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The universe seems neither benign nor hostile, merely indifferent.

Carl Sagan

Absence of evidence is not evidence of absence.

Carl Sagan

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

Carl Sagan

It is far better to grasp the universe as it really is than to persist in delusion, however satisfying and reassuring.

Carl Sagan


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.

Carl Sagan

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

Carl Sagan

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.

Carl Sagan

When you make the finding yourself – even if you’re the last person on Earth to see the light – you’ll never forget it.

Carl Sagan


For small creatures such as we the vastness is bearable only through love.

Carl Sagan

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.

Carl Sagan

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.

Carl Sagan

The universe is not required to be in perfect harmony with human ambition.

Carl Sagan

Who are we? We find that we live on an insignificant planet of a humdrum star lost in a galaxy tucked away in some forgotten corner of a universe in which there are far more galaxies than people.

Carl Sagan

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

Carl Sagan

Science is a way of thinking much more than it is a body of knowledge.

Carl Sagan

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

Carl Sagan

If you wish to make an apple pie from scratch, you must first invent the universe.

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.

Carl Sagan

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

Carl Sagan

If we long to believe that the stars rise and set for us, that we are the reason there is a Universe, does science do us a disservice in deflating our conceits?

Carl Sagan

But the fact that some geniuses were laughed at does not imply that all who are laughed at are geniuses. They laughed at Columbus, they laughed at Fulton, they laughed at the Wright Brothers. But they also laughed at Bozo the Clown.

Carl Sagan

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

Carl Sagan

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.

Carl Sagan


Imagination will often carry us to worlds that never were. But without it we go nowhere.

Carl Sagan

Our species needs, and deserves, a citizenry with minds wide awake and a basic understanding of how the world works.

Carl Sagan


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.

Carl Sagan

Extinction is the rule. Survival is the exception.

Carl Sagan

Our posturings, our imagined self-importance, the delusion that we have some privileged position in the universe, are challenged by this point of pale light. Our planet is a lonely speck in the great enveloping cosmic dark.

Carl Sagan

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?

Carl Sagan

It’s been said that astronomy is a humbling and, I might add, a character-building experience.

Carl Sagan

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

Carl Sagan

We’re in very bad trouble if we don’t understand the planet we’re trying to save.

Carl Sagan

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.

Carl Sagan

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.

Carl Sagan

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

Carl Sagan

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.

Carl Sagan

Today, we’re still loaded down – and, to some extent, embarrassed – by ancient myths, but we respect them as part of the same impulse that has led to the modern, scientific kind of myth. But we now have the opportunity to discover, for the first time, the way the universe is in fact constructed as opposed to how we would wish it to be constructed.

Carl Sagan

In our obscurity – in all this vastness – there is no hint that help will come from elsewhere to save us from ourselves. It is up to us.

Carl Sagan

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

Carl Sagan

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

Carl Sagan

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

Carl Sagan


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.

Carl Sagan

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

Carl Sagan

Who is Carl Sagan?

Astronomer Carl Sagan researched planets and theories of extraterrestrial intelligence at chicago’s university.

He was named director of Cornell’s Planetary Studies Laboratory in 1968 and served on numerous projects with NASA.

An anti-nuclear protester, in 1983 Sagan initiated the “cold winter” concept. He has published a novel, several books and scholarly papers and the 2014 revived television series, Cosmos.