Negative time

Hopefully this is the right forum, am new.

I was imagining the shockwave propagating outward from the point of origin when space and time erupted, along all three spatial axes in all directions "up and down", "forward and back", "left and right". And, similarly, along axis of time - again both directions "forward and back". I'm not sure I'm exactly suggesting two spatial universes "moving" away from one another along axis of time, if so, the "other" would likely function as ours (causality-wise), perhaps even occupy same "space", just would be "moving" in "opposite" direction from the point(s) of origin in the fourth dimension. Either way, I was wondering, couldn't the essentially four-dimensional expansion from the point(s) of origin be along all four axes radially outward in all directions - including both directions of time? Thanks for answers.