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Martin Israel

Martin H. Israel

Professor Emeritus; Department Physics, Washington University in St. Louis

By David Zierler, Director of the Caltech Heritage Project

February 3, 2022

DAVID ZIERLER: This is David Zierler, Director of the Caltech Heritage Project. It is February 3, 2022. I am delighted to be here with Professor Martin Israel. Marty, it's great to be with you. Thank you for joining me.

MARTIN ISRAEL: Thank you for having me.

ZIERLER: To start, would you tell me your title and institutional affiliation?

ISRAEL: Well, right now, I am Professor Emeritus at Washington University in St. Louis.

ZIERLER: When did you go emeritus?

ISRAEL: Technically, I just went emeritus this last July 1. I've only been emeritus for less than a year. In fact, my last non-emeritus year was a transition year, in which I was not doing any classroom teaching. The timing of that was set a number of years earlier and turned out to be just fine because I only had half of my last teaching semester under COVID.

ZIERLER: Just as a snapshot in time, what are you working on these days?

ISRAEL: I am supposedly retired. In fact, I'm working very closely on one of several projects I was working on when I was retired, and I'm still working on data analysis, preparing a paper with my colleagues on the CRIS experiment on the ACE spacecraft, which has a definite Caltech connection. The PI is Ed Stone. In fact, just yesterday at 12:30 my time, I was on the weekly ACE CRIS conference Zoom, in which we were discussing the analysis work, which right now is mainly being done by me with my colleague, also retired, here at Washington University, Bob Binns. Mark Wiedenbeck, who is technically at JPL but is part of the cosmic-ray group at Caltech, Bob and I have been working very closely with him and a total of a dozen people involved in this paper. Basically, the CRIS experiment was designed to measure isotope composition of cosmic rays up to nickel. Nickel, element number 28, was the heaviest that was planned because CRIS was only guaranteed a two-year lifetime with five years as a goal.

In that time, the area I've been most involved with, which is the very rare elements heavier than nickel, with an atomic number greater than 30, at that time, there was no hope of getting any statistics for those particles in the lifetime of ACE. But ACE was launched, as you probably know, in the fall of 1997. CRIS is Cosmic Ray Isotope Spectrometer. CRIS is one of the instruments on ACE, and it is still operating today. The paper I'm working on with my CRIS colleagues right now is on the isotope composition of the elements of charge 29, 30, and so on up to 38, where using a little more than 20 years of data, we're able to get adequate statistics to say something useful that wasn't in the plan. Anyhow, that's the main thing I'm working on now, aside from all sorts of things around the house I've been putting off and are now things I can be doing because I'm, ha-ha, retired.

ZIERLER: More broadly, what have been some of the main areas of research over the course of your entire career?

ISRAEL: The main area has been cosmic rays, and primarily these rare heavy cosmic rays. When I first came here in 1968, I was working with my then-colleague, Joe Klarman, and with Bob Binns, who was actually working with us, even though he was at that time in the research arm of McDonnell Douglas Corporation. We'd been working on the composition of these rare elements heavier than charge 30. Now, until the ACE CRIS experiment, all of the work involved the element composition. We had very large-area instruments with ten square meters or so on stratospheric balloons or on the HEAO3 spacecraft measuring the composition of these heavy elements. My main focus has been the composition of the rare ultra-heavy cosmic rays all the way up to the actinides like uranium, for which we have very, very few, even with enormous detectors. The point is, element composition in the cosmic rays, like in the solar system, drops precipitously as you go up in atomic number. It's a challenge, measuring these heavies. That's most of my research career.

I had a ten-year intermission in the research career when, in March 1987, the dean of Arts and Sciences here was rather abruptly shown the door by our chancellor. Of course, everyone was wondering who would replace him. A week later, I got a phone call from our chancellor, Bill Danforth, the longtime chancellor of Washington U. I had worked with him on some other projects. "Marty, Max and I are sitting here trying to decide what to do." Max Cowan, at the time, was provost. "I wonder if you would come over and talk with us." After a pause, Bill said, "Marty, you might want to have your guard up." Two days later, I was the acting dean of Arts and Sciences. For the next seven years, I was the dean of Arts and Sciences, which is a very exciting business.

