text:
Interview with John Paul Wild
Wild1978tape89B.mp3
Wild1978tape90A.mp3
John Paul Wild, 1923-2008. Interviewed 3 March 1978 at CSIRO/Radiophysics, length of interview: 150 minutes.
Wild, John Paul
1947-67 at Radiophysics; first and second solar spectrographs at Penrith and Dapto; Types I, II, III bursts and explanations; hydrogen spectrum; harmonics in bursts, speeds of particles, plasma waves, etc.; swept-frequency interferometer; in U.S. 1955-56; Culgoora thinking, designing, financing and building 1956-67; overall Radiophysics structure, etc.
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). In preparing Sullivan interviews for Web publication, the NRAO/AUI Archives has made a concerted effort to obtain release forms from interviewees or from their heirs or next of kin. In the case of this interview, we have been unable to find anyone to sign a release. In accordance with our open access policy, we are posting the interview. If you suspect alleged copyright infringement on our site, please email archivist@nrao.edu. Upon request, we will remove material from public view while we address a rights issue. Please contact us if you are able to supply any contact information for Wild's heirs/next of kin. The original transcription was retyped to digitize in 2018, then reviewed, edited/corrected, and posted to the Web in 2018 by Anne Hilten. 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.
Originally transcribed as typescript only by Pamela Jernegan (1979), retyped to digitize by Anne Hilten (2018).
Begin Tape 89B
This is talking with Paul Wild on 3rd March 1978 at Radiophysics in Sydney. So, the first publication you have is Wild and McCready in 1950, but I know you were working on these data before then. Can you tell me how you came to Radiophysics?
Sure. Well, I was – was during the war, during [or] after 1943, I was doing a very rapid two-year type degree at Cambridge. I went straight into the Navy for the rest of the war and a bit more.
Is that in physics?
That was – you mean Cambridge?
It was Maths, part I and Physics, part II. I would have been a mathematician had it not been for the war.
Anyway, the war took me to, I was appointed after a six-month crash training course in radar, joined the Battleship King George V and was assigned up to Sydney for the first time. And Sydney was our base for a number of operations in the Pacific. And during that time, among other things, I got engaged to be married to a Sydney girl and when I returned to England in the ship and had to continue serving in the Navy for an instructional job until February, 1947, when I came back to Sydney. In the meantime, I had lined myself up the job at CSIRO through the London office.
Do they advertise in England?
I just went along to the Australia House and asked if there were any research jobs.
And the first job I applied for, I didn't get and the chap by the name of John Bolton got that job. He was also in the Navy, but he was demobbing from Australia, but he had a slight edge on me. And it turned out that our careers have been very similar. Except that he had been one year ahead of me - both at Cambridge, both in the Navy, both applied for the same job. I think both became Chief Research Scientists almost together. And at one stage we were both joint vice captains at the Radiophysics cricket teams, very similar.
[laughing] Dick McGee has produced a photograph of your old cricket team, which I find delightful. Let me ask you while I think of it. You were in the Navy as a radar officer, and I'm fascinated with the parallels between the sea cliff interferometer and what was known from radar practice during the war. The basic question is: was it a very straightforward thing to, having worked with radar in the war for someone like Pawsey, to say, "Let's put it on the sea cliff." Or was it a very clever thing to do?
I think the principles were really straightforward. I suppose the credit goes for going out and doing it and making it work. Nearly everything is simple after the event.
Right, but the whole business of effects of refraction, and the Lloyd's mirror effect, all this was well known from radar practice.
The first decent piece of work I've seen on the refraction effects was in, in the work done by Pearcey as a sort of footnote to the Pawsey Payne-Scott Royal Society paper. Actually, that was an, the original calculation by Trevor Pearcey. Trevor Pearcey was a mathematician in this division. And that was quite an important contribution. But certainly, I mean, aboard ship we used to do height finding by this technique. We use to have a large Perspex board with all the lines drawn out and you saw where the first detection was and where the first fade was, and that gave a height.
Right. Did you worry about refraction at all or did you not need that much accuracy?
Well, I think it was, strangely, up to the individual. In my case, I didn't. I had charge of the whole height-finding operation, and I calibrated the thing entirely empirically by aircraft runs. I didn't use —
With friendly aircraft, you mean?
Yes, (some of them would go a certain height?), and they would come in and do run after run after run.
So, I would then check for the theory afterwards and in my memory it was a very good fit, but--
What sort of frequencies were these radar?
This one was 45 megahertz. The two, 45 and 80 were the two long-range warning, both were very low frequency.
And what sort of elevation would you first be able to pick up a plane?
Well, if it was at sea level, you could hardly pick it up at all, unless you pick it up on one of the centimeter or one of the microwaves. If it were at 10,000 feet, I suppose you'd pick it up at 50 miles; if it were 30,000 feet, you'd pick it up at 120 miles.
About 10,000 feet, it's two miles. At 30 miles you said is about three degrees elevation -- something like that?
Yes. The 30,000 feet was a fairly accurate one, I think that the other one is rather taxing my memory.
Okay, I was just wondering about that.
The job I actually got was a Research Officer, as it was called, was to work in the test room. It was really doing research associating with test equipment and –
Now, who was it who assigned you to that? Was it – ?
Pawsey. But I was working the week at the (?). And I spent a year or so, that would have been 1947 February, 1947 to February, 1948, about then, in the test room. I was like a fish out of water completely; I wasn't particularly interested in the work. And I was very anxious to get into research, especially what was known as solar noise research. Radio astronomy hadn't been invented as a word then. And the small group was known as the solar noise group, even though some of it was doing non-solar work.
You were undoubtedly hearing about their exciting work.
Oh, yes, yes. I was very glad when Joe Pawsey almost said, "Well, you're not doing much good there, we'd better try you on research," and that was the start. I had the choice, I was given the choice of doing two things: one was to go and join John Bolton who was doing very well at Dover Heights, and the other one was to it – it was suggested that the next step [interruption]. You are being recorded. That's okay.
And the second choice was?
Well, it was a suggestion, really, at the time, was to look into the feasibility of building a solar spectrograph. Since I'd been taking recordings on different frequencies and finding some very interesting time relationships.
So it was Pawsey's initial suggestion –
Pawsey's initial suggestion, right. And it was something that Lindsay McCready had on his books, as it were, to do; but he had various other administrative things, so I came in as the junior boy as it were, on it. I decided that would be a better thing because I'd have much more independence on that than, I mean John is a man of considerable personality, and he had already established himself. So, Lindsay was a very good person to work with in that he gave a few initial suggestions. He was quite a receiver wizard during the war in radar, very modest sort of person. And, he sort of more or less drew the first circuit diagram which helped me, but there was a long way to go, and then he left me very much to my own to develop it.
Let me just ask about McCready since, of course, I can't talk to him. Was his role in the various projects that he was involved in, mainly to build receivers?
During the war, very much so. The (slab?) was (??) through the war.
Right, but in the radio astronomy projects after the war?
Radio astronomy – in the early days, he helped Joe Pawsey getting the equipment together, getting the receivers together. There was often, very much, taking of old wartime equipment and adapting it. And he did that, very much, himself. But when he came to this project he was so preoccupied by so many things that it was in the end left to me, and I had one assistant, Bill Rowe, and Bill Rowe and I sort of put the thing together. John Murray joined us later and it was really, we set out with this sort of shack near the Penrith railway station and we use to go up by train every day. Pawsey, I think it says in there that the total observing period was four months.
Right. In 1949?
That's right (it was?) research for the paper. And towards the end of that time, John Murray joined us, and towards, it was at that time we discussed, in that things looked pretty good, that there was a need for a properly engineered thing.
(This place?) was properly engineered?
Oh, no, it was string and ceiling wax, absolutely. [unclear word] I'm not an engineer, in any sense. But John Murray is a meticulous engineer; and he, on a considerable time scale, I should say, put together the receiver so the next phase which was Dapto equipment.
But just going back to McCready. What I was getting at was, was he involved in the interpretation of the data at all?
Not at all. Obviously, he showed great interest in it, but he wasn't.
Okay. So, now going back to –
He was very much an engineer, (I guess that's why?) he never got very involved in what we would now call the astrophysics side of it.
Going back to building this first spectrograph, what were the problems that you had in building it and how did you solve them?
Well, the point was at that time, to my knowledge nobody had built a swept frequency receiver which had a good noise figure, and it was a question of getting a good noise figure over something approaching 2 to 1 frequency band, and anything you did at one frequency tended to upset the other frequency. So it was matter of, and of course, one had to use in those days, rotating condensers, capacitors --
Mechanical tuning.
Mechanical tuning. The problems I remember most of all were first getting enough power out of the local oscillator over the frequency range. I remember we used an extraordinary tube called a doorknob tube, which is long gone out of existence, but it was sort of shaped like that. It's a great pity that somehow that equipment got thrown away somewhere. It would have been quite a museum piece, because it was quite extraordinary. The other task was getting rid of all the parasitic oscillations, which seemed to want to creep into the system. Yes, the timescale really, for present standards, was fairly short. We threw that together. The aerial was a huge wooden cross with a pivot at the bottom with wires to make it into a rhombic.
Was that pretty, obvious, to use a rhombic aerial you needed a wide band to —
Well, that was really, it was Joe Pawsey's suggestion; he was a real expert on aerials. He was overseas while it was being built, and he was rather distressed when he came back and saw it. He had ideas of building it out of bamboo – he used to love bamboo; it's so nice and solid and he was rather horrified to see this rather heavy thing that was dragged around by ropes. I think that probably, the main thing was that it worked.
