Carl Sagan

For me, it is far better to grasp the Universe as it really is than to persist in delusion, however satisfying and reassuring.

I've written a number of books that have to do with the evolution of humans, human intelligence, human emotions.

Most of the people that I deal with are human. So I've had a lot of experience with that.

No other planet in the solar system is a suitable home for human beings; it's this world or nothing. That's a very powerful perception.

The professed function of the nuclear weapons on each side is to prevent the other side from using their nuclear weapons. If that's all it is, then we've gotta as: how many nuclear weapons do you need to do that?

We are not without empathetic terror when we open Pascal's 'Pensees' and read, 'I am the great silent spaces between worlds.'

The universe seems neither benign nor hostile, merely indifferent.

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.

The boundary between space and the earth is purely arbitrary. And I'll probably always be interested in this planet - it's my favorite.

All of the books in the world contain no more information than is broadcast as video in a single large American city in a single year. Not all bits have equal value.

We hunger to understand, so we invent myths about how we imagine the world is constructed - and they're, of course, based upon what we know, which is ourselves and other animals. So we make up stories about how the world was hatched from a cosmic egg or created after the mating of cosmic deities or by some fiat of a powerful being.

You probably don't need more weapons than what's required to destroy every city on earth. There's only 2,300 cities. So, the United States, by that criteria, only needs 2,300 nuclear weapons - well, we've got more than 25,000!

There is a wide, yawning black infinity. In every direction, the extension is endless; the sensation of depth is overwhelming. And the darkness is immortal. Where light exists, it is pure, blazing, fierce; but light exists almost nowhere, and the blackness itself is also pure and blazing and fierce.

Skeptical scrutiny is the means, in both science and religion, by which deep thoughts can be winnowed from deep nonsense.

We start out a million years ago in a small community on some grassy plain; we hunt animals, have children, and develop a rich social, sexual, and intellectual life, but we know almost nothing about our surroundings.

I am often amazed at how much more capability and enthusiasm for science there is among elementary school youngsters than among college students.

A celibate clergy is an especially good idea, because it tends to suppress any hereditary propensity toward fanaticism.

Personally, I would be delighted if there were a life after death, especially if it permitted me to continue to learn about this world and others, if it gave me a chance to discover how history turns out.

Even these stars, which seem so numerous, are as sand, as dust - or less than dust - in the enormity of the space in which there is nothing.

We've arranged a civilization in which most crucial elements profoundly depend on science and technology.