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Oral History Transcript — Dr. Norman Ramsey

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Interview with Dr. Norman Ramsey
By Ursula Pavlish
At his office in Lyman Hall, Harvard University
February 28, 2007

Transcript

Session I | Session II | Session III | Session IV | Session V

Pavlish:

This is interview number five with Professor Norman F. Ramsey. It is February 28th, 2007. My name is Ursula Pavlish. Professor Ramsey will be leading this interview, speaking on what we left out of our previous discussions.

Ramsey:

I can’t do that well because I haven’t had the opportunity to read what was in the last interview. I’ll talk about it in more general terms.

Pavlish:

That’s my fault that I haven’t had a chance to transcribe it fully.

Ramsey:

That’s all right, no problem. One of the topics that I think is missing is how closely I collaborated with my graduate students in this work. My students and I always both felt that each of their projects was a joint undertaking. We each contributed freely as if we had been collaborating on a paper after they had gotten their PhDs. This worked very well. I gave them a lot of responsibility. They had to debug and often construct the apparatus. They would manage the experiments. We’d argue whether a plan was a good one or if we should do a different one. It was very enjoyable. During the time when I had graduate students, if I were asked to name my fifteen best friends, at least half of them would have been my current graduate students. That was the way we operated on a first name basis. I learned a lot from them, and they learned a lot, I hope, from me. A second thing that did not quite come through clearly in the interviews was the research after the apparatus was built and you tended to talk about new methods which I had invented and how they worked. Then there was an additional often long period for using those methods for a bunch of measurements. Particularly on the properties of molecules using separated oscillatory field magnetic resonance methods, using other sensitive techniques and looking at quite different and important things, whatever we could think of. This, I think, is missing in the other interviews. I have published about five hundred papers of which I was author or a co-author. Now, I would say a third of those are partial repeats, such as historical reviews and things of that kind that I had to write. But then there are also quite a large number, I would say 200-300, which were original, creative papers. Those were mostly done with students, though sometimes on my own. When they were theoretical I would usually, but not always do them on my own. The students, also, had some theoretical papers of their own. The collaboration with students is one of the most pleasant aspects of teaching in a University. I had 84 graduate students plus of minus four. The reason I say plus or minus four is not because I cannot count eighty four but because four of them were either half time my students and half time Dan Kleppner’s students. It is hard to say which was the primary advisor.

Pavlish:

That’s extraordinary, not an average even amongst your colleagues.

Ramsey:

I had a larger number of students almost all have done very well subsequently.

Pavlish:

How did the students choose to work with you?

Ramsey:

That’s a good question. They had a free choice. They would come around for interviews. I would tell them what we were doing, what I could see there might be for them to do. They also heard from other students about whether they liked to work with me or not.

Pavlish:

Those students were already in the department at Harvard?

Ramsey:

Usually the Ph.D. students at Harvard take the first two years of graduate study learning advanced topics in Physics. They take a preliminary reading course with different members of the faculty to see how they like it. By the end of the second year they are supposed to choose with whom they would like to work. They can change. I have had a few students who started with me and moved to someone else. I have had students who started with someone else and then moved over to work with me.

Pavlish:

How did you balance your teaching, your research, advising graduate students, and the other work you were doing?

Ramsey:

That is the worst problem of teaching at a university [laughs]. Each of them should be a full time job. I could easily spend full time with my graduate students on theses. I could easily spend full time making better lectures and talking to the undergraduates. I could easily spend full time on other things, writing papers, et cetera. You just have to seek a balance. Some people don’t or can’t do that, and choose not to do teaching and research in Universities.

Pavlish:

Now, you did additional work. You neglect to mention your leadership roles. For example, your management activities as President of the University Research Association.

