George Wallerstein

Zierler:

Okay. This is David Zierler, oral historian for the American Institute of Physics. It is August 27, 2020. It is my great pleasure to be here with Professor George Wallerstein. George, thank you so much for joining me today.

Wallerstein:

Glad to do so!

Zierler:

All right. So, to start, would you please tell me your title and institutional affiliation?

Wallerstein:

I’m a Professor Emeritus at the University of Washington. I like to call it Professor Emeticus.

Zierler:

When did you go emeritus?

Wallerstein:

1998.

Zierler:

And you’ve been busy ever since, right?

Wallerstein:

I’m still busy, yes.

Zierler:

[Laughs] That’s great.

Wallerstein:

But much slower than I used to be.

Zierler:

That’s fine. That’s fine. Still active in the field. Well, George, let’s take it all the way back to the beginning. Tell me a little bit about your parents and where they are from.

Wallerstein:

Oh. My mother’s side goes back to the mid-19th century. I’m not even sure what state they came into. My father came here in 1900 with a degree in chemistry from a gymnasium and joined his older brother to form a chemistry consulting firm in New York.

Zierler:

Now both your parents came from Germany?

Wallerstein:

Yes. Well, my mother goes back a couple more generations, and my father came from Germany, from Fuerth, which was close to Nuremberg.

Zierler:

But your mother was born in the United States.

Wallerstein:

Oh yes, in 1888.

Zierler:

Where did your parents meet?

Wallerstein:

In New York City.

Zierler:

Where in New York?

Wallerstein:

I’m not sure.

Zierler:

Did your father continue with his scientific career?

Wallerstein:

It was applied chemistry, mostly applications to brewing, and then other things that could be done using special chemicals—enzymes—that enhance fermentation. So, you might say it was fermentation chemistry. Most interesting to other people is that he found an enzyme—that could be useful to get cocoa to ferment and thereby produce a product. There was a chocolate drink called Bosco.

Zierler:

Oh, Bosco! [Laughs]

Wallerstein:

Older people know that, remember that.

Zierler:

I remember it from my grandparents!

Wallerstein:

[Laughs] Well, what Bosco was famous for was that Hitchcock needed something to simulate the blood in the shower scene in Psycho. It turned out that Bosco had exactly the right flow properties, and since the movie was in black and white, it looked like blood.

Zierler:

Right. [Laughs]

Wallerstein:

So that was the blood in Psycho.

Zierler:

That is quite a claim to fame! [Laughs] George, what year were you born?

Wallerstein:

1930.

Zierler:

1930. So, do you have a recollection of the Great Depression? Do you remember from your childhood people struggling?

Wallerstein:

Yes. I saw men lined up trying to get a job. This is on the west side of New York City, on Columbus Avenue.

Zierler:

Now you spent your entire childhood on the West Side?

Wallerstein:

Yes. Yes, we lived on West 81st Street.

Zierler:

West 81st Street. Did you go to public school or private school as a child?

Wallerstein:

I went to private school, the Horace Mann Lower School and then the Horace Mann seventh through twelfth grade in the Bronx. That was probably the second-best high school in New York with Bronx Science being the best. But to go to Bronx Science, you had to be interested in science when you applied for at the age of 12 or something, and I wasn’t particularly interested in science at the age of 12.

Zierler:

When did you become interested in science?

Wallerstein:

Seriously with the dropping of the nuclear bomb in August of 1945. There was a very good write-up in the New York Times by the first science writer. I think his name was William Laurence. He included a lot of background physics in explaining how to make a bomb, or at least how to make U-235.

Zierler:

And that did it for you. That captured your imagination.

Wallerstein:

Yes, that captured my imagination. Yes.

Zierler:

Now being the son of a father in science, was his style to involve you in his career and his research?

Wallerstein:

No, not at all. Fermentation chemistry is too complicated.

Zierler:

So, you really didn’t have an appreciation for what he was doing on a daily basis when you were a kid.

Wallerstein:

No, definitely not.

Zierler:

Right, right. Were you good in high school at math and science? Were you a standout student?

Wallerstein:

I was pretty good, but in that good school—and we were a very good class. There were quite a number who were better than me. One year ahead of me was Francis Chen, now known as Frank Chen, who has worked in fusion plasmas and has written a couple of books on this. I nominated him to be Alumnus of the Year. I haven’t heard if that’s gone through or not. My thesis advisor went to Horace Mann 20 years ahead of me and became my thesis advisor at Caltech. Also, in my class was Michael Cohen whose thesis at Caltech was advised by Feynman.

Zierler:

What was his name?

Wallerstein:

Jesse Greenstein.

Zierler:

Ah, okay.

Wallerstein:

A well-known astronomer of his day.

Zierler:

Now George, I understand you developed an interest in boxing during your school-age years.

Wallerstein:

I was the third smallest in my class, so I took boxing and judo to protect myself. So, I continued the boxing as a featherweight, you see. Also, if you wanted to play football and you weighed 125 pounds, that’s not a good idea, but in boxing, you only compete with somebody your own size.

Zierler:

George, when you talk about needing to protect yourself, I assume you mean in the neighborhood in the west side, not necessarily at school.

Wallerstein:

Actually at school.

Zierler:

Really! Horace Mann was a rough-and-tumble place?

Wallerstein:

One time, John Gambling, actually later to be quite famous in New York, who had an early morning radio program for many, many years—he grabbed me from behind with his arm around my neck, but I had just learned what to do with that and he ended up on the floor in front of me. I was never bothered by anybody else after that.

Zierler:

George, when you were thinking about applying to schools, did you have an idea what kind of major you wanted to pursue?

Wallerstein:

Yes. By that time, I wanted it to be in science. I always was interested in history, but I’m terrible with languages and you can’t be involved with, let’s say, European history unless you can handle two foreign languages. That was a requirement.

Zierler:

Now did you speak German at all? Did your parents speak to each other in German?

Wallerstein:

Only when they wanted the children not to hear what they were saying.

Zierler:

[Laughs] Right.

Wallerstein:

But we did have relatives brought over from Germany, quite a few because we were a Jewish family, and they often spoke to them. When I was very small, I could speak to my grandmother, who came over when I was three and lived here only for a couple of years, after which she died. I didn’t know I was talking a different language. She just used different words than my parents used, so when I talked to her I used her words, and when I talked to my parents I used their words.

Zierler:

Right, right.

Wallerstein:

That’s the way for a child to become bilingual is for two parents, each of them speaks a different language, and the kid learns both without realizing it.

