Kenneth Nordtvedt

Zierler:

Okay, this is David Zierler, Oral Historian for the American Institute of Physics. It is July 24th, 2020. It is my great pleasure to be here with Professor Kenneth Nordtvedt. Ken, thank you so much for being here with me today. 

Nordtvedt:

You’re very welcome. 

Zierler:

To start, would you tell me your title and institutional affiliation?

Nordtvedt:

Well, I was a Professor of Physics up until 1988 at Montana State University. I retired early to do just research as a private contractor. So, I’m a Professor Emeritus, and sometimes part-time employed physicist. 

Zierler:

Have you maintained an active relationship with MSU since you went emeritus? 

Nordtvedt:

I have given seminars there on my most recent work of the last ten years, keeping them informed. I’ve done colloquia for them, updating the lunar laser ranging history, but I’m not a regular up there. I don’t keep an office anymore. 

Zierler:

Ken, let’s take it all the way back to the beginning. Let’s go to Chicago, and first, tell me a little bit about your parents and where they are from. 

Nordtvedt:

My parents were working class people. My mother didn’t finish high school, but my dad did. Although I think he wanted to be an engineer, he went right to work making gears where his dad worked at Illinois Gear and Machine Company. So, my dad started out as an 18-year-old, and by the time I was born in 1939, he was already a foreman, and he went on to work his way up through this factory that made gears to custom order. They didn’t make mass produced gears, but someone would call in and wanted a special gear made, and wanted ten of them or something, then Illinois Gear would make them. My dad was a frustrated engineer, I think. The reason I suspect that is on our vacations in the ‘50s, he would stop at every big dam, and every big open pit mine in the west. He’d stop and check out these places. I could just see his eyes, that he liked big engineering projects. 

Zierler:

Ken, is your sense, perhaps, because of the Great Depression, your parents didn’t have as many educational opportunities as they might have?

Nordtvedt:

Very definitely. They both felt that they had to go to work right away, and that there wasn’t money for college. I’m not sure my mother was interested, but my dad was, I think. He was pretty smart.

Zierler:

So, in a different era, he might have gone on for an advanced degree in engineering. 

Nordtvedt:

Yes, exactly. Now, my parents were not poor by any means. You’d have to call them comfortable middle class going through the Depression. I think my dad’s dad had a job throughout the ‘30s as a machinist: he had a solid job. In fact, my dad inherited a lot in suburban Skokie, Illinois, north of Chicago, when [his dad?] Ok-died in 1938. 

Zierler:

Where did your parents meet?

Nordtvedt:

My great aunt on my father’s side and my grandmother on my mother’s side worked as waitresses in downtown Chicago in the same cafe. I think they introduced, or somehow because of their friendship, they introduced my mom to my dad. I don’t know the full story, but I do know that was the overlap between the two families. Both my parents’ families came from elsewhere in the rural Midwest, but throughout the 1930s, they both lived in Chicago during the Depression and worked there. 

Zierler:

Nordtvedt is an interesting name. Do you know the national origin of that name?

Nordtvedt:

Not only do I know the national origin; I know the original ancestor who took the name. My third great-grandfather—outside of Oslo, Norway—took the name Nordtvedt from a farm where his father had worked. It’s a Norwegian farm name converted into a surname which was common practice. 

Zierler:

Does it mean something?

Nordtvedt:

It means “north clearing,” or the north field of a farm that through the centuries may have grown a little bit, added pieces to itself. The ending “-tvedt” is pretty common for many Norwegian names. There’s even an English version, “-thwaite,” from the Yorkshire area of England, where the Norse settled. It means, “to chop or clear a field.” It’s an archaic word. It’s not present in modern Norwegian today. 

Zierler:

Do you have Nordic roots on both sides?

Nordtvedt:

Yes. My mother is half Scotch-Irish from way back in colonial America. My mother’s other side is Danish-German, right from the border between Denmark and Germany, called Schleswig. So, I’m pretty much Scandinavian, but with a lot of English and some German, too. 

Zierler:

Growing up, were there any Scandinavian customs that you had in your family?

Nordtvedt:

No. My father says that his father did not speak Norwegian at home, although he was born in Norway, my grandfather. So, my dad just picked up a few swear words and slang expressions from his dad in Norwegian. They had left South Dakota when my dad was very young, maybe seven years old. So, he didn’t remember much Norwegian from the neighbors, or anything, in that part of South Dakota. 

Zierler:

Did you spend your whole childhood in Chicago?

Nordtvedt:

I spent my childhood, basically, in the north suburbs of Chicago. I was born in Chicago, but by the time I was one or two, my father had built one of the last custom homes that you could build before Pearl Harbor, when private building of homes was pretty much put on hold because of the war. He got his home done just prior to Pearl Harbor. By the time I went to school, I went to school in Skokie, Illinois, and then later, Niles, Illinois. 

Zierler:

And your dad built the home himself?

Nordtvedt:

No, no, no. He had it custom built because he had to work and bring in some money. There are some old photos showing the house under construction. In our visits there’s the family unit to check out how the bricks were going up. 

Zierler:

It sounds like you had a pretty nice, suburban middle-class upbringing.

Nordtvedt:

Very nice. By and large, good schools, both in Skokie, and then later in Niles. A way of life which is long gone now. It was like, you come home from school, you say, “Hi, mom,” and you go out and disappear who knows where until dinner time. In the summer, you’re gone all day long. Things that just don’t seem to happen these days. 

Zierler:

Right. Ken, when did you start to get interested in math and science and realize that you had a special talent for it?

Nordtvedt:

The first incident I can recall is 8th grade. I got in an argument with our general science teacher. He was also our phys. ed. teacher for eighth grade. Anyway, he was talking about the motion of the moon and how it kept the same face towards us all the time. He said that’s because the moon doesn’t revolve on its own axis like the Earth does. I corrected him politely. I was a polite student. I said, “It has to turn on its own axis once every orbit around the Earth, or the same face will not stay fixed.” He got mad at me for disagreeing with him, but I stood my ground. I said, “No, I think I’m right.” 

Zierler:

Was this a matter of intuition on your part, or were you doing outside reading to understand this?

Nordtvedt:

No reading that I can think of, but who knows? My mother was the one who set the environment in the household. When I was still a little baby, she bought the family an encyclopedia, a complete set about 5-feet long. Huge. So, I would often spend times, particularly in the early days when there was no TV or anything, just going page to page through the encyclopedia on every topic under the sun until I found one that was interesting. So, in the course of that, I may have come across diagrams of space, or orbits and planetary motions and all of that. I had no particular reference at the time. I just reasoned it through at the time that the teacher made his point about revolving bodies, and orbiting bodies. By the 9th grade, the next year, in high school, the homeschool teacher we had one day asked all the kids, “What do you want to do with yourself when you’re done?” I said I wanted to be either a physicist or a politician—a senator, or an architect. So, even then I had a feeling that science was one of the things I really was interested in. Actually, in my life, I’ve done all three. So, I hit them all a little bit. Not fully, but I hit them.  

Zierler:

At that time, what did it mean to be a physicist? How did you conceptualize what that job title meant?

Nordtvedt:

That’s a funny question you ask, because my teacher asked me the same. She said, “I don’t think most of the class knows what physics means. Could you explain to the class what physics is?” I was really on the spot. I had a very difficult time putting it in their terms. About all I could say is, “It’s the science at the basis of everything.” That’s about the only intelligent sentence I could formulate. I said, “It’s at the root of everything else.” That’s how I felt about it. That’s sort of what drew me to it. There’s a part of me that likes to go to those philosophical questions that have faced mankind as long as it has existed. And because I was good at math, I think the combination just inevitably drew me towards physics, where you could ask fundamental questions about reality with the tool of mathematics, among other things. So, I knew pretty early. But by the time I graduated from high school, I wanted to be an aeronautical engineer. Through the early ‘50s, I was in high school, and of course, that was the era of the early Cold War, the development of fancier and fancier jet planes, the early rockets. These things really intrigued me a lot. When I applied for university, I picked aeronautical engineering as my major. When I got into the university, I was given a very generous scholarship by Lockheed Aircraft. When I arrived at MIT my freshman year, I was in the hands of the aeronautical engineering department, and their advisory faculties. But by the end of that first year, I went to the aeronautical engineering department and told them, “The way my physics course is taught versus the way your introductory aeronautical engineering course is taught, I’m just drawn towards physics. I would like to change my major.” I had no idea whether Lockheed would permit that, whether MIT would permit that, or what? But they were all extremely generous and said, “Okay, yeah. You can change majors.” That was a big point in my life, because I couldn’t have stayed at MIT without that Lockheed scholarship, for sure. 

