[Cover of Sullivan's book 2009, Cosmic Noise]
Sullivan's Cosmic Noise, Cambridge University Press, 2009


NATIONAL RADIO ASTRONOMY OBSERVATORY ARCHIVES

Papers of Woodruff T. Sullivan III: Tapes Series

Interview with Francis Graham Smith
At Grenoble
27 August 1976
Interview time: 75 minutes
Originally transcribed as typescript only by Pamela Jernegan (1979), retyped to digitize by Candice Waller (2016)

Note: The interview listed below was originally transcribed as part of Sullivan's research for his book, Cosmic Noise: A History of Early Radio Astronomy (Cambridge University Press, 2009). The original transcription was retyped to digitize in 2016, then reviewed, edited/corrected, and posted to the Web in 2016 by Ellen N. Bouton. There is a considerable amount of background noise in the audio of this interview, traffic noise in the first portion and crowd noise in the remainder, making the interview difficult to hear/understand at times. Places where we are uncertain about what was said are indicated with parentheses and question mark (?).

We are grateful for the 2011 Herbert C. Pollock Award from Dudley Observatory which funded digitization of the original cassette tapes, and for a 2012 grant from American Institute of Physics, Center for the History of Physics, which funded the work of posting these interviews to the Web. Please bear in mind that: 1) This material is a transcript of the spoken word rather than a literary product; 2) An interview must be read with the awareness that different people's memories about an event will often differ, and that memories can change with time for many reasons including subsequent experiences, interactions with others, and one's feelings about an event.

Click start to listen to the audio of tape 68A of the interview.

Begin tape 68A

Sullivan

This is talking with Graham Smith on 27 August í76 at Grenoble. So, can you tell me what your background was before you joined the radio astronomy group at Cambridge?

Graham Smith

I was very much of a physicist, a radio physicist at that. Of course, like some of the other radio astronomers, I came from war-time radar research. Telecommunications Research Establishment in Malrern. And I had no particular interest in astronomy Ė I canít say that I was an astronomer as a small boy or anything like that. I was definitely a physicist, a scientist without and particular leanings, except that I was interested in radio and I obviously felt myself to be more of a practical type than a theorist. So that it was mainly to get back to Cambridge and to finish my degree, but also with an interest in radio, that took me back to Cambridge after the War. And that, of course, took me on into radio astronomy as a research project.

Sullivan

So it could just as well have been radio work with anything.

Graham Smith

It could well have been. And of course, when I joined the group, radio astronomy didnít exist by name. And it was only solar work with, of course, some ionospheric work going on Ė ionospheric work was predominant in the radio group at the time.

Sullivan

Right. How was it decided that you would work with Ryle?

Graham Smith

Well, I knew him, of course, during the war, and I think I picked up and soon shared his enthusiasm for the radio waves from the sun, which was the thing that was going at the time.

Sullivan

Right, but what was the first thing you work on? I donít think it was solar, was it?

Graham Smith

I worked with Martin Ryle on solar work even before I became a research student, because it so happened that we lived in the same house. His house in Herschel Road, he now lives in, was at that time divided into three flats. And one of the flats was shared between my wife and myself and Derek Vonberg and his wife. So we were all closely associated. The third flat was occupied by a zoologist, who had also been a friend during the War. And when Martin Ryle and Vonberg were working on interferometric measurements of the sun, which is just outside the back gate, and so we used to help them move around the antennae, particularly, at the time I remember July 1946 sun spot thing, when it was first shown that radiation actually came from the sun spot rather than the whole disk.

Sullivan

Right.

Graham Smith

We were helping move the antenna around (?) larger and larger spacings to make an interferometer measurement of the diameter. I think it was really this that caught my imagination.

Sullivan

So you never really were a co-author, but you were quite involved with it.

Graham Smith

Well, really only as a pair of hands, but this is what, I think, sparked my interest.

Sullivan

And also, just for the record, I have learned somewhere that thereís a relationship, by marriage, between you and Ryle.

Graham Smith

Thatís correct, yes. I think itís fair to say that my wife introduced her sister to Martin Ryle.

Sullivan

I see. Now, so you helped with the solar work Ė what was your main Ė what were you mainly working on these first couple of years? Was that it?

Graham Smith

I think it was about the time I started when Hey had published the point source in Cygnus, and Bolton, of course, was also working on point sources and was publishing from the southern hemisphere. I think it was Heyís work on Cygnus that really started us, and I then worked with Martin Ryle, modifying apparatus, which was originally for interferometric work on the sun, so as to work on ďradio starsĒ as they were then called, and in fact, at 81 megahertz, and interferometer which consisted of 4 yagis at each end of the baseline, it was for this that we first had to (?) the Cygnus source, and of course, at the same time to our astonishment, Cassiopeia A came up on the same recording a few hours later, and from then on, we were into the ďradio starĒ business.

Sullivan

Right. Is it true that Ė I asked Martin Ryle this Ė in your first paper, Ryle & Smith in 1948, you talk about another source of variable intensity which was perhaps coming through the (?)

Graham Smith

Thatís right, thatís right, yes. That stayed in the catalogues for some years.

Sullivan

What about these variations Ė what did you think they were when you first heard about them?

Graham Smith

The variations in the, you mean in the supposed source, the one that wasnít real?

Sullivan

No, no, no.

Graham Smith

The ones in Cygnus. I think, perhaps, thatís hard to say precisely, but I think we were perfectly prepared to think it was ionospheric effects. And we, of course, spent a lot of time trying to distinguish between ionospheric effects and intrinsic effects, by using spaced receivers and that sort of thing. That developed quite rapidly.

Sullivan

Well, in fact, Iíve just come across two papers, Little and Lovell and yours published together. Could you tell me about that? Thatís one of the few Cambridge/Jodrell collaborations over the years.

Graham Smith

Thatís right. In fact, the observations were made, more or less, independently. But, it was obvious that we were after the same thing, and it was obvious that the two papers should be published together. You see, in fact, those were separate papers published at the same time, right?

Sullivan

Thatís right. But didnít you go up to Jodrell?

Graham Smith

Oh, yes, we went up there and talked and made sure that the paper came out together, because we were obviously on to the same thing. Furthermore, we actually did compare some of the recordings made simultaneously at the two places so as to see if there was anything which was obviously intrinsic to the source. And it was, I think, at that time that we showed at least those fluctuations came from the ionosphere.

Sullivan

So it sounds like, from what youíre saying, it is difficult for me to determine from the published records that you all along suspected the ionosphere. It was just a matter of pinning it down. You really felt it was never intrinsic.

Graham Smith

I think we were open-minded, but at the same time the radio group had a very strong ionospheric background because Ratcliffe was responsible for so much of it. So it was natural that we should turn to the ionosphere as the explanation of it. And in the same way, when position finding started out, then it was natural to look for ionospheric refraction, you see, and in fact, I did quite a bit on that. As you know, it led me to a measurement of the total electron content of the ionosphere, which was, I think, again, an indication of our ionospheric interest under Ratcliffe.

Sullivan

Right. Did you know about the Australian work which was going on, more or less, simultaneously with yours on Cygnus A fluctuations?

Graham Smith

Not really, no. I think that at that time, not being astronomers, we werenít really very conscious of what was going on anywhere else in any kind of astronomy. And we werenít really very conscious of what was happening in Australia, even in radio astronomy. I think itís fair to say that the radio astronomers in Australia probably sounded just the same way. We worked really quite independently, and then found that we were producing answers of the same sorts of problems Ė which produced some interesting situations. [laughter]

Sullivan

At this stage, or at a later stage?

