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Quantum myth 4: The only reality is the measured reality

  1. May 15, 2008 #1
    We are discussing the Demystifier's paper "Quantum mechanics: myths and facts". http://xxx.lanl.gov/abs/quant-ph/0609163

    Previously:
    Myth 1 https://www.physicsforums.com/showthread.php?t=229497
    Myth 2 https://www.physicsforums.com/showthread.php?t=230693
    Myth 3 https://www.physicsforums.com/showthread.php?t=232102

    QM implies that there is no reality besides the measured reality

    The topic here is that the claim "QM implies that there is no reality besides the
    measured reality" is itself a myth. By myths we mean widely repeated statements which, true or false, are not something we can validly assert given our current understanding.

    My first reaction to the topic statement is that it would be exceedingly difficult to define. However, I think what is meant here is that the results of QM imply there are no hidden variables: quantifiable aspects of physical reality which (within the formulation of QM) are unobservable but whose values influence observable quantities.

    My first question has to do with the transition from section 5.2 to 5.3 & 5.4. In 5.2 we are definitely talking about a classical quantity s. All along 5.3 it seems we continue to talk about the same classical system but in a quantum-like formulation. Then in section 5.4 right after eq 40 we find the sentence,

    "The fact is that if this were the case, then it would contradict the predictions of QM!"

    Did we pass from classical to quantum somewhere along the way?
     
  2. jcsd
  3. May 15, 2008 #2
    I think this "myth" is a "myth" itself. I interpret QM not as "a-realist" as far as reality is concerned but rather agnostic. To claim anything about reality beyond the results of experiment would be outside the scope of QM(and science).

    QM does not say whether or not there is a more fundamental reality beyond observation. QM simply does not concern itself with such things.

    Discussing a reality beyond observation in QM, or science in general, is like trying to use science to discuss God, it's just not created to handle such questions.
     
  4. May 15, 2008 #3

    dx

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    If they can influence observable quantities, isn't that the same as being measurable?
     
  5. May 16, 2008 #4

    Demystifier

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    As the titles of subsections indicate, the transition from classical to quantum occurs in Sec. 5.3. Mathematics of this section is classical, but the interpretation in terms of NEW VARIABLES sigma_1 and sigma_2 is quantum. Classically, such an interpretation would be meaningless. This is all explained there, you only need to read it more carefully.
     
  6. May 16, 2008 #5

    Demystifier

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    For an intuitive explanation of EPR, Bell, hidden variables, and all that, by an analogy from everyday life, see also
    https://www.physicsforums.com/blogs/demystifier-61953/sex-quantum-psychology-and-hidden-variables-1477/ [Broken]
     
    Last edited by a moderator: May 3, 2017
  7. May 16, 2008 #6
    Hmm...that doesn't look right to me. With people being used as an example, the (unspoken) assumption that there is something 'beyond' their responses that can be seen. However, in QM, you can't, even in principle, look 'behind' what quantum systems 'say'. This would not be a problem if, say, postulating a 'theory' with a 'something behind' in it implied something in the 'stories' we find that could not be predicted by 'theories' that didn't postulate as such could not accommodate without complications, then a belief in the something 'behind' the stories is justified(as much as the scientific method allows). From what I've seen, though, this is not the case with QM.
     
  8. May 17, 2008 #7
    So is the point of the "sexual" interpretation of quantum mechanics (can we call it that officially? :)) that particles lie?
     
  9. May 20, 2008 #8
    I'm just too busy to post lately and will be traveling for the next month. I had hoped to get through all the myths by now. Thanks to Demystifier and everyone else. I plan to take this up again in late June.

    Todd
     
  10. May 26, 2008 #9

    Demystifier

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    It IS possible that there is something behind QM, but of course not without complications. For example, it must violate some "common-sense" properties such as locality.
     
  11. May 26, 2008 #10

    Demystifier

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    In a sense, yes. More precisely, this property of quantum mechanics is called - contextuality. In different contexts (different measurement setups) particles behave differently.
     
  12. May 26, 2008 #11
    "I would like to think the Moon is there, even when I am not looking at it." -AE
     
  13. May 28, 2008 #12
    But isn't 'realism', in the end, another 'common sense' notion?
     
  14. May 28, 2008 #13

    Demystifier

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    Of course!
    Moreover, in my opinion the realism is more "common sense" than locality, which is why I find the Bohmian interpretation the most convincing interpretation of QM. (See also my blog.)
     
  15. May 29, 2008 #14

    Hans de Vries

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    I would say say that..


    Realism stands in the way of dreams like:

    - mind over matter
    - psychic powers
    - the solipsist controlling the world by brainpower
    - eternal live
    - or just making the slot machine go jackpot by mental concentration.

    Locality stands in the way of dreams like.

