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Interview of Dennis Sciama by Spencer Weart on 1978 April 14, Niels Bohr Library & Archives, American Institute of Physics, College Park, MD USA, www.aip.org/history-programs/niels-bohr-library/oral-histories/4871
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Background and undergraduate years at Trinity College, University of Cambridge, and later return to Cambridge to study relativity under Paul A. M. Dirac, against father's wishes. Work with a Trinity fellowship, 1952-1958, alongside Herman Bondi, Thomas Gold, Fred Hoyle and Raymond Lyttleton, developing and extending steady state theory and doing other broad-scale theory. Move to University of Oxford, 1970, after other posts. Interest in Mach's Principle; abandonment of steady state theory; work of student Stephen Hawking on black holes; development and social context of cosmology. Also prominently mentioned are: Jacob David Bekenstein, Brandon Carter, Lidia Dina, Arthur Stanley Eddington, Albert Einstein, George Ellis, Gilman, William Hunter McCrea, Roger Penrose, Derek Raine, Martin J. Rees, Martin Ryle, Harold Spencer-Jones, Ludwig Wittgenstein; Cornell University, and Kings College (University of London).
I'm interested in background things. I have here from WHO'S WHO that you were born in Manchester in 1926, but I don't know anything else about your family, Who were your parents, what did they do?
My father was a business man who was also born in Manchester, and his father was born in Manchester, and his father came from Aleppo in the Middle East, in Syria.
I was wondering what sort of a name Sciama was.
In fact it was spelled "Shama"; when my people came to Manchester they Europeanized the spelling, and happened to choose that form, My mother was born in Cairo.
What sort of education did your parents have, then?
My mother was educated in Egypt, and my father was educated in Manchester, He went to Manchester Grammar School, which is a famous school in England, but he left at the age of fourteen because his father died and he had to earn a living.
By the way, did you have any brothers or sisters?
I had a brother who died a few years ago.
Yes, three years older.
I see, I just like to ask these questionaire things. Tell me, did you read a lot in your childhood? Were there any particular science books that may have influenced you?
I did read a lot, I was the sort who would read on all possible occasions, including when getting dressed. Not specially science books when I was small, just books, But with the English system of education being what it is, I already knew at the age of twelve that I was on the mathematical side of things, because I sat for a scholarship to a public school (in the English sense; a private school you'd call it here). You either did a difficult math paper or you did the Greek paper, and I already knew then that I was going to do the math paper and not the Greek paper.
I see, What school was that?
It was called Malvern College. Reasonably well known but not one of the greatest, not an Eton or a Harrow or a Winchester, but very good at a lower level.
I see. Before that was your schooling done mainly at school, or partly at home also?
No, I went to a prep school in Manchester. And then I went to Malvern.
And what sort of an education did you receive there, particularly in science?
Well, it was very good.
This was a boarding school, you weren't at home?
A boarding school, yes, I was away from home, The teachers were very high calibre, the point being that these private schools had the means to employ fine teachers. For instance, the man who mainly taught me maths bad obtained a First Class in all three parts of the Mathematical Tripos at Cambridge, which of course in England dominates mathematics very much, The kind of man who wouldn't in fact become a school teacher, these days, with those credentials - the highest you can get.
And there was a good physicist, from Cambridge; he had been at Trinity College and it was partly through him, through the fame of Trinity as a physics college, that I later entered Cambridge at Trinity. So I was prepared, and won a minor scholarship in mathematics at Trinity, really through the very good teaching I obtained.
Yes, In fact, I thought of myself as becoming a mathematician rather than a physicist. This was during the (second world) war, and I was deferred from joining up on the understanding that I would do physics at Cambridge; they allowed me to do some maths and I did some physics. My first year was in maths, and then I switched over and did what's called the Natural Sciences Tripos, meaning physics in finals.
Somehow they didn't regard mathematics as being useful, or what?
Right. Physics was more direct use, they thought, to the war effort; a training purely in mathematics was considered less effective.
Do you think that diverted you from what otherwise would have been a career in mathematics?
I think it was very good, because it's quite clear from my subsequent career that what talents I have are more along the physics line than the mathematics line, I'm not a powerful formal mathematician, and I have a bit of feeling for physics. I'm sure it was good for me to go in that direction.
I see, So there may have already been some feeling on your part at that time?
I didn't realize at the time; I did it because the government requested it.
I see, I didn't realize they did this systematically - you were not a special case but this was a general thing?
I imagine, I dust don't Imow how many people would at that stage have said they wantedto read maths rather than rhysics. But I agree, it's the presumption that I was not the only one they said that to.
your early home life, what sort of feeling did people have about science? I mean your general impression of science?
None really, because there was no academic atmosphere in my home life. My father in many ways had a very fine brain indeed, For instance, he was a very good bridge player, and he was very able with business, and very able in understanding and assessing the world political situation. But perhaps through leaving school at fourteen he had no feeling for akademismus or universities or anything of that kind. He was very upset that I rejected the business which be wanted me to go in.
Which was, by the way?
He was in the cloth trade, the cotton trade, Over one period it was a source of great friction between us, He had a very powerful personality. It was extremely unpleasant.
Was this before you went up to Cambridge, or subsequently?
Also subsequently, because my determination to remain in science and do research kept developing as I was at Cambridge.
This didn't enter when you were thinking of going to Cambridge, this came along afterward?
As far as I can recall, up to about the age of fourteen I would say I was going into the business, I can remember how pleased my father was because I wrote an imaginary letter as if I were in business and I invented a new color to dye a cloth, called "bleen", you see, it was a mixture of blue and green, The suggestion that this showed a little bit of initiative pleased him tremendously, So of course it was very upsetting for him when he realized I rejected his whole life's work to do something that he had no empathy for, Science meant nothing to him, Despite his fine brain it was entirely canalized in other directions.
So it was the influence, perhaps, of these teachers?
I don't suppose so, because I had a particular passion, especially for understanding fundamental physics and astronomy. It's something very deep in me, Of course it's deep in many other people too, but it's not something, I think, that I simply learned. The teachers were gifted at actually teaching the maths needed at that period of one's life it wasn't research level material, I think it's just some very deep thing in me.
Do you have any idea of where it may have come from? This is quite clear in your work, that you have followed this line more than most other people.
I sometimes used to laugh at myself, saying it's an emotional insecurity. You see, I probably like to control reality, and one can't control it very much in practice, the way things are stacked up against one, So I substitute controlling it intellectually. The best way to control it is to understand it, and the deepest understanding comes at the most fundamental level.
That's very interesting. By the way, did you have any formal religious training when you were a child?
No, We're Jewish, but we were never Jewish in the religious, orthodox sense, if I ever believed in God I stopped believing in it very young. I can remember my father telling me he didn't believe in God, how we didn't observe the Jewish orthodox practices. So in any practical sense there was no religious term to what I did or was interested in.
I see, Can you tell me a little bit about being at Trinity. Of course it was during the war, so I suppose it wasn't a very typical time to be there.
The college was smaller than normal, which was probably why I managed to get on the football team, My main concerns were my work and my friends. The war ended while I was still there, I was an under graduate from 1944 until 1947.
Were there any of your fellow students that you kept up contact with later on, for example as scientific colleagues?
Oh yes. I'm still close friends with some of the people i met as an undergraduate.
Whom, for example?
There was a friend called Kenneth Alberman who lives in London. Of course I don't see him very often now, for geographical reasons. Another one Cyril Rashbass.
These were people who went on with the sciences?
They were both at Trinity. Kenneth did chemistry for a bit and then he joined his father's firm, a cosmetics firm, Cyril went into physiology, and he remains a research worker doing that, But I see him very rarely now.
You say you read for the Natural Sciences Tripos.
I read mathematics for one year, and then I switched over to physics. And because of the point at which I took physics, because it wasn't a first year any more, I only did physics whereas if you did the Natural Sciences Tripos from the beginning you did other branches of science as well.
Did you study anything else at this time? For example, did you have much of an interest in formal philosophy?
I did, a little, In fact, I did something which turned out very useful in Oxford: in my first year I attended a whole course of lectures that Wittgenstein gave. He was at Trinity at the time, and lectured in his own rooms in college rather than a lecture room.
That must have restricted the number of people.
There were about half a dozen of us, I think, I sat through the whole term of lectures, Now I dine off that in Oxford, because Oxford is full of philosophers; Wittgenstein is their great hero, so the fact that I attended the course, and indeed he often invited comments and reacted to those comments — I said things which he had to react to this goes down very well.
He was very quick in his personal communications?