About how long would you say it was, six months to put it together or something like that?
Well, I think it was probably, began right about March, 1948. I'm not sure when the observations -
Were sometime in early 1949 they began?
Probably about March, 1949. But of course what one had to do was some spend time looking for a site which was reasonably free from interference and accessible and so on. So it probably took about —
Well, John Murray was telling me about searching for the Dapto site which of course, is much further away from Metropolitan Sydney. How were you able to get by at Penrith which isn't that far away, I guess?
Well, we learned a lot from the Penrith observations. What we used all the time was a monitor, it's an experimental FM station in North Sydney, 92 megahertz, and we went down ready with a truck monitoring the station's signal strength. And, it was about – well, there were many taxis and this that and other, various other things, but it was the dominating signal. But this site at Penrith, it was relatively low compared with the Sydney District. Then when we chose a new site, we were still really plagued by this one signal that was almost an obsession to get away from it, and that's how we went much further.
I see. It wasn't a matter –
And the Dapto site was a very, very good one, because it was screened by these tall hills.
It wasn't a matter of the entire band filling up in the three or four years.
No. Not really, no. It was, lots of signals came in – aircrafts, taxis, mobile sound and – But, we always used this 92 megahertz as by far the strongest, and it was the criterion.
So you got this thing built, and what happened when you put it on the air?
The Penrith one, you're talking about?
I should say, in the early days, we had a movie camera, but we didn't actually have a motor, so we had to turned it by hand. And we changed the aerial every twenty minutes. We changed its position by ropes, adjusting the rope, and Bill Rowe and I used to take twenty minutes watches and when anything came, just looking at the screen waiting for something to happen. First, we didn't know quite what to expect. We knew what these looked like on a single frequency, but the first few that came, there was tremendous excitement, seeing the whole sort of scan rising. Eventually, we rightly identified what it was. Undoubtedly, a Type III burst, one that went across the scan. And, one that moved from high to low frequencies. So, it was quite dramatic. Sometimes a whole week would go by with absolutely nothing, perhaps more than a week. That's an awful lot of work, traveling backwards and forwards, and watching for nothing to happen, or it seemed so at the time.
And then on other occasions it was a huge, tremendous activity.
Were you monitoring this sun optically at all at this time?
We had – I can't remember whether we had a–I think we probably did have a small telescope for the sunspots.
You had one at Dapto.
Certainly at Dapto. But I'm not sure myself whether we – No, there was a great deal of monitoring down in the lab and we did, it was known, you know, of the, not much changed in the laboratory, not much at all, but (?) So we knew when the sun was spotting or refracting.
But you would go out even if there weren't spotting?
Yes, because it's just as important perhaps, to find out what happens in the quiet periods.
Right, you had no idea, of course.
No, and when eventually we got, I don't know whether John Murray told you this, but when we got to Dapto, we had a dreadful first three or four months when it was right in the middle of the sunspot minimum. Nothing happened at all.
Yes, he also said you wouldn't observe at all if there were no spots. You just gave up.
Well, it was –
Maybe not in those first few months, but –
Well, it was automatically recorded then, Dapto, that was on the intensity motivated film, so there was no effort involved. You didn't sit down in front of the thing waiting as if it were, but you could go and –
Right, but didn't he tell me that if the sun were not spotting that you didn't even bother going out to the site? I thought I remembered him saying that (?)
I think we used to keep up a regular, usually five days a week, if there was anything on the weekends, we use to go. It was very irregular, but we closed everything down, the solar observations down for a period when we got a bit fed up with the low level of activity at that time, and we started scintillation (?).
But, uh.
Well, going back to Penrith, a question came to mind. You said that there were swept frequency receivers, but that they were not up to the noise figure. But these were not –
These were not being used in radio astronomy though; these were for some radar application or something.
Sorry, which are these?
Were there any being used in radio astronomy, by your group or anyone?
You mean swept frequency? No, I think ours was the only –
Right, so these were used in radar or something?
Not swept frequencies. No, as far as I know, there were no swept frequency receivers that had very good noise factors around at that time. Most spectrum analyzers had, of that era were, I don't think it even measured a noise frequency (or measure that sort of?) sensitivity.
So, you apparently took a few months of data and began to see some patterns in what you were seeing. Can you sort of describe to me what came out of this?
Yes, at the end of that observing period, I suppose we collected so much film that it seemed to be a sensible thing just to stop and try and make sense of it. I spent weeks, weeks and weeks in the dark room plotting everything out. I think these (?) show you the original plots.
Yes, I'd like [interference]. These large color diagrams that you made by hand. How did you go from the small 16 mm film or was it 8 mm?
I think it might have been 35 mm.
35 mm?
Well, the 35 mm was an A scan – intensity (inverted) frequency (or?) something like that, and then one had to calibrate this for receiver sensitivity. This was done by injecting noise at different levels and it was by no means, anything like that. It was a very curvy thing.
What sort of accuracy do you think you had for intensities or at least the relative?
The relative accuracies I suppose are pretty good. I suppose it was a few tenths of a decibel or something. One had to make corrections for the aerial, the variation, effective area across the –
As the sun went through the beam?
No, I mean the, the -- see the beam followed the sun. I mean twenty minutes –
Well, in twenty-minute increments.
Oh, that was enough.
You didn't need to worry about that, but you mean the frequency response?
-- but, the frequency response (varied?) (and had to make) adjustments for that sort of thing.
So, were these large sequences made up, then, of every second or something like that?
That's right. These are time and seconds and to a second.
It was a matter of scribbling down in a notebook all these sets of numbers, where they crossed the different levels and then plotting it out. But obviously when you had something like this, which is a very dramatic and a beautiful thing, the incentive was considerable to go doggedly ahead and do it. [sound and pages turning] This was another example, this is a Type II burst.
Type II is a slow drift.
A slow drift and Type III is a fast drift. In fact, it's probably the cleanest example that came out of it. These were a few -- some instrumental imperfections, rather mismatches. Yes, that's right.
Were there quite clear demarcations between what you call Type I, II and II; was it pretty obvious that –
Absolutely, there was no, there was a factor of a hundred difference between Type II and Type III in the drift rate.
Very little occurred in between.
Nothing in between. No, it was absolutely discrete.
And what about the Type I?
Type I was an entirely different phenomenon. That was sort of like little things popping up all over the place, like a choppy sea. [papers shuffling] That was entirely different. Then there were all sorts of other nondescript things that we did describe – that sort of thing that doesn't seem to have any character at all, but in actual fact it's probably a collection of Type III like this.
Happening simultaneously? [pw voice unclear]
You see very, yes. You see overlapping and so on, but that's (?).
Unsatisfied, if you like. You see, very often we used to miss the beginning –
End Tape 89B
Begin Tape 90A
We've been looking at the original colored charts that you made up, and you were just telling me about how exciting some of –
Oh, when they actually occurred, [Oh, that is a pen one has set up] one was waiting for long periods and nothing happened, and then these things rose out of the, on the A scan of the cathode ray tube. It was tremendous excitement and whoever was observing would try and turn on the camera as quickly as possible and shout or scream to get the other one on to come and have a look at what was going on.
Sometimes you did miss the beginning, though –
That's right. Invariably we'd miss the beginning. Except of course, when we learned after a while that it was a Type III burst, which were very short. They only lasted about 10 seconds and getting them was very important. But we soon learned that they tended to come in groups. So we'd keep the camera on for, oh possibly, if we missed part of the first, we'd get all of the second or third.
Now this thing was absolutely unique at this time, right? In fact, is it true that the next one wasn't built until the mid or late fifties when Alan Maxwell's –
Right. Maxwell was really –
Well, besides your second one.
1956. I spent the first part of 1956 with Alan Maxwell at Harvard.
I see. Well, we'll talk about that a bit later on. So you had no competition exactly.
No, no competition.
But, tell me now about these three types. You said that they were clear cut as far as very little things, very few in-between cases or maybe none at all. What did you make of that? What did you think was going on?
Taking them in turn, well, not in the right order, but typically you start with the Type II bursts. There had been one example recorded on single frequencies by – I'm trying to think, Payne-Scott, Yabsley and Bolton.
Right. I think that's correct.
And this was one unique example in which there seemed to be a drift from, a very slow drift from high frequency. Payne-Scott had followed these observations up and found no other cases, and she concluded that it was an accident. But, when that first one came, it led to a better dimension, there was a suggestion, I think it came from Pawsey, that it was perhaps due to an output within the disturbance at 1,000 kilometers per second or 800 kilometers a second.
The idea of different frequencies originating in different electron densities was pretty straight-forward?
Not so straight-forward. That really came out of the work, as far as we were concerned, of D.F. Martyn, and out of the quiet sun work. This was a piece of original work by Martyn. It turned out in later years that at a similar time, Ginzburg, in the Soviet Union, had come to the same conclusion and published it. A somewhat similar time.
But you didn't have that translation?
No, as far as we were concerned, it was, we only knew of Martyn's work. And so this, as we found that this was, in fact, a regularly occurring phenomenon, we found more and more evidence to favor that hypothesis. And of course, the ultimate evidence really came with the Dapto work when harmonics came along, and it had to be a resonant frequency. And the plasma frequency was the only thing that –so that was the thing that nailed the plasma hypothesis was the harmonics.
Well, what had it been before that? What else were you considering?
