A Copenhagen: Restriction on knowledge or restriction on ontology?

DarMM

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So? There are nutcase physicists who question the bing bang theory. They might score high on an IQ-test and be thoughtful in other areas, but not in cosmology.
I won't say anything more about this, but people like Asher Peres, Neils Bohr, Jeffrey Bub, Christopher Fuchs, Rudolf Haag and several others are not nutcases. You are engaged in pure rhetoric: "People who disagree with my opinion are not thoughtful at best, nutcases at worst"

Your problem with the Copenhagen interpretation seems to be related to @Lord Jestocost 's opinion on a mind-dependent reality which isn't really a part of Copenhagen type views.
 
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Your problem with the Copenhagen interpretation seems to be related to @Lord Jestocost 's opinion on a mind-dependent reality which isn't really a part of Copenhagen type views.
Not "mind" but "observation" dependent reality.
 

DarMM

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Not in those exact terms but crazy enough that it doesn't matter how you phrase it.
Not anything like that at all is present in most Copenhagen type views. There is no assumption of a mind-dependent reality at all. Nor anything "crazy" like it. If you think otherwise please provide a reference to a standard account of Copenhagen like interpretations that says otherwise.

For example see Matt Leifer's account here, no such assumption (or anything like it) is mentioned (p.7 onward):
 
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"You are the only contemporary physicist, besides Laue, who sees that one cannot get around the assumption of reality, if only one is honest. Most of them simply do not see what sort of risky game they are playing with reality—reality as something independent of what is experimentally established. Their interpretation is, however, refuted most elegantly by your system of radioactive atom + amplifier + charge of gun powder + cat in a box, in which the psi-function of the system contains both the cat alive and blown to bits. Nobody really doubts that the presence or absence of the cat is something independent of the act of observation"

Einstein, in a letter to Schrodinger.
 

DarMM

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That's not a systematic account of the Copenhagen interpretation.
 
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That's not a systematic account of the Copenhagen interpretation.
You mean the Schrodingers cat thought experiment?
 

DarMM

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You mean the Schrodingers cat thought experiment?
No, I mean it is not a systematic account of the Copenhagen Interpretation. Such as the lecture notes of Leifer I provided or Hans Primas's book "Chemistry, Quantum Mechanics and Reductionism"
 
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No, I mean it is not a systematic account of the Copenhagen Interpretation. Such as the lecture notes of Leifer I provided or Hans Primas's book "Chemistry, Quantum Mechanics and Reductionism"
So what is the role of observation in the Copenhagen interpretation, if not the one described by Erwin Schrodinger in Schrodingers cat?
 
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Schrodinger was in fact so disgusted by the Copenhagen interpretation that he regretted having contributed the deterministic equations of QM (Schrodinger Equation).


I don’t like it (quantum mechanics) and I’m sorry I ever had anything to do with it.(Schrödinger)

This is interesting reading:

"But Schrödinger had no better interpretation of the multi-dimensional wavefunction and thus was overpowered in particular during a visit to Bohr’s institute in Copenhagen in September 1926 as described by Heisenberg and in [1]:

  • The discussion between Bohr and Schrödinger began at the railway station in Copenhagen and was crried on every day from early morning to late night….It will scarcely be possible to reproduce how passionate the discussion was carried from both sides….After some days Erwin became ill with a feverish cold. Bohr sat on the bed and continued the argument: “But surely Schrödinger, you must see”. But Erwin did not see, and indeed never did see, why it was necessary to destroy the space-time description of atomic processes.
 

DarMM

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So what is the role of observation in the Copenhagen interpretation, if not the one described by Erwin Schrodinger in Schrodingers cat?
Roughly speaking the same as it is in any probabilistic model. For instance there is an implicit "observer" in stochastic models of stock prices, because the probabilities are adjusted after observations via Bayes's theorem.

The difference between QM and Classical Probability according to the Copenhagen like interpretations is that in the latter one can assume ignorance over some kind of mathematically delineated facts, i.e. there are hidden variables, where as for QM this is not the case. Also in the Quantum case one seems to necessarily disturb the system.
 
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Roughly speaking the same as it is in any probabilistic model. For instance there is an implicit "observer" in stochastic models of stock prices, because the probabilities are adjusted after observations via Bayes's theorem.

The difference between QM and Classical Probability according to the Copenhagen like interpretations is that in the latter one can assume ignorance over some kind of mathematically delineated facts, i.e. there are hidden variables, where as for QM this is not the case. Also in the Quantum case one seems to necessarily disturb the system.
Seems? From Heisenbergs uncertainty principle (which Schrodinger rejected to the day he died): "The thought is now, however, that this only partly explains the phenomenon, but that the uncertainty also exists in the particle itself, even before the measurement is made."

Hence Schrodingers cat "paradox"
 

DarMM

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Yes, the probabilities for different contexts are necessarily altered upon measurement.

