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B Why is Quantum Physics so Strange?

  1. Dec 19, 2016 #1
    I want to be a quantum physicist as a career because i absolutely love the mystery behind certain principles in quantum physics. Especially things like the quantum eraser experiment. I am wondering if there is a reason that quantum mechanics has very weird principles that seem to defy logic, like quantum tunneling.
  2. jcsd
  3. Dec 19, 2016 #2
    I think it is a mystery because the old one isn't known yet.
  4. Dec 19, 2016 #3


    Staff: Mentor

    I would say that you are asking this question backwards. The question ought to be, why do our human minds find the principles of QM "weird"? QM was there before we were; it is just how the universe runs. If our minds have trouble understanding it, that's an issue with our minds, not QM.
  5. Dec 19, 2016 #4
    That very reason is our existence!!! ...
    Because we wouldn't exist if it weren't for Quantum Mechanics!! ... (e.g. there wouldn't be stable atoms ... etc.)

    Thus, even every day life supports QM and Quantum physics.

    [Another example is E=hf, observed all the time ...]
  6. Dec 19, 2016 #5


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    There was a very long thread discussing exactly this. Try a forum search. Hint: start with the links at the bottom of this page.
  7. Dec 19, 2016 #6


    Staff: Mentor

    It depends on how you look t it:

    Also much of the strangeness is 'hyped' by popularization's. Move a bit beyond that to actual textbooks and you will find slowly it becomes less strange.

  8. Dec 20, 2016 #7
    Don't go into theoretical physics because you're interested in quantum "weirdness" - i.e. QM interpretations. By the time you get a degree, funding for this sort of thing will be nonexistent because it's completely useless. In fact, even today such jobs are rare. If you want to be a physicist, concentrate on real physics: the more applied, the better. QM (and the rest of physics) is essential for material science, optics, chip design, weapon design, experimental apparatus like Hubble, gravity wave detectors, and CERN, etc. Funding will always be assured because people make billions from these technologies that build modern devices. The physics involved is actually much more interesting than QM interpretations. If you can't get into some such topic, find a different career.

    That doesn't mean you can't learn QM interpretations also. With "real" physics under your belt you'll know everything that counts: the math, and what it means in practice. You can dabble in QM "weirdness" after you make your first million. I figure in about 20 years, the solution will be understood. It will be simple, not weird.

    Yes, there is a reason: most of the people working on those principles today are not logical. And the less logical they are, the more noise they make. Wait about 20 years for them to retire or at least get out of the way.
  9. Dec 20, 2016 #8
    Nice attempt to land him. But that's more like "grounding"! ...

    I agree about the financial part/issue; and you are right about technology.

    But you are a little cynic and harsh against theoretical physicists etc.

    !! ... so did/were Heisenberg, Schrodinger, Einstein, Bohr, Max Born, De Broglie, ..., Feynman etc. ??!! ... (most Nobel winners - we owe them QM, QED(&QFT..) and more!! ... - so that e.g. you/we can understand Quantum Optics, modern Electronics etc. and make the applications you mention etc. ...) - [they are all "out of the way" now ... , but went down in history for "weird" contributions to science (physics) ]

    Things are not as simple as you say. How do you know that the OP (i.e. ChrisisC) isn't the one that will solve these problems? (e.g./etc.) ... ?
    Perhaps a good advice for him would be to combine both theoretical and applied physics. Budget is always an issue! ...

    Don't be so sure about that!! Otherwise it would have probably been found already (if it was indeed simple) ... [It's been over a century now ... and with the biggest names in history, perhaps ...].

    But even every day life inevitably connects to "Quantum weirdness" [+see my other earlier post above], otherwise we wouldn't exist! ...
    [But of course you might say: we do! ... (and that's all it matters? ...)]
    Last edited: Dec 20, 2016
  10. Dec 20, 2016 #9

    A. Neumaier

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    The answer can be found in this post and the link there.
  11. Dec 20, 2016 #10
    Use a different logic. Use the rules of quantum mechanics, quantum field theory, elementary particle physics as a rock solid guide, work backward and come up with a mental picture of Nature that implies the rules of quantum mechanics. Good luck!
  12. Dec 20, 2016 #11


    Staff: Mentor

    It is 'simple' - we now know that. Its just over hyped.

