system
Given the following post, respond as if you're commenting on Reddit:
human
Could the Big Bang be a local phenomenon?

I know little about M-Theory, but I recall that it explains the big bang as two branes colliding, and the apparent expansion of the (visible, aka local) universe via the ripples in the brane smoothing back out (like pulling flat a crumpled napkin). Wouldn't this mean that the Big Bang was a local phenomenon that did not create the universe, but simply added energy (and therefore matter) to it? And that there could be other "Big Bangs" elsewhere, and at other times? Or am I misunderstanding?
gpt
The big bang was inherently local, but in a way that's perhaps different from what you're thinking. All of space and time came into existence at the big bang, and all points in space were infinitesimally close to each other. If you were to stand still and rewind time backwards, the big bang would appear to happen from exactly where you are, no matter where you are, since all points in space were at essentially the same place at the time of the "bang."

M-theory seeks to explain this with higher dimensional branes, which complicate your notion of "local." In a 3D sense, the big bang happened everywhere, but in a higher dimensional case that may not be strictly true.