Edwin Salpeter

Weart:

You've given me your vita here, so I know that you were born in December 1924, in Vienna. But I don't know anything else about your family. Who were your parents? What did they do?

Salpeter:

Both my parents were physicists. At least my mother had studied with Professor Ehrenhaft in Vienna. She really didn't practice after I was born, but at least she had had a physics background. My father was essentially a practicing sort of physicist-cum-engineer. In his youth he'd been a more or less academic type. He'd even written a book on mathematical methods for scientists. It was rather rare (to do this) it was one of the earliest books. That was not very fashionable in the early twenties. He then went into industry. He managed an incandescent lamp factory in Vienna for a while, and then worked for Philips Electrical Industries, after we emigrated to Australia.

Nevertheless, it was sort of a very physics-oriented home. He'd studied together with Schroedinger, and Thirring was a great friend of his. I certainly knew the Austrian physicists, sort of as friends of the parents, when I was a little boy in Vienna.

Weart:

I see. Did they introduce you to physical concepts?

Salpeter:

Yes. I guess I even remember being taken along reasonably often to semi-popular evening lectures, which clearly were over my head. When I left Vienna I was 13. I remember back a few years before that, so clearly the lectures were often above my head, but at least not all of it, and at least I was used to an academic background. It was obvious to my parents, and therefore indirectly to me, that of course I would end up a physicist or at least a scientist. In fact, the only deviation from a pre-ordained course was when I was in college, an undergraduate in Australia— I almost became a chemist instead of a physicist. As I say, that's the very furthest deviation I ever got from the pre-ordained course.

Weart:

By the way, did you have brothers and sisters?

Salpeter:

I have a half-sister. My father had been married previously. My father was quite a lot older than my mother, about a 15-year age difference. But I really was not very close with my half-sister.

Weart:

Did she live with you?

Salpeter:

No. So really I would see her maybe once a year, or once every two years, so there really was not too much contact.

Weart:

So you were largely brought up as a —

Salpeter:

— as an only child, yes.

Weart:

I see. Did you read a lot in your childhood? Any particular science books that may have influenced you?

Salpeter:

To tell you the truth, what I mainly read as a little boy was Karl May, which is not something well known to Americans, but is in Germany. He's a Wild West story writer for boys. In fact, I even flunked my entrance exam into high school. And there is a dispute — my mother says it was because of anti-Semitism in the schools, that I really should not have been flunked, and my own feeling is that it probably was that I read too much Karl May and did not do enough work. I guess this was at about age 10, from elementary school into the gymnasium, which happens at roughly age 10. So I would say, up to this stage, I certainly didn't do too much academic work.

I guess that shook me up a little, so for a year I had to just essentially study on my own. The system in Vienna is such that it's two-track, somewhat like in England. There's gymnasium and then the realschule. For a year I had to go to realschule and learn Latin and Greek and all that jazz on my own, and then I could go by exam into the second year.

I guess that was a bit of a traumatic experience, and after that I at least started working rather hard. It was fairly clear from my 11th year on that, as I said earlier, I probably would do science, and that I was probably pretty good at it.

Weart:

Did you have any feeling whether it was academic science or industrial, applied science?

Salpeter:

No, not at all, because really that was not a strong distinction. That was not a dichotomy. As I said, my dad had gone absolutely into industry. He was almost a businessman; he was the director of a factory. And yet much of what he did was really rather academic. The firm he ran belonged to one of the outsiders, not the cartel, so they kept on having patent suits between the cartel and his outfit.

Weart:

The cartel was Phillips?

Salpeter:

No, he later went to Phillips which was part of the cartel, but this was a purely Austrian outfit. ELIN, it was called. We were outside the cartel. So much of his life had to do with fighting these patent suits, which in the end were really a matter of having to make technical, almost scientific, inventions to circumvent the patents which the cartel had. So in fact, the background I got there was that there is not much of a dichotomy — that the academic world and industrial science are really quite closely related. And also, as I said, his friends were still active academic scientists. So that, interestingly enough, was not something that I felt one had to make a choice between; it seemed very easy to go back.

Weart:

I see. You mentioned your father wrote a book on mathematical methods, but now it sounds as if he was also involved on a practical side. I'm wondering, was he more theoretically or experimentally oriented?

Salpeter:

Again, it's interesting that in a way it was a bit of both. In his youth, as I say he wrote this mathematical methods book, so at that stage at least he was clearly theoretically inclined. But then once he went into industry, really he became a practical engineer. It was interesting that he still felt that basic science was an important input into that. Then, when Hitler came, we fled to Australia. My dad then started working for Philips. So of course his whole life changed. Then he mainly just wrote articles for them and went back almost to being a theorist. Philips doesn't completely trust outsiders, and I think they were not completely sure that he would not leave the cartel again, so I think they never really let him into their practical side too much.

Weart:

I see. Where did your mother stand in all this, and on science? You mentioned that she had scientific training. Would she have gone on, do you suppose, to become a scientist if she hadn't married? It was difficult for women at that time.

Salpeter:

It was quite difficult. My mother actually had wanted to become an engineer, not a physicist, and the Vienna University pointblank would not take women into engineering. So she did the next best thing, you know, which was physics. I presume she would have kept on with science had she not married and had a child. I had the feeling she was not that unhappy to give up the science. But at least it was something she could fall back on. When we went to Australia, she would coach people for physics exams. She would do a little bit.

Weart:

She maintained her interest in it.

Salpeter:

Somewhat, yes, not greatly. It's not quite like a modern female liberation type. But at least something.

Weart:

Of course, you were quite young, but were these things discussed around your house, the latest things in physics, nuclear and quantum and so on? Did you overhear these conversations between your father and other physicists?

Salpeter:

Yes. I think my father and mother really did not discuss modern advances very much. But as I mentioned, my dad did have friends amongst the academic physicists, and they would fairly often come to the house and yes, I would certainly listen. I can't now reconstruct whether it was science or whether it was science gossip. I don't know quite on which of those two levels the conversations were. But there's no doubt that there were conversations which centered around the academic world. That is a strong memory.

Weart:

Both your parents were Jewish?

Salpeter:

Yes.

Weart:

Did you have any formal religious training as a child?

Salpeter:

Well, you know, I had to go through my bar mitzvah at my 13th birthday, so I guess I had to learn the minimum of what's required to go through that ceremony. We did just a little, rather little. One could describe my parents as what my wife calls "a Yom Kippur Jew". That's a Jew who will go to synagogue twice a year but not really practice it strongly.

Weart:

So your home had religious feelings but not strong ones, you would say.

Salpeter:

I would really rather say that the home had sort of Jewish heritage feelings, and that the easiest way to make that explicit to a child is with the religious symbolism. I would say neither of my parents were really deeply religious themselves. I guess in some ways we did the same to our children later on. Neither my wife nor I could be called religious but we would light candles at Chanukka for our children and play with the dredl — we would do all the social things that go with Jewish holidays, and stress the historic heritage rather than the religious one. And I guess my parents were somewhat similar, but not quite as explicit.

Weart:

I see. It was a matter of tradition. Then you left Austria. Was it after the Anschluss?

Salpeter:

We left quite a bit after the Anschluss, yes. (About January 1939). If you're interested in at what stage a child becomes aware of what abilities one had, etc., I guess there's one memory I have about various stages in childhood. As I mentioned, till I was 10 years old I would really mainly read Wild West stories rather than anything else. When I then had to make this exam into high school, I had to work fairly hard for a while. Then once I was in the gymnasium, since I'd gotten into the habit or working reasonably hard, everything was suddenly quite simple. Also, there was no tracking system in the gymnasium, lots of different classes in parallel. And I really had a pretty easy time. Therefore it wasn't at all clear whether I was better at science or languages, because life was fairly easy. But then when the Anschluss came, when Hitler came, all Jewish children were kicked out of the regular schools, and there was just one Jewish school which was allowed to be open. And essentially, there just weren't enough spaces for all the Jewish children. So the Jewish authorities, in some way or another, selected some fairly small percentage of the Jewish children, by performance in the regular schools, to come to that Jewish school.

So all of a sudden I was in a highly selected school, as if you went from a non-tracking system to a system with very severe tracking. It was a very interesting experience, for suddenly I found that in history and languages I was by no means the best in the class, not even near the top of the class. And yet in physics and mathematics, I probably still was. So that was the first time when I could really differentiate abilities in different subjects.

Weart:

I see, and found that in fact, you were ahead in mathematics particularly or physics?

Salpeter:

I would say mathematics and science. It wasn't even clear; the distinction between physics and chemistry was not that clear-cut, so I would just say, mathematics and sciences put together as contrasted with languages and history and art kinds of things.

Weart:

I see. And then you went to Sydney. I suppose it was simply where your father could find employment?

Salpeter:

That's right, yes. Well, both that it's the furthest away from Hitler that one could go, and also my father had a job lined up in Sydney.

Weart:

This must have been kind of a shock to you, especially anti-Semitism, you must have encountered some. And then being transferred to a different environment.

Salpeter:

Yes. There must have been about a nine months gap between the Anschluss and when we arrived in Sydney, slightly more than that, almost a year. We'd spent 2 or 3 months in London on the way to Sydney. I would say, at least as far as one's academic development is concerned, being away from formal schooling for a year was probably a more important effect on one's academic development than the traumatic shock of Hitler's Germany. Clearly it was traumatic; we were kicked out of the apartment; my dad was arrested; I was rather big for 13 and they almost arrested me, etc. So sure, they were traumatic things. But as I say, most likely having been away from school for a year had a more lasting effect on me.

Weart:

OK. Let's jump through your schooling — you went to Sydney Boys High School, finished in 1940, and then you went to the University of Sydney and got your Bachelor of Science in 1944. Were these choices as to which schools you would go to?

Salpeter:

At that time (they no longer have it) Sydney did have a tracking system and Sydney Boys High School was sort of like the Bronx School of Science type of thing. There was no dilemma in my parents' minds, that they wanted to put me into a school for children who want to go on to the university, and there was certainly no doubt in my mind either. There was considerable doubt as to which class I belonged, because the whole setup, the number of high school years, is very different. And the long and the short of it was that I had to jump: I was really put ahead of where I had been in Austria by a fair bit So again, that was a bit of shock, like the shock I had between 10 and 11. I suddenly again had to work really hard, both to learn English and to make up lost time simultaneously. So that was hard. But as I say, there really was rather little dilemma. There were 8 years of Gymnasium in Austria, only 5 years of High School in Australia. I graduated High School at 16.

Weart:

Then to go to Sydney University?

Salpeter:

No, there was no dilemma at all. At that time there was only one university in the state of N.S.W. you just go to the nearest university and you live at home, because it's cheaper and so on. So there was absolutely no choice whatever. The next choice I had was in about my second year in the university, as to whether it's chemistry or physics that I should really do.

Weart:

Tell me about that.

Salpeter:

Well, I don't know quite why, but socially my friends in college were more chemists than physicists. They were just a more lively bunch, and they played tennis and went bush walking, hiking, things I liked. So as I say, most of my pals were chemists. In fact it's still true that the Australian friends I have from my childhood and from university days are all chemists rather than physicists.

Weart:

Can you reconstruct why it was you chose physics, then?

Salpeter:

It's rather hard to say. Partly that it was pre-ordained, in the sense that my dad had been a physicist, and that it was Nobel Prize winners in chemistry, and I'm sure some of that remained. I guess the other thing that I was fairly clearly more gifted as a theorist than as an experimentalist, and in physics there is a clear-cut tradition of theoretical physics, whereas theoretical chemistry, at least at that time, was not really well developed.

Weart:

Did you have this feeling on the basis of how you were doing in courses, lab courses and so forth?

Salpeter:

Yes. I guess I was rather clumsy. It was partly that my parents felt I was more gifted in theory, and partly that I think I was and am rather clumsy, and at least in those days, you still did things with your hands. Nowadays in experimental science all you do is talk to a computer anyway, so if now a young man starts like I did then, maybe life would be different. But in that time to do experimental physics, you had to do things with your own hands, and I was rather clumsy. That's probably why both my parents and I thought that if I'm in physics, it would be theoretical physics. In fact, I think the reason why I almost became a chemist is that, to my great surprise, I won a prize for experimental chemistry; I think in the second year in university they gave prizes for the various lab courses, and to my surprise as I say, I won one in chemistry. I guess I was slightly shook up that maybe, you know, I'm not that clumsy after all, or maybe you don't need good hands in chemistry, or what-not. So that almost brought me into it.

Also, it was easier to get summer jobs in chemistry. I worked for Imperial Chemical Industries, Ltd., which is the Australian-British equivalent of Dupont. I could have stayed. I mean, I almost had a job for life at the age of 18. It was probably even just that that it's too easy a life that scared me out of it again. There wasn't enough intellectual excitement at ICI. It maybe was unfair, but I was comparing academic physics with industrial chemistry, because that was the chemistry contact I had.

Weart:

That's a reasonable thing. I'm sure most chemists did go on in industry.

Salpeter:

At that time, that's quite true. So I never changed my major. I started and continued purely with a physics major, so it's only in my own mind that I almost switched. And as I say, as far as summer jobs go, I did work as a chemist.

Weart:

What about the other physics students there? Do you recall what were their origins, where were they bound?

Salpeter:

Rather few of the physics students really went on to a real graduate career later on. What few did, mainly went into what is now called plasma physics, which was then electricity in gases, or in particular, radio physics. There are a few of my roughly compatriots whom I still keep up with, who went to Sydney University. One of them is a guy called Ken Champion who works for Air Force Cambridge Research Lab. Another one is Frank Gardner, who is now a radio astronomer, still in Australia. A third man was Peter Thoneman, who went to Harwell, I think, in England (I've lost contact with him; I don't know whether he still is in Harwell or back in Australia). A fourth is W.I.B. Smith, who is now a Plasma experimentalist at Sydney University.

Weart:

Why did they tend to go into these things? Were there some particular professors or courses?

Salpeter:

Two different things. The only man at Sydney University physics department who had a sort of a world wide reputation was Victor Bailey, an Englishman, who was a plasma physicist. So that was the reason for plasma physics — I think Thoneman probably was influenced by him. The radio physics part was essentially that Australian science was not invited in by the British into the atom bomb development at all, but they were into the radar business. So many of my elders, my teachers, were involved with radio physics. We were even exempt from the draft because radar work was considered important, so we would have extra courses which really were radio engineering. There's no doubt that had the war lasted another year or two, I as well as my other pals would have worked on radar, in the radio physics lab of CSIRO.

Weart:

You were still too young to be involved with the draft or the war.

Salpeter:

By my third year at the University. I was over 18, but we were exempt from the draft because of the radio-physics training.

Weart:

Did you have much contact with Bailey or people like that? Do any of your interests go back to that point? Commonwealth Scientific and Industrial Research Organization.

Salpeter:

Yes, they certainly do. In fact, the very first paper I wrote was with another man there who actually in a way I was more influenced by. Because he was also a nice and patient guy, not as well-known, but at least had an idea of what science is really all about, R.E. Makinson; the very first paper I wrote was with him on something related to electricity in gases.* But the big boss of it all was Victor Bailey.** There's no doubt that certainly plasma physics was something I got involved with, at least indirectly through Bailey. The radio physics I had no choice in. As I say, we had to learn it. It was clear that that would be our profession if the war lasted a bit longer. (*With R.E.B. Makinson. "On the Dielectric Properties of a Gas Discharge", Proceedings of the Royal Society B 62 (19)49): 180. The second paper listed on Salpeter's Bibliography - SW)

(** Bailey had discovered the "Luxembourg effect" - how one radio station with powerful transmission of a weaker transmitter at a different frequency. This was a very early insight into non-linear plasma effects. Bailey was a difficult man to get on with, but an impressive one.)

Weart:

So you did some experimental work, a senior thesis kind of a thing?

Salpeter:

Yes, that's right. It was essentially a senior thesis. Some of it was experimental, yes, and- it was fairly clear that on the purely experimental part I really was not good. As I say, that really involved glassblowing your own tubes, it wasn't just putting things together. Especially in Australia at that time, things were fairly primitive, so clearly having to do things with your own hands was a more important aspect of everything, there, than elsewhere and at later times. It was clear, for instance, that Peter Thoneman was very much better at this kind of experimental work than I was.

Weart:

How do you feel now, thinking back about the sort of physics that was covered? Was it up to date? Did you learn modern theory and so on?

Salpeter:

Well, as far as learning really modern things is concerned, except for electricity and gases, on which as I say Bailey was good, and radio physics where the Australians really were excellent, — except for those things, as far as modern theory is concerned, in particular say quantum field theory — I should have mentioned maybe that I did a master's thesis while still in Sydney —

Weart:

— yes, I wanted to get to that. But in your undergraduate —

Salpeter:

Okay. Before that, as an undergraduate, except for those two topics, on anything really theoretical. I must say I was essentially on my own. Sydney was not a particularly good place. The other Australians who later on became active in say, quantum field theory, did not come from Sydney. Dick Dalitz, for instance, came from Melbourne, and Melbourne really was a better place. There was in particular a genuine practicing modern theorist in Melbourne at the time, Bert Corben, the one of Corben and Stehle. Corben had been an associate of Julian Schwinger. He was the one really practicing theoretical physicist in Australia at the time. It was clear that that was so when I was making plans to apply to graduate schools. I made a pilgrimage especially to Melbourne to really ask his advice as to what to do.

Weart:

I see. Tell me about this master's thesis, "Principles of Quantum Field Theory". What was that, or why that?

Salpeter:

Why that? I must say it's not completely clear, why that. I guess I must have sort of had a feeling, as I mentioned, that theory is probably more in line, and so I thought ahead already: I'll have to go to graduate school. Sooner or later presumably it will be theory. Although Australia was far removed, it seemed that quantum field theory was an up and coming thing. A few of us had rather informal weekly seminars, where we would try to teach each other, teach ourselves. This was maybe in my fourth year as an undergraduate, but most of the other people would have been already young postdocs in radio physics — say, people two years older than me who were already doing radar work and radio physics.

Weart:

So there wasn't any professor there really who could guide this master's?

Salpeter:

No, there was certainly no professor there interested in that, but a number of the young people in radio physics — as I say, typically they would be two or three years older than me — just wanted to keep abreast with what's going on in modern theory. They were not intending to become theorists themselves any more, they were already radio physicists, but at least they were interested in it. And there were a few of us younger students in it too. So we had these weekly meeting. Then, I guess it was not easy yet to go abroad. This was —

Weart:

Yes, this was 1945. Actually, the weekly meetings must have started in 1944.

Salpeter:

Yes, so I knew (in 19)44) I couldn't get abroad to graduate school for a while yet, anyway, I had to stay in Australia for a year. So I thought I might as well do a Master's thesis. I thought I would do something which was essentially training for graduate school, and what I did was almost like trying to write a somewhat more readable review article. At that time Dirac's quantum mechanics book was sort of the nearest thing to a text book in field theory.

Weart:

Right. By the way, you have philosophical interests? During your period in Sydney did you learn any philosophy, or any other subjects?

Salpeter:

Not really, no. I went to a few philosophy courses, but no more than Renaissance art. I did not consider philosophy at all an academic pursuit which was going to be related to my scientific work.

Weart:

Your interest in quantum field theory was from the physical side.

Salpeter:

Purely from the physical side. I wanted to become, you know, reasonably cultured or educated, but as I say, I would have put philosophy on exactly the same level as Renaissance art.

Weart:

I see. Were there any other things you had particular interest in? Biology politics, and what not?

Salpeter:

Student politics, I suppose. The Association for Scientific Workers was a slightly left-wing but not very left-wing organization of young scientists, and I was somewhat active in that. But nothing extremely radical. Maybe slightly left-wing enough that when I was making plans to come to America, there was some slight feeling that I might have trouble getting a visa, but in fact I did not have any trouble getting a visa. So in fact, at least in retrospect, it was not really anything very radical.

Weart:

By the way, one question that I ask everybody — when did you first learn about the atomic bomb, that atomic bombs could be built?

Salpeter:

I guess from the newspaper or the radio in Australia just when it was officially announced. I even had the feeling that none of my elders knew either, even though as I say many of them were quite involved in radar work. They had British, Australian security clearance, but I had the feeling that all my elders were equally surprised.

Weart:

Very likely, yes. What was your reaction when you heard about Hiroshima and Nagasaki?

Salpeter:

In retrospect, it's sort of surprising to me that I had as little interest in it as I did. Not to say that I didn't have any interest in it, it's just that in retrospect I'm surprised that the whole thing did not shake one up even more.

Weart:

It was more event in the war, so to speak?

Salpeter:

It was essentially one more event in the war. It was not all that immediately clear to me, even, how strongly science was involved in it. I didn't have strongly the feeling either that science had a hand in the moral guilt of having made it nor that all these events would have an interaction back on making jobs more available in science — which after all are two sociological things that clearly were very important, and that should have been quite obvious to anybody. But neither of those was particularly something I or most of my colleagues thought of.* *(Also, the Australian's hatred of the Japanese at the time was so intense, that there was little feeling of moral guilt even about the dropping of the second bomb. ES)

Weart:

I see. At this time you mentioned that you were thinking about where to go to study. You went and talked to Corben. Did you clearly see yourself as going towards an academic career? That decision had been made for some time already?

Salpeter:

Well, at least there was no doubt that you would have to start in the academic world. Even my father, for instance, who was about as industrial a scientist as I knew, had spent quite a few years after his PhD in the academic world anyway. So it certainly never occurred to me not to be a post-doc at a university for a while even after the PhD. There is no doubt that I knew that I wouldn't have to make any such choices until much later. But also, you know, being a theorist, there wasn't that much thought of industrial jobs, etc. No, I would say, the main question young people like me had was more, how difficult will it be to get jobs altogether? That was more important than the question of would be at a university or would it be industrial.

Weart:

I see. And what sort of job prospects did you expect?

Salpeter:

I expected it to be difficult. I suppose in a way what it really means is that before the bomb era (or the Sputnik era afterwards) the prospects probably in physics were that you probably wouldn't get a job anyway.

Weart:

—possibly not an academic job either.

Salpeter:

But at any rate, there wasn't the fallback position of many jobs in industry. Therefore the prospect was whether you got a good job at a university, or you would be a shoeshine boy. It was more a matter of all or nothing, rather than of what kind of a choice you would make. But somehow I was prepared to take the risk, and if I had to retrain and do something else later on, that was fine too. I didn't have any of the agonizing reappraisals youngsters have nowadays, whether they should go into graduate school, even though, before the A bomb, I think my prospects were equally dim to those of all sorts of prospective graduate students today. Somehow, one didn't mind taking risks. Worse things had happened. You know, we left Vienna with S2 in our pockets, etc. Somehow the slight risk of the job situation being a little bit scary did not seem anything really severe. So that was not at all a dilemma.

Weart:

By the way, how were you supported in university? Was it any financial burden on your family?

Salpeter:

Yes. Not enormously. As I say, I lived at home, I had at least tuition scholarships. So it was not a great financial burden, but certainly it was bit of a burden. I mentioned I did have summer jobs, etc. It was a slight burden.

Weart:

Now, tell me about going to Birmingham. You got an 1851 Exhibition (Scholarship).

Salpeter:

Yes.

Weart:

How did that come about?

