A Quantum nonlocality and "spooky action at a distance"

[GarberMoisha]

What are you referring to here? Do you have a reference?

Max Tegmark

Journal reference:

Found.Phys.38:101-150,2008

I explore physics implications of the External Reality Hypothesis (ERH) that there exists an external physical reality completely independent of us humans. I argue that with a sufficiently broad definition of mathematics, it implies the Mathematical Universe Hypothesis (MUH) that our physical world is an abstract mathematical structure. I discuss various implications of the ERH and MUH, ranging from standard physics topics like symmetries, irreducible representations, units, free parameters, randomness and initial conditions to broader issues like consciousness, parallel universes and Godel incompleteness. I hypothesize that only computable and decidable (in Godel's sense) structures exist, which alleviates the cosmological measure problem and help explain why our physical laws appear so simple. I also comment on the intimate relation between mathematical structures, computations, simulations and physical systems.

https://arxiv.org/abs/0704.0646

 

[PeterDonis]

Max Tegmark

This is off topic in this thread (and probably this forum since the hypothesis has nothing specifically to do with quantum physics). Please start a new thread in the appropriate forum if you want to discuss it.

 

[Fra]

At least even the greatest physicists like Einstein or Schrödinger who in their last years of their life tried to find a unified classical field theory of everything, made no progress at all.

I think that the task is just very complicated apparently even for the greatest minds, especially if the solution maybe requires a bit of a paradigm change. But I don't see why failures of the past, should not discourage us from at least trying to make progress.

This progress is I think not in any conflict with experimental research. Both are needed I think. I'm not suggesting we should all just sit in our closests and think.

Also, there's no way to find new theories without sufficient empirical input.

I see it's similar to trying to find new compression algortims to compress data. You do not need new data, the "empirical input" is to note if the new models requires more compact representation, the same predictions can be made with less memory, computational requirements and less free parameters. This is because the new theories aren't selected as making different predictions (under current data set) but as having a more clever or flexible computational properties. And such things are I think related to problems we see, with renormalizability etc.

It's in this sense i still one can seek an "explanation" to try to understandin the "mechanisms" that allows for strange phenomena such as entanglement. We know it happens, this is not the problem. But it keeps beeing hard, not to accept, but to understand?

/Fredrik

 

[Lord Jestocost]

....... one can seek an "explanation" to try to understandin the "mechanisms" that allows for strange phenomena such as entanglement.

I am skeptical about this.

One should keep in mind a remark by Richard Conn Henry: "The real scandal of quantum mechanics is that so many physicists still insist on thinking about quantum phenomena with classical ideas.” (R. Conn Henry, “The real scandal of quantum mechanics,” Am. J. Phys., 77 (10), pp. 869-870 (2009))

 

[Fra]

One should keep in mind a remark by Richard Conn Henry: "The real scandal of quantum mechanics is that so many physicists still insist on thinking about quantum phenomena with classical ideas.” (R. Conn Henry, “The real scandal of quantum mechanics,” Am. J. Phys., 77 (10), pp. 869-870 (2009))

Fully agree.

But by now, I think it should have be very obvious to residents on here what I refer to has nothing to do with "classical ideas". On the contrary. But the notion of "mechanism" is not reserved for classical mechanics!

/Fredrik

 

[vanhees71]

The true "scandal of quantum mechanics" is very well caught in this letter to the editors of AJP by van Kampen (one of the great no-nonsense physicists when it comes to interpretations of QT and, more importantly, thermodynamics within relativistic physics):

https://doi.org/10.1119/1.2967702

Note the author of the article van Kampen is referring too :-)

https://arxiv.org/abs/physics/0702069v2

 

[Fra]

van Kampen writes, just as someone else often does....

"Actually quantum mechanics provides a complete and adequate description of the observed physical phenomena on the atomic scale. What else can one wish? (It is true that the connection with gravity is still a problem, but that is outside this discussion.)"

