Saturday, May 08, 2021

What did Einstein mean by “spooky action at a distance”?

[This is a transcript of the video embedded below.]

Quantum mechanics is weird – I am sure you’ve read that somewhere. And why is it weird? Oh, it’s because it’s got that “spooky action at a distance”, doesn’t it? Einstein said that. Yes, that guy again. But what is spooky at a distance? What did Einstein really say? And what does it mean? That’s what we’ll talk about today.

The vast majority of sources on the internet claim that Einstein’s “spooky action at a distance” referred to entanglement. Wikipedia for example. And here is an example from Science Magazine. You will also find lots of videos on YouTube that say the same thing: Einstein’s spooky action at a distance was entanglement. But I do not think that’s what Einstein meant.

Let’s look at what Einstein actually said. The origin of the phrase “spooky action at a distance” is a letter that Einstein wrote to Max Born in March 1947. In this letter, Einstein explains to Born why he does not believe that quantum mechanics really describes how the world works.

He begins by assuring Born that he knows perfectly well that quantum mechanics is very successful: “I understand of course that the statistical formalism which you pioneered captures a significant truth.” But then he goes on to explain his problem. Einstein writes:
“I cannot seriously believe [in quantum mechanics] because the theory is incompatible with the requirement that physics should represent reality in space and time without spooky action at a distance...”

There it is, the spooky action at a distance. But just exactly what was Einstein referring to? Before we get into this, I have to quickly remind you how quantum mechanics works.

In quantum mechanics, everything is described by a complex-valued wave-function usually denoted Psi. From the wave-function we calculate probabilities for measurement outcomes, for example the probability to find a particle at a particular place. We do this by taking the absolute square of the wave-function.

But we cannot observe the wave-function itself. We only observe the outcome of the measurement. This means most importantly that if we make a measurement for which the outcome was not one hundred percent certain, then we have to suddenly „update” the wave-function. That’s because the moment we measure the particle, we know it’s either there or it isn’t. And this update is instantaneous. It happens at the same time everywhere, seemingly faster than the speed of light. And I think *that’s what Einstein was worried about because he had explained that already twenty years earlier, in the discussion of the 1927 Solvay conference.

In 1927, Einstein used the following example. Suppose you direct a beam of electrons at a screen with a tiny hole and ask what happens with a single electron. The wave-function of the electron will diffract on the hole, which means it will spread symmetrically into all directions. Then you measure it at a certain distance from the hole. The electron has the same probability to have gone in any direction. But if you measure it, you will suddenly find it in one particular point.

Einstein argues: “The interpretation, according to which [the square of the wave-function] expresses the probability that this particle is found at a given point, assumes an entirely peculiar mechanism of action at a distance, which prevents the wave continuously distributed in space from producing an action in two places on the screen.”

What he is saying is that somehow the wave-function on the left side of the screen must know that the particle was actually detected on the other side of the screen. In 1927, he did not call this action at a distance “spooky” but “peculiar” but I think he was referring to the same thing.

However, in Einstein’s electron argument it’s rather unclear what is acting on what. Because there is only one particle. This is why, Einstein together with Podolsky and Rosen later looked at the measurement for two particles that are entangled, which led to their famous 1935 EPR paper. So this is why entanglement comes in: Because you need at least two particles to show that the measurement on one particle can act on the other particle. But entanglement itself is unproblematic. It’s just a type of correlation, and correlations can be non-local without there being any “action” at a distance.

To see what I mean, forget all about quantum mechanics for a moment. Suppose I have two socks that are identical, except the one is red and the other one blue. I put them in two identical envelopes and ship one to you. The moment you open the envelope and see that your sock is red, you know that my sock is blue. That’s because the information about the color in the envelopes is correlated, and this correlation can span over large distances.

There isn’t any spooky action going on though because that correlation was created locally. Such correlations exist everywhere and are created all the time. Imagine for example you bounce a ball off a wall and it comes back. That transfers momentum to the wall. You can’t see how much, but you know that the total momentum is conserved, so the momentum of the wall is now correlated with that of the ball.

Entanglement is a correlation like this, it’s just that you can only create it with quantum particles. Suppose you have a particle with total spin zero that decays in two particles that can have spin either plus or minus one. One particle goes left, the other one right. You don’t know which particle has which spin, but you know that the total spin is conserved. So either the particle going to the right had spin plus one and the one going left minus one or the other way round.

According to quantum mechanics, before you have measured one of the particles, both possibilities exist. You can then measure the correlations between the spins of both particles with two detectors on the left and right side. It turns out that the entanglement correlations can in certain circumstances be stronger than non-quantum correlations. That’s what makes them so interesting. But there’s no spooky action in the correlation themselves. These correlations were created locally. What Einstein worried about instead is that once you measure the particle on one side, the wave-function for the particle on the other side changes.

But isn’t this the same with the two socks? Before you open the envelope the probability was 50-50 and then when you open it, it jumps to 100:0. But there’s no spooky action going on there. It’s just that the probability was a statement about what you knew, and not about what really was the case. Really, which sock was in which envelope was already decided the time I sent them.

Yes, that explains the case for the socks. But in quantum mechanics, that explanation does not work. If you think that really it was decided already which spin went into which direction when they were emitted, that will not create sufficiently strong correlations. It’s just incompatible with observations. Einstein did not know that. These experiments were done only after he died. But he knew that using entangled states you can demonstrate whether spooky action is real, or not.

I will admit that I’m a little defensive of good, old Albert Einstein because I feel that a lot of people too cheerfully declare that Einstein was wrong about quantum mechanics. But if you read what Einstein actually wrote, he was exceedingly careful in expressing himself and yet most physicists dismissed his concerns. In April 1948, he repeats his argument to Born. He writes that a measurement on one part of the wave-function is a “physical intervention” and that “such an intervention cannot immediately influence the physically reality in a distant part of space.” Einstein concludes:
“For this reason I tend to believe that quantum mechanics is an incomplete and indirect description of reality which will later be replaced by a complete and direct one.”

So, Einstein did not think that quantum mechanics was wrong. He thought it was incomplete, that something fundamental was missing in it. And in my reading, the term “spooky action at a distance” referred to the measurement update, not to entanglement.


  1. ”In nineteen 27”

    ”In April nineteen 48”

    I guess that the transcription was done by software. :-)

  2. Hello Sabine,
    this is the topic that interests me the most.
    At the moment only two spelling mistakes or not even that:
    "here is an example from Science"
    A link would be nice, if you have one.
    "nineteen 47" and the same with 27 looks a bit strange. They are not really errors...
    Best regards and enjoy the good weather

  3. So Dr. Hossenfelder has quantum-entangled all the socks in the Universe somehow so that half of mine somehow lost their partners.
    Seriously though, I appreciate the explanation of what S.A.A.A.D actually referred to, since most descriptions refer to entanglement.

  4. The point is that the case with a global upgrade of the wave function after registration of a particle does not fundamentally differ from the case of two entangled particles (or socks). Both in the first and in the second case, we are talking about a formal transition from knowledge about the statistical distribution to knowledge about a single event (see my blog). I also think that Einstein understood this affinity of situations, and his statements were implicitly about both the first and the latter cases. In my opinion, Einstein wanted to show with this remark that Bohr's interpretation, based on understanding the wave function as a property of an individual particle, is contradictory. Einstein, as you know, offered his own interpretation, which was based on the understanding of the wave function as a description of some statistics of particles, and not one particle. Later this interpretation was called 'ensemble interpretation', and was supported by Blokhintsev in Russia. But Einstein failed to convince most physicists.

  5. Sabine, thanks for raising this interesting question. I always thought that Einstein's "spooky" relates to entanglement.

    But I wonder if the "update" (later called collapse) of the wave function worried him then why didn't he appreciate Everetts relative states interpretation which avoids the collapse?

    I understand that entanglement is just "a type of correlation". But isn't the real spooky thing the fact that the two entangled particles behave as if they were one particle regardless of being theoretically separated light years from each other? In an instant of time the outcome at A fixes the outcome at B.

    1. "But I wonder if the "update" (later called collapse) of the wave function worried him then why didn't he appreciate Everetts relative states interpretation which avoids the collapse?"

      Einstein died 2 years before Everett finished his PhD thesis.

    2. Even so Everett avoids the collapse when the observer updates his knowledge, it is not clear whether he also avoid nonlocality. Not avoiding nonlocality is not necessarily a bug, it could also be a feature. After all, quantum mechanics itself is nonlocal. So when Jim Al-Khalili says "... I think more in the direction of de Broglie-Bohm, because metaphysically I find it hard to buy into an infinite number of realities coexisting just because an electron on the other side of the universe decided to go left and right and the universe split into ..." in Fundamental physics and reality | Carlo Rovelli & Jim Al-Khalili, he is not complaining about Everett being just as nonlocal as other interpretations. Instead, he highlights a case of "the tail wagging the dog", because an insignificant decision of a minuscule electron incredibly far away will split my universe.

    3. Scott, you are right, so one can only speculate how Einstein would have thought about MWI.

    4. Jakito, I think whether the collapse of the wave function is a serious problem is interpretation dependent. MWI followers and instrumentalists don't have this problem. Zeilinger e.g. asks how can a mathematical rule collapse?

      In contrast, however, the EPR results can't be "explained away" and thus represent the nonlocality of quantum mechanics unambiguously. And as I understand it Einstein hoped to disprove what he understood as "spooky" by means of this Gedankenexperiment. At that time he couldn't imagine that he was wrong.

    5. Timm, in many ways I am an instrumentalist. As an instrumentalist, I find it attractive to believe that nonlocal randomness is a feature of QM. But the decision of the electron at the other end of the universe doesn't help to generate randomness where I am. And it could only help me to create nonlocal randomness together with the other end of the universe, if it had a significant entanglement with a "qubit" at my place. The rate of branching of worlds from the perspective of MWI is probably orders of magnitude higher than the rate of actual randomness that can be generated where I am.

      You wrote that Einstein couldn't imagine that he was wrong. Einstein certainly believed that the prediction of QM would be the one actually observed in nature. He probably didn't expect Bell's inequality, but I am not sure whether this is enough to claim that Einstein was wrong. He knew about the riddle of conservation of energy, angular momentum, and linear momentum. He didn't believe in a simple solution to that riddle in the form of particles which explicitly carried those locally preserved properties.

    6. Jakito, regarding MWI I have two main objections, first it's hard to believe that the wave function is ontic, second you have to forget the Born rule. Also that unitarity holds isn't set in stone. So, welcome dear instrumentalist.

      I agree that "Einstein couldn't imagine that he was wrong" goes too short. He was convinced of local realism and that the EPR nonlocality can be taken as a sign that quantum theory is not complete.

  6. Sabine,

    What a delightful topic!

    I liked your emphasis on how Einstein first got himself into hot water with the quantum community he helped create with his brilliant insight into the need for photon quantization. (It’s also ironic that this was the work, not relativity, for which Einstein got his only Nobel Prize.)

    My favorite rendition of the incident in which Einstein first shocked the quantum community is on page 111 of the carefully researched but written-as-if-there book The Age of Entanglement [1] by Louisa Guilder. Einstein’s talk immediately followed de Broglie’s proposal of pilot waves. As a young Frenchman proposing abject heresy to an audience of mature German physicists, de Broglie had gotten a cold reception indeed. Einstein unexpectedly supported de Broglie by pointing out that Born’s wave-collapse re-interpretation of what had previously been wave intensity contained a profound paradox. Einstein noted that “This [Born] interpretation presupposes a very peculiar mechanism of instantaneous action-at-a-distance to prevent the [electron particle] wave from acting on more than one place on the screen.”

    Einstein’s example also highlights a sad episode in more recent physics. All waves become chaotic over time. If that chaos is allowed to become infinitely detailed, it leads to the ultraviolet catastrophe, the generation of infinite energy via the emergence of infinitely complex harmonics. Without quantization, this happens to all waves, even classical waves if one ignores friction. While entertaining, many-worlds was also a colossal waste of time because it ignored Einstein’s point from 1927: Matter waves (electrons) must quantize, just as photons must. Many-worlds is what happens if the observably false ultraviolet catastrophe is applied to matter waves. Thus many-worlds cannot even qualify as a legitimately “quantum” theory. To be precise, it is an entirely classical, conservation-ignoring example of infinite precision math run amok. It’s excellent sci-fi fodder, but it’s not physics.

    Back to spooky action: The most delightful and intriguing explanation I’ve ever encountered of why “spooky action” is not really spooky was by the remarkable Asher Peres. Peres had an utterly unique way of interpreting reality that was impressive for its self-consistency, if nothing else. Peres, for example, quite rightly castigates Einstein for contradicting Einstein by using the word “instantaneous” several times in the EPR paper. It was, after all, Einstein who had vividly shown that this word has no experimental meaning!

    Here is Asher Peres’ explanation [2] of why spooky action at a distance is a figment of our imaginations:

    When Alice measures her spin, the information she gets is localized at her position, and will remain so until she decides to broadcast it. Absolutely nothing happens at Bob’s location. From Bob’s point of view, all spin directions are equally probable, as can be verified experimentally by repeating the experiment many times with a large number of singlets without taking in consideration Alice’s results... For Bob, the state of his particle suddenly changes, not because anything happens to that particle, but because Bob receives information about a distant event. Quantum states are not physical objects: they exist only in our imagination.

    Every time I read that, I agree enthusiastically with every word Peres said and have no real idea what he means. That is, while I understand what Peres is saying intellectually, I cannot think like Peres did. I don’t think many people can. He understood reality differently from most of us and arguably with more self-consistency even than Einstein. What a great mind!

    [1] Lisa Guilder, The Age of Entanglement: When Quantum Physics was Reborn.
    Vintage Books, 2008.

