Carl Sagan

"This is Phobos... Its mean density is known, and it is consistent with organic matter. Deimos... same story."

"Its hard to understand how “conservatives” could oppose safeguarding the environment—that all of us including conservatives and their children—depend on for our very lives. What exactly is it conservatives are conserving?"

"Imagine, a room, awash in gasoline. And there are two implacable enemies in that room. One of them has 9,000 matches. The other has 7,000 matches. Each of them is concerned about whos ahead, whos stronger. Well, thats the kind of situation we are actually in. The amount of weapons that are available to the United States and the Soviet Union are so bloated, so grossly in excess of whats needed to dissuade the other that if it werent so tragic, it would be laughable."

"The idea that God is an oversized white male with a flowing beard who sits in the sky and tallies the fall of every sparrow is ludicrous. But if by God one means the set of physical laws that govern the universe, then clearly there is such a God. This God is emotionally unsatisfying... it does not make much sense to pray to the law of gravity."

"I would love to believe that when I die I will live again, that some thinking, feeling, remembering part of me will continue. But much as I want to believe that, and despite the ancient and worldwide cultural traditions that assert an afterlife, I know of nothing to suggest that it is more than wishful thinking. The world is so exquisite with so much love and moral depth, that there is no reason to deceive ourselves with pretty stories for which theres little good evidence. Far better it seems to me, in our vulnerability, is to look death in the eye and to be grateful every day for the brief but magnificent opportunity that life provides."

"Humans — who enslave, castrate, experiment on, and fillet other animals — have had an understandable penchant for pretending animals do not feel pain. A sharp distinction between humans and animals is essential if we are to bend them to our will, make them work for us, wear them, eat them — without any disquieting tinges of guilt or regret. It is unseemly of us, who often behave so unfeelingly toward other animals, to contend that only humans can suffer. The behavior of other animals renders such pretensions specious. They are just too much like us."

"If you take a look at science in its everyday function, of course you find that scientists run the gamut of human emotions and personalities and character and so on. But theres one thing that is really striking to the outsider, and that is the gauntlet of criticism that is considered acceptable or even desirable. The poor graduate student at his or her Ph.D. oral exam is subjected to a withering crossfire of questions that sometimes seem hostile or contemptuous; this from the professors who have the candidates future in their grasp. The students naturally are nervous; who wouldnt be? True, theyve prepared for it for years. But they understand that at that critical moment they really have to be able to answer questions. So in preparing to defend their theses, they must anticipate questions; they have to think, “Where in my thesis is there a weakness that someone else might find — because I sure better find it before they do, because if they find it and Im not prepared, Im in deep trouble."

"In fact, the thickness of the Earths atmosphere, compared with the size of the Earth, is in about the same ratio as the thickness of a coat of shellac on a schoolroom globe is to the diameter of the globe. Thats the air that nurtures us and almost all other life on Earth, that protects us from deadly ultraviolet light from the sun, that through the greenhouse effect brings the surface temperature above the freezing point. (Without the greenhouse effect, the entire Earth would plunge below the freezing point of water and wed all be dead.) Now that atmosphere, so thin and fragile, is under assault by our technology. We are pumping all kinds of stuff into it. You know about the concern that chlorofluorocarbons are depleting the ozone layer; and that carbon dioxide and methane and other greenhouse gases are producing global warming, a steady trend amidst fluctuations produced by volcanic eruptions and other sources. Who knows what other challenges we are posing to this vulnerable layer of air that we havent been wise enough to foresee?"

"Now, there has been the view that ... if there is nothing special about us in space then maybe there is something special about us in time. ... To me, the principal trouble with this idea is that 99.998% of the lifetime of the universe, from its beginning to now, was over before humans appeared on the scene."

"Every kid starts out as a natural-born scientist, and then we beat it out of them. A few trickle through the system with their wonder and enthusiasm for science intact."

"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."

"It is easy to create an interstellar radio message which can be recognized as emanating unambiguously from intelligent beings. A modulated signal (‘beep,’ ‘beep-beep,’ . . . ) comprising the numbers 1, 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, for example, consists exclusively of the first 12 prime numbers—that is, numbers that can be divided only by 1, or by themselves. A signal of this kind, based on a simple mathematical concept, could only have a biological origin. . . . But by far the most promising method is to send pictures."