Salpeter:

First of all I should say that at that time, at least, there was also no dilemma as to where to go to graduate school. The Australian universities just weren't good enough for doing a PhD, and there just was not enough direct contact with America, and also the system there was so very different. There really was no choice: it was to England, or England and Ireland, that one would go for graduate school. There was just no dilemma on that score at all. There was a dilemma of how to be financially supported; that would have been quite expensive, so for that you did need to have some kind of scholarship. And there just weren't that many available in Australia. There were a few others that weren't quite as prestigious or didn't pay quite as much. I can't even remember whether I had applied for some of these others too, or whether I would have applied later. But at any rate, this 1851 scholarship was one of the better ones to get, and I applied for it and got it. There was again little dilemma. Once I got that, clearly that's what I would do.

Once I got that, I had the choice of wherever I wanted to take it as long as the people took me, but since they didn't have to spend the money most likely they would take me. I then more or less had a choice. So that was a dilemma. That is partly why I went to Corben, to ask for his advice, especially because the people at the university in Sydney were really not up to date with research, of course advised me to go to Oxford or Cambridge. They had been there 600 years, where else would you go? But I already had a sort of a suspicion from the reading I had done towards my Master's thesis that that was not necessarily the best place to go to; in fact, the two places I got interested in were Birmingham and Dublin.

Weart:

How did you get interested in those places?

Salpeter:

I'd already read enough to know that Peierls on the one hand and Heitler on the other were good and active people, and that it looked as though they had young people around them.

Weart:

You had read their papers?

Salpeter:

I'd read their papers and seen that there were other, younger names associated with it. Then I went to consult with Bert Corben. He had been in America but also knew the English scene, so I got details about the various people especially from him, and there was just no doubt in my mind that neither Cambridge nor Oxford was for me. Not that there were not good people; Dirac was still quite active and a good man, but just was not good for students. Heitler was a good man too, but Dublin was just not as good as Peierls. So there was no doubt in my mind, once I had talked to Corben, that Peierls was the man for me. In retrospect, there's no doubt in my mind now either, that at that time Peierls's group was the only sensible group for a theoretical graduate student.

Weart:

At least in quantum —

Salpeter:

In quantum field theory.

Weart:

I suppose you wrote to Peierls?

Salpeter:

Yes. I had written to both Peierls and to Heitler. I've forgotten whether I'd also written, because of the pressure, to Cambridge or Oxford. I really had little dilemma even before I talked to Corben, and after I talked to him, I had absolutely none.

Weart:

What was Peierls' group like? Who were they and how did they interact?

Salpeter:

I even happen to have all sorts of pictures from that year on my desk, because Jenya (Eugenia) Peierls is having a 70th birthday, and I found my old negatives and made prints to send to her 70th birthday celebration. I'll show you the pictures.

Weart:

It never fails...sometimes I carry around a camera so I can make copies on the spot. It seemed too much trouble this time, and that was my mistake. I could have made a copy right now.* Are you in here? (*Copies were made subsequently.)

Salpeter:

Yes.

Weart:

There you are with a mustache. There's Peierls in the middle.

Salpeter:

That's Kynch, Preston (who wrote the book on nuclear physics), Jeffrey Ravenhall (who is now at the University of Illinois), Max Krook (who is now jointly in Applied mathematics and astrophysicist at Harvard), Fred Barker (who is a theoretical physicist back in Australia) George Horton (who is now a solid state theorist in Canada), McManus (I've forgotten whether he's at Argonne or just where) Tony Skyrme (who took Peierls's place back in Birmingham; more recently he went to Kuala Lumper for quite a while), Conrad Bleuler (a Swiss who went back and is now professor in Basle, I think, who remained a field theorist), Jerry Gardner (who went into industry), myself, and then Bruno Feretti.

Weart:

You have a good memory for these people.

Salpeter:

Well, I may have gotten some of them slightly mixed up. As you can see, they're all active.

Weart:

They're all theorists?

Salpeter:

This was the department of theoretical physics and applied mathematics. There was a separate experimental physics group, a department even, and there was reasonably close contact between them, but nevertheless they were quite distinct.

Weart:

How did this group function? Were there particular meetings, seminars, journal clubs?

Salpeter:

Yes, we would have at least one colloquium a week.

Weart:

Just for the theoretical group.

Salpeter:

The theoretical group, yes. There would be also a general physics colloquium, run by the physics department, which was bigger. That would occasionally also have a theorist, but more often than not would be experimental. But this group itself had its own weekly seminar, and occasionally also there would be a genuine outside speaker. Sometimes it would be a journal club, or sometimes we would have an internal journal club in addition. Roughly speaking, there were one and a half theoretical kinds of meetings a week.

Weart:

I see. Were there important informal places that you got together? Did you live together with these people or eat together?

Salpeter:

The whole place was fairly informal. There was quite a bit of social contact, you know, even apart from the departments. There would often be department parties. And also, a few of us even lived with the Peierlses. For instance, in that year the Peierlses had a big house, and they just rented out rooms to their own students or post-docs. Max Krook was already a post-doc, he must be about six or seven years older than me. At that time Max Krook and I stayed with the Peierlses and at a later stage Freeman Dyson stayed.

Weart:

Did you see them for breakfast and so forth?

Salpeter:

Oh yes. Really, it's not just that I rented a room there; we would eat with them. It was more in the style of a British boarding house than just the American style of renting rooms. We essentially lived completely with the family.

Weart:

And talked a lot of physics, I suppose.

Salpeter:

We talked a lot of almost everything, both physics and everything else. Jenya Peierls was more or less a surrogate mother for the whole department. So it was a very closely knit group.

Weart:

How did Peierls function as head of this group?

Salpeter:

It was almost a one-man department. There were people who here would have been called associate professors, I guess — Kynch and Jahn, who had reasonable reputations in their own right. But Peierls' both scientific ability and temperament in guiding young people were so far above them, that essentially I and most of us considered it a one-man department. We all worked for and with Peierls.

Weart:

What did the students think of Peierls? How did they regard him?

Salpeter:

Well, as I think you've gathered already, he was a most remarkable man as far as this group was concerned. He was sort of a father-figure.

Weart:

I gathered he was remarkable and a real leader, but how did he exercise this — ?

Salpeter:

Partly by being involved on all levels. As I say, it was a socially closely-knit group. The Peierlses would look after the social needs of the students. And he had a very similar temperament when it came to the science. There are different levels — one question is, how good is the guy himself? And clearly he was one of the best theorists in the country; but on that level alone I could not argue that he was better than or even as good as Dirac; or one or two other people in England at the time. Nevertheless he was on the same level as the very best. But the important thing is his approach to students. He would give students a problem, give them the freedom to flounder for a while, but then be prepared to step in at just the right time. And that's really a very delicate and difficult thing. I mean, even most people who are very good are not very good at doing that. It is so easy to overbalance one way or the other, either to let the student flounder for too long, or to step in too early, or the third thing of not taking enough of an interest — or not really checking up, even in the end, whether the guy's done it right or not. It's in particular that third thing which I remember rather strongly, where Peierls was different from others — let me put it this way: which he had differently from the bosses I knew in Australia. It may be true of most really good physicists. When some difficulty or question crops up, he wouldn't just make general pronouncements, but he would say, "OK, let's do it right now. Let's see if we can't solve that problem". And do the whole thing at the blackboard.

Weart:

Sit down with you.

Salpeter:

Sit down with you on the spot and really work it all out.

Weart:

I see. He must have had a lot of energy.

Salpeter:

Yes. So clearly there were at least three different levels, on each of which Peierls was excellent. There was just no comparison between him and anybody else I knew on the English scene at the time.

Weart:

Aside from your thesis work, what sort of studying did you do while you were there? Were there courses that you took?

Salpeter:

There were courses, but in retrospect there's no doubt that there was too little emphasis on that. The British system at the time did not emphasize the importance of courses for graduate students. You were able to take them, you were free to take them. I could have taken three years over my PhD rather than two. But you weren't forced to. And as a consequence, I did not learn much mathematics. In retrospect, I clearly would have been a different theorist, had there been more of an American-style system, had I been forced to take more graduate courses. Now, I don't know whether in the end that would have made you a better or worse theorist; you would have been a different one. At any rate, I've always shied away from mathematics in my later life, and I'm sure not having gotten a decent mathematics training in Birmingham had something to do with it. Maybe it would have been worse. Maybe I don't have much mathematical ability anyway, and I would have just gone in wrong directions. I can't say which is good or which is bad, but at least there is no doubt that I didn't do as much formal studying as I would have, had it been in the American system.

Weart:

By the way, had you learned any general relativity theory up to this time?

Salpeter:

A little, but very little. It was not something that really interested me.

Weart:

You didn't read up on it?

Salpeter:

No. As I say, it's only in part the system which was to blame that I didn't learn much mathematics. In part I think I really didn't have much interest in it.

Weart:

Had you had any contact with or interest in astronomy, up to this point?

Salpeter:

Fairly little. In further years I've been trying to reconstruct when my interest in astronomy developed. I'm not aware of very strong interests. I am aware however, as I told you, when I was in Vienna as a little boy, of being taken to evening lectures; I do remember some of them were astronomy ones. And my Dad had German translations of Eddington 's and Jeans' popular books and so on, and I do remember having read them. So in fact I probably had more of an exposure to and interest in astronomy than I was fully aware of. But there was no thought in my mind of ever going into astronomy professionally.

Weart:

I see. At Birmingham did you yourself have much contact with the experimental people?

Salpeter:

Yes, I had a fair bit of contact. I should have mentioned that the boss of the experimental physics department was Oliphant, who was an Australian. He was later on going back to Australia, but he was at the moment in charge of the synchrotron in Birmingham, and was going to go back. He had lots of young Australians with him. In fact some of the young people, people a few years older than me, who were in Sydney or were in the study group when I was in my last year of undergraduate work, were with Oliphant. (Both John Gooden and W.I.B. Smith.)

Weart:

Did that have any role to play in your going to Birmingham, by the way?

Salpeter:

That was just an additional bonus. I mean, as far as resisting the pressure from my elders in Australia as to why I was going to Birmingham, it was very useful be be able to say, "Look, Mark Oliphant, the Big White Father of Australian physics, is there, and all sorts of other Australians have gone there".

Weart:

I see. So he was already very highly regarded in Australia?

Salpeter:

Certainly, yes. So it was very useful in that sense. And of course it was fun having lots of my Australian pals right in Birmingham. So that certainly helped some.

Weart:

Does this mean you knew a lot about what was going on in nuclear physics?

Salpeter:

Yes, certainly. I even wrote a couple of papers which really had to do with experimental work, while still at Birmingham.

Weart:

Written while you were still there.

Salpeter:

Yes, or at least they were started at Birmingham. I probably finished them off later.

Weart:

They were published later on.

Salpeter:

Published later on, but I did them while I was there. I told you that I was sort of annoyed at being clumsy and partly had gone into theory because I was too clumsy to be an experimentalist. I guess I must always have had a bit of a hankering after experimental things, and so I was quite anxious to prove that I wasn't just an ivory tower theorist.

Weart:

I see. I was struck by those papers, by the fact that this was theory which was in close proximity with experiment.

Salpeter:

Yes.

Weart:

I won't say, theory in service of experiment, but —

Salpeter:

Well, almost, yes. I would say one of those two was — I've forgotten what — something about just how you dissociate an H2+ ion which is at almost relativistic speeds,* and that was just something practical the people at the synchrotron were interested in. There's no doubt, that was a purely practical application. (*PROC. PHYS. SOC. A 63 1950: 1295.)

Peierls himself was interested in many things, and he quite encouraged practical things. I don't think he would have pushed me into it, but as I say, I was partly trying to prove to myself that I wasn't just an ivory tower theorist. I was quite interested in the experimental side. And another one was just what I call "house theory" having to do with a nuclear magnetic resonance, just simple theory development.

Weart:

Also, while you spend any time elsewhere, at conferences or travel to other places?

Salpeter:

Yes, I did quite a lot, and also we had a couple of international conferences, some of the earliest postwar international conferences, in Birmingham. I think the first time Heisenberg and Peierls shook hands again— rather hesitatingly, I must say — after the war, was at a conference Peierls arranged in Birmingham.

Weart:

Did any of these conferences have an important influence on you, or did they seem important to you?

Salpeter:

Yes. They certainly were important for finding out fairly quickly who was who everywhere. These two conferences in Birmingham certainly were of considerable importance. And yes, I did travel a lot. I was quite a brash young man, so I would go to places and introduce myself and ask the big shots what they were doing, and so on. I went through England, I went to the ETH*— Pauli was still there at that time. I traveled reasonably far afield, but I guess the ETH was really the main place outside of England that was important. I certainly went to London quite often, partly or mainly for social reasons, but also in part scientifically.** Bristol was another place, and maybe Liverpool, and of course Oxford and Cambridge. (*Massey and Burhop were at University College (in physics) and I also had many Australian friends there in chemistry (e.g. Ron Nyholm, Dave Craig and Allen Maccoll). -ES)

(**Eidgenossische Technische Hochschul, Zurich.)

Weart:

Well, how did all these places impress you? Did Birmingham still seem to be the place?

Salpeter:

Oh yes. Both at that time and now, everything was just like I'd expected it. I must say there were few surprises. There was no doubt then and no doubt now that Birmingham then was, at least for my temperament, by far the best place. There were very few surprises.

Weart:

Now, your main interest in these years, I gather, was still in quantum field theory.

Salpeter:

That's certainly quite true. Even at the time, already, I guess I had the feeling that maybe I was slightly miscast. I had more of an interest in less esoteric things, and somehow I'd gotten pushed into esoteric things, you know, just accidentally, by momentum and so on. And in fact I think it is probably true that I am not really all that gifted in these really esoteric things. My thesis was on the self-energy of the electron, so essentially I could have been in on the early days of quantum electrodynamics and the Lamb shift, and essentially I muffed it.

Weart:

Well, you were around it, in a way.

Salpeter:

But let's say, we didn't stumble on re-normalization theory. Now you can always say, of course, we didn't know about the experiments which were done in America; there was a few months delay-in the news reaching us, but only a few months delay. In retrospect, I could say that I had a chance of having done something important in the heyday of re-normalization theory, and that I didn't. I have the excuse that there was a few months delay in hearing of the experiments, but that's not necessarily a real excuse.* (*The re-normalization deals directly with the self-energy of the electron - the topic I had been working on - I should have been able to think of the "subtraction trick", but I did not. -ES.)

Weart:

Did it seem to you at the time that the United States was where the real things were going on? Or more generally where did it seem to you were the main centers? Who were the main people in quantum field theory in the late forties?

Salpeter:

Certainly both Pauli and Dirac were still clearly some of the greatest people, as well as Peierls, over there in Europe. Incidentally, by that time already I was starting to think of where to go for a post-docship, and again I had no dilemma, or almost no dilemma. The only two places I was considering were Cornell and the Institute.

Weart:

The Princeton Institute (for Advanced Studies).

Salpeter:

The Princeton Institute. Oppie (J.R. Oppenheimer) was still the director. I must say, again I had little dilemma. It was a similar thing to going to graduate school. The Princeton Institute for Advanced Studies was a more prestigious place than Cornell. But in fact, I had really no dilemma that I preferred Cornell, again just because of the scientific temperament of Hans Bethe. It was clear to me that Hans Bethe was sort of the closest to Rudy Peierls, and I knew that his temperament had matched well with mine. So I really had no hesitation that Cornell was the place I wanted to go to, already before the quantum electrodynamics broke. Clearly then, when quantum electrodynamics did break, and Bethe had done his thing in the Lamb Shift, and Freeman Dyson and Dick Feynman were part of the Cornell scene — it then became again more socially acceptable to choose Cornell over Princeton. But as I say, in fact I had little dilemma even before that broke, just because of Bethe's personality.

Weart:

How did you know about Bethe's personality?

Salpeter:

These international conferences. Bethe had already passed through Birmingham once or twice. The contact was quite good.

Weart:

By meeting him informally.

Salpeter:

Yes.

Weart:

Or hearing him speak?

Salpeter:

Yes. Also, in particular, Bethe and Peierls were close friends. Bethe would stay at the house and so on, so we really got to know him — only a few days at a time, but you got to know him fairly well socially. Learning what's what and who's who was really no difficulty at all. As I say, there were surprisingly few surprises. The cues were there, and it all worked out just the way one expected.

Weart:

I see. I'd like to get back a little bit to the field theory business and the advent of the Lamb Shift and all that. Maybe you can give me a better view of it because you were there but not —

Salpeter:

— missed out on it, yes.

Weart:

I'm interested that you did your paper on the self-energy and so on (and you mentioned in the paper that it was suggested by Peierls)*. What was your attitude at the time, if you can reconstruct it, in '47 or whatever, towards these infinities? And how has that attitude changed since? (*Proceedings of the Royal Society A 195 (1948):163)

Salpeter:

I would say the advent of the Schwinger-Feynman-Dyson-Bethe quantum electrodynamics re-normalization theory essentially suddenly, in one day almost, made what Peierls and I were trying to do obsolete. We were doing the wrong thing. Maybe I should explain a little what my thesis was attempting to do. At the time, there were these difficulties, these mathematical difficulties with infinite self-energy.

Weart:

Yes, I looked at your paper, I didn't see your thesis —

Salpeter:

Well, the thesis was just on that.

Weart:

And your paper, I gather, essentially shows that the problem doesn't lie in the misapplication of perturbation theory.

Salpeter:

That's right. The history behind it is that some people thought, well, maybe it is just that we're using the mathematics wrongly. Sometimes if you expand a series the wrong way, it looks as if it diverges, but it's just that you were stupid in the way that you were trying to expand it out. Some people thought that maybe all was well with the theory without having to alter the theory, that we were just solving it wrong. So what Peierls set me to do was to show that no, it isn't just that, but if you start with a cutoff and do things rigorously and then go to the limit, that yes, there really is an infinity.

Weart:

Did people in Peierls' group and so forth feel in general that there was some very fundamental problem, that the infinities pointed to some extremely fundamental theoretical problem?

Salpeter:

Yes. I think we certainly felt at that time that there probably was something fundamental with the infinity, that maybe there would be some real physical cutoff, you know, which made things large but finite. So yes, we had the feeling that the presence of the infinity with the present theory was important, that a new theory probably would have a real physical cutoff in it with a real physical length and mass, and that that all would be quite important. And that's why I say we were beaten to it, or we were barking up the wrong tree.

It became very clear almost overnight, with the Lamb Shift and the anomalous magnetic moment of the electron, that our hunches were just wrong — that the theory was perfectly fine without a cutoff, and that you just had this crazy and rather ugly trick of re-normalization. It's not elegant, but by golly it was clearly right.

Weart:

Is this still the way you feel about it?

Salpeter:

Yes, certainly. Almost overnight it was clear that Schwinger, Feynman, Dyson and Bethe were right.

Weart:

Solved the problem.

Salpeter:

Clearly, it still was inelegant. It's ugly, etc. But you remember, I told you I didn't have much of a philosophical bent. There was no doubt in my mind that I'd just done a thesis on the wrong track. I had no way of knowing beforehand which track would turn out right. It was clear that the ball game was all over by that time.

Weart:

I see. I want to get back, a little later, to a few other papers you did on the Lamb Shift and so on, but I want to ask about your jobs. First you had a fellowship at Birmingham, a DSIR* research fellowship in 1948-49 sort of a post-doctoral thing? (*Department of Scientific and Industrial Research.)

Salpeter:

This was essentially post-doctoral. I got my PhD in just two years, so then I switched from the 1851 Fellowship to a regular post-doc fellowship.

Weart:

I see. Were you working on anything particular at this time?

Salpeter:

No, it's all just the same thing. There was no real difference (e.e. quantum field theory and the "house theory" for the experimentalists).

Weart:

Now, tell me about coming to Cornell. You say there were two places that you were thinking of going, but then how did you go about getting there?

Salpeter:

Let's see. I applied for some kind of English-American exchange fellowship, which I didn't get, I've forgotten even what. It was not just the purely technical thing, it was almost cultural exchange, and I probably was not really the right type for it, my aims in life really weren't that. I dabbled in that a little bit. But apart from that I just applied for an American post-doc.

Weart:

A post-doctoral position.

Salpeter:

That's right. I was intending to come to America only for a year or two, because I knew I wouldn't like America. I clearly was being a bit hypocritical, because for some reason which doesn't tally with what I've just said, I went to the trouble of applying for an immigration visa and not just a visitor's visa, so obviously I must have had the other possibility in mind. Jenya Peierls, who had a great influence on me, predicted that I'd marry an American Girl within 18 months and stay in America, and of course she was right. So there was bit of a dichotomy in what I pretended my aims were and what, probably subconsciously, I was already doing. But anyway there was no dilemma, as a graduate student in Birmingham, that I would have to go to America as a post-doe for at least a year.

Weart:

Why is that?

Salpeter:

It was like ladies' finishing school after a girls' high school. Just the "done" thing.

Weart:

What was your image of American physics or of America in general, before you came over here?

Salpeter:

It was fairly clear that in physics it was a little bit better than England. At least more of it, but probably also, you know, a little bit better. I mean that when the chips were really down somehow the Americans would do it. And after all, in the example I gave it is true that Peierls and I were beaten to it by Bethe & Co.* (*And clearly Feynman at Cornell was an order of magnitude better than any young man Peierls had at the time -ES)

Weart:

That was before you went over actually?

Salpeter:

The news already hit before I went over, yes. As I say, it's interesting that I had already decided that Bethe was my man before all that happened. But the news broke before I physically came over.

Weart:

I see. Did you apply only at Cornell, or did you apply various places?

Salpeter:

I started negotiating with the Institute, I started to write to Oppie. But somehow or other, it was so much clearer that I wanted to come to Cornell that I never got to the trouble of having a formal offer from the Institute which I then formally refused. It's just that I presumably could have gone there.

Weart:

And at Cornell I suppose, because you knew Bethe and were a Peierls student, you didn't have any particular trouble about getting that position at Cornell?

Salpeter:

Well, at least I started negotiating fairly early and it was fairly clear that I would get good letters of recommendation. Bethe also had already met me and so on. So I did not have many fears about getting the post-docship.

Weart:

By the way, what time is lunch?

Salpeter:

Not till 12:30 so we have till about 20 past.

Weart:

OK, you're not getting tired?

Salpeter:

No, no.

Weart:

Because I have a lot of questions about Cornell. Before we get back to scientific matters, I want to ask a few things about the department here in the fifties. Anything that strikes you as having been different since, perhaps we'll get a chance to come back to the later development. Of course it grew a lot in the fifties also. When you arrived there were about 24 people here. Some of the names I particularly noted were Bethe, of course, and Dyson you mentioned, — Carson —

Salpeter:

Well, Dyson came a year or so later.* He was a replacement for Feynman. So when I arrived, it was Bethe and Feynman, and of course Feynman was a very important figure in this. (*Actually, Dyson was at Cornell as a student before I went there, came back to England for a while (about when I went to Cornell) and then came back to Cornell as a faculty member a year or two later. -ES)

Weart:

Right. Phil Morrison was here, Parratt, Sproull, Bob Wilson (I think he was here already when you came).

Salpeter:

Oh yes. He was also a very important figure.

Weart:

I just wondered, how did this department strike you, in particular in comparison with places you'd been before?