    [2] Asher Peres, Quantum Information and General Relativity. Fortschritte der Physik: Progress of Physics, Wiley Online Library, 2004, 52, 1052-1055. Online:

    1. Peres was an antirealist with respect to the meaning of the quantum state. "It is not measurable directly, therefore it's a calculational tool." The real problem is not that it is a calculational tool, but that, as a tool (together with the projection postulate), it is not compatible with General Relativity on microscopic- (how do two states interact gravitationally? what happens at the end of black hole evapoation?), mesoscopic- (what is the gravitational field of a gravcat?), stellar (where does the Hawking radiation originate?) and Galactic scales (why does MOND work better than LCDM for rotation curves and BTFR?). Sabine had a number of illuminating posts about these issues.

      If you ignore gravity, there is not much to worry about, unitary evolution+projection explains nearly everything we observe, and that's as much as an antirealist can hope for.

    2. Terry, there is nothing surprising in the fact that the transition from a statistical function (quantum state) to the values ​​of variables (measurement results) takes place in formalism and in the mind of the researcher, and not in space-time. It would be strange if it were the other way around. After all, the 'quantum state' with measurement does not disappear anywhere. Сontinuing a series of experiments in uniform conditions, you will receive uniform statistical results. Statistics are not tied to individual cases. I think that the failure of Einstein who failed to convince his young colleagues that he was right was also due to the fact that the new generation of physicists wanted to think that in the quantum physics they are dealing with something special that distinguishes this field from classical one. It was a kind of attempt at revolution not only in physics but also in a philosophical approach. Therefore Einstein's objections may have seemed too retrograde to them. Hence their attempts at a total separation of the 'classical' device and the 'quantum system', leading to confusion that physics has not overcome until now. There are differences between quantum objects and classical ones but they are not as insurmountable as Bohr imagined.

    3. Terry Bollinger,

      "When Alice measures her spin, the information she gets is localized at her position"

      Information about what? About Bob's particle, maybe?

      "Absolutely nothing happens at Bob’s location."

      Right, so the particle already had that state (-h/2 in the paper).

      "From Bob’s point of view, all spin directions are equally probable"

      So what? Who cares? The EPR argument does not make any assumption about the distant observer (if any). The only relevant observation is that Alice can predict the result of a measurement before that measurement takes place. This can only be explained in two ways:

      1. The particle had that state since the time of emission, or

      2. The particle acquires that state when its partner was measured.

      1 is the hidden variable explanation, 2 is non-local. So, Einstein's point was that the assumption that QM is complete (the rejection of hidden variables) leads to non-locality.

      Peres does nothing to challenge EPR. His considerations about Bob's view are irrelevant, it's just a red herring.

    4. Fuchs and Peres wrote Quantum Theory Needs No ‘Interpretation’. I understand why Fuchs did that, but it is an utter mystery to me why Peres coauthored that paper. A long time after I read that article, I dived into certain chapters of Peres book Quantum Theory, Concepts and Methods. I was surprised that Peres can actually be quite reasonable, even so I did not trust everything he said. For example, he says in his book that there is no time-energy uncertainty. I don't fully understand his argument, and I am not sure whether he is right or wrong. But because of that article with Fuchs, the possibility that he might be wrong about the time-energy uncertainty occurs to be very real to me. Without that article, I probably would have tried much harder to understand his argument.

    5. Unperformed experiments have no results. Asher Peres wrote this long before he wrote his book Quantum Theory, Concepts and Methods. It is spot on, and highlights a key property of QM. It is actually the title of a paper with only 3 pages, so I just read it. Turns out that paper itself is really good too. In fact, it was so good that I read that other article again, just to be sure that it is really "not great". Indeed, it is disappointing, and represents neither Copenhagen, nor QBism, nor Peres' own antirealism.

  7. "Quantum states are not physical objects: they exist only in our imagination."
    It's interesting why theorists working with information don't consider (at least explicitly don't mention it) that information where to look for is in itself a kind of a guide, e.g. like where to direct a telescope for an astronomer.

    Even Galilean relativity only makes sense to one who has either heard of it (and solved a bunch of issues and observed behavior around himself) or re-discovered after running a lot of experiments on his own, so coming up with a principle. It's true, that it works anyway whether the observer knows of it or not. But it's not true that knowledge of the principle will not change the behavior of the observer. It does change it.

    I'm not sure how physicists deal with it. Sloppily looking over Von Neumann's text it seemed that he proved that whenever we make the cut in QM, the calculations lead to similar results. But that is only for the cases where we know what we are looking for. And information based on what we choose what to look for seems to be neglected.

    I might be terribly confused here, but it's the question that keeps popping up. It's like a lot of tacit knowledge of what is already known is neglected, but which is made available due to collective knowledge in rotation. Like making measurements on different branches forgetting about the information contained in the root from which they branched (yeah-yeah, Markov's evolution and Bell's causality make situations of measurement equivalent, but that's not the point, it seems that prerequisite information for the settings is neglected).

    E.g. an aborigen on an island would not benefit if he discovers Newton's Principia (even if he could read it). And in order to benefit from it, he has to at least study physics, i.e. perform some proof of work. But how is that "PoW done by aborigen" can be metricated and included in the measurement (even if it doesn't change it)? Currently it's implicitly included in education process, peer review and experimental evidence. But from at least one perspective seems to be fuzzy (that of course might be a characteristic of such perspective).

    PS A fantastic video!

    1. Hi Vadim,
      I reckon you're not giving your indigenous islander enough credit. They're on the same level as the average Alice, Bob, or whoever. The only reason I know slightly more than your aborigine is that I've had the benefit of education including science, and the internet. :)

  8. The correlations with entanglement is stronger than the Bertelsmann's socks idea. If a spin 0 state decays into two spin states, usually we think of 1/2 spins say of an electron and positron, then at face value it does seem to fit the socks idea. However, if the electron enters a region with a magnetic field and at the opposite side we have a radio frequency detector the electron spin resonance is found as the positron will transition states. This is for the positron far away from the magnetic field. If the socks had color change with temperature, the warming of one so its color changes will have no influence on the other.

    Realistically I suppose we could think of a photon entering a birefringent crystal with polarization dependent refraction. This produces two parametric down shifted entangled photons. If one photon interacts so its polarization rotates, then so will the polarization of the other photon.

    At the end of it all this is really about quantum phases. The collapse of a wave function is a switch of a superposition of a wave with an entanglement of that state with a needle state. The apparent collapse is then something which lies outside of quantum mechanics, which is a continuous deterministic evolution of a wave.

    1. This comment has been removed by the author.

    2. (after correcting mistakes)
      Lawrence, just my one pence. If the electron enters a region with a magnetic field at the opposite side nothing happens otherwise we would already have the super-luminary connection in action. Thus, in the quantum case, as in the case of socks, if we start to do something with one sock, nothing happens to the second. But with a large number of pairs of socks we can still change the conditions for registering socks at one end, for example instead of all socks start registering only those arriving in an upright position. And then the correlation between the position of the socks in the tangled pairs will 'instantly' change. True, we learn about the change in this correlation only a posteriori when we compare the information on the properties of the registered socks at both ends. Thus, the instant transfer of information from A to B is not work, and the principles of the theory of relativity are not violated.

    3. Igor, I am afraid you are making the usual error of thinking large sample space statistics recovers quantum strangeness. Classical statistics obey the Bell inequalities, but quantum physics violates them.

    4. Lawrence, in addition to the fact that there is some clever way to lead to violation of Bell's inequalities by classical means (see my blog), and to make sure that violation of them is not a property of exclusively quantum systems, there is another important consideration in favor of the absence of fundamental differences between quanta and classics. As you know, in classical mechanics, all events, including, of course, measurements, are distributed in advance and are located in the Minkowski space-time. They 'already are' always, although that time may not have come yet. If we reason in a similar way for quantum systems, and assume that the probabilities of the distribution of measurement results are not true, but only apparent to us due to our ignorance, and all future measurements indeed already exist and are built into the Minkowski space-time, then the question of when the properties of particles born is resolved. The properties of future particles already exist and are distributed in the Minkowski space-time, yet in the future. For some reason, physicists call this 'superdeterminism' but if you look at it, it is in no way different from Newtonian-Einstein's determinism.

    5. Lawrence, in addition to the fact that there is some clever way to lead to violation of Bell's inequalities by classical means (see my blog), and to make sure that violation of them is not a property of exclusively quantum systems,

      I guess I would be more enticed if this were a published paper and even more a report on experiments.

    6. Lawrence, the results in question have been previously published only in my blog so far, but very similar results for the discrete case can be read in: Richard David Gill. 'The Triangle Wave Versus the Cosine: How Classical Systems Can Optimally Approximate EPR-B Correlations'.

  9. I always enjoy your articles, Sabine, though this may be the first I've said so, and this is one of the best. I was beginning to think that I understood quantum entanglement, and even that it was obvious, until I got to the bit where you say "Yes, that explains the case for the socks. But in quantum mechanics, that explanation does not work."

    1. Hi Athel,
      I just wondered if an analogue for socks would be, you don't know if there's a pair of socks or only one until you take your laundry out of the washing machine and put it in a clothes basket. If you leave one in the machine, it's automatically corellated with the one in the basket. You won't find out which state the socks are in - singletons or pairs - until you are in a hurry to go somewhere and you open your sock drawer to find there's only one sock of the pair you wanted.

  10. Quantum theory is best understood as a form of perspectivism not physicalism

    Nietzsche introduced the idea of perspectivism: in the final analysis, all we really have is a manifold of interlocking perspectives. For example, consider the following toy model. If humans are small finite, represent each possible human perspective by a small non-empty subset of {1,...,n} where n is a large natural number. Then, there are minimal perspectives, but no maximal human perspective. Still, there is an ideal finite perspective which sees everything! If n=infinity, then there is still an ideal infinite perspective which sees everything! (God's eye-view!) If one accepts the standard quantum logic, then one has a manifold of perspectives which cannot-by Gleason's Theorem-be embedded into any single perspective! There are now maximal perspectives, but no universal perspective!

    1. That's interesting. But I think there is something universal in all those situations, some invariant, no matter what perspective one is in. And more, it seems that information about that invariant is constantly neglected (at best, indicated).

      I'll reframe it in a simpler space, where it's indicated explicitly. Let's take Kolmogorov's triplet - (Ω, F, P). We've got the space (i.e. the basis for a perspective) - Ω. We've got the measure - P (i.e. the representation or mapping in that perspective). And we've also got F as an event space, initially naively taking it as 'a set of possible sets of elementary events, what can be simpler'.

      We even have no trouble in working with it in discrete spaces. But shifting to continuous spaces, something pops up. Namely, it becomes clear that in order to measure (i.e. produce representation, compress, etc.), we must superimpose some rules on our event space. It suddenly becomes obvious that it has to be homogeneous in some sense to set up adequate measure. So we naturally (for what?) end up with σ-algebra as F.

      What's happened? We had to set some linking between the space of elementary events and measure in order that it would have sense. Based on what did we do it? Based on some tacit 'intuitive' knowledge or logic of the observer that was used to close the space for operations. So coming up with a particular configuration for Ω. Without that knowledge - it would not work.

      That's just an example. But in that example σ-algebra basically encodes some knowledge of invariant (i.e. universal enough configuration for any observer; basically the observer - that is, any observer, ant, god's eye, whatever - converges to σ-algebra in such space), the relation between the space and the measure. And if one starts looking in any system there is always something that contains that (usually) implicitly.

      Now the question is can it be considered explicitly or at least indicated universally enough (at least so that we can be aware of it)? Universal Turing machine? But with included instruction set and metrics how to use it. It always converges to some form of bootstrapping...

  11. Very interesting and intriguing post, thanks.
    "These experiments were done only after he died." Do you here mean the Aspect's experiment about Bell inequality?

  12. For us non-science people, sometimes the "cookies" are too high on the shelf (as I/we may not fully understand the topic without more of a backstory on the subject). So maybe one day you could explain further in more simpler terms, placing the "cookies" on a lower shelf so that we non-science people might more clearly understand. I try to understand but often the concepts are difficult.

  13. Oscillating charges from a distant sun send EM energy to earth across a vacuum where nothing empirical (hypothetical yes) happens.The energy arrives and interacts with certain arrangements of charges (material objects) in a certain definite way.
    Is this spooky action at a distance?

    1. I think the answer is no, because I assume the energy takes time to travel. I think "spooky action at a distance" is instantaneous action at a distance, with no known mechanism of transmittal. See Andrei's comment above. (Which seemed excellent to me.) (Note however that whatever the transmittal mechanism is it cannot be used for instantaneous communication. Any attempt to force one entangled particle into some coded condition would wind up providing an initial measurement and then breaking the entanglement.)

      See "Bell's Theorem" for more information.

    2. Hello Morris,

      no, it's not.
      It's just normal electromagnetic radiation that travels at the speed of light.

      Spoky action is what you get in the following experiment:
      A light source emits pairs of photons simultaneously.
      One photon to the left (A) and one photon to the right (B).
      If you measure the polarisation of the photons, they are always perpendicular to each other.
      So, for example, A is vertical and B is horizontal or vice versa.
      And of course all angles in between are possible.
      But between A and B you always have 90°.

      The experiments were carried out in large numbers and very carefully.
      Some of the places of measurement were 100km apart.
      The result is as follows:
      1. at the start of the photons, their polarisation is undetermined. That is why the sock model fails here.
      2. if the polarisation is measured at A, the polarisation at B is as required above without any loss of time.
      If one imagines that A and B "talk" to each other during the polarisation measurement, then this must take place
      take place at over 1000 times the speed of light.
      This looks like it would contradict the theory of relativity.
      And that is why we speak of spooky action at a distance.
      (My opinion: I like this spooky action because it gives us a chance to explain it for many other experiments.
      But a theory about it is difficult to develop. So far there is none).

      The other explanation is called superdeterminism.
      Sabine is the expert for that.

