I think I'd fall down onto the back of a turtle.
I'm not mathematician or physicist. But I can imagine that space may warp at the edges of a brane making it impossible to get out. Maybe space is sphere shaped. I'll let you know when it becomes relevant.
This is entirely possible. It could be that by flying straight in a direction, you go back to where you were. Whether your left and right shoe you left behind will still fit with your left and right foot, is to be seen. Maybe the Universe is just a huge Moebius stripe, who knows.
That would be a closed Universe, ergo a Universe with a geometry such that a huge triangle would have less than pi as the sum of its internal angles. Like on the surface of the earth. An ant on earth would also go back to where it was if it walked straight.
Observations seem to corroborate the hypothesys that we live in a large scale flat Universe. Ergo one on the very fine edge between being finite and infinite, while being still infinite. And, as such, a Universe whose total energy is zero. I personally believe that this is the only geometry it can have, on account of energy conservation. I think most physicists would agree.
How a Universe, which allegedely "started" very small can be infinite, is left as a simple exercise to the reader.
Ciao
- viole