Sean Carroll

You know, hanging out on the wrong street corners.

I don't know where they pick these things up.

But yes, this is all driven by the very famous philosophy question.

Why is the past different from the future?

Why is there an arrow of time?

Because the fundamental laws of physics have no arrow of time in them.

The answer is entropy and the second law of thermodynamics.

The universe used to be more organized, lower in entropy.

The whole history of the universe is just entropy increasing, disorder and chaos developing all around.

It's not your fault necessarily, but you're contributing to the disorder and chaos all around us.

And that started about 14 billion years ago near the Big Bang.

At the moment of the beginning of the universe, our universe was exquisitely orderly.

It doesn't necessarily look that way, but you run through the numbers and it's true.

Why?

Why?

Why is that true?

Why was the early universe so orderly?

And so I've long wondered about this.

And I wrote a paper years ago now with a woman who was a graduate student of mine at the time, Jennifer Chen, where we proposed that the Big Bang was not the beginning.

of our universe.