Alan Cummings, Astrophysicist, Cosmic Ray Researcher, and Voyager Mission Scientist

After the recent celebrations marking his fiftieth anniversary at Caltech, Alan Cummings enjoys clarifying that he has actually been here for fifty six years. He joined the Space Radiation Laboratory to work with Robbie Vogt in 1967, and as he quips, if not for a building change years ago, he would likely still be working in the same office!

As one of the preeminent researchers in the field of cosmic rays, Cummings has intellectual academic roots that go back to the founding of Caltech. George Ellery Hale's prevailing interest at the turn of the 19th century was in the structure and prevalence of cosmic rays. With the launch of Sputnik and the realization that space exploration yielded profound opportunities to turn space into a physics laboratory, Cummings came of age at a time of new possibilities in cosmic ray research. In the discussions below, Cummings narrates the origins of the Voyager Mission, and he provides important historical detail on the wise contingency planning that made possible the travel of the twin space spacecraft into interstellar space - the great beyond - after visiting our Solar System's outer planets.

When the spacecraft crossed into interstellar space, they helped answer foundational questions about the heliopause - the boundary whereby cosmic rays emanate not from our Sun but from galactic sources. And as Cummings explains, the richness of the data that continues to come in from Voyager suggests strongly the value of a successor mission that will probe even deeper into interstellar space. Looking to 2027 and the fiftieth anniversary from Voyager's launch date, Cummings delights in thinking about his personal longevity and that of the Voyager spacecraft, and he looks forward to this milestone as a once-in-a-generation opportunity to stimulate our collective wonderment for outer space.

DAVID ZIERLER: This is David Zierler, Director of the Caltech Heritage Project. It is Monday, June 26th, 2023. I am delighted to be here with Dr. Alan Cummings. Alan, it is great to be with you. Thank you so much for joining me.

ALAN CUMMINGS: Thank you for having me.

ZIERLER: To start, would you please tell me your title and affiliation here at Caltech?

CUMMINGS: I refer to myself as a Senior Research Scientist and member of the professional staff at Caltech.

Fifty Six Years at Caltech

ZIERLER: Of course the reason we got together in the first place—you're now celebrating 50 years at Caltech. I wonder if you could reflect on that milestone, and what has been so interesting to you after all these decades.

CUMMINGS: Well, time flies! [laughs] It doesn't seem that long, but yeah, I've actually been here 56 years, and actually in the same group the whole time. I got here as a graduate student in 1967 and got my PhD in 1973. Then I immediately was hired into the same group that I just graduated from. If we hadn't changed buildings, I'd probably be in the same office all those years, too! [laughs] Changed buildings two or three times. It has just been amazing.

ZIERLER: After these decades, what are the things that you've worked on year after year, and what have been some of the real points of departure in your research, new endeavors?

CUMMINGS: My graduate thesis work was based on a balloon-borne experiment. Every summer our group took more than one experiment up to Fort Churchill, Canada, and we flew those to the top of the atmosphere with our payload hung under the big balloons, and we recorded data for about 24 hours, typically, and we did that four or five times during the summer. They would be recovered by parachute. We had colleagues going up that did different kinds of experiments. I did one that was really based on Carl Anderson's Nobel Prize work, which was a positron and electron experiment. It had a big magnet in it, it had spark chambers above and below, so you could track the particle, more or less like he did, except he didn't have spark chambers. That's what I did for several years. Several summers, I was involved in that. Then in 1973, just after I graduated, I was the sole person in charge of our experiment that went up there. It failed to come down when the command was sent to bring it down, and the backup timer on it failed as well, so it kept going around the world, one and a half times I'd say, because it landed—the Russians got it, and—I don't know if you want to hear all that story now, or—

ZIERLER: Yeah, we're in it. Tell me!

CUMMINGS: The details of that are kind of interesting. The balloon failed to come home, and so then we eventually packed up the rest of the stuff and went back to Caltech. Then we were being notified periodically—apparently airline pilots would see the balloon floating along and report its whereabouts. Then eventually the balloon ceased being noticed, and then the State Department called. The State Department had heard from the Russians, and they said they had it, and you could come and point out whatever you wanted to have shipped back, and they would do that. I wasn't really supposed to go. I was just fairly new, in a sense. My thesis advisor, Robbie Vogt, was going to go, but he got sick. So at the last minute, I was—I'm going. I didn't have the paperwork or anything, but the State Department was working really hard on our behalf, and a State Department official met me at LAX, gave me my visa and all my stuff I needed, told me all the instructions I needed to know, and off I went. When I got there, my instructions were to go to the tourist desk and I'm supposed to get a taxi to the Hotel Rossiya. I did that, and quite a taxi ride, I have to say [laughs]. Hotel Rossiya no longer exists, actually, but it was the largest hotel in the world at the time. It had like 5,000 rooms in it, so it was like a city unto itself.

