Oral History Transcript — Dr. Christopher McKee
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Interview with Dr. Christopher McKee
Christopher McKee; July 29 and 30, 2002
ABSTRACT: A biographical interview with McKee; covers childhood and education. Discussion about relationship with Edward Teller and classified research at UC Berkeley. Graduate career at Berkeley and impressions of program. Professorship at Center for Astrophysics and later move to Berkeley. Development of three phase model of interstellar medium with J. Ostriker. Interplay between astrophysics and nuclear weapons design including work of Stirling Colgate and Russians. Support of theorists through grants. Discussion about numerical modeling. McKee's experience on Academy decadal survey committees including one he co-chaired with Joe Taylor. Views about building large telescopes and relation between astronomy and physics.
McCray:Chris McKee interview, July 29th, 2002, Berkeley, California, Tape 1. Okay, great. Well as I said, it's a biographical interview, so why don't we just start from the obvious place. You were born in 1942 in Washington D.C. Why don't you tell me about your childhood?
McKee:Okay. I was the son of someone in the military. I was born shortly after World War II started, and I of course have very limited memories of those early days. My father had been educated at West Point and he, I believe, was in the Class of 1929. As you can imagine, the military suffered severe cutbacks during the Depression. Those people who were able to remain in the military were actually reasonably well off, and he and my mother were able to survive the Depression in a lot better shape than most people even though he was at that time a fairly low-ranking person.
McCray:What service was he in?
McKee:He was in the Army.
McCray:In the Army.
McKee:But he early on became interested in the Army Air Force, and so he was one of the initial officers that became part of the Air Force when it was set up at the end of World War II. Because he had the background in the Army, he was not a pilot and his expertise was really in management. And that meant that he did not actually see any combat duty. So we lived in the Washington area until the end of the war and then we spent a few weeks in Paris I believe, and then we were assigned to Wiesbaden in Germany. Of course that was a very difficult situation I'm sure for my parents because we were in an occupied country. And I only have one memory of that time. I was in the backyard. We were staying at a very nice house and I was in the backyard and some German kid dropped a rock on me and ran away.
McCray:On your foot or on your head?
McKee:My recollection is on my back. I don't know. I remember it was very high up and it came down, but obviously I was not injured by it, at least not that I know of. My memory probably exaggerated it.
McCray:How long did you stay in Germany then?
McKee:We stayed in Germany for only nine months, much to my mother's disappointment. She had grand plans for going and traveling all over Europe, but then we moved back to Washington. And so I was educated in the Washington D.C. school system, and at that time I was part of a reverse busing situation in which we were living on Bolling Air Force Base which is in southeast Washington and the schools in that area are not very good, so they would take us by bus every day into northwest Washington.
McCray:Okay. All right. Did you have siblings?
McKee:Yeah, so I had one sibling, a younger brother, who is eighteen months younger than me, and so we were I think at the age separation which made for a maximum amount of friction, which we were constantly fighting. And since I was the older one, I always made sure that I won the fights and so I could get my way, although it was amusing that then if I go forward some years when my brother went on to — well, we both went to Andover, and when he went to Andover he took boxing. And so as soon as he came back from his first quarter at Andover having taken boxing he wanted to go out and set things straight. All of a sudden I turned into a diplomat. Anyway, going back to when I was younger. We lived at Bolling until I was in the fifth grade and then we moved to Ohio at Wright Patterson Air Force Base. And at that point my father I believe was a general, and he rose up and by the time — he stayed at Wright Patterson for a number of years. I was there from the sixth grade, and actually I can't remember when they left. But it was like eight years — which is unusual, because normally in the military people are getting transferred around much more frequently.
McKee:But his expertise, when he came there I think he was working for what was called I think the Air Force Materiel Command, and then it became the Air Force Logistical Command, and he eventually became the head of that and was a Four-Star General at that point. So because of the fact that they were concerned that they would be transferred they decided that after I had been in high school for a year or two that I should probably go off to a private school. Because they didn't want to suddenly uproot me from my last year of school. And so I went to Phillips Academy in Andover. And that I think had a very good affect on me. I had always throughout my school had been one of the top students, and even though I worked fairly hard at school, I had never known failure. And because I knew this would be a step up to go to a school like Andover I went to a summer session ahead of time to try to figure out what it was like. And I took trigonometry and I flunked the first test. And that had just never happened to me before. So that was a real shock to the system.
McCray:Were you nervous about starting the fall then?
McKee:Then by the end of the summer I was able to get on top of things, but it was nonetheless sort of planning out that there is a much higher level. The competition was I think good fun.
McCray:Tell me a little bit more about your parents before we move on. I understand what your father's background— Tell me a bit more about your mother.
McKee:Sure. My mother was born in New Mexico and she was raised in Los Angeles. My grandfather died at a very early age, so I never met him. And I do not recall meeting my grandmother. Apparently my mother brought me up from the east coast when I was a baby and so she did see me. She didn't live long enough for me to actually get to know her unfortunately. So my mother was somewhat musical and spent a year I believe at the Chicago School of Music. She decided for reasons, that I don't know, that that was not going to work out or not what she wanted to do or something, so she did not continue with that. But that was the extent of her college education. Despite that, she was always very interested in books and in music — much more so than my father, who tended to be a much more practical, hands-on — well, he was a management-type of a person and not that interested in ideas per se. So my mother therefore had a big influence on me. I tended actually I think to identify with her, because I also very much love books and so I learned to appreciate classical music through her. The unfortunate thing that happened though was that precisely because I think we were very much alike, as I grew older and initially of course she knew much more than I, so then she was always a great source of knowledge, but as I learned more and more— She had me when she was relatively late in life I think. I don't know exactly what age she was, but in the late thirties. So even though obviously at an earlier stage in her life her mind had been very open and she had been learning more and more, as she got older her mind was less open and so — it tended to lead to some friction. We'd get involved in intellectual arguments.
McKee:So looking back on it, I feel a little bit unfortunate that I was less conscious than I am now that obviously she had done an incredibly amazing job of educating herself, and it's not her fault that she didn't have the benefits that she and my father provided to me.
McCray:Other than your mother's interest in books or music, were there any other influences prior to you going away to private school that stand out?
McKee:Well, I was a Boy Scout and spent a lot of time and energy with that. So eventually I became an Eagle Scout. I was never involved in athletics. My brother and I both learned to play a little bit of golf, and he went on and actually became reasonably proficient at it though. I didn't enjoy it enough, and furthermore this was all going when I was in Ohio, which was during the summer incredibly hot and muggy and just not what you'd like to be doing — at least not what I wanted to do was be out on the golf course when it was so hot and muggy. Ironically now I have taken up golf. Now that I'm older I play with my father-in-law.
McCray:Okay. Did you have an interest in science at a young age?
McKee:Yes. I was always interested in scientific things and I read— In fact I was always interested in things related to astronomy and also in biology. And I think part of the interest in astronomy is because there was some extremely good popular books written like the George Gamow books and books by Fred Hoyle.
McCray:So you read 1, 2, 3, Infinity and ones like that?
McKee:Exactly. Only later did I start reading — well, I think only later did Hoyle start writing science fiction, but I meant the books that he wrote just on cosmology with his views of things.
McCray:Did you read science fiction?
McKee:Yeah, I was a very ardent science fiction reader.
McCray:Any particular authors?
McKee:Yeah. Isaac Asimov and Robert Heinlein were two of my favorites at that time. My thinking about science kind of evolved. My father was in the military. My family, at least on my father's side, has a number of doctors. My grandfather was a doctor in a small town in Southwest Virginia called Saltville. And then two of his sons — that's two of my uncles — became doctors. One went into internal medicine and moved to Winchester, Virginia and one became an ophthalmologist and lived in Johnson City, Tennessee. So I thought that would be a possible direction for me, and also it would be sort of consistent with my interest in scientific things. But I had an amusing experience. I went to visit my uncle who is an eye doctor, and he offered to show me what it was like. He was going to operate on this young boy to straighten the eyes. So I got all suited up and everything so I could sit there and watch. The first thing that he did was, he stuck a needle in the eyeball and I fainted dead away. So they revived me, and I said that this is obviously completely crazy. I should be able to handle this, right? And there's no reason why something like this should make me faint. So I stood up and I was all ready for him to continue. So the next thing he did was he — by this point he had the needle through the eyeball and there was some thread and everything — and so then he pulled on it to straighten the eyeball. And then I fainted again.
McCray:Being a surgeon wasn't in your future then.
McKee:That was not in the future. Well I felt, "Well, if I can't be a surgeon, maybe I could be a research doctor and do medical research." This was of course before the explosion in biological research, and I was thinking that actually — was literally thinking of being a sort of combination M.D.-Ph.D., although I didn't know that those would be the degrees that would be involved, but that you'd be a doctor who was on the research end of things. But then as I got older and got more into things, I just kept on being more interested in fundamental science, so I naturally gravitated toward physics. And in fact, because of my love of science fiction and as I mentioned the book that I read were more in astrophysics rather than in physics, nonetheless I at least initially always thought of that as more like an avocation rather than a vocation and I didn't know what kind of physics I would do, but it never occurred to me initially that I would be in astrophysics.
McCray:Hmm. Okay. Some astronomers had an interest growing up and building telescopes and radio sets and that sort of thing.
McKee:I was never very good with doing things mechanical, so I didn't really make things. So as an experimentalist I was a bust.
McCray:Okay. So the more abstract ideas were what was appealing?
McCray:You would have been fifteen when Sputnik was launched. And also at this time the Cold War was going on, and perhaps more importantly your father was a general. How did these events in sort of the general context, how did that impact your life?
McKee:Well, actually it's interesting you mention about Sputnik because I don't actually remember it having a major impact on my life.
McKee:You know, I thought it was very exciting, but I don't— It was certainly true that in the household that I lived in and milieu that I was in the normal political viewpoint was what we would now call right wing — although at that time it wasn't really discussed. In fact my mother I think for a long time, around that time, was a Democrat, even though I think her political views would be characterized now as being really conservative.
McKee:And my father didn't really talk that much about politics, but I think he was always a Republican.
McCray:Did he talk much at all about military fears of Russian attack and things like that, or was that something that was really present?
McKee:Yeah, he tended to not bring his work home, so he didn't really talk that much about it. But he certainly was very concerned about issues like that. Unfortunately I don't remember when he made this comment to me so I can't remember whether it was at that time or later when he was retired and he was reminiscing, but he did say that at one point he had given serious credence to the possibility that we should have launched a first strike against the Soviets in order to just end their power once and for all.
McCray:Which at that time wasn't an uncommon point of view among people in the military and politics.
McKee:That's right. So fortunately that didn't happen.
McCray:Yeah. Your younger brother, did he also have an interest in science as well, or—?
McKee:He never had any interest in science and he's now a very successful lawyer in Washington.
McCray:So tell me about the transition to Andover. I mean how did you adjust to the environment there?
McKee:So as I said, I think the most thing that's striking my mind was having to learn at a much higher level. And I more or less made that transition during the summer, and so then when I was in— Once I was there — I just there for two years, and so I felt I guess reasonably confident. I was always an extremely studious person, so I worked very hard in order to try to stay on top of my studies.
McKee:And I was able to get in a class called Science Honors. I was in the regular science class for a while and then I got moved into that, and that was a more stimulating sort of combination of physics and chemistry. But you know at Andover they expect you to take a lot of courses. I just took the regular math and science, I was taking literature and history and language and all sort of stuff.
McCray:Did your parents have any—? I'm gathering from what you're saying that by the time you got to Andover you were thinking about a career either in medicine or science. Did they have any particular reaction to your tendency in that direction?
McKee:Well they were generally fairly supportive. I would say my father was a little disappointed that neither one of his sons had decided to have a career in the military, but in addition to the fact that that never appealed to me, since he had been so successful at it, it just seems to me that it would be very unlikely that I would ever repeat his success. I'm not exactly sure why my brother didn't do so. And had I gone to be a doctor, I think they would have been very happy, because they were a little bit worried. I don't know if worried is the right word, but they really didn't know very many academics, if any.
McKee:They did know that certainly it was generally not a profession you went into if you wanted to be economically secure, and so that concerned them. But they never tried to stop me. Or they really never tried to influence me. There was somewhat of a feeling that maybe some other direction might be more what they wanted to. Generally, at least the impression I had, was that I was fairly able to just pursue what I wanted to do in life.
McKee:I didn't feel obligated to follow in directions that they necessarily wanted.
McCray:You graduated from Harvard with a bachelor's degree in '63, so I'm guessing you probably started around '59?
McKee:In '60. So one of the things that happened was that, because I had this excellent background at Andover, I essentially was able to place out of the first year courses at Harvard. And so that's why I was able to graduate from Harvard in three years. However socially I of course started off as a freshman and lived in a freshman dorm. Socially I was a freshman, a sophomore and a junior and then left, in that sense, rather than actually staying there for the fourth year. And so at Harvard then I knew that I wanted to be a physics major, and so I took physics classes. But I also felt that this would be my last chance to get a broad education, so I actually took the minimum number of physics courses that were necessary so that I could take as much other stuff — you know, philosophy and literature and history and things like that.
McCray:Tell me about how physics was taught at Harvard when you were an undergraduate. What types of courses were you taking?
McKee:Well, my recollection is that the courses were not that different (I hate to say) than the way we're teaching physics today — that is, they have sort of an introductory course that's very general. And then you take specialized courses in mechanics and electricity and magnetism and quantum mechanics. And so that's what I did. And I'm trying to remember. I do not remember a very intense lab course experience, and of course I was not that interested in lab stuff anyway, so I may have repressed it. But it's interesting that now, as chair of the department here, you know I look at a lot of the exit interviews from our students, and a lot of the students find the lab course we teach here as being among their very favorite courses. So I don't know whether the fact that I didn't appreciate the lab was because maybe after all these years lab courses are better than they used to be or maybe it's just that even if I took the courses here now I would not be that interested.
McCray:Were there any particular subject areas that attracted or repelled you?
McKee:No, I can't really recall any. It was kind of interesting in a way, because I was in a situation where I knew I wanted to be a physicist but I didn't really know what kind of physics I wanted to do. And of course one of the disadvantages I think of all physics education is that it concentrates, at least the undergraduate level, almost entirely on building up the infrastructure that you need in order to do research today. But that means that generally you're reading about 19th century things and you really cannot get an idea of what the exciting problems are today from taking courses in physics.
McCray:Did you have a sense of what a career as a physicist meant? Do you recall having a mental image, "this is what a physicist's job looks like"?
McKee:Not at all precise, because obviously the only physicists that I knew then were my instructors. Now I did have a summer job. I had a couple of summer jobs, one at National Cash Register and one at the Naval Research Lab.
McKee:Yeah, just different places. I think the National Cash Register, maybe that's when I was still in high school. I can't really remember exactly when it was, but I was working more with more engineering type people. Nonetheless they were in the research parts of each company, and so I could see in that case either the company or the laboratory. And but in the case of NRL it was fairly mission-driven also. Because I didn't know any physicists as friends, I really did not know or have any clear idea of what it would be like — which is kind of interesting. I knew the subject and I knew that it was, perhaps it was attractive because it is in some sense the fundamental, the science that underlays the others. But I did not really have any idea at all of what it would be like to do that, to be a physicist.
McCray:Did you take any astronomy courses when you were at Harvard?
McKee:No. That's interesting. I did not take any. I'm not sure that I even went to the observatory during my three years there.
McKee:Astronomy and physics at Harvard are — unfortunately because of the geography they are somewhat separate.
McKee:Here, this is the astronomy building we are in now and the physics department is right next door, so I wander in between several times a day; whereas at Harvard the distances are considerably greater.
McCray:Yeah, the observatory is right out on Garden Street, so it's—
McCray:Okay. I guess in a way that sort of answers my next question, but I'll ask it anyway, which is, did you get any sense of how the physicists at Harvard or the physics students thought of the astronomy department? I mean just good, bad, indifferent? Were people taking courses between the two?
McKee:The people that I knew, I just don't remember anybody really getting that involved in astronomy. I don't remember any astronomers that were friends of mine. Which is unusual, because you would think that there would be a lot of overlap. And certainly the students who take astronomy as undergraduates, they have to take one of the physics classes.
McKee:But I just don't remember that many.
McCray:Any other important recollections of life at Harvard at this particular time?
McKee:Well, I had an opportunity to take a sort of research course, and so I did take one semester with Richard Wilson who was at the Cambridge Electron Accelerator. And I don't think that I was much use. As you can imagine, being someone with no experimental background and coming in and trying to be helpful at that time an operating electronic accelerator, there wasn't much for me to do. And now I think it would be a lot easier to take students like me in a project like that because they could presumably get involved with data analysis, and there is a lot of stuff that's done on computers.
McKee:But of course at that time they didn't have PCs or anything like that, so that that type of activity would have perhaps been less suitable for those students.
McCray:How were they doing the data analysis at that point?
McKee:I don't really know how they— And one of the difficulties also, this was a project during the term. I didn't do it during the summer. And then because of all the other course work it was something I could devote only a few hours a week to. So I didn't really get a chance to get into it. And again, if I contrast that with a lot of the experiences that the students in physics and also I think many of the students in astronomy have, is they are able to get involved in projects and they can take a larger fraction of time devoted to them. They can also sometimes work on them over the summer. And they really get actively involved in them and get so they really understand what the problem is and so forth. And I really in this brief encounter really did not get an opportunity to do that.
McCray:The style of research that you saw going on at the CEA, did that make any impact in terms of sort of the scale of particle physics? Was that something that interested you?
McKee:I think the CEA was probably on a fairly small scale compared to a lot of places.
McCray:Yeah. It wasn't like some of the later particle accelerators.
McKee:That's right. And subsequently when I was in school then I did not find that attractive. It is certainly true that in this experience I did not see myself fitting in in any way.
McKee:Well, because as I said, I wasn't able to really do anything that was that useful, and I didn't really see how I was — you know, if I had had more time — it wasn't really that I could see a place, a way that I could really contribute, except for I just didn't see that. I hadn't had enough background to understand some of the particle physics issues. I never took a course in particle physics. So there was just a huge mismatch between my background and what I could do and what they were doing, and so I just didn't see how I was going to fit in there.
McCray:Was this a source of concern at all? I mean I realize at this point you were only twenty years old and most twenty-year-olds don't get too concerned about anything, but did you have any anxiety associated with where you might fit in, in terms of the larger science community?
McKee:No. And I think that that may have been because I understood that you had to go on to graduate school, and of course I figured in graduate school I would actually learn how to make this transition.
McCray:Okay. Were there any particular instructors? You mentioned Wilson at CEA, but were there any other ones who had any strong impact on your, affected your career or areas of research that you got involved in as an undergraduate?
McKee:No, I can't say that there were.
McCray:Okay. Well let's talk then about graduate school. You graduated from Harvard in '63 and then came out here.
