EPR paradox revisited, again. hehehe

[Sherlock]

I meant, doesn't what I quoted in post number 117 apply at all times to the "at that time most fundamental, known, theory" ?
Meaning, you could say that about Newtonian mechanics in the 18th century, you could say it about Maxwellian electrodynamics at the end of the 19th century, you say it now about 20th century quantum theory... and probably you can say it too about just any next theory that will come along.

Without getting into a protracted discussion about it ... yes. The point being that physics, the enterprise of quantitatively accounting for the phenomena that nature presents to our senses, isn't a 1-1 mapping of physical reality --- and this is especially true of whatever reality underlies quantum experimental phenomena.

There's just no evidentiary basis wrt which we should expect that (a), (b) or (c) can ever be evaluated as being 'right' (provided they're all generating the same experimental predictions).

On other grounds, not necessarily purely esthetic, there are of course cases to be made for preferring, say, Bohmian Mechanics or MWI or whatever.

In the words of Werner Heisenberg:
"Every description of phenomena, of experiments and their results, rests upon language as the only means of communication. The words of this language represent the concepts of daily life, which in the scientific language of physics may be refined to the concepts of classical physics. These concepts are the only tools for an unambiguous communication about events, about the setting up of experiments and about their results. If therefore the atomic physicist is asked to give a description of what really happens in his experiments, the words 'description' and 'really' and 'happens' can only refer to the concepts of daily life or of classical physics. As soon as the physicist gave up this basis he would lose the means of unambiguous communication and could not continue in his science. Therefore, any statement about what has 'actually happened' is a statement in terms of the classical concepts and -- because of thermodynamics and of the uncertainty relations -- by its very nature incomplete with respect to the details of the atomic events involved. The demand to 'describe what happens' in the quantum-theoretical process between two successive observations is a contradiction in adjecto, since the word 'describe' refers to the use of the classical concepts, while these concepts cannot be applied in the space between the observations; they can only be applied at the points of observation."

 

[ttn]

There's just no evidentiary basis wrt which we should expect that (a), (b) or (c) can ever be evaluated as being 'right' (provided they're all generating the same experimental predictions).

I think the whole point here is to distinguish the present tense from the future. It may be that, for all we can tell today, the different theories make the same empirical predictions. That's (as you say) exactly what makes it hard to decide which one is right. But if history is any indicator, the theories won't continue to be empirically equivalent forever. This is just the natural order of things in science. The geocentric and heliocentric theories of the solar system made identical empirical predictions for what could be observed up to the time of Copernicus, which is precisely why (well, part of why) the debate between the two camps was so vigorous. But then eventually along came Galileo and his telescope (and then even more stuff later) which settled the matter empirically. Same story over and over again in science... to the extent that I think one would have to be crazy to claim that the current debates about QM are somehow fundamentally different.

On other grounds, not necessarily purely esthetic, there are of course cases to be made for preferring, say, Bohmian Mechanics or MWI or whatever.

There are some other grounds, yes, but I don't think it's quite right to call them "purely esthetic". For example, that OQM suffers from the measurement problem is not a mere esthetic issue. As Bell said, this means that OQM is "unprofessionally vague and ambiguous" -- which is surely worse than its merely having equations that "don't look pretty" or whatever.

In the words of Werner Heisenberg:
"Every description of phenomena, of experiments and their results, rests upon language as the only means of communication. The words of this language represent the concepts of daily life, which in the scientific language of physics may be refined to the concepts of classical physics. These concepts are the only tools for an unambiguous communication about events, about the setting up of experiments and about their results. If therefore the atomic physicist is asked to give a description of what really happens in his experiments, the words 'description' and 'really' and 'happens' can only refer to the concepts of daily life or of classical physics. As soon as the physicist gave up this basis he would lose the means of unambiguous communication and could not continue in his science. Therefore, any statement about what has 'actually happened' is a statement in terms of the classical concepts and -- because of thermodynamics and of the uncertainty relations -- by its very nature incomplete with respect to the details of the atomic events involved. The demand to 'describe what happens' in the quantum-theoretical process between two successive observations is a contradiction in adjecto, since the word 'describe' refers to the use of the classical concepts, while these concepts cannot be applied in the space between the observations; they can only be applied at the points of observation."

