"By looking far out into space we are also looking far back into time, back toward the horizon of the universe, back toward the epoch of the Big Bang."

"A galaxy is composed of gas and dust and stars - billions upon billions of stars. Every star may be a sun to someone."

"In the vastness of space and the immensity of time, it is my joy to share a planet and an epoch with Annie. [Dedication to Sagan's wife, Ann Druyan, in Cosmos]"

"We are star stuff harvesting sunlight."

"Atoms are mainly empty space. Matter is composed chiefly of nothing."

"The universe is a pretty big place. If it's just us, seems like an awful waste of space."

"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."

"When we can demonstrate that we can take off horizontally and put something into orbit, then we can begin to talk about increasing the amount of payload. But to say, 'I'm going to do that and put people into orbit' is a real leap."

"As we begin to have landings on the moon, we can alternate those with vertical launch of similar crew modules on similar launch vehicles for vertical-launch tourism in space, if you want to call it that... adventure travel."

"I'm urging NASA to foster the development of what I call 'runway landers.' No, that's not the name of a high stakes gambler from Vegas. It's a type of spacecraft that flies to orbit like the retiring Shuttles but then glides to a landing like an airplane on a runway. Just like the Shuttles do."

"When you go to Mars, you need to have made the decision that you're there permanently. The more people we have there, the more it can become a sustaining environment. Except for very rare exceptions, the people who go to Mars shouldn't be coming back. Once you get on the surface, you're there."

"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."

"Just as Mars - a desert planet - gives us insights into global climate change on Earth, the promise awaits for bringing back to life portions of the Red Planet through the application of Earth Science to its similar chemistry, possibly reawakening its life-bearing potential."

"What are you going to do with astronauts who first reach the surface of Mars and then turn around and rocket back home-ward? What are they going to do, write their memoirs? Would they go again? Having them repeat the voyage, in my view, is dim-witted. Why don't they stay there on Mars?"

"NASA's been one of the most successful public investments in motivating students to do well and achieve all they can achieve, and it's sad that we are turning the program in a direction where it will reduce the amount of motivation it provides to young people."

"You need propellants to accelerate toward Mars, then to decelerate at Mars, again to re-accelerate from Mars to Earth, and finally to decelerate back at Earth. Accordingly, the mass of these required propellants, in short, drives our need for innovative launch vehicles."

"Bringing an asteroid back to Earth? What's that have to do with space exploration? If we were moving outward from there, and an asteroid is a good stopping point, then fine. But now it's turned into a whole planetary defense exercise at the cost of our outward exploration."

"If we go back to the moon, we're guaranteed second, maybe third place because while we are spending all that money, Russia has its eye on Mars. Landing people on the moon will be terribly consuming of resources we don't have. It sounds great - 'Let's go back. This time we're going to stay.' I don't know why you would want to stay on the moon."

"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."

"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."

"There's a historical milestone in the fact that our Apollo 11 landing on the moon took place a mere 66 years after the Wright Brothers' first flight."

"I didn't start skiing until I was 50. My wife Lois taught me how to ski. I'm proficiently conservative."

"When I was a little kid, we only knew about our nine planets. Since then, we've downgraded Pluto but have discovered that other solar systems and stars are common. So life is probably quite prevalent."