McKee:So yeah, I should mention there was an interesting thing that happens. One of those points in your life where a single incident does make a change. Because since I had graduated from Harvard in three years I thought that I should take advantage of the fourth year and actually spend a year in Europe. And because I had been taking German as my language, my plan was to spend a year in Germany. But then just as I was literally about ready to have everything finalized for going to Germany, I was offered a Hertz Fellowship. They were just getting started around that time. And the Hertz Fellowships are very generous fellowships to support people in physical sciences.
McCray:I don't know much about the fellowship program. Could you say something about it?
McKee:Well, it was founded by the Hertzes of Hertz Rent-A-Car, and they were very good friends of Edward Teller, and so Teller knew my father, and so that was I think how I found out about this.
McCray:I'm curious about the Teller-father relation. That's interesting. Did they know each other well?
McKee:Not that I know of, no. It's just that they knew each other in some way.
McCray:Teller wasn't coming over to the house for dinner?
McCray:Okay. So this fellowship was created. What effect did that have then? What did it do for you?
McKee:Well, the thing is that I had to make up my mind. I saw this opportunity that might not be repeated, to have a fellowship and to come here to Berkeley. Because I had applied to graduate schools also. I didn't really — I was keeping my options open. And then when I had this fellowship I decided that rather than go to Germany I would just come straight to register. Also the fact that my father knew Teller then was actually very beneficial to me initially, because then I got a chance to become — I got to know Teller better after I came out here.
McCray:I certainly want to make a note to come back to that, but before we do that, I wanted to know what other graduate schools were you considering before coming out here?
McKee:In all honesty, I don't remember the ones that I had been admitted to. My big recollection is that I also had a chance to go to MIT, and since I had spent my whole life on the east coast I just wanted to do something different, so I wanted to come west. So Berkeley was it.
McCray:Was there a particular area of research that you wanted to focus on?
McKee:No. I would say I was still completely unfocused, and this was also — one of the interesting things that happens now, which I think is very good, is that students come around and they visit campuses and really help support these visits. And there's in fact a lot of competition among the different universities to get the best graduate students. So back then I assume there was also a competition. It's just that it was the competition had not escalated to the point that you're bringing these students out and giving them signing bonuses and things like that. At that time I assume it was just more catch as catch can. So I really had never been out here and I really didn't know what to expect. I just — you know, I knew that Berkeley was an outstanding physics department and that it would be very different than what—
McCray:What was your personal reaction after having spent so much time in the east to coming out here?
McKee:I enjoyed it quite a bit. I had a summer job out at Livermore for two summers, so the first summer before classes started and then the following summer. And so, and through that experience I made some very good friends who in fact we're still friends.
McCray:So you arrived here for the start of graduate school. What happened then?
McKee:Well, as I said, the first thing that I was doing was I was actually working out at Lawrence Livermore. So this was my first opportunity to get involved in something that was more related to research and also was theoretical in nature. And actually these friends of mine and I were working on classified research, so they were much — I guess it was much easier to get clearance at that point than it is today. Again the type of work that we were doing was not particularly exciting. It was more, you know, varying parameters and seeing what happened rather than getting involved in anything related to physics. That was the first summer. As you will see, in the second summer it was totally different.
McCray:Could you say something? I mean I understand that the research was classified and I don't know if it still is, but could you give some general indication of what type of research you were doing when you first arrived here?
McKee:Yeah. Well, it was — I really don't know how much I can say about it, but it was just related to nuclear weapons and to do computational modeling of that.
McCray:Okay. This is sort of off the track, but a colleague of mine is doing research on the history of computing for nuclear weapons design, and as you were mentioning that, that came to mind, and I was wondering how would you do this type of research? Was it by hand or what would sort of the day-to-day life be of this type of work?
McKee:Well, at Livermore they had a very elaborate computer system, so at that time, at least for this work I did not get involved in actually dealing with the computer. I was dealing more with analyzing the results and then we would discuss with my supervisor maybe how we should change things to try to get things to come out differently, but at least at that time I was not involved in actually using the computer. Later as a graduate student I did get much more involved with that.
McCray:Okay. Would you work in large groups or small groups?
McKee:No, this was a very small group. This one individual had — I think he might have had a few students working with him.
McCray:What was his or her name?
McKee:His name was Peter Giles.
McKee:And so I lived here in Berkeley then and then commuted out there. So at the end of that summer I still didn't know what I wanted to do. I then took — you know, started taking classes, and the two major classes that you had to take as a graduate student were quantum mechanics and electromagnetic theory, and those were both very intense. But in addition I, since I had a fellowship and a lot of the other students had to support themselves as GSIs — as graduate student instructors — I was able to take another course. I wanted to try to figure out what kind of physics I wanted to do. Maybe I would try astrophysics. So I came over to the astronomy department. At that time Louis Henyey was the chair, and I asked him what course should I take. And he said well I was in luck, because they had a visiting professor from the University of Washington, Karl Heinz Böhm, and he was going to teach a course in stellar atmospheres, and so that's the course that I should take. And I don't know if you know anything about that subject, but it has a terrible reputation of being one of the most boring parts of astrophysics. Although of course the people who are in the field, I am sure they love it, but it is — I certainly found it very boring. And also partly because at that time I had no astronomical knowledge at all, so I didn't really understand the context in which it was being taught. And so you learn a lot of approximation techniques to deal with how the radiation gets out of the atmosphere of a star. But if you don't know that much about stars and you don't know about why you are trying to do this, it's much less interesting. And so even though I'm sure that Böhm was a perfectly fine lecturer, my conclusion at the end of that semester was that, of all the types of physics there were, there was one that I could definitely cross off the list, and that was astrophysics.
McCray:Yeah. I could understand if you don't have the context for the astronomical context then it probably becomes problems in radiative heat transfer or whatever.
McKee:And there were other courses. I think this is a problem that all physics students coming into astrophysics have is that you don't really know that much about the overall subject and you're being kind of thrown in in the immersion technique. Because since then I have had to get involved in understanding some radiative transfer in order to solve problems that I am really interested in, and then of course all this stuff turns out to be very interesting and useful. It's just that in contrast there is something about cosmology which is going to have an intrinsic interest of its own. A course in stellar atmospheres at least for most people I don't think would find it that intrinsically interesting. You know, if you just keep it in isolation.
McCray:But once you begin to connect it then with these other areas of astronomy, then it becomes interesting.
McKee:So in any case, so I decided that I wouldn't do that. Now another thing — and again this was I guess through a connection with Teller, that at that time Hans Mark was the chairman of the department of nuclear engineering. He invited me to come over and look there to see if I would find anything that was of interest. And I spent — I actually don't remember exactly how much time I spent, but I remember going over there several times and trying to look at various different things that people were doing, and my reaction was similar to the one that I had at the CEA; that is, that this might be interesting work, but there was just no connection between what I saw in terms of my abilities and interests in what they were doing. I just didn't see how I was going to fit in at all. And so I still was at a loss. And but at least I don't recall being concerned about that at all.
McCray:I'm kind of curious as to why you weren't concerned, because I could imagine other people being especially concerned about, you know, you've gone through three years at Harvard and now you're in graduate school and you still haven't quite found your slot.
McKee:Well part of it was that there was no pressure, and I think that's one of the advantages. At least I first thought it was as an advantage at Berkeley as compared to say a place like Princeton, where at Princeton they expect students to finish very quickly. And then in a situation like that if you didn't know what you wanted to do then obviously I'm sure I would have been very concerned. But here, certainly at the end of the first year, you were just taking these basic courses. There was no pressure. Fortunately my second summer I went out and worked at Livermore again. This time I had a totally different experience because I had a chance to work with Stirling Colgate. And so Stirling was of course unlike anybody I'd met up to that point, and in fact even now, forty years later he’s still — a unique individual. I don't know if you've had a chance to talk to him.
McCray:I haven't, but I've heard other people give a similar view.
McKee:Yeah, right. And I mean he is an incredibly dynamic and creative individual. So that he was working on — as I understand it, he was working on five different projects, and he had them organized so he'd just spend one day on each project each week.
McKee:And three of them were classified, so I really didn't know too much about what they were. My understanding is that he was thinking of ideas for example how you could use nuclear weapons as sources of neutrinos to do neutrino experiments, and you know problems like that. Anyway, so he had a lot of things that he was working on which I didn't really know that much about. Then on Thursdays he did plasma physics, and he was one of the earliest people involved in doing numerical simulations of plasmas. And then on Fridays he did supernovae. And at that time he was working with Dick White on the initial paper which I think is one of the seminal papers in astrophysics and certainly defined the basic principles for core collapse.
McCray:How did you get hooked up with him?
McKee:So again I'm not— I assume it was through Teller. I don't remember anything specific, because Teller obviously knew Colgate well so he suggested that. And what Stirling did was he did something which was, I found enormously challenging. He, as I mentioned, was working on this problem of core collapse of supernovae, and one of the issues was what was the equation of state of matter in the core of the supernovae when it's collapsed when you get up to densities that are nuclear densities, but at very high temperatures. Where the temperatures are measured in MeV or tens of MeV, and so things are extremely hot. And this was fascinating, because I had taken a course in statistical mechanics, and so theoretically I should know what this was, but this was the first time when I actually had a chance to try to apply the formal training that I'd gotten to a real problem. And I found it enormously exciting and very challenging, and it made the physics I was using more interesting. Before it had somehow been kind of dry because I didn't really know what statistical mechanics was good for. Now I could see it. And then I'd come in with problems that I didn't understand. And then the next thing that happened is that normally when you're taking courses if you have a question the instructor knows the answer, because the instructor is very carefully telling you the stuff that they know.
McKee:And they've thought about it and, at least good instructors, have thought about it very carefully. So they can generally answer questions that are related to the material. But when you're doing research of course then I would come up with questions and these people who were extremely highly respected physicists working on this full time didn't know the answer, and that also I found very invigorating, that they — that you would have to go ahead and really think about it and solve it yourself. So I found that to be an enormous charge. Now the ironic thing is that in fact Stirling and I never wrote a paper together. Because I would see him — because even though he spent the one day on supernovae, that didn't mean he spent that day with me. He was spending it mostly I guess with Dick White and he may have had some other people working on different parts of the project, I don't know. So I would just see him maybe for an hour or something each week. And then I didn't actually have a chance to finish this project that I was working on, so I worked on it for another couple of years afterwards and wound up publishing that paper by myself.
McKee:But, he did wind up working with another Mc Kee, in fact another C. Mc Kee, named Chester Mc Kee, and so there are some Colgate and Mc Kee papers in the literature on supernovae.
McCray:Spelled the same way?
McKee:The last name is spelled the same, but his first name is Chester, not Christopher. Yes.
McCray:Yeah. I think when I was doing some web searching I think I might have come across this. Okay.
McKee:I actually have never met him. He subsequently went off and as I understand and did geophysics and, rather than staying in astrophysics.
McCray:Interesting. What was the atmosphere like at Lawrence Livermore when you were there? Do you have any recollections of what it was like to do research there?
McKee:Yeah. I found that it was a very dynamic and exciting place. They had, young people there. This was a time I believe when I was there Johnny Foster was the director, and he was a fairly young person. He became director I think in his late thirties or something, so it was a very dynamic place. And then of course anything to do with Colgate, because he has a huge amount of nervous energy, and in fact so much so that it makes it difficult for him to talk in a way, that the ideas tend to spill out and they're not always in a completely logical format.
McCray:What that difficult for you when you first started to work with him?
McKee:Well no, I think on one-on-one conversations I think we could communicate fine. But it's particularly true I think sometimes when he gives talks. And then I remember at a conference that was held in his honor that the person who, his long-term collaborator, Al Petschek, said that he regarded himself as Stirling's translator.
McKee:Yeah. The recollections that I had at that time were quite positive.
McCray:Okay. Two questions come to mind. I guess at this point I wanted to ask you about the relationship with Teller, because from what you are describing so far it kind of seems as if he is a sort of omnipresent figure in the background. What was your relationship with him like?
McKee:Yeah. So I would go and see him periodically, and we would talk about physics. Initially he would talk to me about what it was that I was learning. Teller would be out at the lab during the week, but then on weekends he would have people come and see him at his home. And it would be sort of almost like a schedule. There would be people who would go in for different hours, and he would be sitting there and talking. And about an enormous variety of subjects. I really don't know all the things that were talked about. But as you know, Teller, who in my own opinion, I think he's one of the most brilliant people that I've ever met, and he clearly decided at a fairly early time to devote a lot of his intellectual energy to politics rather than to science.
McKee:And had he continued and devoted it primarily to physics I think he would have achieved even much more fame as a physicist. He did many great things in physics, but I think he would have done a lot more had he done that. But I had the impression even then, and then as I knew him later, that really his intellectual energy was focused primarily in more political issues rather than physics issues.
McCray:Did the two of you talk about any of these issues at all?
McKee:Not very much, no. When I would talk to him it would be primarily about science. And it was interesting. Again it’s this issue that there was sort of a disconnect between the formal education that I was getting and this experience that I had with Colgate. Because I do remember this one time that I went to talk to him, and he wanted to know what I was doing in quantum mechanics. And the person who was teaching quantum mechanics at that time actually skipped over all of the basic quantum mechanics and was going to teach us "S-matrix theory," which was then the current rage in particle theory. And S-matrix theory is a very formal way of describing the outcomes of particle physics experiments. And I was learning it, but it's interesting that if you have an intelligent person sit across from you and ask, "Well, could you explain it?" basically I couldn't explain it. I had learned how to manipulate some of the symbols and everything like that, but I hadn't really integrated it into my own thinking, because I guess it just didn't fit very well. Probably for that reason, although I don't remember formally coming to a decision about particle theory, I think that I never seriously considered particle theory, because again I saw it as being perhaps somewhat more formal than the way that I preferred to think.
McCray:The way that you described S-matrix theory reminded me perhaps of say a medical doctor who knows how to do a certain operation, you know, set a bone or something, but isn't aware of the underlying physical mechanical chemical processes behind healing a broken leg. Would it be similar to that of knowing how to manipulate this tool but not really understanding the basic ideas?
McKee:Except I never — I mean, doctors become extremely proficient at that. Obviously I never acquired any proficiency. Sometimes by having enough proficiency you get to the point where you actually think that you understand it, and you know I'm not sure that I ever got to that point.
McCray:So when you mentioned that this was how quantum mechanics was being taught, did Teller or Colgate have a particular reaction to this manner of teaching?
McKee:I don't remember what his reaction was. At that time Teller did have a position in the physics department. I believe he had was called a 0-FTE , which means that although his appointment was out at Livermore, he was also a member of the department. That was very useful because after this summer working with Colgate then I knew that I did want to do astrophysics. And so he was then very helpful in supporting that. Whereas not everybody in the physics department— This was before the physics department had actually expanded into astrophysics. And so what Teller did was to encourage me to meet with George Field, which I did. That was of course enormously beneficial to me because I immediately hit it off very well with Field, and then became my thesis advisor.
McCray:If we're talking about Field, I wanted to ask. Did you see yourself, as a physicist going into astrophysics, were there particular, for lacking of a better word "talents" that you saw yourself bringing into that area, or certain elements of your training as a physicist that would be transportable into that area of research?
McKee:Well, I guess that I always felt that astrophysics was a type of physics rather than — I didn't see myself going into becoming an astronomer, so I didn't really see it as a change in field. I just felt it was— I felt that astrophysics was a part of physics and so I was now picking out which kind of physics I would do.
McCray:Yeah. That's something that's interesting. Now I think astronomy and astrophysics have really become very closely intertwined. How was that relation when you were a graduate student? The way you're describing it, it sounds almost like astrophysics was — there was somewhat of a gulf separating the astronomers from the astrophysicists.
McKee:That's certainly true from a departmental standpoint, but I'm just saying from an intellectual standpoint. I just had never seen it that way. For example if I had decided to become an observational astronomer then I would have regarded that as probably a change in field, and then this question you raised would have come up. But I just, since I wasn't going to do that it was— And particularly after my experience at Livermore with Colgate, because Colgate was working on a wide variety of different physics things and then he did astrophysics as opposed to plasma physics. It was just a different kind of physics. It wasn't that “Oh, now I have to do something completely different.”
McCray:Okay. Well tell me about working with George Field then. Why do you think the two of you hit it off so well?
McKee:Well, I think Field is an enormously engaging and charismatic person, so at least from my point of view it was very easy to get along with him. I still remember that I came in and asked him a question one time, and so he started trying to think about it, and pretty soon he had covered the whole blackboard with trying to work out the answer to this question I had asked. I was also extremely impressed by the obvious enormous ability that he had to be able to work things out like that just sort of spontaneously. And he was very good in — you know, allowing me to essentially choose the direction that I wanted to go in. So he made a large number of different suggestions of things I might work on for my thesis, and I would read up on some of them and we would talk about them. And in the end it was kind of interesting. The topic that I chose went back to the work that I had done with Colgate.
McCray:Chris McKee interview, Tape 2. Okay.
McKee:The work that Colgate had been interested in then, in particular, was the problem of 2 stream instability in the formation of collisionless shocks. So the basic idea is that at that time — in fact this was shortly after the discovery of collisionless shocks in space. Normally if you have a shockwave — this had been studied extensively in hydrodynamics I'm sure, but everybody assumed that the collisions between particles played a central role. So just now, as now when you have a plane that goes at a supersonic speed it creates a sonic boom.
McKee:And so that just means that you have this jump in the pressure in the air and this pressure, if it is done at high enough amplitude, will then propagate faster than the speed of sound. And that when it goes faster than the speed of sound this causes discontinuity. So you have the gas ahead of the shock which is sitting there, then you have the gas behind the shock which is moving and it is a higher pressure. And then there's this very thin layer in between the shock part where at least in the atmosphere you have the fast particles hitting this, stationary particles, and sharing their momentum and putting them up to speed. And so it's all done with collisions. So then when people went out into space and started looking at what was going on with the interaction between the solar wind in the Earth's magnetosphere. They found that there too there seemed to be a discontinuity, but it was very simple to work out the collision mean free path for the particles, and it's orders and orders of magnitude greater than the thickness of the transition that they saw. So this then suggested that the shocks would be collisionless and that then became a very active field of research and in plasma physics try to understand how that's possible. And in fact it's still an open question. It's a very important question in astrophysics as well.
McCray:So this is something that relates then to the Earth moving through space and having — I can't recall which if your papers, but it was like a bow shock? Is that what it's referred to as?
McKee:Yeah. It's a bow shock. And the key thing, as I say, is the thickness of that shock front is very thin compared to collision, so that essentially instead of having the particles in the solar wind and the particles in magnetosphere undergoing physical collisions, it is that they start streaming through each other, and this relative streaming then excites various plasma instabilities. And these instabilities then cause large amplitude electric and magnetic fields to grow, and then those can effectively thermalize the particles.
