[Bracewell touching up signature pier on spectroheliograph dish]
Bracewell touching up signature pier on spectroheliograph dish. (FBOA image)


[Bracewell, 21 November 2004]
Bracewell writing, 21 Nov. 2004. (FBOA image)


[Bracewell, Swarup, and Pawsey, 1958]
Bracewell and Govind Swarup watch Joe Pawsey carve his name on telescope pier, 1958. (NRAO/AUI image)


[Bracewell circa 1955]
Bracewell, circa 1955. (Stanford University image)


NATIONAL RADIO ASTRONOMY OBSERVATORY ARCHIVES

Papers of Woodruff T. Sullivan III: Tapes Series

Interview with Ronald N. Bracewell
At AAAS Meeting, San Francisco CA
8 January 1980
Interview time: 185 minutes
Transcribed by Sierra Smith

Note: 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 Smith in 2014. The transcript was reviewed and edited/corrected by Ellen N. Bouton and Kenneth I. Kellermann. Any notes of correction or clarification added in the 2014 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, e.g. (?) or (possible text?). 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 and if especially long the interview was split into parts reflecting the sides of the original audio cassette tapes. We are grateful for the 2011 Herbert C. Pollock Award from Dudley Observatory which funded digitization of the original cassette tapes, and for support from Associated Universities, Inc., which funded transcription of this interview.

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.

Part 2 | Part 3

Begin tape 130B

Sullivan

So this is interviewing Ron Bracewell at the San Francisco AAAS meeting on 8 January 1980. Could you first tell me what your educational background was, and then I know you got started in Radiophysics at a very early time.

Bracewell

Well, I went to Sydney Boyís High School and then to Sydney University and obtained a Bachelor of Science Degree in mathematics and physics, and then I continued on to get a degree in engineering in the communications option. The last year of that course was 1941 and the Japanese were already in New Guinea and were preparing to land on the Australian mainland. Shells from Japanese submarines had gone over Sydney and a large fleet had been wiped out in Darwin, although at the time that news was censored. So instead of completing the year 1941, the six or seven people in the communications option of electrical engineering were popped into the Army for six months, where I carried tools for a fitter who was repairing engines in personnel carriers. And then we returned to the university for a short period, about three months, and were graduated earlier than normal and sent to Radiophysics Lab. That would be in about September of 1942. [Note added 2014: Radiophysics Laboratory of the Council of Scientific and Industrial Research (CSIR), later Commonwealth Scientific and Industrial Research Organization (CSIRO)]

Sullivan

Which was on the same campus where you were, right?

Bracewell

Yes, the building was planned by John Madsen, who at that time was head of electrical engineering, and the purpose was to bring physicists and electrical engineers together in an environment where there would be the possibility for consulting and recruiting young graduates. So I donít believe any of us, there were six or seven of us, refused that assignment. We were very obedient in those days. You did what you were told and there didnít seemed to be any alternative other than enlisting in the Army. So we all appeared in Radiophysics towards the end of 1942. Well, that was my educational background up to that point.

Sullivan

So what did you find at Radiophysics and what kind of things did you work on there?

Bracewell

Well, my first assignment was to build equipment for voice communication at 10 cm wavelength. I had never seen 10 cm equipment and I was provided with a magnetron, the E1210v magnetron, which produced about 10 mW of 10 cm energy and told to voice modulate it. So I built a magnificent bunch of circuitry to do that. And if you connected this to a 6 foot paraboloid, you could communicate for many miles. My supervisor in this project was Brian Cooper, who Iíve had close contact with ever since. And he knew everything about circuitry and I guess thatís really where I picked up such electronic experience as I have. After doing that I had one or two other special jobs. I had to do some high voltage testing that required 5 kV. There was a transformer for this. And I very nearly blew myself up but survived happily. And then I got back onto another microwave problem. There was a tube known as a lighthouse triode, it looked like a lighthouse. And it was operated in a double-concentric circuit, one concentric transmission line inside another, with two annular plungers to tune these cavities. It was very complicated to make and the mechanical stability was not good. So I developed a pair of resonance cavities into which the triode could be plugged. There was no retroflex folding of the resonance cavities. It was just a solid device made out of one short cylinder of metal. That worked very well. That was a sort of technical assignment that I found myself pushed into.

Sullivan

I think [Grote] Reber used these same lighthouse tubes in some of his receivers.

Bracewell

He very probably did. They were convenient and most of them would work. Youíd plug them in and they would work. Others wouldnít.

Sullivan

You mentioned in your talk this morning that people knew about [J. Stanley] Heyís secret report of 1942 and they knew about [Karl] Janskyís and Reberís work pretty generally, I think. Do you remember any instances of someone on just his odd free time trying to detect any extraterrestrial radiation?

Bracewell

The only attempt I recall is the late 1945 effort.

Sullivan

But this is now after the war?

Bracewell

Yes.

Sullivan

And part of publishedÖ?

Bracewell

Now just a moment. Attempts were made before then. As a matter of fact, I remember being present as such an attempt in one of the rooms in Radiophysics Lab, but with no antenna worth mentioning, just with a simple antenna.

Sullivan

A dish? A small dish, you mean?

Bracewell

No, with a dipole. And now that I come to think of it, there was another sort of experiment that people used to do with small dishes, in the two or three foot range, which could be found lying around. I remember it being demonstrated that if you took one of these antennas and connected to a sensitive 10 cm receiver, when you pointed it out the window you could get less noise. You see?

Sullivan

Yeah.

Bracewell

Now obviously this is of some astronomical significance, but I didnít look at it in an astronomical way at that time and I always felt it was very puzzling. I never quite understood why it was. Now I understood that room temperature was room temperature but why the sky shouldnít reveal room temperature would have required me to understand the transparency of the atmosphere at a particular frequency, something that was beyond my conceptions at the time.

Sullivan

Do you remember who was doing these things? Could it have been anyone?

Bracewell

Well, I have no idea. But the people that could have been doing it would include John (Goodin?), and Ruby Payne-Scott, and, in that same room, Frank Kerr resided. And one or two others, such as [G. Leslie] Les Wirsu and [R.F.] Treharne, whom you would have never have heard of, I imagine.