Salpeter:

Well, it was very clear to me already very early that Bethe and Peierls were very similar temperaments, on the theoretical side. There was no doubt that Peierls was the best guy for me in England and that Bethe was the best guy for me in America, and again, I never changed my mind on that. It was true that the Princeton Institute was probably more of a hotbed of the brightest young men than here, but I knew I didn't like the temperament. It was a much more sort of cut-throat, nervous kind of place than here. So as I say, there never was any dilemma about having preferred being here to the Institute. Clearly, the Institute was the main Mecca. Columbia and Harvard were the other two sort of good places, at least where one's most feared rivals in quantum electrodynamics were at the time. But the Princeton Institute was the Mecca, where most of the very brightest young men went. There were rather few of the bright young men who, like me, chose to go elsewhere. I just didn't really like the competition very much.

But at any rate, on the theoretical side, I would say, on the whole America was better than England, at least in the sense that there was more of it. There were at least four places I've mentioned, each of which was, on some level, as good as Peierls' outfit.

Weart:

I'm wondering, when you came, whether there was anything that struck you as being different or noteworthy, in terms of the working conditions?

Salpeter:

So far I've only talked about the theory, where I said that America was better but only quantitatively a little bit better, four places rather than one. On the experimental side, it was a very different thing. Oliphant was building synchrotrons and Bob Wilson was building synchrotrons, but there was just no comparison. It was clear that the Cornell synchrotron would really work and this was the forefront, and it was fairly clear that British experimental high-energy physics was not doing all that well. So on the experimental side, there was just an order of magnitude difference.

Weart:

What about in terms of the organization of the department, or the way people got together socially?

Salpeter:

That would have been much more of a shock, had I come from any place other than Peierls'. I mean the American informality, and it was particularly informal here.

Weart:

Even for America, you mean?

Salpeter:

No, let me put it this way. To some extent a main difference between America and England, in most places at that time, was that the British were more formal. There was "The Professor" and hierarchy and so on, almost like the caricature of the Germanic university system. Whereas America was much more informal; each professor was on his own, the boss didn't matter so much, etc. But that did not strike me as a very strong thing personally, because Peierls, in that sense, ran the place in some ways, at least on an informal level, pretty much like here.

Weart:

That's interesting, considering that he was of German background.

Salpeter:

That's right. No, he certainly — leaned over backwards to have the place very informal. My voice hesitated a second ago, because of course, in one way it was Germanic. It worked out like a one-man department. You know, we all worked for Peierls, and if there happened to be two associate professors around, it was not very important in our life. So on some levels—

Weart:

But he didn't impose himself?

Salpeter:

That's right, and there was not a hierarchy. It's not that I worked for Kynch and Peierls told Kynch what to tell me. That's not the way that it worked.

Weart:

I understand.

Salpeter:

So as I say, it did not strike me as a particularly big change. Of course, Dick Feynman's personality was a bit of a shock. You know. But after all he is a bit of a shock on the American scene too. He was more informal than other Americans.

Weart:

Yes, I suppose you must have some Feynman stories. Everyone does.

Salpeter:

Yes. In fact, the very first time I arrived was at lunchtime and Velma was out to lunch, and there was some guy either burglarizing or doing a practical joke on the typewriter. It became fairly clear fairly soon, Feynman was playing some kind of practical joke. Feynman's personality was certainly a very obvious force.

Weart:

Whom did you get to know particularly around here in the early years?

Salpeter:

On the theoretical side, you already mentioned, it was essentially a three man group, in my first year at least — Bethe, Feynman and Morrison.

Weart:

I see, so this was clearly a separate group?

Salpeter:

Well, these were the main theorists. They were almost the only theorists. You see, LASSP*, the solid state thing, really was more slow in starting, and there really weren't any full-time professional theorists on that side yet. This building** was already here, and solid state was in Rockefeller Hall still; so they almost were the only three fully professional theorists. The solid state side yet did not have full-time theorists. The then chairman of the department, Lloyd Smith, was a bit of an applied theorist himself, but I really had little to do with him. (*Laboratory of Atomic and Solid State Physics (at Cornell))

(**Newman Laboratory of Nuclear Studies).

Weart:

So the four of you would tend to get together?

Salpeter:

Not just the four of us; there were lots of post-docs. The three of them were the grownup, real theorists, and then there were lots of post-docs. I was just one of a fairly large number.

Weart:

Was there a theoretical seminar or colloquium?

Salpeter:

Yes, there was quite a bit, about as much as now. We had, apart from the general physics colloquium, one theory colloquium a week. Occasionally we would even have a joint seminar with Rochester.

Weart:

Just for theory?

Salpeter:

Just for theory.

Weart:

Were these colloquia mostly on quantum theory and nuclear theory, or were there different trends?

Salpeter:

Mostly, but there were general culture things too. Phil Morrison was then already, as he is now, a very sort of versatile guy. He was interested in biophysics. He even had some people doing virus work experimentally at that time. So occasionally there would be other things, especially through Phil's influence. I was being paid for doing nuclear physics or high-energy physics or quantum field theory. The distinction between those three was not made at all. Whether it was nuclear physics, high-energy physics or quantum field theory, it was all part of the same game.

Weart:

I see. Where and how in general did theorists exchange ideas about their research?

Salpeter:

You mean inside the department, or between different universities?

Weart:

Inside the department.

Salpeter:

I guess it was really a very similar atmosphere to Peierls's place in Birmingham — in fact of similar size, although America in general was bigger. Peierls' department was about the same size, if not bigger than Bethe's purely theoretical show here. So on the theoretical side, it really worked just about the same. We would have internal seminars; there would be a feeling of social interchange too, dinners, graduate student parties, we would usually all eat lunch together, etc.. One thing was different then from other times, that although I was a post-doc, we were much closer to the graduate students than post-docs usually are, because the graduate students were as old as we were because of the war years. If not older, because many of them had been in the war and had only just come back. So there was, for a few years at least, a different kind of camaraderie than one had either ten years earlier or ten years later, because of the war years.

Weart:

Right, they were veterans and so forth. That must have given them a special character as graduate students.

Salpeter:

I guess they had that too, yes, that certainly is true. In ways, some of us young post-docs felt a little bit immature, compared to the graduate students.

Weart:

I see. Was there much discussion of subjects outside physics, philosophy, politics, biology?

Salpeter:

Philosophy, very little. Politics, quite a lot. By that time it was clear about science and society, etc. The moral implications of the A bomb were certainly beginning to sink in. And so there was a lot of discussion of politics. After all, the Cold War was getting hotter. Politics and military things were quite a bit discussed, especially because Bethe had, you know, had his own involvements with the government quite a bit too. That was a change from Birmingham. In Birmingham, politics and military things were not at all important. Only occasionally; Klaus Fuchs was a friend of the family, and when Klaus Fuchs was arrested that was a big thing, so for a little while there was great involvement. But it was not a part of one's everyday life; Peierls was no longer working for the government, and to the extent he was, he did not involve the young people in it. Whereas here, Hans (Bethe) did consult for the government, was involved with political technical things, and so the young people did get involved in that quite a bit.

Weart:

What sort of discussions would take place? Were there definite sides, people taking distinct different viewpoints?

Salpeter:

Not so much that. It was more just detail, the concepts of first strike, second strike, what is a stabilizing deterrent and what is a destabilizing thing, that kind of thing. Sort of the technical sociological things having to do with strategic warfare were more the kinds of things that were discussed. And also, for instance, a few years later, when the missile gap started being a gap, I had a little dilemma, to start to consult for industry and the government.

Weart:

I wanted to ask about that later. What about the McCarthy time problems, did that raise any problems in the group?

Salpeter:

That was very directly connected I felt, and I think still feel. The fears of the Cold War, you know, the genuine fears of how big is the probability of either side really making a premeditated sudden first strike against the other side, was something which people at least considered quite seriously. I don't know whether that caused the McCarthy era, or the McCarthy era caused it, but at any rate, they were clearly connected. It's not clear what the causal connection was, but certainly the McCarthy era was all involved with this.

Weart:

Did this have any direct effect within the physics department? Any personal problems?

Salpeter:

Yes, very much. For instance, in 1953 I went to Australia for a year, and I had an offer of a permanent job of a chair of theoretical physics there, and I almost stayed because of the McCarthy era. The year I was in Australia was the year Oppie was done in. On the strength of that, I almost stayed on that job, even though for all other reasons I really felt I preferred to return to Cornell. So it very nearly had a permanent effect on my American career.

Weart:

I see. You felt a lot of pressure while you were in the department here?

Salpeter:

Oh, yes. Phil Morrison was in bad trouble. Phil Morrison was, you know, almost in jail. He was called before — I've forgotten whether it was the House or the Senate Un-American Activities Committee, but anyway, he was in trouble. It was quite likely that Phil Morrison would end up jail. My wife's boss was the biologist Mark Singer, who similarly almost ended up in jail. So these things were not just something you read about in the newspapers. It was your bosses and your friends who were involved.

Weart:

You yourself didn't come under any attack?

Salpeter:

I was too young to have been of any influence. I hadn't yet had clearance and so on, so I wasn't under direct attack. It was only after the McCarthy era (but there were still the after-effects of the McCarthy era) when I had my hearings for getting my clearance. You know, there were flashbacks to it and so forth. The McCarthy era didn't stop quite suddenly. It stopped enough so that I would consider working for the government, but there were reverberations of it over quite a few years.

Weart:

I see. So during that time, you were a spectator, so to speak.

Salpeter:

Yes. It really was only after the deepest part of the McCarthy era that I got at all directly involved in either military — in either industrial or government —

Weart:

Whet was that? I want to bring that in when we get to it chronologically.

Salpeter:

My memory for dates is not very accurate. I only know a few points. As I say, between '53 and '54 I spent in Australia, and the Oppie hearings were a very traumatic experience for me so I remember that date very clearly. Then, after I got back, I really don't remember how many years it was before things settled down. I can't reconstruct at the moment (I probably could by going back through the papers) when in fact I first applied for security clearance and did my first consulting. Actually, it could not have been many years later. I think by 1956, already, I probably must have applied for clearance. So it really started being phased out fairly quickly.

Weart:

We'll get back to that. We talked about relations in the department but we skipped over how you met people outside. For example, how did you usually learn about new developments, things that happened outside Cornell?

Salpeter:

Oh, there was a lot of traveling back and forth, at least amongst the theorists, quantum electrodynamics by that time was a red-hot field, and there were just a few centers, and we were all hated rivals and friends at the same time. I would go to Princeton, Harvard and Columbia. I would make the circuit, and they would make the same circuit a few months later. So there's no doubt that never more than a few months elapsed without the various rival groups directly talking to each other.

Weart:

I see. The journals were usually well behind this circuit, I suppose.

Salpeter:

Oh yes. The journals just weren't the thing at all. The pre-prints were an important issue, but in fact we all traveled quite extensively, so often we would hear things before we read the preprint.

Weart:

I see. At that point in your career, about how much time would you say was spent in research? Did you do any teaching, administration?

Salpeter:

Absolutely no administration. Off and on I would do some teaching. I would sort of pinch-hit for Bethe or for other people occasionally, off and on. Maybe it was even formal one term, I was an acting assistant professor maybe. Other terms I just did a bit of teaching which was purely pinch-hitting. But effectively, I was mainly a post-doc.

Weart:

I see. What sort of working hours did you keep?

Salpeter:

I suppose we mainly kept theorists' hours, you know, working starting late and doing most of one's work at night, but nothing extreme. I mean, not like Schwinger. Bethe had quite normal working hours.

Weart:

I don't know about Schwinger's hours.

Salpeter:

Well, Schwinger would almost make a point of only working in the middle of the night, of being completely 180 degrees out of phase with the rest of mankind. He was clearly doing it on purpose, but on purpose for what reason was not quite clear. I guess he was shy, etc. So there was quite a difference.

Weart:

I see, so from Bethe to Schwinger, people had different phases in between.

Salpeter:

Absolutely. We were sort of proud of the fact that Bethe was a normal guy who kept normal hours — most of us were a little bit in between. It was fashionable for theorists to be night people.

Weart:

Was this true of Peierls' group also, by the way?

Salpeter:

Yes. Again Peierls, compared to most theorists, was a very normal person, and again we were all proud of the fact that we were normal.

Weart:

But Peierls' students would tend to go into the night?

Salpeter:

A little bit, because it was fashionable. Somehow, most typical theorists were supposed to be shy and ivory tower types and work at night, and I'm sure some of it was rubbed off socially.

Weart:

By the way, did anybody regularly check the papers from the theoretical group before they were submitted for publication?

Salpeter:

I would say most of us worked so closely with someone, in my case with Bethe — I really didn't work with Morrison much, but there were some who worked with Morrison and it would have been somewhat similar. — one worked so closely with Bethe or possibly Morrison that it wasn't a matter of them checking the paper, they were involved in the work. Even if their name wouldn't be on it, it was fairly clear; you know, when you got stuck you went to him anyway. I just don't know how it would have been, had one done something purely on one's own. Until much later, once I got into astrophysics life was very different, but I presume you're asking about, as a post-doc rather than as a young but independent physicist.

Weart:

Yes. When we get into astrophysics 'I'm sure It will be different. OK, first, you did marry — you married Miriam Mark in 1950.

Salpeter:

Yes.

Weart:

Tell me about that.

Salpeter:

Her background was somewhat similar to mine. Instead of being an Austro-Australian, like I was called in graduate school, she was a Latvio-Canadian. She was born in Latvia; her parents fled to Canada and then came to America just after the war. She did her undergraduate work at Hunter, and then came to Cornell as a graduate student. She is four or five years younger than me. She was a graduate student when I was —

Weart:

In physics?

Salpeter:

No, in biology. Psychology and biology.* (*She got her Ph.D. at Cornell in 1953, nominally in Psychology, but it really was already a topic in Neurobiology. A few years later she worked for Mark Singer, who was then in the Zoology dept.)

Weart:

I see. Has she had a separate career since?

Salpeter:

Yes, she is also a professor. She's even partly in applied physics, just for historic reasons. She's an electron microscopist, and the early electron microscopes were tricky things, so she's partly in applied physics — but mainly in biology.

Weart:

I see. Have you had any exchanges, have your work and hers had any relation?

Salpeter:

Oh yes. We occasionally collaborate. Remember, I told you that even quite early, I liked dabbling in doing practical things, being a house theorist - you know, like a house doctor. If you're not a very good doctor you don't become a specialist, you're just a house doctor. I'm sort of proud of being a house theorist for other groups, and including for her. So we've written a fair few papers together.

Weart:

I see. How do you think the fact that you have been scientists has affected your marriage, your children?

Salpeter:

The strongest effect is just having a working wife, having a wife who has a career. You're not asking about that, or are you? I mean, are you really asking —

Weart:

— no, I'm asking specifically about as a scientist.

Salpeter:

Specifically science, how is it different from if both of us had been lawyers?

Weart:

Yes.

Salpeter:

I don't know. We often get asked, how were the children affected by having an academic working mother, and, so on, so we've discussed that often. That it is specifically scientific —

Weart:

— well, let's say academic. You're both academic working people.

Salpeter:

Yes.

Weart:

Rather than a specific problem of the mother working, the fact that you're both academic.

Salpeter:

That we're both academics? I'm sure it must have had an influence on the children, which they consider both good and bad. The parents would reason with them rather than either letting them get away with things or hitting them; the children both welcomed and resented that off and on. I'm sure that is the most important aspect that they remember.

Weart:

Of course, that isn't academic, that is almost scientific in a way. That would be the application of logic to —

Salpeter:

That is correct. And there's little doubt, I think, in my mind that that is something our children really felt quite strongly, and as I say, both good and bad. That I'm fairly aware of, because we've had a few other friends who've had similar aged children, and some of them — I mean, I know one child slightly older than ours — who even resented that. Her father had it even more strongly than me, this business of just trying to logically reason about everything, just like you would write a theoretical physics paper, although he was a mathematician. That child even verbalized it afterwards, that she resented it, she didn't like it.

Weart:

What about the relationship with your wife, is it similar?

Salpeter:

You mean, do we sort of reason out fights, rather than just fight it? To some extent, yes. Yes. Certainly we verbalize and think out and talk out things, I think more than most people would. I'm sure that is a fairly important ingredient.

Weart:

To come back then to science. Your next papers that I noticed were in nuclear physics. Well, there are a lot of things going on actually, but I did want to ask, though perhaps you answered already — you had already gotten interested in nuclei back in Birmingham. I wondered particularly about after you came here. For example, you did a paper on "The effective range of nuclear forces. Effective of the potential shape."* Another one of these "house theorist" sort of papers — (*PHYSICAL REVIEW 82 (1951): 60)

Salpeter:

yes.

Weart:

Was this being a house theorist to nuclear physicists here?

Salpeter:

Not only here. I guess, as you say, it was sort of house theory, but it was for nuclear physics in general. I would say that was a fairly direct carry-on of Bethe's traditions — I mean, his articles in THE REVIEWS OF MODERN PHYSICS on nuclear physics.* What I was doing there was just carrying on in the same vein. So that was not quite being a house theorist, of really dealing with a specific problem that grew up in this lab. (*With R.F. Bacher and M.S. Livingston, vol. 8 (1936): 82; 9 (1937): 69, 245.)

Weart:

I see, not directly related to a specific group.

Salpeter:

Not a specific group. But it clearly was practical-minded theory in nuclear physics.

Weart:

I see. You mentioned that nuclear physics and high-energy physics and quantum electrodynamics were merged together. You didn't feel that you were making any distinction, that you needed to make a decision, whether to work in one or another?

Salpeter:

Let me say the following. While being in the physics department here at Cornell, in this building (The Lab of Nuclear Studies, which still has that name even though it's all switched to high-energy physics since), nobody would feel guilty if he, say, switched from quantum field theory to nuclear physics to high-energy or round about there. Whereas I did sort of feel guilty when I started working in astrophysics. That was already very different, whereas these three subgroups, at least until very much later, were all part of the same thing.

Weart:

You published papers alternately or in close proximity on what now I suppose you'd call nuclear theory or quantum electrodynamics. I suppose as a general question about your working style, do you keep several things going simultaneously?

Salpeter:

Yes. And also, Bethe certainly does too, and so did Peierls, and you always try to imitate your masters, at least if you have good rapport with them. So yes, there is no doubt that I would work on quite a number of things simultaneously. The really red-hot thing was the quantum electrodynamics, partly having to do with the Bethe-Salpeter equation and partly other things — but although that was the reddest hottest thing, one would work on nuclear physics and all sorts of other things, all at the same time.

Weart:

I see. Why don't we talk about the Bethe-Salpeter equation, in fact, since you mentioned it? I'm interested of course in that. What was the genesis of that work? This is the relativistic equation for bound-state problems.* (*PHYSICAL REVIEW 84 (1951): 1232.)

Salpeter:

That's right, yes. Well, when I knew you were coming I even looked back at my old notes and so on. I even kept a bit of a diary, just a factual thing, and unfortunately there's very little — it's mainly about when I had the car greased, where I bought it and so on. And even in my lecture notes, as we were saying earlier before you put on the machine it's surprising how little was written down about the main aims. The only thing I do remember, at least a little bit, is that the first main aim which Bethe had had in mind for it was about genuinely relativistic problems. I think there was a paper by Fermi and Yang saying that maybe even some non-relativistic looking Base-Einstein things were in fact the bound state of two particles, where the binding energy almost completely cancelled the original rest-mass energy of the two Fermi-Dirac particles. I've forgotten whether there was a proton and an anti-proton that would make a neutral meson, or what-not. But anyway, there was talk of this kind, of the possibility of there being such states which are genuinely relativistic, in the sense that the potential was so strong that the binding energy would almost completely cancel the rest-mass energy. That, I think, was the main rather esoteric aim Bethe had in mind, when he more or less put me onto that problem. It was fairly clear fairly soon that the most practical applications would be to very mundane, almost non-relativistic problems. Pretty quickly, I at least started using it just as a tool in plain quantum electrodynamics calculations.

But again that was partly my own temperament, it was not fully so. The first thesis student I ever had, Jack S. Goldstein (now at Brandeis), did do a thesis on genuine relativistic things. He tried to see what would happen if you got to zero binding energy, if the potential was just so strong that you got a zero binding energy.

Weart:

By the way, in one of the papers in this you thank Feynman and others at the Institute at Princeton, and you thank Gell-Mann and Low for communicating results before publication.

Salpeter:

Oh yes. I remember that quite strongly. That was sort of a slightly traumatic experience too, because it showed up a failing in my scientific ability or temperament or what-not. Bethe had sort of put me on that problem, and he had a reasonably good idea already of just what the equation should look like, derived from fairly intuitive things. Essentially what I did is just (derive it); I never derived it in a very rigorous way, but in a sort of a plausibility argument based on the Feynman techniques. It was was already fairly clear that the equation was going to be fairly useful though, even before any of these papers were published. Our rivals in other places knew a bit about it already, just from this everybody traveling around.

Then finally I went and gave a formal colloquium at the Princeton Institute for Advanced Studies. What happened is somewhat like the apocryphal stories you hear about the Institute at the time — where they interrupt the speaker and don't let him finish and start writing the next paper right there and then. And that's almost what happened to me. I gave a colloquium on the equation, and both Francis Low, who was already fairly well-known at the time, and Murray Gell-Mann, who was just some bright youngster from somewhere or other at the Institute, were in the audience, and got incensed enough at this sort of intuitive plausibility argument that they almost already started making their rigorous field-theoretic derivation of it, right there on the blackboard.

That was a very traumatic experience, in a way. At least in the sense that it is true, we (Bethe and I) didn't have a rigorous derivation. We felt it wasn't all that necessary; we believed the equation anyway. But certainly, they (Gell-Mann and Low) showed not only that it's possible give a rigorous derivation, but they could almost do it on the spot.

Weart:

I'm interested in your style of doing theoretical work. I don't know whether this is a good example to take or riot. How in general, do you derive equations? Row do you sit down and do theoretical work? Bethe had given you the idea. He had given you some orientation as to what that shape would probably look like.

Salpeter:

Yes, he must have almost written the equation down. It's always a little bit vague. I told you, I went back to notes, and there were many more notes than I thought, and lots of calculations that I can't figure out what the hell it was really all about, so it's a little bit hard to say. But I think he must already have given me the equation, almost in the final form.

Weart:

How would you describe the process that you would then go through?

Salpeter:

It's very strange. I can't find it in the notes. I find it hard to reconstruct.

Weart:

Or how in general you would do it now. I know that's a long time back, but some general way?

Salpeter:

Well, I find it hard even about later things, in the following sense. Ninety-percent, if not more, of what a guy like me actually does is. I'm really just slogging things out. It's so obvious what has to be done, and then you just worry a little bit about how you do the details you use slightly false methods, or you try something else. So it's very seldom that you do something which is really what the history books remember. That is, really you. And what's so annoying is that the few times in one's life that one did do something which the history books will remember as having been something new, it's so hard to remember how it came about. At the time, you were much prouder of having invented a little trick that enabled you to calculate something a little bit faster than before. The idea seems so unimportant in comparison to technique, at the time. So it's very hard to reconstruct, you know, when you really had the idea.

There are different temperaments. As I say, I didn't give a damn about a rigorous derivation. Once we'd written it down, once it was fairly clear that there wasn't a fallacy in the plausibility argument and that this was the equation I wanted, I lost interest in the derivation. All I cared about was how does one then apply it.

In a way I was then disappointed in it, because for the relativistic problems it wasn't that easy to handle, and it still isn't. It gets fashionable, now and again, and techniques have improved. But at the time it didn't seem to work well. As I say, I was disappointed that it didn't work all that well for the really complex problems.

