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How important is Bell?

  1. Jul 29, 2011 #1

    DrChinese

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    If you follow some of my posts, you probably already know that I am a big advocate of Bell's Theorem. I thought I would share a little exercise that shows another aspect of why it is important. Deposited today in the preprint archive was the following article:

    Waves, Particles, and Quantized Transitions: A New Realistic Model of the Microworld, by Alan M. Kadin

    He introduces a local realistic model, complete with a bunch of formulae and other support. So naturally, the first thing I do is look at the section where Bell is addressed. After all, no one will read it if that is not dealt with. So I find this:

    "Since the two particles can be far apart at the time the first measurement is made, this would seem to violate (at least the spirit of) special relativity. Alternatively, if no such instantaneous collapse occurs, then each of the two particles must remember their initial preparation in a way that incorporates the final result, via some sort of “hidden variables”. But a general analysis of these types of correlated measurements by Bell has led to a set of inequalities that constrain the existence of “local hidden variables”. A number of experiments have been done, practically all using correlated photons and polarization measurements, and these tend to confirm the standard quantum predictions, as opposed to an alternative explanation based on local hidden variables. These results have been generally interpreted to rule out any alternative to standard quantum mechanics, although some questions about possible “loopholes” in the results continue to be discussed.

    "The present picture questions the real existence of the entangled product states that are used in the conventional explanation of these EPR-type experiments, and instead proposes that each quantum wave represents a localized real-space rotating vector field consistent with local realism. Furthermore, in terms of the optical experiments, the present picture suggests that single photons are necessarily circularly polarized with spin h, in contrast to linearly polarized single photons with zero spin, which are essential to the interpretation of many of these measurements. From this point of view, an electromagnetic wave that passes through a linear polarizer must be a superposition of at least 2 counter-rotating CP photons. It would be interesting to re-analyze the results of these experiments with this picture in mind, to see if this could account for the measured results in a way that does not require non-locality."

    What?? "Interesting"!!!??? Sir, it is not interesting, it's required!!!! Send this puppy straight to the bit bucket 'cause this dog won't fly. Fortunately, most "would be" authors of local realistic theories pause before they send papers like this out because they cannot address Bell properly. And that is another reason why Bell is so important. It provides a line in the sand that is supposed to filter out work like this. But every so often, one comes through anyway. Then all you do is look for the section on Bell...

    :smile:

    -DrC
     
  2. jcsd
  3. Jul 29, 2011 #2

    xts

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    I don't agree. We don't need Bell at all!
    Pauli or Heisenberg - they are pretty sufficient to help us. Or just common sense (more than 2 counter rotating directions?)
    The guy misses much simpler things that Bell's Theorem:
    He doesn't understand, that every phenomenon looks the same regardless what base we prefer to use in our analysis.
     
  4. Jul 29, 2011 #3

    DrChinese

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    Don't say it!!!!!!!!!!!!!!!!!!!!!! :surprised Life wouldn't be worth living anymore.

    Obviously this paper has lots of problems, but the section on Bell (or lack thereof) puts things into perspective for me very quickly.
     
  5. Jul 29, 2011 #4

    xts

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    OK. We need and respect Bell for other reasons (e.g. for nobilitation of quantum engineer profession) but I insist he is not necessary to filter out maniacs.
     
  6. Jul 30, 2011 #5
    From the Physics Virtual Bookshelf at U of Toronto:

    'In 1975 Stapp called Bell's Theorem "the most profound discovery of science." Note that he says science, not physics. I agree with him.'

    David M. Harrison, Department of Physics, University of Toronto

    http://www.upscale.utoronto.ca/PVB/Harrison/BellsTheorem/BellsTheorem.html
     
    Last edited: Jul 30, 2011
  7. Jul 30, 2011 #6
    How can one advocate or oppose a mathematical theorem?!
     
  8. Jul 30, 2011 #7
    Bell's theorem has come to refer to not just the mathematical inequalities but what their violation implies, which is that local realistic models of quantum entanglement are ruled out. I think that DrC is referring to that broader meaning, ie., what might be inferred from the maths in light of experimental results. If I'm mistaken wrt that, then I apologize.
     
  9. Jul 30, 2011 #8

    DrChinese

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    Yeah, what he said. :smile:

    P.S. Thx.

    P.P.S. There might be some theorems which are more useful than others.
     
  10. Jul 31, 2011 #9
    Ok, so you meant the "experimental verification of Bell's inequalities" or "theoretical prediction of a new theory regarding Bell's inequalities", didn't you?
     
  11. Jul 31, 2011 #10
    Actually I think what is important is understanding the ontological and epistemological consequences of Bell. Having predictions is nice and experimental confirmation of predictions is what science is. But it is the consequences that leave you gobsmacked.
     