Sullivan

Yeah. Ok, so we come to the end of the war and the story as you were telling us this morning is that here you had a lot of people without any jobs to go back to and looking for something to do. Can you tell me how that went?

Bracewell

Well, there used to be many informal discussions, people tried to think of things to do with microwaves. We had megawatt transmitters lying around and people knew that you could cook with them. Unfortunately nobody invented a good microwave oven.

Sullivan

No one put the patent on it.

Bracewell

What a wonderful thing to do. And yet we used to cook things in the front of a waveguide and people loved to produce sparks in midair, which would impress visitors. With a little interference pattern, you could create a spark where there would be no spark in the presence of a traveling wave. And, of course, you could light neon tubes freely anywhere. But people didnít think of collision avoidance radar or microwave ovens or microwave spectroscopy. Perhaps microwave spectroscopy was discussed but it didnít seem that you could make a living from it. And there used to be two schools of thought: there used to be people who said immediately when the war is over, the bottom will fall out of radar and you should get back into mechanical engineering where people actually manufacture and sell things. And other felt that maybe there were future lines of development. And cloud physics got off to a good start. Now that undoubtedly was brainchild of Taffy Bowen. And he put a lot of effort into that. He had good global concepts of what the future might contain. So he could see himself discovering what went on inside clouds and then turning that information to the benefit of meteorology, for which he knew there was a demand. So he could see right through to the end of that.

Iíll tell you something else that Bowen did to illustrate that kind of attitude. One day I was down in the machine shop and everyone was backing away from their lathes because an experiment was being run in the following way. You may remember that the hero of Alexandria had a propeller that was driven by steam. You let the steam in at the hub and it runs out along the two arms and there is a short right angle bend at the end. I think that was perhaps called an eolipile. If it wasnít, some related device was. And Bowen had had a thing like that fabricated; a propeller. It was a propeller with hollow blades made of metal with holes at each end coming out of right angles. And he was feeling gasoline into the hub from a carburetor. And this thing really went round. Lighting it was a bit of an exercise. Everyone had to dodge. They thought the thing would fly apart. But it illustrates his mode of thought. The jet engine by that time was understood and he was thinking, ďWell, you have to begin with fuel and you have to have a propeller or something. Letís take a propeller. So why not feed the fuel into the propeller?Ē And if you ask that question, thereís the answer. So that just illustrates the fact that he certainly had the ability to look ahead and to think in unusual ways. After all, the division had been set up to do Radiophysics and here he was inventing a dangerous kind of airplane engine.

Sullivan

So who were the people who were pushing for radio astronomy and on what basis?

Bracewell

Well, [Joseph S.] Pawsey and Ruby Payne-Scott were clearly the driving figures there. What the division of effort between them might have been, I canít say. But Pawsey had administrative duties and he had instructed [Lindsey L.] McCready and Ruby Payne-Scott to go and make some observations. So they had done whatever was needed to modify the radar receiver that was attached to that antenna installation, which was a going concern.

Sullivan

At Dover Heights?

Bracewell

At Dover Heights. And was available for test purposes for substituting one component for another. It was not an active military radar. It was a going radar used by the Lab. So he clearly had told McCready, who was a receiver expert, to modify the receiver and he must have discussed the observational procedure with Ruby, who was a general purpose physicist. And then the three of them made the observations together. Pawsey was present during the observations. He was never noticed as having manual dexterity. And from him I discovered the distinction between dexterity and the ability to plan an experiment. There are people who impress you by their experimental ability but we donít always distinguish between ability to select the right knob and do the right thing with it and to plug the right connector into the right socket and the planning, the intellectual activity that goes into the planning of an experiment. Now Pawsey understood the planning of experiments very well. He understood measurement procedures very well. But he was a little but clumsy with his hands. In fact, you might say conspicuously so and to some extent it may have been a mannerism. But he undoubtedly had in fact carried out a lot of experimental work with his own hands and he directed it quite well. He had the experience and he knew what he wanted done. So he got this thing set up.

Sullivan

Could this have been an early manifestation of what finally killed him, the brain tumor?

Bracewell

I have no idea.

Sullivan

Other people have told me this in a slightly different fashion about putting Pawsey knobs on their equipment so he would twiddle this useless knobs, rather than one thatÖ

Bracewell

Yes, that story was a standard story. Thatís right. I think that probably originated with Ruby. She probably had a knob that was connected to nothing and Joe came in and gave it a lot of twiddling. And then she told everyone, ďI put it there was he wouldnít upset the experiment.Ē Yeah, thatís a funny story.

Sullivan

They started in the fall of í45 on these solar observations?

Bracewell

Yes.

Sullivan

You were not directly involved with these, however?

Bracewell

I was in the same room with many of the principles for most of that period, I would say. I would see Ruby every day and Pawsey would be up in that room nearly every day too. Heíd talk to everyone about what they were doing.

Sullivan

Well your impressions are therefore very interesting to know. Did it seem like they knew exactly what they were doing or was it just a matter of, well, ďWeíll look to see what comes nextĒ? For instance, this morning you described that they certainly understood the whole direction finding technique using Lloydís mirror and so forth. But in terms of what they might expect in the Sun and what they were after, was there a purpose to it or was it just to find out ďWell, letís see whatís there.Ē

Bracewell

No, Iím sure there was a purpose to it. It was known that the Sun was emitting radio noise but it was not known whether it came from restricted regions or was general. And Iím quite sure that that was consciously in the minds of Pawsey and Payne Scott. They went out deliberately to find out how this emission was distributed over the Sun. Now, I donít know this but I would guess that it didnít occur to them that they might also get the altitude of the emission from the rotation of the Sun. It wouldnít have surprised me to learn that neither of them knew that the Sun rotated. The level of astronomical knowledge was not high. But since they had to obtain sunspot sketches as part of this project, they very soon discovered that the Sun was rotating. And it was apparent from the beginning that the radio noise in February of í46 was rotating at a different rate, not much more, maybe 10% more, but noticeably more, and that implied an altitude.

Sullivan

That is was coming from high in the corona.

Bracewell

Yeah, it would be the low corona.

Sullivan

These sunspot sketches, was that a telescope that was set up at Radiophysics?

