By definition, a wave function does not describe a particle's state exactly, we can only know that information when we make measurements and thus collapse the wave function.

This gives us a lot of interesting counter-intuitive facts such as the Shrödinger's cat being 50% dead and alive at the same time until we open the box to measure, or that a particle that's expected to be found here when measured could, with extremely little chance, be found on the Moon instead.

The way I see it, quantum mechanics is just a model that tries to move humanity forward in understanding the Universe. In other words, given the Uncertainty Principle limiting our ability to measure the small stuff, quantum mechanics tries to circumvent that limitation. But in doing so we start to see a lot of absolutely counter-intuitive but most importantly unreasonable conclusions with quantum mechanics, such as the undead cat, the fact that we don't experience a wave function on a macroscopic level, etc. (note when I say "unreasonable" I mean the opposite to conclusions that are counter-intuitive but absolutely understandable with reason like time relativity, which also happens to be proved).

I like to think that there is a specific state for the Universe at all times, and I believe the wave function does not forbid that but rather is a limited approach to understanding the Universe given the limitations imposed by the Uncertainty Principle.

My question is: could it be that reality actually has a specific state but we simply cannot measure it and we rely on less than perfect models to move forward in our understanding of the Universe? In other words, could it be that the absurd conclusions of the undead cat and the particle on the Moon are actually impossible but quantum mechanics fail to set limits on that?

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    $\begingroup$ I suggest you read up on Bell's theorem. The predictions of QM can be distinguished from the predictions of any deterministic and causal theory. $\endgroup$ – puppetsock Jun 14 '19 at 15:29
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    $\begingroup$ @puppetsock To be fair, I think saying that "deterministic and causal" theories are eliminated might be going a bit too far. Certainly deterministic and local theories are eliminated, and it's also fairly commonplace for the definition of causality to rely on locality, but are you certain that there isn't some nonlocal form of causality that still works? $\endgroup$ – probably_someone Jun 14 '19 at 15:39
  • $\begingroup$ Hi. You basically ask if there is a model or not that could predict something more than what quantum mechanics predict, and that prediction is based on an assumption or aesthetic of how the universe could be. It is not a valid question- I believe- of whether or not a perfect model exists because even as a concept we cannot agree what that would mean. Even so, it is possible that no perfect model exist because the universe is not perfect under the standards you assume and is more than perfect from another viewpoint. Thank you but I find the question illogical at least. $\endgroup$ – Constantine Black Jun 14 '19 at 15:43
  • $\begingroup$ @probably_someone Am I certain that nonlocal theories can't work? Pretty sure since you lose an initial value problem and so can't predict the results of experiments. $\endgroup$ – puppetsock Jun 14 '19 at 17:52
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    $\begingroup$ There are no perfect models in physics. However, a desire for the universe to be deterministic is a psychological obsession based on human insecurity. It has no scientific justification. $\endgroup$ – safesphere Jun 14 '19 at 18:02

Mainstream physics is based on the underlying framework out of which all classical theories arise as quantum mechanical. This has not deterred people from working on non local theories that will give the same prediction as quantum mechanics but be deterministic.

Two such come to mind,Bohmian mechanics and the model Gerald 'd Hooft is working with. The latter participated for a time in discussions here and you will be able to find them searching the users, on the left .

The mainstream research follows the classical Copenhagen interpretation. BTW the cat being dead or alive is a bad example of using a live animal instead of a Geiger counter in the decay of particles. The poor cat is just an extension of whether the counter gave a hit , or not.

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