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B Does Quantum Physics really defy logic?

  1. May 9, 2016 #1
    I heard a lot of this "Quantum theory defies the human logic, it's totally illogical but it works!" and I'm trying to understand whether this is true or not. I don't mean by logic some mind blowing stuff, like teleportation is possible. I mean the kind of logic that would be difficult or impossible to form an intuition of, for example linguistic contradiction (like something existing and not existing at the same time).

    I hope I posted this in the right section.
    Thanks.
     
  2. jcsd
  3. May 9, 2016 #2

    jedishrfu

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    From the master of QM presentation Prof Brian Green:



    may answer some of your questions.
     
  4. May 9, 2016 #3

    ZapperZ

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    No, quantum physics does NOT defy logic, because it has a solid mathematical formulation behind it, just like any area of physics.

    What it MAY defy is the "common sense" that most people are familiar with. But "common sense" has been shown to be problematic. Einstein's Special Relativity, when it was first introduced, defied common sense at that time. Yet, we now know its validity.

    Zz.
     
  5. May 10, 2016 #4

    Demystifier

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    Here the most problematic concept is the word "logic". This word has several different meanings in the English language
    http://www.thefreedictionary.com/logic
    from a soft concept of "common sense" to the hard concept of "formal logic". QM may defy logic in the former sense, but not in the latter sense.
     
    Last edited: May 10, 2016
  6. May 11, 2016 #5
    Don't be confused by verbal logic; it is often misleading, for example thinking that attributes seemingly opposite or mutually opposed like convex and concave must somehow logically therefore be mutually exclusive, yet another curious philosopher (Aristotle) pointed out long ago that "...convex and concave are in the circumference of a circle...", that is, both at the same time.
     
  7. May 11, 2016 #6
    Thanks guys for your responses. It was interesting to hear your answers; I don't know why some philosophers and logicians are against quantum mechanics saying it contradicts our logical intuition. For me, everything seems to make sense, except that we're facing stuff we're unfamiliar with.
     
  8. May 11, 2016 #7

    Demystifier

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    Perhaps it's true for philosophers, but for logicians?! Can you give an example of a logician who is against quantum mechanics?
     
  9. May 11, 2016 #8

    ZapperZ

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    What exactly does it mean when you say that these people are "against quantum mechanics"? I mean, they use modern electronics, don't they? How could you be against QM when these devices work BECAUSE of QM? That is neither rational nor logical!

    Zz.
     
  10. May 11, 2016 #9
  11. May 12, 2016 #10

    bhobba

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    A lot of research has been done and it is now known to be at its roots quite simple. Surprisingly its just the simplest probability model that allows continuous transformations between what is known as pure states:
    https://arxiv.org/pdf/quant-ph/0101012v4.pdf

    All that continuity means is something very intuitive. If you have a system in a certain state at time 0 and in another state at time t then it must have gone through some other state at time t/2.

    So exactly what is the bottom line issue with QM? Its simply this. It is a theory about observations that occur in an assumed common-sense classical world. How does a theory that assumes such a world from the start explain that world - that is the rock bottom issue with QM. A lot of work has been done on that deep question and much progress has been made (particularly in the area of decoherence) but some issues still remain. The rectification of those issues is the domain of interpretations and can only be discussed when a particular interpretation is specified. Unfortunately the QM formalism is silent on a number of things so can't answer them - only specific interpretations can eg why do we get outcomes from observations - technically its how an improper mixed state becomes a proper one.

    If you want to discuss that best to start a new thread.

    Thanks
    Bill
     
  12. May 18, 2016 #11
    Something existing and not existing and superposition and wave-particle duality, they are all a little confusing but they're just how some people conceptualize quantum mechanics. And the more confusing ones are old now. QM itself is just a series of equations. E.g. in the double slit experiment, if you input the light frequency/wavelength and the size of the slits, etc, into an equation you'll get the width of the alternating light bars. The underlying mechanism is a different question, which some might explain by referencing a 'superposition', or what have you.

    So, no, but some people explain QM in a way which might seem unintuitive.
     
  13. May 22, 2016 #12

    Zafa Pi

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    Invalidating Bell's inequality and thus refuting local realism is an unintuitive prediction of QM (and verified). No interpretation necessary.
     
  14. May 23, 2016 #13

    Quantum Theory defies human logic for those who have not studied it properly. It is like a child or baby who is first perplexed why a - multiplied by a - is a + but we train our mind to understand this. If quantum mechanics was taught at schools, then the younger generations will understand quantum mechanics a lot quicker than us so they can be the future of those who discover what we have yet to do...
     
  15. May 25, 2016 #14
    Well, among locality and classical realism, the other idea that could be disproved by the experiments is the idea that the detectors are not forcing the particle into a certain state. The idea of a measurement changing the particle is a pretty common one in QM. Exactly what is really happening under the hood, I have no idea, of course.
     
  16. May 26, 2016 #15

    Zafa Pi

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    It ain't just QM. How does mass pull off its trick of gravity? What's happening under the hood with that? There are so many more mysteries it's enough to make your head spin 1/2.
     
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