Of course due to the Kochen-Specker theorem and similar results one cannot simply view this as disturbance in the Classical experimental sense, but that wasn't my claim.

This doesn't lead to any paradox. If the Copenhagen interpretation had an irrevocable issue with Schrodinger's cat it would have been obvious long ago.
 
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If the Copenhagen interpretation had an irrevocable issue with Schrodinger's cat it would have been obvious long ago.
The bloody father of QM, Max Plank, certainly thought it was irrevocable, even before Schrodinger's cat was conceptualized.
 

DarMM

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The bloody father of QM, Max Plank, certainly thought it was irrevocable, even before Schrodinger's cat was conceptualized.
He thought the Schrodinger's cat thought experiment was an irrevocable problem for the Copenhagen interpretation before either that interpretation or the thought experiment existed?

Looks like he took a retrocausal view. :wink:

There simply isn't a problem with Schrodinger's cat in Copenhagen. If you want an exposition of why not I'd recommend Richard Healey's "The Quantum Revolution in Philosophy " Chapter 11.

However at a simpler level you can replicate the "Cat paradox" along with Wigner's friend (a developement of Schrodinger's cat) in a local Classical model such as Spekkens toy model and clearly see there is no paradox. It just relates to the different information of differently situated observers.
 
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He thought the Schrodinger's cat thought experiment was an irrevocable problem for the Copenhagen interpretation before either that interpretation or the thought experiment existed?

Looks like he took a retrocausal view. :wink:

There simply isn't a problem with Schrodinger's cat in Copenhagen. If you want an exposition of why not I'd recommend Richard Healey's "The Quantum Revolution in Philosophy " Chapter 11.

However at a simpler level you can replicate the "Cat paradox" along with Wigner's friend (a developement of Schrodinger's cat) in a local Classical model such as Spekkens toy model and clearly see there is no paradox. It just relates to the different information of differently situated observers.
It's a paradox if you don't have a warped view of physical reality (at least by classical standards). If you do, it's perfectly consistent. In that sense, Schrodingers thought experiment did not serve much purpose.

"Schrödinger did not wish to promote the idea of dead-and-alive cats as a serious possibility; on the contrary, he intended the example to illustrate the absurdity of the existing view of quantum mechanics".

To no avail (for some at least).
 
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He thought the Schrodinger's cat thought experiment was an irrevocable problem for the Copenhagen interpretation before either that interpretation or the thought experiment existed?

Looks like he took a retrocausal view. :wink:
" It was, however, rejected by Planck, as well as Schrödinger and Laue. Even Einstein had rejected Bohr's interpretation. Planck called Heisenberg's matrix mechanics "disgusting," but he gave the Schrödinger equation a warmer reception. He expected that wave mechanics would soon render quantum theory—his own brainchild—unnecessary."
 
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This is the same Max Plank who accepted the theory of relativity long before it was empirically verified or even understood by the scientific community.

Not exactly a dogmatic scientist. But believe the Copenhagen interpretation if you like:-p
 

DarMM

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This is the same Max Plank who accepted the theory of relativity long before it was empirically verified or even understood by the scientific community.

Not exactly a dogmatic scientist. But believe the Copenhagen interpretation if you like:-p
I never said I did, but I have read proper accounts of it and know that Schrodinger's cat poses no issues. Again a similar "paradox" shows up in epistemic states of purely Classical theories. See Spekkens toy model I linked to above.

You also haven't pointed out an actual issue with the interpretation. Just quoted various physicists stating they had a problem. What is the actual issue with reference to a proper account of the interpretation. For example in the Leifer lectures I linked to which of the four assumptions of the interpretation do you disagree with?
 
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You also haven't pointed out an actual issue with the interpretation.
I have the same views as those expressed by Weinberg at 6:00.

 

DarMM

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I have the same views as those expressed by Weinberg at 6:00.
Can you refer to a systematic scientific account and not short offhand expositions and quotes? Very simply look at Leifer's four principles and say what ones you disagree with.
 

Demystifier

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"The Copenhagen interpretation is basically nonsense". "No thoughtful person still holds to it"

Sean Carroll: at 1:50:30
I think that believing in Copenhagen is similar to believing that free will does not exist. Nobody can really believe it in practice, but it is possible to believe it in deep abstract academic thoughts.
 

DarMM

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I think that believing in Copenhagen is similar to believing that free will does not exist. Nobody can really believe it in practice, but it is possible to believe it in deep abstract academic thoughts.
Which part in particular is like this? The no hidden variables I assume.
 
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I think that believing in Copenhagen is similar to believing that free will does not exist. Nobody can really believe it in practice, but it is possible to believe it in deep abstract academic thoughts.
How do you mean that nobody can disbelieve free will in practise? Deep abstract thought? May I refer you to classical mechanics of which we are apart of? Add to that the heat factor due to our brains and it is a clock-work existence in the making.
 

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