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Mass is not the cause of gravity?

  1. Jan 30, 2014 #1
    If the effects of gravity are relative to an objects stress-energy-momentum tensor, is the equation:
    Fg = Gm1m2/r^2
    fundamentally flawed since it is based off the mass of the two objects? Ignoring the "gravity isn't a force" (I understand that it is what is observed due to curves in spacetime) argument if at all possible. Simply put, does this formula accurately predict how "normal" objects will be effected by gravity or is it just wrong?
  2. jcsd
  3. Jan 30, 2014 #2


    Staff: Mentor

    It is accurate enough for rockets, satellites, and all sorts of other purposes. It is a good approximation for many things where the mass energy is the only significant non zero component of the stress energy tensor.
  4. Jan 30, 2014 #3


    User Avatar
    Staff Emeritus
    Science Advisor

    As others have mentioned, it's a good approxiation, but don't expect it to work for relativistic flybys and/or light deflection (where the momentum components become important), or black holes (where the pressure terms become important, even dominant).
  5. Jan 31, 2014 #4


    User Avatar

    Staff: Mentor

    Neither. Take a look at http://chem.tufts.edu/answersinscience/relativityofwrong.htm to see why this isn't an either/or thing where one of the alternatives is "it's just wrong".
    Last edited: Jan 31, 2014
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