Interview with Charles H. Townes on 5 October 1971
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Please bear in mind that: 1) This material is a transcript of the spoken word rather than a literary product; 2) An interview must be read with the awareness that different people's memories about an event will often differ, and that memories can change with time for many reasons including subsequent experiences, interactions with others, and one's feelings about an event.
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Begin tape 9A
Sullivan
This is interviewing Dr. Townes, October 5th, 1971.
Townes
Well, I have always had a number of encounters with radio astronomy in various ways. Perhaps one would say that I’ve flirted with the field for quite a while without being as terribly active in it (?) time in it. I first ran into this radiation in an elementary physics textbook in the early thirties when I was in college, and it struck me then as tremendously interesting observation of radio waves which at that time were completely unexplained.
Sullivan
Do you remember which text it was?
Townes
I think it was a text by Jauncey, called Modern Physics. It was a sort of junior level general physics.
Sullivan
I guess I should take a look at that just for my own interest.
Townes
I think it was Jauncey. I can’t be certain. I believe that’s where it was. And after completing my Ph.D., going to Bell Telephone Laboratories where I was expected to do other kinds of physics, getting involved in the war effort, that was in the mid-forties, that I found that I had a little time waiting around between airplane flights and testing new equipment to do something more interesting to me and I decided to look into what might be a source of these waves. Since I was at Bell Telephone Laboratories, it was easy for me to talk to Jansky, and I went down to visit him and had a very interesting visit. He gave me additional data that was not readily available.
Sullivan
Can you be more specific? Was this stuff he did after his publications?
Townes
This was particularly measurements at very long wavelength intensity of radiation at very long wavelength, which had never been properly published and hadn’t been called to the attention of the astronomical community. I first calculated the essentially the Bremsstrahlung from collisions of electrons with particles along with various other processes. I decided this was likely the source of radiation, and just as I was writing this up, I discovered that essentially the same calculation had been made for x-rays a number of years ago by a Dutch physicist, I’ve forgotten the name for the moment. So, of course, I referred to that work and this end in a publication, a discussion of essentially the thermal, what’s now known as the thermal process for ionized medium integrated over thermal distribution. I’m not sure that paper is very well known.
Sullivan
No.
Townes
It was not an active field at the time, and one of the things I tried to do was to correct one or two previous expressions for such thermal radiation, one of which had the [Planck] constant h in it. I was sure this was really a classical phenomenon. I tried to show why that constant h has come in by mistake and what the mistake was. The reviewers, it turned out, said well, this was not interesting to show that quantum mechanics and classical mechanics were similar. And I took that out, essentially, except the comment that the h really shouldn’t be there. In fact, it was a demonstration that the original, that the early calculation, based on sort of spontaneous emission processes really wasn’t right. And then I examined the experimental data, including the new experimental data, that Jansky had pointed out to me, analyzed it in terms of thermal mechanism thinking at that time well perhaps interstellar medium really was very hot, as hot as a million degrees, because it would take that to explain everything (?) mechanism. Now that we know that somewhere that mechanism is the principle source in some places in synchrotron radiation which I hadn’t imagined was more important.
Sullivan
Where was this published, please?
Townes
That was published in the Astrophysical Journal, 1945 or 1946. [Note added by Sullivan following interview: Actually March 1947]
Sullivan
Do you give the numbers for this long wavelength data of Jansky’s in there?
Townes
Yes, it’s in there, I believe.
Sullivan
So it’s actually the only mention of it in the literature.
Townes
But at least that only mention in the astronomical literature. I think he may have had it in some electrical engineering publication or something like this. Now I, at the same time, was thinking about various kinds of molecular transitions. I had gotten interested in the trouble which water absorption would produce for radar because I was working on k-band radar somewhat over my own objections. It had been ruled that we should all convert to k-band radar and I felt that the water would likely give that radar trouble, but such was the military discipline of the time, that I had to work on it nonetheless. And so I went to some considerable trouble in odd hours to try to show that, in fact, this was likely to give difficulty, but I never convinced my superiors until, in fact, it did run into difficulty and the equipment was junked. Thereby that made equipment available for microwave spectroscopy which I later used, and through the study of water, I got quite interested in molecular spectroscopy. About that same time, I worked, actually, on a number of different processes, some astronomical, some in the laboratory, I was thinking about them, and the hydrogen hyperfine structure was one of the things I calculated. As I believe a number of people actually did independently, Purcell and several other people independently, Purcell and the Dutch group.