Not quick in a sense, He'd sometimes sit for several minutes in silence, thinking out what to say next, He had mannerisms of that kind, which other people started imitating, but I think they were pretty genuine with him. He was a very remarkable man.
Were the other people undergraduates also?
They weren't entirely undergraduates. There was one lady there who I realized later was Miss Anscombe who is now in fact a professor of philosophy at Cambridge, after having been at Oxford for some while, But as far as I recall most of the people there were students; she was a bit older.
Were there other courses that you attended, or teachers, that had a particular impression on you, scientific or nonscientific?
The courses one went to were more or less dictated, except for an extra like the Wittgenstein one, I'm not quite sure how to answer that,
Were there any that made a particularly strong impression on you?
Dirac gave a superb course which I went to in my third year, which was basically his book, But he is a very good lecturer indeed and he was wonderful, Of course be was a legend then, as well as later, So that made a big impression on me.
That's quite difficult actually for someone at that stage.
I'm not saying I understood it all, but he is a very lucid lecturer and the fact that his standing was so high almost a mythical figure as it were .., I got to know him later, because as I'll elain if we do discuss that, in the second half of my being a research student I became a student of Dirac's, But I didn't realize at the time that was going to happen, so for me it was a great prophet speaking.
We will get to that, So by the time you graduated you had already been exposed both to quantum mechanics and relativity, and they were quite deep.
Hot much relativity. In fact I was really selftaught, I did go as a research student to a course on cosmology that Bondi gave, But you see, in those days very few people did relativity; it's not like in later years. I think Bondi occasionally gave a course in it at that time; I didn't attend one, I simply learned the subject by reading the basic books, I remember reading Eddington's mathematical book and so forth, So in that sense, I was to some extent self-taught in relativity.
Had you had much up until the time when, say, you were a research student, after you got your B.A.?
In fact my exam results were very poor in finals, and I had to leave Cambridge, and there was still consciption although it was after the war, I spent two years in the army immediately after graduating. But after six months I got transferred to a government research place which had done a lot of radar work during the war, called the Telecommunications Research Establishment, T.R.E. Through having met Professor Hartree in my last year as an undergraduate - while he couldn't keep me on to do research because of my poor degree, he helped to get me transferred to T.R.E, So while I was still officially in the army earning my five bob a day, I was working on the quantum mechanics of photoconductive materials which were of interest for the purpose of detecting enemy airplanes, And through internal reports I wrote on the quantum mechanics and group theory of these things, I was accepted as a research student back at Cambridge, So I returned to Cambridge two years later, in 1949.
First I wanted to ask, before you left Cambridge the first time, had you much contact with astronomy? Bondi's course that you took was after that?
That's right. No, no special contact, In fact I started research — this is jumping ahead — my first topic in research was in statistical mechanics.
Then the story starts for you when you came back to Cambridge, You came back as whose student?
Temperley was his name. This was my own choice of subject, While reading up on solid state physics and so forth at T.R.E I came across a paper by Wannier in REVEWS OF MODERN PHYSICS on cooperative phenomena, the I sing problem and things of that sort, and I found the discussion rather attractive. So I said I'd like to do research on cooperative phenomena.
At what point did you decide to make your career in physics?
I suppose by then I'd been diverted from my original thought of doing mathematics, I think it may have emerged in my studies in Cambridge, that my formal mathematical powers were not as strong as they might've been, and that probably I was better doing theoretical physics. Although, of course, theoretical physics can be done in a whole spectrum of ways from very formal to less formal, Pure mathematics you have to do formally.
Of course Cambridge was the natural place for you to go, to study physics.
Oh yes, because it's strong in math and physics, and as it later turned out, astronomy, But my mind had no astronomy needs at that time, I told Hartree that I would like to do work on statistical mechanics, and I was allocated Temperley as my research supervisor; I was given a desk, not in the Mond Laboratory, but in an office in the main old part of the Cavendish belong to the Mond. For a year or eighteen months or so I was working on cooperative phenomena, and then I switched over to relativity at that point.
how were you supported during this period?
I didn't get a grant, because of my poor exam results, so I was supported by father, I recall making an appeal to the Cavendish Lab for support, and they found money in a fund called the Scott Fund, which gave me twenty pounds for the year; that didn't carry very far. I confess that I relied on my father, I say that because I don't really approve of my students relying on family means, I wouldn't refuse them on that account, but I feel that if they're good enough to do research, the institution ought to look after them financially.
I see, So this was the period when there was the difficulty as to how your future career would go?
Of course it was awkward, being supported by my father while I was betraying him, But my dedication to science was already very great, although I hadn't yet developed the interests that I later showed in cosmology and astronomy and so forth.
What part did your mother play in this, by the way? Did she take any stand on all of this?
Not very strong, My father was much the stronger personality. She supported me a little bit in a weak way, but not specially effectively, It was simply my own will, My father was extremely dominating, and would no doubt always win against me on anything that I hadn't absolutely set my heart on, but in this case my will was so strong that I won, although it was a very bitter fight.
I see, So then when you left statistical mechanics for relativity, was when you started to work under Dirac?
No, that was a conseauence, I started thinking about gravitational theories and Mach's Principle and so on, I knew already then, very slightly, Hermann Bondi and Tommy Gold, and I talked to them a bit about these things, I remember I asked Bondi to tea one day and told him the thoughts I'd had and I said, "Are they rubbish? What should I do?" He said, "Why not go on thinking about them?" I think that was very good of him, because I'm quite sure in retrospect it was rubbish what I said, as I was very immature at that time, Maybe it was merely my initiative and enterprise that Bondi recognized, But with that encouragement I went on thinking about it, At a certain point it became evident to the authorities that I wasn't working on statistical mechanics any more, and so after some thought they changed my supervisor and they gave me Dirac.
I see, I'm very interested in this transition, Was this after or before you took Bondi's course in cosmology?
I can't remember the relative placing of taking the course and the formal step of Dirac being appointed my supervisor.
In terms of your interest, for example, in Mach's Principle and that sort of thing.
Actually, it's curious to recall my first attempt to do something in gravitational theory which incidentally I sent to Einstein, and got a letter back from him about.
We could find it in the Einstein papers.
Yes, indeed, I got a letter from John Stachel* telling me some details about that; I was amazed to find that he found in the files a complete longhand version of that letter, that was then typed. As I'll tell you later, I had a long conversation with Einstein a week before he died, which is something that may be of interest historically.
You'll have to remind me when we get to that part.
At any rate, I can't recall precisely the relative timings. I think Dirac was made my supervisor when I'd already been working at least a year on this. I was saying that my first essay in gravitation came out with a result that was not in agreement with Mach's Principle. Just as an aside, in an article I wrote but never tried to publish, the one I sent to Einstein, I mentioned that "this doesn't seem to agree with Mach," and I didn't mind at the time. Then, a little later, I was bit by the thought that the Mach Principle point of view was right and one ought to develop a theory agreeing with it, And that was the theory I wrote up for the thesis when I got my Ph.D. But I'd already developed it quite a lot by the time Dirac was made my supervisor; it was no fault of his, but he didn't particularly help me, owing to this history.
Wow, Steady State was in the air at this time?
It was, and indeed it does play a part in my thesis.
Yes, I wondered when you first heard of Steady State?
Well, Steady State was proposed in 1948.
Yes, You were there
I got my Ph.D. in 1953 and my Fellowship at Trinity in 1952, So Steady State was fairly new.
I just wondered if you remember when you first heard of this notion?
No, that I can't remember.
I see. It would have been already there when you came.
But since I got to know Bondi and Gold personally they were both at Trinity then - it must have been a bit in the air, but I don't remember when I first heard of it.
I see, Then you must have become familiar with all of these things, the various cosmologies and so forth during that period.
* Editor of the Einstein papers in 1977 - SW.
Yes. I knew Hoyle slightly. Be was older than Bondi and Gold, and I was perhaps on a slightly friendlier basis with Bondi and Gold. But certainly there is a chapter in my thesis where Steady State ideas do come in. Weart: Tell me about working under Dirac, then.
Well under, of course, is misleading, as I've explained, because I'd already prepared my draft quite a bit. I have one or two Dirac stories that date from then, but I don't know whether they're of interest,
Tell me at least one Dirac story.
There's one quick one and there's one that takes rather long. The quick one is that I went to him one day with some enthusiasm and said, "Professor Dirac, I've just thought of a way of relating the formation of stars to cosmological questions, shall I tell you about it?" And Dirac said, "No," So I went away, So that's one Dirac story. (Laughter)
That's interesting, because it shows already some interests of yours.
