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Richard Feynman

230 quotes

“Once I asked him to explain to me, so that I can understand it, why spin-1/2 particles obey Fermi-Dirac statistics. Gauging his audience perfectly, he said, "I'll prepare a freshman lecture on it." But a few days later he came to me and said: "You know, I couldn't do it. I couldn't reduce it to the freshman level. That means we really don't understand it.”
Richard Feynman (1918–1988) said by 1988 at the latest wikiquote, CC BY-SA 4.0 source
Recorded in: David L. Goodstein, "Richard P. Feynman, Teacher," Physics Today, volume 42, number 2, February 1989, p. 70-75, at p. 75
“Feynman was fond of saying that all of quantum mechanics can be gleaned from carefully thinking through the implications of this single experiment, so it's well worth discussing.”
Richard Feynman (1918–1988) said by 1988 at the latest wikiquote, CC BY-SA 4.0 source
Recorded in: Brian Greene, The Elegant Universe: Superstrings, Hidden Dimensions, and the Quest for the Ultimate Theory (1999), p. 97-98
“Feynman's grasp of the big picture, coupled with his love for knowing first-hand of practical details — from low-level programming to lock-picking — gave him an almost unique perspective on any subject he chose to study. It was this mastery, both of the minutiae of a subject and of its overall intellectual framework, that gave him the seemingly effortless ability to move back and forth between the two levels at will, without getting lost in the detail or losing the overall plot.”
Richard Feynman (1918–1988) said by 1988 at the latest wikiquote, CC BY-SA 4.0 source
“Even when Richard didn't understand, he always seemed to understand better than the rest of us. And whatever he understood, he could make others understand as well. Richard made people feel like children do when a grown-up first treats them as adults. He was never afraid to tell the truth, and however foolish your question was, he never made you feel like a fool.”
Richard Feynman (1918–1988) said by 1988 at the latest wikiquote, CC BY-SA 4.0 source
Recorded in: W. Daniel Hillis, "Richard Feynman and the Connection Machine", Physics Today, volume 42, number 2, February 1989, p. 78-83, at p. 83
“Feynman is becoming a real pain in the ass.”
Richard Feynman (1918–1988) first seen 1986 wikiquote, CC BY-SA 4.0 source
Recorded in: William P. Rogers, during a break in a hearing of the Rogers Commission on the space shuttle Challenger accident, 11 February 1986, quoted in Genius: The Life and Science of Richard Feynman (1992) by James Gleick, p. 423
“An honest men, the outstanding intuitionist of our age, and a prime example of what may lie in store for anyone who dares to follow the beat of a different drum.”
Richard Feynman (1918–1988) said by 1988 at the latest wikiquote, CC BY-SA 4.0 source
Recorded in: Julian Schwinger in his obituary of Feynman, Physics Today (February 1989)
“In the hall, there were 183 new freshmen and a bowling ball hanging from the three-story ceiling to just above the floor. Feynman walked in and, without a word, grabbed the ball and backed against the wall with the ball touching his nose. He let go, and the ball swung slowly 60 feet across the room and back — stopping naturally just short of crushing his face. Then he took the ball again, stepped forward, and said: "I wanted to show you that I believe in what I'm going to teach you over the next two years.”
Richard Feynman (1918–1988) said by 1988 at the latest wikiquote, CC BY-SA 4.0 source
Recorded in: Michael Scott, quoted in The Los Angeles Times, "Caltech Grad's Donation Honors Late Professor" (12 March 1989)
“Several conversations that Feynman and I had involved the remarkable abilities of other physicists. In one of these conversations, I remarked to Feynman that I was impressed by Stephen Hawking's ability to do path integration in his head. "Ahh, that's not so great", Feynman replied. "It's much more interesting to come up with the technique like I did, rather than to be able to do the mechanics in your head." Feynman wasn't being immodest, he was quite right. The true secret to genius is in creativity, not in technical mechanics.”
Richard Feynman (1918–1988) said by 1988 at the latest wikiquote, CC BY-SA 4.0 source
“When I say he didn't like philosophy I meant he didn't like a certain style of thinking that was full of jargon, full of - I'll use his word - "baloney", where people who didn't know what they were talking about pontificated and used fancy words - like "ontological", which I never knew what that meant - as a substitute for simple thinking. That is what he didn't like. And yet, I think in some ways, in some deep way, he was an extraordinarily philosophical person.”
Richard Feynman (1918–1988) said by 1988 at the latest wikiquote, CC BY-SA 4.0 source
Recorded in: Leonard Susskind in a 2018 Y Combinator interview (at 40:33)
“He hated the fact that he participated in the invention of nuclear weapons, and he doubly hated the fact that he had so much fun doing it.”
Richard Feynman (1918–1988) said by 1988 at the latest wikiquote, CC BY-SA 4.0 source
Recorded in: Leonard Susskind in a 2018 Y Combinator interview (at 42:03)
“In this age of specialization men who thoroughly know one field are often incompetent to discuss another. The great problems of the relations between one and another aspect of human activity have for this reason been discussed less and less in public. When we look at the past great debates on these subjects we feel jealous of those times, for we should have liked the excitement of such argument. The old problems, such as the relation of science and religion, are still with us, and I believe present as difficult dilemmas as ever, but they are not often publicly discussed because of the limitations of specialization.”