McCray:Okay. So that's where the collisionless idea comes from?
McKee:Yeah. And so what Colgate had done was focusing on the very simplest case where you just have two beams of particles are going through each other and all you have to worry about is their electrostatic interaction. And he showed that indeed when you had the two streams of particles going through each other, they would apparently suffer a collisionless interaction and they would heat up. It's suggested it might be a viable mechanism to actually serve as a shock. Now, at around this time, Colgate developed another theory with Montgomery Johnson on the origin of cosmic rays, and he proposed that cosmic rays were created in supernova explosions. The idea was, is that when you have the star undergo this explosion it generates this terrifically powerful shockwave inside and the shockwave, when it gets toward the surface of the star, sees a very rapidly declining density gradient. And as the shock sees this declining density gradient that starts accelerating it. It runs away. I'm trying to think about an analogy. You can imagine if you are pushing on something very hard and then all of a sudden if the resistance goes away your arm would accelerate. And it's sort of in a way like that. Another example is the crack of a whip. As it gets thinner and thinner it gets faster and faster, and that's what makes the loud crack. So he what he and Johnson showed was that this process could be so powerful that the outermost surface layers of the star could be ejected at relativistic velocities, and then those relativistic velocities would be able perhaps to count for the observed cosmic rays.
McKee:So this was a very radical proposal. And but I became worried about this in the sense that since he had earlier shown that, when you have two streams of particles go through each other, they stop. How was it if I have these cosmic rays which are now just this stream of very high-energy particles trying to go through the interstellar media, wouldn't they suffer the 2-stream instability and stop and they’d be trapped and therefore they wouldn’t work?
McKee:So I decided that I would generalize the work that he had done to relativistic energies and — because all of the work that he had done was for non-relativistic particles. There were people at Livermore who are very knowledgeable about plasma simulations and I got a chance to work with Ned Birdsall, who was a professor here in electrical engineering and also had connections at Livermore, and Bruce Langdon, who continues to be out at Livermore, and they gave me some good pointers, and I started doing these plasma simulations. And they were very elementary by today's standards. They were entirely one-dimensional.
McCray:What is a one-dimensional simulation?
McKee:Okay. So but in this case we're just simulating two streams of particles that are going through each other. Because the interaction is entirely electrostatic you don't actually have to worry about particles moving in the transverse directions.
McKee:And you would just wind up developing very large amplitude waves that these electric fields parallel to the direction of motion that would actually alter the particles in that.
McKee:So in that sense it was very easy, but on the other hand computers then of course were not as powerful — not even as powerful as our laptops are today. So what I found was, is that I first reproduced Colgate’s results. But then I wanted to see what would happen if I increased the number of simulation particles. And I found that the more particles that I used — I was using a particle and cell method, so you're not really representing individual electrons. Imagine that you take this plasma which has electrons and ions, where in this case I might just do entirely two electron beams going through each other. And then divide the electrons into slabs. This is all one-dimensional. And so like the whole group of electrons that you actually calculate would be in this one slab. But then you would see how they would interact collectively. You didn't really have to worry about individual particle effects. But there is a problem that when you, for any finite number of particles that you are using to simulate the plasma, there are fluctuations in the number just due to the fluctuations. That's going to create electric fields and you are going to get effective collisions. And so what I concluded was that if I kept on adding more and more particles I'd get less and less of an effect. And I eventually decided that what Colgate had found was in fact entirely collisionless, and that you could not mediate a shock. If you had both electrons and ions, you couldn't mediate the shock through electrostatic ways alone. And then I generalized that to the relativistic case and showed that that was true. But of course this then turned things on their head in my thesis because originally I had been assuming that his simulations were correct and therefore that would cause problems with the cosmic ray theory. And in the end I concluded that it was the simulations that were incorrect, and so in fact his cosmic ray theory, at least from that point of view, was still viable. And so it was interesting, because those were problems that Field was not particularly working on. In fact, during that time I think when I first got here, he did some of the fundamental work on interstellar medium, the famous paper of Field, Goldsmith and Habing. And in fact so Don Goldsmith, who still lives here in Berkeley was a fellow graduate student and was working on that, and that was one of the most important papers that Field wrote in interstellar medium physics. And I think at around that time he also wrote a seminal paper on thermal instabilities. But his own interests were moving into cosmology, and so a lot of his work has started moving in that direction. So even though he was a fantastic advisor in terms of talking and stuff like that, we actually never collaborated, and so the papers that I wrote were entirely on my own.
McCray:It's interesting that your work Colgate and then your work with Field, that in neither case you co-authored papers together.
McKee:That's right, and it is unusual, and it's generally unlike the way that I work with my students, although I certainly try to encourage them that if they do something on their own then I try to encourage them to publish it on their own. But generally in most cases, most of my work has been more collaborative. I think that's probably true — I don't know why this is, it would be interesting to ask Field. I think I never asked him this. But, because most of the students he had, I think, he did collaborate with.
McCray:Hmm. How many students did Field have at a particular time?
McKee:I don't actually remember. The other students I recollect, John Rather did a project. I think he then moved into radio astronomy. Susan Ames, who is in Europe someplace, Don Goldsmith. In fact, I can— For Field's 65th birthday we put together this book— This shows genealogy, so to speak, so that you can see exactly.
McCray:Just for the record, this is Physics of the Interstellar Media and the Intergalactic Media. And what year was this? '95. So I guess the conference was probably '94, '95. Okay. Oh, so this is in the beginning of the booking showing Field’s students and so on. Okay. Interesting. This is great. Yeah. So it shows — because this is then my scientific lineage also going all the way back: Charles Young, Henry Norris Russell, Lyman Spitzer and George Field. And then Field was at three different universities, and so he had only one student at Princeton. That was Carl Heiles, who then had a number of subsequent students. And then at Berkeley he had Per Aanestad, Susan Ames, William Brown, Don Goldsmith, John Hutchins, Sandra Kellman, Chun Ming Leung, myself, Peter Meszaros, Telemachos Mouschovias. Another McKee?
McKee:The other McKee worked with Colgate, not Field.
McKee:And then Manuel Peimbert and Paul Woodward. And so one of the interesting things — this is now somewhat of an aside, but one of the interesting things in putting together this genealogy that you immediately become aware of is that there has been a lot of concern, and particularly I think during the seventies and eighties when there was seen to be an imbalance between the number of students that were being produced and the number of jobs that were available, that if everybody reproduced themselves then you would have a rapid exponential growth, and that's obviously not sustainable. But the interesting thing that you can see when you actually track one of these genealogies is that it's more complicated. That it's not that everybody creates two or three people and then you get this exponential growth. Many people do not reproduce themselves at all, because they were not in positions in which they can train new students.
McCray:Right. They leave the field.
McKee:Yeah. Or even if they stay in the field. Many of the George Field’s students are still in the field, but they just are in positions where they don't have students.
McKee:So it makes it a little bit more complicated as to trying to predict what will happen there. In any case, Field was certainly one of the intellectual leaders here at Berkeley and helped make it a very exciting place.
McCray:Tell me how you were doing your research at this point. I understand that you spent two summers up at Livermore and you came to Berkeley with this Hertz Fellowship. I guess first of all, how were you supported after that time? Were you working as a graduate assistant?
McKee:Well, the Hertz Fellowship actually took me through most of my graduate career.
McCray:Okay. It wasn't just a one-year fellowship.
McKee:That's right, yeah. And then for the final year when it was no longer operational then, I went out to work at Livermore. And I worked in the theoretical division there. But I had started doing some computing out there before because of a disaster that befell me. I was doing this computation using the CDC computer that the campus had. And this was back in the days when everything was done with punch cards, so I would sit there and write the program and then it would punch it out and take the deck of cards to have it run on the computer. And the NSF as I understand it — of course this is now, was the impression I had as a graduate student, and so the actual facts may be somewhat different, but at least what I had been told was the NSF had a 10 percent budget cut sometime in the mid-sixties. And rather than just going ahead and cutting everybody's grants 10 percent, they bundled all of Berkeley's NSF money into one package, subtracted the 10 percent and told the campus to deal with it. And so at that time the campus was building Evans Hall. NSF was helping to support it. So obviously that had a zero cut, because it would be catastrophic if you started stretching things out. And then they went ahead and they had some way of deciding as to how large the cuts everybody should get. And I'm sure there were very many famous scientists on the campus who also argued that they should get zero, but basically there was a pecking order established and it was sort of like this acceleration of the shockwave I was describing earlier, that the amplitude grew and grew, and by the time it got to student support for computing it was 100 percent cut. So I had really no way to keep on doing my work. But I fortunately was able then to arrange to go out to Livermore to do it.
McCray:If you hadn't been able to do that, would that have put an end to your dissertation work on that subject?
McKee:It would have caused a very major change if I had not been able to somehow find a way of doing the computing, because that was the focus of my research.
McCray:It is an interesting way of dealing with a budget shortfall.
McKee:(Laughs) It was quite amazing. So then I had an amusing experience when I was out at Livermore. As I said, generally the people there were very supportive and in fact I became a very close friend of Bruce Tarter, who at that time was just a group leader in T Division and was my supervisor in that. He subsequently became the director of the laboratory and just recently stepped down from that position. But they had one of their periodic changes out there, that they you know restructure things and change things. Some areas that had been classified became unclassified and vice versa. In any case, the only experience I've ever had in my life where I literally felt that I had stepped in advertently into a Kafka novel. So, because I would only go out there once every few days, and I went out there and I went to my office that I had been working in for a year, and I had all my computer printouts and everything carefully organized. I was really working away, making great progress. But where my desk had been there was now no desk, there was something else. Where all my computer printouts were, they had disappeared. In fact, I walked into what I thought was my office and it was completely reorganized and obviously lived in, and it just bore no relation to what had been there just a few days ago. And of course the most frightening thing was that all my work, which had been carefully stacked up and organized, had disappeared. And so I frantically started calling around, and this was on a Sunday that I went out there. And so it's hard to get people. Eventually what I learned had happened, is they had made this change and they had taken all my stuff and they stacked it up in the hall so that it could be moved to wherever they were going to move it. But, of course, that evening when the janitors came by, they know what stuff stacked in the hall means. That means that it gets taken out to the dump. Now actually I was extremely lucky, because it turned out that I was in an uncleared area. If I had been in a Q-clearance area, then that they do is first they shred it, then they burn it, and then they bury it.
McKee:But because this was not in such an area, all they did is they took it out into this big area outside Livermore and they dump it into a ravine and then they get bulldozers and they put two feet of earth over it, and then they have a large water truck come by and wet it all down so it won't blow away. And so they actually took me out to where it was that my thesis was buried.
McCray:What are you thinking at this point?
McKee:I was completely panicked, as you can imagine.
McKee:And so then they did the inverse. So you imagine now this giant backhoe going and starting clawing up the earth, and you can just imagine this going through my thesis research. And they scraped off, estimated roughly where that day would have been, and then they started scraping off the dirt, and then they let me kind of poke through. And it's just amazing, because you know I was essentially going through the trash from the whole laboratory, and remarkably enough, I was able to recover several of my lab notebooks. And even more amazing — as I mentioned, at this time all the computing was done with punch cards. I had found — and I have kept them in these IBM card boxes — and I found one box and the front end had been sort of crushed so that it actually sealed the box, and the cards after shaking off a little dust and dirt here, they could go right through the card machine. So that was, again, almost a thesis-changing event.
McCray:That's beyond imagining.
McKee:Right. And so ever thereafter then you know I had a new office and then I would have my stuff there and you could still see at the bottom where the old ones were and still mud-encrusted papers that had been dug out.
McCray:Other than having your thesis research buried alive, did the classification, did that affect your research at all? You mentioned that yours wasn't under the classified umbrella, but did that ever enter into it?
McKee:That's right. No, at that time, since the work I was doing was completely unclassified it really did not have any implication. I can't remember. I think at that time you were supposed to run your — like if you wrote a paper you'd run it through the technical information division in order so that they could give it their seal of approval. I don't recall any bureaucracy associated with it.
McCray:Okay. I had a question actually jumping back a couple years, but when you first arrived at Berkeley my understanding is that the size of the physics classes had grown enormously with many students coming in and people talking about how the atmosphere had changed from say ten years prior to now having to deal with this massive influx of students. Was this something that you noticed at all in terms of just interaction with students or faculty?
McKee:Well, of course I was completely unaware of the change, but it's certainly true that the class, when I came in I was one of a hundred students. So that's two and a half times the current size of classes that we admit today. And in fact the class was so large that the friends that I made turned out were all former Harvard students. Because normally you know if you're in a class then you, everybody has something in common and you get together and you become friends, but if you're one of a hundred people that's not a small enough group. So the amazing thing is that all these people that had been physics students at Harvard — actually because I had been trying to not do too much physics when I was an undergraduate, I don't think I — I may have known one of them, but I really hardly knew them at all. It was only after I got here that I became friends with them because we had something in common. And the only other person who didn't fit that description was a guy named Bob Matthews, who had actually served in the Navy for a while, so and he became a good friend of mine also.
McCray:Did you see any effect that this had just on collegiality in terms of interaction with other students? I mean my guess would be if you had this many people the competition for resources probably would have been fairly fierce. Did you ever see any negative effects along the way?
McKee:No, I didn't, but again, that's because the first thing that I decided that I really wanted to do was astrophysics, and in that case then there was not — that didn't seem to be that competitive, whereas by contrast if— I think it also is something— that in principle theorists can take on more students, and particularly in my case since I was supported. You know, my advisor didn't have to raise money to support me, whereas if you had been doing laboratory stuff, then that is obviously much more limited in terms of the number of students you can take.
McCray:Okay. So if you had gone into high-energy physics or nuclear physics it would have been different?
McKee:Yeah. Well, perhaps. Again, I think one of the things that happened was that at that time there were a lot of students going into particle theory. This is when Berkeley, I think primarily under the leadership of Geoff Chew, was one of the the main centers of particle theory.
McKee:And so there were a huge number of students who were doing that. And I don't recall, talking to friends of mine, I don't recall people complaining about the fact that they were unable to get faculty to work with.
McKee:Subsequently there was of course a lot of problem with people finding jobs.
McCray:Yeah. I mean the bottom sort of fell out I guess around, right around the time you graduated.
McKee:That's right. And it was quite amazing. And again, this sort of shows that — in a way I feel, and I'm not quite sure why this is true, that I was unconscious to some extent of the larger situation. And I remember my wife giving me an article in Science magazine — I believe it was written in 1968 — in which somebody was pointing out that the number of science faculty had been growing exponentially and this had to stop. And I thought this was crazy. I had always assumed that I would go ahead and get my degree and then I would get a faculty position, and that's just way everything happened. You could see it around you. And of course in reality this article is exactly right, and it did come to a screeching halt.
McCray:It seems like a good place to pause. It's just lunchtime, so let's just stop for now.
McKee:There's an anecdote I’d like to share. Because earlier we were talking about the role of physics in astrophysics. And I believe that it was in my second year here — unfortunately I'd have to look back at the records of the physics department to verify this, but at least around that time — the normal department chair went on sabbatical and Emilio Segre became the chair for a year. And so I went and I talked to him and I told him that I decided that I wanted to go into astrophysics. And he told me that, "The physics department does not do astrophysics" and that there were some places that did like Cal Tech or people at Livermore or I could transfer to UC-Davis, but if I wanted to do astrophysics it couldn’t be at the physics department at Berkeley. And so fortunately I talked this over with George Field and we realized that he was just the acting chair for a year, so I just wait until his year was over and talked to the regular chair who was much more amenable to the idea.
McCray:Do you recall a reason that he suggested that?
McKee:Yeah, I definitely got the impression that he felt it was not appropriate in physics. And why he felt that way, I don't know.
McCray:When you were at Berkeley, just on campus in general there were a lot of student protests, things like that going on.
McCray:I'm curious about if that had any effect on you — either your research or just you personally.
McKee:Well, yeah, I did become somewhat involved. In terms of the degree of political radicalism, I think that the physics department tended to be much more conservative than some of the other departments. But I did get involved. I think I was, you know, on a free speech movement coordinating committee for the physics department awhile. I think from the students' point of view everybody was certainly on the side of the free speech movement, and they weren't necessarily in favor of all of the things that were going on, but the administration seemed to have a completely indefensible viewpoint that they were trying to push. And so it was also very exciting to be part of these protests. And so I heard Mario Savio give some of his speeches and they were, he was a really outstanding orator. And one of the things that I find most interesting about Savio is that he in principle could have parlayed this into some sort of political power — or at least more power than he had — because he was an extremely effective orator. Rather than doing that, he deliberately I think tended to withdraw after a while so that — because he didn't want this to become a cult of personality, as I understand. I didn't, actually I don't think I ever met him, but he felt that it was the movement that was important, not himself. But as someone who could give voice to the movement, he was really remarkable. In fact, I don't know we still have this, but we got an old 45 rpm record of one of his speeches where he talks about throwing ourselves in the gears of the university. And when you hear this speech the way he was giving it, you know, just chills went up and down your spine. Generally I don't think that, at least in my case certainly, and I don't remember this affecting my friends. We did not get so involved that we stopped working. We would go out and sometimes you know lunchtime we'd listen to speeches and stuff like that and then we might write letters or something but—
McCray:Were there any splits at all within the physics department along some of the fault lines created by these protests?
McKee:I'm sure that there were, but at that time I was completely oblivious, disconnected from what was going on on the faculty and so I don't really know. Even today my impression is that students, what they find out about really depends completely on their relationships with their advisors. They would find out about that, and then if their advisor wanted to tell them about a split or something they could. I don't remember any sort of cross-information gathering that I could see. You know, it was not— Like I say, we were still primarily engaged in our research.
McCray:And I think also a lot of graduate students — oftentimes I think the academic politics tend to be somewhat opaque to the students, just because they're not something that they're privy to. I also wanted to inquire as to your own personal politics at this time. How would you characterize yourself?
McKee:Well, at that time I was a — I wouldn't say I was always moderate. I was probably somewhat more liberal than today. A few years later in fact in 1969 my wife and I both registered in the Peace and Freedom Party because we were opposed to the war in Vietnam. Not that I necessarily agreed with the platform of the Peace and Freedom Party, it's just that we were dismayed that there was no, of the two major parties we didn't seem to have a way to vote against the war.
McCray:Were you married while you were a graduate student?
McCray:Okay. I'm curious about your wife's background.
McKee:Sure. So I met my wife in the second year, in my second year here, and she was initially actually dating my roommate. I had moved into a new rooming group in my second year, and so we — it was in fact, in retrospect I think it was from my point of view a very good way of having met her, because since she was obviously romantically involved with someone else then. Our relationship was one just purely of friendship, so we actually became friends before we became involved ourselves. And so I had never had a relationship that was nearly as deep as the one that I had with her, so it was sort of a whirlwind thing, because starting at the beginning of the year I really didn't have a girlfriend and then in the fall I acquired a very good girl friend — that is, as a friend — and then in the spring we fell in love and in June we got married.
