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Relativity and accelerating observers?

  1. Apr 20, 2004 #1
    I read in Brian Greene’s book that a founding principle of Einstein’s SR/GR theory is based on… the laws of science should remain the same for all freely moving (non-accelerating) observers.

    I have read that a few times before but worded a little differently.

    My question is, does this mean the laws of science do not have to remain the same for “accelerating” observers?
  2. jcsd
  3. Apr 20, 2004 #2


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    Einsteins theory of relativity addresses the concepts of accelerating observers and much information can be found on the web for general relativity.
  4. Apr 20, 2004 #3

    Like I said I have read what I stated above several times from several sources.

    These sources use different words such as "constant velocity" or "non accelerating" or " inertial" etc...

    Quote: "The laws of physics are the same in any inertial (that is, non-accelerated) frame of reference." comes from this link http://www2.slac.stanford.edu/vvc/theory/relativity.html

    Brian Greene makes similar statements on page 28, 30 and 40 in "The Elegant Universe" book.

    I think I understand now though...Einstein’s 1905 paper spoke in terms of non-accelerated references. But he ended up including accelerated frame references in his 1915 paper?

    So when people say that Einstein asserted, the laws of physics are the same for all non-accelerating observers…. It wasn’t that the laws were any different for accelerating observers it was just that Einstein didn’t know how to incorporate accelerating observers in 1905?

    Is that what had me confused?
    Last edited: Apr 20, 2004
  5. Apr 21, 2004 #4

    yeah i agreee, it seems that non-accleration is been explianed (by newton einstein...)and been set rules to it.

    but accelration will be a little different since it vary so differently. (without a pattern?)
    Last edited: Apr 21, 2004
  6. Apr 21, 2004 #5


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    It was Einstein's ponderings of acceleration that led him to come to his conclusions about gravity which is probably what many people think general relativity is all about, but as the name implies he generalised special relativity to include ALL observers and as a by-product came up with a new theory of gravity.
  7. Apr 21, 2004 #6


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    Kurdt is right, but lemme clarify:
    SR is the theory that stipulates non-accelerating (as stated in your link). Einstein expanded it with GR.
  8. Apr 21, 2004 #7


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    As I understand it:

    SR is the theory of the form-invariance of physical laws under Lorentz transformations.
    GR is the theory of the form-invariance of physical laws under arbitrary transformations.
  9. Apr 21, 2004 #8
    But note that one can easily deal with accelerated particles within the context of special relativity.
  10. Apr 22, 2004 #9
    I am wondering about this, too. Take the kinematics formula ?D=VoT+.5AT^2 and I want to have take relativistic affects in place, would I need to do anything more than just subsitute the time dilation formula into the T variable?
  11. Apr 23, 2004 #10


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    Yes. Both time and length (position) are affected by a Lorentz transformation.
  12. Apr 23, 2004 #11
    I think this point was understated in light of the previous posts: special relativity can handle accelerations due to forces if you are keeping gravitation out of the picture. To describe reference frames under the influence of gravity, you have to expand your understanding of spacetime geometry further than special relativity did--> general relativity says that the geometry is not flat.
    An observer in a truly accelerated reference frame (i.e., non-inertial frame) feels the effects, and for these accelerations you can use SR. An observer in a local inertial reference frame (their own rest frame) will not feel accelerated. The idea of general relativity is that when there are no electromagnetic, weak, or strong interactions acting on an object, its frame is a local intertial reference frame.
    You can make all this precise if you pick up a good book on GR like MTW ("Gravitation") and look at the sections on "accelerated observers" and "Fermi-Walker transporting".
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