Zierler:

Was MIT known in aeronautical engineering as a top program?

Nordtvedt:

I think they and Caltech were sort of the two premier places you would think of, although there probably were others. 

Zierler:

And you took physics courses as part of the aeronautical engineering curriculum.

Nordtvedt:

Well, as a freshman, it’s universal. I hope it’s still that way at MIT, because you have one elective, maybe, your freshman year. You had the mandatory physics course that everybody took regardless of their major, the mandatory chemistry course, the mandatory calculus course. So, that’s the meat and potatoes of your freshman year, and then you had the western civilization humanities course, which was mandatory. It was a great course. And then you had one elective. Aeronautical engineering filled that elective with this introductory course, which tried to teach some of the ideas of aeronautical engineering. But without much calculus, without much physics, I think it was a mistake for them to try that, but they did. 

Zierler:

Do you remember who the physics professor was who really turned you on?

Nordtvedt:

My time in science has been very rare as far as mentors are concerned. I don’t even remember my freshman physics professor, although I thought he was good. I loved the course. But I was a pretty self-sufficient student, so I would rarely go and see him for extra aid or answer of a question. I do remember at the time I admired Weisskopf, who was still there. In fact, we had physics labs, and my particular lab happened to be Saturday morning. MIT still had Saturday morning labs. Niels Bohr came into town to give some lectures on physics my first fall at MIT. I remember meeting both Weisskopf and Niels Bohr when they came to our laboratory on a Saturday morning. Weisskopf was just showing Niels Bohr around, but we were luckily there and got to meet him. It was a big point, because I remember going to Niels Bohr’s public lectures, which were on the early history and foundations of quantum physics and buying up all his books that were in the bookstore. It was an interesting moment. I don’t remember any of my freshman professors as such. The first professor I remember was a guy named Dirk Struik in the math department who taught tensor calculus. That was my first glimpse of relativity. He finished the semester of tensor calculus solving Einstein’s equations to get the Schwarzschild metric, just as an exercise in using tensor calculus. We didn’t go into any of the physics, it was just pure math, but it showed an interesting connection between math and some of the frontiers at that point. Who else do I remember? Oh, yeah. I remember my mathematical physics instructor, Feshbach, who was also an early name in physics from the World War II era, among all the physicists who came from the Manhattan Project back into academia. A lot of our faculty then, ‘55 through ‘60, were veterans of the Manhattan Project. 

Zierler:

Ken, I’m curious if Sputnik had a big impact on you. 

Nordtvedt:

It sure did. I lived across the river in what’s called the MIT student house. It’s a non-affiliate, sort of cooperative fraternity house. When Sputnik went up, which was fall of ‘57, we had access to the roof of our house, there on the Boston side of the Charles River. So, we got up one morning with perfect, visibility, and watched Sputnik go over. It was sort of a momentous event to see a manmade object there, hurdling through space. It was very important to me. I think it had rhythms that showed up several times later in my career, but it was also, in its own right, a great event to be able to experience firsthand. It was like the first or second night after the original launch. It just went right over Boston.

Zierler:

So, you perceived it primarily through a scientific lens, as opposed to a political lens. You didn’t necessarily feel concerned that the Russians were overtaking the United States.

Nordtvedt:

I didn’t think of it in those terms, although I did see the political and strategic sense. Since 1950, I was extremely tuned into the politics of the Cold War. I was in California the summer of 1950 with my grandparents, and that’s when the Korean War broke out. I remember inventing a board game where I drew a map of Korea broken up into little squares and made little war tanks and war pieces for the two sides. My brother and I sort of created a mock war of the Korean Peninsula as the real events were going on. It was sort of the start of my big interest in politics. I’ve had a big interest in politics all my life. During the ‘50s, that was primarily International Cold War politics. It branched out and became broader in later years. I was very aware of the strategic importance of getting objects into space, and having the rocket’s ability to do that, because I was following the rhetoric in the United States before then about whether we should develop ICBMs, and all this. It wasn’t quite clear just how far along our projects in the USA were? I think it was another year or two before we had a first working ICBM after Sputnik. But I didn’t think of Sputnik in that way primarily. I thought about it as a great achievement of man. Whether they were Russian scientists or US scientists wasn’t that important to me, just that man could do this now. It was a whole new playground, so to speak, for mankind. 

Zierler:

Ken, I’m curious if the Sputnik event either created special scholarly or professional opportunities for you that you might not have otherwise had, and if it informed the kind of physics that you wanted to pursue for the rest of your time at MIT and beyond.

Nordtvedt:

It had both obvious inputs, and in connections I never would have guessed would occur down the road another five or ten years. Within a year of Sputnik, there was a group at MIT, particularly at the MIT Instrumentation Lab, which is a very important laboratory. In World War II, it’s where the United States did their most advanced radar development, which was crucial for the United States, both for the Navy and for the Air Force that we develop good radar systems. IT was one of the turning points of World War II. Anyway, this laboratory was still working in radar. In fact, I think they were involved in one way or the other in obtaining the first radar reflection off the moon. I think they were involved in that U.S. achievement. I forgot they did that, but I do know that it occurred back about that time. Anyway, a group there decided, okay, Sputnik has proven that we can easily launch little spacecraft that aren’t too heavy. What about sending up a scientifically oriented spacecraft in which the payload was not chimpanzees, or dogs, or eventually humans, but was scientific instrumentation to make measurements. In fact, they said, “We even have the capability to. send a few hundred pounds to Mars.” So, the Instrumentation laboratory developed the first proposal to NASA, or their predecessor, the NACA—I think it was NASA by the time the proposal got to the government—the first proposal to build a scientific space vehicle. Somehow, I got notice that they were hiring some student help, or at least one position. I applied for it, and the director of this group, Milt Trageger gave me the job. So, within a year, I was working as a student employee in their small research group to develop the first proposal to NASA for a space scientific mission. It would go to Mars and measure various things while in orbit around Mars.

It was supposed to measure various scientific parameters of the Mars environment. That was its goal. I was given a task to develop an attitude control jet system which used liquified ammonia as the basic gas that would drive these thrusters to reorient the vehicle. So, I developed a set of concentric shells to thermally insulate the liquid ammonia from the outside environment. That was my contribution. Then, I went off to graduate school in 1960. I kept in touch with Milt Trageger back at MIT, and I soon learned that after President Kennedy proposed that we go to the moon that his same laboratory, in fact, Milt himself was the director of the project to develop the navigation and guidance system for the Apollo mission. I wasn’t prepared to go right back, because I was still in the middle of graduate work, but then my professor at Stanford, who I wanted to work with, kept his sabbatical at CERN in Switzerland going for a second year. I think life was pretty nice at CERN then. I got frustrated to have to wait another year to start working with him that I decided to see if I could go back without my Ph.D. and work for Milt on the Apollo project. So, by January 1963, I left Stanford without my degree and went back to the MIT Instrumentation Lab.

Zierler:

All the way back from when you were an undergraduate, who was supporting the MIT Instrumentation Lab? Where was the money coming from before Kennedy?

Nordtvedt:

Defense Department, primarily. They were still working heavily on radar; I think that was their main source of income. 

