imsmooth said:
How do we know for sure that the first particle we measure does not have a pre-defined orientation? That seems to be the easiest answer.
DrChinese said:
a. As already mentioned, Bell's theorem and related experiments demonstrate conclusively that there cannot be a predetermined orientation - until there is some kind of nonlocality. Some people equate nonlocality with faster-than-light (FTL), and it is possible there is action at a distance.
I think it's worth noting that there can be "pre-determination", as to explain the
correlation in two different ways, with any "action at distance at all".
1) What is normally meant is a pre-determiniation which is treated as a simple ignorance of the physicsist. Meaning that the physical interactions happens as per known mechanisms partitioned into the hidden variable, and the actual outcome is random selection among them. This is the form assumed in bells theorem and it is the kind of pre-determination that is ruled out. Unless you expose some IMO quite pathological loophole ideas or pathological action at distance.
2) The other "pre-determiniation" that is entirely compatible with QM, is that there is some variable that is created and correlated from the preparation procecure, that
determines the correlation, but the outcome is not determined by simple averaging simple actions, but from actions that account for the uncertainty. Ie. the uncertainty of the hidden variable, affects the interactions themselves, not just the physicists predictions. This forms is allowed still by QM, but we do not
understand it's mechanism. Some don't care, and just settle with that we have a computational model. Some think there is a value to find the mechanism. This form does not require any action at distance, and the "pre-determined" value here can possibly be subjective, in the sense that, a key in these experiments i ISOLATION. Which means that it is fully possible that noone except hte particles themselves "know" this hidden value, and that this influences the interactions themselves. This means that the interacting environment itself, such as detectors etc, also are ignorant to this value. Thus it seems at least within reason, that this kind of intrinsic uncertainty does affect the interaction itself - unlike the Bell type of hidden variables.
Except for those that still seek odd loopholes to the "original" type (1), with (2) I think the options are to seek this deeper understanding or just settle with that the model works, and thinkg that there is no benefit in understandin the mechanism.
/Fredrik