The "concept" I referred to as being an "outside" of space, not the actual big bang.

Obviously that sounds illogical but I mean "outside" as in an area defined as separate from our universe.

I was only partially responding to what you posted, Jack, and the part that was yours that I was aiming at was the "Big Bang is theoretical" part. If General Relativity is true, then Big Bang is mathematically proven.

Of course, but the Big Bang remains undefined nevertheless.

Defining the Big Bang as the expansion of something into nothing is the area that is undefined (but not theoretical, thank you for pointing that out).

Obviously it's very much impossible to define something we know so little of, but with that in mind, I have never read Stephen Hawkin's proof before, assuming you have, how precise can it possibly be and can we tell?

Also, is there a particular book on his proof? I'm actually very much interested in this