William McCrea

Smith:

I know you were born in 1904, but I'm afraid I don't know much else about your family. Who were your parents? What did they do?

McCrea:

My father was a schoolmaster all his life. He was a schoolmaster when I was born. He came from the County Cork in Ireland. His father was a son of the manse in Donegal but he had run away in his early years and settled in the extreme southwest of Ireland. My father was born there. He was living in Dublin when I was born. My mother came from Dublin, from Blackrock; her family was well settled in that part of Ireland.

Smith:

Did you have any brothers and sisters?

McCrea:

Yes. I was the eldest of four. After me there was a brother who became a distinguished surgeon. He died a few years ago. And I had one sister after that who died in middle life. But I have another sister still living. She had been a head mistress of various schools for young children, and is now retired.

Smith:

Were you the oldest?

McCrea:

Yes.

Smith:

What sort of preparation do you think your early home life gave you for a scientific career? Did you find it a very stimulating environment?

McCrea:

I think my father had a remarkable intellect. He took an external degree at the University of London in chemistry. He took it under some degree of difficulty; and it wasn't all that distinguished a degree, but it was an honors degree. He taught chemistry. Afterwards he taught botany as well. He had a very scientific outlook, and encouraged us to take an interest in natural history and in science generally. He had a remarkable instinct for things that were significant, and books that were significant, and people who were leaders in their fields. He didn't read a vast amount, didn't have time for that, but he managed to get the gist of anything very quickly, and he could digest it remarkably well.

Smith:

Did your father have very much formal education, or was he mainly self-taught? You say he took this external degree. What sort of education had he had before that?

McCrea:

I think you'd call it normal. He was at a small grammar school in the southwest of Ireland, where I think he was very well taught. These schools weren't all grammar schools, like those in England; some were private foundations. He had wanted originally to be a doctor, and in those days in Ireland it was possible for a man to be apprenticed to a doctor in practice, and at a certain stage I suppose he would go to a medical school, but my father didn't pursue that beyond a certain stage, and then switched over. He must have had some qualifications at that stage, because he was taken on as a schoolmaster. He taught at a school in Dublin, St. Andrew's College, and then he proceeded to work for a London external degree.

Smith:

What sort of formal education did your mother have?

McCrea:

Orthodox, I think, for a young lady living in that part of Dublin in those days. I don't know her school, but it would be privately run.

Smith:

Did she stay at home or did she pursue a career?

McCrea:

Oh, I think she did some teaching herself before she got married. After she got married, she stayed at home, because she had a fairly large family.

Smith:

We're interested in what effects social and financial position can have on the future scientist. Do you think in some ways your family's position might have given you an advantage in becoming a scientist?

McCrea:

I think it was just the encouragement they gave me, and my father's scientific cast of mind, and the fact that my mother was very willing and eager to encourage me. She taught me at home until I was practically eight. Then, at first I had a rather unorthodox schooling myself.

Smith:

I noticed you'd been educated at Chesterfield Grammar School. When did the family move to Chesterfield?

McCrea:

From Dublin we had moved to Kent, where my father taught in a school for about a year, and then he was appointed to teach in a school outside Chesterfield, and we moved there when I was coming on for three. My parents lived there the rest of their lives. The Chesterfield school was very good. It was the school of Erasmus Darwin. It was also the school of Sir Robert Robinson, the chemist, whom I didn't know much about those days; but in after years, I used to sit on committees and things with him.

Smith:

What age did you enter the grammar school?

McCrea:

I suppose I was eleven. I subsequently went to Cambridge.

Smith:

What did you do between 8 and 11? You say your mother taught you until you were about 8.

McCrea:

Round about the age of 6 — I was sent to a dame school for a bit, and then my parents decided I was going backwards instead of forwards, so they took me home again. Then, from about 8 to about 11, I went to a local elementary school. It was very good, as I remember. I must have learned something there, I suppose.

Smith:

During your time at the grammar school, were there any teachers that had a particularly strong influence on you or any books that you read at school that had a very strong influence on you?

McCrea:

I wouldn't say so, to any marked degree. I was at school at an unfortunate time, in many ways, because 1916 was when I went. That was right in the middle of the First War, and all the regular masters were away fighting, and there was a very temporary sort of miscellaneous staff, as I suppose there was in most English schools at that time. They did their best and did noble work. But they were not outstanding. And of course, it took some time for staffing to pick up after the war. When my headmaster realized that I was set on trying for a Cambridge scholarship, having, I suppose, to find a mathematician anyhow, he evidently picked one that he thought would help me towards a scholarship. He was a man called T. Bradbury, who, I think had a distinguished career at Cambridge, and he certainly did very well for me for about one term before I took the scholarship. But the poor man must have had an illness, and he died just within weeks of my getting the Cambridge scholarship.

Smith:

What influenced you to try and get the Cambridge scholarship? What were the factors that made you decide that you wanted to go to Cambridge?

McCrea:

For as long as I can remember, I wanted to be a mathematician. When I was a very small boy, about seven or eight, I remember going around telling people that I was going to be a professor of mathematics. My father took me aside and said that it might be a little bit more modest just to say I wanted to be a mathematician. Actually I've always thought that being a mathematician is really one higher than being a professor of mathematics. But anyhow, although I don't suppose I was very single-minded about it all my youth, I kept coming back to the idea that I would do mathematics. I suppose I never seriously thought of doing anything else.

Smith:

Your father didn't try to steer you off in other directions?

McCrea:

Oh no. I thought maybe, since he was a chemist, I ought to try to be a chemist. But I couldn't ever be a chemist, because I hadn't the sort of memory that would work in chemistry.

Smith:

Why did you decide on Cambridge? Did you think that was the place mathematicians went to?

McCrea:

Yes.

Smith:

And Trinity College in particular?

McCrea:

Yes.

Smith:

How were you supported during your undergraduate days? You had an open scholarship?

McCrea:

Yes. I got an open scholarship at Trinity which was very fortunate, and I had a county award as well, and these two kept me going. Also after I'd been in Cambridge for a few months, I got a senior scholarship. In those days, there was a special examination for them in one's first Lent term. That scholarship was a bit more valuable than the open scholarship.

Smith:

Were there any undergraduate teachers who especially influenced you? Anybody you especially were impressed by?

McCrea:

I think lecturers in my time were mostly very bad. I don't think I was the only one who thought so, because I have compared notes, in recent years, with my contemporaries, and they agreed, that they were pretty poor, in delivery, and in general presentation. I suppose the man who stands out most in my memory is E. A. Milne. I didn't have very much to do with him as an undergraduate, but I did get to know him a little, and I went to some of his lectures. Then he kindly continued to take an interest in me afterwards, and we ultimately collaborated from time to time.

Smith:

Were there any books that you read during your undergraduate career that were especially influential?

McCrea:

There were books that I used for my undergraduate course work, books by Jeans, and a pure mathematics book by de la Valle Poussin, and one or two books by Birtwistle.

Smith:

Did you ever do any laboratory courses? Or was that out for mathematicians at that stage? I remember reading that Jeans and Eddington had both done lab courses, going to the Cavendish Laboratories for a short time?

McCrea:

This wasn't fashionable in my time. I did no experimental work after leaving school. I'm not proud of it, but there you are.

Smith:

Did you think at the time that the instruction you were getting at Cambridge was up-to-date, right at the frontiers of mathematics? Were you for example being taught about relativity and quantum theory as an undergraduate?

McCrea:

We didn't do things that were right up-to-date, from the start. In those days, however, third year lectures and reading were devoted to work for Schedule B (now called Part 3), and so far as I remember, that was pretty up-to-date. But the ordinary work for Part 2^[1] was fairly routine. I suppose it was all right; it was the groundwork a mathematician really has to have if he's going on.

Smith:

Were there any of your fellow students whom you particularly remember, maybe worked with? Was taking mathematics at Cambridge very much an individual activity or were there groups where you'd discuss problems?

McCrea:

We worked entirely on our own, I would say. We didn't discuss things very much as undergraduates. Occasionally someone would come along and ask me if I could do a certain problem and I'd see if I could help him. But that was about all until we became research students and undergraduate course then I suppose we discussed things a bit more. But there was much less discussion than there is now, I think. There was a Trinity Mathematical Society. We went to that. But the speakers were mostly dons, not ourselves. I never gave a paper. You asked about people in my year or thereabouts. It was a good time. Neville Mott^[2] took the tripos the same year as I did. And R. O. Redman, subsequently Professor of Astrophysics and J. A. Gaunt, was another exact contemporary and he was my greatest friend in Cambridge, but he died in Hong Kong during the war. E. L. Edge who was professor in Edinburgh until recently, was an exact contemporary. I see him from time to time. There was a man H. D. Ursell, who took the tripos with me, and we all supposed he was the top. There was a man Brunyate a very brilliant lawyer. A. H. Wilson, he was an exact contemporary, too. So it was a very good time. In 1963, which was 40 years after we went up, some contemporaries arranged a little dinner in Cambridge for about 20 — of us and all except myself were heads of houses. That's a bit of an exaggeration, but they all were something like that. It was a very good time all around, yes.

Smith:

Did you have much free time to pursue studies of your own when you were at Cambridge? If there was a mathematical problem you were interested in which was outside the lecture work would you pursue that?

McCrea:

Oh, to some extent. I think, looking back, that we seemed to have more time than the students I see around today. These present students seem never to have time to think of anything except their more or less set work, and it's very hard to interest them in anything else very much, so far as I can see. I think Cambridge is maybe a little bit different even still. In our time, there was a tradition of working hard. Working hard meant working about six hours a day, including lectures, for six days a week. That meant about two hour lectures and about four hours reading and writing, and that left quite a lot of time for thinking, reading or talking, and games and so on. I took full advantage of it.

