What is the universe? I don't know, but two of the properties the universe has, it seems to me, are all-encompassing and endlessness. I mean, everything that exists must be "inside" the universe, and (2) there is no such thing as the "far edge" of the universe. Again, we face the same paradox as we did with the nature of God: we can somehow believe (or accept) that every single particle that exists is somewhere in the universe, but that there is no "end" or "edge" to the universe takes a bit more work. It's not something our human minds can explain logically. Maybe we have to take that on faith too.
With God (or the universe, for that matter) we can accept that it has no end, but EVERYTHING has a beginning, right? Somehow, someplace, sometime. The logic problem with the universe is a bit opposite from the God paradox in that we have trouble believing it is endless. Our minds tell us that if we travel fast enough and far enough and long enough, we are going to reach the far "wall" of the universe. We seem to believe everything has boundaries. But if there is a wall, then there is something on the other side of that wall.
If it is not a wall, but some sort of Star Trek "barrier" or "force field" and we step outside the universe a couple of steps, then return... where were we?
Maybe nowhere. Maybe we were just at the library with our head resting on the table asleep until the bell rings.