Why so categorically deny that the foundations of quantum mechanics have anything todo with the theory of spacetime; ie. the one spacetime which QM requires for it's foundation? Can someone define quantum mechanics, without making use of a background spacetime, and claim it describes atomic physics experiments?

Why simplify things to the point that we think the ground we stand on is not important because we take it for granted?

/Fredrik

 

[vanhees71]

It's true that gravity is not adequately described within QT. That's an open scientific research topic and has nothing to do with some philosophical interpretational problems. For everything else QT in its minimal interpretation is simply the science content of this theory. There are no scientific problems with it. The foundational questions around the infamous paper by EPR is settled completely by all the Bell tests in various forms in favor of Q(F)T.

 

[gentzen]

The true "scandal of quantum mechanics" is very well caught in this letter to the editors of AJP by van Kampen (one of the great no-nonsense physicists when it comes to interpretations of QT and, more importantly, thermodynamics within relativistic physics):

Never heard of van Kampen before, and certainly not as "one of the great no-nonsense physicists when it comes to interpretations of QT". In fact
https://en.wikipedia.org/wiki/Seifert–Van_Kampen_theorem
is not even from the same person.
And the letter itself didn't seem to contain any great explanations or insights either. Or perhaps I already forgot them, or maybe I should have read the letter more carefully. Or perhaps van Kampen was preaching to some choir, and I simply don't know enough about that choir, or about previous work of van Kampen related to that choir, which would enable me to get the message of that letter.

The foundational questions around the infamous paper by EPR is settled completely by all the Bell tests in various forms in favor of Q(F)T.

In fact, the content of the letter feels similarly to this statement to me. The grammar feels wrong: "... questions ... is settled ...". It is stated as some fact: "foundational questions ... EPR ... settled ... by all the Bell tests ..." which seems to mix or replace theoretical analysis by experimental confirmation. The way your statement is made, and the way that letter is written doesn't even seem to try to explain anything. It feels more like "here is my opinion, you should know what to do with it"!

 

[martinbn]

Never heard of van Kampen before, and certainly not as "one of the great no-nonsense physicists when it comes to interpretations of QT". In fact
https://en.wikipedia.org/wiki/Seifert–Van_Kampen_theorem
is not even from the same person.
And the letter itself didn't seem to contain any great explanations or insights either. Or perhaps I already forgot them, or maybe I should have read the letter more carefully. Or perhaps van Kampen was preaching to some choir, and I simply don't know enough about that choir, or about previous work of van Kampen related to that choir, which would enable me to get the message of that letter.In fact, the content of the letter feels similarly to this statement to me. The grammar feels wrong: "... questions ... is settled ...". It is stated as some fact: "foundational questions ... EPR ... settled ... by all the Bell tests ..." which seems to mix or replace theoretical analysis by experimental confirmation. The way your statement is made, and the way that letter is written doesn't even seem to try to explain anything. It feels more like "here is my opinion, you should know what to do with it"!

About EPR, I thought that Bohr's reply was crystal clear.

 

[gentzen]

About EPR, I thought that Bohr's reply was crystal clear.

In fact, I actually like Bohr's reply. He certainly tries to explain something, namely the contextuality of QM, and how it applies to the EPR scenario.

 

[martinbn]

In fact, I actually like Bohr's reply. He certainly tries to explain something, namely the contextuality of QM, and how it applies to the EPR scenario.

I wrote it to sound like a joke, but I was serious. People may complain about Bohr, but he is the only one in the philosphy of QM that makes sense to me.

Off topic, by the way how does one formulate EPR within the statistical interpretation?

 

[Lord Jestocost]

Never heard of van Kampen before, and certainly not as "one of the great no-nonsense physicists when it comes to interpretations of QT".

Use Google Scholar, keyword “Ten theorems about quantum mechanical measurements” (a paper by N.G. van Kampen).

You find a lot in “Quantum Measurement Theory as simply explained by N G van Kampen” by M. G. Burt
https://arxiv.org/abs/2206.03219

 

[vanhees71]

I wrote it to sound like a joke, but I was serious. People may complain about Bohr, but he is the only one in the philosphy of QM that makes sense to me.

