Interview with Charles H. Townes on 23 September 1981
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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.
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Transcribed by TranscribeMe (2018), reviewed and corrected by Ellen N. Bouton (2020)
Begin Tape 156B
Sullivan
So this is talking with Charles Townes on 23rd September, 1981 at Berkley, about aspects of his career in radio. We touched on radio astronomy before the early 1960's. You got your degree in physics, I would assume. Is that correct?
Townes
Yes, that's correct.
Sullivan
Can you tell me where and when?
Townes
Yes, I got my degree at Caltech and finished in 1939.
Sullivan
And were you already involved in microwaves spectroscopy -
Townes
No, no. I wasn't at all. I did some work on separation of isotopes and then the spectroscopic measurement of their spins, the spectroscopy in the visible region. So I was involved in spectroscopy, but not in microwaves at all. I went from there to Bell Telephone Laboratories, initially working in some sort of surface phenomenon and electron tube phenomenon. Then the war came along and I was very quickly assigned the job of developing radar bombing systems, and through that got interested in -
Sullivan
In radio techniques.
Townes
- experience in radar.
Sullivan
I see. Now when was the first time you can remember hearing about radio astronomy?
Townes
Well, the first time I heard about radio astronomy, it wasn't a hearing. It was a reading. It was back in my undergraduate days-- I have an undergraduate at Furman University from 1931 to 1935. And I remember reading in some book, physics book, which had a few of sort of the latest discoveries. I remember reading of Jansky's discovery of radio waves coming in from outer space. And it was common in that nobody had any explanation for these, so I was quite fascinated by that, so it stuck in my mind a long time. I've seen tried to figure out just what book that was and I haven't located it. So I remember -
Sullivan
I don't know of any mention of it.
Townes
I remember the words very well, and I remember reading about it, and I was -
Sullivan
An undergraduate physics text book?
Townes
Yes. That's right.
Sullivan
Interesting.
Townes
And to me it was very exciting to hear something, read something about that, and furthermore it wasn't explained at the time. Nobody understood it, and so during World War II, I was doing a lot of, basically engineering work - engineering design systems, the design testing of the radar bomb sites and airplanes - and we had long periods when the airplane wouldn't fly or something like this. I wanted to do pure science in the long run and I didn't mind doing engineering during the war because I felt that was important, appropriate. I decided the time between breakdowns of the airplane and times when we couldn't fly, I tried to do something, pick up some problem in physics and work on it. And so this work of Jansky’s occurred to me, and I thought that's not yet understood, I'll see if I can figure out what can possibly be causing that radiation.
Sullivan
But now it occurred to you from reading 10 years before?
Townes
That's correct.
Sullivan
Not because you were at Bell Labs -
Townes
No.
Sullivan
- and you talked to anybody there.
Townes
No, no it occurred to me from reading before. And I suppose also because I was doing radar work at the time and hence dealing with radio waves. I had done a good deal of work on generation of radio waves also. Early days of Bell Telephone Laboratories I invented several different ways of producing microwaves and so on, and so it was an area that was familiar to me, but it wasn't because of anybody particularly at Bell Telephone Laboratories. It was just something that I realized that seemed to me a fascinating problem and not understood and it'd be a good thing to think about.
Sullivan
When you came up with the idea, did you know about Reber's measurements?
Townes
Let me see. No, I didn't know about Reber's measurements at that time, no. And I was in the field mostly down in Florida testing from an Air Force base down in Florida. I am not -
Sullivan
What year is this? Is this -
Townes
I am not entirely - Well, let me see. I'm not entirely sure did I know about Reber's work. I don't think so. I think when I came back to Bell Laboratories and started talking with people about it, particularly people down in Holmdel, Southworth, and others, I think they mentioned Reber's work. And then I immediately looked it up and got in touch with Reber. And I think that's how it came about but I'm not certain.
Sullivan
Well, now, what year is this we're talking about roughly?
Townes
Well, this would have been about 1943 or 4, probably yeah, probably 43 or 4. It was during the war that I worked this out. War finished in '45. I had written it. I had written it all down, worked it out, and talked to my colleagues about it and so on and so (?). So while -
Sullivan
Even before the end of the war, you had pretty much what turned out to be this paper in ApJ in '47?
Townes
That's right.
Sullivan
I see.
Townes
That's right. And you probably realize that the people who were doing the work at that time were engineers primarily. They were good engineers and they understood a good deal of physics but nevertheless, they weren't oriented in the same way that I was. And for that reason, I looked over the paper. Southworth had been making measurements on the sun and on other things, and that was very exciting, too. And so I read all of his papers and -
Sullivan
Did you know about Hey's discovery which was circulating as a secret report during the war?
Townes
06:03 Hayes? No, not -
Sullivan
Well, J.S. Hey was the one who [crosstalk].
Townes
Oh, Hey.
Sullivan
- first detected the burst radiation at VHF in England in '42 actually.
Townes
I think I did. Yeah, I think I did. I remember knowing about Hey's work fairly early in the game but exactly when I learned about it first I don't know. But on the other hand, people like Southworth must have known about it.