Bracewell

I donít remember how those sunspot sketches were obtained. It will be surely in the acknowledgement to the paper.

Sullivan

That may well be.

Bracewell

It just so happens that I have a copy of the report that existed before that paper was written. And Iíve made this copy for you. This is the report itself.

Sullivan

More or less, the preprint of the paper?

Bracewell

Yes, and it may contain differences, in which case it might in itself have interest. For instance, it has no acknowledgement. Now surely the Proc. Roy. Soc. paper will have, this is the appendix, so if we go back a little bit. [Turns pages] Ah yes, [Clabon W.] Cla Allen is the guy who would have made the sunspot sketches because it acknowledges the Commonwealth Observatory Mount Stromlo and the sunspot sketches would have been made personally by Cla Allen.

Sullivan

I did interview him and so I may have just forgotten. I undoubtedly asked him about these things. What about the question of the quiet radiation versus the disturbed, which of course it was not that clear what was going on at that time. Where they just out to find out where the radiation, not really distinguishing betweenÖ?

Bracewell

Well, Pawsey was aware at a very early date that [George] Southworth had made a mistake in his calculations.

Sullivan

Iíve found that correspondence actually, where he writes Southworth.

Bracewell

Is that so? How interesting. So he must have known, perhaps not in 1945 but it may be that the intensity of the radiation being received was very strong. Now [Jesse L.] Greenstein mentioned this morning his difficulty in converting statvolts per meter. It would have been statvolts per centimeter, I can assure him of that.

Sullivan

No, it was microvolts per meter.

Bracewell

It was, was it?

Sullivan

Itís in Janskyís article, yes.

Bracewell

Well, he may have had difficulty dealing with that as an electromagnetic unit, though one might point out that it is the correct unit for field strength, which is voltage divided by length.

Sullivan

Yes but you see, optical astronomers donít deal with field strength period, only power density.

Bracewell

Well, electromagnetic waves are electromagnetic waves and the strength in electromagnetic waves is measured by its field strength. So I canít apologize for the difficulty over that. I can understand the discrepancy of c/4π because that is a more difficult problem. But Pawsey probably knew quite early on that the intensities being recorded were just unreasonably greater than could be explained by a 6000 degree blackbody. That calculation is easy to do. He knew the Rayleigh-Jeans formula. I donít know how he knew it but I know personally that he did know that. That was part of his stock in trade going backÖ

Sullivan

Well there had been a couple of papers in the early Ď40s, í41, who is it by now? [R. E.] Burgess going through some of these thermal ideas that are so common now, having to do with antennas and all.

Bracewell

I donít remember that.

Sullivan

Burgess is í41, in the Proc. Royal Society.

Bracewell

Is that a fact? Is that R. E. Burgess?

Sullivan

Yes.

Bracewell

I donít recall that. So the information was around.

Sullivan

Some of these ideas were current.

Bracewell

Well, Pawsey very probably was in contact with Burgess. Probably he knew him. Pawsey knew certain things and other things he knew nothing about whatever. For instance, I had the pleasure of explaining to him what variance was. He had never heard of variance at the time we were working together on our book.

Sullivan

In í53 or so?

Bracewell

That would be about í52. He didnít know variance. Now, that was very strange but he did know an interesting assortment of things in physics. Well, he did know the blackbody radiation.

[Interruption, short break]

Bracewell

As to the distinction between the quiet and disturbed Sun, that distinction became apparent immediately because the observations in October of í45 showed big disturbance going on but of course they were not persistent. And when they disappeared, you had the residual left over. So the distinction between the two kinds of Sun came in immediately. Now the classification into all other sorts of bursts and whatnot is much later. I think noise storm was a term that was used quite early but disturbed Sun and quiet Sun were terms that came in very soon.

Sullivan

There were several papers in Nature in í46 trying to straighten this sort of thing out. You mentioned also this morning the famous sentence in Pawsey, McCready, and Payne-Scott paper about the basic Fourier principle. [Note added 2014: McCready, J.L.; Pawsey, J.L.; Payne-Scott, Ruby. Solar Radiation at Radio Frequencies and Its Relation to Sunspots. Proc. Roy. Soc. London A 190, 357, 1947. The paper was submitted as Pawsey, McCready, and Payne-Scott, and is often spoken of that way, but the Royal Society insisted on alphabetical author order]. Now obviously Iím extremely interested in your views on the whole Fourier influence on radio astronomy. Was this generally known by those doing radio astronomy right at the end of the war and first post-war years? Or was this something that only a couple of people understood, do you think?

Bracewell

Well, there were a lot of people in the Radiophysics Lab that understood Fourier transforms and for a very simple reason, that weíd been closely connected with antennas and their radiation patterns. And Pawsey had been working on transmission lines, antennas, and radiation patterns in the period from about 1933 to 1938. So while I would not have said that Pawsey had fluency with things like Fourier transforms, in fact he was a non-mathematical person as regards symbolic manipulation. But there were many people in Radiophysics who were quite at home with Fourier analysis in its mathematical form. I would have been one. Tom Kaiser wrote a chapter in the textbook of radar. Have you seen the book? [A Textbook of radar - a collective work by the staff of the Radiophysics Laboratory, Council for Scientific and Industrial Research, Australia. Angus and Robertson, 1947]

Sullivan

Yes. Yes.

Bracewell

In which, he is explaining that kind of thing. There may even be another chapter in which the Fourier transform is invoked.

Sullivan

Is it fair to say that during the war Fourier transform ideas in terms of antenna theory began to come in because I donít think that it is very prevalent in the Ď30s from my looking at Proceedings of the IRE and so forth.

Bracewell

During the Ď30s you would have had to read Rayleighís papers to be aware of it, either in acoustics or directly in electromagnetic theory.

Sullivan

So it wasnít being used by the practicing antenna engineers? Thatís what Iím getting at.

Bracewell

No. Well the microwaves didnít exist you see, and with the lower frequencies, directive antennas were not all that common. And the only directive arrays were some large transatlantic arrays of towers, things like half a dozen towers in a straight line. It doesnít give you very much freedom to control an aperture distribution. But with microwaves you immediately have that possibility. Things like the cosec² antenna which tries to make echo strength independent of angle of elevation gets you straight away into the Fourier transform relationship between antennas and their patterns. The Fourier transform relationship between visibility and an intensity distribution is quite a different physical phenomenon but of course the formula is the same if you so choose the quantities so that it is the same. The thing is we come in historically with a Fourier transform we are familiar with, then of course for economy of thought we will try to formulate our next subject so that itís the same transform. Then we can use our intuition.