Richard Feynman (1918–1988) first seen 1956 wikiquote, CC BY-SA 4.0 source
Recorded in: remarks (2 May 1956) at a Caltech YMCA lunch forum
“Western civilization, it seems to me, stands by two great heritages. One is the scientific spirit of adventure — the adventure into the unknown, an unknown which must be recognized as being unknown in order to be explored; the demand that the unanswerable mysteries of the universe remain unanswered; the attitude that all is uncertain; to summarize it — the humility of the intellect. The other great heritage is Christian ethics — the basis of action on love, the brotherhood of all men, the value of the individual — the humility of the spirit. These two heritages are logically, thoroughly consistent. But logic is not all; one needs one's heart to follow an idea. If people are going back to religion, what are they going back to? Is the modern church a place to give comfort to a man who doubts God — more, one who disbelieves in God? Is the modern church a place to give comfort and encouragement to the value of such doubts? So far, have we not drawn strength and comfort to maintain the one or the other of these consistent heritages in a way which attacks the values of the other? Is this unavoidable? How can we draw inspiration to support these two pillars of western civilization so that they may stand together in full vigor, mutually unafraid? Is this not the central problem of our time?”
Richard Feynman (1918–1988) first seen 1956 wikiquote, CC BY-SA 4.0 source
Recorded in: remarks (2 May 1956) at a Caltech YMCA lunch forum
“The real problem in speech is not precise language. The problem is clear language. The desire is to have the idea clearly communicated to the other person. It is only necessary to be precise when there is some doubt as to the meaning of a phrase, and then the precision should be put in the place where the doubt exists. It is really quite impossible to say anything with absolute precision, unless that thing is so abstracted from the real world as to not represent any real thing.Pure mathematics is just such an abstraction from the real world, and pure mathematics does have a special precise language for dealing with its own special and technical subjects. But this precise language is not precise in any sense if you deal with real objects of the world, and it is only pedantic and quite confusing to use it unless there are some special subtleties which have to be carefully distinguished.”
Richard Feynman (1918–1988) first seen 1965 wikiquote, CC BY-SA 4.0 source
Recorded in: New Textbooks for the "New" Mathematics", Engineering and Science volume 28, number 6 (March 1965) p. 9-15 at p. 14
“This is all very confusing, especially when we consider that even though we may consistently consider ourselves to be the outside observer when we look at the rest of the world, the rest of the world is at the same time observing us, and that often we agree on what we see in each other. Does this then mean that my observations become real only when I observe an observer observing something as it happens? This is a horrible viewpoint. Do you seriously entertain the idea that without the observer there is no reality? Which observer? Any observer? Is a fly an observer? Is a star an observer? Was there no reality in the universe before 109 B.C. when life began? Or are you the observer? Then there is no reality to the world after you are dead? I know a number of otherwise respectable physicists who have bought life insurance.”
Richard Feynman (1918–1988) first seen 1962 wikiquote, CC BY-SA 4.0 source
Recorded in: On the Philosophical Problems in Quantizing Macroscopic Objects"(ca. 1962-1963) as quoted by Morinigo, Wagner, & Hatfield, Feynman Lectures on Gravitation (2002)
“There is one feature I notice that is generally missing in cargo cult science. … It's a kind of scientific integrity, a principle of scientific thought that corresponds to a kind of utter honesty — a kind of leaning over backwards. For example, if you're doing an experiment, you should report everything that you think might make it invalid — not only what you think is right about it; other causes that could possibly explain your results; and things you thought of that you've eliminated by some other experiment, and how they worked—to make sure the other fellow can tell they have been eliminated. Details that could throw doubt on your interpretation must be given, if you know them. You must do the best you can — if you know anything at all wrong, or possibly wrong — to explain it. If you make a theory, for example, and advertise it, or put it out, then you must also put down all the facts that disagree with it, as well as those that agree with it. There is also a more subtle problem. When you have put a lot of ideas together to make an elaborate theory, you want to make sure, when explaining what it fits, that those things it fits are not just the things that gave you the idea for the theory; but that the finished theory makes something else come out right, in addition. In summary, the idea is to try to give all of the information to help others to judge the value of your contribution; not just the information that leads to judgement in one particular direction or another.”
