Interview transcript

We are now in Lindau, a small town in southern Germany, and this is the celebration, the 50th anniversary of the Nobelprizeträgertagungen and I am here with Professor Donald Glaser. Professor Glaser could you tell us a little bit why did you become physicist?

Donald Glaser: As a child I was always interested in mechanical things and I built model airplanes and radios and circuits and so on. At the age of eight I tried to read about relativity because everybody said you had to be very smart to know relativity, but I could not understand a word. But actually, when I came to high school and was getting ready to go to college I did not know the difference between science and engineering and my parents did not either. Nor did my teachers in high school, so I began in college as an engineering student and it took me about six weeks to figure out that that is not what I was interested in and that physics was really the key to fundamental understanding of the physical world. I found I was really fascinated by mathematics and physics and I could do it very well, so it was easy to make the decision to go in that direction.

There was a problem, which is that at first I had no idea of the difference between the level expected in high school and in college, so I got zero on the first physics exam. And then when I went to my professor and said I wanted to be a physicist he looked in the book, he said, ‘No you can’t be.’ He said that if you get a zero in an exam you can’t get an A in physics and you can’t be a physicist unless you get an A in physics. ‘But’ he said, ‘I’ll make you a deal. If you get 100 on every exam, even though it is illegal, I will give you an A.’ So that is what I did, I worked very hard.

Eventually, if we go very quickly through your career, eventually you received the Nobel Prize in Physics. I know that this was for the invention of the bubble chamber. Could you say a little bit more about that? Could you say a little bit more about how one detected elementary particles before and how you came to the idea of the bubble chamber and how that was developed?

Donald Glaser: As a result of my courses in graduate school at Caltech I became very much interested in the question of the fundamental particles; that is what is the universe made of and how do they interact to explain the properties of things? That is what interested me. I did a thesis in cosmic ray research which was the really only way to study particles produced by very high energy collisions in that time. That was in 1947-48. Using cloud chambers we could get one interesting picture a day. An interesting picture was one which showed a thing called a V particle and we had no idea what that was, but it was clearly something mysterious. Now we call them strange particles for complicated theoretical reasons, and with a slide rule I could compute the relativistic parameters of each picture before I had the next picture, so everything was well matched. But the number of facts that we could gather was much too small to get any theoretical insight and there was an enormous variety with huge errors.

There are a number of very funny things that happened, people would claim they discovered a new particle, and then Hans Bethe, professor at Cornell, also a Nobel Prize winner, calculated that when a particle goes through a cloud chamber it gets scattered by hitting gas molecules so that you can get almost any mass at all. Therefore, none of these particles meant anything. In fact there was a group in Armenia that published a paper saying there was a thing called a veritron, and a veritron was a particle that could have any mass. It was really nonsense, so things were in bad shape and so I set myself the task of trying to figure out a way to increase the rate of collecting data. The main method at the time was the so called high pressure cloud chamber which was a box with gas at about 20 atmospheres and every time you expanded the chamber there was an enormous bang and then you could not do it again for about a half hour. Because the thermodynamics required a long time for stability in order to get straight tracks, so that did not seem like a very good solution. At that time already people were using various kinds of counters with the accelerators, but the cloud chamber really was not very useful with the accelerator, because the accelerator could produce a beam of high energy particles every 5 seconds typically, and the cloud chamber just could not keep up with that.

Anyway, I did not want to work with accelerators. In those days at least I had the ideal that a scientist was a lone individual who thought very hard and focussed on a particular … It was not the idea of a big group of people. In those days the groups were not very big, but I decided what I wanted to do was make a detector that I could put on top of a mountain in cosmic rays in splendid isolation and discover new particles. That was the dream. I asked myself, ‘Well how can you do that?’ The main idea obviously is what you want is a transparent medium in which you can see tracks and which has high density. The ideal thing would have been a transparent lead brick … You can’t have a transparent lead brick, so I began to think what can you do with glass? What can you do with liquids? What can you do with crystals? I had the idea that … This is a cotton shirt but many shirts in those days were made of Dacron. And the monomer of Dacron I think is acrylonitrile which is soluble in. I do not remember, alcohol, water, forgotten. When it is polymerised to make Dacron it becomes insoluble. The fantasy I had was that a particle would come crashing into a big glass vessel filled with acrylonitrile and it would make whatever it is going to do, a spray of particles, and they would turn into Dacron and then I would fish it out and it would be like a Christmas tree and I would measure it. That was the dream. It turns out that I did not get any Christmas trees, but instead the solution gradually became brown. It was an excellent dosimeter, but it was not a particle detector.

No.

