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Proper distance and rest length

  1. Dec 20, 2014 #1

    Could someone check my following statement: The proper distance between two spacelike seperated events can be thought of as the rest length of a rod that connects both events in an inertial frame in which both events happen simultaneous.

    Thanks in advance!
    Last edited: Dec 20, 2014
  2. jcsd
  3. Dec 20, 2014 #2


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    That's correct, and you can always find this frame of reference, by choosing the spacelike vector as one of the basis vectors of an inertial reference frame in Minkowski space.
  4. Dec 20, 2014 #3
    Okay, that makes sense :) Thanks for the quick reply!
  5. Dec 20, 2014 #4


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    One should note that this does not necessarily work in GR. In SR where there are global inertial frames, one can always define a rest frame for such a rod, in GR if the two space like points are too far apart, there may not be a unique way to measure the distance between them (different "straight line paths" may connect the same two points).
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