Off topic, by the way how does one formulate EPR within the statistical interpretation?

Bohr is the main culprit for obscuring QT as a physical theory. I never understood, why he was so famous at his time.

 

[Fra]

Bohr is the main culprit for obscuring QT as a physical theory. I never understood, why he was so famous at his time.

I agree with Martinbn, I find Bohr to express things in honest and clear ways, in particular how QM is defined relative to the classical/macroscopic side of the cut. This to me, both clearly explains that QM can not be defined without a "classical/macroscopic observer". Yet, Bohr to my knowledge never claimed that there is a classical reality that is more fundamental, nor that there is a quantum reality.

Taken together, this both states clearly what QM is AND it's limitations. While others may pretend there is only a quantum reality, but without realizing that without the "macro background" we can not DEFINE QM. I think Bohr never made any exaggerated claims here, he expressed what we know, not more, not less, this is why he has my respect.

/Fredrik

 

[martinbn]

My impression is that if your view and understanding of QM is similar to Bohr's you find him clear. If they are different you find him completely incomprehensible.

 

[vanhees71]

I agree with Martinbn, I find Bohr to express things in honest and clear ways, in particular how QM is defined relative to the classical/macroscopic side of the cut. This to me, both clearly explains that QM can not be defined without a "classical/macroscopic observer". Yet, Bohr to my knowledge never claimed that there is a classical reality that is more fundamental, nor that there is a quantum reality.

This is an unfounded claim. Nothing in contemporary experiments hints at a quantum-classical cut, which can be objectively defined. I've no clue, what "reality" means, because this word is made useless by all the philosophical undertones attached to it.

Taken together, this both states clearly what QM is AND it's limitations. While others may pretend there is only a quantum reality, but without realizing that without the "macro background" we can not DEFINE QM. I think Bohr never made any exaggerated claims here, he expressed what we know, not more, not less, this is why he has my respect.

/Fredrik

The only limitation of QT (QM is of course a non-relativistic approximation, with clear limits of applicability) is its lack to describe satisfactorily the gravitational interaction. This has nothing to do with philosophical interpretational issues though.

 

[Structure seeker]

I'd like to take a post in another thread "number systems in science":

The question is whether we could ever confirm by measurement that the ratio of a circle's circumference to its diameter is π.

The thread has an analogy with this thread: if only what we measure is interesting, there's no need for all the complicated number systems like the reals or complex numbers as just the most common examples. Just the rationals suffice, with error bars.
What @PeroK calls the question in that thread is an example of knowledge that gives great guidance in what is interesting to measure, but it cannot be concluded from measurement. I am sure we will encounter similar results in quantum physics. We would not be able to prove which rational number sequences go to π, since infinity isn't measurable.

 

[Fra]

This is an unfounded claim. Nothing in contemporary experiments hints at a quantum-classical cut

I'm not talking about uniqueness of the cut, it's clearly not, just like there are many possible measurement devices. They aren't only one, but that doesn't mean it isn't important.

But our mesaurement apparatouses, and all the data we get from observations are stored in reliable records, that - modulo special relativity - all observers agree upon. Ie. there is no non-commutativity or no-cloning issues with information sharing of measurement results. This is the classical cut. Without this cut, how can you imagine reliably preparing and repeating experiments, that all observers agree upon?

/Fredrik

 

[vanhees71]

Yes, and this has nothing to do with a quantum-classical cut either. The "appearance of a classical world" out of QT is much better understood today than at Bohr's times!

 

[Fra]

Yes, and this has nothing to do with a quantum-classical cut either.

I guess we simply think differently on this point. Which is not necessarily a problem.

/Fredrik

 

[Fra]

The "appearance of a classical world" out of QT

As you phrase it like this, it to me, seems that you are missing my point?
This is not the even question I am asking.

There is only one world, I think we agree on that. The "classical world" is simply the "macroscopic world". And from this perspective we formulate a QT for small subsystems.

