"There may be aliens in our Milky Way galaxy, and there are billions of other galaxies. The probability is almost certain that there is life somewhere in space."

"I still say, 'Shoot for the moon; you might get there.'"

"If we can conquer space, we can conquer childhood hunger."

"I think both the space shuttle program and the International Space Station program have not really lived up to their expectations."

"To move forward, what's required is a unified space agenda based on exploration, science, development, commerce, and security."

"I was motivated to improve the U.S. strategy of going back to the moon in 1985. That's a long time ago. Going back to the moon would be a great achievement for tourism adventure flights."

"We must still think of ourselves as pioneers to understand the importance of space."

"The much-hyped Ares 1-X was much ado about nothing."

"Being first outside the spacecraft would bring much more responsibility, and I really wasn't looking for that."

"The first footfalls on Mars will mark a historic milestone, an enterprise that requires human tenacity matched with technology to anchor ourselves on another world."

"It's time to open the space frontier to citizen explorers."

"The biggest benefit of Apollo was the inspiration it gave to a growing generation to get into science and aerospace."

"Walking around on the moon was significantly easier than we'd thought it would be. There weren't any balance problems, so you weren't tumbling over."

"I know: If you're looking down at Earth, you're looking through an atmosphere that has a bit of haze in many places and not just occasional clouds."

"Retain the vision for space exploration. If we turn our backs on the vision again, we're going to have to live in a secondary position in human space flight for the rest of the century."

"Going to Mars would evolve humankind into a two-planet species."

"Nobody ever asks who was the seventh person on the Moon. The only thing they know is who's number one and who's number two. Does anybody know who the last man was?"

"I think it's inevitable that there will be Earthlings establishing a presence on Mars. And I would say that it would certainly take place by 2050 or shortly thereafter."

"Exploring Mars is a far different venture from Apollo expeditions to the moon; it necessitates leaving our home planet on lengthy missions with a constrained return capability."

"My first inclination is to be a bit skeptical about the claims that human-produced carbon dioxide is the direct contributor to global warming."

"When science, art, literature, and philosophy are simply the manifestation of personality they are on a level where glorious and dazzling achievements are possible, which can make a man's name live for thousands of years. But above this level, far above,"

"A science which does not bring us nearer to God is worthless."

"Whether a person shows themselves to be a genius in science or in writing a song, the only point is, whether the thought, the discovery, or the deed, is living and can live on."

"Science has been seriously retarded by the study of what is not worth knowing and of what is not knowable."