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Relativity and Quasars

  1. Sep 25, 2006 #1
    Hi all,

    Just a quick question.

    Suppose I am traveling at relativistic speeds. An object moving with respect to my frame has undergone spatial contraction. In my frame, does the object's density increase?
     
  2. jcsd
  3. Sep 25, 2006 #2

    pervect

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    Staff Emeritus
    Science Advisor

    Yes, the density does increase.

    Energy density, the sort used in the stress-energy tensor, increases by a factor of rougly gamma^2, gamma = 1/sqrt(1-(v/c)^2). This happens by a combination of length contraction and the fact that relativisticly moving objects have kinetic energies on the order of their rest mass.
     
  4. Sep 26, 2006 #3
    OK, let's change the situation slightly.

    Suppose I am traveling at relativistic speeds. A quasar moving with respect to my frame has undergone spatial contraction. In my frame, does the quasar become a black hole if it is traveling at sufficient speed?
     
  5. Sep 26, 2006 #4

    jtbell

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    Staff: Mentor

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