Hello, as the title states I'm looking for some help understanding some things about the Big Bang that I'm sure the people here would know. I apologise if this is posted in the wrong section -- I wasn't quite sure where to make it. It's said that the Universe, immediately after the big bang, was incredibly hot and began to expand rapidly. What temperature was it, immediately after the big bang? And, how was such a thing calculated? How fast did it begin expanding, and how was that calculated also? I guess, I'm generally asking for anything to read or watch that could really extend my knowledge of the Big Bang. I definitely welcome as many maths calculations and equations as possible. Anything would help, really. Thank you.