Ramsey:

That was particularly important since we managed the establishment and operation of Fermilab which constructed and operated the world’s highest energy accelerator. I was in that position for 16 years while on half time leave from Harvard University. I also had other management activities that you feel you should do and others that you want to do. I have had both. Some were minor ones, such as chairman of various committees in the [Harvard Physics] department and some where important , big very heavy ones such as being Science Advisor to NATO for a year and a half.

Pavlish:

You were the first Science Advisor to NATO. I remember reading about it that you were not necessarily excited about it.

Ramsey:

It was off my main desire, which was to do fundamental research. On the other hand, we got a lot of good research started amongst the NATO countries.

Pavlish:

What did that involve?

Ramsey:

It involved visiting different countries and giving them advice on what they should do to recover from the war, when they had not been able to do much research. I was responding to them when they sought advice. We invented a couple of very key programs, which are still operational. One was a NATO fellowship program, which we persuaded NATO to do by getting money from the countries that could most afford to pay and giving it to the countries that most needed it. The countries contributed money according to so-called NATO cost-sharing. On the other hand the number of fellowships were proportional to the number of eligible candidates, basically by population. The aim was to encourage more to become scientists.

Pavlish:

What date is it that you were the science advisor to NATO? I will look it up, because I am thinking of contextualizing this in relation to C. P. Snow’s 1959 Reed Lecture on ‘The Two Cultures’ at Cambridge University. He bemoaned the lack of collaboration between scientists and humanists and portrayed the scientists as looking toward the future, and potentially helping developing nations. I wonder if you would have seen this work in that frame?

Ramsey:

Yes, I am familiar with the C.P. Snow ‘Two Cultures’ lecture. No, I did not see this work in that frame. [Indeed, Norman F. Ramsey served as science advisor to NATO between 1958 and 1959.]

Pavlish:

Do you remember what countries you visited?

Ramsey:

Oh yes. They varied from (advanced) countries like England where I was getting this program approved. I also visited two countries that don’t get along with each other; Greece and Turkey (two of the least well-developed countries in Europe).

Pavlish:

Did you travel alone or did you take your family with you?

Ramsey:

Usually I went alone.

Pavlish:

There wasn’t much time for sight-seeing?

Ramsey:

No. They were hard working trips. I set up new scientific programs. And I found on these trips, is that the poorer countries had been given a fair amount of scientific equipment but they had no spare parts so their equipment was not operating. We established a special NATO fund to which they could apply for spare parts. Those countries also had a big currency shortage, which meant that you had to get a lot of approvals to get government money. It required almost as many approvals to buy a spare vacuum tube as it took to buy an airplane. There was too much red tape. The goal was to have less red tape and also to establish a fund from which they could provide vacuum tubes if that was what was needed.

Pavlish:

You had a translator traveling with you?

Ramsey:

No, not usually, the scientists usually spoke English quite well. I guess there were translators sometimes but the scientists even at that time were speaking English or trying very hard to speak.

Pavlish:

These travels were through Europe mostly?

Ramsey:

Europe. We established a fellowship program. [Note, here I ought to have asked how the idea for the fellowship program came about and what Ramsey’s role was in its genesis. Also, did he travel with other emissaries or alone as scientific representative of NATO.]

Ramsey:

Usually alone.

Pavlish:

When you traveled to England initially to help set up the program did you meet with some of your colleagues or teachers from the Cambridge days?

Ramsey:

Yes, and also several I knew during World War II, in connection to radar research.

Pavlish:

You might have met them in London or someplace else?

Ramsey:

Sure. Well, I went to different places, Oxford and Cambridge, but London usually was the main location.

Pavlish:

Would a few names stand out to you of the physicists you met with there?

Ramsey:

Oh yes, I met with John Cocknoft, P.I. Dee and others.

Pavlish:

I think I came across a popularization of Relativity by Dee in the library the other day. Because of my discussions with you, the name rang a bell.

Ramsey:

I see the library’s a good place to be.

Pavlish:

This is a question from a different direction, but I was wondering if you ever met Einstein.