Zierler:

Did you need a clearance at that point?

Nordtvedt:

Part of the facility at MIT required clearance, but our particular building did not. So, I did not need clearance working for Milt as a student, but when I went back later, I think there was some clearance involved. In fact, the first time I actually got clearance, was the summer of 1960, between MIT and Stanford when I worked at Los Alamos for a summer. There, it was a pretty low-level clearance, I believe, but you had to have clearance then. It was still a pretty closed laboratory.

Zierler:

Would you say it was more the department of physics or the Instrumentation Lab that was more influential on your influences and what you wanted to do as a physicist?

Nordtvedt:

When I was at Stanford, other than having this problem with my desired thesis advisor who stayed away too long, I had reached the end of all the course work very early, because I had taken several graduate courses at MIT as an undergraduate. I was very antsy to get a research project going, to get done with school, go out and get a job in the world. So, I eventually took a thesis project from a solid-state theorist, and I started working on the electron phonon system in metals. It was a direct analog to electrons and photons in the vacuum. It was a coupling of fermions to bosons. That’s the problem I wanted to work on in fundamental physics, the electron self-energy problem as it gets more mass due to its interaction with the electromagnetic field. I never got to really do serious research on that project, but the analog I took over to solid state physics. I felt that anything we eventually discover in elementary particle physics will probably turn out to be useful in solid state physics and vice versa. 

Zierler:

That was an intuition that turned out to be pretty correct.

Nordtvedt:

Right on, yeah. So, I left with that work underway. The professor I was working with was Marshall Sparks in the Stanford physics department. I continued working on it when I got back to Boston, to finish the thesis. So, that was influential that they allowed me to do this. I must say: then universities were much more laissez-faire institutions than they are now. I don’t know if I, living today, could have set the higher educational system. Now it seems so locked up from higher levels. But particularly MIT was then such a laissez-faire place. It was a wonderful environment. 

Zierler:

How did the opportunity at Los Alamos come about for you, and what kind of work did you do there?

Nordtvedt:

Just some advertisements: by 1960 Los Alamos had a hunk of federal money to interest future physicists in employment at Los Alamos Lab. So, they would hire people in this transition year between undergraduate and graduate work. I applied for it, and I got it. I was newly married, so my wife and I went out for this adventure in New Mexico. I was put to work on a bubble chamber. Someone was making a bubble chamber to improve their observations of certain particle interactions. I was not given too much guidance. After a few weeks I was sent to the electronics laboratory to try to straighten out some instrumentation, and I blew out a selenium rectifier. According to their alarm system, I just about poisoned myself. The whole laboratory alarm system went off when the selenium fumes got the detectors. Someone came in and rushed and dragged me out into the fresh air. I did not accomplish much at Los Alamos except having a great summer in a beautiful part of the country. 

Zierler:

Did you think about staying on at MIT, or why did you choose Stanford?

Nordtvedt:

I wanted some more advanced theoretical work in elementary particle physics. That’s what I wanted. I originally applied to Caltech and Berkeley, because I knew they had fantastic theoretical physics going on in elementary particle physics. I got my NSF fellowship for graduate study to Berkeley, but by that time, I was somehow drawn to Stanford. I don’t remember what drew me to Stanford because it was not the size of their theoretical physics faculty which was very minimal. They were still trying to fill some valuable posts in that department at the theoretical physics level. But somehow, I heard about Sidney Drell, who was a theorist in the electron self-energy problem. I had taken a course at MIT from another theoretician, who had worked with—who is the Harvard theorist who shared the prize with…?

Zierler:

Schwinger.

Nordtvedt:

Schwinger, yes. Anyway, one of Schwinger’s students got a job at MIT while I was still an undergraduate and gave a course about the electron-photon system in quantum physics, according to the Schwinger formulations. It interested me, that problem, and then when I learned about Sidney Drell at Stanford, I asked Berkeley if I could go to Stanford and take my fellowship that they awarded me with me. Again, they said yes. Although I’ve never had any explicit mentors in my career, I’ve had a lot of mentors just under the radar who always helped me make big decisions. This is another case where I could have easily ended up at Berkeley if they had said, “No, you got that award from us. You’ll have to carry it out here.” It was called an NSF Cooperative Fellowship, which in those days meant we had no teaching duties. It wasn’t a teaching fellowship. It was just a fellowship to get your coursework done and start some research. So, it was a nice graduate fellowship.

Zierler:

Ken, how closely did you follow what Professor Panofsky was doing and the early development of SLAC?

Nordtvedt:

Oh, we would always go and hear the latest word from him. If he didn’t give a colloquium, he or one of his colleagues, including BJ Bjorken, who is a theorist I also got to know fairly well at Stanford, through either seminars or colloquia, or the daily coffee hour late in the afternoon, where we always met every day unless something came up, we would know about exactly what was happening at SLAC and what they wanted to do. To me, it was the most alive part of the Stanford graduate program in physics, things going on in connection with SLAC, both experimental and theoretical.  

Zierler:

How did you go about developing your dissertation topic?

Nordtvedt:

As I say, in my mind, it was a perfect analog to what was going on with electrons and photons in the vacuum, that when I wanted to come up with an interesting problem that I could do without Sidney Drell back on campus, that’s what came to mind to me. Somehow, we got word about some junior faculty at Stanford that were looking for graduate students to work with them. So, I came to Marshall Sparks, told him about my interests, and we eventually worked out this problem of electrons in metals, and their coupling to the phonons, the sound waves in metals. I used a technique from quantum field theory to apply to the solid-state problem. It was called the Quantum Equation of Motion, which is what I did. 

Zierler:

What were some of the broader questions in your field that dissertation was responsive to?

Nordtvedt:

Trying to understand, for instance, the collective excitations of this system in solids. These would be in analog to the elementary particles you might discover from the coupling of fermions and bosons and quantum field theory in elementary particle physics. To me, it was the analog in solid-state physics. It was known for some time, then that there’s a well-known collective oscillation of the electrons called plasmons in metals. I studied them further in my dissertation. At one point, I thought I could use my method to calculate more exactly the binding energy of some of the common metals, like copper or silver, using the method. But by the time I got to pursue that, I was already detoured onto the general relativity path. The general relativity path had its origins at Stanford. 

Zierler:

When you say the general relativity path, do you mean the resurgence in an interest in general relativity?

Nordtvedt:

Yes.

Zierler:

Who drove that? Who was at the vanguard of that trend?

Nordtvedt:

For me it was mainly Leonard Schiff, who was the department head at the time. I don’t think he had taken on any students. He was pretty busy with his department head duties. But he was interested in general relativity, in particular, he was doing some calculations in connection with a possible new experiment to look for what were called gravitomagnetic effects in general relativity. There was an experimentalist named William Fairbanks who had wanted to develop some superconducting gyroscopes, perhaps so sensitive to inertial frames that they might be able to detect some of these strange dragging of inertial frames that occurred in general relativity. In particular, there’s one dragging of inertial frames that puts them into rotation. If you’re near rotating matter, in general relativity, it says that the inertial frames near a rotating body will also slowly be rotating from the gravitomagnetic part of the general relativity tensor gravity. Fairbanks thought that eventually they could put his superconducting gyroscopes in orbit and isolate these gyroscopes from all other influences and see them rotate slowly with the precession of the inertial frame, induced by general relativity and the spinning of the Earth. So, as a theoretical helper to this concept of a space mission, Leonard Schiff got interested in enough general relativity and applied general relativity that he extended a little trick that Eddington did decades ago. Arthur Eddington, in an early book on general relativity, wanted to explain to the people who read his books why or how general relativity made the perihelion of Mercury process, and how it made light deflect. What Eddington did is he put artificial, dimensionless parameters on some of the potentials in general relativity that go beyond Newtonian gravity.