McCray:What year was this then?
McKee:It was '65.
McKee:So at the end of my second year.
McCray:With being married but then also with your research and courses, did you have any other personal interests, hobbies or things like that that you were involved with?
McKee:Other than reading and doing skiing — I did some skiing, but I didn't really didn't have any impassioned hobbies. So anyway, I should mention a little bit more about my wife, because she was in graduate school also. She was in the psychology department, and she had entered in fact the same year that I did and she'd done her undergraduate work at Vassar. And her parents actually live in this area.
McCray:You didn't know her back in Cambridge?
McKee:So her parents in fact — she grew up in El Cerrito, and in fact her parents both still live there. And so she and I both got our degrees at the same time in 1970, and but by that point we had already had our first son, Arthur. So she, during the time that she was a graduate student she actually had, in addition to doing the research and writing her dissertation, she also had baby and as you can imagine as a new mother she certainly spent a lot more of her time trying to take care of Arthur when he was a baby than I did.
McCray:Was she interested, as you were, in an academic career also?
McKee:Yes, she was. Well, I have to qualify that a little bit. When we first met, because she had always been very keen on having a family, so she had thought that really she would maybe just have a part-time job. And in fact I encouraged her to stay in graduate school and get her degree. But at that time we did not look at ourselves as being two people who were launched in the world both of whom were going to get academic careers. We both had the understanding that probably we would be moving around. I would try to find a secure career and she would then do what was the best that she could under those circumstances — which obviously made it extremely difficult for her in terms of developing a career. On the other hand in terms of our family the fact that we were able to have three great kids probably was beneficial. Two years after the birth of our third child, she went to work at the Smith-Kettlewell Institute for Eye Research in San Francisco, and she has had a very successful career in vision research there.
McCray:Did you ever consider doing anything yourself outside of the academy in terms of taking your physics degree and going to work for industry or one of the national labs.
McKee:I did not consider it seriously. I guess that after my experience at Livermore I always felt that if I were unsuccessful in getting a good academic position that I presumably could go there and have a career. Again, because I had had no contact with industry, that was just something that I didn't know about. The other thing — of course once I had made my decision to go into astrophysics then it was far more difficult to get a job in industry in that field, whereas Livermore actively sought astrophysicists since the types of physics that they do is very related to nuclear weapons research.
McCray:I could see if you were doing solid-state physics, that would probably be much more applicable to going to work in industry. Okay. Well, I see that you worked at Livermore '69-'70 as a physicist and then you spent a year in Pasadena at Cal Tech and then on to Harvard for three years or so.
McCray:I don't want to spend I guess a whole lot of time on that particular period, but could you sort of give me a sense of what was involved in moving to these different places and what you found at these different institutions?
McKee:Sure, yeah. So the year that I spent at Cal Tech was a very important one because I had a position in the astronomy department as a postdoc. It was really remarkable because every day I would go out to lunch with famous astronomers like Maarten Schmidt and Jesse Greenstein and Jim Gunn. And, at that time in fact, the astronomy effort there was small enough in scale so that literally as a postdoc I could go out with some of the top people on a virtually daily basis — whereas I then later on was a Fairchild Fellow at Cal Tech, and by that point things had already expanded enough that it was very rare that you could get in a small group. That is, there were more people around. The whole enterprise was much bigger, and so it was much more difficult to do something like that. So that was very valuable for my education since having been educated really as a physicist I didn't really know that much astronomy.
McCray:How did those interactions go? I mean you mentioned Schmidt and Gunn and Greenstein to a lesser extent, but those were some fairly involved observational astronomers, and I'm curious how you as an astrophysicist doing theoretical work primarily, how that meshing of interests went.
McKee:I wound up doing one observational paper with Wal Sargent and he sort of suggested we do a project together, and so actually I spent one night on the mountain at Palomar with him while he was observing. That was certainly very interesting. And at that time John Bahcall was also there, and so I got involved in a project with John on statistics of quasars. I actually don't remember historically how much work John had done on related problems with statistics before that, but certainly subsequent to that he went on and did a lot of work in that area. His wife, Neta, who I believe at that point was a postdoc at Cal Tech, was also involved in that project. And then the third project I worked on there was actually the outcome of an interaction with Willy Fowler, who had his own program in the Kellogg Radiation Lab and would come by periodically. And so he suggested a problem to a fellow postdoc, Bill Quirk.
McKee:Quirk, yeah, Q-u-i-r-k. And so — yeah, so I think you know in terms of making the transition from being a physicist to an astrophysicist that was very important. So when that was — toward the end of that year then I, both — and Craig Wheeler, who was another postdoc at Cal Tech and I were both offered positions at Harvard in the astronomy department. So at that time Harvard in astronomy had — I think it had gone through a difficult period. By the time I got there things had improved a lot, but one of the things, the two main things that improved were that they had hired Dick McCray as a young theorist. And however the reason that Craig Wheeler and I went is that Dick had gotten a job at Colorado and so he was leaving and so they decided sort of to take his one position and somehow they turned it into two. I don't know exactly how they did that.
McKee:Right, yeah. But they had also hired Alex Dalgarno, and so Alex brought in addition to the enormous scientific capability, is such a reasonable, sensible type of person that it made the department run much more smoothly. And so while I was there, in fact, my recollection is that there was not that much strife that I was aware of. At that time the junior faculty at Harvard were not necessarily consulted over there, so there may have been problems that I was unaware of.
McCray:What were the causes of the previous strife?
McKee:I don't actually know who the two different sides were, but the impression I've been led to believe was that David Layzer had exercised a lot of influence and that he, or at least his approach I guess, didn't sit well with some of the other faculty members. But he'd been gone the year or two before I got there. He'd gone up on sabbatical and somehow things had straightened themselves out somewhat. So Layzer in fact by the time I got there I think decided to focus a lot of his energy into education, and he set up a very powerful course which became famous at Harvard. I think it was called "Space, Time and Motion" or something like that, but it was an extremely intense course in which the students — it was a freshman seminar, but it was not — oftentimes we think of a seminar as being sort of a small course involving a small amount of work, but this was an extremely intense course where students really looked at philosophy and science all the way from the Greeks to now on space, time and motion. So they would deal with geometry, they would deal with things like Galileo and how his experiments led up to Einstein. But in addition when they'd get into motion would be not only actual motion but the perception of motion. And for that reason actually my wife then got a position as sort of — well, she wasn't a graduate teaching assistant, but something, sort of a teaching assistant type position to help run one of the sections because Layzer wanted to have her there because she was an expert in the perception of motion. And she found that extremely exciting. It was interesting when I went back for my 25th reunion. They had had everything organized to help people carry bags and other stuff like that, and I started talking to this student, and it turned out that he had just taken Layzer's course. So literally it had been going on for twenty-five years. And it had expanded and really, as I said, it became a very famous course.
McCray:Was the course designed to try to introduce some of these physical concepts to students who wouldn't normally take science classes?
McKee:Yeah. And it was certainly not designed to turn them into scientists either. It was trying to — it was really aimed at being a, I think a liberal arts education, but including much more science than you might normally expect. And the students were— It was a very demanding course. They had to write many papers, and so that in addition to the knowledge that they gained I think in terms of history and philosophy and so forth, they also really were forced to hone their reasoning abilities, their writing abilities, and so forth. The student said he thought it was just a wonderful course he had taken.
McCray:To go on for two and a half decades, that's pretty remarkable. Within a fairly short period of time you were at three major institutions — UC-Berkeley, Cal Tech and then Harvard. How would you at that time compare and contrast them in terms of styles of doing research or just in terms of the general environment. How did they match up?
McKee:That's a good question. As you could tell from my description of my memory of my year at Cal Tech, when I had been a graduate student here I would meet with my advisor fairly frequently, but he was the primary senior person that I would meet with. I don't really recall interacting very much with any postdocs here at Berkeley. Whereas at Cal Tech I was obviously interacting with the postdocs. The other postdoc in astronomy at that time was Jay Pasachoff, who is now at Williams College. And so we obviously interacted a lot, but then we were essentially brought in so that we could interact, as I mentioned, on a virtually daily basis with the faculty. So I found that level of intellectual excitement remarkable. Now whether I — if I had been trained as a graduate student at Cal Tech and come here as a postdoc if I had then had the same interaction with the faculty, that I don't know. But particularly at Cal Tech the way they have the Atheneum and everybody would tend to eat at the same place.
McCray:So you'd go there for the faculty lunches. They have a big faculty lunch on Fridays, but we would just go there every day. And it was much more informal. Whereas here things are much more spread out, and so some people go to the faculty club some of the time, but it's not nearly as—
McCray:Yeah. I can't recall who it was I interviewed, but he referred to the formal faculty lunches as "stuffy lunch."
McKee:That's right. Right. And then when I went to Harvard, it again was very diffuse, and they were in the process of expanding at that time. In fact interestingly enough, George Field was appointed as the director of the Center for Astrophysics while I was there.
McCray:Whipple was there and then Field was the next person I guess after Whipple.
McKee:But the change that was made at that time was that George Field — whereas Whipple had been the director of the Smithsonian Astrophysical Observatory and had built that up.
McKee:What Field realized was that you had the Harvard College Observatory in addition, and they were really sharing the same spaces, so rather than having two separate institutions they should really have just one, and it's called the Center for Astrophysics. So again my memory may not be quite accurate here, but my recollection is, is that the second year I was there he was appointed but he essentially took a year off and spent most of the time up on sabbatical almost, in a house in New Hampshire. But he was sitting there trying to think about how he would try to organize things. And then in the third year I was there he was in the completed new building, the Perkin Building.
McCray:Oh, right. Okay.
McKee:And he was there full time as the director. But again, to give you— Harvard had a lot more idiosyncratic people there. I still remember the first thing I did when I got to Harvard is that I saw that there was going to be a seminar, and I felt that I should obviously show up for this first seminar. This seminar was by Serge Gaposchkin, who was Celia Payne Gaposchkin's husband. And it was one of the more unusual seminars I've been on, I've been to, in which Serge, the main point of his talk was that he had lived and loved on seven continents. It was not that much astrophysics (laughs).
McCray:Six I could see. The seventh is pretty remarkable.
McKee:Yeah. So actually I may be misremembering, but I can't remember him actually talking that much about Antarctica, but it was a completely egotistical thing in which everything was about himself — and also had very little astrophysics in it and it did have to do with various adventures that he had had. I was amazed that this was the style of doing astrophysics at Harvard. But Harvard, of course gave a whole different aspect of the intellectual excitement which I hadn't experienced at Cal Tech as a postdoc, and that is now being, an assistant professor. I was able to start interacting with students, and I found that to be extremely stimulating and rewarding. And there were some really excellent students at Harvard. So indeed the very first student I had was Len Cowie. And then actually he wound up, after I left Harvard he went over to become George Field's student. But Len and I wrote several papers together and I think I had a very productive interaction.
McCray:Did you get any sense when you arrived at Harvard or maybe after you had been there for a year or so of what types of research areas Field wanted to build up at the Center for Astrophysics? I mean, what were some points he was trying to emphasize?
McKee:Well, the thing that's the most dramatic was he wanted to build X-ray astronomy. So he brought Riccardo Giacconi in from American Science and Engineering, and that made a very big difference, because with that we were able to — I mean then Riccardo of course brought in, had a large group, and really this was around the time of Uhuru satellite, so that it was very fortunate that not only do you have this X-ray astrophysics going on, but then there are all these results being discussed, and it was certainly, intellectually that was very exciting. It was interesting. I really did not talk to George that much about what his strategic vision was the Center. I think he— He was extremely busy. In fact I did not see him that much because he was so busy. And the other thing he did was that there had been some complaint about the fact that some of the people at Smithsonian were no longer very active. And it's my understanding that he was able to force some of those people out. And in fact, as you may know, flashing forward thirty years, OMB is putting SAO under scrutiny again, trying to ask whether the money that they are getting is really all justified.
McCray:Yeah. And there was some talk of transferring them to NSF.
McKee:That's right. And so that type of issue is something that there is way, but at least Field was able to, as I understand it, was able to at least address part of that.
McCray:I have sort of a general question. I'll probably ask this same question again later on referring to a different point in time, but when you were at Harvard — or even at Cal Tech — what was the extent of the interaction you were seeing between observational astronomers and theorists and how would you characterize whatever interaction you saw?
McKee:Well, certainly astronomy with Cal Tech I think it was excellent because there seemed to be very close interaction between for example as I mentioned Willy Fowler would come over periodically. And the postdocs, they may have had some observational postdocs. Actually well Pasachoff was, I guess he was in solar astronomy, and I don't remember whether there were any people more on the regular astronomy side who were postdocs. As I mentioned there was this other theorist, Bill Quirk. But we would interact some. Obviously I had a chance to interact with Peter Goldreich, who was a theorist. Jim Gunn at that time was sort of half-and-half. And since then he's gone more into instrumentation and observation. So we were certainly interacting with them very strongly. Then when I went to Harvard one of the things that Field did and organ— Actually I don't know how SAO was organized before Field, so I can't — it may be that he did not institute this, but there were all these different divisions. And I assume that in principle that if he didn't start them he must have certainly reorganized them to some extent along the lines that he wanted. And then people within the— The good thing was is that the divisions then allowed people in the different areas, like say optical and infrared astronomy they could have projects and they could focus on them. The unfortunate side effect was there tended to be a stovepipe effect. Once you were in some kind of a division then you tended not to interact that much with the people outside.
McKee:Well, the thing is, as a faculty member I wasn't in a division. This is just for the SAO people. But a lot of the observational work was being done in the divisions. Certainly when the X-ray group came in and there was very good interaction they certainly welcomed it.
McCray:Chris McKee interview, day 2. Chris McKee, tape 4. Okay, great. Well why don't we start then by talking about the three-phase interstellar medium model and just begin with how you began to get involved in that research and what the prior model was before that.
McKee:Certainly. At the time I was getting involved in this the existing model of the interstellar medium was the Field, Goldsmith and Habing model, which had been developed by my thesis advisor George Field. And this model referred primarily to the neutral atomic hydrogen in the interstellar medium and described it in terms of clouds of cold H I gas, that's neutral hydrogen gas, embedded in an intercloud medium of warm H I that would have a temperature more like 10,000 degrees, and showed how these two different phases could be in pressure equilibrium much in the same way it is possible to have a liquid pressure equilibrium with steam in pressure equilibrium with water. And at that time I was working — this was, work began when I was still at Harvard, and Len Cowie and I had begun working on the problem of the evaporation of cold clouds of gas embedded in a hot gas. Rather than thinking of temperatures on the order of 10,000 degrees, we were thinking of having clouds that were maybe either 100 degrees or 10,000 degrees, but they were embedded in a gas of perhaps a million degrees. And this gas, in contrast to these cooler clouds, would be fully ionized. And so we worked out how such a cloud when embedded in the hot gas would evaporate. Or in fact if the cloud were large enough it wouldn't evaporate, it could actually condense and you could have hot gas condensing onto the cold cloud.
McCray:What would happen when it condensed like that?
McKee:What happens is the hot gas conducts heat toward the cold gas and you get into a regime where there is an intermediate temperature range where the cooling is very intense. And so if that region where the cooling is occurring is sufficiently large then in fact you have more heat going out than coming in from the conduction and it causes the hot gas to flow in and thus essentially stick onto the cold gas.
McKee:So at about that time — this was probably shortly before I left Harvard to come to Berkeley, although unfortunately I don't remember exactly when it was, Jerry Ostriker came by my office and we got involved in a discussion, and he suggested that this work might be relevant to trying to develop a model for the interstellar medium.
McCray:Why was he interested in that problem, do you know?
McKee:In fact I don't know exactly why he was interested in that particular problem. Jerry is a type of person who is interested in a very wide variety of things and is constantly tossing out ideas. Some of these ideas wind up going someplace and some of them I'm sure just wind up sitting on a shelf someplace.
McKee:But in this case he and I resonated very well, and so we started a very productive collaboration. My recollection is the project was much less ambitious than it eventually grew to be, and as time went on and we more work we could see that we could incorporate more and more of what was known about the interstellar medium into our model. And in the end we, the model— I should also say that at about the time we started working on this there was a seminal paper written by Don Cox and a student Barry Smith, and what they proposed is that a component of interstellar medium which Field and his collaborators had assumed were just a very minor constituent, namely supernova remnants which are regions that contain this very hot gas, in fact might occupy a substantial fraction of the interstellar medium. They did this calculation by calculating the rate in which the supernovae occur and then calculating their long-term evolution and determining that in fact long after they cease to be visible — because they're visible only when they're fairly young — they might still have these large balls of hot gas which could then, might interact and form what they call tunnels of hot gas in the interstellar medium. One of the conceptual innovations which Ostriker and I made in our approach was to reverse this topology. So instead of thinking of the hot gas as being embedded inside the cooler gas, we thought of the cooler gas as being embedded inside the hot gas. And although, if the filling factor of the hot gas is say 50 percent, those two viewpoints in some sense are equivalent. But nonetheless it turns out that if you try to approximate that let's say 50/50 situation by assuming that going to model where say the filling factor of cold gas is very small, then in that case it is very easy to carry out calculations for what would happen in the interstellar medium.
McCray:Is it based on a volume fraction or a mass fraction in terms of the number of particles per cubic whatever?
McKee:Right. This is based on the volume fraction, because in fact the mass fraction of hot gas is very small. The typical density of the hot gas would be a few times 10-3 particles per cubic centimeter whereas the mean density of the interstellar gas is about one particle per cubic centimeter.
McCray:A factor of 3 difference?
McKee:Well, a factor of 300 — difference from the mean.
McKee:Yeah. .003 versus 1. So we were then able to calculate the properties of the clouds. As input, we took the observed mass distribution of cold clouds and we then calculated the ionization of these clouds. One of the other, one of the corollaries of having the cold clouds embedded in the hot matrix, since the hot gas is transparent to ionizing photons this meant that the surfaces of the clouds would be ionized, and this would then give rise to what we call the “warm ionized medium”, and this accounted for observations both of people who had been using pulsars to observe how many electrons are in the interstellar medium and then also people like Ron Reynolds. It is Reynolds at Wisconsin who had been making observations of the diffuse Balmer lines emitted from ionized hydrogen. And this model that we had naturally would explain this. It also enabled us to calculate the pressure in the interstellar medium, and that number turned out to be consistent with what was known then. And even now many years later it is still correct within say 25 to 30 percent of the estimated value.
McCray:Have people challenged the three-phase model?
