Interview with Venkataraman Radhakrishnan

Sullivan: 00:02

This is interviewing Radhakrishnan on 26th March 1972 . Well, why don't we start by how you got involved in radio astronomy? You were trained in physics really, isn't that true?

Radhakrishnan: 00:21

Training is the word [laughter]. Yeah, I suppose, it's right to say that I did do some physics at the university.

Sullivan: 00:31

Which university?

Radhakrishnan: 00:32

University of Mysore. It was located, at that time, in Bangalore, strange to relate, a place I'll be going back to. What was the question again, how I got involved in radio astronomy?

Sullivan: 00:48

In radio astronomy, right?

Radhakrishnan: 00:49

[inaudible]?

Sullivan: 00:56

And that was in physics?

Radhakrishnan: 00:58

That was in physics, yes. But nothing to do with-- I was interested in electronics and had always been since [I had a crystal set] radio [inaudible] and transmitters together and so on. Electronic equipment you could buy in India very, very cheaply, war surplus. The stuff just flooded the markets. I remember being able to buy 3-centimeter klystrons for a few cents apiece, and 500-watt tubes for [inaudible]. [inaudible] useful. I really got into radio astronomy only for the first time only in Sweden.

Sullivan: 01:56

Yeah. And then how did you get to Sweden from India? That's not the obvious [inaudible].

Radhakrishnan: 02:02

Well, I was just traveling around, seeing the world, so to speak, and I spent some time hitchhiking around Europe. And I ran out of money just about the time I got to Sweden. So I went to the Chalmers Institute of Technology, whose Electronics Laboratory, the Electronics Laboratory at the Chalmers Institute, was  run by Professor Rydbeck, who I had run into years before when he was on a visit to India. And, in fact, he had said in passing, in India he had said, "Why don't you come to Sweden some time." And I said, "Do you mean it?" He said, "Yes." Little did I know that I would turn up [inaudible]. And so, finally, I got there and decided that I would stay and look around, perhaps a job, but that wasn't easy to get because you didn't have any positions so I decided to stay. So I just offered to work for nothing at the Chalmers Institute for about three months and then I guess they thought I was worth keeping after that [inaudible] decided I wasn't. And I promised to [inaudible]. And well, that's what happened.

Radhakrishnan: 03:33

Actually, I started by doing something in, for Rydbeck in his tube development laboratory. And he was working on a thing called a [inaudible] which is a frequency multiplying device that used the following principles. It took an ordinary electron [inaudible] and then you passed it through a pair of [inaudible] two pairs and you fed them with signals which were in quadrature so you could get this beam to go under the circle, just as you would do to get a circle on the scope. Then you have an anode with a series of holes such that electron beam is going through this plate will strike a hole and then strike the little metal in between and then the next hole and so on. Then you had another electrode beyond this, which would catch the electrons that actually managed to get through the holes. So you'd get a number of impulses on that was equal to a number of holes times the rate at which the--

Sullivan: 04:48

[crosstalk]. Yes.

Radhakrishnan: 04:49

So this way you could multiply.

Sullivan: 04:51

Oh, I see.

Radhakrishnan: 04:53

Then you could have a very complicated arrangement of holes on the first panel such that by using a short radius, you could get a factor five and a slightly larger radius. You could get a factor 6, 7, 8, 10, 200, whatever it is. So this would be one way of putting in a low frequency and getting out a higher frequency, which was precisely related to the input frequency.

Sullivan: 05:19

Yeah.

Radhakrishnan: 05:20

And I don't know whether it was the need for frequency multipliers and radio astronomy [inaudible] that prompted Rydbeck to investigate problem. But anyway, that's what I started doing.

Sullivan: 05:34

Was it ever actually used to?

Radhakrishnan: 05:35

No, I don't think so. So many things at Chalmers Institute it never really found its final use.

Sullivan: 05:43

So after this multiplier, what was your next venture there?

Radhakrishnan: 05:50

Well, before I say that, just reminded of an interesting story. Perhaps the only thing connected with this multiplier that remains vivid in my memory is that, because in Sweden at the time I was working on this multiplier the first month or two after getting there, that I really got drunk for the first time. [laughter] We'd gone to some party or around that, and Swedes are very careful because their traffic laws, very, very strict, in that caught driving under the influence, dragged and they had the licenses taken away forever and things like that. So I went to this party. I was being driven by somebody else. Actually, [inaudible] to eat properly. I was actually eating one meal a day in the students mess or equivalent.

Sullivan: 06:49

Well, in fact, they put you up in the lab during those three months.

Radhakrishnan: 06:52

Oh, yeah. They gave me a room to sleep in the lab and magnificent salary of $15 a month. And so all of the-- there were several people at the party who kept emptying their drinks into my glass, some when I wasn't watching. And I was in the midst of the hooping, philosophical discussion. And then I went into the gentleman's for something or other, and then woke up there about 20 minutes later, sitting on the floor with my head over the john. I passed out. And so I was taken back to the lab to sleep it off, which I couldn't, because I was sick all night. And I had the worst head ever, even including the experiences since then. I was terribly worried about this whole thing because the following morning, Rydbeck was going to demonstrate his rotor form to some very distinguished visitor from Stockholm who was also influential in the funding business. And so Rydbeck was to make the right kind of impressions and so on. And we hardly got this thing working. He was very, very anxious and he'd asked me to make sure that everything would be right. This was the evening before the party, or the afternoon before the party.

Radhakrishnan: 08:16

And I got back from the party, or I was carried back, and I spent all night retching, and I just wasn't in a fit state the next morning to demonstrate any apparatus, of the new or old type, but I was there. I don't think I was very coherent. I was in a terrible panic internally because I thought Rydbeck would notice that something was wrong. And well, just didn't want it to happen at that stage. And then I noticed that he steered the subject onto drink for some reason or other during this demonstration. And it was only much later that I discovered that he'd known all along about this incident. And he was just leaving me alone.

Sullivan: 09:11

But didn't you get it demonstrated?

Radhakrishnan: 09:12

Oh, yeah. Well, then what happened was that, after about three months, I was offered the choice of working on the second floor or on the third floor, which meant either in the tube development department or in the radio astronomy department. I hadn't heard of radio astronomy at that time.

Sullivan: 09:38

And what year is this now?

Radhakrishnan: 09:39

It was 1955. So I said, "What goes on in the third floor?" And they said, "Radio astronomy." And I said, "What's that?" And they said, "Oh, a bloke who has built a hydrogen line receiver, an early form of it, and it didn't work properly, or suddenly it was quite useless. And we were thinking of building a new signal. Would you be interested in the [inaudible]?" So I said, "What's the hydrogen line receiver?" It was all explained to me that you had hydrogen mass quantities outside and this sent out some kind of radiation. You picked this up from a radio server and so on. And I said, "Sure, that sounds interesting, so I'll try it." And by that time they decided to employ me, pay me the right kind of salary and all that, to give me an office.

Sullivan: 10:34

Let me just ask, had there been any observations in Sweden before this time? You mentioned before to me that they had these Würzburg dishes--

Radhakrishnan: 10:43

On other frequencies, they had several, as far as telescopes and receivers were concerned, there was a fairly well-equipped radio astronomical observatory. They had three Würzburg telescopes each 25 feet in diameter. They had two large tiltable arrays and very meteor radar receiver, all sorts of things. It wasn't much astronomy, but there was certainly plenty of equipment around.

Sullivan: 11:14

Did they do any astronomy? I mean, other than atmospheric stuff.

Radhakrishnan: 11:19

Don't really know. I'm sure nothing that mattered.

Sullivan: 11:23

Yeah, I've never heard of any of it.

Radhakrishnan: 11:25

Yeah. So anyway, I took on this job of rebuilding, which was essentially starting from scratch. And that's what I did. I spent three years building this hydrogen line receiver. And I was joined by [inaudible]. I'm sure you know.

Sullivan: 11:45

Yeah.

Radhakrishnan: 11:46

Who's now running the observatory there and [inaudible].

Sullivan: 11:52

Yeah, he's still there.

Radhakrishnan: 11:53

Still there. There's not a lot of work on OH. In fact, I was back there, year before last. I was in this examiner phase of PhD thesis. It was interesting to catch up with old friends again.

Sullivan: 12:16

And what about this hydrogen line receiver? I don't remember any hydrogen line observations that were coming out of Sweden. Is that [inaudible]?

Radhakrishnan: 12:23

No. No. But I think that's about the size of it. As far as I was concerned, I was just building the receiver. And it took that long because I literally had to learn what each little piece of the receiver did. And now I'm more experienced, whatever, but it was very interesting. I remember making a couple of trips to Holland, to Dwingeloo, to look at the marvelous machine that Muller had built, and read everybody's papers on the [inaudible] instruments, and so on. I think on one of my visits here, to Dwingeloo, was on the day or the day after they had detected a 21-centimeter emission from an external galaxy for the first time. And I remember some number like a one-degree signal and I was amazed.

Sullivan: 13:23

And was this the first time for anybody or just for the Dutch?

Radhakrishnan: 13:27

I am not sure. I'd have to think about this. You see, the only people that were interested in the extragalactic 21-centimeter emission at that time was the Harvard group and the [Dutch?] group. And enormous number of papers were produced in Harvard, and all of which were later shown to be faulty somewhere, or left much to be desired, and so on. Now, I'm not sure whether--

Sullivan: 14:00

Was that instrumental effects that were [crosstalk]?

Radhakrishnan: 14:03

Yes. Yes. But I'm not sure we should go into that really. Let's say that all of that work has been redone and not everybody was happy with the results or the interpretation.