There were various theories for frequency drifts; one was a sort of great big concentration somewhere in the solar atmosphere, a concentration of electron density like a bubble that would gradually burst, as it were, a concentration which spread itself. When it came to Type III bursts, we advanced the hypothesis, not immediately. We mainly pointed out that, let me start again. There was a hypothesis by Jaeger and Westfold that, to explain the Type III bursts as different time delays as due to group retardation, and this is looked into in the third of my papers. Now, by a very systematic quantitative argument, we were able to show that this was wrong; this was completely incompatible, from a very general point of view.
And this was in the third paper?
This is the third paper.
The source cannot be fixed. What was the key part of that argument?
The key part of the argument was a subtle one; it virtually measures the curvature, this graph –
Figure 6?
Right. It depicts the curvature of the burst on the time-frequency plane. And what is plotted here is the time interval, the upper part of the frequency range versus the time interval on the lower part of the frequency range, so that a straight line burst, a linear burst, would fall on a 45° line. Now the Jaeger/Westfold hypothesis said that it had to fall in the shaded portion, and not one example in fact did. It fell up here. On the other hand though, the whole thing was entirely consistent with the idea of a source which moved outwards at constant velocity. And later, we didn't push this fact, but many said it was consistent with it. Later on, when further evidence came along at the Dapto, and then we really pushed that hypothesis. We said this looks like the real thing, and met very great opposition because no one had heard of any particles from the sun which at such high-speed ejections at one-third the velocity of light. I remember that I think at the first IAU Conference I went to, in Dublin in 1955, I can remember walking along with the great man, Alfvén, him saying, "You're wrong, you know," and I said, "Well, let's have a bet on it then." I can't remember what the bet was.
Or, if you ever collected? [laughing] So people were willing to accept this slow drift, 500 kilometers a second or something like that, but not the very high speeds?
Oh, what was the other question that came to mind? When you were figuring out these velocities, were you just taking standard models of the electron density versus height?
Yes, indeed. By this time, there were fairly trustworthy models of the electron densities; the solar corona, and due to the work of D.F. Martyn and also, we didn't know it at the time but in Russia by Ginzburg, the notion of different frequencies coming from different levels according to the plasma frequency had emerged. So, this is how we got our velocities, by combining these two facets.
But the actual models that you used were they Smerd's perhaps?
What the actual models really were, were the models used by Steve Smerd as well. The model was really the, known as the Baumbach-Allen –
-- model which came from eclipse data, and what Steve Smerd's big contribution was to work out the radiation from the quiet sun.
Okay. We've discussed the Type III, the Type II slow drift, but you haven't mentioned anything about the correlation with flares. Could you tell me what sort of cooperation you had in these early days between optical and radio, and so forth, also?
Yes, well the solar, the international solar community is a very closely-knit cooperative one. We didn't know very much about flares at that time. In fact, the flare as a solar phenomenon is almost entirely a post-war thing. If you look in early pre-war books, there probably, if there was anyone by (?) the flare hardly gets mentioned. Since the war, it's become the main phenomenon really on that scale, the main phenomenon of solar activity.
Why was it missed? Because people weren't looking at H-alpha perhaps?
I don't really know why it was missed. Probably because people weren't taking so many routine frequent observations. That is, taking pictures every second or so. (?) there was a lot of prominence across recording (?) or (?) or whatever they were.
But you're right, the expense of a monitoring program, is a standard now; it would have been very great then.
Yes, but it was a very early result. Of course, the solar flare was, chromospheric reactions, right from the very word go when they were first observed in the 19th century. The suspicion of their correlation with the aurora magnetic storms. And of course, what the Type II burst has done is to establish almost beyond a doubt that the Type II burst is itself the agency which conveys the, which causes the aurora magnetic storms and links the flares with the (?)
Right, getting here a day or two –
And eventually we identified the phenomenon of the Type II burst as a shock wave.
But that comes a little bit later.
That comes a bit later, yes.
But now what about the correlation with the flares? Where were you getting your optical information from?
I can't remember, this is an internationally available paper.
So it wasn't any local optical astronomer; it was just these standard reports of solar activity?
Well, for instance, I know that C.W. Allen took some interest.
C.W. Allen did, indeed.
But perhaps not directly with you.
Yes, we had a lot to do with C.W. Allen. He, himself, made a very valuable series of single-frequency observations, 200 megahertz, I suppose, and did a lot of good work in helping to classify the various types of phenomenon that you could recognize on single frequency. But I don't think in those days that Mt. Stromlo was really doing any solar work. There was a certain amount of work done at that time: observation of flares, by John Jefferies' group, Marie McCabe from the roof of the laboratory at Sydney University. Oh, there was a fair amount of optical flare, but there was no problem of getting sufficient material.
But you did not develop an actual collaboration, collaborative program with them? That, say we'll be observing next week, will you guys observe next week, or something like this?
Not really. They monitored the sun at that time, which is all we were asking for. Later on, when we were at Culgoora – I think Joe (Benetti?) himself would have been quite interested to develop a program on flares, optical flares and working closely with us, but his own collaborators were not interested in that sort of thing. There's never been a very close, apart from a social one, there's never been a very close sort of collaboration between the optical and the radio part.
Let me ask a more general question. Obviously, you were becoming educated about the sun, and perhaps even astronomy more generally – was this all just a matter of going to the library and reading books yourself? The transformation from a radio physicist to an astronomer?
Oh, I'd be just reading bits and pieces here and there, going to astronomical meetings, and talking to astronomers. Things just rubbed off. There was no systematic attempt, in my case, at least in self-education of astronomy.
Were there ever any, for instance, series of lectures organized in the department?
In Sydney?
Right, where people would bone up on different areas and give a lecture or something?
No, not really. The usual scientific colloquia people would give. I think, people like Steve Smerd occasionally would give some educational talks, but there was nothing systematic.
Well, along this same line, if in the early fifties someone asked you what do you do? How did you answer them? How you describe your –
I'd probably say I was a physicist. It would have been misleading and pretentious to call oneself an astronomer at that time. I think the word "radio astronomy" came in just about 1950, '51, or something like that.
Now you mentioned international meetings or astronomical meetings. When, in fact, was the first time you went to an astronomical meeting?
I went to the Dublin one in 1955.
There were no previous ones in Australia here?
Oh, well, the biggest, it was sort of an international event in Australia, was the URSI meeting that was held in 1951.
52. I think it was.
I think that was the first big international conference for the scientific unions of any kind held in Australia.
Did you present results at that meeting?
Yes, yes, indeed. In fact, it was really the (?) results of the (?).
And this probably afforded the first opportunity to meet some other people. Can you remember anyone?
Well, yes. The leader, the chairman was Appleton at the time, and there were many others who are in that photograph.
Oh, that's right.
That is taken at the time of URSI. There's — [looking at photo]
Mueller, Steinberg, Hagen.
Right. Doc Ewen.
Hanbury Brown who was from the UK.
That's right, at that time.
And Laffineur, M. Laffineur from France.
Now I'm wondering, did you profit at all from this interaction with them or was it mainly?
Oh, very much. It was very exciting, first chance of meeting people from other countries, and it was very stimulating. They came round, I remember at that time, we'd just set up Dapto field station and they all came to visit us, including Appleton, his gray striped trousers and everything; and he gave us very great encouragement, and said all good things.
Okay. Going back to the fourth paper now, is the only one that we haven't discussed, I believe. And that has to do with the "enhanced radiation," as you call it. Could you tell me about it?
Yes, it's become (?) noise storms or Type I storms. That is, continues really to be, the hardest to interpret, but I'm rather out of touch with the subject in the last few years; I'm not sure what advances have been made. But it's believed to be due to radiation from, probably plasma radiation, from charged particles trapped in the strong magnetic fields of sun spots.
But what were you making of it at that time?
Really, very little, from the spectrum. We didn't really want to speculate on things. We didn't get a real clue form the spectrum, but there were clues from the fact that they were very strong, correlated with suns spots, especially large sun spots, that's a result really that Ruby Payne-Scott brought out. So they had to do, certainly seemed to be associated with very strong magnetic fields. But we got nowhere at that time interpreting it.
And did you mention, measure some circular polarization also?
Yes, although that had been established before.
Also, you mention a minimum in the spectrum at 89 megahertz.
Yes, that turned out to be a chance thing. The point is that I think we did have a caveat when we described this that we said: the chances of this happening by chance if everything were independent, or the bursts were independent, is something rare indeed, but in actual fact they're not independent – they're all taken from about four storms. The number was really four and not several hundred.
Small-number statistics. That would have been intensely interesting, but of course, it doesn't show it. And about this time, I did get very interested, since hydrogen was the main ingredient in the sun's atmosphere, I got very interested in the spectrum of hydrogen. And when the hydrogen line was discovered, I got an internal report I'd written on the hydrogen spectrum, dusted it, and edited it, and published it in the Astrophysical Journal. It's one of the earliest papers on this thing.
Right. That was in fact my next question here.
I was very stupid in that I didn't buy the possibility of lines, spectral lines in the solar spectrum.
So that was your real motivation?
That was the real motivation, and ah –
And you did conclude that perhaps this three centimeter line could be visible?
Yes. Well, it's still on the cards.
People have tried. Did you every try it that time?
And, also you recalculated the Einstein A for the 21 centimeter line, which had been incorrect up to that point. I think Purcell –
I don't think (he did that, did he?)? No, I think this was, this was Purcell; I don't think I've taken it –
When you say private communication from him?