Sullivan
I would think they would, yeah.
Townes
And I talked with Southworth every once in a while. I visited down at Holmdel not infrequently, anyhow, because of my radar work. And I would see Southworth down there and talk to him about it and -
Sullivan
And Jansky, I mean, he was there still at that time at Southworth.
Townes
Yes, yeah. Jansky was not terribly active really in the radar region. He was I think still involved in somewhat longer waves and maybe receivers or something and I've forgotten exactly what he was doing.
Sullivan
I think that's right. He was working in nature of noise and interference at low frequencies.
Townes
Right, right. So his work and mine didn't really cross paths very much. But Holmdel was a small place in those days. And so you would see everybody there and I'd see Jansky around and (?) and I, and I talked with him casually about these things and was very pleased in knowing this as he had made this very important discovery. But he was a quiet person and off on another field and he was glad to talk about what he had done and everything, but he was not a gregarious type. And where Southworth was still very active in the field and in microwaves and I had to see him for other reasons anyhow having to do with radar and so on. So I interacted with him a little bit more. And Reber, the papers I had just read. Although, I met Reber a few times, I think perhaps at meetings only.
Sullivan
So it must have been after the war, probably.
Townes
Yeah, after the war.
Sullivan
We just found some correspondence that you had with him.
Townes
Yeah, right. Yeah. And now, what did I say? These people are primarily engineers, but some of the physics was not all that clear to them, and that also made it clear to me that maybe I could contribute something there. And so I worked on various problems, and I think in particular, the interpretation, for both Reber and Southworth, interpretation, in terms of actual temperatures and radiation effects, was not quite correct.
Sullivan
Right. Well, you came across this just plain error in Southworth's, a factor of four or something.
Townes
Yeah, yeah, yeah, right.
Sullivan
I guess as soon as you began working on that.
Townes
Yeah, that's right. And some of Reber's interpretations of how to express this in terms of blackbody radiation and so on, were not quite correct. I don't know, I'd forgotten what -
Sullivan
Well, I'd be interested in your opinion as to - in Reber's ‘39, his first publication in the standard literature, of the fact that he had a dish and he made some measurements at 160 megahertz. He brings up free-free radiation as a reasonable mechanism and goes through some numbers, which one can find errors in, and I think, in particular, he forgot about the Gaunt Factor entirely, in the equations. But I'd be interested in your opinion as to Reber's insight, as to what might be going on out there. Was this just a lucky guess to your impression or do you think -
Townes
I suppose - Reber was very intuitive, and he had ways of describing a radiation mirror. You read his papers, you know they're very poetic in a sense. He talked about the great rushing of noise and all this he's talking. That's the way he went about things. He was not quantitative, really and mathematical. And I don't know. I don't remember that particular reference to free-free radiation. I'm sure I read it at some point, but I don't remember it now, so I can't really comment on it much. Anyhow, he was an intuitive guy who had lots of ideas and some right, some wrong, and he's very creative. And there were, in fact, after I started working on this and, more or less, worked it out. Then I began to find more and more, several places where people had worked on this and had somewhat similar ideas, but they just hadn't really done it quite right. And -
Sullivan
Right, right. Henyey and Keenan do you mean? 1940s.
Townes
I had in fact, I had it all worked out and I presented it, as I talked to my friends at the laboratories, and I think I probably gave a talk or two on it then. So one of my friends at Bell Laboratories I believe mentioned, I think it was - came up this way - one of my friends mentioned the Dutch physicist’s work [crosstalk]. No, no, no. No, the x-ray -
Sullivan
Oh, Kramer's?
Townes
Yes, Kramer's. Kramer's x-ray paper. And said, "Well, you know that sounds kind of similar to the Kramer's x-ray."
Sullivan
That's why this reference came from -
Townes
Yeah, that's right, so I had it all worked out, and then once I saw Kramer's work, well I cut down my own development.
Sullivan
Oh, I see. So you had done it completely independently of [crosstalk].
Townes
That's right. I did it completely independently. When I saw Kramer's work, well I just sliced out a lot of my own development and instead referred to that. Because while it was a completely different wavelength region – completely different wavelength region, and the parameters were all different and so on, the theory was basically similar. And so I just referred to that. But then there were other papers, now Henyey and Keenan. It seems to me there were two papers, I believe Henyey’s trying to do a quantum mechanic development of it.
Sullivan
They extended the theory from the optical, which was quite familiar to them, to the radio.
Townes
Yeah, yeah. And in doing that, they – in doing that, they didn't do it quite right. So they came up with something which involved Planck's constant. And what clearly, I had recognized, had to be a classical thing. And Planck's constant couldn't possibly enter in. There was another development, I'm not sure now, just to (?).
Sullivan
There's no other reference. I was just looking at what you referred to here as far theoretical development. Now, it turns out that during the war, Henk van der Hulst did work out completely this sort of Henyey and Keenan and sort of thing but you wouldn't have known about that.
Townes
No, I didn't know about that.