Richard Feynman (1918–1988) first seen 1974 wikiquote, CC BY-SA 4.0 source
Recorded in: Cargo Cult Science", adapted from a 1974 Caltech commencement address; also published in Surely You're Joking, Mr. Feynman!, p. 341
“All experiments in psychology are not of this [cargo cult] type, however. For example there have been many experiments running rats through all kinds of mazes, and so on — with little clear result. But in 1937 a man named Young did a very interesting one. He had a long corridor with doors all along one side where the rats came in, and doors along the other side where the food was. He wanted to see if he could train rats to go to the third door down from wherever he started them off. No. The rats went immediately to the door where the food had been the time before.The question was, how did the rats know, because the corridor was so beautifully built and so uniform, that this was the same door as before? Obviously there was something about the door that was different from the other doors. So he painted the doors very carefully, arranging the textures on the faces of the doors exactly the same. Still the rats could tell. Then he thought maybe they were smelling the food, so he used chemicals to change the smell after each run. Still the rats could tell. Then he realized the rats might be able to tell by seeing the lights and the arrangement in the laboratory like any commonsense person. So he covered the corridor, and still the rats could tell.He finally found that they could tell by the way the floor sounded when they ran over it. And he could only fix that by putting his corridor in sand. So he covered one after another of all possible clues and finally was able to fool the rats so that they had to learn to go to the third door. If he relaxed any of his conditions, the rats could tell.Now, from a scientific standpoint, that is an A-number-one experiment. That is the experiment that makes rat-running experiments sensible, because it uncovers the clues that the rat is really using — not what you think it's using. And that is the experiment that tells exactly what conditions you have to use in order to be careful and control everything in an experiment with rat-running.I looked into the subsequent history of this research. The next experiment, and the one after that, never referred to Mr. Young. They never used any of his criteria of putting the corridor on sand, or of being very careful. They just went right on running rats in the same old way, and paid no attention to the great discoveries of Mr. Young, and his papers are not referred to, because he didn't discover anything about rats. In fact, he discovered all the things you have to do to discover something about rats. But not paying attention to experiments like that is a characteristic of cargo cult science.”
Richard Feynman (1918–1988) first seen 1974 wikiquote, CC BY-SA 4.0 source
Recorded in: Cargo Cult Science", adapted from a 1974 Caltech commencement address; also published in Surely You're Joking, Mr. Feynman!, p. 345
“And then there's a kind of saying that you don't understand it, meaning "I don't believe it. It's too crazy. It's the kind of thing, I'm just... I'm not going to accept it."... This kind, I hope you'll come along with me, and you'll have to accept it, because it's the way nature works. If you want to know the way nature works... We looked at it, carefully... That's the way it looks! You don't like it? Go somewhere else... to another universe where the rules are simpler, philosophically more pleasing, more psychologically easy. I can't help it! OK? If I'm going to tell you honestly what the world looks like to... human beings who have struggled as hard as they can to understand it, I can only tell you what it looks like, and I cannot make it innocent. ...I'm not going to simplify it, eh? I'm not going to fake it. I'm not going to... tell you it's something like a ball bearing on a spring. It isn't.”
Richard Feynman (1918–1988) first seen 1979 wikiquote, CC BY-SA 4.0 source
Recorded in: Lecture 1. "Photons: Corpuscles of Light" (1979) Sir Douglas Robb Memorial Lectures, University of Auckland.
“All right. I already see you turning off. I can see you say you don't understand me. You can't understand that it could be chance. "I don't like it!" Tough! I don't like it either, but that's the way it is! OK? I don't understand it either. ..."It must be that Nature knows that it's going to go up or down." No, it must not be that nature knows! We are not to tell Nature what she's gotta be! That's what we found out. Every time we take a guess as how she's got to be, and go and measure... She's clever. She's always got better imagination than we have, and she finds a cleverer way to do it than we have thought of. And in this particular case, the clever way to do it is by probability, by odds. ...[L]ight works by probability.”
Richard Feynman (1918–1988) first seen 1979 wikiquote, CC BY-SA 4.0 source
Recorded in: Lecture 1. "Photons: Corpuscles of Light" (1979) Sir Douglas Robb Memorial Lectures, University of Auckland.
“We always have had ... a great deal of difficulty in understanding the world view that quantum mechanics represents. At least I do, because I'm an old enough man that I haven't got to the point that this stuff is obvious to me. Okay, I still get nervous with it. And therefore, some of the younger students ... you know how it always is, every new idea, it takes a generation or two until it becomes obvious that there's no real problem. It has not yet become obvious to me that there's no real problem. I cannot define the real problem, therefore I suspect there's no real problem, but I'm not sure there's no real problem.”
Richard Feynman (1918–1988) first seen 1982 wikiquote, CC BY-SA 4.0 source
Recorded in: Simulating Physics with Computers", International Journal of Theoretical Physics, volume 21, 1982, p. 467-488, at p. 471
“I do feel strongly that this is nonsense! ... So perhaps I could entertain future historians by saying I think all this superstring stuff is crazy and is in the wrong direction. I think all this superstring stuff is crazy and is in the wrong direction. ... I don't like it that they're not calculating anything. ... why are the masses of the various particles such as quarks what they are? All these numbers ... have no explanations in these string theories – absolutely none! ... I don't like that they don't check their ideas. I don't like that for anything that disagrees with an experiment, they cook up an explanation—a fix-up to say, “Well, it might be true.” For example, the theory requires ten dimensions. Well, maybe there's a way of wrapping up six of the dimensions. Yes, that's all possible mathematically, but why not seven? When they write their equation, the equation should decide how many of these things get wrapped up, not the desire to agree with experiment. In other words, there's no reason whatsoever in superstring theory that it isn't eight out of the ten dimensions that get wrapped up and that the result is only two dimensions, which would be completely in disagreement with experience. So the fact that it might disagree with experience is very tenuous, it doesn't produce anything.”