Yes. Yes.
Another thing I wanted to ask you about was the recombination lines are dismissed in a —
One sentence?
Yes, well, this is one of my famous sentences I have written. [beginning to laugh]
[laughing] Sorry to bring it up.
People have reminded me of that many times.
Did you —
But, I think it's a perfectly valid statement that they were just undetectable from the kind of equipment that could be dreamt of at that time.
I believe what you said then was that they would be blended together.
Right, blended together or with, or be distinguishable from the background.
Yes, continuous spectrum. I was just wondering, was that based mainly on the result that van de Hulst had in his famous paper in Dutch, which I guess you had a translation of when you wrote this. Is that true that you had a translation of that?
No, I think, I don't know that we ever managed to get a translation of van de Hulst's paper. It's a very elusive journal, isn't it?
Yes, right. So you were —
My interests were originally in, not the recombination lines, but the fine structure lines. I suppose recombination lines are – no, let's think, recombination lines are different than main quantum numbers, aren't they?
Right. Right
It's my main interest was the fine structure lines, but that sentence was passed off with a minimum of thought.
Okay. That makes sense if you didn't see van de Hulst's paper because he actually did consider recombination lines in that paper and came very close to getting it "right," but he made a slight mistake in the line broadening calculation and concluded that they would not be detectable.
Whereas if he'd done that right, even with the knowledge that was available then, he could have, he might have said at high frequency you could get a few percent line to continuum ratio. But, if you didn't even see that article, now did you have the translation of the Shklovsky article in '48? You refer to that.
I can't remember. I can't remember. I probably did. I probably had it in a –
Now there I can check the date of the translation in the Division here, that might tell you.
Hmmm. Yes.
So anyway, your main motivation for doing this paper, which is primarily known for its 21- centimeter work, was more to do with solar applications?
Right, that's definitely what got me interested to start with. And some of the, I got somewhat interested in lines to use to some instrumental effects in the spectrograph due to mismatches, certain frequencies showed up better than others due to mismatching. Well, until I recognized that they were due to mismatches, I got interested in studying the spectrum, hydrogen spectrum.
You thought they might be real [speaking simultaneously - unclear] I see. That's interesting – I don't think you mentioned that in the paper. That was part of why you wrote it?
I didn't mention the motivation. I don't think one usually does.
Well, you're right, but I would like to put a note in that one should, certainly from a historical point-of-view. It also makes for more interesting reading. But let's move on. In the volume edited by Kuiper on the sun, you put a chapter in on solar radio techniques, and you also had a review article on radio astronomy as a whole in Advances in Electronics and Electronic Physics. So obviously, your work was becoming known and you were writing review articles. In terms of observational radio astronomy when you wrote that article in 1954, you obviously had to make an assessment of the whole field. Can you put yourself in that time and sort of comment on how you saw the field as a whole?
Well, I think that by that time, the Radiophysics Laboratory was so imbued with radio astronomy that, and at that time, one tended to keep track of the whole subject which nowadays is very much harder. And one was in touch with, in Australia, with a lot of people working in various different priorities and also again in international meetings, so it was good education on my part to write that article. It sort of made one sit down and read a lot of literature, make an assessment. Well I tried to keep it with a touch of individuality. I even put up a rather crazy type of radio telescope.
What do you mean "put it up?"
I described an original type of radio telescope, which was a sort of an early version of an aperture synthesis requiring four elements.
I see. I didn't remember that. Can you just tell me now what —
Yes, the possibility of photographing radio brightness distribution.
Ah ha.
So it was a sort of a little bit of a —
So its a bit of a precursor we might say.
Yes it is. This is this sort of thing. [paper shuffling]
So you worked out the —
It was really —
The Fourier theory of it.
Yes, it was really--see the Mills Cross had come along at that time, and this was simulating the Mills Cross with the aid of four elements which were movable. Well, eventually in the final form of aperture synthesis, of course, it's simpler than all that and you only need two elements. But what I'm saying is that I didn't want to merely write a review article without a certain amount of original thought.
And you state here "the outstanding technical problem of radio astronomy today is to improve the resolution,"basically.
Still is.
Clearly that was on your mind. I actually had a note here that I see already you were thinking about image formation.
So I guess it would be fair to say that this is really the first sort of thoughts that eventually were to lead you to Culgoora, is that correct?
Yes. And of course, one, we were surrounded by people who were working in this field, Christiansen —
Although, you hadn't at that stage discovered the rapidly moving sources, I don't think.
I think, yes, we would have got the spectrum by then, but not the interferometer.
Yes, but you probably suspected that there might be.
(?) that was written —
--that was published in 1955, so probably 1954.
Well, the interferometry came fairly, soon after that, a couple of years or so.
Okay. Let's move on now to the work with the second spectrograph. Can you tell me–you already mentioned that you decided you needed a properly engineered thing, so to speak–what were the new characteristics you wanted to have in this second spectrograph?
The most important thing was broad band, much broader band. And we were aiming for something like an (eighth to one band?), I mean three lots of two to one, and this proved to be a very important thing because it immediately paid off. Tipton's reproducing the harmonics, which we couldn't have gotten before. The other thing is polarization, more sensitivity, and circular polarization.
Did you want to be able to look at bursts in different single polarizations or were you able to measure the polarization during a burst?
We tended to, strangely enough, I can't think how we did it, I think we recorded the two side-by-side. Left and right hand polarization. That was one way of recording. Another was to do it in sort of time sharing. And we also introduced the more convenient type of display of intensity (?) display which was much more automatic, much more economical, but one lost the (?) quantitative intensity detail which was just other another sacrifice, but I don't think there had been any such detailed observations in intensity to compare with the Penrith ones.
Is that right?
No doubt nowadays with sophisticated photometers and things, you could probably —
You could do it, but no one (?). Do I remember correctly John Murray telling me that you did have a rough intensity scale that you put on film also?
Right. Yes, that was just a routine calibration just to give a sort of order of magnitude. But it seemed at that time that one, the early observations showed a lot of interesting things about intensity characteristics, but one was looking for more broader characteristics and didn't need that detailed intensity profile.
And like you say, it immediately paid off in terms of finding this harmonic structure which you published in a Nature note. That reminded me, I wanted to ask you why did you not send off the note to Nature about the Types I, II, and III? That seemed to be the style around the Laboratory and that certainly was a very interesting result.
It sort of emerged very gradually, it was quite a low key thing to begin with. And I think it was only at the IAU meeting, I forget when that was 1952, I think.
In Rome?
In Rome, yes, I think. I wasn't there, but I think Bolton and Pawsey were there and it caused a great deal of interest and it was only then that one realized that there was something to it.
And yet the nearest thing to letters to Nature I think, was that Bracewell was in England at the time and he gave a little account of it at the Astronomical Society, and that did actually appear in the Observatory.
Bracewell did a number of things like that.
That's interesting; so identification of radio sources or some of these other things were looked upon in the group here as worthy of a letter to Nature, but this wasn't quite at that stage.
Well, I don't know but we made up for it later on; we soon got in the habit of writing letters to Nature. The other thing, I suppose, was that one was very dependent on presentations, and at that time, (color?) and it was you had the first (?) you have there, the harmonic one, and you had to go to considerable subtleties and develop a good presentation.
So let's talk about this paper. When you first saw this [Wild, Muncy, and Rowe (1953) Nature] that must have been quite exciting also.
Right. Actually, what the history of that is that I think this is the first time the Laboratory ever published a paper in which one of the authors has been a technical assistant and that was Bill Rowe. And it's since become a much more regular thing. But the reason was that he through his own initiative, he went down and recorded, I think it was a Sunday or something like that, and while he was there, he switched the equipment on and then went into (Wollangong?) to do some shopping, and while he was in (Wollangong?) this occurred. And never was a place more deserving to have his name on paper. And he described it to me at the time and we could hardly wait for, I think we did our own processing on the spot, I'm not sure. But I remember taking the film home; it was a very washed out sort of film—a very expanded time scale. But it was quite clear that there were two very distinct frequencies. And one had no idea what the relationship was between the two frequencies. The excitement came when the two-to-one figure came, and I remember that I got it back at home in Sydney and the (?) measurement and it kept on coming up two-to-one, that's (?).
But what about when closer inspection showed that it was really 1.95?
Well, I suppose, it always has the immediate reaction that one is disappointed that it's not something nice and simple. But when once you're convinced that it still has something to do to two-to-one, it becomes much more interesting. And that's a very common thing, I think. You hope things will be simple and straightforward, but it's usually more interesting if it's not.
Right, but it is less information content.
And so did it take you long to come up with the reasoning that you did as to why it was not exactly two-to-one?
I think it was a fairly immediate conclusion. At first almost as a joke, and then realized that there's perhaps not much else it could be.
I'm just noticing here also that you only had this one case when you sent in the letter to Nature. And then you had a note added in proof about a second one.
Right. I think the thing is that it's one case which has so much information, that you only need one case in a case like this.
You had no fear about a birdie in your system?
No fear whatsoever. A lot of my colleagues, including Bernie Mills I think, were very suspicious that it had something to do with an instrumental effect. But, it had one very great safeguard in that the two harmonics most of the time were recorded on two entirely different signals. And so because of that—
Yes, yes, that's definitely (?).
(?) two-to-one.
And the fact that they were not exactly two-to-one was again (?).
Yes, even more so.
Argued against that.