Sullivan
It wasn't published until after the war and then only in Dutch.
Townes
There was something else. I think maybe – I think maybe Menzel had worked out something which he showed to me privately.
Sullivan
Well, and then we just saw some correspondence with Menzel here, so that might have been what you’re thinking of.
Townes
Yeah, there's something either Menzel or Whipple. I talked with Menzel.
Sullivan
Oh, there's a Whipple and Greenstein paper that was in '37.
Townes
Oh, that's probably what it was.
Sullivan
Trying to explain Jansky's results as hot dust.
Townes
Yes, well -
Sullivan
And they said it just can't be that hot when they worked out in essence (?)
Townes
No, it wasn't that. It was some other free-free approximation.
Sullivan
Free-free? I see.
Townes
I think, yeah. I believe it might have been just an informal calculation that Menzel, Whipple, one or the other had done.
Sullivan
Anyway, you found out that -
Townes
And anyhow, I found other people working on it, but nobody had really done it quite right. Now it happens that Henyey’s result numerically isn't all that far off.
Sullivan
That's right.
Townes
All that far off somewhat by accident. And when I wrote the paper, you'll see in this (?), when I wrote the paper, I carefully made the same development, kind of development that Henyey did and pointed out just where the error was, pointed out that this really had to be classical and this was exactly where the error was, and to show that his initial approach itself wasn't wrong. It’s just that if he did right, it came out the same answer that I had, you see.
Sullivan
Yeah.
Townes
That at least, I don't know, you know how the papers get reviewed. I don't know who reviewed this. But anyhow, it came back saying that nobody's interested in proving that quantum mechanics and classical mechanics can't agree, and all of this should be cut out. Well, I didn't think I was trying to prove that. I thought I was trying to show where the earlier calculation had gone wrong, and that if in fact, if you do it that way, it's perfectly all right, you see. But because of the (?), oh okay, cut out a lot of that, demonstrating exactly what the error is in Henyey’s type of calculation. And so as I first tried to figure it out, more or less out of an issue, and then I began to find, which is typically the case. You find that other have done somewhat similar things along the route. I talked with Menzel and Menzel felt that while they really understood that, the problem and the (?) and he showed me some calculations. But again, it was a very broad kind of approximation as I remember, and then he did the (?).
Sullivan
That's interesting. I never heard about Menzel doing anything at that stage.
Townes
Well, it was either Menzel or Whipple. And I know he called in Whipple and said, “You know we know about this, don't we,” and -
Sullivan
“Tell me we do, Fred!”
Townes
And I looked at the material and decided that well, it really was not quite the real thing and I ought to go ahead and publish.
Sullivan
Well, you touched on a couple of things I'd like to ask about. First of all, you haven't mentioned Harald Friis who presumably you were seeing when you worked at Holmdel also.
Townes
Yes, once in a while.
Sullivan
And I wondered if you - having been around Bell Labs at that time - had any opinion on a controversy in essence that has developed as to whether Jansky was suppressed by Friis in some sense, that Jansky really wanted to continue following up on his radio astronomy and Friis kept putting him on very practical matters. Do you have any information?
Townes
I have no direct information. I knew Friis quite well. He's perfectly capable of doing that I would say. He was an engineer who kept his eye on the ball. He was a very good engineer. But he ran the group, and let me say that doesn't seem out of character to me, but I have no direct information.
Sullivan
Yeah, and it is true. I mean I have many other bits of evidence about Jansky's character as you've already indicated being rather retiring.
Townes
Yeah, yeah.
Sullivan
A very forceful personality.
Townes
A very, very modest person who just, you know, he was interested in things and he kept plugging along but he didn't push himself.
Sullivan
Right. Did you ever see any of Southworth's equipment that he used for solar observations, or see him observing, or anything like that?
Townes
I don't think I ever saw him observing, but I certainly saw his equipment, sure. Yeah, I saw his equipment. I talked to him about it. And I knew Southworth. I met Southworth before the war because I was doing some microwave things when I first came there. And I met Southworth before the war, so I was away for long periods of time. But otherwise, in reasonably good contact with a group of people. But Jansky was sort of retiring that, you didn't see him unless you sort of looked him up.
Sullivan
You had to seek him out. I see, yeah.
Townes
Or you'd see him in passing but he was just very quiet.
Sullivan
Well, if I could ask you just a couple of specific questions in this paper. First of all, I'm surprised that you were able to get an agreement with the free-free theory given the six or seven data points at different frequencies that you had. Albeit with a very high temperature, 150,000 Kelvins. But I was somewhat surprised that still the spectrum, spectral shape worked out because shortly thereafter, it wasn't working out very well. And I haven't had a chance to go back and see. It must have been some assumption. I mean that it's a lot of discussion and it was a very tricky thing and I've tried to do this myself.
End Tape 156B
Begin Tape 157A
Sullivan
Charles Townes on 23rd September 1981. Why do you think you came out with this current agreement to a single temperature?
Townes
Well, basically, the points were very few and the pointing and the beams were very - crossbeams.
Sullivan
Yes.