By then, yes, surely. There's another one that's amusing, but it takes too long to tell.
Please do, Go ahead.
Well, once I saw him and I told him what I was doing, and then he said, "Shall I tell you what I am doing?" So, very flattered but rather nervous, I said, "Yes." At that time, it must have been around 1951 or '52, he was working on one of the various versions of a classical theory of electrons which he was playing with at that time, And in particular it was a sort of fluid theory, on the grounds that the particle was a quantum phenomenon and that if you discussed electrons classically at all they ought to be fluids. And he told me that he developed such a theory (I think I'd seen his paper) and he said that the form the theory took was such that the flow in the classical electron fluid was irrotational, but that Gabor had told him that in actual electron tubes one could get electron- streams with vorticity.
So, he said, "I've generalized the theory to include this vorticity effect, and this is how I've done it," And he proceeded to tell me, I understood very little, but obviously I had to say something at the end: I racked my brain for something safe to say. So when he finished I said, "Is that the most general way of doing it?" He said, "I don't know," And I went away. A few weeks later notices went up that Professor Dirac would give a seminar, It was less true perhaps right at the end of his career, but at that time people still flocked to hear the great man talk. The room was absolutely packed.
He gives this talk about classical electron fluid, irrotational and Gabor said and all the story, and "Therefore I generalize my theory in the following way," and then he suddenly said, "At this point Mr. Sciama made a most important remark to me: that that was not the most general way of doing it, And therefore I have done the following." I went absolutely puce; the floor could have opened up and I could have sunk in it. What a false position to be ml But it was funny.
That gives me a picture, How much did you work with him then you would discuss your work with him?
A little bit but not very much, Not through his inattention or carelessness, but I was, I suppose, fairly independent.
I see. Pretty much doing it on your own.
With whom would you discuss your work then?
Q uite a bit with Tommy Gold, whom I'm close friends with ever since. Perhaps even more than with Bondi, because Gold was very interested in Mach's Principle and had a clearer picture than I, at first, about it. Of course once I worked on it nonstop I eventually developed my own views. But I found his criticisms and quickness of mind very helpful.
I'm not quite sure about the relation between the Steady State theory and your work on the origin of inertia, There's a certain philosophical common ground. I wonder, would you say by that time you pretty much believed in Steady State?
I think that came a bit later, There isn't a clear connection, and certainly my theory didn't lead automatically to Steady State, though certain features of it were suggestive of that, I was predisposed, I suppose, as I developed my work postdoctoraily, to get sucked into the Steady State view, But then I found that very attractive for a number of reasons unrelated to Mach, On the other hand, in the Steady State paper of Bondi and Gold there is a long discussion of the Mach Principle. So the ideas have a certain congeniality, but they have no extremely close logical connection, just a natural similarity in texture, in a certain sense.
The three of you were discussing these things, so it would be natural for you to share their philosophical concerns.
Tell me a little more on the origin of the inertia. This was your thesis?
You used 4-vectors and so forth, and you said, "A more complete, but necessarily more complicated theory will be described in another paper,??* The fact it didn't happen until 1969,** I was wondering what happened.
Oh, I found it too difficult to make adequate progress. What I discovered, which had been discovered independently by a number of people, is that the theory had to be very closely similar to general relativity. If you took a tensor theory instead of a vector theory, and you recognized that the gravitational energy itself had to be a source of gravitation (which Einstein had recognized originally in proposing his theory there were various was of it in the theory
* MONTHlY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY 113 (1953) : 34.
** (with Waylen and Gilman) PHYSICAL REVIEW 187 (1969) : 1762.
which showed that even if you started, as an approximation, with a wave equation for a tensor potential, by the time you coupled in, as a source, the gravitational energy itself - which you had to, because everything had to be courled to gravitation then the only set of field equations you would arrive at, from that point of view, were Einstein's own field equations of general relativity. Therefore after some while I realized that I couldn't solve the problem by proposing any other field equation that would do better, And I came to realize that since Einstein's equations are differential equations, it was in the boundary conditions that one would have to find the selection principle for those cases that were to be compatible with Mach's Principle. And that's technically very difficult to handle, as the equations are nonlinear, It was only later through discussions, in particular with Donald Lynden-Bell, that (along with a student of mine that I then joined forces with, and an American who was working on similar lines, a student of John Wheeler) we saw technically how to proceed.
That was Gilman?
That's right. Gilman was a student of Wheeler who became interested in Mach's Principle, I think through my own writings.
So this was a problem that you just kept sort of in the back of your mind all this time?
That's right. But we didn't solve it in 1969, We took a step forward by a technical device that I won't go into, but there were still remaining technical problems. It was a later research student of mine, Derek Raine, who went a fair distance in solving them - in fact, by getting the result I mentioned in my talk today,* that if the universe is homogeneous and it's Machian according to our boundary conditions, then it has neither vorticity nor shear. The boundary conditions that seem to do the trick were really discovered by him, and the mathematics by then had got very complicated.
It seems to get more and more complicated.
I'm afraid so, but I feel forced by the physics to be that complicated. The Maine paper only came out in 1975,
I see, You still have hopes for this —
I still have hopes, but there are still problems.
So you're not committed to that sort of an approach?
I don't know that it's the final answer, but I've been very struck by the development I was speaking about today. The precision with which (we know) the universe does not rotate relative to absolute space, you see: only over the last few years can we say that's a very high precision. And that's most impressive.
And similarly for the shear. Similarly for the shear. * At meeting of Northeast section of American Physical Society, Wesleyan University - SW.
So you're forced into this mathematics, so to speak.
In fact we did the mathematics before some of the analysis I was talking about today, but not before some of the other ones.
Right, I mean philosophically.
Oh yes. Sure.
I see, You did a paper in 1960 on the Einstein-Schroedinger unified field theory,* I wonder whether you ever had much interest in unified field theory?
I did for a little while, but I then stumbled on something which has recently become very popular, which seemed to me to be the real content of what Einstein and Schrdinger were doing, In their work they'd taken the affine connection of relativity and given it a skew-symmetric part which they thought had to do with the electromagnetic field, since that's described by a skew tensor; whereas I believe I showed (and independently Tom Kibble) that it had to do with spin. If a material system had spin, it seemed to give rise to this skew part of the affine connection, which Carton had discovered in differential geometry called the torsion, In recent years this study of torsion has become quite popular. But it's not related to unified field theory any more.
I see. So this was just something that you took up temporarily.
Yes, As a matter of fact, originally to find the equations that would naturally give rise to the Steady State universe, That was the original motivation.
So the things were linked in the beginning. But then I found it had nothing much to say about Steady State, but it threw out this interesting feature relating to spin.
I want to get back to Steady State, but first I want to ask about what happened after you did your thesis. In the first place, did you get any scientific echoes from this?
I'm not quite sure what you mean by echoes.
Did you get much interest in it?
Oh, people were interested in some of the physical parts, The mathematical theory I produced, this vector theory that you mentioned, was very crude by modern standards relativity is now a very highly professional activity extremely crude.
But this was a sort of thing there hadn't been much of.
There hadn't been much at that time, And the physical ideas, one or two of them were quite cute, and very interesting. So when I told, say visitors to Cambridge, my line of thought, I often got a good response
* JOURNAL OF MATESMATICAL PHYSICS 2 (1961) : 472.
because some of the physical ideas were very nice, But the main thing, which was important for my career, is that I did succeed in getting a junior research fellowship at Trinity College, Cambridge, on the strength of that thesis.
Yes, I wanted to ask about that, You didn't sit for exams or anything like that.
No, By then they had ceased to have exams for these Trinity fellowships. It was purely on the thesis.
Who decides then?
The College sets up a committee, and the way the system works is, you have to be a member of the college to be a candidate, and each candidate has one member of the committee who looks after his interests, and he selects two external referees who will report on the thesis, And then they fight it out in the committee.
I see. Who was it on the committee on your behalf?
Nicholas hemmer, who succeeded Max Born as professor at Edinburgh later, I can remember, incidentally — explaining about my father's attitude — my father had so driven me into a corner, saying, "There is no point in your doing this research if you're not very good at it, then you should certainly come into the business," So we had decided (it shows that I had given in a bit) that if I got a fellowship to Trinity it would demonstrate that I had a capacity that would justify going on with research (because I explained to my father the significance of a fellowship at Trinity, which has a lot of prestige in England), and if I didn't get one, then I would give up research and go into the business. That was a very foolish thing to do, because of course you're competing not only with other mathematicians and physicists but with historians and all the rest of them, It's a very chancy business, who succeeds, But I had in fact made that commitment, and then the miracle happened and I succeeded.