Yes, it still remains one of the, one couldn't ask for a better example to come along first. Many, many have come along since, much less impressive.
For my information, in our current understanding is the explanation of this harmonics, and the fact that it's not exactly two-to-one, is that still the basic explanation?
Yes, I think there's very little—that was extremely important at the time to establish. To make a case for the fact that there were harmonics. But I think very little work has been done on that since; once established, it's just become accepted now.
Well, let's see. Let's move on to, oh this paper I wanted to ask you if it's referring to you, and article with Krook and it was just P. Wild, but it was you?
You, at this time, you apparently were in America, in 1956 at an AAS meeting, and was also a thing in the Sky and Telescope about it. And here you are talking about shock waves in Type II and Type III bursts. So can —
I'd completely forgotten that paper.
It was just an abstract, so it never became —
End Tape 90A
This is continuing with Paul Wild on 3rd March 1978. So how did this interpretation of shock waves come about?
Max Krook was a plasma physicist.
At which institute?
This was at Harvard. And I was at Harvard at this time with Allen Maxwell most of the time, but Max Krook had the room down the corridor. He was very interested in these phenomena. He didn't believe our story about Type III bursts being very fast particles; he was convinced that they were some kind of shock wave or shock phenomena, or wave phenomena. We talked a great deal about the slow and the fast types and we must have written a joint paper together. But I can't remember the details.
Well, what I have in the abstract is the Type II were shock waves in the electron ion gas and the Type III were shocks in the electron gas.
Yes, well that's – the latter at least is pure Krook.[laughter]
And the first is Wild, right?
I'm not sure that I understood the whole thing or his theory, but he was a very nice chap and we got along together very well.
Anyway, this explanation for this Type II burst is still in currency?
Yes, I think I came out with it most strongly I think, in a definitive way in, I think it must have been, 1957. Identifying Type II as a shock wave.
And was that a joint paper?
That was at a, yet another IAU meeting.
You mean the Paris symposium? That was 1958. The Dublin meeting perhaps?
What was at the Dublin meeting? It must have been the Dublin meeting.
The reference I have is a joint discussion on solar flares where you talk about Type III and then Type II, and then you get prolonged storminess.
Yes, it was that Dublin meeting, then. We can check that later on.
So you were convinced even before going to the US that there were shock waves involved?
Yes. It was stimulated by the, well the observation of the harmonics. Basically, a non-linear phenomenon in shock waves basically known. There was an element of speculation in it. It was established by suggestion rather than very firm criteria.
Well, since you brought up the Dublin meeting, and I think you also went to the Jodrell Bank symposium, didn't you?
Any recollection of that meeting?
Can you tell me of any recollections you have of your work and how it was received and what you learned about what else was going on?
I think the highlight for me was the paper that you're reading now, was giving a presentation to, what do they call it, a joint discussion. Where I suppose it was the first time I'd given a sort of major contribution to, before an international audience. I suppose I was very nervous before I started, but then I got confidence and it was very well-received. And there was an enormous barrage of questions at the end.
Oh yes, in fact, they are recorded here. Jennison asked, "Have other harmonics been observed?" and you say, "Regret, no."
I think you have to make an allowance for the reporter, you see. And I think Richard Twiss, I know Richard Twiss came (?). That was the first time I'd met him. But that, I think, was the highlight for me. The Jodrell Bank symposium was very interesting, too.
What do you remember from that?
I thought it was, I think the thing I remember mostly was Martin Ryle presenting his source count data, and Joe Pawsey doing a magnificent rebuttal in a way, very modestly, on the basis of Mill's preliminary results. And Pawsey's performance reminded me of Marc Antony's speech. "Brutus is an honorable man, "in reference, to Martin Ryle.
But he absolutely won the day, and I've never seen a better performance from Pawsey. However, that was the (?).
Going back to the Dublin joint discussion, you established a rather nice correlation which is shown in Fig. 5 in this paper, where Type III burst velocities correspond nicely to the implied cosmic ray velocities and the Type II correspond to magnetic storms. This is the first time that anything had been done like this I guess.
Right. Now the cosmic rays, I can't remember, that's right. That turned out, I think, to be wrong in the sense that cosmic rays from the sun which arrived at the order of half an hour or twenty minutes or something like that. I think now those long time delays are not due to relatively slow velocities (or the observed velocity of light?) but much more to (?) differences; and no one there believes, I think that —
You mean going as not directly —
Yes, or going in spirals, this sort of thing. But that made a very nice story at the time, but the correlation has been (?).
But the other one is a valid inference between Type II burst and the magnetic storms?
Yes, that's fair to say.
Well now another point is that you say that there was a great deal of interest in this paper. This was 1955 and yet your results had been around for four or five years basically. Was this simply because they weren't generally known?
No, there were lots of rather new things, but really this is based on the harmonic which is fairly, what was that?
That was 1953 so that was two years old.
1953. Then the fact that the correlation between Type III bursts and flares, which was – have you got that there? That was a letter to Nature - that was Wild, Murray, Ryle, Robertson, and Murray.
1954 in Nature.
Yes. Type III spectra implied velocities of about hundred thousand kilometers a second.
Right. So combine those things and I suppose it was reviewing stuff which had been published a year or so. But it's just a question of having an open discussion.
Yes, but it seems to me that it might well be that many of the solar physicists in related fields just didn't know about this, even though it had been around for a couple of years.
That's quite right, too. At that time, I don't suppose the optical people took very much notice of the writing. They applied to all fields.
I don't think they were reading the Australian Journal of Scientific Research as much as they were reading Ap J.
No, that's right. So it was quite a good thing in a way that radio astronomy had a low profile in astronomy from the beginning.
Why was that?
Well, it I suppose, it allowed the truth to firm up before it was under too much scrutiny.
If you mean that radio astronomers at that time would learn about precession and things like this, I've heard some interesting stories about that in the late forties. Okay, let's move on. You have a paper with Wild, Murray, and Rowe in the Australian Journal of Physics; that was really a follow-up of this —
The whole detailed (?) of the Nature.
Yes. You're talking about longitudinal oscillations excited by fast particle streams. Where was the plasma physics coming from? Was that, once again, just a matter of getting the right book and – ?
No, I think that in this lab, Westfold and Smerd were our theoretical people who used to keep us on the ball with plasma physics. And we picked up what plasma physics we could with their assistance.
I also noticed in that summer of 1955 you went to a discussion on solar flares at University College in London, and there was another London meeting on solar eclipses in the ionosphere.
Yes, I think that was just doing the rounds.
These were not particularly oriented towards radio astronomy?
Not particularly, but they were – this is the paper that came out of that.
Right, on the ionosphere.
Right. There was obviously an interest in this bit of a rehash of the –
Right. Same figures as the Jodrell paper.
And this is not unknown when one's –
Oh, sure. So there was nothing substantially different?
No. It was purely a rehash.
What else do we have? Let's see, you alluded earlier to getting tired of not finding any flares out at Dapto and then beginning to look at Cygnus A fluctuations. Can you tell me about what you found from those observations?
Well, we thought that while activity was so low it might be interesting to look for other applications of that equipment. We did a few simple calculations to see what sort of an aerial one would need and indeed, one could do a very good job of the horizontal rhombic, a very large one. So all that needed was supports and some posts and some wire, which we rigged up fairly, quickly. Quite fixed, it was pointing north; Cygnus comes up north of the horizon. And switched it on the first evening, and it was tremendously interesting spectacle of what looked like a whole series of Type III bursts. And I can remember ringing up Joe Pawsey and telling him – they were all going from high to low frequencies, and he was very, very intrigued. He said, "Perhaps the original explanation of those scintillations was right after all, the fluctuations are right." But they were in fact, bursts —
In the source? Did you really entertain that idea for a while?
We didn't know what was going on. That first night, you couldn't tell until you calibrated everything and saw whether it went below the line as it were. Dips were below the line and the average sort of evened out. Well, after that very high beginning, we then got involved in a sort of taxonomic study almost of the different kinds of fluctuations which produced some very nice optical effects, interference effects. That kept us amused for I've forgotten how long it was, perhaps a year almost. And we got involved in all sorts of correlations and somehow scintillations wore a bit thin after a while, after writing one major and one minor paper, Jim Roberts and I. And we were rather glad eventually to get back to the sun which is a more scientifically interesting subject.
Well, I was going to ask you something related to that, namely, here you spent almost a decade working on the sun and yet you're quite willing to just go off and work on the ionosphere for a year because the equipment is there or something.
Yes, quite right. It was just because of boredom with the sun. I think it's a good thing not to get too stuck in one thing for too long. That's why the next phase after that, of course, was when we went into interferometry.
But still the sun, but a rather different instrument. Let's see if we find anything else before then. Well, there is this sideline here where you and John Bolton proposed a 12 cm. Zeeman Splitting in 1957. How did that come about?
Well, I was doing my 1956 visit to the States; it began in 1955-56 with Cambridge and then Dublin. I was sort of on my way home and my last port of call was in Pasadena with John Bolton. And I had a visit for just a few days there. Really, I can remember it was the morning after a very memorable party that was held with all sorts of very distinguished people, but only (?). We went to Mt. Wilson and Babcock was on measuring magnetic —
Magnetogram (?)
And it emerged out of that, seeing that, and I suggested to John, why couldn't one look for Zeeman effects and spectral lines doing this, and I started sort of thinking about line widths and things and whether it was feasible. John's contribution was really to say, "Ah, what you want is an absorption line because it's much narrower."
And the switching idea?
