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Same experiment performed in different inertial reference frames

  1. Jul 12, 2006 #1
    under which conditions we could say that the same experiment is performed in different inertial reference frames. I have formulated for myself the following answer:
    We say that observers from two inertial reference frames perform the same experiment if the physical quantities they measure are related by the corresponding relativistic transformation equations.
    should i say more?
  2. jcsd
  3. Jul 12, 2006 #2
    Hi Bernhard,

    Most of the times we deal with an experiment performed in one frame and observed from another frame, do you have instances when you are interested in having the same experiment performed in more than one frame?
    If I misunderstood your post above it may mean that your question needs to be clarified a little.
    Last edited: Jul 13, 2006
  4. Jul 12, 2006 #3
    Well perhaps I do not understand what you mean my understanding is that any particular experiment performed in a particular reference frame, inertial or not, should give exactly the same results in any other reference frame.
    However if one measures something from a different frame of reference then the measurements need to be adjusted by relativistic transformations.
  5. Jul 13, 2006 #4
    I have in mind the problem of the wave front relativity. If I consider that at the origin of both reference frames I have a source of light then the wave front is a sphere in both reference frames and we say that in both of them the same experiment was performed. If I consider that at the origin of one of the reference frames I have a source of light then there the wave front is a sphere but when detected from another reference frame it is an ellipsoid and the space time coordinates of the same event genertated by a light signal are related by the Lorentz-Einstein transformations. Can I say that the same experiment is performed in the two frames?
    Sine ira et studio
  6. Jul 13, 2006 #5
    See how I have edited your comment. Here is your experiment:

    Source at the origin of two different reference frames. Measure wavefront in one frame. Measure wave front in other frame.

    If my interpretation of your post is correct, then yes, you performed the same experiment in two different reference frames, namely measuring the shape of the wavefront.
  7. Jul 13, 2006 #6
    Well, first of all, in BOTH frames the wavefront is a sphere since you are using light. Otherwise, the experiment described above would violate both postulats of relativity by detecting a different shape wavefront in the two frames (ellipsoid vs. sphere).
    Yes, you can say that the same experiment is performed in two frames but the cleaner statement would be that it is being performed in frame A and it is being observed from frame B in motion with constant speed v relative to frame A.

    The above experiment is one of the many thought experiments used to derive the Lorentz transforms so you cannot mention the Lorentz transforms until the very end.
    Last edited: Jul 13, 2006
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