If an alien lands on your front lawn and extends an appendage as a gesture of greeting, before you get friendly, toss it an eightball. If the appendage explodes, then the alien was probably made of antimatter. If not, then you can proceed to take it to your leader.

The universe is hilarious! Like, Venus is 900 degrees. I could tell you it melts lead. But that's not as fun as saying, 'You can cook a pizza on the windowsill in nine seconds.' And next time my fans eat pizza, they're thinking of Venus!

We still refer to sunrise, sunset. That only has meaning if you think that Earth is in the center of things, and everything is moving around us. So even though we know intellectually Earth goes around the sun, the language is still pre-Copernican, as we would call it.

I'm often asked whether I believe in Global Warming. I now just reply with the question: "Do you believe in Gravity?"

Something bad happened on both Mars with its dried-up watercourses and Venus with its runaway greenhouse effect. Could something bad happen on Earth too? Our species currently turns row upon row of environmental knobs, without much regard to long-term consequences.

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.

I dream of a world where the truth is what shapes people's politics, rather than politics shaping what people think is true.