“The messy reality of it is that all of these very smart people, including Isaac Newton, were talking to other people.”

“The universe clicks along in perfect accord with the laws of physics forever.”

"Could black holes be the key to a quantum theory of gravity, a deeper theory of how reality, of how space and time works? Well, I think so."

How can the brain — a piece of matter — love? Physics and chemistry explain the material world, but they can’t explain why it feels like something to be alive. This is the mystery of consciousness, according to these experts.

“I like to say that physics is hard because physics is easy, by which I mean we actually think about physics as students.”

“You can be aware of sadness from a point of view that is not merely sad, and you can be aware of fear from a point of view that's not merely afraid.”

"It's a very, very beautiful calculation, but it's the best example I know of the relationship between these rather abstract quantities perhaps and something that you can look at in a telescope."