I have thoughts every day that are themselves tweets.

The methods and tools of science perennially breach barriers, granting me confidence that our epic march of insight into the operations of nature will continue without end.

We didn't go to the moon to explore or because it was in our DNA or because we're Americans. We went because we were at war and we felt a threat.

I would request that my body in death be buried not cremated, so that the energy content contained within it gets returned to the earth, so that flora and fauna can dine upon it, just as I have dined upon flora and fauna during my lifetime

I would expunge the word "aptitude" from our vocabulary, because if you're interested in something, that's all that matters. You'll spend more time doing it, that than anything else, and possibly more time doing it than anybody else. And that's all that matters, because in the end, if you love what you do, you'll be your best at it compared to anything else you might have chosen as a career.

The number of people in the world engaged in this search for catastrophic impactors totals one or two dozen. How long into the future are you willing to protect Homo sapiens on Earth? Before you answer that question, take a detour to Arizona's Meteor Crater during your next vacation.

During the 1970s and 1980s, the popular television soap opera As The World Turns portrayed sunrise during the opening credits and sunset during the closing credits... The soap-opera sunrise showed the sun moving toward the left as it rose rather than to the right. They obviously had gotten a piece of film showing a sunset and played it in reverse... Had they called their local astrophysicists, any one of us might have recommended that if they needed to save money, they could have shown the sunset in a mirror before they showed it running backward.