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What did Einstein mean by “spooky action at a distance”?
- throwaway32341 5y agoI'm curious if Einstein would've been satisfied with the theory of superdeterminism and how it answers the "spooky action at a distance" expression.
- paraknight 5y agoWhat did she mean by the quantum correlations being stronger than the non-quantum ones? She lost me there
- lopuhin 5y agoI think the second paragraph in the wiki page about Bell's theorem explains that: https://en.wikipedia.org/wiki/Bell%27s_theorem https://en.wikipedia.org/wiki/Bell%27s_theorem
- tsimionescu 5y agoBell's theorem has proven that quantum entangled particles do not behave exactly like the socks. To understand it, let's imagine the sock experiment, but with 2 differences: one of the socks is red and fluffy, the other is blue and coarse; and you can't see exactly how red and how fluffy the sock you got is, you can only measure a combination of the two. So, you open your envelope and set your device to measure if the sock is 0.2 red and 0.8 soft (so, either blue or soft), and you get True. If the person who got the other sock set their device to 0.8 red and 0.2 soft, the classical probability that they get True would be 0.5 I believe. But if you perform this experiment with quantum entangled properties, you would see a greater value. Further, Bell has shown that one of 3 things must hold for quantum socks: - either they are neither blue/red nor coarse/fluffy until the measurement; after the measurement, your sock gets some value, and the other sock implicitly gets the opposite value, but there is no real "state change" since they didn't have any state to begin with (we reject realism) - they "tell" each other instantly in what state they were found (we reject locality) - the fact that you were always going to receive the red sock also caused you to choose 0.2 red and 0.8 soft, so what may look like a coincidence is in fact pre-determined (superdeterminism)
- goldenkey 5y agoOr.... consciousness collapses the wave function and solipsism is the nature of reality. Observables are just very large unevaluated expressions that collapse via lambda reduction ala becoming a tautology. As you gain more information, more alpha and beta reductions become possible, and expressions simplify into static values instead of multivariate/dependent expression trees. The universe is a first person JIT experience. Search for Wigner's friend. Relational quantum mechanics is the only logical and consistent epistemology for what all this means. Effectively, nothing ever changes, just extra information allows for simplification of observables backed by large expressions. The universe is inherently lazy, and it's like LISP. PG come at me!
- tsimionescu 5y agoWell, if you go for pure solipsism, that is, your own consciousness is the only thing which exists in the universe, that can explain any phenomenon you want. But objective collapse due to anyone's consciousness does not solve anything - my observation of this particle still causes infinite speed effects on your particle, so the universe is anyway non-local.
- goldenkey 5y agoIt's only solipsism in the sense that my wavefunctions do not have to agree with yours. There is a correlation between us, still. So it isn't like our wavefunctions are going to be radically different. We both are entangled since the Big Bang and even after that many times over as shared information exchanges between us. https://en.wikipedia.org/wiki/Wigner%27s_friend https://en.wikipedia.org/wiki/Wigner%27s_friend
- tsimionescu 5y agoThe article you cite provides various alternatives to this world view. It even contains the fun observation that the experiment has actually been performed, but with photons instead of observers - showing just how important consciousness really is in physical theories. In general, I believe the most obvious interpretation of consciousness is simply as a computational process, so looking at consciousness as a key to QM is incompatible with my beliefs. Furthermore, given the classical-ness of the world we see everyday, I have huge problems believing theories like MWI or these consciousness-based ones that claim the world is entirely quantum everywhere and it's just some kind of accident that it seems so classical to us (contrast to relativity which has a very satisfying answer for why we don't notice the difference from classical mechanics).
- stareatgoats 5y agoPeople with an interest in cosmology and bleeding edge physics can do worse than follow Sabine Hossenfelders blog or Youtube channel. Maybe everyone already does, but personally I discovered it just a few months ago. She is the kind of specialist that we expected to find more of in the early days of the internet: deep knowledge and an interest in and capability for explaining things clearly to non-experts. We need more people like her, if only to be able to evaluate if she is right or not in some key questions (like her opposition to still more powerful particle accelerators). In this case I find her explanation of Einstein's famous phrase regarding quantum mechanics quite rational, which is a novel experience for me when it comes to quantum mechanics.
