From Interview with Richard Feynman by Charles Weiner in Altadena, CA, 4 March 1966, courtesy of Niels Bohr Library & Archives, American Institute of Physics, College Park, Maryland, USA.
Feynman: The Feynman Lectures on Physics. Do you want to talk about that?
Weiner: I think it’s appropriate, because this was a very major activity in this period.
Feynman: Yeah. It’s interesting, now that I think about it, that since that was a major activity in that period, I was complaining that I wasn’t doing any research—I’m really crazy! People have pointed out to me now that it’s really quite silly of me to feel that I wasn’t doing anything in these years, because that thing [The Feynman Lectures on Physics] is something. But I still don’t feel it that way, because when you’re young, you dedicate yourself to some ideal—that you’re going to discover things in physics—and if you do something else, it’s hard for you to rationalize that it should satisfy anybody—it’s just that I was teaching a class.
So anyhow, the story of those lectures is the following. There was a discussion by some group, of which I was not a member, that they ought to revamp the physics course, because many of the students who were pretty good, who were taking physics, were complaining that after studying it for a year or two, all they were doing was pith balls and inclined planes. They had heard so much when they were in high school of relativity and strange particles and wonders of the world, and they would see nothing of the wonders of the world until they were graduate students. And this was very difficult, and they were trying to revamp the physics course. So they had worked out some kind of a syllabus for it, and the question was, who was to give it? I don’t know how they discussed among themselves, but anyway, Sands came over here and he talked me into giving the course.
However, I threw away the syllabus. You know, I decided to give it my own way, of course. But I got the general idea of what was involved. They wanted me to teach the freshman lectures. They wanted to revamp the course. It used to not have any main lectures by a main lecturer, but they used to have sections, with graduate students teaching different sections. The only thing they ever came together for then was an optional sort of cultural lecture that was not directly related to the course, once a week, on Fridays, or maybe once every two weeks on Fridays.
Weiner: Some historical thing, perhaps?
Feynman: Well, it would be different things. I would often be invited to talk there, and I would talk about relativity. It was not part of their course. Sometimes people would talk about something that was directly part of their course, but it wasn’t organized together.
Now they’re going to do a new laboratory. They were going to cook up a new lab, and they were inventing new experiments to go with the lab. They were going to redesign it, so that there would be at least two lectures a week given by a main professor, and then some recitation sections that graduate students would pay attention to, and would I give the lectures, see? They had money from the Ford Foundation for this revamping. There’s a lot of money around for changing the world these days.
So I said, “Okay.” I accepted the challenge for one year, and I tried to make a course that required giving two lectures a week.
Weiner: Didn’t you have to drop all other work, all other teaching?
Feynman: I did, in fact. I can hardly believe it, but my wife tells me that I was working essentially day and night, sixteen hours a day, all the time. I was down here all the time, worrying about these—working on these lectures, because I not only had to prepare the material, I also had to prepare the lecture so it was a good lecture, if you know what I mean.
I had the idea—I got a kind of principle, a number of principles. The first was that I wouldn’t teach them anything that I had to teach over again because it was wrong, unless I pointed out that it was wrong. For example, if Newton’s laws are only approximate, and they’re not good in quantum mechanics and they’re not good in relativity, I start out by saying that, so that they know where they are. In other words, there always should be some kind of a map. In fact, I even thought of making some sort of a great map of things with their interconnections, so we could see where we were. I thought that one of the troubles with all the courses in physics was that they just said: You learn all this, you learn all that, and when you come out the other end, you’ll understand the connections. But there’s no map, “guide to the perplexed,” you see. So I want to make a map. But it turns out it’s not a feasible design. I mean, I just never made such a map.
The other thing is, I wanted to have in it things that would be enough for a good man to chew on, and then also that the average guy should understand. So I tried to invent.
Let me go over the principles. The first was, I’d never introduce anything that was not exactly right without explaining that it wasn’t, and what changed next time. (Another thing was, I looked at books, you see, and I began to realize great weaknesses: for example, like they were teaching in the same book F = ma, and a little bit later that the frictional force is the constant of friction times the normal force . . . as if they were of the same caliber and the same significance. They’re so different in quality and, you know, nothing is made of it.) So that was what the first principle was.
The second principle was: that which is supposed to be understandable, and that which is not supposed to be understandable from what you’ve already said, should be made clear. Because I would find in books that they would give all of a sudden, say, the formula for the frequency of an AC circuit. That was supposed to be more advanced. They can’t derive it now, but they wouldn’t say, “You aren’t going to be able to understand this formula at this level with the reasoning that has just preceded, but it’s an added thing.” In other words, what’s being added in, and what should have come from the other thing? Even if it could have come from the other—but you don’t make the argument—you should say it. I always say, “This is a possible deduction, more or less as follows, but we haven’t tried to deduce it from that.” Or, “This is an independent idea that comes from another place, you see, and you can’t deduce it, so don’t worry.”