Sullivan: 14:16

Okay. So I can check on where the first external HI was found?

Radhakrishnan: 14:21

Yes. As far as I remember, this was Andromeda, M31. And it might have been the first time.

Sullivan: 14:30

[inaudible].

Radhakrishnan: 14:32

Anyway, most of my time in Sweden after '58 - it was the end of '58 - was taken up with this receiver and getting it better and better, and so on. I wasn't particularly interested in observation. I wouldn't know what to look at anyway. It was just that I didn't get round to-- I was still--

Sullivan: 14:56

That playing with it. Yeah.

Radhakrishnan: 14:57

Still playing with the receiver. And what happened next?

Sullivan: 15:05

But did it ever do any observations?

Radhakrishnan: 15:07

I think it was used for some observations later.

Sullivan: 15:11

After you left?

Radhakrishnan: 15:12

Right. But don't forget that this receiver was stuck onto a 25-foot dish, which was getting to be pretty small. At that time the dish--

Sullivan: 15:22

When did the present Onsala dish come along?

Radhakrishnan: 15:24

Oh, many years later. Many years later. At least five or six years later. So that the angular resolution was very poor.

Sullivan: 15:34

So and you can do much that couldn't be done at Kootwijk, or any that hadn't been done?

Radhakrishnan: 15:39

No. No. But there were any number of [agilent?] problems that hadn't been attacked by then. I think there are still many problems that haven't been attacked [inaudible]. Lindblad who was--

Sullivan: 15:52

Which one?

Radhakrishnan: 15:53

The older Lindblad.

Sullivan: 15:54

The big one. Yeah.

Radhakrishnan: 15:55

The big one. He was very interested in observations towards the [empty?] center because they tied up with his model for galaxies and so on, which is, as you know, is tied up with the present density wave business [inaudible]. And I think he was trying to persuade Rydbeck to do some observations. And I think some were done. This was after I left.

Sullivan: 16:25

But in fact, his son has continued to [inaudible].

Radhakrishnan: 16:27

Oh, yes. Oh, yes. But nothing really important came out of that.

Sullivan: 16:36

Okay. Well, so then you went to Caltech.

Radhakrishnan: 16:39

Yeah. There's a little story, recollections, probably worth telling. I decided to go the United States just because I wanted to see the United States the same way that I went to Sweden, not to build hydrogen line receivers, but just to go to Sweden. I was looking around for a job and asked somebody how much money you need to live. And I was told that graduate students live on $2,000 a year or some such thing. And then I wondered if anybody would pay me $2,000 a year. And so I was sort of looking out for a job, and then Rydbeck said, "Leave it to me. I'm going to the United States. I'll get you a job over there." And that's [inaudible]. “It's okay with me if you want to go there.” And he said, "I don't think you should go to the East Coast. The West Coast is the place for you." There's a man called John Bolton there who's just built a new observatory with two big dishes, would you be interested in an interferometer? I said, okay. And the story, apparently, I had this confirmed from both sides. So Rydbeck was in the East Coast, and then he telephoned John Bolton, who was an old friend of his. John was in the West Coast so he called on the telephone and said, "I have someone working at my lab and he wants to come to the United States and I think you should hire him." And then Bolton asked who it was. And Rydbeck said, “He’s from India.” John Bolton said, "No, thank you. I’ve had one already."

Sullivan: 18:22

He had his token Indian.

Radhakrishnan: 18:24

He’d had an Indian and hadn’t enjoyed the experience. Apparently, Rydbeck said, "Well, this one's slightly different. Why don't you try him?" And he said, "Are you sure?" Rydbeck said, "Yes, I'm sure." So the next thing I knew, I was offered a job in California. And then when they sent me their letter of appointment or whatever it was, I found that I was going to be paid $5,250. So I wrote to Bolton in a panic saying there must be some mistake. You misunderstood my qualifications. And I'm sure I know there must be some mistake. And I couldn't possibly do anything to justify that amount of money. So I got a curt letter from John saying, “Why don't you leave that to me? Just do what you have to do.” So that's how I ended up at Caltech. Except that in another little incident, this might be a better interest in the actual process of getting to Caltech. I was driving across the United States. I bought myself a Volkswagen in Europe, which I was taking to California because I was told that was a good way to do things and they were more expensive there. This way I can drive across and see the country. So I happened to drive through Green Bank. And there I met somebody who was-- this was in the early days of Gree Bnank [inaudible].

Sullivan: 20:02

What year is this now?

Radhakrishnan: 20:03

It's '58.

Sullivan: 20:03

Oh, '58.

Radhakrishnan: 20:04

Yeah. And there was just a few people--

Sullivan: 20:07

It's [inaudible] then.

Radhakrishnan: 20:09

Well, no, they had the 85 foot dish dish. And Hein Hvatum, with whom I worked in Sweden, had gone to Green Bank just about then. And I think the only other people at that time I can remember were John Findlay, Dave Heeschen, and Frank Drake. And that was it.

Sullivan: 20:36

That was about it?

Radhakrishnan: 20:36

The beginnings. But I met this other gentleman who was tinkering around with some very old [inaudible] radio tubes [inaudible] some of the most ancient-looking holders for these tubes, and these were fastened by [inaudible] little nuts and things like that, the way they used to be. I mean, it looked like some little antique thing. And he very involved with these things. I was introduced to him, but I catch the name, which I should have. And then he asked me what I was doing and where I was going and I said I was going to Caltech, the Owens Valley Observatory. And he said, "I’ll tell you how get there," so he drew me a map, which way I should go through Nevada and where I should [inaudible] though Death Valley and so on and so on. That was my first meeting with Grote Reber.

Sullivan: 21:32

Aha! Was he actually employed there at that time?

Radhakrishnan: 21:34

No, but--

Sullivan: 21:35

[crosstalk].

Radhakrishnan: 21:36

--no, but Grote Reber was never employed anywhere. The Research Corporation of American supports him, but [honors?] various places by spending some time. Grote Reber is someone that you should [inaudible] talk to.

Sullivan: 21:51

Oh, yes. Agreed. Definitely try to spend a while with him. What is this about RCA then? I mean it's not [crosstalk].

Radhakrishnan: 21:57

Not RCA. Research Corporation [inaudible] of America.

Sullivan: 22:02

Of America.

Radhakrishnan: 22:02

That's not [inaudible].

Sullivan: 22:03

No, what is it?

Radhakrishnan: 22:05

That is a little organization which has money left to it by, I don't know, some donor or other. Maybe they have money invested somewhere. They select, they pick out a few individuals to whom they give money to do research.

Sullivan: 22:25

[inaudible].

Radhakrishnan: 22:26

Right, no questions asked.

Sullivan: 22:28

[inaudible]--

Radhakrishnan: 22:29

And Grote Reber has been supported by this corporation for years and years.

Sullivan: 22:33

I see.

Radhakrishnan: 22:34

Enables him to go to Tasmania or Antarctica or whatever he pleases him to do--

Sullivan: 22:37

[crosstalk].

Radhakrishnan: 22:38

--whatever he likes, whether it's growing beans in order to cover our [inaudible] anticlockwise or clockwise or.

Sullivan: 22:47

I never knew that. Okay, so back to Caltech in '58. And you said the first two Owens Valley dishes have just been built at that time.

Radhakrishnan: 22:59

Yes, one of them had just been connected up and it was being used as a single dish. And the other one had been constructed. It wasn't in operation.

Sullivan: 23:11

These are the present day [inaudible].

Radhakrishnan: 23:12

Right, [crosstalk].

Sullivan: 23:13

Yeah, right. And [crosstalk]--

Radhakrishnan: 23:15

And that was almost at the very beginning of-- actually, Caltech, the very first dish was a 30-foot homemade dish, which was originally installed on Palomar Mountain, believe it or not.

Sullivan: 23:34

Oh, I never heard of that. Who did that?

Radhakrishnan: 23:35

Well, John Bolton, Gordon Stanley.  That was used for hydrogen line observations. I think they were done two halves. Bolton and Harris certainly did one half, and that was published straight away, and Tom Matthews the other half, and I think that never got published

Sullivan: 24:02

Where was the Bolton and --?

Radhakrishnan: 24:04

PASP.

Sullivan: 24:06

Very interesting. And galactic structure [inaudible]? Have to look that up. So--

Radhakrishnan: 24:14

And that dish got moved over to Owens Valley later. I think by the time I got there it had just been moved.

Sullivan: 24:23

So what were the dishes at Caltech first used for? What was the purpose of the [inaudible]?

Radhakrishnan: 24:30

Well they were intended to be used as an interferometer. A high frequency interferometer. And they were intended to do all the marvelous things which in fact they did afterwards. By the time I went there one of the dishes was being used, as I said, just by itself on 960 megacycles. And Harris and Roberts had done a survey of-- well they'd gone through 3C catalogue I think to see how many sources they could see at that frequency. And that was very important at that time.

Sullivan: 25:12

You knew nothing about the spectrum, right?

Radhakrishnan: 25:13

Right.

Sullivan: 25:14

This was Dan Harris and Mort Roberts?

Radhakrishnan: 25:15

No, no, no, no. Jim Roberts. Jim Roberts. So that was a very important paper I believe. A list of sources with their fluxes and 1000 megs [inaudible]. And there was some observation of planets-- I think Jim Roberts looked Jupiter and found that it was giving off much more radiation than one expected it would at that high of frequency. And that was about the same time that Drake and Hvatum did the same sort of thing at Green Bank.