I very quickly just started applying it to the simpler problems, where it was nevertheless a powerful technique. My rivals at Harvard were faster calculators than me, and yet I would occasionally beat them to it, because my use of the B. S. equation for relativistic corrections to non-relativistic systems was a rather more useful, faster method. So to me it very quickly just became a tool for playing the game of quantum electrodynamic calculations.

Weart:

I'm interested in your work following this, on calculations of the Lamb Shift — you could calculate corrections due to the finite mass of the nucleus, and other corrections and so forth. I was curious: Was your main interest here in refining quantum electrodynamics, or was it nuclear? All of this work, beginning with the Bethe-Salpeter equation — was it a probe of the nucleus or a probe of quantum theory?

Salpeter:

Well, it's a bit hard to tell. As I say, the original aim Bethe had was really nuclear physics — I mean, the genuinely relativistic things. Are mesons really nucleon-anti-nucleon pairs? Some of the motivation was nuclear, and some of the applications later on might be again. But there's no doubt that what I mainly was interested in was the hydrogen and helium atom, so it really was quantum electrodynamics. In part, it also really was a competition. There was the rivalry between the Harvard school and the Cornell school.

Weart:

What sort of rivalry was it?

Salpeter:

Schwinger on the one hand, Schwinger and his people, versus Feynman and Dyson and their people, in who can calculate things faster and get the answer. To a fair extent, there was a real rivalry. The temperaments of the two schools were very different, the methods they used in detail were very different and so on. So partly there was just a race.

Weart:

What were the differences in temperament and methods?

Salpeter:

Well, Schwinger is a much more formal and rigorous and mathematically elegant kind of guy, a shy, individual person. Feynman is particularly proud of his Brooklyn accent and so on; as a person, he's the very opposite of formal, and also in his science he's much more intuitive. So there are almost sociological differences as well, which reflect the difference in scientific style. The fascinating thing is that in the end, you'd better get the same number. In fact, the methods in the end — somebody else can come and look at them and in the end say they weren't all that different anyway. In particular, it was Dyson's great strength that he could mathematically look at both rival schools and really see where it all fitted together.

Weart:

I see. They agreed on the problems, at any rate, where the real problems were?

Salpeter:

Oh yes. There was no doubt what the next thing was to calculate, and it was clear you were racing the other guy. It was really only in method and temperament, style that there was a difference.

Weart:

What about the Princeton people? Surely they were in the race too?

Salpeter:

Well, the Princeton people really were not so much a separate school, because after all, it was the Princeton Institute, not really Princeton University. That's where you went after you'd been at the University. So the Princeton Institute would have people from both rival camps.

Weart:

A question in a different vein. Your papers, beginning around 1951, cite the Office of Naval Research for support, particularly some work you did on momentum space wave functions.

Salpeter:

At that time almost all of the nuclear, lab (Cornell Laboratory of Nuclear Studies) was ONR supported. The NSF did not come in until very much later. Which of the Defense Department outfits (supported us) was just an accident. So the ONR was the financial supporter of everything. And not only financial. I had trouble getting my visa to the USA from England and I went to the guy at the US embassy in London, and because I was going to be an ONR employee later on, he helped get me my visa and so on.

Weart:

This is before you —?

Salpeter:

Before I came to Cornell. When I already had my job here, and since it was clear that my salary was coming from the ONR, I could go to the — you know, a sort of half-military, half-science attache in the embassy there. He really was quite helpful.

Weart:

I see. In some of your papers you thank various people for help with calculations. I wonder, who were these people?

Salpeter:

I'm not sure. Probably just graduate students. We did have professional calculators, but they probably were slightly younger post-docs or younger graduate students who helped.

Weart:

Did you do much work involving calculations? These would be the old motor-driven calculators probably?

Salpeter:

You mean as distinct from just horrendous analytic things?

Weart:

Right.

Salpeter:

It was mainly horrendous analytic things. There was in the end some numerical stuff too.

Weart:

I see. So most of the calculations were analytical calculations?

Salpeter:

Yes. very lengthy — I don't mean esoteric, I mean just millions of terms.

Weart:

I understand. Did you ever get much involved with digital computers, by the way?

Salpeter:

Very little. I shouldn't say very little; clearly in the end one did some computing, and yes, I worried whether we should buy a Monroe or a Marchand next and so on. I was even in charge of the ordering at one stage, so yes, these things made some difference, and I worried a little about just which computers to get. But —

Weart:

It wasn't a big element .

Salpeter:

No, it was not a big element.

Weart:

I see. Another general question: In a lot of your papers, you 'thank quite a number of people in your acknowledgments. There may be a list of a dozen people you thank. I wonder whether this is a characteristic of your working style, or just of your willingness to give thanks in your acknowledgments?

Salpeter:

I think these aren't really two separate questions. If you have a gregarious temperament you're likely to both want to discuss things with lots of pals, and then you enjoy giving them a credit byline too. So I think the two go together; they're not really two separate questions.

Weart:

You tend to discuss your ongoing work with a lot of people.

Salpeter:

Yes. And I would say there was very little secrecy. I told you there was a sort of rivalry. Maybe I exaggerated, but nevertheless it was certainly there. And yet there was no secrecy really. You could always visit your rivals and you'd discuss everything with them. It's surprising because in biology, for instance, there's much more secrecy.

Weart:

OK. Sometimes in physics too, of course.

Salpeter:

I suppose in some areas of physics there is too, and of course in astronomy, if we get to that — in some areas in astronomy there's very much secrecy, especially in Britain. So there is a bit of a contrast.

Weart:

Well, Let's backtrack a bit then to astronomy, or at any rate, to your paper on the Three-alpha process, which seems to be your first astrophysics paper. I don't know whether this was the first work you did in astrophysics?

Salpeter:

OK, I'll tell you how I got into all of that, but we'll have to interrupt fairly soon for lunch.

Weart:

OK, why don't we just start with the three-alpha process.

Salpeter:

OK. Well, I really should backtrack a little bit further, to how I got to Caltech. As we were discussing before, nuclear physics was a part of what Bethe and his young men did, almost as much as the other things (quantum electrodynamic things). I guess he would farm out dealing with correspondence to his various young men, and somehow or other, when people wrote Bethe letters about nuclear reactions in stars and what-not, he got me to look into things and then answer the correspondence for him.

Weart:

I don't understand. What sort of questions would these be?

Salpeter:

Well, "what did you mean by paragraph so and so" in some paper. Also, somebody would say to Bethe, "Gee, I vaguely remember somebody measured some cross-sections recently, and what you had in your old paper doesn't work quite well, how would it now look with the new data". That kind of thing. So Hans would farm it out. He got lots of such letters in lots of areas, and somehow or other, the ones about nuclear reactions in stars he would farm out to me to do the letter-writing, I guess, this way Willy Fowler found out that Hans Bethe's young man in this area is Ed Salpeter. So he invited me to come and spend the summer at Caltech.

Weart:

It was his invitation, his idea?

Salpeter:

It was Willy Fowler's idea, and he got me out there very specifically for a summer. I guess this must have been 1951.

Weart:

I think so, yes.

Salpeter:

Very specifically to work on nuclear reactions for stars.

Weart:

And before you went, can you recall whether you had any particular concerns in this?

Salpeter:

No, really very little. I was quite passive — Bethe just passed on that particular correspondence to me. For all I know he could have passed on something about nuclear reactors instead. Now, maybe I oversimplify. Probably I forget that I must have had some interest which I expressed to Hans and that's why he gave me that correspondence and not the one on nuclear reactors. I'm sure I oversimplify. But in my mind then and ever since, it was just that one boss told me to answer these letters and another boss out in California invited me out, and so I worked on it — rather than having had a burning interest and desire in it in the first place.

Weart:

So what did you do when you were at Kellogg (Laboratory, Caltech)? How did this influence you?

Salpeter:

Willy Fowler just told me, "I'm paying you in the summer to work on nuclear reactions in stars, and you work on whatever interests you." Again, unfortunately, what the real impetus was — you know, why the triple-alpha reaction —

Weart:

— why you started working on that — Salpeter — why that in particular, is not completely clear. Although it's semi-clear. It was clear that in the Big Bang, getting past atomic weights 5 or 8 was the big bottleneck. And so it was fairly clear that maybe in the stars you could do something — that clearly was the important next step.

Weart:

Did you see any connection as you worked on this problem with the problem between Big Bang and Steady State?

Salpeter:

Well, indirectly, in the sense that clearly it was important to know whether the elements were made in stars or in the Big Bang. But in some ways it was already fairly clear that Gamow had tried and failed to make the heavier elements in the Big Bang. So in some ways, whichever of the two came out right in the end, one had the feeling that it would be awfully nice if one could make heavy elements in stars. There was the interest, related to the two cosmologies, but it really was not that direct.

Weart:

Did you have much interest in cosmology at that time?

Salpeter:

Indirectly. I'd known Tommie Gold somewhat. Herman Bondi even visited here once or twice. I'd met both of them and Fred Hoyle already in England. So yes, it was an interest — it was an interesting thing.

Weart:

Now they were both Austrians also.

Salpeter:

Both Tommie Gold and Herman Bondi are Austrians, true.

Weart:

Did this have anything to do with your relationship at that time?

Salpeter:

Well, maybe a little. I guess sociologically it was a little bit easier for me to have met them and so on. But I would say not much, no.

Weart:

They would have been heavily into Steady State at that time, I suppose?

Salpeter:

Yes, I guess so. As I told you, I'm not of a philosophic bent. In some ways, as soon as it was clear that even if the Big Bang were right, you couldn't make Carbon-12, as a professional scientist I lost interest for a while in Steady State versus Big Bang. Because it was a matter now of could I make it in stars or not? It really didn't matter, from a practical point of view, which of the two cosmologies was right.

Weart:

I see.

Salpeter:

I was still interested as a human being, but no longer as a scientist.

Weart:

How did you come to the conclusion that triple-alpha was the way to get across this gap?

Salpeter:

I guess I just tried lots of things. It was fairly clear that the one thing stars had which the early Big Bang didn't have, was higher density, so of course you would start— I mean, you first made doubly sure that no simple two-particle reaction worked. I was pretty sure it wouldn't, because otherwise Gamow could have found that. I did try all sorts of things, true, because maybe he just goofed and left something out. But he was a clever guy; most likely if you could do it with two, he would have done it already. So it was fairly clear that the next thing to try was with three. You'd just look around till you found something that would work fast enough. Then the thing I stumbled on was the beryllium-8 resonance, which did make it quite a bit faster than just any old three-body reaction.

Weart:

Fowler's people had been doing some experimental work at Kellogg on that?

Salpeter:

Fowler's people had been and were doing experimental work in general. They hadn't done anything for the Carbon-12 thing until quite a bit later, so there wasn't anything very direct. But yes, they were all set up. You know, the main new thrust in Kellogg on the experimental side was likely to be in this direction. Not everybody agreed. Willy was the one guy who felt very strongly that nuclear astrophysics was the thing for the future, for his machine. Among the other people, some were not quite so convinced that that would be a very main thrust.

There's no doubt that it was Willy Fowler, rather than the Lauritsens — it was Willy who was my "father confessor" in all this, even though at the time the two Lauritsens probably were better-known than Willy. In some of the more technical nuclear things, I might go to them as well, but there's no doubt that Willy was the moving force in what would be nuclear astrophysics. The Lauritsens though were very forceful guys too. They both died fairly early, the father and the son. Had you been there in 1951, it would not have been all that clear; they were very forceful dynamic guys also. Maybe even then not quite as forceful and dynamic as Willy, but almost. In fact the older Lauritsen, Charlie, was sort of really the father figure. I mean, if Charlie said no to something Willy had said yes to, Willy would very quickly change his mind. Charlie was really the Big White Father above it all.

Weart:

There are lots of questions one could ask. In his well-known 1939 paper, Bethe had made a hint about the possibility of a triple-alpha process.* Did you know about that? Did any idea come from Bethe? (* "Energy Production in Stars", PHYSICAL REVIEW 55 (1939):434)

Salpeter:

Yes. Or at least I knew — I can't remember now in which papers and so on — I knew that he'd written down in general how one would calculate three-body reaction rates. Again, the things that really seemed to matter to one then were not ideas but really techniques — as I say, the thing I remember is: Just how does one calculate the three-body reaction? That you had to look for three-body reactions was obvious. That wasn't an idea, it was obvious — what else could you do? And you would just try all of them.

Weart:

But that's what was not obvious to other people, in fact. For everybody else beryllium-8 doesn't exist because it's not there long enough, so you can forget about it.

Salpeter:

That's right. So —

Weart:

— what's peculiar about your thinking was that, to you, that one beryllium-8 atom is always going to be , there's always going to be a little beryllium-8 there. It's a shift in viewpoint somehow. It's seeing a population.

Salpeter:

Yes. But somehow to me, it really wasn't — Let me go back first to three-body reactions. Yes, I was sort of aware of Bethe having shown roughly how one would calculate the rate for a three-body reaction. And I can't remember now what I'd looked up in that, but I knew I could write down how to do a three-body reaction. Then, the business of the beryllium-8 — the other thing that was obvious was that if you had a resonance somewhere — you already had the formula. The resonant nuclear reaction was different from a non-resonant one. And then it was just a fairly obvious thing that it didn't really matter too much whether the resonance was just in some otherwise stable nucleus, or whether even the whole nucleus was only a resonance. It didn't seem to me at the time a fundamental distinction.

Weart:

It didn't seem like the hard part.

Salpeter:

That's right. The hard part was really just going through all the possibilities and trying them. I must say, even in retrospect I don't really think of it as much of an achievement of insight. I really think it was more a matter of knowing how to calculate things* and being systematic enough to run through them all. (*i.e., to have formulae for resonant rates as well as now - resonant ones. -ES)

I think the important thing is really more in not wasting your time too much. In being able to first do a back of an envelope calculation quickly enough — almost just a plausibility thing. I don't know if I make myself clear. It really was a matter of just literally dozens and dozens and dozens of different things you had to try. I think the important ability that was needed was not to get sidetracked. You could easily spend a whole month doing any on of these 50 rates alone, if you really tried to do it properly. And the important thing was that I could, in just one hour or so, have gotten far enough that I knew it within a factor of a thousand — even though it would then take three weeks to really do it properly. To me, that really was the important thing.

But the idea of seeing that it didn't matter too much whether a nucleus was unstable but was still a resonance, that the beryllium-8 was a resonance between two alpha particles — that that was slightly different from just a resonance level in a completely stable nucleus — that did not seem an important thing.

Weart:

I think you explained it very clearly. (Brief pause to check time left to lunch)

Salpeter:

I think this kind of thing is more obvious, for instance, in biology. At least, Francis Crick or Sidney Brenner or both made that remark to me very explicitly: in modern biology, the really big breakthroughs usually were not some really clever idea, but improvements in technique. I remember either Crick or Brenner or somebody, when it came to the breaking of the genetic code, claimed that it wasn't really anybody's cleverness in general thought that was important, but that people had invented techniques so you could more quickly in the lab do something in an hour which before took two days to do. Suddenly, you could just go through al the permutations and combinations and do it. I feel, in a similar way, that my doing the triple-alpha reaction was really more a matter of being able to go through all the other rival things which turned out not to be fast enough.

(Break for lunch)

Weart:

We are resuming after lunch. We were talking about the triple-alpha process. I'm curious as to how this paper was received? What sort of feedback did you get?

Salpeter:

Well, it was fairly clear that it was useful, it was important work. There was quite a bit of interest in it already straightaway. But nevertheless, it was still only one of a number of things. It's always amazing, how out of a whole slew of things only some stick out afterwards. Partly it's also my own doing. I went back over my notes just recently, and I really had gotten the germs of reactions going very far, all the way past 109 degrees, you know, all the way, to urca processes, and somehow I just didn't have the guts to publish any of it, except the triple-alpha reaction. So at the time, to me, that one was only a little bit more important than other things. But then certainly it didn't take very long for people to take an interest in that.

Weart:

Did your success in this one have anything to do with your later evolution into astrophysics?

Salpeter:

More than just the success of this one. That summer of '51 was quite an important event in my life — both in having gotten into this nuclear astrophysics as a whole but also, slowly starting the process of my learning astronomy in general. I met Baade and Schwarzschild and Minkowski and Sandage already that summer, and Jesse Greenstein.

Weart:

That's right, they were all there.

Salpeter:

They were all there. Altogether it was a very traumatic summer. There were also lots of Cornellians and all sorts of other people there and things I didn't know anything about at the time. It was this now-famous VISTA Project, which all happened that same summer —

Weart:

That's right, that's why everybody was there—

Salpeter:

Why all the big shots were there. So it was a very strange summer, and certainly left an indelible mark on me.

Weart:

You didn't know what it was all about.

Salpeter:

I did not know what all those other things were about, except it clearly was military and secret. Even my hosts there, like Willy and all the other Kellog people, were also involved in that.

Weart:

— so their main interests were not in fact in the sort of thing you were working on?

Salpeter:

Well, I would say 50-50 probably.. You know, Willy is a very energetic guy.

Weart:

Right. You say it left a mark on you? In what sense?

Salpeter:

That it certainly indelibly started a general interest in astronomy, which then slowly grew as time went on.

Weart:

I see. I notice, you did continue with some of these reaction rate calculations and so forth; in '52, and after you published papers on reaction rates in stars and so forth. This is just the way things were going, the idea of building up elements, or —?

Salpeter:

I guess, sort of. As I maybe said already, I don't have guts in science very much, and I hate sticking my neck out; and the two things of interest at the time in nuclear astrophysics — energy production in stars, on the one hand, and element cooking on the other — I took much more of an interest in energy production. It is just a matter of guts, in the sense that if you misjudge some resonance or other, as far as total energy production is concerned you never make a very great error somehow.* But when it comes to ratios of different isotopic abundances, you can make a very big error — (*A large error in the limiting rate makes only a moderate error in the required temperature- errors in branching ratios essentially have no effect on the temperatures required for energy production.- ES)

Weart:

— you can be far off, yes.

Salpeter:

And as I say, I sort of didn't have the guts to stick my neck out in an area where the data weren't yet in.

Weart:

Were you becoming interested in the problem of stellar structure, interiors?

Salpeter:

Sort of indirectly. As I said, I started slowly learning astronomy, by asking experts in it — not so much by reading or taking courses, but by asking the people in the field. The man I learned by far the most from was Martin Schwarzschild. The guy I was probably most enthused and stimulated by, rather than learning things from in detail, was Walter Baade. Just because he was such an overpowering personality.

Weart:

Now, let's jump from the summer of 1951 and take a look on through the fifties, up to the end of the fifties. I'm interested in your relations with physicists. You mentioned how you were relating with Fowler and the Lauritsens, also relations with physicists here — then you began to get into the astronomical community and your relationships there. So maybe, if you take those first —

Salpeter:

OK, you mean the sociogram so to speak.

Weart:

Yes, but first let's do it from the physicists' side. Here at Cornell for example, what were your relationships? You continued your relations with people like Bethe and Morrison. One of the first questions I want to ask is, did you begin to distinguish any division among these things, quantum electrodynamics, nuclear physics, and particle physics? Any beginning of a separation into groups?

Salpeter:

Let me try and be historically correct. For about two or three years, starting with that summer in 1951, I had a dichotomy, in the sense that it still was really the heyday of quantum electrodynamics, so much of the racing against the Harvard rival school was then; and I was doing nuclear reactions in stars. So I had two things rather full-time going on at the same time. So it clearly was a dichotomy scientifically. Also incidentally, by that time in general the division between nuclear physics on the one hand and high-energy physics on the other was starting to become a little mare felt. Nuclear energy levels remained the same, and the energy of synchrotrons increased by factors of two or three every few years, so high-energy physics was moving apart.

Weart:

Particularly in terms of for example, Bob Wilson, relations with people like him, that group.

Salpeter:

OK, I'll come to that. First I was saying, there was a dichotomy on a purely scientific level; high-energy theory and nuclear theory were beginning to move apart, because the energy of one by necessity remained fixed and the other one, because of the machines going on, was going further. But that was quite a slow process, and as far as the lab was concerned in general, I mean, it was (and is) still called the Lab of Nuclear Studies and nobody thought of it as historic misnomer... So for quite a few years my doing nuclear reactions (which were applied to stars) was still considered quite in keeping with the mainstream of what the Lab was doing. I clearly wasn't there at the faculty meetings which were deciding on whether to give me tenure or not. But let me give you just the chronological order there. Then we'll get back to the other things, but it has some relevance.

I went to Australia in the Fall of 1953; until then I was mainly a sort of research associate and various kinds of things but I wasn't fully in the academic ladder. The thing I was going to in Australia, in Canberra, was the chair of theoretical physics, so there was some slight pressure on people back here. Essentially, what they got through for me was tenure, as of when I got back, if I came back, in the Fall of 1954.

There were lots of considerations, I'm sure, and clearly my working on nuclear reactions in stars was only considered an asset rather than a hindrance. So as I say, at that time that was not at all a cause of friction.

Salpeter:

Also, at that time the full papers I was writing on nuclear reactions in stars typically were published in the PHYSICAL REVIEW.

Weart:

Yes, I wanted to ask about that. Was there any particular reason they were published there?

Salpeter:

Well, it's always very hard to know, again, sociologically, what the real reasons are. Presumably, partly they were that I felt and wanted to feel a physicist—that's my profession, that's where my bread and butter was, etc. My overt reason for it, and maybe there's something to that also, was that after all, I felt I was writing detailed professional nuclear theory papers that had to be judged first by the peer group who was expert in deciding whether the calculation was right or wrong. Only then should you worry about making the data most easily available to the people who will use it.

Weart:

The astrophysicists could find it.

Salpeter:

Right, so I think in a way it was probably reasonable. I felt this was a new area technologically, not idea-wise, and so one had to have it really established in front of the professional physicists. That in any case was a reasonable reason. Furthermore, my salary check comes from physics and I published in the PHYSICAL REVIEW. So there really was rather little conflict at the time. And things changed, my interests changed, only really quite slowly. I guess the other important event in my development in astronomy was a (University of Michigan) summer school in Ann Arbor, in the summer of 1953. I have photographs from that too, and my lecture notes of the lectures Baade gave. Really the thing that was most memorable for me, again, was Walter Baade. It was a very interesting meeting. Gamow gave some fascinating talks too, and lots of others, big shots gave talks and there were lots of us young people. Bandage was there, both Burbidges were there — you know, lots of young people were there as well as big shots. I was there to give lectures on nuclear reactions in stars. I still have my mimeographed notes.

I was there mainly for nuclear astrophysics, and much of the detail discussing I did with other people was also on that. But as I say, the highlight of that meeting, in my mind, was not the nuclear astrophysics, but Walter Baade's stellar populations and stellar evolution. It was not anything I was working in — I was like the man from the moon almost, in the sense that I'd never had any formal real, astronomy training. But clearly that was something which I felt was important.

Weart:

You would have been talking about the revision of the Hubble. Constant and that sort of thing at this time?

Salpeter:

A little, yes. I guess that, too. But the thing that impressed me mainly — it led in some ways fairly directly to the paper I'm probably proudest of, of all the papers I've written, the one on the luminosity function which I wrote in Australia that in a way was stimulated by Baade's enthusiasm about the stellar populations. Theoretically, technically, I guess I mainly owe things to Schwarzschild. You know, what sort of quantitative theoretical astronomy had learned by that time was all from Schwarzschild.

