Comments by "Lepi Doptera" (@lepidoptera9337) on "What did Einstein mean by “Spooky Action at a Distance"?" video.

  1. Gravity is also not action at a distance. It travels at the speed of light.
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  2. It simply means that there is an irreducible amount of angular momentum that comes from the measurement systems. No matter how we interpret the process, it does not result in a "classical" view that quanta are "objects" that carry all their properties with them. Of course quanta were never supposed to be objects in the first place. That's was always a misunderstanding of nature.
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  3. No.
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  4.  @michange3141592  Why are you guessing all the time? Physics is not a guessing game. You can read the publications about the experiment which contain the theoretical description or you can learn enough physics to figure it out for yourself. :-)
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  5. They are not determined only locally. There is a component that comes with the free field, but then there is another component that comes from the measurement system. The real problem here is that the free field and the field that makes the measurement system are actually the same field. It's only the physicist's divide-and-conquer mindset that tries to distinguish between the two. In quantum field theory we are completely giving up on that concept and we are merely distinguishing between interacting fields (at short distance) and non-interacting ones (at long distance). That's a much more natural way of looking at nature than the two systems approach.
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  6. I know. One can say a lot of things about quantum mechanics but not that it is not confusing the heck out of a lot of people. To me the most surprising thing about it is that we managed to figure it out at all. The problem is compounded by the fact that "local" in a relativistic world carries a very different set of consequences than in a Newtonian (Galilean) world. Relativity is the real reason why there can be no local variables to begin with, but that is rarely discussed at the level of introductions to QM. That is a shame because many of the perceived problems with QM are going away once we start looking at it through the relativistic lens. We are trading those ontological solutions in for a very large number of highly complicated mathematical detail problems in quantum field theory, which explains why almost nobody dares to touch on the intersection of relativity and quantum mechanics at this level.
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  7. I have managed to sort it out nicely in my own mind over the years, mostly by trying to explain it to other people over and over, again. The first few hundred times I was talking complete nonsense, of course, just like everybody else. Eventually it clicked and now I have a number of actually workable analogies and examples, but yeah, it took a decade or two to get there. Feynman really didn't do the the world a service with that statement, if it is by him, that is. Of course he was joking, but most people seem to take it at face value, which is a pity because then it becomes an anti-intellectual statement that defends intellectual laziness. I learned that quantum mechanics can not be treated with logic when I saw that the operator algebras in quantum mechanics are non-commutative while Boolean logic is a commutative algebra. So that's really a hard mathematical fact. We should be teaching these non-commutative structures much sooner, preferably at the middle school level when we teach children "ordinary" algebra. I think it would make student's minds much more open to "unusual" and "unintuitive" ideas if we would show them examples of "what else is out there" early and often.
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  8. Einstein was one of the physicists who pointed out its existence. What he failed to understand (or so we think) is that it was caused by relativity. It is, of course, possible that he did understand it, but if he did, then I just don't know where and how he communicated that to his peers. I didn't read all of Einstein's writings, though, so I might be missing something.
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  9. No. ;-)
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  10. Thank you! You did me an enormous favor. I went back to the paper by Heisenberg which supposedly contains the first mention of "collapse of the wavefunction" and I found an incredibly insightful passage. Heisenberg muses about the transition from atomic electron orbitals to classical orbits and he writes: "Ich glaube, dass man die Entstehung der klassischen „Bahn" praegnant so formulieren kann: Die „Bahn" entsteht erst dadurch, dass wir sie beobachten.". In my translation this means "I believe that we can formulate the emergence of a classical "path" most significantly in this way: The "path" emerges only because we are observing it." He then proceeds to give a physical picture of what observation may do to an atom in a highly excited state (a so called "Rydberg atom"). In other words, intuitively Heisenberg already understood that the classical world is the result of continuous weak observation of quantum systems, something that Mott will explain with mathematical precision just a couple years later (1929) for alpha particle tracks in high energy particle detectors. This is still widely unknow and poorly taught in QM 101 classes, despite its almost 100 year history. I couldn't find anything in that paper that talks about "collapse of the wave function", so far. I need to read it, again.
