It appears to be expanding into at least a 4D space (which we can't visualize with our limited 3D perceptions). Is there an "edge" or "margin" in 4D? Not a clue. Maybe someone whom has done the math could say, since mathematics is the only way we can describe that dimension.

It has been over 60 years since I read the book “Flatland.” At least I think I read it; reading a quick summary on the web I have no recollection of the “romance” part of it, but I was intrigued by the premise: that there is a world where the characters live in 2-dimensions and cannot perceive the third. That is, their world is as flat as a sheet of paper, and nothing more.

So a 3D globe passing through their world is perceived as a circle, beginning as a dot, growing larger and larger until it becomes smaller and smaller and is once again a dot, and then disappears. Anything three dimensional is a line to them, since they can only see the intersecting plane of their sheet of paper.

It occurs to me that we are (and always will be) unable to visualize a fourth or higher dimension because we are the creatures of Flatland, doomed to forever see things only within our own abilities. We may build mathematical constructs but it is doubtful that many people will be able to follow or understand what the others are talking about (much less believe it.) “Hey Harry, tinfoil hat time. Did you hear 1pg talking about 4D? Ha ha ha.”

Anyway, my concept is not of another dimension, it is of total nothingness: no time, no space, no matter, no nothing - and then “somethingness” being created at the extremities, perhaps as it has been since the beginning. (No “big bang”, more of a “big creation event start”, which I think carries a different connotation.