By the way, what were your relations with Boyle at this time?
I knew him much more slightly. I remember goin to him once and telling him that I had a theory that overlapred with his interests, Things he'd written over the previous few years had influenced certain sections of my thesis, but I didn't know him personally as well as I knew Bondi and Gold.
Okay, now I have a few questions about those years when you were at Trinity. It interests me because Cambridge was really the only place that had what one might call a school of cosmology, or more than one cosmologist in one place. Where would people get together to discuss this sort of thing, or with whom did you get together to discuss these things?
Well, not with that many people, because at that time there was no Department of Applied Mathematics and Theoretical Physics that was later founded, and no Institute of Theoretical Astronomy that was later founded. There was the quartet, of which we haven't mentioned Ray Lyttleton, the fourth one, There was Bondi, Gold, Boyle, and Lyttleton, who were famous as a group who worked closely together and were very irreverent, overthrowing the establishment and all that kind of thing.
They were the clamor ingroup in this sense, They met a lot and talked together, But I was younger than them; although I talked a little bit marticularly to Tommy Gold, just him and me as it were, I wasn't one of that group because I was too junior. Simply the fact that they were pushing this kind of idea had its influence on me, I got friendly with a chap called Felix Pirani who was a student of Alfred Schild of Toronto, He came to Cambridge to do a second Ph.D., and we talked relativity together. But there were not many people then to talk to about these things, it wasn't like later times.
I see. There wasn't some pub or whatever where everyone would get together?
There was no everyone. There were one or two of us, I had fellow research students whom I was personally very friendly with, whom I beat over the head and told about Mach's Principle, but they would be mainly working in things like statistical mechanics and so on, because these were the colleagues who had shared my office when I had started in statistical mechanics.
I see, Were there any important seminars or journal clubs or anything like that, in which these sorts of things would be discussed?
Occasionally. There's a club called the Del Squared V Club, which you may have heard of.
Yes, I've heard of it from various people.
It's fairly important within Cambridge. It was as a matter of fact, I believe, historically the first group where Eddington reported the successful measurement of the bending of light at the eclipse of 1919, That met once every fortnight to discuss problems of various kinds and there were talks, I gave a talk once on Mach's Principle and so forth, Yes, there were opportunities to discuss, but there weren't the large numbers of people in the game that developed later.
I see. At this time you were one can't say you were in the physics group did you relate much with the physicists? That is, there were people there that were formally physicists and people there that were formally astronomers, and inbetween people, and I wondered about relations with the physicists and with the astronomers and between them?
Of course I had moved from being within the physics camp to being more concerned with these relativity matters. Through the meetings of the Del Squared V Club and there was another club called the Kapitza Club, which you may have heard of, which met alternatively when the Del Squared V didn't meet, It was named in honor of Kapitza and was supposed to be more on the experimental side, where Del Squared V was meant to be more, as its name implies, on the theoretical side. They met alternative weeks and many of the same people came to both. There were vigorous discussions, I'm not sure this is quite answering your question.
I think so. Would both the astronomers and physicists be there, and perhaps mathematicians?
When you say astronomers - I don't think the observational astronomers came much to those things, it was more the Hoyle and Bondi kind of astronomers who came.
What about the radio people, did they attend these things?
Not, I think, in large numbers, but I became conscious of them a little bit later, That's not completely true, It's another matter, the whole business of the relation between the radio astronomers and the theoretical astronomers in Cambridge is a very complicated subject which may or may not be interesting. A whole book has been written about it, which I'm sure you know well,*
Yes, I know it, You mentioned that you'd been interviewed by Woody Sullivan also about that, so I think we really won't need to get into the Ryle-Hoyle-etc. row.
But I did know about their existence, because I do remember in 1951 I attended a conference in London. Let me just mention this point about it, then perhaps we need not discuss it any more, but just to show that I was beginning to realize they existed already by 1951. If you remember, in 1951 the radio sources that had by then been discovered, the discrete ones, had not been identified optically. And Martin Ryle took the view very strongly that they were all objects in our own galaxy, and that it was their integrated effect that produced the galactic diffuse background, because the synchrotron theory had not come in yet.
And I remember - it's certainly on the record of the conference — both Hoyle and Gold suggesting that it was at least equally likely that many of these sources were extragalactic, the point being they were more or less iso- tropically distributed around us, so either they were very close and didn't delineate the shape of the galaxy, or very far, And there was no reason why they shouldn't be very far, I do remember Hoyle getting up and saying, "The theorists as usual have misunderstood the nature of the observational evidence; there is no doubt that they're in the galaxy."
And of course in 1954 Cygnus A was identified as an extragalactic object, it was all different, But that means I was aware both that there were radio astronomers getting interesting results, and a bit of incompatability and confrontation between them and the theoretical group already by 1951.
I wanted to talk a bit, then, about Steady State, I'm not sure what we should talk about first, There are two things which I guess would represent your first real jump into the Steady State with both feet; one is your model for the formation of galaxies, and the other is your paper with Bondi and Gold on the Stebbins-Whitford effect,**
I don't know which comes first chronologically.
The one that was published first, if I remember right, was the one on the Stebbins-Whitford effect.
Okay, let's talk about the Stebbins-Whitford effect, the problem of excess reddening. Was this a serious concern to you and Bondi and Gold, were you really concerned about it?
It was a matter of serious concern at the time, but it later turned out that the observers withdrew the effect. We were slightly
* D. Edge and M. Mulkay, ASTRONOMY TRANSFORMED (New York: Wiley, 1976)
** ASTROPHYSICAL JOURNAL 120 (1954) : 597.
annoyed that it was withdrawn in a very obscure place— namely, the progress report of the appropriate observatory; Whitford and Code withdrew it, tucked away there rather than blazing it forth - since it had been used so strongly as a weapon against the Steady State theory. We had a certain little discussion of the thing and tried to remove the sting of it when we thought it was a real effect, but obviously when it was withdrawn our little note became obsolete and of no interest. The main thing is, the effect went away.
But I'm curious about what happened, what sort of conversations did you have with people about it - was it very much a subject of concern, did you talk to people and say, you know, you can't really explain things that way, and so forth?
I think so, It is partly my nature to be a bit passionate, so once I decided I liked the Steady State theory, then even though we didn't know it was true — that was what we were discussing — I as it were wanted it to he true perhaps more than an ideal scientist would, I would get very worked up, particularly if the hostile evidence was rather weak, as at the time I believed it was, Later it mounted up, and we all recanted at different times at our own chosen moments as it were, But at that time the (counter) case was weak; it seemed to me too beautiful and desirable a theory to be defeated by weak arguments. So I would get a bit intense and argue eagerly and so forth.
Aside from the source count controversy, at this time, that is in the early 50's, was the Stebbins-Whitford effect the main argument that people came up with against Steady State?
It was really, yes, as far as I recall, Also there were statements by people like Baade that they, being great observational astronomers, knew the ages of galaxies, and all galaxies had the same age, whereas in the Steady State theory you'd expect a spread of ages. That was used as an argument against, which was of course pretty implausible just said like that, But the main argument, I think, at that period, was the Stebbins-Whitford effect, so we had to take it very seriously.
Were there particular sorts of people who would defend you or attack you on this, were there lines of division that you could see?
I often tried to correlate the psychology of people with whether they supported or decried the Stead State theory or were just neutral, I'm not sure I ever got very far doing that, I couldn't help thinking that on the whole the more imaginative people seemed to like the theory, not necessarily think it was true, but at least were sympathetic. Of course David Edge discusses in his book the attitudes of the Cambridge and Jodrell (Bank) radio astronomers, and as groups how they reacted to the theory.
That's still rather specific, Were there other particular places that seemed to be very much for or against the Steady State?
I can't recall, There were places; there were individuals who were snpathetic, like Roger Penrose, whom become very friendly with by then, and other people who never believed it for a moment, and of course in the end were quite right although not necessarily...
Not for the right reasons.
Well, they may or may not, I don't think that's an answerable question, quite honestly, I think many people quite rightly felt reluctant to change a basic law of physics just to have a nice beautiful largescale structure, And that instinct may have been correct, It's a difficult thing, No, I don't think there were specific places; there were probably groups, like Ryle's group, that weren't sympathetic. But why they weren't whether that was a personality thing because of the antipathy with Fred Hoyle rather than direct scientific feelings is a very complicated question. I don't think I know the answer to that.
