Richard Feynman

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Physics isn't the most important thing. Love is.
All mass is interaction.

Richard Phillips Feynman (May 11, 1918February 15 1988) was an American physicist; in the International Phonetic Alphabet his surname is rendered [ˈfaɪnmən], the first syllable sounding like "fine".

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To those who do not know mathematics it is difficult to get across a real feeling as to the beauty, the deepest beauty, of nature...
Our imagination is stretched to the utmost, not, as in fiction, to imagine things which are not really there, but just to comprehend those things which are there.
No problem is too small or too trivial if we can really do something about it.
I learned very early the difference between knowing the name of something and knowing something.
  • On the contrary, it's because someone knows something about it that we can't talk about physics. It's the things that nobody knows about that we can discuss. We can talk about the weather; we can talk about social problems; we can talk about psychology; we can talk about international finance... so it's the subject that nobody knows anything about that we can all talk about!
    • Statement (1965), when told that nobody else at the table he was dining at knew anything about physics and thus they could not talk about it, quoted in Philippe Aghion, Steven N. Durlauf, Handbook of Economic Growth.
  • Principles
    You can't say A is made of B
    or vice versa.
    All mass is interaction.
    • Statement (c. 1950), quoted in Genius : The Life and Science of Richard Feynman (1992) by James Gleick
  • It doesn't seem to me that this fantastically marvelous universe, this tremendous range of time and space and different kinds of animals, and all the different planets, and all these atoms with all their motions, and so on, all this complicated thing can merely be a stage so that God can watch human beings struggle for good and evil — which is the view that religion has. The stage is too big for the drama.
    • (1959), quoted by James Gleick in Genius: The Life and Science of Richard Feynman (1992)
  • On the infrequent occasions when I have been called upon in a formal place to play the bongo drums, the introducer never seems to find it necessary to mention that I also do theoretical physics.
    • Statement after an introduction mentioning that he played bongo drums; Messenger Lectures at Cornell University (1964-5).
  • To those who do not know mathematics it is difficult to get across a real feeling as to the beauty, the deepest beauty, of nature ... If you want to learn about nature, to appreciate nature, it is necessary to understand the language that she speaks in.
    • The Character of Physical Law (1965) Ch. 2
  • Our imagination is stretched to the utmost, not, as in fiction, to imagine things which are not really there, but just to comprehend those things which are there.
    • The Character of Physical Law (1965)
  • Do not keep saying to yourself, if you can possibly avoid it, "But how can it be like that?" because you will get "down the drain," into a blind alley from which nobody has yet escaped. Nobody knows how it can be like that.
    • On the apparent absurdities of Quantum behavior, in The Character of Physical Law (1965) Lecture 6 : Probability and Uncertainity — the Quantum Mechanical view of Nature,
  • The chance is high that the truth lies in the fashionable direction. But, on the off chance that it is in another direction — a direction obvious from an unfashionable view of field theory — who will find it? Only someone who has sacrificed himself by teaching himself quantum electrodynamics from a peculiar and unfashionable point of view; one that he may have to invent for himself.
  • The worthwhile problems are the ones you can really solve or help solve, the ones you can really contribute something to. ... No problem is too small or too trivial if we can really do something about it.
    • Letter from Feynman to Koichi Mano (3 February 1966); published in Perfectly Reasonable Deviations from the Beaten Track : The Letters of Richard P. Feynman (2005)
