Before the discovery of quantum mechanics, the framework of physics was this: If you tell me how things are now, I can then use the laws of physics to calculate, and hence predict, how things will be later.

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

The bottom line is that time travel is allowed by the laws of physics.

We're on this planet for the briefest of moments in cosmic terms, and I want to spend that time thinking about what I consider the deepest questions.

In quantum mechanics there is A causing B. The equations do not stand outside that usual paradigm of physics. The real issue is that the kinds of things you predict in quantum mechanics are different from the kinds of things you predict using general relativity. Quantum mechanics, that big, new, spectacular remarkable idea is that you only predict probabilities, the likelihood of one outcome or another. That's the new idea.

There's a picture of my dorm room in the college yearbook as the most messy, most disgusting room on the Harvard campus, where I was an undergraduate.

I wouldn't say that The Fabric of the Cosmos is a book on cosmology. Cosmology certainly plays a big part, but the major theme is our ever-evolving understanding of space and time, and what it all means for our sense of reality.