Richard Feynman (1918–1988) first seen 1988 wikiquote, CC BY-SA 4.0 source
Recorded in: interview published in Superstrings: A Theory of Everything? (1988) edited by Paul C. W. Davies and Julian R. Brown, p. 193-194 ISBN 0521354625
“God was always invented to explain mystery. God is always invented to explain those things that you do not understand. Now, when you finally discover how something works, you get some laws which you're taking away from God; you don't need him anymore. But you need him for the other mysteries. So therefore you leave him to create the universe because we haven't figured that out yet; you need him for understanding those things which you don't believe the laws will explain, such as consciousness, or why you only live to a certain length of time — life and death — stuff like that. God is always associated with those things that you do not understand. Therefore I don't think that the laws can be considered to be like God because they have been figured out.”
Richard Feynman (1918–1988) first seen 1988 wikiquote, CC BY-SA 4.0 source
Recorded in: interview published in Superstrings: A Theory of Everything? (1988) edited by Paul C. W. Davies and Julian R. Brown, p. 208-209 ISBN 0521354625
“One of the first interesting experiences I had in this project at Princeton was meeting great men. I had never met very many great men before. But there was an evaluation committee that had to try to help us along, and help us ultimately decide which way we were going to separate the uranium. This committee had men like Compton and Tolman and Smyth and Urey and Rabi and Oppenheimer on it. I would sit in because I understood the theory of how our process of separating isotopes worked, and so they'd ask me questions and talk about it. In these discussions one man would make a point. Then Compton, for example, would explain a different point of view. He would say it should be this way, and he was perfectly right. Another guy would say, well, maybe, but there's this other possibility we have to consider against it. So everybody is disagreeing, all around the table. I am surprised and disturbed that Compton doesn't repeat and emphasize his point. Finally at the end, Tolman, who's the chairman, would say, "Well, having heard all these arguments, I guess it's true that Compton's argument is the best of all, and now we have to go ahead." It was such a shock to me to see that a committee of men could present a whole lot of ideas, each one thinking of a new facet, while remembering what the other fella said, so that, at the end, the decision is made as to which idea was the best -- summing it all up -- without having to say it three times. These were very great men indeed.”
Richard Feynman (1918–1988) first seen 1975 wikiquote, CC BY-SA 4.0 source
Recorded in: from the First Annual Santa Barbara Lectures on Science and Society, University of California at Santa Barbara (1975)
“When you're thinking about something that you don't understand, you have a terrible, uncomfortable feeling called confusion. It's a very difficult and unhappy business. And so most of the time you're rather unhappy, actually, with this confusion. You can't penetrate this thing. Now, is the confusion's because we're all some kind of apes that are kind of stupid working against this, trying to figure out [how] to put the two sticks together to reach the banana and we can't quite make it, the idea? And I get this feeling all the time that I'm an ape trying to put two sticks together, so I always feel stupid. Once in a while, though, the sticks go together on me and I reach the banana.”
Richard Feynman (1918–1988) first seen 1963 wikiquote, CC BY-SA 4.0 source
Recorded in: Video interview dated 1963
“Of course if we make good things, it is not only to the credit of science; it is also to the credit of the moral choice which led us to good work. Scientific knowledge is an enabling power to do either good or bad — but it does not carry instructions on how to use it. Such power has evident value — even though the power may be negated by what one does with it.I learned a way of expressing this common human problem on a trip to Honolulu. In a Buddhist temple there, the man in charge explained a little bit about the Buddhist religion for tourists, and then ended his talk by telling them he had something to say to them that they would never forget — and I have never forgotten it. It was a proverb of the Buddhist religion:To every man is given the key to the gates of heaven; the same key opens the gates of hell.What then, is the value of the key to heaven? It is true that if we lack clear instructions that enable us to determine which is the gate to heaven and which the gate to hell, the key may be a dangerous object to use.But the key obviously has value: how can we enter heaven without it?”
Richard Feynman (1918–1988) said by 1988 at the latest wikiquote, CC BY-SA 4.0 source
“I stand at the seashore, alone, and start to think. There are the rushing waves mountains of molecules each stupidly minding its own business trillions apart yet forming white surf in unison.Ages on ages before any eyes could see year after year thunderously pounding the shore as now. For whom, for what? On a dead planet with no life to entertain.Never at rest tortured by energy wasted prodigiously by the sun poured into space. A mite makes the sea roar. Deep in the sea all molecules repeat the patterns of one another till complex new ones are formed. They make others like themselves and a new dance starts.Growing in size and complexity living things masses of atoms DNA, protein dancing a pattern ever more intricate.Out of the cradle onto dry land here it is standing: atoms with consciousness; matter with curiosity.Stands at the sea, wonders at wondering: I a universe of atoms an atom in the universe.”
