Carl Sagan

One of the greatest gifts adults can give - to their offspring and to their society - is to read to children.

If all the suns but ours collapsed tonight, how many lifetimes would it take us to realize that we were alone?

There are huge advertising budgets only when there's no difference between the products. If the products really were different, people would buy the one that's better. Advertising teaches people not to trust their judgment. Advertising teaches people to be stupid.

The dumbing down of America is evident in the slow decay of substantive content, a kind of celebration of ignorance.

That we can now think of no mechanism for astrology is relevant but unconvincing. No mechanism was known, for example, for continental drift when it was proposed by Wegener. Nevertheless, we see that Wegener was right, and those who objected on the grounds of unavailable mechanism were wrong.

'In his celebrated book, 'On Liberty', the English philosopher John Stuart Mill argued that silencing an opinion is "a peculiar evil." If the opinion is right, we are robbed of the "opportunity of exchanging error for truth"; and if it's wrong, we are deprived of a deeper understanding of the truth in its "collision with error." If we know only our own side of the argument, we hardly know even that: it becomes stale, soon learned by rote, untested, a pallid and lifeless truth.'

We are star stuff harvesting sunlight.

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

Our ancestors worshipped the Sun, and they were not that foolish. It makes sense to revere the Sun and the stars, for we are their children.

We live in a society exquisitely dependent on science and technology, in which hardly anyone knows anything about science and technology.

Too much openness and you accept every notion, idea, and hypothesis-which is tantamount to knowing nothing. Too much skepticism-especially rejection of new ideas before they are adequately tested-and you're not only unpleasantly grumpy, but also closed to the advance of science. A judicious mix is what we need.

We are the product of 4.5 billion years of fortuitous, slow biological evolution. There is no reason to think that the evolutionary process has stopped. Man is a transitional animal. He is not the climax of creation.

For all our failings, despite our limitations and fallibilities, we humans are capable of greatness.

Imagine we could accelerate continuously at 1 g-what we're comfortable with on good old terra firma-to the midpoint of our voyage, and decelerate continuously at 1 g until we arrive at our destination. It would take a day to get to Mars, a week and a half to Pluto, a year to the Oort Cloud, and a few years to the nearest stars.

The cannabis experience has greatly improved my appreciation for art, a subject which I had never much appreciated before.

Our passion for learning ... is our tool for survival.

I can find in my undergraduate classes, bright students who do not know that the stars rise and set at night, or even that the Sun is a star.

This oak tree and me, we're made of the same stuff.

We are...capable of using our compassion and our intelligence, our technology and our wealth, to make an abundant and meaningful life for every inhabitant of this planet. To enhance enormously our understanding of the Universe, and to carry us to the stars.

Centuries hence, when current social and political problems may seem as remote as the problems of the Thirty Years' War are to us, our age may be remembered chiefly for one fact: It was the time when the inhabitants of the earth first made contact with the vast cosmos in which their small planet is embedded.

We are rare and precious because we are alive, because we can think as well as we can. We are privileged to influence and perhaps control our future. I believe we have an obligation to fight for life on Earth - not just for ourselves, but for all those, humans and others, who came before us, and to whom we are beholden, and for all those who, if we are wise enough, will come after.