Smith:

What areas outside of science interested you specially?

McCrea:

I hesitate to say it yet I did have an interest in philosophy. I went to some lectures by McTaggart and by Bertrand Russell and I finished on the Council of the Royal Institute of Philosophy for a good many years after the last war. So I can claim some interest in the subject but it was never deep. I was mostly very skeptical.

Smith:

Did you have any strong philosophical influence at that time?

McCrea:

No, I think all the time, I was wondering what it was all about.

Smith:

I wonder what point you decided that you wanted to pursue a career of research — had that always been the fixed aim?

McCrea:

Yes, I would say so. I don't think a young man looks very hard ahead. I wanted to do research. I should have liked, I thought to get a fellowship in Cambridge, and make a career there, and I thought at that time I might enter the church. But I didn't get a fellowship, though I got other things like an Isaac Newton Studentship and so on. However, I was glad that I was cast out into the wilds, after some years. But yes, I think that I never seriously wanted to drop scientific work.

Smith:

Was there any time when you felt particularly strongly that you'd like to enter the church?

McCrea:

Oh, I think so. But I didn't take practical steps. There are an awful lot of influences, of course, at that stage. And by the time that I had got a Ph.D. and was established as a researcher, at least if that's the right word, my father's health was not too robust, and I felt some obligation to help my family. That led to my taking a job, and that led on in due course to other appointments in mathematics and science.

Smith:

After your undergraduate career, you said you took a Ph.D. I believe that you went to Gottingen at one time?

McCrea:

Yes.

Smith:

Was that after you'd done postgraduate work at Cambridge?

McCrea:

Yes, I'd been in residence for two years as a BA, doing research, with R. H. Fowler as my director of studies. Then I got what's called a Rouse Ball Travelling Studentship that was awarded by Trinity College, and I chose to hold it in Gottingen, and I am glad I did; it was a great experience. It counted as a year toward my Ph.D., which I got almost immediately after I got back.

Smith:

How strong an influence was Fowler on your choice of thesis topic? Did you pick your own research area, or did he direct you towards the area that you were working in?

McCrea:

In one way I got a little more direction that I could digest at the very beginning, because Fowler was bringing out his famous book on statistical mechanics, which I think is based on his Adams prize essay,^[3] and the thing was going through the press. He got me to read some proofs critically, and that gave me an entree into the subject, He asked me to do some of the applications of statistical mechanics to the specific heats of gases, and my first one or two papers were on that subject. After that, I think I found my own problems entirely. Fowler was a very good man. He was the best man at Cambridge for looking after research students. But that didn't mean a terrible amount in those days. I always used to say that my chief research problem was to locate my supervisor if I needed him.

Smith:

Did you work with anyone in particular when you went to Gottingen?

McCrea:

No. I went with the idea of remaining a mathematical physicist, although I had already worked a little bit in astrophysics — well, more than a little bit. I had the ambition to work with Max Born, but this was the beginning of the session 1928-29. Up to that time, Gottingen had been full of people like Heisenberg and Pauli and Hund and Jordan but they had all just gone off to professorships in other parts of Germany. Max Born himself was a bit exhausted, and he wasn't working at full pressure. Although I went to some of his seminars and to courses given by his assistants, I felt that the only thing to do in research was to associate myself with the astronomical department, and that I did. They were interested in my work, and I gave seminars in the observatory, in German. But I worked mostly on my own.

Smith:

Who was at the observatory in those days?

McCrea:

The professor was Hans Kienle. The assistant was Otto Heckmann who became a world famous astronomer. He has always been a good friend of mine since those days. We didn't share very close astronomical interests, but he could understand what I was doing.

Smith:

When did you decide that you wanted to focus on astronomy?

McCrea:

I think then — in Gottingen.

Smith:

When you started off with Fowler, did you think you might become a theoretical chemist?

McCrea:

In those days it was just called applied mathematics or mathematical physics. I wouldn't have called it theoretical chemistry although what I did at the very beginning might be called that nowadays.

Smith:

I think you were writing papers on the dynamical effect of turbulence in the chromosphere in 1929. Did you do the work for those papers at Gottingen?

McCrea:

Yes. However, it's interesting you should mention theoretical chemistry, because there's one thing that I like to look back on. I did talk to Fowler a little bit about making molecules. There was no way of doing that in the then current quantum theory, and I couldn't think of anything good. But I happened, I suppose at the time I was in Cambridge, to read the famous paper of Heitler and London. I forgot what year, I suppose 1927,^[4] and I explained it to Fowler, and he got me to give a Cavendish colloquium on it, so that was in a sense the introduction into England of modern theoretical chemistry.

Smith:

How did you get hold of the paper? Was it just in a journal?

McCrea:

I think it was in the journal ZEITSCHRIFT FUR PHYSIK. It just happened that I'd been pondering on the problem without any clues; I don't know what made me think of it. And then, of course, I couldn't help instantly seeing the significance. That's a little sidelight on the history of myself.

Smith:

Was there a lot of discussion amongst what one might term the theoreticians and the experimentalists in the Cavendish? Would you have given your talk to experimentalists as well as mathematicians?

McCrea:

Oh yes. There was only one colloquium, so far as I remember it, which I think had weekly meetings — not more frequently. These things were far less fashionable in those days. I do remember Chadwick^[5] sitting in the middle of the front row; and I got to know him quite well many years afterwards.

Smith:

Maybe if we could move on now to your time at Edinburgh.^[6] What made you decide to go to Edinburgh? Was it just that there were a number of positions vacant, and this was one that you applied for?

McCrea:

And there was a very kind letter that came out of the blue, from E. T. Whittaker, inviting me to go there. I had come back from Gottingen and I was still Isaac Newton Student at Cambridge, and then, in the term immediately after I got back from Gottingen, this letter came from Whittaker, I suppose he had heard of me, perhaps through his son, who was also a contemporary of mine in Cambridge, and it was a definite invitation. That was a wonderful opening.

Smith:

Did you start any teaching when you went to Edinburgh? Did you give lectures?

McCrea:

Oh yes. It was a full lectureship. Whittaker didn't believe in anything less than full lectureships. He wouldn't appoint assistants. So, everyone that went to him became a full lecturer straightaway. I suppose the average load was two full courses at any one time.

Smith:

And what courses were you teaching when you were there?

McCrea:

I was a lecturer in pure mathematics. I lectured on complex variable theory and differential equations, and I lectured on pure mathematics to the students doing the ordinary degree. In those days — no doubt it's all different now, — students did courses toward the ordinary degree for about two years, and then, if they wanted to specialize, they did two years of honors courses and took a final examination in mathematics, or mathematics and physics, or mathematics and theoretical physics, or whatever it might be. The ordinary courses in the department were very good courses, and a great many of the people taking them did go on to honors, afterwards so that the standard was very high. But the courses began at a fairly high level.

Smith:

How much time did you have for research?

McCrea:

I think an adequate amount. Whittaker was very keen that we should all follow our own lines of work. He was the most stimulating man I ever met in my life, and the intellectual climate in his department was wonderful, very refreshing and stimulating. He used to give what he called research lectures twice a week at 3 o'clock in the afternoon. He never lectured for more than about 40 minutes. He would go full speed for that time, on either something topical like — in these days — unified field theories of various sorts, or relativity, or some idea he might have of his own in relativity, or analysis. And some of the work I did was connected with those things, and some of it was continuing my work in astrophysics.

Smith:

When did you develop an interest in cosmology? Was that after or before you got to Edinburgh?

McCrea:

It was while I was there.

Smith:

Was it mainly because of Whittaker’s influence? Or was that a natural development from your own ideas?

McCrea:

I think those two things coming together. Whittaker stimulated me to try to understand relativity seriously. I had never tried very hard before. But then on the astronomical side, I started hearing about the expansion of the universe, as it was called in those days, and the early papers of Lemaître started coming out. These things came together and I got interested in it and started working on it. I started working on the instability of the Einstein universe, from one point of view, and I discovered that George McVittie, who was then an associate of Eddington's was working on it from another point of view. We exchanged ideas and wrote one or two joint papers. That was my introduction to the subject. But another man in Edinburgh in those days who was a very stimulating colleague was W.O. Kermack.^[7] He was a chemist, but he was totally blind as a result of an accident in his laboratory. But he had a wonderful mathematical talent. He got interested in talking to me about cosmology and other things as well, and I read papers to him. He was uncannily quick in grasping things — and not only that, but in working things out in his head, and almost more quickly than I could read them to him. We wrote at least one paper on cosmology, and we wrote papers on differential equations, things like that.

Smith:

Did you become interested in the instability of the Einstein universe, before the Lemaître^[8] paper was printed in translation in MONTHLY NOTICES?

McCrea:

It was about that time. It was a peculiar problem, of course. Eddington spotted that as a result of Lemaître's work the Einstein static universe was unstable. But the instability of a whole universe is of course rather a tricky concept because instability is only shown if a thing is disturbed. And the only thing that can disturb the universe is the Universe itself. So, the thing is, how does it get to start. And my idea was to try and work out the effect of a local condensation; if the background materials start to form galaxies or something like that, would it set this instability going? Well, I wish I had kept to that idea. But it was difficult to follow up, and McVittie had a simpler thought, which concerned the whole universe, not just local condensations. And so that's what was ultimately in our papers.

Smith:

And did you do your collaboration by letter? You wrote to each other?

McCrea:

Yes.

Smith:

Did you have much contact with the Edinburgh Observatory at any time there? For example, would there be regular seminars which mathematicians and astronomers would attend?

