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> There is nothing "obviously wrong" about the standard Copenhagen interpretation Can you tell me how to calculate whether a system of particles will cause ano
by tbabb 8y ago
> There is nothing "obviously wrong" about the standard Copenhagen interpretation
Can you tell me how to calculate whether a system of particles will cause another system of particles to collapse or not?
Can you tell me under what circumstances a system of particles will evolve unitarily or not?
Can you shade the region of the spacetime diagram of EPR where the wavefunction is collapsed? How about in a delayed choice quantum eraser experiment?
If you tell me "you're not allowed to ask those questions" (or "hm, I never thought of that!"), then you're directly illustrating the complaint here about physics!
The common narrative is that Copenhagen, many worlds, and the other interpretations of QM are all equivalent, but they are not. Copenhagen adds an extra physical event-- collapse-- where the wavefunction is suddenly nonunitary. The burden is on Copenhagen to tell me how and when this happens, and in fact to prove that it happens at all. Many worlds, on the other hand, predicts the same phenomenon-- the apparent collapse of a wavefunction to an eigenstate-- without adding unitarity violation, or any other phenomena at all beyond the normal, extremely well-verified mechanics of multi-particle system scattering; it merely treats the environment is a multi-particle quantum system.
Many worlds is the null hypothesis (no, the extra worlds are not extra suppositions, they are predictions of known physical laws), and the burden is on Copenhagen to show that unitarity violation exists, and the burden is extremely high (possibly insurmountable?) for EPR and eraser experiments.
When Copenhagen was devised, most believed that there was some "underlying state" in QM, and that measurement told you something about what the underlying state was. Bell's theorem should have sent a shockwave through the community which forced everyone to reevaluate fundamental assumptions and self-correct wrong ideas. But by accident of history, John Bell was too shy to publish in a major journal, and no one even read his result for four years. The implications of Bell's theorem were slow to diffuse through the community, and so the disruptive moment of reckoning that should have happened never came. By the time it was well-accepted, the narrative in physics had become "you're not allowed to ask about what quantum mechanics means, just shut up and calculate", and so the cognitive dissonance was cast aside. Annealing this attitude and this misstep away is taking excruciating decades.
EDIT: I also don't mean to imply that there aren't deep and beautiful things in modern physics. There are! But physics is concertedly avoiding asking deep questions in areas where (I strongly believe) it is most important. The claim that "the meaning of QM is outside the scope of science" is exemplary, I think, of that attitude.
- andrepd 8y ago>Can you tell me how to calculate whether a system of particles will cause another system of particles to collapse or not? You appear to be somewhat mistaken. Copenhagen interpretation does not postulate any specific explanation or mechanism for wave-function collapse, merely that "upon measurement, the wave-function collapses into an eigenstate of the observable being measured". This, of course, is a physically verified phenomenon. Now Copenhagen purposefully leaves the precise meaning of "measurement" undefined, since in my view there is no convincing empirical evidence that supports a specific mechanism for this phenomenon. Other interpretations posit mechanisms (decoherence (doesn't fully account), von Neumann "consiousness" (not empirical), etc.) for this collapse. My biggest complaint about many-worlds interpretation is how it is in its essence a non-scientific theory, as it makes assertions about an unobservable reality. It postulates other parallel realities that by definition do not communicate. Again, this makes it intrinsically a non-scientific theory. >Can you tell me under what circumstances a system of particles will evolve unitarily or not? Everywhere except on measurement, in which the state collapses. >How about in a delayed choice quantum eraser experiment? I'm not familiar with this experiment. >If you tell me "you're not allowed to ask those questions" By all means, ask as many questions as you want. That's after all the essence of scientific endeavour. But it's not very nice to misrepresent other positions, nor is it to claim everyone else is deluded (without strong evidence on your side at least). >Bell's theorem should have sent a shockwave through the community which forced everyone to reevaluate fundamental assumptions and self-correct wrong ideas. Bell's inequalities force no re-evaluation. They simply prove that the search for a local hidden-variable theory is impossible. It certainly raised important ideas for research, but it does not do anything to discredit established QM. >The claim that "the meaning of QM is outside the scope of science" is exemplary, I think, of that attitude. If a physical argument can be made about this problem, then it's in the scope of physics. Otherwise, it is not. As simple as that.
- naasking 8y ago> This, of course, is a physically verified phenomenon No it's not. There are interpretations in which collapse does not exist, so these experiments are not measuring what you think they're measuring unless you already assume the conclusion. Also, your view on other interpretations of QM are outdated. Arguably one of the more famous results on quantum mechanics, Bell's theorem, would have never existed if not for Bohmian mechanics. Don't discount the value of explanatory power. The fact that other interpretations provide far more explanatory power than Copenhagen makes them far more valuable. Many important results in quantum foundations would have never happened if everyone were a Copenhagenist.