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Oral History Transcript — Dr. Alistair G. W. Cameron

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Interview with Dr. Alistair G. W. Cameron
By Patrick McCray
In Tucson, Arizona
February 10, 2003

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Alastair G. W. Cameron; February 10, 2003

ABSTRACT: This interview with A. G. W. Cameron focuses on selected aspects of Cameron's research including nucleosynthesis and use of computers in research. Covers Cameron's different topics of research as well as various institutional appointments. Also comments on style of research and William Fowler's receipt of Nobel prize. Other topics discussed include: his family background and childhood, graduate work at the University of Saskatchewan, Leon Katz, photonuclear reactions, astrophysics, Paul Merrill, galactic evolution, Iowa State teaching nuclear physics, Chalk River, advising work for Atomic Energy Commission (AEC) and Department of Energy (DOE), hydrogen bomb, origin of the moon, Los Alamos National Laboratory, Stirling Colgate, nuclear astrophysics, teaching at Yale University, big bang theory, Harvard Smithsonian Center for Astrophysics, Fred Whipple, Leo Goldberg, Hans Suess, Harold Urey, William Fowler, Fred Hoyle, Geoffrey Burbidge, California Institute of Technology, National Aeronautics and Space Administration (NASA).

Transcript

McCray

A. G. W. Cameron, tape 1, Tucson, Arizona, February 10th, 2003. The standard way we usually do this is just to start with questions about your childhood, and as we talked about, some of that is covered in your autobiographical essays. A.G.W.

Cameron:

Not really very much.

McCray:

Okay. Well, would you like to tell me about parts of your childhood that strike you as particularly important?

Cameron:

Maybe a few little slightly humorous items, if that helps.

McCray:

Okay.

Cameron:

Probably it may have foretold something about curiosity, but when I was I think about five, possibly six, the family took me along when they were visiting some friends in Montreal in Canada. I was born and raised in Winnipeg. And so they left me alone in the house together with the maid who was preparing a meal for them or something like that. And now the house was on a hill such that the back door was one story lower than the front door, if you get that.

McCray:

Okay.

Cameron:

And the maid was in the kitchen, and she saw something fly by the window, and then I came into the kitchen and went to the back door and opened it and in came a cat which I grabbed and disappeared with. Well then shortly after that again something flickered past the window and I appeared and the lady was beginning to get suspicious so she said, ďYouíre not hurting the cat are you?Ē I said, ďNo, no, no.Ē So I grabbed the cat and disappeared with it again. Then the third time the flicker went by the window the maid took the cat and shut it in the basement. So when the owners of the house came home and when the maid told them about this the wife of the owner was very concerned so she consulted with my mother about it, and my mother said that she would look into the matter, so she came to see me and said, ďDid you throw the cat out the back balcony?Ē ďOh yes.Ē ďBut why did you do that? You donít usually hurt animals.Ē And I said, ďWell, Daddy told me the cats have nine lives and I was checking it out.Ē Needless to say, my father was tickled pink. He was a biochemist.

McCray:

Did you have an interest in science from a young age?

Cameron:

Yeah, very much.

McCray:

And your father was a biochemist, so did your interests tend to gravitate more towards the chemistry side of things?

Cameron:

No, not particularly. It may have been as much toward astronomy as anything else.

McCray:

Did you have a telescope or anything like that growing up?

Cameron:

Nothing like that, no.

McCray:

Okay. Chemistry sets, things like that?

Cameron:

I may have had one once, but I donít think that after trying two or three experiments I probably ever used it again.

McCray:

Okay. So when you were growing up, what do you think were important influences on you in terms of your career choice?

Cameron:

Itís a little hard to say since my father was a biochemist and chair of the biochemistry department in the University Medical College. Of course I met a lot of technical people, which would be primarily medical I assume. In fact Iím told that at that age I automatically called all men doctor.

McCray:

Right. I noticed that from your essay, ďThe Hypothesis with Limited Data.Ē

Cameron:

Oh, I see. Right.

McCray:

Yeah. I liked that.

Cameron:

So anyway, that may have very well influenced me.

McCray:

Okay.

Cameron:

And you know, with parents like that I guess I was encouraged to read about science.

McCray:

Do you remember any particular books that you read that were influential?

Cameron:

Not that far back, no.

McCray:

Okay. What was your motherís background?

Cameron:

Well, she was born and raised in Winnipeg actually. Her father as a young boy ran away from school and joined what was called the Volksney Expedition to the Canadian West. And what was happening was that in Manitoba there was a — I think it was a French Canadian, not a half-breed who had incited the Indians to sort of rebel. And so the expedition was intended to go out and suppress this, which it did. But so my grandfather on my motherís side then stayed in the Canadian West, lived with the Indians a bit, was in charge of Indian sort of groups who helped to hunt for buffalo and that kind of thing while the Canadian Pacific Railroad was being built out across the prairies toward the Pacific, things of that sort. And so eventually he wound up as president — no, itís not president, I think treasurer — of the Winnipeg Grain Exchange. So it was that kind of background that she was growing up in. Both of her brothers became medical doctors and that may have had something to do with how my father met them, met her I guess, but thatís the kind of background that she had. My father was actually born in London, England and his father was a schoolmaster in Malmesbury, which is a little town in England west of London. And so but his forbears before that go back into Scotland where a lot of them were ministers in the church.

McCray:

Okay. So your family background for at least the generation prior was a fairly educated one.

Cameron:

Yes, yes.

McCray:

Okay. When you went to the University of Manitoba to study you chose physics and math I believe.

Cameron:

Yes.

McCray:

Why physics? What was —?

Cameron:

Well, I mean actually I started out taking courses in physics, chemistry and math.

McCray:

Okay.

Cameron:

And then having done that for a while I decided I liked physics better than chemistry, and of course the math was certainly a necessary part of that.

McCray:

Okay. Do you recall the types of courses that you took? For example was quantum mechanics or things like that, were they being taught?

Cameron:

I donít remember whether we had anything significant at the undergraduate level. It may have been a little bit early for that. I mean quantum mechanics really only developed in the 1930s.

McCray:

Sure.

Cameron:

And so from what Iíve read about the development of quantum mechanics in the U.S. it sort of percolated only slowly into the universities here in the thirties.

McCray:

Yes.

Cameron:

And Iím sure it was probably even slower in Canada.

McCray:

Okay. So the types of physics courses you were taking then were more classical?

Cameron:

Standard, yeah. I mean actually I was very interested in nuclear physics. And so that governed what I was going to go into later. I remember actually — [coughs] excuse me — when in my senior year at undergraduate, I wrote an article for the university magazine on nuclear fission and reactors and things like that based on the Smythe Report which I had grabbed as soon as it came out.

McCray:

That came out what, in the fall of Ď45 I think?

Cameron:

Yes. Right. And so actually 1945 was about in the middle of my undergraduate years, so I guess it was sort of a couple of years later that I did all this. But anyway, this is an indication of where I was headed.

McCray:

Was there some particular about nuclear physics that attracted you?

Cameron:

I donít remember. Well, it was just a very interesting new subject and so on, and but whether it had any particular other connotations Iím not sure.

McCray:

Okay. So thinking back to where you were when you were a senior undergraduate about to finish school, do you recall having any particular sense of what type of career path you wanted to follow then?

Cameron:

Well, I got a summer job at the nuclear labs at Chalk River, and that was an indication I was following up that interest.

McCray:

Okay. Did World War II have any effect on you personally?

Cameron:

Well, not very directly. Canada had a basis for deferment from conscription which said that if you were in the top half of your university year you could be deferred. Now this of course diminished the number of people who were being deferred each year but not by a factor of two because of course the women were not deferred, so after a while you get mostly I guess women being deferred — I mean, not deferred but in the class which is not being conscripted. So as long as you were in the top half of that you were okay.

McCray:

Okay. It changes the social dynamics some I imagine too. Your graduate work was at the University of Saskatchewan. Why did you choose there?

Cameron:

Well, also when I finished my undergraduate work my father died at that time, and so I felt the need to sort of take some time out and earn enough money and so on for graduate school. And so having already spent some time at Chalk River it was natural to see if I could get a job there and I did. So I spent I think a couple of years — maybe three, Iíve forgotten — as the most junior of the scientific ranks at Chalk River.

McCray:

Okay.

Cameron:

But while there I was starting to do some research using nuclear emulsions and what we did was to initially soak some nuclear emulsions in heavy water, of which there was a lot at Chalk River. [coughs] Excuse me. And so I then did an experiment in which I took the — I went out where the effluent water from the reactor, the so-called NRX reactor at Chalk River, was flowing literally seconds after coming out of the reactor. Which meant you didnít want to spend too much time in there. And so simply put the plates down and left them there for a couple of days or so, let them get irradiated by the gammas coming from the effluent water. Now what we were interested in particular was the N-16, which was produced by energetic neutrons in the cooling water itself. And so most of the gamma rays of interest were those gamma rays which were just over 6 and 7 MeV. There were at least two main ones. And so then scanning all of those resulted in determining basically how many came out with about 6.2 and how many came out with about 7.1 I think the numbers were. And so that sort of got us interested in this kind of work. I remember Charlie Barnes at Caltech many years ago remarked on that experiment and said it was really interesting, and I was absolutely amazed that he had remembered it. But in any case, the next thing we did was to look into the possibility of desensitizing these nuclear emulsions enough to still record ? particles but not really protons anymore.

McCray:

Okay.

Cameron:

Then we went and we sent them out to the University of Saskatchewan where they had just installed a, as they called it formerly, a 22†MeV betatron, but actually it went up to 28†MeV. And so they irradiated them for us so we could what was in them. What was in them was the kind of disintegrations you get from carbon and oxygen, carbon giving three-prong stars, oxygen getting four-prong stars as they break up into ? particles, nitrogen breaking up into a more heavily ionizing short stub in an ...? And all of these we could identify, and so we published some papers on all of these. But this of course aroused my interest in the whole game of photonuclear reactions.

McCray:

Okay.

Cameron:

And it was natural when the time came to return and finish my Ph.D. program — or actually start it — to think about going there and working in the photonuclear field, which is what I did.

McCray:

Okay. Your advisor was Leon Katz.

Cameron:

Correct.

McCray:

What was he like as an advisor?

Cameron:

Extremely nice. Yeah. I mean, I was probably a hell of a nuisance. [laughs]

McCray:

Why were you a hell of a nuisance?

Cameron:

Well, I would very frequently drop around to his office and say, ďHey Leon, I just thought about this. How about this?Ē A lot of that kind of stuff. So in fact that led to a lot of the things we did, and so I was sort of I guess precocious in that kind of sense.

McCray:

The research that — I mean when you would go and propose these ideas to him, was it more theoretical or more experimental?

Cameron:

Entirely experimental.

McCray:

Okay.

Cameron:

No, I mean there really wasnít any theory going on in Saskatchewan at that time. And so basically we were real pioneers in the photonuclear work. We, Leon and I worked together to sort of manually do an inversion of the Bremsstrahlung spectrum so that we could do a stepwise determination of what the cross-sections were from what we called an activation curve would give as a function of betatron energy.

McCray:

Okay.

Cameron:

So I spent a lot of time working out photonuclear cross-section curves, determining where the giant dipole resonance peak was and particularly as a function of mass number and so on. I remember I had a paper in Phys. Rev. just dealing with that alone, in the empirical sense you know. A bunch of points. This is what it looks like, and the resonance energy comes down a bit as the mass number goes up and all that kind of stuff.

McCray:

Okay. Was that type of work fairly common for the time? These types of empirical experiments, was that sort of the standard approach to it or were more people doing theory stuff and you were doing experimental stuff? How did that work out?

Cameron:

Well, there really wasnít much to the theory. The giant dipole resonance was recognized as such, but the details of how it would vary in mass number and all that sort of thing were not known, and it doesnít vary very much, so there wasnít all that much to it. But on the other hand that wasnít known, so just determining that was pioneering work in its own right.

McCray:

Okay. Were there conferences that you would regularly go to, to present your results?

Cameron:

Yes, I guess the answer was that while I was actually getting my Ph.D. — not many.

McCray:

Okay.

Cameron:

I remember Leon and I drove out to a meeting of the — I guess it was a joint meeting of the APS and a Canadian equivalent in Vancouver and I remember presenting some stuff at that point. But mainly though being first in the field, which is basically what we were, having developed the tools to work out the cross-sections and so on meant that papers could flow almost weekly, certainly monthly.

McCray:

Okay.

Cameron:

I remember I took a certain pride in having something in every volume of the Phys. Rev. for a period there.

McCray:

Thatís an accomplishment. Okay.