Ramsey:

No, I didn’t. He was somewhat before my time. He was doing interesting but rather unrewarding research after I became active in physics.

Pavlish:

You mean physics-ally unrewarding? His physics wasn’t…

Ramsey:

Well, actually, it intrigued me. He was working on a great problem; how to get a unified theory of forces. But, it was too early. Indeed, one of the key interests now is unification of the fundamental forces. But, the work that this made possible hadn’t even been done. For example, Einstein was mostly trying to get a unified theory of elementary particles and electromagnetic theory. People hadn’t yet found out how to even start doing that properly. And he was very interested in gravity. He was working on the right problems, but at too early a time to make progress.

Pavlish:

May I ask you a somewhat personal question about the way physics is done. Einstein’s Relativity contains a lot of thought experiments, say the twin paradox where a twin goes off to a distant star, Alpha Centuri, and comes back younger than the twin who stayed on Earth. These thought experiments, there’s also Schrodinger’s cat, are things that do not really happen. That is one mode of doing physics. It seems like your work is much more like A. P. French’s textbook on Special Relativity, which is about what can we actually measure in the lab rather than these fictional scenarios. I wonder if you ever used these thought experiments?

Ramsey:

Yes, I have, but less. I am primarily an experimentalist and my primary research interest is in designing better experiments. In the process of doing that, you do a number of thought experiments. One thinks: suppose you do it this way, what would happen? One finds that it wouldn’t work at all, so one forgets it. If it looks as if it might work, then it gets beyond a thought experiment. Thought experiments are very helpful and they’re essential for theorists. [According to his facial expressions and this response to my previous question, I think Professor Ramsey seemed to disagree with my objection to the usefulness of thought experiments in science.]

Pavlish:

Returning to your leadership activities. One might trace several trajectories through your career. One might focus on your laboratory work or your theoretical developments. Let’s say we traced an arc of your leadership. During World War II you were the head of the delivery group…

Ramsey:

Yes.

Pavlish:

…and then afterwards you were one of the founders of Brookhaven…

Ramsey:

Yes, that is right.

Pavlish:

…and subsequently the head of the Physics department there.

Ramsey:

Yes, that is right. Co-founding Brookhaven, was my first major leadership position within physics. That led to my heading the physics department at Brookhaven, at which time I learned a rather intriguing phenomenon. The problem with doing administrative work and leadership work is that it distracts from your fundamental thinking about physics. Always, the administrative activity subconsciously takes precedence. Here’s a member of your staff who comes to your office asking a question as to what he should do with a problem. You have to give him priority and see him. That takes time from your own projects and plans. I made a discovery, actually at Brookhaven, that if I did my personal research primarily in one location and my administrative work and policy things in another, I could keep them fairly separate.

Pavlish:

That was around the time when you were at Brookhaven, is that when you’d say you discovered that?

Ramsey:

I guess I discovered it first, and then confirmed it, as science advisor to NATO. I had an administrative office in Paris. I kept my research going with my graduate students, in the United States. I found that worked quite well. Originally I had thought I would spend the evenings in Paris thinking about physics and do my administrative work during the day. Well, it did not work that way. For me, I tend to concentrate on whatever it is I am doing at the time. Having one kind of work in Paris, and the other kind of work in Cambridge, Massachusetts, I could do quite well. That does not mean that I never thought about the other activities, but I gave priority to the work in whatever place you were at. My personal research with graduate students went very well during that period.

Pavlish:

There was no email back then, for students to send you quick questions.

Ramsey:

There wasn’t e-mail that is right. I did make a trip back home every month or so, and when I was there I spent most of my time in Harvard with my students or at home with my family.

Pavlish:

Your family moved with you to Paris?

Ramsey:

That was one disadvantage. They moved with me to Paris during the summer. We decided that for the children’s school it would be better for them to stay put during the winter. But they came over for visits, and I likewise got back for visits. However, that big a separation was a great disadvantage. Later, my biggest administrative activity was President of the Universities Research Association, which was the group of Universities, that under contract with the Atomic Energy Commission, (later the Department of Energy), designed and built the accelerator at Fermilab, which is still the world’s highest energy accelerator. In another month or two it will probably cease to be such, because there will soon be a big international accelerator modeled after what we had made.