The problem is that we can not explain the foundation, based on a theory built on the same foundation? This is the conceptual problem. It is either circular, or (more commonly) a infinite regress where we consider layers or larger and larger "macroscopic systems", and at some point, these are beyond our empirical access, as at some point the whole universe is the "macroscopic system". QT is not even close to corroborated for such systems. This is very different from a piece of metal in a lab or whatever.

/Fredrik

 

[vanhees71]

There's indeed only one world, which is described by quantum theory + a spacetime model (the latter is not yet quantized, which is why we don't have a theory of everything yet). Everything concerning "matter and radiation" is quantum, including the "classical appearance" of the macroscopic phenomena. The fact that there are macroscopic measurement devices is explained by quantum-many-body theory as is the classical behavior of any other macroscopic piece of matter.

 

[gentzen]

This is an unfounded claim. Nothing in contemporary experiments hints at a quantum-classical cut

But our mesaurement apparatouses, and all the data we get from observations are stored in reliable records, that - modulo special relativity - all observers agree upon. Ie. there is no non-commutativity or no-cloning issues with information sharing of measurement results. This is the classical cut. Without this cut, how can you imagine reliably preparing and repeating experiments, that all observers agree upon?

Yes, and this has nothing to do with a quantum-classical cut either. The "appearance of a classical world" out of QT is much better understood today than at Bohr's times!

You are the one who interprets the cut as something that should show-up in experiments.
Who on this Forum really interprets the cut in that way?
Why are you so determined to claim that Bohr and Heisenberg have been wrong, and are responsible for all the confusion caused by QM?

 

[vanhees71]

I thought the aim of all these experiments aiming at demonstrating "quantum phenomena" on ever larger systems are about answering the question, whether QT is really complete or whether there's at some point the necessity of generic classical physics, as claimed by Bohr, among others of the Copenhagen camp. I only stress that so far no such thing has been found but that even really macroscopic objects like the LIGO mirrors show quantum behavior if sufficiently accurately observed.

I think Bohr and Heisenberg are not even wrong, they are just confusing.

 

[Fra]

or whether there's at some point the necessity of generic classical physics, as claimed by Bohr, among others of the Copenhagen camp

I think you "interpret this" (yes, here we go again with interpretations) differently that I do. What I mean with Bohrs clarity, you take as evidence for that he claims that "classical world is needed"!

I interpret it not as a statement about the world, but as a statement of quantum theory itself. I don't think Bohr ever said that QT is fundamental (in the sense of unification of all forces), he just honestly declares that we need the classical context to define it.

This is to me, honest about the theory (not pretending it has universal validity), it is not statement about reality itself. I think Bohr was clear to not make such statements. But I dont know who has the "right" interpretation of Bohr of course?

/Fredrik

 

[GarberMoisha]

I agree with Martinbn, I find Bohr to express things in honest and clear ways, in particular how QM is defined relative to the classical/macroscopic side of the cut. This to me, both clearly explains that QM can not be defined without a "classical/macroscopic observer". Yet, Bohr to my knowledge never claimed that there is a classical reality that is more fundamental, nor that there is a quantum reality.

Taken together, this both states clearly what QM is AND it's limitations. While others may pretend there is only a quantum reality, but without realizing that without the "macro background" we can not DEFINE QM. I think Bohr never made any exaggerated claims here, he expressed what we know, not more, not less, this is why he has my respect.

/Fredrik

If quantum mechanics is fundamental and classical physics "emergent" from it, how come it's impossible to define QT without using these purpotedly emergent macro properties?

 

[Fra]

If quantum mechanics is fundamental and classical physics "emergent" from it, how come it's impossible to define QT without using these purpotedly emergent macro properties?

Yes, that is the right hypothetical question.

IMO the fallacious thinking of, that I percieve is happening, is that you first describe a spatially and temporally small subsystem, from the perspective of the macroscopic environment. And then you extract the mathematical pattern, which suddently is timeless and appearing godlike. Then you for forget about where it came from, and think that the same mathematics is universally valid for any system, even those where the subsystem assymmetry obviously is not fulfilled. (https://arxiv.org/abs/1201.2632)

/Fredrik

 

[GarberMoisha]

Yes, that is the right hypothetical question.