    - Beam me up Scotty teleportation.
    - Extragalactic space travel.
    - Interactive communication with remote civilizations.


    I guess only dull and boring people like me would like to see both of
    them uphold, spoiling all those dreams. I would do a pretty bad job
    as a pop-sci magazine editor. But hey, Realism and Locality also have
    their positive sides...


    Realism stands in the way of nightmares like:

    - The solipsist erasing the world population when he is bored
    - with his live and downloads a new game from the matrix.
    - Your bank account is still there if you don't look.
    - and you bank account is save from the guy who empties
    - slot machines with his mental powers.

    Locality stands in the way of nightmares like:

    - Ultra energetic extragalactic events destroying the world
    - instantaneously instead of taking billions of years to reach us.
    - Remote civilizations whipping us out after they concluded that
    - earth is suitable for colonization.


    Additionally, Realism and Locality are very desirable for people
    who have the more modest dream of understanding and figuring
    out how nature works...


    Regards, Hans.
     
    Last edited: May 29, 2008
  16. May 29, 2008 #15

    Fra

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    I want to make a small comment in defense of observer relative views or "solipsism" :)

    My view of the solipsist (the observer) information view is not that each observer is free to reason arbitrarily about what he sees and thus come up with arbitrarily twisted ideas of his environment.

    IMO, what prevents such absurd things is that due to the feedback between environment and observer. The fact that the "solipsists" are communicating with each other should impose a dynamical selection. I would expect statistically there to be an emergent concensus even among solipsists so that deviations are less like to be stable enough to frequently populate the world. So while no reasoning is banned, the collective pressure from feedback from the environment will make sure there emerges a local consensus.

    So even though one might think that the reasoning of a solipsist is totally arbitrary, the dynamical effect in a network of interacting solipsists would be that after all, the reasoning is not arbitrary because structures that selfcontradict also selfdestruct in a given environment. But there is still a difference as I see it between picturing a fundamental deterministic concensus or a emergent concensus by evolution and selection.

    This is not unlike biology. One might say thay a yeast cell can not live in very hot water.
    But noone can stop us from putting a live culture of yeast into hot water. It will probably live for some seconds and have some inital stress responses powered by internal energy pools in vain as some final struggles. So although yeast cells are not a priori banned for appearing in very hot water, they are simply unlikely to be observed there. So in the emergent sense one can say that there is not living yeast in very hot water. But that doesn't precent that this is transiently so.

    So in the emergent sense, to predict a living yeast cell is very hot water is "wrong". But that doesn't mean they need to be banned from there. They are unlikely to be observerd, that's all. Similarly I imagine that certain type of solipsist reasoning is less likely, and thus wont frequently populate a given enviroment.

    So in summary, a solipsist interpretation of QM doesn't imply that anything goes or that an observer can warp the galaxy by brainpower. Sure an observer can think the galaxy is warping, but unless that is supported by the feedback ina consistent way, such reasoning is not stable and won't persist.

    /Fredrik
     
  17. May 29, 2008 #16
    Just so that words have meaning...

    Einstein Realism- “If, without in any way disturbing a system, we can predict with certainty the value of a physical quantity, then there exists an element of physical reality corresponding to this physical quantity.” (from the EPR paper)

    Einstein Locality- “The following idea characterizes the relative independence of objects far apart in space (A and B): external influence on A has no direct influence on B; this is known as the Principle of Local Action, which is used consistently only in field theory. If this axiom were to be completely abolished, the idea of the existence of quasi-enclosed systems, and thereby the postulation of laws which can be checked empirically in the accepted sense, would become impossible.” (via Wikipedia)

    I freely admit that at times, when attempting to understand quantum mechanics, my intent was to establish realism of some sort. Not for any intellectually sound reason, but because without it, it's a problem left unresolved.
     
    Last edited: May 29, 2008
  18. May 31, 2008 #17
    I hope I haven't been a thread-killer, here.

    These principle of locality and realism are, after all, opinion, even if they can be considered to carry substancial weight due to the source. And the last word on quantum mechanics hasn't been written just yet.
     
  19. Jun 1, 2008 #18
    I just want to point out that there is a distinction between an absence of a solid reality and consciousness being fundamental or conscious thought being able to affect things 'by itself'. I don't think QM and consciousness are fundamentally connected, and it is rather irritating when people conflate the weakened reality seemingly implied by QM with ESP and stuff like that.

    Demystifier, the thing about common-sense notions is not which makes more sense to us, but why nature should follow these ideas on how we think the world should be.
     
  20. Jun 2, 2008 #19

    Demystifier

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    If you have several alternative interpretations of the same phenomenon, how to know what is the correct one? The Occam's razor says - choose the simplest one. But what does it mean "the simplest"? The agreement with common sense is certainly one (though not the only) of the criteria for defining simplicity.
     