McCrea:

No, there were no astronomical seminars. Sampson was the Astronomer Royal for Scotland, and he was a good, kind friend, as I got to know him, but I don't ever remember talking astronomy to him very seriously. The man on the physical side that I got to know, and knew for a long time, was Charles Darwin. He was Taft Professor of Natural Philosophy in Edinburgh at that time. It was a new chair and he was the first occupant. He invited me to collaborate with him in running a colloquium in his department. He was housed in the physics department, not mathematics, and he and I ran this more or less theoretical seminar, I think practically all the time I was there.

Smith:

Were there any particular visitors that you remember to the colloquium which you organized?

McCrea:

The man who sticks in my mind was Polanyi. Otherwise I think we depended mainly on local talent. He was a visitor from outside; I don't remember where he came from at that time.

Smith:

I wonder if we could move on to the Royal Astronomical Society. I wonder when you started to attend RAS meetings? Was it while you were still at Cambridge?

McCrea:

I was elected a Fellow in 1929. And I think probably the very first meeting I went to was the famous one where Milne read his paper on stellar structure. I mentioned this at the Jeans meeting last year. It was a very stimulating introduction. I had communicated papers to the Royal Astronomical Society before that, but I think that was the first time I went, and I didn't read a paper there at that time.

Smith:

What sort of atmosphere was it at these meetings? How many people attended?

McCrea:

The old meeting room was always just about full. I think that meant about a hundred people. The astronomical community was more, in a way, integrated then, even than it is now. It's pretty well integrated still. But in those days everybody knew everybody else, and people like the Astronomer Royal felt, not only an inclination but I think a duty to attend. So did Eddington and everybody like that. You could count on seeing everybody around. It was very nice. You'd see them all at tea-time.

Smith:

It would be a very free flow of information — if you wanted advice on a problem you could just go and talk to someone?

McCrea:

In principle, but I expect you didn't do that an awful lot, but you sort of absorbed it through the pores.

Smith:

Last year at the Royal Astronomical Society you talked about the famous Eddington and Jeans clashes.

McCrea:

Yes.

Smith:

You said they enjoyed playing to a crowd?

McCrea:

I don't know that I said that, but perhaps I implied it. I think they did, a little bit. Yes.

Smith:

So that their clashes, which sometimes read a little bit fiercely in the literature, weren't so acrimonious.

McCrea:

No, I think they were partly tongue-in-cheek, partly, not entirely.

Smith:

If we could move on now to your time at Imperial College, I think you went there in 1932?

McCrea:

Yes.

Smith:

Why did you decide to go to Imperial College?

McCrea:

Whittaker believed in young mathematicians moving on as quickly as they reasonably could. He, I think, regarded his department as a training ground for them. It was a fairly small mathematical world, and he was always on the lookout for suitable openings, for his young men. I imagine he wrote to Chapman, about me. So, there was a Readership there which was actually held by a succession of well-known people. It may be of some interest that my immediate predecessor was George Temple, who was appointed professor of mathematics at Kings College in London, and that left a vacancy. I suppose Whittaker knew about this and mentioned me to Chapman,^[9] I suppose Chapman asked me to make a formal application, because I remember being interviewed by Vice-Chancellor and so on. But I think I was the only candidate called for interview.

Smith:

How did you find Imperial compared say to Edinburgh? Was it as stimulating at Imperial as at Edinburgh?

McCrea:

It was very different, because Chapman wasn't as outgoing as Whittaker, but he was a great scientist. He was one of the great scientists of this century. I suppose — he, more than anybody else except perhaps Jeffreys,^[10] in this country made modern geophysics. But he was a very unassuming man in ordinary life. He had no doubt about his own capabilities, but he didn't parade them at all. But he did attract very interesting collaborators. And when I was there in his own immediate group, he had Cowling,^[11] and Ferraro^[12] was very good too. It was about that time, I think, that the Chapman and Ferraro work on magnetic storms was going ahead. And A. T. Price, and Bertha Swirles, (later Lady Jeffreys) were there and they were all close associates of Chapman. The other professor was H. Levy. He was a very outgoing type of man. He was in fact a pupil of Whittaker's.

Smith:

Were you teaching?

McCrea:

Oh Yes. I did the normal things. But of course I had to switch from pure mathematics to applied mathematics, and in most of my life afterwards, I kept oscillating that way. I lectured on mechanics, statistical mechanics and quantum mechanics and thermodynamics and I suppose electromagnetism. I had my first research students there. The very first two I had were Cecil Gilbert, who has for a long time been a reader in Newcastle, and R.A. Newing, who for a long time has been a reader in Bangor. These were the first two; later I had an Indian, and one or two other people.

Smith:

Did you find that you had as much time at Imperial for doing research as Edinburgh? Or was the teaching heavier?

McCrea:

I would say it was about the same. A difference of course was that in London, one could attend meetings of the London Mathematical Society and the Royal Astronomical Society, and so on, very easily. In Edinburgh, there were interesting meetings of the Royal Society there, but they weren't of first class professional interest in one’s own field, as were the meetings in London.

Smith:

Did you feel in Edinburgh a little bit detached from the main center of activity?

McCrea:

No, because we were well aware of what was going on. I was very fortunate, in that a friend of mine was Dymond, a physicist, a very brilliant man, but he died fairly young. He got me into a physics group that used to meet on Saturday mornings in London. People like R. Peierls^[13] and G. P. Thomson and W. L. Bragg and so on, belonged to it. I must have made quite a number of overnight trips to London for this. So I wasn't cut off. But it was a different matter to be right on the spot after I had moved to London. Talking about Imperial College, I ought of course to say that G. P. Thomson was professor of physics in those days, and I got to know him fairly well, and had contacts with him for the rest of his life.

Smith:

Was there very much contact between mathematics and physics departments? Were there common colloquia?

McCrea:

I think the only colloquium that I ever heard of in those days was one I ran myself, in the mathematics department.^[14] But I think the physicists came. It was on all sorts of theoretical physics. One of my stalwart supporters was Edward Teller, who had just arrived as a refugee. He came a lot and there were some other people like that.

Smith:

Yes. I wonder if we could move on now to your interest in what's called Newtonian cosmology? I wonder how that arose? Was that after Milne had his early papers on Newtonian cosmology?

McCrea:

It's perhaps an amusing little story. One morning at Imperial College, a letter came from Milne, which I slipped into my pocket, because I was just going to lecture. And I didn't know what was in it. But then I had a visitor and after that I went home. I was married then and we were living in South Kensington. I opened the letter late in the evening, and it contained, I suppose, the gist of what became Milne's solo paper on the subject in a tentative sort of way, and he asked me what I thought of this. I sat down then and there and I wrote one letter saying I didn't think much of it. I thought it was a bit freakish, something like that, and I took this letter along to the pillar box (mail box). On my way back, it suddenly occurred to me that I could generalize the whole thing, that it would probably give an analog of the whole of relativistic cosmology. I went back and sat down and wrote out this idea and posted it, in time for the midnight collection. In those days, if I posted by midnight in South Kensington, Milne got it at breakfast in Oxford the next morning.^[15] And by the next day at 5 o'clock, I got a letter from him, "Come on Saturday and we'll write a paper." This was the middle of the week. So we went and spent the Saturday with the Milne’s. He and I wrote our paper. That was the origin of Newtonian cosmology.

Smith:

Had you kept in touch with him since you'd left Cambridge?

McCrea:

Yes. In those days he was a great letter writer. I think all the time I was in Gottingen he used to write to me, and we argued a bit. I pressed on him in letters the idea of the abundance of hydrogen, and never quite persuaded him of that in those days, but he does acknowledge it in his Bakerian Lecture. And then I suppose we must have written to each other when I was in Edinburgh. Certainly when I was in Imperial College, he used to come to a meal with us quite often when he was in London. We sat together on the Council of the London Mathematical Society as well. And he took me sometimes to dinner at the Royal Astronomical Society Club, of which I later became President. In those days, when he was in Cambridge, I used to see Chandrasekhar quite a lot, too. He'd come to see me in London.

Smith:

What sort of problems did you discuss with Chandrasekhar?

McCrea:

It was about that time, I suppose, that the Chandrasekhar-Eddington controversy about the equation of state of relativistic degenerate matter came up. I think we used to discuss that. I didn't, unfortunately, understand all of what Chandrasekhar said. I'm sure now that he was right and I'm sure Eddington was wrong.^[16] But I wasn't so sure in those days.

Smith:

Did you know Eddington very well?

McCrea:

Oh yes.

Smith:

What sort of man did you find Eddington?

McCrea:

He was painfully shy. It was hard to talk to him. But if you put a fairly specific question to him, he would give an answer, taking his time over it. I think the very last time I saw him, or almost the last time, I must have asked him about fundamental particles. I don't remember all he said, but I think he still took the view that the electron and the proton were the only two true elementary particles.

Smith:

Did you know Jeans very well? Would you often discuss problems with him?

McCrea:

In what I said last year, I mentioned the extent of my knowledge of him. There was much less opportunity to get to know him, because he lived in the country. He came to meetings in London, but he didn't move around in academic circles very much. I saw him lots of times, but my personal contacts were rather limited.

Smith:

In Relativity, Gravitation, and World Structure,^[17] I think Milne acknowledges collaboration with you in the section on Newtonian cosmology. Was he there referring to the writing of the chapter? Or was he referring back possibly to the papers you'd written together?

McCrea:

I think it was mainly that… Yes. I don't think we did very much more in those days. But I have written things on it myself more recently. It's been used a great deal in the exposition of cosmology. It's helped a lot in that way. That's the only way a lot of people ever get to understand very much about cosmology.

Smith:

Did you view it as that at the time? Did you see it as a useful tool for understanding what was physically going on?

McCrea:

Yes, I think so.

