Interview with Martin Ryle on 8 June 1981
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The interview listed below was conducted as part of Sullivan's research for his book, Cosmic Noise: A History of Early Radio Astronomy (Cambridge University Press, 2009) and was transcribed for the NRAO Archives by Sierra E. Smith in 2015. The transcript was reviewed and edited/corrected by Ellen N. Bouton in 2016. Any notes of correction or clarification added in the 2016 reviewing/editing process have been included in brackets; places where we are uncertain about what was said are indicated with parentheses and a question mark, plus a notation of the time on the audio e.g. (? 00:50) or (possible text? 10:32). If researchers are able to suggest correct text, please contact the Archivist. Sullivan's notes about each interview are available on Sullivan's interviewee Web page. During processing, full names of institutions and people were added in brackets when they first appear. We are grateful for the 2011 Herbert C. Pollock Award from Dudley Observatory which funded digitization of Sullivan's original cassette tapes.
This interview was intended by Sullivan to be a follow-up and expansion of the 130 minute 1976 interview. However, part of the original interview, approximately 90 minutes in the middle (the entire audio cassette tape 143), was accidentally erased in 1985 by U. Washington Audio-visual Department. No notes or transcription had been made. This transcript, therefore, is of brief audio from the end of Sullivan's tape 142B and a slightly longer final section of the interview from tape 144A.
Please bear in mind that: 1) This material is a transcript of the spoken word rather than a literary product; 2) An interview must be read with the awareness that different people's memories about an event will often differ, and that memories can change with time for many reasons, including subsequent experiences, interactions with others, and one's feelings about an event.
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Begin Tape 142B
Sullivan
So this is continuing from 5 years ago, with Sir Martin Ryle on 8 June 1981 and mainly just a whole series of follow up questions from that interview. [see Ryle 1976 for that interview transcript and audio]
Ryle
2 days and 36 years since D-Day.
Sullivan
That’s right. You might be happy, or maybe not, that I did note D-Day a couple of days ago. I was born 11 days after D-Day, I might mention. So it’s easy for me to remember when it happened. But in your talk that you gave here to the radio astronomy lunch a couple of months ago you mentioned that you went on an exercise after the War of some kind. I was wondering if you would tell me a little more about that, where you went over to the continent.
Ryle
Yes, well, twelve of us went over as observers while the entire North German defense system was kept in action right up from the radar stations through to the group command.
Sullivan
With Germans manning it or...?
Ryle
Yeah, sure, right up to the German Air Marshalls. The idea was to observe what happened when a bomber command did a series of typical raids using the full works of the devices we’d invented to stop them working. And it was spooky, because to find yourself in a control room in the first instance full of these bloody swastikas, it was strange. And even more so to sit around in Denmark where there were 350 Luftwaffe men associated with this very extensive radar station where me and my three people spent most of the operations, just actually observing how the guys reacted, just the effectiveness of various different devices. It was done in daytime to avoid accidents on landing and things. But the only thing that didn’t happen, of course, we didn’t let fighters fight so we couldn’t test all the system.
Sullivan
Did you get any ideas about picking up equipment for later research while you were there?
Ryle
Well, yes, I knew most of it anyway.
Sullivan
So this was really that relevant for the radio astronomy to follow?
Ryle
It was to a certain extent because it showed which devices would immediately be useful. And it did certainly influence the selection of bits and pieces, which we picked up at the end of the War.
Sullivan
You mean which German devices?
Ryle
Oh, yes, I’m talking about German devices.
Sullivan
Ok, let me follow on then, saying that once again in your talk you said that the German equipment was easier to get than the British equipment because it didn’t have the numbers on it and they couldn’t follow it in inventory and so forth. Was that tongue in cheek or was there really some truth in that?