      Many greetings

    3. Thanks Stefan. Maybe I should have said that my comment was tongue in cheek. I realize that the instantaneous occurrences is what required to meet the definition.
      To my mind what I posted above is as spooky as it gets. Add Rutherford's experiment and nothing else after that is really any more more mysterious or demonstrative that we are inherently unable to understand our world. We can know of course. But why recycle this stuff which is old and seemingly not useful?

  14. Terry Bollinger wrote:
    "...Every time I read that, I agree enthusiastically with every word Peres said and have no real idea what he means. That is, while I understand what Peres is saying intellectually, I cannot think like Peres did. I don’t think many people can. He understood reality differently from most of us and arguably with more self-consistency even than Einstein. What a great mind!..."

    Personally, I think there is a deeper question residing in the woods of what Peres is proposing. And it is a question that is based on the fact that Alice could have measured the particle for any number of attributes (such as velocity or position, for example) which can display physically observable results that are completely different from each other.

    So the question is, what is the true nature of the unmeasured quantum realm if indeed its primal state seems to be like some kind of infinitely malleable "cosmic clay," so to speak, that is transformable into whatever it is we wish to see based on the shape and purpose of a measuring device?

  15. Good morning Sabine,

    I hope you are well and sitting comfortably.
    I plan to destroy one of the biggest mainstream belief within the next 90 seconds:

    Please take a sheet of A4/letter size paper (landscape format) to hand and a black or blue pen.

    Please draw with your hand about 25 to 30 small circles (diameter approx. 5mm) in random order on the sheet.

    Now please choose 5 of the 25 circles and colour them in.

    Now please connect these 5 with each other, with a continuous line (10 lines for 5 circles).

    Now please connect about 10 pairs of the remaining circles with each other with a dashed line.
    (it is best to connect neighbouring circles)

    Now please connect each painted circle with a non-painted neighbouring circle with a dashed line

    Now it gets serious:
    The 5 coloured circles connected to each other form a (network) cluster, they form an object.
    The remaining circles represent the environment. This can be a crystal, a laboratory, the universe.
    I call the circles nodes, the connecting lines edges. (Mathematicians call it a graph, others a complex network).
    Within an edge, signals are transmitted instantaneously, without time delay.
    Since the cluster nodes are connected with edges, they know instantaneously what is happening to each other.
    They form a point-like object, so to speak.
    And since the object is connected to the environment at various points,
    it's also arbitrarily large.
    In other words, I have a model that is small and big at the same time.

    You may now think: "Ridiculous".
    Well I assure you: "It is ridiculous".

    But it has the following advantages:

    - It is a mechanistic model for wave-particle duality.

    - I have the chance to fly through a double slit with such an object...
    and to see both slits, as well as to get a point-like effect on the detector behind it.

    - The edges provide the spooky distant effect.
    This can be used to explain
    - Experiments with entangled objects
    - Experiments with Mach Zehnder-interferometers with an object in one arm
    - Delayed-choice experiments

    - If we look at an object from the point of view of its surroundings, "smallness" must be specially created.
    The cluster points could be far away on your paper and form a large object.
    The cluster points could be near to each other and form a small object.
    With this one has the chance that the symmetry of special relativity disappears
    and changes into the gauge symmetry of QCD and vice versa.

    Likewise, all theory calculations that need a cut-off get a natural explanation.
    There are no arbitrarily small distances, at least not by themselves.

    - A muon in the atmosphere can see this atmosphere and "react" accordingly.

    - There is a chance that there are only a few stable arrangements for the clusters.
    One arrangement could then represent an electron and the "opposite" of that could represent the positron.
    And a completely different arrangement in the cluster could be a photon.
    This then gives us the chance to describe the pair annihilation, i.e.
    not only the "before" and "after" but the "how".

    - The same applies to the proton and anti-proton.
    Can one describe how these annihilate to gamma photons,
    you have in your hands the unification of QED and QCD.

    - The Heisenberg uncertainty relation can arise naturally.

    - And so some questions and problems disappear
    - the measurement problem
    - Schrödinger's cat (and dog?), Wigner's friend
    - Question: "Where is the electron?" Answer: "Everywhere and nowhere".

    to be continued

  16. But after these neat words, all the questions and unsolved problems emerge:
    How is an object represented?
    Is it signals that are exchanged from node to node?
    Or is it just the nodes and edges?
    Do nodes and/or edges split?
    If so, how.
    How does an object move?

    What is most important? What is the most important question?

    In the meantime, I have a network in which simple structures emerge.
    If I increase the number of edges in the network above a threshold,
    (very simple) structures appear.
    And if I reduce the number of edges, the structures disappear.
    Near the threshold value, the network is undecided for a while.
    The duration of the "while" looks like a Poisson distribution.
    In my eyes, the network is a good model to study emergence.

    Many greetings, have a nice Sunday and call me if you like the above idea

    PS: Of course you won't call me. Why should you?
    Because of the neat words up there?! No, I don't think so.
    But if physics is a room, we are in opposite corners.
    And now you know what my corner looks like.
    I think that's fair.

    1. So, "all the worlds a graph, and all the fields and particles merely nodes and edges"? I would think Stephen Wolfram would be sympathetic to ideas like this.
      However, just pointing out the obvious, even with the toy model you described, it would already not be trivial to get the electron behaviour right when you vary the distance between slits of a double slit experiment. You either need to complicate the substructure with more and more nodes and edges, or you'd have to have variable length edges. That is, if those structures even correspond to spatial dimensions in a straightforward way. Also, to the best of current knowledge, electrons do not have substructure. This of course means that your nodes and edges do not form part of the "physical" (for lack of a better word) structure of the electron but are rather a modelling tool (just like one view on the wave function). Now, that is not inherently a problem, but it seems you would quickly run in a totally intractable description of just single particle. Most likely, that would also imply intractability for many-particle systems, which in turn would make the formalism useless in practice.

    2. Dear G. Bahle,

      Thank you very much for your kind comment. I agree with all your concerns.
      I share all your concerns.

      My difficulties are even more fundamental.
      So far I have not succeeded
      - creating many objects of the same size
      - a three-dimensional space with metrics
      or more precisely, a three-dimensional space with relativistic symmetry, i.e. a relativistic aether.

      I am well away from the double-slit experiment.

      I am not sure that the path I have pointed out is the right one,
      but I am sure that Modern Physics is extremely bad.
      I am sure that all these endless discussions in quantum mechanics
      have their reason in the use of the wrong mathematics.

      Half a year ago I had compared quantum mechanics with the Kobayashi Maru test,
      this well known "no win" situation.
      One can only pass this test successfully if one changes the rules.
      And that is exactly what I intend to do.

      Thank you for your kind comment

    3. Dear Stefan,
      in the vein of new ideas (or rather old ones in this case), I just remembered an article from last year, which you might find interesting. It's on quanta magazine and deals with intuitionist mathematics (
      Good luck being Captain Kirk ;)

    4. This comment has been removed by the author.

    5. I deleted a question that seemed sensible when I asked it, but probably wasn't.

    6. Bahle / Mulder / Sabine

      Hello G. Bahle,
      I looked at the article in Quantuum Magazine and then at two recent publications by Nicolas Gisin.

      Nature Physics 16, pages 114-116 (2020)

      following thought:
      "Is a real number an object or does it arise as a never ending process?!
      known as intuitionistic mathematics"
      ==> I like the question, but he
      does not turn to physics and leaves the real work to others (in this article)
      at the beginning
      "at any time every number contains finite information"
      at the end
      "story telling is important e.g. how the moon drives the tides"

      I fully agree with both.
      In between, I again miss the physics.

      My rough approach to everything is emergence.
      So far I can create objects
      that are stable and flexible at the same time.
      I also need a minimum number of nodes and edges,
      otherwise nothing emerges.
      Now I can look to see how much the phase transition depends on the exact
      properties of the objects or vice versa,
      how resistant it is to them, and so on.
      ("Results in Physics" is having a hard time finding a reviewer.
      Meanwhile I uploaded it in ResearchGate).

      Gerben Mulder
      I still think the white socks are brilliant,
      because as far as I know, the polarisation at the start must
      be undetermined, otherwise this contradicts the experiments.
      (Possibly superdeterminism provides a way out. Sabine will have to say/explain that).

      Thank you for the blog post, the time and effort you put in.
      Thank you especially for approving my comments
      which run contrary to the mainstream and in one essential point
      also contradict you.
      Thank you for your patience and broadmindedness.

      Bee, hugs to you.

      Have a nice day everyone

  17. Giving physical meaning to mathematical tools used to describe Reality is meaningless, only what is observable have physical meaning, when using a wave function to describe a particle observable behavior, the wave function is a mathematical tool without any real physical meaning, only what can be inferred as observable from it has physical meaning.

    The idea that Reality should follow a single set of Universal physical principles enough to fully describe it is really naive.This Galilean/Newtonian ideal is really outdated.

    Classical Reality is emergent from the Quantum Reality, and Quantum Mechanics is not "incomplete" just because Classical Reality don't follow the same principles, almost in the same way that Real numbers "emergent" from Rational numbers don't follow the same principles.

    All notions that we have about Reality are classical notions, not only because we are classical objects but because basic elements to describe Reality are classical: Identity, measurements, space and time.

    1. It seems that we are talking about different things.
      Mathematics is a tool used to describe Reality, but that tool is not Reality.
      Only what is observable has physical meaning, and many times the same observable results can be explained or predicted using not isomorphic mathematical arguments.
      While the mathematical ideas to describe Reality are always changing/evolving, Reality is always the same and accessible to us only via observable facts.

  18. "If you think that really it was decided already which spin went into which direction when they were emitted, that will not create sufficiently strong correlations." More please, or have I missed this?

    1. Goggle "Bell's Theorem". "Boojums All The Way Down" by N. David Mermin gives some examples.

  19. Hi Sabine,
    A little suggestion! Instead of mailing just one of the blue and red pairs, a more appropriate analogy will be to have say 10000 pairs of blue and red socks, put each of the pairs in two envelopes and randomly mail those envelopes to two of your friends with time stamps on the envelopes. When they compare color of the socks in the envelopes with time stamps, then it will correspond to entanglement!!

    1. Kayshap, Sabine,
      The additional problem of QM is that if the envelopes are opened facing the same way one will be blue and one red, but if one is turned before opening, then both will be the same colour. The logical problem Einstein identified and Bell analysed was that if 'A' reversed her envelope to be the same as B, & found Red she dictates that B finds Blue. But if she decided NOT to reverse it - then B must find RED!
      Many experiments at long range with a 'switch' made at the last instant have born this out (using QM's assumptions). This is the 'faster than c' communication Einstein objected to.
      But it seems a solution satisfying Einstein IS possible, by changing Bohr's original assumptions about the 2nd 'quantum spin' state of conjugate pairs, substituting Maxwell's 2nd orthogonal momenta distributed as Poincare's sphere. (linear and curl). Comprehensible?

    2. No Peter! My understanding is that in the singlet case the two sides have exactly opposite polarizations. So if the two measure at the same time, if one is red, the other one has to be blue. That is why I want the envelope to be time stamped. There is no way the two can get the same colored socks. As far as I know there is no way, Einstein could be right.

    3. Kayshap, Your understanding of the data is incomplete. We ALSO have red/red & blue/blue cases where the setting are opposite! Einstein's objection was on logic; If A reversed her setting 1 light yr away at the last moment, she dictates or REVERSES B's finding! so requiring 'action-at-a-distance'.

      But I agree the PAIR really has opposite polarity. The new 'Discrete Field' model (DFM) solution (today accepted for a Nature journal!) uses Bohr's "detector is PART OF" the system, but BOTH the (orthogonal inverse) momenta in OAM (Linear AND 'Curl'), and simple vector addition on interactions! (but on all 3 axes).
      Einstein WAS then right about QM, but SR was 'incomplete', which he knew, and corrected on the same DFM physical basis in 1952 (Relativity Ed.XV, Appdx. V). He wrote it's; "not yet part of scientific thinking". (it was ignored so still isn't!).
      But I'm sure Sabine may agree most in academia are still not prepared to admit such an update to the 1905 interpretation?

    4. Again no Peter! Singlet state (opposite polarity) is determined by the source. Observers have no control over it. Rest of the matter is a philosophical issue!

    5. True BEFORE the 'measurement' interaction, and of course in current belief, but in fact we know light and electrons are REPOLARISED by interactions! As Bell pointed out we have no access to PRE-arrival state, only POST INTERACTION state!
      Bohr and Von Neumann well knew and stated that detectors modulate findings. That proves the key to the new solution (just passed stage 2 peer review). But it is very new, so unfamiliar.
      As Lorentz, Feynman etc & my mentor Dyson said; "We can't advance without some hypothesis that at first looks wrong".

    6. Sorry Peter! I see that we have been missing each other's POV! To me (and I believe Sabine) the main point is that the spins(color of socks) are correlated since their birth. But your point was that in the actual expt. they are measured along different random directions. But changing direction of measurement has nothing to do with entanglement. For a single electron or a photon it is a special quantum, non classical property that when it is quantized in one direction before and then you measure in another direction, in the second case, it will be superposition of the two states. So in a way you are right that in the actual expt. there are correlations ++,--,+- and -+. Then you can have red/red blue/blue. But this has nothing to do with entanglement. That is because the two observers choose different axes. I am not sure if Einstein was worried about measurement along different axes. I think he was worried about + measurement by one forcing - on the other observer in the singlet case along the same axes. So admittedly the socks analogy stops being perfect in the final analysis of the way experiments are done! May be that is why Sabine said it won't!!

    7. Not quite. I agree with Sabine of course on both initial inverse states AND that those are inadequate to explain the data. I find a key is to use BOTH the (inverse) momenta in OAM; Linear, and also (Maxwell's orthogonal) 'CURL', opposite at each pole, zero at the equator. That then implies Dr B's socks were REVERSIBLE! (or each with the other colour lining). That's where the 'vector addition' at measurement interactions enters the equation. 'Quantum logic' applies. Check out this (top peer scored 2015) "Red/Green sock trick" essay; Make any sense yet?


