Also see:
extract from "The Physics and Relativity FAQ" (just the first specific answer)
Original by Philip Gibbs, 1997. Updated by PEG 1997.Is the Big Bang a black hole?
This question can be made into several more specific questions with different answers.
Why did the universe not collapse...
After an extensive google search, I find that my musing that the Universe is inside a black hole was described in a Nature article ("The Universe as a Black Hole" Nature 240 (5379): 298–299) by R.K. Pathria (1972)
If a sufficient quantity of matter is within its Schwarzschild radius (with vacuum outside), why does it need to be collapsing? Isn't it by definition already a black hole and anything happening inside the event horizon(/Schwarzschild radius) is unknowable and irrelevant to outside observers.
Thank you PeroK and Ibix. I see now that in the same way that gravity at the centre of the Earth is zero, then a homogeneous universe (with no outside vacuum) will not collapse to a black hole. I've just read elsewhere that the big bang is best described as an explosion in time, rather than...
Thank you for your reply, but I'm not sure I fully understand. The homogeneity of matter inside the Schwartzchild radius is irrelevant (to my knowledge) to the existence of a black hole. Or are you saying that the Schwartzchild radius of the universe at the big bang was smaller than the big bang...
From a simple point of view, at the time of the big bang, the full energy/matter of the Universe should surely be within its Schwartzchild radius. Thus the entire Universe is within a huge black hole, and can never escape (i.e. is closed). Is this correct?
What about the period of inflation...