"I'm substantially concerned about the policy directions of the space agency. We have a situation in the U.S. where the White House and Congress are at odds over what the future direction should be. They're sort of playing a game and NASA is the shuttlecock that they're hitting back and forth."

"Science has not yet mastered prophecy. We predict too much for the next year and yet far too little for the next 10."

"This is one small step for a man, one giant leap for mankind."

"I think we're going to the moon because it's in the nature of the human being to face challenges. It's by the nature of his deep inner soul... we're required to do these things just as salmon swim upstream."

"Nature teaches us a valuable lesson: a single spark of imagination can ignite the world."

"To prefer evil to good is not in human nature and when a man is compelled to choose one of two evils, no one will choose the greater when he might have the less."

"Chinese emissions are a problem not just for its own people but also for the world. It has now overtaken the U.S. as the biggest carbon emitter; most of the coal that is burned anywhere on Earth is burned in China."

"They've also asked me now to start on another series that we're gonna do after this Frontier Earth. But it's not science fiction, it's more in the Mystery and Crime division and that's another area I'm very interested in."