Donald Glaser: I tried a number, I tried a spark chamber, which is now much developed, and I had one working, but it did not seem to me good enough. Then the idea of the bubble chamber was very simple, which is that if you have a liquid confined like in a pressure cooker and you can then get it quite a bit hotter than the normal boiling point and then if somehow you could pull off the cover very quickly the liquid wants badly to boil. But if it is very clean and if the walls are very smooth it does not know where to start, and then if you would plunge a hot needle into it, it would start boiling where the needle was, and now my question is, is a very fast ionising particle like enough a hot needle, does it deposit enough energy? I made a calculation and I decided that I should use diethyl ether, mostly because I did not know really anything practical about chemistry. Diethyl ether comes in cans from the chemistry stockroom with guaranteed properties, so I could look up the surface tension, the boiling point, everything. The idea was that I calculated that the boiling point of diethyl ether is about 36 degrees centigrade, I do not remember exactly, and my theory predicted that I had to get it up to 140 degrees, which is ridiculous.

The idea that you could super heat to that degree is really foolish, so I went to the literature and I had probably the most exciting hour I have ever had in a library, because I found the Canadian Journal of Physical Chemistry, I think it was 1924, in which the chemists were trying to decide whether the kinetic theory of liquids was enough developed to predict how much you could super heat. They raised it to 40 degrees, to 50 degrees, to 60 degrees. The experiment was very simple, they had a little test tube made out of fine bore thermometer tubing and they filled it with a liquid under pressure and they put it in an oil bath of various temperatures and they were able to show that you could plunge the tube into the oil bath 40, 50, 60, 70, 80, 90, 100, 120 and it would sometimes sit for a few seconds before it erupted, but they said when you got to 135 it became very irregular. The experiment became really terrible. In those days luckily you could write sort of qualitative feelings in your paper, it did not have to be compressed down to the absolute minimum, so they said to show how bad the experiment is, here is a table of waiting times. 13 seconds, 2 seconds, 108 seconds and so on. I can’t remember but there were 30 or 40 such bad results. I plotted those results, the frequency versus waiting times and it was a poisson distribution, which meant that it was some random event that was … Then I calculated, since I had training in cosmic rays, how often a cosmic ray would go through a tube of that size. It turns out that the rate of hits accounted for half of the poisson decay time and we know that in a typical environment about half the radiation is cosmic rays and the other half is bricks and concrete and so on.

I became very excited and of course the question is have I discovered yet another dosimeter or can I see tracks? Then I built a little chamber about the size of my thumb and put it in a hot bath of oil, just as they had. No, I did an easier experiment first, in which I took two pieces of thermometer tubing, connected by a u-shaped tube so this one could be in hot oil and this one could be in cold oil. This one boiled and it forced all the liquid in here and then I switched and wait to see how long before it boils, and I got results similar to theirs. Then, and of course as we know all good physics happens late at night, so about 11 o’clock at night I finally had things going and one of the other students was working at that time but at this time I was now a young instructor. One of my friends who was a graduate student, he put out in the corridor a big thick lead can with a cobalt 60 source in it. At a certain moment he was supposed to pull the source out and I was 10 metres away. Every time he did that it boiled. It was clear, it was very exciting, but now the question is can I really see tracks? That question required building a chamber, very strong, because the pressure was 20 or 30 atmospheres, something like that. Then I connected the two of them, mechanical piston, and this was in a hot … Then I found out that the engineering department had a movie camera that could take 3,000 pictures per second, so I set up the movie camera, I turned round the crank and started it. And, you know, every time you shoot 1,000 feet of film, but finally I saw tracks. They were crude, but pretty good.

The next step was to take the same glass tubing and make two little tiny Geiger counters. Luckily at Caltech I had learned how to make Geiger counters because R A Millikan, a Nobel Prize winner for establishing the discreet charge of the electron, was president of Caltech and he thought it was very important for the students to learn every technical thing. He was called Uncle Bobby by the students, Robert Millikan. The standard joke was that he’d taking bids to buy a blast furnace, so the students could learn to make their own steel. But we did make our own Geiger, so I knew how to make Geiger counters and I made two little ones, so here is a Geiger counter, here is a Geiger counter, in between is the chamber. And then I could use a coincidence circuit to trigger a flash tube, and then I could get really tiny tiny bubbles. That earned me an opportunity to give a paper in the crackpot session of the American Physical Society because the American Physical Society is very democratic. Anybody who declares a serious interest in physics can join, and anybody who’s a member can give a paper. The meeting starts on Wednesday and goes through till Saturday afternoon, and by Saturday morning or Saturday noon, everybody has gone home, and then all the crackpots are there, so that is when I gave my paper. The first paper I tried to publish was rejected on the grounds that I had used the word ‘bublet’, which I thought was like ‘droplet’, but no, it was not in the dictionary. Anyway, that was the sort of invention phase. Then the next phase was how to apply the thing. I then built a chamber about so big, and I wanted to take it to Brookhaven. I did not have any money, I had my own personal little camera and it was all homemade. The valve which expanded it – I used the loudspeaker from my family’s first radio which I still had and a strong magnet. I applied for time and I got a letter back from the director of the Cosmotron, the accelerator: “It would be an irresponsible use of public funds to allow you to bring this thing to our laboratory.” Unbelievable. Finally my senior colleague knew this man personally and said “Look, he is an OK kid, he will not do anything bad, you should let him try.”

