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Why is Quantum thoery so confusing that no body actually understand it ?

  1. May 12, 2010 #1
    It says that:

    I think I can safely say that nobody understands quantum mechanics....Do not keep saysing to yourself, if you can possibly avoid it. But how can it be like that? Because you will go "down the drain" into a blind alley from which nobody has yet escaped. Nobody knows how it can be like that.
    by Richard Feynman


    what does he mean by "down to the drain" and "blind alley"? . .

    why is quantum world so confusing?

    can anyone just come up with an example would be great



    cheers..
     
  2. jcsd
  3. May 12, 2010 #2
    I mean I have read a few articles about them and I think its mainly to do with possibilities.. I havent gone deep enough to find it confusing.... so can anyone sort of explain for bit .. an example would be great


    thanks
     
  4. May 12, 2010 #3
    entanglement, unitary evolution (continuous, deterministic) and state reduction (discontinuous, probabilistic).

    quantum jumping, I'll state that I had only read the textbooks and listened to lectures for the last 15yrs not as a student but as a hobby, weird I know. Now that I have a bit more spare time I'm taking the time to learn more of the math. I'll say that it to me seems to further divide probabilistic vs state vector.
    just by measuring the momentum of the particle it jumps into an eigenstate of the momentum operator and if I've got this right it's now a wave form and spread over all of space. but if you try and measure this new state it jumps again, I think this is the collapse of the wave function or state reduction to probabilistic. So based on that the measuring is part of the system and each measurement effects it state so that you'll always have a missing piece.
    That's how i see it for now, still learning and I'll say that don't expect it to get easier or make more sense. I enjoy going down the 'rabbit hole' though.
     
  5. May 12, 2010 #4
    There is a fundamental limitation with any attempt to self reference your own design. This is something computer programmers discovered when trying to build the ultimate debugger. We are trying to understand the elementary particles that make up the same tools we are using to measure them.
     
  6. May 13, 2010 #5
    i see..

    cheers ppl
     
  7. May 16, 2010 #6
    I think there is a more fundamental reason here. It's not that we can't understand it because it is confusing. It's not confusing -- it's unimaginable. When we say we understand something this usually means we have explained the new thing in terms we have experienced. It's like going to a foreign culture: there is no decent frame of reference. But then you talk to people and learn what things are like. You gain experience.

    But quantum mechanics is different because we cannot gain this direct experience. So we try and grasp it through analogies. But every analogy is to something macroscopic: is it a particle (read: billiard ball) or a wave (read: water wave). Well, it's a bit of both -- which makes no sense for billiard balls and water waves. Nonetheless that's the way the microscopic works.
     
  8. May 16, 2010 #7

    Fredrik

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    The problem isn't with QM, which is just a set of rules that tells us how to calculate probabilities of possibilities. The problem is with the idea that "QM describes the world out there". It's very tempting to believe that this statement is true, or even obvious, but it's probably not even logically consistent.
     
  9. May 20, 2010 #8
    thats confusing.. :) lol

    i see your point
     
  10. May 20, 2010 #9
    There is also the reality that without an understanding of linear algebra, understanding QM is going to be approximate, and confusing.
     
  11. May 20, 2010 #10
    I think its more like a spider web in a dream*.



    edit:
    *nightmare
     
    Last edited: May 20, 2010
  12. May 20, 2010 #11
    I don't like that Feynman's quote. It's too ambiguous and open to interpretation. QM is a well defined mathematical framework that is based on postulates the same way special relativity is, and it makes reliable predictions up to a certain limit.

    What we don't understand is the theory of everything, if there ever is such an idea.
     
  13. May 20, 2010 #12
    Re: why is Quantum theory so confusing that no body actually understand it ?

    I have a feeling it will be easier to understand than quantum
     
  14. May 20, 2010 #13

    qsa

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    It is classical physics that was confusing for me. Although, I could do it with my eyes shut I could not really understand why. It was the same old thing, we do experiments plot and get the equations no explaination as such( like f=GMm/r^2). Thank god for QM/QFT things make much more sense.
     
  15. May 22, 2010 #14

    Any formalism that makes stunningly correct predictions about the world out there must be describing the world out there. Proposing otherwise is probably not even logically consistent.
     
