Source: The Character of Physical Law (1965), chapter 2, “ The Relation of Mathematics to Physics http://www.youtube.com/watch?v=M9ZYEb0Vf8U” referring to the law of conservation of angular momentum
Context: Now we have a problem. We can deduce, often, from one part of physics like the law of gravitation, a principle which turns out to be much more valid than the derivation. This doesn't happen in mathematics, that the theorems come out in places where they're not supposed to be!
Richard Feynman: Likeness
Richard Feynman was American theoretical physicist. Explore interesting quotes on likeness.The Value of Science (1955)
" 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. 345
Context: 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.
Sir Douglas Robb Lectures, University of Auckland (1979); lecture 1, "Photons: Corpuscles of Light" https://www.youtube.com/watch?v=eLQ2atfqk2c&t=24m2s
Context: There's a kind of saying that you don't understand its meaning, 'I don't believe it. It's too crazy. I'm not going to accept it.'… You'll have to accept it. It's the way nature works. If you want to know how nature works, we looked at it, carefully. Looking at it, 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, okay? If I'm going to tell you honestly what the world looks like to the human beings who have struggled as hard as they can to understand it, I can only tell you what it looks like.
as quoted by K.C. Cole, Sympathetic Vibrations: Reflections on Physics as a Way of Life (1985)
“Physics is like sex: sure, it may give some practical results, but that's not why we do it.”
Does not appear to be from any of his books or cited in a biography. A Google Books search shows that the oldest book citing "physics is like sex" is Scary Monsters and Bright Ideas (2000) by science broadcaster Robyn Williams. On p. 44, this book claims: "Einstein said, 'You do not really understand something unless you can explain it to your grandmother'. Richard Feynman added, 'Physics is like sex: sure, it may give some practical results, but that's not why we do it'." Given that Einstein didn't really say the former, it's likely that Feynman didn't really say the latter.
Disputed and/or attributed
Variant: Physics is like sex: sure, it may give some practical results, but that's not why we do it.
On the numerical value of α, the fine-structure constant, p. 129
QED: The Strange Theory of Light and Matter (1985)
Part 1: "From Rockaway to MIT", "String Beans", p. 25
Surely You're Joking, Mr. Feynman! (1985)
We haven’t any deep understanding of what we’re doing. If we tried to understand what we’re doing, we’d go nutty.
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
Source: QED: The Strange Theory of Light and Matter (1985), p. 14
Part 4: "From Cornell to Caltech, With a Touch of Brazil", "Any Questions?", p. 177
Surely You're Joking, Mr. Feynman! (1985)
interview published in Superstrings: A Theory of Everything? (1988) edited by Paul C. W. Davies and Julian R. Brown, p. 193-194
Source: The Character of Physical Law (1965), chapter 1, “The Law of Gravitation,” p. 13: video http://www.youtube.com/watch?v=j3mhkYbznBk&t=7m53s
“So far as we know, all the fundamental laws of physics, like Newton’s equations, are reversible.”
volume I; lecture 46, "Ratchet and Pawl"; section 46-5, "Order and entropy"; p. 46-8
The Feynman Lectures on Physics (1964)
volume I; lecture 3, "The Relation of Physics to Other Sciences"; section 3-6, "Psychology"; p. 3-8
The Feynman Lectures on Physics (1964)
Source: No Ordinary Genius (1994), p. 82, from interview in "The Pleasure of Finding Things Out" (1981): video http://www.youtube.com/watch?v=NEwUwWh5Xs4&t=24m55s
lecture II: "The Uncertainty of Values"
The Meaning of It All (1999)
how do I say that?"
"Well, you have to use a different word for 'solve,' " they say.
"Why?" I protested. "When I solve it, I do the same damn thing as when you solve it!"
"Well, yes, but it's a different word — it's more polite."
I gave up. I decided that wasn't the language for me, and stopped learning Japanese.
Part 5: "The World of One Physicist", "Would <U>You</U> Solve the Dirac Equation?", p. 245-246
Surely You're Joking, Mr. Feynman! (1985)
Concerning the apparent absurdities of quantum behavior.
chapter 6, “Probability and Uncertainty — the Quantum Mechanical View of Nature,” p. 129
The Character of Physical Law (1965)
lecture III: "This Unscientific Age"
David Goodstein reports http://www.americanscientist.org/bookshelf/pub/feynmaniacs-should-read-this-review-skip-lecture-collection-save-22-simoleons that the entire psychology department walked out in a huff at this point.
The Meaning of It All (1999)