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Speed of light

  1. Nov 9, 2006 #1
    If two objects move away from each other in opposite colinear directions at the speed of light. How long will it take for the light from one of the objects to reach the other?

    I think the answer is never, but not sure.
  2. jcsd
  3. Nov 9, 2006 #2


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    Staff: Mentor

    If you mean that each object is moving at exactly the speed of light, then your question starts out with a impossible situation, because nothing can travel at the speed of light (except light itself, of course). There is no way to answer this question in its literal form.

    If each object is moving very slightly slower than the speed of light, then an answer is possible in principle, but you don't provide enough information to calculate it. The time it takes for light to travel from one object to the other depends on the speeds of both objects, and on how far apart they are when the first object emits the light.
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