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Maybe the bad idea is insisting in having a classical physics pictorical interpretation when there's no reason why there should be one. At some point having jus

by mnl 8y ago

Maybe the bad idea is insisting in having a classical physics pictorical interpretation when there's no reason why there should be one. At some point having just Maths is the more reasonable outlook.

kaolti 8y ago
What is the point of having just Maths if it doesn't help in the actual understanding of the world?
- mnl 8y ago
  All of it: that's the actual understanding of the world, right there. What else should it be? I don't expect the laws of Nature being intuitive for advanced mammalian brains ultimately.
naasking 8y ago
> Maybe the bad idea is insisting in having a classical physics pictorical interpretation when there's no reason why there should be one Actually there is a reason: we see classic physics with our own two eyes every day. We know classical physics exists at the macroscopic level, and so a theory that simply explains the transition from microscopic to macroscopic physics and how this works. This transition is unbelievably simple in Bohmian mechanics, since in principle, it's just classical physics with an extra term to account for quantum influences. The picture isn't nearly so simple for many other interpretations.
- mnl 8y ago
  We think we see classical physics, but this micro/macro divide is not that clear-cut. It's more like a convenient textbook classification. For instance you can build a very macro magnet which is not classical physics at all, you can't explain ferromagnetism without QM. Why don't we fall through the floor? that's not classical. Chemistry makes no sense without QM either. A classical world, albeit nice and easy to mirror with mental images involving differential equations of continuous stuff would fall to pieces. I like Bohm's book on Quantum Physics, but the pilot wave theory... well it doesn't explain anything new and the only problems it might solve are related to prejudices. Besides, the nature of that duplicity is never explained (and very ugly), so you're trading the ignorance you don't like for the one you like. In this kind of situations just go for the more simple and consistent theory as the only thing that matters is measurements. (There's also the problem of getting to some form of QFT with it. Bell has written about this elsewhere, it's not pretty but I'm sure somebody has arrived to a working model by now.)
  - naasking 8y ago
    I think you might be using an overly simplistic meaning for "classical". There is nothing preventing a classical description of ferromagnetism, for instance [1]. Bohmian simulations of atoms has established stability despite the orbits, and would similarly entail the diamagnetism needed for this phenomenon, so classical theories can in fact explain it. > well it doesn't explain anything new and the only problems it might solve are related to prejudices. Correct, it actually explains everything old which prior interpretations like Copenhagen could not. I assume by "prejudices", you're referring to classical prejudices, but I think those prejudices are perfectly warranted. > In this kind of situations just go for the more simple and consistent theory as the only thing that matters is measurements. I disagree! John Bell formed the first no-go theorem because he was a fan of Bohmian mechanics. Without this focus on interpretations and quantum fundamentals, we may never have seen that landmark result or the series of subsequent no-go theorems which have all proven critical to our scientific understanding. Science and physics does not consist solely of measurements; considerations of ontology are at least equally important because they inform the thought experiments which really drive scientific revolutions. > Bell has written about this elsewhere, it's not pretty but I'm sure somebody has arrived to a working model by now There are a few workable models, but Bell was correct to say that non-locality was the unsolved problem of quantum mechanics. Other interpretations let you "solve" it by sweeping it under the rug, but it always rears its ugly head elsewhere. [1] https://physics.stackexchange.com/a/365970/43861 https://physics.stackexchange.com/a/365970/43861