Then he just quoted how the motion of Mercury was sensitive to these relativistic potentials co-efficients, and how the deflection of light as a phenomenon was sensitive to these potentials by quoting the combination of coefficients of the various involved potentials. It was called a parametrized method of Eddington in those days, and then Schiff said, “We have to expand Eddington’s method of parameterizing the metric field of gravity if we want to apply it to these gyroscopes.” It’s the vector potential within metric gravity that’s responsible for how the gyroscope will behave when it’s in free orbit. So, he added a couple more parameters. It’s had two impacts on me: One, it got me thinking for a few hours every week about space experiments to test general relativity. Why not? I’d already been introduced to the idea that we can send things into space. We could propose experiments for NASA to fund to do science in space. So, I got interested in working with Schiff on coming up with some additional ideas for space experiments to test general relativity. During those final months when I was talking with Leonard Schiff, we never did come up with a new experiment, but I was introduced to Eddington’s parameterization scheme as expanded by Schiff. That came back to me three years later when I started on my own problem in Montana.

Zierler:

Ken, do you see a natural progression from your dissertation to your interest in general relativity, or is this more a brand new chapter for you?

Nordtvedt:

It’s a brand new chapter, but both starting from the same origin. The fundamental problem that I had that summer when I went from MIT to Stanford was: there must be an answer to the problem of how much of the electron’s mass comes from its electromagnetic field that it produces. Not the infinity number that the calculation shows. Even the breakthrough calculations of Schwinger and Feynman after World War II that said you could renormalize a fermion boson system, and get infinities but properly handle those infinities, and get finite, interesting measurable numbers in addition to those infinities. There was a standard, classical electron mass problem. I felt, and I still feel that after all these years, it’s still an open question. What is the finite amount of the electron’s mass that is due to its coupling to the electromagnetic field? So, that was the fundamental question I took with me when I went to graduate school. Well, as I will explain soon, that’s like the question brought over to gravity that I made some progress in addressing when I asked the question, “How does the gravitational field alter the mass of celestial bodies?” That’s the analog question in gravity of how does the electromagnetic field alter the mass of the electron? So, by 1966, I was ready to create a research project of my own. I was a brand new faculty member out in Montana. Eventually it occurred to me, I can’t come up with a good idea if I just focus on orbits of bodies and the relativistic corrections to their orbital motion. I’ve got to look at how gravity is affecting the insides of the key bodies which are determining this dynamic: the sun, the Earth, the massive bodies. That became a question of, “How does gravity alter the mass of celestial bodies?” That’s what I started in ‘66 to answer. Fortunately, celestial bodies were not point bodies like electrons. 

Zierler:

You spent some time in Harvard beforehand. 

Nordtvedt:

Yes, I did. When I went to MIT to work on the Apollo program, I had a secret mentor who felt that I was not destined for that kind of work, that I was more of a fundamental sort of researcher. They nominated me for a junior fellowship at Harvard. I still, to this day, don’t know who that person was that nominated me for that fellowship, although I have some pretty good ideas. I went to Harvard and was interviewed by the senior fellows and was awarded a fellowship at Harvard as a junior fellow. So, for the years of ‘63, ‘64, and half of ‘65, I was both at MIT at the instrumentation lab, and at Harvard as a junior fellow. I never was able to make a connection with a research project in physics while I was at Harvard, but I learned an awful lot about one of my interests, which was evolution and natural selection. I would just buy books courtesy of the society of fellows and go to the library. Basically, I just studied evolution and natural selection for two and a half years and finished my thesis in the meantime for Stanford. In fact, I left Harvard a year early to take the faculty position in Montana. That was 1964, which was the big political year when this nobody, Goldwater, got the republican nomination. I would show up at these physics’ seminars, coffee hours at Harvard, wearing my Goldwater button, and quickly realized I was the only one in the crowd. They started giving me strange looks, and that was just part of the bigger scheme of things. I became very uncomfortable with the whole cultural environment by ‘64, ‘65. 

Zierler:

Yeah, Ken, I want to ask you—you probably had opportunities at much more elite universities than a place like Bozeman, and I wonder if culturally and politically, you wanted to get away from both the east coast and the west coast in order to do your science. Is that part of the equation?

Nordtvedt:

A big part of the equation. I don’t think it by itself would have been sufficient because I also, from family vacation camping trips in the ‘50s, I’d come to really love the Rocky Mountains as a region. But when I was still in Cambridge, Massachusetts in ‘64 and ‘65, I did apply to—I think it was a Bell Labs research facility down near Princeton University in New Jersey. I brought my thesis work with me in solid state, and they were going to hire me in the lab to work as a theorist in support of their solid-state laboratory. So, I was willing to stay on the east coast, but it wasn’t my first choice. My ideal choice was to get out of the culture I didn’t like that much and also be able to do physics. To tell you the truth, I think I could have gotten a job at a higher tiered university. There are many tiers in between a college in Montana, which in 1964 was just starting a Ph.D. program, and the top level. But the combination of being my own man and being in the Rocky Mountains meant I left Harvard a year early. 

Zierler:

Bozeman must have been a tiny, tiny town at that point.

Nordtvedt:

It was. In fact, when I went for my job interview in late ‘64, which was just a week or two after the elections of that year, they were still using the silver dollar as the main street currency. If you went into a bar to buy a drink, you’d plunk down your silver dollar. The previous year, in ‘63, when Lyndon Johnson announced he was taking all our coinage off of silver, I’d already started deliberately collecting silver. I would always use a dollar bill to buy anything, no matter how cheap, so I could get change and throw the silver into a can. I knew the price of silver was going to explode once you took the money system off of the metal. I just regretted not having come to Bozeman a year earlier. I could have stashed away as many silver dollars as I wanted. 

Zierler:

It makes a lot of sense between your political inclinations and your love of the Rockies to come out to Bozeman. I wonder if you were concerned at all—you had been operating at a very high level at some of the most elite universities in the world in physics. Were you concerned that your research agenda would take a hit by being so isolated in Montana? Long before Zoom, for example. 

Nordtvedt:

No, I missed having colleagues that I could talk to. I think I was the first theorist hired in Bozeman—I take that back. We had one more already whose focus of career was research rather than the teaching part. So, I had no one in my field. I had no one in the field of either solid state theory—I was hired as a solid-state theorist to support solid state experimental physics, which was the mainstream activity in Bozeman in 1965. There was no one to talk about elementary particles or general relativity, but I was confident enough that I would come up with my own good questions. I still had contacts with some people around the nation who would at least take my telephone calls and my letters if I wanted to talk to them about physics, and my fellow graduate students at Stanford, who I kept in close contact with. I just felt confident I could find my own research program and I could eventually get support for it. NASA allowed me to take some of my work from MIT Apollo program with me to Bozeman, and gave me a one-year grant to finish up a report on what I had done while I was at MIT Instrumentation Lab. So, I knew that if I had a good proposal, I could probably get funded. What I ended up doing for the Apollo program, which they never adopted, was the idea that maybe they needed a backup navigation system that could safely bring the spacecraft back to Earth in that safe corridor for reentry, even if their communications broke down with Earth and they didn’t have the fancy navigation information that Earth was feeding them. They could basically navigate on their own to sufficient precision to land safely. It was something I took from my interest in sailing. How about giving them a sextant and having them take certain stellar to Earth horizon readings and simplify the formulas so that they could, when they were out 30 or 40 Earth radii, coming back to Earth, cut off from Earth communication, get their orbit touched up so that they would enter the safe corridor. They had a corridor where if you entered the Earth more densely than that you would burn up. If you hit the atmosphere more lightly, you’d skip off into space. So, there was a several mile corridor of safe reentry. So, I developed a manual navigation scheme for such events, and then I proposed it to NASA. They invited me to Huntsville to give some reports and talks on it, but they never used it, but it was there. 

Zierler:

In what ways did this project really move the field forward, do you think?

Nordtvedt:

My manual navigation? I know of no one who has ever done anything further with it. I think it was a dead end. 