Sullivan
Are you talking about during the War?
Townes
During the War, yes.
Sullivan
Did Purcell do this during the war? I thought…
Townes
Yes, Van de Hulst and Purcell both, I think, thought about it during the war or immediately after, but I just calculated it and worked on it in my notes. I think Professor Lamb also made that kind of an estimate of what might be done from astronomical sources. Along with looking at what might be done with the moon in the laboratory and a variety of other things. I never did anything serious about the hydrogen fine structure case of feeling that although I should try to measure it. I decided to do laboratory work in microwave spectroscopy because I foresaw a big field there, and Grote Reber had just, had by that time come out with his maps of sky and as I had located those and found them very interesting and helpful. I got somewhat a difficult choice between radio astronomy and what I saw as a new field of microwave spectroscopy. I can’t really detail the precise reasons why I chose the latter now, excepting that it was easier to do in the Bell Telephone Laboratories at that time. They had no substantial telescopes; I could work in my own laboratory with relatively small equipment and with this equipment which was cast off from military radar and was cheap and easy to get. So that field developed so interestingly and quickly that, as I say –
Sullivan
So you weren’t in that before the War? Was there any microwave spectroscopy?
Townes
There was no real microwave spectroscopy before the war, at least no high resolution work. There was some rudimentary work on water vapor absorption at atmospheric pressure, by Dickey, and looking at the atmosphere in his radiometer, and at Columbia University by Lamb and others in a box at room temperature and atmospheric pressure. (?) try to check this problem of radar to see what the problem, how big the problem really was. It was measured just about the same time that one found the operation of the radar was knocked out by water vapor.
Sullivan
Was that only during rain?
Townes
No, no – just any moderately humid day, and particularly since the war with Japan was on, and it was of prime importance in the South Pacific where there was a great humidity, radar was just essentially discarded for sure. There had been a big effort on it prior to that. There was also some work on ammonia. I knew that a few people had worked with ammonia getting absorption of the microwaves because there was the Cleeton and Williams work in the thirties which first discovered this transition of ammonia at atmospheric pressure and very broad sphere. Other people had worked at high pressure, too. I think some work at RCA, some work at Oxford, Bleeny at Oxford and Bishop and perhaps Wolf at RCA. And the thing that I felt was, could be added then as new, was what I realized if one could go down to lower pressures and just get almost arbitrarily high resolution, I think that wasn’t generally appreciated. So what I set out to do was to go down to low pressures and get high resolution, and this high pressure atmospheric work which had been done and arithmetically formed before, so it was started during the war for no great purposes actually, but only in this high pressure form. After the war, then there were three independent places that first did the high resolution work – myself at Bell Telephone Lab, Bleeny at Oxford, and Coles and Goode at Westinghouse. This was a very active field for a long time, a very enjoyable field. Then when the masers came along…
Sullivan
Hold it, before you jump that much – were you or your group the first to measure ammonia and water lines accurately at 1cm?
Townes
We first measured the water line accurately.
Sullivan
And what time was this?
Townes
Well, let me see, it was late 1945 or early 1946, a paper, a fairly extensive paper on ammonia in 1946. Bleeny got fairly high resolution on ammonia and I remember very well I had a paper which has been cleared by the Bell Telephone Laboratories’ Patent Office at the time it had been three years and I had it in the mail box to send off to Physical Review and I got a preprint of Bleeny’s work, so I tore it up. But then we went on and did a more extensive job and more precise job in getting the frequencies accurate and predicting, understanding the frequencies on it – wrote a longer paper later, but Bleeny was the first to get the fairly high resolution. We, I think, were the first to measure accurately, the first to detect saturation phenomenon.
Sullivan
What about for the water vapor?
Townes
The water vapor, we were the first to detect that, basis other than the (?) broad, other than atmospheric pressures. That was done by Merritt and myself and Hogan, I believe. I’m not sure.
Sullivan
(?)