Graham Smith

Well, of course, we very quickly were measuring the positions (?) and (?) the second question and it really very quickly became a competition as to who got an accurate enough answer to be meaningful.

Sullivan

But there were no big conflicts on these early positions that I remember.

Graham Smith

No, there were no great conflicts, but at times we had a more accurate position than they had and so forth, and that was the element of competition.

Sullivan

With the exception of Boltonís very first positions, which were degrees off.

Graham Smith

Boltonís were somewhat off at one time.

Sullivan

That got corrected rather quickly.

Graham Smith

Thatís right, yes.

Sullivan

What about the identifications, while weíre talking about the Australians versus the British? What about the identifications that came out, tentative ones, of Virgo, Taurus, and the Crab?

Graham Smith

And the Crab.

Sullivan

Right.

Graham Smith

And the Crab as well.

Sullivan

How did you view those?

Graham Smith

Well, again, I think itís fair to say that we were pretty blinkered and pretty busy on our work and we didnít have an awful lot of notice of what we happening elsewhere. And so it was some time before it dawned on us that their positions were leading to real identifications. After all, they did get at that time the first tentative identification of the supernova in the Crab and they did get Centaurus A, the first extra-galactic object, and we maybe looked at these and said, ďMaybe these positions arenít good enough for the real identifications.Ē Looking back on it, of course, they were dead right. And I think we all perhaps shared their enthusiasm for these identifications. And again, maybe we could have said right away to optical astronomers, if weíd been talking to them, ďLook, this is whatís happening and itís very exciting.Ē Well, I think at that point, our horizons werenít yet expanded.

Sullivan

Do you think you would have gotten anywhere with the optical astronomers?

Graham Smith

Oh, I think there were one or two people in Cambridge who were interested in what we were doing. Yes.

Sullivan

Dewhirst.

Graham Smith

Dewhirst, in particular, yes. And I think Redman, although heís a man who some people would say was old-fashioned, in fact, would have taken it very seriously. He really was an encouraging chap to talk to.

Sullivan

But now you did do the 1C survey paper to try to make identifications with many nearby galaxies.

Graham Smith

Yes.

Sullivan

And I donít quite understand your remark saying you should have been a little more enthusiastic in trying, because you actually went overboard.

Graham Smith

We did, no, I mean Ė what I meant was Ė I think we should have taken the Australian results more seriously.

Sullivan

Oh, I see what youíre saying.

Graham Smith

We, I think at that time, we were saying, ďThis sort of position accuracy isnít good enough.Ē And in point of fact, it was, as it turned out. And I think that was maybe a mistake.

Sullivan

Well, at least for objects that unusual.

Graham Smith

Thatís right; thatís right. It was, perhaps, a lucky guess. But, it was a very good guess.

Sullivan

One didnít know how low down you were going to have to go before -

Graham Smith

No, no. Thatís right. When we felt that we were getting accurate positions out, because we got this Michelson type interferometer, rather than the Lloydís mirror, and we felt that we were getting more accurate positions. And, of course, we didnít appreciate right from the start how many sources there were going to be, and so we didnít appreciate the confusion.

Sullivan

Well, weíre jumping ahead now.

Graham Smith

I know, but even so, when you talk about 1C, 1C was, how many sources, most of these were wrong and that was a confusion (?).

Sullivan

Iíve never checked that out; Iíve looked at sort of the five or ten obvious ones and tried to see what they correspond to now, but Iíve never actually gone through the whole list.

Graham Smith

Most of them are (spheres?)

Sullivan

I didnít realize that.

Graham Smith

I think it was at that stage that we were saying, fortunately not out loud in publication, but we had definitely gotten several of the extra-galactic nebulae, M31, M33, M81 and so forth. And we could prove with statistics were real because you couldnít have accidental identification of so many sources. In point of fact, I believe those identifications were entirely without foundation because of the confusion problem, even in the 1C days.

Sullivan

I see, well, Iíll have to look at that again more closely. Now, (?) is that you built an aerial steel to do a full survey, having gotten Cygnus and Cas (overwhelming background noise) Can you tell me about that?

Graham Smith

This was really Ryleís inspiration (?) Mostly there were two directions we went. One, to get accurate positions, and that entailed the interferometer which I used a great deal and the two 27ft. dishes. And at the same time, we were developing the larger arrays, trying to see more sources. And I think the development of the OH was very much a joint effort, although, of course, Martin Ryle was throughout the prime mover. The first idea to get a big array was to build a thing in the form of a bedstead and there we made a flat reflecting surface using stretched piano wires on an angle iron frame with a (?) side array of dipoles and we made one for each end of the experimental range we had, and we used that, and then the next stage was really to build two larger reflector arrays. We had all sorts of ideas of trying to make very large areas, collecting areas, cheaply. And we thought of the arrays of Yagis, and other traveling wave sort of antennas, and so forth. But we ended up building the large spherical cylindrical paraboloids Ė those are the ones that really going (?) telescopes.

Sullivan

What was your experience working in radar during the War Ė was it antennas primarily?

Graham Smith

It was largely microwave, they were in those days, coaxial cables so that I found it fairly easy to get on to low-noise amplifiers and coaxial cable techniques, and in particular the things like hybrid arrays and diode switches and things. In fact, I had a paper in the EE about hybrid arrays. That, I would say, was partly sparked off by Bernard Burke who turned up at the Department of Terrestrial Magnetism in Washington when I was there.

Sullivan

This was in 1954 or so?

Graham Smith

This is 1953, I think, yes. But that shows my interest, I think, in coaxial cables and other techniques Ė antennas came quite early, too.

Sullivan

Well, now going back to the 1C survey, what did you think you could do with this besides the identifications that were attempted?

Graham Smith

I think our objective was just to see what it was to be seen in the sky. I mean it was astonishing that the sun produced anything, even more astonishing that there were a lot of point sources in the sky, and the question then came: ďWhat sort of things can we do?Ē Well, the first thing is you try and identify, and second, you may decide that you can find something statistically about the sky. On the first fifty sources, I did, in fact, do a log-n/log-s plot. Which that was the first one.

Sullivan

Thatís right.

Graham Smith

I remember sort of a flash of inspiration that this would be a good idea, and itís so funny to look back and realize that optical astronomers had been having all these thoughts years before, but yet they come as an entirely new idea.

Sullivan

Okay. So it was not based at all on the plots that they had been making of magnitude versus number of galaxies -

Graham Smith

Not at all, I hadnít a clue. I had not been in contact with astronomers.

Sullivan

How were you learning astronomy Ė just reading a chapter in a book when it became necessary?

Graham Smith

Well, you see, I think I was acting much more as a radio engineer, thinking in terms of radio techniques and doing what we could to pick up radio signals from the sky. Now you find, you bump against astronomy, conventional astronomy, almost by accident. For example, when we came to finding that, well, take the time when Cassiopeia A first appeared on the record. This was the third occasion. I remember turning up at the laboratory, and the thing had been set running and there was an interferometer trace of Cygnus just as it should be Ė absolutely marvelous. And then three hours later, or whatever it was, another interferometer trace which subsequently turned out to be Cassiopeia A, but nobody had ever detected this radiation before, we didnít know it was there, it appeared as a fluctuating trace with a different periodicity than Cygnus A. This was a complete surprise. We thought it must be something to do with the way things moved in the sky, but we had no training, neither of us, in celestial coordinates. I went away to think about it, and I remember coming into the Cavendish Lab an hour or two later and saying to Martin Ryle and to Ratcliffe, ďI think itís in a constellation called Cassiopeia.Ē That, of course, became the problem using the Würzburg dishes, which, incidentally, were largely constructed by another chap, Machin, who appears in these early papers.