- jasonwatkinspdx 5y agoI'd add a disclaimer that Hossenfelder has some very strongly held negative views on how resources in the physics community should be allocated, particularly theoretical particle physics. This stack overflow answer is a pretty charitable explanation of why the overwhelming majority of the physics world disagrees with her on these specific meta issues: https://www.quora.com/How-do-theoretical-particle-physicists-respond-to-Sabine-Hossenfelders-How-Popper-Killed-Particle-Physics https://www.quora.com/How-do-theoretical-particle-physicists...
- RedShift1 5y agoWhy the disclaimer?
- jasonwatkinspdx 5y agoThe bulk of her audience are folks without enough exposure to the physics world to understand that while she is very much an expert on physics itself, her meta views on how the community should conduct themselves are fringe.
- tsimionescu 5y agoTo be fair, it seems that that blog post and the Quora responses are older than her book, where she clarified her position significantly more, though your claim about the majority of particle physicists disagreeing with her is likely still correct. The important difference between now and when the answer was written is that she has given her own alternatives: she believes that only theories that resolve an explicit contradiction or open problem in current physics should be considered, such as quantum gravity or dark matter or the measurement problem; while theories that simply fix 'ugliness' should be ignored, such as grand unification. Furthermore, she believes that theories with open parameters whose range exceeds possible near future possible colliders should not be tested, even if the lower bounds on the parameter could be testable - this is true for supersimmetry or WIMPs. Since ruling out supersimmetry entirely requires a planet-sized accelerator, there's no reason to keep building slightly larger ones just in case. Finally, she makes a concrete recommendation: shifting focus to astronomy as a better way to observe high energy particle physics occurring in the universe, investing in much more advanced telescopes instead of bigger particle colliders.
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- choeger 5y agoWait a second. Does that mean the nonlocality was introduced in QM just because distance simply didn't occur in the model? There was no prior theory that predicted you could ignore distance? Later experiments then confirmed that yes, distance does indeed not matter for the wave function collapse? That's ... incredibly unlikely, right? I mean, one simply wouldn't expect a model to simplify things and then learn that the simplification reflects reality.
- JumpCrisscross 5y ago> one simply wouldn't expect a model to simplify things and then learn that the simplification reflects reality Isn't this a refrain in the history of science? Observations inspiring models that illuminate a deeper, truer representation of reality?
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- georgeecollins 5y agoIt's a conceptual fallacy that the underlying mechanics of a phenomena are simpler than the observed data. It's appealing to our way of thinking and aesthetics to believe that the rules that govern are simple. But it may or may not be the case.
- throwamon 5y agoPhenomena is the plural of phenomenon.
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- GistNoesis 5y agoThe non-locality of QM was introduced because of the Fourier transform which is non-local. Mainly because it's the easy way to calculate by hand when you have no computer in the 1920s. [Tinfoil hat warning :] Since then it's a self-reinforcing confirmation bias to avoid the obvious locality of the real world mainly because of geopolitical reasons in the 1960s. /[Tinfoil hat warning :]
- tempestn 5y agoI've really got to think many worlds is the complete version, although I have no idea how that would be proven. Did Einstein get a chance to consider that framing? It seems like it would be up his ally as an explanation for the apparent measurement update.
- Myto 5y agoUnfortunately no, Everett presented the idea in 1957, Einstein died in 1955.
- eigenket 5y agoI am generally positive towards the mwi/Everetian approach, but it should be emphasised that we really don't have a satisfactory understanding of what "measurement" is in the Everetian approach, and in particular I don't think it is at all clear how to reproduce the Born rule.