IMO the fallacious thinking of, that I percieve is happening, is that you first describe a spatially and temporally small subsystem, from the perspective of the macroscopic environment. And then you extract the mathematical pattern, which suddently is timeless and appearing godlike. Then you for forget about where it came from, and think that the same mathematics is universally valid for any system, even those where the subsystem assymmetry obviously is not fulfilled. (https://arxiv.org/abs/1201.2632)

/Fredrik

There isn't even 1 tangible thing anywhere in existence that cannot be described mathematically. Not 1. To claim it's somehow a 'coincidence' is to detract from the real substance that is of real value for the purpose of understanding the world.

 

[gentzen]

I thought the aim of all these experiments aiming at demonstrating "quantum phenomena" on ever larger systems are about answering the question, whether QT is really complete or whether there's at some point the necessity of generic classical physics,

I guess those experiments try to test theories like GRW, CSL, or gravitational collapse models like those of Penrose or Diósi. See for example:
https://plato.stanford.edu/entries/qm-collapse/#CSLExpe

as claimed by Bohr, among others of the Copenhagen camp.

I guess you are simply wrong here. That QT is complete is one of the claims of the Copenhagen camp. And Bohr would have been the last one to claim otherwise.

I only stress that so far no such thing has been found but that even really macroscopic objects like the LIGO mirrors show quantum behavior if sufficiently accurately observed.

And Bohr would have been the last one to expect otherwise.

I think Bohr and Heisenberg are not even wrong, they are just confusing.

Pauli ment something else with his "not even wrong". And you basically repeat in slightly weakened form your claim that Bohr and Heisenberg created confusion regarding QM, but don't explain why you are so determined to do so:

Why are you so determined to claim that Bohr and Heisenberg have been wrong, and are responsible for all the confusion caused by QM?

 

[Fra]

To claim it's somehow a 'coincidence' is to detract from the real substance

Mathematical law is not conincidence, on the contrary - it would be almost unavoidably, when you study a spatially and temporally limited system, that you will find timeless patterns. Just think about, fourier analysis for example. That is the whole point. This is both the power and a limitation. It's not all bad! BUT, how the pattern scales as you increase complexity is not given. I think sometimes we are seduced by the power, and generalized it a bit too far because it's tempting.

A naturalist account of the limited, and hence reasonable, effectiveness of mathematics in physics
"The view I will propose answers Wigner’s query about the ”unreasonable effectiveness ofmathematics in physics” by showing that the role of mathematics within physics is reasonable, because it is limited."
-- https://arxiv.org/abs/1506.03733

/Fredrik

 

[physika]

The grammar feels wrong: "... questions ... is settled ...". It is stated as some fact: "foundational questions ... EPR ... settled ... by all the Bell tests ...

...telegraphical ?

 

[physika]

As well as the fact that nor coarse graining, many body, decoherence (by "quantum" darwinism nor "quantum" broadcasting) explain/describe the "appearance" of macroscopic phenomena.

 

[vanhees71]

I guess those experiments try to test theories like GRW, CSL, or gravitational collapse models like those of Penrose or Diósi. See for example:
https://plato.stanford.edu/entries/qm-collapse/#CSLExpe

Yes, i.e., these are models beyond standard QM, trying to solve the socalled "measurement problem". So far no hint of any such thing has been found though!

I guess you are simply wrong here. That QT is complete is one of the claims of the Copenhagen camp. And Bohr would have been the last one to claim otherwise.

Well, as I said, for me Bohr is ununderstandable. On the one hand he says, QT were complete, but on the other hand he claims that in addition to QT there must be classical dynamics of measurement devices, or is already this a misunderstanding due to his vagueness?

And Bohr would have been the last one to expect otherwise.Pauli ment something else with his "not even wrong". And you basically repeat in slightly weakened form your claim that Bohr and Heisenberg created confusion regarding QM, but don't explain why you are so determined to do so:

I am not determined to do this, it's just an observation.