Zierler:

Now George, growing up in a Jewish family, was your family mostly secular? Were there any Jewish observances that they observed?

Wallerstein:

Very little.

Zierler:

Were you bar mitzvahed?

Wallerstein:

No.

Zierler:

That was not something that was important to your parents.

Wallerstein:

A friend’s bar mitzvah—the most boring afternoon I’ve ever spent! He was chanting in Hebrew or something for three hours. Maybe it was less than three hours, but it seemed like three hours.

Zierler:

So that was not a part of parenting that your family emphasized.

Wallerstein:

No. They would go to synagogue on the Day of Atonement and that’s about all.

Zierler:

Mm-hmm [yes]. George, why Brown University? Why did you choose Brown for undergraduate?

Wallerstein:

Well, there were a lot of better students than I at Horace Mann, so I didn’t think I was going to be competitive for Yale or Harvard. But my brother-in-law, who I liked very much, had gone to Brown, class of 1935 or something like that. He took me up there and showed me around and had me meet a dean or somebody. It was a good balance, and also it was smaller than some of the really big universities. So about, I don’t know, four or five of us got into Brown, and half a dozen got into Dartmouth from that high school. I don’t remember about Yale or Harvard—you know, one or two maybe.

Zierler:

George, were you fairly well-traveled by the time you got to Brown? In other words, did you spend much time outside of New York, or was Providence a pretty far trip for you at that point?

Wallerstein:

We made western trips in 4 summers, you know, in mid-July or August, but the only foreign country I visited was Canada.

Zierler:

What were your impressions of Providence when you got on campus?

Wallerstein:

Well, smaller than New York.

Zierler:

[Laughs] When did you declare your major at Brown?

Wallerstein:

Probably by the end of my freshman year. I did very well in the elementary physics course that I took, so I decided that’s the direction I would go in.

Zierler:

And so you declared the major in physics at the end of your freshman year.

Wallerstein:

I think that’s correct.

Zierler:

Who were some of the professors at Brown that were important to you?

Wallerstein:

Well, Lindsay, who was chair and who taught a course when I was a senior and who was in a vague sense advisor of my senior thesis. And Robert Beyer, who was very well-known in the physics community. I’d say Beyer was a more substantial influence because I took at least one or two courses, and then I was a grader for him in my senior year.

Zierler:

What was Beyer’s focus? What was he working on at that time?

Wallerstein:

I don’t know. His teaching didn’t relate to his research. I think he was one of those who went into ultrasound on the theoretical side. Sound was very important during World War II because ultrasound is what destroyers pinged to detect submarines, and as I said to a German astronomer, especially German submarines!

Zierler:

Exactly! And what about Lindsay? What was Lindsay known for?

Wallerstein:

Probably the Lindsay and Margenau book called Foundations of Physics. It’s still correct. No one explains there that way now.

Zierler:

Oh, wow.

Wallerstein:

It was a very good book…He also wrote several other textbooks; I think one at the elementary level and one at the junior level and mechanics or something like that. But the Lindsay and Margenau book, Margenau was at Yale. Was very well-known in the ‘40s and ‘50s.

Zierler:

George, what was your senior thesis on? What did you work on?

Wallerstein:

The use of analogies in physical theory. In other words, it was sort of philosophy of science.

Zierler:

Really!

Wallerstein:

Yeah. Well, you see, if you were good at mathematics, then you do something that involved a theoretical job. My best friend as a senior, Bill Doyle, did solid state theory, for example, and eventually did a thesis in that. If you were good with your hands and building things, you’d do something that was experimental. Well, I wasn’t good at either one, but I had taken a very good course in philosophy of science from a famous person in the field, Herbert Feigl, one of the original Vienna kreis—kreis is circle—who developed what was then called positivist philosophy. So, I had some background there. I’d also read some of the stuff by the astronomer Eddington who dipped into that stuff, but what he did in that field was crazy. My honors thesis was called The Use of Analogies in Physical Theories. I’ve quoted it recently.

Zierler:

George, what were some of the subfields of physics that most interested you as an undergraduate?

Wallerstein:

Well, nuclear physics because, you see, the nuclear bomb—everybody in physics got interested in that. Also, astrophysics. I had a very good astronomy course at Columbia from Lloyd Motz one summer. So, on applications to graduate schools where you always are asked what branch of physics are you interested in, I said nuclear physics and astrophysics. When I applied to Caltech, I had an interview with someone who, I later found out, had been the youngest person to win a Nobel Prize in physics up to then, who was the chair of physics at that time.

Zierler:

Right.

Wallerstein:

He said, “Well, we get an awful lot of applications in physics, and we only can accept a third of them. But astronomy at Caltech is quite new, and so if you expressed an interest in astrophysics, you can write me a letter which says if I don’t get in in physics, please send this over to astronomy.” I got in in astronomy where Jesse Greenstein was the chairman and saw that I had gone to the same high school as he had. My tuition of $1600 per year was paid by the G.I. Bill.

Zierler:

So, all of a sudden you got interested in astronomy. You were really not interested beforehand at Brown.

Wallerstein:

Yeah, I was. I had a very good course in it with Lloyd Motz, so I was interested in it. Yeah! Particularly interiors of stars and that kind of thing.

Zierler:

What year did you start at Caltech?

Wallerstein:

1953.

Zierler:

And you said that at this point astronomy was just getting started at Caltech?

Wallerstein:

It started in ‘48, and the first Ph.D. got out in ‘52, Helmut Abt. In ‘53, both Arp and Sandage got out, and Sandage wrote a very famous thesis that showed how you could derive the ages of what were then thought to be the oldest stars.

Zierler:

Now when you say astronomy got started in 1948, you mean astronomy as a distinct department. Otherwise, it was being studied within the physics department?

Wallerstein:

Only through one person, the famous Zwicky, but don’t ask me about him because then this will be a very long interview.

Zierler:

Oh. Well, that’s fine with me. I’m going to, then. Let me ask you about Zwicky.

Wallerstein:

Zwicky stories—this isn’t about Zwicky stories. Of course, the Mount Wilson Observatory had been going since around 1900, but that was really separate, although there was some cooperation. But an astronomy program only started in ‘48 when they brought Greenstein in from Yerkes Observatory to head up a new department. Now that time was of the greatest importance, though we didn’t realize it, in stellar astronomy because in 1951 or ‘52, the first metal-poor stars had been discovered. Before that, people thought all stars had the same chemical composition, sort of a creationist philosophy.