  12. Jul 31, 2011 #11
    I would not delve into philosophical questions arising from the predictions of a scientific theory. After all, philosophers had not been aware of these issues before the scientific theory predicted them.
     
  13. Jul 31, 2011 #12

    xts

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    Sure. Scientists hadn't been aware of them neither. That is what constitutes progress - both in science and in philosophy.

    What should worry us is, that majority of philosophers tend to ignore scientific discoveries made even over hundred years ago (they still discuss Leibnizian concepts of time). So we should support those of them, who are worried by implications of Bell's inequality and its observed (by Aspect and his followers) violation and try to incorporate such discoveries into mainstream of philosophy.
     
  14. Jul 31, 2011 #13
    Nevertheless, they had arrived at them following the scientific method. This is infinitely far away for philosophers.

    Who's 'we'?
     
  15. Jul 31, 2011 #14

    xts

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    Not for all philosophers, and we should support those philosophers, who are not that far away. That support is what (as I understand him) Dr.C called 'advocacy'.

    we == those, who respect 'scientific method'
     
  16. Jul 31, 2011 #15
    Scientific method is a product of philosophy. Empiricism is a philosophical stance. The fact that most philosophers wander off into an intellectual waste land does not change this.
     
  17. Jul 31, 2011 #16
    Wrong.
     
  18. Aug 1, 2011 #17

    Fra

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    I agree with ppnl that scientific method belongs to the philosophy.

    The writings I have read that actually describes and defines the scientific method as we know it, and tries to justify it as "rational", are nothing but philosophical papers.

    The most common confusion even by some educated people is that some people tend to think that philosophy is just incoherent ramblings or poetry, which isn't the case.

    The very core of for example Poppers reasoning as outlined in his classic book "The logic of scientific discovery", starts around a classic philosophical problem of induction, and this is what he wants to avoid and seek an as close to deductive description of "science" as possible.

    The original quest for the "scientific method" was the quest for a RATIONAL method for acquiring and establishing objective knowledge. This is as opposed to old times "educated opinions" of priests and other supposedly "knowledgable people". People was seeking a rational and objective way to search for knowledge. This rationality is what is called science, but the abstraction of the method is nevertheless embedded in philosophy.

    I think the idea that science is "obvious" and part of deductive logic is a common illusion. Just read poppers struggle on howto avoid induction in describing science and judge if he was successful or not.

    /Fredrik
     
  19. Aug 1, 2011 #18
    It might be that the idea for the scientific method belongs to philosophy, but the scientific method is not used by philosophers, but by scientists. The empiricism you're quoting was a contemporary to Newton. Do you know how much has science and mathematics progressed since then?
     
  20. Aug 1, 2011 #19

    Fra

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    All I wanted to add is something which I think is actually important in particular in any discussion about the foundations of physics is that there is sometimes a tendency to dismissing away important philosophical difficulties when it comes to justifying certain common structural realism that I would say most (not all) physicists subscribe to. This is the structural realism that is implicit in the "belief" that the laws of nature are fixed and timeless and that science task is to simply "unravel" them.

    All I'm suggesting is that this is often apparent, you can often tell from how a paper is written how the author thinks about these things. And my personal opinion is that alot of physicists are having a somewhat "simplistic" attitude towards the very justification of the scientific method - yet they depend on it.

    (Still this is only weakly connect to the OT so I'll try to fade out my contribution here)

    /Fredrik
     
  21. Aug 1, 2011 #20

    SpectraCat

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    As with most things, there have always been those who just ignored what the "experts" were saying and did what they thought were right. These were actually the first scientists, who hewed to the scientific method before any philosophers had even considered it. Take Archimedes .. he was a scientist by the modern definition, who used experiment and observation to learn about the world, however at the time, the Aristotelians were saying that all knowledge comes from pure thought, and experiments were for dummies. Roger Bacon was another example of a scientist who pre-dates modern conceptions of the scientific method. My point here is that the scientific method *is* self-evident, and stems from the following train of thought:

    Person 1: "I wonder how <dimension> that <property of some object> is?"
    Person 2: "Let's see if we can measure it."
    Person 1: "If you measure it now, how can you be sure it's value won't be different tomorrow."
    Person 2: "Hmm, good point. I don't expect it to change with time, but we can always measure it again to make sure we get the same value."

    The ideas expressed in that simple dialog (particularly the last one) are so "obvious" that people used and relied on them (and still do) all the time without even thinking about it or realizing what they were doing. The Egyptians built the pyramids, ancient man invented the wheel and cultivated crops, Romans built bridges that still stand today ... all by relying on the scientific method without explicitly doing science.

    So, while I understand the core of Fra's point that our *understanding* of the scientific method is based on philosophical insight, the core idea and approach seem to me to be an innate part of human nature.
     
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