 

[Fra]

QT were complete, but on the other hand he claims that in addition to QT there must be classical dynamics of measurement devices, or is already this a misunderstanding due to his vagueness?

For me i read that Bohr means; given a classical background, QM is defined and is complete, relative to the same. Ie QM is a theory that is relative to the classical background. No background - no QM (or QFT for that matter)!

This does not mean that in a bigger perspective (unification) that there is another theory, thay does NOT presume this background. But that would be a theory defined in a different way, so it would not mean that QM as defined on its premises is incomplete.

For me this is clear. QM may be complete given its paradigm. But its still possible that at theory with more universality may be found, that relaxes the foundations of QM.

Two different things for me.

/Fredrik

 

[martinbn]

Well, as I said, for me Bohr is ununderstandable. On the one hand he says, QT were complete, but on the other hand he claims that in addition to QT there must be classical dynamics of measurement devices, or is already this a misunderstanding due to his vagueness?

Why is that a problem? Why should QM be formulated without measurement devices?

 

[vanhees71]

It should not be formulated without measurement devices. All of physics (as a natural science) is about observable and measurable phenomena after all. It's, however, a contradiction to claim that on the one hand quantum theory is complete but on the other that macroscopic objects, including measurement devices, are inherently classical. I think that's more due to Heisenberg than Bohr, because it's usually named the "Heisenberg cut".

The point is that all of matter with all interactions except gravity are describable by QT. There's no hint that at some size of macroscopic object QT would fail and you'd need classical mechanics or classical field theory. The latter are, of course, derivable as approximations of many-body QT (quantum statistics), but they are not invalidating QT for large macroscopic objects of any size in principle, and indeed nowadays with ever more refined experiments ever larger objects can be shown to indeed show "quantum behavior", e.g., the mirrors of the LIGO experiment show quantum-mechanical "zero-point motion".

 

[Lord Jestocost]

If quantum mechanics is fundamental and classical physics "emergent" from it, how come it's impossible to define QT without using these purpotedly emergent macro properties?

To my mind, quantum theory can be understood as a nonclassical probability theory – to put it in this way. One can use classical physics as a FAPP approximation when the inclusion of more variables – so to speak the “degrees of freedom” – into the quantum-theoretical description is no longer necessary to approximately predict observable outcomes.

 

[gentzen]

Well, as I said, for me Bohr is ununderstandable. On the one hand he says, QT were complete,

Einstein attacked QM, and Bohr somehow got the task to try to defend it, at least at the Solvay conference in 1927. Maybe not every one of his defence was perfect, but remember that he had only one night for each of those defenses.
Then in 1935, the EPR paper was yet another attack on QM, a more tricky one, and Einstein's role was tricky too. And Einstein's bomb also made its appearance as Schrödinger's cat in 1935. This time, Bohr worked a longer time on his defence, and only responded to Einstein's paper, but not to Schrödinger's paper or Einstein's bomb.

My impression is that Bohr felt that he was able and expected to communicate with Einstein (and disprove him), but felt uneasy to respond to Schrödinger. Heisenberg did respond to some later papers by Schrödinger, and his response was quite respectful. This further encouraged people to engage with Schrödinger's thoughts, which are probably more responsible for the many different quantum interpretations than Einstein's "suggested thought experiments" or Bohr's answers to them.

but on the other hand he claims that in addition to QT there must be classical dynamics of measurement devices, or is already this a misunderstanding due to his vagueness?

This is a misunderstanding, but probably unrelated to Bohr's vagueness. I guess it is more related to Bohr being cited by many different people, who all try to explain his thoughts, and often do this by highlighting certain features relevant for their current discussion. In your case, this was probably Bell, but Fra/Frederik gives a more current example how this happens in practice. Bohr's thoughts were simpler and more practical than Fra/Frederik's goals.

The confusion for which Bohr himself is mainly responsible is only the role of complimentarity, I guess.