    - mnl 8y ago
      No, they can't explain ferromagnetism. Sometimes you use a semiclassical approximation, but that's a technical term. Don't look into the words used in Physics, this is not a social science, words in themselves don't carry an inherent meaning, they're just labels. You need spin to describe ferromagnetism, there's no room for that in a classical model of charges. I'm not opposed to alternative formulations of QM, but I'd rather prefer people would try to come up with more fundamental theories than QM (if possible) instead of trying to get the same results with something else because for some ideological reason they don't like standard QM. And it really is all about the measurements: Physics is an experimental science. You can think all you want and do crazy math and lots of gedanken, but we need at least a number and see what Nature thinks about it.
jostylr 8y ago
Let's assume the Maths is all we care about. One way to clear it up is to decide what we would need to give to a computer to figure out the results. Let's assume the computer can solve any equation we give it. Bohmian Mechanics: Given Schrödinger's equation, Bohm's equation, the initial positions of the experiment and the measuring apparatus (assuming it is set on autopilot) and the initial wavefunction of the joint experiment and apparatus setup, then we evolve the system and the positions of the stuff in the apparatus will tell us the result of the experiment. Done. Copenhagen Interpretation: We need Schrödinger's equation for the experimental setup, the initial wavefunction of the experiment, and some explicit timing for collapse as well as some stand-in for the eigenstates (we never actually collapse to an eigenstate or anything spiky, but rather to a nearby smooth state, such as a finite sum of Gaussians). We can optionally add-in the apparatus or observer wavefunction and collapse to something with an outcome involving those wavefunctions. It is kind of a mess to tell a computer how to do this, particularly if you have a number of experiments, possibly conditioned on the results of other experiments. It is not an independent time evolution. The Maths fail us in setting up a universe. One could let this multi-experiment setup evolve until everything is done and then collapse at the very end. That leads to less of a mess of specification, but now one has the fact that we are saying reality does not have, in any, even approximate, sense, a definitive experience such as the one we are used to, at any point except for the last one. In some sense, this is the Many Worlds theory. GRW is based on the idea of adding automatic collapse into the equations and that's fine and cool; it hits the wavefunction with a gaussian every so often. One also has to add in something else of an ontological nature, but that can be considered a philosophical issue (though it can matter what one chooses, say from a relativistic point of view). We at least have in GRW a Maths based evolution though it is different than the standard one. The Copenhagen Interpretation is not an actual theory; there is no possible universe where it could be true or implemented. It can be made more specific, but it does require something more and the more one sticks to the Copenhagen spirit, the more of a "on high" specification mess, it becomes. Both GRW and Bohmian Mechanics at least could be true.

