Interview with Geoffrey R. Burbidge, 22 May 1979
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The interview listed below was either transcribed as part of Sullivan's research for his book, Cosmic Noise: A History of Early Radio Astronomy (Cambridge University Press, 2009) or was transcribed in the NRAO Archives by Sierra Smith in 2012-2013. The transcription may have been read and edited for clarity by Sullivan, and may have also been read and edited by the interviewee. Any notes added in the reading/editing process by Sullivan, the interviewee, or others who read the transcript have been included in brackets. If the interview was transcribed for Sullivan, the original typescript of the interview is available in the NRAO Archives. Sullivan's notes about each interview are available on the individual interviewee's Web page. During processing, full names of institutions and people were added in brackets and if especially long the interview was split into parts reflecting the sides of the original audio cassette tapes. We are grateful for the 2011 Herbert C. Pollock Award from Dudley Observatory which funded digitization of the original cassette tapes, and for a 2012 grant from American Institute of Physics, Center for the History of Physics, which funded the work of posting these interviews to the Web.
Please bear in mind that: 1) This material is a transcript of the spoken word rather than a literary product; 2) An interview must be read with the awareness that different people's memories about an event will often differ, and that memories can change with time for many reasons including subsequent experiences, interactions with others, and one's feelings about an event.
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Sullivan
This is talking with Geoffrey Burbidge on 22 May 1979 at Kitt Park in Tuscon and could you start off by simply telling me what your background was as far as education was, were you a physics major?
Burbidge
Yes, I took a bachelor's degree in England, of course, in physics. And then I became a graduate student in theoretical physics in London with some periods at Cambridge. And I got into astronomy, as everyone knows by marrying an astronomer.
Sullivan
Right. And this was in the early ‘50s, when you first came in contact with astronomy?
Burbidge
Yes, around, well, yes, that’s right. I got my Ph.D. in 1951. By then I think I'd already been in astronomy for a year or two.
Sullivan
And what kind of astronomy were you interested in at that time?
Burbidge
I used to go to the RAS [Royal Astronomical Society], but I was really interested...
[Tape issues]
Sullivan
What kind of astronomy appealed to you the most at that time?
Burbidge
I was interested in many things, but the things we started working on were stellar atmospheres, emission line stars, things that my wife had been working on, and so the first papers that I published in astronomy, were in that area. Then we came to the States first in 1951 and I went to Harvard for a year, and from Harvard I went to, Margaret [Burbidge] was in Chicago and we went to Yerkes for a second year, and in ‘53 we came back. And it was in the second year in Chicago that we first got interested in nucleosynthesis in a very peripheral way, and then we came back and I was at the Cavendish in Cambridge, nominally working with [Martin] Ryle. In fact, I was working with Ryle's group two years officially, and it was at that time that we started the work on nucleosynthesis with Willy [William Alfred] Fowler, who was a Fulbright Professor in Cambridge at the time.
Sullivan
Which two years was this?
Burbidge
That was ‘53-55. And what happened was that we had done our first work on abundances in the stars. We were reducing the data that we had got in Texas from the MacDonald Observatory in 1952-53. When we came back to Cambridge, we were reducing that as well as working, well I was working with the radio astronomers with the radio sources. It was in that time that I first became involved in understanding radio sources.
Sullivan
Did they take you on as sort of resident theorist?
Burbidge
I suppose that's what you'd call me nowadays, but they were very peculiar as they always have been, and so I soon found that I was only told about certain things that were going on because in those days they were doing the early log n, log s work. I was not told anything about it.
Sullivan
Even though you were...
Burbidge
I got extremely angry when I was told, "Why don't you come to Oxford and listen to Martin Ryle give the Halley Lecture?" which he gave in 1955. And he's going to tell us something fundamental about cosmology. What he was going to do was demolish the steady state, he felt. And I had never been told anything about what was going on. It had all been hidden from me, and I was so angry that I refused to go to Oxford.
Sullivan
That's amazing - you were there this whole time and...
Burbidge
Well, they were doing the 3C [Sullivan: 2C], and they were making all the corrections and revisions.
Sullivan
The 2C.
Burbidge
Well, was it the 2C? I don't remember. The 1955 Ryle made this great announcement and it was based on the 2C was it? I don't remember whether it was the 2C or 3C?
Sullivan
Sure, this is the 2,000 sources that turned out to be mostly wrong.
Burbidge
But the claim that Ryle made at that time, he went on maintaining and still maintains, and they believed it, though I doubt if I did.
Sullivan
So you had no input whatsoever into this interpretation?
Burbidge
No, for the first time I saw the kind of antagonisms that were present. We used to go in to tea in the Cavendish in the Austin wing and if Fred Hoyle came into tea, then Ryle would send someone from his group to go back and put everything away and see that the desks were clear and lock the cupboards, although Fred never went into the old wing of the Cavendish, but that was the behavior pattern.
Sullivan
Well, since we're on to cosmology, let's follow this drift through. When you saw the evidence that came out from this survey, was it convincing to you at all? As far as its relevance...
Burbidge
I wasn't really very interested; I was kind of a spectator at this debate and in those days I wasn't particularly interested. I was interested, as I always have been, much more in the physics of astronomical phenomena so I don't know that I reacted very strongly in that period, except that I became very aware of the personalities and conflicts involved with those personalities.
Sullivan
Well, certainly I can see by your papers that you were writing mainly about radio sources and background radiation and so forth. Of course later on, in the ‘60s, you certainly got involved very much in the whole cosmology thing.
Burbidge
I don't think I did. I've never written a paper on cosmology, except that I once wrote a comment article pointing out that there were various very dubious arguments in cosmology, but while I worked with Fred Hoyle on many things, we've never written on cosmology.
