"Venus has a runaway greenhouse effect. I kind of want to know what happened there because we're twirling knobs here on Earth without knowing the consequences of it. Mars once had running water. It's bone dry today. Something bad happened there as well."
American astrophysicist and science communicator. He serves as director of the Hayden Planetarium in New York and has hosted and produced science programming and media. He is widely known for public education work in astronomy.