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Oral History Transcript — Dr. Edward Purcell

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Interview with Dr. Edward Purcell
By Katherine R. Sopka
At Lyman Laboratory of Physics, Harvard University Cambridge, Massachusetts
June 14, 1977

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Edward Purcell; June 14, 1977

ABSTRACT: Early life in Illinois; B.S. from Purdue under Lark-Horowitz (1929-1933). Visit to Technische Hochschule in Karlsruhe. Theoretical and experimental work and teaching at Harvard (1934-1941) under Chafee, Bainbridge, Van Vleck. WWII (1941-1946) research on radar at MIT Radiation Lab. Return to Harvard; teaching, Nuclear magnetic resonance and 21cm line research. Discusses government consulting work (1950-1970), especially President's Science Advisory Committee, American Physical Society presidency; teaching at Harvard. Interests in astrophysics, developing physics curricula.

Transcript

Session I | Session II

Sopka:

It is now June 14th and I'm again meeting with Professor Purcell in his office in the Lyman Laboratory of Physics where we will continue the discussion that was begun last week on June 8th.

Purcell:

Perhaps I should say something now about my teaching career in the department and my teaching interests. Most of my teaching actually has been in undergraduate courses, and my involvement in particular in the freshman and sophomore courses goes back to my first years as a teaching assistant. I worked, as I think I mentioned before, in Professor Black's Physics B and later in Physics C under Professor Saunders. I think perhaps Professor Saunders' course was the first one I actually was responsible for, after he retired. Professor Chaffee's course in electron physics, which had been a tremendously interesting course for me as a graduate student, fell to my lot just after World War II and I had a great deal of pleasure in teaching that material, most of which I'd learned first from Chaffee. One of the courses I introduced -- I think it must have been in the middle ‘50s more or less -- was a course in electromagnetic waves for undergraduates called 161, which drew heavily on my experience at the Radiation Lab in microwave circuits. A more recent innovation that I've introduced and tried a few times is a course called "Widely Applied Physics," which was conceived with the idea of introducing physics undergraduates to some other neighboring fields in the hope that some of them might find an interesting direction for their own careers and also I think to indulge my own taste for engineering physics, applied physics of an engineering sort, which has always remained strong. In fact, if I haven't said it before, I'll say now that I really by intellectual taste am almost as much of an engineer as a physicist. Much of what I've done in experimental physics, especially the work that came out of the Radiation Lab, was engineering in style, and I've always found that applications of physics in that field very interesting. I haven't taught many graduate courses. I've enjoyed particularly teaching introductory quantum mechanics and atomic physics. I've never taught advanced mechanics. In fact, I'm not even sure I had a course in advanced mechanics. I did teach thermodynamics a couple of times, enjoyed that because it finally forced me to learn some things that I had really never had command of before. I've been interested … I'm still interested in undergraduate teaching, and I imagine in the concluding years of my membership in the department I shall teach probably only undergraduate courses.

Sopka:

I understand you have given courses under the general education umbrella.

Purcell:

Yes, I gave Natural Science 2 one semester, enjoyed it very much, and I'm sure that there are lots of good courses that can be made for undergraduates who are not physical science concentrators. These are very bright people we have at Harvard, and there are many ways to challenge their interest in science.

Sopka:

The University is in the process of reexamining its program in that area. Do you have any comment on possible directions it will or should move in coming to grips with this group?

Purcell:

I think it's time that the enterprise was re-examined. One always gets a temporary benefit from re-examination at least. I'm not particularly impressed by the formula that the so-called task force on the core curriculum has proposed, but I'm willing to see what comes from it. I find the description of it and some of the justification, as explained in the core curriculum report, really does not express my conception of the university or of the capability of its students. I think it is rather patronizing to the students. Harvard University is a very special place. My ideal for Harvard University is simply a university where every course is a good course, but I don't think one can presume to define minimum requirements for an educated Harvard graduate in terms of a particular set of courses.

Sopka:

How do you feel about the idea that there should be special courses designed for people who are not concentrating in that field?

Purcell:

I think that's necessary, absolutely necessary.

Sopka:

It certainly seems to be in the sciences and the group of courses under the Nat. Sci. designation. Do you think it's also desirable in areas like art and music and sociology? For instance, your physics undergraduates, should they be taking a course designed for non-concentrators rather than taking a course that would be the introductory course in the department anyway?

Purcell:

Well, I'm inclined to think that it doesn't matter so much for the physics concentrators. I'd really rather see them take a departmental course in social relations or history or economics or whatever. The situation is not symmetrical. The other way around we have the problem of mathematical requirements among other things. And also we have a genuine duty, it seems to me, to try to exhibit those aspects of our science which have some usefulness and relevance to the career of a person outside science. I think the physics concentrator can take a course in economics and follow it and decide perfectly well what part of it is relevant to his future concerns, if any. But I think it's too much to expect a student of economics or history or English to do the same for a physics course. Moreover, I think it's a very interesting and exciting and challenging job to look at a science that way and try to explain the ideas to people, and I would insist that what we ought to explain is the ideas and not just the language -- some of the ideas, some of the ideas, by no means all of them. Here we have to take maximum advantage of that wonderful property the human mind has of making a world from one good example. That's the thing that makes courses like Nat. Sci. 2 feasible, that you don't have to cover everything, as long as what you're covering has some important ideas in it.