Sullivan
I see. Well, you had that thing in Nature also...
Burbidge
Was there really a big bang? Well, what I did there was, well that was in ‘70 or something like that, and what I really did there was review in a dispassionate way the evidence for cosmological arguments. I got into a lot of trouble because I was dispassionate, I think. You can't please anybody that way.
Sullivan
So the whole log n-log s controversy and so forth up through the early ‘60s, you were really a spectator?
Burbidge
Yes, what happened was that I got more and more involved with Fred and was working extensively with Fred in other fields - nuclear synthesis and cosmic rays and radio sources and quasi-stellars. And Fred was embroiled in this dispute with Ryle particularly the Cambridge group which was going on in that same period though by the middle or late 1960s, it had more or less died down.
Sullivan
Right. What do you see, as an observer, as the major sources of conflict? Do you think it really was a passionate sort of thing...
Burbidge
Oh yes, it was a passionate, unscientific thing. At least on the side of the radio astronomers, I think. There's no question that I have a very strong feeling that much of what people argue in these areas is based more on their beliefs than on facts. There was this extremely strong, well this great distaste for steady state cosmology, and whenever rod came to hand, people would beat it with - and they beat it with [?] which later disappeared. And then Ryle came and provided it with what he felt was the crowning blow, the log N-log S and that went on and was used as a weapon against it until the microwave background was discovered and then without proving that it was black body radiation, everybody used that - and they're using it now. And that sounds somewhat more secure, but in view of the history of cosmology you don't know.
Sullivan
Well, but is it not fair to say that it goes on the steady state side, and one of the great appeals of it is its beauty in other words, non-scientific.
Burbidge
Oh, yes. But the proponents of the steady state always argued that it was a testable theory. What they were not really aware of themselves, I think, was the extent of which observers would take up positions. And would, observers in astronomy are not at all dispassionate. So I think the steady state people underestimated, you know, their Fred would find ways of trying to explain away the counts, and he would never doubt that they were really the counts, and yet there is very great doubt that in many cases the results were at all very good. I think the most recent discussions of this, for example, were at the Cambridge meeting in 1976, show this - I think that [Kenneth I.] Kellermann makes a very good point there that it's not the observations that have changed, but the arguments to maintain the point of view that people have had for a long time.
Sullivan
Let's go back to the sort of things that you were working on that were related to radio astronomy. The first articles that I have from radio astronomy bibliographies are in 1956 when you began talking about the radio halo and so forth.
Burbidge
That's right.
Sullivan
What was your view at that time, first of all, about the existence of the halo even that was being argued...
Burbidge
Well, I was in Cambridge, and I believed John Baldwin's results. And in fact, that whole work stems from the observations we made there. And John felt he had discovered the halo, the real halo, and one of the first things I published from there was an attempt to show that the halo had, you could put a reasonable set of parameters and explain the halo. I had a cold, turbulent halo which would support, would contain the particles and support the magnetic field, and Lyman Spitzer at the same time claimed independently he had a hot halo.
Sullivan
Which was not taking account of the radio continuum evidence.
Burbidge
No, but I mean, Lyman had a perfectly good argument, I mean, you've got to support a halo and to do that, you either go, you've got to use motion, and so you either use kinetic motion which are associated with heat, which means you've got to have a million degrees or you have turbulence comparable in magnitude to the rotational velocity.
Sullivan
But now, it seems that you were a very early believer in the synchrotron explanation.
Burbidge
That's right. That's right.
Sullivan
For at least in the west.
Burbidge
That's absolutely right. In fact, we didn't really know what was going on in the Soviet Union. Undoubtedly the Russians were first to predict that you would see the degree of polarization that you did, believing that this was really the mechanism for radiation. And the first that I knew of the Russians working in this field was when I was in the Cavendish we didn't know any, the people in the Cavendish didn't know anything of the Russian papers, but I remember [Jan Hendrik] Oort sent Ryle translations of a couple of the early papers, and we were aware by then that they were doing this kind of thing. In the west, there was this push towards plasma radiation, plasma oscillations which Ryle himself...
Sullivan
[Enrico] Fermi...
Burbidge
Well, no, it was just essentially oscillations of plasma, the waves in a plasma.
Sullivan
Okay.
Burbidge
And Ryle was the great believer in this, and I used to have tremendous arguments with Ryle because it didn't make any sense to me- the [?] frequency was wrong, the whole thing didn't make sense. I went through all the mechanisms, and of course, [Hannes] Alfvén and [N.] Herlofson had made the argument that while synchrotron radiation associated with stars. [?] in those days was talking radio stars so that was how it was done, but I don't remember the details. But broadening it, but believing that that had to be the physical mechanism because it was the only one that made sense and realizing that it would lead to a large flux of relativistic particles, I certainly pushed that, because I was convinced that it was right. But there was a lot of disagreement about this and I remember a meeting in London in 19...
Sullivan
‘53?
Burbidge
Well, the early 1950's when this was still being very strongly decried, but...
Sullivan
The one at University College?
Burbidge
Yes. It came to a head much later, but I would say that the Russians undoubtedly made the major predictions. [Iosef Samuelovich] Shklovskii gets a lot of the credit, it's not clear, I mean talk a lot to him and [Vitaly L.] Ginzburg just where the credit lies.
Sullivan
I understand there’s no love lost between those two.
Burbidge
Well, I mean the other man, the man who's now dead, a name I've forgotten, but the original paper was by three of them.
Sullivan
Well, there was [Mansef?] and Ginzburg.
Burbidge
No, it wasn't [?] it was another name- a man who worked extensively on stellar matter and only died a few years ago.
