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In footnotes or endnotes please cite AIP interviews like this:
Interview of Kenneth Ford by Alexei Kojevnikov on 1997 November 15,
Niels Bohr Library & Archives, American Institute of Physics,
College Park, MD USA,
For multiple citations, "AIP" is the preferred abbreviation for the location.
Early education in Kentucky and at Phillips Exeter Academy. World War II service in Navy. College. Graduate work in theoretical nuclear physics at Princeton. David Bohm and J. A. Wheeler. Participation in the crash hydrogen bomb program. Post-doctorate at the University of Indiana. Fulbright year at Heisenberg's Institute. Research year at Los Alamos, 1957-1958. Teaching at Brandeis. Administrative positions at University of California, Irvine and New Mexico Institute of Mining Technology. Subsequent positions at the University of Maryland and biomedical start-up company. APS Education Officer, Director of American Institute of Physics, 1987-1993.
It is November 15, 1997, in Philadelphia. I am Alexei Kojevnikov doing an oral history interview with Kenneth Ford. Professor Ford, if you recall the early days of your school education, the elementary and high school, can you remember any particular event or book, or person, who might have influenced you in making the decision to pursue studies in physics?
I can remember one mathematics teacher, in Highlands High School, in Fort Thomas, Kentucky— I was a 10th grader in her class, and it's not such a wonderfully significant event in a way, and yet it meant a lot to me in that she let me move through two years of mathematics in one year. I had been typically an "A" student, and usually at the top of my class, but I was never pushed or encouraged by any teacher before that to do extra work, to go beyond what was in the classroom. And she said to me, as we got into the geometry course, "You sit in the back of the room; you work through the book. Ignore what's going on with the rest of the class. And when you finish that, then we'll move you into the advanced algebra course." And somehow that was a very meaningful event to me. There is no single book that I can recall that moved me in the direction of physics. But, at that same high school in Kentucky, when I was in the 8th, 9th and 10th grades, I read just about every book in the library that was available that was of the class you call, "Science for the Layman." There were books by Sir James Jeans. There were books by Artur Eddington. I now know, in retrospect, that they were books by actually very fine scientists themselves, not just journalists. And I was very much moved and inspired by those books.
Can you recall what particular interest you found in those books by Jeans and Eddington?
Well, it was certainly the modern physics parts of them. Stories of atoms, and nuclei, radioactivity— the quantum principle. Those were the things that captured my mind. Also some astrophysics, which Eddington discussed in some detail.
Did you pay attention that both Jeans and Eddington were known to derive some religious lessons from science and to connect religious issues with modern science. Did you have any interest in this?
It didn't register with me. I was completely unaware of that. I was just fascinated by the science. I never really made a conscious decision, I think, to become a physicist. It seemed like just a natural progression. By the 10th grade I was sure I wanted to be a scientist, but I didn't yet have clearly in my mind what the differences were between different sciences. By the 11th grade, when I went off to Phillips Exeter Academy in New Hampshire, and had my first physics course, then I just— again, it seemed automatic, following down that physics road, so that by the 11th grade, it was really probable and surely by the 12th grade of high school, I knew that I wanted to be a physicist.
You have mentioned you read nearly all the science books in the school library. Any idea of how many books that might possibly be? It's important how many science books would be in an elementary school library in those days.
Well, probably twenty or thirty— not a large number.
And this includes biology and chemistry, and physics?
No, I didn't read other sciences. I read mostly books about physics. I don't know why. I don't remember now the conscious choice of why, but it held more fascination for me than the life sciences.
I see. You also mentioned that at high school, you pursued mathematics through calculus?
Was it common in those days for, let's say entering college students, to know calculus?
No, it was not common. That was 1944, and it was still a rarity that calculus was taught in the high schools. My last two years, junior and senior years of high school, were spent at Phillips Exeter Academy, as I just mentioned, and that's where I had the calculus course. But even there, at this prestigious prep school, it was only a small fraction of the students who took calculus, quite unlike today when at least in private schools and boarding schools just about every student takes some calculus.
And what was taught of physics, in those days, at the Exeter school? Did you hear about quantum physics?
No. What was taught was standard classical physics.
I think not. I think mechanics and electricity and magnetism. A little bit of atomic physics. I can't remember for sure, but, for instance, we might have done the Millikan Oil Drop experiment.
You have also mentioned your physics teacher at Exeter— Elbert Little? and that you were very much inspired by him?
Again, how common then, in those days, was it to have a male teacher, at high school? Or, could it be that— and I know that sometimes male teachers are very important for male pupils at schools— do you think that has something to do with that?
Again, the private boarding school needs to be distinguished from the public high school. Female teachers were more common in public high school, although, maybe not even predominant. It was more in the elementary grades that women teachers were the large majority. And I had only women teachers, I think, up through the 7th— 6th or 7th grade. But, already in the public high school, in Kentucky, there were some male teachers. And then at Exeter Academy there were more than one-half male teachers. It was, after all, a boy's school at that time. It became co-ed later. In fact, much more than 50%. Now that I think back to it, there were very few women teachers there.
Did you continue to correspond with the physics teacher after you graduated from the Academy?
Yes. I remained friends with him, and with his family. In the summer immediately following my graduation, I went down to Woods Hole, Massachusetts, and worked under him as an assistant in the equipment room for the Marine Biological Laboratory. That was a summer job he held, and as a teacher he went there every summer.
Was it just research work?
Well, he was just providing physics and technical support to the biological researchers. He was not engaged in research. Nor was I. I was just dealing with the equipment room, in minor repairs of equipment. But, I kept in touch with his family over the years, and indeed even today, I remain a close friend of his widow— he's no longer living. She is 81 years old, I believe.
And then after the Academy, you were drafted in the Army, as I understand. How did this happen?
Well, I actually was not drafted. I turned 18 on May 1, 1944, just a month before my graduation. Had I waited until after that birthday, I would have been drafted. But, I had the option — I believe it was from age 17 and a half to 18 — one had the option of enlisting. And I decided that the Navy was more appealing to me than the Army, and therefore I chose to enlist. So, the latter part of April, just days or weeks before my 18th birthday, I enlisted in the Navy.
Did you also took a course in the Navy?
Yes. That was a program that was open only by competition, by examination. It was called, "The Electronic Technician Course." The idea was that with new, relatively higher tech things coming along, like sonar and radar, as well as improved radio transmitters and radio receivers, the Navy would have an increased need for people able to service these things. So, they had this program, "Electronic Technician Training," which required getting above a certain grade on an entrance exam. It's interesting that I later met physicists of just exactly my vintage. People who turned 18 in 1943 or 1944, and a surprising number of them were in this program. Ben Mottelson, for example, a Nobel Prize winner, and now in Copenhagen, was, like me, an electronic technician at the latter part of World War II.
So, after completion of this course, you were supposed to work with radar, and with similar devices?
When learning this, were there any physicists teaching at these quarters— or, was it done by military? Or, how much was it scientific in the training?
I wouldn't call it scientific, but the teachers were remarkable, in a way, because they developed a technique of teaching what they wanted to teach with very great efficiency. Just those parts of electricity, electrical circuits for instance, energy considerations, and so on. They had developed a syllabus, and they were very, very good at it.
Radar, in those days, was a fairly advanced part of physics. And I would assume that teaching included backgrounds of radar, or just how to operate it.
They had very little interest in teaching us any of the theoretical backgrounds. They wanted us to know how to diagnose problems. If a device wasn't working, to figure out why it wasn't working, and to repair or replace the bad part.
Did you have good hands for working with actual instruments and experimental equipment?
We had quite a bit of opportunity to do that, although I was never very talented at it. I actually built a radio and it was such a thrill when I turned the dial and received a station. But, I did not complete that program, that course, because I transferred at that point.
So, what was the different program that you transferred into?
It was called the "V-12 Program."
What did this stand for?
The letter "V"— I don't know what it stands for— nor do I know why the number "12." But, it was called the V-12 Program. It was a college training program. And again, it was developed by someone who took a long view, who assumed the war might last for very many years, and that it was important to have a group of young people coming through college, and out of college, to make potential future officers. I had tried for that program earlier, and not gotten into it, because I failed the eye examination. For some strange reason it required 20/20 vision without glasses, to be admitted to the V-12 Program, and I was a little bit near-sighted, so I didn't make it. That's why I went through the Electronic Technician Program instead.
But, I have to tell a little anecdote of how I did get into the V-12 Program, despite being near-sighted. I went through the physical examination, of which the eye exam was a part. There one is standing in one's shorts, almost naked, in a long line of men, getting your heart monitored with a stethoscope, and with them looking in your ears and your eyes, and so on. But while this line was progressing, the people ahead of me were looking at the eye chart, reading off the letters. So, I had time, before it was my turn, to look at the letters with both of my eyes, not just one at a time, and to hear what the people ahead of me were saying. And so when it came my turn to read the chart, I, in a very confident voice, rapid fire, said a bunch of letters, which I think were mostly correct. But, the bored technician, who was just listening for the cadence— was somebody going to say quickly, "X-Y-Z-Y-N" or was somebody going to say slowly, "O-R— I think that's a B?" He was just listening to the cadence and the speed, and he heard me confidently say a bunch of letters, and wrote down 20/20, and that's how I got into the V-12 Program.
Was that program of studying in the college, still being used in the Army?
Yes. I was still in the Navy— still in uniform, but it was very much like being an ordinary college student. A full load of courses, and you choose the courses.
How about the discipline?
There was a little bit, but not so bad. At John Carroll University, the first place I went, we had to get up early in the morning and do calisthenics. So that was a little bit of militarism. At the University of Michigan, I carefully arranged to take a physics course whose laboratory met in the afternoon when drill was to be scheduled. So, I got excused from drill in order to go to the lab.
Did you decide, at that time, that you wanted to study theory?
Yes. Again, I can't remember it as a conscious decision. It seemed like just a natural flow of events. That's the direction that I was headed.
When did this happen? When did you know that you wanted to study theory?
At the beginning of college, if not sooner. Perhaps even in the last year of high school.
Whom did you know at that time as a kind of model theoretical physicist. Of course, the name of Einstein was probably known to everyone. But, I guess Robert Oppenheimer was not yet known?
No. I'm not able to name any physicist at that time who seemed, to me, like a model. There is an interesting fact about my high school years. The first two years, as I mentioned, when I was devouring all the Science for the Layman books, or Physics for the Layman books, was one period. And then the next period was the junior and senior years at the boarding school, where the pace of work and the demands of courses were so great, that almost 100% of my time and intellectual energy were devoted to those specific courses. I had less time to read material on my own. Less time to think on my own about matters outside of class.
Did you complete this V-12 Program?
No, because the war ended. But, in the space of 12 months, I did get the equivalent of two years of college. I spent a summer period, a four month period, at John Carroll University, and then about an eight month period at the University of Michigan. I had a little bit of a course overload, so that by the time I finished that 12-month period, which by then was June of 1946, I had accumulated two years worth of college credit. I was admitted to Harvard as a junior in the fall of '46.
Was it your decision to quit the Navy with the war's end? Or, was it automatic.
I had the opportunity to transfer to a regular status, but the idea never crossed my mind. I viewed it always as a temporary assignment, only during the war. And the reason that a full year elapsed from the end of the war in Europe until my discharge was simply logistical, bureaucratic. It took a long time to move 1 million or more men out of the services. And the first priority for a discharge were those who had served a longer time, or who had seen active military service. People like me who came in late and who were only going to college, not fighting the war, were low on the totem pole. So, it took a year for them to get around to discharging me.
