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Richard Feynman: 362 quotes32 likes

“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

volume II; lecture 2, "Differential Calculus of Vector Fields"; section 2-1, "Understanding physics"; p. 2-1
The Feynman Lectures on Physics (1964)

“Nature uses only the longest threads to weave her patterns, so each small piece of her fabric reveals the organization of the entire tapestry.”

Richard Feynman book The Character of Physical Law

Source: The Character of Physical Law (1965), chapter 1, “The Law of Gravitation,” p. 34

“Why are the theories of physics so similar in their structure?”

Richard Feynman book QED: The Strange Theory of Light and Matter

QED: The Strange Theory of Light and Matter (1985)

“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 book The Character of Physical Law

same passage in transcript: video http://www.youtube.com/watch?v=-2NnquxdWFk&t=16m46s <br class="br">The Character of Physical Law (1965) <br class="br">Variant: 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.

“I think I can safely say that nobody understands quantum mechanics.”

Richard Feynman book The Character of Physical Law

Variant: I think I can safely say that nobody understands quantum mechanics.
Source: The Character of Physical Law (1965), chapter 6, “Probability and Uncertainty — the Quantum Mechanical View of Nature,” p. 129

“Whenever you see a sweeping statement that a tremendous amount can come from a very small number of assumptions, you always find that it is false. There are usually a large number of implied assumptions that are far from obvious if you think about them sufficiently carefully.”

Richard Feynman

volume II; lecture 26, "Lorentz Transformations of the Fields"; section 26-1, "The four-potential of a moving charge"; p. 26-2
The Feynman Lectures on Physics (1964)

“I hope … that you will find someday that, after all, it isn’t as horrible as it looks.”

Richard Feynman

volume III, "Feynman's Epilogue", p. 21-19
The Feynman Lectures on Physics (1964)

“You will have to brace yourselves for this — not because it is difficult to understand, but because it is absolutely ridiculous: All we do is draw little arrows on a piece of paper — that’s all!”

Richard Feynman book QED: The Strange Theory of Light and Matter

Source: QED: The Strange Theory of Light and Matter (1985), p. 24

“It has been a mystery ever since it was discovered more than fifty years ago, and all good theoretical physicists put this number up on their wall and worry about it. Immediately you would like to know where this number for a coupling comes from: is it related to π, or perhaps to the base of natural logarithms? Nobody knows. It's one of the greatest damn mysteries of physics: a magic number that comes to us with no understanding by man. You might say the "hand of God" wrote that number, and "we don't know how He pushed his pencil." We know what kind of a dance to do experimentally to measure this number very accurately, but we don't know what kind of dance to do on the computer to make this number come out — without putting it in secretly!”

Richard Feynman book QED: The Strange Theory of Light and Matter

On the numerical value of α, the fine-structure constant, p. 129
QED: The Strange Theory of Light and Matter (1985)

“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. There are many things I don't know anything about, such as whether it means anything to ask "Why are we here?" I might think about it a little bit, and if I can't figure it out then I go on 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 the 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.”

Richard Feynman book The Pleasure of Finding Things Out

Source: No Ordinary Genius (1994), p. 239, from interview in "The Pleasure of Finding Things Out" (1981): video http://www.youtube.com/watch?v=NEwUwWh5Xs4&t=48m10s

“Nature isn't classical, dammit, and if you want to make a simulation of nature, you'd better make it quantum mechanical, and by golly it's a wonderful problem, because it doesn't look so easy.”

Richard Feynman

" Simulating Physics with Computers http://www.cs.berkeley.edu/~christos/classics/Feynman.pdf", International Journal of Theoretical Physics, volume 21, 1982, p. 467-488, at p. 486 (final words)

“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.”

Richard Feynman

from a 1987 class, as quoted in David L. Goodstein, "Richard P. Feynman, Teacher," Physics Today, volume 42, number 2 (February 1989) p. 70-75, at p. 73
Republished in the "Special Preface" to Six Easy Pieces (1995), p. xx.

“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.”

Richard Feynman book The Character of Physical Law

Source: The Character of Physical Law (1965), chapter 1, “The Law of Gravitation,” p. 18: video http://www.youtube.com/watch?v=j3mhkYbznBk&t=17m10s

“There were certain things I didn't like, such as tipping. I thought we should be paid more, and not have to have any tips. But when I proposed that to the boss, I got nothing but laughter. She told everybody, "Richard doesn't want his tips, hee, hee, hee; he doesn't want his tips, ha, ha, ha." The world is full of this kind of dumb smart-alec who doesn't understand anything.”

Richard Feynman

Part 1: "From Rockaway to MIT", "String Beans", p. 25
Surely You're Joking, Mr. Feynman! (1985)

“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.”

Richard Feynman

"The Development of the Space-Time View of Quantum Electrodynamics," Nobel Lecture http://nobelprize.org/physics/laureates/1965/feynman-lecture.html (11 December 1965)

“It is to be emphasized that no matter how many [amplitude] arrows we draw, add, or multiply, our objective is to calculate a single final arrow for the event. Mistakes are often made by physics students at first because they do not keep this important point in mind. They work for so long analyzing events involving a single photon that they begin to think that the arrow is somehow associated with the photon”

Richard Feynman book QED: The Strange Theory of Light and Matter

rather than with the event
Source: QED: The Strange Theory of Light and Matter (1985), p. 75-76

“Well, we’re getting a little philosophical and serious, ok? Let’s go back to what we’re doing. One day we look at a map and this capital is K-Y-Z-Y-L and we decided it would be fun to go there because it’s so obscure and peculiar. It’s a game. It’s not serious. It doesn't involve some deep philosophical point of view about authority or anything. It’s just the fun of having an adventure to try to go to a land that we’d never heard of, that we knew was an independent country once, no longer an independent country, find out what it’s like. And discover as we went along that nobody went there for a long time and it’s isolated made it more interesting. But, you know, many explorers liked to go to places that are unusual. And, it’s only for the fun of it. I don’t go for this philosophical interpretation of "our deeper understanding of what we’re doing."”

Richard Feynman

We haven’t any deep understanding of what we’re doing. If we tried to understand what we’re doing, we’d go nutty. <br class="br">Source: No Ordinary Genius (1994), p. 236, from interview two weeks before his death in "The Quest for Tannu Tuva" (1989): video http://www.youtube.com/watch?v=Mn4_40hAAr0&t=51m49s

“The fact that you are not sure means that it is possible that there is another way someday.”

Richard Feynman book The Meaning of It All

lecture II: "The Uncertainty of Values"
The Meaning of It All (1999)

“If we take everything into account — not only what the ancients knew, but all of what we know today that they didn't know — then I think that we must frankly admit that we do not know.”

Richard Feynman

The Value of Science (1955)

“Therefore psychologically we must keep all the theories in our heads, and every theoretical physicist who is any good knows six or seven different theoretical representations for exactly the same physics.”

Richard Feynman book The Character of Physical Law

Source: The Character of Physical Law (1965), chapter 7, “Seeking New Laws,” p. 168