 

[vanhees71]

Einstein attacked QM, and Bohr somehow got the task to try to defend it, at least at the Solvay conference in 1927. Maybe not every one of his defence was perfect, but remember that he had only one night for each of those defenses.
Then in 1935, the EPR paper was yet another attack on QM, a more tricky one, and Einstein's role was tricky too. And Einstein's bomb also made its appearance as Schrödinger's cat in 1935. This time, Bohr worked a longer time on his defence, and only responded to Einstein's paper, but not to Schrödinger's paper or Einstein's bomb.

The EPR paper is anyway somewhat unfortunate. Einstein himself didn't like it, saying it's burying the real argument under "erudition". The way more concise paper is in Dialectica 1 of 1948 (in German), where it becomes clear that the real point for Einstein was indeed inseparability. The answer by Bohr is a complete enigma to me. The real scientific breakthrough was, of course, finally Bell's work translating the vague philosophical "erudition" of the EPR paper into an experimentally decidable scientific question. The results are well known: full consistency of the QM predictions with all empirical findings. If you accept that what EPR had in mind is "local realism" (with all the vagueness of the meaning of these words), then they are clearly disproven.

Schrödinger's paper is much clearer compared to EPR, and I don't know, why it hasn't been attacked by the Copenhagen gang as much as EPR's.

What do you mean by "Einstein's bomb"?

My impression is that Bohr felt that he was able and expected to communicate with Einstein (and disprove him), but felt uneasy to respond to Schrödinger. Heisenberg did respond to some later papers by Schrödinger, and his response was quite respectful. This further encouraged people to engage with Schrödinger's thoughts, which are probably more responsible for the many different quantum interpretations than Einstein's "suggested thought experiments" or Bohr's answers to them.

I don't think that Schrödinger added much to the interpretational confusion, and also Einsteins standpoint is quite clear.

This is a misunderstanding, but probably unrelated to Bohr's vagueness. I guess it is more related to Bohr being cited by many different people, who all try to explain his thoughts, and often do this by highlighting certain features relevant for their current discussion. In your case, this was probably Bell, but Fra/Frederik gives a more current example how this happens in practice. Bohr's thoughts were simpler and more practical than Fra/Frederik's goals.

The confusion for which Bohr himself is mainly responsible is only the role of complimentarity, I guess.

Complementarity is another useless confusion, indeed.

 

[Lord Jestocost]

Einstein attacked QM, and Bohr somehow got the task to try to defend it ....

The following short section in Werner Heisenberg's memoir "Der Teil und das Ganze" puts Einstein’s stubbornness regarding QM in a nutshell:

„Einstein war nicht bereit, sich — wie er es empfand — den Boden unter den Füßen wegziehen zu lassen. Auch später im Leben, als die Quantentheorie längst zu einem festen Bestandteil der Physik geworden war, hat Einstein seinen Standpunkt nicht ändern können. Er wollte die Quantentheorie zwar als eine vorübergehende, aber nicht endgültige Klärung der atomaren Erscheinungen gelten lassen. „Gott würfelt nicht“, das war ein Grundsatz, der für Einstein unerschütterlich feststand, an dem er nicht rütteln lassen wollte. Bohr konnte darauf nur antworten: „Aber es kann doch nicht unsere Aufgabe sein, Gott vorzuschreiben, wie Er die Welt regieren soll.“

(I have refrained from a translation into English)

 

[physika]

experiments to test theories on collapse.

https://www.quantamagazine.org/how-...orld-be-physicists-probe-the-limits-20210818/

https://www.nature.com/articles/s42005-021-00656-7

......

 

[Fra]

This is a misunderstanding, but probably unrelated to Bohr's vagueness. I guess it is more related to Bohr being cited by many different people, who all try to explain his thoughts, and often do this by highlighting certain features relevant for their current discussion. In your case, this was probably Bell, but Fra/Frederik gives a more current example how this happens in practice. Bohr's thoughts were simpler and more practical than Fra/Frederik's goals.

I agree that the issues of unification of all forces, was not a major thing at that time.