Arts and Sciences here is all the sciences I knew something about, plus the social sciences, the humanities, a department of music, a department of education, a department of performing arts. After seven years of that, I was three years in the central administration as one of several vice chancellors. During that time, I was mainly an interested sideline observer of the research work of the cosmic-ray group, which continued with my colleagues here at Washington University. And they were gracious enough to welcome me back into the group when I left – I sometimes jokingly say "escaped" – administration. It was a very interesting ten years, but totally divorced from my research program.

ZIERLER: I wonder if you've ever reflected on how your work in cosmic rays carries on the legacy, really starting with Millikan and the birth of modern physics at Caltech.

ISRAEL: It does in many ways. It sort of carries on with the Millikan work. But my University of Chicago introduction to the field also has great ties to Caltech. In the summer between my third and fourth year as an undergraduate at University of Chicago, I worked as an undergraduate assistant in the laboratory of John Simpson, who is one of the major figures in the early days of real cosmic-ray work, really understanding the composition of cosmic rays. In working in his lab, as often happens in such things, he assigned me to work with one of his graduate students who was working on his thesis research project. This graduate student of his was a fellow named Ed Stone. I worked with Ed there. I met briefly a graduate student who was working in one of the related cosmic ray labs named Robbie Vogt, who was my thesis advisor when I was at Caltech. That kind of starts at the University of Chicago with that group. I've been on and off, mostly on, involved in collaborative experiments involving the Caltech cosmic-ray group. I was talking with Ed Stone just yesterday on our weekly noon CRIS Zoom call. That goes way back.

ZIERLER: Let's set the stage for your graduate work at Caltech. First, what years were you at the University of Chicago for undergraduate?

ISRAEL: It would be '58 to '62. I graduated in spring of '62. I grew up on the South Side of Chicago, about five miles from the University of Chicago. I lived on campus but often went home with friends of mine in the dorm for a home cooked meal on a Sunday evening. But I was at the University of Chicago five miles from where I grew up. There, I worked in several different research groups over my undergraduate career. I did the last thing in the summer between graduating from Chicago and starting at Caltech, I worked in a group out at Argonne National Lab analyzing bubble chamber photographs for Roger Hildebrand, who also did some important cosmic-ray work subsequently in his career.

I had advice from various people about good places to go for graduate work in physics, and one was Caltech. I went with a friend and classmate of mine at Chicago to a few of those grad schools during the summer between my third and fourth year to look at possible graduate schools. I went to several places on the East Coast, including Columbia and MIT. I never went west of Chicago to visit graduate schools. The places I went to on the East Coast obviously were good places, but they just didn't click for me. And I kept hearing from people at Chicago about Caltech. I applied there, along with several other places, and when I was admitted, I went to Caltech. One of the people I knew at Chicago who was a Caltech PhD was Eugene Parker. That's a name you may know. Caltech is involved in what is now referred to as the Parker Solar Probe, named after Eugene Parker for his work with the solar wind.

That was part of my influence about Chicago. But it was just kind of everyone I talked to in the physics department there for advice said Caltech. I went to Caltech. My first year at Caltech, of course, I was mainly taking courses. During my first year at Caltech, I was thinking I may want to be a theorist. I worked during that first summer after my first year with Leverett Davis, who did theoretical work on essentially interstellar and interplanetary medium. I did some work with him, and I decided trying to be a theorist wasn't right for me. Then, I looked around, and after talking with several people, I joined Robbie Vogt in his lab. At that time, Robbie was a new assistant professor. I was one of his first two graduate students. The other one who was there at the same time was Peter Wentzel from Germany. Not long after I'd joined Robbie's research group, he was joined by a research associate, Ed Stone, whom he obviously knew from Chicago. While Robbie was my official thesis advisor, in fact, Ed, as one of the senior people in that research group, was also a big help to me. I learned a lot as a graduate student from Robbie and from Ed. Technically, only Robbie was my thesis advisor, but Ed and Robbie both played major roles in advising me through that thesis.

ZIERLER: What was Robbie working on at that point?

ISRAEL: Cosmic-ray electrons. His thesis work at Chicago had been, actually, the first direct measurement of cosmic-ray electrons. This is work he did with Peter Meyer, who was a professor at the University of Chicago. My thesis, working with Robbie, was a continuation of Robbie's work on cosmic-ray electrons. We built an instrument to measure cosmic-ray electrons. He was also, along with Ed Stone, developing silicon solid-state detectors for measuring the composition of cosmic rays, mainly the light cosmic rays, protons, and alpha particles, which are helium nuclei. He was working on both of those, and I, as a graduate student, was working on the electron project. We built an instrument to sort of carry the next step from his thesis electron work. Peter was mainly working with the solid-state detectors on the proton & alpha detection.

