Bell's Theorem pretty much rules out any local hidden variable theories, and any hidden variable theory that's nonlocal is just regular quantum mechanics with an extra variable thrown in. But, since locality is dependent upon distance, it is also, by definition, dependent upon time...

I can't help but think that this implies that distance (locality) is an illusion. If so, it must logically follow that time too is an illusion (lunch time doubly so...).

Does Bell's Theorem Suggest both Physical Nonlocality and "Temporal Nonlocality" or, am I making a distinction where none exists and Nonlocality is, by definition, refers to the combination of space and time?

  • $\begingroup$ OK I am out of my depth, but without a concept of time, how do we assess that non locality exists? $\endgroup$ – user198207 Jul 3 '18 at 7:50
  • $\begingroup$ I'm guessing people are down-voting this because it's a little vague and asks more than one question. Maybe people could say so if that's the case? $\endgroup$ – user93146 Jul 3 '18 at 16:04
  • $\begingroup$ Hmmmm... "A little vague and asks more than one question", huh? Yep! That about sums me up :-) Seriously though, I still think it's a valid (group of) question(s) and the point I was trying to get at is that time has got to be one of the least understood and most integral element in our current conceptualization of physics. And it seems to me like most physicists just keep ignoring this fact. $\endgroup$ – Thor Jul 4 '18 at 3:49
  • $\begingroup$ Perhaps you could explain why you think the reasoning is circular in your first paragraph? $\endgroup$ – Jon Custer Jul 4 '18 at 16:19
  • $\begingroup$ The speed of light is defined by the length of the meter and the length of the meter is defined by the distance light travels over 1/299792458ths of a second. Pretty circular to use one to define the other, isn't it? As Puppetsock pointed out, the second is currently defined by the vibrations of a cesium atom, not technically by the length of the meter (my definition was of a light second), but defining time as the vibrations of an atom is like saying that time is how fast the clock ticks. It's an observation, not an explanation. $\endgroup$ – Thor Jul 4 '18 at 16:35

Ok, first, you've got the definition of the time unit "second" incorrect.


Generally, if you find that you seem to have uncovered physicists behaving in a grossly silly fashion, it is good to investigate a little more carefully. Maybe they are being silly, but it's not the way to bet.

Next, Bell's theorem is a little more subtle than that. It does not imply non-locality. What it does is say that quantum physics predictions can be distinguished from classical physics predictions of a particular kind, particularly classical physics predictions that are both local and deterministic.

And that means we need to know what local and deterministic each mean.

Deterministic means you set up an initial situation and then the results will be specific and determined by the initial setup. One frequent poetic explanation is a clockwork physics.

Local means that information cannot propagate outside the light cone. You can't get messages faster than the speed of light.

QM is local in that sense, but not deterministic.

Bell's theorem shows a situation where any possible local and deterministic physics will be distinguishable from QM. So, it pushes very hard for us to give up local-and-deterministic physics.

But it does not say "give up locality." Since QM does not give up locality.

And it's actually OK. You can't send messages faster than light using things like Aspect's experiment. So even though such tests do come down in favor of QM they don't tell us we need to kill locality.

A comment asked about the meaning of time. Physics gives an operational definition of time. We see motion. We define time so that motion looks simple. There is a nice description of this in the book "Gravitation" by Misner, Thorne, and Wheeler. (Bring a shopping cart. The book is HUGE.) I hope this link comes through. If not, google for the phrase "time is defined so that motion looks simple" and you will see it in one of the first few hits.


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  • $\begingroup$ Thank you for the corrections. I should have said Light-Second instead of second (en.wikipedia.org/wiki/Light-second). And thank you for pointing out that my question is silly. However, I think you missed the point of my admittedly rambling and poorly articulated series of questions. $\endgroup$ – Thor Jul 4 '18 at 4:00
  • $\begingroup$ If 2 entangled particles are separated in physical space and a measurement is made on one of the particles, the quantum state of the entire system changes, right? And the wave function of the entangled state will collapse faster than the speed of light, right? And Bell showed pretty conclusively that any physical theory that incorporates local realism cannot reproduce all the predictions of quantum mechanical theory, right? So, local realism (locality) is dead, right? And if locality is dead, doesn't that imply that time is dead too? You can't have one without the other. $\endgroup$ – Thor Jul 4 '18 at 4:21
  • $\begingroup$ Please re-read. Local-and-deterministic contains two parts. Killing the combo does not mean killing both parts. QM keeps one. It was a tedious homework assignment in my MSc to prove that quantum field theory does not allow messages faster than light. And various tests of Bell's theorem push in that direction. QM says no to determinism, yes to locality. $\endgroup$ – user93146 Jul 4 '18 at 14:04
  • $\begingroup$ I'm not asking about classical interpretations. I'm asking about foundations. $\endgroup$ – Thor Jul 4 '18 at 15:16
  • $\begingroup$ In order to have a concept of either determinism or locality, it seems like one should (especially at this level) really have a firm and fundamental definition of time. That's the root of what's really bothering me. $\endgroup$ – Thor Jul 4 '18 at 15:22

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