  • You say you are a nameless man. You are not to your wife and to your child. You will not long remain so to your immediate colleagues if you can answer their simple questions when they come into your office. You are not nameless to me. Do not remain nameless to yourself — it is too sad a way to be. Know your place in the world and evaluate yourself fairly, not in terms of the naïve ideals of your own youth, nor in terms of what you erroneously imagine your teacher's ideals are.
    • Letter from Feynman to Koichi Mano (3 February 1966); published in Perfectly Reasonable Deviations from the Beaten Track : The Letters of Richard P. Feynman (2005); also quoted by Freeman Dyson in "Wise Man", New York Review of Books (20 October 2005)
  • You can know the name of a bird in all the languages of the world, but when you're finished, you'll know absolutely nothing whatever about the bird... So let's look at the bird and see what it's doing — that's what counts. I learned very early the difference between knowing the name of something and knowing something.
    • "What is Science?", presented at the fifteenth annual meeting of the National Science Teachers Association, in New York City (1966) published in The Physics Teacher Vol. 7, issue 6 (1969)
  • 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... Details that could throw doubt on your interpretation must be given, if you know them.
    • "Cargo Cult Science", adapted from a commencement address given at Caltech (1974)
If I could explain it to the average person, I wouldn't have been worth the Nobel Prize.
  • 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.
    • "Cargo Cult Science", adapted from a commencement address given at CalTech (1974)
For a successful technology, reality must take precedence over public relations, for nature cannot be fooled.
  • If I could explain it to the average person, I wouldn't have been worth the Nobel Prize.
    • People (22 July 1985)
  • I took this stuff I got out of your [O-ring] seal and I put it in ice water, and I discovered that when you put some pressure on it for a while and then undo it it doesn't stretch back. It stays the same dimension. In other words, for a few seconds at least, and more seconds than that, there is no resilience in this particular material when it is at a temperature of 32 degrees. I believe that has some significance for our problem.
    • Press conference of the presidential commission into the Challenger disaster. (10 February 1986)
There in wine is found the great generalization: all life is fermentation.
  • I think I can safely say that nobody understands quantum mechanics.
    • The Character of Physical Law (1965) Ch. 6
    • The New Quantum Universe (2003) by Tony Hey and Patrick Walters
      • "The Quantum Universe has a quotation from me in every chapter — but it's a damn good book anyway" ~ reviewing the first edition of The Quantum Universe (1987)
    • Unsourced variant or misquotation: I think it is safe to say that no one understands quantum mechanics.
  • 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 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 imaginations adds the atoms. The glass is a distillation of the Earth's rocks, and in its composition we see the secret of the universe's age, and the evolution of the stars. What strange array of chemicals are there 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!
    • The New Quantum Universe (2003) by Tony Hey and Patrick Walters; Epilogue
What I cannot create, I do not understand.
  • God was 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.
    • As quoted in Superstrings : A Theory of Everything (1988) Edited by Paul C. W. Davies and Julian R. Brown ISBN 0521354625
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 more about it.
  • What I cannot create, I do not understand.
    • On his blackboard at time of death in 1988; as quoted in The Universe in a Nutshell by Stephen Hawking
  • We scientists are clever — too clever — are you not satisfied? Is four square miles in one bomb not enough? Men are still thinking. Just tell us how big you want it.
    • Undated personal note, quoted in Genius: The Life and Science of Richard Feynman (1992) by James Gleick
  • I'd hate to die twice. It's so boring.
    • Last words, as quoted in Genius: The Life and Science of Richard Feynman (1992) by James Gleick
  • A great deal more is known than has been proved.
    • Quoted in The Music of the Primes : Searching to Solve the Greatest Mystery of Mathematics (2003) by Marcus du Sautoy