Cameron:

Well, that was how easy it was.

McCray:

Okay. In terms of just being able to produce?

Cameron:

Yeah. I mean you know get something simple and publish it. And so anyway, that was a fair occupation. Then we found out that the betatron had a sufficient energy stability that if we did these activation curves very accurately we would find kinks in them — particularly for very light nuclei. And so that meant we were finding energy levels that were not known ( not very accurately, but they were there that were being excited by the dipole interactions. And so I remember those days as we pretty much mounted a 24-hour operation to really take all the necessary data because you really had to do this in very fine steps and you wanted to do it on a number of different substances. And then we were also investigating photo fission reactions and we sort of got the chemists in the next building over to help us on that in isolating all the fission products — not all of them, but enough to study what was going on. And so it was a very busy time.

McCray:

Okay. While you were doing this work were there people or research groups elsewhere that you were in contact with in terms of exchanging information?

Cameron:

In the photonuclear field you mean?

McCray:

Yes.

Cameron:

I remember at the University of Pennsylvania they had a similar betatron, but they were lagging behind us — for an interesting reason. In Philadelphia they found the winters sufficiently severe that they couldnít build their betatron building during the winter. In Saskatoon the winters are very much more severe but they learned how to build things during that kind of winter. So the betatron building was built there before the one in Philadelphia just for that simple reason.

McCray:

Thatís interesting, because that normally wouldnít occur to somebody to understand that.

Cameron:

Yeah. But anyway, that meant that — I think we had much more pioneering success than the folks in Philadelphia. That may have been a distortion of my memory. Itís something that some historian of science might want to check up on as to see how we did compare to them for example. But that was basically the other main group that was involved. And then of course when I finished, I think when I defended my Ph.D. I had about seventeen publications.

McCray:

Thatís a good number. Yeah. What year did you finish, Ď52?

Cameron:

Ď52, yes. Yeah. And so this meant that I didnít go looking for a job; it came looking for me, in the form of an offer from an out-of-state college. So they were in the process of getting a 70†MeV synchrotron, and I thought well thatís the next logical step to go there and do that. And I did, but when I got there what I found was that they had only a very weak beam current and practically all of their effort was an engineering one aimed at trying to improve that beam current.

McCray:

Okay.

Cameron:

Which didnít really interest me.

McCray:

All right. So that was more of an engineering problem.

Cameron:

Yes, right. And so I had a bit of time hanging on my hands so as part of that I was browsing one day (youíll probably find this in the record somewhere — in the reading room of the Ames Lab there in Ames, Iowa at Iowa State College as it was still then called. And I saw this issue of Science Newsletter and the article about Paul Merrill from Lick Observatory[1] who had discovered lines of technetium in giant stars of class S. So my immediate reaction was, ďWell where in the hell did they get all those neutrons?Ē and that was what launched me into astrophysics, just reading that.

McCray:

Prior to reading that, had you been following any developments in astrophysics?

Cameron:

No. In fact, I had never had an opportunity to take a course in astronomy except at the University of Manitoba, and we were getting into of course World War II at that point. So we had a course in so-called astronomy which I took, but it turned out to be practically nothing but celestial mechanics.

McCray:

Okay. So very classical.

Cameron:

Spherical trigonometry basically. It was just supposed to prepare you for being a navigator or something.

McCray:

Okay. Not really cutting edge sort of stuff.

Cameron:

No. Not really the interesting kind of astronomy. Of course there wasnít too much of the so-called interesting kind of astronomy at that point. Astronomy was all very classical and so physicists had not wandered into the field in any significant number at that point.

McCray:

Okay. Let me just check the tape. Iím going to flip this over really quick.

McCray:

Okay. Iím curious about your move into astrophysics, and I have a couple questions, but the first one is, when you read this paper by Paul Merrill on the presence of technetium in S-type stars and you became interested in astrophysics, what did you see yourself as a scientist bringing to the field of astrophysics? What tools?

Cameron:

I didnít think in those terms. That sort of implies, ďOkay, Iím planning a strategy, a lifetime careerĒ or something. I wasnít. I just wanted to find out how the hell it had gotten the neutrons.

McCray:

So more curiosity was —?

Cameron:

Yeah. And so you know, because clearly there was some nuclear physics going on in that star. The only logical isotope of technetium had only about a 200,000 per year half-life. There was another that has a little over 2 million years, but that couldnít be formed by neutrons. So the issue was clearly the excess heavy elements that showed up on the spectrum of the star were made very recently, and it had to be something going on in that kind of star that would do it.

McCray:

Okay.

Cameron:

I mean that was clearly something very interesting and totally new. So this in fact led — you know, I bought a lot of astronomy and astrophysics books, subscribed to the Astrophysical Journal and started learning how to do calculations and involving thermonuclear reactions and things of that sort. And so when I published the first paper on all of this and submitted it to the Astrophysical Journal — and I didnít find out all of these facts until relatively quite recently — but Chandrasekhar, who was the editor at that time, sent it to a couple of astronomers to review and the reviews came back recommending rejection because, ďThis is obvious nonsense.Ē All this is described by the way in Fred Hoyleís autobiography called Home is Where the Wind Blows.

McCray:

My wife is reading that book right now.

Cameron:

Okay. Tell her to show you the stuff about me.

McCray:

Okay.

Cameron:

So anyway, Chandra wasnít really sure about these reviews. Apparently they were classical astronomers. So he sent it to Fred Hoyle to review. And now Fred, as it happened, was trying to understand the formation of the elements. And he had written already some stuff about this around 1950 published in Monthly Notices, and he desperately wanted to find a source of neutrons. So naturally he was sort of excited to get this paper to review. And so he recommended acceptance, and so that was how my first astrophysical paper got to be published. But it does say something about the insularity of the astronomical community in those days. And I found that when I started going to as many of the Astronomical Society meetings as I could as part of the process of educating myself about astronomy. And more recently I realized it again — because I was looking back into some of Paul Merrillís papers particularly, and a paper from Paul Merrill in those days was something like, ďI looked at such and such a star and it had strong lines of this element and weak lines of that elementĒ and so on along that line for a little bit, relatively short paper, and that was it.

McCray:

Very empirical.

Cameron:

No analysis. No analysis quantitatively about abundances or anything of that sort. That was astronomy in those days, and that was why physicists made quite a difference to it when they started coming into the field in greater numbers.

McCray:

Can you say more about how you taught yourself astrophysics? You mentioned about buying some books and subscribing to Ap. J.[2] and things like that. Can you say more about the process of doing this?

Cameron:

Just reading.

McCray:

Just reading?

Cameron:

Yeah.

McCray:

Okay. Were there people at — or I guess you were at Iowa at this point.

Cameron:

Yeah.

McCray:

Were there people there that you could go and talk to?

Cameron:

None.

McCray:

All by yourself.

Cameron:

All by myself.

McCray:

Okay.

Cameron:

Not even any courses in astronomy there.

McCray:

So there wasnít introduction astrophysics that you could —?

Cameron:

No, no. It was all physics. And I had the background to learn new fields of physics, so I did.

McCray:

Okay. Were there any people outside of Iowa in the astronomy community that you wanted to talk to or that you were able to talk to, to get either on a friendly basis or just to get information?

Cameron:

None.

McCray:

Okay. Iím trying to get a sense of how you understood what the important problems were in astrophysics at that time. How did you —?

Cameron:

Reading every issues of the Astrophysical Journal. Not cover-to-cover, but at least looking at the abstracts of everything.

McCray:

Okay. Which is something you couldnít really do today.

Cameron:

You sure couldnít.

McCray:

Youíd need a lot of time to do that.

Cameron:

Yeah. But it was an exciting time in astronomy actually because Walter Baade just around that time was investigating different classes of stars, finding out which the older ones were —

McCray:

The population work.

Cameron:

And discovering that the abundances of the elements qualitatively but still enough to determine. Abundances were increasing in the stars, going from the oldest stars to the younger ones, and so the whole idea of galactic evolution was arising at that time as a result of his research.

McCray:

Okay. Had you gone back at this point and read papers by Hans Bethe and people like that from the late Ď30s about the different processes for forming elements?

Cameron:

Well, I did that pretty early, yeah.

McCray:

Okay. Were you in contact with any of those people?

Cameron:

No.

McCray:

Okay.

Cameron:

No, this was a do-it-yourself project.

McCray:

Yeah. It sounds like you were pretty much flying solo.

Cameron:

Well, you know, thatís I think important in my career for the reason that you donít just get told something; you have to find it out for yourself, so you learn it better. And I think this is true in any field of physics, that the stuff you have to learn yourself you learn better, and then when you get to the point of teaching it you learn still better. But it helps you to learn it to begin with by yourself.

McCray:

Were you doing any teaching at Iowa at this time?

Cameron:

Yes.

McCray:

What types of classes were you teaching?

Cameron:

Nuclear physics.

McCray:

Nuclear physics. Okay.

Cameron:

I mean I was supposed to be the expert on that. [laughs] It was a relatively new field back in those days even, just immediately post-war.

McCray:

Iím trying to get a sense of the things that you would emphasize. And obviously at this time atomic bombs had been developed and there was an interest in developing nuclear reactors and things like that.

Cameron:

So weíd talk about all those things.

McCray:

Okay. So would you teach it from an applications point of view or would you start with theory first and then the applications? How would you go about doing it?

Cameron:

Basically you have to teach it as theory because you know the classical nuclear physics course starts out by saying, ďOkay, letís look at two-body reactions.Ē So we had to go through that and gradually work up to the rest.

McCray:

Okay. And when you were teaching it, did you get a sense of why your students were taking it? I mean, what about nuclear physics did they want to learn about? Why were they taking the course?

Cameron:

Well, it was a graduate course, and so it was one of those things. I mean nuclear physics was hot stuff in those days, and so actually there were usually two or three faculty members who would be sitting in as well. They probably wanted to get some idea of what all this is about. As you got into World War II, nuclear physics was so new that virtually the existing class of physicists knew nothing about it and had to learn — particularly those who would get involved with the Manhattan Project. Although of course for the Manhattan Project they recruited pretty much everybody who had any acquaintance with the subject.

McCray:

Yeah. If you knew something you got snapped up.

Cameron:

Yeah.

McCray:

Okay. That makes me think of another question. At this time there was work being done at Los Alamos and some of the national labs were developing — Livermore hadnít come online at this point, but did you ever have any inclination to get into the weapons side of nuclear work?

Cameron:

Well, not from the Canadian side, no. I mean Canada has never done any work on the nuclear weapons. The closest I got to this came after I — you see, having — Let me go to the next step in my career which should explain that. Having developed all this while I was at Iowa State, I then felt the need to go somewhere where there was a lot of nuclear physics going on because I needed to learn more about the nuclear physics side of things in order to do research and I needed to know about the astrophysical side of things. I has pretty much absorbed what was known on the astrophysical side, but nuclear physics was still in a state of very rapid development, so I applied to go back to Chalk River and do that, and indeed as things developed when I got there it became obvious that, in order to try to calculate things having to do with nuclear astrophysics, most of the numbers you needed were not available experimentally, wouldnít be anytime soon, therefore you had to take a theoretical approach to understanding and predicting what they would be. And that led to my interest in developing, that is improving nuclear mass formulas — or atomic mass formulas as they were actually called — and then based on those level density formulas, radiation width formulas, all semi-empirical because you took as much data as was known and tried to fit it with things which had at least a basic theoretical basis. And so that wound up with a lot of techniques that actually proved quite useful elsewhere in nuclear physics, and so a lot of people adopted for example the nuclear level density procedures that I had developed and things of that sort. But that at least allowed me to do calculations of a lot of things, particularly including neutron capture cross-sections, energies around 10†kilovolts and 25†kilovolts, that kind of stuff. 10 kilovolts is what you want for a red giant star, 25†kilovolts is what youíve got experimentally, which is close enough usually, at least if you are dealing with nuclei with large enough level densities that you felt that you were averaging over them decently, experimentally.

McCray:

Okay.

Cameron:

And so that led to an interesting episode. 1952 we had the beginning of thermonuclear experiments in the U.S., starting with the MIKE shot.

McCray:

Sure.

Cameron:

And MIKE was of course a major, major thing. And for a long time people were trying to get the data on one of the new isotopes and elements and things like fermium and so on, which had been discovered as a result of the MIKE shot, declassified. And eventually there was enough declassified so that I found papers in Phys. Rev. which would say, ďWell, we have these yields for a certain element and further down these yields for another element, and in between there is this yield which we have interpolated.Ē Well, how the hell did they interpolate it? There is only one logical way in which you could interpolate that. So I put together that data and thereby reproduced the upper half of the MIKE yield curve. And then given that, I could calculate the cross-sections which would have produced that in uranium-238 and its successive neutron capture, fall-ons, multiple capture, and so I wrote a paper which is in — Iíve forgotten where it is. I can find out. Anyways, the title is something like ďThe MIKE Fusion ExperimentĒ or something like that.

