Clown

Well, recall that the surface by definition, is 2 dimensional. It has no center and no edge. You need to go into the 3rd dimension to find an edge, but by then we aren't talking about surfaces anymore, as we've moved onto volumes. Imagining a universe that has a curved volume is not possible with human brains. Much worse, unlike the balloon, there is no "inside" or "outside" in the 4th dimension that universe is embedded in. Useless intuition.

The surface of the balloon does not have a boundary though. Of course our eyes can't help but focusing on that, since we are used to everything having an inside and outside.

NSX, Where is the edge on the surface of a balloon? What happens if you start to inflate the balloon? Does is have an edge or a center then? That's a pretty good analogy used for the real universe.