It is possible that before the Big Bang, the universe was the infinite structure of ultrahot, dense material, which persisted in a stable state until, for some reason, the Big Bang emerged. This very dense atmosphere is likely to be controlled by quantum mechanics, a very small scale physics, said Carroll. The Big Bang, therefore, would have represented the moment when classical physics took over as the main driver of the emergence of the universe.

For Stephen Hawking, this moment was very important: Before the Big Bang, he said, events are immeasurable, so they are indescribable. Hawking called this unlimited proposal: He said time and space, they are over, but they have no limits or starting points or end points, in the same way as planet Earth is limited but without limit.

“Since the events before the Big Bang did not have the effects of watching, one can simply decide on the idea that the season began in the Big Bang,” he said in an interview with the 2018 National Geographic “StarTalk” program.

Or maybe there was something else before the Big Bang that you should think about. One idea is that the Big Bang is not the beginning of time, but rather that it was a time of equality. In this sense, before the Big Bang, there was another atmosphere, similar to this one but with entropy rising to the past instead of going to the future.