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Shooting video in a planet that near to black hole?

  1. Feb 28, 2016 #1
    [Mentor's note: The thread title has been edited to change the level from "A" to the more appropriate "B"]

    Suppose there is planet Z revolving around black hole. Astronaut from earth go in that Planet Z and start video recording and make a DVD . Suppose they played that DVD in the computer in that planet . I hope they will feel every clip i that video is normal. But I think when they come to earth and play that video clip , i hope it will be slow motion video isn't it???? i am little confused.. Help me with your answers please.
    Last edited by a moderator: Feb 28, 2016
  2. jcsd
  3. Feb 28, 2016 #2


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    You posted this as "A" (advanced) level, but it seems more like a "B" (beginner) question. "A" would mean that you wanted an answer at the level of a graduate course or higher.

    The DVD and DVD player in your example are basically just a clock. In GR, the speed of a clock does not depend on any memory of what regions of spacetime it has visited. In other words, effects such as kinematic and gravitational time dilation are temporary, not permanent. There was a theory called the Weyl gauge theory in which such effects were permanent, but that theory is not compatible with experiment.
  4. Feb 28, 2016 #3


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    If they broadcast the video out into space, a static observer further away will see it as slow motion. However, if they send the video clip to earth, it will be normal in every way, just as if it were made on earth.
  5. Feb 28, 2016 #4

    Simon Bridge

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    Lets say instead of video it is timelapse photography ... the camera shoots 1 picture every second according to a clock sitting next to it.
    To watch at normal speed, play back one-frame per second according to a clock sitting next to it.
    The projector on the earth plays back one frame every second according to a clock sitting next to it... so why would it be slow?
  6. Feb 29, 2016 #5
    Thanks for all replies . I got it .
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