Sullivan: 26:07

This Jim Roberts. I don't know him. Where is he now?

Radhakrishnan: 26:12

In Australia. You should know him. Oh, he's done a great many things. He was one of the earlier--

Sullivan: 26:20

At Parkes? I mean is he at CSIRO right now?

Radhakrishnan: 26:23

Yeah, even before Caltech and then at Parkes. In fact, one of the earliest articles that I had seen on radio astronomy published in Nature was written by Jim Roberts.

Sullivan: 26:38

And what was this about?

Radhakrishnan: 26:39

Oh, just radio astronomy in general.

Sullivan: 26:41

When was this? I'd be interested.

Radhakrishnan: 26:44

Oh, don't know when-- middle '50s I should imagine. He was a student of Fred Hoyle’s in Cambridge.

Sullivan: 26:53

Oh, you said now he's with CSIRO. That's a gap in my knowledge. So what did you first work on at Caltech?

Radhakrishnan: 27:04

Oh, we built the hydrogen line receiver. [laughter]

Sullivan: 27:09

Use your expertise.

Radhakrishnan: 27:10

In fact that's what I was hired for. You see I wasn't hired for doing any astronomy at all. I only hired to fix the receiver. And having fixed the, well, I think the first-- it's hard to remember in which order they came. But I spent most of my time playing with the hydrogen line receiver for a start. And the first work that was done with a hydrogen receiver was detection of absorption and the number of [inaudible] forces with John Bolton. He was the one that really got me interest [inaudible] which, in a way, I've been working on ever since. It's been 14 years now.

Sullivan: 28:02

It's been your theme more or less.

Radhakrishnan: 28:03

Yeah, that's when it all started.

Sullivan: 28:08

Can I ask you a question right now about hydrogen absorption? The NRL, McClain and company, were the first to detect hydrogen absorption. But there was a misunderstanding as to what absorption was.

Radhakrishnan: 28:25

The very first paper is by Hagen and McClain.

Sullivan: 28:28

Right, short little paper.

Radhakrishnan: 28:30

Very short. Reading that, it was clear that—or, it's quite clear that they didn't know what was happening. They discovered sort of negative going signal.

Sullivan: 28:47

They thought hydrogen was behind the source of the--

Radhakrishnan: 28:49

That's right. They thought the source was obscuring the emission from hydrogen. And the story that I-- and then there was a second paper that was used from Hagen and Lilley.

Sullivan: 29:01

With Lilley. Correct equation of transfer and so forth.

Radhakrishnan: 29:06

Right, but--

Sullivan: 29:08

I never did see McClain about this. I meant to before I left Washington. But then you were going to say there was a second.

Radhakrishnan: 29:17

Well I think-- I don't know if you're doing the right thing to dig into this kind of history. I can't remember where I got this story from. But I have always believed that it was George Field who really put them on to this. And I think it was also instrumental in explaining some of this.

Sullivan: 29:39

Even to Lilley. I though Lilley was a Harvard physicist and all that.

Radhakrishnan: 29:44

I'm sure George Field had something to do with it.

Sullivan: 00:09

Okay. This is a continuing interview with Radhakrishnan. And, okay, now you mentioned that Jim Roberts was working at Caltech when you were first there on hydrogen external systems.

Radhakrishnan: 00:26

No, no, no. It was [inaudible].

Sullivan: 00:29

Oh, no, I'm sorry, in the thousand megahertz [inaudible].

Radhakrishnan: 00:31

Right. Right. Right. Well, he'd spent many years working on the sun. He's made all kinds of contributions in many, many different fields. Surprised me a bit when you asked me about him. You didn't know much about him. Reason is perhaps less to do with you than with me because I feel that if I was taught radio astronomy at all, it was by two people. One was John Bolton, and the other was Jim Roberts. Both of them were at Caltech, and they were very, very different types. And it was a marvelous education in opposites, which I think is also the way that education should be conducted. You shouldn't have someone who has an extremely balanced view of everything that you should be subjected to an extreme view, so that you can find your own sort of balance in between. And--

Sullivan: 01:26

What had Robert worked on before you came?

Radhakrishnan: 01:30

The sun. He worked with Paul Wild, theory of solar bursts.

Sullivan: 01:34

He's Australian then?

Radhakrishnan: 01:35

Oh, yes. Yes. Yeah, he is. He was one of the very early, among the earliest in the Australian group. The Pawsey, Mills, Christiansen, Bolton, Wild, group. Jim was one of those. And Caltech was rather interesting at that time because the staff was made of John Bolton, who was an Englishman. Gordon Stanley was a New Zealander, Jim Roberts was Australian, Tom Matthews was Canadian.

Sullivan: 02:20

It sounds like the Kapteyn Lab.

Radhakrishnan: 02:22

I was there, an Indian. I think there was another nationality but not a single American on the staff. [laughter] And all the students were Americans.

Sullivan: 02:36

The likes of Barry Clark and Kellermann.

Radhakrishnan: 02:39

Indeed, yeah. That's right. That's right. Bob Wilson, Barry Clark, and Kellermann, Al Moffet, Dick Read, so.

Sullivan: 02:52

Let me just ask about John Bolton. Can you just very briefly tell me where he went? I'm just confused. He both headed the Caltech and the CSIRO. Is that correct? He's been head of both places.

Radhakrishnan: 03:12

Now when you say CSIRO, it's--

Sullivan: 03:16

The Radiophysics Division.

Radhakrishnan: 03:17

No, no. Taffy Bowen was Chief of the Radiophysics Division, John Bolton, and he went back from Caltech, he went back as Director of Parkes Observatory, because the Radiophysics Division, it comprised three sections. One was the Parkes Observatory, John Bolton and [inaudible] observatory with Paul Wild’s [machine?], which he was the director at the [inaudible]. And there's also a section on rain physics or cloud physics. Had to do with seeding the clouds and so on, which was a pet interest of Taffy’s.

Sullivan: 03:58

Okay. So the-

Radhakrishnan: 04:01

John was [staffing, literally staffing?] at the Caltech Radio Astronomy Observatory and handled it all the time we were there.

Sullivan: 04:12

And where is Gordon Stanley now who took over after?

Radhakrishnan: 04:14

Gordon Stanley [inaudible] took over from there.

Sullivan: 04:17

I see. And this may be a little bit confusing. John Bolton's still in Australia now?

Radhakrishnan: 04:26

I believe, yes. [inaudible]

Sullivan: 04:30

I see. Okay.

Radhakrishnan: 04:33

But he is no longer director of the Parkes Observatory. [inaudible] development and Paul Wild and John Bolton had had parallel careers since way back when [inaudible]. I think they were born within a mile of each other, they both came from Yorkshire. They were both in the Navy during the war. They both ended up in Australia. They both got interested in radio astronomy, they got married to Australian women, and they both had a spectacular career, each making [inaudible] extragalactic radio astronomy, radio sources, and Paul the Sun. And their rise in the organization was almost literally parallel and they ended up each heading one of the observatories.

Sullivan: 05:33

Two other sections, yeah?

Radhakrishnan: 05:36

Two observatories that Radiophysics had. Taffy Bowen retired early last year. And Paul Wild became chief of Radiophysics. John Bolton, I think actually retired in administration [inaudible] He just wanted to be relieved of all the administrative responsibilities, so--

Sullivan: 05:58

He was back to science.

Radhakrishnan: 05:59

So he’s back full-time back to science and extremely happy.

Sullivan: 06:05

I think there are a lot of people haven't had the courage to do that, it means less power, less money [crosstalk]

Radhakrishnan: 06:10

But you have to very sure of yourself to do a thing like that. So that's the situation, so he's just a scientist at large.

Sullivan: 06:20

Okay, well, back to Caltech. You worked with Bolton on hydrogen absorption.

Radhakrishnan: 06:27

Right. And that was just using the single dish. Several things became clear to me that that was not the way to go on hydrogen absorption with limitations and so on, and it's just about that time with the Caltech interferometer was being put together to do work in the continuum. And I got interested in this thing [inaudible] didn't have to work with a line. And that was the start of line interferometery anyway.

Sullivan: 07:02

Was that the first place that was ever done, hydrogen line interferometery?

Radhakrishnan: 07:05

Certainly. That was very interesting. It was just one of many things that we did with the interferometer. But I got very interested in interferometry. Anyone who has really played with interferometery somehow or another goes back to using single dish [inaudible].

Radhakrishnan: 07:31

You understand how single dishes work much better and you understand how interferometry works.

Sullivan: 07:39

You also understand [inaudible] information.

Radhakrishnan: 07:41

Yeah, so that was just one of many things done that I got interested in [inaudible]. In fact, the very first time that the interferometer was used on the line was not so much to look for absorption as to- Well, I was interested in doing the Zeeman experiment far better than it had ever been done before and bigger than [inaudible].

Sullivan: 08:12

So it hadn't been really verified before, it was just this tentative report out of Jodrell.

Radhakrishnan: 08:17

Oh, yeah. It was only the Verschuur’s observation a couple of years ago [that put it on sure footing?].

Sullivan: 08:26

Right. So anyway, so you got interested in--

Radhakrishnan: 08:29

Yeah. Well, but that's down on the 21 centimeter line, so we had the interferometer working on that, and of course, we discovered a lot of interesting things and discovered that was the way to do [inaudible] absorption and the only way to do the work. So that led on to a vast amount of work. And Barry Clark then joined then original [inaudible] line interferometer put together by Bob Wilson, Dave Morris and myself because we were interested in doing the Zeeman experiment. And then I-- first time I tried, [I ended up on?] 3C123, which was an order of magnitude weaker than-- no, two orders of magnitude weaker than Cas, or 50 times, perhaps, weaker than Cas. And lo and behold, there was a beautiful absorption profile, something you couldn't have dreamed of doing with a single [90?] foot dish. So anyway, that stuck with me.

