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Time implications for travelling at the speed of light

  1. Feb 4, 2016 #1
    Is my following summary correct :
    An observer will see that time has stopped for a photon as it is travelling at c. From the photon's perspective time is "normal" but this implies that the photon "sees" time for the rest of the universe as moving at infinite speed. i.e. could see the beginning and end of time as an instant.
  2. jcsd
  3. Feb 4, 2016 #2


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    Gold Member

    Not correct, but a common misconception.

    A photon does not have a valid frame of reference. It is nonsensical to try to imagine it.

    1] One of the primary postulates of relativity is that the speed of light in a vacuum is observed to be c in all frames of reference.
    2] A photon always moves at the speed of light in a vacuum.
    3] An object is - by definition - stationary in its own frame of reference.

    Combine 1] 2] and 3] you have a particle that is both stationary and moving at the speed of light at the same time. It is an oxymoron.

    What you want to be asking is:
    What would a (normal, massive) particle observe as it approaches arbitrarily close to the speed of light?
  4. Feb 4, 2016 #3


    Staff: Mentor

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