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Question about this equation

  1. Jun 10, 2006 #1
    T = root((t2 - t1)^2 - (x2 - x1)^2)

    As I understand it, T is proper time as measured in someone's intertial frame, and (x2 - x1)^2 is their movement through space... but in what frame is (t2 - t1)^2 measured?
  2. jcsd
  3. Jun 10, 2006 #2


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    t1,x1 and t2,x2 are both measured in somenone (anyone's) inertial frame.

    Regardless of which inertial frame you chose to measure t1,x1,t2, and x2, the result T will be the same - it will be invariant.
  4. Jun 10, 2006 #3
    Awesome. Thank you kindly ;).
  5. Jun 11, 2006 #4
    Please note that

    [itex]\Delta[/itex]s2 = (t2 - t1)2 - (x2 - x1)2

    may be either positive, negative or zero. [itex]\Delta[/itex]s2 may be either a proper time or a proper distance according to its sign.

    Last edited: Jun 11, 2006
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