But how does people know that for sure without any certain proof to back it up.
Unless of course someone can produce someone as actually being there to give witness of how it actually happened.
Otherwise it's just playing a big guessing game
(The Big Bang didn't 'come about'. it wasn't caused. Spacetime, as a whole, simply exists.) But how do you know that for sure, without any certain proof of evidence.
All a person is doing is taking a big wild guess, without any certain proof that's how it happened.
Well, there is plenty of evidence that looking at space and time together as a single geometry is the right approach. That is the whole point of general relativity, our best description of gravity.
We have very detailed scientific theories that are incredibly accurate with, yes, plenty of evidence to back them up, that show causality is part of the universe, not something outside of it.
We know that there are events that are uncaused. There is NOTHING prior to the events that makes those events happen: they just happen anyway.
From what I can see, you like to label ideas as 'guesses' even if there is an incredible amount of evidence extending back over a century in support of them, including detailed mathematical predictions that are verified by actual observations.