Smith:

Did Milne think that really was what was happening? Or did he view it as a useful aid, so that one could later on look at the general relativistic cases with a little more insight.

McCrea:

I think Milne's attitude towards Newtonian cosmology would be more or less mine. But he would think more in terms of his kinematic relativity,^[18] whereas I would think more in terms of general relativity, for the relativistic side of things. I never could accept his own estimate of kinematic relativity. It was very clever and I suppose showed genius, of a very remarkable kind, but I don't think it helped forward the understanding of the universe very much.

Smith:

Did there tend to be very much contact between the theoretical relativists and the observational astronomers, or did they view themselves as two different communities, with some rather different aims?

McCrea:

No. I think that it so happened that the people in this country who were interested in relativity were mostly people associated with Eddington, and rather led by him. He was a professional astronomer so that in this country there was no separation. Any separation came later. Cosmology was treated in what suppose, you might call, a skeptical and almost amused way by some people. Charles Darwin had a robust sort of attitude towards it, which was very healthy for the rest of us. And he wasn't too convinced that we were getting anywhere, because I suppose he thought the universe must be much more complicated than that. And I thought so myself at the time, and I have pointed out since then that the reason that people didn't think much of it in those days was that these models of Lemaître and Friedman were more like toys and weren't to be taken seriously themselves. I have remarked that they have had to be taken more and more seriously as time has gone on instead of less.

Smith:

I wonder how you heard of the latest observational results from the American observatories, say Mt. Wilson? Would there be a grapevine? Or was it mainly by reading the journals, that you would find the latest information?

McCrea:

Well, you've got to remember that in those days journals came out much more quickly. For example, anything read at one meeting of the Royal Astronomical Society was in print within two months. So you didn't need a grapevine. There were never any preprints, anything like that. If you went to a meeting of the International Astronomical Union, or something like that, you might hear things before they were published. But I don't think there was any need for anything much beyond the established journals.

Smith:

Was there much contact between British and American astronomers?

McCrea:

Yes, I would think that it was just as close as it is now. Of course there were no jet airliners crossing the Atlantic at that time. But it was surprising how often leading American astronomers would turn up in Cambridge or at a meeting of the RAS, as you mentioned yourself that, for instance, Jeans used to go to Mt. Wilson. The International Astronomical Union was always a meeting place for these people. And as I was saying, it was a fairly small community in those days, and people did know each other.

Smith:

I wonder if you remember which journals you read regularly during the thirties? Which would be the most important ones that people would first turn to?

McCrea:

In general of course, thanks to Jeans, the PROCEEDINGS of the Royal Society were regarded as the leading thing for pure physics, but the Zeitschrift fur Physik was also very good. The Annalen der Physik was going strong, but it didn't seem to attract the current work quite to the extent that the Zeitschrift did. But all the astronomical work, practically everything Eddington wrote and Jeans wrote and people like that, came out in MONTHLY NOTICES.^[19] It was the pleasant feature that these things were not as voluminous as they are now.

Smith:

I think from 1935 to 1937, you helped edit THE OBSERVATORY. Were you invited to be an editor?

McCrea:

I don't know if you know how the OBSERVATORY ran in those days? It's not essentially different now, but the financial arrangements are different. It's owned by its editors. It was founded by Sir William Christie, so as to have a sort of independent vehicle, for publication, and ever since, it's been the property of the editors for the time being. In those days, if you were invited to be an editor, the only people who could invite you were the owners, who were the existing editors. And you were supposed to invest in it. I think I invested something like 15 pounds. The other two editors, in those days, were Woolley,^[20] who was to become Astrome Royal, and H. W. Newton, who was on the Royal Observatory staff. They invited me and I remember it was Woolley himself who personally conveyed the invitation.

Smith:

How did you decide on the content of the journal? Would there be meetings of the editors, and you would decide what you were going to put in? Or did you have your own separate sections?

McCrea:

The work was divided between us. I don't remember how it was all laid out, but it worked very smoothly. I think I was largely responsible during my time for reporting the RAS meetings. Part of the time, I was in Belfast, and I used to have to write up my report the next morning, having crossed the sea in between, before it all went out of my mind. Newton I think ran the sort of business end, in those days. We used to be sent on one or two journals like the ASTROPHYSICAL JOURNAL, and if there was anything of particular interest, we would abstract it, or we wrote a little article about it. We agreed amongst ourselves who would report things like that. Of course, we always had a few articles coming in unsolicited. Sir Joseph Larmor used to send us articles from time to time — then, without knowing what they were about, we used to send them to the printer, we didn't learn till they came back from the printer what they were all about, because the writing was so awful, and the only man who could read it was on the staff at the printer.

Smith:

How do you feel the refereeing process has changed, since you first started refereeing papers? Are people more conscientious now than they used to be?

McCrea:

No. I don't think there's been any fundamental change. There's more refereeing. As concerns MONTHLY NOTICES for instance, I think probably when I first had connections with it, most papers were not refereed. They were looked at by the Secretaries, who were by charter, the editors responsible for producing the journal. And they did their best, but I imagine the thing was becoming very difficult. Or at best they would consult somebody informally. I seem to remember when the refereeing form was first introduced. I rather think the London Mathematical Society got one first, and then I think the RAS followed.

Smith:

When could that be?

McCrea:

I should think, in the 1930's. I've always had a vast amount of refereeing to do, and I hate it.

Smith:

Was it possible in those days to send papers which had no referees, and provided it was by somebody who was fairly well known, and then it would go straight in?

McCrea:

I feel that authors had more sense of responsibility then. They felt that there was a risk that what they wrote would be printed as they wrote it. So they were a bit more careful about what they wrote. I don't think any paper I've ever written has had any benefit from refereeing. But I think you have to have referees, as a safeguard. I'd be presumptuous enough to say that a lot of papers that I've refereed have been improved. But I don't regard it as my job to write other people's papers for them.

Smith:

You mentioned when we were talking about commuting from Belfast.^[21] Why did you decide to go to Belfast? What made you decide to go there?

McCrea:

I suppose one factor was that I am an Irishman, and a professorship even at the other end of Ireland, attracted me. But it has to be remembered that in those days, professors were professors, and there were only a few of them, I suppose in about a dozen universities in England, four in Scotland, three in Ireland, or something like that, and most of them just had only the one professor of mathematics altogether so that if one got any one of them, it was quite an event. This vacancy occurred because Semple, who had gone with me to Edinburgh at the very same time, was appointed to Kings College, and so I was especially aware of the vacancy, and I think that I got encouragement from Chapman, who must have agreed that it was about time I thought of something like that. Queens was very famous for mathematics. Larmor had been a student, and there'd been a lot of people of comparable ability.

Smith:

After you moved to Queens, did you find that because you were now a professor that you had to do more administration and teaching than you had at Edinburgh?

McCrea:

Oh yes. But I don't know how administration has managed to multiply the way it has. In those days, the whole university was run by about two administrators. As head of a department, I had no secretary at all, no secretarial assistance whatever. I was at the same time secretary of section A of the British Association,^[22] and I was so busy that I had to pay for a certain amount of typing of my own. That was a private arrangement. I became dean for a while there, and all the deans shared one typist.

Smith:

Did you feel that this administration was biting too heavily into the time you wanted to spend doing research?

McCrea:

Oh, I don't think so. I didn't ever enjoy administration for its own sake, but everybody has to take his share of it. The thing is, not to let it get on top of you. It doesn't do any good to make a fetish of it.

Smith:

What courses were you teaching at Queens? Did you for example inaugurate any courses in astrophysics?

McCrea:

No. As I told you, all along I oscillated. In Imperial College I was I suppose officially in applied mathematics. In practice, I certainly was. But in Queens, I was professor of pure mathematics, and all the applied mathematics was done there under Massey.^[23] He was head of an independent department called mathematical physics. He was succeeded by P. P. Ewald, while I was there. I didn't have anything but pure mathematics in my own department. But I kept on with my own research in astro-physics. Also I had associations with the Observatory at Armagh. Its director, Eric Lindsay was a very good friend of mine. He used to come and see me almost every week, and we'd talk in general about astronomy. I became governor of his observatory; I think I was the first lay governor there — because of course it was founded by Archbishop Richard Robinson about 1790, and governed by the Cathedral clergy. I helped a little bit in getting a certain amount of astronomy started in the university. It didn't amount to a great deal. Then, the war came, after I'd been there barely three years.

Smith:

In 1936, I think you started to think about the evolution of the solar system. I wonder how you became interested in that?

McCrea:

So far as I remember, the origin of my interest was in reading Jean's ideas on tidal interactions between passing stars.^[24] And then my immediate interest at the time I think was aroused by reading Lyttleton's^[25] work on various possible origins. As you may know, in 1936, I arranged a discussion at the British Association on the origin of the solar system, and Sir James Jeans consented to open the discussion. From your question, I think you may have seen a report of it in NATURE that year.

Smith:

What was the generally accepted theory at that time? Did most people believe in some sort of tidal interaction?

McCrea:

Yes. I think the historical side of it is important, because I think it colors people’s ideas to his day. When people first started thinking about the origin of the solar system, there was no general recognition of the significance of interstellar material. So if you had to supply material for forming planets, in the neighborhood of the sun, there were only two ways of getting it. Either it had to be left over when the sun itself was made, or else, it had to be pulled out of the sun. And the only way people thought of pulling it out of the sun was to have another star passing by and raising a tide on the sun. The idea of material left over after forming the sun was clearly the Laplace sort of solar nebular idea. But around 1936 and for a long time afterwards, that idea had fallen into disfavor. Until people started seeing the importance of interstellar material and the possibility of forming from it a lot of stars and planets at the same time, everybody tried to think of some way of pulling material out of the sun or another star.