Sopka:

Presumably you fell that it would be important for the members of the physics department in the future to continue to take responsibility for teaching this kind of course …

Purcell:

Oh, yes, and I think we have in the past. I think our record is really very good.

Sopka:

Yes, I do, too. I was thinking about the future.

Purcell:

Ted Kemble really created Nat. Sci. 2, too, and more than that, he really set the standards high so that it was a course worthy of Harvard University. Well, let me talk now about some other involvements at Harvard, which I don't plan to say very much about: my services as Senior Fellow in the Society of Fellows for nearly 20 years. I enjoyed this very much, and I have a tremendous admiration for the contribution that the Society of Fellows has made to Harvard University, the magnitude of which is obvious if you simply look at the present faculty and see how many of them were Junior Fellows. I was not myself a Junior Fellow, of course, but I knew some of the early Junior Fellows so that when I was invited to become a Senior Fellow -- I guess it was around 1950 -- I had no hesitation in taking on that mild responsibility.

Sopka:

As a Senior Fellow, were you responsible for the choices as the years…?

Purcell:

Yes, that was, in fact, our only important duty: to interview the candidates and elect the new Junior Fellows each year. We interviewed every candidate. Every serious candidate was interviewed by all the Fellows, and I picked up a good deal of general education information listening to my colleagues in literature and history and so on interview these candidates, and also I learned even more from the Junior Fellows themselves over the years, with whom of course we dined every Monday night during term time, and I made very many friends there among the younger scientists and younger humanists. I resigned finally simply because it seemed to me 20 or 21 years of Monday night dinners was perhaps enough, but it was a very friendly and rewarding and pleasant association for me.

Sopka:

Do you think that this concept of the Society of Fellows, which certainly is of great value both to the individuals and to the University, could in any way -- the ideas of it -- be in any way extended to a larger group of people at Harvard or could be emulated at other institutions?

Purcell:

Well, it is already emulated at the University of Michigan. Michigan some years ago established essentially -- I don't think it would be too much to call it a carbon copy of the Harvard Society of Fellows, and it's running full blast as far as I know. It's fairly well endowed. The endowment of the Society of Fellows here did not over the years grow as much as it really ought to have grown. The Society was still operating on Mr. Lowell's original bequest pretty much. But it's flourishing, and I'm happy to say that it seems to me the Society of Fellows is as vigorous and as promising right now as it ever has been. There are sensational young people in it, including women now.

Sopka:

Yes, I interviewed Louise Dolan.

Purcell:

Yes, it's really one of the great things around here. It's just really an immeasurable asset to Harvard. Mr. Pusey really never understood that and never accepted that actually.

Sopka:

In saying that it's of inestimable value to Harvard, is this because it's the bringing together of a group of very bright young people and allowing them to cross-fertilize and then this seeps out into the university structure?

Purcell:

No, I was simply thinking of the fact that it's been the recruiting ground, as it were, for a fair fraction of the Harvard faculty. These are extremely bright people, very productive. They come to Harvard; some of them were of Harvard originally but many were not. If you just go down the present faculty of arts and sciences and check out any who were former Junior Fellows … In fact, if you look at the Harvard administration now, even from Rossovsky; Dreben, who was Dean of the Graduate School; Frank Pipkin, who is Associate Dean; Harvey Brooks, who is Dean of the division; McGeorge Bundy, a dean some time back and just keep going… I mean these people you identify with Harvard scholarship and leadership very often turn out to have been Junior Fellows. It's really astonishing. We made a survey of that some years ago when we were trying to get some money for the Society, and I was astonished by the statistics. I think about half of the math department were Junior Fellows and Gleason, one of the most distinguished mathematicians we have, and several others over there.

Sopka:

Garrett Birkoff was one, wasn't he?

Purcell:

Yes, and Mumford, Lynn Loomis, lots of them. Well, let me go on now to this outside activity -- professional and activities outside the University, which in my case have involved a good deal of work on one or another government scientific advisory committees or projects. The depth of my involvement in these things is really not apparent from the ordinary chronological record, because some of the heaviest involvement was in the form of summer projects or ad hoc projects set up to address a particular problem on which I would be working full time with a group of people for perhaps several months. Just to mention these in what I think is chronological order: I was involved first in a Navy project called the Hartwell Project run by Zacharias and concerned with the problem of anti-submarine warfare in 1950 at a time when snorkeling submarines represented the current threat. Shortly thereafter I was involved in a project for the State Department, which was concerned with the Voice of America broadcasts, which were our propaganda arm in Europe. The Voice of America -- the radio broadcasts were being jammed everywhere behind the Iron Curtain as a rule, although people were still managing to hear them now and then. And our project had a large technical section of which I was in charge, directed as the purely technical problem of how you could prevent the jamming or broadcast through the jamming, etc. We reported -- I think that must have been ‘51, because we reported our findings to Dean Acheson, who was then Secretary of State under Truman. I think actually we weren't able to do much good. We didn't invent a very effective remedy for the jamming. We did, however, as an incidental spin-off, as we would now say, start what's known in radio engineering as scatter communication, ionospheric scatter communication. Some of the experiments we promoted led to the discovery that one could transmit radio waves over the ocean by scattering them off irregularities in the ionosphere. This became known as ionospheric scatter and had some modest utility in later years.

