Hawking believes "God confuses us throwing dice....", why?

[Lord Jestocost]

So we get people like David Mermin saying that the Moon is not there when nobody looks, without bothering to say that that is not part of the practical side of QM that has been confirmed by experiments,

With all due respect, what are you talking about? Do you even know who N. David Mermin is?

Einstein asked the question "Is the moon there when nobody looks?" during a conversation with Abraham Pais. “We often discussed his notions on objective reality. I recall that during one walk Einstein suddenly stopped, turned to me and asked whether I really believed that the moon exists only when I look at it.” Rev. Mod. Phys. 51, 863–914 (1979), p. 907

N. David Mermin has merely used this passage as the title for his paper "Is the moon there when nobody looks? Reality and the quantum theory." Physics Today, April 1985, pp. 38-47.

 

[PeterDonis]

Do you even know who N. David Mermin is?

Sure, he's the physicist who, as I understand it, did not merely title his paper with the question, but argued that the actual observed behavior of quantum systems in experiments means that the answer to the question is "no"--that the Moon is not there when nobody looks. Which, as I said, is not actually what the experiments tell us, since the experiments are consistent with all QM interpretations, including ones in which the Moon is there when nobody looks.

 

[bhobba]

The wikipedia article is a bit short on the subject of entanglement, and spooky action at a distance. Is there a resource that discusses this in more detail from the point of view of the EI?

There sure is - but is at the advanced undergraduate or graduate level and is called - Ballentine- Modern QM - as per my Sig. You probably are not ready for it - you need at least an intermediate course on QM before undertaking it.

But I have written a number of posts on exactly what's going on eg - see post 3 where I also explain entanglement and a small glimpse into what's called decoherence which has had a strong influence on modern interpretations of QM:
https://www.physicsforums.com/threads/entanglement-what-is-it.927145/#post-5853260

Strangely, and he is the odd man out, Ballentine doesn't think so - of course he believes in decoherence but doesn't think it has anything to do with interpretations - interesting isn't it.

Thanks
Bill

 

[Lord Jestocost]

Sure, he's the physicist who, as I understand it, did not merely title his paper with the question, but argued that the actual observed behavior of quantum systems in experiments means that the answer to the question is "no"--that the Moon is not there when nobody looks. Which, as I said, is not actually what the experiments tell us, since the experiments are consistent with all QM interpretations, including ones in which the Moon is there when nobody looks.

Please, use "Google Scholar" and search for N. David Mermin! I think he knows what experiments and quantum physics tell us.

 

[PeterDonis]

I think he knows what experiments and quantum physics tell us.

The specific paper of Mermin's that is being referred to is behind a paywall, so I can't read it, I can only read the abstract, which appears to claim what I said it claimed, but does not give the detailed basis for the claim (since it's just an abstract, I wouldn't expect it to). Without that basis, any claim that Mermin's statements should be accepted simply because he's a well-known knowledgeable physicist is an argument from authority and carries no weight here.

That said, I think it's highly unlikely that the claim (that the Moon is not there when nobody looks) is independent of any intepretation of QM, since realist interpretations, which treat it as an obvious fact that the Moon is there when nobody looks, exist. And if the claim is not independent of interpretations, then it can't possibly be verified by experiment, since, as I've said, all QM interpretations make the same predictions for all experiments. This is simple logic, and if it is correct, then any physicist who says that the Moon is not there when nobody looks, stating it as a simple fact verified by experiment instead of a highly interpretation-dependent hypothesis, must be misstating something.

 

[bhobba]

Sure, he's the physicist who, as I understand it, did not merely title his paper with the question, but argued that the actual observed behavior of quantum systems in experiments means that the answer to the question is "no"--that the Moon is not there when nobody looks. Which, as I said, is not actually what the experiments tell us, since the experiments are consistent with all QM interpretations, including ones in which the Moon is there when nobody looks.

He may have believed that. But the interesting thing about Meriman is, everyone attributes, with regard to QM, shut up and calculate to Feynman. It certainly is the kind of thing he would have said. But it seems it was actually Meriman, and he is a bit uneasy these days about it:
http://gnm.cl/emenendez/uploads/Cursos/callate-y-calcula.pdf

If he kept to that philosophy, and he did say that view has somewhat weakened for him, but it still was a there at least a bit its likely he would, like Feynman was in his later years, attracted to the Decoherent Histories view of Gell-Mann. In that interpretation the moon is definitely there - looking or not (it being looked at all the time by its environment eg sunlight, photons from the CBMR, etc etc.