Zierler:

So, what kind of research did you take on from that point?

Nordtvedt:

It was October of ‘66 when I sent my report off to NASA after I finished it, and I started thinking in the backyard about what to do next. No funding, but I had free time given my teaching schedule. What am I going to work on next? So, I started to think again about a new experiment in space to test gravity. It was in the course of a couple weeks of thinking that I thought it boiled down to calculating the inertial and gravitational mass of the Earth as altered by the gravitational interaction. By the gravitational field energy of the Earth, how does that modify its inertial mass, and its gravitational mass, and most importantly, the ratio of those two masses, which is what we can most precisely measure in any kind of celestial mechanics. What it ends up being is a relativistic correction to Newtonian mechanics, at what seems to be at the Newtonian level because it’s all in the internal structure of the bodies and nothing to do with their orbital motion as such. It makes it directly analogous to the problem of how the electromagnetic field changes the mass of the electron. How do the phonons in metals change the effective mass of the electrons in solids? And now we’re talking about gravity. How does the gravitational theory affect the mass of bodies that have some gravitational self-energy? If I pick up an item off the table, like this, yes, it has some gravitational self-energy, but it is so utterly negligible that even our great-grandchildren will not be able to measure it to that precision. But by the time you get to a celestial body such as the sun, one part in a million of the sun’s mass comes from its gravitational binding energy with a minus sign. The gravitational binding energy of the sun makes the sun less massive by a part in a million. For the Earth, you’re talking a few parts in ten billion. The Earth is lighter than it would be because of the several parts in ten billion of gravitational binding energy. We’re talking about experiments that must measure masses of celestial bodies, actually mass ratios, to parts in a billion, or even less than that, so that you’re really, truly probing higher order of gravity. I thought, well, you probably can because some of the most precision fits of experimental data that we have come from celestial mechanics. Even in those days, I thought, well, we have a fighting chance. So, I started the calculations at end of ‘66, and by early 1968 had published the work. 

Zierler:

Ken, what were some of the advances in the world of experimentation that were relevant to your research at this point?

Nordtvedt:

Well, bouncing the radar off of the moon was the precursor to the future bouncing of radar off of other planets. So, that was a dream that one had to go beyond the ordinary celestial mechanics. Celestial mechanics relied on measuring angles between bodies as they moved around the sky. From a series of very precise angular measurements, we could eventually reconstruct orbits to fairly high precision, but not that great because there’s a limit to how precisely you can measure angles between bodies, particularly solar system bodies. You could no longer measure to the point of that body. By the time you’re going to a telescope, you’re seeing an extended body. So, if you’re measuring the angle between Mars and Venus, you’re really measuring the angle between the edge of Mars and the edge of Venus. So, that takes some knowledge of the shape and structure of bodies. So, it had its limits. But if we could start to tell the distance between bodies in the solar system to high precision, and radar was the first hint that we might be able to do that, at least there was the idea when we started this calculation that we could maybe do experiments that we never thought of doing before in the precision of celestial mechanics.

Then, just in the months ahead of publishing my papers, I came across a paper of a post doc at Princeton who was working in Robert Dicke’s laboratory. Robert Dicke, who was one of the MIT scientists of World War II on radar, had decided that he could do laser ranging to the moon if he could put a nice reflector on the surface of the moon. So, he had put some of his graduate students and post docs to work to develop a laser reflector. One of the persons involved in this project published an initial Physical Review paper in ‘67—Baierlein is his name—trying to investigate what kind of corrections to the relativistic equation in motion from general relativity might make big enough perturbations on the orbits of the moon that laser ranging to the moon might be able to see them eventually. The only one he came up with that was really interesting was his calculation which showed that, indeed, in the coordinate system he used, the moon’s orbits had to be Lorenz contracted. The moon’s orbit was actually a moving body traveling around the sun, and this preferred coordinate system was really the bary—centric coordinate system for the solar system. If you were sitting in that frame, you’d see the flattened moon’s orbit. His calculations, indeed, substantiated that. It wasn’t terribly big, and it didn’t seem to be that interesting, but what really caught my eye was that this was my first knowledge that they were developing laser ranging.

So, in the Christmas time of ’67, I calculated how, if the Earth’s gravitational to inertial mass ratio differed from one, which is what it should be in Newtonian gravity as well as General Relativity, how would that affect the moon’s orbit, and could we measure that with lunar laser ranging? That was my second publication of interest. I showed that the perturbation would be, indeed, very large, an order of magnitude larger than back of the envelope calculations would suggest, and clearly, within the ability of what they were expecting to measure from lunar laser ranging. That was sort of the breakthrough of finding a new experiment to really probe general relativity. So, I went back to the techniques of Eddington and Schiff and extended it to every single post-Newtonian, or every single relativistic potential that pops out of general relativity. And there are several more than they had talked about. I calculated the ratio of the inertial mass to the gravitational mass ratio in terms of this extended set of parameters, and then I searched for what would be the value of these parameters in Dicke’s theory of gravity. Sure enough, in his theory, the Earth would have a gravitational to inertial mass ratio that differed from one. So, Robert Dicke pops into this story in a second way. Not only did he have an experimental lab developing the laser ranging reflector, he was a theorist with some of his other students and they had proposed some alternative theories to general relativity that involved not only the metric tensor field of Einstein, but also a scaler field. It was called the scaler-tenser theories of gravity.

So, he stimulated the search in the late ‘60s for new tests of general relativity with his special scaler-tenser theory. I was able to find it in the literature, calculate what my work would come out with in his theory that would differ from what general relativity predicted. It gave us the basis of a brand-new experiment if we could find an observable to go along with the theory. I did, with lunar laser ranging, find the observable. It was a certain perturbation of the moon’s orbit that has a period of exactly one synodic month. Every synodic month, the moon goes from full moon to full moon. So, it’s the month driven by the phases of the moon, not the month as determined from returning to the same place with respect to the fixed stars. So, there’s a certain perturbation that shows up in the lunar orbit, and the Dicke theory and the Einstein theory predicted a several meter difference in the size of this perturbation of the lunar orbit. That was the key to saying, “We could see that,” if they ever get a reflector placed on the moon.

In the meantime, Robert Dicke was busy with NASA. He was on the science advisory committee to NASA when they were making some last-minute decisions on what to do and what not to do in the mission with regards to what they would carry along with them for show science. I mean, let’s face it, the primary concern of Apollo 11 was to successfully land the astronauts on the moon, to get them to do their photo op, and to get them home safely. But to show the potential of what this new era meant, they wanted to have some scientific experiments that they could set up while they were there to show that this meant you could do new science. The laser reflector had one unique feature: it was passive. It had no electronics, no batteries, no wires. All the astronauts had to do was to set it on the ground, and it will do its deed by other people on Earth. So, Dicke was able to convince the NASA people that this should be part of the few science packages that you actually bring along on Apollo 11, because it has a higher reliability factor. There’s nothing that can go wrong with it. Fortunately, it was taken on Apollo 11, and to this day, 51 years later, we’re still reflecting laser pulses off of the Apollo 11 reflector. It’s part of the four or five reflectors that are used to conduct this whole experiment.

Zierler:

That’s amazing. Ken, can you think of any other experiments in physics that have that kind of a shelf life? 51 years. 

Nordtvedt:

That’s the amazing thing. The shelf life even amazes the people who built it, because they sort of expected there would eventually be some degradation of the mirrors and the reflecting surfaces, or there would be dust that accumulates. As far as I can tell, the observers that I’ve talked to, they’re within 10-15% of the efficiency of that reflector that it had on day one, after all these years. 

Zierler:

That is literally unbelievable. It’s hard to believe it. 

Nordtvedt:

Yeah. Think of a reflector roughly a foot by a foot in size, a little bigger, and it’s able to pump out this scientific data from observatories on Earth. 

Zierler:

What do you think explains, primarily, the longevity? Is it the durability, or the quality of construction?