Sullivan
Oh, [Solomon] Pikel’ner.
Burbidge
Ginsburg tells me that Pikel’ner was really the man who suggested this, and Shklovskii engaged in more publicity than most, there's no love lost in these areas in between the number of people in that way, and I tend to believe that may be true. Then of course, later, it was Shklovskii who certainly predicted that the same effect was occurring in the extragalactic field and used as his test object the jet in M87 and after some considerable amount of time, [Walter] Baade was prepared to go and look. One of the arguments the Russians had and they told me about later was that they were extremely upset that the western observers, [Rudolph] Minkowski, and Baade, would simply not look and try and test these hypothesis. Because these were to these people, to the observers in the west, they were unbelievable - when I first went to Mt. Wilson and mentioned synchrotron radiation, they thought I was a man from Mars. They didn't know what was going on.
Sullivan
This was what year, now?
Burbidge
I came in ‘55. In ‘55 Willy Fowler, we were of course heavily involved in nucleosynthesis, which we thought we were doing most of the time. I used to do this on the side, and Willy didn't really understand what this was about, I think. Willy persuaded us to come back to Pasadena with him and I was given a Carnegie fellowship, I applied for a Carnegie fellowship, and Margaret was working in Kellogg. So we went to Pasadena in the autumn of 1955 and then we were at Caltech so all that work was being done then from then on at Caltech.
Sullivan
Let me ask though, it was plates taken by Baade that showed the polarization in the Crab, and that was before 1955, he was willing to do that at that stage, and of course, they were also very...
Burbidge
No, I don't think- Baade's paper was in ‘55 because I remember using the paper before it was published, when I wrote a paper which was published in ‘56. So I think you'll find that the actual polarization data were not published in that time. You're thinking of the polarization of the Crab.
Sullivan
Yes, that's what I said.
Burbidge
I'm talking about M87.
Sullivan
Right, but I wanted to ask you- you said that the western observers were...
Burbidge
Oh that was earlier and the original observations were made by the Russians and because they were made by the Russians, people in the west didn't want to believe them. Baade was persuaded to repeat them and they were actually published in...
Sullivan
In [?].
Burbidge
No, they were not published [?] they were published in a BAN issue associated with the work of Oort and [Theo] Walraven, I think. I think Welch's [?].
Sullivan
Oh, his was later.
Burbidge
Welch's was a thesis on the Crab and then came later in the 1950s altogether.
Sullivan
Yes, his was sort of a full scale analysis of it.
Burbidge
That's right.
Sullivan
So you're saying that it was only because the Russian sort of uncertain detection, that Baade was...
Burbidge
It was felt that it had better be done properly in the west.
Sullivan
Okay. So is it correct to say, then, that as soon as you saw these early Soviet papers in ‘54 or ‘55, that this seemed to you like it had to be the mechanism for what was going on in the galactic background?
Burbidge
Well, it's a little different from that. I had quite independently decided that it was the only physical mechanism that made any sense. You could sit and look at the western literature, which was basically associated with Alfvén and Herlofson, if you like, and conclude that no other physical mechanism could do this. The Russians had gone further - not only had they asserted that it was the mechanism, they had predicted first for the Crab for the galactic sources, supernova remnants, and then later for M87, that this was the way to test the hypothesis, and then make the jump from the optical radiation being polarized to the radio frequency radiation. So it was really, for me, that sequence of events. But I had had no doubt in my mind, I was just very happy that other people had even worked quite independently and the fact that they had done this earlier, at this point, was not something that worried me tremendously, because I was attempting to explain what to me was fairly obvious, and what to so many people was not obvious.
Sullivan
What importance would you attach to the tie-in between the cosmic ray spectrum of energies and the radio spectrum that the Russians worked on quite a bit also?
Burbidge
Well, I think that was important but to me it wasn't as important. I was interested in the discrete object, and I was not prepared and am not still prepared to kind of take the cosmic argument as strongly in the direction that Ginzburg took his. In fact, as you know, my own view has been for some time that you could do this on the [?] scale and it was this idea applied in the same way to extragalactic sources, that led me originally with Fred, but later with Ken [?] and others that you could make a good case for extragalactic cosmic rays in exactly the same way as Ginzburg and [?] has made one for galactic cosmic rays. The tie-in is, of course, the same physical tie-in all the time.
Sullivan
Okay, well, let's go back to the mid ‘50s again, and as you say, most of your work was on explaining the emission from other galaxies.
Burbidge
Most of my work was on nucleosynthesis, as a matter of fact.
Sullivan
Yes, but relevant to radio astronomy. I have real blinders on.
Burbidge
I understand that.
Sullivan
However, you did talk about radio emission from normal galaxies of which a few had been detected by the mid ‘50s.
Burbidge
That's right.
Sullivan
The Andromeda nebula.
Burbidge
[?] and I wrote a paper about that.
Sullivan
And it was just simply an extension of what we see in the Milky Way- no particular problems with that. But now, of course the real enigmas were in the radio galaxies, in which there was very little detail information except an integrated spectrum and a lot of power. And so, what was your reasoning as to what must be going on in these things?