  21. Jun 2, 2008 #20
    The formulation of quantum theory does not comply with the notion of objective
    existence of elementary particles. Objective existence independent of observation
    implies the distinguishability of elementary particles. In other words: If elementary
    particles have an objective existence independent of observations, then they are
    distinguishable. Or if elementary particles are indistinguishable then matter cannot have
    existence independent of our observation.
     
  22. Jun 2, 2008 #21
    Who gave Ocaam his razor, and where did it get its magical power? Why must he be hacking away with abandon?

    Does this razor hack into General Relativity to preserve the far, far simpler Newtonian Gravity?

    Sorry, few things irritate me more than Occam's razor--ok, nevermind, a lot of things do. I double very much if there is any formal experimental evidence directly intended to test it, or if there is, whether those who invoke it know wjhat the experimental evidence might be.
     
    Last edited: Jun 2, 2008
  23. Jun 2, 2008 #22
    Agreed there. Ever since the movie "Contact" Occam's razor has been cited by virtually everybody - with or without a scientific background - to support an argument.

    The intent of Bill Occam's axiom was not "pick the simplest theory" which is what most people think - indeed, no scientist would take such a suggestion seriously. Most people don't remember what Ellie says at the outset of her explanation: "ALL THINGS BEING EQUAL."

    The razor, in fact, says: don't extend a theory further than necessary to explain what you see.

    So, for example, let's say we have two possible interpretations of quantum theory: 1) a particle's state before detection is undefined, or 2) while we're not looking at it the particle morphs into some other particle which in turn becomes a hairball coughed up by Schrodinger's cat while emitting virtual tachyons back in time to tell itself when it's going to be detected and to make sure it morphs back into the original just in time.

    Theory 1 and 2 are empirically indistinguishable. The Razor favors the first over the second, because the second arbitrarily adds a by-definition unverifiable element which gets us to the same result anyway and probably will lead us astray ultimately, so since you've got no empirical reason to add in in there, just hack it off.

    Mathematically, we can state the Razor as:

    Given a choice between two theories, 1) y = f(x), and 2) y = f(x) * a / a, choose y = f(x).

    But, again, the key is "all things being equal." If a theory produces _different_ results than the first - and those results are experimentally confirmed - neither Occam nor anyone else would tell you to ignore it just because it's more complicated than what came before. Occam's Razor just means be humble with your scientific statements: hypothesize only what you need to to conform to the data.

    And by this definition, General Relativity does win over Newtonian Gravity, because a small set of postulates explains all macroscopic gravitational phenomina, including orbital anomalies inexplicable by Newton. A perfect example of the Razor turning out to be right is special relativity. The aether was assumed, without empirical support, simply because light was a wave and waves needed a medium, therefore lght must need a medium so people concoted the aether. It was not unti lthe aether was abandoned - by Einstein - that the right path - special relativity - was discovered. The aether was an unnecessary element - a/a - that was leading people astray because no one could figure out what was really going on until it was gotten rid of.

    In terms of QM, certain interpretations are clearly superior to others according to the Razor. Cramer's TI, for example, is probably the clearest culprit (and what I was alluding to above). He assumes - by definition - undetectable waves that travel backwards in time to literally tell particles how to behave. Yes, it is nice and intuitive and makes sense to our puny minds, but it is literally f(x) * a / a rather than f(x). And, it has led people astray - look at Cramer's backwards causality research that has accomplished nothing except causing members of the public to donate money that could have been given to legitimate charities.

    Now, if an interpretation comes along that makes new predictions that can be verified or change physics somehow - great! Can a model be tweaked to make calculations easier or assist pedagogically? Perfect. But coming up with haribrained explanations for things going on behind the scenes that can never be tested - that's where the Razor reigns supreme.
     
    Last edited: Jun 2, 2008
  24. Jun 2, 2008 #23
    Where does "generalizing" stand in Ocam's razor? Is generalizing the same as simplifying.
     
  25. Jun 2, 2008 #24
    OK. I get the Ocaams Razor idea. It's not the only argumentative that get's abused untold times. Thanks for the clarification.

    I haven't read the historical development in a while. But I recall that Lorentz and others were busy patching-up kinematics upon the framework of Euclidian Space pulse Independent Time. Length contraction was ascribed to an action resulting from motion through the aether. Einstein endevored because he didn't patch.
     
    Last edited: Jun 2, 2008
  26. Jun 3, 2008 #25

    Demystifier

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    You don't read carefully, so let me repeat. If you have several alternative interpretations of the SAME (!) phenomenon, the Occam's razor says - choose the simplest one.
    For example, light that bends by the influence of gravitation and light that doesn't are not the same phenomenon.
    So yes, the Occam's razor says - choose general relativity. It is simpler than alternative theories of gravity that (unlike Newtonian theory) also explain the bending of light.
     
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