Let's get on then to the modal for the formation of galaxies, I first note it in IAU Symposium#2 (1953) at Cambridge, and then it was published a couple of years later in 1955. How did you come to that? This is a very unique way of looking at something, that the structure of something should he determined simply by the fact that it's in a Steady State.
Yes, Incidentally, you're reminding me now that there was some thing published on it in 1953, That makes it earlier than our discussion of the Stebbins-Whitford effect, which was 1957.
Right these things were going on at the same time?
Yes, they were already going on, It was a question of when one felt that it was worth rublishing. Yes, the idea of the galaxy formation paper* was one of these nice ideas that turned out wrong simply because the whole theory is wrong.
It's a beautiful idea, I'm interested in where ideas came from; after all, the selection of which ones are correct may happen a hundred years later, The interesting thing is where it comes from.
Yes, I suppose it struck me that it was difficult to make galaxies in a universe that didn' t originally have them, And that remains true today; we still don't know how the galaxies formed, and it's a big problem, Bhereas clearly, any single galaxy in the Steady State theory would form in a universe full of them, so why not use the preexisting ones to perturb the intergalactic gas and do the job for you? Then when I played with that, I noticed there were signs that you could make a scheme whereby the Steady State condition alone was enough to determine all the properties of the system. I was quite pleased with that.
I see, so it flowed out of the work itself.
Yes. It wasn't the original idea; it emerged as the work went on.
How did this relate to your conviction that the Steady State theory was a good theory? Did it reinforce it, had you already believed it by that time?
*MONTHLY NOTICES R.A.S 115 (1955) : 3.
I see. What about Lyttleton, how did he fit into that?
Lyttleton really virtually didn't — with one exception later, when he wrote the paper with Bondi that was quite interesting in its way about the charge on the electron and protron not being quite equal — with that one excertion he didn't write on cosmology. But he joined with the others in writing on astrophysical topics. He was the original member of the whole group in astronomy; he got Hoyle into astronomy from theoretical physics through their friendship that occurred through their joint interest in cricket, So he was a key member of the quartet, but more in astrophysical matters than cosmological ones.
I see. Why was it that there were all these people at that one place interested in cosmology? As you describe it, in your own case you just happened to be interested in cosmology and happened to be there, and then all of these other people also.
Neil, Hoyle, Gold and Bondi met during the war working on radar. That doesn't quite answer your question, I think behind your question is something that I've always found mysterious, which is the way groups of people with certain kinds of talent join forces, or have a school in a place, Often it works in the arts, doesn't it, I mean the Renaissance in Italy, or Vienna at a certain period, had a terrific flowering of some kind of thing or a group of things, as would be true in Vienna, To me it's a mystery how that operates.
Nothing in the air at Cambridge, nothing particularly in the institutions there?
Well, there's a tradition in England for interest in cosmology. You see Eddington, who died in 1944 or at the latest in eaaly 1945, had worked in cosmology and relativity as well as astrophysics.
Was Eddington's shadow felt, so to speak?
I don't think so, not at least in the negative sense. Because from the early 50's on there began this fantastic development in astronomy which introduced so many new processes and concepts that were not known to Eddington, His successful work in earlier generations in this kind of imaginative field where relativity, astronomy and cosmology get all mixed up, that encouraged people to work on those things; but the actual texture of the ideas was different because of the fantastic developments that took place first through radio astronomy.
By the way, were you learning astronomy, formal astronomy, at all during this period?
I suppose once I got interested in the Steady State theory I started learning both astronomy and some of the pnysics that one needs to know, like atomic physics, studying the way eases behave in inter galactic space or something of that kind. But again it was mostly self taught, High-energy astrophysics was just being developed then, so there were no courses really.
So you learned from the Journals?
The Journals, and the books, and talking to people.
I suppose there were always people coming through and giving talks.
To some extent, although not as much as later when the Department and the Institute were set up.
Okay. Well, then in 1956 your fellowship was finished, and I have here a number of locations that you were at over the next few years. I'm not quite sure of all the things, In 1954-55 you were at the Institute for Advanced Study at Princeton, 1955-56 you were an Agassiz Fellow at Harvard (this is still while you had your fellowship).
Well yes, it's not very interesting, but since you asked me: the fellowship is for four years but they allowed you to take off two years in the middle, if they were consecutive years where they wouldn't pay you, and then you could take two more years at the end, So when I was in the States for two years at Princeton and Harvard I was not paid by Trinity. And when I came back they took me on again, so that in fact I stretched my time out to 1958.
I see, And is that when you went to King's College (London)?
Then I went to King's College, where by that time Bondi had been made professor of applied mathematics. He had a grant from the United States Air Force to do work on gravity, and I was one of the people he invited to spend a couple of years there, on his contract.
Why did he have a grant from the United States Air Force to study gravity? gas this ARPA?*
No, it was the U.S. Air Force. That period, if you cast your mind back — it was later all changed — but in the early days the Navy, the Army and the Air Force all supported fundamental research, some of which quite clearly had no bearing on defense, Their purpose being, I suppose, at the very least to keep scientists trained so that they could always be used for other purposes if necessary. Later on that practice rather tended to peter out, And they would even support work not in America.
That's very interesting. By the way, did you ever do any defense work?
No. Except I did of course at T.R.E.
Let's see, and then I have, in '60-61 professor at Cornell.
That was on Tommy Gold's invitation, sor at Cornell, * advanced research Projects Agency (Dept. of Defense).
I see. This was while you were still at king's College?
I had two years at King's, and then that was the end of that aprointment, I had at that stage deliberately not even sought a teaching post, because I wanted to spend all my time doing research. So when I was invited to Cornell I gladly accepted.
To do research, in fact?
To go on with research, yes.
By the way, in the meantime you married.
To Lidia Dina, in 1959. I noticed this latest paper that you sent me a copy of, you dedicated to your father-in-law.
Yes, He died last year.
I see. Tell me, a question I always ask people: what was your wife's backround education when you met? Did she have a separate career?
I met her in Jerusalem where she was studying English, She started studying at the University in Venice; she comes from Venice, and she started studying there, But she's also Jewish, and she moved to Israel and she continued her studies at the Hebrew University; she'd been there for two years when we met. Not long after we met we got married, and she came to join me in London where I still am at King's.
Has she had any separate career?
Yes, when we went to Cornell she did her Master's degree in English, and then later in Cambridge she started doing social anthropology, after the children. There was a gap with the children being born. When we moved to Oxford she did first a diploma and then a B.Litt., and now this year she is teaching at Mount Molyoke, where we've been for the year.
Tell me, how do you think that the fact that you're a scientist has affected your marriage, your children?
Well, my children are no good at science, but I don't think that's because I've put them off it exactly, it's just that they're no good at it. I think I'm one of those who rather works hard, rather dedicated to science, so that puts a strain on the family.
But no different from if you'd been a hard worker in business, or something like that?
I suprose not, Businessmen go away a lot just as scientists do, who visit to give lectures and so on.
Let's see, I suppose next you were a fellow at Peterhouse.
Oh, that was later. What happened at Cornell, I applied for a lectureship in mathematics in Cambridge. By then the Department of Applied Mathematics and Theoretical Physics had been set up. That's perhaps just a detail, but it meant that there was a departmental structure, so when this lectureship was advertised I applied for it, and I got it.
So in 1961 we moved back to Cambridge (my wife hadn't been there before), And it was about two years later that I got the fellowship at Peterhouse. That was not a teaching fellowship. I didn't want to do more teaching than my lecturing, and so I refused to be a teaching fellow, but after a couple of years Peterhouse offered me a non-teaching, a non-stipendiary, fellowship, That was of not special importance, the important thing was that I had a lectureship.
I see, And you taught what, physics, astronomy?
My main lectures were mathematics, Being in the math department, I had to teach dynamics and mathematical methods and so forth, for the Math Tripos in other words.
Okay, To get back to your scientific work then — In 1960, it's quite interesting, you said, 'Despite several recent attempts, it is still not possible to decide whether the Universe is in a steady state or whether it has evolved from a much denser configuration... Despite the great difficulties, the next decade promises to be an exciting one for observational cosmology — one in which the correct model of the universe may at last be determined,"* I'm interested, if you can cast your mind back to that time, did you expect, in fact, that it would be determined to be steady state? You were rather noncommittal (in print), where you very optimistic about cosmology at that period?
I was optimistic, but I think my position always was that the model was so attractive that I wished it were true, and I would fight to make it true as long as I didn't distort the evidence, but I had no feeling that it had to be true or that I knew that it was true, So i think being noncommittal in that statement was fair enourh,
Did you have a preference for Steady State? If you could design a universe, would you make it one way or another?