Sullivan: 09:41

Did you ever publish anything on Zeeman [inaudible] at Caltech?

Radhakrishnan: 09:46

There was a paper published by Morris, Wilson, and Clark [Ed. note added 2024: Morris, Clark, Wilson, 1963], three of them. Well, the work went on for quite some time.

Sullivan: 09:57

On Zeeman effect?

Radhakrishnan: 09:58

Indeed, yes. There was a negative result, see. It was the same thing Sandy Weinreb was doing at Green Bank. It was one of the things that [inaudible]—He tried deuterium and he tried [inaudible].

Sullivan: 10:11

Where was that paper, in ApJ?

Radhakrishnan: 10:13

ApJ, yes. And another thing that we were interested in, trying to make the interferometer [inaudible] to measure polarization. One of the first things was done, coming back to Jim Roberts, was the detection of Jupiter's [round?] belt.

Sullivan: 10:39

[inaudible] from the polarization structure [crosstalk]--

Radhakrishnan: 10:44

Well, to show-- best of all, to show that Jupiter was polarized [inaudible], and to show that [inaudible] was bigger than [inaudible] by a factor of 3, and so on.

Sullivan: 10:59

One other question. Is this Bob Wilson the same one that's at Bell Labs?

Radhakrishnan: 11:02

Indeed. Indeed, yes.

Sullivan: 11:05

Well, I think we'd better take a break here.

Sullivan: 11:09

Okay. this is now two days later, 28th March '72. Now continuing the interview with Rad.

[Editor note, 2024:  In the following section of the interview 11:25 to the end of the tape, tape 12B, is extremely difficult to hear and understand Radhakrishnan.  One can occasionally catch names, e.g. Jim Roberts, Drake, Weinreb, NRAO, but not the narrative surrounding them. Additionally, from 26:50-29:09, there is a mechanical screech overlaying the speakers.]

Sullivan: 11:22

Well, now, at Caltech, you worked on--

Radhakrishnan: 11:25

Yeah, before we [get on I should?] probably mention a couple things, just to help you out with the history of 21 centimeter absorption work, what had been done. [inaudible] hardly advertising, but if you're interested in the history of that particular subject, you did most of it by [inaudible]. One of them was Caltech [inaudible]. And then papers one and two [inaudible] two or three, January 1972. Caltech [inaudible] physics of it now [when it is?] talking about-- in the introduction, I've got some [things?] try to [inaudible].

Sullivan: 12:48

Now, you say you got involved with Jupiter at Caltech.

Radhakrishnan: 12:54

Yeah. Well, that was-- it was actually a long, a very interesting subject. And I'll try and condense it because there's [inaudible] interesting history [inaudible]. Jupiter, like most of the planets, is [inaudible].

Sullivan: 13:29

I have interviewed Burke--

Radhakrishnan: 13:31

Right. So you know that's-- Jupiter mainly [inaudible] story of Jupiter. And in fact, [inaudible] whole countries [inaudible]. But apart from that kind of [stuff?], which cover [inaudible] it was expected that Jupiter [would just be?]-- just behave like [inaudible] the very first measurement suggesting that something [was wrong?]. [inaudible] [inaudible] observation?

Radhakrishnan: 15:08

Observations would be [inaudible] small business because [inaudible] I was a bit [inaudible] this part of the story [inaudible] published by [inaudible] he's [inaudible] was the guy that built up the electrons that we can [inaudible] ideas [inaudible] look like that [inaudible] duplicated [inaudible] and tested and he's the guy that [inaudible]. Anyway, he [inaudible] and right [inaudible] time that [inaudible] then [inaudible] this was before the-- I can't remember how it happened. Anyway, [inaudible] radiation [inaudible] as a result of that [inaudible] situated at [inaudible] something like that [inaudible] would show that they [inaudible] radiation [inaudible] three times the size of the sun [inaudible].

Sullivan: 18:38

You said all of this [inaudible].

Radhakrishnan: 18:51

No. No. We detected [inaudible] and then [inaudible] and then [inaudible] there's still my way [inaudible] polarized and then we've drilled [inaudible] positioning heavier [inaudible] there's going to be some variation of the intensity. So [inaudible] you know, you won't get a result, that's to say [inaudible] the chain. So when [inaudible] around, under [inaudible] barrier. And there's no [inaudible] scripture [inaudible]--

Radhakrishnan: 19:39

Yeah, so that was a very big thing in [inaudible] and I would say [inaudible]--

Sullivan: 19:46

It was '58?

Radhakrishnan: 19:49

Oh, no, no. Not '58 [inaudible] and I wasn't there. I lived [inaudible] it was more along [inaudible] operator. And then, oh. Well, this really stuck with me, yes, it did. It went very well. Novice [inaudible] you want my story [inaudible] to do. Next, there are ways [inaudible] going here [inaudible] when we drifted, that's really early [inaudible] been [inaudible] exist [inaudible] and Dave Morris, in [inaudible] distance, he was [inaudible] telling them. Who we were talking about, he was a [inaudible] Morris, and [inaudible] today, four of what I would call discoveries [inaudible] any one of [inaudible] he lived for this [inaudible] this is all we showed.

Sullivan: 21:38

This is not where he navigated?

Radhakrishnan: 21:40

Oh, yes.

Sullivan: 21:42

Around '62?

Radhakrishnan: 21:45

Sure. Polarization, they [inaudible] and this was viewed [inaudible] expect [inaudible] exists. It showed that you identified [inaudible] south, and [inaudible] host you have [inaudible] they showed him that they [inaudible] at all the displays. This was right now, display [inaudible] source. Anyways, you can hear [inaudible] it was actually magnificently [inaudible] and then he sort of handed it over to this business up in [inaudible] the stuff [inaudible] and there [inaudible] was associated with [inaudible] and he ended up being [inaudible] working [inaudible] system very [inaudible]. The same thing happened with [inaudible]. So it was handed over to [inaudible] years [inaudible] that wants to do [inaudible]. It might be necessary [inaudible]. It was an idea [inaudible].

Sullivan: 24:12

So he was around the first person to propose that?

Radhakrishnan: 24:14

Oh, yeah, [inaudible]. The idea is really kicking around the [inaudible]. I think John Bolton had this. As I said, he mentioned this to me once [inaudible] he wasn't [inaudible] how to put it. And we looked at [inaudible] could only find one sentence there [inaudible]. Well, one is led to wonder whether it's the same [inaudible] that's the way [inaudible]. And then well, that was [inaudible] want the [inaudible].

Sullivan: 25:31

What was the next major interest?

Radhakrishnan: 25:35

Well, I think mentioned before that that you're starting this business of using the interferometer to study these absorption lines and showing that it was, in fact, [inaudible] managed to do this [inaudible]. I'm totally interested in interferometers and I still am [inaudible]. And it's almost the more fundamental way of looking in the [inaudible]. So I really got off [inaudible] totally loved [inaudible] this is [inaudible] I tried to use the interferometer to [do things that hadn’t been done before?]. Quite honestly, not stuff that's available [inaudible] the way you want to [inaudible]. But then we can see [inaudible] technique [inaudible] many, many years trying to understand [inaudible] the--

Sullivan: 27:59

[inaudible].

Radhakrishnan: 28:02

Well, all [inaudible] exactly what the [inaudible]-- what the [inaudible] I don't know [inaudible].

Sullivan: 28:31

Oh, yes, yes, I think the [inaudible] the response, I just want to go to [inaudible].

Radhakrishnan: 28:41

[inaudible] means everything.

Radhakrishnan: 28:49

Yeah, but that can [inaudible]. And then I can [inaudible] really spent months and years [inaudible] one where you have to [inaudible] changed on of the [inaudible] because some things [inaudible]. And then I actually focused on [inaudible]. That may seem a little peculiar that they would say why do you want to know the [inaudible] that had been developed a method of measuring polarization which had to do [inaudible] with the angles becoming dual fees so that [inaudible] came up precisely in terms of the [inaudible]. It's in a very interesting field. Yeah. In correlation [inaudible].

Sullivan: 00:04

This is continuing with Radhakrishnan on 28th March '72. The first part of this interview is on tape 12A and B. Now you were talking about your polarization.

Radhakrishnan: 00:16

Yeah, I think it's rather interesting from purely personal point of view, the amount of hard work that went into trying to do something very different that really didn't get there, what I think, there’s a paper, which should have been a very important paper, but wasn't published by Dave and myself. But the trouble with polarization measurements before that time was that they were very crude. And so we tried to develop some technique where you could measure very small amounts of polarization. And as far as I'm concerned, I think you can check this by going into the literature. People couldn't have been sure where they were measuring 1% or 2%. And that was the sort of accuracy to which they worked and they never found anything at the decimeter of [inaudible] and so on. And then after we'd gone through months of blood and sweat, we ended up with a system where we could measure polarization to a 10^th of a percent provided the signal-to-noise ratio was good. In other words, the instrumentals could be taken out to a point. And so we said let's pick six [form?] sources and do this. And we picked six [form?] sources and we [ground?] them up to-  one of them, I think [inaudible], was chosen as a calibrator because it was an H II region. And so we tried to measure the polarization of the others in terms of that to a 10^th of a percent. And the Crab, as I say, had been, its optical polarization had been measured.

