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Photonic boom stack-up

  1. Oct 7, 2012 #1
    Ok quick question if a photon of light bounced off of a spaceship (or anything really) that was traveling at light speed, would the photon double in speed? similar to if a tennis ball hits a racket that is stationary it will lose energy but if the racket is swung towards the ball it will rebound with more energy.

  2. jcsd
  3. Oct 7, 2012 #2


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    Gold Member

    a spaceship has mass, so it is impossible for it to travel at light speed.

    If a photon bounced off of a spaceship traveling at .99c, then the photon, which hit at a speed of c, would bounce off with a speed of c.
  4. Oct 8, 2012 #3


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    Staff: Mentor

    Nothing with rest mass can travel at c, so your question is invalid. Furthermore, light ALWAYS travels at exactly c in a vacuum, no matter what.

    I believe that while light will not gain or lose velocity, it will gain or lose energy. For example a solar sail uses light from the Sun to push it along, which requires that photons lose momentum as they transfer it to the sail. This causes a redshift in the reflecting light.
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