McCray:

Okay. We can look that up.

Cameron:

Yeah. But I was at Chalk River and there was a tripartite agreement between the UK, U.S. and Canada on declassification, and that board would meet from time to time. So the Canadians on their part sent this paper down I guess probably into the U.S. this would be done, and they were quite disturbed by this.

McCray:

Okay. How did you find out they were disturbed?

Cameron:

I heard that the paper was running into some problems which I didnít understand at the time, and after a significant delay it was returned and publication was okay, but I suddenly found that a lot of the people at Los Alamos had some interest in me. I remember going to a Washington meeting of the APS and George Bell, who was the head of theoretical division at that time for some reason I donít remember what, but he drove me somewhere in Washington, something to something. I donít recall that exactly. But at any rate, his message was, with regard to the work I had been doing that led to this paper, ďThink, Al, think.Ē It was quite clear that he wanted as much push from the outside as he could get on getting things declassified.

McCray:

Okay.

Cameron:

And obviously that paper had helped a great deal. I later figured out exactly what it was they were concerned with in that paper.

McCray:

Which was?

Cameron:

I concluded that in the MIKE device, there had been a very significant amount of compression. They were very sensitive in those days to that, because that was the difference between the early ideas about the so-called super and the ideas that Teller was involved with in eventually changing the direction of that research. And all this is in Tellerís recent biographical book. And it was that that made me realize exactly why they were sensitive. The original super ideas were just you immerse a tank of heavy water or something — or maybe liquid deuterium — in just a gamma-ray bath and heat it up that way, and they were having a lot of trouble with that.

McCray:

Right. In terms of getting it to ignite.

Cameron:

Exactly. When they started thinking about actually compressing then things of course you made a lot more easily — because you can get your heat not only by immersing it in the bath but by compression.

McCray:

I see.

Cameron:

So it was that offhand remark — which is just a conclusion from the cross-sections and the yields which led to the neutron fluents, putting together with some reasonable estimate for how long it would take for such an assembly to disassemble, and therefore a timescale. Then you say, ďOkay, I can estimate what the neutron number density is from the fluents.Ē And that neutron number density was sufficiently high that you couldnít get it by doing anything except compressing. And I assume that the tripartite declassification committee must have concluded that, well, since all of this is deducible easily from the literature, they either probably do more harm to say you canít publish this than to say you can.

McCray:

Right. Okay. Can you give me a sense of what your political views were at this time, and specifically what views you had about the development of things like the hydrogen bomb, given what you knew as a scientist?

Cameron:

Well, I wasnít sort of overcome with horror at the whole idea. I found it scientifically very interesting. And so I have never felt the need to refuse to do anything at all related to nuclear weapons for moral reasons, and I think that attitude has been justified by the fact that we had a long period of mutually assured destruction as a result of having these weapons and the world is probably much better off now for having, in fact, had that stalemate in which breaking it would have been catastrophic for everybody than would have been the case where you had a third world war in the meantime.

McCray:

All right.

Cameron:

So that was my attitude there. I wasnít horrified, and in fact Iíve been involved in advisory capacities to the AEC and DOE since then, but my answer has always been a lot of this is interesting.

McCray:

Okay. I donít want to spend too much time on this particular topic, but could you give me a sense of when you were most active in these advisory roles? What time frame are we talking about?

Cameron:

Well, there are two periods. One was — letís see, I was naturalized in 1955 and that could be accomplished after three years of residency because I was married to an American citizen.

McCray:

When did you get married?

Cameron:

I was married in 1955. Okay, that had to be 1958 then.

McCray:

Okay.

Cameron:

Iím still not sure of the timing. But any rate, it was around that period of time. And as soon as I — and by the way, you asked my political views with regard to the nuclear weapons and so on. My political views with regard to the Canadian government were that I was impatient with the rate at which the Canadian government was investing in science. Now I remember the sequence of years.

McCray:

Okay.

Cameron:

I officially immigrated to the U.S. in 1959, and I had married in 1955. That was the sequence. So three years later than that. And I was thoroughly disgusted with the Canadian political situation because the prime minister at that time was a fellow named Diefenbaker and he made big electoral promises about developing the north and that sort of thing which I thought well gee, thatís in the right direction. Then of course he became prime minister, did nothing for science whatever or developing the north or anything else, so I was just thoroughly disgusted. And meanwhile the space age had begun and the Canadian National Research Council formed a committee to decide what Canadian involvement in that subject should be and I served on that and the outcome of the Canadian deliberations as it were, ďWell, maybe we can afford to throw a few rockets up into the stratosphere.Ē

McCray:

Okay. Not very ambitious then.

Cameron:

Totally unambitious when you compare the scale of the U.S. effort which was developing in the meanwhile. And so that led to complete disgust with the Canadian scientific scene and meant that as soon as I was eligible for U.S. citizenship I wanted it. But at the same time as soon as I had it the U.S. Atomic Energy Commission started to do clearance proceedings, because they wanted — because meanwhile Project Plowshare was coming along and a lot of the underground shots having to do with trying to make very heavy elements were being planned and done and so they wanted my advice with regard to the neutron capture aspects of things.

McCray:

Okay, so one of the times then that you were active was in the late fifties, early —?

Cameron:

Well, these are sixties of course by then. And then of course significantly later basically in the eighties I became involved with people at Los Alamos doing simulations on the origin of the Moon by the giant impact hypothesis. And so we were using Los Alamos facilities for that, the Cray XMPs at Los Alamos, to get some of those simulations done — because there was a Swiss postdoc, Willy Benz, at Los Alamos at the time, and I had tried to do simulations of the giant impact using very primitive PCs, and in 1984 I think it was there was the Kona Conference in Hawaii about the origin of the Moon, and thatís where all this stuff having to do with the giant impact came out. And so my simulations were sort of part of that whole discussion and very relevant to that even though they were very crude. And just about three months or so after that I gave a talk about it at Los Alamos, and that was when two things happened. I had said, ďOkay, this is something that really needs supercomputer simulations.Ē So whatís-his-name — I have terrible trouble remembering names these days, part of the aging business. Wayne Slattery was a former graduate student of mine.

McCray:

Tape 2.

Cameron:

Wayne was a postdoc, as I recall now. But he wound up — [unintelligible phrase]...

McCray:

Yeah. Just being careful.

Cameron:

Right. So Wayne wound up in the X-Division for weapons at Los Alamos, and he therefore had access to large amounts of Cray XMP time. Willy Benz on the other hand was a Swiss postdoc who was being supported but of course had to work entirely outside the fence at Los Alamos, but he was developing the smooth particle hydrodynamics methods (SPH).

McCray:

Iím sorry?

Cameron:

He was developing SPH, smooth particle hydrodynamics.

McCray:

Okay.

Cameron:

Which was of considerable interest to a lot of people there. But he was only able to use the Cray XMP in the theory division, theoretical division, and couldnít get very much time on it. But anyway after my lecture he came around and said, ďYou know, I wonder if the simulations you are talking about might be done with some of the weapons codes on the XMP in the N-Division.Ē I said, ďWell, it sounds like an interesting idea.Ē And then a little bit later Willy Benz came around and said, ďThis might be the sort of thing RSPH [?] would work very well.

McCray:

Okay.

Cameron:

And so I said, ďYes, let me introduce you to Wayne Slattery.Ē And so the combination of Willyís code, Wayneís participation and access to X-Division computers and so on got us enough time so we could do lots of simulations, which is what led to the first papers on the subject.

McCray:

Did Willyís codes have any applicability to the work going on in the X-Division?

Cameron:

Yes.

McCray:

Okay. Let me put this in context. I was interviewing somebody recently and we were talking about Stirling Colgateís work and how part of the time he was doing classified work on I guess blast wave propagations and then other parts of the week he would then take that and work on the supernovae work because there was an analog between that. And that struck me as really interesting. Iím trying to get a sense of how common that was for a person to have a foot on both sides of the fence in other words, where what they knew could play in either world.

Cameron:

Not very common. I mean actually have you any plans to interview Stirling?

McCray:

I hope to, yeah.

Cameron:

Okay, but you should certainly do that. I mean heís had a fascinating career.

McCray:

Yeah. Heís on our list too.

Cameron:

But yes, I mean — I mean Stirling is your ideal theoretical astrophysicist, your ideal plasma physicist, your ideal hydrodynamics physicist, all of those put together, and I mean it represents just a marriage of what you need to do on the weapons side and what you can apply using just basic physics principles on a whole bunch of other subjects.

McCray:

Okay. Did you find yourself in that situation often where what you were working on on the civilian side carried over directly and could work in the other, on the other side of the fence?

Cameron:

Well, not really, because I wasnít really working on the classified side. I was just giving advice where I thought it might be helpful. Because I served on the so-called TDAC, the theoretical division advisory committee, for a number of years after all that. And so I saw a lot of both sides, and I made some probably minor contributions to things that were going on in X-Division, but basically it was just that kind of consultation type arrangement. I certainly didnít get anything out of the classified work which I directly applied to what I was doing elsewhere, except maybe some idea of how people did things and things that I would need to read up on.

McCray:

Okay. Other than Stirling Colgate, who are examples of other people who divided their time that way? I find that an interesting idea I guess and Iíd like to follow up on it.

Cameron:

No particular person I know well enough to know how exactly they divided their time. Thereís a question you should ask Stirling. He always likes to talk about Marshall Rosenbluth and people like that who have done a lot on both sides of the coin. Also — whatís the guyís name who used to be at IBM and —?

McCray:

[Richard] Garwin?

Cameron:

Garwin, yes. Certainly another example of that. And if you havenít got those guys on your list, they should be.

McCray:

Garwinís been checked off, so yeah, it was a good interview. Interesting person to talk to.

Cameron:

Good.

McCray:

Iíd like to go back I guess to the late 1950s. I have a question — I guess maybe itís not specifically the 1950s, but Iím curious about your manner of working, because preparing for this interview was difficult because you havenít followed a very linear trajectory in terms of your research topics. So I guess Iím curious about your tendency to switch topics, so Iíd like to talk about that a little bit.

Cameron:

Well, I donít really view it in that sense really.

McCray:

Okay.

Cameron:

I mean, when I really started doing nuclear astrophysics at Chalk River my ideas were simple: start with some hydrogen gas, heat and compress it and see what happens. Okay, so you get hydrogen burning reactions and wind up with a lot of helium. Okay, heat it and compress it.

McCray:

And see what happens.

Cameron:

And see what happens. And so I mean it was that philosophy which led me through the series of nuclear burning stages. As you get toward nuclear statistical equilibrium. And it was in order to be able to do all that that I needed to develop the kind of nuclear tools that I told you about — calculating cross-sections and rates and things.

McCray:

One of the phrases from your essay stuck out in my mind — actually two of them. When you were working on chemical evolution of the galaxy — I mean you are describing it in this essay — you talk about how you wanted to describe the universe, quote, ďthrough the eyes of a physicist.Ē

Cameron:

Yeah.

McCray:

What does that mean?

Cameron:

That meant in terms of — Well, this is in connection with the course I gave at Yale. I donít know if you made that connection.

McCray:

No, I didnít.

Cameron:

Okay. I mean, this is later when I had moved from Chalk River down to Goddard Institute for Space Studies [(GISS)]. And so one of the first things that happened there was that one of the purposes of the Institute for Space Studies was to bring to New York City and its collection of nearby universities a center of activity which would interest people in physics and other areas in being involved in the space program, particularly from the theoretical side of things. So it wasnít long before Vernon Hughes, who was chair of the physics department at Yale, came down and asked if I would be interested in taking on some of the graduate students in physics who had expressed an interest in doing astrophysics — you know, could I lecture on the subject on an occasional basis there. So I said yes, and this in fact led to in particular having the three main people who were involved in the first three years of that, which were Jim Truran at Illinois — well now actually at the University of Chicago, but spent a lot of years at the University of Illinois; Dave Arnett, who is now here at this university; and Carl Henson, who spent his career at JILA. And so I gave a course to them coming sort of every couple of weeks, spending a day, lecturing for a couple of hours and having it tape recorded, and then I would take the tape recording back and have it transcribed and they would write it up.

McCray:

Okay.

Cameron:

I can show you while you are here if you want some of the write-ups that resulted from all of that.