Weart:

Just during the summer at Caltech?

Salpeter:

No. I would occasionally visit Princeton, or we'd meet at meetings. I never spent any length of time in Princeton. But it doesn't take too much time to get enthused or even to get a hint. Between reading papers and asking the right questions of the guy who can give you the right answers, you don't really need that much time with him. I mention that summer in 1953 mainly because it stimulated me to look at things to do with the luminosity function, in Australia a few months later. I'm proudest of it partly because it's a paper almost without calculus, and I always feel the real test of a good paper is, it should be simple. That's rather rare; at least most of my papers are rather lengthy and complicated.

I also mention it partly because it impinges on the dichotomy between physics and astronomy, and possible conflicts and so on. There is no doubt that stellar evolution and luminosity functions — by God, that's astronomy. That isn't nuclear theory applied to something else. That is already astronomy. That was really the first time that it became clear, I was starting to get interested in things which were somewhat outside the mainstream of physics. But it was really quite slowly only that I drifted away from tie mainstream of the nuclear work. Well, I guess many things happened. Quantum electrodynamics — so now I'm talking about after I came back, say '55 —

Weart:

Yes, this sort of thing I think we should talk about up to the 1960's, say.

Salpeter:

Right. I would say it was in the second half of the fifties, 1955 on, that quantum electrodynamics was starting to get to be old hat and my interests in astronomy proper were beginning to develop. Since quantum electrodynamics was old hat, it really was high-energy theory that was getting to be the mainstream on the theoretical side here. Nuclear theory also was slowly beginning to be you know, at least not quite as exciting as before. It still went on for another —

Weart:

It was ending the growth phase —

Salpeter:

That's right. So I guess it was really only starting in the late fifties and maybe the early sixties that there was a bit of a dilemma in my own mind: was I right in getting my full salary check from the physics department, and yet working in astronomy? There were many things going on at the same time. Bob Wilson of course was an important figure in all this, because he always had the feeling that the strength of the Nuclear Lab was in part that it was and should be a closely knit group, and that diffusion was not a good thing.

Weart:

Did he express this directly to you?

Salpeter:

I think he expressed it fairly directly to lots of people. He's a very complex man. He's a perfect example of being a Renaissance Man on some levels, and having completely outside interests and being good at them. So he's the opposite of being a narrow person. But he felt that in running a lab, it was important to have a cohesive group and to work as a team. So clearly, he did not appreciate my working in outside areas, and particularly being in the Nuclear Lab. So I did have some clashes with Bob, on that level.

Weart:

What about your other colleagues? How do you feel your colleagues reacted to the fact that your main work was in astrophysics, the physics department in general?

Salpeter:

Department politics is a fairly tricky thing. There were somethings I'll want kept off the record.

Weart:

Well, you can always go back and edit out anything you like.

Salpeter:

Well, at least keeping it off the record for another 15 years or 20 years.

Weart:

Easy to do.

Salpeter:

Let me fill you in a little bit on the department politics, how various things hook in with others. There had been for quite a while a difference of opinion between the Nuclear Lab, on the one hand, and the LASSP (Laboratory of Atomic and Solid State Physics) people on the other — at least, the non-Nuclear Lab part of the physics Department. The Nuclear Lab stood more for diversity. It was never quite clear whether they really at that time stood for diversity, or merely that they were smaller and didn't want to be swamped by the single cohesive Big Brother. By now, LASSP is just about as big as Newman Lab if not bigger, so these things are quite different now. But as I say, there was this bigger internal departmental politics, between cohesiveness on the one hand and diversity on the other.

Weart:

Who were the representatives for the different views ?

Salpeter:

It really was a matter of which building you were in, essentially. In this building, I would say essentially everybody agreed with Wilson's philosophy. Bethe wouldn't put it on quite as strong a level, but in fact Bethe agreed with the philosophy too. I think on these things, Wilson had stronger feelings and was the leader, but basically Bethe's views were rather similar to his. And essentially almost everybody else in the other building felt the other way. Or at least there wasn't a strong leader there who tried to make one single cohesive group going in some other direction.

Weart:

Are these all solid-state physicists over there now?

Salpeter:

Essentially, yes. Lyman Parratt was an X-ray guy, there were X-ray people, but the younger contingent were all solid state; also statistical mechanicians and so on.

Weart:

"The other building," at that time, was still Rockefeller Hall?

Salpeter:

Yes.

Weart:

To me (when I was an undergraduate here in the early '60s) Rockefeller was always the teaching building somehow, where there were students around, undergraduates, and the people that were over there struck me as the people who were most closely involved with teaching. Was there any of that kind of dichotomy?

Salpeter:

That's really then a trichotomy, and I'm not even counting that. Sure, there were all the people who were just involved in the teaching side, but I'm not counting them at all in this conflict. I'm talking of the more vigorous and active guys in Rockefeller, who were worrying about the research side — diversity versus a single cohesive group.

Weart:

Right. These things I suppose would come out when it came time to hire somebody, for example?

Salpeter:

That's right. Say, should you have open categories, or should you divide up the pie between one line item for the Nuclear Lab, one line item for LASSP?

Weart:

I see.

Salpeter:

To some extent, some of these things are still almost lingering here. The setup has changed somewhat, and many of the younger people in this building don't have this monolithic view of what the Nuclear Lab should be. So that has changed somewhat, but only over the last five or ten years, since Bob Wilson has left.

Weart:

I understand. But none of this involved a split between the nuclear people and the high-energy people? They still shared the same building?

Salpeter:

No. In fact, I would say there were no nuclear people except for Bethe. The younger people who fluxed through rapidly, mainly changed. Even Bethe's post-docs were mainly high-energy people. Occasionally he would have a nuclear guy. So that never was bone of contention, in the sense that Bethe at least in spirit was interested in high-energy physics. He was interested in going along with the changes in the Nuclear Lab. My fights with Bob Wilson, let's say, were not at all like high-energy theory versus nuclear. Bethe's involvement in nuclear theory, I regard merely as cleaning up bits and pieces in what used to be fashionable (and there's still some cleaning up needed to do) and that was fully within the spirit. Even with Wilson's point of view, one could not have faulted Bethe or anybody else on working on nuclear theory, in the spirit in which he did it. Which is very different however from saying, "astrophysics is a new thing and it's something great and different, and we ought to get into it more, and let's start the space center". That sort of thing.

Weart:

That's the next part of the story. Let's continue on with this administrative, political history.

Salpeter:

OK.

Weart:

Gold comes in as chairman for the astronomy department. Already by this time you were interested in astrophysics.

Salpeter:

Yes.

Weart:

That was '59, then the astronomy department became Astronomy and Space Sciences. There was a Cornell University Center for Radio Physics and Space Research. What's the story behind all this? What's this all about?

Salpeter:

Well, I'll tell you. At the time all this was happening, sort of in the early fifties, we had a separate astronomy department. But it was rather lousy. It was run by Mr. R.W. Shaw who — I don't know about his early youth — but not just that he didn't do any research, it's essentially that he was anti-research. That really was properly a political matter — that he still had a few years to go before retirement. We wanted to build up modern astrophysics at Cornell. I guess one way we could have done it was try to do it purely inside of physics.

Weart:

Who is "we"?

Salpeter:

I guess mainly Phil Morrison and I and Ken Greisen and G. Cocconi. Mainly the four of us, with different degrees of involvement. Phil was always the most imaginative; Ken was always the most introspective and quiet; I probably was the most pushing. So as I say, we could have tried to do it inside physics, but for one reason or another — partly I suppose the reason I've already mentioned, that there would have been strife inside physics — we felt that it probably was useful to preserve astronomy as a separate entity. Hopefully with a lot of overlap, but as a separate identity. I must say, I think we mainly invented that Space Center as a subterfuge, to be able to operate without having to have Shaw as our boss.

But that's not what appears on the records; on the records of course we said, "Look, there's nowadays the electrical engineers because of the ionosphere, the chemists because of radio chemistry, physicists, etc., people from many teaching departments, involved. We've got to set up an interdisciplinary research department". And that is a Cornell tradition, to have those things. This lab was meant to be an inter-department place—

Weart:

The Newman Lab?

Salpeter:

Yes. With radiochemistry. Because when it was first founded, it was thought that nuclear chemistry might be important. It was envisaged that there would be both physics and chemistry professors in this building. There wasn't really much in the end. Similarly, the Space Center, by now, is mainly astronomy (plus physics). But even genuinely there was some of that good reason as well. I don't want to have this said in public for 15 years or so, but obviously we mainly did it so we didn't have to worry about Mr. Shaw.

Weart:

You don't have to feel too confidential about it, because I was just looking through the college catalogs this morning, and there is Shaw and he's teaching celestial mechanics and navigation. So I already had a suspicion from the catalog of courses. So, how did it go? Did Shaw kick at this? Did you have any trouble setting up the Space Center?

Salpeter:

He certainly was hot happy about it. But he really had no political clout. Cornell is a pretty flexible place. People that are live wire and obviously doing well in science and can get research grants, etc. — you can usually make an end run around an old fogy. Really, we had very little difficulty from the central administration. It was a time of expansion of universities anyway. So it really was not at all difficult.

Weart:

Was there anyone in the administration who was particularly important for this, or did you just go ahead and get funding and do it by yourselves?

Salpeter:

We certainly had to involve the administration. I can't even remember at this stage who. I just forget who the big shots were.

Weart:

Nobody really played a very important role in this.

Salpeter:

Not anyone at this time except for Corson: Dale Corson, I guess, was more more involved later on because he was Dean of Engineering and had been the physics department chairman during the early developments, so Corson certainly later on was an important ingredient. But at the early times internal university politics was not an important ingredient.

Weart:

I see. It was expanding, so it was not difficult to find funding for new people and so on.

Salpeter:

That's right.

Weart:

What about bringing Gold in as the chairman?

Salpeter:

As the director of the Space Center.

Weart:

Well, and also the chairman of the astronomy department.

Salpeter:

But that was only after Shaw retired. The important thing was the end run of inventing the Space Center, to be able to bypass Shaw. But with the intention of then combining it. Of course, after a while an esprit de corps developed. Occasionally, there's some committee formed that looks into various vestigial things in the university. Somebody comes and says, "Do we really need the Center, why not call it an astronomy department?" And we all sort of hit the roof and get very verbal; and in fact, there really isn't much reason any more for keeping them separate. But having been here so long, somehow one has gotten emotional.

At that time we really did think that the ionosphere people would be an important ingredient. Henry Booker and Bill Gordon were interested in the ionosphere. It was they really who started Arecibo, rather than us. And Tommy Gold thought that applied physicists would be useful for some kinds of engineering things. So originally, we thought there would be a larger number of people from completely different teaching departments.

Weart:

Tell me about the relations, then, between these two buildings. In particular you've been sort of a member of the theoretical physics group in this building, and you're also a member of the space physics group. I wonder how this works out, what the relations are between these groups?

Salpeter:

Well, the only political trauma is the one we have already touched on — I mean, the dichotomy inside the physics department, and my sort of being an alien force inside this building, by representing in a rather extreme form the views of the other buildings. At least for me personally, that is a recurring theme. Between the physics department or complex, on the one hand, and the astronomy and space sciences complex, on the other, really there never was any real friction on those grounds at all. These things are always quite subtle.

I really didn't even make quite clear the main clash I had with Bob Wilson. This was already a fair bit later, I can't even remember, it must have been the early sixties or so, when Lyman Parratt was chairman. I'd gotten some rather lucrative offers from the outside. It was fairly clear that I was going to be one of the higher-paid professors in the physics department, you know, that I was slowly becoming a medium big shot, no longer just a young man; I was suddenly beginning to be recognized for my work in astronomy. After the Bethe-Salpeter equation, it was clearly my work in astrophysics and astronomy that had gotten me the recognition which had gotten me the outside offer which would now get me the raise and higher stature, etc.

Weart:

So it was a question whether you should be kept here or allowed to leave?

Salpeter:

Well, no, it wasn't even that, it was really more on a much more symbolic level. The thing Bob Wilson and I fought over quite bitterly was just whether I would remain a member of the Nuclear Lab or not. Bob Wilson certainly appreciates quality,and he knew I was pretty good, and he was happy at having me at Cornell, but he felt that I was a divisive influence in this building. So the real fight between me and Bob was, should I keep this office? It's not that palatial. It's the office I got my first day as a post-doc in Ithaca.

Weart:

You're retained the same office, I see. Why didn't you go over to the space building?

Salpeter:

I suppose partly just because of this fight, I would think. As I say, it's not that it's a palatial office. Not only that it's a post-doc's office, it's the worst of the post-docs offices, as I was the last one to arrive.

Weart:

I'll describe it. It looks like it's about six meters wide at the most and not over eight meters long, and full of shelves, files etc.

Salpeter:

And I'll say it's the worst, because it has this little gadget.

Weart:

I see, sort of a heat pipe there sticking into the room.

Salpeter:

A heat pipe.

Weart:

Reasonable view.

Salpeter:

It does have a reasonable view, but all the theorist post-docs were on this floor. It's the worst of the post-doc offices. I was the last over because I did have some visa problems. I mention all this, the real estate, to say that it's clearly not that this office is better. There were nicer offices over in the other building. But to Bob, it was a divisive influence if I remained a member of the Nuclear Lab, while being recognized for work in a completely different area. Whereas, for reasons which I find hard to completely psycho-analyze myself on, I felt it was rather important to me to have the principle established that one could be a member in one lab, and yet for one's main interest to be outside.

Weart:

Right. Well, again, about the relations between the two buildings, they're not hostile but do they interact much? Is there much interaction between high-energy physicists or whatever physicists and the astronomers here?

Salpeter:

You're asking not about the two halves of physics, but physics versus astronomy?

Weart:

Yes. Are there a lot of places where the people get together? Is there much exchange of information?

Salpeter:

There's a number of sort of joint appointments. After all, Ken Greison and I and Phil Morrison while he was here, of course, had a long tradition of being in both departments. Much more recently we raised that whole issue again in the sense that we brought Saul Teukolsky, who is a general relativist, with real interests in relativistic astrophysics, to become a member of the physics department and of the Nuclear Lab. So essentially, the feeling is now certainly somewhat different from what it was in Bob Wilson's heyday, in the sense that most of the people in this department welcomed Saul Teukolsky to live in this building and to be a member of the department. I guess we mainly do the contact between the two buildings by having joint appointments. But certainly, to some extent there's also cultural exchange, in the sense that physicists go to astronomy colloquia, and somewhat vice versa.

Weart:

Any eating lunch together jointly, any formal things like that?

Salpeter:

No. No attempt is made to bring physics and astronomy closer in some external way like that. It's just purely that, you know, Gold is an honorary member of the physics department, and some of the physicists are members of the astronomy department, and so on.

Weart:

Do you have a joint appointment, by the way? Are you paid partly through the astronomy department?

Salpeter:

I have one of those (endowed) chairs. So now it's separate anyway. But no, in part because of this well-known fight, I went out of my way to have it arranged so my salary check still comes out of physics. I guess I leaned over backwards to be stubborn — to be stubborn and old-fashioned. It obviously would be easier for me over there, in a way; I have more clout in astronomy than in physics. I really haven't been a physicist for a long long time, etc. Still, although it's now a separate chair so it's got its own endowment, nevertheless the salary check comes through the physics department secretary, not the astronomy.

Weart:

Now, to go from Cornell out into the larger community...(off tape) (Tape #4, Side 1)

Weart:

In astronomy, how did you usually learn about new developments?

Salpeter:

Well, let me first try to reconstruct the chronology of my more formal involvements with astronomy. I can't even remember when I joined the American Astronomical Society, but I do remember when I first became a member of the IAU and went to an IAU meeting. It was the one in Moscow, in 1958 I think.

Weart:

You would have been to AAS meetings before that?

Salpeter:

I would have been to some, but not really a heck of a lot. I remember the IAU because, you know, whenever there are political fights going on you remember a little bit more. I guess it was for the IAU in 1958 that a number of younger Americans were but in who were really physicists, working maybe in astronomy and astrophysics, but genuine physicists, and not astronomers. And I remember there was a fair bit of opposition. There must have been fights, and my and other people's appointments to the IAU were over the dead bodies of some of the old-fashioned astronomers.

Weart:

I see. Who was championing your —?

Salpeter:

I'm really not quite sure. I think Leo Goldberg must have been one of the people who was certainly not old fogyish, and trying to get physicists involved. My guess is that most of the good guys — I mean good not in a political sense, but most of the active research-minded astronomers — in fact were not really old fogyish, but welcomed talking to physicists. There were rather few people who were as old fogyish as (R.W.) Wooley, for instance. You know, Wooley was quite frank and open about being an old fogy, so to speak—old traditions being important to Wooley, not only space was banned but probably the physics applications were too. Even that is slightly unfair; I did have some quite interesting chats with Wooley, my year in Canberra, in '53 - '51i. Even he was quite a good scientist on some levels.

I'm trying to think whether it was mainly by going to meetings, or by reading preprints —

Weart:

— phone calls, traveling —

Salpeter:

Yes, I guess so. I'm trying to think. There never was really anything in my astronomical career that had the immediacy, the urgency, the rivalry, of the quantum electrodynamics race. I just wasn't aware of time having been an urgent matter. But it certainly was in quantum electrodynamics. You had that feeling in other areas. Occasionally I would visit Cambridge, in the middle of the rivalry between Ryle and. Hoyle, and of course there you got this feeling that since there was a rivalry going on, and because of Ryle's sort of paranoiac secrecy drives, everything was melodramatized. But except for there, I never had the feeling that time was of any great essence.

I can't reconstruct whether you found out news in two weeks or six weeks. I somehow didn't really seem to matter. You know, you'd find out sooner or later. Nobody was racing anybody else.

Weart:

Did it seem in general that there was less rivalry, aside from the Cambridge business; not only less time pressure but also less rivalry?

Salpeter:

Well, I think the quantum electrodynamics era was rather special.

Weart:

Yes, that was an unusual one.

Salpeter:

For theorists, I mean, Clearly nowadays high-energy experimentalists on different machines are racing each other. I would have the feeling, in a way, that astronomers are more cantankerous than physicists. That they sort of personally have feuds with each other more. On the other hand, maybe it's true that there's a little bit less racing, because of the old tradition that you divide up the pie in astronomy. You know, if you've been awarded the Pleiades, the next guy can work on the Hyades, but not on the Pleiades. That kind of idea made for less racing against each other in astronomy.

Weart:

Aside from these personal things, were there any differences that you noticed between the feeling of doing astronomical work, and the feeling of doing other kinds of physics theory?

Salpeter:

Well, I think this is really an important and sort of pervasive one. Physicists would consider it shocking for a single guy or group to work on an area without somebody else checking up by doing the same thing. Astronomers would feel it shocking for somebody to poach at least for the first 60 years, let's say on a subject somebody else has made his bailiwick. That I found a continuing source of amazement.

Weart:

Do you think this still applies among astronomers, this feeling?

Salpeter:

Yes, I think at least to some extent. And also, that things are not in a hurry is much more of a feeling in astronomy. Let's say, Sandage and Tamann have been working for very many years now on a catalogue of a fairly large number of galaxies out of the Shapley-Ames Catalogue; they're slowly working away and haven't published any of the data. Now, if you need something specific, one particular thing, they'll give it to you. But nevertheless, they could have made an effort and got it all out in print two years ago, and instead they work on other things. In astronomy people take that as, well, that's the way astronomers work. If this had happened in physics, people would have lynched Sandage. You're just not allowed to sit on data for three years.

Weart:

That's true.

Salpeter:

Whereas in astronomy, everybody thinks "why not? It's better to be careful and to really have it complete". So it's just that the attitude on life, in many of these things, is very different and almost opposite. As I say and as you gather from this example, it's still true to quite an extent.

Weart:

That's very interesting. You are in an unusual position to see some of these differences, sitting here in Newman Lab —

Salpeter:

That's right.

Weart:

Well, let's go back then to '53, '54, when you went to Canberra, and you did your work on the luminosity function. First the business about looking for jobs and why you went to Canberra, and why you came back here, and then what you did.

Salpeter:

OK. I clearly felt a debt to the British Empire. So when I got the offer of a chair of theoretical physics at Canberra, it was quite a temptation. It was fairly clear to me that academically I would be better off here.

Weart:

In terms of your research?

Salpeter:

Yes. And I liked the stimulation of having other people around. I hate being sort of the "leader of men," being the big fish in the little pond and so on. There was no doubt that for me, personally and scientifically, Canberra would not be a good idea, but I did feel gratitude to England and Australia. And then, with the Joe McCarthy era having been at its height then, as I say, we almost stayed in Canberra.

Weart:

You went down to have a look at it, so to speak.

Salpeter:

Yes, I essentially went to have a look, for a year. I already had the promise of the tenure job back here at Cornell, I could also have chosen Canberra instead — they kept the permanent chair open for me while I was there on a sort of one-year visiting professorship.

Weart:

I see. Well, tell me about your work on the luminosity function and the rate of star formation. How did you come to do this sort of work?

Salpeter:

I told you it was stimulated by my having listened to Baade on the two populations, and by having learned about stellar evolution in general, and a bit of statistics, from Martin Schwarzschild. One of the things I was thinking of doing already while I was in Canberra was writing a little book on energy production in stars, which I never finished; I did little bits of it. One of the earlier things was to be just sort of a summary for the physicists of what's known in astronomy, and I figured that the initial birth-rate function ought to be something I'd find in the literature somewhere. I vaguely remembered having discussed the general topic with Schwarzschild and Baade and so on. So at first, I wasn't trying to write a research paper on that subject. I just wanted to put some elementary things in one of the introductory chapters in that book. So I just went to the library.

Weart:

To say, this is how it's defined, so to speak —

Salpeter:

That's right, exactly, define it and what does it really look like. And I searched and searched in the literature and got more and more frustrated, because I just didn't find it. So I just worked it out. But again, as I say, it didn't seem to me that it was something absolutely brand-new. I had vaguely thought, I'm sure Schwarzschild or Baade told me about it already, about some paper — all I have to do is find it. It didn't occur to me that it was something really brand-new. Then when I saw it wasn't in the literature and it was so obviously simple it should have been done, it was a paper I knew I would be pleased with already.* As I say, there really was nothing very new in it. It's obvious that it's something Schwarzschild could have written with his left hand at any time, but he just somehow never got around to it.

(*ASTROPHYSICAL JOURNAL 121 (1955):161.)

Weart:

That's true of a lot of things. Once you think of the idea of doing it —

Salpeter:

— that's right.

Weart:

In the introduction to your paper on the rate of star formation, you mentioned a couple of things that were still fairly new at the time. There were Sandage's HR diagrams of clusters, showing the turnoff from the main sequence, and you also mentioned Hoyle's theory that all the elements were built up from hydrogen. I wondered whether you can reconstruct whether these played any roles, in your thinking, your approach to this problem.

