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April 10, 2026
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"We must be careful not to discourage our twelve-year-olds by making them waste the best years of their lives preparing for examinations."
"Fifty years ago Kurt Gödel... proved that the world of pure mathematics is inexhaustible. … I hope that the notion of a final statement of the laws of physics will prove as illusory as the notion of a formal decision process for all mathematics. If it should turn out that the whole of physical reality can be described by a finite set of equations, I would be disappointed, I would feel that the Creator had been uncharacteristically lacking in imagination."
"What philosophical conclusions should we draw from the abstract style of the superstring theory? We might conclude, as Sir James Jeans concluded long ago, that the Great Architect of the Universe now begins to appear as a Pure Mathematician, and that if we work hard enough at mathematics we shall be able to read his mind. Or we might conclude that our pursuit of abstractions is leading us far away from those parts of the creation which are most interesting from a human point of view. It is too early yet to come to conclusions."
"Imagine, if you can, four things that have very different sizes. First, the entire universe. Second, the planet Earth. Third, the nucleus of an atom. Fourth, a superstring. The step in size from each of these things to the next is roughly the same... twenty powers of ten...."
"Euclid... gave his famous definition of a point: "A point is that which has no parts, or which has no magnitude." …A point has no existence by itself. It exists only as a part of the pattern of relationships which constitute the geometry of Euclid. This is what one means when one says that a point is a mathematical abstraction. The question, What is a point? has no satisfactory answer. Euclid's definition certainly does not answer it. The right way to ask the question is: How does the concept of a point fit into the logical structure of Euclid's geometry? ...It cannot be answered by a definition."
"Scientifically speaking, a butterfly is at least as mysterious as a superstring. When something ceases to be mysterious it ceases to be of absorbing interest to scientists. Almost all things scientists think and dream about are mysterious."
"There is no easy solution to the conflict between fundamentalist Christian dogma and the facts of biological evolution. I am not saying that the conflict could have been altogether avoided. I am saying only that the conflict was made more bitter and more damaging, both to religion and to science, by the dogmatic and self-righteousness of scientists. What was needed was a little more human charity, a little more willingness to listen rather than to lay down the law, a little more humility. Scientists stand in need of these Christian virtues just as much as preachers do."
"Science is not a monolithic body of doctrine. Science is a culture, constantly growing and changing. The science of today has broken out of the molds of classical nineteenth-century science, just as the paintings of Pablo Picasso and Jackson Pollock broke out of the molds of nineteenth century art. Science has as many competing styles as painting or poetry. The diversity of science also finds a parallel in the diversity of religion."
"An awareness of our smallness may help to redeem us from the arrogance which is the besetting sin of the scientists."
"Science and religion are two human enterprises sharing many features. They share these features also with other enterprises such as art, literature and music. The most salient features of all these enterprises are discipline and diversity. Discipline to submerge the individual fantasy in a greater whole. Diversity to give scope to the infinite variety of human souls and temperaments. Without discipline there can be no greatness. Without diversity there can be no freedom. Greatness for the enterprise, freedom for the individual — these are the two themes, contrasting but not incompatible, that make up the history of science and the history of religion."
"A good scientist is a person with original ideas. A good engineer is a person who makes a design that works with as few original ideas as possible. There are no prima donnas in engineering."
"A good cause can become bad if we fight for it with means that are indiscriminately murderous. A bad cause can become good if enough people fight for it in a spirit of comradeship and self-sacrifice. In the end it is how you fight, as much as why you fight, that makes your cause good or bad."
"It is characteristic of all deep human problems that they are not to be approached without some humor and some bewilderment."
"If we had a reliable way to label our toys good and bad, it would be easy to regulate technology wisely. But we can rarely see far enough ahead to know which road leads to damnation. Whoever concerns himself with big technology, either to push it forward or to stop it, is gambling in human lives."
"There is a great satisfaction in building good tools for other people to use."
"... the most important questions and insights and goals are unpredictable."
"There is an enormous variety of things that we never dreamed of, like... black holes, s, quasars, all these unbelievably active goings-on in the universe... [I]n Aristotle's time the universe... was supposed to be quiescent, it was supposed to be perfect and peaceful, and nothing ever happened in the ; and that remained true... throughout all of the revolutions... It remained the general view of astronomers... through Copernicus, and Galileo, and Newton, and everybody else... until just the last 30 years, and now we know it's not like that at all. In fact the universe is full of violent events, and fantastic strong gravitational fields, and collapsed objects, and huge outpourings of energy. ...The things we understand least are the quasars... the most violent and... energetic objects in the universe, and they're totally... mysterious... and... they're rather frequent; and nobody ever dreamed that they existed... [E]ven after they were found it took a long time before people took them seriously. Nature's imagination is always richer than ours."
