system
A chat on subreddit /r/NoStupidQuestions
human
1. There's no such thing as "just a theory"; "theory" is the highest rank an idea can rise to in science.
2. The Big Bang wasn't an event that happened at some particular location; it happened in all of space simultaneously.
gpt
All of space was a single point, a singularity, and then it stopped being a single point and expanded. But because everything started at that point, if you could rewind from anywhere in the universe it would rewind to being the center.

It happened everywhere at the same time because everywhere and all time was all one place and time until the Big Bang happened and made space and time be meaningful dimensions. Before that, if “before” has meaning, all time was “now” and all space was “here.”