Sullivan

Right.

Graham Smith

And became the problem of finding positions with such an interferometer.

Sullivan

Hold it now. How did you get in the constellation of Cassiopeia? After thinking about it, you determined that the fringe rate should be different?

Graham Smith

I decided the fringe rates would be different according to the distance from the pole, so that was my first introduction to spherical astronomy.

Sullivan

Right, and when you say that Machin was the one that built the Würzburg dishes -

Graham Smith

This was largely his. He was also very much engineering inclined, and when it came to the idea that we ought to build an accurate interferometer, where the electrical centers of everything could be accurately determined and so we could find the accurate positions of anything Ė solar sources as well as other things Ė he largely did the construction, and I took over and I did most of the electrical (?) on it. I installed coaxial cables and so forth; he joined in on (?). But to give another example of my lack of astronomical background, when it came to using the accurate interferometer, of course, I had to take account of the fact that this was a kind of instrument which was not aligned on an east-west axis, it was 5° off.

Sullivan

Why was that?

Graham Smith

Well, it was built along a hedge of a field.

Sullivan

Oh, I see.

Graham Smith

Precisely, yes. It was roughly east-west as far as we were concerned, but it became rather important that it wasnít exact east-west Ė it was 5° off. And it was about 20 minutes of arc off level, you see. And it was also an unknown distance apart, which we had to measure very carefully; we had to find out where there was a standard 100 meters, which was not so easy. We found it in the surveyorís department in (?) Hall. At any rate, to find out how to correct for this 5°, I had to learn some spherical trigonometry. I was, in fact, (?) in the tripos examination during that summer and I spent the hours of peace one gets in an examination room working out spherical trigonometry from scratch.

Sullivan

I see.

Graham Smith

And I worked out how to correct for the lack of east-west and the lack of level of the instrument, and Iím proud to say I got the right signs for these corrections, and it was after I had completed my calculations. I found the positions of these sources that I was told that a chap called Bessel had done it a few years earlier.

Sullivan

Youíre referring to the Bessel?

Graham Smith

Yes, of the Bessel functions. And if you look in the textbooks on spherical astronomy, of course, itís all set up there. But I wasnít familiar with these textbooks.

Sullivan

This is not a complete loss, by any means, (?) barely gone through it from scratch.

Graham Smith

Not at all, Iím very pleased to have done it, and I didnít waste an awful lot of time, in fact.

Sullivan

Well, tell me now, I think weíre coming to the stage where you must have determined that you really needed to get good positions on the sources you could get them for, namely (?). So how did you go about doing that?

Graham Smith

I think oneís motivation can be very simply set out as saying you do the next thing that you know you can do well, and it was obvious that we could get the positons on this. We knew of the Australian ďattemptsĒ (?) identify and we thought they were not good enough Ė weíve got to get better positions Ė and we had this accurate interferometer going. So that I spent some time, first of all, I worked at the lower radio frequency Ė 80 megahertz, using the arrays that weíve already talked about. From there you have to worry about refraction, ionospheric refraction, which, of course, turned out to be a subject in itself, but as soon as we got the dishes, we went to a higher frequency, which I remember was 214 megahertz, which was again, corresponded to an old war-time radar equipment. Oh, good heavens yes, I remember we did, in fact, use an array, a radar array, which was an array of yagis on a single mount for a time, and then we went over to the Würzburg dishes.

Sullivan

I see.

Graham Smith

And so that somewhat determined the frequency we worked on, 214 megahertz. Now, thatís not much affected by refraction by the standards of those days, and that was really when I did a to concentrate piece of work which was very much all on my own, the position work. And that led to the position accuracy at about a minute of arc on four sources.

Sullivan

This is written up in Nature.

Graham Smith

Thatís right.

Sullivan

In 1950 or 1951, one or the other.

Graham Smith

Thatís right. I canít remember the exact one, it would be about 1951.

Sullivan

1951, I think. Now having gotten, well, what else Ė I think there must have been more troubles than simply worrying about refraction.

Graham Smith

I donít remember running into any severe troubles. I remember developing techniques, getting amplifiers with good noise performance and so forth. These were war-time radar preamplifiers, disk-sealed triodes, and I spent a little time understanding noise factor of these things and the sources of noise but I understand noise sources in triodes better than I understand transistors. And I think we just made steady progress doing this. There wasnít a real set-back in it. It was just -

Sullivan

The end result was a quantum improvement by a factor of ten almost.

Graham Smith

Yes, I think that one sometimes strikes lucky in the jobs which stare one in the face, which is what happened at that time.

Sullivan

So given that you had these positions, what does one do with them?

Graham Smith

Well, we did, at that time, know one or two people in the observatory. For one thing, we were interested to know what our latitude was. I had discussed this problem, particularly with Dewhirst and Iíd been along there and had talked to him about problems of identification. And he, of course, was the first chap who really tried to identify the Cyngus (?)

Sullivan

I talked to him at Cambridge, and he gave me his side of the thing. And he came up with 11/2 identifications if anyone wants to look at them.

Graham Smith

Thatís right. And at that point, I think the advice to write to Baade came definitely from the observatory, whether it came from, (?) or Dewhirst or Redman, I really donít know.

Sullivan

I see. And also, David Edge has shown me, he didnít actually show me, but he told me about the correspondence between yourself and Baade, which I would very much like to have copies of if youíre willing.

Graham Smith

Yes, certainly. I donít know what the best way of getting them, I hope I can put my hands on the copy. But otherwise, there should be copies in the Cavendish. And David Edge, you said, has a copy.

Sullivan

Well, Iím not sure if heís got copies, or whetherÖ I think, he must have made copies.

Graham Smith

I suspect so. Youíre probably directly in correspondence with him. Why donít you try to get them from him?

Sullivan

Do I have your permission?

Graham Smith

Of course, of course, certainly.

Sullivan

It was very soon, I think, just a couple of months after the Nature article, when Baade got Cygnus and Cas.

Graham Smith

Thatís right, yes.

Sullivan

And I guess he wrote to you at that time. And what was your reaction?

Graham Smith

Oh, it was very exciting. I really was, I think, the first feeling that we were really astronomers. Here were real-life astronomers saying that we had done was exciting. Of course, letís be fair, that had happened on the solar work before there was a lot of interest in the solar work had brought us in contact with astronomers. But here was a completely new field of astrophysics that brought us in contact with the California astronomers for the first time. And that was certainly very exciting, and the thought that weíd gotten objects in which new physical processes were going on was also very exciting.

Sullivan

But now, itís interesting that you say that the optical solar astronomers had shown some interest, because Iíve just been talking with Christiansen and he said that it was very rare that they -

Graham Smith

All right, all right. It was a rare one, but we knew that we were in astronomy doing solar workÖ and weÖ (laughter)

Sullivan

I see.

Graham Smith

I think the (?) work on sourcesÖ I think we really still felt that (?) radio engineers finding out what it was that was coming from the sky, and we didnít feel ourselves as having any sort of place in the community. And I think it was from that time on that we really felt as though we were slotting in. And we would get something from them, and they would get something from us.

