In a theorized multiverse, how are "universes" separated from one other and can they influence each other?

In the kind of infinite space the likes of which we can't even conceive within our own boundaries of distance within our universe, space could be any number of "things" we don't know like the expanding of space time. In the end, although we like to say, yes we know and there are boundaries and things....The whole point of this question is maybe there aren't things that are so easy to comprehend. Maybe space time for how we could understand it now, infinitely expanding in it's own faster than light bubble, with rules and patterns that govern the shapes woven on it's cloth, maybe the real infinite is so complex and huge that there are trillions of these ever expanding self governing space times born from quantum fluctuations like a Boltzmann brain type of idea, where over long enough where time doesn't matter in our sense but just random things we can't explain in space we can't measure now, energy suddenly explodes into something we try to understand from within it. Distances that mean nothing other than the inconceivable infinite space and time between each one so that two may never meet in any one life span before individual entropy into the greater void, and if they do how would we know anything happened or if they ended from that interaction. The point is, we explain everything from what we know as fact from current observation. These questions, even though many will try to answer it from a singular big bang "only fact as we know it observation", which is likely just as right, may also not be so easy to explain. I'm full of shit but I'm also not either, no one knows. Right isn't wrong and vice versa in many ways when trying to think through this in a realistic sense outside of a conventional narrative that we can try to infer.

/r/askscience Thread Parent