Townes
So that the temperatures were not real temperatures. Not the intensities were not real, that's the intensity of any one object. You asked about the calibration. I think the calibrations were pretty much right. I – some of the very long wave stuff Jansky gave me, he gave out what he thought was the right calibration. I would say he seemed to be a very careful person. I think he was probably right.
Sullivan
Now, you didn't use, I was going to ask you about that also – you didn't use anything except Jansky's 18 megahertz stuff. Were you referring, when you say very long wavelengths equal to the lower frequencies?
Townes
I guess it was the 18 megahertz, let me see.
Sullivan
Because in his 1937 paper I think he does refer to some nine megahertz measurements but –
Townes
Well, this is I – whatever he gave me is in here, and so I guess it must have been the 18 megahertz. I do – see, I haven't read this in a long time. Did you see any mention of any other?
Sullivan
No. No. That's the only Jansky.
Townes
Okay, well that's – let me see. Let's see now. [long pause]
Sullivan
It may be that you tried to work some of it out and you finally gave up on –
Townes
No, I put in all the data that seemed available at that time.
Sullivan
Uh-huh.
Townes
I put in all the data that seemed to be -
Sullivan
But for instance, I know one problem with that lower frequency stuff was he took it in '37 at about sunspot maximum, and there was tremendous absorption problems. And it may have been that he just felt that it was just too unreliable.
Townes
I don't remember that. I don't remember. I think I put in everything that was, everything that Jansky – it may have been he ruled it out for some reason, and didn't give it to me. He may have ruled it out and didn't even provide, I think I put in everything that he had. Now, these temperatures, well, so you've got, you see you've got two parameters, you've got temperature, and you've got density. And they do turn out to be fairly good. If they're going to fit the higher frequency then the densities have to be somewhere there, right? And so far as temperature’s concerned, the internal temperature has turned out to be wrong but (?) synchrotron radiation (?).
Sullivan
Well, of course, we probably in retrospect –
Townes
But it fitted fairly plausibly, and also we knew a fair amount about the density of the material. I didn't know very much about the temperature. It was moderate information about density of interstellar lines, and so it looked fairly convincing to me. But of course these beams were very coarse compared to the size of any real sources of things.
Sullivan
Right. They were getting different averages with the (black?) (?).
Townes
That's right. And it was clear from some of Reber’s and Hey's work that they were not uniform at the same time we didn't know how non-uniform. And that fit in with this outfit.
Sullivan
Well, another question I had was why the delay in this? It was sent in in late ‘46 and apparently you had it worked out already in ‘44.
Townes
Yeah. Well, I guess that's the way I do things. I just won't rush them in, and I was busy with the war for – I was doing this at nights in spare time –
Sullivan
This was a side project?
Townes
Yeah, that's right. It was not what I was supposed to be doing. I was just doing it at night in spare time, and then I was taking my time because I didn't seem to be, nobody else in the field at the time. Nobody else working, hey, there's no rush. And, furthermore, see, I was a young man and never published in this journal before, and I think the referees were really very difficult.
Sullivan
It's too bad we don't seem to have correspondence on that in your file, here.
Townes
Well, I think there is some correspondence from Greenstein. Yeah, (?) find some correspondence [crosstalk].
Sullivan
Oh, was it – I didn't actually – as a referee on this –
Townes
Well, I don't think he sent me the referee's comments directly. He sent me his own conclusions on it, you see.
Sullivan
I see.
Townes
And so I had to revise it, and then I guess, I also I revised it when I found Kramer's work. I had written it all up and found Kramer's work, so I revised it all.
Sullivan
That's – I might say that's a typical example of why the published record is not a very good indication of what actually happened.
Townes
Yes.
Sullivan
That's the trouble with ideas. I mean, sort of, prewritten like, "Oh, for sure, you knew Kramer's paper all along and started there." And –
Townes
Yeah, yeah. No, and then I sent it into the general, well, because I wasn't an astronomer, and I'm sure some of the kinds of verbiage that I used and descriptions and ideas were rather different from –
Sullivan
Well, this is very nonstandard in any case, even if you had been an astronomer.
Townes
Yeah, and I think they were suspicious of the whole thing. In fact, you know that field was in not very good review in astronomy.
Sullivan
And why do you say that?
Townes
Well, it just wasn't well thought of by astronomers as being anything very important to astronomy. It was in, probably, 1946, for example, that I came out to the West Coast, I guess, to a meeting or something. And I stopped in to see Bowen who was then running Palomar, Ike Bowen. He had been an old teacher of mine. A very good, very favorite teacher of mine and very kind to me. And I had been to his house a number of times. I knew him very well; I thought very highly of Bowen. And I told him that I was interested in this kind of work and the Bell Telephone Laboratories was a tremendous resource in the field, and there I was at Bell Telephone Laboratories, and I told him I'd done this analysis, and I was thinking of, maybe, going further into radio astronomy and would like his suggestions of what kinds of thing he felt was most important. There he was an important astronomer – what really should one be doing. Well, Bowen told me very frankly, he said, “Well, I just don't think that's ever going to contribute anything to astronomy. I really don't see anything that it can do, that'll be useful, and it's just too coarse of an instrument. So it's never, really, going to tell us anything that we don't know from other sources.” So I remonstrated a little bit, but he seemed very clear about it. So I left saying, "Well, if anything ever occurs to you that might be useful, please, let me know.” [laughter]
Sullivan
Do you think that, perhaps, if you'd gotten a strong amount of encouragement that you might have gone back and done some observations yourself at that stage?