When did you actually transfer to Harvard?
Fall of '46. I was back on schedule, in a way, because I graduated from Harvard four years after I had graduated from high school, even though there was one year in there where I wasn't going to school.
How was physics teaching at Harvard in those days?
I'm trying to think back to specific teachers. I'd say the most inspiring teacher I had was Herbert Goldstein, who at that time was working on, and just had in manuscript form, a book on classical mechanics that later became a very famous book.
Oh yes, I know that book— it was also translated into Russian.
I took a course on classical mechanics with Goldstein, as an undergraduate. I can't remember now whether it was as a junior or senior, but it was considered to be a beginning graduate level course, and he was a very inspiring teacher in the classroom, and moreover an accessible person that I could go to outside of class and talk to. Other teachers were effective as lecturers. Kemble, for instance, with whom I took thermodynamics. Ed Purcell with whom I took a course on electricity and magnetism. I got to know Purcell as a person later. A very admirable person, although I did not, at the time, regard him as that great a teacher for undergraduates.
How about theoretical physics or modern physics?
The most significant course I had in modern physics was an all laboratory course. I cannot now remember the name of the instructor. But, it's a course in which for a whole semester we just did classic modern physics experiments. Spectral analysis and e/m,and oil drop, and so on.
You mentioned that while at Harvard you joined a student group writing a critique of Harvard education. Do you recall what the issue was about?
No. It seemed important at the time. But I've totally forgotten. Typical of students everywhere, at all times, that they feel that the work— that the institution that they are at could stand a lot of improvement. We felt that way about Harvard.
Was it more about the quality of teaching, or about some social or administrative thing?
My memory is vague, but it was about teaching. I think we felt that there were too many large, impersonal lectures. Not enough individual contact between students and teachers. I think we advocated more tutorial opportunities for students. By the way, at the University of Michigan, where I went before Harvard, I would say that the quality of teaching was probably higher than at Harvard, in that—
Well, I'm thinking of all fields. Actually, even in physics. I had one marvelous course in optics and spectral analysis, from a master of the field. His name was Meyer and he wrote a famous book on diffraction and interference phenomena. His course had a large laboratory component. It was the first time that I did any laboratory work with really high precision. It was work with four and five significant figures. It was the first time I used a calculator— a mechanical calculator, where you turned a crank. But, I found that a wonderful experience. And again, they were small classes, with close contact. Because it was still during the war years, the University of Michigan was a much smaller institution than it is now. And incidentally, the women outnumbered the men among the student body.
But then there was, presumably, a big influx of male students into the University, right after the war?
Not so much in 1945, that happened more in 1946. But I remember an excellent course in poetry, as an example, and an excellent course in English, at Michigan.
Speaking about your classmates, are there now physicists among them, or do you recall anyone among them who would become a physicist?
Yes. It turned out that when I graduated from Harvard in '48, there were just seven students in the graduating class of a thousand who were given the Summa Cum Laude designation. Three of those seven were physics majors. I was one of them. Richard Milburn was another. He became a Professor at Tufts University. And Herman Carr, was the third one. He became a professor at Rutgers University. Neither Milburn nor Carr nor I ended up in the top tier of the most distinguished scientists, but we started out with stellar undergraduate records.
Was there some kind of student study groups, or circles, or kind of informal exchange between physics students in those days?
Very little. Very little. Most of my interaction with other students was not with physics students, but with my roommates and others who lived in the house where I lived, but who were not studying physics.
You also mentioned that after you graduated from Harvard, it was partly by advice of your former high school teacher that you decided to continue your graduate studies at Princeton. Would it be common to ask a high school teacher for advice where to go for graduate studies? Or, did you get any advice from your professor at college about this?
Well, let me go back one notch. First of all, the choice of Harvard as an undergraduate institution, which I had chosen before I went off to John Carroll in Michigan, that was on the basis of Dr. Little's recommendation. My high school teacher had a Ph.D. from Harvard. I said to him, "Where do you recommend that I go to college?" He said, "Well, Harvard is a good place, why don't you go there?" And I said, "Okay." I applied only to Harvard. That's the astonishing fact. There are so many contemporary students for whom college application is such a big traumatic and stressful period. I applied only to Harvard and was admitted there. And then, four years later when I was getting ready to go to graduate school, I went back to Elbert Little again— "Bert" Little, as he was called — and asked for his advice on graduate schools. He mentioned several, and I in the end applied to three; Chicago, Caltech, and Princeton. As I recall, I was admitted to Caltech and Princeton. Chicago wrote and said they needed another application fee— another $25, or something like that, and I said, "To heck with that." And so, I dropped my application to Chicago, and ended up with just the two. I took Bert Little's advice, and chose Princeton.
And then I went to John Van Vleck, who was at that time the Chair of the Physics Department at Harvard, and later a Nobel Prize winner for his work in solid state physics, and I said, "Since you're my advisor — we've rarely ever talked, but you are officially my advisor — I thought you should know that I've decided to go to Princeton for graduate school." He said, "What? I just assumed you were going to stay at Harvard? Why didn't you tell me?" But, by that time I had already accepted Princeton.
You didn't apply for grad school at Harvard?
No, I didn't.
Was it common, in those days, for those who graduated from Harvard to stay as grad students there? Because now people, I know, go to other places, rather than staying on.
I think, even then, it was more likely they did encourage you to go elsewhere. But it was, perhaps, more common then for some students to remain at the same institution.
What was the motivation for choosing Princeton? Was it partly the advice of your high school teacher?
An outstanding reputation, I should say, in theoretical physics. A small graduate student body. My class admitted only 12 students that year. So, the small size and the superb reputation were the main factors.
Any names mentioned?
One other factor may have played a role. I'm not sure how much I knew about that in advance, but the fact that there were no specific course requirements at Princeton. One simply had to pass a qualifying examination, typically at the end of the second year. No particular number or type of course was required on the way to that.
Did you know, at that time, who were among the faculty at Princeton?
No, I didn't. I didn't know any by reputation.
Did you know that Oppenheimer was at the institute for Advanced Studies?
I must have known that, but I don't think it had any bearing on my choice. Of course I knew that Einstein was in Princeton. I'll tell you of a recurring nightmare I had as a graduate student. I had an old car, and I drove around town too fast, as many young people do, and I would have this occasional nightmare. I don't mean literally at night, but a daytime nightmare, where I thought, "What if some evening I'm driving too fast down Nassau street and hit and kill Albert Einstein. I don't want that to be what should make me famous in the world."
I wonder whether, in your college days, whether there was any discussion among physics students regarding things related to nuclear physics, military research, atomic bombs? Do you recall any kind of discussions in those days?
We were largely oblivious. No— hardly any awareness and no discussion. We were really cut off from the world of practical politics and international considerations.
But, was there an understanding, for instance, that the bomb and weapons, in a way, contributed to the prestige of the physics profession in that it was kind of important for career opportunities, in physics?
If it influenced others, it didn't influence me, because I never gave a single thought to physics versus some other field on the basis of prestige, or the potential for getting a job, a career, an opportunity relative to some other field. That didn't enter my thinking. I think I would have pursued the physics track no matter what.
You mentioned, there were 12 students admitted to Princeton that year. All 12 in physics?
That's what I meant. The physics group, the first year graduate students, at Princeton numbered 12.
Who, would you recall among them?
Well, it included Sam Schweber.
Oh, was he of the same year?
I'm pretty sure that he entered at the same time I did. He subsequently became a professor at Brandeis University and wrote a book with Hans Bethe on mesons and elementary particles, and more recently a very excellent book on the history of quantum electro dynamics.
And a very big book on field theory?
Which I was reading in Russian.
That's the one he wrote with Bethe, isn't it?
Oh, you're absolutely right. He wrote a separate book, yes. I now remember at Brandeis University he suddenly appeared on the campus with a new Chrysler automobile, and he said, "This was purchased with royalties from my book on field theory." Richard Ferrell, was another classmate. He became a professor at the University of Maryland College Park, where he still is. Alec Pond, another member, did an experimental thesis with Robert Dicke, and went to Stony Brook. Like me, he made a turn toward administration and ended up as an Academic Administrator at Rutgers University. Some of the classmates I had at Princeton, like me, started their graduate work in physics in the fall of '48. Lawrence Wilets did an experimental thesis with Allen Shenstone, and although his inclination was toward theoretical physics, he just decided that the experimental work would get him to his Ph.D. more quickly, and then he could turn his attention to theory. He went to the University of Washington in Seattle, where he still is. Those are a few of the ones who were there.
You mentioned that no specific courses were required. But, did any of the particular courses which you took in those days have importance for you?
Well, I'd say the two most significant ones, the most memorable ones and the most influential ones were a course in introductory quantum mechanics with David Bohm and a course in classical mechanics with John Wheeler. I also had a course with Valentine Bargmann. It was a wonderfully, highly organized, perfectly presented course, and yet, to me, didn't connect to me a much as, say, Wheeler's course. John Wheeler came into the classroom— every day you had the feeling he was feeling his way. He didn't come in with a polished, prepared set of lecture notes. He came in with an idea or two, and started to work through it on the board. One also had the idea, in taking a course from him, that his primary motivation was not to teach us standard classical mechanics, but to find new ways to look at the subject. His new ways would, in particular, try to relate classical mechanics to quantum mechanics. Methods of least action, for instance, and other aspects that dated from the early 19th, or mid-19th century, in classical mechanics, but nevertheless found applications in quantum mechanics as well. That particular course, unquestionably, is what led me to seek Wheeler as my dissertation supervisor.
Was the course on quantum mechanics that you mentioned, the first course on this subject you took, or did you already have quantum mechanics at Harvard?
No, I didn't. I didn't have it at Harvard. Just like calculus was rare in high school, quantum mechanics was rare in undergraduate programs at that time. So, the course with Bohm was my first introduction to quantum mechanics.
And that was, I presume, very close to his book published around that time, shortly thereafter?
Yes. He was working on the book at that time. His teaching reflected his development of the book.
Who else besides Wheeler, on the faculty in those days?
Well, Robert Dicke was on the faculty. An astonishingly brilliant man in both theory and experiment. At that time he was more concerned with experimental physics. Eugene Wigner, a very powerful mathematician and theoretical physicist. I was not drawn to Wigner, as a thesis supervisor, because of his more formalistic approach. Plus, he was a little bit more distant a person. A little harder to talk to. I remember once knocking on his office door and walking in, wanting to ask him a question, and he was quite rude to me and told me that that wasn't the time, and to come back another time. I was a bit shocked, and backed off. Whereas, a person like Wheeler, or Dicke, or most of the other faculty, would have dropped what they were doing in order to answer a student's question.
How about Bohm? Did you consider doing a thesis with Bohm? You might because your first paper was co-authored with him.
No, I didn't. My first paper was with Bohm, and I liked him a lot. Being a younger faculty member, he was almost more like one of the graduate students. And yet, strangely enough, I didn't think of asking to do a thesis with him. I think at that time his main research interest may have been in plasma physics.
Yes. That's correct.
But our joint paper was in nuclear physics.
So, Bohm had interest in nuclear physics as well in those days?
Was there also a course in nuclear physics?
I don't think so. I don't believe I took a course in nuclear physics.
Well, how did you learn it? From books? From original papers?