Another nice feature of Bohmian Mechanics is that it provides one with a beautifully clear counterexample to this kind of philosophical crap.

 

[alfredblase]

hahaha lol

I liked the style of your last sentence, very funny ttn =)

 

[Sherlock]

I think the whole point here is to distinguish the present tense from the future.

Point taken.

... if history is any indicator, the theories won't continue to be empirically equivalent forever.

Changes will be precipitated by experimental phenomena that current theories can't handle. It would be surprising if, say, BM could quantitatively deal with something that OQM couldn't ... wouldn't it? BM isn't predicting anything new, is it ?

There are some other grounds, yes, but I don't think it's quite right to call them "purely esthetic".

I agree, and I didn't. That's what the "not necessarily" in front of "purely esthetic" means.

Another nice feature of Bohmian Mechanics is that it provides one with a beautifully clear counterexample to this kind of philosophical crap.

I wouldn't call observations on, and requirements for, unambiguous statements about the world "philosophical crap". BM might, for all we know, be philosophical crap, but Heisenberg's statement about unambiguous communication of experimental preparations and results isn't. There has to be some qualitative, sensory apprehension of what is being counted --- and it's precisely a qualitative, sensory apprehension of an underlying reality that we don't have.

It is interesting that any empirically viable realistic theory has to be nonlocal. Whether this is a constraint due to intrusive measurements or whether it's due to nonlocality being a fact of nature is still a question in my mind.

Are there any situations in which non-intrusive quantum measurements are made? And, if so, do they shed any light, so to speak, on the problem ?

I'm still in the process of rereading both of your papers to make sure I'm understanding any assumptions involved in your (Bell's) two-part argument.

Every once in a while I get this gut-wrenching feeling that I'm never going to fully understand it. But, it's probably that I just don't know enough yet. So, there's hope.

 

[ttn]

Changes will be precipitated by experimental phenomena that current theories can't handle. It would be surprising if, say, BM could quantitatively deal with something that OQM couldn't ... wouldn't it? BM isn't predicting anything new, is it ?

I doesn't really predict anything new, but that doesn't mean that different theories won't be more or less able to handle new phenomena in the future. Just to give one trivial example, suppose we find some kind of exotic situation in which measurement outcomes don't obey the Born rule. This is easily accounted for in Bohm's theory by saying that we are out of quantum equilibrium. Maybe not so easy to deal with in OQM, since there measurement (and the associated Born rule) is a fundamental law of nature.

I wouldn't call observations on, and requirements for, unambiguous statements about the world "philosophical crap". BM might, for all we know, be philosophical crap, but Heisenberg's statement about unambiguous communication of experimental preparations and results isn't. There has to be some qualitative, sensory apprehension of what is being counted --- and it's precisely a qualitative, sensory apprehension of an underlying reality that we don't have.

But I think Heisenberg's point was that, because of these limitations that are built into the structure of language, it's *impossible*, in principle, to ever give a detailed story for what happens between observations. He argues that it would be a contradiction in terms to imagine such a story. And yet Bohm's theory provides one. (Not that this proves Bohm's theory is true; it just proves that fuzzy philosophical arguments about language and such are often far less rigorous than they appear.)

Are there any situations in which non-intrusive quantum measurements are made? And, if so, do they shed any light, so to speak, on the problem ?

Einstein once said (and Bell repeated, stressed, and clarified) that it's the theory which decides what can and can't be measured. For example, according to Bohm's theory, any time you measure a particle's position, the measurement is non-intrusive in the sense that your measurement outcome simply reveals the pre-existing position. Not so, in Bohm's theory, for some other things such as momentum or (in a different way) spin. But a different theory like OQM says that *none* of these are non-intrusive measurements. So... take a particle prepared in a certain way (and hence with a known wf). Now measure its position. Was that measurement "non-intrusive"? Depends on which theory you believe.