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Gravitational Time and Length Change, Looking for mass formula

  1. Nov 12, 2014 #1
    Hi, Just curious if anyone knows of a formula that would show how mass changes in a gravitational field? I have seen the formulas for gravitational time dilation and length contraction (which are rather similar) and was wondering is mass changes the same way.

  2. jcsd
  3. Nov 12, 2014 #2


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    Gold Member

    Mass does not change in a gravitational field.
  4. Nov 12, 2014 #3


    Staff: Mentor

    What formulas have you seen for "gravitational length contraction"?
  5. Nov 12, 2014 #4
    Just to pick an extreme, a 1kg ball is a meter away from the event horizon of a black hole. So, to an outside observer, time is almost not moving at all for the 1 kg ball and its size has shrunk to almost a point due to gravitational length and time dilation but the ball would still be 1 kg?
  6. Nov 12, 2014 #5
    hmm i just figured since planck time and planck length are related by a factor of c that they would change the same.
  7. Nov 12, 2014 #6


    Staff: Mentor

    What are you basing this on? What formula? Do you have a reference?

    The Planck time and Planck length are not the same as the length of an object or its proper time.
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