Richard Feynman (1918–1988) said by 1988 at the latest wikiquote, CC BY-SA 4.0 source
“The scientist has a lot of experience with ignorance and doubt and uncertainty, and this experience is of very great importance, I think. When a scientist doesn't know the answer to a problem, he is ignorant. When he has a hunch as to what the result is, he is uncertain. And when he is pretty darn sure of what the result is going to be, he is in some doubt. We have found it of paramount importance that in order to progress we must recognize our ignorance and leave room for doubt. Scientific knowledge is a body of statements of varying degrees of certainty — some most unsure, some nearly sure, but none absolutely certain.Now, we scientists are used to this, and we take it for granted that it is perfectly consistent to be unsure — that it is possible to live and not know. But I don't know whether everyone realizes this is true. Our freedom to doubt was born out of a struggle against authority in the early days of science. It was a very deep and strong struggle. Permit us to question — to doubt, that's all — not to be sure. I think that it is important that we do not forget the importance of this struggle and thus perhaps lose what we have gained. Here lies a responsibility to society.”
Richard Feynman (1918–1988) said by 1988 at the latest wikiquote, CC BY-SA 4.0 source
“We are at the very beginning of time for the human race. It is not unreasonable that we grapple with problems. But there are tens of thousands of years in the future. Our responsibility is to do what we can, learn what we can, improve the solutions, and pass them on. ...It is our responsibility to leave the people of the future a free hand. In the impetuous youth of humanity, we can make grave errors that can stunt our growth for a long time. This we will do if we say we have the answers now, so young and ignorant as we are. If we suppress all discussion, all criticism, proclaiming "This is the answer, my friends; man is saved!" we will doom humanity for a long time to the chains of authority, confined to the limits of our present imagination. It has been done so many times before. ...It is our responsibility as scientists, knowing the great progress which comes from a satisfactory philosophy of ignorance, the great progress which is the fruit of freedom of thought, to proclaim the value of this freedom; to teach how doubt is not to be feared but welcomed and discussed; and to demand this freedom as our duty to all coming generations.”
Richard Feynman (1918–1988) said by 1988 at the latest wikiquote, CC BY-SA 4.0 source
“If, in some cataclysm, all of scientific knowledge were to be destroyed, and only one sentence passed on to the next generation of creatures, what statement would contain the most information in the fewest words? I believe it is the atomic hypothesis (or the atomic fact, or whatever you wish to call it) that all things are made of atoms — little particles that move around in perpetual motion, attracting each other when they are a little distance apart, but repelling upon being squeezed into one another. In that one sentence, you will see, there is an enormous amount of information about the world, if just a little imagination and thinking are applied.”
Richard Feynman (1918–1988) said by 1988 at the latest wikiquote, CC BY-SA 4.0 source
“What do we mean by “understanding” something? We can imagine that this complicated array of moving things which constitutes “the world” is something like a great chess game being played by the gods, and we are observers of the game. We do not know what the rules of the game are; all we are allowed to do is to watch the playing. Of course, if we watch long enough, we may eventually catch on to a few of the rules. The rules of the game are what we mean by fundamental physics. Even if we knew every rule, however, we might not be able to understand why a particular move is made in the game, merely because it is too complicated and our minds are limited. If you play chess you must know that it is easy to learn all the rules, and yet it is often very hard to select the best move or to understand why a player moves as he does. So it is in nature, only much more so.”
Richard Feynman (1918–1988) said by 1988 at the latest wikiquote, CC BY-SA 4.0 source
“Poets say science takes away from the beauty of the stars — mere globs of gas atoms. Nothing is "mere". I too can see the stars on a desert night, and feel them. But do I see less or more? The vastness of the heavens stretches my imagination — stuck on this carousel my little eye can catch one-million-year-old light. A vast pattern — of which I am a part... What is the pattern, or the meaning, or the why? It does not do harm to the mystery to know a little about it. For far more marvelous is the truth than any artists of the past imagined! Why do the poets of the present not speak of it? What men are poets who can speak of Jupiter if he were a man, but if he is an immense spinning sphere of methane and ammonia must be silent?”
Richard Feynman (1918–1988) said by 1988 at the latest wikiquote, CC BY-SA 4.0 source
“Incidentally, psychoanalysis is not a science: it is at best a medical process, and perhaps even more like witch-doctoring. It has a theory as to what causes disease—lots of different “spirits,” etc. The witch doctor has a theory that a disease like malaria is caused by a spirit which comes into the air; it is not cured by shaking a snake over it, but quinine does help malaria. So, if you are sick, I would advise that you go to the witch doctor because he is the man in the tribe who knows the most about the disease; on the other hand, his knowledge is not science. Psychoanalysis has not been checked carefully by experiment.”
Richard Feynman (1918–1988) said by 1988 at the latest wikiquote, CC BY-SA 4.0 source
“A poet once said, "The whole universe is in a glass of wine." We will probably never know in what sense he meant that, for poets do not write to be understood. But it is true that if we look at a glass of wine closely enough we see the entire universe. There are the things of physics: the twisting liquid which evaporates depending on the wind and weather, the reflections in the glass, and our imagination adds the atoms. The glass is a distillation of the Earth's rocks, and in its composition we see the secrets of the universe's age, and the evolution of stars. What strange arrays of chemicals are in the wine? How did they come to be? There are the ferments, the enzymes, the substrates, and the products. There in wine is found the great generalization: all life is fermentation. Nobody can discover the chemistry of wine without discovering, as did Louis Pasteur, the cause of much disease. How vivid is the claret, pressing its existence into the consciousness that watches it! If our small minds, for some convenience, divide this glass of wine, this universe, into parts — physics, biology, geology, astronomy, psychology, and so on — remember that nature does not know it! So let us put it all back together, not forgetting ultimately what it is for. Let it give us one more final pleasure: drink it and forget it all!”