Burbidge
Same physical mechanism. And I mean, the key to me was M87 and in 1956, I made a full analysis of the M87 jet, knowing that Baade had confirmed Shklovskii's prediction that it would be synchrotron radiation. Worked out the energetics of the jet, and that was the first time that very large numbers ever appeared in terms of the line of energy that had to present in the magnetic field and in the particles, and then I worked out the minimum energy condition. All those things that people still use stem from that paper and then successive papers in which I discuss the radio galaxies in a much more general way in various places. And then by 1958 there was the Paris Symposium on Radio Astronomy and at that I was asked to give one of the invited papers, I think again, because Shklovskii was not able to come and at that I made a very deliberate attempt at giving a survey at that conference to hammer home the point that these particle problems was solved, that the mechanism was understood. I gave some of the first energetic calculations for galaxies in that paper, and in that era ’57-'58-'59-'60 I started getting very large numbers. And it was just out of the era of understanding the energies, the problem that we still have, but the 1060 ergs in minimum total energy for powerful sources like Cygnus A stems from that period and still as far as I'm concerned, a fundamental problem.
Sullivan
Right now, in fact, on my way to the office here, I stopped by the library to try to get the Paris Symposium- it was missing unfortunately, because I wanted to look at that paper, but...
Burbidge
It was published in ‘59.
Sullivan
Right. Can you remember whether the acceptance, what the degree of acceptance was of this view point. Was it by that time...
Burbidge
I think it was widely accepted. At that point I found that the arguments I'd been having with Ryle I simply didn't have with very many other leading radio astronomers, and the other people were prepared to accept it. I don't think that anybody began to think very hard about the problem for a little while and then some people really began to worry about the very large energy figures. But at that point one kept on hammering, I remember one had to say in all the colloquia, well once you believe in the mechanism, you really have no way of reducing the energies. In fact, I said, and have said continuously and I remember a long debate in the Salt Lake Conference some years later, perhaps 1964, when we had the Salt Lake Conference and that was a very interesting, one of the first ones, the second in astrophysics, in modern times - there was no way to reduce the energies except by bringing the objects closer. There was absolutely no way. Once you had the scale of the system and the measured flux and of course you had the scale for the distance, and the emitted flux for the distance, you had no way- no place to go.
Sullivan
Now was the paper on M87 the one in ApJ [Astronphysical Journal] in 1956- that was the paper that you were referring to here?
Burbidge
That's right.
Sullivan
This Paris Symposium meeting - I'd be interested in your reactions to it in a more general sense, it seems to me it was a rather important meeting in the history of radio astronomy.
Burbidge
It was.
Sullivan
It was sort of the last time that everybody...
Burbidge
I don't remember much about it, it was 21 years ago. I don't remember a lot about it. I remember, I mean I've been to so many international meetings since then, but it certainly was and the field was much smaller and the people were much less. Some of the arguments that went on about log n, log s are still the arguments that- many of the figures remain the same, and I think that the conference that was held at Cambridge three years ago was much more dated. In fact, it was probably the wrong time to hold a conference. I recently said when I reviewed the conference proceedings for Sky & Telescope.
Sullivan
Maybe the wrong place, also?
Burbidge
No, it was the right place; it was the wrong time. I mean, they are the people who have been pushing their argument harder than anybody else for a very long time. There was a time when it was hot and everybody believed them. I think at this point, it's neither hot, nor do a do an awful lot of prominent radio astronomers really believe. I think if you ask Mills, who never really believed it was as simple as that, and Mills is a contemporary of Ryle's, and Mill's had handled this discovery he would have handled it a different way - I mean log n, log s. I think that if you talked to [Bernard Y.] Mills and [John G.] Bolton and Kellermann and so on you don't get the impression that log n, log s is telling us very much.v
Sullivan
Okay. Going back and looking at some of these papers, was it you talked about anti-matter in various papers at this time. Was this, once again, influence by Hoyle?
Burbidge
No, it was my idea, in fact it was, I originally suggested, believe l said something about it in the paper on the jet in M87. I didn't really see how far it could be taken. Fred and I got interested in it and we wrote a paper in 1957, it was published in [?] in 1958.
Sullivan
That's right.
Burbidge
And there we discussed anti-matter in a more general way. The attraction of anti-matter is or was, is that it can provide an energy source if you can take matter of each kind and bring it together, you will get an annihilation product, you'll get gamma rays, neutrinos, anti-neutrinos, electrons and positrons, and so you can get electrons and positrons [?] of about ten percent. The problems associated with anti-matter are all associated with where you can put it, how you bring it, quite the right time. Now Fred and I at the time that we wrote that paper in ‘58, really said in that paper that you can sort of limit the ratio of matter to anti-matter in our galaxy based on the amount of these products that you saw. And of course we had already given it up as a powerful energy source anywhere because of the problems associated with its initial separation and its bringing together, we got into questions of anti-gravity and I remember Dick [Richard] Feynman in one afternoon we agreed with Dick Feynman that it was impossible if you start talking anti-gravity, you get into all kinds of problems of a very fundamental nature. And didn't think that was the way to go. Now of course, more recently Edward Teller and Alfvén rather independently, particularly Alfvén, pushing this idea which I think has to be wrong in that context altogether and I've tried to tell this to Alfvén for many years, but of course he only listens to what he wants to listen to.
Sullivan
Was it more of a problem with the anti-matter to bring it into a confined space like a nucleus where it was becoming...
Burbidge
But it wasn't clear at that time that...
Sullivan
Well that's true, this is still ‘56.
Burbidge
It was not clear.
Sullivan
So you were thinking...
Burbidge
We were thinking of interactions of galaxies and anti-galaxies.
Sullivan
Oh, I see.
Burbidge
But it was a very difficult business and it didn't make sense.
Sullivan
But now you also wrote at the same time, an article in Physical Review in 1957 on the Fermi process.
Burbidge
Yes, that was a great idea I had, and it would still work...