A few little principles like that. Then the problem was to make lectures which would be okay for the average student, and yet have stuff for the advanced student. Then I got an idea, when I was planning these lectures. I would have a cube in the front of the lecture hall which had different colored faces, so that when something was only for the fun of it, for the more advanced student to get him interested, but wasn’t really an essential part of the course, it would be one color face. You see? When there was something that was so basic that it was absolutely necessary to understand for the whole of physics, and everybody should try their best to understand this thing, another color face, and so on. A color face to indicate the importance, the position, of the different subjects. Because what I was worried about was that all the students would try to learn all this junk, and if they do that, then I haven’t got stuff for the advanced student. You can’t do it. It’s just impossible, to have stuff for the advanced student without possibly confusing the stupidest student or the less advanced student.
So I had this cube idea. But I gave that up as being gimmicky, and instead I would write, at all lectures, summaries (which are no longer extant) on the blackboard, of the central items which needed to be understood. Anything else that wasn’t in the summary was just for the fun of it. But those don’t exist anymore.*
Finally, let’s see—I thought of some other things while I was talking. I don’t know.
So, then I started to give the lectures. And at the very beginning, the first thing I wanted to do was get all the students together. At a number of lectures, people don’t understand the logic at the beginning. The real logic of the beginning is, get all these kids from high school to come approximately to the same rough position. For instance, I would talk about everything being made out of atoms—not because I think they don’t know that, but because I want those who don’t know it to know it. I can’t say that, you see, so I tell it in such a way that the ones who already know it are excited by it, because it’s a new way of looking at it, while the ones who don’t know it can just catch onto it, to the level that I need. And so on. So the first few lectures are to bring everybody together.
Also, these lectures were lectures I had given in other places, the beginning lectures especially, so that I could have time to prepare the later ones, you see. And finally—oh, another principle, a very important principle: I wanted each lecture to be able to stand by itself. I didn’t think it was a good idea to have a lecture and say, “Well, the hour is up; we will continue this discussion next time,” or “Last time when we left off, we were doing this, that, and the other thing. Now let us continue.”
So, instead of that, I wanted to make believe to myself that each lecture was somehow or other an isolated masterpiece, you see, of lecturing, in which you had a beginning, and introduction, and you had a conclusion with some drama. So each of the lectures were like that, with some minor exceptions. There were one or two places where I couldn’t do it, where I continued the two lectures together or something like that—but that was another principle. I’m just telling you the guides that made those things.
Finally, my main interest is in physics, and in organizing material. I love to organize the material, and to think about how it goes together, and to discover a new way of looking at something, and how I can explain it and so on. And I’m not the kind of a teacher who’s interested really in the student as an individual. I mean, I’m not worried about: this guy’s married and he’s trying to get his degree, and all these complications. I tried my best to teach the student more or less as the abstract student, with imaginary properties—mixed, mixed, there were many different kinds of abstract students—but not any particular individuals. The subject is the center of my interest in all cases—the subject, not the student but the subject. So, you want to know how I feel about them [the lectures]. What else can I say about them? They’re all published. But I’m trying to explain to you how I feel, myself, about them, and what I thought I was trying to do.
Weiner: Did you get any sense of feedback while you were doing it?
Feynman: No. None whatever, because I had no way to know what was happening. Because I didn’t have any recitation sections, and I didn’t have questions at the end of the lecture. Any questions were supposed to go into the recitation sections. So there was zero feedback, except that there were some exams in which people made up problems. They gave them problems, and they would try to write the answers, in certain exam weeks, you see. And they were so atrocious—as far as I was concerned—they were so zero that I really, in a certain sense, felt discouraged throughout the entire program. Not discouraged to the point of not keeping right on going the way I was going, but in the feeling throughout that it wasn’t working, that it’s useless—but never mind, I’ll do it anyway. I mean, it’s the only way I know how to do it, damn it. But it doesn’t work.
Weiner: How about the people who were directly in contact, with the recitations?
Feynman: People who were directly in contact would tell me that I was underestimating them, and that it wasn’t as bad as I thought. But I never believed them and still don’t.
Weiner: Don’t you think that this type of presentation, the effectiveness of it, is difficult to measure in a traditional examination?
Feynman: Of course it is. But let’s just assume that you’re getting somewhere. But what else do you do? I mean, you asked me what my reaction was. It may be difficult, but I expected them to do better on the simple questions than they were doing. In other words, a person who couldn’t do what they apparently couldn’t do was certainly not understanding what I was talking about. That’s the way I felt about it.