Sullivan

So what was the next step? I gather you did not really go along the identification route yourself.

Graham Smith

No, it was definitely our task to carry on the kind of thing that we had done, and obviously we had begun to do quite well. So then you then have to build a larger array and get more sources and get accurate positions from that. So we were all very much involved in the techniques and actual efforts of construction, and, I as you know, we worked very much with our hands. We got very good at wielding sledge hammers and all that sort of thing. So at that point, I think that I kept going on positions with ionospheric work. I canít remember when would be the last publication of mine on the ionospheric work; it would be about that time, I suppose. And then I think I helped him a lot with the 2C and 3C survey construction work.

Sullivan

If I remember right, youíre not a co-author on the 2C actually.

Graham Smith

No.

Sullivan

But you were working with the (?) -

Graham Smith

We all worked together very much.

Sullivan

Did you get involved in the interpretation of 2C and the definitions of what a radio source was, and so forth? Before it got published, I mean?

Graham Smith

Yes, I think we were still, not so many, but we were in any way differential in than what we did.

Sullivan

And, I canít refrain from asking, as this went along, did you see any problems developing or did you Ö as far as too many sources? Youíve already mentioned -

Graham Smith

No, really no. I think itís a problem which came to us by stages. I mean, each time we realized that we needed more angular resolution; say you build a larger antenna and you get more sensitive, and you see more of the (?) you see. I mean, it isnít until we really reached the 3-C, and after the 3-C had been published, that there is a full realization of the magnitude of the problem.

Sullivan

But, so the comment that you made about 1C was definitely one in hindsight?

Graham Smith

Oh, it was -

Sullivan

No idea at the time -

Graham Smith

Well -

Sullivan

A large fraction of those might be in trouble.

Graham Smith

I donít think there was full appreciation of what a large number of those small sources can be. But, of course, there was an appreciation of the fact that sources were not being seen singly, and that you had therefore had to get better angular resolution before you can really be sure of what youíre doing.

Sullivan

The blending, you mean.

Graham Smith

Yes, there was an obvious blending, but the full horror of the situation Ė that there were a very, very large number of sources to be detected, and much of the blending was a blending of a very large number of small sources Ė I donít think that was really appreciated until the analysis of 3C by Hewish and Scheuer. Yes, I would think if there had been a full appreciation, 3C wouldnít have been published as it was.

Sullivan

2C you mean.

Graham Smith

2C. Well, even 3C had quite a lot in it.

Sullivan

Well, okay, Iím not quite aware; Iíve always thought of 3C as (?) globe-shift problems.

Graham Smith

Well, thereís 3C and 3C revised.

Sullivan

Right.

Graham Smith

And 3C revised is a much sounder catalogue than 3C. And 3C certainly affected not just by lobe shifts, but by some over-optimistic interpretations of individual sources that were not real.

Sullivan

I didnít realize that. 3CR is -

Graham Smith

3CR is sound.

Sullivan

Right. But what were the differences? Checking for lobe shifts?

Graham Smith

Yes, thatís right. And using the stringent criteria about identifying individual sources. That was done by Bennett. But I had quite a bit to do with that.

Sullivan

Can you be more explicit about (?)

Graham Smith

I think thatís a little hard. Bennett set the task which I think was supervised quite largely, of referring back to the original records and sorting out which sources were quite unequivocally right, which behaved (?) proper beam shape in both coordinates. And being as objective as possible, when one could say there was not likely to be a shift when there was likely of being a shift. I mean there were many fewer sources in 3CR that there are in 3C. And that was a result of the weeding process.

Sullivan

I see. I must admit, Iíve looked at 3C, but I havenít looked at 3CR. That came out in 1962?

Graham Smith

Yes, approximately then. If you compare them, I think youíll see that (?)

Sullivan

Okay, well, now if youíll bear with meÖ letís just see if weíve missed any points. Okay, weíve got the 1C survey, we talked about the ionospheric, (?) you had a paper in Nature that we mentioned before on radio stars, and then you also had one about trying to measure the annual parallax.

Graham Smith

Thatís right.

Sullivan

Or proper motion.

Graham Smith

Thatís right. Well, of course, thatís right. This was a long continuing series of observations. I remember observing those four sources throughout a year, without missing many days or nights. And, of course, those four (?) sources came across the meridian at fairly evenly spaced times through the day and night. So I got entirely used to getting up, dashing out and taking observations and going back to bed. And that was because we really hadnít identified them at the beginning of that, so we didnít really know whether they were near or far. We had no clear idea of whether these things were even possibly in the solar system. Certainly we had no idea where they were in the galaxy or extra-galactic. So we thought, ďWell, weíll measure parallax and measure proper motion. Letís just go on the positions.Ē And, of course, we find the ionosphere is a nuisance in that, so you find yourself investigating the ionosphere, and in point of fact, you donít measure any parallax or proper motion Ė thatís the way it goes.

Sullivan

Can I ask you, do you remember sort of what your inclination was Ö I see, it looks like we are going to get inundated here. Storm from the East.

Graham Smith

It may not rain, it come from the East but it doesnít rain every night.

Sullivan

I see. Well, weíll wait. What was your predilection as to the nature of these things?

Graham Smith

The nature of the position shifts?

Sullivan

No, the other sources, radio stars, as they were.

Graham Smith

Certainly when I worked out a log-n/log-s, I was thinking of them as galactic objects. Martin Ryle had some speculations, in a paper in Proc Phys Soc. I remember, as to the nature of things. And I think we were all a bit baffled about the possible radiation mechanism. The idea of the synchrotron radiation was coming out in a paper by Alfvén and Herlofson about that time.

Sullivan

And Kiepenheuer.

Graham Smith

And Kiepenheuer as well, yes. Hadnít really sort of latched onto this, so we hadnít got much of a good physical picture as to what we could do.

Sullivan

You bring that up, of course the Russians really carried the ball with this synchrotron radiation.

Graham Smith

Oh, indeed.

Sullivan

But were you ever aware of the Phys. Rev. articles that suggested this in 1950?

Graham Smith

Yes, I think so, but I wouldnít say that anyone of us saw with a flash that this must be radiation by synchrotron emission, and must therefore, or could therefore, be at a very great distance. I mean, I think one would need to be very perceptive to pick up one of those articles and suddenly see the whole thing as falling into place.

Sullivan

Well, sure it was of course, speculation.

Graham Smith

Itís more gradual than that.

Sullivan

Well, hereís another one, Machin and Smith, ďOn a new radio method of measuring of electron density in the solar corona.Ē

Graham Smith

Oh, yes.

Sullivan

Nature, in 1951. Can you tell me about that?

Graham Smith

Oh yes. I canít remember who had the first ideas on that. I have an idea it might be Machin, but we certainly discussed together the ideas of refraction in the solar corona, and it was obviously part of (?) And the idea is that if you keep on measuring the position of radio source and it gets close to the sun, you may be able to see an extended solar corona. Because of the refraction. And we tried this.

Sullivan

In 1950-51.

Graham Smith

Thatís right. Of course, it didnít work. Because what you see is irregular defraction, rather than a regular refraction. In fact, regular refraction doesnít seem to (?)

Sullivan

This is telling you something about the nature of the corona.

Graham Smith

Indeed, yes. Yes.

Sullivan

So, did you follow it up at all?

Graham Smith

I was in it for a year or two, but then that very much became Hewishís work, and it still is.

Sullivan

Right. I talked to him about that in the recent past. I think weíd better move this inside Ė rain.

