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Speed of light in a blackhole

  1. Aug 3, 2009 #1
    i dont know much about the subject but since ive gotten intrested in it there is something that has been on my my mind.

    if light would pass through the event horizon in a black hole the gravity would be to strong for it to escape. since it cant escape it would be pulled down to the point of singularity of the black hole. my question is that would the force of gravity pulling down on light be able to actually speed the light up possibly faster then the speed of light?
  2. jcsd
  3. Aug 3, 2009 #2
    Light is a massless particle. Though it exhibits some particle properties (duality of light), a photon has no real mass. Because of this, photons do not follow everything that particles with mass do. One of these is speeding up due to gravity. In a black hole, the photon's path with bend and spiral due to the gravity of the black hole until it reaches the center but not speed up.

    The interesting thing that happens is that the photon will lose energy when going towards the event horizon and eventually become invisible once it reaches this boundary (gravitational redshift). But the photon itself will never go faster than c.
  4. Aug 3, 2009 #3
    thank you for that! if light doesnt have any mass how is it that it can be bent or made spiral because of gravity?
  5. Aug 3, 2009 #4


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    Welcome to PF!

    Hi boredjavi! Welcome to PF! :wink:
    In general relativity, there is no force of gravity … "gravity" is just the curvature of space-time.

    Light (like everything else) follows the curvature of space-time. :smile:
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