There's a scientific paper which came out of that with a large number of authors concerned with those experiments. Sometime after that -- I think it must have been in '52, perhaps the spring of 1952 -- I was involved in (or perhaps the fall of '52) a project called Beacon Hill, which was a study of the possibilities of reconnaissance, photographic reconnaissance. This was almost entirely a technical study. People actually worked in Boston for several months. The conclusions of this study were the basis for much of the activity in later years in the developments of photographic reconnaissance both from airplanes and from satellites, and in that sense it marks the beginning of my own connection with projects of that kind. Then in 1954 I was recruited into the rather broad study of the United States defense capabilities, technical capabilities, posture, under Dr. Killian -- the so-called Technological Capabilities Panel, to give it its cover name -- and in this work I was particularly involved in a small group concerned with the technical problems of intelligence gathering.

Sopka:

This was a period when the scientific community was cooperating quite actively with the governmental groups.

Purcell:

Yes.

Sopka:

Apparently primarily because of the real concern of everybody for the tense …

Purcell:

The cold war was on. And I don't recall any… well, there may have been some, but you're quite right in saying that by and large the scientific community was either passive and simply didn't take part in this at all or else they were contributing. Those of us who were involved in these projects were ones who had been more or less continually involved since World War II in military technology and things like that. So it was natural for us to keep in the game.

Sopka:

There was no trouble continuing or extending the working relationship between yourselves and the military and the political leaders at that time?

Purcell:

No, none at all, and this of course … by now we're in the Eisenhower Administration. Killian had extremely good relations with Eisenhower. In fact, a number of the people knew Eisenhower and were trusted by him. We had direct access to the President on any really important matter when decisions had to be made. There was no holding back. The problems were very difficult. Many of them were not solved in any real sense, but there was very active cooperation and exchange of views.

Sopka:

And presumably the military and political leaders were very desirous of any help they could get from the scientific community.

Purcell:

Yes, the people that we were dealing with were people who had gotten such help during World War II and knew how to deal with the scientists. There were many issues that were … well, I don't want to get into this because it's really not part of my activity, either before or since, but you could see the shadow of things ahead in some controversies at that time. I think particularly of the question of the nuclear powered airplane, ANP, nuclear powered aircraft. It was almost the beginning-not exactly … of the hawk-dove split, but the military in the nuclear industry were very determined to make an airplane that was nuclear powered, and every scientific study of the thing showed that it was a bad idea. And yet it couldn't be killed. You could never kill the thing because G.E. or somebody would always revive it. So for about ten years the nuclear powered aircraft was a project which most of us thought was stupid but we couldn't stop. Finally it was canceled, and it would have been stupid. The stupidity grew and grew. But that was the kind of an issue that was typical of ones we have now, very much like the B-1 bomber or the SST and so on. It was perhaps the first sort of example of that kind of thing.

Sopka:

It's interesting to know that because I was trying to get at when the relations began to cool, as it were.

Purcell:

Yes, that was a slight rift in the lute, let's say. The ANP it was called if you ever have to look it up: Aircraft Nuclear Propelled. This terrible object would have flown at subsonic speed and would have been a sitting duck and was not good for anything. The Killian Committee resulted really in the formation of the new President's Science Advisory Committee, and I became involved in that when it formed under Eisenhower. And just about that time we had Sputnik and the dawn of the space age and the pressing questions of policy as to how the United States was going to organize itself to develop space technology and satellites. I was involved in a number of other problems in PSAC, but perhaps the chief one I was involved in was the question of the formation of NASA[1] -- the question of whether the development of space technology should be given to the military or should be the province of a newly formed totally new agency imitating the history of the AEC, or whether, as actually turned out, one should expand the NACA[2] and give it the task of space. There were strenuous arguments on all sides of this question. The future of space science was dimly foreseen, but in retrospect after Sputnik, and after a lot of discussion, and of course thanks to the quite considerable progress that had already been made in rocket technology and the military, the main outlines of the next 20 years in space really became fairly clear.

Sopka:

Was Sputnik really the fuse that it's been considered to be in terms of igniting our space program?