Sullivan

It was really this second Fourier transform I was asking about, the general realization of the relation between the visibility function and what we call the brightness distribution. Now that was even less known than the antenna one.

Bracewell

It wasnít known at all. The first mention of that must surely be the Pawsey, McCready, Payne Scott paper and the mode of thought by which that originated is quite transparent. If you had a point source on the Sun rising above the horizon, through that cosinusoidal pattern you would get a cosine record. And if there was another point source of a different strength of a different location, it would superimpose another cosine wave on that. So Pawsey saw quite clearly, and for all I know Ruby Payne Scott may also, or they may have discussed this jointly, which they probably did, they saw the superimposition cosine waves would account for your source distribution.

Sullivan

But why hadnít this come up in the previous work with airplanes? It seems like this would be a useful concept.

Bracewell

Well, they are point sources and all you are trying to do is locate them. Now if you were tryingÖ

End of Tape 130B

Begin Tape 131A

Sullivan

Ok, this is continuing with Ron Bracewell, talking on 8 January 1980. On the Fourier transform a bit more, Iíve talked to many people from the Cambridge group about its influence on their work. They all ascribe a strong influence to [John "Jack"] Ratcliffeís course on Fourier transforms. Did you take that course or did you see its influence on their work?

Bracewell

Well, yes. Ratcliffe had given this course, a short course of lectures, maybe only as many as five lectures for a number of years running. And I possibly took it about the third go round, maybe just the second time round, but I think it had been given once before anyhow. And after I had been through it, in some subsequent year someone took notes, and then after that the notes began to circulate. I never saw those notes but someone at Manchester, I forget who now, almost published them. And in fact later it was published as a book but with an acknowledgement in it. [Fourier Transforms and Convolutions for the Experimentalist. R.C. Jennison. Pergamon Press, 1961] It very nearly got published without an acknowledgement. The others will have told you that story.

Sullivan

No, Iíve never heard that. There is a book by Ratcliffe?

Bracewell

No, no, no. Ratcliffe never wrote it up, you see.

Sullivan

I see. This guy who took the notesÖ

Bracewell

But someone took notes and they were reproduced for use of other students. It must have been on a random basis as such things are. And then someone, one of the well-known names only it just doesnít come back to me at the moment, very nearly published them. And then someone discovered this and then there was a protest of some kind and it was held up. But I think they ultimately were published with a proper acknowledgement. So Ratcliffe did indeed give a half a dozen lectures. Now, I believe he got his knowledge Ė he was also a non-mathematical person, I should tell you, very noticeably so. Thatís not to say that he didnít know a lot of mathematics, but he did not sit down and solve things mathematically. He thought them out very carefully and once heíd thought it out, he could write it in mathematics. I believe he got his knowledge of Fourier transform from the crystallography group in the Cavendish. There were people in the Cavendish, [William Lawrence] Bragg for instance, who understood three-dimensional crystallography and their diffraction patterns very intimately. They understood that at a very intimate level having starting in the same way that Pawsey started. Pawsey started with cosine responses to a point source and the people in crystallography started with diffraction, Bragg diffraction, from regularly spaced atoms. And they understood that at a very intimate level. And then it became very, very complicated, but you could still understand that if you had lived through the subject. So somehow or other, Ratcliffe had picked up this mathematical type of knowledge, which was unusual for him. But his method of explaining it was entirely physical. What for you and me these days would be the shift theorem of the Fourier transform, for him was a prism. And a cosine, which we think of as having a transform which is two delta functions, to him that would be a statement that a cosinusoidally modulated screen up in the ionosphere would transmit two plane waves at angles of incidence to the normal given by the spatial frequency of this corrugation. So everything had an optical interpretation and would then, for the purpose of these lectures, was to facilitate the explanation of ionospheric phenomena.

Sullivan

Did you see at all the influence of this course on the work of [Martin] Ryleís group?

Bracewell

Yes. Now let me see, many ionospheric projects, all of which were influenced by that work. But the influence on the radio astronomy? Well, yes, the first example one could mention would be [Harold M.] Stanierís attempt as a graduate student, research student, to measure the intensity distribution over the Sun and by making simple interferometric measurements with trifling antennas in different azimuths and in different spacings over some length of time.

Sullivan

Right, I believe that was the first direct use of these kind of principles, but you do see that as sort of coming out of Ratcliffeís course or understanding?

Bracewell

I donít doubt that at all.

Sullivan

Yeah. Did this course have a strong influence on you or were you sort of a Fourier freak before you went to Cambridge even?

Bracewell

Well, I did know a lot about Fourier analysis because I had done my mathematics in a department which had grown up under [Horatio S.] Carslaw, who wrote one of the great texts in the subject. And although Carslaw had just retired at the time I began as a student, all his colleagues were the people from whom I learned mathematics, which was a very rigorous ordeal in those days. So I knew quite a lot about the subject but I had none of the physical interpretation of that. The only interpretations of that ever given by the mathematicians were in terms of synthesizing wave forms, but these wave forms were not physical wave forms. They would say, "Take a saw tooth wave form." Well that was not the output from any oscillator. So it was an eye opening experience for me to find Ratcliffe able to interpret all these things in physical terms and to exhibit the ability to reason in terms of physics with mathematical problems. You take the mathematical problem, you translate it into physics, do the reasoning physically, translate the answer back, and youíve got a mathematical theorem. I remember him going to a talk which [B.] Van der Pol explained how a lightening flash in between two conducting planes would lead, in the distance where dispersion would have taken place, to a wave form that was a J0 Bessel Function. And he had proved this by some incredible integral, which was well beyond the abilities of anybody in the Cavendish. And Ratcliffe came back and reported this to us, and very cleverly proved that he already knew this in terms of multiple reflections arriving at the same receiving point with appropriate time delays. And he was able to derive the asymptotic formulas for the Bessel function in very simple physical terms. When you wait for a long time, this Bessel function has become a very slowly decaying sine wave and that of course is just due to multiple reflections which are more or less now vertical. So the time delay up and back gives you the asymptotic period and you can get the inverse dependence on time from, well, if I had a moment to think Iíd tell you the whole thing. But it was quite a revelation of its kind, how something that was mathematical to him he looked at sort of scornfully. He admitted you could integrate this out, but he would take the attitude, "Well, why do that when itís apparent if you think it would be so."