The Feynman Lectures on Physics (1964)

  • Each piece, or part, of the whole nature is always an approximation to the complete truth, or the complete truth so far as we know it. In fact, everything we know is only some kind of approximation, because we know that we do not know all the laws as yet. Therefore, things must be learned only to be unlearned again or, more likely, to be corrected.......The test of all knowledge is experiment. Experiment is the sole judge of scientific “truth”.
    • Volume I, 1-1, Introduction
  • It is important to realize that in physics today, we have no knowledge what energy is. We do not have a picture that energy comes in little blobs of a definite amount.
    • Volume I, 4-1
  • We can't define anything precisely. If we attempt to, we get into that paralysis of thought that comes to philosophers… one saying to the other: "you don't know what you are talking about!". The second one says: "what do you mean by talking? What do you mean by you? What do you mean by know?"
    • Volume I, 8-2
  • From a long view of the history of mankind — seen from, say, ten thousand years from now, there can be little doubt that the most significant event of the 19th century will be judged as Maxwell's discovery of the laws of electrodynamics. The American Civil War will pale into provincial insignificance in comparison with this important scientific event of the same decade.
    • Volume II, 1-6 end
Far more marvelous is the truth than any artists of the past imagined it. Why do the poets of the present not speak of it?
  • In fact, the science of thermodynamics began with an analysis, by the great engineer Sadi Carnot, of the problem of how to build the best and most efficient engine, and this constitutes one of the few famous cases in which engineering has contributed to fundamental physical theory. Another example that comes to mind is the more recent analysis of information theory by Claude Shannon. These two analyses, incidentally, turn out to be closely related.
    • "The Laws of Thermodynamics"
  • If, in some cataclysm, all 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 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 an enormous amount of information about the world, if just a little imagination and thinking are applied.
Although we humans cut nature up in different ways, and we have different courses in different departments, such compartmentalization is really artificial...
  • 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 more about it. For far more marvelous is the truth than any artists of the past imagined it. 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?
    • Footnote
  • So, ultimately, in order to understand nature it may be necessary to have a deeper understanding of mathematical relationships. But the real reason is that the subject is enjoyable, and although we humans cut nature up in different ways, and we have different courses in different departments, such compartmentalization is really artificial, and we should take our intellectual pleasures where we find them.

The Character of Physical Laws (1964)

  • For those who want some proof that physicists are human, the proof is in the idiocy of all the different units which they use for measuring energy.
  • The next question was — what makes planets go around the sun? At the time of Kepler some people answered this problem by saying that there were angels behind them beating their wings and pushing the planets around an orbit. As you will see, the answer is not very far from the truth. The only difference is that the angels sit in a different direction and their wings push inward.
  • Nature uses only the longest threads to weave her patterns, so that each small piece of her fabric reveals the organization of the entire tapestry.

On flying saucers

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.
  • 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.
    • The Character of Physical Law. Cornell University Messenger Lectures (1964)
  • Anyway, I have to argue about flying saucers on the beach with people, you know. And I was interested in this: they keep arguing that it is possible. And that's true. It is possible. They do not appreciate that the problem is not to demonstrate whether it's possible or not but whether it's going on or not.
    • The Meaning of It All: Thoughts of a Citizen Scientist

Surely You're Joking, Mr. Feynman! (1985)

A collection of reminiscences from taped interviews with fellow scientist and friend Ralph Leighton. ISBN 0393316041
I would see people building a bridge, or they'd be making a new road, and I thought, they're crazy, they just don't understand, they don't understand.
I'm glad those other people had the sense to go ahead.
  • I'll never make that mistake again, reading the experts' opinions. Of course, you only live one life, and you make all your mistakes, and learn what not to do, and that's the end of you.
  • I don't know what's the matter with people: they don't learn by understanding, they learn by some other way — by rote or something. Their knowledge is so fragile!
  • And this is medicine?
    • Comment to the psychiatrist who was examining him and who had stated he studied medicine to become a psychiatrist.
    • Part 3: "Feynman, The Bomb, and the Military", "Uncle Sam Doesn't Need You"
  • I returned to civilization shortly after that and went to Cornell to teach, and my first impression was a very strange one. I can't understand it any more, but I felt very strongly then. I sat in a restaurant in New York, for example, and I looked out at the buildings and I began to think, you know, about how much the radius of the Hiroshima bomb damage was and so forth... How far from here was 34th street?... All those buildings, all smashed — and so on. And I would see people building a bridge, or they'd be making a new road, and I thought, they're crazy, they just don't understand, they don't understand. Why are they making new things? It's so useless.
    But, fortunately, it's been useless for almost forty years now, hasn't it? So I've been wrong about it being useless making bridges and I'm glad those other people had the sense to go ahead.
    • On his emotional reactions after the first uses of the atomic bomb. Part 3: "Feynman, The Bomb, and the Military", "Los Alamos from Below"
  • One time I was in the men's room of the bar and there was a guy at the urinal. He was kind of drunk, and said to me in a mean-sounding voice, "I don't like your face. I think I'll push it in."
    I was scared green. I replied in an equally mean voice, "Get out of my way, or I'll pee right through ya!"
    • Part 4: "From Cornell to Caltech, With A Touch of Brazil", "Any Questions?"
  • I have to understand the world, you see.
    • Part 4: "From Cornell to Caltech, With A Touch of Brazil", "Certainly, Mr. Big!"