I made one slight mistake. I checked in before I changed any money so that I could have cash to eat and everything. When you check in, you have to surrender your passport. So they had my passport in one section of the lobby, and the people dispensing the rubles were in a different part, and they wouldn't give it to me unless I had my passport. So, I'm going back and forth, back and forth, like this. A lot of times, I'm in lines in both places, and eventually I'm in line to get the money, again, without the passport, and I was just kind of really pleading my case. I was just going to break down and cry. I was hungry. I was tired. About that time, a guy walks up to me in a suit and spoke perfect English and he asked me if I was Alan Cummings. He opened up his suit jacket there, and there was my picture. He said, "I was supposed to meet you at the airport but I missed you." Apparently, he was a Russian that was going to go work on the Apollo-Soyuz project, and he was leaving to go to Houston in a few months or something, but he was assigned to help me out. He said, "Are you having any trouble?" Of course I said, "Yes, I'm having trouble." He immediately went over, got my passport, we got the money, he took off. We made arrangements for the next day. Everything was fine.

Except then, getting [laughs]—getting anything to eat was not easy. There was a staircase that—by that time, I knew where the restaurant was, and it was down the staircase, but there was a guard there, with a gate. I went up to him and indicated I wanted to eat, and he just said, "Nyet. Nyet." So, back and forth. I hung around, and I tried it a couple times. But I overheard what they were saying was "bar " and then the gate would open. So I went down there, I went over to him. He knew exactly who I was and what I wanted. But I had to say the magic word, so I did—"bar "—and then the gate opened, and I went. There was quite a scene down there, because nobody was helping you there either, but I grabbed a bellboy and eventually they took me over to a table that had 12 seats at it, and it wasn't full, and I filled it up. When I filled it up, they all jumped up and applauded. Because apparently, at the time, in Russia, in 1973—[laughs] I don't know if it's still that way—they don't serve you until the table is full. So I was a hero.

ZIERLER: [laughs]

CUMMINGS: Then I go over the next day to the embassy. Somebody picked me up. From the embassy, we went over to this fairly new building. I think it was new construction. There was a big lobby, and there were elevators and everything. Right by the elevators was everything—all my pieces and parts, and the balloon plastic. It was the world's largest balloon at the time, a 50 million cubic foot balloon. [laughs] They brought it all. They had a lady there, and I was supposed to just point out what I thought could be salvaged. Pretty soon I realized this thing was a pile of junk at this point. The magnet that I talked about was pretty heavy, and it was in the middle, but the experiment obviously had not come down with the benefit of the parachute, so it smashed to the ground. The magnet fell through the spark chambers and electronics and everything. I looked it over, and I noticed that there were things missing on the electronics board. They had taken off the microdot connectors, which were made right here in Pasadena, or South Pasadena actually, at the time. So, they got those, and there were things—so I started asking, "How did this thing come down?" They said, "Don't ask." Can't ask that.

Then I was looking around—we had these two barograph boxes that inside was a camera which we made down in our lab in Caltech, that took a picture of a barograph every five minutes, and that showed us what altitude we were at. That was important for our data analysis, to know what altitude we were at. I looked in there, and the cameras were missing. I said, "Where are the cameras?" He said, "Oh, a kid off the street stole those cameras, but we had already developed the film for you, so here's the film," and they handed me these two little rolls of film. I didn't look at them then, but I went back to the embassy and put them on a microfilm reader and starting writing it down, all the altitudes for every five minutes, until I got right to the inside of the film, they had spliced on a secret-looking tape, I mean a tape that I shouldn't have, film that I shouldn't have. It looked like a bunch of people in spacesuits, walking out through a winter wood, with guns, machine guns. [laughs] I notified the Embassy staff there, the person there that was helping me, he said, "Oh, well, then, you were going to be it. If they needed a hostage or something to swap; they grab you with that on you, you're in jail." I said, "[laughs] Okay."