Sullivan

It is fair to say then that this kind of attitude of Ratcliffe had a strong influence on you.

Bracewell

Oh, indeed.

Sullivan

Certainly your textbook on Fourier transforms, the beauty of it to me is its physical insights.

Bracewell

Well, I hope youíll buy a copy of the second edition. Yes, and Iíve got my debt to Ratcliffe clearly stated in the preface. And as a matter of fact, I sent Ratcliffe a copy of the book and he wrote back and said that he had been thinking of writing it up himself now that he had retired but since I had done the job he would put his efforts into a couple of other books that he had in mind.

Sullivan

Well, going back to the post war period, when was it that you went to Cambridge again?

Bracewell

1946.

Sullivan

Ok, so it was very early in the middle of these solar observations.

Bracewell

Yes.

Sullivan

Was there anything else you wanted to comment on about what you saw before you left?

Bracewell

A comment about polarization. I know that Pawsey did not go out with the intention of measuring polarization. That was done by D. F. Martyn at Mount Stromlo where [Richard v.d.R.] Woolley was the director at the time. So while there was a little chuckling this morning when it was mentioned that Woolley had been chairman of Commission 40 of the IAU [Radio Astronomy Commission of the International Astronomical Union], he did have some credentials at least through being administrative head of a place where the polarization of radio waves from the Sun was demonstrated by D. F. Martyn, by a very clever polarimeter that might not have occurred to everybody.

Sullivan

Now Martyn, of course, I canít talk to. He didnít build instruments, did he? He was a theorist.

Bracewell

He built instruments.

Sullivan

I didnít know that.

Bracewell

Yes. I walked into his office at Mount Stromlo one day and he had a chart recorder running on the wall which was measuring the diurnal component of atmospheric pressure. And he had done this by connecting a barometer to a bottle stuffed with cotton so that the air could only get in and out very slowly, with a time constant of about a day. As a result the barometer was rising and falling with all the weather components filtered out and only the diurnal, and Iím not sure whether this was the lunar or solar diurnal, it must be the solar component.

Sullivan

Itís a tuned filter, right?

Bracewell

Thatís exactly right. Itís not tuned, itís just a low pass filter. And he was recording thatÖ. Suppose you have a barometer rising and falling, how would you record the height? Well, he was doing that by shining a light on the meniscus and with photosensitive paper behind, who knows what the hell it was doing, but it sure as hell was drawing a line. And here it was at various amplitudes and phases running on and on and on. So he had instrumental ability. But in the case of the polarimeter, he had thought out how to do it. First he conceived the notion. I donít know how that came about, but having got the notion in his mind, "Wouldnít this radiation be polarized? If so, letís look?" Well he must have looked for linear polarization first. I donít recall that, but he must have rotated a dipole or a yagi. And he could do this with a single antenna, you see. This could be done with a single yagi antenna and he must have rotated it and not found any linear polarization. So he said, "Letís look for circular." And he did that by making a T junction in coaxial cable, flexible cable, making one branch a quarter wavelength longer than the other and connecting these two branches to two yagi antennas. And then simply mounting them at right angles and moving one of them backwards by hand until it was a quarter wavelength behind the other to see what that did. And then he could move it a quarter wavelength in front. And he was able to show that there was strong circular polarization. And I donít remember whether he got the sense correct or not, but at least he knew how to do it. Itís one of those subjects where you have to make an even number of errors to get it right.

Sullivan

And of course that result of his was published along with two other reports of detecting polarization of the Sun by [J. Stanley] Hey and by Ryle, and I gather then that from your knowledge that Martynís thing was just completely independent.

Bracewell

Certainly, quite independent.

Sullivan

They were all together in Nature in a couple of weeks. [Note added 2014: 1) D.F. Martyn. Polarization of Solar Radio-frequency Emissions. Nature 158, 308, 1946 (submitted 6 August, published 31 August). 2) E.V. Appleton; J.S. Hey. Circular Polarization of Solar Radio Noise. Nature 158, 339, 1946 (submitted 23 August, published 7 September). 3) M. Ryle; D.D. Vonberg. Solar Radiation on 175 Mc./s. Nature 158, 339, 1946 (submitted 22 August, published 7 September on the same page immediately following the Appleton and Hey article)]

Bracewell

I donít recall that but if you go back and look at the dates of submission and so on, you might find out an interesting sequence of events. It might have been an artificial synchronization.

Sullivan

Now, thatís true. That does happen in some cases. I donít remember in this case if it did or not.

Bracewell

As a matter of fact you are beginning to stir my mind there. This may be one of those dubious cases where we would have to check into that to know, which you could easily find out.

Sullivan

So you went off to Cambridge to get a Ph.D. basically?

Bracewell

Yes.

Sullivan

And why did you choose to go into ionosphere?

Bracewell

Well, I went in to see Ratcliffe when I arrived and he had in his hand a letter of recommendation that Bowen had sent to him. Bowen had been favorably inclined to the idea of my going on leave from Radiophysics to Cambridge. So he had written a letter and in typical Bowen fashion he asked himself what he should write that would ensure the success of this mission. So youíll see what he wrote. Ratcliffe said to me he was very glad to have me there and he noticed all the good things I had done, and he was particularly pleased that I had had some previous experience with the ionosphere. Now, I am a very naÔve person. Iíve learnt, but basically Iím a very naÔve person. So instead of using my brain, I immediately said, "I have no experience with the ionosphere." And a frown crossed his face and his brow furrowed and he picked this letter and he looked at it very intently. He said, "It distinctly says hereÖ" and I think he probably read me the sentence, and Bowen had perjured himself saying that this man had previous experience with the ionosphere. My interpretation is that the purpose was very simple, "Get the chap over there and they wonít send him back." [Laughter] So Ratcliffe didnít worry about that and he must have filed that away for future reference. He never mentioned it to me again. And then he said we have several projects that might be of interest to you and he described three. And since I was there a little earlier than some of the other newly arriving research students, I got first choice. Now, I had the choice of doing something that was a relatively high frequency but I forget what. Now I had been working in microwaves right at the very end of the radio spectrum. And as a radio spectrum had moved up to higher frequencies, I had done so too. So I had been working on the fringe of the spectrum for a long time. Then he had some intermediate frequency thing, 2 or 3 MHz. And then he had a project at 16 KHz, thatís the frequency of the transmitter at Rugby. And I thought, "Well, Iím accustomed to working at the end of the spectrum. This is the low end of the spectrum so Iíll go there." That was my principle for choosing. I knew nothing whatever about the type of work involved. It turned out to be very interesting.

