Do we live in a block universe?

In summary, the conversation discusses the experimental evidence for the non-existence of local hidden variables and the possibility of non-local hidden variables as proposed by John S. Bell. It also explores the concept of a block universe where time is bi-directional and all events are predetermined, leading to a constant amount of information and entropy in the universe. However, the implausibility of superdeterminism is also discussed, with various discussions on the subject in older threads on the Physics Forums website.
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Experimental violations of Bell's inequality (Alain Aspect, et al) proved beyond a shadow of doubt that local hidden variables do not exist. However, in a 1985 BBC interview, John S. Bell said there was one loophole in those experiments that would allow for determinism: non-local hidden variables. Einstein believed that quantum measurements are not indeterminate, but for that to be true in light of Bell's inequality violations, Bell said that every event in the universe would then have to be predetermined -- superdeterminism.

In other words, Bell's theorem gives us only two possibilities: One, where quantum measurements are inherently indeterminate, and another where we live in a block universe where everything is laid out in a predetermined, unalterable timeline.

In a block universe, time would be bi-directional. Past events could be observed as "unhappening" (in principle) simply by going backward along the time axis. Our memories would be erased while going backward through time as well, so there would be no way to tell which direction we were traveling (our "sense" of "time" would just be an illusion). All irreversible processes would be ruled out, meaning that the total amount of information in the universe would have to remain constant. (This is because all information concerning the present state of the universe was already contained in the past. This would be exactly the kind of clockwork universe Laplace envisioned.) But if every process is completely reversible, the total entropy would also remain constant over time, and entropy could only increase in one portion of the universe by importing it from somewhere else.

John Bell himself said that superdeterminism is implausible. I agree. What do others think?
 
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1. What is a block universe?

A block universe is a concept in philosophy and theoretical physics that suggests that the past, present, and future all exist simultaneously and are equally real. This means that time is not linear and everything that has ever happened or will happen is already predetermined and fixed in a "block" of space-time.

2. What evidence is there for the existence of a block universe?

There is currently no concrete evidence for the existence of a block universe. However, the theory has gained popularity among some physicists due to the success of the theory of relativity and the idea of space-time as a continuum. Some believe that the block universe model can help to reconcile the conflicts between quantum mechanics and general relativity.

3. How does the block universe model affect free will?

The block universe model suggests that everything is predetermined and there is no room for free will. However, some argue that our perception of free will is simply an illusion and that our actions are still a result of predetermined causes within the block universe.

4. Is it possible to change the future in a block universe?

In a block universe, the future is already determined and cannot be changed. However, our perception of time may lead us to believe that we have the ability to change the future. The concept of "changing the future" is also debated, as it implies that there is a set future that can be altered, rather than a predetermined one.

5. How does the block universe model impact our understanding of the universe?

The block universe model challenges our traditional understanding of time and the concept of causality. It also raises questions about the nature of reality and our place in the universe. Some argue that it can help to explain the mysteries of quantum mechanics and the nature of consciousness.

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