ZIERLER: What were some of the big theories in cosmic-ray physics at that point?

ISRAEL: There were a lot of things. Ultimately, where do they come from? Where are they accelerated? It was already pretty well-understood that they must've gotten their energy from supernova explosions because you look at the energy in cosmic rays for astrophysical phenomena that could've produced that, and there was that. The main theory, there was a book entitled Cosmic Ray Physics by Ginzburg and Syrovatskii, famous Russian physicists, which, at the time, was the bible for where cosmic rays came from.

ZIERLER: Let's talk about Richard Feynman. When did you first meet him?

ISRAEL: I never, in my time at Caltech, met him. When I got to Caltech, I had an NSF competitive fellowship. But to supplement the NSF stipend, I was given a very part-time job tape-recording and photographing the Feynman Lectures. My job was to sit in the back of the lecture hall, running this good, old-fashioned reel-to-reel tape recorder and snapping a photograph whenever he finished filling a blackboard. My first year at Caltech, the '62- '63 academic year, was the second year that he gave those lectures. The first year, Jim Hartle, a retired professor at UC Santa Barbara, who is now a member of the National Academy of Science, and at the time was a grad student of Murray Gell-Mann at Caltech, had that job. I did it my first year at Caltech. Then the next year, there was some carry-on further work that Feynman did, brushing up some of the earlier lectures, and I recorded those.

My job was to photograph the blackboard any time he finished a blackboard and stepped aside. I made a point whenever possible to photograph it when he was in a typical Feynman-esque position. In fact, one of those photos that I took made its way into one of the early mimeographed volume of the Feynman Lectures, although it is not in the red bound volumes. That was the fun part, capturing him. I never had an opportunity to talk with him. That was my job. The secretaries took the tape recording and transcribed it. Matt Sands and Bob Leighton worked with the transcription to turn the lectures into the written text that's bound in these wonderful red volumes. I drew a couple of the illustrations in the text, but I don't know if Matt Sands, Bob Leighton, or someone else working with them were the one who made the illustrations for the text, using photographs that I or Jim Hartle had snapped. Tom Harvey was the gentleman who was the technician in charge of the lecture hall. He was the man responsible for demonstration materials that the lecturer might use. He was also the one who set up the tape recorder and camera and developed the film. My role was very small.

I will tell you an interesting story of when I did meet Feynman, many years later. I was, for several days, at a meeting of some committee at NASA headquarters in Washington. I've been at various advisory committees at NASA headquarters over my career. I was in the lobby of the hotel where NASA put most of its visitors. I ran into Dick Feynman in the lobby. Of course, he didn't know me, but I introduced myself. The main thing he said to me was, "Well, what brings you here?" He was there for what has become a famous committee meeting. This was the famous Feynman role on the committee that was impaneled to try to understand the Challenger disaster when the Challenger exploded a minute after launch, killing the astronauts on-board. He was there to participate in that. He asked me why I was there. I was there to participate in this NASA committee. He said, "How can you stand coming to these NASA committee meetings? I'm in one, and they're boring and tedious as hell. I will never go again." That was Feynman's view of that committee. I'm sure you've heard the story of Feynman in that committee. He had talked to people at JPL before actually going to the meeting who might be able to give him some insight into what happened, and it was pretty clear to a lot of people that the problem was that the launch was on a very cold day, colder than any previous shuttle launch, and there's a key rubber O-ring that seals one part of the launch vehicle from another. What was suspected, and what Feynman argued for the committee, was that the weather was so cold that the rubber O-ring wasn't sealing. Take a piece of rubber that's normally nice and flexible and make it cold enough, and it gets hard. It's not a sealant anymore, it's a piece of wire stuck in there that doesn't do the sealing job. To illustrate that, Feynman brought with him a small rubber O-ring, and he dumped it in a glass of ice water that was available, took it out, and showed that with a little pressure on it, it snapped. It wasn't an O-ring anymore when it was cold enough. I think that was the final conclusion of the committee with more investigation and analysis, and that's why Challenger went.

