Carl Sagan on Life

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

"The cosmos is within us. We are made of star-stuff. We are a way for the universe to know itself."

"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."

"Because it is clear from the fossil record that almost every species that has ever existed is extinct; extinction is the rule, survival is the exception."

"There is a very stunning range of studies... of interstellar organic matter... the cold, dark spaces between the stars are also loaded with organic matter. ...complex organic materials are everywhere."

"A tiny blue dot set in a sunbeam. Here it is. That's where we live. That's home. We humans are one species and this is our world. It is our responsibility to cherish it. Of all the worlds in our solar system, the only one so far as we know, graced by life."

"The beauty of a living thing is not the atoms that go into it, but the way those atoms are put together. Information distilled over 4 billion years of biological evolution. Incidentally, all the organisms on the Earth are made essentially of that stuff. An eyedropper full of that liquid could be used to make a caterpillar or a petunia if only we knew how to put the components together."

"The Cosmos is all that is or 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."

"The cosmic calendar compresses the local history of the universe into a single year. If the universe began on January 1st it was not until May that the Milky Way formed. Other planetary systems may have appeared in June, July and August, but our Sun and Earth not until mid-September. Life arose soon after."

"When there isn't enough food, the body has to make a decision on how to invest the limited foodstuff available to it. Survival comes first, growth comes second. And in this kind of nutritional triage, the body seems obliged to rank learning, last. It sort of it's better to be stupid and alive, than smart and dead."

"I would love to believe that when I die I will live again, that some thinking, feeling, remembering part of me will continue. But as 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 there’s 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."

"Once upon a time, the best minds of the human species believed that the planets were attached to crystal spheres. ...Both in classic and in medieval times, it was prominently speculated that gods or angels propelled them, gave them a twirl every now and then. The Newtonian gravitational superstructure replaced angels with GMm/r2... as science advances, there seems to be less and less for God to do."

"I wish to propose a doctrine which may, I fear, appear wildly paradoxical and subversive. The doctrine in question is this: that it is undesirable to believe a proposition when there is no ground whatever for supposing it true. I must, of course, admit that if such an opinion became common it would completely transform our social life and our political system; since both are at present faultless, this must weigh against it."

"The organic molecules found in the gas phase in the atmosphere of Titan by Voyager 1 and 2 spacecraft include hydrogen cyanide, cyanoacetylene, butadiene. cyanogen, propylene, propane, acetylene, ethane, ethylene, Methane, likewise. And the principle constituent of the atmosphere, there as here, is molecular nitrogen. It is, I think, very interesting that we have a world in the outer solar system that is loaded with the stuff of life."

"There is in the lovely Martian landscape not a footprint, not an artifact, not even an old beer can, not a blade of grass, not a kangaroo rat, not even, so far as we can tell, a microbe. Mars and the Moon and Venus... the only planets that we've landed on—are utterly lifeless. ...in our solar system we may discover that there is life only on this world. This says that life is not guaranteed, that life requires something special, something improbable."

"When you look more generally at life on Earth, you find that it is all the same kind of life. ...It uses about fifty fundamental biological building blocks, organic molecules. ...with trivial exceptions, all organisms on Earth use... an enzyme, to control the rate and direction of the chemistry of life. ...a nucleic acid to encode the hereditary information ...the identical code book for translating nucleic acid language into protein language. ...At the molecular level, we are all virtually identical."

"Both borderline science and many religions are motivated in part by a serious concern about the nature of the universe and our role in it, and for this reason merit our consideration and regard. In addition, I think it possible that many religions involve at their cores an attempt to come to grips with profound mysteries of our individual life histories, as described in the last chapter. But both in borderline science and in organized religion there is much that is specious or dangerous. While the practitioners of such doctrines often wish there were no criticisms to which they are expected to reply, skeptical scrutiny is the means, in both science and religion, by which deep insights can be winnowed from deep nonsense."

"In fact, the thickness of the Earth's 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. That's 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. 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 haven't been wise enough to foresee?"