Physics grapples with the largest questions the universe presents. Where did the totality of reality come from? Did time have a beginning?

It's hard to teach passionately about something that you don't have a passion for.

I like 'The Simpsons' quite a lot. I love the irreverent character of the whole show. It's great.

When you buy a jacket, you pick the size to ensure it fits. Similarly, we live in a universe in which the amount of dark energy fits our biological make-up. If the amount of dark energy were substantially different from what we've measured, the environmental conditions would be inhospitable to our form of life.

Most scientists like to operate in the context of economy. If you don't need an explanatory principle, don't invoke it.

The central idea of string theory is quite straightforward. If you examine any piece of matter ever more finely, at first you'll find molecules, atoms, sub-atomic particles. Probe the smaller particles, you'll find something else, a tiny vibrating filament of energy, a little tiny vibrating string.

My best teachers were not the ones who knew all the answers, but those who were deeply excited by questions they couldn't answer.