4 ms·

And why is this "natural"? I find the collapse to be the strangest axiom, the rest I can handle.

• SiempreViernes 6y ago
  Well one definition of "natural" could be that it "came from nature", and as the Schrödinger equation perfectly describes non-relativistic events in nature arguably it came from nature just as much as newtons laws of motion. Another measure of naturalness is "simplicity", and the Schrödinger equation is a fairly simple expression. You might argue that it's results don't feel very intuitive, and therefore it is not natural. But then I why you think its intuitive that levers work.
• jfengel 6y ago
  Collapse isn't actually an axiom. It doesn't appear in the Schroedinger Equation at all. It comes in when you treat the measurement apparatus as separate from the thing being measured. When you do that, collapse flows naturally from that assumption. It's a valid approach, and very useful, but many people find it philosophically awkward. An approach that's philosophically easier, but less pragmatic, is to treat the masurement apparatus as part of the system. Now you've got one single enormous quantum system. The math of that is far too complex to actually run, and more importantly, too enormous to hold itself in an unstable equilibrium. It must fall into a more stable equilibrium. The tricky part is when there's more than one stable state. The measurement apparatus exists in both of those states, and returns opposite results. The states are in local equilibria, and don't exchange significant amounts of state with each other. You can call that "splitting universes", if you want, though I think that's needlessly messianic. Like the first one, it's perfectly valid. And pragmatically it acts just like collapse. There's a philosophical question about whether the other states "actually exist but can't be reached" or "don't exist at all since we can't prove it except by inference from the fact that this one exists and follows the Schroedinger Equation so closely". That's "philosophical" in the sense that there is no physical difference between the two, but just one of your mental model. That's a lot of words; sorry about that. But the point is that you don't need a collapse axiom, and if you choose to add one, it's not strange.
  • wnoise 6y ago
    In standard quantum mechanics, collapse absolutely is an axiom. I really have a lot of sympathy for the Everettian no-collapse position, with effective collapse caused by interactions with the environment. Nevertheless, the measurement problem hasn't actually been solved. The Born probabilities haven't truly been derived, except under some truly restrictive assumptions.
    • lmm 6y ago
      > Nevertheless, the measurement problem hasn't actually been solved. The Born probabilities haven't truly been derived, except under some truly restrictive assumptions. True enough, but what else could you expect the experience of being in the Everettian universe to look like? I think it's fair to say that experimental results are at least compatible with reality following the Schroedinger equation without needing a collapse postulate.