Ryle
Well, I think the point was that any British equipment you had to get approval from somebody that it wasn’t wanted any more. Where the German equipment mostly had been looked at and examined and everything measured about it, and it obviously wasn’t any use to anybody, and much of it was indeed sold to scrap merchants and people like that. But it is true that there was no sort of stores procedure for coping with it. And so it was much easier to get a hold of. There was virtually nobody but me at Cambridge University that knew what all these stuff was and so we got the thick of it. Well, I never knew what the code numbers meant.
Sullivan
Well, along that line you told the anecdote in your talk which you also told me five years ago about going down to near (? 04:14) and picking up all this equipment and the story with the scrape merchant and so forth. But you said you came back with five truck loads, I believe, of equipment.
Ryle
Yes.
Sullivan
Can you just give me an idea of what in all this?
Ryle
Well there was one (? 04:30) 27 foot diameter...
Sullivan
Which wasn’t mounted for several years I guess?
Ryle
It wasn’t mounted properly as an alt-azimuth machine. It was used, I think I saw a photograph right just now, as an (? 04:47) interferometer. That was mounted fairly early on but it was not finally mounted till we moved to Lord’s Bridge as a fully steerable machine. But we also got a large amount of, well two small (? 05:06) that were captured at (Boulevard? 05:09), which was the one used by [Harold M.] Stanier in his early measurement at 6 centimeters.
Sullivan
Now what was the diameter of those small ones?
Ryle
9 foot.
Sullivan
9 foot. I see.
Ryle
Well, we talked in feet in those days.
Sullivan
So about 3 meters, ok.
Ryle
They were very mobile. They were on wheels, quickly towed behind a truck so they were nice to push around.
Sullivan
And they had their mounting right with them I supposed?
Ryle
Oh yes, they were fully mounted. They were, in fact, operated by two operators in azimuth and elevation, or three, I think, a range one who kept the thing on target and (? 05:52) mount some drives to a display. They were used for various things (? 06:00) them. Range measuring. With an antiaircraft gun you can measure the angular position very accurately optically, which you catch in the searchlight beam, but the range is always pretty inaccurate. Well that’s the trouble with anti-aircraft, anyway, only important in the first bit of the War.
Sullivan
What else did you bring back?
Ryle
Well, then there was the whole load of this very low loss air core capture cable...
Sullivan
About one inch diameter?
Ryle
No, it was more than that.
Sullivan
Two inches?
Ryle
It was one inch and a half I’d say. Well an inch and a half on the outside. It had some shield on it. And these were part of, well, two German systems which used phased arrays. And therefore they had to have a whole collection of cables of precisely the same length. And they were indeed accurate to a centimeter or so. And these are very valuable because there was no....
End Tape 142B
Middle section, tapes 143A and 143B (interview parts 2 and 3), missing, see explanatory note above.
Click start to listen to the audio for part 4 of the 1981 interview.
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Begin Tape 144A
Sullivan
On 8 June 1981. For the actual meeting at Jodrell Bank in 1955, do you remember any important results from that or any impressions that you have?
Ryle
Well, of course, these early meetings are important because you met up with other radio astronomers. And at that time, I’m afraid, I must say there weren’t very many American ones.
Sullivan
Yes, that’s right.
Ryle
But you met up with the Dutch and the French, who were the most energetic. And that was also true, of course, of the Paris meeting. [2016 note: Paris Symposium on Radio Astronomy, IAU Symp. 9 and URSI Symp. 1, 30 July to 6 August, 1958] You saw the Meudon approach to a large instrument, which was interesting. Well, I knew [Hendrik C.] van de Hulst anyway but, you know, you met all these people. That was the main importance to me of it. You met the guys that you’d often corresponded with, and you saw the way they worked. And that was important too. Astronomically, I can’t really recall anything very special. I think the Jodrell meeting [2016 note: Radio Astronomy, IAU Symp. 4, Jodrell Bank, August 1955], maybe the Paris one too, may have been somewhat confused.
Sullivan
Meetings were somewhat confused?
