>>14
Well, "stuck in a fish tank" implies that there's something outside the fish tank that we could conceivably escape to. When you travel far enough around the Earth's surface, you end up in the same place, but you don't magically "pop out the other side" at any point; there are no edges on a spherical surface, and no center, so there's nothing to pop out of. The universe is like that except in 3 dimensions instead of 2. You go far enough one way and you could conceivably end up back in the same place, but that doesn't mean you "popped out one end" of space, because there is no end. You just traveled around this 3 dimensional surface that curves back on itself.