Well, it must have been through papers. Not so much from books. My thesis work got started after I talked to Wheeler, which would have been in the spring of 1950. Actually in 1949 and '50 he was mostly away in Europe and France, but he came back for a visit and I spoke to him about working with him. I may not have the time sequence exactly right, but he said, "Well, here's an interesting paper by Aage Bohr containing a combined look at the individual particle aspects and the collective, or liquid droplet aspects of the nucleus— why don't you read this and see if there's anything in there that suggests a possible direction of research."
And was this a 1950 paper?
I think it must have been the spring of 1950, yes. That's my recollection. And at the same time, Wheeler himself, with another graduate student, David Hill, was writing a big long paper called "The Collective Model of the Nucleus." Maybe that wasn't his title, but it introduced that term, the "Collective Model," for which Aage Bohr and Ben Mottelson had used the term "Unified Model", a very similar approach.
If we go back a little bit to your first paper, you mentioned that it originated from your talk at a Journal Club. What was the Journal Club?
The Journal Club is a wonderful institution that existed then at Princeton, and may still. I don't know about other universities, but the idea is that once a week, in the evening, the physics faculty and graduate students would gather and there would be typically two or three presentations. Roughly twenty minute presentations, sometimes by graduate students, sometimes by faculty, on a recent piece of work of interest. Usually it was a just-published piece of work. Sometimes it may have been based on a pre-print, although pre-prints were a less significant part of the landscape then than they are now.
Who was determining who was going to report or what was going to be reported? Was there any person running it?
Yes. One faculty member, each semester or each year, was in charge of the Journal Club. And I can't now remember who it was at that time. But, I know that I was assigned to read and report on a paper by some experimental physicists at Oak Ridge National Lab. (Wollan and Shull). What they had measured was the cross sections for scattering of very, very slow neutrons, thermal neutrons, for a whole set of nuclei. They reported on what is called the scattering length, which is a measure of the S-wave scattering, that is scattering in which the orbited angular momentum L equals zero. I was asked to report on this. Since they had made the measurements for a number of elements, I thought, "Well, is there any way one can apply some elementary quantum theory (which I had just been learning in Bohm's course) that might explain, or have something to do with, these experimental results."
So, I took the simplest possible model one could imagine, which is the square well, and imagined a square well whose radius becomes gradually larger— radius is proportional to the cube root of the atomic mass. And then I did a few simple calculations, just with the elementary tools of quantum mechanics that were available to me then as a beginning student, for the S-wave scattering. I realized after a little bit of calculating that there would be certain radii for which there would be resonance effect, and thus you would have a peak of larger-than-average cross section for scattering of the thermal neutrons. As you moved sequentially through the periodic table, from one to larger numbers of nucleons in the nucleus, in principle you should come to certain atomic mass values, certain elements, which would show a resonant peak of scattering. The data from the group at Oak Ridge was somewhat scattered and not terribly accurate, and yet there was enough of it to just be supportive of this idea. One could see a couple of apparent resonances.
I think lithium was the first nucleus that showed a peak of scattering. So, I reported this at the Journal Club with no concept that it was of above-average interest. I just said, "Here are the experimental results, here's my elementary analysis, which suggests that there's some regularity here, and one can see these resonances." And it caused quite a stir of interest among the faculty who were there. "This is significant. This is important." And David Bohm came up to me right after the Journal Club and said, "You have really hit on something there that's possibly important. Let's you and I work on it together and extend it a bit." That's what led to my first paper with Bohm (and my first paper of any kind).
What was his contribution directly?
Well, I can't remember exactly. The original idea was mine, because I developed it in connection with this Journal Club talk. But, he sat down with me and went through the calculations again, and helped me write the paper. So, it was definitely a joint effort.
But, the first original experimental paper on which you reported, was it made by you, the report, or was somebody else assigned?
Oh, I was assigned to report.
Do you remember by whom?
No. Because I can't remember which faculty member was in charge.
Was it the regular obligation to give a report?
Like, how often would you do this, for instance? And how many people would attend?
Most of the faculty and graduate students attended. So, total attendance may have been 50, or something like that. It was in the evening. And typically there were three presentations of 20 minutes each. So, during the course of a semester it was a large number of presentations.
And faculty members would be reporting, just like the rest of the students, on the same basis?
But, Wheeler wasn't there this year?
That's right. Wheeler was away on a Guggenheim Fellowship in Paris. As far as I can recollect, that's the only Journal Club report that I gave. There might have been one other during the year, but I can't remember. This is the one that stands out in my mind. Of course, just to add a word, that paper is significant to me because it was my first one. But more than that, I think it was of some relevance in nuclear physics, because it was one of the very first pieces of clear evidence of transparency in the nucleus. The liquid droplet model and the compound nucleus model had held sway on up through the 1930's and 1940's, and it was only around this time, in the late '40's, that ideas of the shell model were beginning to surface. Maria Mayer, in this country, Jensen and Suess in Germany. What Bohm and I published was one more of the significant early pieces of evidence that, indeed, the interior of the nucleus had a large measure of transparency, since the simple theory I applied would certainly not have applied had the nucleus been an opaque structure. Then, one would not have expected resonance or any kind of periodic behavior from one nucleus to another, but rather a steady trend.
You mentioned in an earlier note that this paper was later attacked.
Yes, that's in your abstract of it. But, you didn't mention by whom.
I don't remember either. I think that the experimental researchers at Oak Ridge were a little bit annoyed because, if I recall correctly, they said I was using their data in preliminary form. I think it was already published. I think I was reporting on a paper in Physical Review, not on a pre-print. But for some reason they felt that it was inappropriate for me to analyze their data. That that analysis should have been left up to them to do. That's the only thing I recall. Robert Adair at Yale followed up with a similar paper, but it wasn't one that attacked ours, it just extended it. It sort of confirmed the picture.
And was it also that time that you were sharing a room with Bohm, or was it earlier or later?
Let me see if I can remember the sequence.
And how come that you shared a house with Bohm?
I can't be certain of the date. I believe it may have been my very first semester at Princeton, which would have been the fall of '48. It may have been the spring. It may have been the spring of '49. But it was within that first year. I lived in the graduate college only one semester. But, what I've now lost is the sequence. Was Bohm first, and graduate college second, or the other way around?
Bohm's was a private house?
Yes. He was renting just a single room in a family's home, on Nassau street. It was a very large room. It had two beds in it. And I guess I must have said something to him about the fact that I was looking for a place to live. And he said, "Why don't you come. There's an extra bed in my room, and it will be inexpensive, we can share the cost?" So, I agreed and did that.
Did you have any personal connections with Bohm, or did this stay together lead to you having whatever discussions with him?
Surprisingly little. He worked late. Typically he would come home and go to bed at 2:00 or 3:00 o'clock in the morning. And sleep late depending on when he had his first class. So, we were kind of non-overlapping. I'd be there in that room and in bed and asleep before he appeared, and I'd be up and out before he woke up. So, even though we lived together, when we did see each other or talk together it was mostly at school, in the laboratory, not in our residential arrangement.
Did you have many discussions about physics in those days with him, or not?
Not very much. Within class, of course, we would have discussions about quantum theory.
Did he, at that time, already have these ideas about interpretation of quantum mechanics or was it at all discussed in the classroom?
My recollection is that he was teaching us very strictly the Copenhagen interpretation of quantum mechanics, and that his alternative views arose either then or later, but they arose as the result of his trying to come to grips with the standard Copenhagen interpretation and teach it. His own doubts, or his own looks at alternatives, I think happened either then or later, but didn't play much of a role in his actual teaching of the course.
And do you recall him discussing politics with you or with any other students?
No. I was aware of his what you might call "left wing liberal leanings." But, it's not something we talked about. I had no inkling of the fact that he was under suspicion in any way, or that he had been a member of the Communist Party. That was not known to me at the time we interacted. It only came to light after the House on Un-American Activities Committee got on his case.
But this was known at Princeton, wasn't it?
No, the fact that he was summoned to the House Un-American Activities Committee— was this known?
It was known in 1950, 1951, when I was on leave from Princeton. So, I wasn't physically there at Princeton at the time of these events. I heard about them second hand.
Okay. Now, if we return to choosing Wheeler as a thesis advisor. You mentioned that, "It was partly thanks to the Russian atomic explosion of late 1949," I quote, that your association with Wheeler turned out to be closer than it otherwise might have been?
Do you recall how you learned about the Russian explosion of 1949, and what your, and maybe some others, reaction to this was?
I was a very unpolitical person, and hardly looked beyond higher than the walls of the campus, but of course I was aware of it. It became a more significant factor with me in the spring of 1950, perhaps it was March or April. Wheeler left Paris in January of 1950, to go to Los Alamos. So, by the time I talked to him about working with him on a thesis, he was already in Los Alamos. He came back from Los Alamos, perhaps in March or April that spring, to visit from Los Alamos to Princeton. That's when I spoke to him about doing a Ph.D. thesis with him.
And that's when he saw the Aage Bohr paper?
Yes, that's right. And he said he'd be delighted to work with me. He gave me the Bohr paper as just a beginning, to have a look at, to read. He said, "However, I'm planning to spend at least the coming year on leave from Princeton at Los Alamos. You should be aware of that. I would be happy if you want to come there, but that's up to you to decide." So then, that's where the Soviet atomic explosion entered the picture, because his decision to go to Los Alamos was based on his concern after the so-called Joe 1 explosion of August of 1949. Another student, John Toll, was already working with Wheeler. He was a couple of years ahead of me in graduate school, a little further along. He was already into his thesis work at that time.
And Hill was also there?
David Hill, I guess, was also working with Wheeler then, yes.
But, he didn't go to Los Alamos?
No, I think Hill was, perhaps, more nearly finished. I can't remember the exact sequence there. But, John Toll did go with Wheeler to France, and worked with him there. So, for John Toll to follow Wheeler to Los Alamos was more natural, since he was already in the middle of his Ph.D. dissertation. Well, he still had to make the decision, because going to Los Alamos meant not merely following one's thesis adviser and working with him, it also meant joining a laboratory and joining the H-bomb program.
So, there was an understanding that if you go there, you have to work with the bomb, not just doing work on your thesis?
Did you have concerns about whether your Ph.D. would be hindered by this?
I had none, although the Chairman of the Department, Allen Shenstone, had concerns when I told him I was thinking about going to Los Alamos, following Wheeler, and asked for a leave of absence from my status as a graduate student at Princeton, he strongly advised me against it. He told me of other cases he knew of students who thought they would take a year off and then, in fact, never came back. That year off turned out to be a turn away from physics, and he strongly counseled me against doing it. He said, "Stay here, get your Ph.D., and then think about what you want to do, and where you want to work." But, I didn't follow that advice. I did follow Wheeler. I had to think seriously then, this was the first time, about this question of weapons work, secret work. Did I want to get involved in it? It was not an agonizing decision, but it was obviously a significant one.
I made the decision to go, of course, partly just to be with Wheeler and work with him, but partly because of my feeling at the time that the world would be a safer place, a more secure world, if the United States got the H-bomb before the Soviets got it. And that was the issue in my mind. If I and all other physicists hung back, and did nothing, then the Soviets would achieve an H-bomb before we did. I felt that would produce instability, danger in the world, that was unacceptable, and one had a duty to try to help the United States get there first. I had a confidence in what you might call the morality of our own country that perhaps got significantly eroded later in the Vietnam era. But at that time, I felt that an H-bomb in American hands would be a good thing. It would help to preserve world peace, and would not be used by the United States as a weapon to threaten other countries or as with means of imperial expansion.