To the OP you can investigate that interpretation further via the following book which the author has kindly made free online:
http://quantum.phys.cmu.edu/CQT/index.html

Thanks
Bill

 

[PeterDonis]

everyone attributes, with regard to QM, shut up and calculate to Feynman. It certainly is the kind of thing he would have said. But it was actually Meriman

He says that "shut up and calculate" sums up what the Copenhagen interpretation says ("says to me" are his exact words); that doesn't necessarily mean it's the interpretation he favors. My impression from what I've read is that he favors non-realist interpretations. But his position could be more nuanced than that.

 

[bhobba]

That said, I think it's highly unlikely that the claim (that the Moon is not there when nobody looks) is independent of any intepretation of QM, since realist interpretations, which treat it as an obvious fact that the Moon is there when nobody looks, exist

Thats true - but these days with our modern knowledge of decoherence it's a lot harder to maintain such a view. When one of the high priests of consciousness causes collapse (Wigner) read some early papers on decoherence by Zeth he realized it was now much harder to maintain such a position and did 180% about face. I think that's when that kind of view really went into decline - its still there - but now very much a minority one.

Thanks
Bill

 

[Lord Jestocost]

The specific paper of Mermin's that is being referred to is behind a paywall...

[PDF]Is the moon there when nobody looks? - Caltech Particle Theory Group

 

[PeterDonis]

these days with our modern knowledge of decoherence it's a lot harder to maintain such a view

The view that the Moon is there when we're not looking? I think decoherence makes it a lot easier to maintain such a view, because it gives an obvious way in which the Moon, or indeed any macroscopic object, can constantly be "looking at itself"--interactions between the different parts of the object are continually decohering it, preventing significant macroscopic superpositions from arising. (This is a heuristic description, hopefully you understand what I mean.) It also allows us to easily dispose of conundrums like the Schrödinger's cat thought experiment: the cat can never be in a superposition of dead and alive because it is continually decohering itself in the dead/alive basis.

 

[bhobba]

He says that "shut up and calculate" sums up what the Copenhagen interpretation says ("says to me" are his exact words); that doesn't necessarily mean it's the interpretation he favors. My impression from what I've read is that he favors non-realist interpretations. But his position could be more nuanced than that.

Yes - I think it is rather more nuanced - he laments the whole thing (from the above):
Among them am I, who hereby put forth the hypothesis that I was the first to use "shut up and calculate" in the context of quantum foundations. I'm not proud of having said it. It's not a beautiful phrase. It's not very clever. It's snide and mindlessly dismissive.

Did that lead him down the same path Feynman took in his later years - who knows.

Thanks
Bill

 

[bhobba]

The view that the Moon is there when we're not looking?

Oh dear - I may have not been as clear as I should have been - I was referring to the idea its harder to maintain the view the moon is not here when not looking - and you correctly detail the reason why that is. And yes I get your drift.

Thanks
Bill

 

[Lord Jestocost]

The view that the Moon is there when we're not looking? I think decoherence makes it a lot easier to maintain such a view, because it gives an obvious way in which the Moon, or indeed any macroscopic object, can constantly be "looking at itself"--interactions between the different parts of the object are continually decohering it, preventing significant macroscopic superpositions from arising. (This is a heuristic description, hopefully you understand what I mean.) It also allows us to easily dispose of conundrums like the Schrödinger's cat thought experiment: the cat can never be in a superposition of dead and alive because it is continually decohering itself in the dead/alive basis.

Regarding decoherence and the related misunderstanding:

Consider a superposition and its evolution in course of time according to the Schroedinger equation. There is no physical process - how irreversible it might be - which is capable to reduce interference terms exactly to zero. You can "decohere" as much as you want, you will never get rid of the superposition. Why don't people get this into their heads? The whole information which the observer had at the beginning of the measuring process remains thus unchanged during the measuring act. Thus, no increase in entropy takes place and, consequently, no conversion of a pure state into a mixed state can takes place. A superposition remains always a superposition as long as mere physical processes are considered. That's physics! There is no way out! The conceptual transition from quantum to classical ignorance has to be put in “by hand” - the role of the observer.

 

[PeterDonis]

Regarding decoherence and the related misunderstanding

Where is this quoted from?

 

[bhobba]

Consider a superposition and its evolution in course of time according to the Schroedinger equation. There is no physical process - how irreversible it might be - which is capable to reduce interference terms exactly to zero.