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  11.  @xiupsilon876  Yes, there has been a lot of theoretical research in that area and even Sabine Hossenfelder has recently published an article about a different type of "hidden variable" approach if I am not mistaken. There are a couple of problems with a phrase like "quantum mechanics is incomplete". What do we mean by that? Incomplete because we can not know position and momentum with arbitrary precision at the same time? That's not a quantum mechanical property to begin with. It's a general mathematical property of functions with L2-norm (that's what the mathematicians call "energy"). It's just as valid for water waves as it is for classical electromagnetic waves as it is for quark and gluon quantum fields. Wifi routers have a protocol that uses time-energy uncertainty to shape radio-wave packets in a certain way. Our engineers are using this principle in mechanical, electrical and information systems daily. This can never be "undone" because it runs into a fundamental mathematical property of continuous functions. If Einstein would have wanted that, then he didn't even realize that the classical world had exactly the same limitations as soon as continua were involved. Incomplete because photons, electrons etc. do not behave like classical particles? Absolutely nothing in the universe behaves like a classical particle. A classical particle in physics was always an abstraction to simplify problems like the Kepler problem to the level where it can be (almost) solved in closed mathematical form. All it ever meant was that we reduce the dynamics of an extended classical body to the dynamics of its center of mass, i.e. we neglect rotations and internal degrees of freedom. As it turns out, there are approx. one dozen single particle Hamiltonians that are integrable (that have general closed form solutions) and some of them (like the three dimensional Kepler problem and the four dimensional harmonic oscillator) are mathematically equivalent. Every other "particle problem" does not have a closed form solution and we can not predict its motion for arbitrary long times. If we connect three or four masses with rigid sticks and ask what the general rotation of these masses are, then it takes about a thousand pages of mathematics and physical discussion to sort out the possible modes of rotation of such systems under symmetry conditions and there is no solution for a completely asymmetric rotator, at all. That system is already completely chaotic. So what, exactly, are we losing in quantum mechanics compared to classical systems? If anything, the hydrogen atom is a much better behaved system than a general Newtonian rotator ever was. Finally, quantum mechanics the way Einstein saw it was not a physical theory. It was more like thermodynamics, a framework that connects different types of physical properties with each other but that does not say anything, at all, about a specific physical system. The physical theory that makes solid statements about nature is quantum field theory. It builds on what Einstein knew, but it goes far beyond it. Even Heisenberg mentions in that paper I just read that he does not believe (this is in 1925, I believe) that a quantum mechanical theory of the electromagnetic field is even possible. Feynman and others gave us such a theory in the 1948 to mid 1950's time frame, i.e. we went from knowing nothing about quantum fields to a complete (if unexplored) theory in another 30 years. That theory happens to be the one that has the best numerical match between theoretical prediction and experiment of all of our theories, to date. It's better than Newtonian mechanics/general relativity in the solar system by a factor of 100 or so, if I am not mistaken. So, then what does it take to make quantum theory complete? A predictive formula of when the next photon will appear in a photon detector? Do we have such a formula for the lottery numbers? The roulette wheels in Las Vegas? When two cars will collide the next time at any given intersection? Whether it will rain at 3:12pm next Thursday? If we do not have those predictors, then why does it bother us so much that they also do not exist for photons? Just my two cents.
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  12. Ah, somebody has never been in a physics lab. :-)
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  13.  @dreamdiction  Of course particles don't exist. Quanta do. You have never measured a quantum? I have. Plenty of them, actually. I do, of course, have a digital camera. :-)
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  14.  @dreamdiction  Sounds good. Now all you have to do is to explain the anomalous magnetic moment of the electron with that. Good luck!
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  15.  @dreamdiction  I merely know something that you don't: the anomalous magnetic moment of electrons comes from the coupling of the electron spin to the quantized electromagnetic field. Good luck explaining a quantum-electromagnetic effect without field quanta. :-)
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  16.  @jjharvathh  Gravity is what holds you on the floor. You need to pay more attention in school. ;-)
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  17. Only because you don't know the facts. There is way too much nonsense about it going around.
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  18. Entanglement is completely independent of distance. That means it doesn't matter at what distance the observations are being made. Nothing ever happens. ;-)
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  19.  @octopusjjsnook  Quanta are small amounts of energy, momentum, angular momentum and charges. We teach this correctly in high school when we explain the photoelectric effect, but if you go to university you are being told in your first quantum theory class that it's all about "particles". That, unfortunately, is not correct. The particle language is a historical artifact that originated in the 1920s at the beginning of quantum mechanics when people were still confused and it has been retained by textbook authors through the years. Most physicists simply adopt this language without thinking much about its implications. For most applications within physics the difference doesn't matter, but if you are really trying to understand what quantum mechanics is and what it actually does, then the difference between a small object and a small amount of energy is absolutely crucial.
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  20.  @michange3141592  Nonlocality is boring. A water wave is non-local.
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  21.  @michange3141592 How did you come to the conclusion that there are two wave functions? And who told you that wave functions collapse? Certainly not nature.
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  22.  @michange3141592  I was trying to help you. I am sorry that you don't like the Socratic method.
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  23.  @michange3141592  You seem to be imbibing a lot of your own ego, though. :-)
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  24.  @michange3141592  I did explain it. Einstein's spooky action at a distance does not exist. Hence my answer was "no". :-)
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  25. What's the hidden variable? That socks exist? So do quantum fields. They are just as "real" as socks, they just happen to behave a little differently under measurements.
