There’s also the theory that it’s a 4d hypersphere, meaning reaching one “edge” will just be the same as making it to the opposite side and nothing else. I love this theory as it adds both an explanation for the expansion of space (the sphere itself is expanding, so all the 3d things are getting further apart) as well as possibly leaving a scientific space for a god. I am an atheist, but if we live in a 4 dimensional (or more) universe, a god could easily exist outside the 3d bounds of it, and would therefore be able to see and interact with any part of it.

Too bad this universal theory is likely untrue and these days not considered a prevailing theory. It just explains so much for me, and could even let string theory exist, but I think the math just doesn’t work out.