Richard Feynman (1918–1988) said by 1988 at the latest wikiquote, CC BY-SA 4.0 source
“The physicist needs a facility in looking at problems from several points of view. The exact analysis of real physical problems is usually quite complicated, and any particular physical situation may be too complicated to analyze directly by solving the differential equation. But one can still get a very good idea of the behavior of a system if one has some feel for the character of the solution in different circumstances. Ideas such as the field lines, capacitance, resistance, and inductance are, for such purposes, very useful. ... On the other hand, none of the heuristic models, such as field lines, is really adequate and accurate for all situations. There is only one precise way of presenting the laws, and that is by means of differential equations. They have the advantage of being fundamental and, so far as we know, precise. If you have learned the differential equations you can always go back to them. There is nothing to unlearn.”
Richard Feynman (1918–1988) said by 1988 at the latest wikiquote, CC BY-SA 4.0 source
“There are those who are going to be disappointed when no life is found on other planets. Not I — I want to be reminded and delighted and surprised once again, through interplanetary exploration, with the infinite variety and novelty of phenomena that can be generated from such simple principles. The test of science is its ability to predict. Had you never visited the earth, could you predict the thunderstorms, the volcanoes, the ocean waves, the auroras, and the colorful sunset? A salutary lesson it will be when we learn of all that goes on on each of those dead planets — those eight or ten balls, each agglomerated from the same dust cloud and each obeying exactly the same laws of physics.”
Richard Feynman (1918–1988) said by 1988 at the latest wikiquote, CC BY-SA 4.0 source
“...Dirac discovered the correct laws for relativity quantum mechanics simply by guessing the equation. The method of guessing the equation seems to be a pretty effective way of guessing new laws. This shows again that mathematics is a deep way of expressing nature, and any attempt to express nature in philosophical principles, or in seat-of-the-pants mechanical feelings, is not an efficient way. ...It always bothers me that, according to the laws as we understand them today, it takes a computing machine an infinite number of logical operations to figure out what goes on in no matter how tiny a region of space, and no matter how tiny a region of time. How can all that be going on in that tiny space? Why should it take an infinite amount of logic to figure out what one tiny piece of space/time is going to do? So I have often made the hypotheses that ultimately physics will not require a mathematical statement, that in the end the machinery will be revealed, and the laws will turn out to be simple, like the chequer board with all its apparent complexities.”
Richard Feynman (1918–1988) said by 1988 at the latest wikiquote, CC BY-SA 4.0 source
“So we have these wide principles which sweep across all the different laws, and if one takes too seriously its derivations, and feels that this is only valid because this [assumed more fundamental principle] is valid, you cannot understand the interconnections of the different branches of physics. Some day, when physics is complete, then maybe with this kind of argument we'll know all the laws, then we can start with some axioms (and no doubt somebody will figure out a particular way of doing it) and then all the deductions will be made. But while we don't know all the laws, we can use some to make guesses at theorems which extend beyond the proof.”
Richard Feynman (1918–1988) said by 1988 at the latest wikiquote, CC BY-SA 4.0 source
“In general we look for a new law by the following process. First we guess it. Then we compute the consequences of the guess to see what would be implied if this law that we guessed is right. Then we compare the result of the computation to nature, with experiment or experience, compare it directly with observation, to see if it works. If it disagrees with experiment it is wrong. In that simple statement is the key to science. It does not make any difference how beautiful your guess is. It does not make any difference how smart you are, who made the guess, or what his name is – if it disagrees with experiment it is wrong. That is all there is to it.”
Richard Feynman (1918–1988) said by 1988 at the latest wikiquote, CC BY-SA 4.0 source
“In general, we look for a new law by the following process: First we guess it. Then we – now don't laugh, that's really true. Then we compute the consequences of the guess to see what, if this is right, if this law that we guessed is right, to see what it would imply. And then we compare the computation results to nature, or we say compare to experiment or experience, compare it directly with observations to see if it works. If it disagrees with experiment, it's wrong. In that simple statement is the key to science. It doesn't make any difference how beautiful your guess is, it doesn't make any difference how smart you are, who made the guess, or what his name is. If it disagrees with experiment, it's wrong. That's all there is to it.”
