Warren Moos

David Zierler:

Okay. This is David Zierler, oral historian for the American Institute of Physics. It is May 7, 2020. It’s my great pleasure to be here with Professor Warren Moos. Warren, thank you so much for being with me today.

Thank you for inviting me.

Zierler:

So to start, Warren, can you give me your title and institutional affiliation?

Moos:

I’m Professor Emeritus at the Johns Hopkins University in Baltimore in the Department of Physics and Astronomy.

One remark I should make is that my full name is Henry Warren Moos, but I am usually called Warren, not Henry. I’m known in the literature as H. Warren Moos or Warren Moos, but rarely Henry Moos. Oh, and also H. W. Moos. So, I travel under several different names. [Chuckles].

Zierler:

Excellent. Okay, great. So let’s take it right back to the beginning. Tell me about your birthplace and your family background and your early childhood.

Moos:

I was born in 1936 in Brooklyn, New York like so many other people on Long Island.

Zierler:

What neighborhood in Brooklyn? I know Brooklyn.

Moos:

Oh, you know Brooklyn? Well, I was born in the Fort Hamilton Hospital, which I only know because when I come off the Verrazzano Bridge and head out on the Belt Parkway, it’s, I think, the next exit, okay?

Zierler:

Okay. [Laughs]

Moos:

But I have no memories of that. I grew up further out on Long Island, first in Queens and when I was about, seven or eight, moved to Nassau County, which I describe as a vast intellectual wasteland, okay? [Chuckles]

Zierler:

Now, were your parents native New Yorkers?

Moos:

Well, it’s interesting. My father immigrated from Germany in the ’20s. He was part of that “lost generation.” If you’ve ever read Remarque, the novelist…

Zierler:

Yeah.

Moos:

…then you are familiar with what happened in Germany in the ’20s. He was too young to go to the war, but he got caught in everything else.

Zierler:

Right.

Moos:

The popular history book The Rise and the Fall of the Third Reich pretty much matches his recollections to me. He finally gave up and left. My mother was the daughter of Newfoundlanders. My grandfather was a high-iron worker, when he came to New York. So in a sense, I’m a son of immigrants, okay?

Zierler:

Yeah.

Moos:

My mother was born in the US, but it was shortly after her parents immigrated here.

Zierler:

Now did you pick up any German from your father?

Moos:

No, and you have to remember that I was a young kid in the late ’30s and ’40s. That was not a good time to have little kids running around the street speaking German to each other.

Zierler:

[Laughs] Fair point. Fair point.

Moos:

Okay. Furthermore, since my mother did not speak German, the incentive was very reduced.

Zierler:

Right. Now you went to public schools through twelfth grade?

Moos:

I went through public schools. I started out in the New York City schools and then transferred to the local district in New Hyde Park on Long Island at about second grade and then went on to Sewanhaka High School, which was the central district high school for that area. I completed my high school education at that school.

Zierler:

Now in high school, were you a standout student in math and science?

Moos:

[Laughs] Oh, boy. You know, I’ve been thinking about that a little bit. No. I was a middling good student. I think maybe a little bit of a misfit. Come on, all teenage boys are misfits, and I was just another one of them. I think my teachers knew I was smart; I was just aggravating, okay? [Laughs] I remember when I look back on it, there was a business teacher who ran the astronomy club, and the astronomy club had a number of us misfits. But here was this business teacher, who actually cultivated young scientists, if you can imagine this.

Zierler:

Really!

Moos:

In my homeroom was a young immigrant from Europe named Alar Toomre. Alar Toomre is professor of applied mathematics at MIT, and he’s well-known for his work on calculations of the dynamics of galaxies. Alar also was a MacArthur Fellow. It’s interesting. You know, here’s this business teacher and he’s turning out talent, and I don't think he was ever recognized for it. It’s just one of those remarkable stories.

Zierler:

Yeah.

Moos:

Anyway, that’s my experience --

Zierler:

Well, you couldn't have been too much of a misfit to get into Brown.

Moos:

Well, that’s another example. I’m, in many ways, a product of the tests. You know, everybody rants against the tests. I want to vote for them and to tell you a success story for the tests. [Chuckles] I had no way of going to college economically, no way. My parents were essentially blue collar and I was casting around looking for a way to go. I passed the New York state competitive exams and got a scholarship—only about $300, really modest, but in those days that was a bit of money.

Zierler:

Right.

Moos:

All of a sudden, people in the high school realized that, hey, we had this kid we were ignoring. You know, it’s very interesting. It’s a very interesting comment on our culture that it so emphasizes social class and it so emphasizes the right kind of polish.

Zierler:

Yeah.

Moos:

I didn't have those things, so among the other things I did, I took a test—the Navy was looking for talent. We were well into of the Cold War. They were looking for officer candidates that would go to college, almost all expenses paid as a Midshipman USNR while qualifying for a career officer commission through the NROTC program. The Navy finally got around to selecting me in the summer of 1953, giving me offers of two places. One of them was Brown; I took it, and of course, that was a tremendous watershed for my life. Brown had an enormous effect.

Zierler:

Now going into Brown, did you have an idea you were going to major in physics?

Moos:

I remember going there and writing…contacting my father and saying, “Should I…” Those days, you wrote , you did not phone. I said, “I’m trying to decide between physics and engineering,” and my father communicated back, “Go with physics.”

Zierler:

Really!

Moos:

Yeah. Well…

Zierler:

What was your father’s profession? What was his background?

Moos:

Well, he was half Jewish, which is another part of the story. His father was a German Jew who married Mary Ziegfeld. You’ve heard of Florenz Ziegfeld?

Zierler:

Sure.

Moos:

Cousin.

Zierler:

Oh, interesting. Okay.

Moos:

A distant cousin. My maternal grandmother, Mary Ziegfeld, was a cousin. The Florenz Ziegfeld branch immigrated a little earlier. So, my father’s background was to be raised in an upper middle-class German environment. He got one year of college, where he studied engineering, before the inflation took everything away, and then a few years later he immigrated to the United States and he became a blue-collar technician in the late thirties. He worked at Sperry Rand as a technician all through the war and until he retired in 1958. It was called Sperry Gyroscope then.

Zierler:

Yeah.

Zierler:

Right. So when you're asking him physics or engineering and he says physics, he’s coming from a background where he knows what he means when he says, “Go to physics.”

Moos:

A little bit. A little bit. Yes. He kind of saw me as a professor, and he knew what the engineers were like. And engineers, by the way, in industry are a very different crowd from academia.

Zierler:

Of course.

Moos:

They want to achieve practical results. Sometimes some of them act as kind of super-technicians and sometimes some of them act as managers.

Zierler:

Right. Right.

Moos:

So he saw me as this kind of more dreamy kind of guy—you know, less practical. Yeah, I think it was probably a comment on me on his part that he said physics.

Zierler:

So who were some of the big names in the physics department in Brown in those years?

Moos:

R. B. Lindsay in acoustics was a big name, but he was busy with University administration. I remember I wanted to work with him on a research project and we even discussed liquid crystals. He became Dean of the Graduate School in 1954. Bob Morse (later the President of Case Western) also was in acoustics, and he did some interesting work in the ’50s on… Well, basically there’s a problem in the ultraviolet attenuation of sound—excuse me. If you put ultrasound into metals at low temperatures, you get an unusual temperature dependence, and when it goes superconducting, this all disappears. It’s well-known, and I noticed recently there have been articles on it, like it’s a great discovery, but in fact… And he, with colleagues, was able to explain the sudden change using BCS theory, which had just been invented. I think BCS—what was that?—’57, ’58?

Zierler:

Yeah, right around there.

Moos:

Yeah, okay. Well, I had just left at that time (1957) and I remember coming back in 1958 and talking to them and they said, “Yeah, we cracked it.”

Zierler:

Wow!

Moos:

You know, the gap in BCS fixed it. So yeah, they did some interesting work, And I actually worked in that lab as an undergraduate and did my undergraduate thesis on the subject. I wrote a theoretical thesis on the variation of the attenuation with temperature above the superconducting point. That’s all gone. I mean, don't ask me to give you details! [Laughs]

Zierler:

No, no, no, but that’s interesting. So Warren, how well established was your identity as a physicist by the time you graduated Brown? Did you go to Michigan knowing the type of physics you wanted to specialize in, or you were still open-minded when you got to Michigan?

Moos:

Well, I had some undergraduate delusions about doing theoretical work, but the ardors of the Michigan graduate courses quickly cured that. Also, I had a lot of other ideas - which completely clashed with my career, especially in the later years. I decided that there were some things I didn't want to do. I didn't want to work in a big group, okay? And another thing, I had worked at Sperry Rand for a couple of summers, and in fact, they wanted to hire me long term, but I said, “You know, I don't want to spend my life building equipment that after three years is going to be junked.”

Zierler:

[Laughs] Right.

Moos:

And here I am at the end of my career… You know, I mean, I have built a satellite. I mean, I’ve worked on a number of major satellites and space missions. I’ve worked in all kinds of large groups, and in particular I spent a big part of my career doing sounding rockets where you launch things into the air and you may not get them back, okay? [Laughs]

Zierler:

Yeah. Right, right.

Moos:

Sometimes they land in the ocean or sometimes they land in the mountains. Sometimes you get them back and you rebuild them, but the point is I look back on that and say you can’t tell how things will work out. Oh, and the big groups. I’ve worked with big groups all my life, especially in my later life.

Zierler:

Yeah.

Moos:

So it’s interesting. So many of these things that you reject when you're younger…

Zierler:

Come back.

Moos:

…as you grow and you get somewhat more senior, you adapt.

Zierler:

Now how big a deal was Sputnik to you? How large that did that loom in your life in terms of your decisions, what you were working on, what you wanted to do?

Moos:

None. Well, it had a big effect at the University of Michigan. David Dennison, who taught me graduate mechanics was proud that after the launch of Sputnik he was able to disappear into his office and calculate the orbit.

Zierler:

Right! Right.

Moos:

There was a huge increase in the enrollment in graduate courses in physics because of Sputnik… I went there in September 1957 and Sputnik was what Oct. ‘57? Yeah. So there was a sudden upshoot. Of course, I only took courses seriously for about two years and then while I started working on my thesis, there was a huge upsurge in enrollment.

Zierler:

Right.

Moos:

It was incredible. I mean, I remember going in my third year to an advanced quantum mechanics class and it was jammed!

Zierler:

Yeah. Yeah.

Moos:

It was quite remarkable.

Zierler:

Right. Right.

Moos:

So I think… Okay. Well anyways, I’ve gotten through the education story here. I was thinking about it this morning. Anyways, although I have reservations, I guess I’m a proponent of the test, contrary to many others. I know the bad things about the test. Actually; in selecting graduate students, I’ve seen this. There are a lot of problems with the Graduate Record Exam, but it is a way of discovering talent that nobody knows about. If, as a country, if you really want to—what shall I say?—break the system and reach out and get a large reservoir of talent, which we did in the ’40s and ’50s, I think some kind of arbitrary test situation is something you have to do. That makes me a proponent of the test.

Zierler:

Okay. Okay.