Ryle
Confused, with really unnecessary controversies about LogN-LogS and things, which, you know, it took up too much of everybody’s’ effort. I mean it was important clearly, but I felt there was a certain amount of trying to prove the other guy was wrong, which was sad because, in fact.... Well, some people are always more difficult than other people are and you can cooperate with some people much easier than others. And I felt, well, never mind....
Sullivan
Well, what you are saying is that people began to lose sight of really finding out what the universe was doing and just backing their own results.
Ryle
That’s right.
Sullivan
Well, science is a human activity to say the least.
Ryle
Yes, but I think the important parts of all these conferences was when you got so and so into a corner over coffee and talked to him - that’s what mattered. And that’s what happened the first time at the Rome meeting [2016 note: IAU General Assembly, Rome, September 1952] with [Walter] Baade and [Rudolph] Minkowski. The rest of it I have no recollection useful at all.
Sullivan
OK.
Ryle
You went to meetings and people got up and said, "I just happened to have 23 slides in my pocket which I thought I’d show you." And that were absolutely irrelevant and you felt a bloody waste of time. But the meeting with individuals and talking about something that you both directly, vitally concerned with, those were important and I think that remains true today.
Sullivan
Well, in fact, I’d be very interested to know. Did you sit down with [Bernard Y.] Mills in the corner and try to hash this through?
Ryle
Yes, yes.
Sullivan
But apparently you weren’t able to get anywhere or were you?
Ryle
Well, we got as far as saying that we obviously got to do something more about this. It’s got to be solved. And we both went back and, well ultimately it was solved. But it was the personal meetings which I recall as being the things that mattered.
Sullivan
Do you remember other people who particularly impressed you with what you were learning from them at these personal contacts?
Ryle
Well, van de Hulst was the outstanding Dutchman. There was that desert, Foreign Legion chap, stayed in the desert too long - what was his name?
Sullivan
Denisse?
Ryle
Denisse, yes. Jean-Francois. He was a great guy. So also was -
Sullivan
[Jean-Louis] Steinberg.
Ryle
Steinberg who had spent the War in Auschwitz or something and got away with it. He married an English wife. They were very kind to us. But they were the two leading lights at that stage and, you know, they were nice, calm, easy chaps to get on with.
Sullivan
Did you feel the French contribution to solar radio astronomy in the 10 years after the War really ever amounted to anything?
Ryle
I don’t quite know what went wrong or didn’t go quite right with the French, because basically they started off very well. I think possibly that they were too closely tied on to Meudon Observatory, which was basically an optical observatory. They had this mad Piccard....
Sullivan
Laffineur?
Ryle
No, Laffineur was alright. I think he was perhaps not all that brilliant, but he had good ideas and he did a lot of optical work. They had this mad Piccard, son of [Auguste]Piccard, who did high altitude balloon work - the most dicey thing I’ve ever seen. Terrifying. 58 (? 05:32) balloons on a string. So it didn’t matter if a few burst.
Sullivan
Was this radio astronomy?
Ryle
No, he was mainly concerned with (? 05:42), whatever they are called, which you had to get above 120,000 feet or something. It was a little aluminum sphere which he built himself. He was a long, thin chap and he could just curl around like that and get inside it. And the lid wasn’t fixed on. You just held it up while the thing took off, and after a minute because the air pressure held it there. And as you came down, it fell off and bonked you on the head to remind you to get ready for landing. He was a mad guy but he survived several flights with that thing.
Sullivan
So why were you saying that the French didn’t seem to - ?
Ryle
Well, I think they probably didn’t give enough cash to radio astronomy to make it viable early enough. And they did built this big parabolic wall eventually, which was a new and interesting concept for building big instruments.
Sullivan
That was ’56 or so when they got to that.
Ryle
Yes, about then.
Sullivan
Ok, the final thing that I wanted to ask you about was, we did discuss at length how the ideas of synthesis developed last time, but I’m still a little unclear in my mind about how difficult it was to measure phase in the late ‘40s, early ‘50s. In other words, if you had...