Townes
I might have. I was actually toying with two ideas. One, going into microwave spectroscopy, and the other one doing radio astronomy, or maybe some combination.
Sullivan
I see.
Townes
And microwave spectroscopy seemed terribly interesting, and we started, we had immediate success when we started out on it right away, and so that kind of directed me. Whether if Bowen had been very encouraging, whether it would have changed the course of my life – [laughter]
Sullivan
It's impossible to say. Right.
Townes
I can't say at this point.
Sullivan
Did you ask other people? I mean, do you remember the attitudes of other astronomers?
Townes
Well, I talked with Menzel, for example, and Whipple, and well, they, I would say they sort of shrugged their shoulders about this, and, "Oh, well."
Sullivan
It's of interest, but don't bet your career on it?
Townes
Well, I didn't specifically ask them. I just, I went up to talk with them and show them what I had, to get their reaction and see what they thought of it. And while they were kind about it, they obviously didn't think there was all that much in it.
Sullivan
Okay. Well, let's move on to the next phase, where you touched in radio astronomy, and of course you worked very successfully in microwave spectroscopy for a decade after the war. And how was it that you came about going to the Manchester conference and looking at astrophysical uses of spectroscopy?
Townes
Well, actually, I had maintained my interest in astronomy all along, and just sort of thought about some of the things from time to time. And one of the things that I thought about was this hydrogen hyperfine transition. But I never did anything about it, and of course Ed Purcell did. And I thought about fine structure things, and so on. So it was in the back of my mind, and once in a while I'd make a calculation about something, but I never did anything very seriously about it, but thinking about a number of interesting things there, closely related to microwave spectroscopy. And I didn't expect that there would be many molecules in interstellar space at that time, but mainly atomic things and (?) complicated processes. Well, everybody knew I was doing microwave spectroscopy, though, and finding references there. And I had a letter from van de Hulst, who said, "Well, we're having this meeting on radio astronomy. And, of course, the hydrogen hyperfine structures is a great thing, and we're all exploiting that, and (?) live a long time and continue to do it. But we'd like somebody with a different point of view to be able to talk about what other things might be done. And they know you were doing microwave spectroscopy, and would you be willing to talk about other kinds of resonances that might possibly be found?" And since I was somewhat interested in astronomy, I said, "Well, sure. I'd be glad to do that." I wouldn't have otherwise written it up because, to me, those things were kind of obvious. Yes, those might be found, and somebody ought to be looking for them someday, and I might even do it myself at some point when I get around to it. But he asked me to give this talk specifically to try to bring in something new and get a different viewpoint in the field, and get a different impression of it and background. And so I said okay.
Sullivan
Well, to the average radio astronomer, certainly, almost all of what you said wasn't obvious at all. Very few people had really considered spectroscopy in any sense at all.
Townes
Yeah. I realized that after I got there and talked with a lot of them, that they really just hadn't thought in those terms at all. But to me, it seemed very natural and I think, yeah. My guess is that other microwave spectroscopists asked to do the same thing, might have also written somewhat similar. It would have been different. I wasn't particularly interested in astronomy but I think another person in the field asked to pick out what might be seen would have picked out maybe the same thing. And how well they picked them out would have been on their knowledge and background in astronomy. In the case of the other people there, more mildly interested only. They were, of course, working on a continuum, they're working on the fine structure. And the molecules, nobody thought there were really molecules there. Other atoms, other atomic fine structure, and hyperfine structure might be a possibility but the sensitivity wasn't very great, that one. So van de Hulst was very complimentary I remember very well. He said that, after my talk, he said, "Well, you know, this is just great. (?) just told us some things they ought to be looking at in the future." But thereafter, so far as I could see, nobody really took it very seriously.
Sullivan
There were a couple of OH searches. Barrett did one at NRL.
Townes
Well, those, yeah.
Sullivan
But really –
Townes
Barrett, Lilley. Now, actually, those were things that I started, however –
Sullivan
Oh, is that right?
Townes
Yeah.
Sullivan
Okay, well, tell me about that.
Townes
Well, I was convinced that some of these things were going to be found. We’d get sensitivity enough, and clearly one of the things that was needed was more frequencies (?). And since I was doing microspectroscopy, I thought well, let's pick out some of the more, one or two of the most likely things to help the astronomers. And by measuring the frequency, then somebody can look for it. So I had somebody working on OH at the time at higher frequencies which were much easier for us. And I realized it's just the ground stage that's most likely to show up. So Jerry Ehrenstein – Ehrenstein? Well, let's see, I guess it was Stevenson and then Ehrenstein and I had just –
Sullivan
This was at Columbia?