[Brief Break]

Sullivan

So an occultation in 1952 was also reported in Nature by you and Machin in 1952.

Graham Smith

Thatís right. I think that was probably the last one that I was involved in there.

Sullivan

Okay. Hereís another set of observations, and this was on the angular sizes.

Graham Smith

Ah, well now this is a different subject that I really moved onto at this point. As you know, you get angular diameters by using interferometers of different spacings. And we didnít have anything on railway lines at that times, we only had an interferometer with a fixed spacing, so I started the idea of using a smaller, portable antenna which I used in conjunction with the two fixed ones to make two baselines that I could use either sequentially or even at the same time. And in that way, I did make the measurements of the diameters of Cygnus A and Cassiopeia A radio sources.

Sullivan

What was the real motivation for getting these angular diameters? To aid in identifications or to learn more of the physics of the sources or what?

Graham Smith

I think identifications first, but again, I think one has to remember that this sort of joy at being able to measure anything and say, ďBy gosh, we can not only measure the positions, we can also measure the diameters.Ē And I think, as a physicist, of a practical experimental turn of mind, on immediately recalls Michelsonís work and said, ďWell, gosh, we can do the same sort of thing that Michelson did.Ē And itís not long before youíre led on to Fourier analysis of the source distribution. In fact, of course, in Australia, Pawsey was onto that with the solar work and he used, I think, he was probably the first person to find out you could use Fourier methods.

Sullivan

Yes, I think so.

Graham Smith

I think that the attitude is the same in both cases; you find a radio physicist who suddenly finds he can apply his interests and techniques into a new field, and you donít sit around saying, ďI wonder what these sources are. If I could measure the diameters, I would be able to tell. How can I measure the diameters?Ē You work the other way, you find that youíve got a jolly good technique and you say, ďWhatís the most interesting ways of applying this technique?Ē And from that, you get the fact that these radio sources have finite diameters, and then you start thinking, ďWell, maybe this tells me something about them.Ē

Sullivan

Right. Would you say that happens at all today? Or is it more the other way today?

Graham Smith

I think itís more the other way today because we have very much more sophisticated radio telescopes, which, of course, are capable of measuring very many more things than they ever will measure. In a way, we were working on techniques which had a limited application because all the antennas and so forth were pretty small, and really weíd say, ďIf we just modified this apparatus or build a slightly better bit of apparatus, we can measure something more.Ē Whereas today, to measure something more, you can go on using the same apparatus on different objects. And so you naturally say, ďWhat are the most interesting objects to do this measurement on?Ē And that takes you more in the way of conventional astronomy.

Sullivan

Yes, yes. Was the thrust to measure angular sizes influenced by the concept of radio stars, that you might well expect that the thing could never be resolved.

Graham Smith

Yes, I think so. Of course, as a technique, it was probably influenced by the solar work, where you can tell if itís a sun spot or the whole corona by measuring its diameter. So that I think there was a clear feeling that you could get into the nature of the source by measuring its diameter.

Sullivan

But for instance, did anyone ever say, ďWell, the stars are a few thousandths of an arc-second in diameter and -

Graham Smith

Oh, I think that we thought it couldnít be the surface of stars that we were looking at. We knew that it would have to be something extended. Oh yes. I mean, I think we thought enough about the nature of the sources to say it canít just be the surface of the star radiation on a black body curve, we knew that very well.

Sullivan

Right, but still, it might be much smaller than an arc second even.

Graham Smith

Yes, of course, at that time that was fairly unlikely thing, because it was very difficult to conceive of a thing which had a brightness temperature as high as these things would have. I think youíll find that sort of concept in Ryleís Proc Phys Soc paper about 1951 or so.

Sullivan

You knew it was not thermal, but still that was a bit (?)

Graham Smith

No, itís clearly not thermal, but you see, the solar radiation turned out to be thermal, quite largely. The corona was at a million degrees, and we knew that even if the thing is not thermal in the sense of being a black body, still it probably had to have particle energies which corresponded to the brightness temperatures we were seeing. That, in fact, has remained true through most of radio astronomy. Itís only when you get to the pulsars that you really have got coherent radiation and the particle energies do not need to be that high. So it was very unlikely that youíd get particle energies that high, and then, of course, there were -

Sullivan

Well, the masers came before pulsars, to be fair.

Graham Smith

Thatís true, the masers did come first. But even if you had particle energies that high, youíve got to start worrying about a mechanism that doesnít get optically thick and we already knew of that concept. So that I donít think we seriously thought that these were stars whose hot surfaces were producing radio waves, no.

Sullivan

Now, I talked with Bernie Mills a couple of days ago about the set of three papers that appeared together in Nature and how they came about at the URSI meeting. What is your version of that URSI meeting and the work in Sydney and so forth?

Graham Smith

Yes -

Sullivan

1952, that was.

Graham Smith

Yes. That was the first big scientific meeting Iíd ever been to, and I was, I think, in a fairly bewildered state. I think itís true that up to that time, I hadnít had a full appreciation of how much was going on in Australia, and itís certainly true that we had been working independently, so a whole lot of observations came together and Ė

End tape 68A


Click start to listen to the audio of tape 68B of the interview.

Begin tape 68B

Graham Smith

Ö whole lot of observations came together and I suppose naturally if one thinks oneís been working alone, one is confronted by other people during the same thing, and oneís immediate reaction is to say, ďWell, my observations must be better, even if theyíre not unique.Ē

Sullivan

Sure.

Graham Smith

And Iím sure this happened quite strongly on both sides. As you know, there was quite a lot of feeling for some years between the Australians and the Cambridge group. And I think it was just that feeling. That instead of finding that one was alone in the field, one was working on very closely paralleled lines. And so there was a pretty strong competitive feeling (?)

Sullivan

Yes. From the, maybe more philosophy of science, itís sort of interesting to ask whether this working on parallel lines was an accident or not. Was it sort of inevitable that once, you know, that if the group had been on another planet, that things would have developed the same sort of way?

Graham Smith

I think that it was almost inevitable. Because what had happened during the War was well-known to both sides. The level of technical expertise was obviously similar in both places. Basic radio research had been held back and so there was a situation which was absolutely ready to be explored, although nobody realized that that was what the situation was. The Australian Radio Physics Division was a strong institution which was able to carry out the basic research, and I think it was perfectly natural that both things did go in that direction.

Sullivan

But this is well after the War, weíre talking about now. Itís seven or ten years after the War and things are still going parallel. Of course, then you had more communication which was (locking?) you together.

Graham Smith

Yes, I think the communication really only started seriously at about this time.

Sullivan

That URSI meeting Ė do you remember anything else about the status of radio astronomy?

Graham Smith

Oh, well, I remember seeing Christiansenís work on multiple element interferometers, the solar work which I admired very greatly. I think that was very exciting, and of course, Wild was also working on the spectrum of solar bursts.

Sullivan

Right.

Graham Smith

I found this very impressive, indeed. And I think it was from that time on that I knew that the Australians were not just competitors, they were really a very serious and (?)

Sullivan

Yes. Well, coming down to the publications again, you have this article in the Proc. of the Physical Society in 1952 about the nitty-gritty details of how you measure the angular diameter of the stars. Radio stars. Now youíve passed over it rather lightly, but it seems to me that this article and a similar one about positions, in which you go through all the equations, like you say, really are sort of basic Ė no one else had done all these things. Someone had to sort all these things out.