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  26. I have done plenty of quantum measurements. I have never seen a wavefunction collapse. Have you?
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  27.  @81giorikas  Can I what? Make a quantum measurement? Sure. What's so hard about it? Do you have salt and a flame? That bright yellow flame color is caused by atomic transitions of sodium atoms.
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  28.  @81giorikas  That was my point. There is no such thing.
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  29.  @81giorikas  I don't do brain surgery, either. Let me know how that clarifies quantum mechanics for anybody.
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  30. Which ones?
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  31. And this is why philosophy is bullshit. Please take a few classes in physics, instead.
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  32. Where has this been shown, actually? I am not aware of such an experiment.
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  33. One can derive the structure of quantum mechanics using basically the Kolmogorov axioms and by dropping the requirement that the probability distribution is real valued. Plenty of people have done it with slight modifications in the basic assumptions as far as I know. I don't find these derivations particularly interesting, though, because the structure of quantum mechanics is entirely free of actual physical content. One needs far more than that to arrive at physical predictions, which brings us to axiomatic quantum field theory. That is, if anything, the real deal, but I don't know enough about it, yet.
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  34. Einstein was wrong about almost everything in quantum mechanics since 1905.
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  35. That is an interesting interpretation, but it's very much out of touch with the usual characterization of Einstein as someone who was in awe and in perfect command of thermodynamics and statistical mechanics. The wavefunction is an ensemble property, which is the core concept in statistical mechanics. I am having a hard time believing that he had trouble making the connection.
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  36. That's the entire problem. Einstein gave photons corpuscular properties in his 1905 paper. Unfortunately for you and him such corpuscular properties had never been observed and are not being observed, even today. They were a flight of fancy back then and are flight of fancy today.
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  37. Have you ever seen a moving photon? I have not.
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  38.  @DavidporthouseCoUk  You didn't answer my question. Have you ever seen a moving photon? That would require you to measure the same photon in two different positions at two different times.
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  39.  @DavidporthouseCoUk  So now you are measuring each entangled photon once. That's still one measurement per photon. Any suggestions how we get to two measurements per photon?
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  40.  @DavidporthouseCoUk  It's much worse than that: there is no photon after the first measurement. :-)
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  41. Not a bad article, as far as the mathematical implications of the formalism are concerned, but it still misses the actual physical ontology, which is not surprising. It was written by a capable theoretical physicist. He thinks in terms of formalisms, rather than the physical systems that the formalism stands for. He gets a lot of things right, including the time scale separation in Schroedinger's cat, but that already happened at the level of the nuclear decay that drives the experiment, so he misses that the "cat is alive" criterion is a mere garnish on the actual physics that has already happened long before we ever get to that level. That's the same physics that Schroedinger missed to understand because he was not a nuclear physicist. It is also obvious that he still can't distance himself from the particle picture, which causes most of the confusion among laymen. It is, in some sense, useful among high energy physicists like himself, because detectors are measuring high energy quanta with weak measurements, which leads to particle-like effects, but it is completely wrong in e.g. quantum optics experiments with optical photons, which comprise the large majority of "mystical" experiments.
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  42. There is nothing strange about that experiment, either, you just don't understand where the sleight of hand is.
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  43.  @PSHomeVideo  OK, let's repeat this one more time: what any one physicist thinks or publishes on the internet is not physics. Nature tells us what physics is. In case of the delayed choice quantum eraser the sleight of hand happens in the fact that the only "non-causal effect" is seen in post-mortem correlations. It does not happen in real time. This tells you, one more time, that any and all attempts to make the wave function of a quantum mechanical ensemble an actual physical property of the system are nonsensical. But then... we already knew that.
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  44. Yes, that was bullshit. It only took one moment to see that. ;-)
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  45. One can't measure the wave function. One can only measure a projection of the wave function and even that would take an infinite number of measurements. In other words... one can't measure a wave function. Thankfully one does not have to measure wave functions because they are not physical. The only physical measurements are scattering amplitudes and those are perfectly well defined in quantum field theory.
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  46. Yes, that was a lot of nonsense. :-)
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  47. The problem with this description is that there are no particles in quantum mechanics. There are only quanta and quanta are not objects. They are irreversible energy transfers from a quantum field to an external system that we usually call "detector". It is not the quantum field that takes on the classical state of spin up or spin down but the detector. The sock example simply shows that one can trivially reproduce entanglement with a fully classical system just as well. There is nothing strange about that part. What is "strange" in some sense is that the quantum version of entanglement with spins produces different probabilities than the classical version.... but then, it does that independently of distance, which tells us that distance has absolutely nothing to do with anything.
