"Avoidable human misery is more often caused not so much by stupidity as by ignorance, particularly our ignorance about ourselves."

"Books break the shackles of time, proof that humans can work magic."

"It is of interest to note that while some dolphins are reported to have learned English - up to fifty words used in correct context - no human being has been reported to have learned dolphinese."

"Every one of us is, in the cosmic perspective, precious. If a human disagrees with you, let him live. In a hundred billion galaxies, you will not find another."

"One of the most tragic things I know about human nature is that all of us tend to put off living. We are all dreaming of some magical rose garden over the horizon instead of enjoying the roses that are blooming outside our windows today."

"I think I've become more comfortable about being a human being."

"One of the most tragic things I know about human nature is that all of us tend to put off living. We are all dreaming of some magical rose garden over the horizon-instead of enjoying the roses blooming outside our windows today."

"I think story-telling is innate in human beings, it's something that we've done since we scrawled across cave walls."

"The leader of an Earth organization who makes a commitment to history - of humans living on Earth, to begin permanent settlement/occupation of not the moon, but of another planet - this leader will have a legacy for history that will supersede Columbus, Genghis Khan or almost any recognized leader."

"The purpose of going to Mars is for humans to first begin to occupy, permanently, another planet in the solar system. The astronauts or pilgrims, whatever you might call them, are going to be very historically unique human beings."

"Globalisation means many other countries are asserting themselves and trying to take over leadership. Please don't ask Americans to let others assume the leadership of human exploration. We can do wonderful science on the Moon, and wonderful commercial things. Then we can pack up and move on to Mars."

"I think humans will reach Mars, and I would like to see it happen in my lifetime."

"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."

"I am excited to think that the development of commercial capabilities to send humans into low Earth orbit will likely result in so many more Earthlings being able to experience the transformative power of space flight."

"Space architectures capable of supporting a permanent human presence on Mars are extraordinarily complex, with many different interdependent systems."

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

"Can you imagine, in 2030, taking a space cruise on the very ship that carried the first human beings to Mars? I can't believe that people wouldn't line up for that possibility."

"A hybrid human-robot mission to investigate an asteroid affords a realistic opportunity to demonstrate new technological capabilities for future deep-space travel and to test spacecraft for long-duration spaceflight."

"To send humans back to the moon would not be advancing. It would be more than 50 years after the first moon landing when we got there, and we'd probably be welcomed by the Chinese. But we should return to the moon without astronauts and build, with robots, an international lunar base, so that we know how to build a base on Mars robotically."

"At the bottom of the heart of every human being, from earliest infancy until the tomb, there is something that goes on indomitably expecting, in the teeth of all experience of crimes committed, suffered, and witnessed, that good and not evil will be done"

"Humanism was not wrong in thinking that truth, beauty, liberty, and equality are of infinite value, but in thinking that man can get them for himself without grace."

"Whatever debases the intelligence degrades the entire human being."

"It is an eternal obligation toward the human being not to let him suffer from hunger when one has a chance of coming to his assistance."