But they said they could send the films back by diplomatic pouch. Which, they did, and they got to Caltech, they got to my lab, after I got back. I showed them around the lab to people. Six months later, the films went missing [laughs] never to be seen again. We did have a Russian postdoc—very unusual in the Cold War, but he was in our group at the time. I've accused him—he became a scientist in the same field I'm in, so I would meet him occasionally at conferences many years later. He denied stealing them—back [laughs]. Anyway, there were quite a few interesting stories there, but they're not really relevant for this, probably. I got back, and we assessed that the damage was too great. I mean, they did ship it back. We looked it over— Robbie Vogt, my advisor—and we just said, "Well, we're not going to rebuild this. That's going to be too much money." And, "By the way, we've got a new project that just started. You can work on that. It's called MJS '77." That was the early name for Voyager. So in November—by the way, I was just in the middle of trying to get married at this time as well. [laughs] I met my wife in March of '73 on her birthday, and we had our first date on my birthday, six days later. Then I went off to Fort Churchill a couple months—in like June. So we hardly had had any dates, but before I left, I had an engagement ring and we were engaged. Then after Churchill ended, that fiasco, I flew to East Texas and she flew to Texas and we met my parents [laughs], and we came back here, and then I went to Russia, and then we got married in October, like six months—three months of which I was out of pocket. I started working in November when we got back from our honeymoon on this project, Voyager, which was just the best thing ever. As I said, and keep saying it, losing that balloon was not that bad of a deal. [laughs] It was a good deal. I might have eventually worked on Voyager anyway, but we were planning another summer campaign at the time, the next year, every year.

ZIERLER: What kind of scientist would you call yourself? What is the umbrella discipline that you are most involved in?

CUMMINGS: That is a good question. I finally settled on astrophysics. We do work in cosmic rays. Cosmic rays is a subject of astrophysics, really, so I'd say astrophysics.

Advances in Cosmic Ray Research

ZIERLER: Because cosmic ray research is such a mature discipline—it really goes back to the origins of Caltech—what are some of the new advances in the field? What is known that wasn't known 75 or 100 years ago, and what are some of the frontiers of knowledge in cosmic ray physics?

CUMMINGS: There are several different aspects to cosmic rays. One of the things was, where are cosmic rays coming from? Where are they accelerated? They're very high-energy particles, near the speed of light, but they didn't start that way. Something accelerated them. That's changing recently as well, but for quite some time now, we were thinking that supernova shocks, shockwaves from stars exploding, go out and accelerate ambient nuclei to high energies and they become cosmic rays. But actually a lot of my studies until we got to the interstellar space part was involved in something called anomalous cosmic rays, which are particles that—they figured out pretty soon, in 1974—they were first detected at 1 AU by other experiments not Voyager, but it became a big subject of Voyager once we got launched in 1977, because they had just been sort of identified as being accelerated pickup ions. From the interstellar medium, this neutral gas in the interstellar medium floats in or blows in to our heliosphere. They're not affected by the magnetic field. The ionized component of this low-energy population of particles get deflected around the heliosphere—they don't get in, because of the magnetic field—but these are neutral, so they are not affected by the magnetic field. They drift in, and something ionizes them. Either solar wind, charge exchange with the solar wind, or with photons from the Sun, by what is called photo-ionization. So suddenly you have an ionized particle sitting there, and then you've got the magnetic field of the Sun blowing out or expanding out, and that carries them out. So they start making helical spirals around this magnetic field that's moving out and they get accelerated somewhere.

We thought we knew that for many years, where it was, and what the process was. Then the two Voyagers reached the termination shock of the solar wind, where we thought that shock wave was doing accelerating—it may be, but the signature was not there at the time we crossed or where we crossed the termination shock. The anomalous cosmic ray energy spectrum which should have changed didn't change. It didn't change there. It changed eventually as you get further and further out. So now, it's still a mystery. We're still working on solving where and how these particles get accelerated. There are quite a few different theories. I'm still working on that data that we collected before the interstellar medium. What's really new, of course, never known before, was what the energy distribution of these galactic cosmic rays is at low energies in the interstellar medium. Nobody had been to the interstellar medium so we didn't know what that was. There was a good reason we didn't know—because of something called solar modulation, where the Sun's magnetic field is carrying particles outward, so what's out there has to fight its way in to get to where we're observing. They have a hard time doing this because of various processes, but one of them is the convection out due to the magnetic field. The low energy part, the energy spectrum could almost be anything out there, and it would look the same inside, where we were, so we couldn't really deduce what it was. That was the big moment when Voyager crossed into interstellar space and measured that energy spectrum at low energies for the first time.

ZIERLER: Given that Voyager is now in interstellar space and it's still discovering important things, do you see need for a follow-on mission, a Voyager 3, or 2.0, or whatever we would call it? Is there more to understand about the great beyond?

CUMMINGS: Yes, there is. There is a mission that has been proposed for many, many years—20, 30 years probably—called Interstellar Probe, and there are active groups working on the design and the development of that. They want to have something that goes at least ten times faster than Voyager, so they've got to come up with new propellant methods, and—but yes, there's parts of the energy spectrum that we are missing with the Voyager instruments. And you want to get further. Voyager is going to last a few more years, but we're winding down, for sure. There is a lot of support for Interstellar Probe, but when it happens, I couldn't tell you. [laughs] It has been an uphill fight. Especially since Voyager has been around. I think when Voyager is no longer around, maybe that will come to fruition.

ZIERLER: As a snapshot in time, what are you currently working on?