Moos:

But as a lifetime educator recognizing the problems…

Zierler:

Right. Sure.

Moos:

…of short-answer testing.

Zierler:

Sure, sure. So at Michigan, what professors did you gravitate towards? Who became your advisor?

Moos:

Oh. Well, Dick Sands was my advisor, and the other important person in my training, who has become better known, was Peter Franken.

Zierler:

Right.

Moos:

Dick is still around, although he’s in his nineties and I think it’s starting to show. Peter passed away. He was the director of the Optics Institute in Arizona towards the end of his career. He was known for his work in atomic physics and optics. He was known for an early experiment on non-linear optics. He did the first laser optical harmonic generation in a solid while he was at Michigan.

Zierler:

Mm-hmm [yes].

Moos:

They both were two young faculty members just arrived when I came, and they were sort of mavericks. Peter in particular was a real maverick, to the point of… I won't go into detail… He was extreme, but I think they were both. They didn't fit into the typical Michigan mold at that time. Both Dick and Peter emphasized treating their research students as co-workers and colleagues. I think Michigan was in fact going downhill when they came. Michigan now is a major institution; I think at that time they had fallen down. So, if that helps describe the environment.

Zierler:

Yeah, yeah.

Moos:

I can remember, for instance, Franken arguing on the phone. We had like… This just shows the times. Our lab was in the second basement of the Randall Lab, and we had one phone, one phone for several faculty members and, I don't know, eight or nine graduate students, okay? [Laughs] So here’s Peter on the phone pacing up and down (because he always paced). He’s talking into the phone and he’s arguing with the editor of the Physical Review Letters. His argument was concerned with Theodore Maiman who wanted to publish his letter on the demonstration of stimulated emission from ruby, and they rejected it because Maiman had been forced by the head of the lab at Hughes to hold a press conference and go public. They said, “Well, you already published it in the newspapers.” I think he ultimately published it in Nature, but in a way, they just completely blocked him. I am not sure how this affected Maiman’s career, but it had a huge effect on the students in our laboratory. The director of the Hughes Lab would come through looking for people and he had no success. [Laughs] I mean, I can remember in my mind I saw him and I said no. You know? He was marked, marked that he had done this to Maiman. But I can remember that. I can remember that experience.

Then I can remember Franken at the blackboard in an adjacent office. The phone was outside one of the lab’s offices. We were at the board and he was explaining to us what stimulated emission was all about and the problem of making a laser. The basic question was would the stimulated emission feedback loop take place in just a few modes or would it take place in many modes? He explained to us that if it was many modes, you wouldn't see much except a shortening of the decay time, and if you could get it in a few modes one could observe the properties of coherent light that we now associate with laser emission. So when I went to work for Schawlow a few years later and he related to me how he had come up with the Fabry-Pérot cavity for lasers on an overnight train ride from Toronto to New York, which reduces the stimulated emission to a few modes, I understood instantly what he was talking about because I’d had that conversation with Franken. Yeah. I think it was a very stimulating environment.

Zierler:

And what was the process for you developing your dissertation topic?

Moos:

Say that again?

Zierler:

The process—how did you develop your dissertation topic?

Moos:

Oh. Well, I announced… I was a teaching assistant and I wanted out. I was very uncomfortable being a teaching assistant. New teaching assistants at Michigan often got assigned to classes where they were not even dealing with freshmen. I was dealing with people who were my age. Education majors, forestry majors, and other kinds of people would take physics in their last year. It was a very uncomfortable relationship as a student playing the role of a teacher to people your age. It’s not easy. It’s not easy. And they didn't treat their TA’s very well. We were put in a different building. It was old and run down. We were separated from the main life of the department. It was just like we were hired help. It was not fun. I was seriously considering leaving. I was actually thinking of leaving Michigan, and Sands kind of picked me up and he said, “Well, this is irregular, but I’ll get you a research assistantship”. Because he had just come, he was looking for talent.

Zierler:

Right.

Moos:

“I’ll let you work in the lab,” and I jumped. I said, “Gee, I want to do this.” I hadn't even passed the requirements to start thesis research. You know, I was still taking courses, but the chance to work in a lab was just great. So there I was, and I was in the lab all the time. The problem that came up was we were doing paramagnetic resonance, which is basically a microwave interaction with an atom with a magnetic dipole in a magnetic field. If you get the right frequency (~2.8 megacycles per gauss), you get a resonance. We were in a resonance group and that’s what we did. We did all kinds of resonances. We did resonance in alkali vapors at radio frequencies. We did it in solids with microwave paramagnetic resonance. So, the question was posed to me: “Can you do paramagnetic resonance in a gas of alkali atoms?” and I got a signal!

Zierler:

And this was your question? You came up with this question?

Moos:

No. It was posed to me as a challenge. “Can you do it?”

Zierler:

Right.

Moos:

I mean it was just a raw question. “Can you get a signal?” and I did it. Then they said, “Well, that’s nice, sonny, but how about we make some meaningful measurements, okay?” [Laughs] “What we want you to do is we want you to measure the density of atoms in the gas. We want you to know how many atoms per cc are in the cesium gas, and we want you to determine what the line width is (which gives the collision frequency for the alkali atoms) , all right?” Determining the density of atoms was a little harder. We eventually came up with copper sulfate as our standard. I’m not sure it was a good standard, but we used the electrons in copper sulfate as a measure and measured the absorption coefficients for both the alkali gas and the copper sulfate reference sample. So, I had to heat the cesium to a decent highly stabilized temperature, to produce a detectable density inside a bulb, a small quartz capsule that was made with quartz selected so that it would not absorb. For instance, if you have quartz with iron impurities, you get a broad absorption band underneath. These are all these little details, but those are the kinds of things that you had to worry about. And of course, I was working on the edge of signal to noise, with all analog electronics and basically, I did my thesis between six in the evening and five in the morning. You know, I would come in at midday, work on all the chores we have to do during the day. At 5:00 when everybody goes home…

Zierler:

Yeah.

Moos:

…then I would have my electronics heating up and you could see. I mean, you could see all the surges coming through on the line. When everything quieted down around 6:00, you started taking data and you worked all night. I did that for, I don't know… I don't remember how long it was—six months, a year, something like that. But in the end, I came up with something. Now the interesting thing about it is in the end, the value may have been wrong. And why was it wrong?

Zierler:

What was wrong?

Moos:

A later measure of the cross-section differed by a factor of 2. The people at Bell Labs later made measurements and they said, “Well, you're wrong.” I never checked. We couldn't check it, because the apparatus had all been torn apart by then. But the two experiments differed by a factor of 2. Well, why could the Michigan result be off by a factor of 2? Best guess is that the copper sulfate, which is a hydrated crystal, had probably changed its composition slightly. You know, it got a little warm. It was in a warm cavity and maybe we had driven some of the water off and there would be a slight change in some of the copper sulfate. That’s our guess. And, of course, I had escaped by that time…[laughs]…and gone on to a job at Stanford with Schawlow, which is another interesting story.

Zierler:

Right. Now Stanford was a post-doc initially?

Moos:

Yeah. Well, I was looking for a job. I didn't know where I was going. I was just looking around. And I’ve got to give credit to Sands because Sands was sick that summer of 1961. He literally got out of his sickbed a couple of times. One of the times was to work with me in the lab, but another time he got up to attend a meeting with Schawlow and talked to him. [Laughs] So I was told, “You go to this meeting,” and I went down and Schawlow said, “Well, I’ve got a job. I’m starting a lab at Stanford.” He was just leaving Bell. He shook my hand and he said, “If you're interested, I have an opening.” I said, “I’ll take it!” okay? [Laughs] It was… Well, that was it. I then finished up my thesis in the fall of ’61 and went to Stanford. My thesis professor Dick Sands lent me the money so I could drive to California.

Zierler:

Wow!

Moos:

Because I had two kids. But anyway, we did drive with two kids. One was an infant and the other one was two and off we went to California. So, it was a big deal. It took me a number of months to scrape a little money together to pay Sands back. It was that tight. So as I said, it’s a great story. I think there were a lot of generous people, and Stanford was a big break. That was the opportunity to get into the big time.

Zierler:

Yeah, right. So what were your impressions of Stanford when you first got there?

Moos:

Let’s see. Well, you know, scientifically it was a wonderful place. A lot of people have bad things to say about the competitiveness and… You know, it was a different kind of a world. It was a very competitive place, but I mean, there were people like Schiff, who was chair. They were quite open. You could talk to them! Felix Bloch. You could talk to these people!

Zierler:

Right. Right.

Moos:

And I never ran into… “I’m too busy,” or, you know, “Who are you?” kind of thing. They were open.

I remember a conversation with Hofstader about the possibility of an interaction between a beam of relativistic electrons and an intense laser beam. I demurred become involved because of my other obligations. There was an interest in doing challenging experiments, which might take many years, particularly by Fairbank and Little. During that time, the development of the technology was under way for a sensitive gyroscope orbiting the earth to study general relativity. This became Gravity Probe B. Francis Everitt came in 1962. We are of similar ages, but I left in 1964. It was time, and I think that was a good move on my part. He, of course, spent most of his career bring that idea to fruition.

Zierler:

Now what was your plan? Did you go there intending to refine and expand your thesis, or were you looking to take on new research, new projects?

Moos:

Well, it was pretty clear what I was doing. Schawlow was hiring me to build a lab. When we came, we didn't even have lab space. They hadn't finished the Varian building, so we were over in the Microwave Lab for the first year or two. So we were ordering equipment. I didn't know very much about optics in those days. All my previous work had been in the microwave region, and, all of a sudden, I was learning all about optical techniques and Schawlow put up with me. [Laughs] He put up with me. Well, you know, you take what you can get, and he needed help and there I was. I actually was willing to work hard. And he was a very open man. We had very blunt discussions about things. Looking back, I realize that he was a wonderful supervisor – one of the best. He was full of ideas and cared about the success of his young colleagues.

Zierler:

What were some of the bigger research questions that you and he were after in terms of the kinds of things that the lab was going to do?

Moos:

Oh. Well, at that point, the laser question was “What can we do with it?!” okay?

Zierler:

Yeah. Right.

Moos:

One of the big things I worked on was trying to do chemical separation using selective excitation of chemical bonds. We may have had some luck with isotopes of bromine, but we did not attempt to go further and use the laser for selective excitation of chemical bonds because of the coupling between normal modes in a complex molecule. Many years later Fleming Crim of the University of Wisconsin, as the NSF Assistant Director of the Math and Physical Sciences Directorate, visited an AUI Trustees meeting. He mentioned that he had done the selective excitation of a bond. I grabbed him. I said, “Tell me how you did this,” and he said, “Well, we just chose the right frequencies.” The secret is usually you have a near-degeneracy of a large number of levels that correspond to different excitation modes in a molecule. In other words, if you excite one mode in a molecule and there’s less than kT to another mode, you excite that one also, okay? So he said, “We had to find a low level of degeneracy,” and that was the secret. He said, “Select a molecule where you could excite a level which energetically was far enough away from other levels (i.e. small compared to kT) that the vibration stayed unique.” Then you were exciting a particular bond, right, whereas if you have a typical molecule where the levels are all close to each other, you think you're exciting one bond, but you're exciting a whole bunch of them and there’s no selectivity in what you're doing. That was the secret. It took a chemist to figure that out. [Laughter]

Zierler:

Now in terms of your involvement, were these… By the time you left Stanford, were most of these research--

Moos:

Okay. But we did get… We also worked on isotope separation, and there we may have done it, but I’m not sure.

