Carl Sagan

Even Johannes Kepler, Isaac Newton, Charles Darwin, Gregor Mendel, and Albert Einstein made serious mistakes. But the scientific enterprise arranges things so that teamwork prevails: What one of us, even the most brilliant among us, misses, another of us, even someone much less celebrated and capable, may detect and rectify.

Who are we, if not measured by our impact on others? That’s who we are! We’re not who we say we are, we’re not who we want to be - we are the sum of the influence and impact that we have, in our lives, on others.

My fundamental premise about the brain is that its workings - what we sometimes call "mind" - are a consequence of its anatomy and physiology, and nothing more.

Every star may be a sun to someone.

After the earth dies, some 5 billion years from now, after it's burned to a crisp, or even swallowed by the Sun, there will be other worlds and stars and galaxies coming into being - and they will know nothing of a place once called Earth.

Our planet is a lonely speck in the great enveloping cosmic dark. In our obscurity, in all this vastness, there is no hint that help will come from elsewhere to save us from ourselves.

.. Think of the rivers of blood spilled by all those generals and emperors so that in glory and in triumph they could become the 'Momentary' masters of a 'Fraction' of a 'Dot'

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.

The prediction of nuclear winter is drawn not, of course, from any direct experience with the consequences of global nuclear war, but rather from an investigation of the governing physics.

Valid criticism does you a favor.

One glance at a book and you hear the voice of another person, perhaps someone dead for 1,000 years. To read is to voyage through time.

Books permit us to voyage through time, to tap the wisdom of our ancestors.

The Earth is a very small stage in a vast cosmic arena.

The brain is like a muscle. When it is in use we feel very good. Understanding is joyous.

The nuclear arms race is like two sworn enemies standing waist deep in gasoline, one with three matches, the other with five.

We are the representatives of the cosmos; we are an example of what hydrogen atoms can do, given 15 billion years of cosmic evolution.

We have also arranged things so that almost no one understands science and technology. This is a prescription for disaster. We might get away with it for a while, but sooner or later this combustible mixture of ignorance and power is going to blow up in our faces.

The dangers of not thinking clearly are much greater now than ever before. It's not that there's something new in our way of thinking - it's that credulous and confused thinking can be much more lethal in ways it was never before.

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.

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.

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