Timeline for Is This Video on Bell's Theorem Wrong?
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| when toggle format | what | by | license | comment | |
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| yesterday | answer | added | tparker | timeline score: 2 | |
| yesterday | answer | added | Ruffolo | timeline score: 3 | |
| yesterday | answer | added | alanf | timeline score: 1 | |
| yesterday | answer | added | Andrew | timeline score: 5 | |
| yesterday | comment | added | JimmyJames | Maybe I'm confused or too focused on semantics but I thought "Bell's theorem" was essentially describing a way to test for locality. It in itself doesn't rule anything in or out, it would be the results of the experiments that would do that. | |
| yesterday | answer | added | schtandard | timeline score: 4 | |
| yesterday | comment | added | schtandard | However, as I understand it, Quantum Mechanics is a local theory, or at least it isn't necessarily non-local. Non-relativistic QM (which is what's referred to here, I believe) is non-local. This is why EPR argued that it must obviously be incomplete, with the complete theory being local. Bell experiments showed that this is wrong, i.e. that reality does feature non-locality. This does not rule out hidden-variable theories, of course, just the local ones. (By "local", I mean local in location space, which is the usual sense, I believe). | |
| 2 days ago | review | Close votes | |||
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| 2 days ago | history | became hot network question | |||
| 2 days ago | answer | added | rob♦ | timeline score: 31 | |
| Jan 29 at 4:11 | comment | added | Gunnar | @naturallyInconsistent, I have no problem with Veritasium and have learned a lot from the channel. However, that does not change the validity of the claims in my question. You yourself stated that Bell's theorem not ruling out local hidden variables is wrong. The video itself doesn't provide precise definitions while calling other textbooks/papers and the standard interpretation of Bell's theorem(included in the first sentence on the Wikipedia page of Bell's theorem) wrong. Additionally, it claims Bell agreed with this, but does not provide a source for this claim. | |
| Jan 29 at 3:43 | comment | added | naturallyInconsistent | No, you cannot make such a claim of them when you are yourself not being precise with the definitions. I think Veritasium is doing a good job trying to educate the public about this theorem and that it is a known issue in the literature that there are multiple conflicting definitions being thrown around. I have many modern problems with Veritasium but this is not one of them. | |
| Jan 29 at 3:19 | comment | added | Gunnar | @naturallyInconsistent, it does seem fair to say the video is wrong or, at best, really misleading because of ambiguous definitions in physics. It also seems fair to point out that the claim is wrong, because the claim itself is stating that other physics textbooks/papers get this wrong, when this is again due ambigious definations. I would have no problem if it stated something along the lines of "based on what we think are useful definitions of these terms, Bell's theorem does not rule out local realism." | |
| Jan 29 at 3:03 | comment | added | naturallyInconsistent | No, the experimental tests of Bell's theorem do rule that out, but it depends very strictly upon what definitions are being used for all those words. Which is what everybody had been telling you up until now. You have to be extremely careful with disentangling all those different definitions, and trying to gotcha a scientist who is already carefully presenting the experiment, is just not the way to make sense of anything. | |
| Jan 29 at 2:41 | comment | added | Gunnar | @naturallyInconsistent, I am not sure I understand. Does this mean Bell's theorem does not rule out local hidden variables as defined by him? | |
| Jan 29 at 2:38 | comment | added | naturallyInconsistent | No, Bell did define precisely what he meant by local and by hidden variable in his paper, precisely because he knew that his result necessarily depended strongly upon what particular definition is being discussed. The status of quantum theory is quite difficult to point out, because it is local on configuration space, especially if you take the Many World Interpretation, whereas if you take any collapse, the collapse is non-local. The correlations are non-local, but there is a theorem proving that such non-local correlations cannot be used to transmit information, and that preserves causality. | |
| Jan 29 at 2:34 | comment | added | Gunnar | @WillO, I do believe that this indicates the video is wrong, or at best, really misleading, because saying "Bell's theorem does not rule out local hidden variables" presents an agreed-upon implication of Bell's theorem and Bell Test in physics; however, if the standard definitions of those words don't exist in physics, then it's not true. It's like if you claim that there is an agreed-upon definition of "blue" between you and your wife, and then state your wife is wrong. | |
| Jan 29 at 2:26 | comment | added | Gunnar | @hft, What I am trying to say is that, according to the accepted principle of locality in physics, quantum mechanics isn't necessarily non-local. Additionally, if there are no accepted standard definitions of those words in physics, then it is wrong to claim "Bell's theorem doesn't rule out local hidden variable theories(according to physics)" just as the claim "Bell's theorem rules out local hidden variable theories" is wrong. The correct claim should be "It is unclear if Bell's theorem rules out local hidden variables, as we cannot agree on a standard definition of those words in physics." | |
| Jan 29 at 1:34 | comment | added | WillO | @hft has already made the key point, but let me put it another way: Different people use the same English words to mean different things. My wife and I cannot agree on whether my favorite sweater is blue or green. That doesn't mean one of us is wrong; it means we are using the word "blue" in two different ways. | |
| Jan 29 at 1:14 | comment | added | hft | (It just doesn't make sense to try and answer a question about a "local hidden variable theory" if it is not even clear that you agree or disagree about what "local" means in the first place.) | |
| Jan 29 at 1:13 | comment | added | hft | "At 38:30, it states: 'So quantum mechanics is non-local...' However, as I understand it, Quantum Mechanics is a local theory..." You need to resolve this before proceeding to the rest of your question. Are you wrong or are they wrong about this locality point? You might start by explaining what you mean by "local" and what you think they mean by "non-local". | |
| Jan 29 at 0:47 | history | edited | naturallyInconsistent | CC BY-SA 4.0 |
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| Jan 29 at 0:39 | history | asked | Gunnar | CC BY-SA 4.0 |