Radhakrishnan: 01:50

Connie Mayer had shown that it was 7% to three centimeters and later it was 3%, 10 centimeters and 21 centimeters. Many people like Westerhout and Rod Davies and so on, had made measurements and gotten nowhere, and given limits of something like 1% or whatever it is. Well we showed that it was, I think, 1.3 plus or minus 1% for the position angle for it. And there was nothing on the other sources. And it's just one of those quirks of fate because we picked the six sources.

Sullivan: 02:24

Yeah.

Radhakrishnan: 02:24

The [inaudible] polarized it that frequency--

Sullivan: 02:27

Did you say 1.3 plus or minus one?

Radhakrishnan: 02:29

Plus or minus 0.1

Sullivan: 02:30

0.1. Okay.

Radhakrishnan: 02:31

Yeah, some thing [inaudible]. And we drew, I think what was perhaps first diagram was shown where you could try and see whether in fact did follow [inaudible] squared law.

Sullivan: 02:47

Yeah.

Radhakrishnan: 02:47

But anyway, I was just mentioning that we started to play with techniques, which is what interested me a great deal, to try and develop different technique and then to use it for something. And then the Australian measurements by [inaudible] and Whiteoak, I think, really broke this thing wide open. Just as we were doing a second survey, 10 centimeters polarization, we read that paper in Phys. Rev. Letters where they measured polarization in 10 sources or so.

Sullivan: 03:24

Which [inaudible] was this?

Radhakrishnan: 03:25

This was the Parkes [inaudible].

Sullivan: 03:27

Some of the first observations like that?

Radhakrishnan: 03:30

Yeah. Oh, yeah. Some of the very first. I think because we found the practically every other source that we looked at was polarized too. It was like 273 and so on. Were all first there. But then by the time we got, there was a conference called Physics in Nonthermal Sources, which [Woltjer?] first talked about the depolarization in Cygnus, Connie Mayer in the meantime had measured Cygnus and so on. So in fact, that had happened before the Australians.

Sullivan: 04:01

This was a NASA conference?

Radhakrishnan: 04:03

Yeah, it was held at Goddard Space-

Sullivan: 04:07

Yeah, I've seen the proceedings.

Radhakrishnan: 04:09

But really, if you're trying to look for historic source, it was really NRL, and Connie mostly, that started the whole business of polarization.

Sullivan: 04:20

Oh, yeah, that's the impression I have.

Radhakrishnan: 04:21

Sullivan:

Absolutely.

Because before that, people said, “You can't do it.”

Radhakrishnan: 04:25

No, no.

Sullivan: 04:26

He was willing to go ahead and do it.

Radhakrishnan: 04:28

Yeah. It was just one pioneer really. But then we were avoiding looking at extended sources at Caltech because we had spent so much time studying instrumental polarization. And we discovered that both axis effects were very, very important and that unless had very special dishes and feeds the moment you had off axis, you could get instrumental effects. So for some strange reason, we avoided looking at extended sources. And finally we got around to it at some stage. We discovered that there were very weird effects. And so immediately we pursued that. And then we realized that sources like Hercules and 3C353 and so on had components that were polarized in different directions. So that eventually became George Seielstad's thesis. But I was very interested in trying to, Barry and I got very interested in trying to sort out the principle of how you measure polarization distributions with an interferometer. All of this business of taking Stokes parameters differently and very many interesting things, like that there was no system you could build which had a response only to one Stokes parameter. Anyway, it's all of that. So that's the purpose. Now, one of the other things that I was trying to make the system for measuring, using the interferometer to measure the Zeeman effect and well, that didn't get anywhere. I decided that the interferometer was the best way to detect OH.

Sullivan: 06:16

You never published anything on the Zeeman?

Radhakrishnan: 06:18

Sullivan:

No, no. Barry and Dave and Bob Wilson did because they carried on. I went off to Bell Labs at a certain stage because they offered us a couple of masers and they wanted someone to go and build the masers at Bell Labs. So I left and they carried on.

Work with Clark in ApJ?

In ApJ. And after there was a very interesting system, too, because it's all very simple these days, but simply by setting the feeds of right angles to each other, you end up with a system which has a positive response to one [inaudible] circular, negative response to the other. So it automatically measures the difference, which is precisely what you want.

Sullivan: 07:04

Right.

Radhakrishnan: 07:06

And then I got interested in OH. None of these really came to anything, so you shouldn't put all these in your book, but probably of interest to you. And I decided that an interferometer was the best way to measure OH. And so we went to a lot of trouble to build receivers and feeds and so on. And this was happening at the same time as many other things. A lot of this polarization stuff came up in the meantime. I think it's rather amusing that you find some of the early papers in polarization measurements from Caltech, which were published, which were at 1420, 1666 and something else. And then I got interested in--

Sullivan: 07:58

What became of the OH, you never did, never published any OH work from--?

Radhakrishnan: 08:02

No, no, no. I had a number of unsuccessful attempts and just about the time--

Sullivan: 08:07

What are you trying to do exactly?

Radhakrishnan: 08:08

Just detect it. This was before OH was found.

Sullivan: 08:14

Oh, that's what's so interesting. Before OH emission was found?

Radhakrishnan: 08:19

Before OH emission was found.

Radhakrishnan: 08:21

Before anything was found.

Sullivan: 08:23

Radhakrishanan: 08:26

I see. And where did you look?

Oh, Cas. But the first time I looked, the first two occasions I looked through the single dish the receiver wasn't working very well. And I remember I ran out of time once and then John Bolton came out and said, "That's enough, you've had enough time on the dish. Get off now."

Sullivan: 08:42

What were you expecting? Certainly not the strong non-thermal signal.

Radhakrishnan: 08:45

Oh, no, no. This was before any other molecule or anything is found along there. It's hard for you to imagine that.

Sullivan: 08:54

Well, but I'm interested. I mean, I've heard, it happens, in many of my first interviews with people involved in the OH game.

Radhakrishnan: 08:59

Yeah. The only paper that had been published before was by Barrett and Lilley, where they look for OH in the sun. It's an NRL preprint or something with a blue cover, which I read backwards and forward many, many times. And I decided I could do this better.

Sullivan: 09:18

So can you just tell me, since this is not published, I mean, what sort of bandwidth were you using?

Radhakrishnan: 09:26

Oh, just 6 GHz, I suppose. I was looking for something like the absorption profile effect. Precisely what Weinreb and Barrett and company did later. It's just that the single dish measurements were very poor. Therefore, they didn't succeed, and the interferometer methods got delayed because I went off [to Bell Labs anyway?]. It just didn't get done. But you must be very careful and I don't think you should bring a lot of this up because it's always like people trying to get credit. I mean, it's always telling their own story. It helps you to understand personalities and so on, and you spend a lot of time working on a lot of things that didn't work out. But it's not- This is well known. Everybody knows. Everybody knows. I was very interested in this sort of thing, but it's not something. So just for you.

Sullivan: 10:15

Okay.

Radhakrishnan: 10:17

Then I got interested in--then I figured that if you could cut down the--if you bring the signal-to-noise down, you could use the interferometer method to look at an enormous number of sources for H-line absorptions. And this is why I went off to Bell Labs, was that I would really do it, and I got the masers. But by the time I came back with them, I got one working and things got delayed. In the meantime, I decided I won't go off and so on. So nothing really came of that other than showing that it could have been done. And it's just a terrible shame that instead of Caltech immediately following the thing and clearing up the subject, which would have left nothing for me to do, five years later. Nothing happened there.

Sullivan: 11:08

What did they do with the masers?

Radhakrishnan: 11:10

They never used them afterwards. I think [David Wilkes?] had tried one once, made it work, but they didn't. Anyway, before. Before I went away, I did something else. There was another problem in which I was very interested, and here again it was a combination of trying to combine a new technique with something that would be interesting astronomically, was to use the interferometer to study external galaxies. The first measurements were made again at Caltech. So one maser on one dish, one on the other, and I was interested in just using the phase. I thought if you started with the H I galaxies, all you have to do is measure the shift of the phase, the different frequencies and positions and so on. So I spent a lot of time putting this machine together. And John Whiteoak, who was a Carnegie Fellow working at the Wilson and Palomar Observatory and it was going to join the radio astronomy group, came over and joined the observation simply because he was interested in this sort of thing.  And George Seielstad was a student there at the time. He was sort of also in it, and that appeared as a paper later by Seielstad and Whiteoak.

Sullivan: 12:37

So this was a hydrogen and external system. This is the first interferometric study of it, Right?

Radhakrishnan: 12:43

Right.

Sullivan: 12:43

I know that paper. Yeah.

Radhakrishnan: 12:44

Yeah. I think a lot of that interpretation has been questioned and so on. But anyway, that was the first sort of thing was done. And I'm trying to remember if there was anything else that was a really important at Caltech. Well, they have been my things anyway during all of this. You see, I spent over a year at Bell Labs , which was one of the most rewarding years I've spent since I was teaching people nothing and learning at a fantastic rate and a sense that, you know, wherever I looked, there was something new and interesting going on.

Sullivan: 13:41

In electronics primarily?

Radhakrishnan: 13:43

Oh, everything. Physics. To me, I never had such an intake of physics since perhaps during university.

Sullivan: 13:58

Okay, well, if you think of anything else at Caltech, feel free to bring it in later. Could you just give me a few facts about your fabled boat trip? I know areas, but. But first, why did it start in England? And how long did it take? And things like this?