Salpeter:

The cluster stuff clearly was important. There Schwarzschild and Hoyle and Sandage were really all working along the same lines. On that score Baade was really using what those three theorists told him. There's no doubt that that was clearly an important thing. Really, the only new thing, I feel, in this paper I wrote in Australia was to really make a distinction between the luminosity function for Main Sequence stars as distinct from other types of stars (especially Giants). And that was already clear, that there was a sharp turnoff, that the turnoff from the Main Sequence was rapid enough compared to either the previous or the later evolution that you can really make a nice sharp distinction. The break there was already clear from even the early work by Hoyle, Schwarzschild, Sandage and others. There's no doubt that that clearly was an important ingredient. Then, as far as the element cooking is concerned, clearly, as I mentioned in 1951 already, that was an important thing. It's not that I developed an interest in it only later. It's just that in '51, I didn't have the guts to write things up on it even though I already had calculations, just because the likelihood of any of these ratios being correct within a factor of 100 was rather small. So I would say, that as an interest was already clear in '51 if not much earlier. That had all the time been clear, that once you did statistics about stellar evolution properly, one of the important things you would be calculating is quantitatively the amount of processing of helium and heavy elements.

As I say, that was already an important issue in '51, and this was after all three years later, so there was nothing really new there. It was really just having once developed a birth-rate function, that you could then start calculating quantitatively just how the heavy elements should build up in the interstellar medium. But the idea of that being a useful thing to do was certainly with us a long time.

Weart:

I understand. You clearly kept up your interest in this. You have a paper on this in 1959.* (*ASTROPHYSICS. J. 129 (1959): 608)

Salpeter:

Yes.

Weart:

You mention in that that a lot of the ideas came from the 1957 Rome Conference on Stellar Populations.

Salpeter:

Yes.

Weart:

Then a little later you and Maarten Schmidt both published improved theories of star formation.

Salpeter:

Yes, that's correct.

Weart:

Do you remember more specifically the interactions on that?

Salpeter:

You mean,'how important the Vatican conference was?

Weart:

Yes.

Salpeter:

Well, it was an interesting conference. It was a sort of an enjoyable and interesting and useful conference. In fact, if you look back on it., I don't think it was a particularly decisive meeting, in furthering or formulating ideas or developments of either Schmidt or Schwarzschild or Sandage or myself. It was almost more an enjoyable meeting because it was the culmination of an era. Lots had happened in that ten-year period, and almost all of it was done. Clearly some minor things were not (finished). Say, at that meeting Schmidt pointed out a blooper I had made in my earlier work, about having talked about volume density of stars whereas you ought to at least have talked about a column of stars, and since the height distribution (in the galaxy) of different kinds of stars in rather different, obviously — you know, I had just goofed. In later papers, both of his and mine, some of these errors were corrected. So there were clearly finer technical refinements that happened after '57.

It wasn't clear at that time that that era was almost over. But in fact, now, in retrospect, it seems to me it was the culmination and summarizing of an interesting ten-year period, rather than the beginning of something new. Clearly that's a little unfair. There are still conferences on this subject.

Weart:

But no longer quite as exciting?

Salpeter:

That's right.

Weart:

In this 1959 paper, you briefly mention the problems of reconciling this work on the rate of star formation with the continuous creation hypothesis. I wonder, in the 1950s, what your feelings were about continuous creation, Steady State — whether it was something important your work should be bearing on.

Salpeter:

To a large extent, what I said earlier about what was already in our minds in the summer of '51 was still true then, in '59, and in a way, is still true now. It seems to me the decisive thing had been Gamow's having attempted to do element cooking in the Big Bang and not succeeding. And therefore, for almost all of these applications, it really made no damn difference at all whether you had the Steady State or the Big Bang. I mean, clearly one is interested in it, and -

Weart:

— what was your feeling about it? Did you have any viewpoint on it?

Salpeter:

Well, yes, esthetically I slightly preferred the Steady State.

Weart:

Did your thinking on it evolve during this period? Did you tend to become more pro or more con?

Salpeter:

No. As I said earlier, I'm not very interested in philosophy, and so the esthetic dispute between the two was not really very important to me. I pricked up interest only when there was something that could be measured and something could be calculated about the measurement. For instance, Cyril Hazard and I wrote a paper on fluctuations of point sources as to what would or would not work (for the microwave background).* (*where we discussed observable tests for some ideas on how discrete point-sources in a steady-state theory might mimic the microwave background.-ES )

Weart:

Right, I noticed that.

Salpeter:

— so would get an interest only when there was something that could be observed, and what could be observed needed somebody to calculate something in order to understand what's going on. I was interested only as a practical engineer, so to speak, rather than for its real philosophic content.

Weart:

I see, Maybe I should jump ahead now, since we're talking about this cosmological question. It's a particular interest of mine so I go ahead and push on that, You had a discussion with V. Petrosian about the possibility of choosing the right cosmological constant.* (*ASTROPHYS. J. (LETTERS) 157 (1969)L87, COMMENTS ASTROPHYS. AND SPACE SCI. 2(1970):100)

Salpeter:

The ghost images and the coasting period with theLemaitre model.

Weart:

Right. This was about the same time that you and Hazard had been working on the microwave background, whether it could be explained by discrete sources, Does this 1969 period represent particular interest in cosmology, concentration on it?

Salpeter:

No, I' think, as I say, I'm really a pragmatist. It's just that if there happens to be something, some individual challenging problem, then I develop an interest. And the two, things, one of them was that there was a question of how could you do better observations on the microwave background that was the stimulation for that paper, And the stimulation for the other — there were a couple of papers I guess on theLemaitre* cosmology, Burbidge's bit about the quasars of red shift 1.95, That was again purely just one very specific impetus from the outside. It looked as though there was a concentration of quasars with red shifts at 1.95, and obviouslyLemaitre models were one particular possibility. So I got interested in it: if you really had that cosmology, how would things really look? (*i.e., two related papers (besides the "comments" papers) on "ghost images" inLemaitre cosmologies. The stimulation from this came from some work by Geoff Burbidge about quasars of redshift 1.95. -ES)

Weart:

I see. To you, cosmology had no particular character, as opposed to other types of theory.

Salpeter:

No, absolutely not, It was just purely again that if the 1.95 is true, and if it is because of the Lemaitre models, then what kinds of optical observations could one do, to really see it? And taking the complexities of nature into account, I' got interested in the ghost images and so on. As I say, was just sort of a pragmatist — again, almost just working as a house theorist rather than being interested in cosmology per se.

Weart:

I'd like to ask you a few questions about your feelings now towards cosmology. How well do you now feel the Big Bang theory is established?

Salpeter:

Well, I would say that it's not so much that the Big Bang is all that well established, but that the Steady State, in its simplest form, is clearly not correct. And to me, the advantage of the Steady State theory was the simplicity. That was really Herman (Bondi)'s and Tommy (Gold)'s and Fred (Hoyle)'s selling point in the early days. Also, "One of the beauties of our theory is that there are no free parameters, and that it is so easy to disprove it, if it should in fact be not correct." And that is no longer tenable. You can still get away with the Steady State, but only by introducing all sorts of extra complexities.

Weart:

Because of —?

Salpeter:

Well, because of the 3 degree background mainly, I guess.

Weart:

I thought perhaps quasar counts, things like that? Or that's not so sure?

Salpeter:

Well, yes, Ok, but that's such a messy thing even on the Big Bang. So I would say, mainly the (microwave) background. Well, no I'm sorry — also, there were a few positive predictions the steady state really made, and that is that you should see young galaxies. And you know, I think we would have seen them and we have seen very few if any.

Weart:

I see. Do you tend to think the universe is open or closed?

Salpeter:

Again, it's an interesting topic mainly to show my lack of imagination or interest in imaginative things. I even am working on that subject. Not as a theorist; I'm involved with some radio astronomers who are doing detailed velocity measurements and so on, and we're going to push further on getting the mass of the Virgo supercluster. The story Peebles started, are we falling into the Virgo supercluster, and if so, at what speed? Which is sort of a mass measurement.

Weart:

You're looking for the intergalactic or intracluster gas?

Salpeter:

No, this is just purely galaxies themselves. It's purely a matter of trying to get absolute distance measurements, versus absolute velocity measurements. It's at 21 centimeters, using the interstellar gas in spiral galaxies, but the aim is purely to measure velocity, and in some way absolute luminosity. The Fisher-Tully method is what we are using — correlation of the rotation velocity with luminosity. So it's purely on galaxies, and just trying to see whether we can really measure how fast we're falling into the Virgo cluster: what the deviation from the Hubble flow actually is.* (*This in turn measures the density of total gravitational mass which, in principle, can tell one whether the universe is open or closed. -ES)

So it's a subject I am directly involved in, as an observer, or at least as a guy who screams at the observers, you know. And yet, I'm not rooting for any side or the other. I really genuinely don't give a damn which way it comes out. To me, 90 is a number that in principle can be measured, like Mt. Everest is there to be climbed — it's a number to be measured, and I want to be part of measuring it, and I don't give a damn whether it's .01 or 1 or what.

Weart:

I see. Now, I suppose that would apply to your feelings about the Big Bang; you mentioned that you preferred the Steady State theory, simply because of it simplicity.

Salpeter:

Because of its simplicity.

Weart:

Not for philosophical reasons?

Salpeter:

No. Not really, Well, it's true that on the religious level, there's good reason why Pope Pius X preferred the Big Bang, and most nonreligious people prefer the Steady State. A singularity, you know, is like God. So clearly that has some slight religious bias, but obviously very minor. You know, in the sense that obviously a singularity is clearly related to a divine being.

Weart:

I understand. Ok, the next thing that I had here — you know better than I the chronology — is your work on plasmas and also your military involvement. I don't know where we should start. Shall I first ask how you got into military research?

Salpeter:

OK. Well, I would say, that's a number of things which all happened at roughly the same time. Number 1, the McCarthy era was sort of slowly dying down. Number 2, although this was a little bit later, the missile gap was suddenly discovered. And number 3, I guess I was just maturing a bit and getting older, and felt I had a bit more time for outside activities. Also as I mentioned, I've always wanted to get away from being an ivory tower isolated kind of a theorist. I wanted to prove to myself that I could be broad. Being called a "Renaissance Man" I guess is the greatest aim in being broad, but nevertheless, being broad in the other direction of being also a grimy dirty engineer, as well as an esoteric theorist, is in some ways also something to strive for. So it was partly that, to be able to prove to myself that I could get involved in practical things too.

And fourthly, just the accident that Arthur Kantrowitz had been a professor here in the Aero School, and went to Avco-Evrett Research Lab. I'd gotten to know him, and so he asked me whether I would be interested in doing some consulting there.

Weart:

Was that the first time you had been asked to do outside consulting? Whether industrial or military?

Salpeter:

I vaguely remember, I had done some purely sort of nonmilitary industrial consulting first, but it really didn't make much impression. I can't even remember when. This was the first really major involvement. And it was not in any way a big step. As usual, you try to imitate your masters if you approve of them, and that was one facet of Bethe's life. I think it was very natural that I would strive to imitate it somewhat too. Also, with the McCarthy era dying down, I guess it was an interim period; one had the feeling one could do something inside and with one's government, but one still was dead scared of "the generals", whoever they were, who still wanted to do a pre-emptive strike that would get us into the Third World War. So there was also on the political level a feeling that by working from within,you could do something towards at least preventing a genuine holocaust.

No, there was little dilemma or soul-searching involved. It was just a matter of all the things happening at the same time. I just barely got my security clearance; I had a couple of interviews, etc.; but there was no great long delay.

Weart:

What sort of research did you do? In general?

Salpeter:

To begin with, I mainly consulted for Avco-Evrett Research Lab. It was all at least directly or indirectly related to missile work. But in some ways, it was fairly indirect. What Kantrowitz was in part trying to do was to scientifically educate the defense industry, and so part of what we were doing was really almost pedagogical. At Avco we almost wrote a textbook, on the kind of statistical mechanics and quantum mechanics and chemistry that one ought to understand for understanding re-entry physics and missile technology and so on.. So some of it was on atomic physics.

Weart:

Re-entry physics, plasmas essentially?

Salpeter:

Yes, but a fair bit of chemistry too, and radar and so on. Then after a while I switched from consulting for Avco to joining the Jason division of the Institute for Defense Analysis. It was a definite switch. It was of some importance, we felt, for political reasons, some of us — I mean, a number of us who were involved in starting the Jason division—

Weart:

I didn't know you were involved in starting it.

Salpeter:

Not starting it; I wasn't in right at the beginning. But at least, many of the people who went into Jason were about the same age group. I can't remember who started it. Some of the large groups who went into it quite early in the game.

Weart:

You were starting to say the move to Jason was important for some sort of political reasons? What were those?

Salpeter:

Two reasons: (1) On the technological side our views would be "filtered" by the company before they reached the defense department, as long as we consulted for a private industrial company which had its own economic interests. (2) On the political side (e.g. stabilizing moves versus First Strike capability) we felt we might be able to have a more direct influence on the defense department if we consulted more directly for them. On the other hand, we felt we would have more clout if we formed a group (so we could reinforce each other ) than if we consulted each individually. We all were rather proud of the fact that we were taking a financial loss, since Jason consulting fees were lower than industry ones.

Weart:

I'm curious about who brought you in, about the mechanics — one of the other scientists came and said, "Why don't you come along to Jason"?

Salpeter:

I just don't remember how it started in the beginning. Later on it became a club. That is, it was the inmates who invited in other inmates, as others left. It was an almost purely internal thing. I'm not quite sure how the first group was picked, but to a large extent, it probably also was that a few slightly older people selected us.

Weart:

Now, at Avco-Evrett, you'd go out there to consult?

Salpeter:

I'd go out there, mainly summer times, occasionally during the month, to actually spend time in Evrett (in the outskirts of Boston).

Weart:

Right. Did you work here also, did you have classified files?

Salpeter:

No. We always felt rather strongly that you shouldn't. Even though I felt quite strongly that it was a good thing for university professors to get involved with government work, I felt it was important to have it geographically and temporally divorced from the campus, to maintain a very complete, sharp division. We were very insistent on that, even though it meant considerable inconvenience.

Weart:

I see. In your first involvement with Jason, did you go someplace to meet with people or how did that work?

Salpeter:

The Jason group, would meet about four times a year for a short time in Washington to get briefings in general, and then there would be a long summer study for almost a whole summer.

Weart:

At one place or another.

Salpeter:

Usually it oscillated between the East and the West Coast.

Weart:

What sort of work did you specifically do in Jason?

Salpeter:

Well, I don't want to go into classified things in any great detail.

Weart:

But you can tell me about the general physics areas?

Salpeter:

Yes. I was just going to say that although politically it was a switch, to give up industrial consulting and join Jason, in fact the kind of things I was involved in was again re-entry physics. It's just that the emphasis switched to a specific sub-area of it, namely, the anti-ballistic missile missile defense story — which is a fairly technically scientific one, because it's really a matter of, can you tell the difference between the missile and a decoy?

Weart:

What do bombs do if you try to disarm things or that sort of thing?

Salpeter:

No, it's mainly just the re-entry physics. They'd gotten down to mainly this: If the defense has an anti-missile-missile, the offense will send a number of decoys (which are cheap) with the real offensive missile (i.e. the one carrying the bomb). The problem for the defense is then: How do you distinguish them? So it was purely the unmasking of the decoy problem; for a long time that was really the major thing I was involved in.

Weart:

That's interesting, because I remember when I was here I knew a graduate student who was involved in the radar problem of distinguishing them on a radar scope, knowing which one was which. Maybe he was one of your students, working on it at the time?

Salpeter:

Probably not, because there was another group. They were all sort of somewhat tied in, but there was some tying in with the Cornell Aeronautics in Buffalo, and they were mainly doing the radar of hard objects. I was more interested in the more sophisticated and complex thing of the wake produced in the atmosphere luring re-entry. At that time it gets much tougher to make the decoy mimic the missile.

Weart:

Right. Is this what you did for Jason all along? Because Jason worked on a large number of different problems.

Salpeter:

Yes. Each of us usually worked on something quite different from all the others, and almost all the time, my major involvement was that.

Weart:

I see, but then you would discuss with others your own problems, that sort of thing?

Salpeter:

Are you asking, (l) how much interaction inside one group or (2) to what extent did the different groups interact —? You see, I wasn't the only one doing re-entry physics, maybe a quarter or a fifth of Jason was involved in ABM work.

Weart:

Right — but you were all together at one place?

Salpeter:

It would depend somewhat. Before the Vietnam War we would discuss most things even between different groups because we all had the same clearance. After a while it started changing, because some of the guys were working on things for which we did not have clearance for access. So after a while things started getting quite a bit more compartmentalized.

Weart:

How would you say the morale in the Jason group changed over time? The morale or the spirit?

Salpeter:

Things got rapidly worse, partly because of two completely different (things). Let me put it this way: for me, two completely separate things happened to coincide in time, which really turned me off defense work, namely, clearly the Vietnam War was getting worse and worse, which obviously made life harder for the whole country; but also in particular for the Jason division. Especially since it was clear that a substantial fraction of Jason was working on things that, although we all had all the normal top clearances the rest of us didn't know about. So clearly there was already that split. The Vietnam War was getting worse. People were getting more polarized; one's political views started to matter, which never had before. So that's the general thing. But then for me personally, the other thing that became clear very rapidly was that this whole anti-ballistic missile defense game was not a scientific question, but was going to be decided on purely political grounds anyway. It became clear that anti-ballistic missile defense would be started, even if it was 100 percent clear that it would never work technically. By that time it was becoming fairly clear to me that in fact it wouldn't work. And also, that was just the time it was beginning to be clear that McNamara would leave the Defense Department.

Weart:

What year was that?

Salpeter:

That must have been about either '66 or '67.

Weart:

I'm not too clear on that, or the ABM (anti-ballistic missile) thing.

Salpeter:

No, but when was it that McNamara left the Defense Department? To me that was the important thing.

Weart:

Why was that the important thing?

Salpeter:

Because McNamara was a sensible guy, whom one felt one could trust on some levels, and who was still trying to make decisions on a technical basis. Even on the anti-ICBM thing, he made various statements, which maybe weren't clear to the outsider, but in fact to us looked like sort of the swan song of a guy who was sensible. He was already saying, "The anti-ballistic missile won't work anyway, but for political reasons we're going to do it, and by God I'm going to resign fairly soon anyway". It may not have read that way in the NEW YORK TIMES, quite, but to us in the game, that's more or less what he was saying. So it was at that time that it was clear that I would probably have left Jason anyway, even if there hadn't been a Vietnam War. But then in addition, things were getting worse and worse in Vietnam anyway, and we began to have political fights at all the Jason meetings, and it was getting quite —

Weart:

Had people become polarized?

Salpeter:

Yes. I mean, to some extent inside, but also, out.

Weart:

With the universities?

Salpeter:

No, not even just outside. There were some non-university people who were associated with Jason, I mean, the IDA* people. The president of IDA, it just so happened, was General Maxwell Taylor at just that time. So he was our boss, in a way, so of course we would always have fights with Maxwell Taylor over Viet-Nam. So life was just getting a little bit unpleasant. (*Institute for Defense Analysis, Inc.)

Weart:

What were the relations like with the military while you were in Jason? Obviously they changed over time.

Salpeter:

We usually didn't have direct contact with the field kinds of generals. It was really ARPA* that was in a way the financial sponsor of Jason, and the people we talked to and debriefed ourselves to. (* Advance Research Projects Agency (Defense Department)

Weart:

These were people you knew anyway. They were funding scientific projects and so on.

Salpeter:

No, not necessarily — it's true that ARPA also funded Arecibo for instance, but that was just accidentally.

Weart:

These were the same people?

Salpeter:

They could easily have been. Just in practice, it happened usually they weren't. But no, you're quite right. ARPA was set up in such a way that they were not supposed to be compartmentalized. On purpose they wanted to have the support of basic research and the applied stuff go hand in hand; they designed it that way. My own contacts, it just so happened, were different people, for my two different hats.

Weart:

I'm still not clear about the relations, and particularly, on the one hand, you have DOD (Dept. of Defense) which has certain defense problems that they're concerned with. On the other hand, one has the scientists who have all sorts of ideas. How did things flow?

Salpeter:

Via ARPA. DOD went to ARPA and said, "Look, we have these kinds of interests and general requirements". And ARPA had scientifically-minded guys who would translate that into a better defined semi-scientific problem. And then we would talk to the people in ARPA. At least, as far as formulating the things was concerned. Once you really were in the thing, you would, say, write reports on various things about performances of radar and missile tracking and so on. I would go out to Kwajalein for a couple of weeks. So we would in the end have contact with the people in the field too, but only on behalf of somebody else. It was really in a way that for ARPA we were checking up on whether the boys on Kwajalein and Roi Namur (ie. Bell Labs staff) were lying or not.* It was that kind of thing; we weren't going there to help the people on Roi Namur and Kwajalein as much as to evaluate their work.

(* Kwajalein and Roi Namur are two small islands in the Pacific Missile Test Range where Bell Labs, had a field station. -ES)

Weart:

It wasn't an operational research kind of idea?

Salpeter:

No.

Weart:

Did you feel though that your ideas were adequately translated through to the other side, the military side?

Salpeter:

You see, to a large extent it was really meant to be sort of investigation and review, rather than help in development. I really felt most of it was a matter of evaluating ideas that were already being tried out, which ones were a fake, which one might work if there was further advance in technology but not at the moment. It really was much more a review. Now, in doing that occasionally we would also invent some improvement, which would eventually filter back. But as I say, this was my own involvement — feeding into the evaluators, rather then to the developers.

Weart:

I've heard this from other people too, and just now it strikes me, where does the military get the ideas from in the first place? Where is the original scientific input in all this system?

Salpeter:

One sometimes wonders if maybe they don't get enough. But they do have, after all, reasonably good scientists indirectly in, say, a place like Lincoln Lab, or ARPA or Aerospace (Corporation). At least, during the missile gap years, there really were quite a number of people who were quite good scientists at these places. For instance, Lloyd P. Smith was the chairman of this department when I came hear in 1949; a few years later on he was the boss of Aeroneutronics, which was a Ford Research Lab. Another example: Bob Becker, who wrote a book on classical mechanics, was at Aerospace and still is. So there really are quite good people who were right in the industries. Mainly really we were there to evaluate, rather than to generate.

Weart:

I see. Now, what about the ABM business? Of course, Bethe was very well-known for being involved in it, but what was your own involvement in that controversy?

Salpeter:

Well, as I say, technically I was just purely involved in the question of, would it work.

Weart:

— and you slowly came to —? Salpeter; And I slowly came to the conclusion that it wouldn't work. It's slightly complex sociologically: I told you before that on the Steady State and various other things of this kind, I have a very open mind. When it came to whether the anti-ballistic missile would work or not, I did not have an open mind. Because it clearly would be a destabilizing influence if it did work. So clearly emotionally and politically, I was very strongly rooting for hoping that it will not work. And similarly, all the hawks in Jason and other places were in a way rooting that it would work. So clearly this was a case that really was quite a political and emotional issue already beforehand. Now, luckily for my own peace of mind, it technologically turned out that it was going the way I was rooting for, that it wouldn't work. Or at any rate, that what the proponents were beginning to say was getting to be purely lies. Just for the purpose of —

Weart:

Were there scientists within Jason who continued to hold out for the ABM?

Salpeter:

You see, it really was taken out of our hands soon. I mean, by the time Nixon made the decision to deploy it, and there had been enough lies said, people lost interest almost in seeing whether it would really work or not. In fact, McNamara didn't lose completely. He won a partial victory of just making a token deployment.

Weart:

Right; in fact we don't have the ABM now.