  20. Hi Sabine
    If I set a sheet of paper on an incline and let it slide down and collide with some obstacle it does not surprise me that, on some microscopic level, every atom in that sheet of paper ‘knows’ that something has happened to the leading edge of the paper. Drawing on this analogy it should not seem remarkable that the wave function of the electron ‘knows’ that something (collapse) has occurred somewhere else within it. But, when Einstein offers his electron thought experiment he is actually being very careful to NOT make the same sloppy assumption that I have just made because he had devised no foolproof experiment that would corroborate that statement. He was just being a very careful scientist.

    1. Hi Brad, just pointing out the obvious. It's not that every atom in the sheet of paper will eventually (<- key word) know that something happened to the leading edge.
      The key point and the reason why this analogy does have nothing to do with the problem here is that the "knowledge" of the leading edge stopping will only arrive at the trailing edge after a delay, with a maximum speed of c. So, if you had a sheet that's one lightsecond long, it would take one second or more for the end of the sheet to know the front stopped.

    2. Hi, G. Bahle

      I apologize for being terse, science writing is not the same as storytelling. I know that information travels at a finite speed. But, in his 1927 correspondence Einstein didn’t want to acknowledge that the trailing edge of the wave appeared to know instantly that collapse had occurred, without some corroborating evidence. So he alluded to that strangeness

    3. Hi Brad,
      it seems i misunderstood your argument.
      What i wanted to highlight was that Einstein was not worried that the wave function collapses, but that it does so instantaneously, which raises questions in regard to special relativity. Basically, spatially separated events that happen at the same time in a given reference frame are time separated in others. Or, simultaneity is not rotationally invariant (i.e. no global clock). Anyway, it's an interesting area of research. You'll also find many posts / videos on this blog that deal with this in one way or another.

  21. Back in the 90s I read a beautiful romantic tale of entanglement where one of the two correlated particles could be made move in a certain way and the other, far away, moved in sympathy; this does not seem the case?

  22. Is it possible to put it this way: entanglement is the condition that enables "spooky action at a distance"? In other words the socks in the envelopes may be white as long as the envelopes are closed but the act of opening one of the envelopes paints the sock in it red or blue with 50% chance. And the other sock becomes, regardless of its distance, instantaneously blue or red.
    So you can transfer a one bit’s number instantaneously to guy on Mars. Unfortunately the number is random and therefore it does not contain information.

    1. Hello Gerben Mulder,

      yes. I would say it exactly like this. "White socks" was a really good idea. Thanks for that.

  23. Sabine wrote: And in my reading, the term “spooky action at a distance” referred to the measurement update, not to entanglement.

    I think the reason people say Einstein's comment about spookiness refers to quantum entanglement is because quantum entanglement operationally involves the kind of measurement updates that he described in 1927, even though his original description involved the wave function of just a single particle.

    In general he was talking about the fact that a measurement in one location affects the wave function in another location. That's the generic peculiar or spooky "action" he has in mind, and in 1927 he described this in terms of a single particle's wave function, whereas in the later EPR scenario the point is made more vividly by considering the wave function of two particles.

    In both cases he was referring to what could be called entanglement of the distant parts of the wave function. It just so happens that he first considered the entanglement between the distant parts of the wave function of a single particle, and then later considered the entanglement between the distant parts of the wave function of two particles. In both cases I think the "spooky action" refers to the measurement update. (Answer: The correlations may or may not be spooky, but they are not technically an "action", e.g., no conveyance of energy or information.)

    It may be a matter of semantics whether we apply the word "entanglement" to the parts of a wave function of a single particle, or restrict the use of that term to the parts of a wave function of multiple particles.

    1. Amos,

      "I think the reason people say Einstein's comment about spookiness refers to quantum entanglement is because quantum entanglement operationally involves the kind of measurement updates"

      I suspect that this is correct, but if you think about it for a moment this makes absolutely no formal sense. Entanglement is a property of the wave-function, it's independent of the update. And entanglement itself is locally created. There is nothing problematic about two particles propagating apart and creating a non-local correlation (as the example with the socks illustrates).

    2. Yes but socks do not violate Bell's inequality. Einstein did not know about Bell's inequality at the time but he did understand that QM created a problem with locality.

      Also Einstein clearly applied his logic to entanglement with his EPR argument.

    3. ppnl, "Yes but socks do not violate Bell's inequality." Who said they did? As Sabine made clear, they can't. They CAN however give some 'relationship', i.e. antiparallel, adequate for the 'entanglement' within the data and any solution. I find a 'black box' mechanism then CAN give Bells inequalities, if not with Bohrs assumptions. Bell himself insisted one would be found (along with Einstein & many others, including Weinberg, as his quote in Sabine's book).

  24. Entanglement is a property of the wave-function, it's independent of the update.

    I think Einstein's 1927 comment was referring to the entanglement of the wavefunction of the electron at various locations on the screen. As you noted, he said that the probabilistic interpretation of the wave function requires a “peculiar mechanism” for preventing an action to occur at more than one location. In crude terms, if we imagine the wave function as some kind of probability-inducing pixie dust that is sprayed over the entire screen (as needed to account for 2-slit interference, etc.), there needs to be some way of ensuring that this "dust" never results in a particle at more than one location. So the pixie dust (wave function) must be entangled in this sense. I think that was Einstein’s point.

    Feynman famously argued that the 2-slit experiment (single particle hitting a screen, as in Einstein 1927) is sufficient to exhibit the only mystery of quantum mechanics. His point was that this already shows the entanglement of the wave function, which seems to have been what Einstein had in mind in 1927.

    There is nothing problematic about two particles propagating apart and creating a non-local correlation

    Terminology in the literature varies, but classically we can have two locally correlated things that then become spacelike-separated by normal subluminal transport, whereas I would reserve the phrase “non-local correlation” for a correlation that arises at spacelike-separated events, involving the (assumed independent) selection of measurements performed at those separate locations (e.g., based on information from outside the past light cone of the other measurement).

    This kind of procedure highlights the entanglement of the wavefunction (of two particles) in a palpable way, but, as Feynman said, it’s still the same entanglement of the wave function that is already exhibited in a more primitive way by the single-particle wave function on the screen, and this is what Einstein referred to in 1927.

    Naturally we set aside superdeterminism in a discussion like this, since that would put everything in a completely different context. I don’t think Einstein had superdeterminism in mind when he made his spookiness comments, so that would be a separate topic.

    1. Amos, 'one-particle wave function' is just a metaphor for a probability distribution function in many homogeneous experiments with one particle. 'Interference of one particle' is therefore also a metaphor, denoting the probability distribution of detecting one particle in multiple experiments with one particle. No probabilistic function can guarantee the conservation of the number of particles without violating relativistic locality. But the interpretation of quantum mechanics, in which the wave function is secondary, and reflects the behavior of real particles in an ensemble of experiments, perfectly guarantees this.

      Einstein was right. However, he was unable to defend his understanding of quantum theory, perhaps because he did not fully formulate the interpretation of ensembles at the origins of which he stood. And one more thing: no special 'superdeterminism' is needed here. The usual classical Einstein's determinism is enough, when all events of both the past and the future, including the results of measurements, are distributed in the Minkowski space-time. Thus, the whole world already exists, and it is what it is, and it cannot be different. There is no 'true probability', there is only our ignorance of the future. The movement is illusory, in fact, all events are already built into the 4-dimensional continuum, and only our consciousness moves at a certain speed, which leads to the visible speed limit.

    2. "Amos, 'one-particle wave function' is just a metaphor for a probability distribution function in many homogeneous experiments with one particle. 'Interference of one particle' is therefore also a metaphor, "

      No, it isn't. Factually wrong.

  25. Currently, the most convincing experiments in the field of "psi" is the Feeling Future experiments DARYL BEM.

  26. I read over my earlier “just an aside” comment about the Many-Worlds Interpretation (MWI or many-worlds) and realized that I covered one critical point a bit too glibly in my haste.

    Most folks are accustomed to thinking of MWI in terms of “splitting universes” whenever a quantum decision occurs, but that was not the logic by which Everett originally derived his idea. Everett’s key idea was much simpler, and its simplicity was part of its appeal: The Schrödinger equation is everything.

    That is, in Everett’s framework, the key to understanding quantum mechanics is to keep elaborating the wave equation and never worry about some annoying and mysterious concept of “collapse” in a wave function. Instead, you permit the wave function to become more complex and detailed as it expands and interacts with other Schrödinger wave functions. Within this increasingly chaotic and detailed wave function, all of those split universes emerge as “signals” encoded as subsets of the increasingly complex overall wave function of the universe (or, in MWI, multiverse). This view can be profoundly appealing for folks who like waves: No collapse, and instead just waves forever, expanding according to beautifully smooth differential equations. From a wave perspective, this expansion even feels more straightforward rather than bafflingly complex.

    There is, of course, more to it than that. For one thing, there must be some mechanism by which those “subsets” maintain a coherent view of just one universe for observers within them, rather than seeing the entirety at once. I rather suspect this is at least partially why space-as-entanglement ideas sometimes pop up within the MWI perspective since the entanglement becomes the method by which the overall and extremely chaotic universal wave function sorts itself out into an expanding and quickly near-infinite number of universe-like subsets.

    It’s all for naught because it disregards the subtle underlying driver of all quantum wave “collapse,” a driver that Einstein noticed way back in 1927: the absolute and unforgiving conservation of mass-energy. Einstein did not disagree with Born’s probabilistic interpretation of the quantum wave intensity since even at that time, experimentation had demonstrated the Born leap-of-faith to be unnervingly effective at universally describing actual results of quantum experiments. Einstein got his Nobel Prize for recognizing that somehow, quantum mechanics prevented electromagnetic waves from becoming infinitely detailed and thus infinitely energetic: the ultraviolet catastrophe. By elaborating the very similar electron case to an exceptionally tough audience back in 1927, Einstein pointed out that quantum mechanics similarly did not permit the wave functions of electrons to become infinitely detailed and thus infinitely energetic, which would have allowed it to show up at multiple locations on the screen by violating conservation of mass-energy. The case of electron waves acquiring infinite detail and mass-energy had no name at the time but by straightforward analogy would have been called the “infinite mass” catastrophe, the unlimited replication of electrons in violation of mass-energy conservation. The name we would use for it now is many-worlds.

    For just that reason, I sincerely suspect that had Einstein lived long enough to encounter MWI, his dismissal of it would have been instantaneous and likely a bit on the derisive side. (Notice how hard I’m trying not to say “he would have broken out howling in laughter.”) Einstein knew there was a locality problem with quantum mechanics, but as seen in his dismissal of de Broglie’s pilot waves and Bohm’s later reincarnation of the same idea in more detail, he never, ever took the cheap paths out of that conundrum. Casually allowing an unquantized universal Schrödinger equation to violate the mass-energy conservation rule he created with his most famous equation would likely have struck him as a cheap path indeed.

    1. I agree that to understand Einstein, one should not neglect "a driver that Einstein noticed way back in 1927: the absolute and unforgiving conservation of mass-energy". Bob Doyle (The Information Philosopher) in "My God, He Plays Dice! How Albert Einstein Invented Most Of Quantum Mechanics" defends Einstein. (He also includes analysis and translations of papers by Einstein from 1931, 1933, 1936, and 1948 as part of that defense.) Boyle highlights in various places the importance of conserved quantities for Einstein, and ironically calls them "hidden constants":

      'There may be no hidden variables, local or nonlocal. But as we saw in the previous chapter, there are “hidden constants.” Hidden in plain sight, they are the “constants of the motion,” conserved quantities like energy, momentum, angular momentum, and spin, both electron and photon.'

  27. I think you are right on that Einstein meant way more than entanglement by “spooky action at a distance”.
    I think a real concern is the speed of gravity with superposition and wave collapse. If you have an electron in superposition where is the center of gravity? And then upon detection you now know 100% where the centre of gravity is. Was that shift instantaneous and faster than the speed of light - this would break causality.
    Now some would say centre of gravity is not information, but certainly where the gravitational force is interacting on he particle creating that centre of gravity must be.
    Now we say the gravitational force of that electron is small so who cares, but it must be there. Or alternatively is it NOT there and if so, why?
    (And could this problem fit in with electrons in atoms, why isn't gravity seemingly acting on them. If gravity is there an aberration, shouldn't they be wobbling and then flying out?)
    That is on par I think with the entanglement concern, if when you decide the spin of the one particle by observation how did it communicate with the spin of the other almost instantaneously.
    I wish Einstein were here that could ask him where and what gravitational curvature of space-time by a particle in superposition would be.

    1. If as I like to think, everything is discrete as Zeno's argument suggested, then certain effects (perhaps including the effect of an electron's mass on its nuclear orbit) don't reach the minimum increment and are therefore zero. Sort of the negation of the the ultraviolet catastrophe on a small scale. (The negation of the wobble catastrophe?)

      I understand experiments have not detected any discrete effect in the Lorentz Transformation with high confidence, which puts a very low limit on discreteness there, but it seems to me a discrete universe would in principle work as well (and in fact better, as in the ultraviolet catastrophe) than a continuous one. (I can't rule out some sort of mixture, though.)

      Meanwhile, the issue of when gravitational force could cause collapse has been discussed at this site previously and recently, my one opinion being that gravity would not collapse events in which its effect is not relevant, such as the spin of an entangled particle (in most cases), whether a cat is dead or just sleeping, and whether a C60 or larger molecule is diffracted by a vertical grating in a vertical gravity field. (The last case is in accordance with experimental results and perhaps lends some credence to my discreteness/minimum-effect hypothesis also.)

