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Is black hole a hole?

  1. Jan 23, 2015 #1
    if I compress a heavy body to a very small point object such that its density is almost infinity, I get a black hole. but how can a point mass be a hole?
    why do scientists call it a black 'hole'?
    what I mean is, if I were to be pushed into a black hole, will I collide with that point mass?
    Also we know that even light cant escape a black hole. but if a black 'hole' absorbs the light ,it gets some energy ##hc/\lambda## (assuming that the black hole is a point mass.) But as time passes the energy of the point mass keeps increasing and it will become unstable right? what will happen? will it explode by emitting all its energy?
    [pleas forgive me if my questions sound stupid]
  2. jcsd
  3. Jan 23, 2015 #2
    The term "hole" is rather whimsical, and if I recall correctly, was actually meant derisively by the person who brought it up first. It is not literally a hole in the sense that what goes in disappears. The matter that goes in still is there. It just *looks* a bit like a hole.
  4. Jan 23, 2015 #3


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    The term 'black hole' is referring to the event horizon surrounding the hypothetical singularity. It's not a point-like object, although the singularity may be thought of as such - still, it's better to think of it as a 3D object of infinitesimally small volume.

    It's called a hole, because things fall in and not come out of it, and it's called black because even light doesn't come out.

    You don't need to compress a body to a point to get a black hole - compressing it below its Schwartzschild radius (depends on mass) is enough. For very massive objects the radius can be huge. (look it up on wikipedia, the formula is very simple)

    If you add mass(=energy) to a black hole, it'll increase its radius. There is nothing in the classical treatment of black holes that would allow the material to escape by any means, so the singularity could not become 'unstable' and explode.

    There have been some quantum-mechanical approaches that allow black holes to lose mass and/or explode (Hawking radiation and more recently Planck stars - look them up!)
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