What Do You Care What Other People Think? (1988)

There are all kinds of interesting questions that come from a knowledge of science, which only adds to the excitement and mystery and awe of a flower.
We have found it of paramount importance that in order to progress, we must recognize our ignorance and leave room for doubt.
  • I have a friend who's an artist, and he sometimes takes a view which I don't agree with. He'll hold up a flower and say, "Look how beautiful it is," and I'll agree. But then he'll say, "I, as an artist, can see how beautiful a flower is. But you, as a scientist, take it all apart and it becomes dull." I think he's kind of nutty. [...] There are all kinds of interesting questions that come from a knowledge of science, which only adds to the excitement and mystery and awe of a flower. It only adds. I don't understand how it subtracts.
  • In particular, she had a wonderful sense of humor, and I learned from her that the highest forms of understanding we can achieve are laughter and human compassion.
    • Commenting on his mother's influence.
  • 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 damn sure of what the result is going to be, he is still 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 — to not be sure. I think that it is important that we do not forget this struggle and thus perhaps lose what we have gained.
    • "The Value of Science," address to the National Academy of Sciences (Autumn 1955)
There are the rushing waves
mountains of molecules each stupidly minding its own business
trillions apart yet forming white surf in unison.
Here it is standing: atoms with consciousness; matter with curiosity.
Stands at the sea, wondering: I... a universe of atoms
an atom in the universe.
  • 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 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.

    • "The Value of Science," address to the National Academy of Sciences (Autumn 1955)
  • Is no one inspired by our present picture of the universe? This value of science remains unsung by singers, you are reduced to hearing not a song or poem, but an evening lecture about it. This is not yet a scientific age.

Six Easy Pieces (1995)

  • If an apple was magnified to the size of the Earth, then the atoms in the apple would be approximately the size of the original apple.

The Meaning of it All (1999)

The Meaning of It All: Thoughts of a Citizen Scientist (1999) ISBN 0738201669 A collection of three guest lectures Feynman gave at the University of Washington.
Some people say, "How can you live without knowing?" I do not know what they mean. I always live without knowing. That is easy. How you get to know is what I want to know.
If you ask naive but relevant questions, then almost immediately the person doesn't know the answer, if he is an honest man.
  • Some people say, "How can you live without knowing?" I do not know what they mean. I always live without knowing. That is easy. How you get to know is what I want to know.
  • It's a great game to look at the past, at an unscientific era, look at something there, and say have we got the same thing now, and where is it? So I would like to amuse myself with this game. First, we take witch doctors. The witch doctor says he knows how to cure. There are spirits inside which are trying to get out. ... Put a snakeskin on and take quinine from the bark of a tree. The quinine works. He doesn't know he's got the wrong theory of what happens. If I'm in the tribe and I'm sick, I go to the witch doctor. He knows more about it than anyone else. But I keep trying to tell him he doesn't know what he's doing and that someday when people investigate the thing freely and get free of all his complicated ideas they'll learn much better ways of doing it. Who are the witch doctors? Psychoanalysts and psychiatrists, of course.
    • Third lecture. David Goodstein reports that the entire Psychology department walked out in a huff at this point [1].
  • The third aspect of my subject is that of science as a method of finding things out. This method is based on the principle that observation is the judge of whether something is so or not. All other aspects and characteristics of science can be understood directly when we understand that observation is the ultimate and final judge of the truth of an idea. But "prove" used in this way really means "test," in the same way that a hundred-proof alcohol is a test of the alcohol, and for people today the idea really should be translated as, "The exception tests the rule." Or, put another way, "The exception proves that the rule is wrong." That is the principle of science. If there is an exception to any rule, and if it can be proved by observation, that rule is wrong.
  • No government has the right to decide on the truth of scientific principles, nor to prescribe in any way the character of the questions investigated. Neither may a government determine the aesthetic value of artistic creations, nor limit the forms of literacy or artistic expression. Nor should it pronounce on the validity of economic, historic, religious, or philosophical doctrines. Instead it has a duty to its citizens to maintain the freedom, to let those citizens contribute to the further adventure and the development of the human race.
    • "The Uncertainty of Values"
  • The first ... has to do with whether a man knows what he is talking about, whether what he says has some basis or not. And my trick that I use is very easy. If you ask him intelligent questions — then he quickly gets stuck. It is like a child asking naive questions. If you ask naive but relevant questions, then almost immediately the person doesn't know the answer, if he is an honest man.
  • Looking back at the worst times, it always seems that they were times in which there were people who believed with absolute faith and absolute dogmatism in something. And they were so serious in this matter that they insisted that the rest of the world agree with them. And then they would do things that were directly inconsistent with their own beliefs in order to maintain that what they said was true.
  • The fact that you are not sure means that it is possible that there is another way someday.