Pavlish:

The LHC [Large Hadron Collider at CERN]?

Ramsey:

The LHC. That will be even higher energy.

Pavlish:

I’m sorry, I’m a little bit ignorant of the history here. Is the history of the founding of Fermilab already written up?

Ramsey:

Yes, there is some write-up of it. The Director of Fermilab asked me at one time to write up my end of the endeavor. That is included in the annual reports of Fermilab and is in the Fermilab 1987 Annual Report 20, 157 (1988).

Pavlish:

The reason I ask, is that I do not want to burden you by asking questions about what you have already put on paper.

Ramsey:

Yes.

Pavlish:

Rather, if we could talk about things that you haven’t written. You have written a lot, even about the history.

Ramsey:

My impression is that history of science publications tend to fall into two groupings. There are histories written by the active scientists who were doing the work and these tend to end up as scientific reports or papers in proceedings of scientific meetings. Then there is the writing of specialists in History of Science. Those two types of publications tend to be separate, which I think is too bad. Frequently if you look at a history of science collection you may not find the history papers written by the research scientists themselves.

Pavlish:

I do have one historical article you wrote, called I think “Nuclear Magnetic Resonance: The Early Years”. In it, you actually address this problem, but slightly differently. You say that for a scientist to write history there is a dilemma. The scientist naturally has his or her inner perspective, and it is understandable if the scientist expresses this aspect of the history. However, this might leave out the work that other people have done. The goal in the history of science would be to stay true to the history of the discipline [of physics] while integrating the different viewpoints. It seems like since the beginnings of quantum mechanics and relativity, it seems like the history of physics written by historians of science is written about particle physics and high energy physics mostly.

Ramsey:

I have that impression too. Those tend to be pretty conspicuous fields. They also have some money associated with them, so that they can pay to get their histories written up, whereas the other smaller fields aren’t as well funded. A large fraction of the magnetic resonance budget would be small compared to the high-energy budget.

Pavlish:

Your work on molecular beams, your work in magnetic resonance, the separated oscillatory field method, all fit within the larger framework. The interesting thing would be to show it from a holistic perspective but also to connect it to particle physics because it also connects.

Ramsey:

Oh yes, it connects.

Pavlish:

You also do work in particle physics. That might connect it to the historiography in a nice way. Historians of particle physics would be able to relate to it, through the connections.

Ramsey:

Definitely it relates, but frequently the relation is not emphasized.

Pavlish:

Your textbook, Nuclear Moments, grew out of the two parts you wrote for this collected volume Experimental Nuclear Physics edited by Segre.

Ramsey:

Yes, that’s right.

Pavlish:

This was published in…

Ramsey:

Quite early.

Pavlish:

1960 [sic, that was the second printing. It was first published in 1953]. And your textbook came out one or two years later [sic, 1953, same year]. One part written by Hans Staub on “Detection Methods,” one part written by Bethe and Ashkin on “Passage of Radiation Through Matter,” your parts on “Nuclear Moments and Statistics” and “Nuclear Two-Body Problems and Elements of Nuclear Structure,” and Bainbridge on “Charged Particle Dynamics and Optics, Relative Isotopic Abundances of the Elements, Atomic Masses.” Here we have a [textualized] program of nuclear physics, an umbrella concept. There is the theoretical and particle aspects, and then you are addressing more the…

Ramsey:

That was done fairly early. The field has grown a lot since then. That is probably the reason the publisher branched of one of the things I wrote because a lot of people in that field would read it. It is hard to write an equally detailed book on all those topics in a finite sized book.

Pavlish:

You did do work in nuclear and particle physics? Am I correct in assuming that the part you wrote for this book is not that, is it?