Nordtvedt:

Well, they made it sturdy so that no foolish failures could occur. It had no moving parts, and no electronics. It starts out as a robust design, and fortunately, they built it robustly. Also, it says something about the environment of an atmosphere free vacuum in space, sitting there on top of a rock. So, it’s a combination of the two. You can think of all kinds of things they could have done wrong in the construction that would have meant decades of unfiltered sunlight would have deteriorated it, but nothing did. 

Zierler:

How much contact did you have with NASA yourself during these years?

Nordtvedt:

Not too much. I did with the lady who eventually was the administrator of my grants. I think her name was Nancy Roman. She was the one who I talked to periodically about what I was trying to do, whether my grants should be extended for future years, periodically. Because of my work on the theory of what lunar laser ranging could do, I was invited to one of the Apollo launches. This is a story that is actually pretty funny, but it shows you about the real world. I was in the middle between some marriages at the time, but I had a blind date for that weekend in Minneapolis. I gave up the chance to go to this live launch of Apollo to go on my blind date. So, I missed the opportunity. Then, a week or so later, my dad learned about this. He has the same name as I do, and did he give me hell for not giving him my ticket and my letter of invitation! He said he would have gone to Florida to witness the live launch of one of the Apollos that I gave up on. To this day, I regret my choice, in that case. I never saw a live Apollo launch. I’ve seen a live launch of the space shuttle because of my later work on NASA programs. To this day, I think my dad had a better sense of values than I did because blind dates are blind dates. This one didn’t turn out to be that important. 

Zierler:

Ken, I want to switch gears a little bit and ask you about how well your planning was in terms of going to a more conservative place like Bozeman as we’re getting into the late 1960s and early 1970s. As you knew at the time, of course, as you saw campuses erupting in places like Columbia and Berkeley, had those movements reached a place like Bozeman, or was it relatively quiet there during those years?

Nordtvedt:

It was instantly relatively quiet, as I had hoped. It was just a matter of time before trends in our big urban areas did seep out and affect the whole nation. So, I remember, by the early 1980s, the atmosphere at my campus in Bozeman had gotten sufficiently polarized that some people from the humanities department on campus wanted to hold a so-called discussion symposium on President Reagan’s Strategic Defense Initiative. It turned out that they invited only opponents. I got teed off and—

Zierler:

When you say, “they invited opponents only,” who’s they?

Nordtvedt:

The organizer, who was a faculty member, who then went to the dean and got their okay. That’s how something like this developed. At first, I talked to him and said, “You can’t hold a symposium and not at least put one person on this panel who presents the other point of view.” They refused, so I fought it in a local newspaper as a complaint about the faculty bias! It eventually had an impact a year or two later. I think it’s what got President Reagan to put me on the National Science Board for a three-year appointment in 1986. I had put an editorial in the paper presenting the other side of the story on why I thought the Strategic Defense Initiative was a good move. By 1986, there were some openings on the National Science Board, and apparently there was a story that certain senators wanted to put some people on this board to get the National Science Board to officially issue a statement in opposition to the Strategic Defense Initiative. The Reagan administration wanted to make sure that the board would not get involved in such political matters. In some roundabout way through various people in the administration, my name came up. I think, that’s why I got appointed to the board. Senator Ted Kennedy’s staff did contact me by telephone when my nomination was announced, and for some strange reason, he interrogated me over the phone, not about my wisdom or views about science policy in general, which is what the science board was supposed to be concerned about, but he wanted to know what my position was on Strategic Defense Initiative. So, I think this rumor was probably correct, that there was a move to try to stack the National Science Board to embarrass the President. But later it never came up. People counted votes, and they eventually decided that the board would not do that, so the issue never came up in the three years I was on the board. 

Zierler:

When you talk about your support for SDI, do you see that primarily as a function of your political inclinations, your scientific inclinations? How do you parse that out?

Nordtvedt:

That’s a valid question. I appreciated the doubts that people raised about its quick feasibility. Indeed, that came to pass, but I thought there were sufficient doubts, and the level of vitriol that was coming out of the Soviet Union over the SDI initiative, that it would be sufficiently worrisome within the political realm in the Soviet Union that it would enhance our position with them vis a vis various military treaties, and settlements on weapon testing, and all the issues that were coming up in the Cold War, short of actual war. Therefore, from the point of view of the balance of power between us and Soviet Union, it was a good move by our president to do so. So, that was essentially the thrust of my editorial. It wasn’t yet a proven thing, but it certainly has the potential, and it should be pursued at the research level. That was a far step from deployment. So, today what do we have? We have a world in which we still probably can’t stop ICBMs with very high efficiencies, but we certainly have a very effective ability to stop short range ballistic missiles. Israel uses them extensively. Other nations use them. So, I think it was the right move at the right time by President Reagan. 

Zierler:

What would it have taken from a physics perspective to see SDI fully realized?

Nordtvedt:

Well, I think the progress on super computation—all the things we’ve seen happen since in computer power, coupled with the power in super lasers with intense power, I think those were then the two questions. I think there’s still the two governing factors that tell you how far the military can intercept things like ballistic missiles. I think, then, that the average person probably, even within the field, would have underestimated the progress we’ve had in computation power and laser power since then. So, the people who were trying to make judgments then had to probably do so on a basis of a slower technological advance than we have seen. 

Zierler:

When President Reagan appointed you to the National Science Board, what special opportunities did you think that this presented you, both in terms of your expertise in physics and in your political interests? 

Nordtvedt:

Well, by then I had already retired from Montana politics, and I had no real political ambitions. 

Zierler:

Just for the record, we should state you were— 

Nordtvedt:

I had political interests. I had political values that I wanted to see sustained in the world, certainly. They were never diminished. I saw my role there as being one to try to present a voice for pure science as funded by NSF. Now, the science board is the regulatory board for NSF. So, we ultimately okay their budgets. They set them up. They create them, and then those budgets went to the National Science Board. NSB approved them, and then they would go to the president’s administration. So, I didn’t want more and more fields which I consider to be pseudoscience, or politicized science getting greater strength within the NSF bureaucracy. That was a very general goal I had without specifics. I wanted NFS’s main vision to be the pursuit of knowledge in the pure science sense of the term. Or a better word than pure, the traditional science sense of the term. If political issues did come up, I would probably have been a loyal supporter of the administration’s point of view because I generally saw eye-to-eye with them. In fact, no political issue ever came before the board in the three years that I served. It may have behind the scenes. A lot of things that happened between the NSF and the board took place behind the scenes between the director of NSF and a few very influential, long-term members of the board, people who had made being on the board their semi-career and had been on there through at least two or three cycles of 6-year reappointments.

I think the real power lie there, but every so often, a maverick out of the blue proposal could come before the board, and then you never know what that would be. In fact, I, in my final month on the board, did raise such a disturbance, or a difference of opinion on the board. I nominated Edward Teller for the annual medal that the National Science Foundation gave to civilian science. Of course, he is persona non grata to a very big segment of the intellectual community of the nation, not only for his stance on the Cold War, but more particularly on his involvement on the whole Oppenheimer hearings in that era of the early ‘50s when Congress was heavily involved in whether there were too many Commies in key departments of government, etc. Oppenheimer was a real hero in the physics/science community. When Teller made testimony that didn’t sound supportive of Teller, he took a real hit in the physics community for that. So, my nomination, was very badly received, so they appointed in his place, Linus Pauling, and they had the votes to give the award to him. Linus Pauling, of course, was equally politically involved on the other side of the fence throughout that whole era.

Zierler:

On the way other side of the fence. 

Nordtvedt:

Yes, of course. So, they were just saying, “Well, you’re going to bring something in from the blue. We’ll show you.” And they did. 

Zierler:

Ken, I’m curious if your tenure in the Montana State Legislature, in what ways did that inform your political acumen, and how might you have put that to good use during your service in Washington?

