Atheism and the existence of peanut butter

[polymath257]

Sorry, I misspoke. We *can* detect causality violations.  There are observations hat have been made that exclude *any* hiddent variable theories that are local.

Excluding local hidden variables doesn't really mean we ruled out causality... the possibility of global hidden variables is wide open. So, my question stands, how do you know that causality is violated in the first place ?

Quantum theory is an acausal theory. And it is far superior to the globally causal theories like Bohms, which do not have generalizations to relativistic theories.

So, unless you have give very good reasons to think that causality is NOT violated, in spite of Aspect's experiment, you cannot assume that it is *proven* that causality always holds.

Classical physics is known to be wrong. That is why we currently use quantum physics. And quantum physics is NOT a causal theory: it is a probabilistic theory.

And we have done so: look up Aspect's experiment related to the EPR paradox. The observations violate Bell's inequalities which *must* be satisfied by any locally causal system.

I thought classical physics are a good approximation when we don't need all the precision of modern theories.? Newton's model of gravitation didn't become garbage because Einstein figured out a better model, we can still use Newtonian mechanics for a great deal of practical purposes.

Engineering mechanics is applied Newtonian mechanics for the most part, because a mechanical engineer doesn't really have to worry about crazy spacetime curves when designing mechanical systems......

Yes, classical physics is a good *approximation* in many cases. This includes cases that are above the atomic level or where speeds are much less than those of light, or where the gravitational forces involved are rather weak.

But, in the case of causality in the early universe, it is badly wrong. Most of the previous conditions fail at that time: the effects of subatomic particles are dominant, the speeds involved are relativistic, and the density of mass is enough that general relativity is required to be accurate.

Again, let's say there no local causal agent, force, etc. , does that also mean there is no causal agent altogether ???

No, but it does require that anyone insisting that causality always holds mus make a good argument for a global hidden variable theory. In particular, such a theory must work better in some way that quantum mechanics.

If classical physics, being a good approximation of reality, preserves causality, it should be safe to say that the subtleties of causality at the quantum level are more due to incomplete information (uncertainty principle) than to a real violation of causality.

Classical physics only applies at the macroscopic level. We *know* it is a bad approximation at the subatomic level. The reason it works at the macroscopic level is that there are enough individual particles so that the averages are predictable.

Furthermore, we *know* there is going to be a point in the early universe where quantum gravity is going to be required. That will be an inherently non-classical theory.

And, no, the violations we have seen for local hidden variables are not simply due to a lack of information. Quantum mechanics is a *local* theory, but it is not a causal one. And yet, it is *by far* the best physical theory we have ever had.

At this point, insisting on causality as necessary is almost laughable. Even a global theory has to abide by such stringent conditions as to make the local theory that is acausal much better as a physical theory.