Going into orbit around Earth - where the space station is today, and where the space shuttles and John Glenn and all those folks go-that's three-eighths of an inch above a schoolroom globe, just FYI. That's not very far from Earth. Yes, you are off Earth, but you're not really going anywhere yet. The moon was the only real destination.

My investment of time, as an educator, in my judgment, is best served teaching people how to think about the world around them. Teach them how to pose a question. How to judge whether one thing is true versus another.

I don't want people to say, 'Something is true because Tyson says it is true.' That's not critical thinking.

Some molecules - ammonia, carbon dioxide, water - show up everywhere in the universe, whether life is present or not. But others pop up especially in the presence of life itself. Among the biomarkers in Earth's atmosphere are ozone-destroying chlorofluorocarbons from aerosol sprays, vapor from mineral solvents, escaped coolants from refrigerators and air conditioners, and smog from the burning of fossil fuels. No other way to read that list: sure signs of the absence of intelligence.

Italy valued cathedrals while Spain valued explorers. So worldwide, five times as many people speak Spanish than Italian.

Some air you inhale was exhaled by Cleopatra.

I remain fearless of airplanes after 9/11. But during a trip to Los Angeles on a Boeing 767, I couldn't keep my mind from drifting: What's the largest piece of this airplane that could crash into the World Trade Center, explode out the other side, and survive intact? The landing gear? My computer battery? My belt buckle? My wedding ring?