McCray:

Yeah, Iíd like to see that.

Cameron:

And so basically my philosophy in giving the series of lectures I did during those three years was the first year I did it on nuclear astrophysics specifically, because that was what they were going to be looking to do their theses on. Then I decided all right, over the next two years I want to look at the universe as a physicist would see it — meaning not that you are tied to certain methods of observation or experiment, but rather what is the physics of everything that goes on from all the way that way to all the way that way; in other words, everything geophysical as well as astrophysical. And thatís what I meant by seeing things through the eyes of a physicist. And in order to do that I had to learn a hell of a lot myself, which was very, very helpful in my later career, just having to do that. And so I was going through the Landau-Lifshitz books in a major way. Of course excerpting this and that, but that was sort of the basis of most of the physics that wound up in those lecture notes. So basically the combination of astrophysics and geophysics that emerged from that was very, very useful in tying the astrophysics to the planetary physics and the origin of the solar system and all those other things that I have dabbled in. So it may have looked like a nonlinear career to you, but in fact itís linear when you take this particular step in there.

McCray:

Okay. And of course if itís linear to you or it makes sense to you thatís really all that matters.

Cameron:

Well, I mean it should hopefully make sense to others as well when you see these details.

McCray:

Okay. Well, can you say more about the approach you took to try to unite geophysics and astrophysics? Was there a particular place that you would start and then go from there?

Cameron:

Well, itís mostly a matter of looking at the basic physics you know. You do hydrodynamics. Well, where do you find hydrodynamics? You find it in stars that do things quickly, like explode; you have hydrodynamics in the oceans; you have hydrodynamics in the atmospheres of the Earth and the planets. And so that forms a basis for how you describe what goes on in astrophysical topics and in geophysical topics. You want to talk about the structure of things. Well, spend a lot of time looking at the structure of stars and the visions of stellar structure and how stars evolve and so on, and then you apply the same things to the interior of the Earth and other planets. I mean the equation of state is very different but the approach is much the same. I mean thatís the way a physicist looks at it.

McCray:

All right. As you were doing this did you get any sense of how people who were more specialized in astrophysics or geophysics what their reaction was to what you were doing here?

Cameron:

Well, I mean very few people would see the whole picture of what I was doing. It was interesting. The graduate students I told you about were interested in their own right, so they actually methodically went and talked to people in all of the different experimental groups at Yale to see what was going on, and they themselves were interested in what everybody was doing, rightly so, but they were disappointed that each one of those groups was only interested in what itself was doing and not what anyone else was doing.

McCray:

Okay.

Cameron:

And that shows up the insularity with which most physicists approach their subject. And it also demonstrates I think why doing astrophysics alone or even geophysics alone or in combination and from a theoretical point of view at least makes you learn a lot of different topics, different subjects in physics in order to understand the whole of what you are going to be dealing with. Now the trouble with most astronomers is they donít learn nearly enough physics. The trouble with most people doing the geophysical sciences is they donít learn enough physics either. They donít have time. The lack of time to really get a comprehensive view of the physical background of everything youíre dealing with is a major problem in graduate physics education as I see it, and I guess I would say I was curiosity-driven to have to do this myself and then given the challenge of this course — which I took on partly because I needed to challenge myself — then I got this broader perspective.

McCray:

Tomorrow Iíd like to ask you more specific questions about your work on nucleosynthesis, but as a prelude to that I wanted to ask you if you had any particular preference for one cosmological view versus another.

Cameron:

You mean like do we have an open universe or closed one, that kind of question, or what do you mean?

McCray:

I was thinking more in the sixties did you have a preference for a steady state or Big Bang universe or did they —?

Cameron:

Well, the steady state never really appealed to me, because I guess there were all these magic things happening by hypothesis, and whereís the physics in that? And of course this isnít to say thereís a whole lot of physics and understanding in the Big Bang at that time or even today at this point, although we are sure a lot closer to it at this point than we were then. But no, I mean from the — I would say okay, given that we have a universe and itís expanding and we have some idea what went on fairly early on, the issue is, ďOkay, how do things develop in it?Ē That was really much more my approach.

McCray:

All right. So if I understand what youíre saying [unintelligible word] what happened at the very beginning and then start with what you know and then see how —

Cameron:

I mean there was a Big Bang and then out of this we had a — matter was very hot and it cooled down and formed elements, and hydrogen recombined and we started to get gravitational instabilities and make galaxies and things like that, so thatís where the details become physically treatable. And so that was where my interest in those things lay.

McCray:

And what about the period before where the details were physically treatable?

Cameron:

Well, I didnít see how I could attack it. I mean I had some interest in the issue of what can one say about the very hot dense plasmas that you get as stuff comes out of the Big Bang, but well, sort of the analogy is in looking at neutron stars. For example the process of doing a whole bunch of investigations in different areas which resulted in a bunch of publications in the Astrophysical Journal in 1959, not only about going through all of the burning stages as you get up toward nuclear statistical equilibrium but also asking the question, okay, you get like north endpoints. So what happens if youíve got something more massive than the upper limit? You have the work of Oppenheimer with Wolkoff on the neutron stars, and with Snyder on continued collapse, meaning black holes. So I had a strong interest in those things. And the nuclear physics which went into determining what the structure of the neutron stars was, and I guess my main contribution to that was to realize that when you got to very high densities, never mind the temperatures, because just having very high Fermi levels is enough, what happens when you have a sufficiently energetic head-on collision between two particles living at the top of the Fermi sea of whatever baryons you had or whatever hyperons you are dealing with. And it was clear that you needed at least in the vicinity of the threshold needed to have a head-on collision in order to conserve energy and momentum simultaneously. But as soon as you crossed the threshold energetically, being able to create new particles that way, you could and should. So I was therefore the first to indicate that you should get all kinds of hyperons in the interiors of very dense neutron stars if they really get close to the point where they would go over into a black hole collapse. And so that kind of thing was sort of close to the issue of what things were like in the very hot but very dense environment of the Big Bang. But I never saw anything that I could really do with that.

McCray:

This might be a bit off track, but perhaps not. Do you have any particularly strong religious views?

Cameron:

No.

McCray:

Okay. Because for some people those religious views have affected their views about particular cosmologies I guess.

Cameron:

Oh. Well no, I would say no. I mean I can describe basically my religious views mostly by saying what Iím not. Iím not a Christian, Iím not an atheist, and Iím not even an agnostic. Now, that sounds contradictory Iím sure.

McCray:

Somewhat, yes.

Cameron:

Okay. The issue is, the question of whether there was a creator is certainly undecideable by anything we know experimentally or observationally. The issue is however one that — where one can live with the ignorance of not knowing how it happens. Like many famous physicists have said, you know, one of the things you have got to deal with in physics is you have your observations and youíve just got to say after a while, ďWell, thatís the way the universe is. How can we understand it? How can we formulate laws that describe it?Ē

McCray:

Okay.

Cameron:

So basically I would say that I have no religious views either way. Iím just completely open to whatever observations and experiments tell us, if they ever do.

McCray:

Okay. Thinking about the different areas of research and topics that you have addressed, you have mentioned a little bit before, but is there a common thread going through it that you can easily name?

Cameron:

Iím not sure I really understand that question.

McCray:

Toward the end of this essay you talk about, it says, ďThe core of intellectual approach in trying to understand the universe is to seek consistency everywhere.Ē

Cameron:

Yes.

McCray:

And that sentence stuck out for me, and I was wondering if you would say more about that. Or does that come back to what we were saying earlier about that?

Cameron:

Well, I havenít really addressed it, but certainly you try to formulate theoretical pictures of things and particularly about how this originated or how that happened or something. And then you get some observational evidence which seemed to contradict that. Well, thatís fine. In fact in the interview with Ursula Marvin that I gave you that issue sort of is described. Because I have the reputation of continually changing my mind. And so she enters question about that in there. And so her question was, ďWell, but you immediately will change your mind when confronted with some ugly new fact,Ē and I will say yes, but I never regard it as ugly. Itís interesting, itís challenging, itís thrilling, itís all those things, itís beautiful, and why not? I mean, if you want to understand that new fact as part of a general context of how the universe developed or how different parts of it work, then you have to modify things in such a way that that is accounted for in such a way that itís also consistent with everything else you know.

McCray:

Okay.

Cameron:

And thatís basically what I mean by search for consistency.

McCray:

I see.

Cameron:

Science is always bringing new facts, whether regarded as ugly or not, to light. And weaving those into the web, a different kind of web, is therefore a really interesting challenge and just a general intellectual interest-wise.

McCray:

Have you received criticism or elbows in the ribs at all from colleagues for this willingness to change your mind?

Cameron:

I wouldnít say criticism. Just that, ďOh, Al Cameron has changed his mind again,Ē you know, kind of ďcanít believe anything he says, heíll say something different tomorrow,Ē that sort of approach. But nevertheless some things have stuck for a long time.

McCray:

Such as?

Cameron:

Oh, well, the question of the origin of the Moon, introducing a giant impact. I mean that was — previously there were three main theories and nobody could decide between them and the Apollo project didnít help either, so that stirred things up. And of course other people contributed ideas relevant to that as well, but that kind of thing gradually becomes accepted. And so a lot of things that I have advocated over the years have taken a while to sink in but have become accepted.

McCray:

Okay. Iím going to pause just for a second.

Cameron:

Sure. When Fred was director of it and in fact my appointment in Cambridge was entirely Harvard with no Smithsonian component other than the curtsey one involved as being an associate director. Initially, as you see of planetary sciences and later on of theoretical astrophysics and in those days, well I donít know how much you know about the history of things there. Maybe I should review some of that for you.

McCray:

Okay.

Cameron:

It goes back to the time that Donald Menzel was in charge of the astronomy department and observatory and he attracted the Smithsonian up to Cambridge when his advice was sought on what the Smithsonian needed to do about their astronomical observatory.

McCray:

It was in D.C. prior to this?

Cameron:

Thatís correct. And he said well what you really need to do is move it to a place where there is a good astronomy department and have a director from that and thatís better than going to Cambridge and Menzel recommended that Fred Whipple should be the director so he became director. Then after Menzel retired, and Goldberg became the director of the Harvard Observatory, then things didnít go very well for the two institutions trying to co-exist.

McCray:

How come?

Cameron:

Well, administrative jealousies and things of that sort. Particularly with the onset of the space age and the fact that the Smithsonian grew from a small group into something which was obviously quickly going to surpass the size of the Harvard College Observatory itself. I mean these are growing pains and you have difficulties of personalities on both sides of the fence. So, this is why when George Field was offered the directorship of the Harvard College Observatory, he was sort of approached by the Smithsonian side as to what should be done and there was a big sort of outside committee which made recommendations about what the future of the observatory should be. Anyway, the net result was that Fred Whipple one day got a call from Washington saying we wanted to discuss with you your retirement. This took him by a big surprise but the idea was that there would be a single person at both observatories and that would be George Field.

McCray:

Okay

Cameron:

It took a while for all of this to happen. Georgeís first year in Cambridge, or his first year in that position in Cambridge, he had lived there quite a bit before that was to think primarily about how he was to proceed to implement all of this and so he had the idea of the Center for Astrophysics which would have divisions and so on, and that was when he approached me on the basis of coming in primarily because he knew I had a strong interest in both astrophysics and the planetary sciences and I was meanwhile getting very tired of New York and itís grime and crime and all that. So I was quite happy to go along with that general idea. So anyway, that led to my going there in 1973 and at that point, you see, Menzel had long since retired, Goldberg retired. Goldberg was down here running NOAO next door and he hadnít really retired in the sense that Menzel had, but he had officially retired because he was eligible to become emeritus but he came down here to Tucson and I think that the tension between he and Fred Whipple contributed probably to his decision to come here.

McCray:

Okay.

Cameron:

Because they did not get along at all well.

McCray:

Just a difference in their personalities?

Cameron:

Partly that but partly I think the competition for resources and things of that sort and how you live together in the same sets of buildings and things like that. I mean everything that could contribute to friction, would.

McCray:

Okay. How could you, I mean, this might sound like an obvious question, but how could you tell that they did not get along. Was it just that they didnít speak to each other or was it the way they talked to each other.

Cameron:

Well anything you said to Fred Whipple about Leo Goldberg would lead to an outburst.

McCray:

Okay.

Cameron:

I donít think I quite triggered anything quite similar on Leo on the occasions that I saw him but it was clear he was not happy with Fred.

McCray:

Okay. After you arrived at the Center for Astrophysics, where there particular projects or instruments developments or things that you wanted to encourage?

