## The size of the universe at the big bang?

 Quote by justsomeguy Marcus Post #20 in the balloon sticky answers that question pretty well. Short answer: Yes, the universe was expanding faster than the speed of light at that time.
That was very informative! Thank you.

 Quote by phinds Then you did not read it in a refereed article but in some popularization, since it is not true
Probably so.

 Quote by phinds No, it EXAPANDED enough, not condensed, that the plasma fell out into matter and let the light through
I obviously meant to say that matter condensed enough to let light through.

Anyway thanks for all the answers.

This might be dumb but it is just a thought. If we say the universe was infinitely small at the big bang, it should never be able to grow into finite size right? Just like an infinite size should not be able to contract into a finite size?

 Quote by Dead Boss Sorry, I misunderstood you. But I still don't see how your claim follows from the paper you provided.
It follows from their analysis, whose details I do not know entirely. But the quote I mentioned before translates exactly into the claim. Basically you get an estimate for the probability distribution for the curvature density parameter $\Omega_K$. This distribution is roughly Gaussian. For a Gaussian distribution, the probability of being 1.5 standard deviations away from the mean is 7%. Hence the probability 100-7 = 93%.

 Quote by clamtrox It follows from their analysis, whose details I do not know entirely. But the quote I mentioned before translates exactly into the claim. Basically you get an estimate for the probability distribution for the curvature density parameter $\Omega_K$. This distribution is roughly Gaussian. For a Gaussian distribution, the probability of being 1.5 standard deviations away from the mean is 7%. Hence the probability 100-7 = 93%.
Thanks, now I understand where the 7% comes from. But I still don't get why negative curvature means finite universe. Can't infinite universe have negative curvature as well?

 Quote by JohnLuck This might be dumb but it is just a thought. If we say the universe was infinitely small at the big bang, it should never be able to grow into finite size right? Just like an infinite size should not be able to contract into a finite size?
OK, pick any number greater than zero for your size of the Universe. It is greater than zero, so it isn't infinitely small.

You can say something loose like "the series 1, 1/2, 1/4, 1/8, 1/16... becomes infinitely small as the series progresses." But no specific number in the series is infinitely small.