Purcell:

Well, certainly it was very important. There were other things, though, that aren't quite so well known -- namely, the development of intercontinental rockets and so on. There's a recent paper by Herb York*and one of his students which addresses exactly this point: what were the various developments to which the present status of space and space technology can be traced, and you really ought to look at that to get it straight. You see, there was the decision to try to develop long-range rockets that followed a study by von Neumann and Wiesner -- I think it's sometimes referred to as the von Neumann Committee -- a classified study of that or the possibilities there. We were concerned at the time with the open aspects of space science and making sure that people understood the possibilities that could be opened up by satellites. We prepared within PSAC, a few of us, what we called a Space Primer. This was to be issued by the President for everybody to read, and it explained what satellites do and what we can expect from them and so on. Two or three of us worked on this and in particular Edwin Land and myself -- perhaps one or two others, but Land and I wrote most of it with the help of Frank Bello, who was then associate editor of FORTUNE magazine and has been for many years associate editor of SCIENTIFIC AMERICAN. [3] I think our little Space Primer really stands up very well.

Sopka:

Was that published as a government publication?

Purcell:

Yes, government publication, and I think I still have one. It's tucked away somewhere. We talked about eventually going to the moon. Our time table wasn't too far off, although it was a little more expensive than what we said. We talked about weather satellites and what that might do and a number of things like that, which have all come true. The people that needed to be educated were not merely the public at large but people in responsible positions in Washington.

Sopka:

Who was the President at that time?

Purcell:

Eisenhower. Herb York and I had a little talk that we prepared that we gave jointly, equipped with some charts for the easel and so on, and we went around Washington giving this little tutorial lecture on space. We gave it twice in the Cabinet Room, once to the President and the Cabinet and once to the President and the Security Council. Eisenhower is one of the people I've given the same lecture to twice. We went over and gave it to the State Department and went around various other places to tell these fellows about space. I think what we told them turned out to be really true.

Sopka:

How did they respond at the time? Were they, in other words, ready to accept this broader picture rather than just military capability?

Purcell:

Yes. They responded like good students. They were interested. Each was interested in his own way. I recall that the chairman of the Security Council at the time was a fellow named Bobby Cutler, who was a Boston lawyer. And he kept insisting that we give him a legal definition of outer space. It was clear that we were heading into a time when the notion of what a country had jurisdiction over would be very difficult to deal with. In fact, as we pointed out, if you imagine the country's boundaries going out from the center of the earth out through the country in a cone, you see -- if you go far enough out, the cone is moving with the speed of light. So you can't stay within the United States without moving faster than the speed of light! But in fact this foreshadowed a very important question that I was greatly concerned with later -- namely, the question of the freedom of space, the freedom of the skies, for satellite reconnaissance and indeed for airplane reconnaissance, which was to confront us in such a painful way in the U-2 development. And then later on to confront us, but really be resolved, by the course of events in satellite reconnaissance. So alongside of these activities, I was involved in many of the technical developments or at least keeping track of many of the technical developments in photo reconnaissance from aircraft and from satellites. The U-2 project was really an outgrowth of the studies we made in the Killian Committee. The eventual program in satellite reconnaissance, now a very active operation in both major powers, grew out of that. And the question of freedom of space really got resolved, more or less resolved, simply by going ahead and making the assumption that space was open to all. Really the only way one could have met Cutler's demand for a legal definition of outer space was to say that outer space is free, but then you have to say when is it outer.

Sopka:

Something like the 12-mile limit.

Purcell:

Yes. Well, it's easier because you can say that if the thing is in orbit, that's outer space. Well, this was just to explain some of my own involvements in Washington over the years beginning in 1950 to 1970, roughly speaking.

Sopka:

Did this require your spending considerable time away from Cambridge? Did you have to spend much time down in Washington?

Purcell:

I traveled to Washington a great deal during that time. It was all in cut-up pieces of two or three days at a time.

Sopka:

I see. You didn't have to pick up and go and settle some place for three or six months.

Purcell:

No, that only occurred in the case of these summer studies that I referred to.

Sopka:

You were a member of the President's Science Advisory Committee in two different intervals. During the second one, the '62 to '65 -that would have been under President Kennedy and then President Johnson…

Purcell:

Yes. Well, I went back on the committee when Jerry Wiesner went in as Kennedy's adviser, not immediately because Kennedy, after all, became President in '61. Then I can't remember when that period of membership in PSAC ended. Does it say in your list? What does it say there?

Sopka:

It says the first one was 1957 to '60, and the second…

Purcell:

Was ‘62 to ‘65, yes, and so two years under Johnson.

Sopka:

I was wondering whether there were any differences in the political and personal climate between those two periods.

Purcell:

Oh, yes.

Sopka:

In terms of whether you felt serving on such a committee was a suitable and effective role for you to be playing?

