4 ms·

I can't see what's so hard about it either. Nor what would be the problem with something like hidden states/variables. Why would it be so hard to assume that th

I can't see what's so hard about it either. Nor what would be the problem with something like hidden states/variables. Why would it be so hard to assume that there could be hidden states in partcles which we simply can't measure (maybe not yet)? Why does the world has to be directly measurable? Who told people that they ought to be able to measure every single variable directly (like hidden state of a quantum particle), why are they assuming that?

mrmonkeyman 7y ago
Those hidden variables have to violate known physics in order to exist. So that's a pickle.
- marcus_holmes 7y ago
  well, that's the point isn't it? They're saying that "known physics" is wrong
  - brain5ide 7y ago
    incomplete
tsimionescu 7y ago
You should look into Bell's theorem. It is mathematical proof that (discounting superdeterminism) there is no way to explain QM observations with local hidden variables. You could have hidden variables, but only if they produce effects at infinite speed. The big problem with infinite speeds is that, somewhat like superdeterminism, they mean that you can't do fully controlled experiments. If effects can propagate at infinite speeds, the whe universe has an impact on any experiment, including the state of your measuring apparatus and so on. That doesn't make them impossible, but it explains why they are disliked in theories.
- Erlich_Bachman 7y ago
  I know that they cannot be local. My point of view is "just let them be global, build theories from there", global hidden variables don't interfere with any intuitions about the world for some reason.
  - tsimionescu 7y ago
    The problem is you can't really build theories from global hidden variables. If the details of any experiment depend significantly\* on the state of the entire universe, until we can account for the entire universe in our measurements, we might as well stop measuring. \* even with Newtonian physics, the universal attraction of any object does have non-0 values everywhere, but we know that the influence is negligible. However, with global hidden variables, the speed a billiard ball will take when I hit it may depend on the size of a planet in a different galactic cluster.
    - snarfy 7y ago
      I also have a hard time disbelieving in global variables. We have a lot of evidence validating quantum field theories, and the fields in QFT are global.
      - vincent-toups 7y ago
        Only in a trivial sense. Quantum Field theories are explicitly local theories, constructed from Langrangians which purposefully have and express Lorentz invariance, exactly to maintain locality. In any case, quantum field theories are good at predicting stuff but almost certainly not descriptions of the true fundamental dynamics of the universe, given their known and relatively well understood divergences.
    - naasking 7y ago
      > If the details of any experiment depend significantly\* on the state of the entire universe, until we can account for the entire universe in our measurements, we might as well stop measuring. Every experiment does depend on the entire state of the universe, even in QM, but those influences are typically small due to symmetries. At the quantum level, many of these symmetries no longer apply.

mrmonkeyman 7y ago

Those hidden variables have to violate known physics in order to exist. So that's a pickle.

marcus_holmes 7y ago
well, that's the point isn't it? They're saying that "known physics" is wrong
- brain5ide 7y ago
  incomplete

tsimionescu 7y ago

You should look into Bell's theorem. It is mathematical proof that (discounting superdeterminism) there is no way to explain QM observations with local hidden variables. You could have hidden variables, but only if they produce effects at infinite speed. The big problem with infinite speeds is that, somewhat like superdeterminism, they mean that you can't do fully controlled experiments. If effects can propagate at infinite speeds, the whe universe has an impact on any experiment, including the state of your measuring apparatus and so on. That doesn't make them impossible, but it explains why they are disliked in theories.

Erlich_Bachman 7y ago
I know that they cannot be local. My point of view is "just let them be global, build theories from there", global hidden variables don't interfere with any intuitions about the world for some reason.
- tsimionescu 7y ago
  The problem is you can't really build theories from global hidden variables. If the details of any experiment depend significantly\* on the state of the entire universe, until we can account for the entire universe in our measurements, we might as well stop measuring. \* even with Newtonian physics, the universal attraction of any object does have non-0 values everywhere, but we know that the influence is negligible. However, with global hidden variables, the speed a billiard ball will take when I hit it may depend on the size of a planet in a different galactic cluster.
  - snarfy 7y ago
    I also have a hard time disbelieving in global variables. We have a lot of evidence validating quantum field theories, and the fields in QFT are global.
    - vincent-toups 7y ago
      Only in a trivial sense. Quantum Field theories are explicitly local theories, constructed from Langrangians which purposefully have and express Lorentz invariance, exactly to maintain locality. In any case, quantum field theories are good at predicting stuff but almost certainly not descriptions of the true fundamental dynamics of the universe, given their known and relatively well understood divergences.
  - naasking 7y ago
    > If the details of any experiment depend significantly\* on the state of the entire universe, until we can account for the entire universe in our measurements, we might as well stop measuring. Every experiment does depend on the entire state of the universe, even in QM, but those influences are typically small due to symmetries. At the quantum level, many of these symmetries no longer apply.