Richard Feynman (1918–1988) said by 1988 at the latest wikiquote, CC BY-SA 4.0 source
“It is not unscientific to make a guess, although many people who are not in science think it is. Some years ago I had a conversation with a layman about flying saucers — because I am scientific I know all about flying saucers! I said “I don’t think there are flying saucers”. So my antagonist said, “Is it impossible that there are flying saucers? Can you prove that it’s impossible?” “No”, I said, “I can’t prove it’s impossible. It’s just very unlikely”. At that he said, “You are very unscientific. If you can’t prove it impossible then how can you say that it’s unlikely?” But that is the way that is scientific. It is scientific only to say what is more likely and what less likely, and not to be proving all the time the possible and impossible. To define what I mean, I might have said to him, "Listen, I mean that from my knowledge of the world that I see around me, I think that it is much more likely that the reports of flying saucers are the results of the known irrational characteristics of terrestrial intelligence than of the unknown rational efforts of extra-terrestrial intelligence." It is just more likely. That is all.”
Richard Feynman (1918–1988) said by 1988 at the latest wikiquote, CC BY-SA 4.0 source
“One of the most important things in this 'guess — compute consequences — compare with experiment' business is to know when you are right. It is possible to know when you are right way ahead of checking all the consequences. You can recognize truth by its beauty and simplicity. It is always easy when you have made a guess, and done two or three little calculations to make sure that it is not obviously wrong, to know that it is right. When you get it right, it is obvious that it is right — at least if you have any experience — because usually what happens is that more comes out than goes in. Your guess is, in fact, that something is very simple. If you cannot see immediately that it is wrong, and it is simpler than it was before, then it is right. The inexperienced, the crackpots, and people like that, make guesses that are simple, but you can immediately see that they are wrong, so that does not count. Others, the inexperienced students, make guesses that are very complicated, and it sort of looks as if it is all right, but I know it is not true because the truth always turns out to be simpler than you thought.”
Richard Feynman (1918–1988) said by 1988 at the latest wikiquote, CC BY-SA 4.0 source
“[T]he Mayan[s]... had a scheme for predicting... when Venus was a morning... or . ...[T]hey had a rule for... making corrections and... had a very good way of predicting when Venus was coming up. ...Suppose that the professors (the priests in those days) ...were giving a lecture ...to explain ... these wonderful predictions ...He would say, "What we're doing is counting the days, just like you're putting nuts in a pod." ...[The students] did not know a quick and tricky way to add 365 x 8. ...These students were learning ...the laws of arithmetic. Something... to us now, because we have public, free, general education, almost everybody has to... learn... by a tricky scheme... The waitress, just an ordinary person, in two minutes does that. How..? ...She's ...counting ...415 pennies ...then ...287 more ...and telling you how many pennies you would have got if you counted ...beginning to the end. But it's highly educated and very trained to... do that... quickly. ...In the 14th century [it was] mathematicians... who could do that.”
Richard Feynman (1918–1988) said by 1988 at the latest wikiquote, CC BY-SA 4.0 source
“What the students are taught ...now ...about physics ...The numbers are much bigger... so enormous you can't count them directly, and so we've invented a fantastic array of tricks and gimmicks for putting together the numbers... without actually doing it. ...We don't actually ...draw 7,000 arrows and find... the end point... just like we don't actually count 415 pennies... We do it by... the tricks of mathematics, and that's all. So... we're not going to worry about that. ...[Y]ou don't have to know about mathematics. All you have to know is what it is... tricky ways of doing something which would be laborious otherwise.”
Richard Feynman (1918–1988) said by 1988 at the latest wikiquote, CC BY-SA 4.0 source
“[I]n the years we have developed enormous abilities in mathematics and it takes a long time to train the students, and so they're very highly educated in that, but if you ask them why. Now we go back to the Mayans... [W]hy the rule? ...They don't know. They don't understand... The more accurately they can do it... adds nothing to their understanding... The student who is able to make these calculations of Venus... Mars, the Sun, the eclipses and everything else is a super priest, doesn't know why, any better. And if you were to explain that it was nothing but counting days, you would be reduced to the truth... and to an honest statement that he doesn't understand it.”
Richard Feynman (1918–1988) said by 1988 at the latest wikiquote, CC BY-SA 4.0 source
“Amplify. ...[W]hen we have a device like this and we put it in the dark... it goes click, click... Every once in a while a light particle comes in: a photon. This is a particle in every sense. ...[I]f you have a very weak light... and... you put two cells out, and there's just a few... [photons] coming, then it goes on one or the other... the particle is either here or there. ...It is particles, in every way, whenever you can detect it. ...If we were ten times more sensitive to light, then in the dark, we would see... little flashes, little tiny... dots of light, the nerves would go off just like the photomultiplier, in spots. But the human eye is not quite that sensitive, and it takes 5 or 6 ...photons ...to make one nerve fiber go off. ...So we cannot detect, with the eye, light quite low enough to notice the fact that it comes in the form of rain drops.”
Richard Feynman (1918–1988) said by 1988 at the latest wikiquote, CC BY-SA 4.0 source
“For each reflection you make an arrow. This arrow... for the reflection from front surface, and this arrow... from the back surface... and... you tie the arrows together this way... [Y]ou put the tail of the other one on the head of that one... and you put these two arrows together by this rule, and you look at [the vector sum,] how far off you've come from the end... You count the number of beans you put in the barrel, I mean you make these pictures. ...[T]hen you ask, "How big is this circle [whose radius is the vector sum of the front and back arrows] in area?" And that area represents the probability... If the circle area is big, then you get a high probability, if... small, you get a small probability.”