McKee:Yes. Interestingly enough, the principle person who has challenged it is Don Cox, who was of course essential in providing one of the key ideas at the beginning. And he has decided that — for reasons which I'm not quite sure — that somehow he feels that the filling factor of this hot gas is probably small. In a recent he wrote a few years ago he concluded it was perhaps 20 percent of what we calculated. In that case it could be a significant component of the interstellar medium, but it would still be a minor component and if you ignored and concentrate on 80 percent of the volume you'd probably still be able to get most of the properties of the interstellar medium correct.
McCray:Okay. And sometimes whenever groups bring up an opposition to an idea in science they tend to be based that maybe particular institutions like the Princeton school or — is there anything like that effect, where there is institutional bias against this idea, or does it not break down that way?
McKee:No, I don't think so. And I think in fact of course it's very healthy to have people challenging and criticizing ideas. I think in reality the three-phase model that we have is probably, is undoubtedly a drastic oversimplification of reality. As I mentioned, one of its big advantages is that it makes is possible to calculate properties very easily, and usually these turn out to be consistent with observation, but there is — one of the key aspects of the theory involves this work that as I said that I've done with Cowie on the evaporation of clouds. And that is one of the aspects for which there is no direct observational evidence. And in a way I think that is — it's certainly disappointing that that was a centerpiece of the theory and people haven't really been able to go out then and see that. On the other hand, these observations are sufficiently difficult that I don't think you can say that the current observational situation contradicts the existence of this thermal evaporation either. In terms of the theory of thermal conduction, at that time we were using a fairly simple theory that just included magnetic fields really only as a fudge factor. People have made some progress on that, and at least in the very latest work this sort of overall numerical reduction seems to perhaps be plausible and so perhaps we were okay on that. But there is also the possibility of various plasma instabilities that might affect the heat flux. We did not worry about. And so that still remains to be seen.
McCray:When you first proposed this three-phase model, was it in an article or was it first tested at a conference?
McKee:There were no actual conference papers. There were — I think we gave some talks on parts of it, but there was the — in fact the first paper that we wrote came out in the Astrophysical Journal in 1977, and that then has become my most cited paper.
McCray:What effect did that have on your career?
McKee:Well, I think it had a very important effect on my career. By the time it came out I was here at Berkeley, and at that time I had also — the papers that I had done with Cowie on evaporation came out. I had some work with Roger Blandford on relativistic blast waves, and that came out about the same time, so I had done some very — at least in my view — important work on a number of different pieces all around the same time. And as a result, Roger Blandford and I were offered the opportunity to both go to MIT and try to build up their theoretical astrophysics group there.
McKee:And at that time Roger was on the faculty at Cal Tech. So we gave this very serious consideration, but in fact some of my colleagues here — particularly Claire Max — suggested that instead of trying to build up theoretical astrophysics at MIT, why don't I try to build up theoretical astrophysics here at Berkeley. And that sounded like certainly a great idea. And I received a lot of support for doing that, particularly I would say Kinsey Anderson was then the director of the Space Sciences Lab, provided some financial support and we were able to set up an organized research unit which in fact is I think — it's either the last or one of the very last organized research units set up on the Berkeley campus, because shortly after that the Regents became concerned about this proliferation of organized research units, so they tried to clamp down.
McCray:What's an organized research unit?
McKee:So what it is, is basically a unit on the campus that is set up to foster research that crosses departmental lines. Now in this case the departmental lines were actually not that — the barriers were not that high, because between physics and astronomy — but it also carried with it a certain degree of funding, about $50,000 a year, which was enough to support— Actually I can't remember how many postdocs we could support initially, perhaps two. Now it can support one postdoc. But even now we're attempting to try to use the theoretical astrophysics center and get more funding for it so that we can have a regular supply of postdocs. And the result of this was actually very beneficial for Berkeley. At that time we had these four young professors — myself, Jon Arons, Frank Shu and Joe Silk, and we were able to attract some really outstanding postdocs, such as Simon White, Dick Bond and Mitch Begelman. So Dick Bond is now the head of CITA, Simon White is now a director at Max Planck Institute for Astrophysics in Garching [in Germany], and Mitch Begelman is on the faculty at the University of Colorado.
McCray:So it served as a launchpad then for several people's careers.
McKee:That's right. And so it was an extremely stimulating and vigorous time for the whole theoretical effort here.
McCray:After the '77 paper then did you continue to work in that area?
McKee:Yes, I continued to work on various problems in interstellar astrophysics. In fact, as I had mentioned, because I had been working with Cowie. Cowie, for a postdoc, went to Princeton, and he was working with Ostriker. And they in fact then took some of these ideas that Ostriker and I had worked on for the interstellar medium and applied them to the intergalactic medium.
McCray:Is the difference as obvious as it sounds, interstellar versus intergalactic?
McKee:The primary difference is that they were working on a scale large enough so you have to take Hubble expansion into account, and then they were worried about or thought about how this might induce the formation of galaxies, and so they were working on a cosmological stage.
McKee:Meanwhile the three of us then collaborated on a couple of papers with applications of the three-phase model. Particularly, we had a paper where we did some numerical calculations that validated some of the key ideas that we had in the paper.
McCray:What is required to extend the interstellar medium model to the intergalactic medium? Is it just a matter of scale?
McKee:Well as I said, the principle effect was to include the expansion of the universe. The second principle effect was once — actually historically I don't know whether this was included in our initial work or not, but as we now know, much of the matter in the universe is so-called dark matter and is really made up of something we don't know what it is.
McKee:And this matter interacts with ordinary matter only through gravitation. So whereas when you have a blast wave propagating through the interstellar medium, it sweeps up all the gas in front of it. When you have a blast wave going in a galactic medium it sweeps up all the gas but it leaves behind all the dark matter — at least initially. However there is a change in the gravitational field, and so eventually you wind up building an expanding structure in the dark matter as well. And that expanding structure then, just through gravitation winds up holding up almost a discontinuous structure in the density of the dark matter that sweeps outward. So but then they were interested in how this could then, in these regions of compression you might induce the formation of more galaxies.
McCray:Because in these areas of compression you are getting greater density and that's where galaxies are more likely to coalesce?
McKee:That's right. Now since then that model is not the one that people think fits the data today. But again, when the — in fact it was the cold dark matter model that came in and supplanted the explosion model they had worked on. But again, just as I mentioned before, the fact that Cox has been criticizing the three-phase model of interstellar medium. Before people knew the model was in better agreement with observation having two models to compare the data with was certainly a much better situation for the observers to be in.
McCray:Since you began to work in the area studying the interstellar medium, could you give a general summary of how astronomers perceptions of it have changed as a result of this model? Has there been a sort of global shift in understanding or thinking about it?
McKee:Well, I think that it had the effect that it provided a context in which observers could interpret a lot of their data. For theorists, it encouraged them to look at the interstellar medium in a more global sense and there has been a lot of work done on that and trying to then consider the relationship. Although the original model that we worked on really just referred to the plane of the galaxy. Other people, particularly Ikeuchi in Japan, has considered how the supernovae that go off in the disc of the galaxy might create large structures that would vent into the halo at the galaxy, and then the overall goal eventually is to be able to include not only the diffuse gas but also include the molecular clouds from which stars are formed. So people have attempted to do this, but so far there is no very convincing quantitative model that pulls it all together.
McCray:Okay. You mentioned yesterday, and I just want to make sure we touch on it, the connection between some of the weapons work and the work that you're speaking of now. Can you sort of bring that together?
McKee:That's right. Well one of the things that's related to the work that I did in interstellar medium was the theory of blast waves, and the original work on blast waves was done in Russia by Leonid Sedov and in Britain by G. I. Taylor. But Sedov went ahead and I think did a lot more work that I am familiar with and wrote a very important book on how to deal with problems of this type.
McCray:It is translated into English?
McKee:Yes. Although it was unfortunately out of print for many years. I'm not sure whether it is in print now or not.
McCray:What's the title?
McKee:I think it's Similarity and Dimensional Methods in Mechanics. In any case, this work was initially done in connection with weapons programs in the respective countries. But a most famous physicist, an astrophysicist in Russia, was Zeldovich, who passed away recently, and he was deeply involved in developing weapons for Russia but then evolved into doing astrophysics later in his life, and certainly he wrote a couple of well-known texts on shockwaves and high-temperature phenomena — which my understanding is, was probably originally based on work that he did for the weapons program. So people for example at the weapons labs here in the U.S. at Livermore and Los Alamos recognized this for some time. I think that they would often hire astrophysicists because I think both because in some cases — particularly dealing with supernovae for example — the problems are very similar. You are dealing with explosions. And the other aspect is that astrophysicists by necessity have to know a wide variety of physics in order to deal with all the things that go on in astrophysics and similarly in weapons design it's often very eclectic as well.
McCray:You mentioned Stirling Colgate as an example of somebody who had a foot in both things.
McKee:That's right, yeah. And so Colgate I think was perhaps the person that I know best who exemplified that, because he would spend several days a week working on a classified research and then a couple days a week on unclassified research. And even his non-classified research was in totally different areas — in plasma physics and one in astrophysics. And as a result of the work in astrophysics he and someone else at the lab, Richard White, wrote a seminal paper on supernovae in which they for the first time carried out a numerical model of the collapse of a massive star and pointed out that the, that as a result of the collapse you would emit copious amounts of neutrinos, and these neutrinos — although normally we think of them as having no interaction with matter — that the density in temperature would be so high that they would actually be able to interact with the surrounding matter and blow it apart. So they had just a very crude phenomenological way of doing that. The ironic thing is that although they were able with their very crude approximations to make stars that explode, now it is I think more than thirty years later and people are still having trouble actually. They put in a lot more physics and they're having a lot more trouble making the stars explode, but meanwhile observationally we know that they do.
McKee:And it's probably the case that some of the basic physical ideas that Colgate and White have are correct. It's just that in reality the situation is far more complex than they could envisage at that time, and certainly far more complex than they could be able to simulate on the computers of that era.
McCray:Do you think there's a large intellectual debt on say supernovae explosions that it owes to work that was done on weapons research?
McKee:That's probably true. Actually it would be worthwhile I think to ask someone like Colgate who is more familiar with both sides. Because although I have worked at Livermore while I was a graduate student and I worked out there a couple of summers since then and so forth, I have never really done any weapons research myself — other than this very first summer, but that is before I came to Berkeley. But certainly if you look at it historically and think of the people who were devoting themselves primarily to weapons research during the war and shortly afterward and see what they did later, I would think that it made a big difference.
McCray:You talked yesterday a bit about your relation with Edward Teller. I was curious, did that continue as your own career progressed, or was that something that existed for a period of time and then ended?
McKee:Well, it existed throughout the time that I was a graduate student, and he in fact was one of the three members of my thesis committee.
McCray:I mean, what was he like on your committee?
McKee:Well, at Berkeley we don't really have a thesis defense. There are just three people that have to read the thesis and sign off on it. So I had given him my thesis and I went to meet him at his house to get his comments and critique, see how much more work I would have to do. And so he said, "Well Chris, could you explain it to me?" So I launched into a discussion of chapter 1 of my thesis and he said, "No, no, no, no, no." He wanted one sentence for each chapter. And so I gave him the one sentence version for each chapter. He said, "Sounds good" and he signed it.
McKee:I want to emphasize that it wasn't that this was the first time that he knew what I had been doing, because I had been seeing him regularly during my graduate career, and so he knew what I was working on. But the thing is, is that because I saw him sufficiently and frequently once every few months, and since he was not at all working in an area remotely related to what I was doing, I found that I would really have to spend a lot of time in each of our meetings sort of reminding him of what we had already talked about before rather than being able to go on and get involved in what my problems were at that particular time. I think it's also perhaps partly a matter that as a student working at that time I was naturally involved in the minutiae of my thesis, because there were many, many details and they all have to be exactly correct in order to make the whole superstructure hang together. And that's not the way his mind works. He naturally tends to want to look at the big picture. So it was somewhat of an impedance mismatch between — the student was having trouble with some detail and he was trying to get the big picture. So I did talk to him at some time after that. I would see him every once in a while, but I found that he was sufficiently involved in political matters that it was just very difficult to actually him get very involved. For example, I've mentioned that he would have people come and meet him at his home here in Berkeley and those conversations then would generally be very intense because he would devote his entire attention to whoever he was talking to. However several times I visited him at his office in Livermore and I found this very frustrating, because he had his secretary making calls to the east coast, and so whenever she was successful in actually getting someone that he wanted to talk to, then our conversation would go on hold while he had the phone conversation and he'd finish that, when we could resume.
McKee:I didn't really find a very productive way to see him. So, but as I think I mentioned yesterday, he is certainly one of the most brilliant physicists that I have ever had the privilege of meeting, but the amount of intellectual energy that he put in to the political side as opposed to the physics side really meant that he could not do nearly as much I think as he could have done in physics.
McCray:Teller of course became very involved in the 1980s with the Strategic Defense Initiative. I see on your bookshelves that you have several books devoted to “Star Wars”, and I was curious if there was any connection there at all or just for no other reason other than just curiosity how those books ended up on your shelf.
McKee:Certainly. I'm not sure there was any connection. I personally was always extremely skeptical of the Strategic Defense Initiative, and Berkeley has a very interesting program called Freshman Seminar Program where you can teach small groups of students. They don't really have to be freshmen, but you teach small groups of students and you can just pick a topic that you — the instructor picks a topic and then you see whether these students come. So I picked Star Wars. And I would get some students with technical backgrounds and some students a little more in political science. Then what I would do, I would give some lectures on some of the physical principles involved. I would also invite someone who was a well-known person opposed to Star Wars, and then I tried to get someone from Livermore whom I thought would then be a proponent. A physicist named George Chapline. He was I would say lukewarm on the issue. You know, I tried to give the students different viewpoints, and then I would have them give talks on the issues also. And then I would then get books. At that time books were appearing that were just popular reading. That’s how I have so many of them.
McCray:I have some general questions just about some of the research that you've done, and I was wondering. As you were working on the main areas of research that you've been involved with, were there people from other branches of science that were of particular help, for example plasma physicists? Were you working or interacting solely with astrophysicists? How did those collaborations — even informal — come about?
McKee:Almost all my collaborations have been with astrophysicists. One exception — well, there are two exceptions. There was — this again goes back to my Livermore days that as soon as I finished my thesis I was interacting with Montgomery Johnson, who was a good friend of Edward Teller and Stirling Colgate. And as I think I've mentioned, Colgate and Johnson had this theory about the origin of cosmic rays as to why they were arising in these supernova explosions. But there was one part of the theory which they really hadn't been able to resolve very well, and that was this issue of exactly what would happen when you had the shockwave and it was like cracking the whip. So now I'd cracked the whip, I'd had the shockwave accelerate, but what's going to happen to this very relativistic gas behind the shock? How will it expand out? And so during the summer after I got my degree I worked with Johnson and we solved that problem. He had never really done any astrophysics himself. Then in the mid-eighties I did a collaboration with Claire Max. She's currently both at Lawrence Livermore and a professor at UC-Santa Cruz. But at that time she was in laser fusion and she's the wife of Jon Arons, who until recently was the chairman of astronomy here. And so her training was in plasma physics, although now she's completely changed careers and she now is an optical astronomer working on adaptive optics.
McCray:Hmm. Interesting transition.
McKee:Right. It's really a very interesting and impressive transition. But at that time, as I said, she was — and she was working on laser fusion. And because from our conversations together it became clear that there was this possibility of combining the type of work that I had done with Cowie with what would happen if you actually have a little pellet and you radiate it with laser beams and heat it up and have it implode. So we wrote a couple papers on that, but unfortunately after that I guess our paths diverged so that really didn't lead to anything.
McCray:Okay. In terms of where you're presenting the results from your research, has it also been primarily at astronomy-astrophysics venues, the work you have been doing.
McKee:No, I think it's primarily been astrophysicists though I tend mainly to go to conferences which are focused.
McCray:Okay. And you mentioned the Copernicus satellite earlier. I wanted to ask have there been any other instruments or telescopes that have been important in your work in general, in verifying or helping confirm some of the ideas? I'm trying to get a sense of the importance of different instruments, if at all.
McKee:Right. The Hubble Telescope has also done absorption line spectroscopy and that's relevant, and then most recently there's the Far Ultraviolet Spectroscopic Explorer [FUSE] spacecraft. So that's the first satellite that actually since Copernicus that had the ability to measure spectra in this wavelength. So one other project I did several years later was when I went down and visited Cal Tech as Sherman Fairchild Fellow. This involved what we called reverberation mapping. So when I was at Cal Tech I was devoting most of my effort toward trying to understand quasars, and in fact so I interacted there. In addition to Roger there was another person who was visiting there, Greg Shields, who is now at Texas. And we had an interesting thing in which we tried to get the then-current models for the emission line regions of quasars. You have this supermassive black hole with very exotic processes, all happening near the event horizon. The black hole is surrounded by this accretion disk which is feeding gas in and there, it's presumably a very powerful outflow and producing a jet, so a lot of complicated stuff going on. But if you go just a little bit farther out you get to these gas clouds which have a temperature of over 10,000 degrees and obey physics that we think we understand, just simple atomic physics, and furthermore they are sitting there glowing, so they are actually providing us with all this information. Because you can see from their relative intensities of various emission lines. So we were focusing it on that, and I remember we had a one-day meeting, Spring 1981, I think, and so we sort of listed some of the conclusions that you could draw from the data as it existed then. And the conclusion was, is that the emission line regions didn't exist; that is, that using the then-current views of what was going on they were just mutually inconsistent.
McKee:Which obviously shows you there's a big failure of understanding. So what I decided to do with Roger was to say, "Well, obviously we need to find out more information, so how are we going to do that?" And people had already talked about this possibility. If you have quasars and their light varies in time, then it takes a certain amount of time for the light to go from the quasar to this cloud that's emitting these emission lines to the observer. Say I have a flash of light from quasar, so you would see that right away. And then later on you might see what had happened when this light went a different way and heated up this cloud that emitted some emission lights and you saw that.
McCray:Why the delay?
McKee:Simply because it takes light a finite amount of time to travel.
McCray:Okay, but the period of time it takes for some process to take place within that cloud—
McKee:Is very short.
McKee:And so that's a very important point. It turns out that the densities in these clouds are high enough so that's a negligible amount of time.
McKee:Now of course it also then, the amount of delay depends on where the cloud is, because in fact if it was exactly along the line of sight then there would be almost no delay. And if it's behind the quasar at a given distance then that's going to be the largest possible delay. People had sort of worked this out. What we showed was that it was formally possible to go ahead and take observations of this type and invert them — that is so you could look at say a series of observations of the intensity of the continuing radiation which reflects what's going on right near the black hole.