That's the only time I met Feynman. As I understand it, he had nothing to do with producing the written text known as the Feynman Lectures. It was his responsibility to create the lectures, to give the lectures, and from there on, the production of the written text was Bob Leighton and Matt Sands. People like me had no excuse for meeting Feynman.

ZIERLER: What was the initial idea about recording his lectures? Was it understood how historically significant they were, that they should be captured, transcribed, and ultimately published? Was that the plan from the beginning?

ISRAEL: I don't know. I just, in the last few days, reread Feynman's introduction and what Leighton and Sands wrote in one or another of the introductions to these volumes. Apparently, the physics faculty at Caltech had realized that teaching from the standard physics text, the standard first- and second-year physics course, particularly for the very bright undergraduates who came to Caltech, was deadly boring. Not very interesting. I think they were thinking of writing a new text. According to one of the Feynman's introduction to the book, there was, at one point, talk about, "We'll all agree on the outline, and different members of the faculty will take responsibility for a few lectures and one or two chapters. We'll make a text out of that." As I understand it, the decision was that that's not the way to do it, you need some integrating thought. When they asked Feynman to do these lectures, it was certainly with the plan in mind of recording them and turning them into a textbook. I don't know if people recognized how historically important it would be. I will tell you that the last couple rows of the lecture hall, when I was back there operating the tape recorder, were filled with graduate students because all of us grad students understood very well that, "Wow, this is a new insight." We all learned from his freshman and sophomore physics lectures. It was quite clear to all of us that this was more insightful than any of us had had when we were undergraduate students, and we were learning things.

ZIERLER: Tell me about Feynman's lecture style. How did he convey all of his insights into physics?

ISRAEL: First of all, I'll say he was very animated, which is something I tried to capture in the photographs I took. Someone at Caltech probably has all those photos, and in them, you will find many examples of an animated, interested, excited guy talking about these things. The idea was, he wanted to give new ideas. He talked about all sorts of things. He brought in some talk about lightning. "Where'd all that electricity come from?" I remember he said one time, when he was riding the subway in New York, he noticed an advertisement for a company that made pasta. When he was talking about stress and strain–and this is something I've done many times to people's amazement–he noticed that there was a picture that showed a woman holding an uncooked piece of spaghetti. She'd obviously broken it, and it broke into three pieces. In each hand, there was one piece, and something from the middle of it was flying off. If you haven't seen that in the book, go home and try it. Take an uncooked piece of spaghetti, grab the ends, and bend it. I guarantee you're going to find a piece from the middle of it flying off. Having done that, he then went through the analysis that if you take a uniform object and strain it by bending it this way, there will be two points where the strain is the greatest. It will not be uniform all around. Contrary to most people's intuition, it will not be the spot right in the middle. There will be two points, a little bit on either side of the middle of this piece of spaghetti where this strain is greatest.

And he did an analysis to show that. Obviously, one of those two will be the spot that breaks, then the piece will flip back, and there will have been enough strain in there that it will flip back fast enough that the other spot will also break, and that piece will go off. A lecture on stress and strain could be deadly, lots of math, ho hum. But he introduced it by breaking a piece of spaghetti. It gives you a sense of Feynman's approach. As he said in the introduction to the book, he knew he was dealing with really smart guys. And they were all guys. That's another story. And he knew that the typical physics course bored such smart guys terribly, so he was going to make it interesting, which he did. He also made it interesting by introducing quantum ideas. The standard way of teaching quantum mechanics is, you had to start with the Schrödinger equation, and you show solutions of that for the hydrogen atom. He realized that the real interesting part is the quantum nature. He started out by talking about the Stern-Gerlach experiments, which are ways that you can separate particles with different magnetic polarization, up, down, sideways.