Zierler:

Why would that be a creationist philosophy? Because it would imply a God made all the same stars?

Wallerstein:

If everything in the universe has the same chemical composition, how did this happen? Well, the simplest answer was that’s how it was created.

Zierler:

Right.

Wallerstein:

Okay? [Laughs]

Zierler:

So, this discovery was one notch in favor of the universe not having a creator.

Wallerstein:

Yeah. A couple of stars were analyzed by Chamberlain and Aller, two people you know of…

Zierler:

Of course.

Wallerstein:

…and you certainly have interviewed Aller before. The stars that were metal-poor was a factor of 1% of the solar heavy element content. Then the other was the discovery of technetium in stars. Now there is no stable isotope of technetium on the Earth, except that it’s created in the laboratory and it’s used for a variety of medical treatments. It was used to eliminate two lumps on my right arm. It gives you 7 MeV photons, and it’s the only source for that. It has a half-life of six hours, but it was found in stars. There’s no long-lived isotope, so when it was found in stars, it must have bubbled up to the surface where the spectral lines were identified by P.W. Merrill—three strong lines in the blue. It means that nuclear reactions had to be going on in stars, and not just to convert hydrogen to helium and generate energy, but to build up elements as far as technetium, which is number 43, and all the way to lead.

Zierler:

George, what were some of the technological advances in the late 1940s that allowed for these discoveries to have been made?

Wallerstein:

I think it was the high dispersion spectrographs designed by Bowen, who was director of the Mount Wilson and Palomar Observatories.

Zierler:

Would you say that these advances were part of the thinking that Caltech needed a separate department for astronomy, because the field was growing?

Wallerstein:

No. Bowen was the director of the observatories and never had much to do with Caltech, although I’m sure they would have asked him what he thought about building up a department. I don’t know. That’s the history of Caltech, not mine. [Chuckles]

Zierler:

So, what was your sense, if you did have one, why Caltech decided to have a separate department of astronomy?

Wallerstein:

I don’t know. I’m sure that’s in the archives at Caltech. I assume there was a committee meeting and they decided what to do. That was also the time they got rid of meteorology because they had a terrible person there.

Zierler:

Did you work with Zwicky?

Wallerstein:

No. Everybody knew him, but nobody dared to work with him. No. He had no research students.

Zierler:

What kind of courses did you take in the physics department? I’m curious. Being in the department of astronomy, in terms of curriculum and course requirement, what were their expectations in terms of what you needed to do in the physics department?

Wallerstein:

They had quite a few. Certainly, the basic quantum mechanics—that was one quarter. The second half got very complicated, and I didn’t take it. And one quarter of thermodynamics. I needed more than that, so I took the Tolman’s textbook with me when I went on an expedition to Greenland. I spent a summer as an assistant on a glaciological expedition in Greenland. I was navigator and pit digger. I’d been a navigator in the Navy, so that fitted perfectly, and I had spent a previous summer on a small glacier with a graduate student Mark Meier at Caltech, so I didn’t have to spend the summers in Pasadena. It was a long time before I did that.

Zierler:

[Laughs] George, we skipped right over your naval service. When did you serve?

Wallerstein:

1951 to 1953 during the Korean War.

Zierler:

Where were you?

Wallerstein:

I was an ROTC student as an undergraduate because I signed up for this in ‘46. It was so near after the war everybody either had been or was expected to serve in the military in some way or other, so I signed up for ROTC. It’s much better to sleep in a state room on ships than in a foxhole who knows where. [Chuckles] So I had two years in the Navy, ‘51 to ‘53. It was an easy war. The North Koreans didn’t have a Navy. And my excellent captain was George Baker. [Laughs]

Zierler:

Right, right. George, how did you go about developing your dissertation topic?

Wallerstein:

The first research project I did there was on the light curves of the variable stars in the globular cluster M2. It has four Cepheids. Cepheids in globular clusters are different from the general field Cepheids. This was pointed out by Baade around 1952. But they’re quite rare. Arp, during another project, got plates for a large number of Type II Cepheids in globular clusters, and M2 was the most promising one because it did have four Cepheids. The only one that has more than that is Omega Centauri, but that’s at a declination of -47, so you can’t observe it from the Northern Hemisphere.

Zierler:

I see. George, what were some of the major questions more broadly in astronomy during that time, and in what ways did your dissertation research help to answer those questions?

Wallerstein:

My dissertation research on the “Spectra of Type II Cepheids” was pretty marginal. It didn’t answer any important questions. [Chuckles] I was just lucky that I got the votes of the committee. The big question—a lot of it was origin of the elements. You see, this is what Fowler at Caltech had been working on, originally just experiments on the hydrogen to helium cycles, and then he was going into heavier experiments. This was the time that Geoff and Margaret Burbidge showed up. Fowler’s work was very much on the origin of the elements on the experimental side. Geoff Burbidge was on the theoretical side, and Margaret Burbidge was the observational member of that team. Then they had Fred Hoyle on this team, also on the theoretical, perhaps a more speculative theoretical side, but he was one who came up with lots of new ideas. He didn’t mind being wrong, you know. He already had tenure. [Laughs] But no, he was the kind of person who never minded being wrong. If you look at his papers before World War II, you’ll see he has some really wrong ideas in that stuff. Nobody bothers to do this, though somebody has certainly written his biography. I don’t know. I’m sure it’s been done, a scientific biography for him. Also, at Caltech was Harrison Brown who had analyzed the composition of meteorites.

So, origin of the elements wasn’t my thesis. It was what I went into as soon as I completed my degree in ‘57. I couldn’t find a job, but Greenstein got a contract to do chemical composition of stars, and that fitted in exactly right, both the whole project with Burbidge, Burbidge, Fowler, Hoyle, Greenstein. He could hire several post-docs, so he hired me for a year, and after a year, I was able to get a position as an instructor at Berkeley for two years and then became an assistant professor. But it was through Otto Struve, who had moved from Yerkes Observatory to Berkeley, that I got the position at Berkeley.

Zierler:

George, I’m curious if during your time at Caltech the word cosmology was in use. Were people talking about cosmology or was that too early at that point?

Wallerstein:

Well, a few people were, but it was considered something that was a bit nutty.

Zierler:

[Chuckles] Who was talking about cosmology?