"There’s very good news from the asteroids. It appears that a large fraction of them, including the big ones, are actually very rich in H2O. Nobody imagined that. They thought they were just big rocks … It’s easier to get to an asteroid than to Mars, because the gravity is lower and landing is easier. Certainly the asteroids are much more practical, right now. If we start space colonies in, say, the next 20 years, I would put my money on the asteroids."
"All the books that I have seen about the science and the economics of global warming, including the two books under review, miss the main point. The main point is religious rather than scientific. There is a worldwide secular religion which we may call environmentalism, holding that we are stewards of the earth, that despoiling the planet with waste products of our luxurious living is a sin, and that the path of righteousness is to live as frugally as possible. … Environmentalism has replaced socialism as the leading secular religion."
"I believe global warming is grossly exaggerated as a problem. It's a real problem, but it's nothing like as serious as people are led to believe. The idea that global warming is the most important problem facing the world is total nonsense and is doing a lot of harm. It distracts people's attention from much more serious problems."
"My first heresy says that all the fuss about global warming is grossly exaggerated. Here I am opposing the holy brotherhood of climate model experts and the crowd of deluded citizens who believe the numbers predicted by the computer models. Of course, they say, I have no degree in meteorology and I am therefore not qualified to speak. But I have studied the climate models and I know what they can do. The models solve the equations of fluid dynamics, and they do a very good job of describing the fluid motions of the atmosphere and the oceans. They do a very poor job of describing the clouds, the dust, the chemistry and the biology of fields and farms and forests. They do not begin to describe the real world that we live in. The real world is muddy and messy and full of things that we do not yet understand. It is much easier for a scientist to sit in an air-conditioned building and run computer models, than to put on winter clothes and measure what is really happening outside in the swamps and the clouds. That is why the climate model experts end up believing their own models."
"The biggest breakthrough in the next 50 years will be the discovery of extraterrestrial life. We have been searching for it for 50 years and found nothing. That proves life is rarer than we hoped, but does not prove that the universe is lifeless. We are only now developing the tools to make our searches efficient and far-reaching, as optical and radio detection and data processing move forward."
"In desperation I asked Fermi whether he was not impressed by the agreement between our calculated numbers and his measured numbers. He replied, "How many arbitrary parameters did you use for your calculations?" I thought for a moment about our cut-off procedures and said, "Four." He said, "I remember my friend Johnny von Neumann used to say, with four parameters I can fit an elephant, and with five I can make him wiggle his trunk." With that, the conversation was over."
"The laws of nature are constructed in such a way as to make the universe as interesting as possible."
"Anyone who compares the bibliography with the reprinted papers will notice that mathematics and physics have not been given equal treatment. There is a strong bias in favor of mathematics. The bias arises from the fact that mathematical papers, provided that are correct and not trivial, have permanent value, whereas most papers in physics journals are ephemeral. For this reason, it is customary to publish complete collected works of mathematicians but only selected works of physicists."
"The bottom line for mathematicians is that the architecture has to be right. In all the mathematics that I did, the essential point was to find the right architecture. It's like building a bridge. Once the main lines of the structure are right, then the details miraculously fit. The problem is the overall design."
"The whole point of science is that most of it is uncertain. That's why science is exciting--because we don't know. Science is all about things we don't understand. The public, of course, imagines science is just a set of facts. But it's not. Science is a process of exploring, which is always partial. We explore, and we find out things that we understand. We find out things we thought we understood were wrong. That's how it makes progress. (2014 interview)"
"As we look out into the Universe and identify the many accidents of physics and astronomy that have worked together to our benefit, it almost seems as if the Universe must in some sense have known that we were coming."
"I have felt it myself. The glitter of nuclear weapons. It is irresistible if you come to them as a scientist. To feel it's there in your hands, to release this energy that fuels the stars, to let it do your bidding. To perform these miracles, to lift a million tons of rock into the sky. It is something that gives people an illusion of illimitable power, and it is, in some ways, responsible for all our troubles — this, what you might call technical arrogance, that overcomes people when they see what they can do with their minds."
"Thirty-one years ago [1948], Dick Feynman told me about his "sum over histories" version of quantum mechanics. "The electron does anything it likes," he said. "It just goes in any direction at any speed, forward or backward in time, however it likes, and then you add up the amplitudes and it gives you the wave-function." I said to him, "You're crazy." But he wasn't."
"I am acutely aware of the fact that the marriage between mathematics and physics, which was so enormously fruitful in past centuries, has recently ended in divorce."