Townes
At Columbia.
Sullivan
Yeah.
Townes
So we set up a little system just to measure that long wavelength transition and we measured it and published it. Well, then another one, Alan Barrett was another one of my students. And he had been working on microspectroscopy and I had given the topic to (?) radio astronomy. And Alan was interested in radio astronomy. He said, “Look, I would like very much to go into radio astronomy. Can you advise me on what I might do?” And the NRL was the most prominent place in the field at that time.
Sullivan
Especially in the microwaves then.
Townes
That's right. A very outstanding place for microwave work at that time. And perhaps the biggest type of (?). And so I suggested (?) and to look for OH. And Alan was already pretty knowledgeable about microspectroscopy. Well, I can't really say for sure whether I suggested to him that he look for OH. I know he asked me what he should best do and we talked about it, and in any case, he picked it out. By the time that he decided to go there, he wanted to look for OH, but we had just measured OH, you see.
Sullivan
I had forgotten it was a recent laboratory measurement because I do remember from the NRL report that came out of that, that the frequency was some 50 megahertz off of the frequency that we know today.
Townes
Uh-hmm, no, no. Uh-hmm.
Sullivan
No?
Townes
No. No, no. The frequency had to be right.
Sullivan
My memory is that he was using an older measurement to –
Townes
Oh, well, now wait a minute. Alan, let me see. It may be the first time that Alan looked that we hadn't yet measured the frequency.
Sullivan
I think that must be.
Townes
That's possible. That is possible and I don't remember. I’d have to look it up.
Sullivan
But you do remember him searching at a much better frequency?
Townes
I'd have to look. I'd have to look through that.
Sullivan
I can check. I've interviewed Barrett and I can't remember. Well, I can check there also.
Townes
I have the – of course he eventually, he ended up (?) Weinreb at MIT. I kind of think he did look up (?) times for it. He was very persistent about it fortunately. Let me see if I can find this paper now on the OH, published paper on OH. And it may be that what happened is Barrett looked for it first and then I decided, well, why don't we measure it, so –
Sullivan
Yeah, so he doesn't have to search all over.
Townes
So that he will know (?). And then he looked again, that might be the case.
Sullivan
Well, I can check that NRL report to see what he cites there, what frequency he's using and so forth.
Townes
And then, Alan was very persistent about it and he kept going and he found it. And I had (?) MIT by that time. (?) he found it.
Sullivan
Now, so this was a direct example of the paper that you gave, announcement of it.
Townes
Yeah, but I'm not sure I –
Sullivan
But really, I know others, either you directly or anyone else that read a paper -
Townes
No. No, I know of no – I know no other efforts that came out of that. And it was only the interest in our group that got that going. Now, Sandy Weinreb was very instrumental in finding it, and you'd have to ask Alan about his interaction with Sandy. I assume that Alan had brought the subject up – looked for that particular thing.
Sullivan
And Sandy had the means?
Townes
Sandy had techniques. One other thing I comment on that's purely hearsay but I think an interesting story, Norman Ramsey told me after we had found ammonia that he, a few years earlier than that, he had a plan to look for ammonia.
Sullivan
Now, you're talking of mid-'60s – you know, his plan –
Townes
Yeah. Maybe this is – I'm not – yeah, it'd be mid-'60s, I guess. It might have been early '60s. So he had planned to look for ammonia and Ed Purcell had talked his student out of it, and so discouraged his student that he just didn't want to work on it. And that's the reason Norman said, "Well, he didn't convince me it wouldn't be there, but he convinced his student (?) so I've got to look for it." And he said the argument was that ammonia would simply come (?) with black body radiation. Now, whatever radiation was there, it'd all be ground state (?) because of radiation effects. And you couldn't possibly expect to see ammonia. He said, "Well, it did sound a bit as if it the density was low." If anybody thought it was, and most people thought it was at that time. And so Norman said, "That's what stopped me. It wasn't I was discouraged, the student was so discouraged that he wouldn't do it." So there was that one other applicant. Now, whether Norman had seen my paper or not, I don't know. Whether he had read my paper. It's not a paper that is in the area that Norman would normally be reading, but on the other hand, he's a (?) reader (?).
Sullivan
Let me ask about another thing that we've skipped over is that you gave a similar paper, I gather, at the January '54 conference in Washington DC, which was, in essence, something to get radio astronomy going in the US. It was the beginnings of NRAO and so forth. Do you remember that conference?
Townes
I don’t very well –
Sullivan
I don't know exactly where it was held in Washington, but it was January '54 –
Townes
Well, I don't remember it very well. I remember I continued to be interested in the field and talked to people about it. So I never really worked at it. And I was interested in seeing the thing pushed. But I –
Sullivan
What I wanted to ask was –
Townes
It is not illogical, but I don't definitely remember a conference.
Sullivan
Were you at all a part of the move to get a national observatory going? I mean, did you feel this was a lack in US?
Townes
Yeah. Yes. Yes, that's right. I wasn't terribly active in it, but I did talk to people about it and try to urge it and so on. Yeah.