Wallerstein:

Well, certainly Hubble was, but Hubble died in September of ‘53. That’s when I arrived at Caltech. In fact, Millikan died in the same year, the first president of Caltech, same month, in September of ‘53. Sandage told me that Chandrasekhar had told him that Hubble was to have gotten a Nobel Prize in 1953, which he fully deserved, but he died in September and the prize isn’t announced until October.

Zierler:

Oh.

Wallerstein:

I don’t know who they found instead, though. You can look it up. That’s sort of interesting, if that story is correct.

Zierler:

When you say that cosmology was considered a bit of a nutty idea, in what way? Why was it a nutty idea?

Wallerstein:

Well, the rate of expansion of the universe was still nothing like what we’re talking about now—that is, the Hubble constant. It had been shrunk by the work of Baade’s, but it was still, I don’t know, 100 or 150 or 200 or something like that. It almost got down to 50, but it has stabilized now around 70. Anyhow, the largest redshift that had been obtained—and this is with a 200-inch telescope; that was the main reason at one time to build a 200-inch telescope—was 30,000 km/s. That’s z = 0.1. [Laughs] That was because they had to do it all photographic, and the noise on photographic plates when you took a long exposure—and that may have been a three-night exposure with the 200-inch on the faintest galaxy that they’d been able to reach. So, nobody knew what to do. Going to a longer exposure just got you more noise on the plate, and so six nights wouldn’t have gotten you a more distant galaxy.

Zierler:

Right.

Wallerstein:

That was all they could do until around 1960 when quasars showed up and also new technologies for electronic detection began to appear to become the standard detectors in the 1980s.

Zierler:

Now George, when you were looking at the origins of elements, looking back would you understand that field of study to be a component of cosmology?

Wallerstein:

Well, it was considered by that time that stars did it all. In other words, the creationists were out of business. [Laughs] Until Penzias and Wilson found the 3˚ background radiation. McKeller in Canada had such a hint of a background radiation. And this was summarized in a famous Burbidge, Burbidge, Fowler, and Hoyle paper of 1957. Quite remarkably, in the spring of ‘57 I was getting the last observations on my thesis. The Burbidges were at Mount Wilson and they were using the 100-inch and I was using the 60-inch. I asked Margaret, “What are you working on?” Then she said, “Well, Willie and Fred are working with us to produce a review paper on the origin of the elements,” and that was of course the B2, F, H paper that came out in Reviews of Modern Physics in late 1957. It’s still considered to be a fundamental paper on the different processes in stars. Of course, there are vast numbers of subprocesses and various things like that.

Zierler:

George, why was that paper so fundamental? What was it about that paper?

Wallerstein:

Above all, it showed that you could produce almost all elements in stars with the help of supernovae for some of the heaviest ones which you can’t produce in stable stars. The supernovae were discussed there, but not much was known about them except that the light curves and there was type I and type II. One showed hydrogen lines and the other didn’t. But very little was known about them. But I think they pointed to supernovae as explosive nuclear synthesis or something like that in B², F, H. Otherwise, you see there were 2-neutron capture processes one could produce elements up to lead. The rest had to be done in Supernovae which could build up the heavy elements.

On July 13, 1958 I was observing with the 60-inch and its spectrograph. We got a phone call from Leland Cunningham at Berkeley that the repeating Nova RS Oph had an outburst. Following the advice of Capt. Baker, I had planned out what to do in case of a Nova outburst, so I started taking spectra. It showed rapid changes from night to night and observations with Alfred Joy showed cosonal lines after a couple of weeks. While at Berkeley I figured out how to generate temperatures in the circumstellar gas around the red giant companion of the Nova. We needed a few million degrees. A detailed model was worked out by Cusinelli, Wegner and myself but the paper was rejected. The manuscript circulated in “Zamizdat” form. We predicted X-rays from RS Oph that were lay or round.

Zierler:

George, when you got to Berkeley, did you continue on with your research in the origins of elements or did you work on new things?

Wallerstein:

Almost completely on chemical composition of stars. It was not specifically on origin of the elements, but chemical composition of stars.

Zierler:

Now were there people at Berkeley to work with on this field, or you were basically on your own studying this there?

Wallerstein:

I was on my own there, but I still worked with people down at Caltech. It’s not very far from Berkeley to Caltech. You can either buy an airline ticket, but then after a while I decided instead of that I’ll buy an airplane and learn how to fly. So, then I would fly down there sometimes myself. So, I flew a Cessna from about 1962 until I had a heart attack in 1995.

Zierler:

And you went back and forth that whole time.

Wallerstein:

Yeah, back and forth wasn’t on a weekly basis. I mean, it was a couple of times a year and then would stay for a week. I continued to use the Mount Wilson and Palomar telescopes for quite a long time.

Zierler:

So, it was the telescopes that compelled you to keep returning to Caltech. That’s what it was.

Wallerstein:

Yeah, that’s right. But there were also a lot of interesting things going on. Greenstein hired interesting post-docs, you know, who were also working on the chemical composition of stars, so there were a lot of attractions.

Zierler:

Were there not good telescopes for your purposes in northern California?

Wallerstein:

The Lick Observatory built a 120-inch and that was finished just about the time that I got there, or maybe a year or two after I got there. The large spectrograph was designed and it was the most effective one I’ve ever used. It was designed by George Herbig. I hope you were able to interview him while he was still alive. I would call him the best astronomer in the world in the second half of the 20th century.

Zierler:

Oh, wow. Wow.

Wallerstein:

Oh, yes. Any time I had a new idea, either he had done it or he’d tried it and it didn’t work. [Laughs]

Zierler:

George, can you talk a little bit about the science behind using telescopes to learn about the chemical composition of stars? How do telescopes tell us those kinds of things?

Wallerstein:

Well, there wasn’t any other way. You had to have high-dispersion spectra and measure the strength of the spectral lines in the high-dispersion spectra and model the stellar atmosphere. That’s all there was.

Zierler:

How would you go about doing this? These are calculations? These are pictures? What does it look like?

Wallerstein:

I used photography from 1955 to 1985 and digital-detectors from 1985 to my last observing on the 31st of December 2018. Actually, almost exactly 30 years [chuckles] with photographs and 30 years with digital detectors. The digital detectors are so much better, but they were a little long in developing, you see.

Zierler:

Why were the digital-detectors better? Better resolution?

Wallerstein:

Well, they’re quantitative. If you do photography, you have to get a relationship between blackening of the photographic plate and the intensity of the light that fell on it. That was nonlinear both at low end and the top end. So, you often made errors of 10 and 15% and maybe even more in measuring line strengths because the calibration of the photographic plates, though you did it the best way you could, there were always some uncertainties that were very difficult to overcome. Also, they were vastly more noisy than digital detectors are.