Right, and the switching, yes. That was part of it; that was really Babcock. And the following day I wrote that short note and put the idea on paper – never has such as short article been responsible for wasting so much time by so many people, but —
Well, eventually not wasted.
No, not eventually, but it did seem at one stage as though people were spending years and years of Ph.D. time not getting anywhere.
Once again, neither you nor Bolton tried this yourself?
I think what we were saying was that when more sophisticated instrumentation comes into play, as it were, larger dishes and so on, and at Jodrell Bank, I think, at that time (main effect?). It was very much as passing thing that just arose out of a few days visit.
Now I understand, it obviously looks strange amongst all these other papers here. Now, there's a paper here with Steve Smerd in 1957 in Phil Mag. where you talk about strip scan solar observations and how to interpret them.
That was written by Steve in my absence, and I tried very hard to get out of the authorship, but I think it was (?). However, I did give a, I thought it was much too complicated the way he presented it, but I did give a very simple version of it in another paper that was probably same IAU, maybe —
Jodrell Bank Symposium?
Jodrell Bank Symposium – that was a very simple version of it. Steve was working on this problem, and I just came up with an idea which helped simplify (?).
Okay. Let's go back to the States again where you went to another AAS meeting and talked about the association with Zerin, erupted prominences and 167 megahertz bursts.
Yes, well, while I was in the States, I spent about 3 months at High Altitude Observatory in the wooden huts of the time. Which is quite — . Sidney Chapman was there most of the time; Walter (Robertston?) was there, too. And Hal Zerin and I did a comparison, I was very much interested in the radio side of things and Boulder had a very large collection of optical records which they didn't do anything with, and also, sorry, of radio records which they didn't do anything with, and also miles and miles of prominence film. So, I suggested that we get together and look for correlations. The paper which eventually appeared, this one —
In the Australian Journal of Physics.
Yes, that was the paper.
Right. But now perhaps the interesting thing that came out of this in my view is that you found that when they got to the center of the disc that you got the noise tones. Was this the first indication of some directionality in the radio bursts or did you have some earlier?
I think there must have been indications of this from the early days, even very early papers by Ruby Payne-Scott. And even before that, even Hey might have –
Hmm. I don't remember that, but it could well be.
The directivity of — well, it probably wasn't Hey because he didn't recognize the phenomenon of (?) storms. But I think the concept of directivity probably was earlier than that, but this was tying it up with the —
Tell me about the rest of your stay in the U.S., in particular, which radio places you visited and what your assessment was of what they were doing.
I can't remember what places I went to, but the main places were Harvard for about three months, and then Boulder for about the same time, and then Michigan, Fred Haddock, also for about three months, and then to the west and spent some time, again, with Maxwell just before he went on the air at Ft. Davis. And it's a rather a (sore ?) to say, but it was there I actually (?) first U-burst, which was (?) published.
I'm sorry, I don't quite get what you're saying.
A U-burst, Type III which —
Right. What did you say about it?
Well, this was really the first Harvard discovery, the U-burst, but we got one isolated at some point, but they got and recorded (a vast number?).
What was the ability that they had that enabled them to see them easier?
I'm not sure. I think it was probably just a matter of a pretty small sample of activity that we'd recorded up to that time.
Was it detected with an 85 foot dish?
Well, they did have an 85 foot dish. I don't know, but they were a very common phenomena, you know.
But now were you more or less the technical advisor for the spectrograph?
It was Donald Menzel, really. Or was it Menzel or no, maybe it was Leo Goldberg, Menzel and Goldberg between them. No, it was Donald Menzel; Leo had gotten along to Michigan. Yes, I suppose at that time I was – they wanted to start off in this field, and I was the only one in the group that had done it before. So it was a very instructive time.
In the Harvard spectrograph, what were the main differences from your own?
Well, of course, one of the main differences is that they did it in the American style, which is to subcontract. I think it was (?). And so everything was very professionally done, factory produced and all this sort of thing. Yes, this sort of method of budgeting is entirely different than ours. But probably quite sensible when you consider (?) and everything. I don't think I made a very big contribution or anything really more than could be cut out of the papers. Bits here and there. Although I think there may have been a few — Yes, there were a number of things where they were quite clearly doing the wrong thing. But they could have been cleared up in a couple of days, so my main interest at Harvard was probably talking with all the astronomers and graduate students.
Such as Menzel?
Well, there were a whole lot of graduate students. Donald Menzel himself I saw quite a bit of because for a while I actually stayed with him in his house.
So, did you learn anything in terms of equipment in your stay in the U.S. or was it mainly only some astrophysics that you were learning?
Well, I don't think I did very much because I wasn't, one was so remote from the technical scene, which was really in the airborne instrumental labs. And certainly, I did go around the labs, but of course, you don't learn very much.
Right. I mean when you visited Michigan or Caltech.
Well, I think that probably I encountered some people that were, was it Henry Jasik, the antenna king?
I think so. And then there were a whole lot of people at Michigan involved, was it then or later? In optical transforms and things like that, which was interesting to me, too.
Once again, this is leading on to Culgoora and (?).
Yes, but on the whole, my main interest in instrumentation is in systems as a whole, I think, and I've never been, I've never done much nuts and bolts engineering with my own hands. I'm not very interested in systems.
Okay. Let's move on to the next major instrument you were involved with which was the swept frequency interferometer I believe. You operated the Dapto Station until the early sixties, I guess.
But at what stage did you feel the need for something else?
It was stimulated by, oh, you mean the swept frequency interferometer?
Well, I think it was essential to keep things moving. We scooped the cream out of the pure spectrum by itself there were some very important (?) hypothesis was a hypothesis and nothing more. It needed really confirmation. And a few quick sums show that you could put together an interferometer without too much effort which could answer a lot of these questions. In actual fact, it was quite a lot of effort.
What period was it developed over?
I suppose it started when I got back from the States.
We had started a bit of this before with scintillation work. We had some interferometric measurements for the Cygnus scintillation work, but the whole thing had to be completely changed. Servicing. Needed delay lines and all sorts of things.
I don't know whether you've had a look at the paper on the interferometer.
Not the paper itself, but the abstract.
It was quite an extraordinary (Keith Robinson?) for while it was operating there were tremendous noises going on all the time; windows going in and out and moving parts, (?) recorder.
I guess Kevin Sheridan was working with you.
Yes, Kevin was, well this was the time Kevin was more or less removed forcibly, against his will, to do it.
On this?
On this.
What was he doing before?
He was the Bernie Mills, but Pawsey actually, while I was away, just before I returned, Pawsey said that Dapto needed reinforcing technically, which it certainly did at that time, since John Murray. And Kevin, very much against his will, was transferred.
Well, if I remember correctly now, Murray was taken off to go to the hydrogen line receiver because that needed reinforcing.
Right. Right. And that left us with a void; we had Jim Roberts and myself, who were both physicists. When I went away and Max Komesaroff who was not at all a practical man, but very much the dreamer and philosopher; so we had a very almost zero technical competence. Then Bill Trent who was the technical officer added very solid support on the technical line, but not in the way of engineering. And Kevin was a tremendous boon. And as I was saying, it was against his will to begin with, but it took about six months and then Kevin, you can ask him yourself, but I think he was pleased with it then.
In that it got him into solar work?
Well, yes, and I think in a working environment which was probably much better than his previous one.
It seems to me that well, I get the picture that Pawsey is sort of looking at all these small groups, I guess there were five or six of them at least, and sort of moving the pieces around.
Yes, I think this is a good example. I suppose that (?) that maybe we weren't aware of, but I suppose that's what happens within the CSIRO Division. The way they work is to let things run and then every now and again review things and see how best to use the resources.
And you get reassigned and that's it?
Well, I think it was, Kevin's reassignment was quite, almost against his will, it was quite an unusual one. Usually you talk someone into it.
I guess that's the problem of management. Okay. So now with this interferometer, what were you able to establish? What were the main results that came from that? I see two papers here with Sheridan and Trent, and Sheridan and Neylan.
Right. The, I can remember that when I came back from America I found Dapto in a state of rather low morale. And I got working hard on the interferometer, and there was some skepticism as to whether it would ever work.
Well, all sorts of things. Like would open wire transmission lines be suitable for linking two elements or would there be too much leakage or too much continuation. It was also very complicated. Keith Robinson talking about lots of parts moving and all sorts of things that can go wrong. I can remember that Jim Roberts left us about that time.
Went to Caltech?
No, at that time I think he'd left Dapto to go and work out some of the solar results. And then he was going abroad I think to some IAU meeting.
Paris Symposium?
Did you go to that meeting?
No, I didn't. I stayed behind to try and get some results to present at the symposium. And Jim left, I think it was about five weeks before the symposium because he was going to Russia to a Moscow meeting. At the time he left, we had nothing to show whatsoever. We had no results from the interferometer. During the next five weeks, we almost got the picture clear but it was the first five weeks of operation, and we were able to confirm the plasma hypothesis and get a number of interesting results about Type IIs and Type IVs, and that was quite a useful, that was quite a significant contribution, I think.
What was the key to this confirmation?
[pages turning] Let me see. Can we switch this off a moment?
What was this Wild, Sheridan, and Neylan paper that you say was a key?