Salpeter:

Exactly. So in some ways it isn't even clear who won and who lost. It almost was that a compromise was made that there would be a token deployment. So in a sense we lost; on the other hand, we also won, because nobody ever tried again to really see whether it would work. You know, if there really was a possibility of it, by now by God it surely really would work. So as I say, in a way it was sort of a draw. I got disenchanted at the same time as in any case one would have lost interest in the problem technically. For political reasons nobody was interested in it, so it just all dissolved simultaneously.

Weart:

You were quite involved. You must have written some reports and so forth?

Salpeter:

Oh yes, that's right.

Weart:

Did you ever think of going to the public in the sense that Bethe did, that sort of thing?

Salpeter:

Not really, I guess. I'm sorry in retrospect that when I left Jason in a huff, I didn't make more of a stir, trying to do publicity. I should have done a little more, but even if I had I really couldn't have been very effective. I mean, it's a very non-linear thing. You know, it's like being an opera singer or a rock star. If you're just a little bit not quite as famous as some other guy who can make a stir, you just make no stir whatever. I just didn't have enough clout to really have been able to do anything. It's a sobering thought in some ways. I've never gone back to anything to do with the Defense Department.

Weart:

I see. What about industrial work consulting, have you done any of that?

Salpeter:

Not really. I consult for IBM, but that's on purely scientific things. No, I really haven't — not that I have any objections to that. I have gotten clearance again. I'm on a visiting committee for Los Alamos. So it's not that out of principle I'm still staying out of it. I guess it's just like Camelot has gone. The illusions are gone. It's just another era, and you don't want to attempt to recapture that kind of thing. (Short conversation on how much time remains)

Weart:

OK. The next block of questions I had was about your work on plasmas. How does this tie in to your military work? Was this how you got interested in plasmas in the first place?

Salpeter:

I'll tell you, it's very curious that purely by accident in a way, I got into it from two different angles, but it was exactly the same story. It all has to do with Arecibo. Arecibo was originally invented by the ionosphere guys, purely for ionispheric backscattering, so the Space Center wasn't all that strongly involved. It was mainly Henry Booker and Bill Gordon who were then in Electrical Engineering at Cornell, who were pushing it, rather than Tom Gold and me. But clearly we were somewhat interested.

In fact, believe it or not, I got first interested in the theory of the ionospheric backscatter through Jason and not through Cornell — just because it was going to be 10 million dollars worth of ARPA money. Somebody had read an old paper of (David) Pines and (David) Bohm, and looked at it in detail and decided that if that paper was really right, the ionispheric backscattering at Arecibo wouldn't work. They went back to the money-giving guys at ARPA, who decided they'd better start having that looked into. Since I was on Jason, I was asked to look into that. And in any case, it was a Cornell project, so suddenly I had two reasons for trying to find out what the story was.

Let me tell you briefly what the bone of contention was. In the early days of plasma theory, people like Pines and Bohm worked on a model for a plasma theory where you have electrons as they really are, but where the positive ions are replaced by a uniform background of charge. There are lots of interesting things for that simplified case, and they worked that out. Somebody went into those papers and tried to apply that to the Arecibo backscatter. But the Arecibo backscatter, although it scatters off the electrons, mimics the density fluctuations of the ions; the electrons just follow along with the ions, under the wave length conditions we were going to work in. And so if you didn't have positive ions, but a uniform positive background of charge instead, you wouldn't have seen it at all, or rather you would only have seen the electron plasma line (which I then later on invented or discovered or what not) but not what would have been the main component.

As I say, there was a big furor in ARPA — if those guys were right the whole thing wouldn't have worked at all. Booker and Gordon had done the sensible thing from scratch, in a semi-intuitive way, and of course they had the right answer qualitatively, but nobody had proved it formally. So I got involved in writing a few papers and really doing the theory of what the backscatter would do in great detail.

Weart:

By the way, were you connected with the whole Arecibo story of building it up? Or you say that's something you weren't too interested in?

Salpeter:

Politically it was Booker and Gordon who were pushing it. They would say then later on, you know, Gold, Drake and Salpeter muscled in. But as I say, at first, it was mainly to be an ionosphere thing rather than radio astronomy. I got interested in this calculation, as I say, because of this blooper which was soon fixed up. But in the meantime, by having done it all in detail, I had discovered that you would also get a back reflection from the electron plasma frequency itself. That was a cute, slightly esoteric new thing. So I got interested in it; I have had an interest in Arecibo for quite a long time. Then soon Gold and Drake got in the act somewhat too. There was great friction between the two halves (Gold and Drake versus Booker and Gordon). I was somewhat in between. So although I never was involved on the administrative side or anything official, there was the Arecibo Technical Committee which I was the boss of, which tried to partly adjudicate, you know, look at scheduling of times and so on.

Weart:

Adjudicate between —?

Salpeter:

Well, between the two feuding houses, Booker and Gordon on the one hand, and Gold and Drake on the other. Or generally, if there was feuding.

Weart:

Was this the problem of the division between ionospheric and radio astronomy?

Salpeter:

Yes. So as I say, I was involved on the sidelines, I had no official position. The Arecibo Technical Committee was just purely advisory, so when the history books are written my praises will not be sung officially, because this wasn't a particularly official committee. But I felt quite involved, mainly in pouring oil on troubled waters, that kind of thing.

Weart:

How did that all get straightened out? I guess there's still some —

Salpeter:

Well, that's hard to say. You could say that on paper, it looks as though the radio astronomers squeezed out the ionosphere guys. On the other hand, the most permanent staff at Arecibo is the ionosphere group. Since the resurfacing of Arecibo, radio astronomy has not gotten any new money; the ionosphere guys just got three million new dollars. So it really isn't true that one side got squeezed out by the other. It may be true that Bill Gordon left largely or partly because of unpleasantness. It is hard to say. But at any rate, at Arecibo now the ionosphere is well and flourishing.

Weart:

There'll always be the problem of what to use this unique instrument for.

Salpeter:

Yes. But in fact, I think there is relatively little friction now. In some ways, my role in Arecibo has changed completely. I've sort of stopped being involved on the semi-official side as soon as it became a national facility. I was almost publicly defrocked when Arecibo became a national observatory, because there were fears that there would be too much Cornell domination anyway, and to yet have a non-NAIC* Cornellian like me being involved was a bad thing. So essentially I was kicked out of the committee, and there is now a genuine non-Cornell international committee. Instead, I've become more directly involved with the real observations. (* National Astronomy and Ionospheric Center)

Weart:

Getting back to your work on plasmas. Were there any intellectual connections between your work on plasmas and your work on re-entry shocks and that sort of thing? Was there anything that carried over?

Salpeter:

Yes, there was some little bit of an overlap. Some of it is even, in the unclassified literature. I have a couple of papers together with Sam Treiman on electromagnetic backscatter.* That's at least mathematically related to ionospheric backscatter, although in detail it is quite different. It was stimulated by the question of radar backscatter from missile wakes. (*JOURNAL OF GEOPHYS. RESEARCH 69 (1964) p.869; JOURNAL OF MATHEMATICAL PHYSICS 5 (1961) p.659.)

Weart:

I see. Is there any intellectual connection between your work on plasmas and work on controlled fusion? Did you ever have any connections with those people?

Salpeter:

Only indirectly. A surprisingly large fraction of my PhD products have become plasma theorists. I've never quite understood why they've done that, but there is this indirect connection. I've never myself directly worked in it.

Weart:

By the way, the paper on plasmas which I particularly noticed is the one on electron density fluctuations in a plasma, where you find the frequency spectrum for electron oscillation.* (* PHYSICAL REVIEW 120 (1960):1528)

Salpeter:

Yes. That's the first one of the series, which was purely designed for the workings of Arecibo. I wrote it in a rather more esoteric manner, but that was the application. Then in the JOURNAL OF GEOPHYSICS, I then would have somewhat more practical-sounding things, but essentially all they were was just applying this. Incidentally, I wasn't the only one who invented these things. There really were three groups who more or less calculated almost the same thing simultaneously. Not in as fine a detail to include this plasma line I'd invented, but for the main features — there were three rival groups working independently, and getting almost the same answers.

Weart:

I see. That happens to be a very highly cited paper, I find. Evidently people choose it as the one they will cite.

Salpeter:

Well, I think it's because it's written in a somewhat unusual style. Namely, I wrote it as though I'd never heard of plasma physics. And it's almost true. You know, I started with Newton's laws and Coulomb's laws, and that's it.

Weart:

I wanted to ask, how did you learn your plasma physics? Did you find yourself entering a new intellectual area, also encountering new people in this area?

Salpeter:

I could have, but in fact I didn't. I almost genuinely started with Newton's laws and Maxwell's equations and just did it from there. And it was sort of cute. People were interested in the fact that a guy could do that. It was, in a way, a piece of bravado. It caused a stir because I could do it starting absolutely from scratch, without needing a book on plasma physics. I could get the answer in only six or eight printed pages.

On the other hand, it is also true that Norm Rostocker and Marshall Rosenbluth just a year later showed that, by knowing textbooks in plasma physics, they could derive that same result in one printed page. So I'm not saying that it's no use at all, that you don't need the books on plasma physics. It's merely that you can start from scratch. Whether it's a good thing or not, is not so clear.

Weart:

Right. Back again around 1960, you were also working on matter of high densities, white dwarfs, even neutron stars.

Salpeter:

Yes.

Weart:

This was apparently partly at Caltech and partly at Cambridge. I was wondering about the circumstances of this work.

Salpeter:

No I'd gotten interested in that already quite a bit earlier; there was some time delay. I think the ANNALS OF PHYSICS paper I'd written on matter at high densities was still before my sabbatical. At any rate, I had started developing an interest in these things much earlier. I can't quite remember what started the interest, quite generally in neutron stars. And other people too; I only went along with the fashion. In part, it was quasars — the first few quasar papers, we all thought it would turn out to be neutron stars. For instance, at the first Texas Symposium in Dallas, the year Kennedy was shot -

Weart:

— this was later; this was after your first papers.

Salpeter:

Oh, I'm sorry, you're quite right. It's just that the interest in the observational aspect of neutron stars started, falsely, with the quasar observations.

Weart:

Right, but you seem to have been interested before that came along. I was struck by your interest in what for that time were really very extreme cases.

Salpeter:

Extreme cases, yes. I must say, I can't really quite remember how I got into it. That's one of the few cases where there weren't any really obvious observational things at the time. I keep on saying I like being a house theorist, but I must admit, occasionally I get interested in just doing something because it's pretty, and it would be nice if it really were there, and it's interesting to calculate on it. I always was interested in statistical mechanics anyway, so that was one of the few things I did for astrophysics where I mainly got into it because it was a pretty, elegant application of basic theoretical physics. But white dwarfs were already a practical thing, too. So the papers I did in Australia — in '61, was it?

Weart:

You were in Australia in '60.

Salpeter:

Yes, '60 - '61, I wrote a couple of papers there on white dwarfs. That the Chandrasekhar limiting mass is not just a limiting thing but a maximum mass at finite density — so those things had some practical applications already too. But as I say, I think I was for once interested in it just because it was pretty.

Weart:

Also you must have come back by way of Cambridge?

Salpeter:

Yes, I spent half a year in Sydney and half a year in Cambridge.

Weart:

I see, this was your sabbatical.

Salpeter:

It was my sabbatical, yes.

Weart:

I notice you've also spent time at various other places. You spent time at Caltech, not just in '51 but since then.

Salpeter:

Yes.

Weart:

You spent time in Tel Aviv, Rmat Aviv.

Salpeter:

Yes, that' correct. That's just the location of Tel Aviv University. Yes, Cambridge I go back to often; Caltech I go back to often; and I have a permanent arrangement with Tel-Aviv, I spend time there every few years.

Weart:

Why do you do this?

Salpeter:

Well, Caltech, really because it's in a way my alma mater as far astronomy goes. I really started astrophysics there, with Willy Fowler in Kellogg in particular — Schwarzschild, Minkowski, Baade happened to be at Caltech when I was there. So Caltech, because I feel it's almost like my third university, so to speak. Cambridge, partly because I feel still a guilt or loyalty or something to the British Empire. They really educated me for free, and so on. Having this for Britain in general, Cambridge is just the most pleasant and stimulating place.

And Tel Aviv, partly because I happen to have had a young post-doc here, an assistant professor, who was from there. I like Israel, I like going back. I like being involved in places.

Weart:

Did you ever feel a need to be out of here and in other places, because for example, there are no big telescopes here, that sort of thing?

Salpeter:

No. The optical telescope story is important, but you don't need everything on the premises. I would put it differently — that as it is, I'm very interested in the Virgo cluster because you can do 21-centimeter work at Arecibo, which happens to look at the Virgo cluster. If I were at a place with an optical telescope, I'd be interested in different things — in detail. But I don't think you could say you feel the need for one location more than another, because you couldn't be at a place where you had both Arecibo and the Hale Telescope within walking distance of each other anyway. It's just that I think you pick slightly different topics, to some extent.

Weart:

Now, you mentioned a little earlier the first Texas Symposium. I wanted to ask also by the way, are there any other conferences you'd point to as being particularly -

Salpeter:

You mean, as being really important to me, if not to other people to me?

Weart:

Yes.

Salpeter:

Well, this Ann Arbor thing in '53 clearly was an important stimulus.

Weart:

Yes, but other than the ones you've mentioned?

Salpeter:

Well, while I was still in quantum field theory or high-energy physics, the Rochester Conferences were quite an important stimulus.

Weart:

I see. Which was the first one you went to?

Salpeter:

I've forgotten when it was, the first one. I went to all the early ones, because Cornell and Rochester were really very close. Marshak and Bethe were close, the departments were close, there were joint seminars. So all of us here were at all the early Rochester Conferences, so that clearly was quite and important thing. But on the astrophysics side, I can't think of any which were really very important. I went to two of these Vatican Symposia, and the first one was certainly very memorable, but as I said, only as an aftermath. The second one I went to was on nuclei of galaxies and it really wasn't a subject I was in very much. I was at one Solvay Conference, which I thought was not a very useful thing.

Weart:

What about the Texas Conferences?

Salpeter:

I thought the Texas Conferences were fun, but they're more educational; I don't consider them a working conference. They're not really for a fairly small number of people getting together in detail. I feel they're useful for the younger people as an educational experience, but not as a working conference. Although I am in some ways gregarious, I don't like working conferences and sessions very much. I don't usually get much out of Aspen and so on.

Weart:

You prefer smaller groups.

Salpeter:

That's right, or at least informal contact rather than an organized meeting I'd rather visit a place for three days and talk to them, and them visit here, and get the contact that way.

Weart:

I see. What about the first Texas Conference, where all these things came out? Did it make a strong impression on you?

Salpeter:

No. In fact it was just a matter of embarrassment. These things get arranged long beforehand, and I was asked to give a talk on neutron stars as explaining quasars. That was the reason for giving a review talk on neutron stars. In fact nothing much had happened about the theory of neutron stars in the meantime. It was to be important because that's what quasars were. Long before the actual conference, it was clear already that it wasn't that at all. My memory of the first Dallas Conference — the main memory is that it was soon after the Kennedy assassination. But apart from that unpleasantness, my other main memory is that I was embarrassed to have to give a talk on neutron stars and quasars, at a time when it was obvious that they have nothing to do with it.

Weart:

I see. And still before the pulsars.

Salpeter:

And still before the pulsars. It's memorable only in embarrassment, nothing else.

Weart:

But you did go on then to make models for quasars as contacting bunches of stars. So at some point you became interested in these problems.

Salpeter:

Oh, you mean this fragmenting disc business? (Pause to check on paper)

Weart:

OK, I'm talking about accretion of interstellar matter by massive objects.* (*ASTROPHYSICAL JOURNAL 140 (1964) :796)

Salpeter:

Oh yes, that is quite true. In fact I'm even rather proud of that, because there's a factor of Q.06 of the maximum gravitational energy release you can get out of accretion under certain circumstances. I'm proud of having gotten that number a few years earlier than most people. You wanted to know how did I get interested in that topic?

Weart:

Yes.

Salpeter:

I think that time again, I was reacting to somebody or other who had written a paper which I considered wrong or crazy or something. It must have been somebody else who had suggested the possibility of super massive things in the galaxy, for some different purpose. So I mainly wrote that paper just to show that that guy was nuts. I can't even remember who he was and what he was, trying to sell, but an any rate I decided, if there were really these very super-massive objects right in our galaxy, let's see what they really would do. And I decided one of the things they would do would be accretion. I'd learned about accretion from Bondi, and Hoyle had done lots of work on it, so I was familiar with accretion. So as I say, it was for this not very noble reason of disproving somebody else's things that I got interested in that.

Weart:

I see. As I read it, what comes out from it is a quasar model in effect, a reasonable model for a quasar. You have a lot of stars falling together, and some of them begin to interact and so on.

Salpeter:

Yes. I thought though, that that part of it was not new. People had already -

Weart:

People had talked about that.

Salpeter:

Yes. So I really wasn't intending it as a quasar model so much. In retrospect, what I'm proud of was the technical things - it solved a number which professional relativists should have written down earlier. And also, I had at least worried about what accretion would really look like, and realized the dynamics would lead to standing shock waves and so on. I'm told I got the story slightly wrong, and people have tried to do it better since.

Weart:

Right. If you had to make a quasar model now, what would you say now?

Salpeter:

That's again more like some of the other things I mentioned; I'm completely open-minded. I refuse to have any hunches or any direction I'm rooting for, when it's a complex enough thing like that. I'll suddenly get interested in quasars again, I'm sure, then I feel there's something cute that could be observed, which they need my calculations for.

Weart:

OK. I think we'd better pause now. (one hour break)

Weart:

OK, we're resuming after having attended a seminar on intergalactic hydrogen. Now I've covered most of your work up to 1970, I think. We haven't talked about the book, Bethe and Salpeter,* but perhaps we'd better talk about that in connection with teaching. Is there anything else about your scientific work before the 1970s that you think we ought to talk about?

Salpeter:

There's nothing that I consider particularly memorable that we haven't discussed. There were a number of topics that we have left out. For instance, stellar evolution calculations, which were an interesting topic and had to be done, but there's no particular glamour. The glamour in that thing was in the early postwar years. It was Schwarzschild, Hoyle, Sandage and Company; they pet the groundwork, and then the rest was filling in detail. So I don't think there's any one memorable thing. (* Quantum Mechanics of One-and Two- Electron Atoms (Berlin; Verlag', 1957))

Weart:

Was this work, for example in stellar structure, work you carried along on the side, then? You'd do a paper occasionally.

Salpeter:

Yes and no. I mean, in the sense that it was at least indirectly connected with the nuclear reactions in stars. I got interested in highly evolved stars — the onion layer kind of things, which had carbon and oxygen in the center, helium in the middle and hydrogen on the outside — just because that's of interest for element cooking. But after a while these things develop a life of their own. Because really in a way it was rather that the element cooking was the reason you had onion layers in stars. Then it became just purely a problem of doing the numerical work.

Weart:

How would you do this, when you'd carry on several topics during a given year? Do you work a week on one and a week on another, or is it whatever you happen to be stuck on at the moment?

Salpeter:

Well, I really would not do myself at all most of the work in areas which already are going concerns. I just would use graduate students or postdocs here. Incidentally, I don't ever use a computer myself. All these things always done through young people, and in particular stellar evolution calculations involve really quite extensive codes, and I've never even developed the know-how myself. I would just, say, get some post-doc who had done such work before, so he had a code, and one maybe modified it slightly as one went along, but it's always the youngster who did the work anyway.

Weart:

How does this develop? I notice as time passed that your papers tended more and more to do collaborations with your students.

Salpeter:

Yes, students or post-docs.

Weart:

How did this develop over time? Have you been aware of any particular moment when you moved more to this mode of doing things?

Salpeter:

First of until you're a bit older, you're not so able to really work directly with students. And secondly, I suppose as you develop more and more different areas, you can support a larger number of students — in the, sense that I think at least it would be a mistake to have a team of young people working on the same subject. Maybe they would feel less lonely than my students do, but I think they'd have less of a sense of really being an independent person. So I wouldn't ever want to have more than one student at a time on a particular kind of topic. So as time went on and I had a larger number of areas I was sort of an expert in, I could keep more people busy. The other thing I feel usually fairly strongly about is, I don't like taking on young people in an area I've only just gotten into. I mean, unless there are some other experts around. I've gotten involved with radio astronomy graduate students, but I make sure that there's always some genuine radio astronomer who's also associated with the student. And even then, you can sometimes bungle. We made a blooper a year or so ago on a technical thing, we underestimated the side lobes at Arecibo; it's the boss who should have noticed this, not the graduate student. It was something I wasn't an old enough expert in and we made a mistake - in print! This mistake reinforces me in thinking I'm right in feeling that one shouldn't put graduate students and young people onto new areas. I feel it's always important for me to go into new areas myself, but you shouldn't take on the young people until you've become something of an expert.

Weart:

How do you choose an area? I noticed since 1970 or whatever, you've entered a number of fields — the HI regions, stellar model calculations involving mixing and neutrino problems, Jupiter, and now this purely observational work, different from what you've done before, on the Virgo cluster. How do you decide to enter new things like this? Why pick these?

Salpeter:

It varies. Usually it's that I'm sort of a pragmatist — it's some opportunity. But whether the opportunity is that there's something of importance, which I have an unfair advantage of having technical skills that are needed, or whether it's something else — that varies. Let me take the most obvious and concrete example, the 21-centimeter radio work at Arecibo. It was known already two or three years before the finishing of the resurfacing of Arecibo that it would be resurfaced. So it was clear what kinds of things would be possible. Then I guess I looked around at what kinds of topics one could do at Arecibo that both were important, and (in which) Arecibo would have an unfair advantage over the other guys; and also what are problems for which my own scientific temperament is fairly suitable.

Well, I suppose I like reasonably simple things. I don't mind simple things then becoming complex when you look at them in detail, but it ought to be somewhat simple to begin with. I felt that neutral atomic hydrogen is simpler than complex molecules, and so even though at other times I've had an interest in making complex molecules, somehow I had the feeling that work on 21-centimeter neutral hydrogen would be more what I'm suited for.

Weart:

But this change to doing something observational is quite a change. It didn't seem that way to you?

Salpeter:

Somewhat, but not all that much. I didn't mention it in detail, but when we were talking about electron density fluctuations in a plasma, I told you that more or less by doing the theory completely I stumbled across the reflection from the plasma line, which was not the thing for which Arecibo was built. But it was much harder to look for it, and I thought it was worthwhile looking for. And so I was very much involved in having that thing pushed observationally.

Weart:

You mentioned you were on a technical committee, which I suppose involved some of these things.

Salpeter:

The technical committee really was meant to be more an overlooking and advisory and refereeing committee.

Weart:

I see — you weren't involved with technical aspects of the work actually.

Salpeter:

Yes. But I was involved. One of my then graduate students, "Rick" F. Perkins, who is now a plasma theorist at Princeton, teamed up with a radio engineer at Arecibo and they did do the early observational work on that. So I was already indirectly involved, with observations already then.

Weart:

I see. Have you ever done any observing yourself?

Salpeter:

You mean actually twiddled the knobs?

Weart:

Yes — on any instrument?

