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What is the motion of a singularity

  1. Dec 18, 2004 #1
    If all 4 dimensions of a singularity are zero.

    How do you describe the motion or evolution of a singularity, in space-time?

    For example the motion of a singularity, ie black hole at the centre of every Galaxy and Quasar as it evolves through space-time, if all it's 4 Dimensions are zero?


    Terry Giblin
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  3. Dec 18, 2004 #2
    Black hole singularities may not radiate gravity, but they certainly absorb gravity fields. The mass of the black hole, which resides largely in its singularity, moves in accordance to Newtonian theory, taking all outside sources of gravity into consideration, at least to second order. There may be relativistic corrections and mass inflation; but most of that information is trapped in the black hole. All the interaction with the outside world, except for absorption, happens at the event horizon. So gravity fields actually move the event horizon in space, and the singularity goes along for the ride.
  4. Dec 18, 2004 #3


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    All of this only has to be considered if we still believe that a "singularity", as defined many years ago, is either a point, or Kerr ring with a depth of zero. I don't know if it is being discussed much here on PF, but there are now TONS (a lot) of papers/theories/revisions seeming to kick the "infinite density" singularity out on its butt. I don't remember when, but I think that Marcus provided a bunch of links on this within the last few weeks. I'm too lazy to look it up, and I have to finish another telescope for delivery next week. Busy, busy, busy..... :yuck:
  5. Dec 18, 2004 #4
    We all know that singularities are not really singular. It is just a convenient way to characterize a location in space. The outside world still "sees" the mass of the black hole at the event horizon.
  6. Dec 18, 2004 #5


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    Not really. About every day someone answers BH questions by explaining the "infinite density" of the singularity but finite mass of the BH. I'm not one of those, though.
  7. Dec 19, 2004 #6


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    Terry they dont all have to be zero!

    a singularity can have extent in one or more of the 4 dimensions.
    there can be a surface of singularity, or a 3D hypersurface of singularity,
    or a singularity can be along a line------it can have a worldline.

    In the case of ordinary Schw. black hole, the singularity is one dimensional.
    It has extent in only one dimension.

    But Black Hole singularities are not the only kind of singularity, so there are plenty of other possibilities.

    Where did you see it said that "all 4 dimensions of a singularity are zero"?

    Maybe I am missing something, this is news to me.
  8. Dec 19, 2004 #7


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    I assumed terry was talking about time dilation. That, of course, is a mixed frame reference and does not apply.
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