Cameron:

No, not really. I mean the major thing at that point was getting Riccardo Giacconi to come and bring much of his group from further down the river and of course it was clear that that was going to be a big thing. The governance of the center started out with 8 divisions and then one of the division associate directors left and George decided to merge two of them and so we wound up with seven which is how we have seven today. Then, a lot of the meeting of course which decided on what should be done involved just exactly those seven people plus George Field, plus his main assistant on the SAL side, a fellow named Gregory, John Gregory and so you know there would be discussions about things that way. George Field did not give his associate directors much monetary authority. In other words, they didnít really have any significant amount of money they could play with. So, basically, they were mainly making recommendations to George as to how the funds should be spent in their particular area.

McCray:

And then he would decide what to do?

Cameron:

Yes.

McCray:

Did that continue after Irwin Shapiro took over or did that stop?

Cameron:

To a large extent yes.

McCray:

Okay.

Cameron:

So the governance then, for practical purposes, involved George in order to get more advice I guess. What we call the kitchen cabinet and the kitchen cabinet consisted of George, of course himself, Riccardo Giacconi, Herb Gursky and me.

McCray:

Gursty is now at the Naval Research Lab.

Cameron:

Yes.

McCray:

Okay. So this was sort of a distilled version of the larger group.

Cameron:

Thatís right and it also involved probably what would be considered the stronger personalities.

McCray:

Okay.

Cameron:

So you could have your in-house fights without disrupting everybody else.

McCray:

Based on what you saw, what where relations like between the Harvard faculty and the CFA people?

Cameron:

By Harvard faculty, you mean outside of astronomy or what?

McCray:

Harvard astronomy.

Cameron:

Okay. Everybody on both the Harvard and the Smithsonian sides were in a division somewhere. And so I think in general, everything was harmonious and it didnít matter which side you were on. If you were an associate director, it did matter, in a way. For example, in the times that I spent as an associate director, I had to deal with the Civil Service procedures on the Smithsonian side. Had to evaluate people and that kind of thing. I had a courtesy appointment on the Smithsonian side so that it made it all legal in order to be able to do that. But working relationships I would say were quite cordial in general.

McCray:

Okay. And at this time the Uhuru satellite was being prepared, more or less. I mean it was launched in about Ď72, Ď73.

Cameron:

I think Uhuru may have been up before the center was formed.

McCray:

Yeah, youíre right. But then they were getting ready to launch the Einstein satellite and at the same time they were building a multiple mirror telescope, so, you know, there was quite a lot going on there in terms of activities.

Cameron:

Right. Well, I think we already gotten to the point where we had the, what we call the OAOís I think.

McCray:

Yes the Orbiting Astronomical Observatories. Yeah, those were launched, what in the late Ď60s or early Ď70s I guess. A couple of them were launched when Goldberg was still there.

Cameron:

Right.

McCray:

Okay. Your own research, while you were there, as you noted in your essay, Iím using this a lot, you said that you tended to oscillate between the astrophysical and planetary science problems.

Cameron:

Right.

McCray:

How did you do this? Did you work on one project at a time or did you keep several irons in the fire. What was your particular style?

Cameron:

Well, it depended. I mean at the Goddard Institute for Space Studies, where I had previously been, and I think we might be talking about those days as well.

McCray:

Yes.

Cameron:

Other than at Cambridge or including Cambridge later. At any rate, there were a lot of people. Postdocs, visiting faculty from elsewhere. Things like that. Also faculty at institutions in the New York area and so a certain amount of stuff was done, particularly with postdocs or visitors to the Goddard Institute for Space Studies. So that would depend on who was there, whether I was interested in what they wanted to do, or whether they became interested in what I wanted to do, or whatever. I mean thatís how collaborations get established.

McCray:

Okay. Did you have more of a tendency to work alone or where there particular collaborators that you would work with all the time or how did that tend to work out?

Cameron:

Well I guess all my life Iíve had a tendency to work alone. It probably goes back to that time when I had to learn everything by myself.

McCray:

Right. Okay.

Cameron:

But then there were also the collaborations that became established. In particular, with regard to the origin of the moon problem. I mean that was a collaboration which continued for some time. Initially, with Vince and Slatterly at Los Alamos and me in Cambridge, and then Willie Benz had an interesting situation. He had a post-doctorate fellowship from the Swiss Science Foundation which allowed him to go where ever he wanted and more or less paid his salary where ever he was and so this is basically what was sustaining him at Los Alamos.

McCray:

Okay.

Cameron:

And so that meant that it made sense after a while for him to come to Cambridge, which he did. And so he was a postdoc of mine in Cambridge for a while and they didnít have to pay for him which was nice [laughter] and later on, then he actually got an appointment.

McCray:

In Cambridge?

Cameron:

In Cambridge. In astronomy.

McCray:

Okay.

Cameron:

As an assistant professor. And then he ventured and migrated down here and got a job at OAO.

McCray:

Okay. I have a question about the formation of the earth-moon system and you mentioned the Apollo landings and I would like to know what your thoughts are in terms of how important the Apollo missions were to developing models of lunar formation. Did they have any affect at all?

Cameron:

Not initially. Thereís a book I mention by this psychologist who was....

McCray:

Right, I remember itís in your essay.[3] Yeah.

Cameron:

Actually I tracked him down and asked him if I could borrow his book because I had lost mine when I was writing that essay simply because I wanted to verify exactly what had happened in regard to it. But basically, what he found was that, because he went around and was tracking the opinions of the so called moon scientists as the Apollo program proceeded as so he had had several interviews with me along with everybody else during that period.

McCray:

Mitloft.

Cameron:

Mitloft, yes. Itís an interesting book to track down if you really want to follow up on that.

McCray:

Okay.

Cameron:

Because what he concluded was that in fact, at least half of the so called moon scientists that he was interviewing, had no interest at all in the origin of the moon. They were interested in what the moon was like and the question of the origin of the moon was just an idle speculation. And, you know, what you want to do is find out what itís like now. There were those who had some concerns about that problem. Generally started out with a preference of one of the three theories and stuck with it through thick and thin.

McCray:

Regardless of the evidence.

Cameron:

The evidence didnít say much one way or the other. The only thing the evidence said was that they were all wrong [laughter].

McCray:

Okay.

Cameron:

So anyway, thatís the situation with regard to the impact of Apollo initially, there really wasnít one, the question of origin. You had this stalemate without having developed a preference for any one of the classical theories. So when we put forward ideas about the lunar impact, this had initially had very little interest. I remember giving a talk back in those days at the annual Lunar and Planetary Science meeting in Houston and I made a diagram which showed, about the collision, it sort of showed a round thing, a smaller round thing on top, and somebody made a comment about this cosmic schmoo [laughter] and everybody laughed uproariously. So it wasnít taken very seriously until the [???] meeting approached and then people started working on it as the Kona proceedings will tell you.

McCray:

Okay. I think at that point itís five. I think now it might be a good time to quit. We could pick it up tomorrow. Cameron — Tape 3. Okay, weíre good. Well, I guess Iíd like to start just at the beginning and what got you interested in the question of elemental abundances. You mentioned this paper by Paul Merrill on —

Cameron:

Well that was what got me involved in astrophysics. And specifically in nuclear astrophysics. And I donít know whether I was the first person to use the term nuclear astrophysics or not. I may have been.

McCray:

Okay.

Cameron:

But you know, you do all these calculations about what will happen in a stellar interior and you know what you compare the results against, and thatís where the meteorites come in, the issue of okay, youíre predicting the abundances of certain elements and isotopic distributions within those elements, but it would be nice to have some kind of checks, which is why after the [Hans] Suess and [Harold] Urey paper came out in 1956, which was just one year after my first publication, sort of more like two years, after I started getting into astrophysics, that really crystallized everything in the field because given a good abundance distribution you can look at the isotopic abundances in detail and deduce what the mechanisms were. You may not be able to deduce the abundances precisely without knowing the cross-sections and so on, but you can say, ďWell, the only way in which I can get these things made is so-and-so.Ē

McCray:

Suess and Urey were chemists, right?

Cameron:

They were chemists. Suess actually started doing this before Urey did. Suess sort of involved Urey with it. But Urey was interested in the abundances for a number of reasons, and for a number of years Urey, and particularly in connection with the solar system and the Sun, was looking at the discrepancy between meteoritic iron abundances and what was thought to be the solar iron abundance, and they were discrepant, and Harold always used to pick the solar abundance for reasons that happened to fit his ideas better, whereas I revised the Suess-Urey tables several times over the years and in the process of doing so I have always had to think, ďNow, am I doing the right thing for iron?Ē

McCray:

Okay.

Cameron:

And eventually — and I always chose meteorites, because it seemed more reasonable. And in the end it was justified because the stellar abundance of iron changed to agree with the meteoritic abundance. So that removed that as a bone of contention.

McCray:

Okay. This question of abundances. Was there something in particular about this problem that you found interesting?

Cameron:

You mean in the process of advising the tables or what?

McCray:

What was it that — was there something specific about the problem that fascinated you or that intrigued you in a particular way?

Cameron:

Well you know, physicists predict something. Sort of like an experiment, check that out, right?

McCray:

Right.

Cameron:

So the abundances of the elements and we were checking out the calculations we were doing just in exactly the same sense.

McCray:

Okay. One of the things I guess I find interesting about this period was that you have different approaches and data and theories coming from different disciplines and all converging on a common problem. And you took the approach of — you mention in your essay here that it seemed appropriate to proceed on a nuclear physics basis, and other groups didnít proceed in that way. I would like to get some idea of how people coming from these different approaches interacted with each other.

Cameron:

Now are you thinking about abundance tables or what?

McCray:

I guess Iím thinking specifically about how it applies to nucleosynthesis.

Cameron:

Well, I donít really know what youíre thinking about, about other groups doing it in different ways. The only difference I would say is that you had Willy Fowler and his people saying, ďWeíve got to have experiments to actually determine all of these things,Ē and he was right. If you can do it that way you can do it that way and thatís the best way to do it. The trouble is, when you have something that involves in principle a huge amount of data, like in calculating the slow neutron capture of the s-process, then you have got on the order of something like seventy-odd elements with isotopes which are involved in that process, and you only have data for some small subset of that. The rest you have to estimate somehow either by calculation or by interpolation or something of the sort. So thatís really where you want to touch base with the observation and experiment as much as possible.

McCray:

Okay.

Cameron:

And so I mean my whole purpose in revising the Suess-Urey table was that that was sort of entirely empirical but it was based on data and the procedure was to interpolate elements that you didnít know the abundances of in such a way that their odd mass numbers varied smoothly. Well thatís fine everywhere except at closed shells generally speaking, but the closed shells have important effects. So basically my purpose was to say okay, we understand what the processes are for studying the processes. We can do a bit in reverse now and try to say okay, using what we understand about the processes and things like closed shells and how they affect cross-sections and that kind of thing, one can do better than a straight empirical interpolation just for smoothness of odd mass numbers.

McCray:

Okay.

Cameron:

So it was two-fold then. There were new measurements of abundances in meteorites coming along all the time, and the data on the cross-sections was improving all the time, so it became worthwhile to redo that table every few years.

McCray:

Okay. Did you receive criticism from different disciplines or different groups of people that you were giving too much weight to taking a nuclear physics approach?

Cameron:

No.

McCray:

Okay.

Cameron:

No. I would say the major skepticism initially was from Willy Fowler who said, ďWe donít have the data, and I donít trust your calculations.Ē

McCray:

Why didnít he trust your calculations?

Cameron:

Well, he didnít trust anyoneís calculations. So, I mean but in the end, some years later, he was very strongly involved in making use of the calculations himself via various postdocs and so on. In fact thereís an interesting paper by Don Clayton which was published in Meteoritics and Planetary Sciences a few years ago. In fact itís referred to I believe in Ursula Marvinís interview. You might want to look that up, because itís an interesting paper, because it deals with how one determines the abundance of iron — which I was talking about before — and in a sense the difference between the Caltech approach and my approach which was to use computers to calculate things and they werenít using computers to calculate things initially.

McCray:

I mean itís really interesting, because you were working on this more or less by yourself and using computers — Hoyle, Fowler and the Burbidges are using observational data, telescopes and equipment I guess at the Kellogg Lab.

Cameron:

Mm-hm [affirmative].

McCray:

So obviously you thought your approach was better. Did you ever have any inclination to try the approach that they were taking?

Cameron:

Well of course I didnít have access to the equipment.

McCray:

Okay. Do you feel that the equipment that you had available to you then —?

