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Rel. vs. QM - take 2

  1. Jun 22, 2005 #1
    Rel. vs. QM - take 2!!!

    I have my own views on the question of between the two, QM or Relativity, is one more fundamental. It seem that Rel. is based on fundamental principles, i.e. the principle of relativity. As I see it this could never be violated but some of the foundational principles of QM could turn out to be incorrect but the result would not be as drastic. Any ideas?
     
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  3. Jun 22, 2005 #2

    ZapperZ

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    Please note my comment at the end of the earlier incarnation of this thread. Unless you define clearly what you're asking, this thread will still not progress beyond what has occured.

    Zz.
     
  4. Jun 22, 2005 #3
    In a discussion when one needs clarity they ask the person who used the terminology about specific terms. Ask a specific question and I will see if I can clear it up.
     
  5. Jun 22, 2005 #4

    ZapperZ

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    So it wasn't clear in my comment what I was asking for? Oy!

    OK, define "relativity principle" and "fundamental".

    Zz.
     
  6. Jun 22, 2005 #5
    By RP I mean the laws are physics are the same in all reference frames. Fundamental is a bit harder. If something is fundamental it applies more broadly than in particular cases. For example, the principle of relativity is more fundamental than Newtonian physics because the RP applies to areas beyond that covered by Newtonain physics.
     
  7. Jun 22, 2005 #6

    ZapperZ

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    You will note that in physics, saying "the laws of physics are the same in all reference frames" is what physicists use to explain physics to others. Keeping in mind that every concepts and ideas in physics MUST have an underlying mathematical description, this is the reason I asked you earlier IF what you meant by "relativity principle" is covariance under galilean transformation. So can you please explicitly specify if this is what you mean or not?

    If you find that defining what you mean by "fundamental" is hard, then I'm sure you will agree that considering something to be "fundamental" may be an exercise in futility. You'll argue that so-and-so is fundamental, and I'll argue that no, so-and-so is not fundamental based on what I understand to be fundamental.

    Zz.
     
  8. Jun 22, 2005 #7

    robphy

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    I have to chime in here to address some comments in the now closed earlier incarnation of this thread

    I think it's more accurate to say that "historically, SR was motivated by E&M".

    As I suggested in (my post, #2 of the "mass of the photon" thread), if the photon had a nonzero rest mass (implying modifications to the Maxwell Equations as a description of E&M), then SR would be fine by replacing "speed of light" by "[finite] maximum signal speed".

    Let me further suggest that:

    if before 1905 and before Maxwell we had been technologically advanced enough to routinely travel at speeds close to 3x108 m/s or have accurate-enough clocks, we would have been able to deduce SR from kinematical experiments (e.g., the clock effect/twin paradox scenario) or from mechanical experiments (e.g., collisiions).

    After this, we would have taken pleasure to find (or demanded [see reference below]) that the completed Maxwell's Equations are consistent with our newly formulated SR. (Along these lines, look at Jammer and Stachel in "If Maxwell had worked between Ampère and Faraday: An historical fable with a pedagogical moral" American Journal of Physics -- January 1980 -- Volume 48, Issue 1, pp. 5-7).

    So, in summary, let me suggest that
    [classical] E&M is merely one (but certainly an important one) of "the laws of physics that is the same for all inertial observers".
     
  9. Jun 22, 2005 #8

    Tom Mattson

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    I agree. SR isn't derived from EM theory, it's derived from the postulates. EM theory is just an instantiation of one of the "laws of physics" referred to in the relativity postulate. SR is underneath all correct formulations of mechanics, electrodynamics, QM, QFT, and beyond.
     
  10. Jun 22, 2005 #9
    That is not true. Look at Einstein's first paper on SR. On the first page he states essentially what I said. Of course you can formulate the statement in a more concise mathematical form but that doesn't change the meaning.

    Are you trying to trap me by using Galilean? Believe me, I know more about SR than you think I do. I ask questions that seem simple to people who have never thought deeply about the subject. Anyone can learn how to solve problems and recite what they read in books but it takes a more keen mind to ask the right questions. This was even taught to me as an undergraduate.

    I really think what you are writing is a waste of your time.
     
  11. Jun 22, 2005 #10
    Excellent and very helpful post and thanks for the link.
     
    Last edited: Jun 22, 2005
  12. Jun 22, 2005 #11
    Fundamental means something 'forming or serving as an essential component of a system or structure'.Fundamentals are something which form the basis for other fields/processes . Q.M is itself a some of numerous laws, a study of deepest secrets of objects, their detailed study keeping in view the old but still-existent laws.

