The Time 100

Alan Stern: “The combination of hands-on and bureaucratic experience gives him a unique feel for the physics responsible for getting machines off the ground and the politics responsible for keeping them flying.”

John Mather: “It was his analysis of COBE data that earned him the 2006 Nobel, which he shared with University of California cosmologist George Smoot.”

Neil deGrasse Tyson: “You can think of Neil deGrasse Tyson as the Carl Sagan of the 21st centuryas long as you envision a Sagan who’s muscular, African American and as cool as his predecessor was geeky.”

Richard Branson: “Virgin Galactic, Richard’s foray into commercial spaceflight, may seem like the ultimate quest. A final stamp on an amazing career. It won’t be. He will hear about something that everyone else thinks is outrageous and make it a reality.”

Tullis Onstott: “Wondering whether extraterrestrial life exists? Tullis Onstott, 53, has found itsort of. The fact that the living things he’s discovered make their homes nearly two miles below the earth’s surface may disqualify them from the extra part of extraterrestrial.”