Cameron:

Well, the equipment I had available to me gradually became computers. In fact, after I left Iowa and went to Chalk River for the purpose of trying to do a better nuclear physics approach to nuclear astrophysics, at that time nobody had computers, but one of the people in Chalk River took one of the accounting machines that the accounting people had using IBM plug boards. He put some germanium diodes in the plugs themselves and thereby was able to convert a plug board so that when it was plugged in you had a card-programmed calculator. And the way you used this was to have some punched cards which are punched in such a way that you input some data and do some calculations and then output some results in some of the fields in the cards. And so you prepare these and leave huge boxes of cards and say to the accounting people, ďPlease keep the hopper full.Ē Well thatís actually how I did some of the very earliest calculations, as an indication of the way I was headed. Then after a while I had a call from the head of the accounting department saying they are going to have an IBM 650 in Ottawa for a couple of weeks and would you be interested in going down to see a demonstration of it. And I said, ďOnly if I can have a chance to try and run something on it.Ē So the IBM people sent up a manual, and that computer was something that involved two thousand words on a rotating drum and a two-address system so that you had an address for an upper end of some sort — sorry. You had things in counters. You had an operation and then you had an address where you were to store the results of that operation, and then you had a second address on the drum which was where you were to pick up the next instruction. And so to get the best speed out of it you had to do your timing right so that after doing a one instruction here you said, ďOkay, I go around the drum to here and the next one should be over here,Ē and youíd do all that programming in machine language.

McCray:

Okay.

Cameron:

And so I did something. I did the s-process in a very crude way by grouping sort of like ten mass numbers at a time in a sequence to see what would happen, and so we got the program punched on cards, took it down to Ottawa, it was about 130 miles away, and fed them in, and the impossible happened.

McCray:

It worked?

Cameron:

Yeah.

McCray:

What was the output like then?

Cameron:

The output was fine. It said that you capture things in iron and you got the abundances of the heavy elements increased by factors of several hundred to a thousand or so — which was the basic characteristic of the s-process. And so that was when I first understood that that was basically the way it would happen. So after we did that for a while and had the result, and then said — this was the first week — ďCan I come back next week and run something a little bit larger?Ē

McCray:

Did they let you?

Cameron:

Yeah. They said, ďWell, how about such-and-such,Ē like Wednesday evening or something, ďWeíre having a farewell party for one of our people that day, so weíll be downstairs and you can come in. You can run into the evening if you wish.Ē So I went back and programmed everything one mass number per variable and it was a much larger program as you can imagine, got those cards punched, and took them down to Ottawa and fed them in and the expected things happened.

McCray:

Okay.

Cameron:

It didnít work. So that was when I had to learn console diagnostics and impressions at the same, you know, in real time. There were four errors, got Ďem fixed, and we ran hours and hours. And the party went fortunately quite late, so I would keep going down there and saying, ďCould I have another box of blank cards?Ē to get all this output. Finally drove up back to Chalk River in the not so wee hours of the morning, the trunk of the car loaded with boxes of output ready for the accounting people to list for me the following day. But that was the basis of having the first real set of output.

McCray:

Astronomers often say their ability to do science is constrained for example by how much telescope time they have or how big of a telescope they have. Do you feel anything similar in terms of your work, having been constrained by the capabilities of computers?

Cameron:

Absolutely.

McCray:

Okay. So while astronomers were always looking for a bigger mirror for example, you were always looking for a faster machine?

Cameron:

Mm-hm [affirmative]. That was why when we started doing calculations on the giant impact from the Moon. We were fortunate to be able to use the Cray XMPs in Los Alamos, but not only just in Los Alamos but in X-Division where the time was not constrained. That made a real big difference. And then the interesting thing was, when Willy Benz came up to Harvard we started getting some Sun workstations. And the first one we got we found it interesting that we were able to run it at about one-seventh of the speed that we were getting on the Cray XMP at Los Alamos. Partly because the program was not optimized for any kind of parallelism in that machine, and so therefore it was not optimized for the Cray, but it was sure optimized for the Sun, which didnít have any parallelism capability. So that indicated okay, yes, we can — you know, you have all the time you want on your own Sun. You are a little bit constrained even in X-Division at Los Alamos. And so that basically indicated how I should proceed. Eventually of course it came down to using PCs and this is why you see all these around here.

McCray:

Okay. At least — what do you have, six here?

Cameron:

Yeah.

McCray:

What was your reaction to the B2FH[4] paper when it came out?

Cameron:

Well, I had independently done much of the same thing myself, and you know these are not things out of the blue. There were a lot of precursor publications and things like that, and so my reaction was I agreed with most it but I disagreed with some of it.

McCray:

What did you disagree with?

Cameron:

Well, the B2FH paper classified the nuclear processes into several categories. One of them was what they called the d-process, which was just you know you capture alpha particles, neon, magnesium, silicon, sulfur, argon, calcium, all the way up. I said, ďI donít think thatís the way it happens.Ē It didnít in the end, when we worked it out. So, but apart from that I mean, the basic stuff was pretty much in agreement.

McCray:

Did you feel that there was a competition between yourself and the group at Caltech in this area?

Cameron:

Not in the sense that you frequently do have competitions between different teams of physicists for the same sort of thing. We werenít pursuing exactly the same sort of things. Willy was of course trying to make measurements of a lot of the critical cross-sections, and not trying to solve the general picture in any intensive way, he, not until later at least. Meanwhile I was trying to determine what were the successive nuclear burning stages, which is why I didnít agree with the alpha process, and the endpoints. You know, it occurred to me, okay, one endpoint is a white dwarf and of course another endpoint is a neutron star that nobody but Zwicky believes in, but it seems absolutely necessary. So that led in the first place, when you look at a white dwarf and have a really high density and moderately hot plasma which is electron-degenerate, at least the concept — well, okay, I mean you know these things form crystals and so on and you have natural vibration frequencies, and whatís the rate at which those vibration frequencies within those lattices are going to lead to nuclear penetration through the barriers. And hence the pyconuclear reaction was the outcome of doing that. And then as far as the neutron stars are concerned, I described to you yesterday how it was apparent that you had to worry about a heavy baryonic content in the equation of state, which of course we didnít know how to calculate in those days. So all one could do is to — at least at that stage, all I could do was to neglect nuclear courses which were not sufficiently well understood between all the constituents and calculate them just as pure non-interacting Fermi gases and get some idea as to what came in when as you just raise the density and then make some models of it.

McCray:

Were you having a lot of interactions with either Suess and Urey or Hoyle and Fowler and that group at the time?

Cameron:

I wouldnít say a lot of interactions; I was having some. For example we were talking about the late Ď50s. In those days there was a Gordon Conference on Nuclear Chemistry and they started every three years having a session on nuclear astrophysics, and so Willy and I would usually wind up at those sessions together, and so I would see him on those occasions. I would go to Cal Tech occasionally and see him there. And I didnít see Hoyle very much. A couple of times meetings in England, yes, but not all that much. So it was — you know, we were pretty independent.

McCray:

One of the reasons Iím asking about these interactions was in getting ready for this interview I came across this letter that Burbidge wrote I guess to the Ap. J. in 1960 critical of the approach you were taking, and then your response to it.

Cameron:

Yeah.

McCray:

And thatís what got me thinking about coming at this problem from two different directions.

Cameron:

Right. Well, I mean Burbidgeís approach basically says you know, you donít know the data, you are making some assumptions, they are not justified. And I am saying, what else can you do?

McCray:

Okay. In 1959 you published a lot of papers.

Cameron:

That was the result of having the access to the first computer that Chalk ever got which was the thing called the Datatron 205, and that was interesting in itself. It was — I would say it did calculations on a millisecond timescale, which we would not regard as very fast, but compared to a hand calculator it was. And so I got in the practice — I mean, that was how I did the calculations associated with doing the many, many reactions involved in the later stages of nuclear burning to try and follow — you know, if you had a reaction, say d-process or something, okay, what happened to the protons, that kind of thing, and you had to do it all together as a network. So that was basically how all those calculations were done and several of the Ď59 papers were in fact those nuclear burning processes. But also the pyconuclear reactions, the neutron star stuff, all of these were involved in that period. And the way in which it worked was that at Chalk River at the time people didnít really appreciate what you could do with computers and therefore they were not used, and that particular one was not used outside of normal working hours except by me. So the typical pattern would be in the afternoon Iíd say, ďWell, what do I do next?Ē So I would decide what I wanted to do next and I would pull out a bunch of programming sheets and write up the program for it. And so people would be about like 4:15 or so people would be heading out of the Chalk River plant for the buses to take them back to Deep River, which is where they lived, and I would be heading over to the 3 Building which is where the machine was and punching cards for what I had programmed, and when everything was clear I would be feeding them in and debugging them and getting the thing running.

McCray:

Did you have assistance or were you working all by yourself?

Cameron:

By myself. So then I would — it would probably be close to 6:00 before everything looked like it was running all right. I would probably go over to the plant cafeteria and grab some supper, and then come back and check to see that everything was going fine. And usually it was by then. So I would leave instructions for how to take the problem off the machine the next morning when people came in, and on a weekend it would be the same sort of thing except that I would normally be running all weekend. So I would come in on Saturday and see if everything was running fine, and if it was fine Iíd go home and same thing on Sunday. But it wasnít always running fine in those days of tube machines, and so I would frequently find that, okay, the machine has stopped, what do I do about it. The first thing is I give it a kick, which usually didnít work. Then I would look at the pattern of lights on the tube packages in the many cabinets that they had for the thing. And this was a decimal machine such that anything over ten would be a forbidden combination in terms of the — youíd never get that number ordinarily, and frequently there would be an error which would make it stop on that. That I could usually fix by rummaging around in the customer engineerís office and finding a similar package and yanking the old one and bring the new one in, and I was usually back on the air. If I didnít find that kind of forbidden combination to give me a clue what to do, then it was a matter of phoning the customer engineer at home and saying, ďIím stuck. Canít get the machine going. Please come in.Ē As you can imagine, I was not terribly popular with that guy. But anyway that would be — he would usually —

McCray:

The papers that were coming out in 1959, the response that you were getting to these papers, did it vary depending on whether it was nuclear physicists who were commenting on it or astronomers or chemists?

Cameron:

Oh, it varied all over the map. I donít really remember much in the way of comments because of course at Chalk River I was the only one working on the subject, and I would only get comments if I went to a meeting and told people there something of the sort usually. But also in 1959 in the fall I went off to Caltech for a year.

McCray:

How was that arranged?

Cameron:

Oh, Jesse Greenstein had previously said if I wanted to come to Cal Tech for a year or so to work on things he would be glad to support me with his Air Force contract, so I basically just took him up on that. And that meant that I was in Robinson, which is the astronomy department building at Caltech.

McCray:

Okay. So you were in the astronomy — I guess itís not a department but whatever, a division.

Cameron:

Well, yeah, they have a division with different groups and I might as well call them departments. So anyway, Fritz Zwicky was essentially just across the hall from where my office was, and he of course was very pleased with me from the neutron star point of view, because he had been advocating this for many, many years and no one had been paying attention to him. In fact he used to rub people the wrong way, and that had an awful to do with you. You know, he had been abrasive and that sort of thing. And he was very much a loner in his own right. I remember a story about him where he was always trying to get better crystal gratings for use with solar spectroscopy, and somebody found a way of using sub-gratings together to make a bigger one and very successfully was using this. And the first Fritz ever heard about it was he attended a talk by the guy who was demonstrating what he had done with it, his reaction was, ďWhy didnít you tell me?!Ē [said with an accent with ďwhyĒ sounding like ďvieĒ] [laughs].

McCray:

I hear the accent. So you were working with Greensteinís group, this is funded by the Air Force.

Cameron:

Yeah.

McCray:

Iím just curious why the Air Force was funding work in stellar abundances.

Cameron:

Well, the Air Force was funding virtually everything in those days. The Air Force was the equivalent of NSF in those days. I mean NSF I guess was probably just getting started up.

McCray:

Yeah, it was only about a decade old at that point.

Cameron:

Yeah. And so you know the Air Force had gotten in the game really quite early, and so had the Navy, and it was all an effort I think to fund scientists in the universities and thereby get them interested in advising with regard to military programs.

McCray:

Did you ever meet with any Air Force people?

Cameron:

No.

McCray:

So you all had free reign pretty much?

Cameron:

Yeah.