Ryle
It’s entirely how far you were going.
Sullivan
Ok. But if you’d had the computer at some early date, then when could you have done aperture synthesis with what baseline at what frequency? Can you give me some idea of that?
Ryle
Well, John Blythe was the first. When was that when he did it?
Sullivan
Well, that was ’56 or so.
Ryle
No, it wasn’t.
Sullivan
It was published in ’57, I’m quite sure. Maybe I should rephrase the question. Can you give me an idea for specific examples how well you could measure phase at a certain frequently with a certain baseline in the late ‘40s, let’s say, and then in the early ‘50s?
Ryle
Well it was no different.
Sullivan
It was not different. What were the limiting factors?
Ryle
Well, it was noise, attenuation of the cable, just that the reflected wave coming back got so weak that we couldn’t measure the minimum accurately. If you had two cables, it was different. You could do round trip things and (? 08:15) arrangements. But we didn’t have enough cable. But, I mean, there is no problem in the John Blythe experiment. That could have been done in 1946. That, in fact, was the apparatus we used, which was a brass standing wave detector standing about 8 feet long, because it was a long wavelength, with a rather nice size actually. He was proud of it. But it was, in fact, based on a German one I’d pinched for shortwave work (? 08:50) the method of locating the probe accurately along it as it moved along.
Sullivan
What exactly was it now?
Ryle
It was a standing wave detector.
Sullivan
A standing wave detector, right.
Ryle
Which you have a thing 8 feet long and you’ve got to align the probes so that it stays accurate to about 1/50th mm all the way. You had to do something rather special.
Sullivan
So that’s interesting. So if the concept had been there, you say that you could have done the Blythe moving T experiment right at the end of the War technically?
Ryle
Well apart from the computing.
Sullivan
Yes, right. And you could have done the computing if you’d been willing to spend a hell of a lot of time with a lot of people with pencil and paper presumably.
Ryle
Well, you’ve got (? 09:41) strips, which is the quickest way of doing it.
Sullivan
So is it correct to say, then, that the ability to measure phase was not any kind of a limitation on doing aperture synthesis?
Ryle
No, well, phase measurement was an established fact of life which one had done during the War. One had to do this.
Sullivan
It only became a problem when you started going to the higher frequencies.
Ryle
It was just a function of the attenuation of the cable, so it was the relationship between frequency and distance.
Sullivan
And even with these good quality German cables you had, this became a problem... well what was the actual attenuation? Can you give me a rough idea of how much at a given frequency?
Ryle
No. Look up the best cable of that sort of size which somebody makes. It will be about the same as that.
Sullivan
Today you mean?
Ryle
Yes. It was as good as any cable that has ever been made. It was 98% velocity of propagation. It was very little. (? 10:55). It was a very nice design.
Sullivan
Really then, it was just a matter of when you had the computing power, and the idea, of course, available, that you could then do the moving T, and you could do the experiment with Ann Nevill in two dimensions.
Ryle
At the North Pole.
Sullivan
Right and so forth. It was really that that was the limiting factor. Is that a fair statement?
Ryle
Well, there was of course mechanics and money involved in moving, say, a couple of large Würzburgs along a railway track. You’ve got to make a railway track and that costs money. And unless you are going to survey each position as you go, it’s got to be a good (? 11:39), it’s got to be steady anyway, even if it’s not straight. So I mean it was an expensive game, but that could well have been our next instrument instead of the 4C aerial. As indeed it was discussed, rather than the 4C aerial, if the computing had been there. But the computing in the general case was very much worse that the computing in the North Pole case, which itself was very much worse than the one dimensional 4C synthesis.
Sullivan
Ok, well thank you very much again. And that ends the follow up interview with Martin Ryle in Cambridge in his office in the Cavendish Lab on 8 June 1981.
End of Tape 59A