Purcell:

Oh, yes, I felt it was at that time. In fact, in ‘64 when Johnson was elected on his own, we were quite enthusiastic for his election. I remember being. Of course, he was running against Goldwater. There was already, of course, a polarization in the physics community dating from ‘54, from the Oppenheimer case and all that. And then with much more substance … Well, a polarization which also involved the question of arms limitations: the hawks vs. the doves as the way to characterize it. Let's say Teller, the Berkeley-Los Alamos, the whole Teller axis against the scientists that wanted to proceed toward arms control, which Teller was against basically. And that was really a very strong polarization, and we saw that all through the … You can see that very clearly in the latter part of the Eisenhower Administration in George Kistiakowsky's book.

Sopka:

His recent DIARY OF A SCIENCE ADVISOR?

Purcell:

Yes, that tells you a great deal. You see, I was on the committee under George during all those years, and that book is a very accurate reflection of what went on. It's just a diary so that it's not a continuous narrative, and lots of things are left out, but it gives a very clear picture of the struggle. The real struggle there was between the hard liners who didn't want any arms limitations at all and the whole test ban treaty, you see, with the idea of stopping nuclear testing: a very important period there. I was involved in that somewhat but not nearly as centrally as were the people who were more directly involved with atomic weapons, but I saw a little bit of it. And that was the polarization then which of course grew somewhat more broad and more plain when the Vietnam War finally came and really … I continued to be on a PSAC panel, as we called it, into the Nixon Administration. The panel that was concerned with reconnaissance, although I was not a member of PSAC. We would have a special panel on some subject and it would have scientists who were not members of PSAC but who were experts in that particular subject.

Sopka:

Did the final date of ‘65 have any particular significance for the ending of your formal serving on the PSAC Committee?

Purcell:

I think we had a term. I think by then my term simply came to an end in ‘65. I didn’t sever all my connections with PSAC until the middle of the Vietnam War when I finally wrote a letter just resigning flatly from everything. I'm ashamed to say how late it was. I think it wasn't until maybe the bombing of Laos, and then I just withdrew from all government connections. Anything connected with the White House I resigned from.

Sopka:

You were presumably specifically disenchanted with what was going on at that time. Would that extend in general to your feeling about scientists and yourself in particular working with the government operations?

Purcell:

No, not if the government's doing something sensible, but here the government was engaged in a crime, which we were all a little slow in recognizing. Or at least I was slow in recognizing how bad it was.

Sopka:

At the present time are you involved in any such governmental consulting?

Purcell:

No, only by way of the National Academy, to the extent that the Academy performs studies. I am on a committee or have been on a committee that reviews Academy reports on controversial issues, and I've just finished reviewing one. But I'm responsible there to the Academy …

Sopka:

And not to any particular administration?

Purcell:

… and not to any particular administration. No, I have no connections at all with the present administration nor the previous one.

Sopka:

Could we turn for a moment to your work within the American Physical Society? I notice that you were president during one period, and of course you must have been involved in this matter of the split within the physics community that you mentioned before, about the doves and the hawks. Do you feel that the political and military developments have had a great impact on life within the physics community in terms of cordiality between its members and the difficulties of a president of a physical society at that time when …

Purcell:

Well, the split between the nuclear weapons doves and hawks the hawks vs. the arms limitation people -- was not really echoed as such within the Physical Society. The number of physicists who were actively supporting Teller's views, just to use that as a way of defining it, was really a very small fraction. These were the weapons physicists by and large and not all of them even. The conflict in the Society during my term of vice-president elect, etc., etc. -- two or three years there when I was actively involved -- the conflict in the Society was basically a division between those who thought the Society should be changing in the direction of taking an active role in public affairs and taking care of its members and taking positions on public questions and those who thought it should stay as strictly a society devoted to papers in physics, physics research as such. I suppose if one could characterize it by extremes, the most extreme on each side, you might pick Karl Darrow and Charlie Schwartz as the opposite ends of the spectrum.

Sopka:

Would you care to comment on your own view?

Purcell:

Also at that time the thing was exacerbated by the general ferment in the universities and so on and the upheaval of ‘68, ‘69 and ‘70 in the universities, which set the pattern for some of the agitation within the Society. I think in those years the Society managed pretty well not merely to balance off so that one ended up with a Society as a whole more or less in between, but actually to start some constructive evolution of the Society in some wholesome new directions that it seemed to me at least when I was an officer that we couldn't turn our backs on some of the changes that were desired. And I must say the members of the Society responded extremely well. I found the two years I was closely involved rather agonizing because it was not something I like to do, or do well, but offsetting that was the really quick and generous response of anybody in the Society that I asked to help. I mean, it was really amazing how people responded. So that we organized the Forum, and just by a lot of telephone calls we recruited people to take an interest in that, and these were people whose views ranged not quite as wide as the spectrum between Charlie Schwartz and Karl Darrow but pretty widely, and they worked together. The present complexion of the Society, I think, is simply the further evolution of that.

Sopka:

You feel then that it weathered the storms of the late ‘60s and early ‘70s. Do you feel it's now moving in directions that you would approve of?