Nordtvedt:

I came in with a well thought out mission and legislation I wanted to get enacted. I was previously involved as just the average citizen person. It’s not like I was totally non-political. But if you recall the late ‘70s, it was a period of super double-digit inflation in the United States. Interest rates on corporate bonds were reaching the high teens. Home mortgages were reaching 12%. You were getting comparable 12% on government bonds. I thought of inflation as destructive to good government, in the sense that today’s trillion-dollar stimuli packages—today’s finances in government are so different than the atmosphere then. It’s like day and night. Then, even both Parties paid homage to fiscal responsibility, balanced budgets, minimal deficits.

Anyway, I was particularly irritated with the income tax system in Montana which had tax brackets which weren’t keeping up with inflation. They weren’t changing with inflation, and therefore they would constantly drive people into paying more and more real taxes just because of inflation. So, I invented an inflation indexing bill. Basically, that was the center piece of my campaign. I won in a university district that normally voted for the other party and shocked everybody by winning. It had no merits on my part. I was not that great a campaigner except I had a clear vision of what I wanted to accomplish. I got in; I got my bill passed as a freshman. The governor from the other party vetoed it at the last minute, and I worked with a person running for the U.S. Senate to get it passed by the citizens directly by initiative, and we won by 70%. It was an overwhelming success and it opened up some doors for me in the three terms I served in tax policy as a legislator. What I learned about it is that to be effective in politics, you also have to get elected. You have to run campaigns and you have to build up big networks. I still wanted to primarily do physics, so I couldn’t really devote sufficient energy to both if I wanted to carry forth in both areas. So, after three terms I did not run for reelection and went back to physics.

Zierler:

I wanted to ask you, Ken, when did you get involved in gravitomagnetism? 

Nordtvedt:

I knew about it ever since my time at Stanford, because that was the theoretical heart of the gyroscope experiment that Fairbanks and then Frances Everett at Stanford, who later became the head of the project—they wanted to measure some effects on gyroscopes during free fall motion in gravity that are transmitted by the gravitomagnetic part of Einstein’s theory of gravity. So, that’s where the term comes from. The gravitomagnetic word got invented because just like there’s a piece of the electromagnetic field that’s responsible for magnetism, there’s a piece of the tensor gravitational field of metric gravity that’s responsible for some forces or interactions that give rise to precessing gyroscopes in free space, just under the influence of gravity. I came to know Frances before I left Stanford, and I would periodically be in touch with Stanford. I’d known that mission from a distance ever since the early 1960s. I followed it. The level of precision that they wanted to measure got superseded by other experiments. It was such a long mission from the ‘60s until it finally—through about 2005, was it? I forgot the year now, but sometime this millennium. The other experiments in gravity, including lunar laser ranging and light deflection experiments, or light propagation experiments, radar ranging between Earth and other planets, those experiments had become so precise in testing general relativity that I didn’t believe by the time of our millennia that there was anything new to be learned about the laws of physics from the Gravity Probe B project. They wanted to put a gyroscope into orbit.

In the meantime, it had been having so many delays, cost overruns, requests for more funds, that I just stated now and then—I didn’t make an obsession about it—but my opinion that the experiment was no longer worth the money that we were sinking into it. It didn’t teach us much new. And then finally I wrote a paper pointing out that if we took the gravitomagnetic potentials out of the computer program that calculates the motion of the Earth and the moon around the sun, we would no way be able to fit the lunar laser ranging data. But the gravitomagnetic potentials are crucial in fitting the lunar laser ranging data to the precision that we fit them. Therefore, in some sense, we’re remeasuring the same thing. So, that was the thrust of the paper that I wrote most recently on the subject. That was still when the mission was—I can’t remember the dates anymore. Oh, I know. There was another delay after the gyroscope mission took place. There was an enormous delay in them analyzing the data and then publishing their results. I think there was about a five-year delay. To me, it’s not that big an issue, but on the other hand, I don’t think I was wrong in my assessment of what it taught us about the gravitational interaction.

Zierler:

Ken, would you tell me a little bit about your decision making surrounding the time when you retired, relatively early in your career, to pursue full-time work as an independent scholar? What were the factors leading to that decision?

Nordtvedt:

Part of it was the atmosphere which I saw developing on my campus here in Bozeman that was more and more, as each year went by, seemed more reflective of the national environment in academia. It was a culture which I was less at home in. Probably most important, I’d have to say, was by then I was hoping I could get a career that was more and more dominated by research and having less teaching responsibilities. I could never work that out with my department head, so I early decided to retire. I thought I had enough contacts with both NASA and NSF that if I had some good research to do, I could submit proposals to either of those agencies as a proven research scientists, and get them to consider my proposals along with all the others, and get funded in an honest system. And that’s exactly what I experienced in the years after 1987 when I retired. I became sort of a contract physicist going directly to these agencies. 

Zierler:

Did you ever consider pursuing employment full-time with NASA?

Nordtvedt:

You know, there’s an informal level before any agency at NASA sends you a letter in print, but someone that you know there, or you know via one other person, they’ll contact you at a meeting or by phone saying, “We have certain scientific administrative jobs that need funding in the near future. Would you be interested in applying for one of these?” I think once NASA approached me concerning the—it’s been a long time. I think it was the gravity program at one point. It was fundamental physics within the gravity program. It was a big, important, but sub part of the gravity program at NASA. I was informally asked if I would consider applying for such a position. I thought about it, but I think this was by the 1990s when this informal offer had come forth. By then, I had had nine months experience in political government administration, and that may have had an effect. I had served as the State Director of Revenue for a new governor in our state of my party. My party hadn’t had a governor for a long time. Twenty years or so. So, I agreed to be Director of Revenue to get his administration off the ground. After nine months, I found that I’m not an administrator. I got so wrapped up in working on his behalf, promoting his tax policies that I never really got into doing all the things I could have done administratively to try to move the Department of Revenue into a better direction. So, I decided I was not a good administrator by the end of nine months and left his administration, after we got though the legislative session. Montana has one relatively short session every two years. Much less than a government in, say, California or New York! 

Zierler:

I’m curious, in what ways were you able to do physics research more efficiently being untethered as a contract physicist?

Nordtvedt:

I felt very free. I think that I realized the bounds of where I could make a contribution. I never went beyond those bounds in the kind of grants I submitted for funding. When I realized in probably 2010 or so that I was running out of what I thought were contributions I could make to what I saw going on in NASA, I just stopped making grant proposals. That was a little premature because I think I had a renaissance with brand new research program about five years later that I thought was very important. Nevertheless, I had plenty to do after 2012. I think 2012 was my last year of having grant support for my research, and I believe it was NASA rather than NSF. That’s when a grant ran out, and I didn’t bother to ask for a renewal. But if that had happened five years later, I probably would have asked NSF for a renewal grant for the kind of question I got into starting about 2015. 

Zierler:

Now, what was your work related to Northwest Analysis?

Nordtvedt:

That was the business name I used starting in 1988 after I retired from Montana State University. I used that fully for all my publications and grant proposals through my last one which probably occurred about 2010, or 2008, or something like that. That was my business name as an individual. 

Zierler:

What do you see as some of your most significant research accomplishments during that time?

Nordtvedt:

It’s hard to say. I went to a lot of committee hearings and gave my two cents on proposals. I never knew how they got folded in or not on final decisions. I made proposals for a few interplanetary ranging missions, for instance, the extension of laser ranging to between planets, which could be done to much higher precision than the radar ranging that has been done between planets. So, by this time, the problem was that NASA’s funding faded for that kind of work. Fundamental physics never really got going after the Gravity Probe B. It never had any more big missions. They had a few good missions, like they had a ranging mission that pushed one of the limits on the propagation of light that was done by NASA that involved close passage of Mars, and some of the other planets, and went out far. In the meantime, we were able to measure time delay of light propagation through the solar system due to the gravitational potentials. That was a good NASA experiment, but it needed no more theoretical support. It was a well-proven concept that just happened to have synergy with this NASA mission of sending a science package to the outer solar system. I don’t think decades down into the future my work during that period was going to have any big impact on the world. I did the best supporting that I saw, what were the best possibilities at the time. I did a lot of publishing which I thought was writing review type papers for how lunar laser ranging pushed our knowledge of general relativity further by the ‘90s and into our millennia. More and more big review type books and things came forth that wanted chapters written explaining that physics. A lot of my work involved doing that. But work I’ve done since then has much promise, I believe.

