[greenslime (OP)]

Would it be like a game of Asteroids where you pop out the other side or something like Earth where you just go round and round?

[Mad Mark]

We are already on the edge of the universe. If you want to go inside you got to go back in time.If you want to have a quick stroll outside our universe you got to pop into the future.

[Soul Surfer]

This is a question that has exercised many great minds for a long time and there is no answer at the moment although there have been several false alarms where people have thought that they have spotted evidence that our universe is a closed structure like the surface of the earth  but in three or four dimensions.

[graham.d]

I don't think there is any evidence to suggest the universe is "bounded" so the concept of an edge has no meaning in any usual interpretation of the word. The universe should really be considered as having at least 4 dimensions with some recent theories postulating 5 dimensions. With just 4 dimensions the universe can be either infinite (and maybe flat) or closed (as SS describes) and finite. The evidence at the moment suggests it is "flat" (a Minkowski metric) but this view fluctuates wildly with various theories about the nature of dark matter (which seems sufficient to close the universe) and dark energy.

[yor_on]

Maybe it only exists in our minds