The Big Bang initial state

Question

I saw the excellent answer here: Did the Big Bang happen at a point? but I have a hard time imagining the initial state. If the distances between all points in the universe were zero at the Big Bang, how is it not a single point in space?

Answer 1

We don't actually know what happened right at time 0 -- our present theories give a singularity there, an undefined point like dividing by 0. So it's not accurate to say it's a point, it's just something undefined. There is hope that a quantum theory of gravity might allow us to describe the beginning of the universe better, for example by providing a maximum density or other condition. But for any time $\epsilon > 0$ we can find in classical models a finite density of the universe, and space at that time is fully 3 dimensional. (It should be noted that the particular choice of time coordinates is somewhat arbitrary -- time is relative after all -- but the usual choice in cosmology is known as cosmic time in which the average density of the universe is uniform.)

Answer 2

We just mean that there are points of the universe outside of our observable universe, and those can be slightly outside of the position of the Big Bang that we all started from.