Zierler:

Yeah, yeah. So by the time you had left Stanford, did the lab accomplish what it set out to do? Did you leave mid-project?

Moos:

We did many things, okay? I mean I’ve got a long list of publications from that era. A lot of the things were just elementary solid state physics kind of things trying to understand the properties in materials. In fact, it prepared me [?] for my early years at Hopkins. And we built a highly productive lab, which was no small accomplishment.

Zierler:

Sure!

Moos:

Schawlow’s background was atomic physics, but he had transferred his interest to laser materials. What he often did was trying to understand the properties of ions in crystals. When I went to Hopkins after two years as a post-doc and one as an acting assistant professor — and I went to Hopkins in 1964 as an assistant professor—I went there because they had the world’s foremost program in rare earth materials.

Zierler:

Who was the driving force behind that at Hopkins? Who made that such a big program?

Moos:

That was Gerhard Dieke. Gerhard Dieke was a Dutchman of the old school. He was very austere. He was significantly older than me; in fact, he died… I think it was in the mid ’60s when he died, I think, a year after I came. He was very austere. I mean he was the kind of a person, if you wanted to use a spectrograph in one of his labs, you had to ask his permission. He had 13 graduate students and a monstrous laboratory. Even though he was Chair of the Department, he maintained control.

The rare earths are kind of unique because the excitations in the lower part of the optical infrared are between f electrons which are somewhat shielded against external electric fields . So, if you put them in a solid, the atoms are ionized, but they’re sort of in a cage, if you will, a quasi-static electrical cage which will split the f-electron levels and shift them slightly. But they still remain very narrow. They’re very narrow, and that’s not true of, say, transition metals. Transition metals bond and actually form whole new systems which are tied into the chemical properties of the crystal. So rare earths only shift a little bit when you go from crystal to crystal, and you can think about them as atoms, like free atoms that are in a cage. That’s why they were so interesting as a phosphor or a laser material. In fact, there’s major, major engineering and commercial use of these things even today. In fact, I’m going to get to that.

So, when I came to Hopkins and I’m casting around knowing what to do, the first thing I said is, “Well, let’s look at the rare-earth emissions; let’s pulse excite the emissions and let’s see if we can measure lifetimes and things like that.” I had several excellent graduate students such as Les Riseberg. He had come from Harvard, spent a year abroad, and then came at the same time I did to Hopkins. He did his undergraduate work at Harvard and he was a very bright man. He ended up as an executive at Verizon in later life, and he died young in his fifties. There was Bill Gammon (Gardner), who has spent many years at Bell working in basically various research processes. They just a very diverse talented group of people. I won't go and name all my students, but the point is it was a very exciting time and we were able to make unusual measurements.

One of the things that we did—and there’s a paper by Riseberg and Moos which is considered to be important. It’s not my most heavily cited paper, (The ApJ Letter paper announcing the successful launch of the FUSE satellite is.) but it’s up there because the importance of rare earth phosphors and even today, workers in this area frequently reference it. The fundamental question is: If you excite a level in a rare earth ion trapped in a host solid, will it radiate? The answer is the way it’s quenched is it emits phonons, and then the question becomes how many phonons must be emitted simultaneously because the maximum energy of the phonons in a given crystal host is limited by the stiffness of the lattice. Several phonons must be excited to conserve energy while depopulating a level. So, it’s a multi-order process. If you think about it from the point-of-view of quantum mechanical perturbation theory, this is like a third or fourth term in a Hamiltonian, okay?

Zierler:

Mm-hmm [yes].

Moos:

So, you’re way out in the expansion. [Chuckles] And the interaction depopulating the level rapidly gets weaker as the number of required phonons increases. So if you have to emit five phonons and the radiation lifetime is reasonably fast, it’s going to radiate. But again, if it emits three phonons, you're probably going to quench it. Okay? There’s a competition between the radiation and the phonons, and that simple idea is very, very useful for people who are designing things that emit light.

Zierler:

Are you working with these people? What’s your interaction and collaboration broadly?

Moos:

Nothing.

Zierler:

Nothing.

Moos:

I just happen to get a notice every once in a while… You know these various outfits that go around looking at your publications and who quotes you, okay? Who cites you? Then they send you an email: “You were cited.” So yeah. At first, I couldn't believe it. This is a paper that was published in 1968, and I’m getting an enormous number of citations and I said, “Gee!” So that’s it.

Now at the same time, about a year after I came—I came in ’64—I got very involved with a gentleman by the name of Bill Fastie. Bill Fastie was a research professor at Hopkins, but he was a real character. Bill had no degrees. As a graduate student at Hopkins, he had worked for Hermann Pfund during the Second World War, and basically gone off into industry and made his reputation and then came back. Dieke hired him back because of his instrumentation skills, and he was a research professor, even though he somehow got through the system without ever obtaining a degree. He came to Hopkins as an undergraduate, and in those days you could go straight through. You didn't have to stop for a bachelor’s degree.

Zierler:

Yeah.

Moos:

He was the kind of person they pointed to when they said, “We should stop doing this anymore.” [Laughter]

Zierler:

Although I’m sure not everybody was like him, though.

Moos:

No, but… So, it was just a certain tradition at Hopkins that we’re in the business of producing PhDs, not buying them. [Chuckles] So we occasionally do hire people without degrees.

Zierler:

Now when did the merge of the physics and the astronomy departments—when did that happen?

Moos:

Well, I’m coming there. I’m going there.

Zierler:

Okay.

Moos:

Bill… You talked about Sputnik. Bill had what I would describe as a near-religious experience with Sputnik, okay, and he decided that he had to get into this. So, he started flying sounding rockets which examined the atmosphere of the Earth. These rockets would go up about 100 miles, and because you were up high enough above the ozone layer, you could look at the ultraviolet emissions from the atmosphere spectroscopically, all right? I told him, “Gee, that sounds interesting,” and then went back to my solid-state work. But you know, I had to get promoted so I was busy in the lab.

So, one day in 1965-- I came in ’64. In the fall of 965 he walks into my office and he looks at me. He was a big, tall man—6’3”, 6’4”. I’m sitting at my desk and he leans over my desk and looks down at me and he said, “Did you know that you're going to help launch a rocket in two weeks?” [Laughs] A comet had been sited, and NASA decided they wanted to observe it They said to Fastie, “Can you do this? Do you have enough spare parts? We have enough parts to put a rocket together to carry your instrument” and we did it. Thus, I got my boot-camp introduction to the space business.

Zierler:

Spare parts? What kind of system is this where you have enough spare parts and of the right kind to build a rocket?

Moos:

Oh, an Aerobee rocket. It was a sounding rocket, which only goes up to roughly a hundred miles, giving an observing time of about 5 minutes above the absorbing atmosphere. NASA probably launched 40 of them a year or something like that. So, they had a warehouse of rocket parts including the rocket motors. You know, they had everything needed, and Bill had spare spectrographs and we actually put this thing together and launched it from Wallops Island within two weeks. But for me, it was just a fantastic experience.

So then… That was in the fall, and I came in on Thanksgiving. In those days, some people actually worked the Friday after Thanksgiving, okay? [Laughs] It wasn’t a full-fledged holiday. So, I was in there; it was pretty quiet. I ran into Bill and I said, “Bill, you shouldn't just specialize in looking at the Earth’s atmosphere. You shouldn't be looking just at the Earth’s atmosphere. You ought to be doing things like the planets. Do the atmospheres of remote objects.” He looks at me and he says, “Young man, you want to do the planets?” Six months later we launched our first rocket to look at Venus, okay? [Laughs] It failed, and we were to go through a series of failures. Then we had some spectacular successes. The sounding rocket business had a very high failure rate. It’s cheap, but the failure rate is high. But it’s a chance to try unusual ideas.

So, we were at that point. We had designed sub-arcsecond pointing that was competitive with the Copernicus satellite which would launch several years later in ’72 . I mean, this is now… We’re in the space-technology dark ages in the early ’60s and we actually made it work, all right? It took us a couple of tries, but we did it, and then… The first thing, of course, with that kind of a try is you say, “Gee. We’ve got all these questions about the data. We’ve got to do it again.” Well, there were some more failures and then a spectacular success. After that, we were able to establish a program of flying rockets to do astronomy, and I and my colleagues, Fastie, others continued to do that. In fact, we’re still doing it. But of course, then the next step would be to move into doing things in orbit, right? That would be the next step.

Zierler:

Right.

Moos:

But I did receive tenure, actually, based on the solid state work, okay? This was a hobby, all right, doing work in space. [Laughs] But at that point I became a free agent and I could pretty much do what I wanted.

Zierler:

So Warren, I want to ask you. In terms of this transition, in what ways did your solid state background sort of serve you well moving into what was initially a hobby in terms of rockets and--

Moos:

Well, you know, in some sense it was atomic physics all the way.

Zierler:

Yeah. Yeah.

Moos:

Okay? Now I mean, when I was doing the work on the solids, I had to learn a lot of solid-state physics, which made me unique in my department—you know, an astrophysicist who understood condensed matter. It was an opportunity, but I was able to… I have found over the years that you always have to bring something to the party, okay? So here I was wandering into astrophysics. What I was bringing was a knowledge of optics, okay, and instrumentation, and I had to learn the astrophysics. But about this time that I was doing this, Alar Toomre reappeared in my life. Alar was a professor at MIT. I mentioned him earlier.

Zierler:

Yeah.

Moos:

He sent me a letter that said, “Hi!” I mean today you say hi, but whatever the equivalent was. He says, “So you too are pretending to be an astrophysicist.” [Laughs] I had just published something in ApJ Letters. In fact, that’s interesting because that was around the early ’70s, and that’s when a lot of physicists moved into astrophysics.

Zierler:

Yeah. Yeah.

Moos:

I wasn’t unique.

Zierler:

Right. So what do you think explained that trend? What were the larger structural issues that were going on?

Moos:

Oh, I think opportunities. Astronomy historically has pretty tremendous emphasis on phenomenology, and it has to. It’s an observational science, you see the phenomenon and you give it a name. In some ways, astronomy for a physicist is a little hard to learn because there’s no rationale to it. The stars are labeled O, A, B. You know, I mean there’s no logic to this. It’s all historical. If you think about it, names are given which are names of people or just names of what the stars were labeled—the A star, the B star. I think that’s part of it, that in some ways astronomy was closer to geology and botany than the physical laboratory sciences. My astrophysicist friends would be insulted, but… And the physicists saw an opportunity and they just moved in and I think it was a great marriage. By the way, I’m not attacking astronomers They had the data. They had made these exquisite measurements, which were very, very difficult. So no, I’m not attacking them. It was a great marriage and it allowed physicists to move over. Particularly in the instrumentation area, there were great opportunities because we could build the instruments. They didn't know how to build the instruments. They wanted to build instruments, but they weren't trained. They didn't have the right training. An astronomy PhD did not prepare you to do highly technical instrumentation work. Yeah. I think that’s probably the heart of it.

