Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Issue with Copenhagen Interp

  1. Jul 4, 2007 #1

    First post.

    I have been doing alot of reading in quantum physics, and I am really riled up about some things. First off, I get the feeling when reading those who defend the Copenhagen Interpretation (CI) that they are earnestly trying to put one over on me.

    I'm a rational guy. I believe scientists should hold on to rationality. To embrace irrationalism is the end of science.

    When CI people say that the spin of a particle is non-existent UNTIL it is detected, how can this be proven? I don't know of ANY rational test that can be performed that could prove that spin is non-existent until it is detected. You cannot know the spin of a particle until you detect it. The spin is there to be detected, but it is not known until it is detected.

    I just listened to a lecture on EPR, and how tests were done in the 1990's that showed that when a non-spinning radioactive particle decays into two particles that go off into their own seperate paths far far away from each other, that neither particle has any spin UNTIL one is detected, and when that detection determines the spin of one particular, supposedly proven is that the other particle far far away all of the sudden responds by spinning in the opposite direction.

    I'm trying to figure out how an experiment could actually prove this. My view is that the particle decays into two particles that have opposite spins from the get go. When you detect the spin of one, you can go far far away and detect the opposite spin of the other because that is the direction of the spin determined from the get go!

    Also, the double slit experiment is predicated on the fact that real existent waves travel through both slits while the particle only goes through one. The CI interpretation speaks of these obviously real waves as non-real "probability waves."

    What appears to me as the rational interpretation as to what is going on is that a 'particle' is particular localization within the broader underlying non-local wave that seems to pervade all of reality. Underlying all of reality is some existent "stuff" that acts wave-like. It is all pervading and non-localized. A particle is where some of this "stuff" is in a localized form while still organically related to the all pervading wave-like "stuff." When you forcefully propel this particle at the double slits, it is not going to travel all by itself but ride on and with the wave-like "stuff". The movement of localized "stuff" (particles) is never apart from the causal movement of the nonlocalized "stuff" it is organically connected to.

    For instance, consider a body of water. The water is non-local stuff. Then, take a few ounces of this stuff and freeze it into solid localized "stuff." Then propel this "stuff" through the water, and you have your particle and wave. The ice moves through the water, but it travels with and is guided by the waves it creates.

    This is sort of what Bohm was saying with his pilot waves, right?

    All feedback to my thoughts appreciated.

  2. jcsd
  3. Jul 4, 2007 #2


    User Avatar

    Staff: Mentor

    How can it be proven that the spin DOES exist (with a specific value as opposed to a superposition) without observing it?
  4. Jul 4, 2007 #3

    Well, if you detect something with a spin, you would simply use reason to then assume that the spin was there already (unless something about your detection apparatus physically caused the spin. But, if no causal link is known, no necessity to assume it.)

    I just get the sense that a bunch of this Copenhagen stuff is unwarranted and illogical (esp. from a philosophical point of view), and something I read tonight seemed to shed some light on this. I read a statement that said that Niels Bohr and the CI came out of logical positivism. That's why to the Copenhagen people, the question of whether a particle has position or momentum PRIOR to being measured is a MEANINGLESS thing to ask.

    It's not as though these people have concrete experimental proof that a particle prior to measurement is ontologically indeterminate. They CHOOSE to believe it is indeterminate because of the impossibility to measure both position and momentum simultaneously, and the gist of logical positivism is that whatever is not experimentally verifiable simply does not exist for all sense and purposes and it is wholly meaningless to even speak of it.

    So, what's going on here is that because Bohr and Heisenberg could not experiementally measure something, their logical positivism inclined them to take the view that the thing is ontologically and really indeterminate prior to observation/detection/measurement.

    But that is simply allowing oneself to be shortchanged by a logically false philosophy like logical positivism.

    And it leaves "us" scratching our heads trying to figure out why these people came to these irrational conclusions. But if indeed they were guided by logical positivism, I can now better understand the "why."
  5. Jul 5, 2007 #4


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    I do say, you would probably get a better reaction if you just said this -- your post makes it look like you have already assumed it cannot be proven, and may even be unwilling to listen to how it could be proven.