by mnl 8y ago

Maybe the bad idea is insisting in having a classical physics pictorical interpretation when there's no reason why there should be one. At some point having just Maths is the more reasonable outlook.

kaolti 8y ago

What is the point of having just Maths if it doesn't help in the actual understanding of the world?

mnl 8y ago
All of it: that's the actual understanding of the world, right there. What else should it be? I don't expect the laws of Nature being intuitive for advanced mammalian brains ultimately.

naasking 8y ago

> Maybe the bad idea is insisting in having a classical physics pictorical interpretation when there's no reason why there should be one Actually there is a reason: we see classic physics with our own two eyes every day. We know classical physics exists at the macroscopic level, and so a theory that simply explains the transition from microscopic to macroscopic physics and how this works. This transition is unbelievably simple in Bohmian mechanics, since in principle, it's just classical physics with an extra term to account for quantum influences. The picture isn't nearly so simple for many other interpretations.

mnl 8y ago
We think we see classical physics, but this micro/macro divide is not that clear-cut. It's more like a convenient textbook classification. For instance you can build a very macro magnet which is not classical physics at all, you can't explain ferromagnetism without QM. Why don't we fall through the floor? that's not classical. Chemistry makes no sense without QM either. A classical world, albeit nice and easy to mirror with mental images involving differential equations of continuous stuff would fall to pieces. I like Bohm's book on Quantum Physics, but the pilot wave theory... well it doesn't explain anything new and the only problems it might solve are related to prejudices. Besides, the nature of that duplicity is never explained (and very ugly), so you're trading the ignorance you don't like for the one you like. In this kind of situations just go for the more simple and consistent theory as the only thing that matters is measurements. (There's also the problem of getting to some form of QFT with it. Bell has written about this elsewhere, it's not pretty but I'm sure somebody has arrived to a working model by now.)
- naasking 8y ago
  I think you might be using an overly simplistic meaning for "classical". There is nothing preventing a classical description of ferromagnetism, for instance [1]. Bohmian simulations of atoms has established stability despite the orbits, and would similarly entail the diamagnetism needed for this phenomenon, so classical theories can in fact explain it. > well it doesn't explain anything new and the only problems it might solve are related to prejudices. Correct, it actually explains everything old which prior interpretations like Copenhagen could not. I assume by "prejudices", you're referring to classical prejudices, but I think those prejudices are perfectly warranted. > In this kind of situations just go for the more simple and consistent theory as the only thing that matters is measurements. I disagree! John Bell formed the first no-go theorem because he was a fan of Bohmian mechanics. Without this focus on interpretations and quantum fundamentals, we may never have seen that landmark result or the series of subsequent no-go theorems which have all proven critical to our scientific understanding. Science and physics does not consist solely of measurements; considerations of ontology are at least equally important because they inform the thought experiments which really drive scientific revolutions. > Bell has written about this elsewhere, it's not pretty but I'm sure somebody has arrived to a working model by now There are a few workable models, but Bell was correct to say that non-locality was the unsolved problem of quantum mechanics. Other interpretations let you "solve" it by sweeping it under the rug, but it always rears its ugly head elsewhere. [1] https://physics.stackexchange.com/a/365970/43861 https://physics.stackexchange.com/a/365970/43861
  - mnl 8y ago
    No, they can't explain ferromagnetism. Sometimes you use a semiclassical approximation, but that's a technical term. Don't look into the words used in Physics, this is not a social science, words in themselves don't carry an inherent meaning, they're just labels. You need spin to describe ferromagnetism, there's no room for that in a classical model of charges. I'm not opposed to alternative formulations of QM, but I'd rather prefer people would try to come up with more fundamental theories than QM (if possible) instead of trying to get the same results with something else because for some ideological reason they don't like standard QM. And it really is all about the measurements: Physics is an experimental science. You can think all you want and do crazy math and lots of gedanken, but we need at least a number and see what Nature thinks about it.

jostylr 8y ago

Let's assume the Maths is all we care about. One way to clear it up is to decide what we would need to give to a computer to figure out the results. Let's assume the computer can solve any equation we give it. Bohmian Mechanics: Given Schrödinger's equation, Bohm's equation, the initial positions of the experiment and the measuring apparatus (assuming it is set on autopilot) and the initial wavefunction of the joint experiment and apparatus setup, then we evolve the system and the positions of the stuff in the apparatus will tell us the result of the experiment. Done. Copenhagen Interpretation: We need Schrödinger's equation for the experimental setup, the initial wavefunction of the experiment, and some explicit timing for collapse as well as some stand-in for the eigenstates (we never actually collapse to an eigenstate or anything spiky, but rather to a nearby smooth state, such as a finite sum of Gaussians). We can optionally add-in the apparatus or observer wavefunction and collapse to something with an outcome involving those wavefunctions. It is kind of a mess to tell a computer how to do this, particularly if you have a number of experiments, possibly conditioned on the results of other experiments. It is not an independent time evolution. The Maths fail us in setting up a universe. One could let this multi-experiment setup evolve until everything is done and then collapse at the very end. That leads to less of a mess of specification, but now one has the fact that we are saying reality does not have, in any, even approximate, sense, a definitive experience such as the one we are used to, at any point except for the last one. In some sense, this is the Many Worlds theory. GRW is based on the idea of adding automatic collapse into the equations and that's fine and cool; it hits the wavefunction with a gaussian every so often. One also has to add in something else of an ontological nature, but that can be considered a philosophical issue (though it can matter what one chooses, say from a relativistic point of view). We at least have in GRW a Maths based evolution though it is different than the standard one. The Copenhagen Interpretation is not an actual theory; there is no possible universe where it could be true or implemented. It can be made more specific, but it does require something more and the more one sticks to the Copenhagen spirit, the more of a "on high" specification mess, it becomes. Both GRW and Bohmian Mechanics at least could be true.