McCray:

They wrote a check and you —

Cameron:

Yeah, yeah, pretty much. And but basically that was where two things happened. Shortly after I got to Cal Tech, John Reynolds at Berkeley published his discovery of the Iden [?] 129 extinct radioactivity in meteorites. And so that made a big difference to me, because it meant okay, that really is closely connected to nucleosynthesis and so that got me interested even more so in meteorites, but also in questions about the history of the Galaxy and what the discovery of extinct radio activities would mean in terms of timing events on the galactic scale. So I worried a bit about that. But more so, even so, the fact that meteorites were involved in so many things now meant I had to understand how they were formed and how they fitted into things. And so actually a great deal of my time at Cal Tech was spent reading the literature in the astronomy library having to do with that whole subject.

McCray:

Did you interact much with Greensteinís group at all?

Cameron:

Well, the word group is not really appropriate here because I mean the people I would go to eat lunch in the Atheneum with typically would be like Maarten Schmidt and Bev Oke and things of that sort. In other words, and they were not in any sense in Greensteinís group. They had professorial appointments and so they were doing their own things. But of course everybody was interested in everything else that other people were doing, and so in that sense I was interacting widely with a group of us who would walk to the Atheneum and have lunch together and so on.

McCray:

You mention Schmidt and Oke, and both of them were pretty —I mean they are observational astronomers.

Cameron:

Yeah. Well, pretty much everybody I was talking to was an observational astronomer.

McCray:

Right. So how did you fit in as a theorist?

Cameron:

They were very surprised I didnít want to observe.

McCray:

Did they offer to take you?

Cameron:

No.

McCray:

They never said, ďLetís go up to the 200-inch andĒ —

Cameron:

Oh, well I mean I went up to see it.

McCray:

But never at night.

Cameron:

Never at night. But you know, basically as a tourist almost, except the tourist didnít get quite the same treatment in terms of being shown around the place.

McCray:

Sure. But you were never tempted to become an observational astronomer or learn any of the —?

Cameron:

No, because I didnít see anything that I could do that would be decisive in the general research program I had. You know, if you are dealing with just the question of abundances. In putting together an abundance table actually I was mostly involved with looking at what the meteoriticists were determining, but stellar abundances were important as well, and in particular in trying to understand the history of the Galaxy as far as nucleosynthesis was concerned. But you need to look at everybodyís results, and what you could do yourself would be a very minor thing compared to that. And so I was never tempted, because I was much too busy doing my own thing theoretically.

McCray:

Did you spend any time at the Kellogg Lab and with the people there?

Cameron:

Oh, I would go and see Willie from time to time. Probably rubbed him the wrong way by doubting all of his theories.

McCray:

Do you mean that seriously?

Cameron:

Yeah I mean seriously, yeah.

McCray:

Were your personalities different in that sense or just(?

Cameron:

Well, people in the field used to talk about the West Coast school and the East Coast school in terms of what we were talking about as nucleosynthetic processes and so on. That was an exaggeration. Don Clayton actually came to one of the summer schools that we ran at GISS, and he apparently enjoyed it and we had our chats and so on. When he went back to Caltech Willie apparently made some disparaging remarks about me, oh, ďAl thinks that what weíre doing here is terribleĒ and so on. And Don said, ďNo, Willie, youíve got it all wrong. He couldnít have had more praise for you.Ē So I noticed a certain change in Willieís attitude at that point, or afterwards.

McCray:

I understand the idea of an East Coast and West Coast approach is overly simplistic, but just in keeping with that distinction could you give me some sense of what would have characterized the West Coast versus East Coast approach?

Cameron:

Experiment versus theory. At Kellogg they were measuring things ( basically what I have already described. I was alone — well, after a few years I was working frequently with one or two postdocs at GISS, so in that sense I suppose we had a West Coast, I mean East Coast school, but it was never very numerous. But you know, I was interacting in some people interested in relativity, particularly with regard to formation of neutron stars and black holes and things of that sort. And that was at GISS. So that — it was a different approach. I mean we couldnít measure things on the East Coast.

McCray:

Thatís interesting. I have heard of that East Coast/West Coast division in astronomy, but I never really thought of that carrying over into nucleosynthesis work.

Cameron:

Well, it was specifically for nucleosynthesis. That East Coast/West Coast difference was specifically nuclear astrophysics and not in astronomy generally. I mean you know, practically all the best observational astronomy was on the West Coast anyway — or close to it either in Arizona or Hawaii.

McCray:

Sure. The next question I have is difficult to ask in a delicate fashion so Iíll just —

Cameron:

Donít bother. I mean donít bother being delicate.

McCray:

Oh. Well, in getting ready for this interview I mentioned to a few astronomers that I was going to interview you. They made the comment that with the nucleosynthesis work that you did pretty much singlehandedly what the B2FH did as a team.

Cameron:

Yeah.

McCray:

And I was curious what your reaction to a comment like that would be.

Cameron:

Well, itís true.

McCray:

Okay. Does it bother you that the B2FH paper generally tends to be cited more and get more credit as it were?

Cameron:

No, because the equivalent one on my part was a large series of lecture notes from an invited series of talks I gave in the physics department at Purdue. Thatís the so-called Chalk River Report CRL 41. And that has pretty much all the same stuff, but of course it was not a regular publication. So it is very natural that the B2FH paper should be much more cited in that respect. The fact is it had preferential treatment. Ed Condon was the editor of Reviews of Modern Physics at the time, and apparently Willie ran across him somewhere and said that they had put this long paper together and they were thinking of sending it to the Reviews of Modern Physics, and then Condon said, ďFine. Send it in and weíll give it expedited treatment.Ē And as Don Clayton likes to say, ďWillieís comment to that was, ĎThose were the daysí.Ē [laughs]

McCray:

I guess you canít do that so easily now. The other indelicate question is sort of a follow-up on this, but I mean Fowler eventually went on to win the Nobel Prize, which he shared with Chandrasekhar.

Cameron:

Yeah.

McCray:

Any regrets about not being included in that for the work that you did?

Cameron:

No. I think that — I mean, Willie — that was devastating to the B2FH group actually, because actually all of that was announced when we were having a meeting at — Yerkes Observatory in Wisconsin. Yeah. And so that led spontaneously to a big party, and of course Willie got a call from Sweden early that morning and apparently the first thing he did was to phone Fred Hoyle and to say that he was thinking he should decline the Nobel Prize because no one else in the group had been awarded it, and in particular Fred hadnít, because Fred had had a lot of the basic ideas they were using before Willie had, and Fred said, ďDonít be a goddamn fool.Ē So Willie didnít — But I could tell during the day — because you know we had a celebratory dinner that night — I could tell at the time that he was concerned that I might have felt unfairly left out in the same way. And I didnít. And part of the reason I didnít was Willie got the prize not only for B2FH but for all those measurements of cross-sections that were critical to understanding the nuclear burning process. And I consider that actually much more important than the B2FH stuff. And particularly in terms of what Nobel Prizes are given for.

McCray:

They usually favor experimental results.

Cameron:

I mean if you look at the Nobel Prizes that have been given for work in astrophysics of any sort, all of them have this in common that the astrophysical aspects of things cast light on fundamental physics. And thatís why pure astronomy never has got a Nobel Prize in physics. Itís because that became a means which cast light on really fundamental questions in physics. And so — you know, certainly I didnít regard what I was doing as casting any fundamental light on physics, and I donít think it did. It was merely saying okay, Iím using some physics to try to understand whatís going to happen in stars.

McCray:

Did you and Fowler talk about this explicitly after he got the prize at all, or it just never really came up?

Cameron:

Well, I used to see him in later years a fair amount. Those were in the days when I was chair of the Space Science Board.

McCray:

Okay.

Cameron:

And Willie had served on the Space Science Board some years earlier, and so I invited him to repeat that experience. And so when we were having board meetings in Washington, usually we would both be at the Cosmos Club and come down and have breakfast together on the days of the meetings. So, you know, his attitude toward me in later years was less competitive.

McCray:

All right. Well, those were the indelicate questions.

Cameron:

Okay. Well, I didnít feel they were indelicate.

McCray:

Okay. Tell me about your work on the Space Sciences Board. I know itís covered to a fair degree in the essay, but what did you see as particularly important about what you were doing with that?

Cameron:

Well, the key thing that happened there was — I mean I need to back off a bit and — When I was employed at GISS of course I was a NASA employee, and so any advising that I did in committees was always a NASA internal committee, and then when I went to Ushiba [spelling?] and later on to — Well, when I went to Ushiba I was still mainly working on NASA internal committees, but certainly when I went to Harvard I started to get involved more in the example committees, and I went to Harvard in Ď73. In í74 — letís see. Yeah. In Ď74 I was asked to join the Space Science Board, and so — no, sorry. I was asked to join COMPLEX, which was one of the committees of the Space Science Board, the committee on planetary and lunar exploration. And so after I was on that for the first year, then I was asked to join the board itself, and so I spent that year still on COMPLEX. But that was the year that Jerry Wasserburg became chair of COMPLEX, and Jerry had some rather important ideas about that which can be roughly summarized as this: What the Space Science Board has been doing is to endorse NASA programs — or not. Usually they do. Okay? And Jerry, very intelligently, said, ďLook. What youíre doing is saying that such-and-such a program by name is good, go with it.Ē And what NASA could then do was anything that they liked, as long as they called it what you had said was good. And so he said, ďThatís not the way to operate. What you need to do is not to endorse a given program but to outline a program which will have a certain list of things that should be measured, and it will all be done of course with knowledge about the technological capabilities for doing these things, but youíll say Ďmeasure this and thatí and so on to such-and-such degrees of precision, and do a program of this, all across space science program with varying priorities.Ē And that was basically new, and the Space Science Board in those days used to take the reports of the committees that it would have and to extract things that it liked from those reports and put those into its own report. So its own report was the only thing that mattered as far as NASA was concerned. So when the time came at the end of that first year when we had been working on the strategy document for the outer planets, as it happened, Jerry said to the board, ďThis is a strategy. I want the entire report endorsed by the board.Ē Iíve never seen such an internal fuss as that board had at that moment, because everybody else had produced their report and none of the others were demanding that their reports be endorsed in whole as a total, whereas this one was. And of course the chairs of the other committees were all upset that you know this one should get precedence over everybody else, so there was a lot of internal jealousy there. But so there was a final vote on whether the board should consider this, and the outcome of that was barely in favor, but with the proviso that all of the important policy statements in the report should be extracted so they could be looked at as a group and ready the next morning. Well, Jerry must have been up all night or something getting this done, but it was done, and much of the day was spent discussing all of those things, and so it was endorsed. Well, then the board had a major discussion, ďIs this what each committee should be doing?Ē And the answer there was yes. So, then the board chairmanship was becoming vacant. Richard Goody was chair at this time, and so then the governing committee of the Academy or actually technically of what you call it, the —

McCray:

NRC?

Cameron:

The NRC, yes. So in due course I guess I had, during the year I had already spent on the board, become noted for the fact that I was being quite critical of a lot of things that were being talked about, and probably for that reason as much as any the next outcome was that I was asked to become the chair. So the issue was then, ďOkay. Iím the chair. Every committee has to produce a strategy document, and weíve got to concentrate on getting those done.Ē Well this took time, partly because the chairs of the various committees usually had no idea of how they should be proceeding to do this. And as a result, for many of them not very much was done, and what in practice I had to do was to wait until those chairmanships became vacant and then appoint somebody as chair, if possible, who had previously served on COMPLEX and knew what it was all about, having gone through what you might call the Wasserburg Tutorial. And so we came to the end of my three-year term, and I said, ďWell, okay. I donít want to try and influence anybody about how you choose the successor,Ē so I just asked a group of people on the board to form a little committee to talk about that and decide how one should proceed. And in due course I was totally surprised when they said, ďWell, weíve decided that your strategy business is unfinished and we want you to finish it with a second term.Ē Well I didnít see how I could say no to that, so that was how I became chair for six years.

McCray:

I see.

Cameron:

And by the end of that six-year period we pretty much had almost all of the strategy documents pretty much in hand. Some of them took one more year to really get finalized. But that was the underlying theme through that entire process, was getting the strategy documents done. When I was chair, I created some temporary committees, particularly on data processing, which was in very bad shape scientifically within NASA at the time. Basically you would have a mission which would go out and take a lot of data and then NASA would never have any money to fund, you know, prepare for people to use to analyze that data. And that was a very bad situation. We corrected that.

McCray:

You got money for data analysis?

Cameron:

Yeah, as part of the planning process of any kind of project you were putting together. And basically how to optimize the data analysis capabilities and procedures themselves. But I guess the main innovation I had with regard to the way meetings were run was that I said, ďI want all of the committee chairs to come early so we can have a meeting in the evening beforehand and discuss progress.Ē And those were quite useful. We generally did that.

McCray:

To get a sense of what was to come then?

Cameron:

Yeah, what kind of problems people were having and whether we could do anything about them and so forth.