Well, the key diagram in that really was again, a colored one, in which it was showed about a dozen or more examples of limb flares. Once the position of the limb flare was shown and the level at which the radio emission, four or five different frequencies, as measured by the interferometer was shown in four or five different colors. And every case the Type III bursts coming from (?). And in every case, it was regular sequence, the low frequency being farther out and the high frequency being close in. And it was quite a, it had to be very carefully interpreted, the results, because we had to make allowance for ionospheric refraction which was quite tricky, but —
And different at the different frequencies?
Right. And so one also had to study what happened during the continuum storm, and you could see the way the different frequencies at the time moved about. On some days there was an enormous swing, and obviously results were meaningless, and on other days, it was very well (?). You had to sort all those things out. But what emerged quite convincingly was the confirmation of the plasma hypothesis.
And these very high speeds?
You said that at first, you referred to 55, that there was a lot of disbelief about these five speeds.
Had they been accepted by this time?
Well, as a result of this, I think this had to come first. Of course, one could still argue that it might be a particle, that it might be a wave rather than a particle. And the next step was really taken by one of my colleagues, quite a junior one at that time, Ron Stewart, who did a systematic investigation of the, not at any speeds, but accelerations of Type III bursts and came to the conclusion that on the whole, speed tended to be constant throughout, so that the lower one was dealing with Newton's first law of motion.
As opposed to electro-magnetic phenomenon?
Right. Well, plasma phenomenon, a plasma wave was never, you couldn't imagine a plasma wave remaining constant velocity over the enormous range —
Andy density, yes.
And I show that out of this Type III phenomenon, it's one of the most puzzling things in plasma physics, it's a problem of extreme interest now, I think in it's own sake, how a bunch of particles manages to keep emitting plasma oscillations of plasma waves, manages to maintain its identity all the way.
You mean coherent (?)
Right. All the way from lower solar atmosphere, and now we know right out of space because of the Type III bursts we've picked up, close to the earth.
That's still a puzzle?
Yes, and a plasma theory of very sophisticated puzzle that doesn't bother most astrophysicists.
I wonder if you know enough to turn your back on it. So that was perhaps the primary result that came from the swept frequency interferometer, would you say?
How long did that instrument operate?
Not so very long. I think we did the right thing when we got our results and then closed it down.
And when was this closing down?
I can't remember if it was eighteen months or —
Something like that, yes.
Yes. Then we operated, then we got increasingly, well, what it led to is the (?) radio heliograph. I suppose I started thinking about a radio heliograph while I was still in the States. It was the obvious next step, trying to get radio pictures of the sun.
And so, in fact, from 1959 or '60 when the radio heliograph went into operation, which was 1967?
Between about 1960 and 1967, my attention was almost entirely devoted to a little bit of dabbling in interesting records that came along, but mostly thinking about that heliograph.
So can you just outline for me what the sequence of critical events in the design and construction of the radio heliograph were? I guess going right back to the States?
Well, I suppose the —
Click start to listen to the audio for tape 91A of the 1978 interview.
This is continuing with Paul Wild on 3rd March 1978. So what were the main criterion specs you had for the heliograph.
I suppose that you could almost write down what was wanted in nearly every respect. For instance, you wanted to really take pictures of the sun, you wanted to take them very frequently to get those characteristics and one second seemed to be the natural time. One needed polarization, circular polarization, or perhaps more general polarization. Whatever configuration you used, it was quite clear that you needed not only (?) and things to sweep across the picture was also delay lines which might have a coherency because a little calculation showed that if you didn't get any reasonable sensitivity which would more or less get past the quiet sun than needed, you had to use a reasonably broad band of (?) megahertz. So you had to have the delay lines which added considerable complexity to it. But the key parameter to define, and this is an arbitrary one, purely determined on effectiveness and cost, is the angular resolution, and the first design I had was something which—[Interrupted by someone bringing copies]. Originally, I had a design which was two-thirds the size of the (??), but in his infinite wisdom, Joe Pawsey suggested perhaps one should probably, and so the next step was (?) of one and a half. So (we extended to 64 and went to 96?).
This related to the frequency of operation, of course?
Well, the frequency was determined, the original frequency was 18 megahertz, now it's a number of frequencies, to try and get the lowest frequency at the greatest height and subject to being able to work with the refraction index and the scintillations, and yes, that was —
You didn't want that to be bothersome.
Right. I mean 18 is still tricky, but it's still very difficult, but it's a lot better than (40?).
And the idea of the low frequency you said was to get the outer parts of the corona so you could follow something longer?
Well, I suppose it was to (?) the work being done on the inner part of the solar atmosphere and the unique features of radio to look outside, and I think the thought was to go up as far as possible. Since then, we've added these extra frequencies – 40, 80, 160, and 320. So, then of course the very big decision was deciding on the configuration, and the idea of a circle appealed to me very much. Because of the general symmetry – it was almost inevitable that one was going to get imperfections through the phase errors and so on because the frequency of 80 megahertz, you can't use all the sophisticated techniques and so on using sources to calibrate on because of the ionosphere. So, there were inevitably going to be bad side lobes and I was very scared of using crossed (type?) array, that all the side lobes would get concentrated in one direction, and as it is, the side lobe due to phase errors are distributed –
So you're not just raising the general noise level.
Right. Or at least the distributor was (?) but they certainly show up (?). The other thing that I liked about a circle was the possibility of, well, it's more compact that the cross and you only need half (?) although it did require more land. Probably a marvelous thing in land investment. And we had hertz for interesting analogue displays eventually, which have yet to come to fruition. It was much more elegant certainly, configuration.
What sort of thing are you referring to now?
Either optical or electro-optical in particular. Even using ultrasonics, which was something we went through all these –
Ah yes, yes. That's right.
The possibility of central calibration (?) I suppose the early mathematician in me which never materialized felt very fascinated with all the (?) associated with circular array turned out to be a very elegant thing theoretically.
And I suppose it was exploring a new line which felt so good, but effectively something like the cross over circle (?) aperture synthesis (?) too fast.
What did you find you'd get in 2 arc minutes?
About 3.8 I think at 80 megahertz, so much better as you go.
And what you said there was that you would have loved to have more if you could have.
Oh, yes, oh, yes. I mean as it is two –
So that was the thing that could give depending on the budget.
Yes, we were very, very lean with our budget. We even limited the declination of the individual aerial elements which is now a thing to regret probably, because it tended to become of increasing importance as a cosmic instrument.
What range – only in the ecliptic?
No, it's a bit more than that. But, it (?). However, at that time money was so scarce.
Well, (?) 96's.
That's right, and well we didn't, (?) let me say another big thin,g it was a question that I knew a circle would work if you could get the (?) components properly. And another big step as far as I'm concerned is when I discovered that the J-squared synthesis method where you could, purely the electronic thing by (?) the aerial at anything you wanted within the resolution and I suppose — We drew up a proposal. I meant to ask Sally [Atkinson] if we ever got it. Every project like this has to have a proposal drawn up and it would be interesting to see if it is here.
Yes, I'll definitely to check that out.
This was the thing which we submitted to the Ford Foundation through Pawsey.
Which year was this now?
I think it might have been 1962, 1961-62. And of course, the very big moment was when the funds came through from Ford Foundation.
Which was when?
I suppose it was round about 1962. And then it was all stops out from there. Quite a big reorganization in the lab, too. Lots of people were dedicated to the — Well, Kevin Sheridan was one very key person to mainly the electronics and Maston Beard for the computer side. He was tremendous. They all were; I suppose Kevin was the biggest single (?); and Keith McAllister who worked on the building of the aerials and so on.
What about the decision on the antennas? Was it clear that you wanted paraboloids?
I think that was just a matter of what was the cheapest way of getting our collecting area. And so these were, as you probably know, they're (hardly?) paraboloids, 24 flat surfaces or 25 flat surfaces.
Have they been able to work at 320 without modification?
They'll work at 320, yes; that's about as far as they will reasonably go. They are pretty efficient at 320.
Let me ask you a question about the Ford Foundation money. I'm struck by the fact that for Culgoora as well as Parkes as well as Molonglo cross, that American money was all or a large part of the funding. Is this "a prophet has no honor in this own country?"
Well, you might well ask that. We remind our government of this fact over and over again. It seems that it's part of our system, I'm talking about CSIRO, not the universities, were well catered for in operating funds. It's just one of these things, you know, that eventually in any organization which is given so much money about 70+% goes into paying salaries and there's sort of nothing left over. (?) . It becomes very hard to get the rest. So, I think there's a great deal of sort of mistaken judgement on the part of how these funds – It's unfortunate.
But there's no analogue to the National Science Foundation or something like that?
Well now, you see, this is just beginning to function because there's been nothing like that. But now there is a thing called ASTEC.
What does that stand for?
Australian Scientific Technology Counsel – which advises the government and in fact, it has one very big item before it now which is a synthesis array telescope and this is the first time, really, that the government has been making these sorts of decisions.
They've always been able to set up some sort of arrangement there that then would put off making any financial outay. In other words the government tends to be a political animal, not an interest in science.
So now this, still does it have to be a separate bill to be funded – this synthesis telescope?
It had to be extra money right outside the usual, and we're making it a completely national project and not an, although CSIRO might well become the managers of it, it'll be done as a national project and getting all the universities to be represented.
But there was no such agency at that time?
So it was everyone trying to scrounge money from where they could. And, America has been (?).
There are no such large foundations in Australia?
I think it just goes with the very large foundations tend to be (?). You just need to get over a critical size and then (?).
In the actual construction of the Culgoora from 1962 on when you got the money, was there any major design changes made or any major stumbling blocks that were encountered? Or did it all go pretty smoothly?