Zierler:

In terms of what you had to learn on your own, I mean, how did you do that? Did you hit the textbooks? Did you talk to your colleagues? All of the above?

Moos:

Yes. [Laughs] I did a lot of reading, you know. I bought a lot of elementary books, or talked salesmen into giving me a copy. Yeah. I had to start with the elementary books and work my way up. Yeah, yeah.

Zierler:

Right. So maybe now is a good time to talk--

Moos:

Well, in some cases there were no books. For instance, in planetary astronomy, in planetary physics, that’s another story. I don't know if you know this. There were virtually no planetary astronomers in the United States in the ’60s.

Zierler:

Now when you single out the United States, is that to say that in other countries there were?

Moos:

No. There still aren’t. The growth was fastest in the United States. Why? Because the United States was designing missions to go to the planets, and because we were sending missions to the planets, we built a science community to go with it. There was a huge number of people employed in this community in the ’70s, and then it crashed because the government decided they were going to cut back on the number of missions. But I was part of the Voyager project, all right? That was a part of that growth. The Voyager mission to the outer planets was a big deal.

Zierler:

Right.

Moos:

The leading Voyager ultraviolet proposal came from a group led by Lyle Broadfoot at Kitt Peak National Observatory, Darrell Strobel, also at KPNO, a group of people from Harvard, which included Alex Dalgarno, Mike McElroy and others and also Tom Donahue at Michigan. It was a very distinguished group of people, and except for Broadfoot, largely theoretical. I submitted a proposal and basically NASA said, “This person knows how to build things, and you’ve got all these theorists.” [Chuckles] It was a shotgun marriage. They said, “You want the project to go to Broadfoot and Harvard.? Put this guy on the team.” [Laughing] It was one of those things, but I mean that’s the way they did business. Well, that’s not crazy. It was simply let’s put some talent on the team that knows how to do certain kinds of things. I don't know if it worked that well, but it was a great experience. It was a great experience.

Zierler:

So maybe now is the time to ask about the merging of the departments of astronomy and physics.

Moos:

I haven’t talked about it yet. I’ll tell you what finally led to it was the arrival of the Space Telescope Science Institute. Now I can give you a whole lecture on that one. [Chuckles] I actually have a lecture. But I’ll give you the short version. The short version is Princeton looked like the shoo-in. Princeton was not well-organized. In fact, we had decided as a group that--

Zierler:

When you say shoo-in, shoo-in for what? What do you mean?

Moos:

What?

Zierler:

When you say a shoo-in, how so?

Moos:

There had been an enormous mass of money that had gone into Princeton. In earlier years, Lyman Spitzer had a huge effect on the space program. Even though he was a theorist, he had a gift for understanding experimental issues. He, of course, was the PI for the Copernicus satellite, the third of the OAO series and the most challenging one. There were three Orbiting Astronomical Observatories. For the first one, the major instrument was from Wisconsin, and there was another instrument, which came from England and never really worked well. Then the second one went into the ocean. That was supposed to be Goddard’s mission, and the third one was Princeton’s. The Princeton mission was a superb mission. It had high angular resolution on the sky, high spectral resolution and sensitive detectors that counted individual photon events. It was just great. I have a lot of friends from then and several played key roles in the FUSE mission, for which I was the Principal Investigator.

In fact, I used OAO-3. I remember Jeff Linsky from Colorado giving me a shove at an American Astronomical Society meeting and saying, “Go ask them for some time.” [Laughs] And I did! I marched up to the distinguished professor Spitzer and I told him my story that I’d seen this spectral signal from a star with my sounding rockets, which indicated Lyman-alpha emission. It was marginal and I really needed his satellite to do it, correctly and they took the data. So it was that kind of thing.

So yeah, we were starting to develop an astronomy program, and at that same time, I’d had a hand in bringing Art Davidsen to Baltimore. He was a young graduate student who finished up with Stu Bowyer at Berkeley and came to Hopkins. We were starting to get the nucleus of an astrophysics group. Richard Henry had come from Naval Research Lab in the ’60s, and about the same time Paul Feldman came from Columbia and NRL. But we had a small group and we thought to ourselves, “We can't do this. We’re not big enough. We’ll never get anything like the institute here.” It really looked like the enormous amount of work that was going on at Princeton, they should have had it—but they did not appear to be well organized! They just weren't… I don't know. I don't know exactly what it was. They didn't know how to do it, okay? It is important to remember that going to the federal government and asking them to fund an institute is a very formal and demanding process. It is very different from the peer reviewed competition most scientists are used to. As a consequence, most university scientists are not prepared to get involved in this kind of activity.

Zierler:

Hmm.

Moos:

Nationally, what happens is the intermediary for a government funded institute is usually a non-profit or for-profit corporation. Somebody comes in between you and the government. Princeton ended up going with two different corporate non-profits who listed Princeton as the selected site. That’s already confusing. Meanwhile, we at Hopkins had decided we weren't, so to speak, eligible. We had said, “Nah, we’re too small. We’re a niche player.” All of a sudden, John Team the President of AURA (Associated Universities for Research in Astronomy) entered the game. This young faculty member, Arthur Davidsen, who I had helped bring in—not I personally, but I had a hand in bringing him in some, I don't know, half a dozen years earlier—had already made professor and he was our representative to AURA, which at that time was the big astronomy organization for managing ground-based optical astronomy facilities.

Zierler:

Yeah.

Moos:

They used to run Kitt Peak and all kinds of places. And AURA is still around. So the President, John Team, approached him and said, “You know, AURA hasn’t put in a proposal, but we’re thinking about it, and we’re thinking about doing something different. Would Hopkins be interested?” So Davidsen comes back to Baltimore and he gets us in a room and he says, “This is going to happen.” [Laughs] It was a wild ride! We assigned, Dick Henry, who normally commuted from Washington, to pick up John Team at the airport and bring him in to Hopkins. We told him he had to drive through certain neighborhoods (the nicer looking ones) and to avoid other neighborhoods. [Laughter]

Zierler:

Yeah! What’s your sense that this was a major opportunity about to happen?

Moos:

Well, yeah! Well, you know, it was funny, though. I… Okay, now I’m going to tell you an inside story. I went to the dean and the dean said, “Well, I don't know if we’re interested.” Dick Zdanis was the associate provost with a science portfolio, and he had been a professor in the Department of Physics. He was kind of cool. I think that between then and the meeting with Team, Fastie and Davidsen, two very irrepressible individuals, got to the upper echelons of the University, including President Muller. But I was in the room when the president walked in to greet John Team, and Steve Muller, who was taller… He wasn’t a tall man, but he was taller than some of us. And he had his various henchmen gathered around, you know, four or five of them. John Team was there and probably Fastie and Davidsen. There might have been one or two other people; I don't know. But anyway, Muller puts his hands in his pockets, you know, and kind of… I remember he had a suit jacket or a vest on, and stands there and kind of draws himself up and said, “Well, we are really interested in this project. We want a part in this, and I am prepared to put up $2 million,” which in those days was big money!

Zierler:

Yeah. Yeah.

Moos:

“I’m prepared to put $2 million towards…” basically to build the building. We thought that was half the building cost. Well, it turned out to be less than half, but the point is he was willing to put up a significant amount of university funds to get them there. (By the way, many years later, when Dick Zdanis and I talked at an AUI Board meeting. He told me that none of the other people from the University administration had an inkling that this offer was coming – Muller had cooked it up himself.)

Zierler:

Now from his perspective, what do you think? Where did this interest come from?

Moos:

Muller was a gambler in the best sense. He understood what it took to change a place, and he understood… By the way, I’m going to tell you some more stories. I’m going to wander off here, okay? I’m going to tell you this is a Shakespearean tragedy, okay? [Laughs]

Zierler:

Great!

Moos:

Anyways, he put the full resources of the university at the service of AURA. We had the Applied Physics Lab doing management studies. We had his Senior Assistant, Jill McGovern, watching over the whole project and reporting to him. It was a big deal, okay? Those were the days when Schaefer was running the city. I’ll tell you one story that has to do with that, but one had this feeling that everybody was pushing to make this happen.

Zierler:

Yeah.

Moos:

NASA came to Hopkins for a site visit and I was part of showing them around. I remember after showing them our facilities, a number of players met with NASA in a large room, I believe somewhere in Shriver Hall at Hopkins. We had a problem. The problem was that the building was going to go on the edge of park-like land, of an undeveloped ravine between Hopkins and the community. However, the people near the edge on the other side of the ravine—they couldn't even see anything, but they said they had this lovely view and they thought we were going to build a building and ruin their view—a building on our land , okay? [Laughs] They were correct that there would be a building of modest size, but they wouldn’t see it most of the time because woods were in the way. But local activists took up their cause and things got noisy. NASA was saying, “Well, wait a minute now. We have a schedule for the Hubble telescope and we want to build the building. We don't want to get caught in some kind of a community brouhaha.”

So, I was in this room with a bunch of others. Well, The Mayor of Baltimore, Schaefer, couldn't come, and he sent his head of planning, who introduced himself. He said, “I’m the head of planning for the city of Baltimore. Mr. Schaefer couldn't come because he had an emergency and he couldn't leave city hall, but he asked me to deliver a message. The message is “The Space Telescope Science building will be built.”

Zierler:

Wow!

Moos:

And Schaefer had [overlapping voices].

Zierler:

This is a dramatic moment!

Moos:

Yeah, and this is the Schaefer, remember… You remember the duck… I don't know if you remember this. You may be too young for this, but Schaefer, when the construction of the Aquarium didn't make his announced schedule, put on an 1890s bathing suit and duckies and went in the pool with the seals at the aquarium. [Laughs]

Zierler:

I’m not aware of that story, but okay.

Moos:

Oh, okay! That made the… I mean I was on sabbatical. [Laughs] I was on sabbatical at the University of Colorado, and the Boulder Daily Camera had it on the front page! I mean it was a big deal, you know? Yeah, he was that kind of a person. So then we had a politician who knew how to make things happen, all right?

Zierler:

Yeah. Yeah.

Moos:

With everything. At that time, it was so great. One of our arguments in our proposal was we have this fantastic stock of prime housing that sells at a low price. I mean we turned the lemons into lemonade and said, “That’s going to be attractive to young astronomers because they don't have money,” okay? [Laughs] They could afford the housing, which was lower in price compared to many other parts of the country.… It’s true, you know. All these things are true. You couldn't do it today after Freddie Gray and all the rest.

Zierler:

Yeah.

Moos:

But somehow the city appeared to be on the upswing, and we could sell it. So we actually came out with a pretty strong proposal. In addition, Goddard wanted it. Goddard didn't want to drive to… You know, it’s a long drive from Goddard up to Princeton. It’s only 45 minutes to Hopkins!

Zierler:

Sure.

Moos:

So Goddard, which had the major oversight, wanted it at Hopkins because they could… They would have loved to have it at the University of Maryland, right?

