To live in the hearts of others is to never die in those we leave behind.

We are at a crossroads in human history. Never before has there been a moment so simultaneously perilous and promising. We are the first species to have taken evolution into our own hands.

But down deep, at the molecular heart of life we're essentially identical to trees.

Human history can be viewed as a slowly dawning awareness that we are members of a larger group.

I don't know the answer. Maybe no one knows. Maybe when you grow up, you'll be the first to find out.

If I finish a book a week, I will read only a few thousand books in my lifetime, about a tenth of a percent of the contents of the greatest libraries of our time. The trick is to know which books to read.

Not explaining science seems to me perverse. When you're in love, you want to tell the world.