Sullivan

But there was no choice outside of ionosphere work? Because of this letter, I guess.

Bracewell

No, I had applied to Ratcliffeís group on Pawseyís recommendation. Pawsey knew Ratcliffe. We didnít know Ryle. Ratcliffe everyone knew was a great man and of course he was the producer of Ryle in a real sense. So Ryle wasnít known at that time.

Sullivan

Can you briefly tell me what your work was at Cambridge, in particularly what influence it might have had on later radio astronomy you did? I say briefly because itís not directly radio astronomy I gather.

Bracewell

Well, most of my previous experience had been with instruments, either with electronics or with waveguide equipment. Microwaves, I became deeply familiar with microwaves and electromagnetic boundary theory problems that go with that. But my experience then at Cambridge for the next three years was entirely in observational work. The planning and executing of observations and as it happens building the necessary equipment, which was quite arduous and explains why one gets by with the minimum equipment when you have to build it oneself. You think very hard about whatís the minimum that will do it. If you have to order it and it is just a matter of paying money, youíll do it a more complicated way. So I learnt there how to plan observations and think out observations in terms of equipment. That was a new sort of experience for me. That was couched entirely in terms of ionospheric measurements and rather simple electronics but the measuring problems were very delicate and interesting. I also then began picking up solar influences and that caught my interest because I had had some background interest in astronomical things. And when I found that we could see the Sun when we were picking up a radio transmitter, I became interested in that. And Ratcliffe wasnít very impressed by that. He regarded that as a mild aberration and a diversion from my true duties.

Sullivan

You could see the Sun with what kind of receiver?

Bracewell

With a 16 KHz receiver tuned to a transmitter about 90 kilometers away. The effect is that there is an interference being the ground ray and the once reflected sky wave. And since the wavelength is about 19 kilometers, if the ionosphere happen to move down just a few kilometers then the two vectors that are combining would show a change in resultant amplitude. So that we could monitor movements of the reflecting level as small as a kilometer and probably less. And this is a very sensitive detector, we could see the effects of solar flares, which were much too weak to be detected as fade-outs on short wave.

Sullivan

But it could be detected directly by the existing (?)?

Bracewell

No, no. Not at all. And as for a comparison with the spectroheliograph, we were in direct communication with [M.A.] Ellison, who was the only person observing flares in Great Britain. And we would send him lists of flares, none of which he could see unless they were very big. For a long time he resisted the notion that we could detect flares that he couldnít see. But whenever he got a thundering big one, we would send him the record and ours would be colossal. We had a very sensitive technique for that. And the first paper I wrote based on work I did in England appeared in the Monthly Notices with my colleague Thomas Straker on observations of flare effects on very long waves. [Note added 2014: Bracewell, R.N.; Straker, T.W. The Study of Solar Flares by Means of Very Long Radio Waves. MNRAS, 109, 28, 1949.] So there was a slight astronomical connection there, otherwise that work wasÖ

Sullivan

Geophysics?

Bracewell

Right, you could call it geophysics. Yes.

Sullivan

What about your relationship now with the Ryle group? You were telling us at lunch about the Saturday morning journal club or whatever.

Bracewell

Yes, we would meet on Saturday mornings with all the radio astronomers and all the ionomers. And we would do various things. People would report on journal articles or they would report on work that they themselves had just done. Or there might be a discussion on some topic that had been circulating, instrumental problems that people were engaged on, how you would do this or how you would do that. One fellow was trying to make a machine for computing autocorrelation functions. There was an instrument somewhere which was churning out data on punched paper tape. And it must have been the intensity of some down-coming wave from the ionosphere or it might have been a phase. I think it was probably a intensity. The problem was, "Whatís the autocorrelation function?" And a great machine was built into which you fed this tape and by banks of relays and other incredible telephone equipment, it would remember a hole that had gone by and would multiply it by another hole that had gone by. This was a total analog device. It looked like a Heath-Robinson machine. That sort of machine would be bandied about in discussion and people would argue about whether it was the right way to do it and usually theyíd conclude that it was not a good way. And then the man would go away determined to prove them wrong and make it work over the weekend.

Sullivan

Over the next six monthsÖ

Bracewell

No, no, come back next week and say, "I told you so." Nothing like a little competition like that to stimulate activity.

Sullivan

So Ryleís group at that time would be only one of many under Ratcliffe?

Bracewell

No, Ratcliffe lived in the old Cavendish, the old original building where the neutron had been discovered and so on and so on. And the nuclear and X-ray people had moved into the new building. So the ionospheric people and the radio astronomers were all in a sequence of rooms on the first floor [Note added 2014: not the ground floor]. So we were all in very intimate contact.

Sullivan

I see. And the ionospheric were pretty much one group and the radio astronomers a second.

Bracewell

There was a noticeable division there because Ratcliffe was directing all of us and Ryle was in charge of the other. Ratcliffe was nominally in charge of the whole thing but the de facto separation was quite clear.

Sullivan

Were you in frequent contact with the early students under Ryle or colleagues like[Frances Graham] Smith and who was that fellow, [Derek D.] Vonberg?

Bracewell

Vonberg, yes. I knew Vonberg. Vonberg graduated and took a job in industry or with the post office, I forget which. And I remember us all feeling that that was sort of a traitorous thing to do. Hereís a scientist just goes away and gets a job, throws away all his abilities for the benefit of mankind. So Graham Smith came along, Iím sure only a year or two after I did. But we all knew one another very well.