How confident were you and Wheeler at that time that the H-bomb was possible?
There was no evidence that it was possible. I should add one other little incident that helped convince me. Edward Teller came that spring, in April or May, to Princeton. He made an appointment with me and I remember going over to the Institute for Advanced Study. It was a very pleasant spring day, and we sat outside on the steps of the Institute and he gave me a hard sell as to why it was important for me to come and join the project in Los Alamos. Wheeler had not given a hard sell. Wheeler had said, "That's where I'm going. It's my personal decision. I think it's important. But, you make up your own mind, and if you come, fine. If not, fine."
How confident were you that Soviets were working on the H-bomb?
I assumed it as a matter of course. I mean, after their atomic bomb explosion.
Because, there was still, I think, a controversy in the press in the United States about whether to go ahead with the project or not. And I think some people were raising ideas that maybe some kind of mutual abstinence from developing the H-bomb was possible, through whatever talks between the United States and the Soviet Union.
Do you recall any reading, or any kind of paper?
Yes, because in January 1950 Truman issued his order that there should be a crash program to develop an H-bomb? I think that was part of what convinced Wheeler to join the effort. He was recruited by Harry Smyth and by Teller.
How about other graduate students? Did any other graduate students have opinions of this issue?
I certainly encountered no counter opinion. No one other than the Chair of my Department counseling me not to go. And in fact, a year later when Wheeler moved back to Princeton, and when we created Project Matterhorn, we continued the bomb work in the vicinity of Princeton. There were a couple of other graduate students who willingly joined the effort, including Larry Wilets.
When was the first time you arrived at Los Alamos?
June of 1950.
Was it necessary to get security clearance beforehand?
Was it difficult?
No. I can't remember how long it took, but it couldn't have been more than weeks, or a month perhaps. Maybe it was quicker then than it is now. The Korean War started on my way out. That's how I remember the date, because I had bought an old automobile, a surplus vehicle from the Army, for a couple of hundred dollars, and with a friend, overhauled the engine. Mostly my friend overhauled the engine. I tried to help. But, I drove that across the country from Princeton to Los Alamos.
You drove all the way through?
Yes. During the course of those few days of travel, that's when the Korean War started.
What were the disciplinary conditions associated with the security clearance? What were you allowed to do, what were you not allowed to do at Los Alamos?
Well, there were no restrictions on behavior. There were no restrictions on travel. No restrictions on whom you could talk to, or not talk to. The only restriction really was that you couldn't take any classified material out of the laboratory, and you couldn't reveal anything in any classified material. Actually, you could take classified material out, because we did sometimes in traveling. You could check it out, provided you had it always in your possession. You could carry secret documents with you if you went somewhere else to a meeting.
Now, in your earlier memo, you mentioned the temptation to discuss the working personalities and the spirit and the life at Los Alamos at that time. But, you didn't go into detail. Maybe you can give some points now, about the spirit of the work there, and life at the place?
Well, first of all, the spirit that was evident to me, as a young researcher, a graduate student, was entirely positive. I was 24 years old when I went there, and blissfully unaware of whatever stresses and strains existed. Later I learned that between the director of the laboratory, Norris Bradbury and Edward Teller, there existed enormous strain and conflict, which permeated some of the other top people in the lab, but none of that made the slightest impression on me. All I was aware of was that I was working with an extremely bright, committed, bunch of people and that it was an exciting time. It was a wonderful spirit. A wonderfully informal spirit despite the pressures. In fact, when the laboratory, for instance, went on a six-day week, we felt quite relaxed.
So, it was Wheeler and his little group, which consisted of John Toll and me and a couple of other young people that gathered around him. At one point we were, as I recall, five people in one office. That led, obviously, to informal interactions. There was a coffee room. Coffee and pastries were served every morning in the Reines Raum, named after Fred Reines, where we gathered. And then there was all this intellect. Not only Wheeler and Teller, but people like Conrad Longmire, and Ted Taylor, who were already there, and Marshall Rosenbluth, who came that year, and people coming as regular visitors: Enrico Fermi, Hans Bethe, John Von Neumann, Bob Richtmyer. I could not have been in any other place where I encountered so many extraordinary physicists in that short span of time. Just getting acquainted with, and working with, Fermi and Von Neumann, for instance, was a tremendous opportunity.
Did you actually work with Von Neumann, or did you work with Wheeler most of the time?
I worked primarily with Wheeler. But, when Fermi came for a visit, or when Von Neumann came for a visit, a consulting visit, they typically stayed at least a few days, or a week, and sometimes even longer than that. They sat around talking with us, exchanging ideas, finding what we had done, making suggestions. So, in effect, I was working with them as well.
For Wheeler, this was the first experience in working on a military project, was it not?
No. Because he was part of the Manhattan Project in World War II.
Oh. But, he was working on that at Princeton?
No. He went to the Metallurgical Laboratory in Chicago, then to Wilmington, Delaware, and then to Richland and Hanford and Washington. He was a key figure in the design and analysis of the big plutonium producing reactors. He was involved only peripherally with Los Alamos. Well, he made a few visits to Los Alamos. And his recent graduate student Richard Feynman was at Los Alamos. Wheeler got to see him and they did some work in pure physics somehow, slipping it into the cracks during the war.
Did you have an opportunity to work on your thesis while in Los Alamos?
Yes, I did. Wheeler was given a large house on what is called Bathtub Row, meaning he was in one of the original houses from the Boys School. These houses contained bathtubs, unlike all the new housing built during the war, which had only showers. So, accordingly it was called Bathtub Row. Wheeler had one of these large houses. He and his wife and three children occupied it, but one large back room he decided to turn into a study, and he had arranged for three desks to be put in there. That was interesting.
In this room, as you recall, there were five of you working in his office?
No, the five in one office was at the laboratory. At his home, he set up an office just for the three of us, John Toll, myself and himself, to work. That was just for pure physics. We did not do any work on bombs there.
In what time of the day did you work there?
Nights and weekends. We often would come there after supper and work for a couple of hours together. Not necessarily talking to one another. Perhaps just the three of us sitting there working on our own things, and then sometimes on weekends. Wheeler, throughout his career, has been a marvel at managing to always keep alive some pure physics, no matter what applied work he was doing at the same time. And that was an inspiration to his two graduate students.
Could it be said that because of this particular setting you had a better possibility for interaction, and for communication, at Los Alamos than at Princeton, where you were just sitting in this room with several other people?
Oh, I'm sure. It gave both Toll and me the chance to meet and work with other distinguished physicists of the kind I just mentioned, who came as visitors, plus the chance with my own thesis advisor, to have a much closer relationship. One that has led to a lifetime of friendship.
Did you have free time, not devoted to physics, at Los Alamos?
Strangely enough, yes. It's hard to remember how, when one's worked a 40-hour week or more at the laboratory and a whole bunch of other hours devoted to trying to make some progress on one's thesis research. Yet I also remember lots of picnics, hikes in the mountains, and trips to Indian festivities, and so on. Somehow or another, we managed to have quite a bit of fun.
Any female company?
Yes. I also did folk dancing and square dancing at Los Alamos and I met some young ladies through that.
Who were working at the laboratory?
Yes. Even to the extent of getting engaged to one of them. An engagement that was later broken off, but that happened. And then, some of these outings I mentioned, the hikes, the trips that we took, were boys and young women together. There was a devastatingly beautiful young woman named Miriam Planck, spelled the same as the famous physicist Max Planck. She was part of our little group. These were all people in their 20's who had some fun together. She subsequently married a physicist and moved to Santa Barbara where he became a professor.
What was your own contribution to the laboratory work?
Well, I was very much a junior partner. The important ideas that were developed came from Teller, Wheeler, Ulam, and some of the other senior people. Carson Mark, the head of the Theoretical Division although not an originator of the important scientific ideas, was a master orchestrator, who got the best out of everybody. He was one of the best research administrators I have ever encountered. My personal role, and John Toll's, was more in carrying out a lot of calculations, learning how to program the primitive computers that existed at that time, pushing through differential equations to the form of numerical solutions. So, we were the back-up team of junior assistants.
Was this your first experience with numerical calculations?
Yes, it was.
And your first experience with computers?
With what particular computers?
They could barely be called computers. They were called "CPC's", card programmed calculators. They were gigantic machines, larger than a refrigerator. They were IBM accounting machines which had been slightly modified through wiring circuit boards to do things like extract square roots or take sines or cosines of numbers. They were programmed by punched cards. Punched cards were fed through the machine. There were no stored programs. In that sense, it was not really a computer. A giant step from that machine toward the modern age was the storage of the program within the machine.
But Los Alamos didn't have yet a stored-program machine at that time?
No, not yet. As I recall, they had three card programmed calculators. We had our set of punched cards which we fed through the machine. They went through at the speed of approximately one per second. So, that meant each second the machine could do one addition or subtraction. Or, maybe in two seconds it would do a sine, or a cosine. That was the rate of calculation.
Were there also human computers at the lab?
I mean, those with mechanical calculators?
Yes. It's interesting that you use the word "computer," because that's in fact what we called them at that time. A person who did computation on a mechanical calculator was called a computer.
Basically because our modern word "computer" comes from that.
Actually, it was more common for us to call them computresses, rather than computers, because they were all women, mostly young women. They used Marchant and Friden calculators. Calculators were no longer the hand-cranked type, they were plugged into the wall. They had little electric motors that turned them. But, they still did just the basic operations of plus, minus, divide and multiply.
And were they doing the same task as the IBM calculators, or the tasks were different?
They were doing pretty much the same tasks. You might say there was an overlap period when there was duplication of some of the work, with the young ladies at their Marchants, or with our punched cards.
Who was trusted more, the human computers or the IBM computers?
That's a very good question, because in both cases, the only way to get absolute trust in an answer was to do it twice. If we had an important calculation that seemed critical, and it was being done by these young ladies at their calculators, we would have two different ones doing the same calculation. If they both got the same answer, we assumed it was the correct answer. And the same with the computer. We'd do the same calculation more than once, to see if it gave the same answer.
Did you use human computers to check the machine? Or, did you use the machine to check the human computers?
Well, I think it was more complementary than checking one another. What the young ladies worked with were, in modern terminology, what we call spreadsheets. They were given the labels of the rows and columns, and instructions of what to do, and they simply started with numbers. And marched across and down the page, filling them in. It might be, for instance, the numerical integration of a differential equation. But it was all laid out by the person who gave them the work to do in terms of incremental step-by-step things to do.
And you also mentioned the CPC's in New York. That was a different job, or was it the same job?
Same job, it's just that we started using that when we moved back. In the spring of '51, we actually needed more computer time that was available at Los Alamos, so we used some CPC's at Sandia Laboratory in Albuquerque. I went down there and worked all night as I remember. Midnight to 8:00 A.M., on the Sandia machines. I took a certain pleasure in being housed in a bachelor officer's quarters, because I had never been an officer. But as a civilian I was allowed to be treated as if I were an officer. And then, after we got back in the summer of 1951, to Princeton, and started Project Matterhorn, we continued these calculations on the CPC in New York.
In New York, where?
At the IBM headquarters.
I don't know if it was the headquarters building but it was an IBM office.
So, was it rented time?
Yes. It was rented time. The IBM graveyard shift.
Graveyard shift means midnight to 8:00 A.M.
Oh. Because it was cheaper or—?
They were available then. IBM itself was using those machines for its own purposes during the day and they made them available to us during the night.
I see. How many CPC's were there at New York?
