Hal: > Philosophically the real question is not why QM is non-local, because > there is no a priori reason the universe should be local.
Nature is earlier than man. And man is earlier than natural science. Thus sometimes (Einstein, essentially) we refuse even the possibility of non-locality. > The question is why the universe is so nearly local; This is a good question. Bell and Eberhard (at the end of '70s) made simulations about that. It was shown that any possible deterministic theory, reproducing all QM results - at they thought it was possible to build such a theory - would cause a very strong non-locality (v > c). Thus it is possible that QM rules are a good 'compromise', seen from the point of view of an evolving universe (or universe as a computer). I think it is possible to translate all that in Chaitin terms (complexity). One who wrote something on this subject is (perhaps) Yurtsever. > why it appears to be local for all practical purposes, > if it is built on non-local underpinnings; Difficult question. There are a lot of papers showing 'quantum-like' patterns in sociology, economy, etc. They also find 'interferences', performing experiments :-) > why the non-local connections are unable to affect causality. This might be a trap. There are dozens of (different) proofs about the 'peaceful coexistence' between QM and SR. But, as far as I know, in all these proofs there is the QM 'tensor product' rule (imposed by von Neumann, among many other possible products) which seems to forbid v > c (Kennedy says that, Fuchs says something different). Anyway the other problem is the "collapse", which is out of the Schroedinger equation, which (if 'physical') could be non-linear, etc. Essentially the "collapse" is out of QM. Now it is possible to think that any proofs saying that QM does not allow superluminal speeds (of informations) are illogical, and flawed, because of that (sometimes hidden) assumption of "collapse", which is out of QM.