That's an old argument. We are talking physics here - not pure math. Would you consider 1/googleplex physically important? There are quantities so small in physics that FAPP they are zero.

To be even more precise the decoherence models show it quickly falls way below our ability to measure. What about the future - who knows - we may actually be able to measure it - but its so small I doubt it.

Thanks
Bill

 

[Mario Rossi]

You can "decohere" as much as you want, you will never get rid of the superposition.

So the observer effect does not make a quantum system 100% deterministic, right?

 

[bhobba]

So the observer effect does not make a quantum system 100% deterministic, right?

Its not that.

In decoherene models quantum features, most notably interference effects, quickly decay to nearly, but never exactly zero. Some, and I have discussed the issue with a few of them, believe this means the whole decoherence program is wrong. I know from experience they will not be budged from that position, which of course they can adhere to if they wish. However nearly everyone exposed to it recognizes if it quickly goes way below our ability to measure and is so low its doubtful even future progress in measuring such things will not detect it then you can take it as zero.

Its one of those philosophical points that polaritises some.

Personally I think it grasping at straws and it does explain why we don't generally see quantum effects here in the macro world, but as a judgement thing I can't prove it because its a matter of opinion on what an explanation is. All I can say is that it doesn't solve it is very much a minority view.

Thanks
Bill

 

[Mario Rossi]

All right Bill, thank you. Aren't there ways to prove the ontological side? I suppose not yet. And what do you think about that story on von Neumann's discovery (the hidden variable is the cosciusness ecc.)? Thank you all for the help.

EDIT: Another question: what do you guys think about the delayed choice ereaser experiment that seems to be a "retrocasuality" proof?

 

[Lord Jestocost]

Where is this quoted from?

That's my try to translate a section in the book "Philosophische Probleme der modernen Physik" by Peter Mittelstaedt (published 1976!). But you can also read the paper "Why Decoherence has not Solved the Measurement Problem: A Response to P. W. Anderson" by Stephen L. Adler (https://arxiv.org/abs/quant-ph/0112095). And again, please, use "Google Scholar" and search for Stephen L. Adler.

 

[bhobba]

All right Bill, thank you. Aren't there ways to prove the ontological side? I suppose not yet. And what do you think about that story on von Neumann's discovery (the hidden variable is the cosciusness ecc.)? Thank you all for the help.

Philosophy and science parted ways ages ago - ontological side - what you even mean by that; shrug. I can look it up of course and refresh my memory - I did a course in philosophy once. Let's say my teacher, Petra, consigned me to the merely material. I also started a graduate certificate in philosophy, but it wasnt to my taste being not really concerned with the ideas themselves, but its history - and there were other issues that I won't go into to do with my arthritic condition and getting to the uni library to do research, so I gave it away.

For Von-Neumann's issue - see here:
http://philsci-archive.pitt.edu/12443/1/VNProof.pdf

A sad corner of science.

Thanks
Bill

 

[Lord Jestocost]

So the observer effect does not make a quantum system 100% deterministic, right?

Let me answer with a section of the paper “Decoherence, the measurement problem, and Interpretations of quantum mechanics“ by Maximillian Schlosshauer (https://arxiv.org/abs/quant-ph/0312059)

II. THE MEASUREMENT PROBLEM

One of the most revolutionary elements introduced into physical theory by quantum mechanics is the superposition principle, mathematically founded in the linearity of the Hilbert state space. If |1i and |2i are two states, then quantum mechanics tells us that any linear combination α|1i+β|2i also corresponds to a possible state. Whereas such superpositions of states have been experimentally extensively verified for microscopic systems (for instance, through the observation of interference effects), the application of the formalism to macroscopic systems appears to lead immediately to severe clashes with our experience of the everyday world. A book has never been ever observed to be in a state of being both “here” and “there” (i.e., to be in a superposition of macroscopically distinguishable positions), nor does a Schroedinger cat that is a superposition of being alive and dead bear much resemblance to reality as we perceive it. The problem is, then, how to reconcile the vastness of the Hilbert space of possible states with the observation of a comparatively few “classical” macrosopic states, defined by having a small number of determinate and robust properties such as position and momentum. Why does the world appear classical to us, in spite of its supposed underlying quantum nature, which would, in principle, allow for arbitrary superpositions?

And now, with respect to decoherence and the measurement problem:

Joos and Zeh remarked on decoherence as a source of spatial localization: "Of course no unitary treatment of the time dependence can explain why only one of these dynamically independent components is experienced." (E. Joos and H. D. Zeh, Zeitschrift Phys. B 59, 223–243; 1985).