Oh, very much.
Would you make it steady state?
In fact I have some quotation in an article in the SCIENTIFIC AMERICAN, something about this beautiful model, the great architecture of the universe — I can't remember now — but anyway some crack as though God had bungled things. Partly, I think, because it's the only model in which it seems evident that life will continue somewhere, On the conventional view, if the universe recollapses we'll all get crushed, and if it expands forever, then everything dies out when all the fuel is spent, So life is a very transitory thing, whereas on the Steady State theory, even if our galaxy ages and dies out, there will always be new, young galaxies where life will presumably develop.
* "Observational Aspects of Cosmology," VISTAS IN ASTRONOMY 3 (1960 : 311)
And therefore the torch keeps being carried forward, I think that was probably the most important item for me.
Do you think this played a role in the thinking of other people also?
I think it must have done.
You would have discussed these things with Bondi, Gold, whatever?
Oh yes. And also my colleagues working in other subjects; we would obviously discuss each others' work and views. It wasn't only that; also, the general beauty of having a Steady State was rather attractive. But if you ask me for the one single thing that dominated, it was probably that life would always exist some way.
That's very interesting. I used to be a fan of Steady State myself.
I suspected it from the way you were asking me questions.
Tell me now about this other thing, about how rapidly the correct model of the universe may be determined. How has your thinking changed? In 1960 you wrote that there was a chance that in the next decade it would be determined, and I wondered how your thinking has evolved, about how possible it is to come up with a correct model, What would you say now about the next decade?
Well, as between Steady State and Big Bang, I was right, although I'm not claiming anything for that, If you now mean between the different Big Bang models in particular we still don't know whether the universe will recollapse or will expand forever
Yes, I particularly mean that.
I think that there is a good chance we'll resolve that proolem in the next ten years, partly through the Space Telescope.
Do you have any preference for that?
Sometimes I've had a preference for the universe that just expands forever with the velocity tending to zero, the Einstein-de Sitter model, I once hoped, but that hope has not been realized in our work up to date, that Mach's Principle would lead to the unique model of the Universe, and then the hone was that it would be the one I've just described, But the work we've done so far has shown that all these highly symmetrical models, the Robertson-Walker models, seem to be Machian. Which may be a weakness of our Mach Princinle still.
I see. There's a hope that can be determined by these general considerations?
Oh no, let it be determined observationally by all means, And I would perhaps hope it would be, You see, if you take these Newtonian analogues of Milne and McCrea, the Einstein-de Sitter model is the one where the total energy of the universe is zero, the kinetic energy and the negative gravitational potential energy just balancing. Well, if you think that kinetic energy manifesting inertia is due to gravitation, then you might intuit that the most Machian way of having one made by the other would be if there's equal amount of energy, which would give you uniquely the Einstein-de Sitter model, I still have a secret hope that that might turn out so, but it may well not.
Aside from these general things, in terms of whether you would prefer, for example, a universe that oscillates, that bounces and starts over again?
There's no bounce; this is a misrepresentation in some of the earlier books and so on, Because of the singularity theorems, which had not been proved at the earlier times we were talking about, but that we now know to be so, if you take the existing theory, there is no bounce. If the Universe recollapses into a singularity, the theory breaks down at that point. Modern work would say that by quantizing gravity one might eliminate the singularity, but one doesn't know whether that is so or not, Perhaps we'll talk later about modern work on black hole dynamics, but at any rate quantum gravity may well play a role in removing the singularity. But in the best theory we have to date, there is no bounce.
But there might be.
There might be; there might be a bounce in nature, and there might be a bounce in our next theory.
But in terms of whether you would prefer to live in a Universe that reconstitutes itself, or not?
You mean because there might be life in each cycle or something?
Or something like that.
I think I would need to know the theory a bit better. Because even with a bounce you'd think that the entropy made each time survives till the next bounce, say the entropy in starlight. So each bounce is a little bit different from the previous one. You see, in the old days some people said, it's a kind of Steady State theory to have an oscillating universe; if each bounce is identical to the previous one, then in a certain global sense you've got a steady state, But if the Second Law of Thermodynamics works the conventional way we think it does, then after each bounce there's a bit more radiation present because of all the extra starlight made in that oscillation.
So the character of the universe does change from bounce to bounce, and no doubt eventually gets so hot that life is not possible or something. I think perhaps on the grounds of a possible link with Mach's Principle I would prefer a Universe that only just expands forever, but the present evidence is rather against that, the denterium and so forth.
Let me pause, by the way, to ask about the time. (Short pause) Let's try and go through some of these earlier things fairly quickly. I did want to ask you about advanced and retarded potentials and Maxwell theory, you did some work on that and I found it quite interesting. Did you approach this also as means of checking on Steady State, was it very much tied in with Steady State ideas?
At that time already it bad been suggested by other people that the Steady State theory seemed to be the one that fitted a full discussion of advanced and retarded potentials. This was the work of (J.E.) Hogarth. And to some extent of Boyle and Narlikar, although I can't quite remember whether their work came after mine, But Bogarth certainly was before me, So I looked into it from a particular technical point of view, using the Kirchoff integral representation. I think I came to the conclusion that it didn't particularly support the Steady State theory.
That's right. You came up with the conclusion that it would work within the Steady State theory but that it could also work within a Big Bang.
Yes, I felt that other people working on the problem had not paid sufficient attention to the role of the surface integral in the discussion.
I see, But you were not so committed to Steady State that you felt that this was a pity or whatever?
I can't remember whether I thought it was a pity or not, but I suppose I wasn't prerared to fudge the discussion.
I think the next important story is getting on to your business with flees about the quasars. This is what you were referring to earlier?
No, I really meant that some of the work that some of my students did, I think, is the most important work I've had any relation to; they essentially did it, but perhaps they wouldn't have done it if they hadn't actually been my students. The particular work with Rees on the quasar distribution was the piece of work that in point of fact made me drop the Steady State theory, so it has a personal interest for me, but perhaps not for anyone else.
I'm not sure who your students were, That's not easy for me to find out by looking through your papers, so maybe you should tell me which particular pieces of work you mean.
I was thinking of Stephen Hawking and Brandon Carter and Martin Rees, primarily, and George Ellis, who did some of his work with Stephen Hawking, I had quite a number of other research students who have done significant work, and their total accumulated effort is very considerable in the general area of relativistic astrophysics. But the most brilliant work was done by the ones I've mentioned.
Let's get to them, But first I do want to ask about this business with Rees, Of course, in 1963 you had challenged Ryle's conclusion from the source counts; we won't get into that in detail, but you had suggested that there were local effects, Then in early 1966 you tried to extend this to quasars and also you used it against the microwave background, A lot of things were coming along at this time, and you already wrote that "the demonstration that the microwave background consists of black body radiation ... would almost certainly enable the steady-state model to be ruled out."
And if your rather risky model for the distribution of local quasars, I'm quoting, "falls," you said, "it looks as though the steadystate theory of the universe falls with it ." So it appears from the published papers that even before you and Rees did the redshift intensity plot for quasars, you must have been feeling that the Steady State theory was getting hard to defend because of the microwave background?
That's certainly true, yes. It was getting a bit shaky, but I wasn't prepared to abandon it at that stage, because the blackbody character hadn't been sufficiently well established at that time and one could find these slightly artificial models of the discrete population of radio sources, Although slightly artificial, I felt the price wasn't too high for the virtues of the Steady State theory, as judged at that time.
But it was getting perhaps more and more ad hoc.
Oh yes. I was preparing my mind for the trauma that came along. When I'd looked at the distribution of quasars a bit and the local population and all that business, then I started plotting out this redshift distribution, At first, as a matter of fact, I thought it was coming out to favor the Steady State prediction. But Martin Rees, to whom I showed these data, gave them a critical look and said be thought it was coming out the other way, hostile, So we did some more on it together, and it seemed quite clear that he was right and it was hostile, We were the first, in fact, to publish analysis of the kind that Maerten Schmidt in particular did later, with much more detail, much better data, But we were the first to point out that this distribution was hostile to the Steady States theory.
I see, So what Rees did was not so much to suggest a different way of looking at the data as saying, come back and look at it again,
In effect, I was plotting it out in a certain way and it looked good to me in terms of the theoretical prediction of Steady State, That's no doubt an example of the mind wanting a certain result, And while he had worked with me on other aspects of Steady State a little bit at that time, he had no particularly great investment of emotion in the matter, Looking at the plot I was making, he felt that I hadn't made a good story of it and that in fact if you looked at the plot the right way, the argument went the opposite. Then we looked at it more closely together and found that he was right.