[Editor note 2024:  An account of the boat trip, Radio Astronomers at Sea - Martin Ryle and V. Radhakrishnan: Correspondence, 1963-1966: The Voyage of the 'Cygnus A' from the UK to Australia, edited by W.M. Goss, David Morris, Geetha Sheshadri, is available.  Contact the NRAO Archivist.]

Radhakrishnan: 14:25

Oh, you want a few things? Well, this is something I'd been planning since I was 18. In other words, I have been planning for some--some 15 years at least, before it actually took place. And I just been, I'd just been waiting. This is often the way that I have an idea, but I sort of wait for the right moment. You never know when it's going to arrive. When I was at Bell, [Jack? inaudible] in whose group I was working, he said, "Do you know, there's a new kind of boat?" I said, "What is it? "He said, "Oh, it's got three hulls installed in it. Trimaran, with a bloke in California was designing them and this started the whole thing off. And then when I went back to California, I went and saw Piver who was the designer. And then I decided that's the kind of boat I wanted. Partly because it was different of an element, extra element of adventure and this thing.

Sullivan: 15:39

Yeah.

Radhakrishnan: 15:41

And then the thing that appealed to me about this was also that was very cheap because Piver’s designs were meant for home builders. And he claimed that you could have a boat, certain accommodation, for a fraction of price. Now, I wasn't going to spend years building a boat and I wasn't very sure that I could make good job. So I started looking around for cheap places where I could get one built. You see, I wrote to Australia and found out, because I thought I would go to Australia next, and so on and so on. And then I remembered an interesting conversation when I was visiting Martin Ryle on the way to some conference in Europe. And then I said, "Martin, you’ve got this boat, canvas trimaran. [That’s when he?] informed me that he had built the first trimaran in England." Martin's a great sailor. That was a little one--

Sullivan: 16:36

Yeah.

Radhakrishnan: 16:37

--he was familiar with. And then I said, "Oh, I'm interested in buying or getting a Piver trimaran, is there any place where I can get it built?" And he said, "Yes, they're built at Cox Marine in Great Yarmouth which is 25 miles from here." And one thing led to another and before I knew what, his secretary had fixed up an appointment for me the following morning, I rented a car and drove off, you see. I placed an order for--

Sullivan: 17:03

I see.

Radhakrishnan: 17:05

--for one. And then I went back to the States and, well, I thought about it a little more. I think I told them I would order one but I didn't actually send them the money. Then I went back into saying, but this was it. And that was the time I had to do this. So I placed an order and sent them part of the money that was made through all the business of selecting people. And I knew that this is one of the most difficult things to do. And I know any number of skippers have come to grief for, because they've picked the wrong crew. And so on. I knew so much about the difficulties of doing this that I wasn't going to make any mistakes. So I told myself, I think I made out all right. But it was interesting that during all this, and I was doing some calculations about the amount of money that it cost me to get this boat and so on and so on. I had it all written up to my blackboard and Dave Morris walked in. [By that time] I had known Dave for years, worked with him. I never ever mentioned the word boat and he never been [on one?]. And then he said, "What are you doing? What's all this about?" And I said, "I’ve decided I'm going to sail to Australia and I've ordered this boat. I’ve been doing my sums on board and finding that I'm short of money, but I'm damned if I'm going to give this thing up. I just have to find some other way of getting the money because I'm going and I'm going in a few months." And Dave said, "I have some money." And I said, "Are you crazy? Do you know what this means? This boat's 35 feet long running across the oceans and so on. Have you ever been on sailboat before?" Not that I had that much experience, but anyway, I wanted to do this, so.

Sullivan: 18:50

Yeah.

Radhakrishnan: 18:52

And Dave made one of those classic remarks, typically brilliant remarks. And he said, "You're not suggesting that one should spend one's life doing the sort of thing we are doing here, anything is better." And that was it. It had never occurred to me, but I realized in that instant that was the kind of man I wanted.

Sullivan: 19:18

Yeah.

Radhakrishnan: 19:20

So that was how Dave got on the trip-

Sullivan: 19:22

Now, you already had a job in Australia?

Radhakrishnan: 19:25

Yeah.

Sullivan: 19:26

Yeah. But Dave--

Radhakrishnan: 19:26

John Bolton had left Caltech years before that. In fact, he was the one who gave me my job at Caltech but he left a couple of years after I went to Caltech. So a lot of this work that I've been telling you about was after John Bolton left. [crosstalk]--

Sullivan: 19:47

[inaudible].

Radhakrishnan: 19:49

Yeah. And when he left, he said, "Why don't you come to Australia?" I said, "Yeah. I'd been wanting to go to Australia. [inaudible] big telescope. It was perfect." And so, I wrote off at one stage before this boat business came up in its immediate form. And he gave me a job. And then I got this chance to go to Bell Telephone Labs to build these masers. When Joe Pawsey was there for the ‘61 IAU in Berkeley, I told him, "Look. I just can't come to Australia. I want to go to Bell Labs to build this maser." And use it and so on. "Can I have another year--" at that time, [inaudible] they suggested it would only take two or three months to put the maser together so I thought I’d have another few months to a year, so that [inaudible]. I didn't realize how complicated it was. Joe Pawsey said, "Oh, that's very good-- it's useful to have someone who knows about masers and so on." And so that was a year-- two years, and then I reapplied for the job, and then I said I'd be there in six months or eight months. And by the time I got to Australia, I've had that job for over four years and they kept it for me. [inaudible] thing that could happen. But Dave didn't have a job.

Sullivan: 21:10

He got it after he got to Australia.

Radhakrishnan: 21:12

Well, I think he applied. So I got the boat in England because it was cheap and it sort of gives me a chance of going across both the Atlantic and the Pacific. And I think on his way to join me - because he passed through London, I think - he put his application in with the Australian [inaudible].

Sullivan: 21:37

But he didn't know about it till he got to Australia.

Radhakrishnan: 21:39

Something like that.

Sullivan: 21:40

Okay. So how long did it take you now from--

Radhakrishnan: 21:43

18 months.

Sullivan: 21:43

18 months. From England to the Panama Canal was how long?

Radhakrishnan: 21:48

Well, we did it the wrong way. That was perhaps the only thing that I would change if I had to do it again, so to speak. That's the ratio of time spent, the different places along the trip. It took us, we spent a year between the date of leaving the place where the boat was launched in England-- we actually cruised on the coast of England for a while and then Europe and so on. Between the date we left Great Yarmouth and the date we left Panama was one year.

Sullivan: 22:30

And your six months--

Radhakrishnan: 22:31

And only six months across the Pacific, whereas it should have been the other way around because the Pacific is twice as long and there are twice as many interesting islands. So--

Sullivan: 22:44

And how many people was this across--

Radhakrishnan: 22:47

There were only three permanent members of which Dave was the only truly permanent crew member. There were two others who were interested-- two Americans who were interested. Dan Harris--

Sullivan: 23:01

Who I've heard of, yes.

Radhakrishnan: 23:02

Well, he was a graduate student, also a radio astronomer at Caltech. And there was another friend of mine who was in the [inaudible] Science and Engineering. And because I decided that we couldn't have more than three on long trips from the point of view of loading the boat, and the weight of water and food and so on. I asked them to split the trip between them, and Dan Harris was to go across the Atlantic and Sid Shaw would go across the Pacific. So that's how it worked out. Dan, who was then in Italy at the time he left Caltech, he got a degree at Caltech, and then he went to Bologna. And he quit the job there and joined us in England and went across the Atlantic. And he got off at Arecibo, took a job there. And then Sid Shaw joined us the rest of the trip.

Sullivan: 23:56

And what was the length of this boat? That's one other factor there.

Radhakrishnan: 23:58

35 feet.

Sullivan: 23:59

35 feet. Okay, so this brings us to CSIRO, in what year?

Radhakrishnan: 24:09

Christmas Eve, '65.

Sullivan: 24:12

The end of '65. And what did you begin working on there?

Radhakrishnan: 24:17

Gee, I don't think I did anything much for a year or two. I was interested in doing something about the Zeeman business which hadn't broken yet really.

Sullivan: 24:32

You mean the [inaudible] at Green Bank.

Radhakrishnan: 24:33

Yeah, but I got interested in other things and delayed building a feed and so on. So nothing ever really came of it. The antenna group did succeed in producing a very, very fancy feed, which I think is perhaps the best one in the world for that sort of thing. And we did publish one paper on it. And this was very, very recent. It was a lot after--

Sullivan: 25:04

On the feed-

Radhakrishnan: 25:05

No, I mean one Zeeman measurement on Orion.

Sullivan: 25:10

Oh, yes, that's right. In Astrophysical Letters.

Radhakrishnan: 25:12

Yeah, I just thought the synthetic profile and all was something. But that was after the fact. But I was mostly interested in-- well, I was playing around with hydrogen line absorption. I started playing around with it. And then I was interested in line interferometry. So I thought it's time to do OH interferometry because it had never been done before. So I went through hell getting that interferometer to work on OH. At that time, it didn't have a--

Sullivan: 25:47

Which interferometer? The 60 foot

Radhakrishnan: 25:49

The Parkes interferometer.

Sullivan: 25:50

210, but that was already there when you got there.

Radhakrishnan: 25:52

Right. It just managed to--

Sullivan: 25:55

Who was the guiding force behind getting that--

Radhakrishnan: 25:56

Oh, John Bolton.

Sullivan: 25:58

[inaudible] interferometer [inaudible].