    On the other hand relativity has not been 'derived' or 'deciphered' from some other fundamentals.It is a fundamental itself.It gives us the solid statemtn that 'mass changes with velocity' , 'laws of physics remain the same for the same inertial reference frame' , 'the velocity of light in vacuum is constant for all inertial reference frames' .

    Infact QM itself uses the laws of relativity like 'mass changes with velocity' and how pions behave when viewed from different inertial reference frames , that is , the half-life of a particle changing when travelling near relative-speeds.Evidently QM is experimental study , the phenomena is first observed , the QM reasons are structured and the theory is produced whereas relativity had no experiments for backup but after its advent, it has become an important part of all analysis both quantative and qualitative.
     
  13. Jun 22, 2005 #12

    Nereid

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    To answer a question that you didn't ask ... if 'Relativity' = 'Einstein's Theory of General Relativity', then we can say, with a very high degree of confidence, that at least one cannot be 'fundamental'. Why? Because they are mutually inconsistent in the Planck regime ... and 'fundamental' thus has an operational meaning, something like 'provides a good top-level/OOM accounting for observable phenomena'. Now this isn't saying very much; all those furiously busy developing String-Theory/M-Theory, LQG, etc start from the position that the two (QM, GR) are incompatible, and are looking for ways to make a theory (or large sets of theories) which 'reduce' to QM and GR in their respective domains.

    So, one conclusion I draw from this is: if there is no regime in which you can test your duelling theories, experimentally or observationally, in what sense could you say either is 'more fundamental' than the other?
     
  14. Jun 22, 2005 #13
    GR is only inconsistent in the plank regime if we assume that QM is correct. That is the whole point of this post. Which of the two (most likely) could eventually turn out to be wrong. To me it seems that relativity is move fundamental in this sense than QM. that is, it is something that will underly all theories.
     
  15. Jun 22, 2005 #14
    So what you meant by 'fundamental' was that which of the two describes more accurately the physical laws, given any condition. i.e., relativity is more fundamental than Newtonian physics because it is more accurate under more circumstances.
     
  16. Jun 22, 2005 #15

    robphy

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    In spite of the remarkable agreements that standard-GR and standard-QM have with current experiments in their domains of applicability,
    one could take the view that, in all domains,
    "standard-GR is correct and standard-QM is wrong", or that
    "standard-GR is wrong and standard-QM is correct", or that
    (my opinion) "standard-GR and standard-QM are both wrong".

    Clearly, each theory in its standard formulation uses some physical and mathematical structures that are mutually incompatible. I think it's fair to say that current research efforts in quantum gravity and unified theories look to peel away at the structures, with different camps holding on more tightly onto some features and less to others. (For example, in GR, are the Einstein equations fundamental? is the metric, the connection, or something else more fundamental? is the continuum manifold structure fundamental? is the causal structure? In QM, is the Schrodinger equation fundamental? is the wave-function fundamental?)

    With few experimental results to guide us, it's hard to say which way to go. But that's part of what that wing of theoretical research is about. Each camp takes their favorite set of "what is fundamental to them" from standard-GR and standard-QM, turns the crank (which is the hard part!), then see what comes of it (hopefully something that can be tested by experiment). As a by-product of the successful theory, we will probably find revised or possibly brand new formulations that encompass GR and QM.

    my $0.02
     
    Last edited: Jun 22, 2005
  17. Jun 22, 2005 #16

    ZapperZ

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    How is this a waste of time? You DID tell me to ask you DIRECTLY if I have trouble in clearly understanding what you meant, didn't you?

    This isn't the philosophy section where handwaving arguments can suffice. I ASKED you if you meant covariant galilean transform is what you meant when saying that. Why are you insulted with this? If it isn't, then DEFINE it. And don't use Einstein paper to justify what you are doing - that is a 1905 paper. We have accumulated significantly MORE knowledge since then and have made significantly clearer definitions of a number of things.

    You are also forgetting that what Einstein described in words is a reflection of a clear mathematical description of his ideas. In YOUR case, it appears that you started with a "description" without having any mathematical form. So do not equate what you are doing with what Einstein was doing. You are not even close!

    I am still waiting for you to define what "relativity principle" is and what "fundamental" is.

    Zz.
     
  18. Jun 22, 2005 #17
    suck my balls.
     
  19. Jun 22, 2005 #18

    Doc Al

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    On that note. Closed.
     
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