Anything else you're interested in is not going to happen if you can't breathe the air and drink the water. Don't sit this one out. Do something. You are by accident of fate alive at an absolutely critical moment in the history of our planet.

The Earth is a very small stage in a vast cosmic arena.

Avoidable human misery is more often caused not so much by stupidity as by ignorance, particularly our ignorance about ourselves.

The Apollo pictures of the whole Earth conveyed to multitudes something well known to astronomers: On the scale of the worlds - to say nothing of stars or galaxies - humans are inconsequential, a thin film of life on an obscure and solitary lump of rock and metal

There is a reward structure in science that is very interesting: Our highest honors go to those who disprove the findings of the most revered among us. So Einstein is revered not just because he made so many fundamental contributions to science, but because he found an imperfection in the fundamental contribution of Isaac Newton.

My long-time view about Christianity is that it represents an amalgam of two seemingly immiscible parts-the religion of Jesus and the religion of Paul. Thomas Jefferson attempted to excise the Pauline parts of the New Testament. There wasn't much left when he was done, but it was an inspiring document.

Our passion for learning ... is our tool for survival.