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Might be a stupid question, but it has been bugging me for a week. Pre big bang conditions look like an universe mass black hole to me, so what force acted against the massive gravity at the beginning, making it expand?

Limiter
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    We dont' know anything about the big bang itself all of our current knowledge of physics breaks down at approximately $10^{-43}$ s after the big bang happened. We can speculate based on various models derived from theories of quantum gravity, but we have no definitive answers yet. – Zo the Relativist Dec 05 '14 at 20:57
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    Doesn't "pre big bang conditions" require there to be a pre big bang time in which conditions can be? – RedGrittyBrick Dec 05 '14 at 22:03
  • I think there are a number of unanswerable questions (1) Is the Big Bang an effect without a cause? (2) Was there an equal and opposite reaction, and if so, where did it go? (3) If a singularity is inherently unstable that it initiates a Big Bang, how could it ever have existed in a state of stability in the first place? – iantresman Dec 05 '14 at 22:22
  • Sometimes Big Bangs happen; sometimes they don't. When they don't, there's no universe full of strange creatures to wonder why they happen. ( :-) ) – Carl Witthoft Dec 05 '14 at 23:04
  • Pre big bang conditions look like an universe mass black hole to me - I find this a most remarkable statement. I do wonder with what faculty the OP has been able to 'see' said conditions. – Alfred Centauri Dec 06 '14 at 00:15

2 Answers2

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The Big Bang was not like a black hole. See the canonical question Did the Big Bang happen at a point? to see why.

The evolution of the universe from the Big Bang onwards is determined by the FLRW metric and the initial conditions. The FLRW metric is given to us by Einstein's equation, but we have no theory to explain why the initial conditions were what they were. At the moment we just have to accept them. Given that it's such a fundamental issue there have been many, many suggestions for how the universe managed to find itself in just the right initial state to evolve into the universe we see around us today. However these are all just speculation.

Community
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John Rennie
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There were no "pre big bang" conditions. Not physically and not even theoretically.

Time itself started with the big bang. How can there be a "time" before the start of time itself?

Imran Roy
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