Smith:

How did your astrophysical interests develop during the 1930's? Did you find you would work on the same problem at different times, or did you expand into new problems? I think you were pioneering a modern treatment of stellar atmospheres.

McCrea:

Yes.

Smith:

In 1936 you were working on the solar system. It seems a very wide sweep.

McCrea:

I think I'd done a lot in between. I was interested, am still interested, in certain aspects of mathematical physics, and I had written a paper with a collaborator on the wave equation. I think the idea that I had then was one that has proved important ever since. Some people couldn't understand why they were getting peculiar predictions concerning molecular combinations. I happened to notice that they were looking for solutions where the boundary points were singularities of the differential equation concerned, the wave equation and this made a lot of difference to the derivation of eigen-solutions. That was one of the things. And then, I got interested in the problem of one gas moving through another. That is a problem which, again has been of great interest in recent years, when people are interested in, for instance, the segregation of materials in a possible solar nebula. I wrote a paper on that subject, I think about 1935, and with one of my pupils at Imperial College, I wrote same rather simple papers on the propagation of radiation through a moving atmosphere. That was a development of the earlier work you've mentioned on model atmospheres. We didn't get very far, but once again this was a pioneering paper in a subject which is quite a large subject these days. And we've already talked about the Newtonian cosmology that also came in the 1930's.

Smith:

You mentioned that there were some papers in collaboration with your pupils. I wonder if we might talk a little bit about the pupils that you had. Are there any that come to mind, that you especially remember?

McCrea:

Oh yes. The ones that I mentioned just now were of course graduate students. But I have been fortunate, in most places where I've been, in the undergraduates I've dealt with as well. In Edinburgh, about the first student I ever had there was R.A. Smith, who recently was president of the Royal Society of Edinburgh, and Frank Smithies, who has been a mathematical don at Cambridge all his life. He was one of my students there. Again, there were H.D. Haddow^[26] who is high up in the civil service, and Henry Daniels who is professor of statistics in Birmingham, and I could mention quite a few others, including Frank Westwater, a colleague of Fred Hoyle's at one time. And it might be interesting to mention that in those days, at Edinburgh, amongst Whittaker's research students; there were A.G. Walker, of the Robertson-Walker metric, and Mursi Ahmed from Cairo who afterwards became a cabinet minister in his own country, and there were future professors, of mathematics, Lamb, who was at the Royal Military College of Science, and Gormley and Timoney who were professors at University College, Dublin. That was in Edinburgh. And then, at Imperial College, I've mentioned some of the research students. In Belfast, being partly wartime, I didn't have very many graduate students, but amongst the undergraduates were David Bates, who is now Sir David Bates, and James Hamilton, now professor in Copenhagen, and Murray MacBeath, professor of pure mathematics in Birmingham. There was Gordon Foster who is now professor at Dublin in statistics. There was the unfortunate Henderson Ramsey. I say unfortunate because he died early in life after a very brilliant start in physics. There was another brilliant man called Unwin who was killed in the war, and there was also Edward Simpson, who is now very high up in the English civil service. In Belfast also, in the mathematics department, we had for a while students who afterwards distinguished themselves in chemistry and engineering, as professors in different parts of the world. It was very stimulating, of course, to have those people around.

Smith:

What's been your normal method of guiding your students’ research? Do you tend to let them get on with their own problems, and just checking what they're doing to make sure they're not going off the rails? Or do you tend to set problems for them which they go on to solve?

McCrea:

It's a great question. I've tried usually to give them a problem to start with. I was always more favorably disposed towards a would-be research student if he came and said he wanted to work on some particular thing. That showed that he thought something about it and knew some of the problems that were going at the time. And I would rather deal with a student who had to be dissuaded from some idea, than a student who had no idea at all to begin with. But I think if you've got a good man going on one thing, it should lead to another, and so on. I think having given him a starting problem; usually other problems arose as he went along.

Smith:

I wonder if we might go on to the war period. Was your astronomical research practically ended by the war?

McCrea:

Rightly or wrongly, I took a resolve at the beginning of the war that I would lay aside my own personal research. I thought it might be rather selfish to pursue it. I did have the idea that instead of doing research, if I had any time available, I would write one or two books. Then the only book I did write in the war was a little book on algebraic geometry in three dimensions, which had quite a vogue, and has only rather recently gone out of print. But if you're asking what else I did do, I got involved first of all in the Home Guard and the University Air Squadron in Belfast, and I was commissioned in the RAF Volunteer Reserve from early 1941 to the end of the war. But then in 1943, at the beginning of that year, I went to the Admiralty to do operational research in Blackett's group. Blackett^[27] and his colleagues were the great pioneers of operational research in the war. They started in this line with Coastal Command in the Air Force, but by the time I joined them, they had moved to the Admiralty and it dealt chiefly with anti-U-boats operations. It was a very remarkable group when one looks back on it. Blackett and Bullard and E. J. Williams were the great leaders. There was also Henry Whitehead, and Henry Hulme and Andrew Huxley — in fact, it looks as though half the Royal Society were in it! Besides that, my former pupils Hamilton and Ramsey and my colleague Lindsay from Belfast were all in it and I think did very well indeed.

Smith:

What sort of leader was Blackett?

McCrea:

I think he was very good for a group of that sort, in the sense that, he believed in getting people that he thought would contribute and then left them to it, most of the time. He would occasionally either breeze in or else send for one, and propose a problem, — expect an answer pretty soon — then forget that he'd asked. But he was of course involved in advising on many aspects of the war, and obviously had a tremendous influence. It was a great privilege and inspiration to work with him.

Smith:

Whereabouts were you working? Was it in England?

McCrea:

At the Admiralty in Whitehall. But we went round the country a good deal. Maybe I went around a bit more than some of the others. I spent quite a while in total in the naval headquarters in Liverpool and Plymouth. I even went on various trials in the Irish Sea and in the Clyde, and that sort of thing. And then after the war — immediately after the war ended in Europe — Henry Hulme and I went to Germany, and interviewed a good many of the leaders of the German Navy, who were ready to talk about their operations.

Smith:

Is that because you were a good German Student?

McCrea:

By then I had lost any fluency I'd ever had, but I did understand a bit, and Hulme was good. It was partly because we did understand German, but partly because, I suppose, Blackett or Williams thought that what we'd been doing gave us very much the best sort of background for seeing these people. It was very interesting, and as I say, they were quite ready to talk, because they just regarded the war as a professional exercise. There was no question about them giving away any secrets then. We weren't called on to give anything in return. We were the victors.

Smith:

I wonder if we might move on to your association with Royal Holloway College.^[28] I wonder why you decided to return from London to Belfast. Was it because you enjoyed London more than Belfast?

McCrea:

I suppose, partly that. I'd been happy in Belfast, and had had very good students, but I suppose, I thought one had to get moving after a reasonable interval, and this seemed to be an opportunity. I don't think it was disloyal to Belfast, because. I'd been away for quite a while and it didn't make all that difference to them whether I went back or they got someone else after the war. Actually H. R. Pitt,^[29] who afterwards was Vice-Chancellor of Reading University, was my successor and did very well there.

Smith:

Although you went back to London, I think you were still a member of the governing board of the school of the theoretical physics at the Dublin Institute of Advanced Studies?

McCrea:

Yes.

Smith:

I wonder how the board functioned. What was your job?

McCrea:

It was like the governing board of any scientific institution. I think we probably advised on the recruitment of staff. I suppose that would be the main thing. And I remember, we arranged the sort of discussion meeting that was all that was possible in the years just at the end of the war. We had Dirac and Eddington there, for a series of talks and meetings. It was a very well worthwhile enterprise.

Smith:

Schrodinger^[30] was in Dublin during these years. Did you come into contact with him?

McCrea:

Oh yes, fortunately, very much.

Smith:

What sort of a man was he?

McCrea:

A fascinating character. He was very vivacious and had ideas on everything. He was very ready to talk about them, in a very quaint form of English, which I think he rather cultivated, because he found it went down well. And he was of course the widest ranging of all these people. I think, comparing him with Dirac^[31] and Max Born for instance, that Schrodinger covered a much wider field. He may not have been as deep as they, but I think he made up for it in the width of his interests.

Smith:

What impressions do you have of Dirac? Was he a good speaker? (Was he at all gregarious like Schrodinger?)

McCrea:

I think gregarious is the last word you would apply to Dirac! He is a friendly man, of course. His way of being a good speaker is quite different from Schrodinger's. Every sentence is absolutely perfect and finished. But it's delivered in a rather dry fashion, and you have to develop a taste for that sort of lecture. But if you do, and if you can take it down or keep it in your mind and then think about it, you will find everything is there.

Smith:

How would you compare your period at Royal Holloway with your period say at Imperial or Edinburgh? Were the working conditions similar? Did you have to spend more time on administration or teaching?

McCrea:

I must say that I always thought that it was part of my vocation and obligation to do a fair amount of undergraduate teaching. I think that if one enters the university system at all, one ought to do that. I regarded it as a privilege to do it, and I enjoyed it. But I don't think I did too much of that. It was an incredibly busy time, because we were building up after the war, and there was not only the undergraduate teaching, but I got a steady stream of graduate students, and of course so did my colleagues as the department increased in size. I had very good graduate students there. There was Kenneth Dodd, one of the early ones, who did the very first application ever of modern computing to astronomy. He did in one night, with the first computer in Manchester, more solutions of the restricted three-body problem than had ever been done in the whole history of astronomy. He has remained in computing, not in astronomy. And I had F. I. Mikhail who's a professor in Cairo now and has been for a great many years, and William Davidson, who's a professor in Otago in New Zealand. He wrote a rather well-known paper on Mach's principle. There was Jack Hogarth, who has long been a professor of applied mathematics in Queen's University, Kingston, Ontario. Then there were Iwan Williams, who's a reader at Queen Mary College, and Patrick Dolan, who's a lecturer in Imperial College, and Derek McNally, who's an Assistant Director of the London University Observatory, and was secretary of the Royal Astronomical Society for a long time, and Rex Agacy, who's a lecturer in James Cook University in Australia, and Michael Rowan Robinson who's a reader at Queen Mary College, and Petros Florides who's a Fellow of Trinity College, Dublin. These people, and a number of others, did PhD’s with me — in Royal Holloway College. And we had some extremely good undergraduates who did PhD's with other colleagues, Valerie Myerscough, a well-known worker in the borderline between astrophysics and atomic physics, and Gillian Peach who is in a somewhat similar field, and a good many people like that who have made names for themselves in the scientific world. It was a very stimulating period.

