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Why I hope QM is incomplete

  1. Feb 19, 2013 #1
    It is ok for physics to distinguish between me and a rock out somewhere on the surface of mars ? Who am I but a bag of chemicals ?

    Why would my action of observing be of any significance ?
    Why should the moon be "paged-in"/from-into-existence when I "observe" it and other times it is allowed to go for a walk(even if it is only a change in probability of finding the moon).
    Why is my observing the moon any different from a "rock observing the moon" ?

    I am a computer engineer, and recently started reading QM. I was displeased with what I inferred. Can somebody confirm this understanding that I have come about QM?
     
  2. jcsd
  3. Feb 19, 2013 #2
    Don't worry, you don't have any special significance in QM.

    The word "observer" in QM has unfortunate connotations, suggesting some special role for intelligent entities or whatever. There is no such special role. An "observation" is just the word we use to talk about an interaction between a system and its surroundings. So a rock is just as capable of being an "observer" as you are.
     
  4. Feb 19, 2013 #3

    micromass

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    Let me guess, you are reading a Pop Sci book on QM and not an actual physics book??

    If you want to understand QM, then you really need to go into the physics and you need to work out the math. If you resort to Pop Sci books, then your understanding will always be flawed.

    Anyway, I'm not a physicist at all, so I'll leave it to somebody else to give a scientific response.
     
  5. Feb 19, 2013 #4
    Hence, everything is getting observed by everything else always. If that were true, why special cases for a human's act of observation ?
     
  6. Feb 19, 2013 #5
    Source suggestions ? I have background in higher math and physics being an engineer.
    FYI, I mostly read from google.

    Links like : http://plato.stanford.edu/entries/bell-theorem/
     
  7. Feb 19, 2013 #6

    Bill_K

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    Because for the most part, human beings are more talkative than rocks. But right now, at the OPERA experiment under the Italian alps, stacks of photographic emulsions are "observing" tau neutrinos.
     
  8. Feb 19, 2013 #7
    I get that quantum phenomenon is not macroscopic.
    But is't a macroscopic phenomenon a function of 'n' microscopic ?

    If the non-determinism as shown by QM applies to microscopic entities, when do the laws of QM suddenly give up and the law of classical mechanics start ? When we observe.
    But why only then?
     
  9. Feb 19, 2013 #8

    phinds

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    Who told you there is a special case for human's observation ? Have you been watching "Through the Wormhole" or similar junk?
     
  10. Feb 19, 2013 #9
    I second what The Duck wrote. Observation in physics usually means measurement by an instrument (sometimes human). In the context of QM, this is connected to the collapse of the wave function. See also Observer (quantum physics).
    Not in the context of mainstream QM; wave functions evolve by themselves without collapsing. A physical interaction with an instrument/object/observer (observation) yields a wave function collapse (many possible outcomes->one single outcome).
    Humans have no special role in mainstream QM/physics. Some interpretations have tried to address it in this way though, but it is quite far from mainstream views (and I personally don't think it's fruitful at all to mix QM with human consciousness). When you get into QM you will soon find out there are unresolved issues (e.g. how to interpret QM), see Interpretations of QM. The so-called Measurement problem is one of the most central questions.
     
    Last edited: Feb 19, 2013
  11. Feb 19, 2013 #10

    atyy

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    In the textbook Copenhagen interpretation (eg. Landau and Lifgarbagez), quantum mechanics is incomplete. This is because it needs a measuring apparatus which is "classical", and not governed by quantum mechanics.

    In the Bohmian interpretation, quantum mechanics is incomplete. Here the measurement problem is solved, and the problems of quantum mechanics are the problems of statistical mechanics (the postulation of the initial distribution is unjustified).

    In the many-worlds interpretation, quantum mechanics is generally thought to be complete. I'm not sure about this, but that is what I seem to read.

    There is a chapter discussing this in http://books.google.com/books?id=3PSHDohngVgC&dq=quantum+aharonov&source=gbs_navlinks_s (Chapter 3: Is quantum mechanics complete?)
     
    Last edited: Feb 19, 2013
  12. Feb 19, 2013 #11
    well, any QM literature says "wave-function collapses" when observed.
    I inferred that at microscopic level, everything is understood as a probability without any cause of that probability being bizarre.
    Eg. cat dead/alive, moon present/absent, Single Photon both a particle and wave.