I only remember one, but there must have been more than one. There must have been several.
Did these calculations require developing any new mathematical methods of numerical calculation, or any mathematical tricks?
Yes and no. The tricks of integrating differential equations, for example, using the Runge-Kutta method, had been, I think, developed mainly by astrophysicists and astronomers who were the leaders in numerical computation in the pre-computer era. They were the first people to do serious challenging numerical computations. I think between the astronomers and the applied mathematicians, these numerical methods, had been largely developed already. We just took them and applied them. But there were subtleties involved, because some methods could produce unstable results, results that became meaningless, due to the finite step size, and others that were more reasonable and had higher accuracy. So, as we did the calculations, we were not only checking that we were getting the answers that we wanted to get from the equations, but we were checking that the numerical methods were approximately reproducing the continuous equations.
The question I was about to ask was, whether at that time, during these numerical calculations, you had any knowledge of the idea of the stored program computer, and that people were already working on the "Maniac," which was a stored program computer.
I honestly don't remember being very conscious of this important transition, from the external card programmed calculator to the stored program computer. I had to be somewhat aware of what was going on at that time. The early work of the "Maniac" computer at Los Alamos was taking place. We knew that John Von Neumann was developing ideas for a stored program computer. We knew that there was a computer called the "ENIAC" back east.
Did you have any experience with it?
No. I never used the ENIAC. Later, in '51 or '52, we graduated from the CPC, in New York, which became obsolete, to a couple of other machines. One was called the SEAC, which stands for Standards Eastern Automatic Computer. Standards being the Bureau of Standards. We used that computer many hours in Washington, D.C. And also the Univac— the first Univac, which was still in its factory in Philadelphia. I understand that that first Univac was scheduled, or the first commercially available Univac was scheduled, for delivery to the United States Weather Service, and that organization kindly agreed to delay its receipt of the machine in order that we could use it for the H-bomb calculations.
How crucial to use the Univac?
It was very important. Even though that step from the CPC to the Univac and the SEAC was not such a huge step, it was in a sense a huge step because it really made it possible to make meaningful calculations with more parameters and more variables, and to get more trustworthy answers, than would have been possible on the CPC.
And you also mentioned that there was a competition between Fermi and Ulam?
Stan Ulam and his associate, Cornelius Everett, a mathematician at Los Alamos, one summer— I think it was the summer of 1951— entered into an informal competition with Enrico Fermi, who was aided by the computress Miriam Planck, to see who could complete a calculation first. I can't remember specifically what calculation. It had to do either with igniting a thermonuclear reaction in deuterium, or with the propagation of a flame, a thermonuclear flame, once ignition had occurred. I'm sorry, I don't remember which of those it was. But in any case, they approached it by different techniques. Ulam wanted to use the Monte Carlo technique instead of the differential equation technique. Fermi used the differential equation technique, with the help of his assistant Miriam. It was all very good humored, and the funny thing is I can't even remember now who won if anybody won. It may be at the end of the summer they both had reached similar conclusions, which supported one another. But, I remember personally being amused at the time, because Fermi seemed to be very interested in his calculations, when he had such a lovely computress to work with him.
But, your calculations were meant to be the differential equation approach?
Was it thermo-dynamical equations or—?
Everything was included. That is, thermodynamics, the equations of state of the materials involved, the nuclear physics processes, the electromagnetic energy processes, everything stirred together.
And were there any occasion to check them, or how accurate those calculations were?
Well, in those days the way one checked the accuracy of computer calculations was to do one complete cycle by hand. For one set of parameters, you did it entirely by hand and then found out if the computer gave the same answer. If it did, you would assume that you had at least written the program correctly. Then you could put in other sets of parameters. Regarding accuracy, there were two other questions. One, of course, was how accurately is the physics represented in the approximate differential equations one is using, and then the second question is how accurate do the numerical methods really deal with the differential equations? On the latter we could experiment by using different step sizes, and different integration techniques. Besides Runge-Kutta method, there were various other methods of numerically handling differential equations. Thinking back, we spent many, many hours; we used the CPC in New York, for instance, eight or ten hours a night for weeks on end. So, we're talking about hundreds, many hundreds of hours of calculating time. And a lot of that time was spent in these modes of checking one's accuracy. Trying different approaches, trying different interval sizes, and then tweaking the parameters. We had to discover the sensitivity of the final results to the input equations and to the numerical methods.
And to the step-size?
The step-size and the method. And then, the sensitivity to parameters. If we assumed a certain value— let's say, the opacity in the material or a certain coefficient came into an equation of state, we had to vary that a little bit and see how it affected the final result, how sensitive the final results were to it. We had to check the whole set of assumptions.
And the ultimate goal was, I presume, calculating the yield of the explosion?
Yes. At least at Project Matterhorn, when we were back in Princeton. The major goal there was calculating the yield, but there are prior steps, mainly handled by people in Los Alamos— calculating the yield of the atomic bomb trigger, calculating the flow of its energy, and its radiation. These processes went on prior to the ignition of the thermonuclear fuel. It just happened that the work was divided up in a way that the Princeton Matterhorn Group, with which I was associated, was mainly concerned with the final stages, the thermonuclear burning. This meant that we were the ones who, in the end, made a prediction of the yield of the first test.
And what was the prediction?
Our final prediction was seven megatons of energy released, or yield. It's my understanding from reading unclassified sources since that the yield was approximately ten megatons. I think all things considered, it was remarkable that we were able to get that close.
When did you make this prediction? Back in the east, or still at Los Alamos?
That prediction was made with the computations at SEAC.
So, that's when all of you were back to the east coast?
That was in the summer of 1952 when the Matterhorn group was in Princeton. That final prediction was made a month or two prior to the actual test.
Now, how did it happen that you returned back to the east to work on Project Matterhorn? Was it just again following Wheeler?
It was again following Wheeler, that's right. John Wheeler himself decided that he wanted to return to Princeton for various reasons. Family reasons, personal reasons, professional reasons. He had a nice home back there, and his children were in school. That was one aspect of it. Another aspect was that he and Teller had very little success in attracting top scientists to come and join the project in Los Alamos, and he hoped that in Princeton he might have better luck. The environment there, a more academic setting, might make it possible for him to recruit some additional top scientists to join the project. A hope that turned out not to be true. He had no more success, in fact, and so the Project Matterhorn work was carried on largely by junior people, like myself. The third consideration of his was that it looked in the early stages, the 1950-1951 period, that it might be a very long road to the H-bomb, many years. That was a consideration too. He certainly didn't want to spend many years in Los Alamos. He might have considered a second year there, but he was looking at a multi-year project. That was another reason to go back to Princeton.
So, ideas, at that point were rather pessimistic?
Yes. Up until the so-called Teller-Ulam idea in '51.
When did he make the decision to return to Princeton?
Not long after arriving in Los Alamos. Well, he came to Los Alamos first in January or February of 1950. And then I and some other young people joined him, coming in the summer of 1950. I think that fall, no later than November or December, he was already talking to Norris Bradbury, the Director of the Los Alamos lab, about the possibility of setting up a separate laboratory at Princeton. So that happened prior to the Teller-Ulam idea. The actual move to Princeton came in the following May or June.
But, at that time, you already knew of the Teller-Ulam idea?
And was it known to everybody who worked at Los Alamos?
Oh, yes. There were no compartments. There were no significant compartments at that time. Everybody involved in the H-bomb work had a pretty full knowledge and full briefing on everything.
How did they learn of this? Was it a seminar? Was it internal reports distributed in written form?
Well, we certainly heard about it from reports.
Or, was it just word-of-mouth?
Well, both. First, we heard it from the people involved. Ulam and Teller. Then they got together and drew up a little report for the record. But, it was their oral reporting that—
Was it also sufficient there to run seminars with public discussion? By public I mean physicists involved in the project.
With a formal presentation and some kind of discussion?
We had frequent little seminars, devoted to reporting on the classified work that was going on. But sometimes a visitor like Fermi or Von Neumann would also give a general interest report on unclassified material.
And these were attended by all people? By all physicists who worked at Los Alamos?
No. I'm talking about seminars that were just for the Theoretical Division. Something called the Family Committee was also established. It involved representatives from all parts of the lab: those who would be involved in the actual machining of metal, the parts that would make the bomb, those involved with the high explosives, every different aspect, those who would be involved in the tests in the Pacific. Every part of the lab was represented on that Family Committee. All the critical ideas were shared at that level, which the individuals could take back to their respective divisions. But in terms of reports or discussion of the kind we were just talking about, that would refer just to the Theoretical Division.
But, for your own work on Project Matterhorn, wasn't it kind of a direct continuation of the work in Los Alamos. I mean the kinds of things you were doing there?
Except for the location?
It was a change in locale.
Well, the controlled fusion program also started at Matterhorn.
But that's a separate program, as I understand?
It was a separate program, but we occupied the same building and it had the same name, "Project Matterhorn." There was "Project Matterhorn B" for bomb and "Project Matterhorn S" for Stellerator, with Wheeler and Lyman Spitzer being co-directors. There was quite a bit of talk and interaction, because even though thermonuclear explosions and controlled thermonuclear power are very different concepts, they have a lot of things in common, and we shared ideas.
Was the level of secrecy equal in both projects? Were they allowed to come to your seminars, to your talks? And the reverse?
Yes. Although, it is an interesting question. I don't remember whether the people involved in the controlled thermonuclear work were excluded in any way. I think at that time that was still considered secret work also. The international openness on controlled fusion came later.
But, basically, would you run the seminars together, or would you run two seminars with people allowed to visit each seminar of each group?
I think that we went freely to each others seminars. We're talking about a very small number of people.
In Wheeler's section of Matterhorn there were probably not more than 20 people. In Spitzer's section there were even fewer, a dozen or 15. And some of those were support people, clerical, and so forth.
Who was the main theoretician in Spitzer's group?
Spitzer himself. And then, Ed Frieman. I think he subsequently became a professor at U.C. San Diego.
And all of those boys who worked with Wheeler in Los Alamos returned to Princeton?
No. Only two. Only Toll and myself. The others stayed on as permanent staff members or longer-term staff members at Los Alamos. I remember the name of only one other at this moment, Burton Freeman. He remained in Los Alamos for some years after that.
Did you personally have more time to work on your thesis when you went back to the east coast?
Initially not. In 1951, 1952, it was a similar schedule to that at Los Alamos. It was full- time work on the project and part time evening and weekend work on trying to pursue my thesis. As it turned out, I wasn't making a whole lot of progress, as a matter of fact. I was learning things, little bits and pieces of calculations, in that whole two-year period, from 1950 to 1952. There wasn't a whole lot of thesis progress. But then in the fall of '52, shortly before the test in the Pacific, I essentially took leave from the project and became a full time graduate student again, for one year. Then I worked intensively. And in the space of less than a year I was able to complete the thesis, getting it done the following spring.
You mentioned you were not very well paid while at Los Alamos and while at this project.
Oh, no, well paid. It's just that by modern standards, it doesn't sound like a lot. I think I was paid almost $5,000 a year, which then was a perfectly good salary.
How was it, compared to regular spending of a grad student?
I would say, at that time, a graduate student stipend for a teaching assistantship was probably in the range of $1,500, maybe $2,000.
Per year. My first faculty job was, as I recall, around $5,000. So actually even as a graduate student prior to my Ph.D., I was making as much money as I made a couple of years later with a Ph.D.