Smith:

I wonder if we might return now to cosmology, because the period after the war saw the birth and development of the steady state theory in which you've been intimately involved. How did you become interested in the steady state theory?

McCrea:

I was secretary of the Royal Astronomical Society when the paper came in. It was in 1948, in the recess in the summer and as, Secretary i+++++++++++++++++++++++t was my job to get a referee. I couldn't, so I referred it myself, and recommended to myself that it should be published: This was the Bondi-Gold paper.^[32] I sent that to the printer and arranged in due course for Bondi and Gold to talk about it at a meeting of the Royal Astronomical Society in Edinburgh. I think it was October of that year. It was the first ever meeting of the Royal Astronomical, society outside London. By then the Hoyle paper^[33] had been received, and Hoyle talked about it as well. That was, in practical terms, my reason for special interest. But of course, scientifically, it appealed to me very much. I went on to try and explore a bit further the connection between the steady state theory and general relativity, and I wrote a paper about 1951 which I think carries that aspect about as far as it will go.^[34]

Smith:

You talk about negative pressure, positive density and negative pressure. How was that received by astronomers in general? Did they think this was playing about with the mathematics? Or did they think there was something that you could call reality there?

McCrea:

It wasn't all that profound. But I think that if people were inclined to accept the idea of continual creation, it wasn't too much for them to accept the idea of a zero-point effect, or what they call in these days vacuum fluctuation.

Smith:

Vacuum fluctuation?

McCrea:

Something like that. Yes. So that it was, in a sense, all of a piece with the other ideas on the subject. But there was one thing I didn't know at the time, that Einstein himself had talked about a negative pressure in this very connection, at one time. You see, in order to get his steady state — Einstein's steady state universe is of course the static universe, for he didn't have continual creation — he had to introduce the cosmical constant, and he didn't like that. In one of his expositions, he used a negative stress instead of the cosmical constant, and I hadn't noticed that until long after I'd written that paper. So it had a respectable ancestry.

Smith:

Was there a great deal of opposition to the introduction of the idea of continual creation?

McCrea:

No. It had a sort of esthetic appeal, in various ways. I think partly because of what Bondi and Gold called the perfect cosmological principle, people accepted it. I think that in order to get anything like a cosmological model, you have to have a cosmological principle, and the cosmological principle that people first of all talked about applied to homogeneity and so on in three dimensions. But then, what Bondi and Gold said in effect was, why three and not four? Because of course, the spirit of general relativity would be to have a thing like that apply in four dimensions instead of three. Esthetically it was a more natural thing than what it replaced. But physically of course, it had implications that were very difficult to accept in some ways, but in other ways not, because the rate required for continual creation that would keep the universe steady was far below anything that could be observed directly. But the other thing that appealed to people was what Gold emphasized most strongly, and that was the vulnerability. Any one contradiction with observation made the whole thing collapse or would have done. But from 1948, for about 20 years, there was no contradiction that was accepted as an absolutely clear-cut contradiction.

Smith:

What impact did the first and second Cambridge Radio Survey have? — did astronomers tend to view the steady state with more suspicion after these surveys?

McCrea:

I think they ought to have done. But I think it's fair to say that the results of the first survey at any rate weren't all that clear. If you took them at their face value, they did contradict the steady state. But you know, the Cambridge Survey and some of the others didn't agree. In any case, the most obvious departures from anything like the steady state occurred at about the limit of the instrument performance, so that people weren't quite convinced. I don't think even the radio astronomers were quite happy that the effects at the crucial part of the range were secure. But in any case, I think when the second survey one came along, I suppose it was by 1961, Hoyle had various arguments — which I think were not quite valid — which suggested that the steady state could be squared with Ryles observations.

Smith:

Did you discuss your work on the theory very much with Hoyle? Did you correspond about it?

McCrea:

I don't think so. I used to see him quite frequently, and we had discussions, but I think that was all.

Smith:

Would you say the steady state was the most popular theory of cosmology during the fifties and early sixties? Was it most accepted then?

McCrea:

I think that's over-simplifying the thing. I don't think one 'accepts' or doesn't 'accept' a thing like that. One regards it as having a certain degree of plausibility. There was no doubt that it made an appeal, and there was no doubt that a lot of astronomers were disappointed when it obviously had to be given up, in any simple form.

Smith:

Was that because it esthetic appeal was so great? People felt, this theory looks so esthetically pleasing, and then it must have something to recommend it?

McCrea:

I think that was partly it. But it was rejected for logically the wrong reasons. Ryles’^[35] observations were frankly and clearly contradictions. But the supporters of the steady state didn't give it up for that reason. They should have done. But they gave it up because the relativistic cosmology predicted the background radiation^[36] — which of course the steady state didn't. But there is no logical contradiction between the existence of background radiation and the steady state theory. It shows the curious way scientists minds work, because they're more impressed by a positive prediction that succeeds than by a contradiction which is a flat contradiction.

Smith:

I wonder whether the fact that there were mistakes in the first two Cambridge surveys, made people a little bit skeptical about accepting the results of the third Cambridge survey. When the third catalogue came out, it seemed to be in contradiction with steady state, but because the first two surveys contain some spurious sources then people were a little bit hesitant about accepting the third survey. Maybe that's why they still hung onto the steady state.

McCrea:

Yes. That's again perhaps a simplification of the position. You may remember that not only were there contradictions between one survey and another, but surveys at different radio frequencies didn't seem to agree very well. I remember, the Australians did a survey like that, getting a different gradient for the number-count from the Cambridge one, and you couldn't accept both of these:

Smith:

Did the detection of the 3°K radiation come as a great shock to cosmologists?

McCrea:

No. I wouldn't say that. I have to confess that I myself was rather cool at first, because I thought that such a small effect could be almost anything! But that was one point of view which was too naive. But the other thing was that Gamow had predicted this a long time ago. He had predicted himself something more like 50 degrees, but then his co-workers — R. A. Alpher and some of the others, — almost immediately got 5 degrees, which is a very good shot. This prediction had been forgotten, bit was very soon recalled. The fact that so long ago, the ordinary relativistic theory of the expanding universe had predicted this was, I think, the most powerful argument in its favor.

Smith:

Were people very surprised at the detection of quasars?

McCrea:

This was another of these curious psychological effects. People had found this redshift increasing with distance, as they thought and as we all believe, and then, in 1960, Minkowski found what was up to then the biggest red shift and that was half the speed of light. What really should have been the question was, why didn't they find still bigger ones and bigger ones. If the Hubble Law was right, they ought to have gone on finding bigger and bigger ones. And yet, when the big ones did come along, they didn't believe them, at first, to be the same phenomenon. A lot of people thought it must be something different, gravitational effects, or something else. Of course, a lot of them still don't accept that the red shifts are wholly “cosmological.”

Smith:

There was some resistance right at the beginning to the cosmological interpretation?

McCrea:

Yes. But the other thing was that, although, on the whole, I think people wanted to accept that they were cosmological red shifts, quasars have never helped forward cosmology in any way. I think they will ultimately. But I think it's still true that the problem has hitherto always been to explain quasars, and not to use quasars to explain other things.

Smith:

I wonder if we can move on now to your work on stellar and planetary formation. I believe you started in 1957 a series of papers on these topics. I wonder what inadequacies in the existing theories led you to begin this work. Did you think that the state of theory was really unsatisfactory and that something could be done with it? Had you got a novel idea which you wanted to try out?

McCrea:

It was a mixture. There was no accepted idea about star formation, up to the 1950's. There was a vague belief that the Jeans critical mass played a part, and that in some way or other, condensations were brought to a state of gravitational contraction, and that every star was the result of such contraction of raw material. This of course was, in a way, a relic of the old Helmholtz idea about energy generation of the stars that ascribed it to gravitational sources. But apart from that sort of general acceptance that gravitational contraction was involved, I don’t think there was any clear picture. And as far as my interest goes, I came on the work of Ebert on the gravitational collapse of isothermal polytropes, or parts of isothermal polytropes. This was a very classic paper.^[37] He suggested that certain objects in the sky, that are usually called “elephant trunks,” bits of interstellar material, would be brought to gravitational collapse by the pressure of hot gas on cold gas. This struck me as being extremely enlightening and plausible, but with one serious objection, that I didn't think it would form stars. I thought the mass required would be the mass of a cluster of stars, not just single stars. I tried to develop this idea, and I think I did get it across. It's been accepted ever since ordinary stars are formed in clusters. I don't think this was a revolutionary idea, because the importance of cluster-diagrams and so on was accepted by then, and all I did was to say that the ideas on star formations seemed to square with that idea, and the notion that stars in a cluster are about the same age. But then, I had to find an idea for forming the individual stars, and I thought that you might get a temporary star formed in the central region of a forming cluster, and that would give this pressure-condensation over again, a repetition on that smaller scale which would then give you the stars. I was in California when I got this idea, and I talked about it at various seminars, and at one in particular Hoyle was present and Feynman^[38] as well. Hoyle stressed the difficulty of the angular momentum.