Sullivan
And you felt the concept of a national observatory was a fruitful way to go as opposed to more moneys to individual universities?
Townes
I just don't remember, definitely, enough what my attitude as to how to do it at the time. I remember perfectly well being insistent that the US ought to be doing something, and not the British do everything in the field, British and Australians, and we ought to be doing more, and I was pushing on that. I'm not sure what organizational ideas that I was urging. I know the particular objective of a national observatory, I know. Whether I especially urge it, I just don't remember.
Sullivan
Well, the last topic before my cut off date is your involvement to the maser as a radio astronomy receiver. Can you tell me how was that you put this thing on the NRL dish and what your basic goals were in doing that?
Townes
Yeah. Well, I went abroad in '55, '56 on sabbatical and basically I decided at that point that microwave spectroscopy for physicists had been brought up to a point that I wasn't interested in pursuing it very much further. I felt (?) largely an important thing in chemistry chemistry but not so much in physics anymore. And I had just finished the book with Schawlow on microwave spectroscopy. I thought it was a good time to change fields if I wanted to change fields. And so I went abroad, debated myself what I should do. And astronomy was one of the things I was considering strongly and I did some sort of calculation (?) while I was in France. And I was interested in time standards and so on. But during my sabbatical, I also did some work on electronics of the maser, solid state maser. And in fact, I published in France. Not many people know about it but it's published in Comptes Rendu, and people don’t read that very much. In fact, the French people don't read it much, especially (?). And I said well, I (?) but the (?) since I'm a guest in France –
Sullivan
Would be a nice gesture.
Townes
- that I ought to publish in a French publication.
Sullivan
That's interesting. I didn't realize that either. So that is a first maser –
Townes
First solid state maser. Masers, as far as ammonia, first solid state. And then, and so I kept on working it. And then I worked on noise theory when I was in Japan (?).
Sullivan
On this same sabbatical?
Townes
On the same sabbatical, yes. And by the time I came back, I was convinced that really I ought to work on the related field. And it's related to electronics. That while I do some other things that I shouldn't leave masers and leave microwave spectroscopy. And I was interested in astronomy. And so I married the two of them. I'm trying to build a maser that really is going to be useful. Now, you know, any new thing there are lots of these people who think, well the old thing is (?). So I remember very well going to a few meetings. One meeting in particular I remember was in Colorado where radio astronomers were.
Sullivan
The URSI meeting in '57 in Boulder?
Townes
That might have been it. That might have been, yeah. (?) and so on. A few astronomers were interested and many weren't. I remember Ewen saying specifically, “Look, we've got good receivers. What we need is big antennas at this point. But we don't really need any change in the signal. The signals are fine. What we need is bigger antennas.” It was completely logical. You need both but – And I don't think all the astronomers took that point of view, but they regarded masers as some kind of curiosity.
Sullivan
Were you thinking of them as amplifiers from the very beginning though, or did that idea only come up?
Townes
No, at the very beginning, in the origin of masers really was basically to generate very short waves. My primary interest initially was generating very short waves, particularly on the infrared, and you’ve seen my first notebook actually, there was talking about something about half a millimeter. But then I got started in the microwave region because I felt, well, it was easiest to go with microwave first, and then (?) later. And then I realized that (?) good amplifiers and I got a good time scale and so on, and so I get into that. Because of my interest in radio astronomy, I decided well, let's build some good amplifiers and show people they really would work, and do some astronomy with them, and so I was doing that. I would have kept on going on that excepting for the fact that I was asked to go to Washington for a couple of years in ‘59, full time, so I cut off both the maser work record and also (?).
Sullivan
Now how is it you got it hooked up with NRL?
Townes
Well, NRL was one of the best places around in the field.
Sullivan
That's right. There was also Barrett and you got –
Townes
And Barrett had gone down there and I knew the people. Well, I'd seen them at meetings. I’d been there for various meetings and we’d talk about these things, and it was. one of the best places around and an obvious place to get associated with.
Sullivan
Well, I guess you had a 3-centimeter, right?
Townes
3 centimeters.
Sullivan
And so that was the biggest collecting area.
Townes
That’s right. (?) so it was the obvious place to go.
Sullivan
Right.
Townes
And the people are very friendly and cooperative and –
Sullivan
Were there any special problems in adapting the maser to the field as opposed to being on the bench or –
Townes
Well, yes. Yeah. But just a lot of (timing?) problems and Giordmaine was a very good man.
Sullivan
Yeah. I was going to ask you. Tell me the roles of Alsop and Giordmaine.
Townes
Well, they did theses in this area, you see, and this was – Giordmaine was a senior student and Alsop my [inaudible]. They worked together and they were two students who built this and Giordmaine said, primarily Giordmaine’s thesis. And (?).
