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How can black holes have electrical charge, and spin?

  1. Nov 25, 2014 #1
    If the star's mass supposedly collapses into a single point, and it ends up having "said" zero volume, then how can people say that the hole has a specific spin or that it can have an angular momentum?

    Does it mean that the singularity is somehow still spinning, or maybe the spacetime around it is just being dragged for some reason?
    This subject has been confusing me quite a bit whenever I think about it.
     
  2. jcsd
  3. Nov 25, 2014 #2

    Orodruin

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    Where would the charge and angular momentum of the star go otherwise?

    On a related issue: Elementary particles are also modeled as point like, yet can carry both intrinsic charge and angular momentum.
     
  4. Nov 30, 2014 #3
    Sometimes the BH's gravity field is referred to as a 'fossil' field-

    http://math.ucr.edu/home/baez/physics/Relativity/BlackHoles/black_gravity.html
     
  5. Dec 1, 2014 #4
    Turns out Kerr and Newman black holes do NOT contract into points. They contract to circles... which still have zero volume, because zero thickness throughout their nonzero circumference.
    Reissner black holes are point charges, just like Schwarzschild black holes.
     
  6. Dec 5, 2014 #5
    Last edited: Dec 5, 2014
  7. Dec 5, 2014 #6
    In short: the laws of conservation (angular momentum, charge, mass-energy, etc.) still work during the process of creation of a black hole. So if a star had some angular momentum/charge before it collapsed, the resulting black hole will also have some (assuming the angular momentum/charge was not radiated away during the collapse).

    Also, the claim that black holes have "zero" volume is simply incorrect.
     
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