After reading this question, I feel I understand why quantum mechanics is so confusing (and so often confused by the media): It can be either local (if A causes B, then there must be time for a signal to travel at the speed of light from A to B) or real (the definition of which is a bit fuzzier to me), but not both. The confusion stems from the fact that it makes more intuitive sense for a layperson (like me) to view it as non-local: I.E., that faster-than-light communication is possible.
However, scientists seem to agree on the other option, the "non-real" option. My question is this: Is this an option? The way I interpreted the answer to the linked question is that any consistent theory of quantum mechanics can be either non-local or non-real. Therefore, if you get enough scientists together, they can form a theory based on non-locality, and it will explain the universe just as accurately as the current theories based on non-realism, just in a different way.
If this is true, then why have scientists agreed on non-realism? If this is not true, where did I go wrong in my interpretation?
Best Answer
The answer to the linked question is misleading (and I've left a comment there). You don't get to choose between nonlocal and non-real. While experiments violating Bell's inequalities do imply that no local, hidden-variables (i.e. real) theory is consistent with QM, that theorem must be taken in context with an earlier argument it's supposed to be a reply to, namely, the famous paper by Einstein, Podolsky, and Rosen (EPR). That paper argues that local QM theory implies that there are hidden variables (not quite the same as saying that local QM is always realistic, but it is in the context of entangled states). Taken together, the logical conclusion is that no local theory consistent with QM works - you're stuck with nonlocality.
You still have a choice between realistic and nonrealistic theories (or perhaps theories that are not completely realistic but do contain some hidden variables), but to produce predictions consistent with Bell's inequalities they will have to be nonlocal. The classic examples are Bohmian "pilot wave theory", which is realistic but highly nonlocal, and traditional QM, which is nonrealistic, but with its nonlocality apparently (?) being limited to some esoteric situations like particle pairs being generated in entangled states. Note that both those theories give the same predictions, so in that sense they are indistinguishable. That means it's probably an empty question to ask whether "reality" is realistic or unrealistic, or at least you can't tell based on those theories, since both the realistic theory and the nonrealistic theory provide equally good representations of reality.
To answer your question about why scientists have settled on the unrealistic theory (i.e. QM), it's because, compared with the only viable realistic theory (so far), which is Bohmian mechanics, it was developed first, it's easier to use for computation, and it has proven highly useful and successful. Bohm never intended pilot wave theory for everyday use; he just wanted to demonstrate that a realistic theory could be made.