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Does black holes exist all around us?

  1. Apr 20, 2009 #1
    I read Wikipedia about black hole and interpreted it as such: that black holes exist all
    around us, most of them are very, very small.

    Suppose we have a drinking water glass (just suppose its mass is 10kg)
    hence at radius 1.48 E-26 m (far smaller than even the radius of an electron)
    there exists a black hole at the centre of mass of the glass.
    (by the calculation done using escape speed equation, plugging in the speed of
    light as the escape speed, we can get the value of r, in which any particle
    even in the speed of light cannot escape from.)

    because by calculation, the escape speed;v of any object inside the
    radius will be greater than the speed of light hence it cannot escape, even light cannot.

    so there is a tiny black hole at the centre of the glass. Am i right? please explain if not.

    Thank you

    here's the extract of the article in http://en.wikipedia.org/wiki/Black_hole
  2. jcsd
  3. Apr 20, 2009 #2


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    Gold Member

    Welcome to PF, V.
    I think that microscopic black holes are still open for conjecture. For a 'real' black hole, you need a body of at least 3.2 Solar masses in order for the gravitational collapse to take hold. The most likely place for that to occur is in a red giant star that goes supernova. If SpaceTiger is still around here, he's definitely the go-to guy for this.
  4. Apr 20, 2009 #3


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    Science Advisor

    No, the meaning of the radius you calculated is that if the mass of the glass were concentrated into a volume less than that radius, then a black hole will form.
  5. Apr 20, 2009 #4


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    Science Advisor

    Right. As you shrink your radius you also shrink your mass, so there is no point at which there is a black hole inside any object that, well, isn't a black hole.
  6. Apr 20, 2009 #5
    I see.. it makes good sense for me
    So for a black hole to exist, the 'critical radius' (of which any object cannot escape from
    without moving at v>c) must be bigger than the volume of the object itself (which creates the black hole).
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