    But on observation everything arranges itself according to laws of classical mechanics.
    Thus, cat is either dead or alive and the photon becomes a particle and does not show interference pattern.
     
  13. Feb 19, 2013 #12

    atyy

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    Yes. The "wave function collapse" interpretation is called the Copenhagen interpretation. This is the most common interpretation, and it is incomplete. Try the reference in post #10 as a starting point. I don't believe there is any consensus as to whether any interpretations are satisfactory.
     
  14. Feb 19, 2013 #13

    I read somewhere that officially Heisenberg declared QM closed and a complete theory. It was 1 of the Wikipedia page about QM.
     
  15. Feb 19, 2013 #14
    QM is incomplete in the sense that:

    Though we can mathematically describe/predict/model the things that happen on micro/quantum scale in an accurate manner

    however we don't understand QM conceptually/in-reality yet.
     
  16. Feb 19, 2013 #15
    1>
    I do not want to include "Humans consciousness" in QM.
    I believe consciousness = chemical reaction.

    But (some)QM literature makes the act of observing by a human unique.

    2>

    My main issue with QM is :-

    *why should the non-determinism (even in form of probabilities) exists at microscopic level ? Am I the only one who finds it absurd ?
    Cat is dead or it is alive. why does it needs to be both ?
    A photon "knowing" that "ahead-lies-a-slit-and-I-should-behave-like-wave" makes more sense. This "knowing" can be due to something we do not know. Maybe the structure of space. Makes more sense than accepting that the moon may have gone for a walk right now.

    *what point do QM laws give up and classical laws start ? Observation ? Why only our observation ?

    3>
    I will read up more on the links/books you folks have provided here.
    Thanks for your replies. Appreciated.

    PS: wishing I had chosen physics. This is so interesting :)
     
  17. Feb 19, 2013 #16
    universe creation explanation not available, no observers, rocks, whatever....
     
  18. Feb 19, 2013 #17
    This thread reeks of dishonesty and/or ignorance.

    The assumption that human observations are equivalent to a rock observing is absolute nonsense.

    How would you explain the double slit experiment where a 'measuring device' was left on but the information leaving the measuring device was not allowed to reach its destination and viewed (by humans) AND STILL resulting in a an interference pattern?

    When the information leaving the measuring device was allowed to pass through and be observed, a double slit pattern was observed.

    Naaaa nothing special going on here.
     
  19. Feb 19, 2013 #18
    Btw,
    Well, this is a little tricky question, you know :smile:. I could agree with you in some sense, but on the other hand disagree. Where do we draw the line between microscopic and macroscopic?
    In a sense, yes, "classical" macroscopic physical behavior can be seen as emerging from the behavior of miscroscopic systems (gravity is still a problem though, but that's another story). I'll give you some examples of "macroscopic QM" (there are more);

    * Superconduction (e.g. SQUID)
    * Superfluid Helium (clip)
    * The double-slit experiment is a macroscopic demonstration (clip)
    * This is a macroscopic demonstration (clip) of the Uncertainty Priciple.

    Bonus material: The color of gold is a demo of microscopic relativity, pretty interesting I think + also the liquidity of mercury. Provided by me just to show macroscopic results of microscopic behavior.

    (see also Macroscopic quantum phenomena)
     
    Last edited by a moderator: May 6, 2017
  20. Feb 19, 2013 #19
    I would personally choose other literature (at least at first). I see no reason to cloud one's objectivity by introducing humans as special. But it's my personal opinion of course. A quite interesting question (from a psychological perspective IMO) is why some people seem to resort to the human perspective when discussing QM. It seems... unusual. We don't seem to need any human perspective when discussing, let's say, thermodynamics or relativity.
    No, you are not alone :smile:. But I would personally not call it absurd, but interesting, because:
    I agree with atyy.
    Yes!
     
  21. Feb 19, 2013 #20

    mfb

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    I would like to add Bose-Einstein condensates to the counterexamples of DennisN.
    That literature is bad then, unless this option is just mentioned as one of many interpretations (and I don't think it has many supporters).
    There are interpretations where the time-evolution of the universe is deterministic, in particular the de-Broglie-Bohm theory and many worlds.

    Superpositions exist in all interpretations in some way. Otherwise, you could not perform double-slit experiments.

    No, it does not fit to experiments. You can decide what you want to measure even after the photon passed the slit(s).

    To get an interference pattern, this information has to be destroyed in a very fundamental way - in a way not even a rock could "observe" it.
     
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