this post was submitted on 26 Jan 2025
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[–] milicent_bystandr@lemm.ee 4 points 1 month ago (2 children)

Quantum results are hard to explain, but proven (by experiment) to be real. There's a particular mathematical/logical definition of something being 'real' and 'local', that I've still only half got my head around, and it should be true but isn't.

The main experiment is two particles that, if you check one, it affects what you'll see in the other in a particular, but subtle , way. And it's proven mathematically impossible to find an explanation where they don't either communicate faster than the speed of light (so, not 'local') but the effect actually happens ('real').

The trick is in the statistics - the pattern of results - that match up between the two particles in this very particular way. And one way to explain it is that different options are also happening, but in a different universe - i.e. every time two different things could happen, reality splits into two realities, one where this happens and one where that happens.

That's for specific quantum events, but some think those such quantum events underlie all choices and possibilities in reality. So, scale up that idea and you get 'infinite' (actually just very very many) parallel universes, one for every possibility that could ever have happened, branching off into more each time a (quantum) choice happens.

[–] pcalau12i@lemmy.world 1 points 1 day ago (1 children)

Quantum nonlocality really is a misnomer. Nothing is nonlocal about it. We know from the No-communication Theorem that there is no physical interaction you could carry out with one particle in an entangled pair that would affect the state of the other particle, and we know it is compatible with special relativity, which is a fundamentally local theory, as such a unification of the two is how we get quantum field theory.

"Local realism" is also a nonsensical term. There is no agreed upon rigorous definition of "realism" and its introduction to the scientific literature has only served to confuse the discussion and promote quantum mysticism because people think because Bell's theorem supposedly shows that "local realism" is false that you there have to choose between locality or realism, but not both, and since we know the universe is local, we have to conclude there is no objective reality, devolving into mysticism and idealism.

This isn't just a problem in popsci articles but even in published scientific literature. This "local realism" hogwash has caused even otherwise respectable physics to publish nonsense about how reality doesn't exist. The term "realism" is never used in Bell's theorem and has tn relevance to it. Bell's theorem is about local hidden variable theories, and it is complete nonsense to conflate hidden variables with "realism" as if your only choices are to believe the reality is deterministic or to deny reality even exists! What kind of options are those? What about a third option that reality exists and it is just nondeterministic?

What Bell's theorem shows is that quantum mechanics cannot be replaced with a local hidden variable theory, and since we know the universe is local, that means it cannot be replaced with a hidden variable theory. It forces us to accept nondeterminism, it doesn't force us to deny reality, nor does it prove there is nonlocality.

[–] milicent_bystandr@lemm.ee 1 points 1 day ago (1 children)

What about a third option that reality exists and it is just nondeterministic?

There's still a pattern in the results, so by one means or another we want to explain the results. Just calling it nondeterministic, if I understand right, would be just saying you can't predict it from prior observations.

So, whatever language you use to describe this puzzling situation, the puzzling situation thus far remains.

since we know the universe is local

A priori? Or because it best fits with Relativity? It sounds about as strong as saying, "we know time is universal." It's obvious, has to be true, but apparently not how the universe functions.

[–] pcalau12i@lemmy.world 0 points 1 day ago* (last edited 1 day ago) (1 children)

There’s still a pattern in the results, so by one means or another we want to explain the results. Just calling it nondeterministic, if I understand right, would be just saying you can’t predict it from prior observations. So, whatever language you use to describe this puzzling situation, the puzzling situation thus far remains.

I mean nondeterministic in a more fundamental sense, that it is just genuinely random and there is no possibility of predicting the outcome because nothing in nature actually pre-determines the outcome.

A priori?

Through rigorous experimental observation, it's probably the most well-tested finding in all of science of all time.

Or because it best fits with Relativity? It sounds about as strong as saying, “we know time is universal.” It’s obvious, has to be true, but apparently not how the universe functions.

So we can never believe anything? We might as well deny the earth is round because people once thought time is absolute now we know it's relative, so we might as well not believe in anything at all! Completely and utterly absurd. You sound just like the creationists who try to undermine belief in scientific findings because "science is always changing," as if that's a bad thing or a reason to doubt it.

We should believe what the evidence shows us. We changed our mind about the nature of time because we discovered new evidence showing the previous intuition was wrong, not because some random dude on lemmy dot com decided their personal guesses are better than what the scientific evidence overwhelmingly demonstrates.

If you think it's wrong show evidence that it is wrong. Don't hit me with this sophistry BS and insult my intelligence. I do not appreciate it.

Maybe you are right that special relativity is wrong, but show me an experiment where Lorentz invariance is violated. Then I will take you seriously. Otherwise, I will not.

[–] milicent_bystandr@lemm.ee 1 points 1 day ago

I think you're getting angry at the wrong things and taking me too far. I didn't at all mean we can't believe or trust physical reality. Neither do I doubt special relativity, or specifically the Lorentz invariance.

I wasn't meaning to insult your intelligence, but now I feel you've done that for me.

[–] apolo399@lemmy.world 3 points 1 month ago (1 children)

They don't "communicate" faster than light, the wave function itself is non-local and collapses non-locally.

[–] pcalau12i@lemmy.world 1 points 1 day ago

It can, under certain conditions, contain information about things at a distance, but a function is not a physical entity and its reduction is not a physical process, so none of this reflects anything superluminal actually going on in physical reality.