The Pleasure of Finding Things Out (1999)

The Pleasure of Finding Things Out : The Best Short Works of Richard Feynman, edited by Jeffery Robbins ISBN 0-14-029034-6
Science is the belief in the ignorance of experts.
  • I can live with doubt, and uncertainty, and not knowing. I think it's much more interesting to live not knowing than to have answers which might be wrong. I have approximate answers, and possible beliefs, and different degrees of certainty about different things, but I’m not absolutely sure of anything, and in many things I don’t know anything about, such as whether it means anything to ask why we’re here, and what the question might mean. I might think about a little, but if I can’t figure it out, then I go to something else. But I don’t have to know an answer. I don’t feel frightened by not knowing things, by being lost in a mysterious universe without having any purpose, which is the way it really is, as far as I can tell, possibly. It doesn’t frighten me.
    • The Pleasure of Finding Things Out.
  • Science is a way of trying not to fool yourself. The first principle is that you must not fool yourself, and you are the easiest person to fool.
    • From lecture "What is and What Should be the Role of Scientific Culture in Modern Society", given at the Galileo Symposium in Italy, 1964.
  • Science alone of all the subjects contains within itself the lesson of the danger of belief in the infallibility of the greatest teachers in the preceding generation ... Learn from science that you must doubt the experts. As a matter of fact, I can also define science another way: Science is the belief in the ignorance of experts.
    • Pages 186-187. Based on transcriptions from an interview made in 1981.
  • The remark which I read somewhere, that science is all right as long as it doesn't attack religion, was the clue I needed to understand the problem. As long as it doesn't attack religion it need not be paid attention to and nobody has to learn anything. So it can be cut off from society except for its applications, and thus be isolated. And then we have this terrible struggle to try to explain things to people who have no reason to want to know. But if they want to defend their own point of view, they will have to learn what yours is a little bit. So I suggest, maybe correctly and perhaps wrongly, that we are too polite.
    • From lecture "What is and What Should be the Role of Scientific Culture in Modern Society", given at the Galileo Symposium in Italy, 1964.
  • We absolutely must leave room for doubt or there is no progress and no learning. There is no learning without having to pose a question. And a question requires doubt. People search for certainty. But there is no certainty. People are terrified—how can you live and not know? It is not odd at all. You only think you know, as a matter of fact. And most of your actions are based on incomplete knowledge and you really don't know what it is all about, or what the purpose of the world is, or know a great deal of other things. It is possible to live and not know.
    • From lecture "What is and What Should be the Role of Scientific Culture in Modern Society", given at the Galileo Symposium in Italy, 1964.