    2. JimV,
      Yes, I think there is a, as Sabine put it, phase change; perhaps a minimum increment of energy density (absolute, i.e. including the zero-point energy). Above it and you are in real position with a centre of gravity on spacetime. Below it and you are in superposition with no center of gravity on spacetime. Like a rock that sinks in water while paper gets to float. Observation causing collapse in my mind then is you putting in the energy to cross that density.
      I like it because now the very hot and dense gets ionized and goes into superposition while the very small and cold go into superposition.
      Virtual particles have no gravity. Electrons through the double slit experiment would have no gravity? But what about an electron in superposition around a nucleus?
      In trying to work out some math I went to electrons which are in superposition around the nucleus.
      I need some help though because I am all over the place now.
      Went to the Earth-Sun system as the analog, how does it deal with aberration (gravity retardation) because the Earth doesn't fly away even though aberration should cause it to (the Earth you'd think due to causality would be rotating around a wobble based on the suns position 8 minutes 20 seconds ago). Well maybe what is preventing that from happening is an analog which shows gravity isn't applying to the electron.
      That uh did not work out. Instead thanks to a poster on here read a Feynman lecture that shows that an electron in a field also does not appear to have aberration because it has been offset by the past constant velocity (with no impact of acceleration) to a pseudo projection point.
      I thought that was crazy because if you are at a velocity and accelerate that means your center of gravity will end up projected "incorrectly" as if you were at a constant velocity and vis versa. Well, wait a minute.. I do feel a gravitational force back in inertia. (Sidebar, if this is true then the center of gravity for a galaxy will be projected based on the retarded velocity and not the real velocity and thus uh, not where you think it should be?).
      S. Carlip who argued that this is what is happening in the sun-Earth system (1999) notes that this cancellation is due to gravitational radiation as I think happens with an electron at velocity with electromagnetic radiation in Feyman's lecture.
      So now I am thinking well.. aberration should send you flying off to space but giving off radiation should have you crash into the center so maybe energy pulling you in = energy pulling you out and the speed of light is a result of it being the value you need for aberration to cancel out gravitation (making this virtual particle stable and everything else gone?). Right now I think what science believes is keeping the electron from "falling in" I think is the Heisenberg Uncertainty principle in that you can have a lot of momentum or a lot of location but not both. Is there some equivalence there?
      So now I am learning Feymen and "Lorentz Transformations of the Fields" but taking a step back.. none of this now would prove no gravity so... : ( .
      I'm hoping Sabine does some video that can somehow help connect this all.

    3. It seems to me that the concept of superposition of spacetime is not general covariant. That is, probably, it will not make sense to Einstein.

      Penrose's theory of gravitational induced collapse is based upon the idea that superpositions of spacetimes violates general covariance. He tries to make sense of it, through trying to specify a way that the violation is still consistent with quantum mechanics. I think it fails, essentially because when speaking of general covariance, there is no intrinsic scale.

    4. Mistake I made in my above post. My thought is that the speed of light is such that it ensures the force to make an electron collapse by loss of energy re electromagnetic radiation is equal to the force of the wobble brought on by electromagnetic aberration trying to throw the charge out... just as it appears for the Earth-sun system the force of the wobble brought on by gravitational aberration is countered by the velocity dependent offset. I just can’t see that being a coincidence, maybe everything else ends up winking out as a virtual particle.

  28. Craig, those are good and intriguing questions.

  29. I think Einstein meant that correlations in spacetime need a proper mechanism which might explain deeper than statistics.

    1. Eusa,

      That’s exactly it! And we are never going to find such a mechanism because we cannot even conceive a “definite and familiar domain of objects (Gödels proof)” that produces random numbers, let alone all the subtleties of quantum mechanics.

  30. I like that view! Yes.

    I am still getting to grips with the implications of my latest (amateur) paper on Jan 2021 on antiparticles and the nature of space, but what you have written above fits. My paper brings together two ideas into one whole. (1) Farnes has negative mass causing DM and DE. (2) Chappell has time being dependent on an overall background twist in space in geometric algebra. Geometric algebra can set an overall background of space with a positive twist or a negative twist (either ε = +1 or ε = -1) The universe has say ε = +1 which sets the universe's time direction and the direction of the thermodynamic arrow of time. If one treats an elementary particle as a universe, it has its own, independent value of ε. So it can be travelling with or against the universal arrow of time. So a particle can carry its own spacetime with it very much like carrying its own piece of carpet with it. In the usual analogy (which I normally dislike) a particle/antiparticle can ride on a convex piece or on a concave piece of carpet as appropriate to it.

    Meeting the Bell correlation is trivial to calculate using backwards-in-time positrons, paired with forwards-in-time electrons. Although IMO I have shown very simply that this works, it still remains for me to show why QM also meets meets the Bell correlation. I suspect that if GA is an alternative way of representing space equivalently to QM, then the possibility of + or - time directions in GA must be somehow embedded in the QM calculations using Projection operators and the Pauli matrices. (I have of course followed (Susskind's) QM calculations in a shut-up-and-calculate fashion.)

    Just a few points: in QM, if two measurements are instantaneous, which measurement dominates? A or B? Or could the results fibrillate (joke).
    In my model, the positron measurement dominates as the electron gets imposed on it by 'entanglement' the polarisation of the partner positron.

    Austin Fearnley

  31. Einstein… “For this reason I tend to believe that quantum mechanics is an incomplete and indirect description of reality which will later be replaced by a complete and direct one.”

    I love that quote and find it ironic that current evidence suggest it’s also appropriate to substitute general relativity for quantum mechanics; yet, that thinking is too disruptive for many to consider seriously, even if strong empirical evidence suggest otherwise. We continue putting too much effort trying to squeeze round balls into the square framework we’ve adopted.

    A serious effort should be made to restate the foundations of these theories with assumptions that agree with this part of an Einstein quote you used, “…physics should represent reality in space and time…”. The foundations are too obvious, too simple, and too compatible with testable observations to continue being ignored in favor of squeezing adaptations of our current theories into the mathematical framework we’re stuck in. Unless we start over from the bottom up I believe we’ll never have compatibly or definitively answer the nagging inconsistencies we find in our observations.

    1. "Unless we start over from the bottom up I believe we’ll never have compatibly or definitively answer the nagging inconsistencies we find in our observations."

      What nagging inconsistencies in observations do you have in mind?

    2. You asked Louis; "What nagging inconsistencies in observations do you have in mind?" Are we really so used to the 'weirdness' of QM we forget it's a logical inconsistency? ..or (EPR) paradox? John Bell certainly thought "the founding fathers were in fact wrong" ..somewhere. (p.171).
      I certainly agree with Louis. Do you not?

  32. If two measurements are close enough in time and far enough apart in space then simple special relativity tells us that which measurement happened first is observer dependent. Since no physical information or object traveled between A and B it cannot matter anyway. All you have is a correlation that you cannot even see until information is sent at <light speed from one to the other.

  33. Didn't Schrödinger come up with the idea of entanglement to explain the EPR paper? And the EPR paper embodied Einstein's spooky action at a distance. So while entanglement and spooky action at a distance may not be exactly the same thing, they are very much related.

    1. Not sure what you mean. The EPR paper uses an entangled state. It isn't *called* an entangled state in the paper. I can't remember off the top of my head who came up with this term. (Other than that the German term is "Verschränkung").

    2. Peter,

      Einstein didn’t see non-locality (spooky action) as a consequence of entanglement per se, but as a consequence of entanglement + the assumption that QM is complete. This quote is, I think, relevant here:

      “It seems hard to sneak a look at God’s cards. But that he plays dice and uses ‘telepathic’ methods (as the present quantum theory requires of him) is something that I cannot believe for a single moment.”

      The conclusion of the EPR paper is that QM is incomplete.

      The argument in the EPR paper is based on the existence of entanglement, which enables one to predict the outcome of a distant measurement by performing another measurement locally. The possibility of making such a prediction proves (in the absence of non-locality) that the distant measurement must be predetermined, hence QM must be incomplete since it cannot account for that predetermination.

    3. Actually I think it was the other way around. Schrödinger developed the idea of entanglement first and Einstein tried to explain it as hidden classical states that would complete quantum mechanics.

    4. The word "Verschränkung" first appeared in a letter Schrödinger wrote to Einstein in response to the EPR paper. Its translation "entanglement" is also due to Schrödinger. The EPR paper was not influenced by Schrödinger's development of his idea. Schrödinger's decision to publish his idea on the other hand was strongly influenced by the EPR paper (and Bohr's disappointing reaction).

      Schrödinger concludes his famous cat paper as follows: “Perhaps, the simple procedure of the nonrelativistic theory is only a convenient calculational trick, but it has at the moment attained a tremendous influence over our basic view of Nature.” The abstract of another paper on entanglement by Schrödinger from 1936 ends: "It is suggested that these conclusions, unavoidable within the present theory but repugnant to some physicists including the author, are caused by applying non-relativistic quantum mechanics beyond its legitimate range. An alternative possibility is indicated."

      I interpret this as an active attack on Bohr's obscurantism, which doesn't even acknowledged that a unified theory of QM and (special) relativity was not yet available (in 1936). Later papers by Schrödinger get even more explicit in his attacks on Bohr's obscurantism.

  34. @Amos points out "In general [Einstein] was talking about the fact that a measurement in one location affects the wave function in another location."

    I think this is the core of the problem. It might be, however, that no change (of state) following a measurement is necessary. Encoded in the state are all correlations that come out in measurements. If you measure something in one place (say the existence of an electron) you measure something related in another place (say the non-existence of an electron). These correlations are in the state, and no change of state after a measurement is necessary to make it happen this way. In particular no collapse of wave function.

    There are, of course, equivalence classes of states that offer identical measurement outcomes. For example a singlet state of two spins where one particle has been measured in z-direction (result: pointing down) and another state where a single spin has been prepared in z-direction pointing up.

    In both cases, a measurement on the (remaining) spin yields a result conforming with a measurement on a spin pointing up in z-direction. Having, in the first state, measured the first spin does not imply, however, a change of the member state of the equivalence class. Such a change indeed would have space-like consequences (for the most likely non-physical wave function), but the change of state is not necessary to explain the measurement results. So maybe it doesn't happen at all.

    In fact, no collapse of a wave function has been necessary since the Big Bang. It is merely a matter of convenience to describe states with equivalence class members that do not require to take explicitly into account all measurements since the beginning of time in order to evaluate (via correlations the consequences for) the remaining measurements.

    1. Ok but this does not address violations of Bell's inequality. It is this violation that makes it look like a measurement here changed a state there.

  35. If it wasn't for coherence and superposition, life would not exist. Quantum biology has shown that light energy is transferred between process centers in green plants via superposition of the exciton created by an incoming photon. The exciton exists in a state of superposition and that charge separation will take all possible paths to the process center where the photon energy is converted to sugar and oxygen. This transfer of energy is 100% efficient and happens instantaneously. The transfer of energy in living things is something that spooky action does very well.

  36. When Sabine says “If you think that really it was decided already which spin went into which direction when they were emitted, that will not create sufficiently strong correlations. It’s just incompatible with observations.” what makes it incompatible with observation. Can someone point me to an explicit example of the incompatibility?

    Watching Alain Aspect’s video at shows what must be the QM probability curve vs Classical Mechanics at 39m15s, but then at 54m34s he shows a plot of experimental results where the violations occur. This video seems to be the most detailed (layperson) explanation that I have come across or maybe it is too simplistic.

    Is the probability curve just translated into a “violation” curve by the EPR experiments?

    Is the big deal about QM Entanglement/Measurement just that QM does not match CM and the difference maxes out at 22.5 degrees? And if that is the case is it a big deal that polarizers have this mode of operation? It is just a fact of life and I see no problem with that. The correlation is made at pair creation and read with polarizers that work the way they do.

    Or is it that this polarizer operation 'cannot be' or 'is not' explained by QM and we need a better explanation of reality?

    1. Peter, I've found your last line correct. But did the Aspect video reveal he had to discard over 95% of his data to make it fit the QM prediction? That's not in his short paper but is in his thesis. Others such as Weihs/Zeilinger with different kit then did the same, still not able to find the source of the 'rotational anisotropies'. Some may suggest 'confirmation bias'! Is that fair?

    2. Peter Becher,

      The point is that classical mechanics cannot produce the quantum probabilities without using faster than light information transfer. See this video:

      Peter Jackson,

      The last line you reference is wrong. QM predicts perfectly the polarizer operation. Classical mechanics will not allow it at all.

      It is true that Aspect had discarded a lot of data because photon detectors were pretty inefficient at the time. But first, that is no longer true. And second, no it is not confirmation bias. Not fair at all.

    3. ppnl,

      "classical mechanics cannot produce the quantum probabilities without using faster than light information transfer"

      If by "classical mechanics" you mean Newtonian mechanics with contact forces only (billiard balls) I agree. If you include field theories (classical electromagnetism, general relativity) your claim is unsupported by evidence.

      In fact, any complete (fundamental) theory that does not include hidden variables must be non-local in order to account for EPR/Bell correlations.

    4. Peter Jackson
      Aspect was mostly talking about his 1982 experiment that had better equipment than his earlier one. He did not mention rejecting that much data but did mention something about the noise levels of detectors or something like that.

      That video is one I watched a while back when looking into EPR experiments. It is great along with its companion video from 3blue1brown. But both videos go on about how strange/unknown the effect is at 22.5 degrees.

      So is it just that the math of QM is good at describing the effect at various polarizer angles but cannot explain why a given photon with vertical polarization has a 85% chance of going through a polarizer set at 22.5 degrees? Put another way, QM cannot explain the physical interaction in the polarizer that results in a sine wave transmission curve.

      Thanks for your statement “The point is that classical mechanics cannot produce the quantum probabilities without using faster than light information transfer”. I just didn't see it having anything to do with greater than speed of light effects, but when you put it that way, that in order for CM to get the QM results the polarizers would have to be switching to get the 85% rate. Now that makes sense.