Ramsey:

No. What I wrote about was standard nuclear and particle physics. At Harvard I was in charge of the construction of the Harvard Cyclotron which we used for nuclear physics experiments, but only up to about a hundred GeV [giga electron volts].

Pavlish:

That was more of an administrative position when you were getting that up and running?

Ramsey:

Yes, but I was also doing nuclear physics research experiments.

Pavlish:

Would you relate that to your leadership as President of the Universities Research Association?

Ramsey:

I was asked to manage this construction of the Harvard Cyclotron because Bob Wilson (with whom I later collaborated quite closely at Fermilab) left Harvard to go to Cornell. An intriguing thing is that the accelerator was designed primarily by Bob Wilson and built primarily by my associates and me. Later when I was at Fermilab, Bob and I were again in close cooperation. I was President of the Universities Research Association (URA), which is the organization with the government contract to building and operating the accelerator. We chose Bob Wilson to be the director of the laboratory.

Pavlish:

That might be somewhat analogous when you chose Maurice Goldhaber to come to Brookhaven where he later became Director.

Ramsey:

That’s right. Up to that time I became President of URA. I had been doing both molecular beam fundamental experiments, and also high energy nuclear and particle physics experiments. When I took on the URA responsibility, I decided I would drop all my personal research in the high energy and nuclear field and limit my high energy activity to running the new laboratory and making it work well. I would channel all my personal research efforts, work with graduate students and so forth, into molecular beams and low energy research. If you look at my successive papers, you’ll see that my nuclear and particle physics work dropped off, within an extra year or so of publications coming out. But basically, it stopped.

Pavlish:

That was a conscious choice.

Ramsey:

That was a conscious choice.

Pavlish:

You liked the molecular beam experiments more?

Ramsey:

I thought that I had a better chance of doing fundamental things. I could do small experiments with graduate students, which I enjoyed. The high energy activities had to be done with larger groups. I didn’t feel that I could play as key a role there as I would in the lower energy experiment. Also, I had a feeling that it would help me retain my sanity. With the administrative job of running the lab, of managing a place like Fermilab, there are all sorts of headaches that come up. It is a nuisance. Most of these, the director of the lab, Bob Wilson, would take care of. I was heavily involved in the major decisions.

Pavlish:

That involved collaborating with and meeting with politicians?

Ramsey:

It involved all sorts of things; meeting with the Atomic Energy Commission, later with the Department of Energy representatives. There I had the following separation: When I was at Harvard, I was concentrating on low energy molecular beam research but there was an important meeting pertaining to Fermilab I would give that priority, but I would try to keep myself free while I was at Harvard. That went very well. Fermilab prospered and we did some very good molecular beam experiments, fundamental physics experiments at Harvard. I did not attempt to do any personal proton scattering experiments nor high energy particle experiments. But I was busily concerned in trying to make it possible for the best experiments to be done at Fermilab.

Pavlish:

You were appreciated for that.

Ramsey:

Yes, I think the scientists appreciated that. I had to be reelected every year and they kept me there for about sixteen years before I retired.

Pavlish:

Did you go to Washington a lot?

Ramsey:

I went to Washington and Fermilab approximately one day a week.

Pavlish:

Throughout your career did you travel a lot?

Ramsey:

Yes, I did a fair amount. Usually, I’d say the trips were giving colloquia on my experiments or going to Washington or Fermilab. Then there were large international meetings. In fact, I helped found the organization, the so-called International Conference on Atomic Physics (ICAP). This meets in all sorts of countries: the US, Europe, Japan, Russia. The last meeting was a very good one, in Austria.

Pavlish:

That gets together physicists from all over the world. I would like to look into that a little more: when was it founded? Did you get together with a group of your colleagues and say, “Hey, let’s do this?”

