penultimate Amazing
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"As long as it is admitted that the law may be diverted from its true purpose -- that it may violate property instead of protecting it -- then everyone will want to participate in making the law, either to protect himself against plunder or to use it for plunder. Political questions will always be prejudicial, dominant, and all-absorbing. There will be fighting at the door of the Legislative Palace, and the struggle within will be no less furious." - Bastiat, The Law |
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#61 |
Featherless biped
Join Date: Aug 2008
Location: Aporia
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Appreciating your posts here, Ziggurat.
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Click here to help our friend Foolmewunz and his family in his health crisis |
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#62 |
Penultimate Amazing
Join Date: Jun 2003
Posts: 44,866
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But the jigsaw can't be put together more than one way. Time reversal symmetry (or more specifically, CPT symmetry) means that for the present to have more than one possible past, it would also need to have more than one possible future. And that would require that the laws of physics are not deterministic. But as far as we can tell, they are deterministic.
Quantum mechanics measurements look random (wave function collapse), but that only happens when you stop doing quantum mechanics. Wave function collapse is a heuristic for getting from your quantum mechanical description to a non-quantum description, there's no reason to think that there's an actual collapse process. |
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"As long as it is admitted that the law may be diverted from its true purpose -- that it may violate property instead of protecting it -- then everyone will want to participate in making the law, either to protect himself against plunder or to use it for plunder. Political questions will always be prejudicial, dominant, and all-absorbing. There will be fighting at the door of the Legislative Palace, and the struggle within will be no less furious." - Bastiat, The Law |
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#63 |
Penultimate Amazing
Join Date: Apr 2004
Posts: 11,055
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Here is how I understand the HUP:
"He also famously enunciated the uncertainty principle, which states that the more accurately one were to measure, say, the position of a quantum particle, the more uncertain becomes one’s knowledge of its momentum, and vice versa." That is from Feynman. Sent from my Moto C using Tapatalk |
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The non-theoretical character of metaphysics would not be in itself a defect; all arts have this non-theoretical character without thereby losing their high value for personal as well as for social life. The danger lies in the deceptive character of metaphysics; it gives the illusion of knowledge without actually giving any knowledge. This is the reason why we reject it. - Rudolf Carnap "Philosophy and Logical Syntax" |
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#64 |
Penultimate Amazing
Join Date: Apr 2004
Posts: 11,055
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The non-theoretical character of metaphysics would not be in itself a defect; all arts have this non-theoretical character without thereby losing their high value for personal as well as for social life. The danger lies in the deceptive character of metaphysics; it gives the illusion of knowledge without actually giving any knowledge. This is the reason why we reject it. - Rudolf Carnap "Philosophy and Logical Syntax" |
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#65 |
Penultimate Amazing
Join Date: Apr 2004
Posts: 11,055
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If our particles behaved like classical objects you might have something like the following:
https://photos.app.goo.gl/qZRZE4r1u1FsbdbN6 And if so you could measure information about the later states and work back and find the original: https://photos.app.goo.gl/DnFyXT7vEA2kS57z6 However if there was a limit to the precision to which you could measure these then you could not get back the original, not even close. So this is what you cannot do in a quantum system. So what is the information about the later states that would allow you to get back and read the original word? Certainly no kind of measurement would allow you to do this. I suggested earlier that if you knew the quantum state at the end you could evolve it backwards and get the quantum state at the start. Is that what Carroll means? |
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The non-theoretical character of metaphysics would not be in itself a defect; all arts have this non-theoretical character without thereby losing their high value for personal as well as for social life. The danger lies in the deceptive character of metaphysics; it gives the illusion of knowledge without actually giving any knowledge. This is the reason why we reject it. - Rudolf Carnap "Philosophy and Logical Syntax" |
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#66 |
Penultimate Amazing
Join Date: Jun 2003
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We can get pretty close. For example, you can measure if an electron is in the ground state of a hydrogen atom. We know that wave function with incredibly high precision.
But we can’t solve any quantum 3 body problems exactly (true in many classical cases as well), and even some 2 body problems have to be approximated, so we can’t get to exact. But there’s no theoretical limit on how close we can get. |
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"As long as it is admitted that the law may be diverted from its true purpose -- that it may violate property instead of protecting it -- then everyone will want to participate in making the law, either to protect himself against plunder or to use it for plunder. Political questions will always be prejudicial, dominant, and all-absorbing. There will be fighting at the door of the Legislative Palace, and the struggle within will be no less furious." - Bastiat, The Law |
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#67 |
Penultimate Amazing
Join Date: Apr 2004
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So you are saying that if you have, say, three particles in a closed system then theoretically you could do a measurement on them and infer the quantum state so that you could evolve it back arbitrarily far back in time and find the prior quantum state of those three particles?