      Again, the only mystery then is that CM and QM ‘cannot explain the physical interaction in the polarizer that results in a sine wave curve’. Would that be a correct statement?

    5. Peter Becher, I agree it's common belief that "the only mystery is that CM and QM ‘cannot explain the physical interaction in the polarizer that results in a sine wave curve’. But I suggest the solution to that also explains the Aspect etc majority discarded data. (Weighs/Zeilinger etc. followed suit). That "rotational anisotropy" was indeed dismissed as you suggest, but the solution predicts the FULL data set. The impossibility of a classical solution only results when using Bohr's starting assumptions. Bell agreed these were wrong and a classical solution exists (p.171). Shocking? It will be for most! The paper is imminent. For now consider the DFM inverse Cos^2 distributions of the 2 (Maxwell) orthogonal (OAM) momenta of the Poincare sphere.

  37. Good morning Sabine,

    I really find this topic the most interesting, because
    the experimental setup is simple and the costs are low.
    The results have been confirmed
    by different groups in many parts of the world
    and there is still no satisfactory solution - which makes it so fascinating.

    I prefer "spooky remote action". It looks the simplest to me.
    If one takes "spooky remote action" as the basis/basic assumption for our world,
    one loses all the beautiful and helpful mathematics (differential calculus).
    I am aware of this.

    You favour superdeterminism.
    I'd like to know what that is, how it works.
    Maybe you have time for a blog post when you get a chance.
    After all, it is your "baby".

    Many greetings and have a nice day

    1. Hi Stefan,
      Dr. Hossenfelder wrote a 'guide for the perplexed': I'm still somewhat perplexed but did find the paper helpful.
      I would love to see a video in Sabine style on the subject.
      Have a good one.

    2. I probably don't understand this comment, but it seems to be asking for more information from Dr. Hossenfelder on super-determinism. I happen to know that Dr. H has written at least one blog post on the subject, and some papers which are available on arXive. Dr. Tim Palmer has worked with her on this subject and also has some papers on arXive.

      Google ("Sabine Hossenfelder superdeterminism") quickly gives me links to these sources, as well as reviews by others. So I wonder if Stefan Freundt has read that material and wants more, or was unaware of it.

      (What I took from those readings is that superdeterminism, or lack of statistical independence between detector settings and measurements, at first glance sounds like a conspiracy theory, but actually encompasses a much larger range of possibilities. I see a vague analogy between this and how some people look at the complexity of DNA life in this universe and conclude our specific physical laws are the only way to produce life, and therefore must be fine-tuned. The actual range of possibilities could be much larger, in my opinion.)

    3. Hi JimV,
      After my 'tizzy' about Superdeterminism a few months ago I made a concerted effort to understand the subject as well as I could. I found Superdeterminism to be both reducible to a basic premise and rather hard to accept in its entirety. My take-away is that 'whatever will be, will be' so if one is making a major decision, stressing about it won't change the ultimate outcome, so one may as well remain as calm as possible. (So I'm enrolling in a Bachelor of Music, since I already did anyway, if I 'choose' to then do so.)
      All other explanations, I'll quote the experts.
      The question of Superdeterminism vs. the possibilities of life in the Universe is yet another intriguing layer to this.

    4. Hello C. Thompson,

      I have looked at the article.

      When reading an article some questions are helpful:
      Why was the article written?
      What gap in knowledge is it trying to fill?
      Is there a derivation?
      What is the start of the derivation? What are the assumptions?
      Have I understood this? If the assumptions are already unclear, the rest will not become clearer.
      What are the conclusions? What is the result?
      By the way: derivations and results are most of the time correct.
      Well-educated people can follow a derivation and anyone can check results.
      Checking the assumptions of a theory is much harder,
      often impossible.
      (The mainstream is sometimes very good at accepting false premises.)

      If I am confused about an article, I do just that.
      If an article is good, the article does that automatically.

      "Superdeterminism is presently the only known consistent description of nature that is
      local, deterministic, and can give rise to the observed correlations of quantum mechanics."
      That answers the first question. That is good.

      Question: What is superdeterminism? What is the problem?
      The 2nd page above answers that:
      "The one unfamiliar property of superdeterminism is the violation of statistical independence."
      "That is because once we drop Statistical Independence, there is nothing preventing us from
      developing a consistent local and deterministic theory"

      I can understand that: In the experiments on entangled objects, there must be no correlation
      between the measured object and the detector. Or vice versa: if there is a correlation between measurement object and detector,
      then this correlation can/will also be responsible for our result.

      Then the article goes into the following things:
      - hidden variable
      - finetuning
      - conspiracy
      - faster-than-light speed

      I didn't understand all that in detail.
      But I trust Sabine.

      What I miss is a concrete example or an idea,
      how object and detector get their correlation.
      The article says: If they correlate with each other, then everything is fine.
      And I ask: Very nice, but how is this correlation formed?
      I see a big explanatory gap here.

      And then there is something else, right at the beginning:
      Why does a good scientific theory have to be "local"???
      (Abstract 1st sentence)
      A theory must be local to justify the use of differential calculus.
      I think:
      The mathematics must be appropriate to the problems.
      The mathematics must fit the problems.
      And not the other way round:
      I consider the problems until they fit the available mathematics.

      Many greetings

    5. Hello Sabine,

      as the diabolical Zorg said in the movie the "5th Element":
      "If you want something done, do it yourself."

      That's probably the only belief we have in common.
      That's a pity. It's really too bad because.
      - Your English is better than mine (by a factor of 10..100)
      - You are very well connected in the mainstream (by a factor - I don't know such a big number)
      - You know more publications and experiments than I do (by a factor of 10..100)

      Many greetings

    6. Stefan,

      "And I ask: Very nice, but how is this correlation formed?
      I see a big explanatory gap here."

      Scientific theories explain observations. They never explain their axioms. If you see an "explanatory gap" you are confused about what requires explanation to begin with.

    7. I found the paper helped me get the gist of the workings of Superdeterminism and how to show the effects experimentally, but the parts that were mathematical went over my head. I need to re-read it to refresh my memory.
      As far as axioms go, if the author doesn't understand correctly they don't have a leg to stand on, but as far as I could tell, the Guide for the Perplexed is rock-solid; Dr. Hossenfelder is a careful author.
      My biggest issue with the Guide is I remember the muffins/weight-loss/amputation example better than the passage on retro-causation, but I won't forget the paper due to that.
      To understand the entire paper I'll need to actually study physics.

    8. If the issue is what sort of mechanism could cause the experimental results to seem random yet correlated, I think Dr. Tim Palmer's papers propose a chaos-attractor mechanism. I think Dr. Hossenfelder does not endorse any specific mechanism, but proposes experiments which might shed some light. (Just my superficial opinions.)

      I think the main purpose of their joint paper was to explain that a super-determinism model need not be just a coincidental result of initial conditions at the Big Bang (referred to as a "conspiracy theory" by several other scientists), but might have some mechanism which would allow us to make better predictions (once we understood it). I think it is fair to say that the paper has not convinced many of the conspiracy-theory skeptics (extrapolation from the two or three I know of).

    9. Also Stefan, There's a lecture Dr. Hossenfelder gave on Superdeterminism that I just remembered on YouTube.

      Again, the mathematics went over my head but it was interesting.

    10. @Jimv, I can get why it looks like a conspiracy/too fine-tuned. It's weird.
      The objections I've seen and read (3 or 4 of them) are metaphysical/philosophical in nature and object to the bald premise without taking into consideration anything extra Dr. H added by way of further explanations of how Superdeterminism plays out in life. They ask, 'what about morals? What about fun?!' As if Sabine Hossenfelder is some sort of soulless creature without ethics, which is entirely absurd.
      I'm yet to encounter a solid scientific argument.

  38. Koennten Sie bitte Ihre Meinung aeussern. Ist theoretische Voraussetzung der Existenz der Zufälligkeit als ein natürliches Phänomen äquivalent zum Verstoß gegen Energieerhaltungssatz? Jede Veraenderung des Objekt als Stand seiner Energie (Beginn der Bewegung, Richtungswechsel, Geschwindigkeitsänderung, Bewegungseinstellung usw) impliziert extra Energieanwendung. Trotzdem, wenn ein Teilchen als "Wellezustand" ihre Wellenfunktion selbst aufhört, ist diese Veraenderung ganz ohne Ursache und ..ohne extra Energieanwendung. Ob es was anderes ausser Verstoß gegen Energieerhaltungssatz bedeutet (ausser dem Fall, wo es um Viele-Welten-Interpretation geht)?

  39. I am getting a phishing warning for this site from google. I clicked the feedback link to let them know about the error.

    I had to laugh at the warning that this site is dangerous since certain status quo physicists might feel that way.

    1. Quite ironic seeing that this site is hosted by Google to begin with!

    2. Dr. H wants your soul. :-9

  40. The four essential processes by which a multicellular organism is made: cell proliferation, cell specialization, cell interaction, and cell movement. In a developing embryo, all these processes are happening at once, in a kaleidoscopic variety of different ways in different parts of the organism.

    Without non local quantum entanglement, the development of multi celled organization would not have been possible. This ability to network matter/energy may be central to the weak Anthropic Principle. Quantum entanglement and its associated quantum processes as a fundamental life principle may be what makes both us specifically and life in general possible.

    1. I resisted responding to your previous statement about "life", assuming that you meant specifically "life of the sort we know" but now that you say "life in general" I must object (as an alternate opinion).

      We do not know and cannot know the requirements of "life in general" other than some sort of complex physical laws which allow for computations, but elaborations of cellular automation rules have been shown to produce reproducing structures and Turing-complete ability. This implies to me that a) it is difficult to assess in advance whether any set of physical laws is capable of producing self-reproducing organizations which can do computations, and b) there are probably many more such sets than we can imagine.

      Of course any life we find in this universe will use the physical laws that occur here, that is just a tautology.

  41. Hi all,
    For whatever it's worth, I think the easiest solution to information transfer is that everything is predetermined and all that any observer and/or measurement will do is bring a uncollapsed/entangled wave, particle etc. to the state that continues what was set in motion at the Big Bang. (Superderminism.)
    Previously in the video/post 'Schrödinger's Cat - Still Not Dead' after looking at superposition on a larger-than-quantum scale, Dr Hossenfelder asks which of 3 assumptions is wrong:
    1. No Superdeterminism.
    2. Measurements have definite outcomes.
    3. No spooky action at a distance.

    In the case of Sabine's Random Socks and for the discussions in the above comments, I think the wrong assumption is 'Spooky action at a distance'.
    I acknowledge that there's possibly issues with my idea that I may be ignorant of or haven't considered; if so, I welcome them being pointed out.

    1. Hi Paps57
      Not only have "we" missed something and do not understand the mechanism of light propagation, the physics community has totally ignored the possibility of any real mechanism. Most just use the math and shut-up-and-calculate mentality.
      The only way to get a real explanation is to work with a light medium like every other wave in nature.

    2. Hi Paps57,
      It had never occurred to me that light needed to be propagated, it just seemed to move along from its own energy. I don't know what else to think of.

    3. Paps57
      I do not disgree that we are missing something important. Probably true of everything!

      Q = T3 + 0.5Yw
      (The electric charge, Q, is related to weak isospin, T3, and weak hypercharge) (from Wiki)

      The electric charge is related to weak isospin, and the higgs field has a property of weak isospin (+ 0.5 or - 0.5). The vacuum is not 'nothing' and I believe that the higgs field cannot be removed from a vacuum. The electron has a property of weak isospin but the photon does not.

      I have a naive preon model for elementary particle compositions. A long time ago I suggested that a photon behaved like a boat with two counter-rotating engines. Such a boat travels fast. A (chiral) boat with say two left-rotating engines and no rudder would stay approximately in one spot but would still require the seemingly perpetual motion engines. So, paradoxically (?), in my naive model it requires engine motion to stand still. The engines are at several levels down the chain within elementary particles, and as energy increases with small time intervals, there may be enough energy to give the appearance of perpetual motion.

      Austin Fearnley

    4. @Dr Hossenfelder
      Could you shed any light on this?

      Maybe electrons emit photons with enough thrust to propel them? (Although that seems too simplistic to be valid).

    5. Empty space isn't nothing. It's empty space.

    6. If the space is empty, then isn't there nothing in it?

    7. "Empty space" means it's a vacuum state. It doesn't have "nothing" in it, it has quantum fields in the ground state in it. And in any case, as I said, space itself is arguably something and not nothing.

    8. @Dr. Hossenfelder
      Thanks. I wasn't sure if that's what you meant.
      Do you have any enlightenment for the question of how photons travel?

    9. C Thompson,

      We calculate how photons travel either with Maxwell's equations or with QED, depending on whether quantum effects are relevant. I don't understand why people ask "how" questions but when you give them an answer they dismiss it because they don't understand the math.

    10. Dr. Hossenfelder,
      Thank you, your answer is appreciated. I'll follow that information up.
      I don't dismiss answers so much as I am not equipped to understand said maths. I am piecing together some understanding as I go along from online resources and slowly making progress.
      I guess people want to be spoon-fed easy answers.

    11. People will probably show up to defend Aristotle, but my recollection is that in his physics, objects tended to stay at rest unless some force was pushing or pulling them, and Newton corrected that to, objects in motion tend to stay in motion unless something resists that motion, such as friction. I believe Newton, as do I think all engineers who have to calculate things that move, such as turbines.

      Newton also believed that photons are particles, i.e., objects, which obey his law. QM tells us that particles also have properties similar to waves, the magnitude of which depends on their size, so baseballs no, photons yes. Still they also have a particle nature which dominates in some situations. So I don't have a problem with them continuing to move until something absorbs them. Note however they move through different media at different speeds and c only applies in a vacuum. Perhaps in a vacuum which had no quantum fields (if that were even possible) c would be slightly larger, but we have no way of testing this. (My mental model of this, for what little it is worth, is that media which photons move through causes them to bounce around and travel a longer distance than the straight lines used to calculate their measured speeds. I don't walk in straight lines either so my pedometers show more distance traveled than a map shows between A and B.) (Another possibility it that they get absorbed and re-emitted in the media, with a slight time gap between. I myself do not have that problem though, so far.)

