How can black holes even exist?

  • Thread starter Tachyonie
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  • #1
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Main Question or Discussion Point

Ok here is a thing I dont understand: How can a blackhole exist? There are several things bugging me about black holes:

1) The more concentrated the matter is, the more deformed spacetime is and the slower the time is (from our point of reference). How can Black Hole be created in finite amount of time from our perspective?
2) Shouldnt the expanding of space prevent black hole from being created? Pulling the matter appart just around the borders of black hole creation?

3) Hawkings radiation, how can a black hole be evaporated by hawkings radiation? Once the mass lowers under the critical mass needed for black hole it should not undergo the process of radiation and should start gaining the matter back, no?

And something extra:

4) Just want to know, during Big Bang, when all the matter was super concentrated, the super inflation prevented the space from becoming one big black hole by stretching the space so fast that the matter could clump togever?

Thank you for answering my dumb questions. :)
Cheers
 

Answers and Replies

  • #2
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The matter, on large scale is uniformly distributed, but this isotropy is broken by the mass of the object, this object create a gravity that contrasts the expansion anti energy.
 
  • #3
mgb_phys
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Ok here is a thing I dont understand: How can a blackhole exist? There are several things bugging me about black holes:

1) The more concentrated the matter is, the more deformed spacetime is and the slower the time is (from our point of reference). How can Black Hole be created in finite amount of time from our perspective?
It's only really distorted inside the event horizon - what happens inside the event horizon is anyones guess.

2) Shouldnt the expanding of space prevent black hole from being created? Pulling the matter appart just around the borders of black hole creation?
No more than it would stop planets or stars forming.

3) Hawkings radiation, how can a black hole be evaporated by hawkings radiation? Once the mass lowers under the critical mass needed for black hole it should not undergo the process of radiation and should start gaining the matter back, no?
Hawking radiation means it may be impossible for micro black holes to grow, the effect on stellar size black holes is very small.

4) Just want to know, during Big Bang, when all the matter was super concentrated, the super inflation prevented the space from becoming one big black hole by stretching the space so fast that the matter could clump togever?
You can regard the initial universe as sort of the opposite of a black hole - this was one of the early models.

Thank you for answering my dumb questions. :)
They're very good questions.
 
  • #4
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Durin inflation the velocity of expanding was c?
 
  • #5
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Durin inflation the velocity of expanding was c?
No, it was order of magnitude greater.

I can't link in this forum yet, but someone posted a nice link to an explanation of what inflation was.

Just check out "Cosmic inflation" on wikipedia, you should find all the answer you need.

Or there is always the library for more valid info.
 
  • #6
Wallace
Science Advisor
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you can always type out 'www dot awesomewebsite dot com' or something like that if you know a good site and can't yet post URL's.
 

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