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Speed of light dilated

  1. Aug 24, 2009 #1
    I am interested to know if the following special relativity scenario is generally accepted in physics.

    Consider a space ship that is travelling close to the speed of light relative to some observer.
    The time on the space shift will run more slowly than that of the observer.

    If a light beam is emitted from the space ship, will the observer see the light beam travel more slowly than light in the same frame of reference as the observer?
  2. jcsd
  3. Aug 24, 2009 #2


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    Staff Emeritus
    Science Advisor
    Gold Member

    The observer will always measure the light as moving at c relative to himself. This is one of the two postulates of Relativity.
  4. Aug 24, 2009 #3
    The reason I asked is that I was watching a science program on BBC1 'Bang goes the theory' last week and they stated that light would seem to go slower in the scenario mentioned.
    I would have assumed that they would have had expert advisors and that such an error wouldn't have been broadcast to the nation.
  5. Aug 24, 2009 #4


    Staff: Mentor

    No, the light beam will travel at c. Don't forget, in addition to the time dilation there is also length contraction and relativity of simultaneity.
  6. Aug 24, 2009 #5
    The time of the observer as seen from the space ship also appears to run slower. Each observes the other's time as running slower.
    The only possible way to tell who might be traveling "fast" and whose time might be relatively slower is by who has felt the force from acceleration...and by appropriately comparing elapsed clock times..
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