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How can a black hole be infinitely small?

  1. Dec 30, 2015 #1
    Hi everyone. First post here!

    It's an odd thought and relax I'm expecting to be wrong but the more I think about this the more interested I get.. Let's say you're chilling in the centre of earth, you feel no (little) pull because the gravity of earth cancels out in all directions.

    If a black hole is infinitely small how does it's own gravity hold it in because there is no direction that the matter would be being pulled as its in the centre of itself?
     
  2. jcsd
  3. Dec 30, 2015 #2

    Orodruin

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    You are trying to apply Newtonian physics to a black hole, which is a situation which is far from being possible to describe in the Newtonian limit. It is simply not describable in those terms.
     
  4. Dec 30, 2015 #3

    mathman

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    Where did you get the idea that black holes are "infinitely small"? From the outside, black holes are defined by their event horizons. What happens inside is an open question of current theory.
     
  5. Dec 30, 2015 #4
    Yeah I don't actually like that idea but it does appear to be the most common theory in research. The event horizon is not a physical border, simply a specific area of space with special meaning.
     
  6. Dec 31, 2015 #5

    Orodruin

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    Be careful here! The event horizon is not a spatial surface, it is a null surface.
     
  7. Dec 31, 2015 #6

    mathman

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    The idea of a "singularity" results from applying General Relativity without taking into account quantum theory. Applying both leads to contradictions, so what is really going on is an open question.
     
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