End of Tape 119B
Sullivan Tape 120A
Burbidge
You see, I had originally in Chicago, when I was there in the early 1950's, gotten to know [Subrahmanyan] Chandrasekhar very well and Chandra used to take me down every week to the Fermi Institute or what was then the Institute, I forgot what it was called, but Fermi was there and Chandra was working with Fermi on cosmic rays acceleration processes. I used to sit in on these discussions sometimes, and I got somewhat interested in the cosmic ray problems. The Fermi mechanism was the popular acceleration mechanism in those days.
Sullivan
Right.
Burbidge
Essentially you have charged particles colliding with interstellar clouds and they attempt to reach equilibrium with the clouds and so [?] energy up - of course, they never do reach equilibrium. And so I suddenly one day had the bright idea that if you have a cluster of galaxies and bounced charged particles off galaxies, then you could gain even larger factors ultimately and these particles trapped in galaxies you would get very highest energy cosmic rays. And so that is what that paper was all about.
Sullivan
I see. Did it have to do with the association which was beginning to come clear in the late ‘50s between radio sources and clusters of galaxies?
Burbidge
No, radio sources. I can't remember, there were some radio sources in clusters but what I was trying to understand there were some early results which suggested there were very high energy cosmic rays which could not be confined to the galaxy, which must escape and might very well have come from other galaxies. There was a fundamental problem and still is, how do you make these very high energy particles? Now people sometimes appeal to pulsars and other things, but this was one way of doing it. But I really was not in any obvious way, relating it to radio sources though I haven't read the paper for years.
Sullivan
Well, one thing that motivated you was the false 21 cm observations, I believe, indicating that there was gas in clusters. I'm not sure about that, but...
Burbidge
Well, that led to quite a different investigation. The Agassiz station dedicated their 60 foot telescope around 19- I don't know, the middle 1950's...
Sullivan
1956, I think.
Burbidge
And Dave [David S.] Heeschen announced, he was a student at the time, that they had detected 21 cm radiation from the Coma cluster and the Hercules cluster and another cluster, I don't know what the other one was, it could have been the Perseus cluster. And I don't think that any of these results were correct, but I knew about the Coma cluster but I knew about the Perseus cluster. I'd never heard of the Hercules cluster. So I went to Baade and asked him about the Hercules cluster, and he brought out this beautiful set of plates of the Hercules cluster, which is a marvelous cluster of galaxies. Nothing whatever to do with radio astronomy. And Margaret and I started a study of the Hercules cluster, which was one of the first clusters which was studied, or studied by us, and shown not to apparently obey virial theorem which is another major [?], nothing whatever to do with radio astronomy.
Sullivan
My present work on the Hercules cluster is directly following in that sort of thing- more red shifts...
Burbidge
Well, that's how it came about and the results which led me to look at the thing turned out to be wrong.
Sullivan
Well, now you had a paper in ApJ in ‘58 in which my summary says that radio sources in clusters of galaxies may not just be a single abnormal galaxy, but also from intergalactic clouds that have a weak magnetic field.
Burbidge
I don't remember much about that.
Sullivan
It indicates that you were being influenced by the association of the galaxies and the clusters.
Burbidge
I imagine so yes.
Sullivan
But now, here's another paper, an IAU [International Astronomical Union] Symposium in Stockholm where you were talking about the magnetic field in general in all kinds of radio sources, all the standard ones, Cas, Taurus and so forth.
Burbidge
Yes.
Sullivan
So no matter whether it was a supernova remnant or a galaxy or an unidentified source you were quite content that the synchrotron mechanism looked like the way to go?
Burbidge
Yes. I felt that the Crab would settle the issue for galactic sources, and M87 had settled it for extragalactic sources, and I saw no reason to argue another direction. I was not unhappy that some supernova remnants showed no appreciable optical radiation and I felt that you could do something about the physics using the synchrotron theory, that's right.
Sullivan
When was it that the problem of all this energy coming from a small location arose? Would you say that was getting into the early ‘60s?
Burbidge
Well, it wasn't so much the location, what really happened was that from the beginning as soon as I'd found these very large energies, I realized that the fundamental problem was: how can this much energy be released in these modes? And the original argument was that in some mysterious way, extragalactic radio sources are associated with collisions between galaxies. And that was pushed very hard by Baade and Minkowski. Baade because he felt he could see two galaxies in Cygnus A, and none of the rest of us, well, he used to look at his plates and say, "Well come on, Walter, it has to be - it is." Then there was a result of 1275 where you saw two sets of velocities.
Sullivan
Right.
Burbidge
Which we later did a detailed study on that optically and concluded that it was matter being ejected, as I think Minkowski had argued though he was very unsure. That was in 1965 that we wrote that paper. Later on various observations have made some people want to go back to the idea that there are two galaxies involved, which I certainly don't believe. But there was this argument about collisions between galaxies.
Sullivan
And Centaurus of course...
Burbidge
But it became obvious early on that this was not the explanation. You had single galaxies like Centaurus; you had, well, there was no evidence in many systems for any other galaxy around and quite a number of the radio sources appeared to be fairly undisturbed ellipticals. And of course, you also could do a simple calculation of the frequency with which you would see collisions. And that's what [Viktor A.] Ambartsumian did; Ambartsumian also attacked the collision hypothesis. And then you had the argument that even if you did have collisions, there was no obvious way in which you could get all this energy out, because only the gas would interact and it was not clear how you would accelerate the particles; it was not clear that you could get a magnetic field; it was certainly not clear that you could get a double lobes. And so independent of the structure in the radio source, the detailed structure, it was clear it was not collision. The anti-matter argument didn't work. Shklovskii tried in fall of matter, that didn't work. No obvious reason why that should work. That led me in 1961 to propose a multiple theory of supernovae, change reactions of super novae, which I liked and still like. It's an attractive idea. You pack the stars in the system close enough together so that one explodes and another one is triggered, which triggers another one. Although I was told, "Well, we already don't believe it works, it's got this kind of declination wave hypothesis that's been played with." Which in those days was related to classified work which of course, caused some problems. But at that stage, I became convinced at least, that it had to come out of the very small volume and this was independent of any observations which didn't really bear on that in the scales that I was talking about.