Smith:

What year would this be?

McCrea:

1956. And I think I took this very seriously, probably too seriously at the time, and so I looked around for a different way of dealing with the angular momentum problem, and this ultimately led to my idea about what I call 'floccules.' I still was convinced that stars were formed in clusters, but I thought the process of fanning single stars was some sort of aggregation of turbulent elements. And I still think that is right, and I think other people are coming to this view. I happen to know for instance that Professor M. M. Woolfson in York has just written a paper which I've communicated to the Royal Society, on this very idea. He has a rather more sophisticated view that I have, but basically it involves pressure effects and turbulence effects such as I invoke. I don't think Woolfson would object to my saying that.

Smith:

When did you decide to extend this to the formation of the planets?

McCrea:

I think that was when I wrote my first paper on the subject. When I presented my ideas on the floccule mechanism to the Royal Society in 1960, I was interested in the fate of the angular momentum, which had been the difficulty that Hoyle had pointed out in the original process. In this floccule idea, most of the angular momentum goes into the relative motions of the stars, and not into the spin of the individual stars, and that's all right… But there must be some material that has too much momentum about any condensing center to get into it, and this seemed to be exactly what was wanted to form planets.

Smith:

When did you find that out? Had you been mulling that idea over before you wrote your paper in 1960?

McCrea:

For about a year, I suppose. Yes.

Smith:

I wonder if you might return now to your work with RAS. From 1946 to 1949 you were a secretary. What did you have to do as the RAS secretary?

McCrea:

By charter, I think it is, the secretary is responsible for editing the society's publications. And this was the biggest responsibility, and still is, for the secretary of the Royal Astronomical Society. In those days there were two ordinary secretaries and a geophysical secretary. The ordinary secretaries had the responsibility of organizing the council meetings and the ordinary meetings of the Society, and of course, there's a fairly heavy correspondence. In short, you have to edit the journals and see that there's a supply of speakers for the meetings, and keep things going generally. I wasn't secretary very long, but I did introduce one or two new features. I introduced the “away” meetings of the Society which are still going on, of course, but in a slightly different form. In my time they were additional meetings. I think they have been very well worth-while. I also introduced the idea of junior members, and I think that has brought in young people at a stage earlier than would otherwise have been the case. It was the time of reconstruction after the war, of course, and I think that was really why I couldn't stay more than three years with it, because it made such heavy demands on my time. Besides, several things went wrong in those days. The heating system broke down, and I had to cope with that, and other such practical things. I had to deal with changes of staff and of printers, and with paper-rationing, and so on. Looking back, I don't know how I did it, on top of everything else. But it was very stimulating and exciting.

Smith:

From 1961 to '63, I think you were president of the RAS. What did you do as president?

McCrea:

Of course I sat in the chair at the meetings! I did one or two slightly novel things. We had the first meeting of the Society devoted to anything like space astronomy. I don't remember all the program, but we went to the big lecture theatre of one of the engineering institutes for that, and I remember Sir Harry Massey came, and we had other speakers who were interested in this development. That was one novel thing. And then we had a visit to Belfast, for an “away” meeting and we also had one to the Royal Observatory, which was a novelty for the Society as such. And we had an historical meeting; to commemorate Bradley's discovery of aberration in 1725. The occasion was the bi-centenary of the death of James Bradley, who died in 1762; the Society enjoyed having a little history for a change.

Smith:

From 1968 to 1971, you were the RAS foreign correspondent. Does the RAS foreign correspondent stimulate correspondence between RAS members and scientists in other countries?

McCrea:

I said a moment ago, there were two ordinary secretaries. Well, the charter provides for three, and historically the third was always the foreign secretary. It really was necessary in the old days to have somebody like that who would deal with the foreign correspondence; because of course not many foreign astronomers in the old days could visit us. They had to have dealings by correspondence, and it requited one secretary to devote himself to all that sort of thing. Well, then, sometime about 1960 or so, the Society decided that it needed to use the third secretary-ship for the geophysical secretary-ship, so they started having a “correspondent”, as they called it, which I think is an old term revived, not in our society but in other societies. Even when I was foreign correspondent, I think I had a job to do because I made it my duty to look after foreign visitors when they came to meetings and other things but now most foreign visitors come not only to the Society, but to visit some center in this country. Usually someone from the center looks after them, and it isn't really necessary to have somebody in the Society devoting himself to that. So no foreign correspondent has been appointed for the past year or two.

Smith:

In 1966 I think you became research professor of theoretical astronomy at the University of Sussex. Does the title imply that you were free of administration and teaching responsibilities?

McCrea:

To some extent. I think if we have a moment, I ought perhaps to remind you of the history of this. All this is pretty well known now. It's been in newspapers and things like that, so it's not giving away secrets. From soon after the war, I was advocating the setting up of a National Institute of Theoretical Astronomy in England. I didn't want to centralize work in theoretical astronomy, but I thought that if it had a center where people could go for various lengths of time, and meet other people working in theoretical astronomy it would be good for the subject in this country. Most people that I talked to in astronomy agreed with this, and we got it written into various reports of the National Committee, which worked under the Council of the Royal Society. And I think maybe our recommendation was even passed on to the University Grants Committee. But nothing much happened for a long time. And then, somehow or other, we got a little Royal Society committee, more or less ad hoc, set up to deal with this. In due course I was asked to preside, and I think Bondi was secretary. We outlined what we thought would be the type of thing to be set up, and we were agreed then, that the obvious place to have it would be Cambridge. Then Hoyle, who I think was still a member of this little group, undertook to find out if Cambridge would like to have it. After a long time, he came back with word that Cambridge really didn't want it. Then we suggested that it should be in Sussex, because this would be the nearest place to the Royal Observatory, and thus there would be a good case for having it there. By that time, Sussex University was being founded. I don't think it had got off the ground, but all the arrangements were being made. John Fulton, who is now Lord Fulton and who was the Vice-Chancellor designate, was very keen on the idea, and so was the Astronomer Royal, Woolley. Then, I suppose it would be around 1961, the Government set up a body under Sir Burke Trend, who was something high up in the civil service, to report on civil science in the United Kingdom and its organization. Just before that, our recommendation had been passed on by the Royal Society to the Advisory Council in Science that was presided over by Lord Todd. We understood that they were favorably disposed, but that the thing had to go into abeyance with anything else in that line until after Trend had reported, and any enactment following from it went through. In due course, as you know, the Science Research Council was set up, and it would have dealt with this matter. But in the meantime, Cambridge let it be known that they did want the Institute after all. I don't remember all the sequence of events, but they are well documented in Cambridge and in the Science Research Council. There was a long discussion as to what form it should take. Cambridge more or less had to have it. I think the attitude was that they had been the first choice, and because of this Trend business and so on — although Sussex had wanted to have it — no agreement had even been signed with Sussex. It had been expected of course, but it couldn't have gone through by then. And so, the idea was accepted that Cambridge should have an institute. But it was not then proposed to be a national institute. It was very much linked with Hoyle's tenure of the Plumian Professorship at Cambridge. Obviously, Sussex wasn't then going to have a national institute either, or even anything that would be called an 'institute'. But it was encouraged to apply for a grant for theoretical astronomy. In advocating a national institute, I had all along assumed that if it came into existence, I would not be in any way associated with it. I couldn't advocate it and then get a job in it! And I didn't want to anyway. But when Sussex had been, as I thought, rather badly done by, and when they invited me for this other thing, that was not to be an institute at all, I felt almost bound to accept their invitation to come along and get it going. That's why I got here, briefly. But it was part of the understanding that if the SRC supported theoretical astronomy, the university should have a professor supported by the university grants money as well. And so almost my first job was to help them to find a professor, and they found Professor Roger Tayler, who's happily still here. I continued to run things for about a year, and then Tayler became director of the Astronomy Centre, about 1967. And it's been going ever since.

Smith:

Have you kept in very close touch with the Royal Greenwich Observatory

McCrea:

The Science Research Council set up several bodies and among them there was the Royal Greenwich Observatory Committee, and I was the first chairman of that. I was chairman from the setting up in 1965 until 1971 so that we had a very close link. My successor was Sir Martin Ryle, but his successor was Professor Tayler at Sussex. So the link continued. The connections are quite close.^[39] You asked about science in these years. In Sussex, I've had a number of research students, of course. Again, I like to think they've been good. And I could name Rowan-Robinson (who came with me from Royal Holloway College) and Bayliss, particularly, and Tom Peterson, who is teaching now and not researching, and a number of others. Some of my work has been related to their interests. Amongst these I have had a revived interest in observable relations in cosmology, which was a thing I started a long time ago. With some of my students here; I have developed these topics, partly bringing in quasars. And then, I've been interested all along in my time here in quasars themselves. About 1966 or '67, I revived the idea of temporary stars in connection with a possible mechanism for quasars, and I still think that is quite a plausible possibility. I developed that more recently in a paper that I gave to the Royal Observatory, at the Tercentenary Symposium in 1975. It was published quite recently, partly as a theory of quasars, but partly as a theory of Seyfert galaxies as well. I have developed my work on the solar system. I was scientific director of a NATO Advanced Study Institute in Newcastle a couple of years ago. You may have seen the volume that's since come out, on the origin of the solar system, edited by Dermott. I have a long paper in that, on the origin of the solar system, with some special emphasis on the origin of satellites.^[40] More recently, I have a theory that hasn't been published yet, on asteroids. I think it's quite amusing. I've had a draft for a long time, but I had so many things on hand, I haven't published it. I've had a paper in draft form, two years or more, on the first stars. I have an idea how the very first condensations were of the dimensions of globular clusters, and I think the first stars were made in globular clusters. It's a development of my old idea of what are really forming Population 1 stars in galactic clusters. Now I suggest that Population II stars were originally formed in globular clusters.