    This is not the thread to discuss it but if you really do believe its 'weird' start a thread detailing it. I am pretty sure once understood properly the weirdness will 'disappear'. But don't take my word for it - start a thread and we will see.

    I once thought it weird thinking particles in many places at once, superluminal communication, cats alive and dead, yada, yada yada. Slowly as I learnt the real thing from books like Ballentine they all evaporated. There is a deep issue - namely why we actually get outcomes at all, and we have interpretations that explain that. The thing is we cant tell them apart. That's not good - but weird - well I suppose it depends on what you mean by weird - for me - no - but that's just an opinion.

  13. Dec 20, 2016 #12
    Relativity is weird!

    Did Newtonian physics seem weird in Newton's time? Is there anything in classical mechanics that still seems weird to anyone?
  14. Dec 20, 2016 #13

    A. Neumaier

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    Yes, even to Newton himself - he didn't like action at a distance!
  15. Dec 20, 2016 #14


    Staff: Mentor

    Well actually there is eg the first law follows from the second - so why have it. But start a thread in the classical mechanics section if you want to explore it.

  16. Dec 20, 2016 #15
    That's more like a "structural weirdness" (of the theory), thus minor.
    But the 1st law did in fact come first anyway, before the 2nd was discovered ...
  17. Dec 20, 2016 #16
    I myself believe it is in fact simple, but not fully conceptually resolved and understood.

    Moreover, I pretty much support the Standard [Copanhagean] Interpretation of QM ... (Probabilistic interpretation of the wave function, superposition principle, selection rules and filtering principle, and relation between observer and instrument, etc.) ... which is "a bit weird" ...

    But there are [still] [unresolved] issues, at least at the conceptual level, regarding e.g. the profounds of the exact nature of the relationship between counsciousness (observer) and measurement [process] (instrument) ..., that could even lead to non-realism and idealism, or even animism.

    Other more formalistic [open(?)] problems involve the possible incompleteness of QM, Bell's inequalities, Hidden Variables and more ...

    To say "it is in fact simple", one has to answer adequetly all these questions and problems, and more ...
    These are [still - as far as I know] nice and neat open fields for research
    , no matter what anyone else sais/ has to say. And [probably] they will still bring "bread" and opportunities both for theoretical and experimental physicists in the future!! ...
    {So I would probably say, for the OP, "Trust and follow your heart and intuition ...", "consider all views and available data and information ... and make your own good choice! ..."}

    By the way, Particle Physics (e.g. either theoretical or at CERN) is a different domain, but they are related ...

    Overall, keep an open mind ..., and never say [QM] "it's simple" or "weird"! ... It's both!!!
    Last edited: Dec 20, 2016
  18. Dec 20, 2016 #17
    I wasn't aware of this. Sounds a bit like debating postulates in Euclid.

    -Dave K
  19. Dec 20, 2016 #18
    With both quantum mechanics and relativity, the more you understand it, the less "weird" it seems, and the less you understand it, the more "weird" it seems. From the point of view of physicists, quantum mechanics is not "weird" at all. If you are a physics professor teaching a class in quantum mechanics, or writing a textbook on quantum mechanics, your goal is to make it seem as intuitive as possible. If you are a popular science writer trying to write a magazine article or tv show for the general public, your goal is to intentionally make it seem as counter intuitive as possible because you are catering to a niche audience that enjoys being freaked out by supposed "quantum weirdness". It's fine if your initial interest was originally sparked by reading popularizations when you were kid, but after that, if you want to actually learn the subject, don't believe anything you read in popular accounts, and instead read actual physics textbooks.

    I could not disagree more strongly with this statement! The more "applied" physics is, the less "real" it is! The less "applied" physics is, the more "real" it is!