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The non-theoretical character of metaphysics would not be in itself a defect; all arts have this non-theoretical character without thereby losing their high value for personal as well as for social life. The danger lies in the deceptive character of metaphysics; it gives the illusion of knowledge without actually giving any knowledge. This is the reason why we reject it. - Rudolf Carnap "Philosophy and Logical Syntax" |
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#68 |
Philosopher
Join Date: Nov 2006
Posts: 9,357
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Someone may have made this point already. Ziggurat mentioned "knowing the end state of a system". The current complete end state of the age of the dinosaurs would involve knowing about photons that are currently millions of light years away and we have no hope of ever "catching up" to.
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#69 |
Penultimate Amazing
Join Date: Jun 2003
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You would need to know quite a lot about the system to begin with in order to arrange an appropriate measurement. The accuracy of your solution would be constrained by your calculation methods, which would have to be numerical approximations since there aren't analytic solutions to 3-body quantum problems. Furthermore, many quantum systems are chaotic, so that linear growth in extrapolated time would require exponential growth in required computation. But otherwise, sure.
All that really means though is that quantum mechanics is deterministic. |
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"As long as it is admitted that the law may be diverted from its true purpose -- that it may violate property instead of protecting it -- then everyone will want to participate in making the law, either to protect himself against plunder or to use it for plunder. Political questions will always be prejudicial, dominant, and all-absorbing. There will be fighting at the door of the Legislative Palace, and the struggle within will be no less furious." - Bastiat, The Law |
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#70 |
Penultimate Amazing
Join Date: Apr 2004
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Say Alice models three particles moving in a confined space and starts with expectation values for the momenta and position of each particle and then evolves this system forward, say an hour or two, there would be for each particle one momentum and one position that was the expectation value for that particle?
So that Bob, without knowing the details of Alice's calculation, could get those expectation values and infer the calculation Alice was doing and evolve the system back to get to Alice's original values at significantly better accuracy than a random guess? That would surprise me. Alice would have the information to evolve the system back to it's original state, but I am surprised that Bob, knowing only the results of a measurement on the system, could do so. |
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The non-theoretical character of metaphysics would not be in itself a defect; all arts have this non-theoretical character without thereby losing their high value for personal as well as for social life. The danger lies in the deceptive character of metaphysics; it gives the illusion of knowledge without actually giving any knowledge. This is the reason why we reject it. - Rudolf Carnap "Philosophy and Logical Syntax" |
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#71 |
Penultimate Amazing
Join Date: Apr 2004
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Again, it my previous understanding that it was the evolution of the wave function in time that was deterministic and reversible, not individual observations made of that system.
Indeed there is a whole description of when to sum probabilities as interfering probabilities and when to sum them as non-interfering probabilities that would not make sense if this were not the case. Sent from my Moto C using Tapatalk |
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The non-theoretical character of metaphysics would not be in itself a defect; all arts have this non-theoretical character without thereby losing their high value for personal as well as for social life. The danger lies in the deceptive character of metaphysics; it gives the illusion of knowledge without actually giving any knowledge. This is the reason why we reject it. - Rudolf Carnap "Philosophy and Logical Syntax" |
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#72 |
Penultimate Amazing
Join Date: Jun 2003
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Why should that be so, if the laws of quantum mechanics are deterministic?
Well, in order to do any measurement, you need an interaction. Which means that if you want to model what happens during a measurement, you can't only model the system you're measuring, you have to model your measurement apparatus too, because the interaction affects the time evolution. So in order to trace what happens from after a measurement to before a measurement, you have to know not only what the system is doing, but what the measurement apparatus is doing. And how do you determine the quantum state of your measurement apparatus? You can't. You have to stop using quantum mechanics. Which is how the artifact of "wave function collapse" gets introduced as if it's a non-deterministic process, even though quantum mechanics is deterministic. |
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"As long as it is admitted that the law may be diverted from its true purpose -- that it may violate property instead of protecting it -- then everyone will want to participate in making the law, either to protect himself against plunder or to use it for plunder. Political questions will always be prejudicial, dominant, and all-absorbing. There will be fighting at the door of the Legislative Palace, and the struggle within will be no less furious." - Bastiat, The Law |
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#73 |
Penultimate Amazing
Join Date: Apr 2004
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Because, as I said, the thing that is deterministic is the evolution of the wave function in time and not the individual observation.