But I think the success is perhaps that Bohr simply acknowledged the practical matters that simply appeared mandatory to define the new theory that was just born. Not more and not less. This is how practical matters such as approximate classical reality even required to collect statistics becomes principal matters.

So while others have tried to "overthink" or deny the observing context, Bohr seems to firmly insisted that it was required because the laboratory and all it's data is effectively classical. This basic simplicity is to me the key to clarity, which paradoxally stands strong in many attempts to overthink giving QM meaning without this context.

(The question of, what another theory would be like formulated without the premise, was likely not something that concerned Bohr. It was a sufficiently major task to fine the theory give the premise)

/Fredrik

 

[gentzen]

What do you mean by "Einstein's bomb"?

I read in Moore's biography of Schrödinger that he received a letter from Einstein where he described a similar experimental setup using an explosive instead of a cat, before Schrödinger had finished his famous cat paper. See for example SEP ERP 1.3 Einstein’s versions of the argument:
"In the August 8, 1935 letter to Schrödinger Einstein says that he will illustrate the problem by means of a “crude macroscopic example”.

The system is a substance in chemically unstable equilibrium, perhaps a charge of gunpowder that, by means of intrinsic forces, can spontaneously combust, and where the average life span of the whole setup is a year. In principle this can quite easily be represented quantum-mechanically. In the beginning the psi-function characterizes a reasonably well-defined macroscopic state. But, according to your equation [i.e., the Schrödinger equation], after the course of a year this is no longer the case. Rather, the psi-function then describes a sort of blend of not-yet and already-exploded systems. Through no art of interpretation can this psi-function be turned into an adequate description of a real state of affairs; in reality there is no intermediary between exploded and not-exploded. (Fine 1996, p.78)

[...] The similarity between the gunpowder and the cat is hardly accidental since Schrödinger first produced the cat example in his reply of September 19, 1935 to Einstein’s August 8 gunpowder letter. There Schrödinger says that he has himself constructed “an example very similar to your exploding powder keg”, and proceeds to outline the cat (Fine 1996, pp. 82–83). Although the“cat paradox” is usually cited in connection with the problem of quantum measurement (see the relevant section of the entry on Philosophical Issues in Quantum Theory) and treated as a paradox separate from EPR, its origin is here as an argument for incompleteness that avoids the twin assumptions of separability and locality."

The following Nautilus piece seems to know even more details of how Einstein inspired Schrödinger to invent his cat: How Einstein and Schrödinger Conspired to Kill a Cat

 

[vanhees71]

It's of course no paradox and it's exactly to the point of what Einstein wanted to say in the EPR paper (and he clearly said it only later in his Physica 1 paper of 1948). His real quibble was with the "inseparability" of far-distant parts of entangled quantum systems.

 

[martinbn]

It's of course no paradox ...

Usually in physics by "paradox" is meant an unintuitive consequence of the theory, like the twin paradox. None of them are actual paradoxes.

 

[Fra]

His real quibble was with the "inseparability" of far-distant parts of entangled quantum systems.

And I think Einsteins original view is sound, that there has to be a "hidden variable", of some kind. My view is no different. Not to explain the outcomes, but their correlations.

How it can explain the correlation and not the outcome, is exactly what we still do not understand. All we know is that kind of HV Bell envisioned does not work, because it assumes it's hidden from the ignorant exprimenter only.

I think Einstein wanted to understand, what others settled with describing. What progress is made until today?

/Fredrik

 

[vanhees71]

Nature doesn't care about our human quibbles due to wrong pictures/worldviews. She behaves as she does, and all very accurate empirical evidence confirms the probabilistic predictions of QT and no "local realistic hidden-variable model" (in the sense defined by Bell) can be right. That's an interpretation-independent empirical fact!

 

[GarberMoisha]

Yes, because even atoms are just useful models of experience.
Throw them the right way and they will interfere with themselves like the good probabilities that they are. Probability of experience.

 

[GarberMoisha]

If this doesn't make your head spin, I don't know what will.