zlacker

>>qqqqqu+(OP)
Bell's theorem. It somehow proves that quantum physics is incompatible with local hidden variables, but I could never see an understandable explanation (for me at least) of just how it works.

>>lpelli+ag
Yudkowsky's explanation[1] is the first one that worked for me. I later found Quantum mysteries for anyone[2] helpful. The latter has less soap-boxing.

1: https://www.lesswrong.com/posts/AnHJX42C6r6deohTG/bell-s-the...

2: https://kantin.sabanciuniv.edu/sites/kantin.sabanciuniv.edu/...

>>scioli+Hh
I started to read the first one but his insistence that Many Worlds is true was too frustrating. Many Worlds Theorem seems specifically useful at saying "the variables aren't hidden because everything before wavefunction collapses actually plays out in different worlds.

But, we specifically have no way of proving that theory. So now we're back to the essence of the original question - if these things seem random why do we know that they're in fact deterministic without any hidden variables?

>>Shamel+Vm
Well, I'd recommend to read the whole series. It's not so bad as it sounds. There are so many steps from where you are to appreciating the utter weirdness of Bell's experimental result. Not the weirdness of any theory (or an interpretation, which Many Worlds actually is) but of the basic experimental result.

If you are properly amazed by it, rejecting MWI or any crazy-ish borderline-conspiracy theory seems suddenly a lot harder.

I feel the whole Yudkowsky's QM series in fact served to deliver that one post.

>>kubanc+dq
Why isn't the MWI another form of hidden variables (a supremely non-parsimonious one at that), where the hidden variable is which of the many worlds you happen to inhabit?

>>sooheo+8f1
I think you can make an argument for viewing it that way, depending on exactly what you mean by "you".

But IIUC, one of the remarkable things about MWI is that it would be a local hidden variable theory!

This is a very important property to have because the principle of locality is deeply ingrained in the way the Universe behaves. Note that (almost?) no other quantum interpretation is both realist and local at the same time.

Maybe you wonder, how is it possible that MWI can be considered a local hidden variable theory if Bell's theorem precisely shows that local hidden variable theories are not possible?

I think that it was Bell himself who said that the theorem is only valid if you assume that there is only one outcome every time you run the experiment, which is not the case in MWI.

This means that MWI is one of the few (the only?) interpretation we have that can explain how we observe Bell's theorem while still being a local, deterministic, realist, hidden variable theory.

>>wizema+mC3
For it to be local (causality does not propagate faster than light), it must be superdeterministic (all the many worlds that ever will be, already are). For it not to be superdeterministic (many worlds decohere at the moment of experimentation), it is also not local (the decoherence happens faster than the speed of light, across the universe).