For example I have something that can emit an electron and a backplane that can detect an electron then there is one and one only probability distribution about where the electron will land on the backplane. There is not one and one only position on the backplane on which the electron will land. If this is not the case then I have seriously misunderstood quantum physics. |
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The non-theoretical character of metaphysics would not be in itself a defect; all arts have this non-theoretical character without thereby losing their high value for personal as well as for social life. The danger lies in the deceptive character of metaphysics; it gives the illusion of knowledge without actually giving any knowledge. This is the reason why we reject it. - Rudolf Carnap "Philosophy and Logical Syntax" |
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#74 |
Penultimate Amazing
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"As long as it is admitted that the law may be diverted from its true purpose -- that it may violate property instead of protecting it -- then everyone will want to participate in making the law, either to protect himself against plunder or to use it for plunder. Political questions will always be prejudicial, dominant, and all-absorbing. There will be fighting at the door of the Legislative Palace, and the struggle within will be no less furious." - Bastiat, The Law |
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#75 |
Penultimate Amazing
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The non-theoretical character of metaphysics would not be in itself a defect; all arts have this non-theoretical character without thereby losing their high value for personal as well as for social life. The danger lies in the deceptive character of metaphysics; it gives the illusion of knowledge without actually giving any knowledge. This is the reason why we reject it. - Rudolf Carnap "Philosophy and Logical Syntax" |
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#76 |
Penultimate Amazing
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The non-theoretical character of metaphysics would not be in itself a defect; all arts have this non-theoretical character without thereby losing their high value for personal as well as for social life. The danger lies in the deceptive character of metaphysics; it gives the illusion of knowledge without actually giving any knowledge. This is the reason why we reject it. - Rudolf Carnap "Philosophy and Logical Syntax" |
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#77 |
Penultimate Amazing
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The non-theoretical character of metaphysics would not be in itself a defect; all arts have this non-theoretical character without thereby losing their high value for personal as well as for social life. The danger lies in the deceptive character of metaphysics; it gives the illusion of knowledge without actually giving any knowledge. This is the reason why we reject it. - Rudolf Carnap "Philosophy and Logical Syntax" |
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#78 |
Penultimate Amazing
Join Date: Apr 2004
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We could start with something easy.
Say we have a wave packet for a single particle moving through free space. As it evolves through time the wave packet spreads (as I understand it). You can take a measurement of this and then from the measurement infer the shape of the wave packet and evolve it back to get the original wave packet. So how do you go about it? How do you get a measure of how spread out the wave packet is, for example, from the measurement? |
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The non-theoretical character of metaphysics would not be in itself a defect; all arts have this non-theoretical character without thereby losing their high value for personal as well as for social life. The danger lies in the deceptive character of metaphysics; it gives the illusion of knowledge without actually giving any knowledge. This is the reason why we reject it. - Rudolf Carnap "Philosophy and Logical Syntax" |
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#79 |
Penultimate Amazing
Join Date: Jun 2003
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It does. You talked about measurements. But measurements, in the sense you mean them, are not quantum mechanical. Their non-deterministic appearance may be an artifact and not any actual randomness. The Everett many-worlds interpretation, for example, involves no real randomness or non-determinism.
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"As long as it is admitted that the law may be diverted from its true purpose -- that it may violate property instead of protecting it -- then everyone will want to participate in making the law, either to protect himself against plunder or to use it for plunder. Political questions will always be prejudicial, dominant, and all-absorbing. There will be fighting at the door of the Legislative Palace, and the struggle within will be no less furious." - Bastiat, The Law |
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#80 |
Penultimate Amazing
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Did I suggest they are?
It seems to me that the problem I am outlining is precisely because they are not quantum mechanical and therefore cannot be considered to be part of a deterministic, reversible system. Whether or not they are actually deterministic is neither here nor there since the problem is with reversibility as I have said. |
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The non-theoretical character of metaphysics would not be in itself a defect; all arts have this non-theoretical character without thereby losing their high value for personal as well as for social life. The danger lies in the deceptive character of metaphysics; it gives the illusion of knowledge without actually giving any knowledge. This is the reason why we reject it. - Rudolf Carnap "Philosophy and Logical Syntax" |
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