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  48. That is not a problem because you can only look once at quantum mechanical socks. After that they are gone forever.
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  49. Yes, most people instantaneously misunderstand. Absolutely nothing happens... at any distance. ;-)
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  50.  @gerbre1  Trump claims that Obama is not a US citizen. Dude. Science is NOT what anybody claims. Science is the rational explanation of observations. The observations show that absolutely nothing is happening. The weird thing is that it's relativists like Susskind who are making these claims and the absence of physical action at a distance is a relativistic effect. IF there was a tiny FTL wormhole, then it would automatically violate special relativity and none of us would even exist. ;-)
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  51. Wave functions don't collapse. That's just an unphysical terminology that is said to have been invented by Heisenberg but that was understood as a formal, rather than physical process early on. It probably took up its current esoteric meaning in a game of Chinese Whispers over time.
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  52. Bohm can't predict anything other than ordinary quantum mechanics, it just uses some additional unneeded nonsense to do so.
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  53.  @seditt5146  And there is that troll, again. :-)
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  54.  @seditt5146  You got to try harder, kid. :-)
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  55. Does the probability distribution of a dice collapse when you throw it? Why not? If it doesn't, why should a wave function collapse? It's ontologically the same thing as a probability distribution.
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  56.  @Pengochan  I don't know where this idea comes from that the wave function is the state of the system. If it were the state of the system, then it could make more than just ensemble predictions. In reality a wave function can't predict much at all for a single experiment.
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  57.  @Pengochan  The wave function does not match the single experiment at all. It only matches an infinite repetition of experiments. You are confusing yourself. A single photon makes only one dot on a screen. A single dot is not an interference pattern. This is a typical example of people not seeing the trees through the forest. It is really simple: one is one. A single photon is a single photon. As soon as you are talking about "interference pattern", you are talking about an ensemble. You really need to pay attention to the language that you use and what it actually means in reality. I have never seen a particle. Neither have you. We have observed quanta, but they only occur at the interface of a quantum field and an irreversible system. They can not be found empirically anywhere else. It is not good to assume the existence of physical properties where they have never been observed. That's religious/magical thinking, not physics.
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  58.  @Pengochan  Yes, you get interference in an ensemble. That's what wave functions describe. There is no interference in single quantum experiments and there are no physical descriptions of single quantum experiments. That's the first two minutes of QM 101. What, exactly, is your issue with these facts of nature? I have seen a coronavirus. There are plenty of electron microscopic images of them online. At that point I stopped reading because you stopped making sense.
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  59.  @Pengochan  I am an experimentalist in the field of high energy physics. I have never seen a particle detector. I have only seen and built detectors for quanta. Now, you may not know why quanta seem to behave like particles under weak measurement conditions. That's your problem, though, and it can be easily remedied by reading Mott's 1929 paper titled "The wave mechanics of alpha-ray tracks". Happy reading! You also need to learn to count. A single quantum experiment produces exactly one measurement. It can never produce destructive interference.
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  60.  @Pengochan  Now you got it. There are no tracks or any other "particle properties" until weak measurements are being made. That is exactly the mechanism by which "classical physics" emerges from quantum mechanics. It is amazing that this is still not being taught much in QM 101 classes. I did, by the way, find an article by Heisenberg from 1927 where he suggests exactly that mechanism and he sketches it out for the example of Rydberg atoms. So we can be sure that even the founders of quantum mechanics had this more or less "in the bag", at least intuitively. Why the internet is still speculating about this triviality is the only mystery here.
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  61.  @Pengochan  For a single copy? There is no description for a single copy. We can't predict the outcome of a single experiment. The wave function is the description for an infinite ensemble of copies. It's no different from dice. I don't know what the next outcome will be when I make a throw. It could be 3, it could be 1 or any other number. All I know is that if I make enough throws, then on average all outcomes are equally likely for good dice.
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  62. ​ @Pengochan  An ensemble is just a large number of identical repeats. The wave function is the physical description of the ensemble. Even when you say "one could have an ion with spin 1/2 prepared" you need to be careful what you mean. Do you mean you have ONE ion prepared into a certain spin state or do you mean that you have a pure spin up state of an ensemble of ions prepared? Most people mean the latter. If I do exactly one measurement on one member of a mixed state ensemble, then I can't even tell that it's a mixed state ensemble. I will always get an individual pure state as the answer, I just don't know a-priori what the answer will be.
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  63. Entanglement is a bonified term in physics and "spukhafte Fernwirkung" is a meme that sprang from Einstein's failed understanding of quantum mechanics.
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  64. No smart person will tell you that. A smart person will say that we don't have the necessary data to proceed with the theory. :-)
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