  16. May 22, 2010 #15
    That is absurd.
     
  17. May 23, 2010 #16

    No. What is very obviously absurd is that an ape-like creature that historically has just descended from the trees, actually thinks that reality MUST conform to his/her prejudice and intuition. I don't think that nature, the world, reality, or call it whatever, cares about how you want the world to be. In a wider context, everything is absurd - how reality works is absurd, existence is absurd, life is absurd, self-awareness is absurd, but it's a brute fact. Face it or suggest a reason why it must NOT be absurd.

    It must all be stemming from the fact that we thought for so long that we understood reality and existence. We do not, and this is exactly 100.00% certain. We have no proper understanding of what is going on, how it is going on and why it is going on. We are still dumb animals born in a fairly absurd reality. Face this fact, or join the religious who think they have the important answers figured out.
     
  18. May 23, 2010 #17
    So the choice is to remain monkey or be a man? Hurm....

    I think the thing QM is that it's concepts are fairly simple on the surface but have a level of complexity at the bottom that you would need a super computer and 10 years at MIT to understand. So while everyone thinks they understand QM at the basics the reality is only a select few really get what its saying about the world. It's sorta like poker or chess :) Everyone thinks they know how to play yet only a select few end up at the championships year after year. Sorry if this comment gets the thread locked :( :(
     
  19. May 23, 2010 #18

    Fredrik

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    You don't even seem to realize that the claim you made is only based on your own prejudice and intuition. The truth of the proposition that QM describes the physical system under consideration even at times between state preparation and measurement does not follow logically from the truth of the proposition that QM describes the system immediately after each measurement.

    It's quite bizarre that you take what I said as evidence that I think reality must conform to my prejudice and intuition. The only unsual thing I've done is to let go of the prejudice that every theory that makes accurate predictions about probabilities of possible results of experiments must be a description of reality at all times.

    I'm not saying that QM isn't a description of a physical system. I'm saying that maybe it is, and maybe it isn't. The information we get from experiments just isn't enough to rule one of these options out. I'm also not saying that the idea that "QM describes a physical system at all times" is logically inconsistent. As far as I know, it isn't. But it does seem to imply the existence of many worlds. So as far as I can tell, the idea that QM describes reality and the idea that reality consists of only our universe, can't both be true.

    There are times and places where comments like these are appropriate, but this is definitely not one of them.
     
  20. May 23, 2010 #19
    Quantum mechanics as a tool is understood by those who use it, professional physicists. What knowbody knows is why nature is this way. Most specifically, from Feynman, nobody knows why or how quantum interference takes place in nature. But that it does, and that it quantum theory is incredibly accurate is not in dispute.

    As to the absurdity or not of asserting that QM describes thecreal world, it's a matter of fidelity. The 4 elements, air, earth, fire, water describe the world to a certain fidelity. The fidelity of QM is a lot higher but it is not the last word in understanding the physical world. In fact it's just the opening sentence. Humans have not addresed the how or why of it yet.
     
  21. May 23, 2010 #20

    I understand your unwillingness to say specifically that QM describes the system between measurements, but if everytime we do a measurement/observation we get an accurate result that exactly conforms to the calculations, what could it be that the said formalism is describing except reality itself? How could it even be otherwise? We have to be logical and logic dictates that if said theory makes correct predictions(so far QM is the most successful theory there is in physics), then it must describe reality. Be specific, how could it be otherwise? How could the world be different than QM describes, if QM's predictions are always accurate to a striking degree of precision?




    Right. But what is the other option and how would that be? We have a theory that makes correct predictions but you are saying it might not be a description of reality? How so? Are you proposing abandoning causality at certain level? If so, we'd be essentially abandoning science as we know it. I am not saying reality isn't that way, but if there is no fundamental cause as to why things happen the way they do at the macro scale, that'd be the end of the quest for answers to the deep philosophical questions. And abandoning causality opens the door to a myriad of "God did it" interpretations.




    Correct but MWI could be said to be "flowing" out of the QM formalism and experiments. As such, it is also a correct description of the world out there, as per qm formalism. Even between measurements and interactions.
     
    Last edited: May 23, 2010
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