The compromise was that they would not let me have beam time, but you know the accelerators are surrounded by big blocks of concrete with a shielding and they are put next to each other and some radiation escapes from the crack between. I was allowed to set up a table about this size, actually a card table, outside of a crack in the shielding. But then I did not have any information about when the pulse was going to come. Luckily Jack Steinberger, who is here, was doing a real experiment, he was already a lot older than I and so he let me connect a coax television cable from his electronics to my little circuit. Then I took the film into the dark room and I came out and out of 36 exposures there was something, I can’t remember exactly, I think 27 pi-mu-e decays and in those days that was not known except from balloon experiments, very difficult. I was waving this film around and pretty soon the director came running out, so from then on there was no problem getting money. It was early days after the war, it was 1951 or -52. There was plenty of money but still there was already great conservatism, but once I had that then I could build bigger and bigger chambers and that is how it went.

That was a fantastic story.

Donald Glaser: There is another aspect of it which I have not written anywhere or told publicly, which might amuse you. When Enrico Fermi heard of this he invited me to come to Chicago to give a talk. I did and everybody was very polite and he was very polite and they were very congratulating and so on. He said: “But Doctor Glaser, why did you think this would work?” I told him my theory and I had a detailed thermo dynamic theory which I had worked out, because it was a difficult experiment. I had little kerno engines with pistons going in and out of a bubble and I had to know what is the surface tension of a bubble and what is the vapour pressure. I had to know whether when a bubble is less than a micron, do macroscopic values of properties of liquids apply? I calculated all that and that predicted these 140 degrees and it really was correct. Fermi kept asking me and I could not figure out why he cared. Then I asked one of the young physicists who was my age, afterwards, how come Fermi cared? Fermi also had the idea of a bubble chamber and he proved that it could not work. How could that happen? When I told this story to Emilio Sègre he did not believe it, he said, “Fermi never makes mistakes. And certainly not one of that magnitude.” Then I learned that Fermi had written a textbook of thermo dynamics and I found a mistake in it which precisely had to do with what is the vapour pressure over a concave surface like the inside of a bubble. Because there was a well-developed thing for the vapour pressure over a droplet called the Thompson equation with logarithmic … anyway we do not need all that technology. But the point is that he made a very subtle mistake, it was a diagram that was drawn wrong. That subtle mistake and I just have always been so grateful that I did not know about his book or I would never have tried either.

I can tell you, I got that book in the 1960s because it came out in a second edition or something.

Donald Glaser: You have that book?

Yes, but of course I could not find that mistake I mean that …

Donald Glaser: Yes.

… it was special. That was a very special story you told us and I think that we are very grateful for that. For me the really mysterious thing is now you have told us something which clearly shows that you did something, you enjoyed it, it was fascinating to be in the library, with the journal, in the laboratory at night and at the Cosmotron and so on. But I know that since you received the Nobel Prize you have started doing something else. Could you tell us why a little bit?

Donald Glaser: It is very easy. As I mentioned I was hoping that I would sit by myself on a mountain and discover particles. But it turned out that this gadget, the bubble chamber, was ideal for the accelerators and so I was trapped, I had to work with accelerators, and so I did and I took car loads of students and equipment and so on. But I did not like that, and finally the last paper that I contributed to, there were 23 authors and we had to go to Geneva to agree on the final draft because we had so many pictures that I sent them to many countries and so then there were Italians and Germans and so on, everybody, so we had to come together to agree, because maybe we used different standards of measurement and so on. And I could see that that was the trend and it used to be until then that if I had an idea that I was excited about, a whim, an impulse, I could go to the lab and collect my students and try to persuade them that this was worth doing and we could start on it a few days later. But in high energy physics you had to submit things to committee after committee after committee and so you become essentially a combination politician-administrator in which the science part is a very small part.