Weiner: How long did you do this? Three years?
Feynman: I did this for a year, and then they started to work on me for the second year. And I said, “I prefer to do the first year over again. This time I want to make up problems that go with the material, and to make some improvements, but mainly to make up problems to go with the material, so that it would really teach it.” And to make some improvements of things I didn’t care for.
Then they worked on me, and I’m glad they did—in some way, anyway. They said, “Look, nobody’s ever going to do this again. We need this second year.”
I didn’t like to do the second year, because I didn’t think I had great ideas about how to present the second year. I felt that I didn’t have a good idea on how to do lectures on electrodynamics. But, you see, in these challenges that had existed before about lectures, they had challenged me to explain relativity, challenged me to explain quantum mechanics, challenged me to explain the relation of mathematics to physics, the conservation of energy. I answered every challenge. But there was one challenge which nobody asked, which I had set myself, because I didn’t know how to do it. I’ve never succeeded yet. Now I think I know how to do it. I haven’t done it, but I’ll do it someday. And that is this: How would you explain Maxwell’s equations? How would you explain the laws of electricity and magnetism to a layman, almost a layman, a very intelligent person, in an hour lecture? How do you do it? I’ve never solved it. Okay, so give me two hours of lecture. But it should be done in an hour lecture, somehow—or two hours.
Anyhow I’ve now cooked up a much better way of presenting the electrodynamics, a much more original and much more powerful way than is in the book. But at that time I had no new way, and I complained that I had nothing extra to contribute for myself. But they said, “Do it anyway,” and they talked me into it, so I did.
When I planned it, I was expected to teach electrodynamics, and then to teach a subject which would really be all the different branches of physics, using the same equation—like you use a diffusion equation for diffusion, for temperature, for lots of things, or the wave equation for sound, for light, and so on. In other words, the second half would have been something like mathematical methods of physics, but with many physics examples, so I’m teaching physics at the same time as the mathematics. I would teach Fourier transform, differential equations, and so on. It wouldn’t look like that, though. It wouldn’t be organized the usual way. It would be in terms of subjects, the point being that the equations are the same in so many different fields. So the moment you deal with an equation, you ought to show all the fields that it comes from, instead of just talking about the equation. So I was going to do that.
But then I had another possibility. Maybe I could teach quantum mechanics to the sophomores; nobody expects that to be done—that would be a miracle. And I had a crazy upside-down way of presenting quantum mechanics, absolutely inside out, in which everything that was advanced would come first, and everything that was elementary, in the conventional sense, would come last.
And I told these guys about that, and they kept working on me. They said I had to do it, that the mathematical thing that I was talking about, other people may some day do, but that this thing would be so unique, and they knew that I would never go for another year. I must do this unique thing, you see—even if it kills the kids, they can’t learn it, and it’s no good. I don’t know what the situation is, actually, whether it’s worthwhile or not. I should try it. So I did. And that’s Volume 3 on quantum mechanics. But Volumes 2 and 3 were really one year, just like Volume 1 was.
Weiner: This represents two full years you put in.
Feynman: Right. Well, one is ’61–62, and the next is ’62–63.
Weiner: And since then, of course, as you mentioned yesterday, you have better feelings about it . . .
Feynman: Somewhat.
Weiner: Because of their use beyond Caltech.
Feynman: Well, I haven’t yet, but people have pointed out I ought to. And I may be gradually coming around to understanding that. But what I insisted that I was doing, from the beginning, was teaching this particular group of students, and that’s all that I could do. I kept saying, “You cannot live beyond the grave. You teach these students, that’s all it’s going to be, and there won’t be any way to get this to anybody else.” I think it’s roughly true. If I listen to the lectures that other people give, on the basis of these books, I see all kinds of flaws, errors, weaknesses, and distortion. And it is true that you can’t live beyond the grave. But there must be people living who aren’t listening to the lectures of some professor, who are sitting just reading the book and thinking for themselves. They must get something out of it. So, if I keep some hope that that’s worth something to them, maybe I can feel better about the whole thing. I think that, in regard to the particular students that I was really aiming at, which was my avowed purpose that I’d set—I wasn’t caring about the books or anything, I was only caring about the students—I think that the result was nowhere near worth the effort.*
* Feynman’s lecture summaries are preserved in blackboard photos kept at the Caltech Archives; they will be published in enhanced electronic editions of The Feynman Lectures on Physics. See http://www.basicfeynman.com/enhanced.html.
* Two decades later, speaking of The Feynman Lectures on Physics, Feynman said, “There is all kinds of stuff there, more basic physics points of view, and so apparently they are useful. I must admit now that I cannot deny that they are really a contribution to the physics world.”—from J. Mehra, The Beat of a Different Drum (1994)