McCray:

Iím going to flip this over here. Itís about to run out. (Tape 4) I was curious also about the Gordon Conferences that you organized. And they had the title, if I remember right, ďChemistry and Physics of Space.Ē

Cameron:

Yeah.

McCray:

And it sounds very broad.

Cameron:

It was.

McCray:

What types of people were attracted to come to a meeting like that?

Cameron:

The original idea was to get people who would be a mix of people from the astronomical side and from the meteoritic and planetary side. And as things turned out, we would usually have a large number of meteoriticists, some people from elsewhere in the planetary community, and a handful of astronomers — people like Lawrence Aller for example often came to those, and Harold Urey often came, Hans Suess, Jerry Wasserburg, lots of people. They were an outgrowth of the Gordon Conference on Nuclear Chemistry that I had already told you about, and they were held every three years, and after about the third one of them, or at the third one of them, I was talking to Ed Anders and I said, ďYou know, we ought to see if we can do this as a topic every year,Ē and he agreed. And so we contacted the administration of the Gordon Conferences and said you know, ďHow do we go about having one on a different topic?Ē And so we got all that information and rounded up, you know, did a proper proposal and rounded up letters of endorsement from various people in different fields, that sort of thing, and so the Gordon Conference on the Chemistry and Physics of Space was launched, and it was intended to be very broad, and it was. I wasnít the chair every year. I was a chair the first year and Anders was vice chair, and then, in a later year, I became chair again, but as we got closer to the Moon landings, the Apollo program finally was maturing, people became very busy preparing for that and the attendance at the Gordon Conferences tended to decline. And so then finally there was a disastrous one, because John OíKeefe was the chair, and so he made it mostly on tektites, on which he disagreed with most people in the community. And so that was a disaster, poorly attended, and the Gordon Conference people just said, ďChop it up.Ē

McCray:

Okay.

Cameron:

So that was — you know, a very nice thing when I look back on it with great pleasure. When Apollo came and the lunar samples came back and so on, then everybody was too busy for quite a while to go to meetings except the most important ones where all the data got presented, like the Lunar and Planetary Science Conference in Houston. But later on NASA started thinking about establishing the Origins program.

McCray:

I wanted to ask you about that. Thatís a good topic. How did that come about?

Cameron:

Iím not quite sure who had the idea initially but —

McCray:

Iíve heard that it was Wes Huntress.

Cameron:

It might well have been.

McCray:

Okay.

Cameron:

But he wasnít really involved in the planning. There were a series of meetings for planning purposes to see what should be involved, about three of them I think. And so as part of — then there was a smaller group put together as a committee to actually do something about the program.

McCray:

What types —

Cameron:

Basically they are going to put out an announcement of opportunity and people could propose to get money and stuff like that.

McCray:

What time frame is this?

Cameron:

Oh, I have to try to think. I guess it was somewhere in the Ď80s.

McCray:

Okay.

Cameron:

Iíve forgotten exactly. But anyway, this is a group of people basically set up to advise the Origins program as it was established. What do they call it? A working group kind of thing.

McCray:

You were on this?

Cameron:

And I was on that.

McCray:

Who were some of the other people?

Cameron:

Oh, I donít really remember. That could be determined, but basically when that group had its first meeting, I said what we need to do is to have a regular meeting once a year at which people can, involved in the Origins program, can come and talk about things, and it should not be probably something under NASA sponsorship — I mean not under — as a NASA meeting as such. It should be under an independent organization. And so I suggested that a Gordon Conference on origins which would operate something like the one on the chemistry and physics of space had done would be appropriate. Since I had been involved in the initial organization of that one, it was natural that I would agree to become chair of the first of the Origins ones. And so we went through the business of establishing that one. I knew the ropes a bit. And that then came about.

McCray:

Okay. What types of topics were being discussed at it?

Cameron:

Well, the intent was to go across the board, have half-day meetings on quite diverse topics — astrophysical problems, meteoritic problems, planetary atmospheres, you name it, thereís probably a half-day session before many years have gone by.

McCray:

Iím trying to think of the missions now that are associated with Origins. There is Terrestrial Planet Finder, Space Interferometry Mission, and I guess whatís now the James Webb Space Telescope. Do you have any reaction to seeing these programs come out of the Origins theme?

Cameron:

No. Well, my only reaction they donít do it broadly enough. For example, one topic which has been skimped on is the origin and development and history of galaxies. That is now of course a very hot topic in astronomy. Iím not sure — I donít think the Origins program is still doing much on that. The Origins is still largely tied to planetary things like Terrestrial Planet Finder and so on as you mentioned really came out of the planetary aspects of the origins rather than the astronomical ones, although the astronomical ones were very heavily involved in developing that program. But the impetus I think was really from the planetary side and also from the origins of life side, and the question of the prevalence of life in the universe and all the rest of it.

McCray:

Do you think thereís life elsewhere?

Cameron:

Do I think? I think very definitely there has to be. As time has gone on, I think the probabilities of, you know, what is the probability of getting a sun-like planet — sorry, sun-like star — and having a suitable planet there for life. We used to talk about it being close to unity, and I think as weíve come to understand a lot of things about planet formation better those probabilities have gone down a whole lot. I mean such things as the fact that we have a significant major moon associated with us. It has a very stabilizing effect on our climate, because it prevents the axis from doing this sort of thing. [Wobbling motion gestured]

McCray:

Okay.

Cameron:

So that kind of thing is important, but the whole question of origins going back to the question of the Big Bang, development of structure, all those things are now heavily studied using space telescopes and things, various kinds, but I donít think that those programs had their origins, in the different sense, in the Origins, in the other sense, program. I think those are really coming out of the astronomy community as such.

McCray:

Okay. Did you have any reaction or personal reaction to the discovery of the first exo-solar planets?

Cameron:

Well, I heard about it ahead of time.

McCray:

How so?

Cameron:

This was when Willie Benz was at Harvard. He had been visiting Geneva I guess that summer, so when he came back he told me about it, and it got announced I guess a couple of months later. But in the meantime we were talking about, ďGee, you know something that close to the star? How can that be?Ē and we were trying to figure out the mechanisms and so forth. So in that sense it wasnít surprising that the planets would be discovered; what was surprising was how close the Jupiter-like thing was to the star.

McCray:

Yeah. Okay. I have a couple of questions to wrap up. We havenít said much about your personal life and I was wondering if there was anything that youíd like to make a note of.

Cameron:

I donít know. What are you actually planning to do with all this?

McCray:

The interview?

Cameron:

Yeah.

McCray:

Well, it gets transcribed and it eventually goes into our libraryís archive for other people to use.

Cameron:

But it doesnít involve a publication I donít believe.

McCray:

No.

Cameron:

No. Okay.

McCray:

Actually let me just pause this for a second. [recorder turned off, then back on]

Cameron:

Thatís fifty years or something.

McCray:

Yeah. Okay. Yeah, so I was just curious if you had any notes about your personal life outside of work that —?

Cameron:

Well, Iím going to let you ask what you like in that regard, because I donít know what is really very relevant to these considerations.

McCray:

I gather you were married at some point.

Cameron:

I was, in Ď55, yes.

McCray:

Okay. Are you still married?

Cameron:

No, my wife died. Well, we were living in an apartment here in Tucson and having our house built, so unfortunately she did not, was not able to actually move into it, but she died just shortly after having seen the almost-completed house and being very pleased with it.

McCray:

Okay.

Cameron:

And that was a misfortune.

McCray:

Yeah. Hobbies, things like that?

Cameron:

It would be hard to say. When I was a youngster I guess reading science fiction was my main hobby.

McCray:

What were your favorite authors?

Cameron:

Oh, people like E. E. Smith, John Campbell, that sort of thing.

McCray:

Do you think they affected your work at all?

Cameron:

No, not my work. It may have affected my choice of what I wanted to do, but probably not greatly. But I mean subsequently I really havenít had any serious hobbies, because my work has been my hobby.

McCray:

Thatís a good thing.

Cameron:

And so you know as I got into all of these interesting questions that I had been trying to pursue, each one of the different fields that I have had to try to learn something serious about has been expanding I guess probably exponentially. I think it would be difficult for anyone nowadays to easily cover as many fields as I have, but thatís mainly because I got into them when the astrophysical applications were much less well developed or understood than is the case today. Now of course the amount of knowledge involved is huge. Astronomy has changed drastically since the time I became involved with it, much more quantitative, much more analytical, much more theoretical, all of which is to the good. But the same thing has been happening but more slowly in planetary sciences. That is getting there as well. And so keeping on top of all of these things as well as I can has really taken up virtually all of my time and is probably mainly responsible for my not having any other serious hobbies. Reading science fiction went out the door long, long ago.

McCray:

Your career is interesting in this sense, because you have worked in so many different areas, and it really strikes me as a model of interdisciplinary work, and I wonder — I think you have sort of answered this question, but Iíll mention it anyway — but I got the sense that one really couldnít have a career like yours now, just either for institutional reasons or just because of the amount of information thatís out there.

Cameron:

Well, institutional reasons is a serious matter. The compartmentalization of things in university departments is very bad in terms of any kind of interdisciplinary type of stuff. But in terms of how easy is it to do today, I think there should be a greater attempt made to teach these things, but you canít teach interdisciplinary things nearly as well as you can learn it on your own. At least thatís my own experience. And basically learning things on your own — at least for me — has involved a particular problem that I wanted to pursue which drives me to something that I know nothing about, and so I have to learn something about it. So thatís sort of a problem-oriented type of learning which crosses the disciplines. As I say, itís been a full-time job. When I was chair of the Space Science Board a lot of time had to be devoted to the work of the board and its committees and all the liaison that I had to do with other committees of the board and other committees of NASA. But there were a few meetings every year, scientific meetings, that I would say, ďThese must have priorityĒ in order that I keep abreast of what was going on — things like the Lunar Planetary Science Conference in Houston in the spring for example, or particular problem-oriented meetings that would be had from time to time. Though it was important for me to go there and see what was happening, at the same time the service on the Space Science Board was very educational in its own right. I mean, that prompted me to learn much more about the origins of life problems and associated medical stuff than I otherwise would have, because well I had to know enough about the field to choose a new chairman for example from time to time.

McCray:

So that was a spur to do the self-education process that you are describing.

Cameron:

Yeah. I mean, if you want to learn something, teach it to yourself. Thatís that gives you a much better feeling for the way to proceed with investigations. And of course thatís important in another respect. When NASA tries to promote its collaborations between people in different fields, and that doesnít work nearly as well as collaborating with yourself.

McCray:

What do you mean?

Cameron:

In other words, say you want to have somebody working, a meteoriticist collaborating with an astrophysicist. Well these guys — I mean they donít even talk the same jargon. A collaboration that far apart is very, very hard to actually produce anything worthwhile, simply because probably people in one field donít ask the right questions of people in the other field. So when I talk about collaborating with myself it means that I made an effort to understand both fields, even if theyíre very, very far apart. And in that sense in trying to think about the way I investigate problems, the way I think about them is not so much a mathematical approach in thinking as many people have, like whatís-his-name that was at Caltech, ďSurely youíre joking, Mr. Feynman.Ē [laughs] Dick Feynman for example. I mean thereís a guy who really thought in terms of symbols. I donít think that way. I think about the scenario and how all the different aspects of the scenario would react with one another. And that then leads to relatively simple usual calculations, often back-of-the-envelope type that I can do to really try to understand that better, and eventually probably some more elaborate simulations or something of the sort. But, so collaborating with myself merely means that I know enough about more than one subject that I can ask the meaningful questions across the boundary and think about it in a unified fashion. And when Iíve often talked about, you know, a so-called ugly fact, and you know coming up in something, and the question is, ďHow does it interact with everything else Iíve been thinking about?Ē Well, often the things that it interacts with cross disciplinary boundaries. And so thereís this quote ďuglyĒ unquote fact over here which is making me change something over in a very different area — simply in order to get consistency in the scenarios.

McCray:

Which takes us back to the consistency thing we were talking about.

Cameron:

Yes. Yeah.

McCray:

I think weíd better wrap it up for now.

Cameron:

Okay.

[1] Paul Merrill was an astronomer at the Mount Wilson and Palomar Observatories at the time.

[2] Astrophysical Journal

[3] A.G.W. Cameron "Adventures of Cosmogony" in vol. 37 (1999) of Am. Rev. of Astronomy & Astrophysics, pp. 1-36

[4] E. Margaret Burbidge, G.R. Burbidge, William A. Fowler and Fred Hoyle, "Synthesis of the Elements in Stars," Reviews of Modern Physics 29(4)(1957): 547-650