      Anyway, talk of photons needing some motor or rocket to move reminds me of Aristotle, and I refuse to go back to his physics, which would make many of the calculations I have done incorrect.

      (I apologize for inflicting my mental models on possible readers. Dr. Hossenfelder is of course right that it is the math that is important, but many of us need some sort of story to remember the rules with.) (Dr. Scott Aaronson says that the Many Worlds Interpretation, which most laypeople detest, is actually the story that seems most helpful to the students he has taught QM to. Which doesn't make it right, but somewhat useful.)

    12. Louis de Broglie thought light was a double particle and Andre Michaud has written some papers with that in mind. Michaud has some interesting points but I don't see it as anything final.

      At some point a type of space medium (the 'nothing' of empty space) will be recognized as the medium of light waves and a good explanation of the medium will solve most of these questions. It only makes sense that all waves need a medium, it just needs to be figured out.

    13. Thanks for elaborating, JimV.
      I'm not apologising for inflicting myself upon this blog and I don't think you should either.

    14. I have not mentioned 'engines' and 'counter-rotating screws' in my online papers as they are (very) hypothetical features at sub-preon level. I think of the chiral engines as not disobeying Newtons Laws and they would require a force to stop motion. It is only a means of giving mass to a fermion. A massive particle will not simply depart at near speed c without an external force. But a photon will. I use the engine analogy to imagine how this might happen. This did arise as a question needing an answer in my preon model. If I can build 'two photons' from 'an electron plus a positron' by rearranging (four types of) preons, then there should be some property within the preon arrangements that allows the photon to move at speed c but prevents the electron from doing so. Some arrangement allow c and others do not, hence the counter-rotation idea.

      Back to entanglement...
      I followed Susskind's course on entanglement and, in it, he calculated how QM breaks the Bell Inequalities. I am not clear that his proof is sufficient as it seems not random enough. He used Projection operators to project a singlet-entangled particle(s) onto the up direction and also onto the 45-degree-angle diagonal direction. But his singlet is |up, down> - |down,up> which is already parallel with the 'up' projection target direction.
      Are there any calculations already done with the general case of using the same projection operators but using a generalised singlet say |m, opposite_of_m> - |opposite_of_m, m> where m is a random direction?

      Austin Fearnley

    15. RE: "Are there any calculations already done with the general case of using the same projection operators but using a generalised singlet..."

      N. David Mermin, in his popular-science book, "Boojums All The Way Through" presents a couple different examples of possible experiments similar to Bell's example (seeming to rule out hidden variables) and gives the parameters of the experimental setups and the calculation results, but does not go through the calculations themselves (unless they are in an appendix which I haven't gotten to--checking ... no, but he does reference some old papers and an old Scientific American article, circa 1970's).

    16. @Paps57, I don't think there's been any attacks as such.
      We asked questions and got answers from the subject-matter expert. That I don't know what Maxwell's equations or about QED is for me to sort out. (I'm happy that I actually got an answer from Dr. Hossenfelder at all, given how beneath others' knowledge levels I am.)
      I took JimV's remarks on Aristotle to refer to how ideas have progressed.
      As far as I can tell, the blog exists to host discussions like this one, where multiple people can contribute.
      I hope you do find out more beyond just the official answers, and you share them on this blog.

    17. Paps57, I'm with C Thompson, don't think of questioning as attacks. I like your questions and thoughts. Keep thinking about and asking "HOW"! (even if Sabine cannot understand why we do it)
      I have read how de Broglie got hammered by Bohr and others and lost sight of his insights into the possible true underlying workings of "particles". It took him decades to sort of get back to them but seems to me that he never went deeper with his ideas on the 'high frequency energy center of a corpuscle'. I don't think he thought much about the aether in his day since E had disavowed it and de Broglie grew up with that. I just have a deep feeling that a space medium is the key to the underlying nature of the universe. Not sure if I will be able to show it well or prove anything but who knows.

    18. C Thompson, On the 'nothing of space' the mathematical model has all those "quantum fields" for particles. It allows for the accurate calculations of QM.
      As Don Lincoln mentions in at least one of his videos the holy grail would be to find a "Single Stuff" that would unit all particles and forces. As I mentioned for Paps57, that would be a space medium. So "space is not empty", it can be empty of 'sensable' stuff; matter, light, etc, but the space medium would be the 'non-emptiness' of space and the basis for all that sensable stuff and would be the 'single stuff'.
      The properties of the space medium will determine the ultimate answer to the title of this blog post.

    19. Peter:

      "Keep thinking about and asking "HOW"! (even if Sabine cannot understand why we do it)"

      You entirely missed the point. What I said is that I don't understand why people ask how-questions but then ignore the answers that you give them. How does gravity work? Einsteins field equations. That's the best answer we have and it's a remarkably successful and accurate answer. How do photons propagate? QED. And so on. What all those people with their "how" question want is a dumbed-down interpretation which they will then complain doesn't work, which of course it doesn't. Same problem with quantum mechanics.

    20. @Dr. Hossenfelder: I asked you specifically because I hoped you would answer from better knowledge; as I said up-thread now it's on me to take it from there. Any time you answer my queries I appreciate it.
      I don't know if Paps57 or anyone else was expecting a 'dumbed-down' interpretation.

      @Peter Becher: Thanks for your answer too.

    21. Sabine
      I did get your point but you seem to miss our point. We ask 'how' to try to find a deeper explanation of how things do actually work in nature.
      You say "How does gravity work? Einsteins field equations. That's the best answer we have". GR is a good mathematical description of how gravity works and that is fine. I don't know if you think or have said 'the GR curvature of spacetime IS gravity' but many physicists seem to think that. But saying that is like saying a QM description of water IS water, just try to drink a page of math or computer output.

      A good quantum version of gravity will probably never be had because it is getting further and further from what the actual cause of gravitation is. It would be really good if physicists actually tried to find this fundamental cause but they are too lost in the math, as some smart person once wrote a book about.

    22. Peter,

      Maybe read the book again because in it I explain how to find better explanations. It's not by asking nonsense questions and demanding intuitive answers. That's a stereotypic crank approach.

      And I am not a platonist, and not a realist either.

    23. Would anyone like to give an answer to my comment at the top of this thread?

    24. I'm not really qualified to have an opinion (although that rarely stops me from giving one) on which of the three axioms is wrong, and unlikely to give one that hasn't already been discussed in the previous blog post where those axioms were presented. However, from what I can tell, most physicists would stake their honor on the choice of super determinism being wrong. (I encountered this most recently at Dr. Scott Aaronson's blog.)

      The reason (I think) is that QM gives precise mathematical recipes for calculating outcomes of events at the quantum level without assuming SD, and nature appears to agree rather perfectly with those recipes, and nobody (yet) can conceive of any way (except the most fantastic set of coincidences ever) how SD could produce those results. It is mind-stretching to conceive there might even be a model for that. It is also mind-stretching to realize, as Einstein and others pointed out, that QM results imply that all of reality is not real all of the time, but can become real instantaneously (or close to it) across large distances, when it needs to. However, Bohr and others argued from the very beginning that nature was telling us that, and we needed to accept it.

      So you can have a) a method that works and implies certain uncomfortable facts; or b) a method which could eliminate the uncomfortable facts if we knew how to implement it, but so far nobody does. Most physicists prefer a), and teach physics accordingly.

    25. JimV,

      "QM gives precise mathematical recipes for calculating outcomes of events at the quantum level without assuming SD, and nature appears to agree rather perfectly with those recipes"

      Yes, but the choice is not between QM and superdeterminism. Superdeterminism does not imply a denial of QM, only of QM's completness.

      If QM is assumed to be complete one has to deny locality and hence go into conflict with relativity. If one wants locality, superdeterminism is the only choice.

      The reason most physicists reject superdeterminism is because they not know or understand the consequences of EPR and Bell arguments. Very few of them would openly deny locality (Tim Maudlin is one of those few).

      "nobody (yet) can conceive of any way (except the most fantastic set of coincidences ever) how SD could produce those results"

      I can conceive a way. The source and detectors interact electromagnetically, being aggregates of charged particles. The correlations are the effect of those interactions. This is the explanation for any correlation ever observed. Non-local effects were never found.

      "Einstein and others pointed out, that QM results imply that all of reality is not real all of the time, but can become real instantaneously (or close to it) across large distances, when it needs to. However, Bohr and others argued from the very beginning that nature was telling us that, and we needed to accept it."

      "Reality" is a red-herring in fact. What is at stake is the existence of hidden variables and locality. Locality implies hidden variables. The rejection of hidden variables implies non-locality. You cannot explain EPR correlation in a local way by denying "reality".

      "So you can have a) a method that works and implies certain uncomfortable facts; or b) a method which could eliminate the uncomfortable facts if we knew how to implement it, but so far nobody does. Most physicists prefer a), and teach physics accordingly."

      No, we either have a complete/fundamental QM and physics is non-local, or we have superdeterminism. Both options require a reformulation of some accepted physical theories. Non-locality requires a reintroduction of an absolute reference frame and a reformulation of relativity. Superdeterminism would replace QM completely. 't Hooft seems to be doing just that:

      "Explicit construction of Local Hidden Variables for any quantum theory up to any desired accuracy"

    26. Sabine
      It is unfortunate that they are seen as nonsense questions.
      Little hope for the foundations in that.

    27. C Thompson
      I suppose I helped steer your question in the wrong direction, but it was mostly a statement.
      You mention:
      "Dr Hossenfelder asks which of 3 assumptions is wrong:
      1. No Superdeterminism.
      2. Measurements have definite outcomes.
      3. No spooky action at a distance."
      You state:
      "I think the wrong assumption is 'Spooky action at a distance'."
      So do you think 'spooky action', or 'no spooky action' as 3 states, is wrong?
      In my opinion 3 is the only one that is correct.
      1. Superdeterminism is extremely unlikely.
      2. Measurements are not definite but follow the probabilities. If they were definite then #1 might be correct.
      3. There is 'no spooky action at a distance'. As Sabine said in this video "But there’s no spooky action in the correlation themselves. These correlations were created locally".
      So then there are no spooky actions in the detection because that is the way the polarizers work. The probabilistic ability for the polarizers to pass photons according to the QM sine wave function is just how they work.
      The "spooky-est action is what is going on in the polarizer for any given photon at any given polarizer/photon angle. And this is where, as I mentioned elsewhere, that CM and QM both cannot explain what is going on in the polarizer. It is also why I feel that the HOW questions (by cranky people like me) are so important. I feel that once the polarizer action is explained 'how' it will be will be able to be done by a Classical Mechanics solution that matches QM.

    28. Mr. Andrei, we have discussed your EM-based super determinism before. My guess is that if EM configurations of experimental settings had a strong influence on measurement results, than placing two sets of such equipment next to the active one would vary the experimental results as the settings of the non-functional equipment were varied, but in actual experiments of that sort no effects would be detected. (I don't know if it has been tried.)

      Secondly, your model, as you have admitted, cannot be calculated and a model without predictive ability is not much improvement on no model. But as my friend Mario says, if it lets you sleep soundly at night, that is worth something--to you. Currently I am not usually able to sleep soundly myself, but it isn't the lack of a rigorous SD model that bothers me.

      Lastly, about reality, those are the terms which Dr. N. David Mermin attributes to Einstein in his book, but perhaps he was mistaken, or Einstein was. My impression though was that Dr. Sabine's post which we are commenting on supports that broader interpretation of Einstein's views.

      In any case, my opinions are not worth a hill of beans, and perhaps the impressions I have of what others in the physics community think are not either.

    29. @Peter

      I agree that:
      1. Superdeterminism is unlikely.
      2. Measurement outcomes are determined by probabilities.
      3. There is 'no spooky action at a distance'.

      1. I prefer retrocausality (of antimatter) to superdeterminism. It is easy to show that retrocausality can produce the Bell QM correlation. (My June 2020 online paper.)

      2. This is a difficult one as 'are the outcomes really random [maybe allowing free will]' or are the outcomes only apparently random [maybe removing free will]. But I can leave aside the free will issue here. The important point is that hidden variable static vectors cannot underly the Bell experiment measurements. The quantum Randi test rules out a measurement being solely determined by a hidden variable (static vector) and a detector setting. [And I have tried enough computer simulations to believe this.] So the same (= 'same' hidden variable) incoming particle meeting the same [= 'same' detector setting] detector can have different results (so 'no counterfactual definiteness').

      Peter wrote: "I feel that once the polarizer action is explained 'how' it will be will be able to be done by a Classical Mechanics solution that matches QM."

      I already have a Classical model of an electron that gives the Malus Law results. (See my June 2020 paper online.) The electron in this model has a (varying) hidden variable. Imagine the electron pointing upwards. It is not static but is precessing and nutating so that it is pointing always in the same upwards hemisphere. But it points mostly |up> and less frequently points at 90 deg away from |up>. So if you take |up> polarised electrons and measure them at 45 deg setting then more than expected would pass through the 45 deg filter. You might expect 75% to pass the filter (Classical correl = 2 * 0.75 - 1 = 0.5) but in fact 85.3% will pass the filter (2 * 0.853 - 1 = 0.707 = Bell QM correlation), as the hidden variable is more often pointing towards |up> than you would expect. Every |up> electron would look like this so there is only one hidden variable and it applies to all electrons. The hidden variable is not a tag to be used to identify an individual electron.

      3. The only QM proof of the Bell correl that I have seen is flawed (Susskind online lecture). It finds the value 85.3% but is really just proving the Malus Law. And I can do that with my classical model. But I am trying to find a more general QM proof of the Bell correlation or calculate it myself.