McKee:And the intensity of one of the emission lines and process these so that you would be able to determine what the typical distance was between the quasar and the gas cloud and even determine whether this gas was located in a disk or whether it was kind of flying around in random orbits. We considered a number of different possibilities. The astronomer Brad Peterson, who is at Ohio State, then set up this very large international project to monitor quasars. It takes a huge amount of data gathering to do this. And he was able to get people to do this that were able to go ahead and gather data, and the principal result that emerged was that the emission line regions were ten times smaller than we thought. And so if you go back to this case that I had said before where things were contradictory. There was a significant error. The regions were ten times smaller than we thought, and the best picture that has been developed to try to explain this in a natural way is actually a theory by Norman Murray, who is at Toronto, Canadian Institute for Theoretical Astrophysics which has an acronym of CITA, C-I-T-A. So but I think that was kind of interesting that at that time you know twenty years ago you could tell that things weren't working, and we went ahead and provided some theoretical impetus to this effort that then ultimately did have a big impact.
McCray:What are the implications of the emission region being ten times smaller?
McKee:Well, what it meant was is that all the theories that people had had before, couldn't work. So the theory that Murray developed was that the emission line region, rather than being sort of a series of clouds that are orbiting around each other was actually— excuse me [interruption; recorder turned off, then back on...] We were talking about the quasar emission line region. So the picture that he had, rather than having these clouds floating around, which was a picture we had before, in fact are an outflow from the surface of a disk and that the gas gets very, extremely rapidly accelerated up to very high velocities close to the disk, and you build up enough of a shielding layer so that the gas is able to self-shield itself against this radiation, which by being ten times closer in it means that now the radiation is a hundred times more intense.
McKee:So you have to somehow be able to shield yourself from this in order to get the ions to exist in the same state that you thought they were existing farther out.
McCray:Okay. So it really does create a completely different picture of what's happening in that area.
McCray:Okay. When you look sort of at the overall landscape of the research that you've been involved with, do you see any central themes or common threads running throughout it?
McKee:Yeah. I think that in terms of subject matter a lot of it, and particularly more recently, has had to do with interstellar astrophysics, and that started probably in the early seventies. In terms of — approach a lot of the work that I have done has to do with applications of hydrodynamics to problems in astrophysics. So for example we talked about the model of the three-phrase interstellar medium.
McKee:So one of the key things we had to work out was how supernovae expand in a medium which has you know a cloudy medium where you have thermal evaporation going on. In the work that I did with Blandford, that obviously had relativistic shockwaves in it. Although I had mentioned earlier that I haven't done much on gamma ray bursts, I did do one project with two of my recent students on gamma ray bursts in which we then took an idea that was originally due to Colgate and that included the work that I had done with Montgomery Johnson in showing how actually you might be able to make gamma ray bursts from supernova explosions. And so again, being able to work out some of the basic dynamics of what's going on I think has been a continuing theme. Another theme actually, although what I've done, in this case I've tended to collaborate with people, has been in terms of the spectroscopy of astrophysical plasmas. So in the early years for example with Bruce Tarter, who as I mentioned, had developed this code that described ionized gases, and then I've also done a lot of work with David Hollenbach who is at NASA-Ames, on interstellar shockwaves, what they look like. And in this case Hollenbach really brings to bear a lot of the expertise on the molecular processes and to making those determinations.
McCray:Okay. I think that might be a good place to pause. We said we'd wrap up today around 3 o'clock, and it's right there.
McCray:Okay. I'd like to spend some time talking just about the support of theory and the role of theorists in general in astronomy. So some of this will go back to what we talked about yesterday, but I sort of wanted to push a little bit further with this. Maybe just a general way to start would be, when you started as an assistant professor, what was your general sense of the status of theoreticians?
McKee:Certainly. Well, I think in general theorists were held in very high regard. The people that I knew about were here at Berkeley. In my graduate career George Field had been one of the most distinguished members of the faculty. When I was at Cal Tech I had a chance to interact with John Bahcall and Willy Fowler and Peter Goldreich, and they were obviously outstanding theorists. Of course shortly after that Bahcall left to move to the Institute for Advanced Studies, which is one of the top positions in astrophysics in the country, and in fact my former advisor, George Field, moved to take over the Center for Astrophysics. So it seemed to me that in general theorists were held in very high regard in the field.
McCray:Okay. How were they supported financially? When you started, where did the funding come from, and has that changed over time?
McKee:When I first started out I was not really aware much of funding issues. That's a thing that's changed in a very major way since I was a student. When I was a student, I didn't have to worry about it because I had this Hertz Fellowship. Then when that ran out, I was able to spend my last year as a student out at Livermore, so I never had to — and nor did my advisor have to — worry about funding me. And then I had a postdoc and I was oblivious to funding issues there. And when I went to Harvard the students were supported and I do not recall actually trying to apply for money. I didn't try to apply for money until I came here. By contrast now I have several students, mostly in collaboration with one of my colleagues, Richard Klein, who is an adjunct in this department and actually works out at Livermore. We have all our students involved in writing proposals. Some of them have been able to get what's called Graduate Student Research Program Fellowships from NASA, so they have to write that. Most of the students now that I have at the present time at least are involved in numerical simulation, so they are deeply involved in writing proposals to get computer time. So by the time they get their Ph.D.s they are going to be quite sophisticated at grants whereas I was clueless until I came here. And there was not that much money, because as I mentioned earlier, we had these four people, Arons, Shu, Silk and myself who were all I think first rate, and we submitted a proposal to NSF and were rejected. I think we were rejected twice. And finally one of us — I believe it was Frank Shu called his mentor, who was I believe C.C. Lin back at MIT and then I don't know whether our luck changed or whether any strings were pulled or what happened, but in any case on the third try we were finally able to get a grant.
McCray:What was the proposal to do?
McKee:Well, it was a very broad proposal because it covered the research of all four of us. Mine was interstellar astrophysics, Shu — actually I don't recall whether he had started working on star formation yet or not. [Jon] Arons was on pulsars I think and [Joe] Silk was in cosmology. So it was a very broad proposal, and we were asking for postdoc, and so when we were able to get a postdoc that actually worked out very well because then all four of us had to agree on the person.
McCray:Who was the postdoc?
McKee:I'd have to look back. I honestly don't remember.
McKee:But we were often able to, by having this process where all four of us would get together and try to pick the best postdoc then we tended to get really outstanding people. Unfortunately from NSF's point of view they tended to not like to have group proposals, and I think their logic is, is that it's possible for the strong members of the team to pull along weak members of the team, whereas if you split people apart then everybody is evaluated on their own. But particularly when it comes to supporting postdocs, I think that is their logic but it’s fundamentally flawed, particularly when there is not more money involved. Because they split us into two halves. So I think I was with Arons and Silk and Shu were together I believe. So that meant that we then each had to apply. Well now of course we had two grants to take care of and we had two postdocs. But now the postdocs, instead of being the best person the four of us thought it would be the best person that two of us thought. Obviously your own interests come up. And then after that NSF split each of the pairs into singles. And of course by the time I got to a single postdoc then I could really no longer pick the best person. I had to pick the best postdoc who was going to do work in interstellar astrophysics, because if I picked someone who was going to go off and do something completely different, then it would not really be very fair. When I went to try to renew my grant then it didn't work very well.
McKee:That's why, as I mentioned a few minutes ago, that the establishment of Theoretical Astrophysics Center and being able to also get support from the Space Sciences Laboratory was invaluable then in being able to allow us to bring in the very best postdocs.
McCray:Okay. Did you sense — and I think maybe, perhaps you were alluding to this, but did you sense that there was any bias say in the 1970s when you were starting on as an assistant professor, perhaps associate professor? Any bias in terms of giving grants to theorists?
McKee:Well, I was just not sufficiently aware of what was going on. I do know that more senior members of the theoretical community who served on the field committee for the National Research Council did feel that more support was needed for theoretical astrophysics, and they made two proposals. One was that NSF in the astronomy division have a separate section for theory. And that recommendation was repeated in the Bahcall committee report also, but in both cases NSF ignored it. The other recommendation which was much more successful was that NASA should get involved in this quarter too, and that led to the Astrophysical Theory Program which has been extremely valuable.
McCray:We talked yesterday where the NASA support was a bit more programmatic, where the NSF if it's successful could be at the researcher's own whim I guess.
McCray:Looking back over a thirty year period of time, do you sense any broader change in terms of a willingness to support theoretical work or a lack thereof?
McKee:I think that as far as NSF is concerned there is certainly no institutional bias against it. They just put it up for peer review. The problem that theorists have — and this goes back to this continuum of theory that I discussed yesterday, where you can at one extreme have theorists working extremely closely with observers and modeling their data. So they're not necessarily creating new models. They are perhaps using existing models but doing in some cases very sophisticated data analysis in order to try to see how you adjust the parameters to get the models to agree with the data. And at the other extreme you can have people who may be somewhat disconnected from data and just thinking about very fundamental problems.
McCray:Who would examples be of people who are on this continuum?
McKee:Well, I would mention for someone who has been extremely good I think at working very closely with observations is Mike Shull. Now Mike, in addition to working very closely with observations, has also done more, a broader theory as well. That is, when I mentioned this continuum of theory, it's not that you can necessarily place individuals. There may be some individuals who just fit in a narrow range of that. Some of them — I'll use Shull again as an example of someone who has been very successful at interacting closely with observers and also theorists. Then someone at the other extreme would be Donald Lynden-Bell, who recently retired from Cambridge. In fact it's very interesting, because he wrote a paper, I believe in the late sixties, called "Dead Quasars," in which shortly after the discovery of quasars, he realized the idea that they involved supermassive black holes, an idea that rapidly gained currency. And he realized that although most of the quasars we had been seeing were fairly high redshift, then those black holes would still continue to exist. And so he discussed how they were still in the nuclei of galaxies today. Lo and behold, there was absolutely no observational evidence for this, with the exception of our own galaxy where people, led by Charlie Townes, I think for the last fifteen years or so have been making observations suggesting that there is a black hole in our galaxy. But more recently the Hubble Space Telescope has just blown the field wide open by giving data that showed that essentially all galaxies have massive black holes and there's a very tight correlation between the mass of a black hole and the velocity dispersion of the stars in the bulge of the galaxy that contains the black hole.
McCray:The more massive the black hole the greater the velocity?
McKee:That's right. So this is the kind of thing where you know Lynden-Bell worked out this theory, and it had no observational implications for decades. And you could imagine that if you were trying to get support for that. Particularly — well, and here's I think the reason that the theorists were saying they wanted to have a separate section. Because you could imagine theorists might find this problem theoretically very interesting, and I think that it would be very worthwhile doing — whereas observers would say, "Well, I'm not going to be able to do anything with this that I can see," so they would much rather— Even though they might say, "Well look, this is very good work," I would much rather provide the support for the research that is going to help them today. And, of course, in reality it's not that one form of theory is better than another form of theory. You really need both kinds. If you don't have the fundamental theory going on, then at some point — it's like the debate that our society has between pure and applied science. The pure science of today becomes the applied science of tomorrow, and the fundamental theory of today becomes the thing that people use to model tomorrow. But if you have none of the people doing the modeling, then you can get things to be completely disconnected. If you take general relativity as an example, it was a field that had very little contact with experiment. And where there were opportunities to get contact with experiment, for example, in doing solar system tests, then they would be able to make advances. But as long as there is no interaction with data, there is some fundamental mathematical problems they can work on. Now with the impending arrival of gravity wave observatories, then I think that stimulated a great deal of more interest. And of course there's still no signals have been seen, but I anticipate that an explosion of activity once we start getting signals, and particularly if the signals are different than what people have been predicting all this time.
McCray:Are you optimistic that signals will be detected from facilities like LIGO?
McKee:Well, I think that it's likely that by the time they build LIGO-II and get it in operation, then we'll see. I'm very skeptical that LIGO-I will see anything.
McCray:Okay. One of the things that I'm curious about, and this sort of leads into a couple other questions, but for some — have you participated in any large collaborative projects that involved the cooperation between observers and theorists?
McKee:I have not really gotten involved in any large project like that. I had an opportunity to get involved in the reverberation mapping project that Brad Peterson set up, but my feeling has always been that unless I'm going to really play a very active role in the research then I shouldn't be involved. In other words I didn't just want to have my name on the papers.
McCray:As the token theorist?
McKee:Yeah, well actually there were some other theorists who did get involved. One of my former students, Julian Krolik, I think did play an active role in that.
McCray:What was the name?
McKee:Julian Krolik. But you know if I could have seen myself really being able to contribute something to it then I would have, but it seemed to me in the work that I had done with Roger Blandford I had sort of laid out what the basic program was and then trying to translate that into reality took — well, it took a lot of clever thinking to go from abstract mathematics to know how to deal with data, and then it took an enormous amount of observation and so forth that Peterson had led. And as I mentioned yesterday, I think the overall program has been extremely successful. In fact just to give you an example, one of the interesting things of course that we predicted is that we'd have this correlation now between the mass of the black hole and the velocity dispersion of the stars, and so it's sufficiently good now that people think that they can just really measure the massive black hole from that. Now you can also try to measure the massive black hole from reverberation mapping techniques.
McCray:What's reverberation mapping?
McKee:This is an idea that Roger Blandford and I worked out. And there have been some astronomers before that who have done similar things that were less sophisticated. And it basically relies on light travel time. That's in order for you to map out the spatial structure of the source that you cannot resolve. It might take light say some hours to travel a distance in a source. You can then resolve distances on the order of light hours in extent, but if that is a billion parsecs away, a few light hours is many orders of magnitude smaller than anything that we can resolve even with very long baseline interferometry.
McKee:In our paper we had shown how you know in principle you might be able to measure things like the mass of a black hole with simple logic. Well, they've gone ahead and done that, the observers of that, with a reverberation mapping. But of course there are a number of assumptions that went into our theoretical work and I think if you, even tossing that aside and just look at what the observations and how they got them, there are a number of assumptions. They are plausible, but you don't know that they are correct. But what they've done recently is to show that in those sources in which you can use the Hubble Space Telescope to measure the mass of the black hole directly by studying the properties of stars near the black hole. By using the reverberation technique, you find that the masses agree.
McKee:So this essentially validated the reverberation mapping. The Hubble Space Telescope which is extremely powerful can really only do this for the very nearest galaxies, whereas with reverberation mapping you can do this for galaxies at the edge of the universe.
McKee:And so the thought is that now you will in fact be able to perhaps even see how the massive black holes grew in redshift. And that's something that if you'd asked me twenty years ago when Roger and I were working on this whether that would ever be possible, I would have thought that would just be far too much to ever hope for.
McCray:The availability of new tools, workstations and supercomputers and things like that, how has that technology affected the work of the theoretical astrophysicists?
McKee:Well, it's had a number of effects. I'll mention one of the effects which I think is unfortunate right off the bat, and that is, as you walk down the hall of this or any other astronomy department or physics department you will see everybody has a computer on their desk. And generally there is a person in front of it. Whereas prior to that, people would be sitting there calculating with pen and paper. But I think that that was much more open to interaction. I think in some sense the computer has replaced the one-on-one interaction and direct communication. Of course at the same time now it has opened up the possibility of interacting with people who are far away, so it's made it a lot easier for me to carry on collaborations with people in different countries for example. But that I think is a small negative. The positive things are I think really major. If you just think about what you can do with a workstation, — there are many problems in astrophysics. For example, earlier we were talking about blast waves. There are analytic theories for the very simple cases of blast waves, and but as soon as they started getting more complicated, then the analytic theories no longer exist. On the other hand, if you are talking about one-dimensional or say spherically symmetrical or hydrodynamics, it's something that you can do on a computer very easily. And by being able to do it on the computer and then relate that back to analytic theory you can make very rapid progress.
McKee:So an example of a recent project that I have worked on with two of my former students had to do with gamma ray bursts, and we were calculating the propagation of a relativistic shockwave in the atmosphere of a star. Our conjecture was putting the meat onto a theory originally proposed by Colgate was that the shockwave would be able to accelerate some of the gas up to relativistic energies and create the situation where you could get a gamma ray burst. And based on work that I had done earlier with Blandford and also with Montgomery Johnson, we had analytic predictions for what might happen, but there were some parameters that were floating around in theory that we didn't really know what they were. By using the numerical techniques, we were able to go ahead and actually determine what these were and also validate the fact that the analytic theory which has lots of assumptions, was in fact right, and then use that to then make contact with observation. The other thing which is most powerful is to go beyond the workstations and now work on supercomputers. Because it's really becoming sort of a whole other mode of science, which is numerical simulation. And in the case of most physics, we know the physical principles and so if you ask, in terms of doing experiments, or doing it on the computer, you're not going to discover new laws. If you are dealing with hydrodynamics it's not that you're discovering new laws. We know what the laws are. The only place where numerical experiment is critical is that in many of the problems which we don't have good solutions for, the scale — that is the range of density scales or time scales — is too great even for modern supercomputers.
McKee:So a very good example of this is the classical problem of turbulence, which still remains unsolved after all these centuries, and in this case you measure the tendency of the system to become turbulent by a number called the Reynolds number, which is the product of the velocity and the size scale divided by viscosity. Well, in astrophysics because the length scales are so enormous, you have Reynolds numbers that are huge. But even in Earth laboratories it is possible to create a situation where you get extremely high Reynolds numbers. And the amount of computer time that it takes to simulate a turbulent flow I believe goes like the Reynolds number to the nine-fourth's power, and that is almost cubed. And as a result it would take almost a thousand times more computer time to calculate a Reynolds number of 10,000 than one of a thousand.
McKee:And even though according to Moore's Law, things are doubling every eighteen months, to get a factor of a thousand, that's 210, so you'd have to wait for eighteen or fifteen years before it— And that's only one order of magnitude. Whereas right now I think the highest Reynolds number that has been simulated is of order of a thousand, and astrophysics Reynolds numbers are like 1015.
McCray:A ways to go?
McKee:Right. Now of course it could be that things stop changing; that is if there is a range of Reynolds numbers where things change and then once you get above some Reynolds number things don't change and you don't know that. This is a key example of where there is a limitation on numerical simulation. But, on the other hand, for a lot of what people are doing in trying to observation you can simulate. I think there's been a real improvement in the last decade that if you go say to simulation ten years ago — particularly in fields that I was familiar with, I had the impression that if you looked at the results of simulation you would find results of two kinds: you would have results that whether you expected them or not, as soon as you saw them you could derive them on the back of an envelope. That is, they just follow pretty directly from you know conserving energy, momentum, and basic things like that. But then there would be some results that you hadn't expected and after scratching on the back on an envelope you still couldn't derive. And the problem is, is that a decade ago, at that point I think you could not — although the people doing the work of course said that "therefore this is happening," in reality I think in many cases it was just numerical artifacts. And you couldn't really tell was this sort of an unexpected thing so you are actually learning something from a numerical simulation, or is it a numerical artifact and it's just misleading you. But now because both computers are more powerful and the algorithms are getting more powerful, I think that you are in much better shape in that.