Sullivan

But you did not take part in discussions with them about the results they were finding?

Bracewell

Yes, they would discuss that on Saturday mornings. I donít believe that there was any air of secrecy at that time that in any way compares with what later developed.

Sullivan

This business about Vonberg is interesting. I havenít been able to track him down in England but was that a bit of a setback to Ryleís group? I mean that was sort of half the staff that he had gotten trained more or less and heís all of a sudden gone.

Bracewell

Vonberg was a tall, rather striking fellow, rather imposing, and itís conceivable to me now, though I donít know for sure, that there might have been an element of competition between the two of them, and that may have accounted for them splitting. But I doubt whether it represented any substantial loss to the activity, I very much doubt that. Like yourself, Iíve never heard of Vonberg since. I donít believe that he had anything like the scientific capacities that Ryle had. I really donít know, thatís just a guess.

Sullivan

Once again at lunch today you were talking about how you became in correspondence with the people in Sydney about whatís going on and would sort of stand up at these Saturday mornings. Could you sort of repeat what your role was there?

Bracewell

Well, when I arrived in Cambridge I found they regarded the work in Sydney as extremely backwards and I perceived immediately that this resulted from about an 18 month delay in information. When I left Sydney I saw advanced things being done and then when I arrived in Cambridge it seemed to me to be about the same, different, but similar state of development. Whereas their attitude was, based on what theyíd just seen published, that they were well ahead of the competition and were in no danger of being overtaken. Well, it wasnít like that at all. So I tried to disseminate a little information from Sydney and I published two or three short letters to The Observatory based on information that came through from Sydney with the approval of the management. I told them what I was up to. And tried to close that gap. I felt very idealistic. I suppose when you are young you do and I felt that a freer flow of information was a blow struck against entropy. One had a duty to do it.

[Note added 2014: The three articles to which Sullivan and Bracewell are referring are: Bracewell, R.N. An Instrumental Development in Radio Astronomy. Observatory, 70, 185, 1950; Bracewell, R.N. Radio Stars or Radio Nebulae? Observatory, 72, 27, 1952; Bracewell, R.N. A New Instrument in Radio Astronomy. Observatory, 73, 200, 1953]

Sullivan

And in fact, the first three the publications I have here on my list are Observatory 1950 through 1953 where you are talking about Payne Scott and [Alec G.] Littleís three element interferometer locating bursts, radio stars or radio nebulae based on [John "Jack"] Piddington minutes and [Bernard Y.] Millsí observations, and then Mills Cross. But this radio stars or radio nebulae, it seems to me from reading that paper that it is more your synthesis of some information that they had sent you. Is that correct? You had more of yourself in that one. It wasnít just a reporter.

Bracewell

Well, I was trying to behave like a reporter but also I have an interest in exposition. I like to try to explain things to other people. Iíd have to look at it again to see just exactly what you are referring to. But that sounds about right. I would be trying to explain it a little better than the originators explained it. I think my description of the Mills Cross would be in that category. Itís not quite a good description where anyone can understand. And itís not original. Iím sure Mills looked at it the same way. But whether he got it written up, I would have to look into the papers. But it was a good explanation of the Mills Cross and I tried to put that into the record.

Sullivan

Now it seems like from what you said that the Sydney people were willing to send you this information, that they were not fearful ofÖ

Bracewell

I think that must have been written from Sydney after I got back.

Sullivan

í53 is the date on it.

Bracewell

Yes, well, I would have been back in Sydney then.

Sullivan

But when you were in Cambridge there was no problemÖ?

Bracewell

Well, there were communications taking place. I donít know who Pawsey might have been writing to but Ruby Payne Scott was certainly writing to Ryle. Well, now that Iíve said that, I believe that is another way of saying that was Pawseyís way of communicating with Ryle. I know from other examples. For instance, Pawsey communicated with Reber by having me write. And so this would have been his way of communicating with Ryle.

Sullivan

Why does he use this technique?

Bracewell

Well, Iíll tell you the Reber story first. Reber was on top of Maui and he was getting a little fed up with the circumstances there and had discovered that there is a hole in the ionosphere over Tasmania which nobody else knew. Well it was known because it was in the books as a matter of fact, but no one you met in the course of casual conversation knew that Tasmania was any different from any other equal southern latitude or southern magnetic latitude. But sure enough here is this hole over Tasmania having something to do with structure of the geomagnetic field I suppose, but never-the-less. But Reber had found that it would be the best place for him to peer through and that Maui was not as good as heíd hoped. So he wrote to Pawsey asking for assistance in setting up an installation in Tasmania. He wanted the Radiophysics Lab to back an ionospheric venture. Well, it was quasi-ionospheric because he had in mind that he would be able to peer through this hole and look at the galactic radiation from beyond. There would be terrible problems of diffraction, but itís a clear, original idea, typical vintage Reber. No one else had thought of it and if they had, they wouldnít have given it a try. So that perplexed Pawsey because although there were resources available, he wanted to spend these resources in the most scientifically productive way. It was very cost effective, the type of thinking he used to go to. But he didnít want to offend Reber by turning him down. So what he did was also typical vintage Pawsey. He gave this to some rabid reviewer who in this case happened to be me. So he said, "What do you think about this? Take it away and read it." So I read it through and I found three or four things that were wrong, that were just not right. So I went back to Pawsey and gave him a little list, the sort of reviewing one does on a paper. My first comment, "This is all wrong." Second comment, "This is very dubious." Third comment, "This is jumping to a conclusion which is not substantiated." I was not taking a global view because it was not my responsibility to make a decision to commit funds or to embark on a new program. I was reading that paper in a microscopic, proofreading type of way. So I gave Pawsey my list of comments, most of which were negative as far as I can recall. And Pawsey then responded to Reber by sending him my handwritten, list of nasty remarks. So I discovered years later that Reber never forgot this. In case what Iím telling you now leaks out, I wonít report how I found out that Reber never forgot it, but I canít blame him.

Sullivan

So this is how you ended up writing Reber?

Bracewell

Thatís right. I never wrote the letter and as a matter of fact, Pawsey is not the one who told me that he sent this piece of paper.

Sullivan

Not even that?

