Quotes from book
The Character of Physical Law

Name: The Character of Physical Law
Author: Richard Feynman

The Character of Physical Law is a series of seven lectures by physicist Richard Feynman concerning the nature of the laws of physics. Feynman delivered the lectures in 1964 at Cornell University, as part of the Messenger Lectures series. The BBC recorded the lectures, and published a book under the same title the following year; Cornell published the BBC's recordings online in September 2015.

“Mathematics is not just a language. Mathematics is a language plus reasoning.”

Richard Feynman book The Character of Physical Law

Source: The Character of Physical Law (1965), chapter 2, “The Relation of Mathematics to Physics”
Context: Mathematics is not just a language. Mathematics is a language plus reasoning. It's like a language plus logic. Mathematics is a tool for reasoning. It's, in fact, a big collection of the results of some person's careful thought and reasoning. By mathematics, it is possible to connect one statement to another.

“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.”

Richard Feynman book The Character of Physical Law

statement after an introduction mentioning that he played bongo drums; Messenger Lectures at Cornell University, p. 13
The Character of Physical Law (1965)

“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.”

Richard Feynman book The Character of Physical Law

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 <br class="br">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!

“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

“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

“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

“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

“Nature's imagination far surpasses our own.”

Richard Feynman book The Character of Physical Law

Source: The Character of Physical Law (1965), chapter 7, “Seeking New Laws,” p. 162: video http://www.youtube.com/watch?v=-2NnquxdWFk&t=29m20s

“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.”

Richard Feynman book The Character of Physical Law

Source: The Character of Physical Law (1965), chapter 6, “Probability and Uncertainty — the Quantum Mechanical View of Nature,” p. 127-128

“A person talks in such generalities that everyone can understand him and it's considered to be some deep philosophy. However, I would like to be very rather more special and I would like to be understood in an honest way, rather than in a vague way.”

Richard Feynman book The Character of Physical Law

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

“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.”

Richard Feynman book The Character of Physical Law

Source: The Character of Physical Law (1965), chapter 2, “The Relation of Mathematics to Physics,” p. 58

“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 book The Character of Physical Law

Source: The Character of Physical Law (1965), chapter 2, “The Relation of Mathematics to Physics”

“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.”

Richard Feynman book The Character of Physical Law

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)

“It is impossible, by the way, when picking one example of anything, to avoid picking one which is atypical in some sense.”

Richard Feynman book The Character of Physical Law

Source: The Character of Physical Law (1965), chapter 1, “The Law of Gravitation,” p. 27: video http://www.youtube.com/watch?v=j3mhkYbznBk&t=37m16s

“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.”

Richard Feynman book The Character of Physical Law

Source: The Character of Physical Law (1965), chapter 3, “The Great Conservation Principles,” p. 75

“This is the key of modern science and is the beginning of the true understanding of nature. This idea. That to look at the things, to record the details, and to hope that in the information thus obtained, may lie a clue to one or another of a possible theoretical interpretation.”

Richard Feynman book The Character of Physical Law

Source: The Character of Physical Law (1965), chapter 1, “The Law of Gravitation,” p. 15: video http://www.youtube.com/watch?v=j3mhkYbznBk&t=12m45s

“So in order to understand the physics one must always have a neat balance and contain in his head all of the various propositions and their interelationships because the laws often extend beyond the range of their deductions. This will only have no importance when all the laws are known.”

Richard Feynman book The Character of Physical Law

Source: The Character of Physical Law (1965), chapter 2, “ The Relation of Mathematics to Physics http://www.youtube.com/watch?v=M9ZYEb0Vf8U”

“It is not unscientific to make a guess, although many people who are not in science think it is.”

Richard Feynman book The Character of Physical Law

Source: The Character of Physical Law (1965), chapter 7, “Seeking New Laws,” p. 165-166: video http://www.youtube.com/watch?v=-2NnquxdWFk&t=37m21s <br class="br">Context: 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.

“The method of guessing the equation seems to be a pretty effective way of guessing new laws”

Richard Feynman book The Character of Physical Law

The Character of Physical Law (1965)
Context: …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.