Richard Feynman Quotes

The Quantum Universe has a quotation from me in every chapter — but it's a damn good book anyway.

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.

One of the miseries of life is that everybody names things a little bit wrong, and so it makes a little bit harder to understand things than it would have been if they had been named differently.

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.

We 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 younger 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's 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.

Tell your son to stop trying to fill your head with science — for to fill your heart with love is enough!

The question of whether or not, when you see something, you see only the light or you see the thing you're looking at, is one of those dopey philosophical things that an ordinary person has no difficulty with. Even the most profound philosopher, when sitting, eating his dinner, hasn't any difficulty in making out that what he looks at perhaps might be only the light from the steak, but it still implies the existence of the steak, which he is able to lift by the fork to his mouth. The philosophers that were unable to make that analysis and that idea, have fallen by the wayside through hunger!

All right. I already see you turning off. I can see you say you don't understand me. You can't understand that it could be chance. "I don't like it!" Tough! I don't like it either, but that's the way it is! OK? I don't understand it either. ..."It must be that Nature knows that it's going to go up or down." No, it must not be that nature knows! We are not to tell Nature what she's gotta be! That's what we found out. Every time we take a guess as how she's got to be, and go and measure... She's clever. She's always got better imagination than we have, and she finds a cleverer way to do it than we have thought of. And in this particular case, the clever way to do it is by probability, by odds. ...[L]ight works by probability.

And then there's a kind of saying that you don't understand it, meaning "I don't believe it. It's too crazy. It's the kind of thing, I'm just... I'm not going to accept it."... This kind, I hope you'll come along with me, and you'll have to accept it, because it's the way nature works. If you want to know the way nature works... We looked at it, carefully... 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! OK? If I'm going to tell you honestly what the world looks like to... human beings who have struggled as hard as they can to understand it, I can only tell you what it looks like, and I cannot make it innocent. ...I'm not going to simplify it, eh? I'm not going to fake it. I'm not going to... tell you it's something like a ball bearing on a spring. It isn't.

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.<P>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.<P>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.<P>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.<P>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.

The first principle is that you must not fool yourself — and you are the easiest person to fool.

We've learned from experience that the truth will 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.

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; other causes that could possibly explain your results; and things you thought of that you've eliminated by some other experiment, and how they worked—to make sure the other fellow can tell they have been eliminated. <p>Details that could throw doubt on your interpretation must be given, if you know them. You must do the best you can — if you know anything at all wrong, or possibly wrong — to explain it. If you make a theory, for example, and advertise it, or put it out, then you must also put down all the facts that disagree with it, as well as those that agree with it. There is also a more subtle problem. When you have put a lot of ideas together to make an elaborate theory, you want to make sure, when explaining what it fits, that those things it fits are not just the things that gave you the idea for the theory; but that the finished theory makes something else come out right, in addition. <P>In summary, the idea is to try to give all of the information to help others to judge the value of your contribution; not just the information that leads to judgement in one particular direction or another.<p>

Science alone of all the subjects contains within itself the lesson of the danger of belief in the infallibility of the greatest teachers of the preceding generation.

Energy is a very subtle concept. It is very, very difficult to get right.