Zierler:

Right. Even better, as far as they’re concerned.

Moos:

But they couldn't pull that one off. Next best was to have it at Hopkins. So they were--

Zierler:

I wonder if Georgetown was ever in the mix.

Moos:

No. No, Georgetown was not in consideration.

Zierler:

Okay.

Moos:

But there was a Princeton site. There was a Chicago site. There were several proposals and there were three or four sites, okay? In the end, I think Princeton blew it because of their lack of organization , but I don’t have any inside information. Well, this was probably small beer for Princeton.

Zierler:

Yeah.

Moos:

It was small beer, and we treated it like a really important project because Muller recognized that this was a way to revolutionize the Homewood campus, which had paled with respect to the medical campus.

Zierler:

Right.

Moos:

It helped to take care of a major problem for Hopkins.

Zierler:

Right.

Moos:

He then went on to fund a huge increase in the size of the department and in funding for the department. We said, “Look, you're getting this wonderful influx of astrophysicists across the street, but they’re not part of the university. They’re part of AURA. They’re working for AURA, which if we want to take advantage of this, we have to have astronomers who are on the staff at Hopkins.”

Zierler:

Yeah.

Moos:

And the University management bought it. So, we increased our astrophysics size and about the same time we created the joint department, okay? I don't remember the dates. I think actual creation of a new department, if anything, came earlier. In any case, after the NASA selection of Hopkins for the STScI site, it was clear that we had to recognize that we were now a major department in that area.

Zierler:

But bureaucratically it was the new entity of astronomy glomming onto the established entity of the physics department. Is that a fair way of putting that?

Moos:

Yes, that’s right. Yes, I think that’s fair. It was not taking a well-established astronomy department and merging it with a physics department, okay?

Zierler:

Right. Right.

Moos:

There’s a long history of mergers and divorces of physics and astronomy in larger universities. We’re a small university. You’ve got to keep in mind that Hopkins is a very small university.

Zierler:

Sure. Sure.

Moos:

So this was a way to optimize our resources. You know, were we going to have a weak, small astrophysics department or were we going to have a major department? That led to the point—and Muller bought it— if you're going to build up astrophysics, you have to strengthen the physics side as well as the astronomy side.

Zierler:

Sure. Sure.

Moos:

And it worked! I really do think the physics side is specialized. If you’ve got a small department, you have to specialize.

Zierler:

Right.

Moos:

So, the physics side also has prospered, and one additional reason it’s prospered is because physicists regard astrophysics as part of physics.

Zierler:

Yeah. Yeah, yeah. So was it a smooth process overall, the merge?

Moos:

No. It was not…except that at some point we all looked each other in the eye, and we said, “Look. If we don't hang together, we’re going to hang separately” kind of thing. “We’ve got to figure out how to function so we’re not at each other’s throats.” And it’s worked. Basically, we all took—what shall I say?—an oath of being reasonable with each other, okay? [Laughter] Yeah, that’s all you really have to do. I mean you just have to say, “Well, look. We want to succeed in our respective arenas. What’s the most credible way to do this?” and the answer is not by destroying each other.

Zierler:

So in what ways did the merger affect your own research and the kinds of projects you were able to do?

Moos:

It didn't touch me. I remember by that point I was pretty senior. I don't know what my age was, but I was senior enough that I could do what I wanted to do. The big thing when you do this is you show courtesy to each other, and if you're making a hire in astrophysics, there’s a little bit of a tendency to defer to what the astrophysicists say, although if you think they’re nuts you should say so. But no. Or maybe a better way to say it is astrophysicists have a burden to explain to the rest of the department why they want to make a certain hire, okay? That’s the other side of it, all right? I don't think that’s been a really serious problem. On the other hand, the astrophysicists have to make an attempt to understand why, say, an appointment in high energy physics is being made.

I know that in some departments there are hatreds and so on that build up over the years, and they do. I mean I’ve seen that happen in my department, and these kinds of politics can be very difficult. It’s not easy. I think it worked at Hopkins because I think in the end it’s self-interest that rules the day. In other words, you have to decide, “Are we stronger apart or are we stronger together?” and then we say, “Well, I don’t agree with these people, but I’ve got to work with them,” kind of thing. That’s the kind of thing. Now there are some people with whom it’s always difficult to work with. And as time went on in the department, certain people left. You know, things eased out. Things work out, and I think the astrophysics… Yes, the astrophysics became very strong and certain areas like high energy, perhaps… High energy had dominated the department when I was there, okay? They took over most of the department. They had half the appointments. A number of those people aged and retired. As you know, the funding in high energy physics has gone way down.

Zierler:

Yeah.

Moos:

And they made certain strategic errors. For instance, I don't know if you know about the funding in experimental high energy physics, the difference between the NSF and Department of Energy.

Zierler:

Sure. There’s a rich history there.

Moos:

Okay. They went the NSF route, which was a mistake, and once you go NSF, you cannot go DOE.

Zierler:

What do you mean? It’s like a black mark?

Moos:

I have been told that there’s an agreement between the two agencies, which may or many not be official – I do not know - that they will not double-fund. You can't apply to both.

Zierler:

You mean sequentially. You don't even mean at the same time. You mean once you get funding from one, that’s it for the other.

Moos:

Well, it is tough to abandon a working relationship on the chance you will get something new – when the probability is high that you would end up with nothing.

Zierler:

Right, right. So, you're saying if they had gone to DOE first, that would have been the more fruitful arrangement.

Moos:

Yeah. Yeah. So certain faculty made that mistake and their needs grew and the NSF shrunk. They were impoverished. That was part of it. There was a certain arrogance on their part. More recently, I think a number of us realized that an area, which actually has turned out to be fruitful, is the interaction between people who do high energy physics and astrophysics. On the theoretical side, there’s a really enormous overlap.

Zierler:

Right.

Moos:

Well, what is dark matter, to give an example, okay? That’s a huge area, really, that high energy physicists are exploring, but it’s also a very important problem in astrophysics. What is dark matter? Even more important is the question of dark energy.

Zierler:

So Warren, I think maybe at this point it would be good to ask sort of broader questions about some of your major research projects, and obviously a good place to start would be ultraviolet spectroscopy, if you want to just talk about that in broad terms, some of the major projects in that field.

Moos:

The ultraviolet spectral region, which I’ll arbitrarily set as the wavelength regions from 3000 down to 300 Angstroms, is of enormous importance because most of the astrophysically important atoms, ions and simpler molecules have their strongest electronic transitions in this region. It is important, not only for measuring the abundance of these species, but also for determining the correct values for stellar energy production and hence nuclear processing in galaxies. Early in my Hopkins career, when I started cooperating with Bill Fastie, I started to master what was then relatively new technologies and suddenly became an expert. I’ve found over the years, that when you enter a new area, you have to bring some kind of expertise as your ticket of admission. So, often my ticket was that I knew more about ultraviolet spectroscopic and in particular ultraviolet astronomical techniques than most people. Yes, and so that got me a ride onto various committees, various projects. That’s why I was on the Voyager project, you know; and on and on.

Zierler:

Right, right.

Moos:

That’s always been my ticket, and then in later years, my experience with designing space missions got into the mix.

Zierler:

So Warren, in the field what have been some of the principal advances in ultraviolet astronomy over the years and your contributions to that field? How have you helped move the needle?

Moos:

Well, there have been a couple of serious technical problems. One of the basic problems which we haven't completely solved is our quantum efficiency is modest, you know, 20% in our detectors. Furthermore, we have mirrors that reflect at about 60-70% at best, and if you go far into the ultraviolet, it’s down to 40-50%. For mirror optics, to have aberration control, you have to have multiple reflections. You cannot control optical aberrations with just one or two reflections. You need multiple reflections; you need three or four, sometimes more. You take 0.7⁵, or in a more extreme case 0.5⁵, that’s… What’s that? 1/2⁵? Yeah, 1/32. So, if you're down to 3% transmission and you throw in a 20% quantum efficiency, you only get less than 1% detected throughput. Well, that’s horrible, okay?

Zierler:

And these are technical limitations?

Moos:

Yeah. There are a lot of people who sweated a lot of bullets trying to change it, okay? Now we have seen some improvements. CCDs are almost 100%, and we are able to extend them into the far blue and even into the ultraviolet

Zierler:

What is CCD?

Moos:

Charge-coupled device.

Zierler:

Okay. MOOS …But then we had to come up with filters that wouldn't leak visible light because the CCDs are very sensitive to visible light. The basic problem we have is astrophysical sources often look like black bodies that peak in the visible or in the blue… And if you want to go into the ultraviolet, you're on the other side of the peak of black body curve and the flux in the visible is enormous compared to the ultraviolet. In addition, the transmission through the optics is much higher for visible light compared to the ultraviolet.

Zierler:

Right.

Moos:

You’ve got this enormous flux of photons at longer wavelengths, and if a little bit leaks through and your detectors see them, you're dead. All right? Scattered light. It’s the bane of all optical systems. A superb grating scatters 1 part in 100,000 even 1 part in 1,000,000 but often gratings are worse. Well, the old gratings used to be 1 part in 10,000. So yeah, these kinds of technical problems will just destroy you. Yeah, and it was important to have a knowledgeable person who understood these things.

Then our optical coatings. One of our problems is molecular monolayers of contaminating material, particularly hydrocarbons, can easily be deposited on the ground or in space. These monolayers absorb the ultraviolet and destroy our throughput. So, contamination control is an important issue. In addition, the optics, which are coated with aluminum are additionally overcoated with a thin layer of transmitting material to prevent the formation of Al2O3 (sapphire) which absorbs in part of the ultraviolet.

For the FUSE mission, we used a lithium fluoride overcoat on bare aluminum to extend the bandpass below 1,200 angstroms. Unfortunately, LIF is hydroscopic and the lifetime in typical laboratory conditions is a few hours. You coat an optic and then a few hours later it’s dead. For the FUSE mission, we had to apply such coatings not on small optics, but on mirrors that were about 40 cm across and store them in laboratory conditions for several years. [Chuckles] We go from hours to years, all right? This is a technical problem all right, the solution to which involved flowing super clean and dry molecular nitrogen through the instrument, including both the grating and spectrograph. Oh, and by the way, the hoses which you use to flow gas to keep the optics from going bad can leach hydrocarbons that will coat your optics. [Chuckles] So you have to choose your hoses. Every accident that can happen has happened.

Zierler:

Right.

Moos:

I’m not talking about theoretical things, all right? So every accident that can happen has happened. We coated our optics for the FUSE satellite, the Far Ultraviolet Spectroscopic Explorer. We had only two reflections to improve the throughput. We had a mirror and grating, both near normal incidence. The gratings were about a foot across and the mirrors were about 40 cm across. Both were protected by the flowing nitrogen. In the middle of the night, alarms would go off and we’d be out of flowing nitrogen, and one of us would have to get up and go into the lab and refresh the liquid nitrogen that was heated to supply extremely dry nitrogen. I mean there was that kind of thing going on.