Smith:

You've also written on the cause of the Ice Ages. How well received was that idea?

McCrea:

This is an aspect of the work that I mentioned earlier about interstellar matter in the Galaxy. One idea that I've been developing in recent years is the possible effect on the solar system of its galactic environment, because, as you know, the sun and the solar system go around the Galaxy about once in 200 million years, or something of that order, and each time it goes round it traverses probably two main spiral arms, with the associated dense clouds of intergalactic matter. If this picture is right, which I think it undoubtedly is, it must have some consequences for the solar system. I think going through dense clouds may be the way the Ice Ages were started. This idea was proposed first by Shapley. I didn't know that when I revived the idea. But I did know, of course, that Hoyle and Lyttleton^[41] had proposed this before the war. I was reviving that idea, but with the new feature of associating it with the structure of the Galaxy. It's a big field and I'm still working on it — partly with my colleagues. We were interested in possible effects on climate. The sun is more likely to get near to a supernova outburst when it goes through a spiral arm than at other times. We think that might possibly have catastrophic effects when it happens. Also, as I suggested in a Halley Lecture a couple years ago, I think that comets may be formed only in these dense clouds, and that is when the solar system picks up our supply of comets.

Smith:

When you view your career as a whole, what do you think are the main themes that run through it?

McCrea:

I suppose, in trying to answer a question like that, I shouldn't be too embarrassed by modesty. If I try to take an objective view, I think perhaps my contribution has been in introducing general ideas, rather than solving very isolated problems. One of my first papers was the very first paper on forbidden transitions, which of course is a very common subject nowadays. And then, I mentioned the matter of hydrogen abundance, in talking about my discussions with Milne. I think perhaps I did pioneer the idea that hydrogen is the most abundant element in the constitution of a star. I don't know how much to go on! I did, I think, write the first paper on non LTE, as they call it, that's non-Local Thermodynamic Equilibrium. And then, I wrote the first paper on the role of turbulence in a mechanical way in the support of parts of solar or stellar atmospheres. And you have yourself mentioned model atmospheres. Thousands of papers have since been written on this subject. Also I did write the first paper on observable relations in cosmology. Just to be very brief, l Whittaker was I think the first to point to the importance of working out observable quantities in relativity. When you measure a distance in astronomy by means of a prescribed set of operations, for example, the result is to be described by an invariant, mathematically speaking. And Whittaker got a number of these quantities, expressed in terms of the coordinates used in the model. But I suppose I then got the idea that what's really observable is, in the simplest case, the relation between two of these things. There's no use expressing just one of them in terms of unobservable things like coordinates. So you must express the relation between it and other observable quantities. And of course people are still writing papers on such observable relations. And then we've talked about Newtonian cosmology. We haven't talked about random paths on a lattice, which is something else I worked on. Again I think it’s fair to say that the work I did, partly in collaboration with Kenneth Dodd, just after the war, in a sense rationalized the subject of accretion in astronomy. Before that, some people thought it was utterly unimportant, and other people wanted to explain everything by accretion. I think we introduced an element of common sense into it, showing that it could be important, but only under sets of very special circumstances. Another thing we haven't talked about is that McNally and I did pioneer work on molecules, the hydrogen molecule in space. I think we showed in a way that hadn't been done before that molecular hydrogen could be very important, and I think everything that has happened since confirms that. I did introduce the idea of uncertainty in cosmology, which is a semi-philosophical concept that involves the nature of physical laws. I think it will prove to have some significance. You know what Blue Stragglers are? People seem still to be interested in ideas I put out on the subject. And we've talked about star formation in clusters and the formation of stars and planets generally and the origin of the solar system. And then, as I say, I've been interested in this idea of the interaction between the sun and the solar system and the spiral arms, and other features of the Galaxy, with a view to accounting for various effects like, amongst other things, the existence of comets. And, as I mentioned a moment ago, my present interest is in the first stars. Those on a purely scientific side, but I have taken an increasing interest in the history of astronomy, and I've produced a little history of the Royal Observatory, by request, in connection with the Tercentenary in 1975.

Smith:

Which out of all these things have given you the greatest satisfaction?

McCrea:

Satisfaction is a rather, invidious term. So far as intellectual satisfaction, pure intellectual satisfaction goes, I think there's nothing like pure mathematics. I haven't mentioned that very much, but I have done things in pure mathematics. I think that gives the greatest purely intellectual satisfaction. But I don't think it's the most significant thing; it's hard to pick out anything that gives more general scientific satisfaction than anything else. It may be this idea of the significance of the structure of the Galaxy for the phenomenon on this planet. It is something rather appealing since it brings a great deal of astronomy together.

Smith:

Tell me about the main things you've done, outside of working at your astronomical career?

McCrea:

Humanly speaking, the main thing in my life has been my family. I've been very close to them, to my family life, and of course, one can't have a family without it taking time, and one enjoys that.^[42] I used to play a lot of games and I do a lot of walking. I now do, in connection with my work a lot of traveling. We haven't talked about visiting other places.

Smith:

Yes. I know you've done a lot of traveling for the British Council, the Royal Society?

McCrea:

Yes. I've done that, and I've been visiting professor at variousEbert places. I can't help being interested in the traveling itself, seeing places and more particularly the people in them. At one time, I did a fair amount of rock climbing. Nothing very staggering, but I enjoyed it and went with real climbers. And I've done a bit of painting, although I don't have much time for that.

Smith:

Would you mind telling me about your religious beliefs if you have any? Do you have any strong convictions?

McCrea:

Yes. I'm a practicing Christian, and Anglican, and I can claim a real faith. I know there are many problems and puzzles, but one is conscious, at the very least, that there must be a purpose in one's existence.

Smith:

Has your science ever made you doubt that?

McCrea:

I don't think doubt is quite the right word, because I think the form in which one expresses this, especially to oneself, must depend on one's whole intellectual experience, and background. And no doubt, if I could get into the mind of a non-scientist who professes to be a Christian, we would find that our interpretations were somewhat different. I don't think one's conviction is a result of any very intellectual analysis. I think it's a matter of trying to live in a certain way, and trying what works. It's a pragmatic sort of thing. But I don't think it gets any weaker. It may become a bit harder to express, but as a basis for life, I find it grows stronger.

Smith:

To draw to a close, I wonder if there's anything we've left out? Is there something of interest that we've missed?

McCrea:

Well, I think you've covered a great deal of ground in detail. It occurs to me that we haven't talked very much about some societies. I've had close associations with the British Association for the Advancement of Science, and have tried to do something for that. I have been president of its section A. And the Mathematical Association, too, is a thing I've been very attached to, and I've been president of that association. Also I have associations with the Royal Irish Academy and the Royal Society of Edinburgh.

Smith:

Are you very concerned with the image that people have of science? Are you interested in popularizing science?

McCrea:

Yes. I don't think I'm good at it, myself. I've taken what opportunities I had. From time to time I've lectured for the W.E.A.,^[43] — bodies like that. I think of course that a man like Fred Hoyle does a very good job, and in a way, I'd like to be able to do something like that, but I don't think I've got the talent. I think we owe it to the people who support us, to let them know what we're trying to do. But I think it's a very difficult thing to do that. One's best service to others is surely to use one's talents in the way they seem to be effective. If one strives to help a university to fulfill its proper functions that is a service to the community. I hope it is, anyway. I think we'd be in a bad way if we didn’t have universities. And I think the undergraduate work is of paramount importance. Obviously there'd be nobody to carry on in the next generation, if we didn't foster our undergraduates. I suppose we could go on talking forever! But I can't think of anything at this moment that you haven't at least touched upon.

Smith:

Is there anyone that you would feel is a good subject for an interview like this, someone who has been in astronomy or astrophysics for a long time and has a good memory?

McCrea:

Well, presumably if I mention anybody, he has full freedom not to do it if he doesn't want to do it?

Smith:

Yes.

McCrea:

If that's understood, I'm quite willing to mention at least one name, and that is Cowling, Professor T. G. Cowling. He's a remarkable character, and I think it would be a shame if his experience was not put on record.^[44] You’re asking about astronomers, I suppose?

Smith:

Yes, astronomers and astrophysicists.

McCrea:

A man who would give you a very interesting talk, from a general astronomical point of view, but somewhat different from Cowling's or mine, would be G. J. Whitrow, who worked with Milne more closely than anybody else. He's a very good relativist himself. He's a very good talker, in the sense of expressing himself with great eloquence. I think perhaps you'd like to think of him. I take it you're thinking of fairly senior people?

Smith:

Yes.

McCrea:

What about Sir Bernard Lovell. He would be marvelous. And one thinks of Sir Martin Ryle if you regard him as sufficiently senior. He's been going for a long time. He and I were elected to the Royal Society on the same day.

McCrea:

What about Sir Harold Jeffreys? His memory is remarkable.

Smith:

That's food for thought, anyway. Also what about H. H. Plaskett? Yes, I think a member of the Institute went to see him in Oxford but unfortunately he was ill at the time. The interview had to be cancelled. So I don't know if it will be done in the future.

McCrea:

He's better.

Smith:

Good.

McCrea:

His son is a colleague, and I was asking him only a few days ago and his father is much better. He'd give you an extremely interesting account — if he wasn't too reticent, — because he knew the Harvard school very well indeed, and I think has a very clear memory of it. He knows both the Canadian and the Harvard astronomical background. Also he was probably Milne's closest friend at Oxford.

Smith:

Yes, it would be very good.