Graham Smith

Thatís right. I think that it was fortunate that I got in on the group which was using the 2-element interferometer rather than the group which was using the reflection in the sea. This put me in a position to do just that work.

Sullivan

Well, why do you say that? Because the two element proved in the end to be more useful in its -

Graham Smith

The more accurate technique, yes. The refraction, the reflection in the sea is not a good thing because youíre looking at the horizon, which is not a good place to look if youíre worried about refraction, either in the atmosphere or the ionosphere.

Sullivan

Right, but I still donít see quite what youíre saying because there are just as many, in fact, one could argue there are more problems that need to be worked out in terms of making it work, you know, tide levels, and all this sort of thing with the sea interferometer.

Graham Smith

Yes, there are more problems. But what I mean is that it was fortunate not to be involved in the sea interferometer, which is where the Australians were. I was fortunate to be involved I the two-aerial thing, where you can select the situation in transit. I was just there at the right time to work out how to use it.

Sullivan

I see. Okay, hereís the one in the Monthly Notices about the position of the radio star.

Graham Smith

Yes, I remember that. I once presented that paper in front of the Royal Astronomical Society, which is the first paper I presented to them. In fact, you will find that one of the positional astronomers in Royal Greenwhich Observatory, Andrew Murray, remembered my presenting this paper. Of course, he was already a positional astronomer at the time, and I think he must have regarded it with a certain amount of amusement. My elementary exposition of the principles of positional astronomy which were involved in this. The thing I remember mostly was that I drew a fairly accurate circle on the board Ė at least I didnít make a botch of that!

Sullivan

Do you remember at all what sort of reception?

Graham Smith

I think people were pleased to see that accurate positions were coming up. Possibly some of the conventional astronomers were beginning to think that the radio astronomers were becoming respectable if they were able to make positions to anything like that accuracy.

Sullivan

Moving on. Oh, this must have been a very (?) thing: apparently you looked for radiation of Jupiter. But before we get to that, we should go to your sabbatical, I guess it was.

Graham Smith

Yes, this was just after I came back.

Sullivan

Can you tell me about that?

Graham Smith

That was, I think, a result of Ratcliffeís influence in the group, because I was very fortunate to go to that conference in Australia. And I came back via the States, and Ratcliffe said that I should call in at DTM. He, of course, had close connections with it because of its Director, Merle Tuve. And he said I should go there, and that was my first experience in the States. And soon after I got back to England, and I was invited to go there for a year. They were already interested in radio astronomy, but they had started largely on the hydrogen line, and I felt this wasnít quite my way of working because I knew a lot of people were working on the hydrogen line, or were starting to, and I thought I would just be one amongst many. So it wasnít particularly interesting in work on the hydrogen line, but they were starting up work on lower frequencies, recording the sun and so on. So it seemed to me that it would be a good place to work for a while. And so, the only trouble was that I had a family Ė a wife and three children. My wife was expecting a fourth, and so I reckoned this made it quite impossible. I went to Ratcliffe and said, ďLook, Iíve got this extraordinary invitation. I canít imagine why theyíre inviting me, but in any case Ė I canít go because my wifeís expecting a baby.Ē His comment was quite straightforward: ďThey have babies in America as well.Ē Which, you see, hadnít apparently occurred to anyone. So I went. And I had a marvelous time, because itís a very good institution, very open-minded about directions of research, and I was given a free hand and told to think of something new to do, if I wanted to do something new. So I said, ďOkay, I donít want to work on the hydrogen line, letís try to pursue low frequency radio astronomy Ė since everyone else is going up in frequency, letís try and go down.Ē And so during that year, I was largely responsible for the big array on 21 megahertz which subsequently discovered the signals from Jupiter. I worked with Bernie Burke, who, of course, was still there and we had a great time building this array.

Sullivan

Iíve talked with Burke and Franklin about that discovery. Were you influenced by the fact that it was solar minimum to go to low frequencies at all?

Graham Smith

Yes, I think this was in mind, that this was a good time to do it. It should be done at some time anyway and this was a good time to do it.

Sullivan

And, in fact, did you get to do any observations yourself?

Graham Smith

Scarcely. We just about got the thing working and I left the thing parked, so to speak, at the declination 22° because the Crab Nebula came up and IC443, and it was a good way of leaving the thing running to test its stability. And Bernie Burke will have told you the consequences, that that happened to be the declination that Jupiter was at. It was an incredible piece of luck.

Sullivan

I see, but it was your decision to pick these sources?

Graham Smith

I think so, yes. Well, you know, Bernie Burke and I worked together on this and we said, ďWell, letís leave it running thereĒ and we did.

Sullivan

When you visited America, did you go out to talk to Baade and Minkowski?

Graham Smith

Yes, I did. I met them. Merle Tuve was and is a marvelous character and he said that I must cross the States and visit Pasadena, and so the whole family got in a station wagon and we just went across, somehow or another. And so I met them there. In fact, I did some radio astronomy in California. One of the ideas that we had was that it might be a good idea to see if there were any genuine fluctuations, which goes back to the fluctuation story which correlates with the very large distances. And so I took out with me a 38 megahertz receiver, and I did install that temporarily on Mt. Palomar for a few days. I ran one at DTM at Washington, you see, and I took another one out to Palomar.

Sullivan

This would be when?

Graham Smith

This was 1953.

Sullivan

This was the first radio astronomy done at Caltech.

Graham Smith

I canít say. It wasnít very good radio astronomy. I did run this equipment and a couple of dipoles on top of Palomar, a most inappropriate place with a transmitter not far away. But it made it quite clear that all the fluctuations, scintillations, and all the fluctuations we could see were ionospheric scintillation. None of them seemed to correlated over a large distance. Which is what we were after.

Sullivan

Right.

Graham Smith

We wanted to see if there were any correlation over large distances.

Sullivan

This little experiment had never been published.

Graham Smith

No, it wasnít worth the energy. I can see from the reprint there it showed some pulsars which might have been correlated over a distance of some 100 kilometers or so.

Sullivan

You may remember I wrote you a letter asking you, a couple of years ago, what, in retrospect, were these things? And you wrote back that it was still a complete mystery.

Graham Smith

Itís still a complete mystery. It may have just been a fluke Ė I think it was just an accident, I donít know.

Sullivan

This will (?) for the 1950 Nature.

Graham Smith

Yes. Well, I think we still had that in mind, that there might be something which would correlate over a large distances.

Sullivan

It could be a mixture of intrinsic and (?)

Graham Smith

Sure. But nothing ever came up again, so that line died after a time.

Sullivan

Now, so when you got back, you heard about the Jupiter discovery, I guess.

Graham Smith

Thatís right, and I said, ďWell, letís try and get some radiation form that at the frequency we had available - Ē

Sullivan

38 and 81.

Graham Smith

Thatís right, and darn, we couldnít pick it up.

Sullivan

Which I suppose was a -

Graham Smith

Sure, it was a surprise. That, of course, was narrow band radiation.

Sullivan

No other source was acting like that. Okay. Next, I find Adgie and Smith, 1956, on the spectra of four sources and of the background radiation. Can you tell me about that?

Graham Smith

Yes, thatís right. I think I became more interested in galaxies than the point sources. I think you can see from the authorship of the survey papers that I wasnít very much in the point source game from then on. I became more interested in the Galaxy and working with Adgie we decided we would try to measure the spectrums there if possible, using sealed arrays. And of course, we measured the point of sources as well, we tried to get the spectral index by using sealed arrays at a series of frequencies, and that was, I think, quite a successful experiment, sort of academic stuff, if you like, it didnít produce anything very exciting.