      I like 't Hooft's (superdeterminism?) idea of the particle hidden variable changing instantaneously or just after a detector setting is chosen, even with rapidly changing settings. [Thanks to JimV for the arxiv reference.] This is also what happens in my retro model. When a positron is measured, the positron travels backwards in time to the source [just as it appears to do in a Feynman diagram] immediately after it is re-polarised by the measurement to take on a new polarisation equal to that of setting of that detector. This really makes the physics again equivalent to Malus and not a general QM solution for a Bell experiment. And I have a classical model to give agreement with Malus's Law. So 'not spooky'. (I have computer program code online that gives Stern Gerlach measurement outcomes using this classical model.) The precessing and nutating motion of the electron makes the measurement outcome a variable which is dependent on the time of the measurement, and that gives an apparently random aspect to a measurement.

      Austin Fearnley

    30. In response to: "I already have a Classical model of an electron that gives the Malus Law results."--Austin Fearnley

      That sounds like a result of a lot of clever work and research. At first glance, it seems more like a new interpretation of QM (the Fearnley Interpretation) than a classical model, because it incorporates quantum randomness and is not explicitly deterministic, and adds no new predictive ability to QM (that I can see--but my vision is getting worse and worse). I have not tried to apply it to all quantum experiment situations, such as EPR, so I don't know if it qualifies as a complete interpretation. But as far as I understand it, it seems the randomness of the polar orientation is the key element which would cause it to match other interpretations.

    31. @JimV

      IMO more dogged determination than 'clever work', but thanks for the first ever appreciative comment on my physics work!

      JimV wrote: "I have not tried to apply it to all quantum experiment situations, such as EPR, so I don't know if it qualifies as a complete interpretation."

      I have used computer simulations of my model in a conventional Bell experiment. It cannot provide the QM correlation without the positron acting retrocausally. The retrocausality turns the Bell experiment into a kind of Malus Law experiment. My model works for Malus's Law.

      The strange thing is that Malus's Law calculations dovetail nicely into the Bell QM correlation calculations in the limited circumstances when the incoming particles are already polarised along one of the detector settings. That's what Malus is about: take a polarised beam of particles (all polarised in the same direction, say zero degrees) and then measure them as a detector setting 45 degrees.

      But QM calculations are supposed to cover any random polarisation angles of incoming particles. My model cannot cover this without using retrocausality. I am now trying to see if QM really can do this. The only QM Bell calculations I have seen have the incoming beam as entangled |up, down> -|down, up> particles which are then projected onto the |up> axis. That part of the calculations looks to me more like a Malus situation than a generalised Bell experiment.

      I expect QM will work in the generalised case but maybe QM has retrocausality already built into it covertly. My next step will be to try to simulate a Bell experiment testing QM calculations based on random polarisation directions of incoming particles instead of |u,d> -|d,u> directions.

      Austin Fearnley

    32. JimV,

      "My guess is that if EM configurations of experimental settings had a strong influence on measurement results, than placing two sets of such equipment next to the active one would vary the experimental results as the settings of the non-functional equipment were varied, but in actual experiments of that sort no effects would be detected. (I don't know if it has been tried.)"

      All matter in the universe interacts electromagnetically, not only the devices used in a particular Bell test. There is nothing special about them, they are just large groups of atoms, like chairs and tables. Earth, Moon, and everything else in involved in this interaction, so placing another small peace of equipment near the experiment is not expected to make any difference.

      "your model, as you have admitted, cannot be calculated and a model without predictive ability is not much improvement on no model."

      The point of this model is not to make predictions, although it could, in principle. The point is to show that Bell's claim, that classical physics is in conflict with QM is unsupported. Classical electromagnetism cannot be shown to be in conflict with QM. The fact that we cannot simulate that experiment is not very relevant. We cannot simulate any system with more than 100 particles or so. We cannot simulate a tree or a cat or a pot. But we don't assert that those systems imply some failures of some physical principles. If one makes that claim, the burden is on him to provide evidence for that claim.

      In a Bell test a photon source we know nothing about (the microscopic conditions at the emission locus are unknown) produces some photons with some polarization. So what? What does this prove? Nothing at all. I am looking forward to see someone providing some evidence that such an observation contradicts classical electromagnetism. Until then, I have no reason for concern.

  42. When I first became acquainted with the “Spooky action at a distance” conundrum, probably in the 80’s, I assumed that the correlation between distant entangled photons or electrons was 100%. Later, I discovered it was only an 85% but still above the 75% predicted by chance (going from an August 1, 2019 article on titled “Entangled Quantum Particles Can “Communicate” Through Time”). That article refers to correlations through time rather than through space, but I think the same percentages apply. So one day it dawned on me that 85% experimental correlation directly linked to an idea that I had developed following a 1996 epiphany which postulates real, very specific, hidden variables as the basis of de Broglie, or matter, waves. I’m positive that I noted this down in one of multiple ‘ideas’ notebooks, but realized it needed to be studied in more detail to determine its viability.

  43. Paps57 ,So in the case of the particle that crosses the grid, it travels with an accompanying wave, and when the particle has not yet crossed the grid and its accompanying wave has passed the two openings and interferes with each other; It does not matter through which opening the particle passes and to the interference of the two components of the wave they decided where the particle goes; with a single opening the solution is another; could it be so?

  44. You are going to drive me crazy; I explain ; I think Einstein uses quantum entanglement to argue that quantum mechanics is incomplete; I said "I believe"; I put an example; two classical bodies with a given mass and speed collide, after the collision I measure the speed of one and immediately know the speed of the other without having to measure it; just doing a little calculation, this would be a kind of classic entanglement, mathematically the two bodies are a unique system after the collision; It seems to me that Einstein makes the like with his quantum particles; How could the final result be known if they are telling us that it is not defined and that it is probabilistic? ; If the result can be known, it is that there is something else that defines it (hidden variables) or there is magic (spoky action); It's what I think he meant. Please , Am I wrong?

    1. I am not sure this helps, but from N. David Mermin's book, which I have referred to above, If you excite a calcium atom to emit two photons, and select a polarization angle (rotating a polarized lens which the photon goes through), it is random whether the photon is polarized for that angle or not. An experiment is set up to pass both photons through (different) polarizing lenses, each set randomly (independent of each other) to either -60, 0, or 60 degrees (from the vertical). The settings take place after the photons are emitted but before they reach the lenses. The spacing of the lenses and detectors is such that information of one lens' setting would have to travel faster than c to reach the opposite photon before it reached its lens.

      After thousands of random runs of this experiment, the statistics are that whenever the two random lens angles were identical, both photons had the same result: either both made it through the lens, or neither did. However, over all cases in which the settings differed, the two results agreed only 25% of the time. If the photons each carried identical polarization values for the three possible settings (e.g., pass at -60 degrees, pass at 0 degrees, blocked at 60 degrees, or PPB), The statistical agreement should be at least 33%. Quantum Mechanics predicted the 25%. The >=33% assumes each photon has fixed values for polarizations of the three angles at the moment of creation, and these values are not dependant on the random lens selection. (Just enumerate all the possible pairs of settings, assuming each occurs the same number of times--roughly--over many random trials, and compare to possible random photon pre-settings.)

      According to Dr. Mermin, Einstein et al wrote their EPR paper assuming that the QM prediction of 25% (for the above experiment, they had a similar but different experiment in mind) had to be wrong, but did not live long enough to learn the above results, which took place years later. Meanwhile, Bohr wrote a response, basically saying that reality does not have to have the fixed nature which we see ("classical behavior") in our daily lives.

      One perhaps glib rationalization of the QM result is that if all three polarizations of a photon were "real" at its creation, the photon would be over-determined, in violation of the Uncertainty Principle. (Dr. Popper later objected strenuously against this interpretation--that the UP is in fact a law of reality, but the consensus is against him.)

      My very-under-baked feeling is that reality not being entirely "real" (in Einstein's terms) is perhaps consistent with a universe which ultimately started from nothing. (But no one should care what I think! Science just tells us how things seem to work, not why.)

  45. Quite an interesting topic, for sure. I like the example of transferring momentum by bouncing a ball off a wall... not 'spooky' at all. But is there a way to introduce spookiness, say, by bouncing two balls off the wall at the same time? Can the wall be used as an intermediary to entangle the momentum of both balls little bit? More importantly, is there a way to determine whether the correlation is due to spookiness or local effects...?

    1. Hi DJ,
      Only if both balls were able to hit exactly the same part of the wall at the same time, I imagine.

  46. This comment has been removed by the author.

  47. People think of space as somewhere so far out there that there is nothing you can bump into, but if you put a very expensive thermometer way out there it would register a temperature so empty space is at the very least not completely empty.

  48. Photons in Spaccceee...

    Its an unusually cool day in Southern Oregon. As I write this. I have an electric heater turned on about a meter from my feet. Photons are leaving the heater and warming my feet quite nicely. How do they do this? How do they get from the heater to my feet and why would that short travel by anything different from what they do in empty space?

    You could say they warm the air near the heater and the air travels to my feet on air currents. But even so they still have to get from the heater to the nearby air molecules to warm them up. How do the photons do that? The distance is shorter but it should be clear that the principle is the same as for empty space.

    So why is it more mysterious how photons travel in space and not anymore mysterious how they travel from the heater to warm my feet?

  49. Hi Steve, IMO: We're used to prosaic everyday stuff like radiant heaters so we don't think about it. Space is mysterious because it's beyond our (non-scientists') ken, first-hand.
    I didn't really think about how photons travelled at all until Paps57's comment. I just thought of heat transfer in terms of vibrating atoms and energy transfer.
    To your earlier comment, that makes sense. If there's a measurable temperature, there's at the least some energy.

  50. Good points by Steve Bullfox, relative to the space we are in, which contains the Cosmic Microwave Background radiation. However, not every physicist I have read is sure that space was not infinite and empty except for the Big Bang at the Big Bang. In which case there is still space that no material or radiation has reached, and although there is no thermometer there to read it, it has a temperature of absolute zero. (Since virtual particles have to borrow energy from the vacuum it seems to me their effect would average to zero, but of course I could be wrong, and for that matter I don't like the infinite space concept anyway.) (Boy are we off-topic, I almost hope this gets moderated.)

  51. While reading several comments above, a naughty problem crossed my mind: Suppose a mafia big shot on earth holds one of two entangled electrons while his companion on March holds the other one. The two partners in crime made the following deal: the companion will measure the spin (up or down) at 10:02 pm. If the spin is up he will chop off the head of some hostage, if down he will release the hostage.
    At 10:00 pm the big shot measures the spin (up or down) of his electron and at 10:02 pm the hostage loses his head. Question: did the big shot cause the death of the hostage? Hint: the distance between the earth and March is 10 light minutes.

  52. Jimv,
    I once had a conversation with my fundamentalist Christian brother in law about why there is something rather than nothing. He thought that that is the case was proof of God. I said to him there might be a lot of nothing somewhere, but there has never been not no nothing nowhere around here. We still talk, but not on that subject.

  53. T get a better layman’s understanding of this, I recommend:

  54. Ms. Hossenfelder, thank-you for your fantastic videos. Your logic is piercing and your arguments are compelling.

    Regarding spooky action at a distance, I feel like perhaps there is an unwarranted presumption about "distance". We proclaim that space and time are intricately linked but then all references to "local" rely on the colloquial definition of word (i.e. spatial distance only). In fact, literal contact between two objects does not generally occur at all, so "local" is not just loosely defined but factually in error.

    I believe that if we define objects to be in contact which share an interval distance of zero then we can recover a local theory from QM.


  55. Does this basically come down to the quantum probabilities communicating with each other so they "know" when to cancel out. So catching one electron couldn't produce another from the probabilities of being found elsewhere?

  56. Dr. Hossenfelder,

    Very interesting subject and very interesting conversation.

    You wrote that:

    "Entanglement is a correlation like this, it’s just that you can only create it with quantum particles. Suppose you have a particle with total spin zero that decays in two particles that can have spin either plus or minus one. One particle goes left, the other one right. You don’t know which particle has which spin, but you know that the total spin is conserved. So either the particle going to the right had spin plus one and the one going left minus one or the other way round."

    I think that what worried Einstein was that, at the time of the 1927 Solvay conference, some people were saying that, while the total spin was conserved, the particles themselves didn't "know" which spin they each had. The spins were undetermined - even for the particles themselves - until a measurement was done. Only then would the particles have their spins defined instantaneously regardless of the distance between the two particles. It meant that for two particles separated by a galaxy, the measurement of the spin of one particle "informed" the other particle to adopt the opposite spin, not because the spins were already determined from the start when the particles were in contact but because of the rules of Quantum Mechanics.

    Of course, it was a position that Einstein could not accept (since there was a potential violation of one of the tenets of the theory of relativity). He believed that particles had definite characteristics even when we don't "look" at them whereas some others thought that only measurements "gave" particles their particular values (like position, momentum, spin, etc) leading to this notion that reality depends on the observer whereas Einstein believed that reality was independent from our observations.

  57. If we live in a universe which creates itself out of nothing, without any outside intervention, particles, particle properties must be as much the cause, the source as the effect, the product of their interactions (with all other particles within their interaction horizon), then can we avoid the conclusion that their communication then must be instantaneous?

    1. Anton,

      I don't know but what I can say is that it is a big "IF".

      Also, when you speak of "a universe which creates itself out of nothing, without any outside intervention, etc", are we still dealing with physics... or metaphysics?

  58. There's nothing spooky if we are living in a simulation (sic). Particles reference their states by pointers. The state is changing at the pointer location which is then access by both particles.

  59. To assume that the universe has been created by some outside intervention is metaphysics. The challenge to physicists is to find out how it manages to create itself.

    I think that the confusion about ‘spooky action at a distance’ originates in our present notion of time, the assumption that (ignoring velocity and gravitational time dilation) it is the same time, that time passes at the same pace everywhere.


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