Purcell:

I think it's moving in directions that it really had to turn to. It wasn't really a question of weathering the storm and coming out intact in your original condition, although some of the people would have liked to have seen that happen. But it was a question of adaptation to the new world, changing world, and development of institutional means to deal with some of the problems that physicists could see they had, including a shrinking number of jobs. So I don't see how the Society could have maintained its pristine role as a publisher of abstracts and papers. One would have had to invent some other society in parallel if it had.

Sopka:

Are you in favor of the Physics Society taking stands on public issues, not necessarily right at the moment but as a policy if some issue arises in the next six months or two years? Are you in favor of the Society going on record with a consensus, or is the idea of a consensus within the physics community impossible in view of the spectrum you mentioned?

Purcell:

I would not argue for any general inflexible principle. I think you have to look at each case. You have to ask first: "Is there a genuine consensus in the Society and not just a few people who want to make a lot of noise?" Had I said anything before about what my present interests in physics are, what I'm doing myself?

Sopka:

Not really. I think it would be valuable to have you discuss that.

Purcell:

Well, for many years now my own research interests have centered in some problems in astrophysics and then more recently in biophysics. These are very specific problems which I became intrigued with because of some of the elementary physics involved, and for want of anything else to do creatively, I've been working on problems connected with the interstellar medium particularly and interstellar dust. This has been going on really now for many, many years. I've published a number of papers, but I can’t really say that the subject has been advanced very much by them.

Sopka:

Is this an area that's new to the astrophysical community as a whole and that you are becoming involved in at the same time that they are, or is it an established field where it's a new interest for you?

Purcell:

Well, it was an established field actually, and the problem that caught my attention is a problem that's 25 years old involving the alignment of the interstellar dust presumably by the interstellar magnetic field resulting in the polarization of starlight, which was observed as long ago as 1950. I just found that a number of interesting physics problems are presented by this. There's still no quite satisfactory theory of the interstellar dust alignment, and in a way this was also an outgrowth of my work on the 21 centimeter line and the involvement through that with problems of the interstellar medium.

Sopka:

What techniques do you use for studying the interstellar medium? Is that radio astronomy?

Purcell:

No, not directly -- nearly all optical astronomy. Well, I'm sorry: radio astronomy as far as interstellar gases are concerned. The interstellar dust solid particles are completely transparent. As far as radio astronomy is concerned they have no effect whatever directly. But the interstellar dust is emerging now as a very important and critical component of the interstellar medium. For one thing, it is the catalyst for interstellar chemistry, at least for basic reaction of hydrogen molecule formation. And the original condensation of the medium for protostars and stars and planets, the dust may well be -- most likely is -- involved in a very important way. So I've been able to make some contributions to the subject, I think, but it's still a rather messy subject and one that I find as a physicist not terribly satisfying in that the observational data are sufficiently meager and limited in their kind that one has really no way of getting rid of theories. There's a lot of speculation, and the speculation keeps churning around again and again, and you can't really weed out the nonsense.

Sopka:

Is this an area where the data can be expanded through the use of telescopes mounted on satellites?

Purcell:

Oh, very much so. In fact, there's been an enormous progress. That's one big change since I began dipping into the subject. The big important change has come from the use of these satellite telescopes -- OAO II and OAO III, Copernicus, have provided material that is just completely new. So there are now things that call out for explanations, and, in fact, I think already one could say that Copernicus has provided the material to demolish a number of theories, and things are looking up. And there's no question but what satellite telescopes are going to eventually be the means by which this subject is finally settled. There's no doubt about that.

Sopka:

I guess then from what you said just now and what you said earlier that your own assessment of the total space program is that this is a very worthwhile thing for the scientific world from a long-range point of view.

Purcell:

Oh, yes. In fact, the large space telescope, which unfortunately is now in financial support trouble and is being shot at from various sides, is certainly one of the most important projects we could possibly be engaged in at this time in science. There's just no question that it will broaden the astronomical horizons a major amount. I enjoy working on the interstellar medium simply because it gives me a kind of license to follow astronomy and at least listen in on the really sensational things that are going on in astronomy now.

Sopka:

The work that you have done -- has it been on your own or in collaboration with local astronomers or astrophysicists?

Purcell:

Well, it's been on my own to a considerable extent, but I have enjoyed lots of discussions. In particular, I suppose my major paper on the grain alignment was one done in collaboration with Professor Spitzer at Princeton, who is one of the leading astrophysicists of the interstellar medium and from whom I've learned a great deal.

Sopka:

Did you and he get together through a meeting of common interest or was there any other reason why you happened to collaborate with him?

Purcell:

Well, he had been writing related papers on this, and I had on my own adopted another approach, and we decided to get together and write a paper in which we brought the two different approaches together, and this was a very educational experience for me because Lyman Spitzer knows so much astronomy and I know so little. But I enjoyed it very much and I think it was a fairly definitive paper as of that stage of the development.

Sopka:

Are you associated with any of the activities here in Cambridge of the Harvard College Observatory and the Smithsonian Astrophysical Observatory?

