Carl Sagan Quotes

[Censoring] knowledge, telling people what they must think and what ideas are impermissible, which lines of evidence may not be pursued, is the aperture to thought police, foolish and incompetent decision-making, and long-term decline.

You’d be surprised how rarely something like that happens. In the long run, the aggressive civilizations destroy themselves, almost always. It’s their nature. They can’t help it. In such a case, our job would be to leave them alone. To make sure that no one bothers them. To let them work out their destiny.

Practitioners of pop science were once called Paradoxers, a quaint nineteenth-century word used to describe those who invent elaborate and undemonstrated explanations for what science has understood rather well in simpler terms.

all the atoms that make each of us up — the iron in our blood, the calcium in our bones, the carbon in our brains — were manufactured in red giant stars thousands of light-years away in space and billions of years ago in time. We are, as I like to say, starstuff.

Los hombres crecieron en los bosques y nosotros les tenemos una afinidad natural. ¡Qué hermoso es un árbol que se esfuerza por alcanzar el cielo!

It took the Church until 1832 to remove Galileo's work from its list of books which Catholics were forbidden to read at the risk of dire punishment of their immortal souls.

Einstein's prohibition against travelling faster than light may clash with our common sense, but, on this question, why should we trust common sense? Why should our experience at 10 kilometers-an-hour constrain the laws of nature at 300,000 kilomters per second? Relativity does set limits on what humans can ultimately do, but the universe is not required to be in perfect harmony with human ambition.

I can remember one occasion, taking a shower with my wife while high, in which I had an idea on the origins and invalidities of racism in terms of Gaussian distribution curves. It was a point obvious in a way, but rarely talked about. I drew curves in soap on the shower wall, and went to write the idea down. One idea led to another, and at the end of about an hour of extremely hard work I had found I had written eleven short essays on a wide range of social, political, philosophical, and human biological topics. . . . I have used them in university commencement addresses, public lectures, and in my books.

Books permit us to voyage through time, to tap the wisdom of our ancestors. The library connects us with the insights and knowledge, painfully extracted from Nature, of the greatest minds that ever were, with the best teachers, drawn from the entire planet and from all of our history, to instruct us without tiring, and to inspire us to make our own contribution to the collective knowledge of the human species. Public libraries depend on voluntary contributions. I think the health of our civilization, the depth of our awareness about the underpinnings of our culture and our concern for the future can all be tested by how well we support our libraries.

In our earliest history, so far as we can tell, individuals held to an allegiance toward their immediate tribal group, which may have numbered no more than ten or twenty individuals, all of whom were related by consanguinity. As time went on, the need for cooperative behavior — in the hunting of large animals or large herds, in agriculture, and in the development of cities — forced human beings into larger and larger groups. The group that was identified with, the tribal unit, enlarged at each stage of evolution. Today, a particular instant in the 4.5-billion-year history of Earth and in the several-million-year history of mankind, most human beings owe their primary allegiance to the nation-state (although some of the most dangerous political problems still arise from tribal conflicts involving smaller population units). Many visionary leaders have imagined a time when the allegiance of an individual human being is not to his particular nation-state, religion, race, or economic group, but to mankind as a whole; when the benefit to a human being of another sex, race, religion, or political persuasion ten thousand miles away is as precious to us as to our neighbor or our brother. The trend is in this direction, but it is agonizingly slow. There is a serious question whether such a global self-identification of mankind can be achieved before we destroy ourselves with the technological forces our intelligence has unleashed.

Vigorous criticism of new ideas is a commonplace in science. While the style of the critique may vary with the character of the critic, overly polite criticism benefits neither the proponents of new ideas nor the scientific enterprise. Any substantive objection is permissible and encouraged; the only exception being that ad hominem attacks on the personality or motives of the author are excluded. It does not matter what reason the proponent has for advancing his ideas or what prompts his opponents to criticize them: all that matters is whether the ideas are right or wrong, promising or retrogressive.

Science invites us to let the facts in, even when they don’t conform to our preconceptions. It counsels us to carry alternative hypotheses in our heads and see which best fit the facts. It urges on us a delicate balance between no-holds-barred openness to new ideas, however heretical, and the most rigorous skeptical scrutiny of everything — new ideas and established wisdom. This kind of thinking is also an essential tool for a democracy in an age of change.

what’s the difference between an invisible, incorporeal, floating dragon who spits heatless fire and no dragon at all?

Evolution often uses this strategy. Indeed, the standard evolutionary practice of increasing the amount of genetic information as organisms increase in complexity is accomplished by doubling part of the genetic material and then allowing the slow specialization of function of the redundant set.

The Cosmos is all that is or ever was or ever will be. Our feeblest contemplations of the Cosmos stir us — there is a tingling in the spine, a catch in the voice, a faint sensation as if a distant memory, of falling from a height. We know we are approaching the greatest of mysteries.