Were you able to use any of the skills learned at the Los Alamos Project when working on your thesis? Or, were these two completely separated?
There was tremendous overlap, not so much in specific information as in technique. I think I matured so much as a researcher in the Los Alamos and Matterhorn work that it made it possible for me to work much more quickly and effectively once I really settled down to do the thesis work. The numerical techniques, as an example, I found useful in the pure physics.
In your thesis?
Yes. Just the computational skills and comparing experiment with, making graphs. There's just lots of little technical skills that contributed to the maturing of one's abilities as a theoretical physicist which certainly carried over.
Now, I would like to go back to your thesis, and the topic of it. So, it's a little bit back in time. One thing is not clear to me. Is the word "Collective Model of Nucleus" the same as "Liquid Drop?"
What's the difference?
Collective Model as I used it has the same meaning as what Aage Bohr and Ben Mottelson called "The Unified Model." It means taking into account both independent particle aspects and liquid droplet aspects. In simplified language, the interior of the nucleus is viewed as a gas of almost independent particles, but the periphery of the nucleus, or the surface, has properties that behave like a liquid droplet with a surface tension and with an energy associated with deformation, and so on.
Somewhere in the preface of your thesis, you refer to this Collective Model of the Nucleus saying that it's a model of Wheeler and Hill. Did you have any particular paper in mind for this?
Yes. That model was developed extensively in a paper by Wheeler and Hill, a paper that originally Niels Bohr was to be a co-author of. But finally Niels Bohr decided that he had not been enough of a major contributor and he asked that Wheeler and Hill go ahead and publish it under their own names without his name.
Was it during Wheeler's stay in Europe?
It was under development then. The paper was long delayed. The first draft of it was done in 1949. Wheeler took it with him to Europe and sent a copy of it to Bohr, I think, as early as the summer of 1949. There's a very amusing letter in the file from Niels Bohr to John Wheeler in which Bohr (I paraphrase), says, "Thank you so much for this draft. I shall take it with me to my summer home and study it. Please allow me a week or two." I don't remember the exact time span, but he implied a very short time. "For me to just glance over it and perhaps make a few small suggestions, and I'll send it back to you." Well, it was like three years later when it was actually published.
It not untypical of Bohr. I see you have collected papers of Wheeler here. Do you know if the word "Collective" was already used in that paper, or did it come later?
No, they introduced the word "Collective Model" in that paper.
In the draft?
As far as I know. Now that I'm not sure of.
I'm puzzled a little bit, because more or less back at that time Bohm in his work on plasmas also thinks about collective and individual models, but that referred to plasma. And that was also at Princeton. I was just wondering whether these things had anything in common or were they completely separated?
That's a very interesting question. I don't know the answer to it, whether there's any linkage between that language, that description between Bohm and Wheeler.
Do you know of any interactions between the two, as far as physics is concerned? Was it Wheeler who brought Bohm to Princeton.
Wheeler visited Bohm in Berkeley, soon after World War II. He was very impressed with Bohm, and with his promise, and very attracted to the fact that Bohm was interested in fundamental questions of quantum theory and its interpretation. So Wheeler was the principal person who recruited Bohm to come to Princeton. He convinced his department that that was a good appointment, the department endorsed it, and Bohm was invited. How much they actually worked together after Bohm got there I don't know. I think, in fact, very little. I think Wheeler got a little bit disillusioned, or at least he felt that Bohm's approach and style just didn't match his own, so they didn't make a good working team.
Was it about Bohm's work on plasma or about Bohm's work on the interpretation of quantum mechanics?
It was the latter that caused Wheeler some concern. I think he felt that Bohm's work on the interpretation of quantum mechanics was just going too far into the speculative domain outside of what we would call science, which is an interesting comment, because Wheeler himself has been very willing to do what some people would call speculate. His definition of what science encompasses is pretty broad.
All right. So your working thesis started with the pre-print of Aage Bohr?
But that pre-print, I assume, was kind of influenced by the Wheeler and Hill paper? Or, wasn't it?
One doesn't know. Historically it's an interesting question, because Wheeler was in Copenhagen in the fall of 1949 discussing some of these ideas with Bohr. They were looking over their planned joint paper. Niel Bohr's son, Aage, was back and forth between Copenhagen and Columbia University of New York, and was talking over some of these ideas with James Rainwater. So, who had what idea first, is unclear. It probably is clear that there was some influence in both directions. As it turned out, the Aage Bohr paper was published first.
When was it?
Well, I mentioned a pre-print that I saw was in the spring of 1950. When it actually was printed, I don't remember. Probably in my thesis work I was a little bit more guided by that paper than any other. That original pre-print of Aage Bohr that Wheeler gave me to look at was the most influential paper guiding my work. I took off from that and tried to apply those ideas of the combined independent particle-liquid droplet model to a whole bunch of different phenomenon. Quadrupole moments, magnetic moments, energy level structure. Out of that probably one of the most significant things I learned was to understand the pattern of regularity in the first excited states of even-even nuclei. That led to a separate paper which I published prior to completing my thesis.
Yes, that's in Physical Review of 1953. And you mention that there was some sort of a discovery in this. And this was before you heard of work by Bohr and Mottelson?
Yes, that's right.
When did their paper come out?
Soon thereafter. I'm sure that they were working on exactly the same ideas at the same time I was. It was a natural thing, based on that original Aage Bohr paper, for Bohr and Mottelson to extend the idea from a single particle to two or more particles, two or more nucleons, and consider even-even nuclei. It just happened that I had the same idea and it happened to get into print a little sooner. But, in the end, Bohr and Mottelson actually went much further than I did. I was probably the first one to take the step of understanding regularities in the rotational states of even-even nuclei. I owed a big debt there to Gertrude Scharff-Goldhaber because she had collected so much of the data, and organized it, and it became so much easier to analyze as the result of her efforts. But even though I did that one thing first, Bohr and Mottelson did that and much more later. So, very soon thereafter, they published a much more extensive and detailed wonderful treatment of all kinds of nuclear properties based on the same model.
Were you working just by yourself on this thing, or did you discuss this frequently with other students also?
I was working very much alone. I felt independent and capable at that time so I didn't really talk much to Wheeler about it. Every now and then I'd touch base with him.
Did you see any of Oppenheimer?
Very little. In the spring of 1953 or perhaps still the winter of 1952-1953, a few months before completing my doctoral thesis, Oppenheimer invited me and John Toll and John Wheeler to come over to the Institute and give kind of a joint seminar. I think he announced it to his Institute colleagues by saying, roughly, "Here are these people from Matterhorn who have been devoting themselves to developing the H-bomb over the last two years, but also they have been managing to do a little pure physics at the same time. And here today I'm bringing them to you for them to give a little talk on what their pure physics work is." So, Wheeler gave a talk, John Toll gave a talk, and I gave a talk, probably on this even-even nuclei question. And what I mostly remember is Oppenheimer's graciousness and kindness. I had seen him in seminars become cruelly mean to people like Wolfgang Pauli or other visitors. But to me, a graduate student, he was wonderfully kind and supportive.
Was it at this time that he was experiencing some political difficulties, or not yet?
Not yet. Not to my knowledge.
How much were you aware of at that time in the following years of the political troubles— as someone like you would view personally in those days?
Well, I was very much on the periphery, but I was aware of the fact that Oppenheimer was expressing opposition to the development of the H-bomb, for various reasons, from technical to moral. But I was also an accidental participant in what may have been the critical moment in changing his point of view. In June of '51 there was a meeting of the General Advisory Committee of the Atomic Energy Commission, meeting at the Institute for Advanced Study. They were meeting in a first floor room on, if I remember correctly, a Sunday morning. Maybe it was a Saturday morning. It was a weekend. Wheeler was scheduled to make a presentation on the latest results of our calculations on the CPC in New York. I was working every night, all night, that week prior to that meeting trying to get the latest and best results that we could.
The night prior to this meeting at the Institute for Advanced Study, I took a morning train down from New York with the latest results, went over to the Matterhorn building, got out a very large piece of paper, maybe about two feet by three feet in size, a large rectangle of paper, and sketched out a graph showing our latest calculation of thermonuclear burning, still very crude of course, because of those calculations, yet extremely encouraging. I then rolled up this large graph and drove over to the Institute and walked up to the first-floor window of the room where the meeting was in progress and either rapped gently on the window or signaled through the window to catch Wheeler's attention. As it happened, Wheeler had just taken the floor. It had just become his turn to speak. He interrupted his speech, walked over to the window, opened it, took from me this large graph, carried it back and pasted it on the blackboard for all to see. And then, at that moment, according to the reports of those who were there, Oppenheimer suddenly decided, "This does look encouraging. I think they've really got something. It looks like it's going to work after all."
Now, your thesis was completed in April, 1953, defended in June? Besides Wheeler, were there any other physicists involved in discussing the results?
I was invited to give a Departmental Colloquium that spring. It was sort of like a replay of the Journal Club event. Because back when I gave my little presentation about neutron scattering in the Journal Club I thought it was of no particular consequence. David Bohm and a few others realized that it was significant.
Was Bohm still there?
No. I'm referring back to earlier. Now, on this occasion, the spring of '53, I think my feeling was that I had simply done some fairly obvious calculations based on this unified model, or collective model. I didn't attach great significance to them, but several faculty members at Princeton saw that there was, in fact, something of significance, of above average interest there so they invited me to give a regular departmental colloquium talk. Not all graduate students get such an invitation because they're mostly for outside speakers to come in. So that was, in a sense, the first time I realized that perhaps what I had done was not totally trivial.
Did you give talks on this elsewhere? Like seminars or colloquiums?
Yes, I did.
Of course I had to apply for a job. I was recommended to two places. One was the University of Rochester and one was Indiana University.
By "recommended," what do you mean?
By Wheeler. You know, it was the senior networking. These were not advertised jobs. I guess Wheeler had become aware that there was a post-doctoral position available at Rochester and one at Indiana University, and somebody in nuclear physics would be appropriate for either one. So I went to Rochester and gave a talk there. I met with Marshak, the chair of the department, and his colleagues. They did not offer me a job. Then I went to Indiana University. Actually even prior to going out there for an interview, I had attended a conference at Indiana University and participated in it. I gave a talk at that. I recall the Goldhabers being there, both Maurice and Gertrude Goldhaber. That apparently caught the attention of the Chair of the Indiana Department.
Who was that?
Alan Mitchell was his name. That led to an invitation later that spring for me to come out again and interview for a job. And I was offered a job. That's where I went in the fall of '53.
And was it post-doctoral, or was it an Assistant Professorship?
It was a post-doctoral research appointment— temporary. I can't even remember now whether it was just specifically for one year or for more than one year. But I no sooner got there than I was invited to teach a course. Emil Konopinski was scheduled to give a graduate course in mathematical methods of physics. For some reason he was burdened with other duties, or other courses, and he asked me if I'd be willing to teach that course. I said I'd be glad to try. So I did, in fact, get into teaching. My title didn't change.. I was still called a research associate, but it gave me an opportunity to teach, teaching experience. Then I was offered an assistant professorship in the second year.
While working on your thesis were you in any contact with the Copenhagen group, by correspondence or any other kind of exchange?
You know, I can't remember that now. It would have been certainly extremely logical for me to have communicated with Aage Bohr, and I think I must have, but I can't remember the details now.
Didn't you keep any correspondence from him?
Okay. All right. So now, returning back to you starting your teaching career. Did you have to develop some kind of teaching philosophy at that time, or you just wanted to follow certain models of teaching that you would have regarded among your teachers?
