[sirchtruth]

We don't know, because everything that we know about spacetime breaks down under the conditions of the Big Bang.

Ok, how do we know it "breaks" down, and what the conditions were of the BB?

I'm not following...unless you are talking about dimensions yet discovered?

[ahayes]

Ok, how do we know it "breaks" down, and what the conditions were of the BB?

Because spacetime curvature goes to infinity, and our current models can't cope with this.

If you're interested in singularities you might read Kip Thorpe's Black Holes and Time Warps. It's very interesting and accessible. Of course this is chiefly about black holes and the Big Bang was more like a white hole if anything, but it gives you some idea why we can't really say much about the nature of a singularity.