Ramsey:

That one had a funny history. The first meeting was not on atomic physics. We had these good methods for measuring nuclear magnetic moments. I was at that time, chairman of the Physics Department at the new Brookhaven National Lab. But we hadn’t any equipment there yet. One of the things I did was to arrange a summer meeting to consider a particular question, which was: what was the best method of measuring the magnetic moments of radioactive nuclei? We had been measuring magnetic moments for about seven years because we did that before the war, starting in 1937. By that time, Purcell and his associates, and Felix Bloch and his associates, had [independently] invented NMR. Which is essentially the same kind of magnetic resonance but you detect transitions not by the effect on the molecule but by the effect on the oscillator that induces the transition. Also, microwave spectroscopy of a Charley Townes and others was coming along well. The obvious thing for us at the Physics Department at Brookhaven to do was to measure nuclear magnetic moments of radioactive nuclei because Brookhaven would have facilities for handling the radioactivity. One of the first people I hired there was Victor Cohen, a former graduate student of Rabi’s who had done some of the early experiments on molecular beams. But, with these new experiments that had been recently invented, we did not want to start off with an obsolete technique. So, we called a conference with all the leading people in that field. It included Townes, Rabi, Purcell, and Bloch. The primary purpose was to decide whether we should start a big program to measure the magnetic properties of the nuclei of radioactive isotopes at Brookhaven. We invited all the key people [in the field]. The meeting was in one sense a great success, in that everybody learned a lot from each other. It was the first time we had an organized meeting since Brookhaven by that time had a budget. We could afford to invite people.

Pavlish:

This was held at Brookhaven?

Ramsey:

Yes, this was actually at Brookhaven. We decided it was a great meeting and that we should do it every other year, at least. But, in one sense, the meeting was a disaster. The object was to decide whether there should be a big push to use molecular beam techniques for measuring nuclear magnetic moments. At that time, in the molecular beam field, we had been measuring nuclear magnetic moments for five, six years. We knew we could do them, but we knew each one was difficult. We had to develop a source. We had to heat the sample. Then, it corroded the slit-jaws that guide the beam. There were all sorts of problems. A new element usually took between two weeks to a month to work. But we could do it, and it was worth doing. The other techniques represented were new and had only measured one nuclear magnetic moment, hydrogen. They also knew approximate the value of that magnetic moment was when they started. So they just re-measured it more accurately. They were enthusiastic that they could probably do a nuclear magnetic moment every day or so, and that this would clean up the field. It seemed obvious that the molecular beam technique was a bit obsolete. So we did not start it there. So, Bill Cohen started at Brookhaven to measure atomic hyperfine structures. Well, time went on. It was time for our next meeting two years later, and the other techniques had not discovered/ measured a new nuclear magnetic moment.

For various reasons it was very difficult when they did not know where to look. For example, in NMR you have to have a very strong field in order to get a big signal. On the other hand, in a very strong field the resonances are separated a long distance apart. They also are intrinsically very narrow. Therefore it was just a long search when they did not know where to look. Likewise in microwave spectroscopy, the search was difficult. But there was one person, K. F. Smith, in molecular beams who had not been invited to the conference, because we did not know he was working in the field. He was in England. He did not get the “benefit” of our meeting so he went along and began measuring a couple of nuclear magnetic moments of radioactive isotopes by molecular beam techniques, which worked out very well. So we discovered that this first meeting had given us misinformation as to that particular question. After that, I encouraged one of my best graduate students, Bill Nierenberg, to go to Berkeley to set up a highly successful program to measure radioactive isotopes. Now a large number of them have been made. Most of the first measurements have all been by molecular beams. After those results were available, NMR techniques could re-measure them more accurately.

Pavlish:

When you say that all the experiments had been with hydrogen, was that across the board? Was that true for molecular beams, as well as for NMR, and for Townes’ work?

Ramsey:

No. The molecular beam method worked well for first, measurements but the others did not because of their difficulty in searching. Hydrogen is the biggest magnetic moment, easily available and it value was well known form molecular beams. And it is abundant; it is in water. It is very easy to measure by NMR.

