One of the nice things about math and science is it’s obvious, you get the answer or you don’t get the answer.

There are many aspects of time we just do not understand. That’s the thing about writing a popular book: You realize the things you understand because for those you can give a really simple explanation. But some things about time I just don’t know how to give simple explanations for, even though I can tell you mathematically what’s going on.

Science is a combination of theory and experiment and the two together are how you make progress.

Speculation and the exploration of ideas beyond what we know with certainty are what lead to progress.

Scientists actively approach the door to knowledge—the boundary of the domain of what we know. We question and explore and we change our views when facts and logic force us to do so. We are confident only in what we can verify through experiments or in what we can deduce from experimentally confirmed hypotheses.

When I was in school I liked math because all the problems had answers. Everything else seemed very subjective.

I did not set out to explain the extinction of the dinosaurs. I'm a particle physicist, and I was actually thinking about dark matter along with some collaborators.