Townes
Yes, that’s right. Then there was also HDO, a variety, we worked on a variety of molecules then and a number of them, I remember, (?) same molecules, that had been turning up. OCS was a great test bed for microwave spectroscopy as was ammonia. In fact, it’s interesting that many of the new things as I start on a new field, ammonia seems to be a kind of test case. Ammonia was the origin of the maser, of course, the first maser. And we did our first work in molecules in space and tested a lot of hyperfine theory, transition theory, and so forth through ammonia, it’s a very good molecule. Now, let’s see, I continued to be interested in radio astronomy, but simply too occupied with another field to do very much about it. I took a sabbatical shortly after the maser had been discovered and made to work, and to try to decide what I should do, feeling that work for physicists in microwave spectroscopy was no longer as interesting and no longer as needed, because the chemists were doing a good job and I felt from then on it would be more efficiently done in chemistry laboratories.
Sullivan
This was a sabbatical?
Townes
Taken in 1955 and 1956. I took a sabbatical in France and in Japan.
Sullivan
From Columbia?
Townes
From Columbia. And while I was in Paris, I worked a moderate amount on various astronomical problems. Radio astronomy, I remember talking with Denisse at some length about some of these problems and a certain number of calculations of things that I felt might be going on in interstellar space and in various radiating objects.
Sullivan
Was this all spectral line?
Townes
No, no. Some of this was continuum. And thinking about what might be done. I eventually decided that I would, in fact, pretty much drop microwave spectroscopy per se and work on masers and their extensions, including a maser amplifier for radio astronomy. So we built, Giordmaine, Alsop, and I built a ruby maser eventually to do astronomy with and that was put on a telescope through very happy cooperation with NRL, I think that was the first maser to be used telescopic.
Sullivan
Well, that was simply the best telescope available at that time.
Townes
Yes, right, Now I would have pursued that work further, several others of us working on this. Alan Barrett had gone down to NRL [Navel Research Laboratory] about that time and was interested in radio astronomy and I had a couple of other students who were interested in radio astronomy, Bill Rose, Arnold Penzias, and possibly a few others. And was working on radio astronomy, and then I was asked to go down to Washington to do what I considered was an important job and I regretted very much having to leave, just when things were so interesting and we were trying to build the first laser and we were doing this work on radio astronomy. I was very much torn as to what I should do. But I decided I really couldn’t look myself in the mirror and turn down a possibility of doing something that I thought was important in national problems, so I was out there for two years.
Sullivan
This is what two years now?
Townes
That was 1959 to 1961.
Sullivan
Can you tell me what this was?
Townes
Oh yes. I was Director of Research for the Institute of Defense Analysis, which was working with the Defense Department, the State Department, to some extent with the President’s Science Advisory Committee, and generally trying to look at security and policy problems which were very troublesome in those times. Sputnik had just gone up and people were very worried about the future and relations to the Soviet Union and what was going on – there weren’t enough scientists in Washington, I felt, trying to help. Well, that was 1959 and 1961. During that time, I also did a little work in astronomy with a person there at the Institute of Defense Analysis who was interested named Schwartz – trying to point out that in addition to communicating by radio with extraterrestrial life there might be a possibility, there was a possibility, of communicating by laser, but one should not be so restrictive in the frequency range over which you considered such communication. But, of course, I was mainly busy with administrative type things, government problems, political, and technological policy problems. Then from there I agreed to go to MIT. I went directly to MIT and then I was…
Sullivan
Excuse me, before we go any further, I want to backstep. I’m familiar with your paper from the Manchester Symposium in 1955 about –
Townes
Oh yes. I forgot about that. That was done while I was on sabbatical leave, or about the time I was on sabbatical leave. I wrote that partly because I was interested and partly, also, because someone asked me well, now, could I help out in saying, if there were any other things that might be looked for. And would I, and I said, well sure. One of the things I’ve been calculating and I think might be looked for, but I thought they were all fairly obvious sorts of things. However, I was prevailed on to give a kind of review paper. I was told, well, astronomers didn’t know as much about these things as they might and would I please give a talk on what might be looked for. It was because of that that I prepared this thing, many cases the kinds of things I’d been thinking about just in my own notes, but not dealing with publication. Thinking I might possibly work on them some time, but I’ll throw all these things together in this paper in ‘55 and attended the meeting there in Manchester.
Sullivan
You say they were obvious to you, but I don’t think they were obvious to other people, though. As you found out perhaps.
Townes
Yes. I was surprised in a way. I was surprised in a way, that that was the case. There were things which were sort of common to the field of microwave spectroscopy and ought to be pretty well known and I felt it was really a question of looking, of a number of known things, but I was told that well, many astronomers don’t really know which ones are there or might be there, which ones are more favorable, and would I please give kind of a general discussion of what might be some of the more favorable ones. And I remember Van de Hulst being at least very gracious in thanking me for helpful paper and that I’d been perfectly surprised how useful, in fact, it turned out to be.