Zierler:

Did you achieve tenure at Berkeley, or were you always at the instructor level?

Wallerstein:

First I was promoted to assistant professor and I was promoted to tenure, except I got a phone call from the University of Washington a few weeks before that was to happen. So, I never became an associate professor. But I had just completed my instrument rating with flying the Cessna, so I wanted to fly in some dubious weather rather than simulated instruments. Simulated instruments, you put a hood over you so you can’t look out the window and you only look at the instruments in front of you. But I wanted to do the real thing and a chance even in the summer to fly up to Seattle was a chance to do real instruments in bad weather. So, I took it, and I came up there and I had a good interview.

I’ve always liked the idea of living here in Seattle because my hobby of meteorology is something you can practice up here much more than you can in central or Southern California. [Chuckles] Another interest of mine is mountaineering, and although you can do a lot of rock climbing in California, I was never good enough to climb in Yosemite. I mean I could…I was a mountain climber, not a rock climber. But I climbed the higher peaks in the Sierra Nevada. They’re much more accessible from Southern California than from north. Anyhow, here you have snow and ice climbing, and you’re not far from the Canadian Rockies and coastal region. So, if mountaineering is important to you, this is a lot better place to be than in Berkeley. Berkeley had the high prestige then. I mean, the two scientific universities, with the largest number of members 117; the National Academy of Sciences were by Harvard and Berkeley.

Zierler:

Now you weren’t looking to leave Berkeley. You were recruited essentially out of the blue.

Wallerstein:

Yes. That’s how you got a faculty appointment. Now we opened a position and got 300 applications for it.

Zierler:

Right, right.

Wallerstein:

Isn’t that…I mean…But the three who we hired were the top three on our list. Each one had another offer and came to us instead. All three were women, by the way. This was not affirmative action; they were the best candidates.

Zierler:

Right. George, do you have a sense? Who was it at the University of Washington that was most interested in recruiting you?

Wallerstein:

The chair of the committee at that time was Larry Willetts, who had done some astrophysics himself and was one of the designers of the hydrogen bomb, by the way. He was a friend of Teller’s, I presume. Anyhow, he was the chair of the committee, but others like Dave Bodansky in the physics department were interested in this. He was a nuclear physicist and he spent a sabbatical down with Willie Fowler, in fact. Said it was the best of his sabbaticals while he was here. He unfortunately died in the meantime, though his widow is still around here, Beverly Bodansky.

Zierler:

Now Washington, like Caltech, had its own astronomy department. You did not join the physics department.

Wallerstein:

No. I was asked which I wanted to do because we were going to have four positions altogether, and I said I preferred astronomy to physics. Small groups in a big physics department don’t carry much weight. [Laughs] I knew this from others, of course. Astronomers can explain to theoreticians what they’re doing, but the connection with solid state physicists is nonexistent. So, it’s impossible, or at least extremely difficult, to get the solid-state physicists to vote for a new faculty member in astronomy, and they sometimes dominate a physics department.

Zierler:

George, was your sense that when you were recruited, this was part of a broader effort at the University of Washington to gain stature in the field?

Wallerstein:

Yes, by creating four positions at once. So, Paul Hodge and I were two observers, and then we decided to have two theoreticians. The first one we hired was Jim Bardeen. He’s a very interesting person if you can get him to answer with more than a monosyllable. [Laughter] His father won two Nobel Prizes, and Willie Fowler said that he was smarter than his father. Jim had done research on rotating black holes, that is still quoted. So, he’s the first one we recruited. I knew him anyhow through skiing and through mountaineering, and he had a girlfriend up here who he met and went skiing with. We had every advantage over his other offer, which was to be a post-doc with Chandrasekhar. Chandra said, “I’ll pay you enough that you can go skiing anytime you want,” and I said, “We’ll pay you less, but you can go skiing every time you want. You’re not flying out of Chicago; you’re driving up for the day from Seattle.” When he came up here for a visit, we went skiing on one of the best snow days I’ve ever run into in the Cascades. It was not Cascade cement. It was not Cascade ice. It was six- or eight-inch powder on a firm base. [Laughs] So, he came here. That gained us a lot of prestige with physicists, both in our University and around the country.

Then we hired Karl-Heinz and Erika Böhm, whose stellar atmospheres and stellar interior stuff was very well-known. They were ready to leave Germany at that point. But it was almost about as late as they could leave Germany because of retirement considerations and so on and so forth. Erika Böhm came on my research grant until Theodore Jacobsen, who had been here since 1928, retired at the age of 70, and then she took over Theodore’s position. So, we had two more professors here. That was altogether a very strong, small department with 2 observers and 3 theoreticians.

Zierler:

Now George, when you got there, were you still focused pretty much exclusively on the chemical composition of stars?

Wallerstein:

Mostly, yes, but when you get a telescope, sometimes you see something else that looks interesting and you can take a spectrum of it and measure the wavelengths and intensities and so on. On the advice of Greenstein, I read the literature, and not just what was coming out, but old stuff. In one paper on spectral of irregular variables, which were the semi-regular, very cool stars, type M5 or something like that, I noticed a footnote where Joy said, after stating what the emission lines were, “The nature of this star may be different from the others in this list.” It was. It was called VY Canis Majoris. It had a very large circumstellar envelope with emission lines including low excitation lines like sodium and potassium. I found the potassium lines. No one had seen potassium lines in stellar spectra before.

Zierler:

What’s the significance of that? It requires a large, low-temperature envelope.

Wallerstein:

Later rubidium. These are resonance lines. It also was a very bright infrared star. In fact, someone doing infrared work said, “Oh, by the way, we found an interesting star. Maybe you would like to take a spectrum,” and then apologetically said, “Well, it won’t take you very long because the star is at declination -25.” I said, “That’s VY Canis Majoris!” It was! [Laughs]

Zierler:

George, what were some of the significances of these findings? What did it tell us more broadly about the origins of the universe and what stars were made of?

Wallerstein:

I don’t deal with the origins of the universe.

Zierler:

But isn’t that connected?

Wallerstein:

I deal with the origin of the elements and the evolution of stars…Well, we did find the three most metal-poor stars. The ones that were discovered around 1951 were a factor of 100 metal-poor, and we got up to 500. That was, I think, about 1962 or so. I’m not sure.