- eternalban 5y agoThis is a great 1985 Danish documentary (it's in English) that details Einstein & Bohr's fundamental disagreement regarding the interpretation of QM, and Alain Aspect's 1980-82 EPR experiments showing the violation of Bell's Inequalities. Both the historic elements and Aspect's groundbreaking experimental setup are detailed. It's a little gem featuring interviews with a young Alain Aspect, John Bell, David Bohm, Abner Shimony, John Wheeler, & a very excited Holger Bech Nielsen. It is very accessible yet hugely informative, and somehow (with that soundtrack) enchanting. Quantum Entanglement - Atomic Physics and Reality: https://www.youtube.com/watch?v=BFvJOZ51tmc https://www.youtube.com/watch?v=BFvJOZ51tmc https://en.wikipedia.org/wiki/Alain_Aspect https://en.wikipedia.org/wiki/Alain_Aspect https://en.wikipedia.org/wiki/Aspect%27s_experiment https://en.wikipedia.org/wiki/Aspect%27s_experiment
- kergonath 5y agoThere are several good seminars by Alain Aspect on YouTube as well, ranging from highly technical to accessible vulgarisation.
- ZeroGravitas 5y agoI'm no expert, but I thought that Einstein was pointing out the flaws of the Copanhagen interpretation of quantum physics. Sean Carrol gave a talk about his new book and his claim is that quantum mechanics is pretty straightforward, and all the spooky weirdness is only needed if you try to ignore the implication that the data supports the-many world interpretation. https://youtu.be/F6FR08VylO4 https://youtu.be/F6FR08VylO4 i.e. similar to the sock example given, when you open the envelope you find out what universe you are in, the blue sock or red sock universe and that tells you information about the other sock in your universe. But another you is finding the other color sock in a different universe.
- jiggawatts 5y agoBut physics is so much more mysterious if everybody carefully refuses to acknowledge the mere existence of the clear and obvious answer.
- TheOtherHobbes 5y agoMWI people keep making these strong claims and ignoring the very credible criticism of them. https://www.quantamagazine.org/why-the-many-worlds-interpretation-of-quantum-mechanics-has-many-problems-20181018/ https://www.quantamagazine.org/why-the-many-worlds-interpret...
- ZeroGravitas 5y agoThat's a very philosophical rather than physics-based rebuttal. He appears to be saying it can't be true because it would make life/and or the concept of self meaningless. Whereas I would say that a theory that suggests we are meaningless temporary blips in an infinite universe is probably a much greater indication that it is true than otherwise.
- fsh 5y agoMost interpretations of QM make identical predictions for the outcome of any possible experiment. This makes the field fundamentally philosophical rather than scientific.
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- emrah 5y agoEntanglement isn't like how it's described in the post at all. Entangled particles are correlated across spacetime in a way that goes beyond "instantly knowing there is red in one envelope when blue is in the other". First of all, we don't know which color is in which envelope at the start. And revealing of one instantly determines the other physically regardless of whether it came up red or blue. So entanglement is "spooky action at a distance". This property doesn't constitute FTL communication though since we can't encode any information this way, we don't know what the particles will reveal when measured. We just know that measuring one will affect the other particle no matter how far apart they are physically. So I imagine Einstein meant both.
- headmelted 5y agoI was trying to think of a way to explain this to a family member a while back who had a background in mechanical engineering. The best example I could think of to analogise it were meshed gears. There is no messaging happening between them. When one rotates, the other rotates in the opposite direction at the same exact time because they are interlinked. They are two parts of one connected set. That entangled particles are interlinked in this way shouldn’t be surprising. Having what to us seem to be arbitrary distances between the particles could simply mean that they’re interlinked outside of the three spatial dimensions we’re used to perceiving the universe in - but this last part is just my own understanding and I’m quite happy for someone who knows better to tell me if (and why) it’s wrong.
- TeMPOraL 5y ago> There is no messaging happening between [meshed gears]. Isn't there? Atoms rub against atoms, electric fields interact and transfer forces. The gears communicate by touching, but it happens so fast that it looks instantaneous. This can be experimentally verified by weakening one of the teeth of one gear, and driving some load with that gear set - eventually, the weakened tooth will break off.
- rleigh 5y agoThere is messaging through physical contact. It occurs at the speed of sound as opposed to the speed of light.