Salpeter:

Actually I did more in those days. I did sort of twiddle knobs, and ordered bandpass filters, when the ionosphere work was going on. Largely because Arecibo was newer and it was a more helter skelter informal place. Right now, I don't really ever do any twiddling of the knobs or punching the computers — but remember, I don't do it with calculations either. I do not punch cards. I just scream at graduate students and post-docs, they punch the computer; and I do exactly the same with the observational stuff. That's not to say that I don't like looking at the details. I love staring at the raw data rather hard — the same with a printout from a calculation. For me, the radio astronomy at Arecibo is really no different from theoretical work, in the sense that it all comes by our computer anyway, and the important thing is having hunches as to what's right and what's wrong, and where you shouldn't waste your time and effort or where you should. So I don't find it as different from theory as one might expect.

Weart:

Particularly your kind of theory -

Salpeter:

— which is this kind of practical theory anyway. But anyway, to finish a little bit, which kinds of areas — as I say, neutral hydrogen rather than molecules, because my own scientific temperament goes a little bit more that way; and the next thing would be just pragmatic things. For instance, one potentially interesting thing is young star associations and doing something in relation with the Copernicus (satellite). Now, Arecibo just happens to be so situated that there's nothing much on the way. I mean, there's some but not much. Of all the interesting molecular clouds, only one out of 17 are accessible from Arecibo. But when it comes to galaxies the nearest and richest and most interesting cluster is Virgo, and the nearest and of the rich ones is Coma, and by God, they're both exactly at the most accessible direction from Arecibo. So although I'd never done any galactic work before, it was fairly clear to me that galaxies are one thing that Arecibo has an unfair advantage over other telescopes in.

Weart:

Do you have a particular interest in some of these problems? We were just talking recently about intergalactic gas, and the problem of the missing mass in galactic evolution. Any particular interest in that kind of thing?

Salpeter:

Yes. In fact, a number of our projects at Arecibo are in one way or another related to that. One of the ones we have (in fact that's the one where we made a blunder by having underestimated the intensity of the first side lobe), we are trying to extend rotation curves in edge-on spiral galaxies as far out as one can, in order to see whether it's really true that the total mass increases linearly. If the linear rotation velocities would keep on staying constant with increasing distance, the mass would be increasing linearly with distance also, which would mean that there is invisible matter there. That was one very specific project we did, just to see whether that is so. Another study will be binary galaxies, to get from the relative velocities at least statistically the viral theorem mass of the pairs of galaxies. The third one I mentioned already, trying to see deviations from Hubble flow, in the vicinity of the Virgo super-cluster, again to measure the mass of the Virgo super-cluster. So a large number of these investigations are fairly directly involved with measuring total mass. I would say the fact that there happened to be a number (of studies) which related to total masses was really just happenstance. What I'm trying to say is, the problems I pick are really more pragmatic. They should be of interest scientifically, and we should be able to do them better — either the instrument is better or the direction is better.

Weart:

But it's not because you have a burning curiosity about this specific matter?

Salpeter:

Absolutely. Hardly ever is it that I have a burning interest in one particular topic, and whether that's the right instrument or the wrong one, that's what I'll push. That's the attitude some people have, and that is not at all my attitude. I don't mean to say that I'll do hack work just because it's easy. But I have the feeling that there are interesting problems in any one of a large number of areas. So I prefer to pick not one that's a preordained interest, but one where it looks as though one can get results in a hurry.

Weart:

I'd like to shift ground now to a different question. Funding. In looking through the acknowledgments in your papers, I particularly noticed ARPA* funding, and then later on, for the last ten years or so, you've been regularly getting NSF (National Science Foundation) grants for theoretical studies in stellar structure, 50 to 150 K a. year. First, what are the circumstances for your getting ARPA funding? How did that come about? (*Advanced Research Projects Agency (Dept. of Defense))

Salpeter:

I'd even forgotten the ARPA funding. The Nuclear Lab in the old days was mainly ONR (Office of Naval Research), and only later on it switched to the NSF. NSF grants we've had now in stellar structure and evolution and theoretical astrophysics in general, as you say, for about ten years — I'd forgotten the ARPA involvement.

Weart:

Possibly it referred to Arecibo?

Salpeter:

Yes, my hunch is that it's just that the Arecibo funding was all ARPA until it became a national facility. So anybody who was employed by Arecibo would have gotten his money from ARPA. It would be that. I might possibly have given a credit byline to ARPA if it was something involved with Jason. I mentioned that there were a couple of things I did in the unclassified literature, but which were really done for military applications.

Weart:

I see. It was not that you specifically went to ARPA to get grants.

Salpeter:

No.

Weart:

Well, tell me about your NSF grants then.

Salpeter:

OK. I am trying to remember the various stages. For quite a while, as I say, I was still on the high-energy theory ONR grant. My work was outside of that area and I didn't use a heck of a lot of money from it, but for quite a long time the group sort of carried me on their backs. Although I was telling you earlier my fight with Bob Wilson was on a purely symbolical level, to some extent theorists in this building did carry me financially, so to speak. But then as time went on, as the Space Center grew, I took more and more of my funding from over there. At first I would do it sort of 50 - 50 and would not be the principal investigator in grants; or in the early days of the Space Center, Tommy Gold typically would have some fairly big grant, and I would have been named as one of the people working on it. Then some of my graduate students would be paid partly by that. Others would be paid by here. As time went on, and it became clearer and clearer that I was shifting more and more to astrophysics, the center of gravity of the funding shifted more to the Space Center. I've forgotten how long ago, but some time ago I started getting a grant where I was the principal investigator. I've been on that now for a long while.

Weart:

How does that get renewed, do you simply send in an annual thing to renew it?

Salpeter:

When I was young in the game, as an individual principal investigator, for a few years it was in the form of grants for one year at a time. When I became better known in astronomy I managed to switch to a Continuing Grant. For a while the Continuing Grant was for a five-year period; since money has become tight at NSF the grants are now for a three-year period; ie. I apply for renewal every three years.

Weart:

Does it seem automatic? Is there ever any question as to whether you are asking for too much or too little or whether it might not be granted?

Salpeter:

There's always haggling as to whether I'm asking too much; they never think that I'm asking too little. Yes, certainly on the details there is always haggling as to am I asking too much? Is it unreasonable to have that much for travel? and so on and so on; in finer details there is quite a lot of back and forth. When funding got tough in general, certainly we were cut too. As far as fear of it drying up completely is concerned, I would be somewhat surprised. There's some security in having a fairly large outfit. I should have made it clear, it's not my grant; it's really at the moment a grant for all of theoretical astrophysics at Cornell, not counting planetary stuff.

Weart:

It's over a hundred thousand dollars, so clearly it supports a number of students.

Salpeter:

That's right, but also it supports all the theoretical astrophysics faculty. So there's some security. Even if I should suddenly become senile or have a fight with people at the NSF or something, you know, it's not just me, it is the Cornell theoretical astrophysics school.

Weart:

Right. Is it given in effect as block grant? Is there any discussion, give and take, as to what work should be included under this grant?

Salpeter:

There might have been; I've been fairly lucky. In fact, I would say I have been quite lucky, and I've really had rather little on that level. As I say, I expect to and do get quite a bit of flak from the NSF on the detailed budget. Both they and I feel that's very reasonable; it's their money, they ought to have a say in what fraction you spend on travel versus computing money, etc. But no on what kind of subjects you work on. And partly, I suppose, since I feel fairly strongly about that, some of that must have rubbed off. In fact, I've never had any queries back. The preamble to every one of my proposals for this thing makes a big point of saying, "The mainstay of Cornell theoretical astrophysics is the versatility, the pragmatism, working on borderline areas, applying theory to very new things elsewhere; you cannot predict, you can't be programmatic, etc." I make a big spiel, you know, the kind of spiel one has to give Congress every now and again, I always put in at the beginning. And I mean it. That is an important characteristic of what we do here.

And not only me, all of us. Tommy (Gold) also loves working in lots and lots of different areas — I'm not saying his scientific temperament and mine are the same, but on this level they certainly are. It's clear that all of us like working on any area in theoretical astrophysics. So we would be pretty unhappy if somebody told us, "No, you just work on this particular line." But we've never had even any queries on that.

Weart:

Aside from the funding have you noticed either as a grantee or referee or on panels or anything, any evolution in the way NSF gives funds?

Salpeter:

I have not been on any NSF panels.

Weart:

Or as a referee?

Salpeter:

Even as a referee, I can't really tell how it's being used. In particular, I don't really have a good knowledge of how they select which proposals they send to a particular individual. They clearly don't do it at random. I don't quite understand for what sociological reason, but for some reason or another they usually don't send me crackpot or borderline things. I get those where it's almost sure that they're excellent. I'm not saying that I feel they just collect my letters without looking at them; clearly there are finer cues. They may also be interested in whether a guy looks as though he is overextending himself, or is too modest, or whatever, so I presume they get something out of my letters, even though they are usually about people who are so good that obviously they'll get funded one way or another. It's very seldom that I'll get something where it's quite likely that the guy will be turned down.

Weart:

In any case, this sort of relationship doesn't seem to have changed much over the last 10 or 15 years?

Salpeter:

What I'm really saying is, I can't tell. I just don't have the statistics. I neither know how what I get sent is selected, nor do I really see what the outcome was, and certainly not what my input did to the outcome, so I'm absolutely completely unable to judge. I have no feeling about the administrative sociology of the NSF. I haven't been on panels much. It's interesting that although my funding is from the NSF and I have rapport with the NSF, I know more about NASA.* Even though I disagree with them pretty strongly on most things more than with the NSF. Because for NASA I have been on more panels. (* National Aeronautics and Space Administration)

Weart:

We should talk about NASA briefly, but first I want to ask you a few questions about your teaching. On one of your Who's Who things you put yourself down as an educator, or they put you down.

Salpeter:

They put me down as an educator. I wouldn't have used the word.

Weart:

Were there any formal courses you taught that you think had particular importance to the department?

Salpeter:

Important to the department?

Weart:

In terms of the development of the curriculum.

Salpeter:

No, I don't think so. Let me be a bit more specific. We have mainly two types of courses, if you're talking about graduate courses. Let me talk separately about graduate and undergraduate courses; most of my teaching has been graduate teaching. On that, there are two types: the bread and butter courses, meaning the things that the first and second year students take almost irrespective of their area; and then, the really more advanced kinds of things. Now, the more advanced kinds of things are clearly just whatever whoever is giving the course has been doing the last few years and is interested in.

Of course that's important to the few students who take the advanced courses. But that's not developing any curriculum. That's just an extension of your interaction with your own graduates. It's a slightly bigger group, but it's only an extension of that, and after all, your interaction with your graduate students is not like university teaching. It's like the apprenticeship system that the trades had in the Middle Ages. That's really the way to describe your relationship with your graduate students. So I don't call the seminar type of advanced course developing a curriculum. And then the bread and butter courses really haven't changed that much. Each of us teaches it slightly differently, but I don't think I've had an influence on the way a course will be taught the year after I drop it.

Weart:

Tell me about your graduate students, then. You have several at one time? Graduate students and post-docs.

Salpeter:

Yes, although quite often it's also not 100 percent clear whose student, especially whose post-doc, an individual is. I have several at a time, but each of them might consider that they have more than one boss. In some cases it will be clear that I'm their one and only boss. In other cases there may be two or even three professors for someone.

Weart:

Are there some particular students or post-docs we should talk a about, that have been through here?

Salpeter:

Well, I gave you the list —

Weart:

Maybe it's enough that I have the list, rather than to try and talk about —

Salpeter:

You might be interested in some kinds of statistics about them. I think I mentioned one statistic already, that a surprisingly large fraction, I don't mean fifty percent but more than ten percent of them have gone into plasma theory, even though I consider myself not at all a professional plasma theorist. There must be some interesting piece of scientific sociology — that I've never quite understood — on this point, why. I can tell you where most of them are and what they've done and how many of them I've kept contact with and so on. My guess is, you probably would be more interested in the overall statistics. It's not as though, you know, two of them won the Nobel Prize and the rest ended up in jail. There's no dichotomy like that

Weart:

Looking at them as a group, have most of them gone into the academic world?

Salpeter:

I would say more have gone into the academic world than into other things. A few have ended up in government research labs and very few in industry.

Weart:

Have they all stayed in research?

Salpeter:

Well, let me go through the list. Some of them I've even lost contact with. Let's say, on the first page, one ended up in one of the AEC sort of development establishments rather than research. On the next page all of them are academic.

Weart:

I guess what I really want to ask in, have any of them or many of them had severe job problems? We've heard a lot about the job crisis and so forth. Have any of your students run into difficulties?

Salpeter:

Frankly, no. I would say, maybe less than one in five have left the academic world, if you include Los Alamos as the academic world; one or two are at places like that. One is at Atomic Energy of Canada. But of course, the financial crunch is only say six or seven years old, and they will reverberate around the post-docs for a while, so it's a bit early to say how it will all turn out. But on the whole, it is surprising how large a fraction of them have remained in the academic world. I guess it's probably because of that I'm surprised, on the other hand, that a number of them have not stayed in astronomy.

Weart:

If you compare the students now in the 1970's with the students when you first came here in the fifties, or even back in Peierls' group (of course it's a different field) and their attitudes towards work and particularly towards astronomy, have you noted changes?

Salpeter:

I can't really think of much. I told you already that those early postwar years graduates who were veterans clearly were different. That's a very different kind of thing. Apart from that, if you use as your base of how things change, the changing attitude of undergraduates at universities from the early postwar years, when there was a complete political apathy (on a level which to somebody like me coming from Britain or Australia was just horrifying and which would obviously lead to disaster, and that's how the McCarthy era came about in the eyes of an Englishman or Australian like me), compare that with the student involvement and relevance, etc., in the sixties, and now back again, the trend to a strong student apathy — if you start with that kind of baseline of change, compared to that I cannot tell any difference at all in the attitude of graduate students. Not to say it isn't there, but it's such a subtle thing compared to these very strong changes in what is after all the bigger backdrop, the university student population as a whole. I am always surprised how invariant the graduate student attitudes and even abilities are.

Weart:

Have you been concerned with the public's attitude towards astronomy?

Salpeter:

A little but not very much. I mean, I don't have much involvement with really public public speaking. Or if I do, it's usually only to people who are already interested anyway. So no, I haven't tried to lobby to Congressmen from Timbuktu, so it's not really something I have any good feeling on. Let's see, I don't know whether you wanted to come back to undergraduate teaching?

Weart:

Well, is there something about that we should get back to?

Salpeter:

Not really much. Merely that it's interesting that, if anything, I've gotten more involved with undergraduate teaching as I got older, rather than less. Usually universities are accused that all the heavy undergraduate teaching is forced on the youngsters and the big shots don't do any. I claim that is not true.

Weart:

Why have you gotten more interested?

Salpeter:

I must admit, maybe it is just because universities are accused of the big shots pushing all the undergraduate teaching on the youngsters. maybe I'm just being aware of that accusation and volunteered to do some undergraduate teaching.

Weart:

I see, not that you're particularly drawn to that as opposed to graduate teaching or whatever.

Salpeter:

No. It's not that big an involvement. But nevertheless, proud of the fact that I teach "Physics for Poets" kind of stuff.

Weart:

I see. Well, to get back then to NASA — but first you were on PSAC?* (*President's Science Advisory Committee)

Salpeter:

Yes, but it was only the Space Science Panel of PSAC, so in a way that really was overseeing NASA.

Weart:

Right. And then you were on the NASA Astronomy Missions Board?

Salpeter:

I'm now on the Physical Sciences Committee of NASA, or at least I was: President Carter ordered all committees disbanded at least temporarily, so we've been "defrocked" for the time being.

Weart:

It's interesting to know how these boards worked and I don't know much about it — do you know how you were chosen?

Salpeter:

No, I certainly don't know how I'm chosen. But also I should say that any views I express about NASA are not likely to be really useful, because I'm prejudiced against NASA, I have a particularly jaundiced view. I misrepresent.

Weart:

OK. I would be interested at any rate in hearing what your particular view is.

Salpeter:

Well, my view at least of the NASA boards and committees I've been in contact with is that they are mainly a snow job. I mean, that they mainly use scientists on their committees to help them justify decisions they have already made. I clearly exaggerate; it's just that it's something I consider so repugnant, it gets me so annoyed, that I over-react.

Weart:

Do you think you're alone in your view?

Salpeter:

Maybe I'm not alone in my view, but I guess I'm almost alone in speaking out strongly. Because for some reason, I've never bothered getting NASA funding myself.

Weart:

— Tommy Gold has —

Salpeter:

— sure, there are some people who are even more courageous, because Tommy did have NASA grants, and he kicked up a big fuss. But Tommy is particularly rare. I'm not a fighter, I'm not normally courageous. But neither are most people. Tommy's braveness is the exception; my cowardice is not an exception, but more the rule.

Weart:

Maybe more than you think there are people around share your views.

Salpeter:

That's right. It is my hunch that probably more people are around that share my views. On the other hand, I told you that I think my views are prejudiced and even slightly incorrect. The reason I say that is that in spite of all my ranting and raving about NASA, it is still amazing how much good science has come out of NASA. In particular, the thing that always makes me feel worst about my attacks on NASA is that if you compare how much American space science has achieved with how little the Russians have — it gives you food for thought. On some levels, we're always fond of saying, "Look how much more sensible the Russians are organized; the equivalent they have to the head of NASA is Sagdeev, who is a real scientist— what a change from all these politicians over here," etc. And then you look and see: they spend about as much money as we do, and don't produce 10 percent of what we do in real science.

Weart:

Tell me more about how these boards function. A meeting is scheduled, you go down to Washington, and what?

Salpeter:

I'm sure it really varies enormously, depending on the committee, and also the year and who was in charge. This new one, this Physical Sciences Committee, I've only had one meeting in.

Weart:

Well, let's talk about PSAC, the Space Sciences Board, and the Astronomy Missions Board.

Salpeter:

PSAC was rather different. That was helping PSAC evaluate things, so that again was like a referee.

Weart:

Tell me about that. How did that function? What were the main decisions or arguments that went on?

Salpeter:

It varied. It really went over the whole program of NASA. I mean, some things, quite detailed things, of are they really right in the particular payload they're selecting? And there were others like, are they right in the method they're using? Like the question I just raised, is it true that they're using their committees wrongly by just using them for whitewash? It ranged all the way from broad social questions to detailed payloads to can one make an evaluation as to how much emphasis one should give on medical science in space compared to the physical sciences? It really was a very broad thing.

Weart:

Were there any persistent groupings, persistent differences of viewpoint?

Salpeter:

Between different people?

Weart:

Or even between different groups on these boards?

Salpeter:

This PSAC Space Science Panel was mainly university scientists, and they really did not represent — it's not as though half of them were university people and half were, the Defense industry, let's say, so that there was a dichotomy.

Weart:

Right, but even in terms of a certain group that would favor manned work, another group that favored unmanned, that sort of thing?

Salpeter:

Well, some minor ones. But the major ones, 90 percent of all scientists on any of these boards, of course would have favored unmanned things. But you know that's unpractical. It's the manned stuff that gets the money, etc. So there was much more of that group being academic versus either NASA management or versus reality, I'm not quite sure which. I never know about NASA's insistence on manned space flight, whether they're really right that that was the only way to get money from Congress.

Weart:

I see. The Board as a whole felt that it was not being listened to so much?

Salpeter:

No, the P.S. Advisor at least listened and also that particular board was at least more realistic. It was usually rather more mature and older people. I was probably the most naive on that board. The PSAC Space Panel was mainly fairly experienced older guys, so there was very little ranting and raving at any of the meetings.

Weart:

What about the Astronomy Missions Board? Of course, you were on that right after they started the first Apollo moon landings, so you were on it at a turning point, a critical time for NASA.

Salpeter:

Yes. That was a more lower level committee, and I felt we probably had some little bit of input. We were partly writing blurbs for clarifying things or publicity if you like. We would have some input on,say, favoring one thing over another. I would say the one thing that was very positive in the end that partly came out of that era was the Uhuru satellite — that particular board really tried to push that. NASA higher-up management hated like hell having all these tiny little satellites. They would have much preferred to be able to put 100 million bucks into one thing. Then they would be sure that Walter Cronkite would be there; whereas if they had 50 little things, they have all this business to do of monitoring it, and Walter Cronkite wouldn't be there. The higher-ups were all against something like a small Explorer-type satellite. So that was a bit of a fight.

Weart:

The board pushed that.

Salpeter:

The board pushed that. Now, luckily the scientific medium-level management of NASA in the end pushed also so that's not something we brought in over the heads of all of NASA, but at least we helped.

Weart:

You didn't have direct contact with those people, you furnished reports?

Salpeter:

With the real higher-ups? I'm trying to remember. Nancy Roman, I think, was the boss of that committee, and she was always there. People one level above her, we would only see quite quite rarely. So there we mainly worked through her. With this present Physical Sciences Board, I guess it's Ischiac Rasool and Noel Hinnes that one feeds into. But as I say, it may be a bit unfair; I was only at a single meeting. I was particularly annoyed at that one, but it's hard to say whether one single meeting is characteristic. I had the feeling even more than in earlier days that that whole committee was there just to whitewash things that were already done, or at least to help them sell things, rather than that there was any interest in having this group help in real-decision making. Maybe I'm being unfair, but at least it's a clear-cut statement.

Weart:

Well, I'm not sure what else to cover. We've covered a lot of ground. Is there anything else that we should talk about?

Salpeter:

I can't at the moment think of anything much.

Weart:

Have you had any extracurricular activities?

Salpeter:

You mean, my own personal hobbies?

Weart:

Yes. Outside interests.

Salpeter:

No, just hobbies rather than real outside interests. I mean, sports — I like skiing, tennis, swimming. I used to do hiking, and traveling, looking at ruins. I would have liked to have been an archeologist. I love to listen to opera records But I don't have some second hidden outside professional-like interest like some people do. Just hobbies. I like photography, which is connected with hiking and liking to go on sightseeing trips to out-of-the-way places.

Weart:

What do you suppose it was that has attracted you to astronomy and kept you in it. Obviously you're at a place with a lot of temptations to go off to biophysics, high-energy physics, all sorts of areas? Is there anything about astronomy particularly that attracted you, kept you?

Salpeter:

Well, it hasn't been all that long, and I am going more and more into biology. So I'm not even sure whether it's that universal. I think it's fairly clear that I got pushed away from high-energy physics; the large groups necessary is one thing that didn't appeal to me.

And somehow you need more formal theory. I sort of feel my own scientific temperament is not really very well suited for doing good work in very abstract theory. At least, the abstract theory is fairly important in it, or at least for the more interesting things it's important. While I was in it, what I was doing was mainly being clever at doing very painstaking calculations a little bit cuter than other people; or faster. But that's not really very satisfying. It's not something you feel that's very important. In that area, the really important things are the lofty, esoteric, hifalutin mathematical kinds of things, and my temperament is not well suited to that.

Whereas, I feel that in astronomy it is more simple-minded engineering types of things that are important. You know, I told you the paper I'm proudest of is one that almost has no integral calculus in it. You couldn't do that in high-energy theory; you couldn't write a paper that you're proud of without calculus. So I think it's fairly clear why I stayed away from physics.

Astronomy is a subject that keeps changing. You've noticed my span of attention is not particularly great in any one area, so I like going from thing to thing. But luckily astronomy really has been, not so much growing but changing so rapidly, over the last 20–25 years, that I've never gotten bored with it. I can keep on working in something that's quite brand new and which I'm awfully naive in, yet in some ways it's satisfying. Nevertheless, I am getting probably more and more interested in biology. I spend more time with my wife and her post-docs.

Weart:

Well, I think this is a good place to stop.

Salpeter:

Good.