Quote Originally Posted by wendylove View Post
Entropy has to be really low at the time of the big bang, so no explosion.
Agree..

It amazes me however, considering the Universe itself has a well-defined thermodynamic arrow of time. But this doesn't address the question of why the initial state of the universe was that of low entropy? If cosmic expansion were to halt and reverse due to gravity, the temperature of the Universe would once again increase, but its entropy would continue to increase due to the continued growth of perturbations and eventually blackhole formation. Kind of makes you wonder.