And we then went the route, remember I've got this extensive background in theoretical physics and nucleosynthesis, so we then went the route that it had to be nuclear energy or it had to be gravitational energy. And by 1962, I was pushing this multiple super-novae theory and I always remember it was ‘62, I think it was ‘62, it was probably the summer of ‘62, yes, it was the summer of ’62. We were in Cambridge in England. And I was pushing this argument very hard, we were mostly still doing nucleosynthesis, but Fred and Willy were there in Cambridge, and I remember arguing with them for days and days that it had to be this kind of theory. None of them liked the model supernova theory, and I think if you talk to them, you will find that it was true that this persistence of mine that you've got to find some explanation that they first started thinking about massive objects and gravitational collapse, which led them in ‘63, to publish a paper in which they argued that that must be the energy source in which they argued that they would turn a blind eye and deaf ear and a cold shoulder to any questions about where these things originated but it was collapse of massive objects. Then in 1964 Margaret and I, Willy, and Fred wrote a paper in ApJ in which we for the first time argued in a more general way that massive objects were responsible for these phenomena and that they could also give rise to black holes ultimately and in a section of that paper which Fred and I discussed- well, it was written by all of us, but I remember Fred and I talked about stars belonging to black holes and of course we got into terrible trouble by, in those days, optical astronomers were not prepared to believe that black holes existed anywhere. I remember asking Chandra why he thought this was the case and he said, "Well Geoffrey, they simply won't believe in anything they can't see. And that's why they only believe in white dwarves and they won't believe in neutron stars." So it was through that sequence of events that led me to argue that you could only get this vast amount of energy from gravitational sources, which is where I think the problem stands right now.
Sullivan
So the large energy requirements were a real problem long before you had the small volume as an observational...
Burbidge
Well one knew that in a certain sense that if you were going gravitationally it had to come out of a small volume.
Sullivan
But I'm talking about even before, in the late ‘50s, even before you could...
Burbidge
Well I would say that by 1961 when I wrote that multiple supernova paper, it was clear what kinds of emissions were required. And you'll find the scale after, I mean there were a number of people who wrote on the subject and there became a flood of people all pushing a few ideas in the early ‘60s. And then, of course, the quasi-stellar came along and the arguments were made based on them, but the energetic problem did not start with the quasi-stellars, they started in the main with the radio galaxies.
Sullivan
Right. Now, you alluded to the double lobes in Cygnus A and there were a couple others which were discovered by the late ‘50s, I guess Centaurus primarily, seems to me that this issue was avoided by everyone.
Burbidge
Well, we used to discuss it; I remember John Bolton argued that they must be, what's the plural of Taurus- Taura, I don't know. And we immediately convinced ourselves, I remember at Caltech in the discussion that we couldn't do it that way because the relative frequency different orientations was totally wrong. The double nature was indeed, avoided and continued to be avoided for a very long time. One knew that it had to be an axis in the system which would do it, early on one was aware and I may have said in various publications that the one obvious way to get a spherically symmetrical explosion to become axis-symmetric would be to simply have a rotation axis or something like that, and you have a matter and a plane and the expansion won't go in the plane, but it'll go perpendicular to the plane. But that problem certainly was avoided.
Sullivan
I guess only with the mile telescope in the late ‘60s when you began to get all these doubles, was it taken up again.
Burbidge
No, I think earlier than that that everybody accepted that the majority of them were double. I mean, the...
Sullivan
That's right.
Burbidge
Three-quarters of them are doubles, have been around for much longer than that.
Sullivan
That's true. Owen's Valley stuff were in the early ‘60s.
Burbidge
It was one of the well-known observational facts, but it wasn't really the point that people thought about. I mean, I don't feel the subject has advanced a great deal in many number of years. What happened is that the gravitational energy in some mysterious way is now also all associated with black holes and double radio sources are somehow associated with relativistic beams. But this is because people like Martin Reese are pushing very hard on an ingenious idea which I don’t think is probably right, but the problem that we still don't understand is the way in which we get the energy out in the form that we see it. There's no obvious reason. Gravitational energy should be converted relativistic particle and/or magnetic flux at high efficiency, and that still remains the case.
Sullivan
Or why it should be shot out into pairs.
Burbidge
Well, it is shot out, because the sources down here that you see down here, well, the only thing is that you've got to feed something out there and there again, the question is that do you feed matter out and continuously pump things out here or do you as Martin Ryle has always described my ideas of more recent years, do you eject power stations?
Sullivan
Right. Now, more generally, if you can think of the influence- now, my study is ending in the early ‘60s. So up to that point, if you could, what would be your comments on the influence of radio astronomy on the course of astronomy from your vantage point?