Sullivan

Yes, but someone had to do this sort of thing.

Graham Smith

Oh, yes, I think it was a good thing to do.

Sullivan

Iím interested in your comments that you more or less dropped the radio star work which seems like it might have been natural for you having gotten these positions and they were eminently successful in helping with identifications, why not press on with it?

Graham Smith

I think it was a conscious decision within the group, that we had to diversify our interests somewhat, you know, to spread out amongst the members of the group.

Sullivan

I see.

Graham Smith

So I think I became more interested in Galaxy at that time. If you look ahead a bit to satellite work, that was because we might be able to measure the low frequency radiation from the galaxy. And I think that during these years, well I still am interested, in Galaxy actually, the interstellar medium and so on.

Sullivan

Okay. The next one I see here is Baldwin and Smith, 1956, looking at M87.

Graham Smith

Yes, thatís right. That was another shot like Jupiter just to see if you could get something slightly unusual. Thatís an interesting observation, I donít think Iíve ever really looked back to see whether what we saw in the form of a halo around -

Sullivan

Well, (?) extended low level radiation with very intense central peak.

Graham Smith

That central peak was there all right, but the low level stuff over a rather large area, Iím still not really quite sure whether there was anything in that at all. But thatís what we did.

Sullivan

Well, but isnít it true that Virgo A does have a halo even in todayís observations?

Graham Smith

Iím not quite sure that itís all that big.

Sullivan

I see.

Graham Smith

(?) degrees weíre talking about. Iím not really quite sure that thereís any structure which can really account for those observations.

Sullivan

(?) looked at, at such a low frequency since then.

Graham Smith

Well, exactly, yes I think itís still a thing that should be checked up on.

Sullivan

And hereís an article with OíBrien and Baldwin in Monthly Notices on the Galactic Center.

Graham Smith

Oh, on the Galactic Center, thatís right. Well, another shot to measure diameters and so on.

Sullivan

(?) between 38 and 500 megahertz.

Graham Smith

Yes, okay.

Sullivan

But was it pretty clear that this Sagittarius A was probably the center of the Galaxy or was that what you were trying to determine here?

Graham Smith

Oh, I think the experiment was just on, as one might have done it, on almost any radio source, but it was obvious that this could be the center of the Galaxy and might be a more interesting one than any other. I donít think, again, we started off saying, ďWe will work on the Galactic Center what can we do in the Galactic Center.Ē Itís much more, ďHereís an interesting radio source where we might be able to do something.Ē

Sullivan

Thatís something Iíll have to learn because Iíve been trained in a rather different style.

Graham Smith

I think you have to appreciate that in those days, one was measuring everything that one could measure.

Sullivan

Yes.

Graham Smith

Thatís certainly not true now.

Sullivan

Okay. Costain and Smith, Monthly Notices, 1960.

Graham Smith

Oh, yes.

Sullivan

This is skipping ahead now.

Graham Smith

This is -

Sullivan

Getting a .8-degree beam at 8 meters.

Graham Smith

Thatís right. Well, you see, we were very much occupied in moving observatories at that time, and Costain and Smith referred to the new observatory at Lordís Bridge. So that a lot of work had gone in, including a lot of sheer constructional work on that array at that time. That array, of course, was for identifying anything you could see, partly the point sources and mainly to synthesize the map of the Galaxy with good resolution at low frequency. That interests me, it really reflects my interests in galactic structure.

Sullivan

So I always thought that John Baldwin was the primary one who was interested in the galactic background, but it appears that you were, to be you and Baldwin together.

Graham Smith

I think he certainly took over my interests eventually.

Sullivan

But even then though, he was working on the radio halo.

Graham Smith

He was, itís quite true, yes.

Sullivan

I guess he never got involved in the halo controversy.

Graham Smith

Not really, no, I think that was (?)

Sullivan

Along about this time, I donít want to go into it here, but Sputnik came along and Iíd be interested in your account of what happened.

Graham Smith

Oh, well, that was very exciting. We were all, I think, taken completely by surprise by Sputnik. But now, letís think, who was it? I canít remember his name, moved on to Birmingham and worked with things like flight of birds and so forth. George somebody.

Sullivan

Whitfield?

Graham Smith

Whitfield, thatís right. George Whitfield Ė he was the first to get Sputnik, because a great enthusiast as he was, he dashed straight off to the observatory and showed that you could pick up signals from this thing with almost a piece of wet string. And within a day, we were discussing this, and realizing that we could again measure something that maybe nobody else was measuring. Itís again the same philosophy, you see, you donít decide to work on satellites, so what can you do Ė itís, ďWell hereís something which we can do which is new. And it looks as though it could be very interesting and bring in a new field,Ē and so forth. So we all started joining in with enormous enthusiasm. We were very soon realizing that we could measure an orbit or some parameters of the orbit and we all worked like mad on this for several days. It was very exciting, and we then found ourselves in the position of being the ďauthoritiesĒ on the orbit of this darned thing, because, of course, when Jodrell got word of it a bit later they were doing radar from the rocket phase which was a different thing. So we were the authorities on the orbit. And, in fact, we, Martin Ryle and myself, became the first people, as far as I know, to publish a new navigation system using satellites.

Sullivan

Thatís right. I came across that in a list of Cambridge publications.

Graham Smith

Itís a very amusing thing, because of course the people in the States had been working like mad on this and hadnít published anything because it was classified. Just the way the (?) came along, yes. So that, of course, had remained a very interesting subject (?) and I find myself almost back in the field again now because such satellites are used for time comparisons, you see. Anyway, we went along, again as innocents not knowing anything much about all this, and after a couple of day, I was asking a mathematician friend of mine, David Reese, a member of my Cambridge College, about all these satellites and things and how you could possibly measure them. Orbits, procession and so forth, and he gave me one or two elementary lessons, but, of course, we ran into trouble with this one because we found the height of the satellite orbit changing, and we didnít realize how elliptical it was, so after a while, we were terribly excited (?) the thing was coming down to lower altitudes. That was the orbit precessing. It was sometime before we learned, we learned from the (?) people including the then Science Correspondent of the Guardian, Maddox, who was at one time a (?) physicist.

Sullivan

I see.

Graham Smith

And he was, at that time, Science Correspondent, and joined the team of reporters who actually watched this operation, and we were discussing this problem about the change of altitude and he said, ďWould this help?Ē And he brought a book out of his pocket, which heíd got from the States with some relevant information in it.

Sullivan

I see, so the journalist helped the scientist.

Graham Smith

Yes. So that lasted for, well, it was a nine-day wonder, I suppose, orbits of satellites.

Sullivan

Iíd like to ask about a couple of meetings; namely, the Jodrell Bank Symposium in 1955. You gave a talk there about the galactic center. But more specifically, Iíd like to ask about the atmosphere of it.

Graham Smith

I think at that time we were beginning to feel that we were slotting in to a much larger community. At that time, that was the time, I think, when the Russians presented their work on synchrotron radiation. Which again, of course, one doesnít grasp things straight away, but we began to realize that there were some good physics here which weíve got to understand. I think it was a year or two before we really grasped what they were saying, but, nevertheless, there was a feeling that this was a good solid scientific discipline that there was lots to be found out about structure of the Galaxy, possibly structure of the Universe, physics of sources, and so on. I think it was actually a very constructive meeting from that point of view.