In a way the Nobel Prize set me free because I knew they would not fire me if I did not publish something for two or three years. That allowed me to go into molecular biology, which had always interested me, because when I was a graduate student at Caltech was the time that Max Delbrück and others were doing their very exciting work, really working out what molecular genetics was. In those days physicists could do that. Because it was mostly a question of being very clever about combinatorics and logic and so on. And it did not require much skill or knowledge of chemistry, either. I wanted to do that and when I got my degree I went to Delbrück who was a tough character, a nice man but very strict. I told him I had been enjoying his seminars and he had seen me around. I said: “Could I be a post doc in your lab?” and he said: “What’s the matter, can’t you get a job in physics?” I was so frightened that I went away and then some years later we became friends, he invited me to teach a course with him on theoretical biology at Caltech. So I went into molecular biology, quite seriously, and worked on, mostly on control and repair of DNA synthesis in bacteria and also in mammalian cells. I suppose the most important thing to come out of that was a study of zero derma pigmentosum which assessed skin cancer, that people are very vulnerable to, who are deficient in repair mechanisms for damage caused by ultraviolet light. Such people can live completely normal lives if they stay out of the sun, so mostly they sleep during the day and they go out at night. But it is known now that there are seven enzymes, and we need not talk about, but the mechanism is now well known and I was not the only one, many people working on it. But we worked on it at some length.

Then at a certain moment some friends approached me and said: “You know, a lot is known about DNA but it has not done humanity any good.” We formed the first biotech company, I did it with a couple of friends, and also I had students in molecular biology that could not get interesting jobs and that was another reason for starting it. I had two kids and I was concerned about graduate school for them, so there were many motives, financial and otherwise. That was a very exciting time. One of our consultants was Ham Smith who was here at this meeting, so we became good friends. That was a very exciting time, but it had the disadvantage that it industrialised molecular biology and also molecular biology became to be more and more biochemistry. I am not good at biochemistry. I do not enjoy it probably because I am not good at it, so I quit. I continued with the things that our little company … I was chief, chairman of the Science Advisory Committee, but I did not have any real business responsibility. That is when I went into neurobiology, which is what I work on now.

I think this story is so fantastic. First you have this when you developed the bubble chamber and you know, almost classic way, I mean this hour in the library and what happens late at night and so on. Then when you get the Nobel Prize you sit down and you think about what to do, do something else. I do not know. I mean we have 706 Nobel Prizes have been given out since 1901.

Donald Glaser: In the sciences or altogether?

Yes.

Donald Glaser: In the sciences?

No, this is all in all subjects. I do not know of any other case where the reaction to getting the prize is what you did. I mean to sit down and to think can I do something else? Many people have drifted into other areas, but not immediately like that. From having thought about it and saying: “Now I’ll take this possibility.” I think you have given us a very very good interview, and I did not have to ask any questions.

Donald Glaser: I’m sorry.

It was very special I think, so I think we should thank you very much. Is there something more you would like to say to young people around the world?

Donald Glaser: Sure, I mean the usual advice which I believe very seriously, is that in picking a profession or having picked a profession, to pick a particular subject, you should try very hard to find one that you really are interested in. Because whatever you do it is going to be very difficult and it is going to take a lot of persistence and if you have to force yourself to do it, you will not be as good at it. It is not good to say: “I am going to suffer for 20 years and then I will finally have the answer.” But you have to enjoy the process within reason and be very very interested in it. That is the idealistic advice. The realistic advice is you also have to ask can you earn an honest living if you do this? That is tougher and it is much harder now than it was after the Second World War where there were many opportunities and even academic jobs were very easy to get. When I got my degree I had five offers from different universities and I had done a respectable thesis, but not heroic, and it was pretty easy.

The problem is, and now it is unfortunate, but the result of the difficulty in finding a good job makes the students very conservative. They want to end up, quite reasonably, as a certified expert in some field which is in demand. If you say: “Hey, I have this idea and it is really exciting if we can do this” they are not willing to gamble, and you can’t blame them. The same thing happens with assistant professors. Until you have tenure you have to be conservative in order to survive, so only the most courageous risk takers can be lucky enough to do something which is far out. By the time you are an associate professor you can’t stay up till midnight every night. Everybody here has been talking about your people are most creative before they are 30. Well, part of the reason is that before you are 30 you have a lot more energy and endurance and it takes hard work and concentration and a very good memory for the mistakes you made. But I tend to forget some of the mistakes I made, which I did not used to do, so I think there are good biological reasons why you do better … What I think is needed is something they have been doing at Harvard for some time, which is called I think a junior fellowship. Anyway, what it amounts to is roughly a five-year appointment with a guarantee of no evaluation, no reports, nothing, until the end of the five years. I think that one of the political speakers on the first day spoke of a thing like that. I think that is really a very very important thing. Because it still will be risk taking. A student will still have to try something, say, “Well I have five years in which to do this wild idea and if it works it is wonderful.” But as whoever supposes, if it does not work, you end up teaching school in a small provincial town, which is a bit severe, but anyway my advice to students is to make some kind of a trade-off. But they know that. They do not need us to give them advice.

I think your advice was very good and I do not think that everyone thinks about those things that you just told them. Thank you again very much.

Donald Glaser: Another component obviously is to have an honest self-image. There’s a lot of people who want to write symphonies, they want to write great novels and so on, and they do not have the talent. It is very important to have self-knowledge in order to make this risk benefit calculation sensibly.

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