Burbidge
Well, I think one of the greatest influences was associated with- prior to these developments, everybody assumed that galaxies were very stable, long-lived, slowly radiating objects, and violent events in galaxies had never been conceived of. At least for me, I think that what radio astronomy did above all in the extragalactic field was demonstrate that violent events in galaxies are fairly commonplace. The paper that we wrote in 1963 with Allan Sandage, Margaret and I had reasonable amount of physics where we put together all the observations bearing on violent events and made for the first time, I think, a strong case that there were explosive phenomena in galaxies which could sometimes manifest themselves in the form of radio emission, sometimes in the form of high velocity gas, sometimes in the form of high [?]. All those things really you could put together- in that paper I wrote most of the text and Margaret and Allen provided a lot of the figures and we put it all together, it was I think a very powerful piece of argumentation using circumstantial evidence. People swallowed it. They believe it. There's a hint of a reaction against explosive phenomena now, but perverse people like Phil Sullivan- no not Phil Sullivan- Phil [Philip A.] Morrison but that has it's, I don't know why that is, but radio astronomy first clearly put us on that track, if it's the right track if it's the wrong track, it's the wrong track. And of course the other thing that radio astronomy did was help us find quasi-stellars. But I think that it those aspects which above all, to me, were the most striking in terms of the overall direction of extragalactic astronomy. As far as galactic astronomy is concerned, radio sources have not been that important, except as far as the supernova arguments are concerned where you have to take on faith that radio sources do arise from supernovas.
[Break]
Sullivan
Well, you've mentioned the bringing to the fore the violent activities in galaxies, of course, the Seyferts had been around since the early ‘40s.
Burbidge
Yes, but no one had paid much attention.
Sullivan
It was just a minor...
Burbidge
We wrote the first paper looking into the Seyferts again in 1959, NGC 1068, and it was certainly, I mean, they'd just simply been ignored. What you have to realize is that 20 years ago, there wasn't [?] astronomy. The interest was largely in stellar evolution and nucleosynthesis, which I suppose we had a lot to do with.
Sullivan
Yes, it wasn't much...
Burbidge
And [?] diagrams for clusters. And when we first started going into extragalactic studies in 1957 when we first went to Yerkes on the faculty of Chicago, not very much was going on. I think a lot of the interest in extragalactic astronomy came through radio astronomy and through a very small number of us who were interested enough and got people excited about it.
Sullivan
What about general ideas about the interstellar medium, do you think it's changed in any fundamental way?
Burbidge
I've never really written papers on this. I suppose in the galaxy they have, but I can't say that I've had a lot to do with that.
Sullivan
I'm asking you as an observer of the scene.
Burbidge
It's hard for me to say, I think that of course the arguments about the interstellar magnetic field have always been heavily intertwined with the radio arguments, and the arguments based on cosmic ray physics. The models for the interstellar medium the hot gas and cold gas, which components really exist, I don't think have been grossly effected by radio astronomy.
Sullivan
Okay. One final question is, you've made a couple of allusions to it but more explicitly the general acceptance of radio astronomy into optical astronomy, I'm sort of interested in, as someone who was sort of on the borderline between the two...
Burbidge
On the borderline looking in...
Sullivan
Can you name an era when you think that to be a radio astronomer was not just to be an engineer who knew how to build antennas, but were accepted at astronomical conferences as one who knew what he was talking about?
Burbidge
You mean when did that happen?
Sullivan
Yes. Is that a valid question at all?
Burbidge
I don't know. First of all, I think that some radio astronomers, Ryle is an extreme example, never wanted to accept that optical astronomy could provide hardly anything. I used to have this running argument with Ryle about this; he felt, I mean, he used to get very antagonistic about optical astronomy, he felt it could all be done by radio methods, and I used to challenge him and I'd use this in questions to students in the following way, I said, "All right Martin, let us suppose that the earth is continuously covered by a thick blanket of cloud, and always has been; what do you think we could learn about the universe using the radio technique - all the radio techniques at your disposal?" The fact is that I think you'd learn very little. First of all you can't learn the scale of anything, you would see something rising and setting, you might by now even make radar measurements and find that there are bodies out there called the planets as we now know them. I don't think you would know anything about the scale or the size and the shape of the universe really. You certainly wouldn't know anything about scale. The problem with radio astronomy is still, as it does in other fields of astronomy apart from optical astronomy, is that there's no way of measuring distance. So I think that radio astronomers got to have the optical astronomers. The most successful radio astronomers are astronomers who have learned something about astronomy; and the least successful are those who have largely remained electrical engineers. The Cambridge people learned a tremendous amount of astronomy; Martin was an exception in this kind of argument and of course, doesn't really use the argument himself because all of his cosmological arguments are based on some level on optical observations, shaky though they may be.
Sullivan
He made exactly the same comment at the 1976 meeting.
Burbidge
Well, he doesn’t change. I mean, he's found...
Sullivan
I find that incredible.
Burbidge
As Fred Hoyle once put it in a rather brutal way because Fred has suffered Ryle and he's gotten to the point that he doesn't suffer him very well, Fred says "Well, he's always been rewarded for putting his hand in the till." And now Martin and, of course, you were probably present when he gave this, because I got up and you remember how he took up against me? Well, that is the measure of the way, that reminded me of the way it was those years before. And it reminded a lot of other people. John Bolton said "well, that shows the younger people just how it really has been." And it really was like that.
Sullivan
That really was the only thing like that in the whole conference. I think it the only time he made a remark in the whole conference.
Burbidge
I touched a nerve again, and I was being doing that for years. No, that's really the case. Martin is an extreme example. Martin's a genius, let's face it. But he's not, I mean he, more than the most of us- it is a very dubious game that he's played. But he's a genius as far as an engineer, as a designer, in many ways. It’s no surprise he’s won the Nobel Prize at all but I think that that attitude is one that's extreme.
Sullivan
Let's look now at radio astronomy more as a whole. Would you say that there was a transformation at some stage or is that difficult to say?