Bracewell

I discovered this in a most indirect fashion, to say the least. Well in any caseÖ

Sullivan

What about with Payne Scott and Ryle?

Bracewell

That would have been Pawseyís way of communicating with Ryle. He would say to Ruby, "Why donít you write to Ryle about this?" And she would write the letter, show it to him, Iím imagining, and he would say, "And you could also point outÖ" And she would send the letter. Now she was a pretty tough cookie. And she would write a non-diplomatic letter, all her speech and conversation was non-diplomatic, verging on rude. And so these letters to Ryle I think one could guarantee were of the nature, "I told you so," or "I told you so last time," "Only a fool would believe that." Iím sure they were very offensive letters, but quite in her normal, everyday style. And Ryle had corresponded with her and the argument they were having was over the existence of sporadic bursts. Now Ryle had put a lot of emphasis on the fact that you had to have a loud speaker attached to your solar recordings because hearing them permitted you to distinguish between non-solar phenomena, most particularly vehicles rumbling down the road. You could hear them coming and you could become acquainted with the sound and you would watch the chart recorder pouring out and if you heard ignition noise from the truck going by you would write that on the chart recorder. If an airplane was going overhead, at the same time there would be a little burst which of course would be of much shorter duration, just a spike on the record because the plane was only there for a brief time. So Ryle knew how to identify airplanes. But Ruby also knew airplanes. They werenít as numerous in Australia, of course. So she knew she had things that were not airplanes, which she called sporadic bursts or isolated bursts. And Ryle had never reported these. Well, perhaps he had published a record showing one and she had written to him saying, "This is an isolated burst." And he written back saying itís an airplane. So they had a couple of interchanges on this. And then when I got back to Sydney, I had some of Ryleís records with me and Ruby immediately pounced on these and said, "There they are. There they are." And she probably wrote him a letter saying, "I told you so. There are these bursts all the time, you see."

Sullivan

These were the records you had looked at in connection with your ionospheric work. Apparently Ryle had let youÖ

Bracewell

Yes, I needed to make a correlation study between sudden phase anomalies due to solar flares and bursts of solar noise that occurred at the same time. And I have here with me a Xerox copy of one of these records that I am referring to.

Sullivan

From March í47.

Bracewell

This jagged curve is the solar chart made by Ryle. Itís full-scale and hand traced. That is a hand tracing of which I made considerable lengths. Thatís the 29th of March of 1947.

Sullivan

Of his original record, right.

Bracewell

As you can see there are two important bursts and then things got quiet. And then is a post burst increase that runs on for quite a long timeÖ

Sullivan

Half an hour.

Bracewell

Coming later. Then the smoother curve is our record of what the ionosphere was doing. The ionsphere went down and then recovered slowly. Itís a very uniform thing. And undoubtedly this follows quite closely the integrated ultraviolet from the flare because itís quite in keeping with the visible observations made with the spectroheliograph. We have many cases of the line widths measuring the spectroheliograph agreeing in the general profile with this. Of course, the visible ones usually started when the flare was near maximum because thatís the first time theyíd see it. So our sudden phase anomalies always began before the optical observations. But as you can see from the second example I have here, we have a case where possibly the solar noise sets in a few seconds or maybe a minute or two before the phase anomaly. So this was the sort of analysis I was doing and all I can say is that the situation was then as it is now. The solar noise is a very irregular thing compared with the general course of the flare itself.

Sullivan

But your sin was in showing these tracings toÖ

Bracewell

Yes. Now Ryle knew I was making these because he had them filed in drawers in his office and I was there for days laboriously tracing these on long roles of tracing paper. Searching through my list of times and dates, finding his record, and if there was something interesting, as with these two cases, I would trace his whole record. He could see by the way by the interference pattern of his two element interferometer. Thatís all superimposed on this. And quite possibly this diminution may be an interferometeric minimum but you can see there was a sudden cessation of noise but perhaps that minimum, which looks kind of round, we can tell by the timing you see. Thatís probably an interference minimum. So you need skill to read those records but never-the-less. But these things here are quite possibly sporadic bursts. There are several of them. They are probably type three bursts and the kind of thing that was in contention.

Sullivan

It would occur to me that if this was one of his main early correspondence with Sydney, that this may have been something that turned him off to Sydney, this kind of treatment from this Australian woman.

Bracewell

Thatís possible.

Sullivan

I just donít know. Well, the next publication I have in your list, actually there is one other before we get to your textbook. Bracewell and Roberts, í54. [Note added 2014: Bracewell, R.N.; Roberts, J.A. Aerial smoothing in radio astronomy. Aust. J. Phys., 7, 615, 1954] When did you go back to Australia now?

Bracewell

In 1950.

Sullivan

In Ď50, I see. So well then the question is before we get to í54, what things did you start working on?

Bracewell

Well, for two years I did ionospheric measurements in Australia similar to those Iíd done in England. As a matter of fact I made very long wavelength observations on the boat on the way back to Australia. I had a little room on the bridge and an inverter and I made observations of GBR [Note added 2014: radio station] for thousands of miles. And then I continued that sort of work in Australia, working with Keith Big, who later became famous for discovering the control that Io exerts over Jupiter radiation. So he and I rattled around New South Wales to different distances from a transmitter and made lots of observations. I did that for a couple of years. And the data that we had accumulated disappeared one day. I had books full of data, so no paper was ever written on that. I expended two years of my scientific life, and all the data disappeared.

Sullivan

Could you be a little more explicit about disappeared? Stolen? Taken by the trash man?

Bracewell

Well, it sure as hell wasnít taken by the trash man because we had quite a lot of it distributed around. I donít believe that explanation. Just how it disappeared I donít know.

Sullivan

Well since itís not radio astronomy data I wonít probe any further.

Bracewell

Perhaps in the course of your inquiries you could ask people.

Sullivan

Right, "Did you take Ron Bracewellís data in í52?"

Bracewell

I think it would have happened in í52.

Sullivan

Someone trying to get you off this project.

Bracewell

Well they got me into radio astronomy. So in 1952Ö

End of Tape 131A

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Modified on Tuesday, 23-Dec-2014 10:50:11 EST by Ellen Bouton, Archivist (Questions or feedback)