Zierler:

George, I wonder if you can—

Wallerstein:

After that, they become very rare, more metal-poor stars. Up to about a factor of 200 or so, there are lots and lots of them. Beyond a factor of 1,000 there are very, very few.

Zierler:

George, I wonder, though, if you can explain a little more. If you’re looking to understand the origins of elements, how different is that from the origins of the universe? What’s the break there?

Wallerstein:

The basic work on the origin of stars was all done by George Herbig, who I mentioned before. Gas and dust clouds get together someplace in the galaxy and they cool off by radiation. When they cool off, they shrink. If they shrink enough, then they cool faster and so they can shrink down into high enough densities for something the size of a star to condense out of it. They form in clusters. This is telling you all what George Herbig did, not what I did. So, stars lose mass, also. This was demonstrated by an astronomer at the Mount Wilson Observatory, a good friend of mine who unfortunately died in his late forties or so, named Armin Deutsch. He showed that from one of the very large cool stars (this was Alpha Herculis) that the gas coming out of Alpha Herculis was being silhouetted against a couple of companions, and you could show that this gas was leaving the star and there was no way for it to come back. The other red super-giants like Alpha Orionis and Alpha Scorpii showed the same thing, but you couldn’t prove with them that the gas that came out didn’t go out and then fall back in. So, this meant that both gas and dust were being ejected largely by the red super-giants, and in fact, one of the new…The number one new faculty member who we hired works on just that—on the red supergiant stars which are losing mass. In fact, she just wrote a book. Her name is Emily Levesque.

Zierler:

Oh, right.

Wallerstein:

She’s recently published a book on this. It’s a very good book. She sent me a copy for free because she was an undergraduate at MIT when somebody told her, “Oh, somebody found an interesting infrared star called VY Canis Majoris,” and so she found the paper that I had written on it. I tried to get her to come here to be a graduate student, but she didn’t. She went to Hawaii. Then I tried to get her to come here to be a post-doc, but no, she went to Colorado to be a post-doc. Then when we had an open position which later became three open positions, she was one of the applicants. I wasn’t on the committee; I was long-since retired by then. She was the number one candidate, and she’s assistant professor with us now.

Zierler:

George, were you still going down to Pasadena for your telescope work, or were there telescopes in the Pacific Northwest?

Wallerstein:

Well, no. No, that came to an end. For a while I went to Kitt Peak and Cerro Tololo and then we developed here the Apache Point Observatory with a 3.5-meter telescope and a very good Echelle spectrograph. So, I used that starting about in 1995 and have used it from then until 2018. Of course, I don’t go down to New Mexico anymore. We control the telescope by computer from here. Now this is one of the first that was effectively remotely controlled by computer.

Zierler:

Now were you involved in that, in developing a system for remote control via computer?

Wallerstein:

Not really. In setting the parameters we needed for a good high-resolution spectrograph, yes, but this was mostly done by Don York at Chicago. They were part of the consortium. I’m sure he was in charge of the spectrograph. We discussed this, but I never was responsible for producing any piece of hardware.

Zierler:

George, over the course of your many decades studying stars and working with telescopes, what would you say are some of the most significant discoveries you’ve been a part of?

Wallerstein:

Oh, that’s sort of hard to say because there was no single Nobel Prize paper there. [Laughs] But it’s such a big field that a lot of us were taking interesting steps. I think my work on the G dwarfs, which was published about in 1962 it was the first big data in astronomy. I did a survey of 30 G dwarfs running in metallicity from twice that of the sun to about 10% of the sun. We found a lot of stuff in there. We found, for instance, the alpha elements—that is, those whose main isotopes nucleus consists of an integral number of alpha particles like magnesium, silicon, calcium, and titanium—behave differently from what are called the iron-peak elements. When the iron-peak elements were deficient, the alpha elements were less deficient, and that tells you something about what’s developed in an advanced evolution of stars and ejected into the interstellar medium because these G dwarfs are young stars. What you see on the surface is what they started with, and that showed up in my survey of G dwarfs. I also recognized an error in the distance to the nearest star cluster, the Hyades.

Zierler:

Over the years, George, in what ways did technological advances, either with computers or with telescopes—how did that improve—

Wallerstein:

Above all, with detectors and computers.

Zierler:

Now why detectors?

Wallerstein:

The charge-coupled devices that came into…There were stages of development, but for users the charge-coupled devices became available about in 1985—earlier than that—they were somewhat experimental.

Zierler:

Why were detectors a game-changer?

Wallerstein:

Well, they’re 50 times as sensitive as photographic plates. [Laughs] Is that convincing?

Zierler:

[Laughs] I mean, if you can explain—

Wallerstein:

Also, the data was digital right there! You didn’t have to convert the photographic blackening into intensity, which is not easy because it was nonlinear.

Zierler:

So, the detectors were less labor-intensive?

Wallerstein:

Like what?

Zierler:

They were less labor-intensive?

Wallerstein:

Oh, the photographic certainly were labor-intensive, and these were substantially less labor-intensive, yes. The computer did the work.

Zierler:

But it’s not just that it was less work. You’re saying that they produced better data as well.

Wallerstein:

They were far more accurate, and they were 50 times more sensitive. In other words, it took 200 or 300 photons to get what you needed rather than 2 or 3 photons in a CCD so that the exposure times came down by a factor of 50 to 100, and that allowed you to go to a vastly larger number of stars. If you convert that into the volume of space that you can survey, you find that it’s absolutely enormous.

Zierler:

What did you learn about stars as a result of detectors?

Wallerstein:

The chemical composition of an awful lot of them. If you want to know what I learned, you go to the Astrophysical Data Systems and look it up and they’ll list all the papers I wrote on the subject. No single one that I might hope will be useful for the Nobel Prize, but an awful lot of them. And there were a lot of other interesting papers of a similar level, you see, because there are so many unusual stars whose chemical composition is interesting. So, a lot of people have been working on these things. Probably David Lambert from Texas was certainly one of the leaders, and Chris Sneden in Texas and George Preston at Carnegie also. In fact, when I retired in 1998, if Lambert and Sneden had been in Boulder, Colorado, I would have moved there, but I didn’t want to live in Texas. So, I had to stay independent here rather than join an excellent group working on chemical composition of stars.

Zierler:

George, I’m curious. Can you talk a little bit about…In what ways did theory influence your work, and in what ways did your work influence the theory behind the composition of stars?

