[pmontra]

Wouldn't the center be the Big Bang and the 3D Universe at the current time (if Relativity lets me write about a current time) be the 3D surface of the 4D sphere (or spheroid) that the Big Bang is creating by keeping to expand?

[eggn00dles]

the big bang happened everywhere

[defrost]

With the caveat that by some awkward metric 'everywhere' was much smaller when it happened.

[gitaarik]

Well, that depends whether the universe is infinite. In any case, everything was closer together and hotter.

[defrost]

Infinities come with a spectrum, some are smaller than others . . .

[s1artibartfast]

and some universes are finite.

[nitwit005]

It's more correct to just say location had no meaning until something existed in the universe.

There's really no way to know if there was something in existence before the big bang however. We just lack evidence of such a thing.

[Certhas]

I think "the big bang happened everywhere" is more correct than your take. The big bang dlrefers to the early period of a spacetime with an initial moment. At that initial moment the distance between all points is zero. But there still are a full 3d set of locations. Starting at this initial moment, distances between points grow quickly. Thats the bang.

It is true that in GR you can't speak of "before" the big bang, but the big bang itself is a feature within time. It happens at the first moments of time and everywhere in space. And if you replace the initial singularity with a dense quantum foam and thus are able to extend time into the past in some quantum sense, the big bang doesn't go away.