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I have never fully understood that idea, even after reading Hossenfelder's posts about it. The idea that there's a "block universe" and everything is predetermi
by iainmerrick 4y ago
I have never fully understood that idea, even after reading Hossenfelder's posts about it. The idea that there's a "block universe" and everything is predetermined is comprehensible, sure; but what's the exact mechanism by which Bell's inequality is violated in experiments? Doesn't that require the universe to have been carefully set up to look as if it's acting in a weird non-local way, on an experiment-by-experiment basis? I assume I am just misunderstanding the idea, though. Any suggested reading material much appreciated!
- superposeur 4y agoAgreed — superdeterminism is not so much a theory as a theory-for-a-theory at this stage (a vague guess at the form such a theory might take). It is a sign of the much greater maturity of the physical collapse models that their parameters can be constrained by experiment. The ability to be constrained is a good sign, not a bad one. I love John Preskill’s standard nod to superdeterminism in his writings: without mentioning it by name he says “I leave it up to the reader to decide how seriously to take this possibility” (get it?)
- naasking 4y agoI think the right way to look at it is that superdeterminism is an umbrella term for a class of theories that have a certain property. Like some interpretations of quantum mechanics are "psi-ontic", meaning the wave function is considered physically real (like many worlds), vs. "psi-epistemic" where the wave function is considered a reflection of our knowledge of reality (Copenhagen).
- naasking 4y agoWe had a recent thread about an article from Tim Palmer who has a good take on this: https://news.ycombinator.com/item?id=33223391 https://news.ycombinator.com/item?id=33223391 The idea is that the natural laws are fractal, which when mapped out trace many state space configurations. But with a fractal there are always gaps in state space that remain no matter how much you zoom in or out; fractals preserve certain structural invariants at all scales. So the idea is that counterfactual reasoning sometimes fails in a fractal universe, because statistical independence no longer works as a general rule (your counterfactual could lie in one of those gaps). He first published this idea in 2009 under the name "invariant set postulate": https://en.wikipedia.org/wiki/Invariant_set_postulate https://en.wikipedia.org/wiki/Invariant_set_postulate His paper with Hossenfelder is also a good overview: https://www.frontiersin.org/articles/10.3389/fphy.2020.00139/full https://www.frontiersin.org/articles/10.3389/fphy.2020.00139... Superdeterminism gets an unnecessarily bad rap.
- iainmerrick 4y agoSuperdeterminism gets an unnecessarily bad rap. If determinism is true, don't you mean "necessarily"? :)
- pdonis 4y ago> Doesn't that require the universe to have been carefully set up to look as if it's acting in a weird non-local way, on an experiment-by-experiment basis? Yes. That is a big reason why most physicists do not favor superdeterminism.
- geertj 4y agoI am not so sure. In my understanding of the block universe, causality doesn't really exist, and the universe is simply a consistent solution with boundary conditions both at the beginning and at the end of time (as well as in space). The game of life is perhaps a nice analogy here. On the 2d grid of the game of life, a glider seems moving in a certain direction when time moves forward. But in the 3d grid, where time is the third dimension, a glider is just a static volume of space. The reason we experience time is that the evolution of the block universe does depend on the dimension you look at (e.g entropy generally increases in the positive time dimension), and because our consciousness is an emergent property of a self-sustaining structure within the block universe, it's plausible at least that we perceive movement in time different from movement in space. I realize this is very sloppy wording but I'm having trouble finding better words to describe my intuition here.
- pdonis 4y ago> In my understanding of the block universe, causality doesn't really exist That's one way of interpreting it, but superdeterminism does not entail or require this. Superdeterminism can be formulated just fine for a universe that evolves in time from some initial state according to causal processes.
- kgwgk 4y ago> what's the exact mechanism by which Bell's inequality is violated in experiments? It’s not violated - it simply doesn’t apply because it’s predetermined that the measurements that are done work well together. The experimenters follow the script.