Well, maybe the most significant thing to say is I wanted to take it seriously and do it well. It's not that I wanted to introduce any new innovative techniques. Here was a group of beginning graduate students at Indiana University, a small group, less than six or eight kids, young men. And so I used the standard mode of lecturing to them, assigning reading, assigning problems, giving tests. Nothing innovative about the general structure of my teaching. But I did work at it. I did try to make it interesting and tried to integrate the methods into larger physics issues. And it seemingly went well. In that very first course I had quite a reputation of being a pretty good teacher.
Did it take much time from you?
Yes, it took time. But a majority of my time was still spent on research.
Whom did you work with, if anybody, at Indiana? Was there any physicist particular, who was important for you? Either as a senior or of your age?
Not at the more senior level, no. Well, Emil Konopinski — eventually we did write one paper together, although it wasn't based on work from that early period at Indiana. But he was somebody I liked to consult with. Especially on mathematical methods. The person I worked with as a collaborator was Carl Levinson. He and I did some work together on nuclear structure calculations. Other than that it was work with graduate students. I think my first graduate student, my first Ph.D. student, William True, became an effective collaborator as well.
Let's see, with Levinson you had a series of publications on the so-called independent particle of a model of the nucleus?
How was that different from the collective model of nucleus?
Only in that the emphasis was on the structure of the energy levels based on the quantum orbits of nucleons within the nucleus. Not so much concerned with deformation, particle moments, or rotational states. It's not that we could have ignored those collective aspects of the nucleus, but the focus must have been more on the independent particles.
I see that very soon after, you took your leave?
Yes. I had a bad, bad record in terms of longevity in one place. I think there were only two years in full-time research and teaching, before I just felt I would greatly profit by having a year off to devote fully to research. Not just to devote to research but also to learn new things. Because I felt, "Here, I seem to be locked in this low energy nuclear structure work. If I'm going to look toward a career in physics, I need to think of doing more than just that." So part of the reason for requesting a leave so soon was to learn new things. And in particular, I wanted to learn field theory, more of the physics related to elementary particles. The second reason was just to have more time for research. Because I did take my teaching seriously. And even though I didn't have a heavy teaching load I devoted many hours to it.
What influenced your decision to go to Germany?
Was it his non-linear theory at that time?
No, just his general reputation. I'm trying to think why Germany? Well, I applied for a Fulbright Fellowship and that limited the number of countries— that implied going overseas. One couldn't use a Fulbright Fellowship for study elsewhere in the United States.
Were you recommended by a senior physicist to a Fulbright Fellowship?
Who did recommend you?
Wheeler. I'm sure I must have called Wheeler. Perhaps also Konopinski and perhaps others at Indiana. I applied for the Fulbright and then came the question of Germany versus other countries, I could have considered Copenhagen, I could have considered Great Britain. I could have considered France. I was not a linguist, but I knew more German than French. So, that was one consideration. I had studied German in school enough that I could read it fairly well, although I couldn't yet speak it. So that made me think more of Germany than France. And then it was just Heisenberg's general reputation. Indeed I'd say it was the reputation of Göttingen as a center of theoretical physics that lead me there.
So you arrived there in '55?
Yes, that's right.
What was your impression of West Germany at that time?
I had been there in 1949, so I had a very early post-war impression.
Just as a tourist, or—?
Essentially as a tourist in the summer of 1949, yes. Going there with a student group. Also Göttingen. I went to several places, but mostly Göttingen actually. Well, one's first extended stay abroad is always exciting no matter what. New culture, new people. I enjoyed Göttingen a lot.
Was the level of life very much different from the American life at that time?
Oh, yes, of course. Because well, one simple thing, refrigerators were not common. People shopped every day because they didn't have refrigerators. Little things like that, you could see the difference right away.
No hamburgers and no milkshakes.
No hamburgers in Germany? Okay.
But, we adapted. And formed some friendships. In terms of a culture, one's aware of the fact that it's a more structured society. A little less than, the easygoing flexibility that you encounter in America in various ways. One is that you addressed people, even those you know quite well, with a formal "Sie" as opposed to the informal "Du." Toward the end of that year there my wife and I became "Du und Du" with Gerhart Lüders— Gerhart Lüders and his wife Inge, being a young theoretical physicists at Heisenberg' institute. That was a big event. In America we would have been Gerhart and Ken from day one. But there we worked up to it very gradually.
Did this influence academic life or just research and physics?
Well, I think by and large the hierarchy was not good for academic life because Heisenberg enjoyed perhaps too much status. He was, at the same time, revered and ignored.
Ignored in what sense?
Well, in that the young physicists didn't lean on him, or rely on him, or consult with him. They regarded him as the big gray eminence at the top of the pyramid. He got the utmost respect. One little example: The first time I was invited to give a seminar talk at the institute, I came in and sat down, and then when everybody was gathered, everybody was ready, and it was time for me to talk, then Heisenberg walked in. And then— all the students rapped on their desks to applaud the great Heisenberg who had walked in to listen to this lecture. I met a few times with Heisenberg and enjoyed those times. He was helpful. Even though we didn't spend a lot of time together he could instantly grasp the kinds of things I was working on.
Did you talk in German with him?
No. English. But at the same time, there he was behind double doors. You had to go through a secretary, open one door, and then go through a little vestibule, open another door, and then you'd get to Heisenberg. And our talk was interrupted when we did talk. Meetings in his office were interrupted with conversations with high officials of the German government and so on and elsewhere. So there was some disconnection. It was regrettable because he was such a brilliant person. He was such a wonderful person in many ways, but he had become disconnected from the day-to-day theoretical research in his own institute. And there was some lack of respect for what he was doing.
Among his own junior people there at the institute. They didn't really have much respect for his work then which was on non-linear particle theory.
Was he more or less kind of alone there in pursuing this research?
He seemed to be lonely. Yes, he worked, I guess alone, too. But, I really got the impression he was lonely. He had to play the part of being the great Heisenberg, and that provided a barrier to his informal interaction. Heisenberg did speak rather nostalgically about his early days in Leipzig, how things were informal, more fun, how they'd play Ping Pong and they'd have picnics.
He didn't learn to play Ping Pong?
I saw only ping-pong or table tennis.
Did he give talks about his research to people at the institute?
Not while I was there. I had a sense that although I was a stranger and a newcomer, in some ways he felt it easier to talk to me than to the German researchers because being an American, and a visitor, the barriers of hierarchy of rank didn't exist so much and he felt it easier, perhaps, to be open and informal with me than he did with people like Lüders and his own group.
Were you the only American at the institute at that time?
I think I was.
The only foreigner?
No, not the only foreigner. There was a Japanese, Nishijima, who later became very well known, who went to Illinois. And there was an Indian (from India), whose name I now forget — perhaps, Bose. All I remember about him is that he solved the problem of German grammar by making every noun feminine.
Well, that's possible. Did Heisenberg talk to you about American physics, and how his non-linear theory was received in the United States?
No, he didn't. He didn't really talk to me personally about his own physics at all. When we met it was either for just an informal chit-chat conversation, or for me to report to him telling him what I was learning and getting his reactions to it.
Besides Gerhart Lüders, who else was there? Was it just theory or was it both experiment and theory?
Just theory in Heisenberg's institute. The professor of experimental nuclear physics was at another institute.
How many people, approximately, were there?
Well, I don't know. The group I worked with was no more than about five. Five or six. Including the foreigners. Including Nishijima, Bose (if that was his name), and myself. There were also Lehmann and Zimmerman. (They wrote a famous paper with Symanzik.); Lehmann, Lüders and Zimmerman. Those are the three names of young German theorists that I remember now.
Was it possible to talk with Heisenberg.
I would say not. By that, I mean I don't believe that any of the young researchers there would have openly disagreed with Heisenberg or challenged him in a seminar setting. By the way, I might mention, this young group I was with — Lüders and Lehmann, and a couple of others were active weekly in communication by letter with Wolfgang Pauli. They had much more interaction with Pauli in Zurich, (I think that's where he was), than with Heisenberg in their own institute. There were a lot of wonderful letters that went back and forth between this group and Pauli.
Were these letters circulated?
Well, I don't know. I saw them but they probably didn't circulate outside that group. Whether they were shown to Heisenberg or not, I don't know.
In topics these younger physicists worked on, were they connected to Heisenberg's research or were they somewhat distanced from that?
They were probably distinct. They were working mainly with the formal aspects of field theory.
Was there anybody with whom, I mean, topics you worked on at that time? Did you find a good person to communicate with in that institute?
Yes, these other young people. Lüders, in particular, was very, very helpful to me.
Did you work on similar topics, or was it just because you learned something new?
I was just trying to learn the theory. It was a whole new field for me. And out of that year I did write one paper called "Ghost States in Field Theory." [GERMAN LANGUAGE].
Did you publish in German?
No, I published in English. But some way or another it got into the newspapers. Maybe that was through Heisenberg dropping remarks, or a reporter he knew, I don't know. But, suddenly it was in the paper, a little report, "Geisterzustände im Atomkern".
Did Heisenberg, at that time, seem to be a politically important statesman?
Yes. He was clearly a national force. Personally, I don't know what influence he had or how important he was considered by others, but it was clear that he was involved in a lot of things outside his own institute.
And probably made many statements in newspapers.
Yes, he was a person who was consulted and responded to reporters inquiries.
What was your attitude then to his non-linear theory?
I had none. It was outside my scope of interest. And I just didn't pursue it.
Did it have any attention from American physicists? Or was it mainly ignored?
I don't know. I think it was mainly ignored. But, whether there were some Americans who pursued it and took it seriously I don't know.
But was it discussed in Germany in popular publications other than professional physics journals?
I have a vague recollection of having seen one or two newspaper articles on it just based on the idea that anything Heisenberg does, or says, or thinks is important. And thus some newspaper reporter was trying to explain the ideas for the public.
Did you feel that somehow the German theoretical physics, in a way, in terms of topics, was different from the American physics at the time?
My very limited exposure there suggested a little bit more emphasis on formalistic mathematical physics as opposed to physics directly and closely related to experiment. But, that's not a valid remark for German physics as a whole because I didn't know.
Did you feel that there was some kind of inferiority complex among Germans, among physicists at that time? That could be different, perhaps in relation to atomic weapons and these experiments. Or was it at all discussed?
I never talked about military weapons work with any of my German friends.
Not even if it was World War II time work?
Strangely enough not. And I certainly never had any sense of what you might call an inferiority complex on their part.
You don't think there was, on their part, an inferiority complex?
I don't think so. At least I was unaware of it.
Did you have any problems getting permission to go abroad because of your involvement in Los Alamos work?
But did you need any permission at all?
I don't honestly remember. It's possible that one condition of the security clearance was requesting permission to leave the country, but I don't now recall that that was the case.
But at least after 1953 you were not engaged in any classified research?
I did return to Los Alamos for subsequent summers. I also worked at Convair, a corporation in California, one summer in 1956 I believe. And at Lockheed Aircraft also on classified work. And at Ford Aeronutronics. So, my security clearance was extended and covered this additional consulting work over the following few years. I don't remember exactly when it finally stopped. I did make a personal decision later, I can't remember when, probably in the late 1960's, probably after the Vietnam War became a major issue in this country, a personal decision to do no more secret work and no more weapons work.
Was your involvement in Los Alamos known to German physicists? Did you mention it at all?
Oh, I'm sure they knew. Yes.
Were they interested at all in this?