Quite amazing changes in design. For instance, when Maston Beard, computer exper,t came and the original design had all sorts of these incredible (?) extraordinary gearboxes and things instead of doing it by electronics. The computer age was just sort of coming in at that time and so there were no conceptual changes, or very few conceptual changes, just with synthesis going in after the very beginning. There were continual minor adaptations all the way through.
Sure. But there were not major crossed (?), or major screw-ups?
Well, we did – I don't know how we managed to get through on the budget – we did have to come back for another eighty thousand dollars. We had five hundred thousand to begin with and getting that extra eighty was perhaps more difficult than getting the original five hundred.
From the Ford Foundation?
But there were no matching funds in this case at all?
Oh well, I mean half the lab went into it.
Well, yes, except for that. But no capital funds?
Not capital funds, but I suppose that in the end that (?) put in more probably just because it has a budget of, I don't know, in those days I suppose it was 2 million or something. And —
You think it was half the Lab's effort or —
Well, in the last year it might have been approaching that.
Yes, but you've got these reprints now. The late fifties. But —
This is the Paris Symposium one which was really summarized, I think, this is one of the best (?) work we did for the (?) stuff was fairly (?) but it got a lot of the way there.
The Australian Journal of Physics Papers?
Right. [Looking at reprints] And this is an example by the way, of the interferometer working on the noise storm on a good day and on a bad day. You can see the low frequencies having much more swings. This is a constant source, what could be assumed to be a constant position source.
The black —
That black was probably the extrapolation when you'd taken in the square law wave length or something.
This position on the unrefracted source is (?) —
Right. This was the key diagram which I think you'll agree is fairly convincing.
Ah yes. Figure 7 which shows the burst moving out with the lower frequencies being –
Plus it was a one-dimensional instrument so it was a little piece of presentation there. These lines are infinite.
Yes, yes. But now just to finish the Culgoora story which is obviously related to this, what would you say are the principle scientific results that came out of the first Culgoora observations? Did it really open the field or did it just —
Of course, I could answer that better by showing you the film, but although it was very useful in following up Type III bursts and Type II bursts, it completely gave a new picture on Type IV bursts. It showed that, well, it almost started, I don't know whether, Type IV comes into your menagerie, but —
Yes, I've talked to Boischot.
Yes, and one could see that it was the first time that they were not one type, but a whole lot of different phenomena. Sometimes there were great loops that go out, and sometimes they were polarized blobs, blobs that went out to enormous great distances. I think you should see the film on this.
Okay. And you've been able, I think, to measure speeds of course much more accurately. And even some apparent faster than the speed of light? Do I remember correctly?
I'm getting mixed up with quasars. I thought you had some effects where it seemed to be going at the speed of light?
No, I think you can say that, I think you can make the assumption if two blobs appear —
Oh, that was it. Appearing in the —
And obviously, if one (?) the other if it involves the speed directly from light, so they both must have come from the same (?).
That's what I was thinking of.
And there are all sorts of interesting things like that. Multiple sources which seem to trigger one another.
Well, let me just close by asking you a couple of very general questions. First of all, you mentioned in your historical article about these staff meetings of the solar physics group which were held monthly or something like this?
Solar noise group. Which was really radio astronomy.
Can you sort of tell me how these were run? Was it just a matter of each person sort of reporting on what he'd done?
We used to go through the different phases. This I suppose is now going back to 1948 or 1949. There were times when these meetings were held very regularly and other times when they seemed to be stopped altogether. But when they were really running, I think it was, well, they would just sort of meetings held perhaps once every fortnight. All the different groups and I suppose (?). All the different groups, I suppose a dozen or 16 people.
But do you remember them as being particularly useful or critical or were they just —
It was mainly progress reports. Keeping everyone informed of what everyone else was doing.
Because you were so scattered around?
We all tended to have different field stations for one reason or another because of different requirements or something. Also, it was a time when one sorted out people treading on other's toes or pressing each other's borders or something like that.
Okay. The second general question is how would you characterize the roles of Bowen and Pawsey in the development of the Laboratory?
Taffy Bowen was the overall organizer of the Lab. He very much, somewhat autocratic in his way of running the lab and determining what programs he should conduct. His main most important period, I suppose, was early on when we were in the transition from wartime to peacetime in which he identified the various areas that he wanted to go into. So he was very much the chief of the division. Joe Pawsey, on the other hand, was the scientific leader and scientific inspiration. They worked together very well up to a certain point, and then gradually fell out.
Was Pawsey also working with you on the heliograph ideas in the late fifties, early sixties?
Well, he took a very great interest in it. He wasn't involved in any of the design, but he did when I came along and said, "Okay, it'll work. It'll get the quiet sun. It has enough sensitivity to get the quiet sun if we integrate with 70 seconds." There was some discussion of raising money. He did go home and do the calculations himself in his own way crude and agreed. But no, tremendous support, but he didn't get involved in design details.
Okay. And finally, Radiophysics, of course, has been a — one of the world leaders in this field from the very beginning. In particular, up through 1960 or so, to what would you ascribe this leadership? What were the key ingredients?
I suppose it was due to the fact that one had a wartime variety of radio techniques and was looking around for something to do. Partly by chance, partly by Pawsey's insights, and strongly supported, I think, by Taffy Bowen who saw this field as a very good one. And I think the very enlightened policy of CSIRO at that time, which allowed good science to go on in a government laboratory even though it wasn't directly involved with industrial things.
Most CSIRO divisions are much more applied in their —
Much more. But, it was recognized that here was a very good scientific field and a way of keeping good scientists together, etc. So that was a very enlightened thing. As I mentioned earlier on, the bad feature of that was Australian science doesn't get properly funded, kept from (?), this was a very good thing and it seemed to produce the people. The people came along – people with, conditions were set, and I suppose the rest of it was a matter of individuals. But I think it had very little to do with being situated in the Southern Hemisphere.
You mean, you've heard that apparently?
Describing yourself?
I had very little to do with that at all.
Well, it certainly national for the sun.
I think it would certainly apply and the Southern Hemisphere certainly applies when you talk about hydrogen line work. I think there the clear leadership was in Holland, and I think we were the number two. But we had a good stab at the skies ourselves. But certainly I think the rise of Australian radio astronomy had very little to do with that.
Well, I have never entertained that idea, I'll tell you.
Well, of course nearly everybody has – everybody outside.
Even the people —
I mean, good heavens, these first source identifications, for instance, Taurus and Virgo are quite accessible to the north. Centaurus is not.
I'm speaking about non-radio astronomers. I don't know. I think that we were very lucky in being involved in a new field. It's so much easier to contribute. There was a very nice remark that I heard at a recent lecture given by Dirac, who gave a talk on the evolution, development of quantum mechanics. And he started with Niels Bohr, and worked up through Schrödinger and Heisenberg and so on, until it was obvious that he was about to come into the picture himself. And then he said, "I should preface my next remarks by saying that at that stage, it was possible for a third rate physicist to produce first class results." He said, "Now it's very difficult for a first class physicist to produce third class results." I think there's a lot in that.
Did you feel that at the time at all, or is this sort of only something you just recognize now?
I was conscious that this was a marvelously exciting thing at the time, I think. Very conscious of the fact that it was a very new field and perhaps a bit concerned that nobody seemed to recognize it as a field at that time. Certainly astronomers, or certainly the Australian optical astronomers had no —
When you say nobody, do you mean physicists also?
Well, I suppose in a way, I suppose some physicists did. Pawsey was a very good PR man in a way, among the scientists, but I think it was regarded as a bit way-out.
When did the change-over take place, would you say?
I suppose it was round about what was the Rome IAU meeting?
Or round about that time the word "radio astronomy" came into being. Well, still not locally. We had the gentleman who became Astronomer Royal, Sir Richard Woodley. I heard in private later on, it must have been the late fifties, he made the remark that in ten years' time radio astronomy would scarcely be heard of.
It would map the sky and that would be it, right? So when was this change of heart that happened in Australia in optical astronomy, would you say?
Oh, it hasn't.
It still hasn't?
Still hasn't. Except, no. The introduction of the Anglo-Australian Observatory that –
Which is actually right here in your own grounds.
Right. And then there's a second event that has happened and has just come because (??) there has emerged tremendous interest and support for the synthesis telescope. So it's all really happened in the last few years.
What about Bart Bok, though?
Sorry, you're quite right. You're quite right. It was an isolated period.
The late fifties.
Yes, I left him out altogether. So it shows you how much dependent it is on personality.
Indeed, well, thank you very much. That ends the interview with Paul Wild on 3rd March '78 at Radiophysics in Sydney.
John Paul Wild
Papers of Woodruff T. Sullivan III, "Interview with John Paul Wild ," NRAO Archives, accessed January 17, 2021, https://www.nrao.edu/archives/items/show/15301.


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Q: No pinch zoom for text I'm using the alpha version of the android app on the first generation nexus 7 tablet.
The font size is a little bit small for my liking and I'm not able to pinch zoom to increase the font size.
Is this a feature that is planned in the release?

A: Font size on Android SE app has been marked as a duplicate of this, so I'll reopen discussion here.
Easy control of font size within the app should be a high on the wish list for developers.  First, it constitutes an accessibility issue, and second, a usability issue.
I am fully aware that I can change my system fonts, and that this would resolve the issue with this app.  That said, After years of fairly rigorous Android use, I haven't ever had to do that with any app I've ever used, and suggest there's a reason for that.

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