And what if the universe was finite? I mean, couldn't we imagine that what we call "universe" (all existing mass and energy) has limits? Not physical limits (something we could touch), but some kind of limit behind which there is no existence (I haven't said there is nothing, or emptiness. Just that speaking of something behind that limit would have no sense). What if, when the Big Bang happened from the original singularity, it created "its" own space and time? By essence, "behind it" would have no meaning, as it would be everything, without exception. In that condition, even the "where the Big Bang took place?" would have no meaning.
I personally don't believe of any supra-being or so-hidden God somewhere, but what I am deeply sure is that there is some part of the Reality that we cannot reach (or even think about), because we belong to this universe. If I may compare, I would say that we are like a baby in the center in a huge room, surrounded by a unique wall without windows or doors. Steps by steps, eventually we will arrive at a point where we'll understand the presence of the wall (perhaps even see it?), but we have nothing (and, as I believe, will never have) to cross or see through that wall.
So in short, I believe that the universe is finite, but not "in" something bigger. And don't ask, I am absolutely unable to prove anything in what I said. To tell the truth, I'm not even sure to deeply understand what is the "space" and "time", I mean, in a more global scheme...