I remember at the FUSE launch on a Delta rocket. I was in the launch command center and all of a sudden, one of my techs calls on the line. He wants to go out and watch the launch. I had to harangue him in profane language explaining that his job was to watch the flow meter. [Chuckles] You know, it was a critical job to monitor the flow of dry nitrogen through the instrument right up until the rocket lifts off from the tower. The point is we were flowing dry nitrogen even when the satellite was on the rocket in the tower right up to launch. So, that’s the kind of thing you have to do, all right? It’s not heroic. There are all kinds of what I call technical issues and if you don’t pay attention, you fail. It’s a very technical area, all right?

Zierler:

Yeah. Yeah.

Moos:

You know, physics is like that.

Zierler:

Right.

Moos:

Experimental physics is like that. We’re doing experimental physics in a rocket! I mean, this is hard. Sorry, but it’s hard. And people who know how to do that are in short supply.

Zierler:

Is that because you need engineers? I mean, you need people that can blend the engineering with the physics? Who exactly is in short supply?

Moos:

This is not a job for theorists.

Zierler:

Right.

Moos:

This is for real hands-on experimentalists.

Zierler:

Right, right.

Moos:

But I think there’s a little bit of a point there to make. These experimentalists have to be able to talk to the theorists, and they have to understand what the science problems are. These are not engineers. These are not people who are primarily interested in the technology. These are people who want to do the science and they have the technical skills to do it. In addition, they have to be in good communication with the people who will help them aim design of the experiments at the most important problems and interpret the data. Otherwise they can't design the experiments correctly; nor can they interpret the data correctly, all right? So it’s that marriage. It’s that marriage.

Zierler:

So I wonder. We just had the 30th birthday of Hubble, right? I wonder if you could talk a little bit about your entre into Hubble from the ultraviolet perspective, what your work was in that area.

Moos:

I knew the people at Goddard pretty well, and they approached me when they were planning the Space Telescope Imaging Spectrograph They were proposing that STIS be installed on a HST repair mission, and asked me to be on the team because they needed a person in particular who knew something about planets and what measurements were needed in the ultraviolet. In addition, with Goddard’s support, Dr. Mary Beth Kaiser joined my group and had a significant role in the wavelength calibration of STIS.

They did not need my ultraviolet technical experience because Goddard has a lot of ultraviolet expertise. It is probably the home of it, you know. If I were to go to the NASA labs and say, “Who knows more about the ultraviolet than anybody else?” it’s Goddard, all right?

Zierler:

Yeah.

Moos:

So they know. They’ve always had strong groups in that area. I don't know if they still do, but historically they have had strong groups.

Zierler:

Right, right. Then in terms of this project measuring dark energy from space, I would love to hear about that, given all the inherent mysteries there.

Moos:

Do you know Chuck Bennett?

Zierler:

I do not, no.

Moos:

You know the COBE mission, which measured the microwave background?

Zierler:

Yes, sure.

Moos:

Okay. Well, Chuck was an Investigator on that project.

Zierler:

Okay.

Moos:

He was a young guy, just starting out, but he played an important role. He had a follow-on mission called WMAP, which mapped the fluctuations in the Cosmic Microwave Background (CMB). WMAP was later followed-on by Planck. So, Chuck’s mission was a game changer. He didn't get a Nobel, but he came close. You could argue that the WMAP mission made the field of cosmology respectable. With the data from the mission, one could do a number of important calculations of cosmological interest for the first time. At about that time, he moved to Hopkins from Goddard. People were talking about, wondering about a mission to go further and try to understand the nature of dark energy, and Chuck started thinking about it. In the same time frame, Karl Glazebrook published several papers about large galaxy redshift surveys. I participated in one of them. I don't know if Chuck participated in any way, but it is likely conversations with him were involved in about the same time frame. The basic idea was that we could the redshifts to measure the distance to galaxies as a way of determining the characteristic spatial wavelength of galactic clustering. You get this clustering in galaxy production due to fluctuations in the density of the plasma (coupled to photons) at the time the universe became neutral at about 400,000 years after the Big Bang.

Zierler:

Mm-hmm [yes].

Moos:

So, what we see in the clustering today is due to the baryon density clustering then, essentially acoustic noise in the plasma. By the way, Baryon Acoustic Oscillations have been detected and the associated wavelengths determined from ground observations, okay, but if we could do this from space, we can make a significant improvement in accuracy and redshift range.

Zierler:

Okay.

Moos:

All right?

Zierler:

Yeah.

Moos:

All right. It’s neat. This is a complicated story. Well, maybe I can cut to the chase. So, we went through several mission designs, okay, and I would say some bad designs with some good designs. We ended up realizing that we couldn't do it in a simple way in low-Earth orbit. It had to do with the cooling of the detectors. It’s hard to do in low-earth orbit. I think I was asked to participate largely because I had been involved in a number of missions and had some idea of how they should be designed. I knew only a little about infrared detectors. I didn't know anything about dark energy. I just walked into this, all right? All right. One of our team… Let’s see. Adam Riess…

Hey, I’ve got to tell you the rest of the Muller story. I told you Muller was a gambler. Adam Riess was a young astronomer who was originally at the Space Telescope Science Institute across the street. Other institutions were considering recruiting hin, so JHU and STScI gave him a joint appointment as Professor at Hopkins and Research Astronomer at the STScI. He received a Nobel Prize for his work using supernovae to study dark energy. So, here’s Muller’s gamble. You know, Muller was fired because of his gambles, okay?

Zierler:

Really!

Moos:

Yeah.

Zierler:

Not because of this. Something else?

Moos:

Medical school. He bet on buildings and it got very expensive and the trustees pushed him out. But anyways, his bet at Homewood paid off. We got the first Nobel at the Homewood campus of the Johns Hopkins University. The Medical School has a number, but we’d never had a Nobel before. But we couldn't tell Muller because he had Alzheimer's. Isn't that terrible?

Zierler:

Yeah. That’s sad.

Moos:

I mean he had bet on this department. He had put all kinds of money into it, and, in the gentle way he was noted for, rammed it down the dean’s throat and…

Zierler:

So you're saying he deserves a piece of that Nobel himself in a certain sense.

Moos:

Because it was his vision. I would say his recognition of the opportunity that led to the institute, that led to the building of the faculty at Homewood in physics and astronomy and provided a climate so this young man would come and take a joint appointment. Adam was originally at the institute and he came across the street and took a joint appointment with us. He was happy to come, because we had built an astrophysical faculty that he respected. So, when the prize came, that was a big deal. That was a big deal. Yeah.

So anyway, I’m really off the subject. We’re going to fix that later, but the point is we left that hanging before and I just wanted to come back to that and tell you this is a Shakespearean tragedy that when this great… Now Muller had many bets, and so many things probably paid off. But the point is that it was just this wonderful, bittersweet thing that here was this fantastic celebration. You know, Daniels is now the president and he was very proud of this, but the person who had really kind of started it was not able to understand his success.

Zierler:

Yeah.

Moos:

Okay. All right. So we’ll get back on dark energy. So I worked for a number of years then because NASA knew me; I was a known quantity. I was on various committees and I chaired one or two of them having to do with dark energy. I think the reason was I had done the FUSE mission and NASA knew that I knew how to do missions. That’s not trivial, to know how to design a mission. While I can't really say I’m an expert on dark energy, I can say I probably developed a lot of expertise on how to do it from space, all right? In the end, I ended up being in semi-retirement. I was still teaching, but I was working part-time. I even got involved in WFIRST. (It is now called the Roman Space Telescope. I got to know Nancy Roman over the years, and I am excited to see her contributions recognized. To say more would require another interview!) WFIRST was a telescope that was given to NASA by the National Reconnaissance Office. You're a US citizen; I can tell you these things.

Zierler:

I’m not just a US citizen; I’m a former employee of the Department of State, and I had a high-level clearance for over a decade. But this is an unclassified environment. [Laughs]

Moos:

Well, you know, there are funny laws. The ITAR laws in this country are weird, but let’s not go there. Anyways, I believe the National Reconnaissance Office had a project with Boeing that went bad and they canceled the project. I assume it was NRO; I don't know that for sure. But they canceled the project when they were quite deep into it. They had already built one full telescope and had a bag of parts for a second one. Although the mirror was the size of the Hubble Telescope. there was a dramatic improvement in the optics. The field of view was much larger than Hubble. So, the telescope wasn’t any larger than Hubble, but for certain kinds of science or certain kinds of remote observations, it was much more effective because of the dramatic improvement in the field of view. It would be like having about 100 Hubbles working in. parallel. So, this looked like a good thing for doing survey missions, and NASA said they had been told “You can do anything with it you want, but you can't look down.” All right? [Laughs]

Zierler:

Right.

Moos:

So NASA assembled a band of astronomers led by David Spergel at Princeton, and we spent I guess a year, maybe two years thinking about what you could do with it and arguing that you should do a dark energy mission and a lot of other science, okay? Now I get into things that are… There was a tension there between how you should study dark energy. If you went with Hubble-class resolution per pixel, and used a gigapixel detector - that’s 10⁹ pixels, which is a huge detector for a space mission, still, the total angular field of view would be very small. The instrument will not be suitable for doing baryon acoustic oscillations, the kind of thing I and others had been thinking about. It was suitable for other studies in dark energy, but not that. The reason is the angular resolution per pixel is very much less than the typical distance between the density maxima, set by the wavelength of the baryon oscillations. If you think of this wavelength-distance as setting the size of quasi-independent data points, only a very limited number of independent number data points can be measured in an individual observation. A large number of observations are required in order to obtain enough independent data points to provide reliable measurements of the baryon acoustic wavelength. As the mission has multiple goals, that observing time simply is not available. Effectively, you're limited by shot noise caused by the limited number of samples. If we had made the pixels two or four times larger even, I think it would have made a significant difference. Four times larger would be huge. That would have done it. But that was the decision that the committee made, and that sank one approach to dark energy. They could do it, but in the opinion of people who think about these things, it’s not going to be as significant as it should be. Yeah.

Zierler:

Warren, I wanted to ask another very broad-based question. Especially in terms of the depth of your partnership with NASA, right, I wonder if you can reflect on exactly how that partnership works. Is it a 50/50 relationship? Is Hopkins providing as much as it’s receiving in terms of the interplay of research, of expertise, of instrumentation? What is Hopkins getting out of this relationship, and what is NASA getting out of this relationship? Is it roughly a 50/50 split?

Moos:

I think that’s the wrong question. I believe NASA has interests as an institution. It is funded by Congress to achieve goals. We can have a big conversation what those goals are, okay? There are nominal goals and there are real goals, but whatever they are, NASA has to go back to Congress every year and they have to say, “We did this and that.” The Congressional Committees have to say, “Gee, that looks pretty good,” or “Ugh,” you know? They have to have a good feeling or a bad feeling, and sometimes what Congress thinks… I mean they have their job. They have to educate Congress. They have to work with Congress, and sometimes the things that Congress wants are not quite the same things we scientists want, all right?

Zierler:

Sure.

Moos:

Let’s understand all that.

Zierler:

Sure.

Moos:

So NASA is in between…in this bartering process, right? I believe that people at NASA want to do the right thing, but they also work for Congress. They work for Congress and they work for the President, and whatever the goals of those people are, they have to be taken into account, all right?