McCray:I interviewed an astronomer at CFA not too long ago, and one of the things we talked about were computer algorithms. This person was an observational astronomer, so we were talking about programs for processing observational data. He was talking about how he was concerned that some of his students were working so much with these algorithms and just putting junk in and junk was coming back out but it wasn't like it was when he was a student where he had to write the algorithms himself. And I was wondering if there is any of that concern in the theorist's world as opposed to the observer's world.
McKee:I think there certainly is. Now so far the students that Richard Klein and I are working with, we have very powerful tools that we have because people both at Lawrence Berkeley and also Lawrence Livermore Lab who are working on numerical algorithms to do very sophisticated hydrodynamics. Then we get access to that. Now they're not generally interested in things like gravity, so we have to add in the gravity. But that means that the students, at least the ones we've had so far, get involved in actually making some change to the code. Now these codes are so complicated that even our best students who have worked the most time on it, still there are vast parts of the code that you know they don’t know about and there are problems then he has to go back to whoever it was that actually wrote that code. There's sort of a difference between an experimental physicist and an observational astronomer. An observational astronomer goes and uses a telescope. He does not build the telescope. Whereas physicists generally have tended to build their own experiments. But as, if you're sufficiently out on the cutting edge, if we were doing some kind of a calculation which had never been done before, then obviously we have to write the code. But if you're working on something like hydrodynamics simulations then this is something that people have been doing for decades and they'll be doing for more decades, and so there are more and more sophisticated codes that are being produced. So, but there is a real issue. In fact there was a person, Mike Norman—
McKee:Michael Norman, who was at the National Center for Supercomputing Applications in CSA. This was the Illinois Supercomputer Center. And he is now at the University of California-San Diego.
McCray:Do they have another supercomputing center there?
McKee:That's right. And he developed a code called Zeus, which was a general purpose hydrodynamics code, and just recently there was a paper that came out that pointed out that Zeus — which people had been just using, he made it available to the whole community, which was great and people have done a lot of things with it, and this person wrote a paper saying that there are some very simple problems which Zeus fails at. I don't know that this in fact is correct. It may be that when Norman responds he will be able to successfully respond to this, but it certainly is something that is very worrisome, and the magnetohydrodynamic version of that code you have a student who is developing an MHD code using in our framework, and so he went back and used—
McKee:Yes. That's magnetohydrodynamics.
McKee:So adding the magnetic fields to the hydrodynamics makes life much more complicated. So he found that although we had been under the impression, I don’t know if the people who wrote the code [Mike Norman and Jim Stone] actually ever said that it was accurate to second order, but in fact in many cases it is only accurate in first order, and I think people, since most codes are generally accurate to a second order people — and certainly I'd been assuming, but it turned out to not be true. So having these codes which are made public and then people can use, there can be severe limitations because people don't know or fully appreciate what the problems are. On the other hand, again if I use my telescope analogy, you can't have everybody build their own Keck Telescope.
McCray:Yes. It would be nice if they could.
McCray:I'm aware that in the weapons design community there are these codes that get passed almost from generation to generation. I think they call them legacy codes. Is there anything similar to that in this field that you're working on, that the codes that you're working with are the ancestors of things that were developed twenty years ago that have just been successively refined and elaborated upon, or does each generation of students just start from scratch and build anew?
Well, the only hydrodynamics codes that I'm aware of that are public were the Zeus codes. Software, like many other things you know, anything that can break will break. But the problem is that if you are the one that has put out the code and someone is using it and they can't get it to work then of course they're going to call you up and ask you. So you're taking on a considerable responsibility to do that. And most people don't have the time or the resources to do that. Also it means that, you know, documenting the code extremely well in order to minimize that. You have to have it extremely well documented so that someone can get it and understand how to work it without having to call you up. But there are some codes, particularly that have been very widely used, not for doing calculations of that type but for analyzing data, and these are spectroscopic codes. Well, so Gary Ferland, who is at the University of Kentucky, has a code that he calls Cloudy and this code will calculate the properties of gas that's exposed to ionizing radiation all the way up through X-rays. And so he developed it initially for cases where we were modeling the gas around quasars, but it now is used to model any photo-ionized gas. And then John Raymond at the CFA developed a parallel code whose name I don't know which is to calculate the properties of collisionally ionized gas. It is just hot gas, and it's used a lot in the X-ray astronomy community and also I believe in solar physics, analyzing the solar corona.
So, in both cases, these people developed these codes decades ago, and they have been continually updating them with more modern data. And then people do just use them as tools. And one of the interesting things that happened is that, particularly if you think of the case of X-ray astronomy, the telescopes and the instrumentation are getting much more sophisticated. So you have a case where you can go ahead and make a prediction and then you send up an instrument that now all of a sudden can see things that nobody could see before, and you find that the code doesn't do so well. And this happened when the Japanese launched the ASCA satellite and they found a complex of lines around one kilovolt that was not in the codes, and it turned out to be due to a set of transitions of highly ionized iron that people just hadn't included before, but then when they did include them then they got all of a sudden much better agreement. But there is a sort — particularly this kind of code where you are directly comparing with data all the time — and you can also compare with laboratory data because we keep measuring.
McCray:So it really goes through this iterative process.
McKee:Yeah. So it's going through an iterative process. In each case they are constantly getting better.
McCray:Okay. Let's talk about the decadal survey. You were on both the 1990 Bahcall survey as well as the co-chair of that at the most recent one. How did you get on the Bahcall committee? How did that work?
McKee:Well, actually I don't know. I assumed I was on the Bahcall committee because Bahcall invited me. Certainly one of the key steps that was involved in putting together the committee that I co-chaired with Joe Taylor was assembling the committee, and Joe and I did that ourselves. Obviously we got huge amounts of input, but everybody that was appointed to the committee was appointed as a result of our decision that this is someone we want on the committee.
McCray:These committees are interesting because they're so influential, but they're also frustrating because the Academy seals the records pertaining to them for a very long period time. I can't recall if it's fifty or seventy-five years, but I'll never see them. So really the only way people know about the process is through interviews and whatever gets published, down the road whatever gets built. But with Bahcall committee, the major recommendations that came out of it were all pushing infrared astronomy, Gemini telescopes, SIRTF, things like that. What are your recollections or are there any anecdotes before we talk about the Taylor-MC KEE committee? What are your recollections of the Bahcall survey in terms of what the major issues were?
McKee:Well, the interesting thing — and this also happened then in the 2000 survey is that the structure of the process was one which really is different I think than some NRC committees. Some NRC committees, really it's just a committee and they meet and then they have to reach a decision. In the Bahcall — I don't know how Field’s survey worked, so I can really only speak about the Bahcall committee and then our committee — is we also had all these panels, so that altogether you had at least a hundred people that were very directly involved. And so now by the time you get to a hundred people in a field as small as astronomy you are actually tapping into some significant fraction of the most active researchers — you know, a few percent at least, and of course there are many different institutions and each of these people is then consulting with their colleagues. And so in each of the sub-areas, for example like in ground-based optical astronomy, things that came up with Gemini, you would have a group of optical infrared ground-based astronomers and they would work up their recommendations just in that field. I wasn't really involved in that, so I don't know whether there were any contention. I was on the theory and laboratory astrophysics panel and we didn't have anything very contentious about what we did, because there wasn't that much money involved.
McKee:But in some of these others I could imagine — unfortunately since I wasn't on those panels I don't know, but they would eventually decide on some, you know, what their priorities were, and once they had those priorities straight then of course that would be brought to the whole committee.
McCray:You were on the main panel as well.
McKee:And I was on the main committee as well. And so then we would see how all these different recommendations would interact. And by the time they came up, we had a lot of presentations so that it was a procedure that seemed to work very well in terms of building a consensus. You know, there was another thing that particularly in case of recommendations of the Bahcall committee — I think this to some extent is true of our committee also — that a lot of the projects that were coming up and being reviewed already had long histories. So SIRTF had been underway in one guise or another for over a decade and the Gemini telescopes, you know, each one of them was well on their way you know just through the normal NSF procedures, so it was not something that was completely new. And so I think that helps a lot.
McKee:So I don't really recall there being anything of great contention. My recollection from hearing about it, and it might be worthwhile to talk to people on the Field committee in 1980, is that there was more debate there and in particular some radio astronomers are unhappy because there was some discussion of having a large millimeter dish telescope and that somehow didn't get recommended highly enough and in some people's views it dropped through the cracks. Other people felt that was the wrong way to go so it was just as well. And the radio astronomers themselves were I think split on that. I think there was a key aspect of the operation of both the Bahcall committee and our committee that we had — from the point of view of science, astronomy may look like this one small field. When you actually get into it there is a huge diversity of activities and people are working both on problems that other people might not understand — I mean it can go all the way from extra-solar planets to the microwave background radiation. Just really, if you think about the physics involved, they are just absolutely different. And so in terms of the observational techniques from radio waves to the highest energy gamma rays, so there is a very large diversity. On this committee you then tend to have people who represent these different areas. And that means that there is not a majority of people from any one field. Like when you look around and say, "Well, how many people do optical astronomy?" Well, because if you look proportionally the overall community there is this huge number of people who do optical astronomy. But I don't actually know if you looked at the committee how many were there were. It would be probably a fairly small number, a fraction.
McKee:And that meant that it becomes impossible for one community to sort of push its agenda. Like if you want to get, say, an infrared project pushed to number one it's not because you're going to have all the infrared astronomers voting one way and that's going to be enough to push it over the top. The only hope you have is in fact to convince people who do X-ray astronomy or theory or solar astronomy or something else that this is really a great thing. So it's the people — really, in each case things are being decided by people who are not really in the field. And I think that that type of principle is fundamental to having a successful priority-setting exercise.
McCray:So what were some of the arguments being made to advance the infrared agenda that could have this cross-disciplinary appeal to the solar community or the radio community?
McKee:The strongest argument was just the revolutionary increase in sensitivity. And one of the things that characterizes astronomy is that serendipity often has played a very important role, so that if you look at when every — well, you take Hubble as an example, there have been many surprises that have come out. And people who were, when they were originally designing Hubble there were certain projects which they hoped to carry out. But you know there's been a wealth of discoveries that were unanticipated, and that's been true generally whenever you significantly extend the sensitivity of an instrument either in terms of light-gathering power or maybe spectral resolution or what region of the spectrum you are looking at. So in terms of the technological advances that had occurred relative to other fields SIRTF was going to open things up dramatically compared to what was available. Now, skipping ahead to our own survey, the optical UV community was very much interested in having a successor to the Hubble Telescope, and they suffered from — and I should say that my own research personally would have benefitted from that enormously if they had been able to convince everybody that we should have an 8-meter version of Hubble.
McCray:So not NGST in its current form, because that's primarily infrared.
McKee:That's right, because that's infrared. Right. Or maybe in addition. I think everybody would agree that NGST would have been a higher priority, but you might have imagined it somewhat lower down on the list.
McCray:Was it ever talked about, configuring NGST in such a way that not only did it go up to 25 microns but could also go down to .2 micron?
McKee:People felt that would just be far too expensive.
McKee:Or even debating about extending it down to .6 microns. For a long time there was a debate about whether to include between .6 and 1 micron.
McKee:In any case, they described the science that they could do, and there were some interesting problems, but there was nothing that was revolutionary. And the primary reason for that is because their increase in their capability was basically just simply due to the increasing collecting area over Hubble. So Hubble is a 2-1/2 meter telescope, you now want an 8-meter telescope and you can take the ratio and square it and that’s — they used to get it back to ten or something. That’s all you were getting. It’s not getting a thousand fold gain.
McKee:Now there is technology that people are working on which would essentially enable you to take a spectrum at every point of the image.
McCray:These are integral field units?
McKee:Well, yeah, but this is even more direct. Like in X-ray astronomy, where the detector which measures the location where the photon comes in, it simultaneously measures energy. And so these are superconducting Josephson junction or transition edge sensors. Two different technologies that people are working on. And it was felt that during the coming decade these technologies will presumably advance and that it's possible that by the next decade's survey that would be sufficiently advanced. Then if you put up this 8-meter telescope in addition to this factor of 10 that you get in sensitivity you are going to get a factor of 100 in information because essentially every time you take a picture you are going to get a spectrum with a resolving power of 100.
McKee:And that would of course be — then you are talking about in some sense a factor of 1000 gain, and then you probably would do amazing things.
McCray:Like the politicians say, “then you're talking real money.”
McKee:Right. But in this case you are talking about a real chance for having major advances. So this idea that you can compare recommendations even though they are completely different scientifically and completely different in terms of the wavelength and so forth, that how much of a gain are you going to make with all this technology. But then it has to be coupled with “what problems are you going to address?”
McCray:So it's not just enough to be able to say, "We have this great gadget."
McCray:You have to be able to do something with it.
McKee:And so one of the problems that the optical/infrared panel of the most recent survey looked at was the idea of building up on optical and infrared interferometer from the ground. And people — there were concepts that people had talked about. For example, building an infrared version of the Very Large Array. I think in terms of this technology advance I don't know how they would have done it, but they probably could have come up with some bigger figure of merit which would show a truly huge gain over the instrumentation we have available now. But then when you ask, “Well, what problems could you address?”, the problem is that if you want to do interferometry in the optical for example that actually it has to be a very bright source. You are now going to be able to look at a very small piece of the sky, but that tiny piece of the sky is able to put out enough photons for you to see it. And so basically those things are called stars. And so being able to make beautiful maps of red giant stars or something like that would be — you know, quite possibly I'm sure we would learn things, but in terms of the overall picture of astronomy, what are the major problems that we're dealing with. Is trying to get a better handle on red giants one is of the key problems?
McCray:Okay. I was curious. The 2000 committee was the first one to have two co-chairs.
McCray:How did this happen?
McKee:Well, what happened was initially Joe Taylor was asked to chair the committee and my understanding is that he was unwilling to do everything. And so then I was contacted and then after talking with Joe we agreed we could do it jointly. And in fact the division of labor that we came up with is that I would concentrate primarily on the mechanics of actually running the survey and writing the report, and then he would be the person who would be primarily responsible for selling the report. And that is because — it's probably because in his position as dean at Princeton he was quite busy. I was able to get some time off and actually part of my sabbatical was used in writing. At times it was taking up practically all my time. The fact that he has a Nobel Prize and is a very highly respected figure in the field, so he would be in an excellent position to be able to do the selling.
McKee:Also it's more convenient for him on the east coast to hop on the train and go down to Washington.
McCray:One interpretation in looking at the geography of the two co-chairs, Bahcall was at Princeton and chaired the last one, one can see that there might have been some outcry of bringing another Princeton astronomer to chair the next one, this is becoming too dominated by — and Field did the last one, so you know you are sort of getting this east coast bias which kind of goes back to that historical east-west tension in American astronomy, and I was curious if that had anything at all to do with, "Well, we'd better get someone from the west coast, because otherwise it's going to look like it's just the eastern establishment."
McKee:I don't know. There was a committee. I believe the committee that was doing this selection was chaired by Tony Readhead. And I don't know all the considerations. As you can imagine — as I emphasize that the choice of the committee was extremely important. We came out with an excellent report, and that was based on the fact that the people who were on the committee really did an excellent job. I had the situation recently in which I was on a committee, in which it was not set up in this way, that it was just picked by somebody I guess, but not by the chair. That is, whoever was picking the committee picked the committee and then twisted someone's arm to be chair. And it was the only committee I’ve been on in which the committee was just absolutely split down the middle, and you know we had only one meeting. At the beginning of the meeting we were split, at the end of the meeting the split was the same. There was absolutely no change of anybody's mind.
McCray:Was this the National Academy panel?
McKee:No, it wasn't. Actually I'm not supposed to talk about it.
McKee:But I'm just saying that what it brought home to me was — because never having seen a committee like that, I didn't know they existed. Because these are all highly respected people. We just absolutely could not agree. We could not even understand — at least I never understood what their viewpoints were, and I'm sure they may have wondered why it was that I was saying what I did. The way that we set up our decadal committee was that I, you know, for each of the different panels and so forth I would get the panel chairs. Once we had a panel chair, we would go ahead and let them do the same thing and try to set up their committee. But you know I would call around in different fields, like let's take solar physics which I know very little about. So I would call the top people in solar physics and get their recommendations and find out about the people. And after you start talking to people you find that there are some people whose names keep on coming up even from very different people.
McCray:Yeah. Did you keep a notebook?
McKee:Yeah, so I kept very elaborate notes on that.
McCray:Did you save your notes?
McCray:Okay. Because I remember talking to Bahcall, and he said he kept a little black notebook but he destroyed it after the process.
McKee:No. I didn't have a little black notebook. John did mention that sometimes he would get some very negative remarks. I wasn’t getting as many negative remarks, but there were certainly, there were cases where people — particularly one of the things that I was concerned about was I wanted to get people who were outstanding in their field, but you wanted to have people who could reach a consensus, and there are some people who are brilliant scientists and one of the reasons they are brilliant is they are very single-minded, they know the right answer, and they just charge ahead.
McCray:But not a good committee person.
McKee:No. Yeah, but that's not what you want on a committee.
McCray:Okay. Since the Academy records are sealed, are there any anecdotes about the process of preparing the report that you can share?
McKee:Well, there are no amusing stories that emerged. In general, as I said, I think things worked extremely well. One of the panels that worked the hardest — and this was true with Bahcall’s panel and that was the committee on policy, public policy. You can image that there are a lot of — that is an issue where people have very different opinions.
McKee:Well, one of the issues which was probably one of the most contentious issues we dealt with, although in the end people did come to a consensus at least on the main committee, had to do with the National Optical Astronomy Observatories.
McKee:And they came in for severe criticism in our report.
McCray:Yeah. The language in these reports oftentimes is bland sometimes, but I was surprised when I read it that the — this was one of the first reports where there is actual, fairly pointed criticism basically saying that the National Optical Observatory was broken and it needs to be fixed. And I was surprised to read that.
McKee:That's right. So as you can imagine, there was a lot of debate about that. Not everybody agreed with the statement. But this is being considered by two separate panels, because the optical and infrared panel actually they were concerned about it. In addition the policy panel was also concerned about it. But we were able, in the end, to get a consensus, and I pushed very hard to not water the recommendation down any more — I wanted to have as strong recommendation as could get a consensus of that committee and not have it turned into milk toast. And I think that this had a very salutary effect, because, since the time when we began our work. Unfortunately I don't know the exact time line, but the leadership at AURA changed and the committee structure has been changed, the director of NOAO is different now and the director of the National Solar Observatory is different.
McCray:Did the National Solar Observatory—? I mean I know it's broken off from NOAO. Did that happen after the report came out? I can't recall.
McKee:It was in process and is something we encouraged.