Radhakrishnan: 25:59

Oh, a number of people that did various bits but he was the one who wanted it. The first major use of that instrument was Ron Eker's thesis.  [inaudible] used very clever method of using two frequencies, one of which is three times the other. And the ratio of the maximum to minimum baselines was three to one. And so they had fringes on two frequencies, and they could use the lower frequency fringe to give them a phrase reference for the higher frequency because the high frequency would get resolved for the lower frequency. It was really clever way of getting-- it was also the first interferometer where you could actually make measurements with one telescope charging down the railroad track.

Sullivan: 26:50

Well, it's actually moving that way, yeah.

Radhakrishnan: 26:51

Oh, yeah. All of those measurements were made in the telescope moving. So it was a very interesting instrument, but I wanted to use it for line work. And I sort of put it together here where I started the line observations and eventually W49, OH and different polarizations and so on. And by the time I had the machine put together and started making observations, they were suspended behind.

Sullivan: 27:27

[inaudible]?

Radhakrishnan: 27:28

Right, [Cuddeback?] and so on from Caltech. But he looked at--

Sullivan: 27:34

So you never published--

Radhakrishnan: 27:34

Oh, yes, it was published, but it's no big--

Sullivan: 27:37

Where was this published?

Radhakrishnan: 27:38

In Australian--

Sullivan: 27:41

On W49 OH interferometer positions?

Radhakrishnan: 27:44

Not positions, it was just showing the sizes of the two blow-ups and something with the polarization. But it wasn't a complete study. It was a way for [inaudible]. Then I spent a long time looking for the OH in Magellanic Clouds. There is another minor paper there.

Sullivan: 28:02

Right, I’m familiar with that one.

Radhakrishnan: 28:05

Then I [inaudible] interested in really doing this line stuff seriously. Why don't you turn it off for a moment. Now, I want to make one remark about this Magellanic paper on the unsuccessful search of OH in the Magellanic Clouds. You really make a great [inaudible], don't mention this. I mean, if you want because it's a trivial thing. But there's something that's interesting about it. I'm sort of ashamed about having published that paper because it's one of the few papers that I've written when I've found nothing. Now, you could actually argue and say that it's very important that you announce that you didn't succeed in doing something so other people won't waste their time looking for the same sort of thing. Everybody has his own pet aversions and so on, and one of mine is that the kind of impressions with people who publish negative results. And it's hard for you to appreciate the number of-- you ask me what I’ve been doing. I said that most of the time that I've achieved nothing, therefore I don't publish [inaudible]. But I spent an awful lot of time looking for things which I haven't found and which I could never bring myself to write a paper [inaudible]--

Sullivan: 29:39

And you don't try to safe things either. I mean, you try something new.

Radhakrishnan: 29:42

No, for example you see, you asked what I was doing. I spend an awful lot of time looking for H II+ in Australia. For example, there was this business about the-- remember the first non-thermal—there were a couple of sources in which non-thermal OH emission was detected and found-- I mean, anomalous OH emissions detected in front of non-thermal sources, W28 and W44. I think [inaudible] did one and somebody else had done another, which immediately prompted the question-- this was years ago—in my mind as to whether this was an amplification of the signal from the continuum source behind or what is-- and so on. Because I always have kicked around the connection with the OH II regions where it hadn't yet been shown that the [OH emission regions?] were actually, had been removed from the H II centers and-

Sullivan: 00:02

OK, this is continuing with Radhakrishnan on 28th March '72. First part of this-- or the last part of this interview is on 11B. The first part is on 12A and 12B. This is 13A.  That sounds confusing.  Because it is. [laughter].

Sullivan: 00:20

Okay. Now, are you working on looking for OH emission, but with any continuum sources background?

Radhakrishnan: 00:26

No. No. Yeah, as I was saying, the detection of OH emission in the direction of two non-thermal sources, two [inaudible] [W38 and W40?], raised the question as to whether these sources merely provided physical conditions in their neighborhood to provide the same kind of OH emission as you found close to each of the regions, or whether they were providing a continuum radiation, which is a single input to the masers that existed everywhere, waiting, so to speak.

Sullivan: 01:05

Now it’s whether the input or the pump that was a limiting condition to seeing--

Radhakrishnan: 01:08

Exactly. And so the experiment that I did was to look in the direction of the number of extragalactic sources at galactic frequencies, sources like 273, M87. [inaudible] it is [353?] and all the rest, just to see if there was any OH emission. Obviously, OH emission [inaudible] sources. But there were some that would've shown that you had regions which were pumped, but which needed an external stimulus. And needless to say, the result was [inaudible] because it needed be published.

Sullivan: 01:47

And you also looked for H II+?

Radhakrishnan: 01:50

H II+. Yeah. That was-- these two separate sessions trying to do that.

Sullivan: 01:59

Line at around 1400 megahertz?

Radhakrishnan: 02:01

There are several lines with different probabilities. They're all in the neighborhood of the hydrogen line and frequencies, somewhat less, I think, [1440, 49?] [inaudible]. And so different probabilities. Look, two of the last probable ones in the direction of number of continuum sources. I was really looking for the [beam?] absorption.

Sullivan: 02:34

Well, that brings us to your hydrogen absorption study.

Radhakrishnan: 02:41

Well, hydrogen, all of the hydrogen absorption work has been [broken?] up [inaudible] that's actually in this ApJ Supplement [inaudible]. And number one deals with development of the instrument which really took a long time. It took a long time to think how to do it, and the instrument is described and so on in paper number one. Paper number two deals with the observations that were specifically designed to establish or to disprove. They took a long time [inaudible] long time. And it's interesting that in the two or three years prior to--in the last three or four years, we might say, from '68 and '69 and so on, more and more people had started talking about, [inaudible] time. It almost became something fashionable to assume, but it was never really, properly, demonstrated. And I think there's very little doubt that Clark's work [inaudible]. Then there was a lot of connected work on galactic sources, which helped establish distances and so on, other ways to describe it was [inaudible]. I've already [inaudible].

Sullivan: 04:16

Right. No, no. And we haven't covered your pulsar? How did you get off on the pulsar kick?

Radhakrishnan: 04:31

Oh, I didn't really get onto it. In fact, I was rather against doing anything on pulsars, simply because, another pet aversion of mine, and I call it the bandwagon syndrome. I know [inaudible]. And when pulsars came out, Parkes, as usual, we were always ready to get in second in a big way, very apt to get into the pulsar game.  And looking out for people to do it, it was suggested that I should really tackle this problem because it's very important. I said I [wasn’t interested because? inaudible] I thought it was [inaudible] any number of people I could name [inaudible] spend all their time doing this sort of thing. But it turns out I ended up at Parkes, it might have actually been during some other session, but very shortly after the pulsar [inaudible] [was discovered?]. And I think we were really just trying to look at this pulsar. It's almost an interesting story even if [inaudible]. And so we just wanted to look at this pulsar. Because the way to do it, which is now a pretty standard way, it would be to put some [inaudible] frequency. [inaudible] afterwards.

Radhakrishnan: 06:15

We had a [inaudible] this was triggered off with a single generator and sort of set the right frequency. And we thought the pulsar would just sit there and integrate and we could look at it. Then the pulsar kept moving. So almost as if [inaudible] would always do this for me as you will appreciate when I finish the rest of the story. Now, this annoyed me because I wanted to see where the-- I wanted to see what the pulse shape looked like. So I'm just [inaudible] out of curiosity. And no matter how we twiddle this, this goddamn oscillator, we couldn't get the pulsar to sort of stay where it should be. It kept drifting. So at that time we had just been setting up frequency very roughly, although Cambridge published the [inaudible] or something like that. So we said we better do this carefully. if we want to [inaudible] set it up [inaudible]. So we better take location of the Earth [inaudible] so we ran this frequency on the program, calculating line breaks and see if this is all accurate [inaudible] and the damn pulsar just kept drifting. And this point we were really interested in [inaudible]. I just couldn't understand why it wouldn't stay still.

Radhakrishnan: 07:48

Looking backwards, I think the frequency we put in on the [inaudible] was drifting and so on. It was clear the pulsar frequency, the pulsar seemed to have a frequency [different from what was?] published. But the difference wasn't in the seventh place there was something off. About a 1000 times-- the error was a thousand times the accuracy of the published measurements. And this really intrigued me. And I wait, and I wait, and I wait. It was something like 1 part in in 61,000 [inaudible]. And I just slipped into laying the [inaudible] and I had to find out how. And then it occurred to me that I was looking for all sorts of crazy and unlikely [inaudible]. It occurred to me that the error-- the difference between the apparent theory that we had and the very precise paper that Cambridge had published. The difference was something like 1 [inaudible] in 64,000 and 60 per thousand etc., etc., something in the hundreds, was precisely the number of pulses per day. So I said, "How could this be?" And then it suddenly occurred to me that Cambridge had missed one pulse per day. And I thought, “How could this happen?” [So I put my hat on and?] thought about the way that they did their measurements, because they could only see the pulsar four minutes a day with their kind of instrument.

Radhakrishnan: 09:26

So you could never get the period by looking at the pulsar over one day. You have to look at several days and more days you look at-- the more set of--

Sullivan: 09:33

[inaudible]

Radhakrishnan: 09:34

--eliminate. And they've done everything right, but they’d actually missed one pulse per day.

Sullivan: 09:40

Interesting.

Radhakrishnan: 09:41

So there's a paper that was published [inaudible] counted one wrong. But it was also very important, it appeared important at that time because everybody and his grandmother was planning [inaudible] and they all integrated using the [inaudible] period.