- hyperpallium2 5y agoAren't fields - magnetic, electric, gravitional etc - also spooky action at a distance? EDIT Thanks all!
- pantalaimon 5y agoNo they are limited by the speed of light
- fsh 5y agoNo, these fields are all local. Disturbances propagate at the speed of light and an event in one place cannot cause an effect in another place instantaneously.
- dogma1138 5y agoThey are just action at a distance, which was used much earlier than QM and GR to depict basically anything that didn’t require physical contact like gravity and electromagnetism. “Distance” is still a factor in fields hence locality, the action isn’t instantaneous and is governed by the universal speed limit and the amplitude is also affected by distance. Entanglement works instantly and regardless of distance hence the spooky part.
- amelius 5y agoWhy didn't he apply his "equivalence principle"? If two particles behave in the same way, they must be the same particle!
- ziofill 5y agoQuantum physicist here. If two particles are entangled, the very value of the entangled properties does not exist locally (if it did it would be a hidden variable, with crazy consequences, but there are even cases where pre-existing values are forbidden algebraically, like for the GHZ state). Entanglement only gives us a promise of joint behaviour like "if the particles are in the Bell singlet state and we measure them with the same measurement settings, the results are going to be opposite" (notice that the promise is only about the values being opposite, not about what they will be locally). I believe that what Einstein meant by spooky action is exactly about this: that a particle seems to know which settings have been used for the measurement of the other, because if the settings are different then the promise can be broken.
- pmoriarty 5y ago"the very value of the entangled properties does not exist locally" Does physics have a definition for existence?
- ziofill 5y agoYes! (and good question) In this case we use Einstein's definition of local hidden variable (which he called "element of reality"): "If, without in any way disturbing a system, we can predict with certainty (i.e., with probability equal to unity) the value of a physical quantity, then there exists an element of reality corresponding to that quantity."
- pmoriarty 5y agoIf I may infer that this statement has been interpreted as not a conditional as it is stated verbatim (in the form A -> C where A is the antecedent and C is the consequent), but instead is a biconditional (in the form A <-> C), then it seems to be stating that to exist is to be certainly predictable. That's a curious definition of existence. And now that I think about it a bit more, it seems like it's not really talking about what existence is, but rather the consequences of existence and the consequences of certain prediction. That's not quite the same as a definition of existence, is it?
- ergocoder 5y agoIs there an experiment that shows the entangled particles are NOT set before they are separated? It seems to me that it's fairly easy to explain why one particle correlates to the other. Both of their properties are set before they are separated. We just didn't measure those properties beforehand. I've read and watched a lot of quantum physics on youtube. This kind of refusal is always elusive, as in nobody has an experiment to negate this explanation (or maybe I miss it). Wave-particle duality is another one that doesn't feel real, especially when we fire one electron and we say "electron interfere with itself". It seems we think of it as a wave simply because the electron is too small for us to see. And that's it. Somehow we come up with this convoluted explanation with catchy name "wave-particle duality". This one is also elusive. Is there an experiment that refuses this explanation of how wave-particle duality isn't real?
- geeB 5y agoThat would be a local hidden variable. See https://en.wikipedia.org/wiki/Bell%27s_theorem https://en.wikipedia.org/wiki/Bell%27s_theorem and https://en.wikipedia.org/wiki/Bell_test https://en.wikipedia.org/wiki/Bell_test
- lamontcg 5y ago> a lot of people too cheerfully declare that Einstein was wrong about quantum mechanics. Einstein Podolsky and Rosen put down the scientific and theoretical foundation for testing enganglement in Quantum Mechanics. Treating it like just a horse race where Einstein was "wrong" is missing the contribution they made by designing the experiment (refined by Bell and tested by Aspect). What is interesting is that Bohr was "correct" but his contribution is mostly a bunch of untestable philosophical nonsense. The better contribution to science here is Einstein even though nature decided that his hunch was wrong. And there's a lesson in here somewhere about human nature and how we value people who just make lucky guesses that pay out and we call people who change their mind after more information comes in "flip-floppers".