Pavlish:

At the time of the conference, people had not started looking for radioactive elements?

Ramsey:

Yes.

Pavlish:

Because you did that even before the war, when you were working as a graduate student you looked at hydrogen and others elements.

Ramsey:

Yes, but we did that with molecular beams.

Pavlish:

I know that. The conference was held at a time when there had not been any measurements of nuclear magnetic moments of radioactive elements. There had been experiments using all these techniques to find nuclear magnetic moments of non-radioactive elements.

Ramsey:

Yes, but the final measurement was usually by molecular beams.

Pavlish:

The main interest for looking at nuclear magnetic moments of radioactive isotopes?

Ramsey:

Well, to understand nuclear structure, basically. In other words, a good theory of the nucleus, (and now, there are quite good theories available) has to account for, is the magnetic moment of the nucleus.

Pavlish:

And that changes as the atom decays.

Ramsey:

Well, it changes when the atom decays: it is a different atom.

Pavlish:

It is a discrete jump?

Ramsey:

Yes.

Pavlish:

Did you tell the others when you were holding the conference what your motivation for organizing it was?

Ramsey:

Yes. They were told what it was for. And they all very honestly described what they were doing. But they were fooled by the fact that the one thing they had looked at was too easy.

Pavlish:

Many of them were your close collaborators, your friends.

Ramsey:

Sure, they were good friends of mine. In any case, coming back to your question about the International Conference on Atomic Physics. We did have a second meeting even though at that time we realized that in some ways we had reached the wrong conclusion. We did have a second meeting. It was still a molecular beam meeting. Then, some other atomic physicists doing other kinds of measurements wanted to join in. Over the next few years we developed a broader conference. What’s called the First International Conference on Atomic Physics was probably six years after this minus six meeting that started it. They were periodic from that point on.

Pavlish:

Every two years?

Ramsey:

They still are going every two years. One of the best meetings we’ve ever had was this last one.

Pavlish:

That is good to hear that people are still doing exciting research [in the field].

Ramsey:

Very exciting. A lot of new things have come about, and some of the old methods are still very interesting. Particularly interesting are some of the new investigations on ultra-cold atoms. There’s even getting to be some theoretical interconnection between atomic physics and condensed matter physics.

Pavlish:

You would say that back in the last fifty years or so, there has been a separation between atomic and condensed matter physics.

Ramsey:

Oh yes. And there still is. They are different but they are coming closer. What happens is that you make Bose-Einstein condensations and now they can make condensates also with fermions. You can observe phenomena with those condensed gases that are analogous to what you get in solid state. You can investigate them under a wider variety of transitions. For example, one of the more exciting things is that you can start with atoms and condense atoms as fermions. Change circumstances a bit and those atoms pair up, and in pairs they become the equivalent of bosons.

Pavlish:

The same atoms would be condensing as either fermions or bosons?

Ramsey:

Yes, depending on the circumstances. And you can go from one to the other. [pause] There is another category of my molecular beam experiments that I have not said anything about. The last major apparatus that we built was very good. We took advantage of everything we had learned previously and we had very good students, and associates. We built a long apparatus, much longer than this room. So far, I’ve only discussed when we did deflecting with inhomogeneous magnetic fields. In this one, we had the choice of doing the experiment with either electric fields or magnetic fields, focusing or not. That one we used for quite a large number of students’ PhDs. Rick Freeman, for example, did his thesis on it. When I finally fully retired from Harvard, Jim Cederburg, one of my former graduate students asked if Harvard would be willing to give that apparatus to his college. So, they could use it for research and teaching. I persuaded Harvard University to do so, so it was given to St. Olaf’s College, MN. I checked by phone recently and it is still running and producing good, publishable results. It investigates the internal properties of molecules whose properties can be measured only with it. There is no other operating machine at the time that can measure these. There are many many molecules so they have an unlimited field.