Purcell:

Well, I've been involved for quite a long time, not in an active observing way but in a more administrative way, with what we call NEROC, the Northeast Radio Observatory Corporation. This runs the Haystack Radiotelescope, and I've been involved with all the people and one of the officers of the NEROC Corporation. And although I don't do any work at Haystack, I've followed what they do and I've been involved in all of the discussions and trying to get budgets and grants and so on. In running Haystack, for several years now we've been running it on an NSF grant as a radio observatory. It's a very remarkable instrument.

Sopka:

Where is Haystack located?

Purcell:

It's near Groton where MIT had the Westford Laboratory out there. I forget the name of the hill, but there are several radar antennas out there, and the Haystack antenna was originally a Lincoln Laboratory installation but it's now run as a purely scientific installation. NEROC is a corporation involving a lot of universities and colleges in this vicinity. Harvard and MIT are sort of the main, most active ones, but Yale and Brandeis and B.U. and a dozen or so are formally involved, and it's a laboratory to which any radio astronomer can apply for a time there for a project, and it's very busy and does very good work. It's a very active member of some of the long baseline interferometery networks, and works with the Goldstone antenna in California and with the 140-footer in Green Bank and with antennas in Russia and other places. So I have been involved in that work and also in the attempts to get a big antenna. This thing up here [picture on wall] was a proposal we made several years ago. We spent about $1 million of NSF money designing this, and then it was finally not approved for construction but it would have been enormous -- a 400-foot antenna. I was involved in the planning on that.

Sopka:

Does it appear that money will still continue to be available for the continuation and extension of this kind of activity from NSF and other sources?

Purcell:

Well, the big national project now in radio astronomy which is going on is the Very Large Array, which is being completed in New Mexico under the aegis of the National Radio Astronomy Observatory, and that's a couple of hundred million dollar project. And essentially we were competing with that. The decision was made not to fund a very large dish of this type but to fund a very large array at that time, which I think was the correct decision. And that's going together very well. It's proceeding. They've already got ten or twelve of the antennas finished. But radio astronomy is an extremely fruitful and lively subject now and could easily absorb and put to good use more money than the NSF has to spend on it. Money is very tight. But there's no shortage of new discoveries of both sort of local significance and cosmological significance. Interstellar chemistry is a big field now. Bill Klemperer over here is in the middle of that figuring out all of the reactions that must be going on to make all these molecules.

Sopka:

That is quite exciting, to consider that you have a kind of laboratory situation way out there under conditions that you couldn't duplicate in the laboratory, and yet you can get the information about what's going on.

Purcell:

Right.

Sopka:

That would presumably indicate that there would be an expected flow of bright young minds into the field where there is such an active, exciting topic.

Purcell:

Yes, yes, although I'm not sure that the number of jobs … Well, radio astronomy doesn't take many observers to tie up a big telescope. Put it that way. The long baseline interferometry has an interesting future. There's a project now to measure continental drift.

Sopka:

Oh, I didn't know about that.

Purcell:

Yes, it's so accurate now that one is on the verge of being able to measure the distance between two continents to half an inch; and if so, then you can see them move from year to year as they drift.

Sopka:

That's really exciting. Then your other interest now in biophysics is bringing you down out of space into…

Purcell:

Yes. Well, that grew out of my friendship and association with Howard Berg, who was here at Harvard as a Junior Fellow and a graduate student in physics and is now a biologist. In fact, he's chairman of the department of biology at the University of Colorado. I don't know that this subject will continue to offer opportunities for me, but I think at the moment we seem to have found a little soft spot where the applications of rather elementary physics can clear up some of the questions that are relevant to the biological system, questions having to do with the physics of the bacterial environment. And I find it very interesting because I've always been puzzled by the fact that so small an organism as a bacterial cell-only a micron or two in size -- can carry on such a complicated life. And I think I'm beginning to see how at least the physics of that can be understood. Not to say that the important problems aren't biochemical -- they of course are. But I think the physicist going into a bacteriological problem has simply got to admit that what's going on is biology and chemistry and that just importing a little physics is not going to answer the important questions. But there are some questions that need to be taken care of that way.

Sopka:

Did you need to teach yourself some biology …?

Purcell:

Not very much because I'm looking at problems … It's rather like the astronomy. I didn't really… how shall I say? I don't need to teach myself a lot of general astronomy, because the problem is fairly well defined. I, of course, have to rely on an astronomer in that case or a biologist in this case to define the problem for me and to say when my calculations are relevant or not relevant. I, of course, learned a little doing this, but very, very little.

Sopka:

Is this a quantum mechanical realm in biology when you're working with this?