Joos states in another article: “Does decoherence solve the measurement problem? Clearly not. What decoherence tells us is that certain objects appear classical when observed. But what is an observation? At some stage we still have to apply the usual probability rules of quantum theory.” (Joos, E. (1999) ‘Elements of Environmental Decoherence’, in P. Blanchard, D. Giulini, E. Joos, C. Kiefer and I.-O. Stamatescu (eds.), Decoherence: Theoretical, Experimental, and Conceptual Problems (New York: Springer), pp. 1-17.)

Or, as Nikolaus von Stillfried remarks: “In his Essay 'Lifting the fog from the north' (Nature 453, 39; 2008), Maximilian Schlosshauer describes how the process of decoherence can explain the famous double-slit experiment. An electron interacting with innumerable quanta in the photographic plate (and its environment) becomes entangled with all of them — and the resulting collective wavefunction is so narrow that it appears particle-like.

But the question remains as to why the wavefunction narrows in precisely the location where it does, or - as Schlosshauer puts it - "Why is a single spot here and not there?"

The author's somewhat 'foggy' answer is suggestive of a version of Everett's 'many worlds' idea (see Nature 448, 15–17; 2007), in which all possible branches of the wavefunction continue to exist autonomously. But this interpretation merely shifts the question to "Why do I find myself experiencing the branch/world with the spot here and not the branch/world with the spot there?" ("Decoherence does not get rid of the quantum paradox", Nature 453, 978-979 (19 June 2008))

 

[jerromyjon]

what do you guys think about the delayed choice ereaser experiment that seems to be a "retrocasuality" proof?

I think that if you don't abuse the "wave-particle duality" nature of light, that it has attributes of both until measured, then there is no retrocausality. It cannot be some "hidden local variable", that much is certain... but when anything interacts with photons it has a measurable effect. This short video I saw yesterday makes it ever so obvious.
https://www.physicsforums.com/media/bells-theorem-the-quantum-venn-diagram-paradox-youtube.653/

 

[bhobba]

Let me answer with a section of the paper “Decoherence, the measurement problem, and Interpretations of quantum mechanics“ by Maximillian Schlosshauer (https://arxiv.org/abs/quant-ph/0312059)

A much better source is his book Deoherence And The Quantum To Classical Transition.

For a more complete definition see page 49 - Section 2.5 - The Measurement Problem and The Quantum To Classical Transition where a much more careful definition is given. It's in 3 parts, but since this whole thing had been done to death and posted before I will not do it again - besides reading the book and going through what it says is a much better way to understanding than quotes without the rest of the context. Suffice to say the problem has 3 parts:

1. The Problem Of The Preferred Basis - to the OP colloquially it would be why does a position measurement for example give a position measurement.
2. The Problem Of The Non-Observability of Interference Patterns - obviously referring to here in the macro world - and of course under some circumstances is observable - just one example of why context is so important
3. The problem of outcomes. Colloquially why do we get outcomes at all - more technically exactly how is a particular outcome selected - even more technically how does an improper mixed state become a proper one.

Decoherence solves the first 2 despite some of your other quotes - the one that's the issue is 3. It requires specific interpretations to resolbe it and they all do it in a different way. In the Ensemble Interpretation taking that into account you get a slight variation called the Ignorance Ensemble where the answer is 'somehow' it becomes a proper mixed state. My view on that somehow is who cares - you can't tell the difference between a proper and improper mixed state so why worry. Ballentine thinks decoherence is of no value and many many other views exist. What would have Einstein thought? Well he thought QM incomplete so he would likely believe the key question is that how - and so it goes.

Decoherence has NOT solved the measurement problem - I will repeat it for emphasis - it has NOT solved it - but it has shifted the issue somewhat. In a previous paper I linked to by Weinberg, while I can't get into his head, where he said both Bohr and Einstein were wrong its likely that's what he meant - they didn't understand the real issue which only emerged after they died. Of the originals Wigner was quickly converted to it - Dirac - well he was always the odd person out concentrating more on the actual math rather than musing about what it means - but its likely, since its based on simply a mathematical analysis of the formalism, he would he been converted to it as well.

Thanks
Bill

 

[Blue Scallop]

The different QM interpretations all make the same experimental predictions, because they all use the same underlying math of QM. That's why they are called "interpretations" instead of "different theories".