Unsourced

Nature uses only the longest threads to weave her patterns, so each small piece of her fabric reveals the organization of the entire tapestry.
  • Our imagination is stretched to the utmost, not, as in fiction, to imagine things which are not really there, but just to comprehend those things which are there.
  • Science is what we have learned about how not to fool ourselves about the way the world is.
  • All fundamental processes are reversible.
  • Einstein was a giant. His head was in the clouds, but his feet were on the ground. Those of us who are not so tall have to choose!
  • Dear Mrs. Chown, Ignore your son's attempts to teach you physics. Physics isn't the most important thing. Love is. Best wishes, Richard Feynman.
  • Don't worry about anything... Go out and have a good time.
  • I cannot define the real problem, therefore I suspect there's no real problem, but I'm not sure there's no real problem.
    • On the idea that there is an inherent problem with Quantum Theory
  • If you can't explain something to a first year student, then you haven't really understood it.
    • Variant: "If you can't explain it to a six year old, you don't really understand it."
    • Sometimes attributed to Einstein
    • Cf. this from Kurt Vonnegut's novel Cat's Cradle:
Dr. Hoenikker used to say that any scientist who couldn't explain to an eight-year-old what he was doing was a charlatan.
  • It is in the admission of ignorance and the admission of uncertainty that there is a hope for the continuous motion of human beings in some direction that doesn't get confined, permanently blocked, as it has so many times before in various periods in the history of man.
If it turns out there is a simple ultimate law which explains everything, so be it — that would be very nice to discover. If it turns out it's like an onion with millions of layers... then that's the way it is.
  • It doesn't matter how beautiful your theory is, it doesn't matter how smart you are. If it doesn't agree with experiment, it's wrong.
  • Mathematics is not real, but it feels real. Where is this place?
  • Nature uses only the longest threads to weave her patterns, so each small piece of her fabric reveals the organization of the entire tapestry.
  • People say to me, "Are you looking for the ultimate laws of physics?" No, I'm not... If it turns out there is a simple ultimate law which explains everything, so be it — that would be very nice to discover. If it turns out it's like an onion with millions of layers... then that's the way it is. But either way there's Nature and she's going to come out the way She is. So therefore when we go to investigate we shouldn't predecide what it is we're looking for only to find out more about it. Now you ask: "Why do you try to find out more about it?" If you began your investigation to get an answer to some deep philosophical question, you may be wrong. It may be that you can't get an answer to that particular question just by finding out more about the character of Nature. But that's not my interest in science; my interest in science is to simply find out about the world and the more I find out the better it is, I like to find out...
  • Physics is like sex. Sure, it may give some practical results, but that's not why we do it.
  • Religion is a culture of faith; science is a culture of doubt.
  • The theoretical broadening which comes from having many humanities subjects on the campus is offset by the general dopiness of the people who study these things.
  • The same equations have the same solutions. (Thus when you have solved a mathematical problem, you can re-use the solution in another physical situation. Feynman was skilled in transforming a problem into one that he could solve.)
  • The wonderful thing about science is that it's alive.
  • There are 1011 stars in the galaxy. That used to be a huge number. But it's only a hundred billion. It's less than the national deficit! We used to call them astronomical numbers. Now we should call them economical numbers.
  • What does it mean, to understand? ... I don't know.
  • 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.
  • When you are solving a problem, don't worry. Now, after you have solved the problem, then that's the time to worry.
  • Know how to solve every problem that has been solved.
  • You know, the most amazing thing happened to me tonight. I was coming here, on the way to the lecture, and I came in through the parking lot. And you won't believe what happened. I saw a car with the license plate ARW 357. Can you imagine? Of all the millions of license plates in the state, what was the chance that I would see that particular one tonight? Amazing!
  • I am not happy with all the analysis that go with just classical theory, because nature is not classic, dammit, and if you want to make a simulation of nature you’d better make it quantum mechanical and by golly it is a wonderful problem.

Disputed

  • Shut up and calculate!
    "If I were forced to sum up in one sentence what the Copenhagen interpretation says to me, it would be 'Shut up and calculate!'."