Wallerstein:

Oh, that’s too broad. You’ll have to wait until I write my autobiography.

Zierler:

[Laughs] But generally, you were…

Wallerstein:

There was always work on what goes on in the interiors of stars and what bubbles up to the surface like the technetium. That’s the best example. That’s the absolute proof that nuclear reactions occur in stars. I mean, Bethe showed that the conversion of hydrogen to helium provides energy from the sun and stars, but that didn’t tell you what went on in the deep interior of stars. But once you got something which required the build-up of technetium which was number 43-something and the weight is 97 and 99 (there are two isotopes)…

You know, bad countries like North Korea and Iran say they need some U-235. Nobody in the United States believes that, except a few nuclear physicists and medical physicists. The only way to get high-energy photons to evaporate the two lumps that were in my right arm was technetium-99, and the only way to get technetium-99 is to start with U-235. One of the fission products is molybdenum-98, and that decays into an excited state of technetium-99, and that’s what you’ve got to use. There isn’t any other possibility. I have a little booklet that has all the different energy levels of all the nuclei. That’s the only way to get anything like 7 MeV protons which are used to evaporate two lumps, and they did the same thing for my sister; had the same problem…because she complained she had to go to the hospital every day, you see, which I did too because they can’t give you too much at a time or they’ll burn a hole in your arm. You get a small dose five days a week for six weeks.

Zierler:

George, I’m curious—

Wallerstein:

And it’s correct. They can only do it starting with U-235 as far as I know of.

Zierler:

I’m curious if there were any research endeavors at NASA that were of particular interest to you.

Wallerstein:

Yes. The Hubble Space Telescope I used in cooperation with Ed Jenkins at Princeton to look into interstellar lines in supernova remnants, and that’s very worthwhile.

Zierler:

And this was only possible with the Hubble?

Wallerstein:

Yes, because these lines are all in the ultraviolet. You can’t do it from the surface of the Earth.

Zierler:

What did you learn as a result of working with the Hubble?

Wallerstein:

Well, you learn about the dynamics of what’s going on in these clouds from measuring the different radial velocity components. It’s been quite a while since I’ve done that, like 40 years. [Chuckles] Some others have taken over doing that kind of stuff.

Zierler:

Are you waiting with anticipation about the Webb telescope?

Wallerstein:

Not really. I’m getting too old to start a new program with a new telescope. I’ll be interested to see what they find. Our former chairman, Bruce Margon, is involved with it, and I’m sure he’ll be a user of it. His diplomatic skills were essential for developing the Apache Point Observatory.

Zierler:

Right.

Wallerstein:

Without him as chairman, I don’t…Some of us were working on this. I was trying to get the financing for it, which I was completely unsuccessful at. Bruce Balick Princeton, Chicago, ourselves, and New Mexico State.

Zierler:

George, I wonder if you could reflect. You’ve been involved with so many different telescopes and observatories. Do any stick out in terms of being most important for fundamental discoveries?

Wallerstein:

They all have. The 60-inch that I used as a graduate student probably less so, but it might have been around 1900 or 1910 or whenever it was first built because it was the biggest telescope then. But by the time I was using it, it was a smaller telescope. I mean, the 200-inch was there. The 100-inch was there. Some 84-inch and 72-inch telescopes were around, so it wasn’t…Size made a big difference when it came to an optical telescope, and the two Keck telescopes were a really giant step that way. And now they’re building the Thirty-Meter Telescope, and a 40-meter I think is about finished by the Europeans Southern Observatory. They also looked into a 100-meter telescope and decided you just can’t do it. It’s too big and if you build something that big, the steel begins to bend. [Laughs] So, a 100-meter ground-based telescope—in other words, it’s the size of a football field.

Zierler:

Right.

Wallerstein:

[Laughs] And it’s got to move also! No. That doesn’t work. But probably the best telescope around is ALMA in Chile, which is a radio telescope with a wide range in radio frequencies.

Zierler:

Is it fair to say that materials—limitations aside in terms of building a telescope so big that it bends—is it fair to say that in the world of telescopes, bigger is always better?

Wallerstein:

Yes.

Zierler:

Why is that?

Wallerstein:

Well, if it’s twice the size, you get four times as much light, so you can observe the same thing in ¼ the time.

Zierler:

Can you talk a little bit about the differences in what they offer between land-based telescopes and telescopes that are launched into orbit?

Wallerstein:

Well, in orbit you get the ultraviolet which doesn’t come through the atmosphere. It’s as simple as that. That’s the simplest way of explaining it.

Zierler:

But that begs the question without that limitation, why should there ever be land-based telescopes?

Wallerstein:

Because we can build a 30-meter land-based telescope—and we’re doing it, or they may have even finished it by now—and to launch into orbit a 30-meter telescope is something we have not yet figured out how to do.

Zierler:

Mm-hmm [yes]. But if we could, we would.

Wallerstein:

The cost of building it on the ground is a lot. The cost of launching it into space—of course, you’ve got to assemble it there because you’ve got too much mass for one liftoff. So, it would be one flight after another, and we only barely are able to reach the space lab now that’s in orbit.

Zierler:

Forgive me, but the cost would be astronomical.

Wallerstein:

Yes.

Zierler:

[Chuckles] George, I want to ask you about a different aspect of your career we haven’t discussed yet, and that is your role as a teacher to undergraduates and a mentor to graduate students. So, first, I’d like to ask you teaching undergraduates, what have been your favorite courses to teach at the undergraduate level?

Wallerstein:

Well, there it would be junior and senior level. Yeah. I did until the mid-1990s teach the elementary course now and then, but wherever I was, there was always somebody of greater personality to teach the elementary course, and that’s a lot of it.

Zierler:

And you did all of your teaching in the department of astronomy or you taught from the department of physics also?

Wallerstein:

Always in astronomy. I never taught a physics course. I did teach the basic course in our department of Atmospheric Sciences. Weather was always my hobby and enjoyed teaching it.

Zierler:

And that would include astrophysics. Have the terms astronomy and astrophysics been more or less stable over the course of your career, or have the meanings of those terms shifted over the decades?

Wallerstein:

That’s a little hard to say, and it’s very complicated. Many of the present big-time projects like Gaia and the LSST are old-fashioned astronomy of positions and motions. That’s 19th-century astronomy, a thousand times more accurate than it was then and a hundred times fainter, but that’s traditional astronomy—positions, motions, and colors. Yeah, and colors. Colors were really 20th century, but still, that’s traditional astronomy, getting basic data on stars.