If experiments in the future can determine say the trajectories of the bohmian particles or prove there are really different worlds where the branches exist, then it's no longer an interpretation but a theory? It's just weird that all the intepretations were tailored to match the math of QM as if constraining them to certain dynamics. But you are right that to avoid getting sinked in interpretations for a lifetime.. one must focus on the math and instead spend time to understand road to a fuly interacting non-perturbative quantum field theory.

 

[phinds]

If experiments in the future can determine say the trajectories of the bohmian particles or prove there are really different worlds where the branches exist, then it's no longer an interpretation but a theory? It's just weird that all the intepretations were tailored to match the math of QM as if constraining them to certain dynamics. But you are right that to avoid getting sinked in interpretations for a lifetime.. one must focus on the math and instead spend time to understand road to a fuly interacting non-perturbative quantum field theory.

If I understand it correctly, you have this backwards. The interpretations were not tailored to fit the math, they are INTERPRETATIONS of what the math means physically, so of course they all use the same math.

 

[Blue Scallop]

-

If I understand it correctly, you have this backwards. The interpretations were not tailored to fit the math, they are INTERPRETATIONS of what the math means physically, so of course they all use the same math.

Here are the confusing parts.

Map = Model = orthodox shut up and calculate Quantum Theory

Territories = Realities = Bohmian Mechanics, Many Worlds, etc.

So if someday BM trajectories can be observed or branches in MWI can be seen then it becomes or make the quantum theory become a different theory? but I don't understand the shift from map to territories. I mean. Is Map a theory too? Or are both Map and Territories considered as both Theories. Can you give an example where a Map or Model is a theory and example where territories or reality is a theory? This distinction is important to get the gist of it all. Thanks.

 

[bhobba]

If experiments in the future can determine say the trajectories of the bohmian particles or prove there are really different worlds where the branches exist, then it's no longer an interpretation but a theory? It's just weird that all the intepretations were tailored to match the math of QM as if constraining them to certain dynamics. But you are right that to avoid getting sinked in interpretations for a lifetime.. one must focus on the math and instead spend time to understand road to a fuly interacting non-perturbative quantum field theory.

Of course if it somehow is possible to experimentally tell one interpretation from another then we know some interpretations are kaput - that's Feynman's very famous explanation of science:


Just as an aside when faced with any issue, not just in science, but in general life, the first thing I do is watch that video and say - how does it solve the issue. Here is an example - here in Australia we want to spend Billions on education in something called Gonsky without going into it - it's not important to the point I am trying to make. You watch Feynman - well you have this guess - spending money on Gonsky will raise education standards. You now do an experiment - you hunt around for those that have investigated this issue and you find the number one expert here in Aus, possibly the world, Professor Hattie at the University of Melbourne on EVIDENCE based education, has shown what it want's to do is useless, by analysing data from thousands of schools worldwide. Hypothesis failed - Gonsky useless. But just to show how stupid people can be they don't care and want Gonsky anyway. Also as Feynman said - they say we live in a scientific age - well basically it's not what he observes. Read his book about the Challenger disaster. He solved it - scientifically - but his solution was relegated to an appendix. There is something deep in us that, on occasion, grates against the scientific method in general life - it's a very strange phenomena.

Thanks
Bill

 

[bhobba]

Here are the confusing parts.

Map = Model = orthodox shut up and calculate Quantum Theory

Territories = Realities = Bohmian Mechanics, Many Worlds, etc.

That is so loaded with philosophical 'assumptions' you have almost guaranteed an 'argument'.

Watch Feynman's video - its the answer.

Thanks
Bill

 

[Blue Scallop]

That is so loaded with philosophical 'assumptions' you have almost guaranteed an 'argument'.

Watch Feynman's video - its the answer.

Thanks
Bill

Feynman didn't talk about map and territories.. so if there is something wrong with the arguments (actually they are not arguments.. I was just asking... hope someone can correct it or I will ask it again and again in the future when the simple questions (whose answers are not obvious to us) aren't directly addressed or resolved.

 

[bhobba]

Feynman didn't talk about map and territories.

That's correct.

Its got nothing to do with science. He explains what science is.

Its people that try to 'expand' on it and come up with things like - the map is not the territory, reality is what our theories tell us etc etc. Its not science - its philosophy. I believe in some of the things - in fact both of what I mentioned, but it's philosophy, not science, and that's why you are almost guaranteed an 'argument' because in philosophy you never actually reach a conclusion - you simply dialecticaly deconstruct and discuss things. Its a legit area, but not what we discuss here and engenders long threads going nowhere that the mods correctly shut down.

Thanks
Bill