Richard Feynman (1918–1988) said by 1988 at the latest wikiquote, CC BY-SA 4.0 source
“[T]he size of the arrow depends upon the... materials... [Y]ou make an arrow, and depending upon the time it takes for the light to get from the source to... where you... count it, you turn that arrow like a clock... round, round, depending on how much time it takes... every second it goes around... 1 followed by 15 zeros [10^{15}] times... It doesn't take light very long to get from the source... but it still turns a lot of times... It's like the roulette wheel and just the moment it hits the counter, it happens to be setting at some angle... It can look like a small angle when you're done, but you had to turn... like a clock hand after 25 years... it can start at 2:00 and end up at 2:15. ...That's ...the arrow for the first surface. Now the arrow for the second surface. Rule: same as the arrow for the first surface... [rotated] in the... opposite direction... When you go from air to glass it's one way... glass to air you change it around. ...You start this way for the second surface, and you turn this [arrow]... for the time, and when you get finished with this roulette wheel in the second one it comes out so. And now you add them together... and that's the laws of... light, and that will tell you whether it reflects or doesn't reflect.”
Richard Feynman (1918–1988) said by 1988 at the latest wikiquote, CC BY-SA 4.0 source
“I start with the simplest phenomena... the first... is the phenomena of light. Early on, when light was being investigated by Newton, he thought that the light that came into the eye was like a rain of particles, like rain drops... [M]ore light meant more particles... and one kind of color light would one kind of rain drop and another... would be a different kind of rain drop... over the whole spectrum... and if we would some day have sufficiently delicate instruments, we would presumably discover that it was like a pattering... [I]t would go click, click, click when the particles came raining down. ...He also discovered ...the light from the soap bubbles or light from thin films... The brightness of reflection... depends on how thick the film is. As the film gets thicker and thinner, it gets brighter and darker. That was hard for him to understand from the point of view of particles. Finally a theory of waves was invented which explained that very easily... until we measured light very precisely... and lo and behold, to our horror, it behaved like particles.”
Richard Feynman (1918–1988) said by 1988 at the latest wikiquote, CC BY-SA 4.0 source
“If we try to say how big a photon is, or how it's spread out, or what it looks like, we're going to get into some difficulty with some experiment. It isn't going to behave that way you'd expect. ...[I]t's going to be impossible for me to tell you how big a photon is, where it is... Nevertheless... I'll tell you a series of crazy rules by which you can tell exactly what will happen in any experiment with photons... without ever being able to say what a photon looks like... in the sense of some sort of model of waves in space. ...And so to make a complete theory, we cannot do it with a model. We can only make an incomplete theory and what my purpose is today is to tell you the complete theory, not the incomplete approximations...”
Richard Feynman (1918–1988) said by 1988 at the latest wikiquote, CC BY-SA 4.0 source
“Finally, I must tell you what the arrow is for the net result. When a thing can happen in alternative ways you do what we call "add the arrows"... I know how to add numbers. How do you add arrows? The rule is... you simply put one arrow head on the tail of the other... I just draw the second arrow off from the first one... exactly parallel... it's drawn the same, but it's centered, it's moved... it's tied one onto the other, head to tail, and the result, it's supposed to be the sum. The adding is this net arrow that you would get, from where you started [from the beginning of the first arrow] to where you ended [at the end of the second arrow]. The way of thinking of it, that is rather nice, is to think of each arrow as indicating the direction of a step to be taken. If we take a step, on this plane, this way [the distance and direction of arrow #1] and then take a step that way [the distance and direction of arrow #2] and we say, where did we actually move? We could have done it all in one step, this one [from the beginning of arrow #1 to the end of arrow #2]. So this is the one step which is the equivalent of the succession of the other steps. Adding means putting together steps... The square of the [summation] arrow determines the probability of the reflection.”
Richard Feynman (1918–1988) said by 1988 at the latest wikiquote, CC BY-SA 4.0 source
“I want you to think of an arrow in another way... Here is an arrow... Now if we multiply, you have to think in a different way than for adding. There's an arrow... and imagine there's a [different] standard arrow... always horizontal and has unit length, that's the standard unit arrow. Now suppose I have a second arrow and I want to multiply them... [W]hat do I mean by multiplying? ...Let me first describe this [first] arrow [number 1] ...compare it to the standard arrow and ask for the relation... You can turn... and shrink it. So an arrow describes... how much I have to shrink the standard, and how much I have to rotate it to get the arrow I want. Now multiplication of arrows means that you do these rotations and shrinkings in succession. ...Now if I take this arrow [#2] ...this red [arrow #3] is the product [of arrow #1 and arrow #2].... It bears the same geometric relationship to the purple arrow [#2] as the blue one [arrow number 1] bears to the black one [standard arrow]. In other words it's supposed to be turned the same degree and shrunk the same degree as the blue one [arrow #2] is to the black [standard] one. In other words this [arrow #1] is to that [standard arrow], as this [arrow #3] arrow is to that [arrow #2].”
Richard Feynman (1918–1988) said by 1988 at the latest wikiquote, CC BY-SA 4.0 source