Sullivan: 10:06

Everybody went back.

Radhakrishnan: 10:08

Yeah [inaudible], and so on.

Sullivan: 10:13

This was verified. Your [theory?] was correct.

Radhakrishnan: 10:16

Somebody actually had the bloody nerve to say that these [inaudible] public way. And he's just lucky that I didn't [laughter], right? Tell him where he can take his confirmation. Not only did we [inaudible] but appeared that we explained precisely why it was different. Well we also published the [inaudible]. Anyway, that was the first thing. [inaudible] next time [inaudible] I went to help Max who was doing some [inaudible].

Sullivan: 10:50

Maxwell?

Radhakrishnan: 10:51

Max [inaudible]. And he was going to look a whole [inaudible] and he hadn't found any. And I was looking at the [inaudible]. And I was trying to keep this thing still because it looked like the-- I wanted to see what the polarization looks like. And so I did the same thing. You calculate the period. You set it up and you allow for the rotation of the Earth and so on. [inaudible] sit still and then I looked at the [inaudible]. Again it wasn't quite still and [inaudible] then. It seemed to be all wrong. And so another big investigation provided that [inaudible] stand still [inaudible] because the period of the pulsar was changing.

Sullivan: 11:38

You didn't know about any secular changes or--

Radhakrishnan: 11:40

As for the second pulsar it was found to change its period, [Crab thing had just been published?].

Sullivan: 11:45

All right. So did you know there was one that had a secular change.

Radhakrishnan: 11:49

Right.

Sullivan: 11:53

That was--

Radhakrishnan: 11:54

This was the second pulsar now.

Sullivan: 11:56

Right, therefore the second [inaudible] had changed. I was trying to think--

Radhakrishnan: 12:01

Yeah, just beginning a pattern on the [inaudible]. That time had stopped [inaudible] I was I mean, the Crab pulsar was so fantastic, one didn't think of [that almost?].

Sullivan: 12:09

Yeah. I'm trying to think. Who established the Crab change. Was it--?

Radhakrishnan: 12:14

Arecibo.

Sullivan: 12:15

Arecibo?

Radhakrishnan: 12:16

Yes.

Sullivan: 12:17

Oh, yes. [inaudible].

Radhakrishnan: 12:18

Oh, yeah. [inaudible]. So anyway, [inaudible] changed the period. And that was published in the paper and according to that paper it was really not the period change of pulsars. But it really had to do with [inaudible] wrote this paper [inaudible]. That is the paper that established the rotation of [inaudible] pulsar, it showed that you had a repeating pattern of polarization which-- no matter what the polarization is due to, it must be tied up to the magnetic field in some way. The magnetic field actually affects the pulsar in some way. And the only way that you could get the same pattern repeating, despite the fact that every body in the universe rotates, it was only that the pulse that would [line? tie?] up with a certain longitude. There was no other explanation for that. The logic is irrevocable. So that paper, and we had the further fact that the period change-- if the whole polarization was to change in a period and so on.

Sullivan: 13:33

Do you have an oblique magnetic field [model?] on that?

Radhakrishnan: 13:35

Oh, yeah. Oh, yeah. You see it was only suggested-- it was more or less clearly established that it had to be rotating on [inaudible] pulsar. And then I felt that I had to really [show?] to prove that the change in the position [of the polarization?] was not yet [inaudible] rotation of any kind. For example, even if you had a rotating object, then you had a plasma cloud, for example, that was going around with it, and then as the thing rotated, you would look through different lengths and see different fields and therefore the Faraday rotation would be different and therefore you would get rotation and polarization. So you had to separate the Faraday and any intrinsic change in the polarization. And I feel the only way you can do this was to look at the [inaudible] frequency and see if the rotation is the same [for all angles?]. At that time, I went to [Molonglo?]. By this time, I had [inaudible] experience in getting processes to stop, so I could look at them. I had this thing all set up and I went to [inaudible]. There was no way I could get this thing to stop. I spent a whole week just trying to [inaudible]. And I decided-- you must remember until something is found and published and established, and you see something very new, [inaudible]--

Sullivan: 15:10

Right. Oh, you don't know what the hell is going on.

Radhakrishnan: 15:12

Yeah. But I came to the conclusion that the pulsar had suddenly changed its period. And I said, "How could this be?" And I came to the conclusion that the only way this could happen was if the radius had changed in some way. And I remember Fred Hoyle was there, and I told him this, and I said, and this is the [inaudible] part now, [inaudible] [mine was?] 45 degrees. No one else had any equipment anywhere [inaudible]. And I know [inaudible] change [inaudible] neutron stars and so on [inaudible] and work on this [inaudible] Hoyle got a telegram saying that the [JPL people?] those telephone cords [inaudible] had also observed this because they were able to go right down to the horizon with their 85-foot dish. Amazing. So we had to publish the paper. So I took back [inaudible].

Sullivan: 16:22

That was a very [inaudible].

Radhakrishnan: 16:23

Yeah. [inaudible] for the prediction of the change of state of the pulsar. Because--

Sullivan: 16:32

Did [inaudible]?

Radhakrishnan: 16:34

And [inaudible]. Two papers came together. [laughter] And [inaudible].

Sullivan: 16:37

[inaudible], doesn't it?

Radhakrishnan: 16:39

No, no, no. [inaudible].

Sullivan: 16:40

Did they also propose a change in--?

Radhakrishnan: 16:45

Some such thing [inaudible].

Sullivan: 16:47

[inaudible]?

Radhakrishnan: 16:48

Yeah, I was really-- I remember the discussions I had with Fred where I was trying to show him [inaudible], that it couldn't be due to a satellite. The thing was going in an elliptical orbit, so I was trying to [inaudible] was going around. It couldn't possibly be, that it has to be something absolutely [inaudible] because there were two straight lines. It was clear from our data. [inaudible] we came down to [inaudible], they had this thing that was something like two orders of magnitude. And I had the personal satisfaction of having going through all this [inaudible].

Sullivan: 17:27

So three times [crosstalk] did not stop you.

Radhakrishnan: 17:29

Yeah. But anyway--

Sullivan: 17:31

[inaudible].

Radhakrishnan: 17:33

Yeah. But the thing is, at that time, after having sorted this out, I then looked at the total frequency, and showed that independent frequencies, every observation were the same for every part of the [inaudible], see? Even after the period change and so on. And that paper, which was in Astrophysical Letters [inaudible] magnetic pole [inaudible] and so on. In a sense, it was [inaudible]. I don't know if you've ever been to [inaudible], but if you want to get the history of that straight, I would work out actually everywhere else on both of them from 1969 to today. I won't review as [inaudible] review talk somewhere. The first time I really sat down and worked is the Physical Review paper, which takes up absolutely everything else. Everything I've done.

Sullivan: 18:47

The first year?

Radhakrishnan: 18:48

Yeah. The first 15 months. And everything that's been done since.

Sullivan: 18:53

[inaudible] paper. Yeah.

Radhakrishnan: 18:54

Yeah. [inaudible]. 90% of what's known, they had already been [inaudible].

Sullivan: 19:01

Oh, I see what you mean. Where was this paper done?

Radhakrishnan: 19:04

That was in the Australian [Astronomical Society?]

Sullivan: 19:13

Do you want to on the tape, or would you rather not, say something about the business about the Parkes and never quite reaching its potential?

Radhakrishnan: 19:27

I'd rather not. I feel very strongly about it, but I'd rather not.

Sullivan: 19:34

Okay. Is there anything at Meudon that--? You were hired to look into problems in the millimeter interferometer.

Radhakrishnan: 19:48

Yeah. The only thing I came up with was to suggest that they use redundancy to get to the [inaudible]. It's hardly a contribution. The idea was to [inaudible] in '58, and then [inaudible] five years ago. It could be [inaudible] radio astronomer.

Sullivan: 20:17

Yeah. Well, the final thing I'd like to ask you about is the Raman Institute. You left Australia, and you could've worked just about anywhere, and you came and worked here, I think, and stayed in "mainstream" radio astronomy. But now you're going back to India, and what do you hope to do there? Is it regarding radio astronomy necessarily or--?

Radhakrishnan: 20:53

No. No. [inaudible] radio astronomy. Then I didn't really-- lots of radio astronomy [inaudible] are very different. A very special instrument developed in the next few years. You could just as well--

Sullivan: 21:17

[crosstalk]--

Radhakrishnan: 21:18

You could just as well [inaudible].

Sullivan: 21:19

Your main requirement is that you [inaudible] a novel technique or an entirely new approach to some problem in physics in a broader sense.

Radhakrishnan: 21:28

Something like that. It's [inaudible] my reasons for doing anything are very similar to my reasons for joining the [inaudible] laboratory. I can't spend the rest of my life going around doing radio astronomy every time that we [inaudible]. I mean, there's no point in just extrapolating this [inaudible].

Sullivan: 21:53

Yeah. Yeah. No, I know [inaudible].

Radhakrishnan: 21:59

It's not that it's been unsuccessful. I'm not about to lose my job. I'm not about to [inaudible]. There must be more to life. I mean, I want a bigger challenge. I mean, I want bigger rewards, and you can't get that unless you accept the bigger challenges. Even in Australia, it's more-- even if you fail, there's more satisfaction in-- it's better to have loved and lost than never to have--

Sullivan: 22:28

Right, exactly. And you never know unless you try. Well, thank you very much for all the time you spent.

Radhakrishnan: 22:36

My pleasure.

Sullivan: 22:40

That ends the interview with Radhakrishnan on 28th March, 1972.