Sullivan

You say, ďpossibly the structure of the Universe,Ē but that wasnít the way it was worded then.

Graham Smith

Not, really, no. No, no. When we say, ďexploring the Universe,Ē thatís a broad term. No, not cosmology, we werenít really on to it then. When was the Paris Symposium?

Sullivan

1958. That was well after the storm had passed.

Graham Smith

Right. So we were talking about -

Sullivan

(?) in 1955.

Graham Smith

So we were well into it.

Sullivan

And I guess also there were some optical astronomers there which was also rather different.

Graham Smith

It was exciting. Thatís right. I think that was really the beginning of modern radio astronomy.

Sullivan

Now, at the Paris Symposium, the paper that you specifically talked about was radio astronomy and the planets, and when I made this (?) I was going to ask you why, in the world, that, but, now I see.

Graham Smith

Oh, I know why there was -

Sullivan

A loose connection anyway.

Graham Smith

I know why. Lovell was asked to give this paper originally, and he asked me if I would do it. (Laughter) Thatís one reason why, I think, I was interested at that time in radiation from the moon, in particular, thermal radiation from the moon. Just as a piece of physics, it was an interesting thing to try and work out. For example, sunlight reflected from the moon, and what would you expect the temperature of the moon to be and so on.

Sullivan

In microwaves, you mean.

Graham Smith

In microwaves, yes. So that, yes I was interested in the physics of radiation from the planets. Jupiter was part of it, I suppose.

Sullivan

Did you ever publish any of this lunar work?

Graham Smith

No. I think it only came out in that report of that meeting at Jodrell, or the Paris Symposium, rather.

Sullivan

The Paris Symposium, right. Well, the final publication I have here is, of note, is 1960, in which you gave a talk somewhere some technical meeting, about some receiver technology needed for the future of radio astronomy. What did you think at that time?

Graham Smith

Well, Iíd been interested in technology all along. Thatís fair. I think I was probably one of the people doing most about switching circuits and low noise amplifiers and so forth. And it was quite clear that we had to improve low noise amplifier technology, that was the great thing that we were after. I donít think that I was thinking in any particularly original way about aperture synthesis and those things, I was much more interested in the electronics, the amplifiers. So thatís what I was talking about at that time.

Sullivan

Well, in fact, your name is not on any of the publications to do with aperture synthesis, (?), Hewish, and (?) and so on.

Graham Smith

No, no. Thatís right.

Sullivan

But explicitly, though, what were you saying? Were you thinking, for instance, that masers were the way to go?

Graham Smith

Oh, yes. I think that I was very much concerned about the relationship of noise temperatures to background temperatures and I would be pointing out that the sky background temperature fell with a certain law, and expected noise temperatures with known techniques would fall with different laws and so forth, and if we could possibly get lower noise temperatures at higher frequencies, then you would have a very much greater sensitivity, and you could extend to somewhat higher frequencies.

Sullivan

I see.

Graham Smith

I think it is in noise temperature terms that I was thinking, rather than in the aperture synthesis terms. That was being done so well by Ryle and Hewish anyway.

Sullivan

The paper was only on receiver technology.

Graham Smith

Yes. Well, thatís why the paper was on receiver technology.

Sullivan

Now, Iím going to the early sixties, and I donít have the bibliography, can you tell me, when did you leave Cambridge?

Graham Smith

1964.

Sullivan

So thatís a very natural place then, can you tell me what you worked on up to Ė

Graham Smith

At that time, I was working on satellite radio astronomy.

Sullivan

While still at Cambridge?

Graham Smith

Yes. We did an experiment on a rocket carrying a low frequency receiver high up. And this was the precursor of an experiment in the satellite area, too.

Sullivan

When did that go on?

Graham Smith

Early 1960s, I canít remember the date.

Sullivan

The first rocket went up.

Graham Smith

The first rocket would be about 1960 or so.

Sullivan

And Ariel 2?

Graham Smith

And Ariel 2, year or two later. So I havenít got the exact dates.

Sullivan

Right, and this was published when?

Graham Smith

Ariel 2, some of it got published, surely in Monthly Notices, I think. Yes, thatís right. "Temperature of the Galactic Background at Low Frequencies."

Sullivan

And how low did you go?

Graham Smith

Oh, this is about 3 megahertz, in fact, it was betweenÖ I think weíve got to go out because theyíre [Brief break] Something in Monthly Notices on the spectrum of the galactic background done at low frequencies. The thing is that itís been somewhat superseded by work from Walsh, whoís now at Jodrell Bank, Haddock and Walsh did a very good experiment.

Sullivan

Thatís right. He told me about that.

Graham Smith

It was on exactly the same subject. The answer wasnít too far wrong anyway, but, of course, this satellite in just the same way as Walsh and Haddock discovered the ionospheric noise bands, you see, and that was a bit worrying. And led to an experiment in Ariel 3.

Sullivan

Pardon my ignorance, but I donít know what the ionospheric noise band is.

Graham Smith

Oh, the ionosphere produces some radiation at resonant frequencies, and itís got a lot of resonant frequencies because youíve got magnetron (?) and different modes and so on.

Sullivan

I see.

Graham Smith

And you do get powerful noise bands which are generated by high energy particles in the ionosphere exciting some sort of resonant radiation. I donít think the thing is really properly understood; itís rather like (?) synchrotron radiation.

Sullivan

So, this galactic background work with the satellite was on outgrowth really of your interest in the fifties.

Graham Smith

Of trying to measure the spectrum of the galactic background, thatís right. Yes. Now, this was still going on when I moved to Jodrell because, in fact, there I had to hand the thing over the Walsh, more or less, who also arrived at Jodrell about the same time. And he took the thing over. So that one stopped in about mid-sixties.

Sullivan

Okay. Iíd like to ask you a general question about the group at Cambridge; it seems to me that that was a very coherent group that has always been close as compared with CSIRO or NRAO today.

Graham Smith

Itís a very stable membership, too.

Sullivan

Thatís true. Although some of the other places have, too, but they havenít had this coherency. I was wondering if you could say how this came about, do you think?

Graham Smith

I think itís largely the strong personality of Martin Ryle. Itís also possibly a Cambridge phenomenon. I think itís actually hard to analyze because if you get a good, strong group going anywhere, it may well be the same thing Ė that coherent (?)

Sullivan

You say a Cambridge phenomenon, do you mean a tradition of the Cavendish laboratory?

Graham Smith

Cavendish and Cambridge University, as a whole. Cambridge is, it has a reputation, perhaps I think, rightly of being somewhat an isolated place. And being quite content to get on its own.

Sullivan

And all sort so sciences.

Graham Smith

All sorts of science topics, yes. I mean, it does very well on its own, so it doesnít have to bother too much with other people, and it does, I think, carry on without too much reference with other people. And it does tend to produce coherent research groups which stick together.

Sullivan

I see, so radio astronomyís not an exception really then.

Graham Smith

I donít think so, no.

Sullivan

Okay. To close, youíve made many useful remarks about the development of radio astronomy, but can you think of anything else as you look back, especially up to the early sixties, as to how the field went that you might Ė

Graham Smith

I think weíve covered it pretty well.

Sullivan

Okay. Well, thank you very much. That ends the interview with Graham Smith on 27 August Ď76.

End tape 68B


Modified on Wednesday, 07-Sep-2016 09:17:05 EDT by Ellen Bouton, Archivist (Questions or feedback)