Quotations about Feynman

The electron does anything it likes... It just goes in any direction at any speed, forward or backward in time, however it likes...
  • Thirty-one years ago [1949], 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.
  • If that's the world's smartest man, God help us.
    • His mother, Lucille Feynman, after Omni magazine named him the world's smartest man; as quoted in Genius: The Life and Science of Richard Feynman (1992) by James Gleick
  • The Feynman Problem-Solving Algorithm:
      (1) write down the problem;
      (2) think very hard;
      (3) write down the answer.
He is by all odds the most brilliant young physicist here, and everyone knows this. ~ J. Robert Oppenheimer
  • Shortly before midnight on February 15, 1988, his body gasped for air that the oxygen tube could not provide, and his space in the world closed. An imprint remained: what he knew, how he knew.
    • James Gleick in Genius: Richard Feynman and modern physics
  • There are two kinds of geniuses: the 'ordinary' and the 'magicians'. An ordinary genius is a fellow whom you and I would be just as good as, if we were only many times better. There is no mystery as to how his mind works. Once we understand what they've done, we feel certain that we, too, could have done it. It is different with the magicians. Even after we understand what they have done it is completely dark. Richard Feynman is a magician of the highest calibre.
  • In fact he is all genius and all buffoon.
    • Freeman Dyson, who described Feynman as "half genius and half buffoon" years earlier.
  • He is by all odds the most brilliant young physicist here, and everyone knows this.
  • 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 Steven 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.
    • Al Seckel anecdote concerning Feynman's perspective on Hawking's ability to do the mathematical equations that his work requires in his head, at feynman.com.
  • Richard Feynman became so exasperated [at the National Academy of Sciences] that he resigned his membership, saying that he saw no point in belonging to an organization that spent most of its time deciding who to let in.
    • Gregory Benford, "A Scientist's Notebook: Scientist Heroes" in The Magazine of Science Fiction and Fantasy (4/1996)
  • There were 183 of us 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."
  • This verse is for Richard Feynman, He was not a simple simon.
    • Jeff Coffin (of Béla Fleck and the Flecktones) in the song "Ah shu Dekio" (during a live show recorded and released on DVD as "Live at the Quick")
  • Why should we care about Feynman? What was so special about him? Why did he become a public icon, standing with Albert Einstein and Stephen Hawking as the Holy Trinity of twentieth-century physics? The public has demonstrated remarkably good taste in choosing its icons. All three of them are genuinely great scientists, with flashes of true genius as well as solid accomplishments to their credit. But to become an icon, it is not enough to be a great scientist. There are many other scientists, not so great as Einstein but greater than Hawking and Feynman, who did not become icons. ...

    Scientists who become icons must not only be geniuses but also performers, playing to the crowd and enjoying public acclaim. Einstein and Feynman both grumbled about the newspaper and radio reporters who invaded their privacy, but both gave the reporters what the public wanted, sharp and witty remarks that would make good headlines. Hawking in his unique way also enjoys the public adulation that his triumph over physical obstacles has earned for him. I will never forget the joyful morning in Tokyo when Hawking went on a tour of the streets in his wheelchair and the Japanese crowds streamed after him, stretching out their hands to touch his chair. Einstein, Hawking, and Feynman shared an ability to break through the barriers that separated them from ordinary people. The public responded to them because they were regular guys, jokers as well as geniuses.

    The third quality that is needed for a scientist to become a public icon is wisdom. Besides being a famous joker and a famous genius, Feynman was also a wise human being whose answers to serious questions made sense. To me and to hundreds of other students who came to him for advice, he spoke truth. Like Einstein and Hawking, he had come through times of great suffering, nursing Arline through her illness and watching her die, and emerged stronger. Behind his enormous zest and enjoyment of life was an awareness of tragedy, a knowledge that our time on earth is short and precarious. The public made him into an icon because he was not only a great scientist and a great clown but also a great human being and a guide in time of trouble. Other Feynman books have portrayed him as a scientific wizard and as a storyteller. This collection of letters shows us for the first time the son caring for his father and mother, the father caring for his wife and children, the teacher caring for his students, the writer replying to people throughout the world who wrote to him about their problems and received his full and undivided attention.

    • Freeman Dyson, "Wise Man", New York Review of Books (20 October 2005)
  • Murray Gell-Mann angered [Feynman's] family at a memorial service by asserting "He surrounded himself with a cloud of myth, and he spent a great deal of time and energy generating anecdotes about himself." These were stories, Gell-Mann added, "in which he had to come out, if possible, looking smarter than anyone else."
    • James Gleick in the prologue to Genius: The Life and Science of Richard Feynman (1992)

External links

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