McKee:I should emphasize that the NSO did not come under criticism — the solar physicists in general were much happier with the NSO than optical astronomers were with the NOAO. I think if I could just expand on that a little bit. One of the things is that the division of opinion on NOAO to some extent is a reflection of the difference between astronomers at major institutions who have access to major facilities and by and large believe that NOAO should be a major facility and should have some thing that it's doing that is unique and be at the forefront, and that the National Optical Astronomy Observatory of the United States — which is the leading power in science in general and astronomy in particular — should have an observatory like that
McKee:A flagship. It's not that it's supposed to duplicate other things; it should really be doing something outstanding. Whereas there are many astronomers who are primarily at smaller institutions who do their observation at NOAO and just want to make sure that they have access to telescopes.
McCray:Both bigger and smaller telescopes?
McKee:Yeah. That is certainly true that if you have put all your money into 30-meter telescopes then the amount of time on that is necessarily limited, and if you do away with all the little telescopes then that is going to be a disaster. So we tried not to be too prescriptive, but I think what we were trying to get to was a situation where — there was no political agenda involved — that NOAO should be investing on telescopes based on the science that could be done. And there is some good science that can be done with small telescopes and that's a good reason for having some small telescopes. But that's the reason why you should do it, not because you are trying to do a WPA project for astronomers who need to use them in order to do their work.
McCray:I'm curious. I mean those two different viewpoints — and if this is sensitive we could seal this part of the interview if you want — but I'd like to get a sense of which people emerged as representing these different viewpoints, because that may be important down the road for understanding this period.
McKee:Actually since I did not participate in those panel meetings I can't say. The chair of the public policy panel was Andrea Dupree.
McKee:And the chair of the optical infrared panel was Alan Dressler.
McKee:And I don't know whether you will be interviewing either of them anyway.
McCray:I'll be talking to them at some point.
McKee:Sure. And he might be able to tell you more. I think that that would be interesting.
McCray:Okay. Just as a theorist seeing this contentious debate within the optical/infrared community, as a relative outsider, what was your take on all that? Why do you think there is this tension?
McKee:Well, I mentioned one of the sources of the tension. The other source of tension which has been changing is that there were people who had access to private facilities and those that didn't, and if you go back several decades then in fact Cal Tech had Palomar, UC had Lick and Arizona had a telescope, Texas had a telescope, and places like Harvard, Princeton, Yale, Chicago. Chicago had Yerkes, but that is not really very good for working on. So there were many places which had outstanding astronomy departments that had access to no telescopes at all. This caused a split certainly between the haves and the have nots. In that case it wasn't necessarily between the major research universities and the non-major ones. And then as time has gone on, a larger and larger fraction of the major research universities and even those that are not at the very forefront but some smaller universities have been able to buy in, get pieces of telescopes. And so now I believe that probably over half of the astronomers in the country have access. But there are many astronomers, for example, at NASA research centers that employ large numbers of astronomers and their access is purely through NOAO. So it’s basically, I think, a split between the haves and the have nots.
McKee:And one of the problems which the O/IR panel — and I think also the policy panel — grappled with was this idea of how you can try to instead of considering the NOAO completely separately from the private telescopes, that really we should consider it as part of a single system.
McKee:And then you try to optimize the whole system, you try to— And one of the key ways of doing this was the moderate initiative that we recommended, which was the telescope system instrumentation program.
McKee:The observatory directors formed a group called ACCORD, and this had the beneficial thing of getting all the observatory directors talking to each other and being on the same page, but they at least in my view tended to want to have a policy that would maximize their flexibility rather than one which would necessarily make the system as a whole work the best. But in the end, I think that we were able to work out a compromise that everybody accepted, and I should say that even though from my perspective the observatory directors seem to be perhaps too self interested, in reality it's absolutely critical that they buy in to the program if it is going to succeed. And furthermore they're in a much better position than I to appreciate the problems. It's one thing for a theorist to think that some system is going to work that's based on high-flown principles and another thing—
McCray:But they're the one that has to work with it and then live with it.
McKee:And a lot of times the practical things that are involved. On the other hand but the principle has been established that through this TSIP [Telescope System Instrumentation Program] program there will be access, at least in some form, that will be provided to all the astronomers who don't have access to telescopes, so that if an observatory like Lick Observatory gets somebody to build some instrument, then in exchange they are either going to provide time on one of their telescopes or they might provide some service to the community or some data set or something, but in any case all this would be determined in a peer review process so that it's not that the director of Lick gets to decide what he's going to give to the community. I mean if he decides to not give enough, well then his proposal won't be rated very highly and so he won't get the money for the instrument. And so it's I think a good way of trying to strike a proper balance between the different needs. But there is a very interesting example. To show you this split, and it can actually occur even in a single person. So one of the people on our committee was Jerry Nelson. And Jerry is justifiably famous for the work he did in designing the Keck Telescope. So the top recommendation of the ground-based optical infrared panel was to build essentially a giant Keck, the giant segmented mirror telescope. And Jerry's role in developing that recommendation, as you can imagine, was absolutely critical. Now, well, because he was the one who assured the rest of the committee that it was physically possible and that you know could be done for a finite amount of money. The science case of course people can show was very strong. Now it was realized that even if the various technological breakthroughs which Jerry said were needed in order to make this reality occur.
McCray:Adaptive optics for one.
McKee:Yeah. Exactly. It was going to be very expensive. Although on the adaptive optics he certainly was talking about — but even just in terms of the structure that if you took the Keck telescope and said that the GSMT [Giant Segmented Mirror Telescope] would scale by the cube of the aperture which is what it would do if you just built a giant Keck, then that would already be twenty-seven times more expensive than the Keck — so that would be $2.7 billion. So you need to have really clever ideas, such as those— If you had done that for Palomar, if you had taken Palomar and said, "Well now we're going to build Keck," then you never would have been able to afford Keck. And so you have to do similar technological improvements in order to be able to build the GSMT. So but despite that it was realized that it would be impossible for NSF to have the hope of being able to do this, and there was always the hope, as Jerry knew because he was pushing this at Santa Cruz and people pushing at Cal Tech, that there would be a privately built telescope and that perhaps the NSF role would be to provide operating money for — depending on how much money they could actually raise for the construction, and NSF would come in and provide some. But it basically, in our recommendation we said that the cost should be split.
McCray:That's one of the interesting things, that it gives a price, but I assume that the report gives NSF’s contribution, and then there’s this mysterious private amount which would be given.
McKee:Well, in our planning it was half.
McCray:Half. Okay, okay.
McKee:It was supposed to be split. Okay. But now — so that's Jerry Nelson as a member of our panel fully supporting this, and of course this plan would then naturally guarantee half of the telescope time would be available to the community and then half of course to be reserved for whoever provides the other money. But then, even while he was on the panel — and of course much more so now that he’s not on the panel anymore, if you talk to Jerry Nelson, the astrophysicist at UC-Santa Cruz, he wants to have absolutely nothing to do with NSF. And so they’re pursuing CELT, California Extremely Large Telescope.
McKee:And they're working and have made enormous progress in terms of the design. I think there has been some limited contact with NOAO and my impression is that people at NOAO would be very interested in getting involved because they see this as their future. But they are being held at arm's length because the people involved with CELT feel that the amount of bureaucracy which you bring by involving any government entity is just not worth the costs.
McCray:So if they can do it on their own?
McKee:Yeah. So ideally, if they can get enough money — despite the fact that he signed onto this recommendation that it would be 50/50 and committed to that half, if in fact someone gave him enough money to build the whole thing and operate it, that he would I think just say, "Well, let NSF team up with somebody else to build their own 30-meter telescope."
McCray:Interesting. I mean if that happens and CELT is built and it's basically for California astronomers, it almost is a return to the old days of you know when the biggest telescopes were the 200-inch and the Lick to a lesser degree and then there was everybody else.
McKee:That's true. Now, but a difference is that the idea of building these telescopes has spread so that although CELT is as far as I know the most advanced concept, people at Carnegie and a couple of universities are thinking about their own version of a very large telescope. And in our recommendation we acknowledge the possibility that rather than cooperating with a private entity NSF might do it internationally. And there is certainly great interest in Europe in terms of doing this. The Europeans have been thinking of a much larger telescope called OWL, which would be 100 meters in size. One of the points that Jerry made, which I always found extremely persuasive, was that even if you decided that you were going to build OWL that due to the scaling law you could build a 30-meter telescope for 5 percent of the cost. And so you'd probably want to go ahead, rather than having it jump by a factor of ten in the size all at once, it would be much better to have this prototype where you only have a factor of three and work out the problems there before you did the next phase.
McCray:Interesting. In terms of how the recommendations are faring, I'm trying to think. I mean you had NGST, you had the millimeter array—
McKee:Well actually the millimeter array is a part of the Bahcall recommendations.
McCray:Okay. You have the giant segmented mirror telescope, you have the Large Synoptic Survey Telescope [LSST]—
McKee:Right. We have Constellation X.
McCray:Okay. Yeah, I'm less up to speed on the space ones. But what's your sense of how they are faring?
McKee:I think that things are going reasonably well. NGST has shrunk a little bit since we discussed the original, and we were discussing in 8 meters and now it shrunk to 6 1/2 and I'm not sure, I think that by the time this was actually printed we were able to get it on the 6 1/2.
McCray:Still 8 meter.
McKee:Oh, still 8, okay. So but nonetheless if it stays at 6 1/2 meters that would be adequate to do most of what we want. And since this is our highest priority, I think that there is a reasonable chance that it will survive. I think if you look at the history of SIRTF or the history of any of these major projects, it's like the Perils of Pauline. You know, they constantly have to be rescued. And I'm sure that will happen with NGST, but I think that there is very strong support in the community for it, so I think that that is in good shape. And we just talked about GSMT so that although I would certainly be concerned as to whether there will be a general access to GSMT, that I'm not so sure, but I think — I'm very confident that there will be a GSMT built.
McCray:But there probably won't be a dozen of them the same way that we have 8- to 10-meter class telescopes now.
McKee:That's right. At least unless there is some sort of a technical breakthrough in terms of the cost.
McKee:Now again, going back to Nelson's point about how you could build a 30-meter for 5 percent of the cost of the 100-meter, my understanding is that the Europeans claimed that they could build the 100-meter for a billion dollars, and if that were true then you could build CELT for only $50 million. Now that of course, only 10 percent of the cost that we were preparing for, but so either you know—
McCray:And it's less than it costs to build a single Keck telescope, so it's kind of hard to imagine.
McKee:That's right. But so the point is, is that either the Europeans are being hopelessly optimistic in their numbers, or maybe it is that they're assuming that the CELT would not be built for awhile and that things would continue to come down in price.
McKee:And certainly if it did get down to that price range then you could imagine—
McCray:Yeah, many of them being built. Okay.
McKee:But then in terms of Large Synoptic Survey Telescope, there is certainly a lot of interest in that. It hasn't — and there is some preliminary work being done on it — and as the NSF’s budget is very strapped, and astronomers in general I think are very resentful of the fact that astronomy has not been adequately funded by NSF.
McKee:And I think that if you look at by any measure in terms of either the quality and quantity of science on the one hand or in terms of popular appeal — which is something I think NSF has to be somewhat cognizant of — that astronomy would rank near the top. Yet if you look at where the money's been going, it’s basically level funding over the past decade.
McCray:Any thoughts on why that's the situation?
McKee:Well, the only thing that I can think of is a combination of hostility at the top of the organization and people being in charge of the astronomy section who weren't sufficiently articulate advocates.
McKee:It's complicated. When you talk to people at NSF, I mean they certainly — Joe and I talked to Rita Colwell and she indicated that she would be supportive and so forth. It's just that we haven't seen any evidence of that.
McCray:Yes. Okay. I have a final set of questions which are much more general in nature and sort of go back to the relationship between physics and astronomy, and I'm mindful of the fact that you are now department chair of both the physics and astronomy departments?
McKee:No, just the physics department.
McCray:Just the physics?
McCray:Okay. Remind me again of the relationship between the astronomy and physics.
McKee:Yeah. They're totally separate departments.
McCray:Okay. So you sit in the astronomy department, but you actually chair the physics department.
McKee:Yeah, my research office is here in astronomy and my administration office is over in physics. As I was mentioning, the history, during the first few years that I was here at Berkeley my research office was also over in physics, but I was essentially an isolated theoretical astrophysicist there, whereas the theoretical astrophysics physics activity was over here, and then particularly after we started bringing in these postdocs they were all located here, so it made much more sense for me to move my office here where all the intellectual activities are in theoretical astrophysics.
McCray:Okay. Well I think that puts you in a good position to answer these questions about the relationship between the two. I mean historically physics and astronomy — not astrophysics, but I mean physics and astronomy — have developed as largely autonomous fields, but how distinct do you see physics and astronomy as separate areas of research and also in terms of the communities? How much are they a part and where do they touch?
McKee:Okay. They I think historically have always had a strong connection. If you go back to a lot of the work that was done in say the first half of the 20th century was on stars and stellar structure, and that was sort of a joint enterprise with observational astronomers and theoretical physicists. What’s happened, in the second half of the century was the opening up of whole new wavelength windows. And in the case or radio astronomy that tended to be done I think by electrical engineers who were familiar with technology. But in other areas, both particularly infrared and X-ray astronomy, gamma-ray astronomy, tended —
McKee:Yeah. It was physicists moving into astrophysics. And so this has now created a situation where you have many people who are moving from physics into astrophysics and astronomy. There is not many examples of the other way around. If you're going to be an instrument builder you probably need to have a vast amount of basic knowledge that you get as an undergraduate and certainly in graduate school to do it. So in those areas the interaction is very close. What's happened even more recently then is with the explosion in interest in cosmology. Then you get a whole new group of physicists, particularly I think particle physicists are now becoming interested in astrophysics. This phenomenon could have happened with the others too, but essentially in any field of science I think there is sort of a community and there are certain things that people know about, and then when you have people coming in from some different field they have a different culture and different approach and sometimes there's some period of adjustment while people that get used to each other. In the case of NSF, although most of the astronomy is supported by the astronomy section, now the physics section in NSF has an astrophysics piece and they are actually supporting some astrophysics work. It gets back to this issue I mentioned about who it is that assists on peer review panels. Because it would be interesting to know if you were to do an experiment in which you had say one of the astronomy sections peer review panel, you take the panelists and put them to review physics proposals and put the physicists and have them review the astronomy proposals, the outcome of that review might be completely different than it is when they have that done now. So, in any case, I see this as you know a very beneficial process. We actually have a case here at Berkeley that as chair I have been trying to improve, and we have a very strong astrophysics effort up at Lawrence Berkeley Lab that’s led by Saul Perlmutter.
McCray:So that the supernovae work.
McKee:And historically there has been very limited interaction between that group of people here on campus.
McKee:Just because of the separation between the two or — ?
McKee:Well, that's certainly part of it, but there are some aspects of the physics department — for example the high-energy physicists spend half their time up at LBL. So there's obviously — and they have LBL colleagues that they treat as members of the group so that in fact their LBL colleagues participate in voting on faculty choices and stuff like that. It's one for all and all for one. And I think that in principle that's good, because that really means that you then can take full advantage of the resources at LBL. Whereas in astrophysics we have the exact opposite situation where there is a very limited contact. Also personality clashes because as you probably know there are two different teams that are involved in this supernova project, and one of them is led by [Saul] Perlmutter and the other is led by Brian Schmidt, but a key member of that second group is Alex Filippenko, who is a member of the astronomy department here. And so Alex, as I understand it, was initially teaming up with Perlmutter and they didn't get along for one reason or another, and then Alex joined this other group and now at least in the past there has been a lot of friction between these two groups and in any case my hope is that through the physics department, which is, you know, separately you could try to reduce this division, and really take advantage of the potential synergy which you get between having a major national lab right next to the campus. There is a lot of support for that in the physics department.
McCray:Okay. How does an astrophysicist work as a department chair for a physicist?,
McKee:Well, so far it seems to have worked out fine. No one has complained. Obviously I attempt not to show any favoritism to astrophysics and no one has complained about that, so I think that things are going well. One of the only — one of the things I did was have a strategic planning exercise for the department. Being an astrophysicist and therefore on the outside I made the suggestion that we combine the condensed matter group with the atomic physics group and call it quantum physics, because it seemed to me that they basically were dealing with the same types of problems and there could be some useful synergy between the groups. And what the groups told me in response was that whereas there could be some useful synergy there, they are completely different groups and they did not want to be joined together, so they stayed apart. But that was something that presumably the condensed matter physicists never would have thought of, because they were — Well, they might have wanted to merge something else.
McCray:Yeah, yeah. Interesting.
McKee:But it's interesting, one of our former people who was here in fact was a Berkeley student and was a professor was Steve Kahn, and he went to Columbia, and he just stepped down from being chair there. And then I was talking to someone who had been a postdoc here, Avishai Dekel, and he had been just stepping down the chair at the physics department at Jerusalem University. So astrophysicists are taking over. And as I mentioned Joe Taylor for example. I don't know. I assume he was chair, although I don't know that.
McKee:And of course Jerry Ostriker was provost at Princeton for a while.
McCray:Yes, yeah. I guess he's left that position now. He's now at—
McCray:Yeah. One last question. Most general. Since you've entered the field of astronomy's astrophysics, what is the single biggest change that you recognize?
McKee:In the science content of the field or the sociology?
McCray:How ever you wish to interpret it.
McKee:All right. Well I think I'd have to say since I entered the revolution — the biggest revolution is space astronomy — that now a very substantial fraction of everything that we're learning about the cosmos comes to us from satellite observations. And when I started they had only recently discovered the Earth's radiation belts, and they have been— I think when they were doing sounding rocket flights they discovered the soft X-ray background while I was a graduate student, but you know the idea of actually seeing — and maybe a source or two, but they were just really beginning, whereas now they are measuring incredible details about individual sources. So I think that's been the biggest revolution.
McCray:How about within the community in terms of its makeup or its organization?
McKee:Well, I think that probably — certainly one of the biggest changes has just been the quantity. The size of the community now is much larger. And I think that there is much greater diversity in where people are. Here again I'll mention NASA has established a number of laboratories, and so many astronomers and astrophysicists who work there. And if you go back prior to the advent of NASA, then the people were probably either at universities or at — well, I'm not actually sure, because NOAO — well, actually I don't exactly when NOAO was established, but I think it was in the fifties or something.
McCray:AURA was founded in '57. NOAO itself was 1984, but it was Kitt Peak.
McCray:Then Cerro Tololo in the 1960s.
McKee:That's right. So basically if you go before that, people were just at university observatories so that now you have national observatories and national laboratories, so there is much greater diversity of sources. In terms of diversity, there are certainly many more women in the field now than there used to be. I think it's good, and that's I think something that's continuing to occur.
McCray:Okay. Well, I don't have anymore questions, so why don't we stop here.
McKee:Okay, all right. Great.