You said "trauma"; did this in fact cause you much dismay?
Yes, I had a bad month.
Worrying over it?
Oh yes, feeling very upset not I think because I had been shown to be wrong, because I never said I thought the theory was right, there was no grounds for thinking it was right, as it were, if you see what I mean; it was rather that one would like it to be right for these other reasons, I was upset that it wasn't right.
You were upset that we were not looking at a Steady State Universe?
*NATURE 211 (1966) : 277; 210: 351.
I see, So then of course you came out publicly very definitely against Steady State, I'm curious as to what effect this may have had on your relations with Hoyle, Bondi, Gold, Surbidge and so forth?
Oh, none particularly.
Because they were more or less still...
Well, Hoyle was complicated because he first recanted before I did and then unrecanted his recantation, so the details were a bit complicated. But it certainly didn't affect my relationship. We may have had arguments, of course, of various kinds according to the way our views were going, but it didn't make any problems.
There's one other thing that may have played a role here, I'm not certain about the chronology at the time, but you published the redshift flux density thing in the September NATURE and in the August one you and Rees published a paper on the inverse Compton effect in quasars, showing that quasars could be at cosmological distances, which was contrary to the results of Hoyle, Burbidge and Sargent, who had thought the inverse Compton effect losses might rule out quasars at great distances.* I wondered if this particular wrinkle might have layed some role in your thinking at that point?
I think the point was that one had to take a view as to where the quasars were, because if you thought the quasars were local, you could also get out of the radio source count, You could say the radio source count (slope) being steep might be due to quasars, and if the quasars were local then the steepness was not cosmological.
But I was rather reluctant; that is, one of my earlier models had said that there might be a class of quasars that is local but one whose redshifts hadn't been measured; I never wanted to say that if a quasar had a large redshift it was still local.
I see, That's a little difficult to take.
Yes, We know that Hoyle and Burbidge tried that for many years, but to me that was pushing too hard to keep the Steady State theory. So I never took that view. The inverse Compton discussion related to questions of how distant the quasars were, and I think our analysis showed that you could have the quasars at a cosmological distance, I somehow wanted that to be so; otherwise it was just too much of a good thing.
Okay, now, you mentioned Martin Rees as a student, and I wondered what other things you might want to say about him as a student and also the other students that you had at Cambridge.
I suppose my most brilliant student in astrophysics was Martin Bees, and in relativity were Stephen Hawking and Brandon Carter and George Ellis.
*NATURE 211 (1966) : 805, 1283.
Were they also at —
They were all at Cambridge.
I see. What was the order? Rees was first?
No, George Ellis was in fact the first research student I ever had.
I see, How did that come about?
When I took up my lectureship he'd already been accepted as a research student by the system; I wasn't there to play a part in this issue. He wanted to work on relativity, so he worked with me. He got to know Hawking when Hawking became a student of mine, and then they published this wonderful book together, THE LARGE SCALE STRUCTURE OF THE UNIVERSE.
Tell me a little more about that, How did they come to these problems? I'm particularly interested in Hawking and this whole business. I don't know myself, because I'm not close to these things, but everyone seems to feel that Hawking's results have been extremely important. Tell me about Hawking.
Well, Hawking was a special case also because of his physical disability, which was only beginning to show itself at the time that he came to me.
So it was quite a normal relationship at that point.
He knew that he had a degenerative disease, but we didn't know what the prognoses would be, and I'm afraid it just did get worse and worse pretty steadily. It became evident by his third year that he was exceptionally able, What he did then was to take a piece of work of Roger Penrose, who's another very able relativist, who proved the first singularity theorem for collapsing stars in 1965, and Stephen Hawking for the last chapter of his thesis adapted those methods to the case of the whole universe, But it wasn't a straightforward adaptation; he also contributed a lot of his own.
Yes, it's quite a difficult problem.
I wonder, what role did you play in this?
I encouraged him, I was a close personal friend of Roger Penrose and therefore I knew about his work, I can't remember whether Stephen first saw it from a lecture or a paper or my telling him, But at any rate, all my contribution really was, was to create the ambience at Cambridge that these problems were discussed, But hawking decided to adapt the discussion to cosmology and I encouraged him, but it was all his own work.
I was impressed, and still am impressed, by this way of thinking about the universe, this dealing with metrics on a large scale and so forth. How natural do you think it was at that time, was this a new this entire way of looking at things?
Well, it was natural to Roger Penrose, because he was a pure mathematician by training. He did a thesis on algebraic geometry under Bill Hodge at Cambridge, and when we got friendly personally, my interests in relativity infected him a bit and he came over to do relativity.
But then this extension to cosmology also?
I was going to add, in Hawking's case he only discovered that he was gifted at topology in the process of working on these ideas. Then he found that he could do them with relative facility. So a lot of his work after that became global generalizing.
I see, simply because that was a talent of his?
And the problems were important.
Right. And then of course the other development which is connected is the bringing in of quantum theory and thermodynamics.
That came much later.
Yes, but perhaps you can tell me how that all came in. I can't ask Hawking.
Well, first of all there was work on black boles. His first major work was a variety of singularity theorems which he continued doing after his thesis, And then he started getting interested in black holes and producing very good black hole theorems. We're now talking about the very early '70's. And there was floating around the idea that thermodynamics had to do with black holes, although Hawking himself was a bit skeptical.
I see. This was a problem people were talking about?
Well, in 1973 Bekenstein suggested that you could call the surface gravity of a black hole its temperature, and the area of its horizon its entropy. Hawking at that time thought this was going much too far, because there were certain analogies to thermodynamic behavior, but they were very limited, One thing a black hole couldn't do was to radiate, so it couldn't get into equilibrium with black body radiation that had the same temperature as the alleged temperature of the black hole, So I remember him being rather skeptical of Bekenstein's suggestion, for good reason of course; although in the end it turned out differently, at the time he was right, you see, Then I remember him saying one day that he was going to look at the connection between quantum theory and gravity.
It just came to him that this would be an interesting problem?
People had tried to do this before, and he'd never gone into that before.
You say between quantum theory and gravity, not specificaily black holes at that time?
I can't remember at what point he said, let's apply it to a black hole, But since a black hole shows such extreme general relativity behavior, as it were, it would not be an unnatural place to start looking. Given that so much work on black holes had been done, particularly at Cambridge and particularly by him and other colleagues like Brandon Carter, who had obtained a very important result on the uniqueness theorem for rotating black holes.
We were full of black holes, whereas early people who had combined quantum theory and gravity that was all done before the great explosion of interest in black holes. I can remember when I first heard of his results, I visited Cambridge once and I met Martin Rees and he was so agitated; he said, "Have you heard, have you heard what Stephen's discovered, it changes everything."
And that was the radiating black hole, This showed, you see, against what he criticized Bekenstein for before, that in fact the surface gravity really was the temperature, because a black hole does radiate and can get into equilibrium with black body radiation, That's a work of genius, in my opinion, that discovery.
It's one of those things that one can even understand; even someone who doesn't go through all the mathematics can physically see it, Does Hawking have a sort of physical intuition? Does he physically see his way to it or does it come out of the mathematics?
I think both, I think he has a very deep understanding of physics and he has a powerful mathematical technique as well.
And in this case the results surprised him, so to speak?
Yes, It's a result that no one else could believe at first, it looked so outrageous. And on the whole those of us who couldn't of course instantly master the technique because it involves quantum field theory and so on, a very specialized business - on the whole we were prepared to believe it I think just because the answer was so thermodynamic, Because at least some of us, including Einstein incidentally, had great faith in the universal power of thermodynamics.
Oh, you were going to tell me about your last conversation with Einstein.
Well, the only one I had with him took place at the end of my year at the Princeton Institute, April 1955, I wanted to see him of course, and I plucked up courage only at the end of the year to go and see him, It was literally a week before he died, and I was with him for over an hour and a half, That was a great experience for me.
What did you talk about?
I started out a bit nervous of course. I'd read that he had a hearty laugh and a simple sense of humor, so I thought I' d start out in the following way. Originally, of course, the very phrase Mach's Principle was Einstein's own phrase for that idea, And he'd used the principle as the guiding light for constructing general relativity, But he later came to feel that the principle wasn't so important, and in the autobiographical notes which he wrote for that Schilpp volume* he had said that he came to disown Mach's Principle.