So we have to provide them with both technical…mostly. Mostly we provide them with technical and scientific success, either by helping them select missions or even helping them to implement missions. Or sometimes we provide wisdom. Whatever it is, we provide things they need that they don't have in the government, and… For instance, they don't typically… The big labs can do things that are technically tough. They might grimace a little. They are slow to gamble on the crazy things. I don't know how to explain this.

I with others developed early microchannel plate detector systems that enabled us to go from looking one wavelength at a time to looking at many wavelengths at a time, and I actually demonstrated it in a rocket flight, all right? That was done in a university. The microchannel plates were developed by the night vision program, by the government putting money into the microchannel plate manufacturers for night vision goggles. You know what I'm saying? There’s this kind of a marriage back and forth between the scientists and technologists and the government. We’re always kind of like pushing the edge, all right? You know, they produce the plates and then we figured out a way of coating them with cesium iodide so it was sensitive in the ultraviolet. On and on and on, okay?

Zierler:

Right.

Moos:

We figured out how to package it in an instrument that would go up 100 miles in a rocket, and as soon as the residual gas had outgassed, a door would open, and we could take observations. I mean it’s all those things. So there’s this funny marriage that goes back and forth, and I don't think it’s a case of one funding…doing something for the other. I think it’s a marriage of convenience, and when you figure that out, you realize that they’ve got things they want satisfied as well as you.

Zierler:

Sure. Sure.

Moos:

Then they get along.

Zierler:

Sure.

Moos:

The NSF is different, but all parties in the government have their goals. Whatever they are, they have their goals and you have to understand that, just like we have our goals.

Zierler:

So Warren, to bring the narrative up to the present day, I wonder if you could talk a little bit about your decision to become emeritus and the kinds of research and other projects that you’ve been involved in in more recent years.

Moos:

Yeah. Are we going to come back and talk some more about this?

Zierler:

No. I mean, it should be a self-contained interview, so what do you want to return to?

Moos:

Well, I’m just thinking about talking about the rest of my career. I need to talk a little bit about what happens to an aging professor and how one can contribute? [Laughs] I tell you what. How would you like to take a break and then spend about a half hour finishing this up?

Zierler:

Okay. Sure. You want to break for a few minutes and we’ll come back?

Moos:

Yeah. Give me a break and then I’ll come back and then we’ll be done.

Zierler:

Okay. That works for me.

Moos:

All right. Let’s see. I had a contact with Riccardo Giacconi, Director of the Space Telescope Science Institute, over a number of years when he was Director. There was a temporary director for a while, and then Riccardo was hired. This happened, while I was away on sabbatical. After returning, I remember telling him how excited I was about his decision to take the job. If you're a new person on the block and you're just coming in from the outside and a faculty member says, “I’m really excited that you came, it is always nice to hear.” So, I was on his good side. [Laughs] He and I always got along. But you know, I had only limited contact with him over the years

At one point I was approached to take on the job of the project scientist for the Hubble telescope. In the end, I decided not to take the job, but I remember having a conversation with him about, “Should I do this? Does this make sense?” I went to him. I said, “Well, does this make sense to do this?” In the end there were reasons why I didn't do it. Among them, it would have meant that I had to give up the FUSE project and it also would have meant I had to give up being a university professor, and somehow I didn't want to do that. That was a personal decision.

But he approached me in… I’m trying to find out the year. Let’s see. I was on the board of AUI (Associated Universities, Inc.)… Here it is, 2001. So, Giaconni approached me sometime in probably 2000 or 2001. He was then the president of AUI and asked me if I would be interested in serving on the board. I said yeah and got involved. The trustees were a wonderful group to work with and they taught me a lot. At that point, there were several things going on. The National Radio Astronomy Observatory (NRAO) was AUI’s largest responsibility, with the construction of ALMA (Atacama Large Millimeter Array) on the way. Also, AUI became interested in a possibility of an institute for Space Station. I worked with Ethan Schreier, then the vice president who eventually became president. In the end, NASA abandoned the idea for a time. There is such an institute in existence now, but we never took it up again.

I became the chair of the board in 2004, three years later after joining the board, and I was kind of a witness to the trauma of the early days of the ALMA project. In addition, I was a member of the Board’s ALMA oversight committee until I left the board in ’16.

Zierler:

Warren, I want to ask. What were your interests in joining? What were you looking to accomplish? What did you see as the big questions that you wanted to be a part of answering?

Moos:

Oh. Well, it’s very interesting. The reason they wanted me was I knew something about big projects. You know, I’d been involved in STIS as a Co-Investigator. I was the Principal Investigator for the Far Ultraviolet Spectroscopic Explorer mission. I had been chair of my department. You know, they were looking for that kind of background. One of the problems with AUI was that the board consisted primarily of a group of distinguished scientists and additionally several members with extensive university and similar administrative experience, but there were no scientists with any large project experience. So, it was a natural for me to come in and be involved. I guess since Giacconi knew me from former years, he said, “Well, this guy’s not too terrible.” [Laughs] And they decided to ask me. That was a great experience, especially to watch the creation of the ALMA construction project and to see it through to completion.

There was a lot of tension with Europe. One of the big problems, interestingly, was there’s always so-called noble work. [Chuckles] There’s always the question of who does the noble work and who does the grunt work, okay? We in the United States had unique access to radio frequency detector technology. Our detector technology in the United States is better than anybody else in the world. As the Director of the Research Laboratory at NRAO said to me, “We are at the lunatic fringe of radio engineering,” okay? It’s incredible what those people do. It’s very, very unusual. There are things in your phone that they can reduce to a chip. I mean it’s that kind of thing. We’re so far advanced compared to typical radio engineering that it’s hard to believe. And a lot of the stuff we do is at very low temperatures. The detectors are run at the temperatures of pumped liquid helium with extreme refrigeration because we have to work at wavelengths where kT would kill us.

I going to insert a parenthetical remark here. At the present Apple is one of the richest corporations in the world because of cell phones. Likewise, 5G communication systems are major sources of international controversy. The frontline engineering of high frequency radio systems plays a major role in both of these two enterprises. Yet, the Director of the NSF (April 2004 – May 2010) Dr. Arden Bement made it clear to AUI that his sources in industry were telling him that research investments in visible astronomy would have a much greater economic payoff for the nation compared to radio astronomy. It is always hard for government officials – or anyone else - to guess the future of technology!

So technically, compared to Europe, we were far ahead. We wanted to have one vendor build the radio antennas, which are 12-meter dishes, and they would have to work down into the submillimeter range, which means that you have to hold the tolerances on the dish to a fraction of a millimeter, okay? I mean that’s basically optics. If you're going to work in a wavelength range, you’ve got to hold the tolerances on it the optical surfaces to a fraction of those wavelengths. So, for centimeter waves, you hold things to a fraction of a centimeter, say a millimeter. But when you start talking about wavelengths of a millimeter or less, it gets tighter, several thousandths of an inch. In addition, you have to ship the antennas, which are 40 feet in diameter, across the world, put them at 16,000+ feet and use them over a wide range of temperatures from winter to summer. It’s challenging, all right? It’s challenging to hold those tolerances.

In addition, we wanted to have one vendor and have one design because that also meant it’s easier to analyze the data, which requires combing the data from all of the antennae in the array. However, the Europeans said no This battle went on for over a year, and the project got held up. The project was held up because the Europeans would not agree to that, and in the end they won. We had to give in. They built half the antennas their way, and we built half the antennas our way. It turns out, in the end, they built better antennas than we did.

Zierler:

So what did they do right that you didn't do right?

Moos:

I not completely sure, but on the base of our antennas and in the cabin there’s a large array of electronics, and the vendor likely didn't completely account for the heat put out by those electronics. That heated the dish, okay? In certain configurations, the dish would warp. Remember, you're trying to hold tolerances to a fraction of a millimeter (a few thousandths of an inch) over a diameter of 40 feet. It warped and we got astigmatism, and the European antennas didn't. But at that time we didn't know that, all right? We said, “Let’s do this. You send money and we’ll… We’ll even let you make part of each antenna, but we want to do the final assembly here in the United States,” and it held the project up.

Meanwhile, the commodity boom started. The cost of commodities shot up and there were huge increases in cost. We had to go back to the National Science Foundation. In addition, we hadn't done enough engineering in the early stages, so there were things that were kind of the “I forgot” kind of thing. That often happens in big projects. That’s a very common phenomenon and often doesn’t show until you start to do more detailed design work. The NSF doesn't spend enough money up front, by the way. That’s a standard problem. They don't spend enough money up front, and then they get burned.

Zierler:

Is that unique in terms of your earlier comment about you can't double dip with DOE and NSF? Would you say the same of DOE, or is this uniquely an NSF issue?

Moos:

DOE would say it’s an NSF problem.

Zierler:

[Laughs] Okay.

Moos:

DOE can run space missions; NSF can't.

Zierler:

Right. Right.

Moos:

I’ll rest my case. I’m not saying DOE hasn’t had their mistakes, too. I know less about big DOE projects, but I do know that they do big engineering projects, and NSF has limited large project experience inside the agency. So, the fact that we didn’t have enough money up front for more detailed studies, and then this battle with the Europeans which led to an increase in commodities leading to a huge cost increase—we had to go back to the NSF and say, “We’re broke. We’re not going to make it. We’re not going to make our contribution.” In the end, they found the money and they told us, “Don't come back.” But we were on a tight budget.

So here we are. We went ahead. We built the thing, and in the end, we were literally at the last million dollars trying to… [Laughing] In the end, we were actually trying to figure out where the money went down to the last $100,000 because we might have to pay for the overrun out of AUI reserves, which were quite limited. It was really quite interesting, but it was a great experience and I enjoyed it very much.

But there were a lot of tensions between us… The partners were Europe, Japan, United States with Europe and United States being the major partners and Japan a smaller but still significant partner. But the tension between the United States, or North America, and Europe was very large.

Zierler:

When you say North America, that’s because Canadian involvement is a significant part of this?

Moos:

Yes, it was a significant amount of money for Canada, and their contribution was through us, okay? They were part of our team. I just mention that in passing. I felt that we on the United States side showed a lack of sensitivity in understanding how the Europeans work, all right? I do blame that on us.

Zierler:

You mean like there should be greater cultural sensitivity? Is that the idea?

Moos:

Well, not cultural… Well, let me explain how Europe works, okay? [Laughs]

Zierler:

Please do. I’ve been wondering myself. [Laughs]

Moos:

Okay. If you have a big enterprise—it can be European Space Agency (ESA); it can be the European Southern Observatory (ESO, with whom we were dealing—the way these enterprises work is the governments get together every few years. The various finance officers, the treasurers or whatever they are, all meet, and each says, “Well, we can guarantee that we will contribute this many euros per year to the running of this agency.” All right? The commitment is for a period of time, for maybe five years. And they commit. They’re on the hook. Nobody is going to come in and change it.

Zierler:

Right.

Moos:

So there’s a flow of euros from the countries to the space administration or to the European Southern Observatory or whatever, okay? Now why do they do that? They don't do it because they love astronomy. They do it because these agencies are going to turn around and buy things from the various countries. So if you're Germany and you're giving money, or you're England and you're giving money, you expect that the funded agencies are going to come back with a purchase order to buy things from you, okay?