    What do you think physics is? The goal is physics is not to put new products on the shelf at Walmart. The goal of physics is to understand the Universe. The most "real" physics is advanced theoretical particle physics, high energy physics, string theory, other attempts at quantum gravity, and cosmology. There is no "practical application" of the discovery of the Higgs boson at the LHC, gravity waves at LIGO, neutrino oscillation, dark energy, the AdS/CFT correspondence, brane worlds, Monstrous Moonshine, etc. The farther your work is removed from your mundane daily life, petty human affairs, and our limited experience, the closer it is, potentially, to uncovering the deep truth of the Universe at the most fundamental level, which is, after all, supposedly the goal of what I consider "real" physics.
  20. Dec 20, 2016 #19
    This is a baffling statement.
  21. Dec 20, 2016 #20
    I would think that the perception of weirdness is not a linear function of how much you know. Is not one's appreciation for it's weirdness raised by understanding enough about physics to know why it is weird to begin with? The curve is likely to slope back down as ones understanding grows.

    I'd almost be surprised if there is no xkcd comic with the above written as a plot.

    -Dave K
  22. Dec 20, 2016 #21
    I wouldn't exactly put it that way.
    I think the problem is that applied and experimental sciences (not just physics) are subject to improper (incomplete) induction:


    But they are still very usefull and important!

    On the other hand, all theories are subject to falsification (Popper..) ...
    So, my two friends, "you go figure ..." ...

  23. Dec 20, 2016 #22


    Staff: Mentor

    That is very interpretation dependent. We have interpretations where its trivial (eg BM), Neutral (eg Copenhagen) and those where its a big problem (eg many minds).

    Now we are talking about a genuine issue in QM. It's a mater of opinion if its weird - physics is not a game of semantics - you make your own mind up if this and other genuine issues are weird - I have laid my cards on the table and said IMHO its not weird and I do not think most people would classify this sort of stuff as weird - interesting yes - but weird - no. Still its just semantics.

    The issue is this - pick anything about QM that worries you - in your case the consciousnesses link - we have interpretations where its a non issue and those where it's front and center. That is a big problem - science is about deciding via experiment and no one has figured out an experiment to decide it. BTW these days consciousness being involved in QM is only in very backwater interpretations - its way out of favor.

    How it became involved and why its out of favor has an interesting history - but should be in another thread. Also it must be said just because its backwater it doesn't make it wrong - no interpretation is better (or worse) than any other - the choice is purely a personnel matter.

  24. Dec 20, 2016 #23


    Staff: Mentor

    The second is a definition so how can it be a law?

    But this is not the place to discuss it - go over to the classical mechanics section.

    The answer has relevance here because it involves QM - at rock bottom the 'why' and proper laws of classical mechanics depends on QM and symmetry. But here is not the place to discuss it (the book on its proper presentation is Lanadau - Mechanics - but that is just by the by - it needs its own thread). Newtons laws are not laws in the usual sense - they are a paradigm that says - get thee to the forces. You cant prove or disprove a paradigm - but since they have been used for centuries cant be discarded either. Its like relativity - the laws of physics are the same in all inertial frames - that's not a usual law either - strictly speaking its a meta law - a law about laws. Its slightly vacuous since it depends on what is meant by law - to a physicist its obvious - but a philosopher might have issues. Note we don't discuss philosophy here so it not a problem.

  25. Dec 20, 2016 #24
    Based on this I have a question that I think is relevant. If I understand correctly (I am a math guy and haven't done physics in awhile) the current learning paradigm is Classical Mechanics --> Relativity --> QM

    Now QM seems "weird" possibly coming from a classical approach until the shock wears off. But is it possible that, given enough time, experimentation, and better ways of organizing our understanding, that the learning paradigm will be shifted to match the "real" paradigm (sorry for overusing the word 'paradigm') so that QM actually comes first?

    This might be like proposing we teach mathematical logic and peano axioms before arithmetic, before algebra, before calculus. You can't make the case for the average student who has to take a few math classes, but you might make the case for someone who has decided to study mathematics.

    -Dave K
  26. Dec 20, 2016 #25


    Staff: Mentor

    Indeed it does.

    Read Landau -please - its perfect for a math guy.

    The true basis of classical mechanics is the principle of least action (plus symmetry of which the principle of relativity is an example) which follows from QM (the principle of least action that is - symmetry is everywhere in modern physics).

    Now the interesting twist is its one of the true basis of QM as well (ie all our theories can be expressed that way)- see:

    That's just plain mysterious - it seems nature at rock bottom is governed by minimum principles. We don't know why - yet.

    Last edited by a moderator: May 8, 2017
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