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Define red-shift

  1. May 11, 2012 #1
    Could some one explain what red-shift really means when we're talking about the EH of a BH?

    Thank you.
  2. jcsd
  3. May 11, 2012 #2
    EH of a BH? Remind me what that stands for.

    Redshift for moving bodies is caused by the Doppler Effect.
  4. May 11, 2012 #3
  5. May 11, 2012 #4
    Oh! In which case you have to understand that observers under higher gravitation appear time dilated to observers under lower gravitation. So those of us watching an observer falling into a black hole will see that observer slow down (and, in fact, if I understand correctly, never cross the event horizon), and any sort of waves they send back will have more infrequent peaks due to the time dilation. And so we see redshift in light waves.
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