Zierler:

Yep.

Moos:

They won't admit it, but they all have spreadsheets and they’re counting, okay?

Zierler:

You mean they want to act like this is just about pure science, but really the money is a factor.

Moos:

It’s about building high-tech industry in your country.

Zierler:

Okay. Okay. That’s useful.

Moos:

Okay. That’s why Finland has high-tech industry that can produce space-qualified components. Why else would Finland have [that]? Because they put money in the pot and they want it to come back.

Zierler:

Sure. Sure.

Moos:

That’s why the European Space Administration has an observatory in Spain in VILSPA, okay? Because they put money in the pot. [Unintelligible] So the same thing goes on with the European Southern Observatory. They expect… They don't expect it will be perfect, but they expect that the balance, on average over a period of years, they’ll get back what they put in. All right? The salaries for their astronomers, the salaries…whatever it is. So that’s the way it works. And they expect a share in the prestige.

Zierler:

Yep.

Moos:

Right? So, the European agencies are very good at their relationships, and just because the Americans want to do it a certain way, they’re not going to do it that way.

Zierler:

Sure, sure.

Moos:

Yeah. And Riccardo Giacconi had been the director of European Southern Observatory before he took this job! He knew this!

Zierler:

Of course.

Moos:

But he felt that the best way to do it scientifically was that one manufacturer would do the job.

Zierler:

Do you think that he was…

Moos:

No, I think--

Zierler:

I mean, what was his thinking? Was he going to--

Moos:

I knew Riccardo. That’s the way he operated. Riccardo always wanted to do what was best, and he said, “This is the best way to do it.” For instance, when Riccardo was the Director of the STScI the software tools provided by a NASA contractor were poor. As described to me by the staff, junk might be a better word. Riccardo recognized that new software tools that were continually updated were necessary for a steady flow of results from Hubble. He prevailed with NASA on this as well as staffing the STScI with first class astronomers and not just spacecraft jockeys.

Zierler:

So was that naïve? How did you interpret this?

Moos:

I don't call it naïve. It’s hard to call Riccardo Giacconi naïve.

Zierler:

Ideal? Idealistic?

Moos:

No. Stubborn. Yeah.

Zierler:

Stubborn. Okay.

Moos:

Yeah. He knew this was the best way to do it. In his opinion, this was the best way to do it, and he wanted to do it that way, yeah. That’s the only thing I can attribute it to. I had no personal conversations with Riccardo about this. I don't know, but he certainly had the background that he knew. He understood the way the Europeans thought. And there was this business of noble work. The Europeans wanted to be able to say, “We did this. We did noble work,” you know?

Zierler:

Right, right.

Moos:

They didn't want to… In particular, they wanted to see it happen so that they could farm out some of this work in Europe. They identified companies in Italy and France that were going to do the work. But in the end, we had this experience. Also, I have to admit that some of the overrun problem was just immature engineering. I’m not trying to say the whole overrun was due to this one thing. Some of it was due to the immature engineering, and we had to go back to the well, to the National Science Foundation, and say, “We’ve got a problem,” and the NSF was not happy. But they did come across. We were on the block to be canceled, and in the end the United States decided to go ahead, but it was touch and go.

Zierler:

How did that decision come about? What was the timing of that decision for the US to go ahead?

Moos:

I am unsure. I believe Michael Turner from Chicago, who was temporarily at the NSF, may have had a role, but I am not sure.

Zierler:

Sure.

Moos:

He came in for a year or two years, and I think he had something to do with it. But it was a big call. It was a big call. Then of course the Director had to approve it. (Ethan Schreier, who was the President of AUI during construction is a much better source for the details of how the decision to go ahead was made.) Look, ALMA was a very important project, and in the end, it’s been superb. It’s produced… It has resolution that’s better than Hubble. How do you do that? Well, the answer is we have a huge footprint, okay? These millimeter waves… Remember, it’s λ/D that counts, and λ is large compared to, say, visible. But D is huge, all right?

Zierler:

Right. Sure.

Moos:

We have, I think, a 5- or an 8-km space on a plateau. It’s huge. So, it was… The other thing is that ALMA can see through the dust. Those wavelengths penetrate through dust, so we can see processes that you can't see in the visible and ultraviolet, all right? We can see into star-forming clouds. We can actually see, for instance, the tracks in a dusty disk where newly formed planets are sweeping up the dust. You can see it in the images of these clouds. Sometimes there’s one. Sometimes there are several tracks. It’s the only thing it could be. These are planets going around the star, and they’re sweeping up the dust. So it’s great. There are some things we can't do, but I think it’s been a very fruitful, very fruitful machine. I mean, you probably haven't followed it, but if you talk to astronomers, they’ll tell you that ALMA has been a very useful machine.

Zierler:

Yeah, yeah. In your view, what are some of the big questions that it’s helped answer or provide clarity to?

Moos:

From a scientific point, I’m not qualified to really discuss that because I was so wrapped up in the implementation. However, if you think much about it, you realize that at these wavelengths, it’s a molecule machine. It can see all kinds of molecules, so it can see all kinds of chemistry going on, which means that you can actually say something about a range of astrophysical problems. A big problem in astronomy is chemistry, believe it or not—not the kind of chemistry that chemists traditionally thought about, but the chemistry of molecules at very low density. How do larger molecules form? Presumably on dust? What are the abundances? Trying to understand those things is a really, really big problem. The millimeter range, because that’s the rotational range of molecules, is very rich. In fact, it’s so rich that we need and are creating a goldmine of new spectra. Literally. the reference spectra do not exist; we don't have them. A lot of the astrophysical species are very hard to create in the laboratory and study. At this point, I’m not even competent to talk in more detail about it. I haven't used it for my own research, and my background is atoms. [Laughs]

Zierler:

So, Warren, I think that gets me to, you know, before we broke to what would be my last question, and that is talking a little bit about the work that you’ve been involved in in more recent years.

Moos:

Well, of course I told you about WFIRST, and that was during my retirement. … The joke I make is that I retired three times from Hopkins.

Zierler:

Listen, I say this all the time. It’s like I’ve never met a physicist who’s actually ever retired. They’re just going on to do different things.

Moos:

The first time, which I think was in the ’70s, I gave up my endowed chair, and they issued me a research professor title. Let’s see. I’ve got all this written down here. I became…let’s see…acting director… Yeah. Well, that actually doesn't… Let me see. Ah, here we are. Ah, here we are. In 2008 I became a research professor, and I was research professor for some number of years until ’16 when I actually turned 80. In that eight-year period, I was basically on a hunting license. I had funds set aside left over from various projects that I was able to use. The university funded me to do some special projects for them, and I won't go into those details. Then the government came to me. That was mostly things they wanted me to do it for free, but I did some various projects in dark energy. Then I got involved in WFIRST. That was also on my dime. They said, “This is a great project. We want you to help us, but we can't give you any money.” [Laughs] That’s standard practice, and finally--

Zierler:

So Warren, if we had to pigeonhole you, given all the projects that you’ve been involved in and given the big transition into astro--

Moos:

Well, I didn't tell you about everything. I just told you about some of it. I also was involved in thermonuclear plasmas, these large, magnetically confined plasmas at tokomaks and similar devices. In fact, we had a quite successful plasma physics program at Hopkins supported by the Department of Energy, which I started at the end of the sixties. We trained a number of students in atomic physics and spectroscopy with most of them doing their thesis work on major. plasma machines. A large fraction of these went on to spend most of their careers working for the DOE. Because of all my other projects, I encouraged others to take the program over and it was successful for many years, only ending within the last few years. So, I am hard to pigeonhole.

Zierler:

So, my question is at the end of the day, how do you identify yourself. If you had to say the kind of physicist that you are, if you had to choose?

Moos:

Probably an opportunist. [Laughter] Yeah. I would say in my early years I was involved on the edge of quantum electronics with a big emphasis on atomic physics. That flavor went through my early faculty years when I was doing solid state physics, but it was still atoms in a cage. I mean it was the same kind of thing. In the late ’60s continuing into the early ’70s, I started to move into astrophysics. It was an evolution in which I moved away from physics related to quantum electronics. Along the way I did some plasma physics which I mentioned just recently, but that was kind of a target of opportunity in which we set up a program that the government needed. That looked interesting and we did it. At one point I had thesis students working at Department of Energy Laboratories with novel spectroscopic instruments developed at Hopkins. So how do I characterize myself? I think as an experimental scientist. And as you age, your ability to manage projects goes up. Yeah. It’s very hard to pigeonhole me.

Zierler:

I gather as much, which is why I wanted to see if you could yourself. [Laughs]

Moos:

No. But you know, I think that’s good…

Zierler:

Sure. Sure.

Moos:

…because it means you have a broad intellectual grasp of a lot of things…

Zierler:

Absolutely.

Moos:

…the big picture.

Zierler:

Right. Okay. So, I said that was my final question, but I’ll really make this my final question now. Maybe a better way of getting to that answer is, you know, as you look toward the future and you think about the kinds of things that still interest you and the kinds of things that you remain curious about, what do you gravitate towards in terms of thinking about particular things that you want to remain involved in, the kinds of things that you’re eager to see advances being made. What area or areas might jump out at you in terms of that forward-looking kind of question?

Moos:

Well, I don't know. I mean I don't know where dark energy is going, and I don't know if and when they get there, I’m going to understand it, okay? [Laughs]

Zierler:

But when you say “when they get there,” you think it will happen?

Moos:

[Laughs] I don't know. One of the problems with dark energy is our datasets are so limited. We have a picture that dark energy exists. We know that the simple picture for the expansion of the universe doesn't work, but we don't have a good picture of what happens over time, all right? We don't know. We don't know, and therefore, a very simple picture where it’s just a parameter works. Will it be more sophisticated than that? Maybe, but it may also be in a way that I don't conceive of. Yeah. Sometimes in physics, old problems get solved by new discoveries, that seem to come of nowhere. That’s part of the fun

Zierler:

Sure.

Moos:

It’s just something out of left field, which leads to a way of looking at the problem.

Zierler:

Right.

Moos:

So I can't tell. I do feel that the background that I’ve been given enables me to pick up Physics Today and look at articles and read all kinds of articles, not because I want to make an advance in it, but I have a sense of “Yeah, yeah…” As an example, there might be an article on meteorology, which bears on things from tomorrow’s weather to global warming. I’m just saying, if you have this kind of a background, you can do that; you can look at articles and say yeah, that’s why that’s interesting, all right? I think a lot of scientists have a broad grasp of their field, and that’s a gift. It’s been fun. It’s been fun to do that.

Zierler:

Well, Warren, it’s been great speaking with you today. I really appreciate your time and perspective, so thank you very much.

Moos:

Okay. Then what you're going to do, you're going to turn this into typescript.

Zierler:

That’s right.

Moos:

You’re going to ship this to me and I’m going to pay the penalty for having talked so much.

Zierler:

[Laughs] Well, I’m going to cut the interview here. I’ll cut the recording.

[End]