Burbidge
Yes, well, it's slow, obviously came in the ‘60s. There was a time when John Bolton didn't want papers published in ApJ and for some reason, he believed in the ASP not ApJ. But I, it's unclear to me, I think they're still different breeds in many ways because I think there's still many radio astronomers who are sure there's a better way to do optical astronomy. But I am quite convinced and everything I've learned about astronomy still leads me to believe that scientists, astronomers are extremely technique dominated. I can name very few first class astronomers who can manage to move effectively from one part of the electromagnetic spectrum to the other. Name me an optical astronomer who's become a radio astronomer or an x-ray astronomer. Name me an x-ray astronomer who become- and so on. And this has something to do observationally at least with technique. But I think by the late 1960s there was less of this kind of separation. But there's a body of knowledge that you have to learn in order to do astronomy which covers a very wide range of physics and I've never taken any astronomy courses and there are many physicists in astronomy have not. But you simply have got to admit there is a very good likelihood that other people have done things. I remember the Cambridge people in the early days discovering parallaxes, discovering [?] book actually.
Sullivan
Precession.
Burbidge
And I remember telling you where to point and being miles off and I remember always in the early days when we were in London in the early days of when you identify radio sources, they gave Margaret a position at the University Observatory and later on they came and gave us some different ones, which were way off and well they just discovered sidereal- they just were learning it all.
Sullivan
Sure.
Burbidge
And they were trying to learn it all from various principles rather than accept that there was a literature in the field and most things of this kind had long ago been worked out.
Sullivan
What about on the other side, looking at the optical astronomers who, the whole technology was beyond their ken, they were working with DC amplifiers at most at their telescopes.
Burbidge
Well the optical astronomers still, I mean, I'm not sure what you're driving at because the optical astronomers still are not very interested in high energy phenomena in astronomy which is where radio astronomy is at. They're still quite surprised. I mean, after all normal stars go through their lives and normal galaxies go through their lives it is thought under the influence of gravity moving or acting rather slowly, and nuclear forces, and radio emission is just kind of a little blip in the system. It may not be at the beginning, it may not be at the end, it may not be sometimes when certain things [?] but there is a whole breed of optical astronomers who still don't think it’s a major part of astronomy. And it can lead you to discovering new phenomenon, but it doesn't necessarily- most of the photons in the universe apparently have energies around an electron volt, most of the energy in the universe I should say is carried by photons.
Sullivan
Right.
Burbidge
The microwave background overwhelms everything, that's radio emission. If it comes from where people said it does then there was a time when it dominated, but if you want, I mean, the radio astronomers time is passed a few billion years ago.
Sullivan
That's an interesting point. But you say most optical astronomers sort of ignore the radio as being a minor point of astronomy. That may well be true, but do you think that's true as far as the important thrust of astronomy as a whole? In other words the best part of...
Burbidge
Yes, some people say that I am an iconoclast. I don’t think I am, but I would say the following I said it last week when I made a speech at the dedication of the MMT, the next twenty-five years of astronomical research, [Don ?] talked about this too, Don talked about it in terms of the new telescopes, I thought well there's no point in doing the same thing. The part about astronomy I think that is most disturbing things to me is that it's still not a hard science as physics is, I guess, or even biology is getting. And the reason for this is that there's so many phenomena in the universe that we can go and look at in a very schematic way and we can find out or we can discover something remarkable that we've never predicted and we build a picture of the universe based on these fragmentary ideas and we build ourselves a large inverted pyramid. We don't really test the foundations, we don't really study enough of the details in enough objects that we're quite sure of what we're doing. Probably the most certain parts of astronomy are still associated with stellar structure and stellar evolution up to a red giant stage and I hope nucleosynthesis. I'm leaving out the solar system where you have more things to talk about. But my theme was that for the next 25 years should be devoted to really looking very hard at this whole structure and attempting to see if we can make parts of it reasonably sound rather than just asserting that it is so. I gave as a series of statements which most people believe in but which I think there is very little foundation for the following: "Everybody thinks that galaxies are old, what is the evidence?" "Everybody believes that the virial theorem holds, what is the evidence?" "Everybody believes that most faint radio sources are very far away, what is the evidence?" In my view, the evidence is marginal or nonexistent in nearly all of those cases.
Sullivan
Yes.
Burbidge
My view was and is that we should spend far more time working to establish the reality or non-reality of these beliefs than in pushing on into these exciting areas where you are straining every nerve to get a red shift of one for some reason which is rather...
Sullivan
Apparently then you don't believe it's built into astronomy, the fact that we can only observe from one direction and can never go out there.
Burbidge
Oh, it's built in, what I'm trying to say is that we could do far better. For example, I mean, if you want a mindless program which would probably help us a lot, I would say a field I know extragalactic astronomy, everything that we base our ideas on is probably based on having looked once, maybe twice in a few cases, at a few thousand extragalactic objects. Let's start off by getting a million red shifts. See whether we still believe in isotropy, whether we still believe in the Hubble or what do we believe?
Sullivan
Well, there are a few people who are getting a few thousand now, anyway.
Burbidge
But a few thousand is a few thousand. You can...
Sullivan
It's a hell of a lot better...
Burbidge
The number is a function of time and it hasn't gone up that much. You know, and there are these terribly difficult problems associated with observer's belief, for example, if an observer is trying to find distant galaxies and he finds a 19th magnitude object on the plate he assumes before he observes it that red shift of about .2, and I have often challenged some of the people working in this field because they know how difficult the observations are and what the spectra really looked like, just to exchange information. If Jim Gunn gave his tapes to Margaret and Margaret gave hers to Spinnard would they actually get the same answers? And everybody says when I say this among experts, "Yes, well that's a very good question, but nobody would ever dare do it." But what I'm trying to say is that the whole thing is based on not very much and there's an awful lot of belief we've worked so hard we've played so long, we must be right, we can't be wrong.
Sullivan
Okay. Well, thank you very much. That ends the interview with Geoff Burbidge on 22 May 1979 at Kitt Peak.