That actually doesn't have to be a problem at all, as the more we've come to learn from what we think of 'empty space', the more we've found out it's actually not truly empty at all.

Quantum effects constantly produce particles and antiparticles "out of nothing," only to have them disappear few moments later. And space itself can either be almost flat or curved, depending on the amount of matter it contains.

I think whenever entropy seems like a problem, it's probably solved by how things work on a (multi-dimensional) quantum level anyway.



I don't believe in invisible walls either, but from the perspective of logic there doesn't have to be a brick wall at the end that would end our 3-dimensional experience of our universe.

If time and space just curves around into a sphere, we wouldn't even notice that we're in a limited space as if we're swimming in a gigantic fish bowl.

I don't think anything 'outside' of such a curved space would be definable, even though we're used to the concept of things 'inside' and 'outside' of something.

Why does there have to be anything 'outside' of a potential limited universe? From a perspective of logic, there's no reason to as far as I can tell.

Then again, if something expands, it will need theoretical room to do so. Hence at some point there must be a solution to our dimensional space in whatever bigger existential frame everything might float.