Sullivan
I came across another reference where I think it was Penzias was working with a 21-centimeter maser –
Townes
Yeah. That's right. Penzias was another student of mine and he was interested in astronomy and in masers and we decided to try to look for intergalactic (hydrogen?), and so he built a maser in that area and by then there were some commercial companies involved, and there was a little commercial company in Long Island, the name of which slips my mind at the moment. It had some very good people in it, and they were interested, and they had some commercial contracts (?). I’ve forgotten, but it was in this general frequency range.
Sullivan
I see.
Townes
So Penzias and I started semi-collaborating with them and had a useful interaction there. And then Arnold took his receiver down to (?), Maryland Point –
Sullivan
The 84-foot, the first dish in there. Yes.
Townes
Yeah. And we had a lot of big – we got a lot of noise (?) all over the place, (?) pick up.
Sullivan
Ground pick up, you mean, (?) illumination (?).
Townes
Yeah. That's right (?).
Sullivan
Which of course is (?) critical since you had such an improved system (?).
Townes
Conditional (sensitivity?), yeah.
Sullivan
Right.
Townes
So I'm obviously (?) some kind of a (useful opportunity?). I realize now this OH paper was done by my students. I think my name wasn't on it so that's why I don't have –
Sullivan
Oh, I see. Did you take part in the observations at NRL?
Townes
Yeah, certainly. Oh, yes.
Sullivan
What recollections do you have of – I mean, did they go very smoothly, was it just pretty clear cut?
Townes
Yes, they went fairly smoothly. We had – the maser had to be faded a little bit, (medium?), and adjusted carefully and so on, but I would say they went really quite smoothly, the first ones did. And we immediately got an order of 19 improvement and (?) roughly and Arnold there was very pleased with it and he measured the rising temperature of – checked his measurement temperature of Venus from a different side and the back side and Venus temperatures, and then we did make some other measurements. I wouldn't say we did really a lot of science because we just didn't have time. We built a maser and then got it working and some did some preliminary things. The (?) thing was the system for hydrogen line hyperfine structure, primarily because of all the radar pickup that we had down at Maryland Point. We had a substantial struggle with screening that out.
Sullivan
With Penzias’ system?
Townes
Yeah, Penzias’ system. But we eventually got it and he got a reasonable measurement, but by then I was – it seems to me by then I had already moved to Washington to do this semi-government job, so I was pretty tied up with that, whereas I helped Arnold some out in the field. I wasn't as full time involved in that as I was in the earlier 3 centimeter when I was there pretty much all the time. Every time we observed.
Sullivan
What was the main thrust of Penzias’ thesis?
Townes
Well, it was to try to look for intergalactic hydrogen.
Sullivan
I see.
Townes
That's right. We built a maser in that frequency range and looked for intergalactic hydrogen.
Sullivan
Another related question is was the maser just too experimental, too tempermental that you could leave it down in NRL and they could use it? There was no program that went on after that.
Townes
No, no. I think they weren't prepared just to take it on and do it all themselves. I got tied up in Washington, and Giordmaine and (?) Bell Telephone Laboratories and so on, but if I had been there, if I had not been tied up in Washington, I would've gotten another student and we would've continued on and done some more science with it. But as I say, I just felt obligated that I ought to take that job in Washington to help (?) out.
Sullivan
So that's why it was just really an isolated thing and then they really weren't using it for astronomy for several years? Yeah, that's right.
Townes
Yeah, I got it and we demonstrated it worked, it's profitable, but then you had to get some new group of people who were willing to go into it far enough to be able to do it.
Sullivan
Right. One final question, I'd be interested in your ideas on the interaction between radio astronomy and specifically microwave spectroscopy, but experimental physics. How have the two had an impact on each other? Has radio astronomy changed what the physicist has been doing in any sense or has it always been more that radio astronomy is only a part of experimental physics or –
Townes
Yeah, I think it's – because in my case it's changed what I've been doing, but I would say in the physics as a whole, what primarily is done is emphasize certain particular kinds of measurements of interest to astronomers and so those measurements are made by physicists and chemists, but otherwise I don't think it's had a big impact. General involvement of very sensitive receivers has had a somewhat broader impact. Some of that has come through (?). On the other hand, it seems to me, radio astronomy has been enormously affected by electrical engineers and physicists and mostly those who've done techniques and brought out new things and then it's become very –
Sullivan
So you think the direction has been more that way than that the influence of radio astronomy on physics, it's been more the other way around.
Townes
Yeah. Yeah. Yeah. That's right. Except, well, I don’t know whether you've heard people use the approach that astronomy really is a very applied field, because astronomy applies all the other sciences in order to suit certain particular goals. It applies physics and mathematics and anything else it can get its hands on. It could go after any particular rather than specific kind of goal, you see, and so because it's an applied science in that sense, we generally think of applied science as something that produces something useful. But that isn't necessarily so. This applies to all the other sciences and because it’s applied science, and in that sense the flow of information and techniques is naturally from the other sciences into astronomy. That's a large part of it. Now astronomy then sometimes finds out things which affect the other sciences such as (relativity?), spectra, (?). The flow of techniques tends to be in the other direction.
Sullivan
Okay, thank you very much. This finishes the interview with Charles Townes on 23rd September 1981.
End Tape 157A