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Traveling a light speed from one clock to another

  1. Jan 5, 2012 #1
    Einstein is riding the beam of light away from the clock tower so the hands of the clock don't move. Suppose the beam of light he is riding on is going from one clock tower and directly to another clock tower. Would he see the hands of the clock that he is traveling toward move?
  2. jcsd
  3. Jan 5, 2012 #2


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  4. Jan 5, 2012 #3
    Obviously; that's the Doppler effect. And he would see the hands of the approaching clock move at (almost)* infinite speed.

    PS: Welcome to physicsforums. :smile:

    *"almost": it's impossible to travel at light speed
  5. Jan 5, 2012 #4
    Thank you for the welcome and the answer.

  6. Jan 6, 2012 #5
    The assumption of this is impossible. No observer can reach the speed of light, and inconsistencies arise when you forcibly choose light-like observer.
  7. Jan 9, 2012 #6
    Actually, in this case no inconsistencies arise: at the limit the measured clock frequency will be infinite. As measured from the perspective of the (impossible) "moving frame", this is due to all clock cycles accumulating together (like the sound of an airplane when it reaches the speed of sound). And as measured from the perspective of the "stationary frame", the observer's clock will, as it reaches the (impossible) speed of light, stand still so that any clock frequency that is compared to it will be infinitely faster.
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