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Relativity vs. QMwhich is more fundamental

  1. Jun 21, 2005 #1
    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 21, 2005 #2


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    Since Relativity is based on ElectroMagnetism it can hardly be considered fundamental. There is a lot of physics behind the "c is constant in initerial reference frames" .
  4. Jun 21, 2005 #3
    Relativity is based on the principle of relativity. I would consider this more fundamental than E&M because it is a principle that is independent of any description of a particular phenomena.

    In addition, I was talking about the principle of relativity not the other postulate you alluded to.
    Last edited: Jun 21, 2005
  5. Jun 21, 2005 #4


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    The constancy of the speed of light can only be postulated given Maxwells equations and the Michelson Morley experiment. E&M is fundamental, Relativity is derived, given E&M.
  6. Jun 22, 2005 #5
    you don't know what you are talking about. From what you have written you have not indicated that you understand the principle of relativity, which is not the same as the special theory of relativity. What led Einstein to work on special relativity was based on his work with E&M, this is true. In particular, velocity dependent forces seemed to indicate a preferred reference frame. Either the principle of relativity or Maxwell's equations were mistaken. In the end it was Gallean relativity that was incorrect, but the principle remained. Einstein didn't throw out the principle of relativity but modified it.
  7. Jun 22, 2005 #6


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    In the future you may want to be a bit more specific, Generally the term Relativity has come to mean Special Relativity. Perhaps you should rephrase your question.
  8. Jun 22, 2005 #7
    No, relativity means special and general. If I meant special relativity I would have said that. Either way, nothing changes. Even if we were only taking about SR what you said was not correct. SR is based upon 2 postulates one of which is the principle of relativity and the other the constancy of the speed of light in all inertial reference frames. The whole point is that no inertial reference frame is any better than another. Maxwell's equations do not obey Galilean transformations. In fact, the general wave equation does not obey it. The difference is that with mechanical waves you can resolve the problem by measuring speeds relative to the wave's medium of propagation. Since they found no either the incompatibility of Maxwell's equations and Galilean relativity presented a problem that could not be resolved by previous methods.

    My point is that to develop a consistent theory of QM you must incorporate (at least) SR. Now it is possible that relativity will be further advanced if some aspects of QM are incorporated into it. But the idea that the laws of physics do not depend upon the choice of a coordinate system will still apply.
  9. Jun 22, 2005 #8


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    I am finding this discussion distasteful, you need an attitude adjustment.

    Proof to me that c is constant without reference to E&M. If this postulate is incorrect all of Special Relativity is nonsense.

    I have no way of reading your mind, look through threads in these forums to see how frequently the term Relativity is used in place of Special Relativity. I would be foolish to assume anything else.

    Perhaps now that you have cleared the inherent ambiguities in your question someone else will discuss it with you.
  10. Jun 22, 2005 #9


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    it's not incorrect, but it's not the whole of it (at least not the whole of "relativity" with the "special" omitted). anything "instantaneous", gravity, electrostatic forces, whatever, has speed of propagation that is limited to c and is that limit is the same for all inertial reference frames.

    although our textbooks use a "light clock" to illustrate time-dilation in SR, it doesn't have to be a light-clock. any clock will slow down as it is perceived as whizzing past you at high velocity, not just a clock based on E&M propagation.

    finally, the "M" of E&M is not fundamental at all. it is a derived "pseudo-force" that is just a manifestation of electrostatic forces with SR taken into consideration. so it's really "E" + "SR" = "E&M". if there was no E&M, there would still be relativity. but if there was no relativity, there would be no "M" in E&M.

    BTW, i think relativity and quantum mechanics are about different issues (high speeds and gravity vs. very small particles) and have different postulates that do not necessarily support or contradict each other. they're both equally fundamental if such a judgement must be made. they could have been formulated in reverse historical order and they may be tied together with a Theory of Everything if some such is ever to be made.

    r b-j
    Last edited: Jun 22, 2005
  11. Jun 22, 2005 #10
    I agree that if the postulate regarding the speed of light is wrong then SR is in trouble. You are still missing the point. It is the principle of relativity that is fundamental, not the part about light.

    If you are going to justify your incorrect use of terminology because everyone else does you should look to do better. If you understand relativity (meaning you have thought about it and are not just repeating textbooks) you would have caught onto my point from the initial question.

    Instead of trying to win a lost argument let someone else post who knows the stuff. For an example on a good board see my question on the lorentz force in two frames.
  12. Jun 22, 2005 #11
    Metrictensor, you do need an attitude adjustment. Integral is a good moderator, a good communicator, and a very good physicist. He is scarcely wrong on anything that he posts.

    Reading this thread, I would have interpreted your original question the same way Integral did. That said, get back on topic.
  13. Jun 22, 2005 #12
    You have a real problem with boundaries. who cares if he is a good physicst. And who really cares if he is scarcely wrong. You don't seem to think much either. Let me try to follow your logic. Because he is usually right he must be right here/

    Maybe because you both don't know what you are talking about.
    Last edited: Jun 22, 2005
  14. Jun 22, 2005 #13

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    I'm going to shut this thread down, as it's getting a bit too nasty and personal.

    metrictensor, I think you have asked an interesting question. I invite you to ask it again, in another thread; maybe a fresh start will allow us to discuss it in a civilized manner. :wink:
  15. Jun 22, 2005 #14


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    Before this thread deteriorates any further, let me point out one important thing. Notice that in your very first posting (or even the second) in this thread, you did NOT define what you meant by "relativity principle", nor did you define what you meant by "fundamental".

    Now you could argue that such a thing is "obvious", but as you can clearly see from what has transpired, it isn't! The closest you came to defining what you meant was when, as a reply, you said:

    If covariance under galilean transformation is what you meant by "relativity principle", then say it as such. This then clearly defines the mathematical operation of that principle which, after all, is what is required in physics for something to be unambiguously defined. If what you meant by "fundamental" as a principle that cannot be further derived via First Principle, then say it as such.

    ONLY after these things are clearly defined can there be any meaningful discussion. If not, we'll continue to argue who said what and who meant what.

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