There are basically three states that a particle of spin one can have, which is with the magnetic field, opposed to the magnetic field, or zero component along the magnetic field. Or in the simpler case of a spin one-half particle, it's either with or against the magnetic field. Those are two states. How you can work with a multi-state system didn't require any Schrödinger equation in the basic concept. He introduced that. He introduced these sophomores to quantum mechanics by avoiding the complex math and emphasizing the nature of quantized states. In those days quantum mechanics was taught only in later-year undergraduate or in graduate school. When I was an undergraduate at Chicago, the faculty had made quite consciously the decision to teach us undergraduates nothing about quantum mechanics. They thought that was for graduate school because you needed to be much more sophisticated in physics and math to even begin to understand quantum mechanics. At least, that was the idea when I was an undergraduate at the University of Chicago, late ‘50s, early ‘60s. Feynman said, "There are important parts of quantum mechanics that people should understand," recognizing that a lot of the students in this intro course are not students who would take any more advanced physics course. They might've been chemistry majors, biology majors, but they all had to take physics. For them to leave without knowing anything about quantum mechanics was terrible. He figured out a way to introduce many of the key concepts of quantum mechanics without burying it in the math. Now, he did introduce math of various sorts, including in his lectures on quantum mechanics. But not a solution for the hydrogen atom with the Schrödinger equation. That's not easy math. That's why the standard thing was to keep that for undergraduate seniors, or better yet, graduate students. Feynman said, "That's terrible."

ZIERLER: What about particle physics? In what way did he convey some often latest ideas about particle physics at that point?

ISRAEL: I don't recall that in the lectures. I bet there was some. If I look through the printed volumes, I might find some. If it were there, it would be in volume three, which I just happen to have here. He did talk about bosons and fermions. I don't think there was anything beyond passing comments to what was going on in particle physics at the time.

ZIERLER: What do you think the significance of that is? These were not important concepts for freshmen and sophomores to grasp yet? Was there not much excitement happening in particle physics at that point?

ISRAEL: There certainly was excitement. It was around that time that quarks were being introduced, the eightfold way, all sorts of things. He recognized that the majority of the students in the class were students for whom this would be their only physics class. I think he recognized that the basic concepts of quantum mechanics were important in chemistry, and for that matter, biology, biochemistry, and so on. I think he felt it was important beyond just physics. For me to guess what was going on in Feynman's mind is ridiculously humorous on my part, but my guess is that he was looking at what might be things that involved these non-physics majors as they moved forward, and I don't think the basic ideas of particle physics were seen as likely to have an effect in science more broadly, where it was quite clear to him that quantum mechanics was quite essential to chemistry, obviously, but other science as well. That's my speculation about that very good question. I hadn't thought about it, and that's my best guess. I wish you could still ask him that question.

ZIERLER: On the basis of capturing the imaginations of students who might not take additional physics classes, what about the ways that Feynman talked about the universe? Did he talk about astrophysics or astronomy? Was the term cosmology in use? Did he talk about cosmology at any point?

ISRAEL: I don't recall that. One of the things I remember him saying, he talked some about beauty in the work. He said, "These equations are beautiful, but on the other hand, if we were all colorblind and someone published a paper about arcs in the sky that have interesting spectroscopic characters that appear after a rainstorm. Would anyone say, 'Oh, those are beautiful,' in the same way that when we look at a rainbow, we say, 'That's really beautiful'? If you were colorblind, and all you had was a spectroscopic analysis showing there's this arc of raindrops there, and you get mainly one wavelength from this edge, another wavelength a little further out, a different wavelength further out, people would say, 'Eh, that's interesting.' Would anyone look at that paper and say, 'Oh, that's beautiful'? Not In the same way as when we look at a really clear rainbow." That was another Feynman-esque thing that sticks in my mind.

But he liked to pose questions, and as I said, there were a lot of graduate students in the back of the room. He posed a question that, when I taught a course in electricity and magnetism for undergraduate juniors here at Washington U, the textbook essentially used an adaptation of this problem that he set for his Caltech students. Those of us who were grad students–I lived my first three years there in a grad student dorm, Keck House, which was brand new when I moved into it, went back discussing this. This was the problem: Picture a plastic insulating disc. Embedded all along the periphery are little metal balls, which are charged. They all have, let's say, a positive charge. This disc is free to rotate. In the middle of the disc, there is a coil of wire attached to a battery. The initial conditions are, this coil has current going through it, and this disc with these positively charged balls embedded in the plastic is stationary. Now, suppose you cut the connection to the battery for this coil. Suddenly, the electric current in the coil goes to zero. There was a magnetic field out where these charged metal balls were, produced by the DC current in this coil. That magnetic field just changed dramatically.