"It has been generally believed that only the complex numbers could legitimately be used as the ground field in discussing quantum-mechanical operators. Over the complex field, Frobenius' theorem is of course not valid; the only division algebra over the complex field is formed by the complex numbers themselves. However, Frobenius' theorem is relevant precisely because the appropriate ground field for much of quantum mechanics is real rather than complex."
"The public has a distorted view of science, because children are taught in school that science is a collection of firmly established truths. In fact, science is not a collection of truths. It is a continuing exploration of mysteries. (New York Review of Books, 2011)"
"Inspired by the impact hypothesis, a group of astrophysicists led by Carl Sagan decided to try to model the effects of an all-out war and came up with the concept of "nuclear winter," which, in turn, generated its own wave of media coverage."
"Astronomer Carl Sagan noted that even when it is viewed from so far away that it is a pale dot, Earth is discernibly blue."
"When my husband died, because he was so famous and known for not being a believer, many people would come up to me—it still sometimes happens—and ask me if Carl changed at the end and converted to a belief in an afterlife. They also frequently ask me if I think I will see him again. Carl faced his death with unflagging courage and never sought refuge in illusions. The tragedy was that we knew we would never see each other again. I don't ever expect to be reunited with Carl. But, the great thing is that when we were together, for nearly twenty years, we lived with a vivid appreciation of how brief and precious life is. We never trivialized the meaning of death by pretending it was anything other than a final parting. Every single moment that we were alive and we were together was miraculous-not miraculous in the sense of inexplicable or supernatural. We knew we were beneficiaries of chance. ... That pure chance could be so generous and so kind. ... That we could find each other, as Carl wrote so beautifully in Cosmos, you know, in the vastness of space and the immensity of time. ... That we could be together for twenty years. That is something which sustains me and it's much more meaningful. ... The way he treated me and the way I treated him, the way we took care of each other and our family, while he lived. That is so much more important than the idea I will see him someday. I don't think I'll ever see Carl again. But I saw him. We saw each other. We found each other in the cosmos, and that was wonderful."
""This is a deathwatch," Carl told me calmly. "I'm going to die." "No," I protested. "You're going to beat this, just as you have before when it looked hopeless." He turned to me with that same look I had seen countless times in the debates and skirmishes of our twenty years of writing together and being wildly in love. With a mixture of knowing good humor and skepticism, but as ever, not a trace of self-pity, he said wryly, "Well, we'll see who's right about this one." Sam, now five years old, came to see his father for one last time. Although Carl was by now struggling for breath and finding it harder to speak, he managed to compose himself so as not to frighten his little son. "I love you, Sam," was all he could say. "I love you, too, Daddy," Sam said solemnly. Contrary to the fantasies of the fundamentalists, there was no deathbed conversion, no last minute refuge taken in a comforting vision of a heaven or an afterlife. For Carl, what mattered most was what was true, not merely what would make us feel better. Even at this moment when anyone would be forgiven for turning away from the reality of our situation, Carl was unflinching. As we looked deeply into each other's eyes, it was with a shared conviction that our wondrous life together was ending forever."
"We can judge our progress by the courage of our questions and the depths of our answers, our willingness to embrace what is true rather than what feels good."
"The fact is that far more crime and child abuse has been committed by zealots in the name of God, Jesus and Mohammed than has ever been committed in the name of Satan. Many people don't like that statement, but few can argue with it."
"You can't convince a believer of anything; for their belief is not based on evidence, it's based on a deep seated need to believe."
"If it can be destroyed by the truth, it deserves to be destroyed by the truth."
"Atheism is more than just the knowledge that gods do not exist, and that religion is either a mistake or a fraud. Atheism is an attitude, a frame of mind that looks at the world objectively, fearlessly, always trying to understand all things as a part of nature."
"If we are alone in the Universe, it sure seems like an awful waste of space."
"Somewhere, something incredible is waiting to be known."
"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."
"The whole idea of what happens when you read a book, I find absolutely stunning. Here's some product of a tree, little black squiggles on it, you open it up, and inside your head is the voice of someone speaking, who may have been dead 3000 years, and there he is talking directly to you, what a magical thing that is."
"We go about our daily lives understanding almost nothing of the world. We give little thought to the machinery that generates the sun light that makes life possible, to the gravity that glues us to an Earth that would otherwise sent us spinning off into space, or to the atoms of which we are made and on whose stability we fundamentally depend. Few of us spend much time wondering why nature is the way it is, where the cosmos came from, or whether it was always there, if time will one day flow backwards or whether there are ultimate limits to what humans can know. What is the smallest piece of matter, why we remember the past and not the future, and why there is the universe?"
"The prediction I can make with the highest confidence is that the most amazing discoveries will be the ones we are not today wise enough to foresee."
"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 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."