Sullivan
Did you publish any of your calculations on continuum radiation?
Townes
No, no, I never published anything more then. Let’s see…
Sullivan
You’re up to going to MIT.
Townes
Yes, MIT. Well, of course, I thought it was important at MIT to promote astronomy and astrophysics and tried to help out there in building strong groups in astrophysics and encouraging Lincoln Laboratory and so on, and a number of people came to MIT during that time, some people, friends of mine, people I’d known – Bernie Burke. Bernie Burke published a paper with me earlier in microwave spectroscopy, he was a student of Strenburg’s (?), but he came down to Columbia and we worked together on one particular problem. I knew him quite well and Alan Barrett. Well -
Sullivan
I guess you were just too busy administratively at MIT.
Townes
I was pretty busy, and what work I was doing in the laboratory was on lasers, quantum electronics, and (?) optics. And when I left administrative work was when I decided to do astrophysics. Now, my own present astrophysics was some combination of radio astronomy and infrared astronomy and trying to cover a rather broader frequency range. And it was, I guess, natural for me to bo back to look for ammonia and some of the things I’d always thought might be there. Astronomers weren’t able to talk me out of the possibility that they might be there, although a number of astronomers tried.
Sullivan
When did you go to Berkeley?
Townes
We were lucky and had two very good people. Dave Bryant and Al Cheung to do it. I went there in 1967. In the Fall of 1967.
Sullivan
So then you must have started right in.
Townes
Started immediately.
Sullivan
And the twenty foot nicely –
Townes
The 20 ft. dish was available then and one of the reasons I went to Berkeley was because of the combination of the radio facilities and the good optical facilities at Berkeley, plus a strong astronomy department and people that were interested. So these are the reasons I went there, and I felt that that telescope would be very suitable for exploration of molecular lines and Jack Welch turned out to be interested and was very cooperative. We started out to look for ammonia as our first (?). As it turned out, some molecules are still stronger, and ammonia, surprisingly, has not been explored much yet. But I think it will. We of course, Al Cheung wants to do (?) much more widely, I think, than more ammonia around than he found, and probably a good deal…
Sullivan
So you’re probably familiar with what Zuckerman and …
Townes
Yes, that’s very nice additional results. And I think that and other (?) well, that’s about all I can think of.
Sullivan
I was just going to ask you if there’s anything particular about the Hat Creek whether, in the discovery or any anecdotes or whatever that you remember. Was it all a straightforward thing – you just built the radiometer and –
Townes
Well, yes, so far ammonia’s concerned, it was fairly straight forward. We knew what had to be done in order to try to look, we knew about what kind of precision we could get with the receivers available, and we wanted to use what equipment was available to look first. And we looked and there it was. We looked at a number of sources, of course, the, I think we had some advice from Professor Weaver as to what would be some of the darker, bigger clouds and we looked immediately for those.
Sullivan
You were trying to look in dust clouds, figuring they had to be protected.
Townes
Yes. That’s right, I was trying specifically to look in dust clouds, thinking that that’s where the molecules are most likely to be, the highest concentration of matter and where there was some protection. Now there is an amusing anecdote in connection with water. I had not believed that the water line would be likely but felt that well, there we were, at the right frequency and good antenna, and good equipment, we might as well try it, and other people thought the same thing. Well, let’s give it a try. We tried it in Sagitarrius first where we found ammonia and sure enough, there was a weak water line, it was very puzzling, it shouldn’t be there. Then along about Christmas time 1968 I was having a Christmas party for all of our students, associates, and Al Cheung, because he’s a tremendous worker and enthusiast, he wanted to use that time, he had an opportunity to use the antenna, and I told him “Well, by all means go ahead, I’ll invite you to another party”- so he missed the party and he was up at Hat Creek looking at other sources in the water, and I got a call from him in the middle of this party and we were all drinking egg nog together, alcohol, and said “Well, it must be raining in Orion” – there was an enormous signal across the water. So we congratulated him and we all drank a toast to him and the water in Orion.
Sullivan
And what about W49 or was that an even greater surprise?
Townes
Yes, that was still, of course…
End of tape 9A.