    The crucial point is correlation between spins measured about different axes. If one detector is rotated, for example, 10 degrees from the other one, then the two detectors will give opposite readings most of the time, but not all of the time.

    Then you make these hypotheses (I think this is enough):
    (1) The spin about any axis is already determined when the particle pair is created1
    (2) The configuration of your detectors do not influence the creation of the particle pair
    (3) the configuration of one detector does not influence the measurement at the other detector
    (4) All of your trials are independent
    (Bell's theorem, incidentally, assumes even less than this!)

    Then, you can rigorously prove a certain inequality involving the observed correlations between different detector settings.

    Quantum mechanics predicts that inequality can be violated. Experimental evidence agrees with QM's prediction.
  6. Jul 5, 2007 #5


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Please demonstrate.
  7. Jul 5, 2007 #6


    User Avatar
    Science Advisor

  8. Jul 5, 2007 #7

    Thanks for the links. I read a couple of things that portrayed Bohm as believing that the interference pattern in the double slit test was caused by actually existing waves along with the particle, rather than the notion that the pattern is the result of some "probability wave" that doesn't have any ontological status apart from the act of human observation collapsing it into a particle. Since then I have been trying to find links, so your links are very welcome.

    What I find interesting as well is that it seems like many look at Copenhagen as opening the door to mysticism, yet Bohm who had an opposing view himself was a mystic. This seems to show that whatever one's view on the quantum reality, it can provoke mystical behavior. :-)
  9. Jul 5, 2007 #8
    No, that's not quite true. I have been searching for books and articles on the web that would explain to me, in a way that I can get my rational mind around, how the CI can be true. I really don't have any prejudice in my mind against it, other than the fact that it's utter irrationalism irritates me. If I can be helped to get my mind around it, and if I can see clearly that experimentation has clearly proven it, I'd have no problem accepting it.

    But, the books I have been reading and lectures listening too, I get the sense that alot of logical errors are being made when interpreting the results of experiements. Reason and logic is being completely let go.
    Last edited by a moderator: Jul 5, 2007
  10. Jul 5, 2007 #9


    User Avatar

    No offense to my former teachers, there were great but from what I remember my QM courses, they simply weren't designed to motivate QM in a general setting of scientific methods. Introductory courses and books are seemingly design to teach the student a formalism that is known to be very useful. The motivation were often historical overviews and the arguments at the level that "A predicts B, B is empirically supported, thus A makes sense". But to analyze this further, you'd probably have to look beyond QM.

    If you want a deeper understanding of the model in a more general setting, beyond it's straight application, it might be that you have to find it on our own.

    Standard courses provides standard answers to standard questions. If you settle with them, you're done. If not, the chance is that you're on your own.

    IMO, this can't be sensibly disucssed without falling back to basic scientific methods and it's philosophies, that's where some of these issues start.

  11. Jul 5, 2007 #10


    User Avatar
    Science Advisor

    I would say that Bohm became mystical only much later, not when he proposed his "Bohmian" interpretation.
  12. Jul 5, 2007 #11
    Don't you wish we could ask Niels Bohr, what you want is to delve into the history of Copenhagen. If you want to resolve why exactly it is the way it is.

    This web site I personally found very helpful and it clears up a few questions about exactly what it means.


    Bohrs influences.

    Who said philosophy was useless eh ? :smile:

    A brief excerpt:-

    Last edited: Jul 5, 2007
  13. Jul 5, 2007 #12
    Hi, Dog! Glad to meet you here again.

    I say. But I did not read your essay.

    Regards, Dany.
  14. Jul 5, 2007 #13
    Hi thanks, yes need some maths advice and I have got back on track with the coursework so I have some free time :smile:

    Another advocate of the Philosophy section should not increase your post count camp I see :smile:

    I didn't actually expect people to read it except maybe the op :biggrin: but the infos their if they want to take a look.
    Last edited: Jul 5, 2007
  15. Jul 5, 2007 #14
    Will be my pleasure if I may help

    Regards, Dany.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: Issue with Copenhagen Interp
  1. A Copenhagen Bug (Replies: 57)