Pavlish:

Why would that be? Why hasn’t somebody replicated it?

Ramsey:

The first thing, it is chemical molecular physics, which is interesting physics. In fact, in the work we have done before, we found that when we have gotten results from it, then it is possible to develop a theory of the molecule that is reasonably consistent. They are not necessarily expecting to find revolutionary new discoveries. It is still important and on different molecules. Different people need different properties of different molecules. But it is not as much forefront physics as it would be if it were at Harvard and we were finding out a new property of a nuclei or a quark.

Pavlish:

Why would that be? To me, perhaps it is a personal bias and wrong to say it. It seems that finding out the properties of molecules might be at least as interesting, if not more interesting than finding the properties of quarks.

Ramsey:

Well, as a result of these experiments, there is now a fairly good theory of the molecules. So, you can calculate many of these things.

Pavlish:

I see, so you may be able to calculate a property and be 97.5% sure that it is correct.

Ramsey:

Maybe it is being only eighty percent sure of the calculation. But pretty sure that you know what the phenomenon is, then, you can do calculations that are more accurate. It is interesting physics and chemistry.

Pavlish:

Whereas with quarks the theory is up in the air?

Ramsey:

Exactly. It is a little analogous to what it was like some generations ago in condensed matter physics, where just measuring the density and other properties of matter was fundamental measurement. But, there was not so much [theoretical] understanding that followed. Now, there is more understanding.

Pavlish:

That is in condensed matter?

Ramsey:

Yes.

Pavlish:

The reason I ask is that when I hear the word “standards” associated with physics I think of ‘National Frequency Standards’ and I think of atoms and transitions between energy levels.

Ramsey:

There are many standards. Standard of time, length, color, etc. One of the standards is the standard of mass. That is one of the hot topics now. At the present time, the standard unit of mass, which is the kilogram, is a particular substance, which they store in a safe in Paris. And there are half a dozen exact duplicates of it. But the ratios of these duplicates change a little with time. What they are trying to get is a fundamental constant for measuring mass. Ideally, in terms of saying how many atoms you put in, and defining Avogadro’s constant rather than measuring it.

Pavlish:

It would be fantastic to get you speaking next to this instrument, to make an instrument like this one [now at St. Olaf’s], understandable to people outside physics. One problem is how to make something that is cool, hip, interesting, neat for physicists, likewise enticing for non-scientists who do not have the theoretical training or background. I think Feynman did this popularization really well. How might one lead a law student, say, to appreciate the beauty of this experiment [gesture outside window at law school campus]?

Ramsey:

I think you can do that. Enough of it is on the outside. It is true that the delicate parts and the vacuum inside where the particles go are on the inside. On the other hand, the coils that support them, and the place for the electrostatic field show from the outside. I think you can do a pretty good job of showing what you do, show what the forces look like and how it works. But yes, it is too bad that of course the smaller experiments are the ones that get thrown away.

Pavlish:

This one wasn’t!

Ramsey:

That is right, it is still in use. In fact, St. Olaf’s college is primarily an undergraduate college. They are doing publishable research with undergraduates using this machine. The only complication is that the machine is too big to move from there to here. It means that a group would have to go there to see it. [turn off tape to discuss travel plans to St. Olaf for filming]

Pavlish:

Professor Ramsey is traveling to Jordan in May to attend a conference or a meeting, of a group of Nobel prize-winners?

Ramsey:

It is a meeting to see if we can’t think of something to help the international situation in that area.

Pavlish:

You were recently at a conference, a meeting of Nobel Prize-winners in New York City, a few weeks ago?

Ramsey:

Yes.

Pavlish:

Is that something that has increased traveling?

Ramsey:

Yes, the one in New York City was more social, a very nice dinner and celebration put on by the Swedish Council. One meets a lot of friends there.

Pavlish:

The meeting in Jordan is more of a thinking time.

Ramsey:

Yes, that will occur in May.

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