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What is the hardest question to ask a quantum physicist?

  1. Jan 20, 2010 #1
    My friend thinks he can answer any question related to Quantum physics (although he claims he wont be able to answer known unknowns i.e 'the mass of the Higgs-Boson particle'). However, I would like to challenge him with a series of the hardest questions anyone on this forum can put to him.

    I promise to post his answers up on this blog for you to see what he comes back with.

    Many Thanks!
    Last edited: Jan 20, 2010
  2. jcsd
  3. Jan 21, 2010 #2

    Char. Limit

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    Why do you study this stuff?

    Just kidding, although I have always wondered that.
  4. Jan 21, 2010 #3


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    What is the fine structure constant (really)? And why is it very nearly 1/137?

    Iono, there's some weird stuff in Quantum that'd be pretty hard to answer...
  5. Jan 21, 2010 #4
    A good one is to prove mathematically that gauge theories with spontaneous symmetry are renormalizable.
  6. Jan 21, 2010 #5


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    "Which interpretation of QM is the correct one?"
  7. Jan 21, 2010 #6


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    Is the moon there when nobody looks?
  8. Jan 21, 2010 #7
    i also think this is a challenging one-is the moon there when nobody looks?
    ie. the epr paradox.
  9. Jan 21, 2010 #8
    It's really a matter of degree. The deep metaphysical questions that people have posted are really not on target to my way of thinking. The problem is that you don't have to get very deep into the subject at all before the calculations become excruciatingly difficult. I would say that if your friend is capable of doing the standard calculation of the energy levels for the Hydrogen atom (the actual wave functions, that is: not the simplified Bohr atom) with nothing but a pencil paper (no look-ups except for the fundamental constants h and q etc.) then his claim has at least a grain of truth to it.
    If he can calculate the ground state energy of the helium atom, then he is pretty good. If he can calculate the first excited state of helium, then he is at the very highest level. We should forgive him if he cannot readily calculate the boiling point of water or the electrical conductivity of copper.
  10. Jan 21, 2010 #9
    Why is that such an hard question?
  11. Jan 21, 2010 #10
    Your friend obviously knows very little, to have claimed he knows so much.

    I would ask him to solve the hydrogen atom by path integral methods, and explain clearly why Feynman wasn't able to do it. If he can do this then he is arrogant and clever, rather than arrogant and stupid.

    (This is not a known unknown - Kleinert did it in 1979 so it is certainly doable, but you can imagine that if it left Feynman stumped, it is not an easy problem even though the H-atom is almost the first bit of QM anyone studies.)
  12. Jan 21, 2010 #11


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    hmm … just quote to him what both Bohr and Feynman said :wink:

    "Anyone who thinks he understands quantum mechanics, doesn't understand quantum mechanics" :rolleyes:
  13. Jan 21, 2010 #12


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    Because it can be reduced to "Is electron there when nobody looks?", which is a hard question because it is not known (or at least there is no consensus) what is the correct interpretation of quantum contextuality, entanglement and nonlocality.
  14. Jan 21, 2010 #13


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    And what about those who think that they do not understand quantum mechanics? :tongue2:
  15. Jan 21, 2010 #14
    "I send a single photon through a thin slit. Tell me the exact point where this photon will hit a screen after the slit".

    I'm impatiently waiting for the answer...
  16. Jan 21, 2010 #15
    If he claims to know so much, why don't you just ask him something you want to know? Try to expose him by legitimately taking him up on his offer.

    Ask him to explain the EPR "paradox" and its solution.
    Ask him to explain why quantum cloning is impossible. (it violates conservation of probability)
    Ask him to explain non-commuting variables and what they mean for the uncertainty principle.
    Ask him to explain the quantum harmonic oscillator and its energy spectrum.
    and I could go on..

    Any physics grad should be able to talk about those.

    If he knows something, he should be able to talk meaningfully about these.
    Otherwise, you'll have exposed him as the fraud he is.
  17. Jan 21, 2010 #16
    Well can it be reduced to that question? What is to look at an electron? Isn't it basicly interacting with it? Independently of anyone "looking" at the moon or not, the moon itself is always a system of interacting particles wether it be the photons emitted from the sun or the moon particles themselves. As far as my interpretation of QM goes, the moon is always "being looked upon" wether it be by a conscious being or not. Is this interpretation correct?
  18. Jan 21, 2010 #17
    I'm starting to wonder why everyone seems so intent on exposing the individual in question as a fraud. Are there no circumstances wherbey someone could reasonably claim to have a proficient overall grasp of the subject, to the point where any reasonably posed problem should have a calculable solution? I previously gave the example of a helium atom: if someone can look at the problem and write down the correct differential equations, and set up some reasonable program for seeking out numerical solutions, then can he not claim to be able to have answered the question?

    I also have the impression that there are plenty of people who post regularly to this discussion group who feel they are qualified to "answer any question relating to quantum physics". Again, why do we assume that the person in question is any different?
  19. Jan 21, 2010 #18
    I think answering the question I raised requires a much deeper understanding of quantum theory that even calculating numerically the atomic spectrum of Helium. In fact maybe showing that "gauge theories with symmetry breaking are renormalizable" is maybe too much to ask, and your proposal is more reasonable/realistic. I also do not make the claim that we could not find another even more difficult technical question. But I certainly agree that asking "interpretational" question is not a well posed problem. Nobel prizes and world known experts in general do not agree on interpretation anyway.
  20. Jan 21, 2010 #19


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    Is reality deterministic?
  21. Jan 21, 2010 #20


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    I knew someone was going to ask that. :biggrin:
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