Zierler:

On the graduate level, George, who have been your most successful graduate students over the course of your career?

Wallerstein:

Oh, that’s a little hard to say. Probably Verne Smith in chemical composition of stars is certainly one of them. Peter Conti at Colorado became the chair of the AUPA Board. K.S. Krishna Swamy at the Tate Institute became a “Distinguished Professor.” Very successful was Jason Cardelli in the field of interstellar gas and dust, but he died at about age 50, young for astronomer.

Zierler:

Certainly.

Wallerstein:

So that takes a little bit. Doug Geisler is a good choice, who went down to Chile, became chairman of the Physics and Astronomy Department at one of the Universities of Conception in Chile.

Zierler:

Very good. George, just to bring the narrative up to the present, I know it’s wonderful you’ve been busy since you’ve been emeritus. What have been some of the research that you’ve been doing in recent years?

Wallerstein:

Oh, let’s see. With my Alzheimer’s [or Asperger’s?] I’ve forgotten. [Laughs] A lot of it is still chemical composition in stars cooperating with different people. I’ve often had a post-doc here. Stars in globular clusters, metal-poor stars, stars with unusual elements in them—and still the Type II Cepheids.

Zierler:

Who have been some of your important collaborators in recent years?

Wallerstein:

Let’s see. In recent years…It depends on how far back you want to go. I think I would rather have time to think, to figure that out because every one of them has written a lot of papers themselves, I would say. It’s sort of hard to say, hard to come up with that, honestly, and get the judgment done, a carefully conceived judgment because that’s a serious question.

Zierler:

Certainly. Well, George, for the last part of our conversation, I’d like to ask you a few broadly retrospective questions about your career, and then one last question where I’ll ask you to think about the future a little bit. So, first, I want to ask you generally what do we know about stars over the course of your career that were unknown or were mysterious or that were poorly understood when you began in this business?

Wallerstein:

Practically everything that we now know about stars except for their positions.

Zierler:

So, what do we know about stars specifically? What do we know now that we didn’t know 60 years ago?

Wallerstein:

We know their intensities through the whole spectrum from the ultraviolet limit that Hubble can reach to far out into the infrared. The infrared involves a lot of ground-based technology developed by several people like Neugebauer at Caltech and Leighton at Caltech and other people who developed infrared technology. Infrared has been a very technology-driven type of science, and it goes further back than most people know.

When I was looking for a senior thesis at Brown, Lindsay suggested to me to look into the determination of ocean temperatures through infrared observations, and he told me who at Woods Hole to write to about this. Just remember this is 1950. I wrote to him, and his name was Stommel, I think, but he was incidentally the one who figured out how the Gulf Stream goes, a very well-known oceanographer. So, I wrote to him and he wrote back and said, “That’s all classified.” [Chuckles] Infrared technology was. “And you can’t be cleared in time to write a thesis which is due in May.” This was his answer in September or October.

This is mostly for spy satellites and things like that that infrared was developed, and that was going on long before anybody knew about it. Also, the Russians were doing the same thing, I’m sure, at that time. So that’s one thing like that. That was completely—Infrared has been completely technology-driven and that sort of laboratory stuff to develop high intensity and low noise. I know almost nothing about it. I mean, I will quote an infrared magnitude for a star, but that doesn’t tell me I know how they got it.

Zierler:

George, you mentioned that we know everything now about stars, except for was it their positioning?

Wallerstein:

The positioning is what we’ve been working on since 1800, but it’s just vastly more accurate now with the Gaia satellite and the LSST, which is called the Rubin Observatory now and is just being constructed. We’re getting pretty close to finishing it. But that will be doing it…I’m not sure how that will compare in accuracy with Gaia. I think it will go much fainter, though.

Zierler:

Why has star positioning been such a difficult field to wrap our heads around?

Wallerstein:

Well, because background…I don’t do that kind of astronomy. You’d better ask Zeljko in our department. He’s the guy who’s in charge of the Rubin Observatory project.

Zierler:

Well, George, for my last question I’d like to ask you. You know, of course, we cannot predict the future, but perhaps using powers of extrapolation from your long tenure in the field, what do you think are the most exciting avenues of research that remain to be studied in how we understand stars and what they’re made of and where they come from?

Wallerstein:

Why don’t you ask somebody who’s 60 years younger than me?

Zierler:

[Laughs] I’m asking you.

Wallerstein:

No…I’m not a…I don’t know how…Cannot…There are so many subfields in astronomy which are so important that can be reached with a huge variety of instruments that are now available that there’s no way I could answer that question off the top of my head, or maybe if you gave me a lot of time to do it.

Zierler:

Well, maybe an easier way to rephrase the question was if you were just starting out as a graduate student now and you had the same interest in star chemical composition that you’ve always had, what would be the kinds of projects that you would want to work on?

Wallerstein:

Oh! That requires deciding what I’m going to work on for either the next three years or the rest of your life is something I don’t answer with one or two minutes to think about it.

Zierler:

Maybe the easiest way to ask the same kind of question is you’re still active. You’re still working, and so what are the things that you would like to accomplish for the remainder of your career?

Wallerstein:

I’d like to understand the dynamics of the atmospheres of Cepheid variables. That is, a way that a pressure wave at lower levels develop and becomes a shockwave as it goes out. That’s one of the things I’ve been working on all the time, or with an eye to it. Something else would be…Let me see. Well, I had it in my head for a moment and lost it again. Oh, the populations of stars in the bulge of our galaxy. We have a project going on to understand the Cepheids in the bulge of our galaxy because there are turning out to be about three different types of type II Cepheids. That’s getting sort of…But this is something I have an assistant working on now to learn the type of Cepheids that are in the bulge of the galaxy because the globular clusters in the bulge are quite different from the globular clusters in the halo.

Zierler:

George, why is this a compelling area of research for you?

Wallerstein:

I know what the problems are, and I know how to go after them.

Zierler:

So, you’re confident that there are going to be concrete advances made in this endeavor?

Wallerstein:

There are going to be concrete advances by me if I can continue to get the necessary support to hire an assistant.

Zierler:

Well, on that note, George, I want to wish you a lot of luck on that endeavor, and I want to thank you so much for spending the time with me. It’s been a lot of fun talking to you and hearing all of your insights and recollections over your long and important tenure in the field.

Wallerstein:

Okay! And for Zwicky stories, there are quite a few people you can ask for that.

Zierler:

Absolutely. Okay.

[End of recording]