So knowing that, I went to see him and I said, "Professor Einstein, I've come to talk about Mach's PrincipIce and I've come to defend your former self * ALBERT EINSTEIN, PHILOSOPHER-SCIENTIST, Paul Schilpp, ed. (Evanston, Ill. : Library of Living Philosophers, 1949).
against your later self." And it worked: he said, "Ho, ho, ho, that is gut, Ja!" Like that, really laughed. So that put me a bit at my ease, So then I talked about my way of doing Mach's Principle and he talked about his work and his doubts about quantum theory and so on, It was a wonderful experience.
Tell me now about going to Oxford. How did you come to go to Oxford, and what did you find there? I don't know much about astronomy at Oxford in this period and I'm quite curious.
Well, there wasn't very much theoretical astronomy there, The reason I did (go) was that I had a heavy lecturing load in Cambridge and a lot of research students by then. I had about nine or ten, I found that load was very heavy. So when All Souls College advertised a senior research fellowship including mathematics in the subjects that you could do - not believing I would succeed, because they had no tradition in science at All Souls, they had one scientist at that time as part of a fellowship of 65 — still they included mathematics in the list of subjects, so on the off chance I applied. Because there were no duties at All Souls at all, you just do what you like, I mean you have to be in Oxford, but you don't have any teaching duties, So I did apply and I was successful, So I moved to Oxford in 1970.
And what was the scene there for theoretical astronomy?
There was a reader in the theoretical physics department, Dickter Haar, who had one or two students at the time. That was the only activity. But I made a deal with the professor of astrophysics, who wanted a theoretical group in his department but the university had never given him the funds for a post. So when I said I would build him up a theoretical group of the kind I used to have in Cambridge, he was quite pleased that that should be. That was nothing to do with All Souls as it were, I joined the astrophysics department.
Who was that by the way?
Donald Blackwell; he is still the professor now, We got money from the Radcliffe Trust to put a small building up, a wooden hut (it is quite comfortable actually) on the lawn in front of the main building, and that's where my theoretical group worked.
Students, and I have post-doc and senior visitors. And also Roger Penrose, a little after I moved to Oxford, got the chair that E.A. Milne had originally, and he has a relativity group at the Mathematical institute, which we have close contact with.
So you have considerable relationships with the mathematicians?
And also ter Haar has built up his group in theoretical physics, and we have rood relations with them too.
I see, What are the feelings amongst all these people, specifically about cosmologists? I think one could fairly say that you're a cosmologist; I wonder how people feel about that as a specialism?
which people do you mean?
The physicists, the mathematicians, and particularly other astronomers that you meet.
I think that with the recent observational developments of quasars and the three-degree black body background, cosmology is taken much more seriously now than it used to be, Also, my work is as much relativity as cosmology, and I've done some work on black holes myself and their thermodynamics. And that development is exciting to physicists as well as to astronomers, and so the fact that I do that kind of thing you see, you're right to ask, in the sense that when I was originally doing cosmology, it was considered not a respectable part of physics, and therefore one was a bit liable to be disregarded or written off on that account. That's much less true today, for the reasons I just mentioned about the observational developments, but also the black hole work has physicists' respect. So if one is associated with working in that field, one isn't any longer considered as very much on the sidelines.
I see, Do you feel that the fact that during your early career you were particularly in cosmology had an effect on your career?
Not I think on my career, because I got positions of the kinds I wanted, I got a lectureship in math at Cambridge, and then I got a senior research fellowship at All Souls - I don't know how much you know about All Souls, but in England it has a very particular prestige. And the fact that I was one of the few scientists there (there are only one or two of us) in a sense is a prestigious thing. So although on one hand my being a cosmologist must have made many people feel I was very much on the sidelines if not an actual crank, on the other hand I can't say it had any bad effect on my career at all.
This was simply a feeling that you had from talking to people perhaps?
Oh, I certainly did in the early years, yes, (A) being a cosmologist, and (B) supporting Steady State. Because as I explained, there were a variety of reactions to Steady State, but for many people, it wasn't respectable to suppose matter could be continuously created. On top of cosmology anyway not being respectable. So things have changed since those early days.
I just had one other question. you've written a number of popular articles, SCENTITIC AMERICAN and COMMENTARY, and you did a book, THE UNITY OF THE UNIVERSE*, popularizing, and I wondered why you did this sort of thing?
Well, I think it's very important to do it, The community as it were pays a few of its members to study these problems, the results of which are of consequence for all people. If I don't sound too grandiose, I think my way of looking at it is the following.
None of us can understand why there's a Universe at all, why anything should exist; that's the ultimate question. But while we cannot answer that question, we can at least make progress with the next simpler one, of what the Universe as a whole is like. Everybody must care about that one way or another, more or less, A few of us devote our time to find out, supported financially and spiritually by the whole community. *
Garden City, N.Y. : Doubleday, 1959. results of our findings or our musings. And therefore one ought to give popular lectures, ite articles and books of a popular kind, as one's return to the community.
How do your colleagues feel about this? Do you feel that many astronomers support you?
On the whole, yes. There was a time when writing popular books was looked at with disdain; I don't think that's so true today.
How do your colleagues feel about this? Do you feel that many astronomers support you?
I wouldn't like to say when the climate changed. Of course, it depends a bit on how much one does of that compared to how much technical work one does. One has to get the balance right. If you do nothing but write popular articles, you will be suspected of trying to make money. But if you do technical work and discharge your responsibilities that way, that's now quite acceptable. The particle physicists have discovered that they ought to do it.
Do you feel there's a connection between this sort of thing and fundraising?
Indeed, If you want to be cynical, you can say you should do it for fundraising purposes. Obviously that's an element in it, that I wouldn't deny for a moment, but I really take seriously this feeling i have that we owe it to the community to tell them our results. And they're interested in the results, as you can see by the fact that good popular books sell well, good popular talks are usually packed out, I've had these Luce lectures in Mount Holyoke and we've had three or four hundred people coming essentially every week for eight weeks.
Do you feel that there's been a change in the attitude towards these things?
No, I wouldn't say that, I think there's always been, I remember a remark that G.M. Hardy made in his "Mathematician's Apology," when he went to a British Association meeting in Leeds in the '20's, and there was a talk on textile science to which ten people came; there was a talk by Eddington on the origin of the Universe that 500 people went to. No, I think the public have always been interested. There's always been people, as Eddington and Jeans in their time, who believed it was important to popularize, It's just that I would feel that in very recent years it's become more widely recognized that it's a very respectable and worthy thing to do.
I want to switch to one other topic, you're in a very good position to comment, if you would, on the differences between the British and the American astronomical communities, because you've spent a lot of time back and forth in both of them, I wondered what differences you notice?
I think the main difference is that for some curious reason (a point we did touch on earlier) the British have a tradition of taking very seriously this rather speculative work that I have admittedly spent most of my own life in. There aren't that many cosmologists in America, I'm not saying there aren't any, but somehow England is more strongly associated with that despite its small size, Certainly in the way of really innovative ideas, both in relativity and in cosmology, I would say we have a particularly strong tradition, In straight astrophysics, this country (USA) is very fine, and in the lead, We're also quite good in England but I wouldn't make the same remark. It's specifically in the more speculative parts that we have (a lead), which is curious in a way, because we have a great tradition for being empirical and pragmatic as well.
Surposedly, yes. Is there anything in the structure or the way the departments are set up?
I think myself that one element in it is the system of junior research fellowships at colleges, particularly at Oxford and Cambridge. You see, these colleges are financially independent. It 's not like the colleges of Harvard or Yale, which are not financially independent. There are alternative sources of funding for bright young people; you don't only go to the Science Research Council, our equivalent to the NSF, where if they don't like your project because it's a bit way-out you've had it.
There might be ten or fifteen colleges you can apply to, all looking for brilliant, exceptional young people even if they're a bit wild sometimes, and who will back a hunch. Over the years there's been a tradition that this exists, That must be important, because that encourages young people to work in these fields, because they know that they have more chance of getting a fellowship perhaps if they do something brilliant, even if it's a bit off-beat, than something very much in the center but a bit dull.
That's very interesting. That applies to a certain extent to yourself, in a way.
I suppose it does, yes. And I think Britain's remarkable standing in the world of science, given its size, is due partly to this, in general; that' s apart from specific concentration on things like cosmology. The cosmology strength is one aspect of that more general thing. I don't think it can be only that, but I suspect that may have a lot to do with it.
That's very interesting. That's an argument that I haven't encountered before which certainly makes sense, Well, I've run through my questions. I want to thank you very much.