Purcell:

Well, the quantum mechanics of course comes into the elementary chemical reactions, but the scale of phenomena that I'm concerned with here are not that. They're a somewhat larger scale, and the physics is classical physics of a very old-fashioned kind as far as the fluid is concerned, and then the part that's been interesting to me is the part that involves fluctuations and Brownian motion and things like that. In other words, the bacterial cell is small enough so that Brownian motion -- its own Brownian motion -- is a non-negligible movement, and it's dealing with a few enough molecules so that fluctuations in the number of the molecules is not completely negligible. But still this little machine has got all kinds of wonderfully working parts to it. An easily stated important problem, of course, in that whole area is in the physics of the cell membrane. What is the cell membrane and what is the actual mechanism that controls its permeability to different things? Of course, there's an army of biologists working on that as the central problem in cell physiology, the properties of the membrane. And I haven't yet had any ideas for contributing to that. That would be much more important than what I've been doing.

Sopka:

Your recent comments then certainly highlight the aspect of the centrality of physics to a number of these other disciplines.

Purcell:

For me this is just kind of intellectual sport. I have no illusions that my personal contribution here is going to change the course of science at all, but it gives me a chance to keep my mind active, to be learning things, and to follow fields where there are other extremely important developments going on and have some glimmer of what they mean. Howard Berg and others now really have their hooks on some of the behavioral aspects of bacteria, E. coli in particular; and I think a great deal is going to be learned about that. It's fascinating stuff. And from my sort of seat on the sidelines I can follow that, earning my way in by a little bit of elementary physics.

Sopka:

You've been able to witness during your professional career a different area of excitement of physics essentially in each of the decades.

Purcell:

Yes. Well, of course, the central excitement in physics is one I wish I could follow -- particles. We're in tremendous times in that. If I had some way of understanding what is going on there well enough to sort of take part in it, I would much rather do that than all this other stuff, because clearly that is fundamental. There's no question about it. And the cosmology, too, is fascinating. We're at this point in the study of the universe. We've discovered the relic of the big bang.

Sopka:

Well, I gather then that although you're personally reaching the Harvard initial state of retirement, that you have lots of things which will keep you busy for a number of years.

Purcell:

I hope so, but, you know, I can't be sure. It's just a question of what will turn up next.

Sopka:

And also that your interest in teaching will continue.

Purcell:

Yes, but I think one has to be very careful to recognize the time when one should stop teaching.

Sopka:

Speaking of teaching, we missed one topic that we were going to have you comment upon, and it goes back in time to the development of PSSC. Would you want to make a few comments before we reach the end of the tape on that?

Purcell:

Yes. PSSC was one of the many times in my life when I have been enlisted under the banner of Jerrold Zacharias. In most of those times I was glad afterwards that I had, and this was certainly the case in PSSC. We wanted to do something about the teaching of physics in high schools, and whether we did any good in the end or how much good we did is still a matter for debate, but we certainly loosened the situation up. I had a lot of fun. We made movies, high school movies, and I made two of those and learned a lot about that. I'm certainly glad I took part in that. In a way it was also a forerunner of the Berkeley physics course, in the conception of which Zacharias also took part, although the real leader in that was Charles Kittel. And ten or twelve years ago I put a lot of effort into my contribution to the Berkeley physics course in the shape of Berkeley Volume II, and I'm very glad I did that because I just have taken a lot of satisfaction in having written what I think is a good book. And the freedom to do it and the inspiration to do it and the support while doing it came from the Berkeley group. Really it was one of the memorable experiences of my life, that Berkeley chapter. The book ought to be revised, but I somehow haven't gotten very far toward revision of that, and I don't know whether that will ever take place. As I look at what I really ought to be doing as opposed to what I enjoy doing or end up doing, it's probably true that I ought to be revising Berkeley Volume II.

Sopka:

That's the section on electricity and magnetism?

Purcell:

Yes, that's on electricity and magnetism. Of course, I've never received any royalties for that book. None of the people did. The NSF supported the project, and all the royalties go to the U.S. government, so although the book has sold very well and is very widely used -- not only here but also in Europe -- it has been translated into seven or eight languages -- I never made a nickel out of it. We were paid a lump sum for writing it, a rather small sum.

Sopka:

Well, I hope that you decide to revise it.

Purcell:

Yes, I think it ought to be revised, but whether I can actually organize myself to do that and complete that job is… in a nutshell, that's what I ought to be doing. There's no question about it. I might even put it into MKS units. Perish the thought.

Sopka:

What units is it written in now?

Purcell:

Good old Gaussian CGS, part of the counter-revolution. But in Europe now it's not even legal to use a book that is not in MKS.

Sopka:

Oh, I didn't realize that.

Purcell:

Oh, yes. I don't think you could adopt such a book if you were a teacher in a German or European university…

Sopka:

Well, I thank you very much. I think we've covered…

Purcell:

We've certainly covered more than anybody wants to read.

Sopka:

Oh, no, I don't think you should say that at all. I'm very pleased with the wide range of topics we've covered. I can't think of anything further to ask you about. We'll be in touch.

Purcell:

All right. Okay.

[1]National Aeronautics and Space Administration

[2]National Advisory Committee for Aeronautics

[3]The Space Primer is reprinted in full as an appendix for James R. Killian's book SPUTNIK, SCIENTISTS AND EISENHOWER, Cambridge, Mass.: MIT Press 1977

Session I | Session II