I never had anything I would call a probing question that I recall. It didn't come up.
Did they share with you any dealings of their life during the Nazi Regime? Because those young physicists, I presume, would probably be of the same age or more or less of the similar age, like you?
Yes, a little older.
But they would have been, at least school and maybe college students, in the war years. And maybe they could have even been involved in the military.
Yes. No. It's strange now to think back on it. How could I have spent ten months in daily communication both in the laboratory and outside with Gerhart Lüders and his wife and yet never talked about their World War II experiences? Yet I don't have any recollection of it.
Did you go out with your German friends? What were outside laboratory activities?
Oh, we'd go to Ratskeller now and then. We entertained one another in our own apartments. Lüders lived in an apartment in the same block where I lived, Kantstrasse. And Lehmann, likewise, we were at his house once. But, they were not well off. I'm trying to think what my stipend was. I think it was $1,200 a year. That was a princely salary.
By German standards?
By German standards. I was making more money with my modest Fulbright Fellowship than these young physicists were making as their regular salaries. They couldn't have many luxuries. But there was the occasional party in someone's home.
Were there any kinds of activities, outings, picnics, for the entire institute with Heisenberg— doing something other than just laboratory work?
I remember only one. It was an evening social gathering. It was made particularly pleasant by the fact that Heisenberg and one or two of his children played music for us. I think it was piano, violin, and cello. Something like that.
At someone's home?
No, it was at the institute. They took over the cafeteria room, the lunch room, of the institute for this evening party.
Any foreign visitors of status that you recall coming or giving a talk or seminar— it is not likely there would be French coming to Germany at that time. But could there be any visitors from Scandinavia or Britain?
I don't remember any. No. And in retrospect that's surprising. Because nowadays, if you spent a year at any major laboratory you would certainly encounter a large number of foreign visitors coming through. But that was not yet the case at that time.
Since you mentioned the name Lüders, something in my head is saying Lüders- Pauli, but I don't know exactly what it is.
Nor do I, but it probably is the same Lüders. If he had done some joint research with Pauli, that would help to explain why this active correspondence was taking place. It amused me at the time because it was so in keeping with what I had heard about Pauli's character. The group would send some ideas to Pauli, and back a few days later would come a letter saying "entirely wrong — "Alles quatsch" you don't know what you're talking about." And then they would respond. And pretty soon after two or three exchanges, Pauli would say, "Well, you know, I think you've got some quite good ideas there— I approve of what you're doing."
Did any of the Germans consider going to the United States for Fellowships? I mean among the younger people?
I don't recall any of them speaking of that desire. Which is interesting. Of course later on in '61 when I visited Prague, I so well remember how the young physicists there were extremely eager to get out and to come to Western Europe or to America.
At that time, I think, with many Europeans, regardless West or East, at that time, West in particular, would go to the United States especially when post-graduate studies, but many French would come. I don't know how it was about Germans.
To my knowledge, Lüders never came to America. I don't recall him ever taking a leave of absence. I think his entire career was spent in Germany.
Did you have any correspondence with him after you left?
Yes, occasional. You know, the Christmas card type of correspondence. And then a couple of years ago I learned of his death and we then wrote to his wife, Inge, expressing sympathy. Because even though we hadn't been in touch for those many years, I still felt a certain bond. After all, we had drunk Brüderschaft together.
What was the main thing you learned in Germany?
Field theory. I'm not sure I'd say I learned it very well, but—
In what particular form? How was the field theory at that time, discussed? Was it a period of hope, or a period of pessimism?
Oh I think it was a hopeful theory then. There was a feeling that this approach, although it was quite formalistic and mathematical, and seemingly divorced directly from experiment, there was still a hopefulness that it would have an important bearing on understanding elementary particles and would have a bearing on experiments later.
And did you use this in your work at that time?
Well, I mentioned the theory in the paper on ghost states. So, that's based on what I learned there.
Anything after your return back to the United States?
Very little. I guess I should look at my own CV.
That's the early one.
As I look over my own list of publications, the Ghost States paper, published in 1957, based on my work in Göttingen, stands out as distinct from a whole series of other papers all of which are related to nuclear physics. But not totally distinct because there was a later paper (1962) on possible mechanisms of very high energy resonances. That was certainly an outgrowth of what I had learned earlier in field theory. And then there was one on a possible quantum of length. I don't even find that now, but I did write a paper on that subject. Oh 1968, Electro- dynamics and the Quantum of Length.
Was this Heisenberg's idea about the Quantum at Length?
I don't think so. You know I went back and looked at that paper not so long ago and I couldn't understand it at all!
Heisenberg entertained this idea as early as 1931.
And then he would recurrently return to it.
Well, I thought at the time I was making some small contribution toward the subject, but as I say even now, I go back and I have trouble understanding my own work. But those few papers indicate that the Göttingen experience did not change my direction, it just sort of broadened me a little bit, enriched my background a little bit, but most of my subsequent work remained in nuclear physics.
Did you yourself have any contacts with Pauli?
Have you contacted him personally?
No, no. Him personally?
I saw him at Princeton when he was at the same seminar I was. I've never met him.
Could Heisenberg speak English?
Heisenberg's English was excellent, yes.
And he talked English to you?
After your stay in Göttingen, did you return back to Indiana?
Besides this Fulbright Fellowship, did you apply for a research grant?
Yes, I did. I can't remember when I first applied to the National Science Foundation. Well, in fact I can't even remember to what agency I first applied. So, I only have the recollection that research funding was not a problem for me from the time that I first sought it, which would have been in the late 1950's, until the mid-60's. Actually it was a period of less than 10 years when any research proposal I submitted was basically approved. I didn't need a lot of money, just for travel and graduate students, and for summer salaries, and my own salary in the summer. The first time that I had got a proposal turned down was sometime in the 1960's after I went to Irvine. Perhaps 1965 or 1966.
Did you apply for grants from military agencies, from the Department of Defense?
I don't think so. As far as I recall, it was only the National Science Foundation.
After your year in Indiana, you took another leave and went to Los Alamos. Right? You said you had a leave in 1957, or 1958, at Los Alamos?
Was it an entire year?
What was your experience?
I went back to the Theoretical Division at Los Alamos, but I was engaged in pure unclassified nuclear research, which Los Alamos was then supporting. So even though I was inside the laboratory and I had to have security clearance to be there, I was not working on military projects or weapons, or secret work.
How about participating in discussions at Los Alamos?
Well, I sat in on seminars but I don't recall getting involved in anything of a classified nature while I was there.
Was the spirit of the place any different from the earlier time that you were there?
It had become a little bit more bureaucratized. It was larger. There were more groups. And there was a little bit more of what I would call "dead wood." Do you know that expression? "Dead wood" means a person who is sort of burned out, who is physically there, but is no longer a major contributor to the intellectual life of the place. The first time I was there in '50-'51, I felt that everybody I encountered, everybody I worked with, was very alert, intellectually stimulating, and just first rate in terms of ability. By the time I went back, not so many years later, '57-'58, I began to see that there were some people who were settling into comfortable lives but were no longer particularly productive. And it was still a period when the laboratory had pretty much all the money it needed, so it could support people who were nonproductive as well as people who were productive.
And they were not yet experiencing any difficulties at that time?
That's right. Eventually, Los Alamos had more budget crunches, more budget difficulties, and had to let go some people, which I felt was probably healthy.
I'm not saying negative things about Los Alamos in '57-'58, just contrasting a little bit. To me, it still represented a marvelous environment for work. I liked being there very much. I liked the resources: the library resources, and the people, and of course, I liked the place. The physical surroundings were wonderful.
Did you need for your own work, some intimate relationships with people doing experiments, knowing their results first hand discussing with them, and so on. And was it in this regard, Los Alamos a better place then say Indiana?
No, Los Alamos was not better in that regard. Most of my work excluding things like ghost states and quantum of length, most of my work was pretty close to experiment. At Indiana I did profit specifically from having experimental nuclear physics right there in the same building.
Who was doing that?
Larry Langer was one. Milo Sampson. Thompson. There was one kind of funny event when I was at a meeting in Washington, D.C. and I met my Indiana colleague Larry Langer there. And I said something about, "I think there should be an excited state in the Zirconium 40 nucleus at such and such an energy with zero angular momentum. Is there any chance you could figure out a way to check and measure it?" He went back and within a week or so had verified the existence of that state. So that was a very nice interaction with experimenters. But in general I would say even though most of my work was close to experimental, it didn't particularly require that those experimenters be in the same building or the same town. I could communicate with them elsewhere. I did a lot of work on Muonic atoms, for instance.
Who were these people doing measurements?
Of the transition energies of muons falling through the states were— not where I was, but—
Who were they?
I can't even remember the names now, where the work was being done.
I believe it was in California, but I don't know.
Indiana, to my knowledge, doesn't have a big experimental facility. I mean, at least, nowadays.
Well, it had a cyclotron.
Oh, did it?
And it had, through the old fashioned work in nuclear physics based on radian activity, beta decay, gamma decay. Small scale nuclear physics. But it also had a cyclotron.
Were you in any contact with experimental physicists at Los Alamos? And did you need anything from the work they were doing. Or at the time when you were at Los Alamos?
No. In the H-bomb work we were more in communication with them. Because of the important cross-sections they were measuring. But there was a time later when I was doing pure physics there, I had very little contact with the experimental people.
And in the early days when you needed cross-sections, would you have to wait until they checked the cross-sections for your calculations?
I think the experimentalists were probably ahead. I think they had measured deuterium- deuterium and deuterium-tritium cross-sections in enough accuracy that those were available data.
Was there any feedback from you to them? Like asking to do these experiments and things like that?
Yes, there was close contact. People in the theory division did, I think, request specific additional measurements.
We are soon finishing this side and we may be done for today. Just a few more questions, or otherwise I will forget them later. We talked earlier about Bohm and Wheeler— did you continue your contacts with either one of them after you moved to Indiana?
Yes, with Wheeler. I've kept in close touch with him non-stop from those days until the present. He and I actually re-converged to write some papers together in 1959. Papers on semi- classical scattering theory. A series of three papers with Wheeler.
And there was also another paper you co-authored with Les Foldy? How did you happen to know him?
That was a Los Alamos connection. Foldy's home base was in Cleveland. I believe at Case institute of Technology in Cleveland.
He is now there.
Is he still living?
As far as I know. I think he is still a Director. I think he is at Case Western now.
Oh, yes. That's become a combined University.
Wasn't he at Case during those days?
I guess he was at Los Alamos during the war, but he was not at Los Alamos on a regular basis while I was there He came as an occasional visitor. I must have met him at Los Alamos.
So, was this paper a result of your stay at Los Alamos?
In 1959. Effect of the Recoil on the Elastic Scattering of High Energy Electrons by Zero Spin Nuclei.
Oh yes. Foldy and Yennie, too. That was kind of funny, because it was a paper in which the three of us had independently ideas on the same subject. It's not that we worked together in one place. Yennie was in Minnesota. Foldy was in Ohio. I was in New Mexico. But somehow or other we got into communication and realized that we had interest in the same problem so we put our efforts together and produced a joint paper even though we never worked together in the same institution.
But, did you ever have any contacts with Bohm after he left the United States?
No, I didn't.
At one place in your earlier recollections you kind of expressed some interest about Foldy and his commitment to research.
Yes, I admired Foldy (as well as Feenberg) for a continuing commitment to research on into elder years, when so many physicists get distracted by other duties and commitments.