Suppose that you were a 2-dimensional being: you're flat, like a drawing on a piece of paper, ok? Just
suppose that, all right? Now, suppose that you lived, not on the flat surface of a piece of paper, but on
the surface of a huge sphere, a ball. Ok? You're on a teeny bit of that ball, and because you're flat,
you can't look up off the ball. You can only look around on its surface, even though the ball, a sphere,
is 3-dimensional. You don't see that, just the surface (there's an old book, called "Flatland", by a guy
named Abbot, that you might try to get for a bit more on this). You can inferthat it's a sphere, by
taking various measurements... but you can't see it, because you're stuck on the surface. Are you
with me? Now. You can look far off, but still on the surface of the ball, and things fade out... it's a big
ball, and you can't see around it (otherwise you'd see the back of your 2-dimensional body)... it's just
too big. You ask, "Is there something at the edge of the universe?"
Well, weare beings on the surface of a 4-dimensional sphere (actually there may be more than that...
but we don't need to think about that to deal with this question). But since we're stuck on the surface,
that surface, which is 3-dimensional, is all we see. We don't see into the 4th dimension to see it as a
sphere, just as the flatties, above, don't see into the 3rd dimension from the surface of theirsphere.
We inferthat it's 4-dimensional. So... is there something at the edge of the universe?