If you look at Maxwell's equations, you'll see that the changing magnetic field will produce an electric field, which will in the same sense all around this coil, where there are these charged metal balls. Obviously, the charged particles will feel a force from that electric field, which will push the disc to start rotating. The initial condition was that the plastic disc was stationary. After cutting this wire, this plastic disc is rotating. "What about conservation of angular momentum?" Feynman asked. We all went home, and there was plenty of discussion among the graduate students to try to come up with an answer to that. Suggestions that were obviously wrong, like, "Well, there was angular momentum. All the electrons in this wire that were carrying the current were going around, and now they've all stopped, and that angular momentum was transferred." That didn't work. You could show that it didn't matter whether the charge carriers were negative going this way or positive going that way. The disc would end up rotating in the same sense either way, so that idea can't be right. I don't remember what all the other harebrained ideas were. Of course, the answer, which he gave, I don't know, maybe a week later, is that E cross B has momentum. There is momentum associated with perpendicular electric and magnetic fields.

There was angular momentum in the electromagnetic field around this stationary disc when the current was going. When the current had stopped completely, and there was no more magnetic field, there was no more momentum in the E cross B because there was no longer any B field, and the conservation of momentum was that the momentum of the E cross B field was transferred to angular momentum of this rotating disc. That's the kind of thing Feynman did. It wasn't a homework problem in the sense of, "Now, solve this problem. You've got to figure out which equation to plug numbers into." It was nothing like that. It was the basic concept that electromagnetic fields can carry momentum. If they're oriented in the right way, it could be angular momentum. Again, that's the kind of thing that Feynman did, which really engaged people. I know the undergraduates were also engaged. At least, the smarter ones were busy trying to think about it. And he hadn't taught anything about E cross B fields having momentum associated or that electromagnetic waves carried momentum. He hadn't gotten to that point yet. These were just simple things that came from, more or less, electrostatics and conservation of angular momentum, one of the most basic things that had been introduced way earlier in the course.

ZIERLER: Did Feynman discuss his own work? Did he convey all of the advances he was making in quantum electrodynamics, for example?

ISRAEL: I don't think so. I don't recall that in these lectures. I do remember when he received the Nobel Prize, and there was a lot of discussion in the department about it. But I don't think any of that came up. I don't think anyone talked about Feynman diagrams or anything like that in that first- or second-year course. Maybe I missed some things. I didn't know anything about Feynman diagrams myself my first year as a graduate student.

ZIERLER: What about Feynman talking about the physics at Caltech specifically, some of the research at Caltech that was contributing to these advances? Did he bring a sense of institutional pride to his lectures at all?

ISRAEL: I don't remember that. But that's not to say there wasn't any of it that went on and went over my head. It was something like 60 years ago.

ZIERLER: What about Feynman's sense of history? Did he talk about the way physics research had advanced in historical context at all? Did he convey how important Paul Dirac was, for example?

ISRAEL: I don't recall any of that. I'd be surprised if there weren't at least some passing comments made about the history of it. But I don't recall that.

ZIERLER: Let's move onto the mechanics. You do the audio recording, then what do you do with it at that point? You bring it to the secretary?

ISRAEL: I just turned off the tape recorder and went on to my classes. Tom Harvey, who was the guy who set up the tape recorder, took the tape, and I assume he was responsible for giving it to the secretary or someone else who gave it to the secretary. Of course, those were days when photographs were taken on film and not by pulling out my handy little cell phone. Similarly, Tom took the camera, and for all I know, Tom was the one who actually developed the film and made the prints, which were then passed to Leighton and Sands. They used those in connection with the transcript to decide what sketch belonged in the printed material. The printed material initially came out basically in loose-bound pages of mimeograph. The idea was to get the printed material in the hands of these students as quickly as possible. The red bound volumes that you're probably familiar with was the second step. The first step was the transcripts, edited heavily, I understand, by Leighton and Sands.

The transcripts were edited and turned into mimeographed pages that were then clipped together with temporary clippings. Those were distributed so the students in the class got them. I don't remember exactly how quickly, but certainly within a week, they had the written text, complete with at least preliminary sketches. I'm not quite sure how long it took to get that into the bound book. The volume one book is copyright 1963, and the lectures that appear in volume one were, for the most part, in that first year before I came, which was the academic year '61- '62. I have volume three here, which is copyright 1965. The bound books took a year and a half or two years to come out, but the students in the course had the material in a week or a few weeks in mimeographed form.