Zierler:

Ken, what’s your sense of the state of general relativity research today? What are some of the big unanswered questions, and what might it take in the future to achieve those answers?

Nordtvedt:

Well, to me, it’s going to probably involve the very early universe. If we can start to get signals of any kind, electromagnetic or gravitational wave signals, from earlier and earlier in time, we may be able to start to see some very odd phases of universe growth by the laws of general relativity, or phases of growth that just can’t be explained by general relativity without something else in the very early, compact stage of the universe. That’s one thing that can be done. In gravity waves, when we can start to see gravity waves routinely in an abundance, coming from the extremely early universe, where they don’t necessarily have to come from well-established objects, like little black holes, or neutron stars, or other such bodies colliding with each other. But where big hunks of the early universe were undergoing dynamics and creating gravitational radiation from the Big Bang. Again, it’ll be gravitational wave labs that will be in the frontier of that. Whether NASA does that or NSF does that will always be a tug of war. If those kinds of experiments can be done best in space, where you could eliminate the ground vibrations, just think of the present gravitational wave detectors we have on Earth. A big part of the budget of those labs are taken to isolate them from all the stuff going on in the Earth, the little vibrations and noise. It’s a noise suppression issue. It may be that the future labs even of gravitational wave physics will occur in space. And that, of course, will be back to NASA, probably. 

Zierler:

Well, Ken, I think for my last question, I want to continue on that vein. I know you’ve been retired, mostly, since 2012, but from your vantage point, keeping track of what’s been going on, what are some of the most exciting developments in the experimentation area where you see the most possibility in the future, either in the near term, or the long term, in really making fundamental discoveries in the field?

Nordtvedt:

Fields of gravity?

Zierler:

Yes.

Nordtvedt:

Gravity specific? I think this is theoretically tainted, but the question of making the laws of gravity compatible with quantum mechanics, I think, is the biggest fundamental theory question we have right now. Gravity physics is the only domain of physics that does not come out of quantum mechanics. So, the unity of gravity into the world of quantum theory sits there as the ultimate plum of unification. 

Zierler:

How do we know that ultimately, they should fit together? After all of these years, why can’t we be satisfied that they belong separate because they are separate?

Nordtvedt:

That’s a good question. I think I would counter just with, “don’t be impatient.” It is sort of arrogant of these theorists to think if my generation hasn’t found something, what’s going wrong here? Look at how long the humans lived with Newtonian gravity. Several centuries. Quantum mechanics is so compellingly right about everything else other than the gravitational interaction. As someone who wants to go back to the root of things, which we started this interview with, I’m convinced that the money has to be bet on gravity being successfully wedded to quantum mechanics as well. If I had the energy of a 19-year old again, I would probably be picking that as my subject when I went off to graduate school—how to unify quantum mechanics and gravity. The other question, which could be related, I’m not sure—I don’t see the relationship right now—is within quantum mechanics, there is this unanswered question about the multiverse, or the parallel universes. Quantum mechanics, if you take it totally seriously, in my mind, implies that the quantum mechanical wave function of the universe is constantly breaking up into parallel branches every time there’s an interaction. These parallel branches must all be existing. There’s no way that you can just turn them off. This idea was founded when I was a graduate student by some student of John Wheeler. Everett, a student of John Wheeler at Princeton. It’s still an open question, but there’s a part of my mind that says the argument is compelling. That’s what the wave function of the universe is doing, and we just got to learn whether there are empirical consequences for the particular branch that we happen to be talking in, or working in, or living in. So, to me, those are the big questions that remain in physics that have remained for as long as I’ve been around. I think they’re very interesting. 

Zierler:

Are you more bullish on a theoretical breakthrough, or an experimental breakthrough to get over the transom?

Nordtvedt:

I think both those breakthroughs are sort of like playing the stock market. It’s a very speculative, gambling thing to make a bet about. They require major new things happening in either domain. Once I say that, I’d have to give the edge to experiment. Experimental science moves at its rate. It’s sort of like a turtle. It always moves along. There are fast turtles and slow turtles, but it’s a moving turtle. It step by step moves along, always coming up with new instrumentation that can make measurements more and more precise. As long as the experimentalists are willing to take advantage of all those new breakthroughs, then they’re bound to come up with new phenomenon by sheer accident that can’t be explained with in present theoretical understanding of the universe. On the other hand, there’s no such turtle in theory. There are those who are moving along and getting more and more out of existing theory, but we need major breakthroughs in theory, and they just happen by sheer inspiration or accident coming from who knows what? Who knows whom, where, or what? And I don’t think they’re as predictive as the inevitable march of technology and the things it can do, which means the latter always measures something that was never seen before. 

Zierler:

What might be some branches of theory where you would be most bullish on a breakthrough in the nearer, longer term future? For example, are you someone who holds out hope that there’s a big breakthrough to be had on string theory or supersymmetry?

Nordtvedt:

I was more interested in supersymmetry, which was called different things through the decades of my adulthood. The idea of finding symmetries in nature and exploiting them to their fullest. String theory always seemed to me to be too cute to be compelling. I could see investing months or even a couple years into pushing something to the limit, but I couldn’t see people putting a whole career into theoretical string theory without experimental connections. It always seemed too divorced from the rest of science to me. But I worked on some of the early symmetries that were being talked about even before Gell-Mann came up with the whole SU 3, and the quarks, and all that. In fact, as a graduate student at Stanford, I went with a carload of faculty and students to hear Gell-Mann’s seminar when he first gave it at Berkeley on quarks. He named them quarks. It was before he had the courage to say they probably represented the fundamental building blocks of hadrons. To him, they were still mathematical toys that were working too well to be ignored. They meant something. It was an interesting era—the whole idea of symmetries between the different elementary particles. I went to Schiff once and I asked for some money to do some work on the then best computer that Stanford had. I wanted to program a little model which unified some forces, so I was going to build some composite nuclear systems. I forgot, even, what they were. He thought the idea was so far out that I could sort of see his eyes curling up, but I only asked for a few hundred dollars then for work on this computer, so he gave it to me. Several years later, one of the faculty at Stanford that I had worked with, Sheldon Glashow, and others, in unifying the weak interaction with electromagnetism, actually showed that a similar symmetry that I was trying to work on then was, in fact, a true and productive one. 

Zierler:

Well, Ken, it’s been an absolute pleasure spending this time with you. I really want to thank you, and I specifically want to note, talking to someone with your political inclinations is a rarity in this field, as you can well appreciate, so I’m very happy to, as a matter of equal representation, or at least proportionate representation, I’m so happy to hear your views and that they’ll be a part of the historical record. I take your point quite seriously when you said earlier that at a minimum, there should be at least one other representative at the table, so that that representative has the opportunity to share the opinion or perspective that otherwise would be silenced. So, for that alone, it’s been tremendously valuable, even beyond all your contributions and insights in physics, to be able to have this talk. 

Nordtvedt:

Thank you for that. Science has been that community of our western culture that was, to me, the origins of this whole notion that societies like ours thrive when a wide variety of viewpoints get to be heard, and that there’s a free flow of ideas. I always valued that in the world of science, and whenever I see it diminished, it’s bothersome because I view this world of science as close to home. It was my home during these years and decades, and I hope the scientific spirit prevails into the future.

Zierler:

Well, Ken, that’s an extraordinarily important perspective, and I take it to heart. So, again, thank you very much. 

Nordtvedt:

You’re welcome.