Richard Feynman citations

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Richard Feynman

Date de naissance: 11. mai 1918
Date de décès: 15. février 1988
Autres noms: Richard Feynman Philips, Richard Phillips Feynman, Ричард Филлипс Фейнман

Richard Phillips Feynman est un physicien américain, l'un des plus influents de la seconde moitié du XXe siècle, en raison notamment de ses travaux sur l'électrodynamique quantique, les quarks et l'hélium superfluide.

Il reformula entièrement la mécanique quantique à l'aide de son intégrale de chemin qui généralise le principe de moindre action de la mécanique classique et inventa les diagrammes qui portent son nom et qui sont désormais largement utilisés en théorie quantique des champs .

Pendant la Seconde Guerre mondiale, il fut impliqué dans le développement de la bombe atomique américaine. Après la Seconde Guerre mondiale, il enseigna à l'université Cornell puis au Caltech où il effectua des travaux fondamentaux notamment dans la théorie de la superfluidité et des quarks. Sin-Itiro Tomonaga, Julian Schwinger et lui sont colauréats du prix Nobel de physique de 1965 pour leurs travaux en électrodynamique quantique. Vers la fin de sa vie, son action au sein de la commission d'enquête sur l'accident de la navette spatiale Challenger l'a fait connaître du grand public américain.

Pédagogue remarquable, il est le rédacteur de nombreux ouvrages de vulgarisation reconnus. Parmi ces livres, les Feynman lectures on physics, un cours de physique de niveau universitaire qui, depuis sa parution, est devenu un classique pour tous les étudiants de premier cycle en physique et leurs professeurs. Il raconte aussi ses nombreuses aventures dans plusieurs ouvrages : Surely You're Joking, Mr. Feynman! et What Do You Care What Other People Think?. Ce tome est lié au soutien moral que sa première épouse Arline lui donnait, l'encourageant par ce biais dans sa poursuite intellectuelle en tant que libre-penseur.

Citations Richard Feynman

„[…] nous avons toujours eu (chut, chut, fermez les portes!), nous avons toujours eu beaucoup de mal à comprendre l'image du monde que nous offre la mécanique quantique. Du moins, en ce qui me concerne, parce que je suis assez âgé, je ne suis pas encore parvenu à me convaincre que tous ces trucs-là étaient évidents. OK, ça m'énerve toujours. Ainsi quelques étudiants plus jeunes… Vous savez ce que c'est : à chaque nouvelle idée, il faut une ou deux générations pour constater qu'elle ne pose pas de vraie difficulté. Il n'est toujours pas évident pour moi qu'il n'y a pas de vrai problème. Je ne peux pas définir le vrai problème donc je soupçonne qu'il n'y a pas de vrai problème mais je ne suis pas sûr qu'il n'y ait pas de vrai problème.“

—  Richard Feynman

[...] we have always had (secret, secret, close the doors!) we have 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 youngest 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 is 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.
en

„Si, dans un cataclysme, toute notre connaissance scientifique devait être détruite et qu'une seule phrase passe aux générations futures, quelle affirmation contiendrait le maximum d'informations dans le minimum de mots? Je pense que c'est l'hypothèse atomique (ou le fait atomique, ou tout autre nom que vous voudrez lui donner) que toutes les choses sont faites d'atomes - petites particules qui se déplacent en mouvement perpétuel, s'attirant mutuellement à petite distance les unes les autres et se repoussant lorsque l'on veut les faire se pénétrer. Dans cette seule phrase, vous verrez qu'il y a une énorme quantité d'information sur le monde, si on lui applique un peu d'imagination et de réflexion.“

—  Richard Feynman

If, in some cataclysm, all of scientific knowledge were to be destroyed, and only one sentence passed on to the next generations 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.
en

„il s’agit en quelque sorte d’une caractéristique de la simplicité de la nature.“

—  Richard Feynman

sur le fait qu'il existe de nombreuses manières de formuler une même théorie, Discours de réception du prix Nobel.
Citation rapportée

„The philosophy of science is as useful to scientists as ornithology is to birds.“

—  Richard Feynman

Attributed to Feynman, many times, by the British historian of science Brian Cox.
Disputed and/or attributed

„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?“

—  Richard Feynman, livre The Pleasure of Finding Things Out

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)
The Pleasure of Finding Things Out (1999)

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„What I cannot create, I do not understand.Know how to solve every problem that has been solved.“

—  Richard Feynman

on his blackboard at the time of death in February 1988; from a photo in the Caltech archives http://archives.caltech.edu/pictures/1.10-29.jpg

„This dying is boring.“

—  Richard Feynman

last words (15 February 1988), recalled by sister Joan Feynman, in Christopher Sykes, editor, No Ordinary Genius: The Illustrated Richard Feynman (1994), p. 254

„And therefore when we go to investigate we shouldn’t pre-decide what it is we are trying to do except to find out more about it“

—  Richard Feynman, livre The Pleasure of Finding Things Out

Source: No Ordinary Genius (1994), p. 251-252, from interview in "The Pleasure of Finding Things Out" (1981): video http://www.youtube.com/watch?v=NEwUwWh5Xs4&t=45m21s
(Also in book The Pleasure of Finding Things Out (1999) p. 23.)
Contexte: People say to me, "Are you looking for the ultimate laws of physics?" No, I'm not. I'm just looking to find out more about the world and 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 and we're just sick and tired of looking at the layers, then that's the way it is!… And therefore when we go to investigate we shouldn’t pre-decide what it is we are trying to do except to find out more about it… My interest in science is to simply find out more about the world.

„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.“

—  Richard Feynman

" New Textbooks for the "New" Mathematics http://calteches.library.caltech.edu/2362/1/feynman.pdf", Engineering and Science volume 28, number 6 (March 1965) p. 9-15 at p. 14
Paraphrased as "Precise language is not the problem. Clear language is the problem."
Contexte: 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.

„We've learned from experience that the truth will come out.“

—  Richard Feynman

" Cargo Cult Science http://calteches.library.caltech.edu/51/2/CargoCult.htm", adapted from a 1974 Caltech commencement address; also published in Surely You're Joking, Mr. Feynman!, p. 342
Contexte: We've learned from experience that the truth will come out. Other experimenters will repeat your experiment and find out whether you were wrong or right. Nature's phenomena will agree or they'll disagree with your theory. And, although you may gain some temporary fame and excitement, you will not gain a good reputation as a scientist if you haven't tried to be very careful in this kind of work. And it's this type of integrity, this kind of care not to fool yourself, that is missing to a large extent in much of the research in cargo cult science.

„The real problem in speech is not precise language. The problem is clear language.“

—  Richard Feynman

" New Textbooks for the "New" Mathematics http://calteches.library.caltech.edu/2362/1/feynman.pdf", Engineering and Science volume 28, number 6 (March 1965) p. 9-15 at p. 14
Paraphrased as "Precise language is not the problem. Clear language is the problem."
Contexte: 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.

„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.“

—  Richard Feynman

The Value of Science (1955)
Contexte: 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 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.

„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.“

—  Richard Feynman

volume II; lecture 1, "Electromagnetism"; section 1-6, "Electromagnetism in science and technology"; p. 1-11
Contexte: 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.

„And this is medicine?“

—  Richard Feynman

Comment to psychiatrist who examines Feynman and states he (the psychiatrist) has studied medicine.
Part 3: "Feynman, The Bomb, and the Military", "Uncle Sam Doesn't Need <u>You</u>", p. 159

„Lorem ipsum dolor sit amet, consectetuer adipiscing elit. Etiam egestas wisi a erat. Morbi imperdiet, mauris ac auctor dictum.“

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