ZIERLER: Was your sense at the time that Sands and Leighton intended for this to become a bound series of volumes?

ISRAEL: I think so. It was quite clear that they thought this would be a new physics textbook that would be widely used. What emerged was, I think, within a couple years, that it wasn't a good textbook. It was wonderful material for understanding electromagnetism, understanding quantum physics, all sorts of basic concepts. Some of the material in there, as I said, was subsequently used by other textbook writers. For a while, I was teaching one of the sections of the freshman physics class here at Washington U, which was first-year physics, chemistry majors, and first-year engineers and second- or third-year pre-meds, of which we have a lot here at Washington U, and that was basically taught in five or six separate sections. For several years, we used a new text, which I like and many of the students did not like. Six Ideas that Shaped Physics, written by Tom Moore, who's at Pomona, I think.

For example, in these texts, he introduces quantum mechanics in Unit Q using exactly Feynman's things with the Stern-Gerlach experiment and the basic ideas of specific energy states, how you convert from one to another, and so on. I'm sorry to say that most of the physics books used these days do not take advantage of Feynman's introduction to quantum mechanics the way that Tom Moore did. In a sense, I like Tom Moore's book just as I like the Feynman Lectures and find it interesting and useful for my understanding. Most of the students did not think it was a good textbook in somewhat the same way that after a couple of years at Caltech–I don't know exactly when--they stopped trying to use the Feynman Lectures as the text for the introductory physics classes.

ZIERLER: This would be totally anecdotal, but do you have a sense if students came into these lectures not intending to pursue additional courses but ended up doing just that as a result of the way Feynman conveyed these ideas?

ISRAEL: I would bet that the answer's yes. But I didn't have much contact with the undergraduates. Obviously, during the lecture, I was just sitting in the back. In addition to the lectures, the course involved recitation sections of, I don't know, a dozen or so students per section. Many of those recitation sections were led by faculty, not by graduate gtudens. I know Robbie Vogt taught at least one recitation section. Those people, I'm sure, had more contact with the students than I did and would probably be able to give you firsthand details. A lot of those students aren't around, but Robbie is very much around, even though he's in his 90s. I am still in email contact with him. His mind is perfectly fine as far as I can tell, and his memory of things is perfectly fine. That's a question that I bet he would be able to answer firsthand in the sense that I know he had contact with some of the students who were taking that class.

ZIERLER: For the last part of our talk, a few reflective questions, given how you were present at the creation. For you personally, as you emphasized, you were a graduate student, but there was still much to learn from these lectures, even though they were designed for first- and second-year undergraduates. In what ways did being in Feynman's presence, being there for his lectures, influence your subsequent career in physics?

ISRAEL: I would have trouble saying that it influenced my research career, since my research was in astrophysics, and that really didn't come up in these lectures. But it certainly has affected my role as a teacher. After all, I'm a professor at a major university. As such, part of my job is doing research, and part of my job is teaching. Over my career, I have taught everything from the freshman physics class for science majors, and some physics classes for non-science majors, mainly astronomy for distribution courses taken by history majors and other non-science majors. I've also taught courses aimed at advanced undergraduate physics majors and some graduate physics courses. Teaching has been part of my work, and certainly, as I've indicated, some of what he talked about there comes up in my classes, and I use it some, but it's not in a conscious way. I didn't say to myself, "Well, let me see if I can teach this the way Feynman taught it." It wasn't a conscious effort to, in any sense to emulate him. It was more just his way of describing things helped me understand things in a way that I could explain them better. It was more indirectly that it helped my teaching. I can't say it had any effect on my research career.

ZIERLER: What do you see, with the Feynman Lectures, that his unique gift was? He's advancing the field in tremendously important ways, but he's also conveying the ideas in a way that's accessible, even elegant. In seeing this in person, how did he do it?

ISRAEL: As I've indicated, he did it partly by his enthusiasm. It was infectious. That was part of it. Part of it was tying it to simple puzzles that made people think, like the question about conservation of angular momentum when the electric current in the coil is disconnected, and bringing in things like breaking uncooked spaghetti. It was mainly just his approach to making things exciting, interesting, and new.

ZIERLER: Well, Marty, this has been wonderful, spending this time with you. I'm so glad we were able to do this and capture your connection to the Feynman Lectures. I'd like to thank you so much.

ISRAEL: You're very welcome.