Maybe a bit off topic, but i've always wondered why most physicists dismiss the possibility of superdeterminism to escape Bell's theorem.
Are there any physicists here who would like to elaborate?
Not a physicist, but I've been studying QM as a hobby for thirty years. The problem with superdeterminism (SD) is that if QM is true then SD is not falsifiable. SD says that all experimental outcomes are deterministic but derive from hidden state, i.e. some sort of "Cosmic Turing Machine" (CTM) calculating the digits of pi or something like that. So now what? The CTM has to be perpetually hidden from us, otherwise we could examine its state and predict the outcomes of quantum experiments, and that would violate QM. So if QM is true, then the CTM necessarily has the same ontological status as an Invisible Pink Unicorn (IPU). In fact, the deterministic calculations underlying SD may well be carried out by a literal IPU. If QM is correct then there's no way to determine this, even in principle.
Bell-inequality experiments still that leave room for hidden-variable models that fall short of full superdeterminism.
Relatively recent experiment using photons from stars in the Milky Way "Cosmic Bell Test: Measurement Settings from Milky Way Stars" http://web.mit.edu/asf/www/Papers/Handsteiner_Friedman+2017.... The experiment excludes local-realist models with local hidden variable younger than 600 light years. Similar test with cosmic microwave background could push the limit to the early universe.
Not a physicist, but in my mind the basic obstacle to superdeterminism is that in the initial state at t=0 you have O(S) degrees of freedom but throughout some chunk of spacetime there will be O(S * T) Bell violations (where 'S' is "amount of space" and 'T' is "amount of time"). The degrees of freedom you get is fixed, but the constraints grow with time; the system is asymptotically overconstrained. So at first glance you'd guess "no superdeterministic solution exists".
If a solution did exist, it would probably be because of some convenient symmetry or law w.r.t. how the Bell violations played out. But you can use the behavior of arbitrary computer programs to trigger Bell tests, and computer programs are not a well behaved sort of thing. So that makes it seem unlikely for a set of O(S*T) Bell violations out in the world to follow a well behaved pattern that could be compressed into O(S) bits. Like, suppose I decide to dovetail through all computer programs, running a Bell test every time one of the programs halts. This would appear to force the initial state to encode information about solutions to the Halting problem, without the benefit of encoding it into a process that executes over time. But the Halting sequence is algorithmically random; incompressible...
From the Aspect’s piece I linked to in another comment:
“Yet more foreign to the usual way of reasoning in physics is the “free-will loophole.” This is based on the idea that the choices of orientations we consider independent (because of relativistic causality) could in fact be correlated by an event in their common past. Since all events have a common past if we go back far enough in time—possibly to the big bang—any observed correlation could be justified by invoking such an explanation. Taken to its logical extreme, however, this argument implies that humans do not have free will, since two experimentalists, even separated by a great distance, could not be said to have independently chosen the settings of their measuring apparatuses. Upon being accused of metaphysics for his fundamental assumption that experimentalists have the liberty to freely choose their polarizer settings, Bell replied: “Disgrace indeed, to be caught in a metaphysical position! But it seems to me that in this matter I am just pursuing my profession of theoretical physics.” I would like to humbly join Bell and claim that, in rejecting such an ad hoc explanation that might be invoked for any observed correlation, “I am just pursuing my profession of experimental physics.”
Why would a physicist embrace superdeterminism? Present science holds the falsifiability of a theory as a necessity for its utility. Under the light of SD every experimental result may be impossible to interpret as supportive of a theory.
Free will seems to be the most difficult philosophical question. Accepting SD invalidates the scientific method's approach to learning about the world.
You may be interested in other non-local hidden variable theories as a way to sidestep Bell's Theorem & the Copenhagen interpretation.
There is an analog of free will that works even in a cellular automaton. For that you need two things:
1. the part of cellular automata describing a thinking entity can be separated from the rest of the world: that is changing states of cells anywhere outside of it doesn't change the state of the entity itself.
2. it is not possible to replace the computation describing this entity with anything simpler.
2 means that any method of predicting what this thinking entity choses is completely equivalent to that entity living and making the choice it wants by itself. And 1 means that the part of network is indeed a separate entity.
With superdeterminism 1 can not be true, and a spin change of a single particle far away triggers very complex change in behavior of all thinking entities that were close to that particle in the past.