“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 of the late 20th and early 21st centuries, he bridges complex cosmic concepts for broad audiences. His work on the Cosmos television series and public lectures makes astronomy accessible, while his writings and media appearances champion evidence-based reasoning and critical thinking.