Question about the big bang
Why exactly is the common wisdom that the universe was one infinitely dense and there was no time before the big bang?
If I understand correctly, we get the idea from measuring the rate of expansion of the universe and then "running the simulation" backwards with that speed (Very sloppily speaking)
What I don't understand: If one had a similar measurement of a normal explosion, and were to run that simulation backwards one would definitely not reach such odd conclusions. Obviously for a host of other reasons, but maybe you get my point, which I guess is:
Why don't people conclude: It must have been extremely dense, with extremely strange states of matter, that our current models likely do not describe well, so basically we don't have any idea what exactly happened around that time...
Why be so sure about statements like, "time did not exist before the big bang" or "the universe was infinitely dense"?