CUMMINGS: I'm working on several Voyager projects. One is, we published an article in 2016 that got a lot of interest. It was the galactic cosmic ray spectrum of all the elements, in interstellar space. Now I'm working on one that tells what the isotopes of the elements are, the energy spectrum of the isotopes. That's coming next. I'm working, as I said, just this morning right before you got on, on what's going on between the termination shock and the heliopause, with the Voyager 1 and Voyager 2 intensities, and how they behave.

The Two Spacecraft that Could

ZIERLER: How long do you think the Voyager spacecraft will be able to continue on? Can we game out their power supply to any degree of specificity?

CUMMINGS: Yes, there is that, and they have taken steps at JPL to extend the mission, extend the power, by doing certain things. We've already turned off our heaters to the instruments and gotten really cold, and we didn't know if they were even going to work or not. Mostly they work, still. We have a lot of redundancy, especially in our instrument, the CRS, so we can overcome—we've got lots of different telescopes. If one goes, there's others that we can use. So we're in pretty good shape, really, with that. We need to save about four watts per year, and that's roughly what an instrument takes, the bigger instruments. So at some point pretty soon, we're going to have to start shutting off instruments, and not just heaters. They're sort of gaming that out to maybe as far as 2028, in our case. I think the last instrument can go past about 2030 and get some information.

ZIERLER: So it will cross the 50-year mark, from launch in 1977.

CUMMINGS: That is the hope. There is going to be a big celebration at the 50-year mark, I think, and they're gearing up to do that.

ZIERLER: Tell me about the Space Radiation Laboratory. Are you one of the founding members of the Lab?

CUMMINGS: No, I was a graduate student that got into the Lab. My thesis advisor was the founder, Robbie Vogt. He came from Chicago, the University of Chicago, in 1962 or something, or 1963? I got there in 1967. Ed Stone was sort of the cofounder. He came from Chicago I think in 1964. So they had been there just a few years. I'm not sure if the Space Radiation Laboratory had its official name by the time I got there or not. But it was a group, of those two professors and maybe a few—well, not much else. There was engineers. We had these experiments that were being constructed right there in the lab and taken to Canada. That was mostly what we were doing. We were getting into the space business also. We had instruments on IMP. Ed brought data analysis from Discovery, I think, that he got at Chicago. So we were definitely shifting our gears towards trying to get—way above the atmosphere [laughs]. "How about in space?" And we did that. There have been many missions. Robbie and Ed were excellent at winning proposals. That's one of the amazing things about my career is that I've been able to be there—because this is all soft money. It's money you get by winning proposals. We just had one mission after another that just kind of kept everything going, all the engineers going and everything. It has been amazing.

ZIERLER: That's a 50-year career on soft money, you're saying. That's incredible.

CUMMINGS: Yes, that's right! [laughs] It's hard to believe. But the backbone of it all has been Voyager. Voyager has been there for the 50 years, and there has always been money coming in from Voyager, so that has really helped, tremendously. In addition to being able to do data analysis on Voyagers, I have also been tapped to be the instrument manager for lots of different instruments on different spacecraft, missions that we got involved in. Just finished up—the last one was our instrument on Solar Probe called EPI-Hi. Solar Probe was launched in 2018. We're through about 16 orbits of the Sun, now, I think. That's still an ongoing thing. There are Zoom calls every week on that, and there's data analysis going on. Then we had STEREO, which were twin spacecraft around the Sun, at 1 AU, roughly. We had instruments on both of those. ACE—Advanced Composition Explorer—that had two instruments I was instrument manager for on that. And ISEE-3. Just about every time one gets launched, it seemed like there was another one coming on. I've analyzed Voyager data all along, but that has been a half-time kind of effort, typically.

ZIERLER: I wonder if you're well-positioned to comment—Ed Stone and Robbie Vogt of course are two Caltech legends, have done so much important work together. Two very different personalities. I wonder if you can comment on their dynamic, how they complemented each other to produce all of this incredible science.

CUMMINGS: Yeah. Of course, they're totally different personalities. I can tell you that being a student of Robbie's that he was very forceful. I would just characterize him by never having lost an argument. [laughs] He was just—dominant. I think it was very helpful in persuading NASA or whatever to do what they're supposed to do. But it was hard on the students, as well, I would say. He was sort of a perfectionist, and he instilled that in me in a lot of ways. He would go to Fort Churchill, in the summer, and he was up there with us, and every day, day in and day out, what a miserable place to be. I can tell you that. There is not much fun going on up there! But Ed is just totally opposite. He's very calm and I felt like the smartest guy I ever met. He was a multiplexer supreme. I like to tell the story where he was in my office. He was actually the director of JPL at the time. He'd be up at the board, and writing, and the secretary would come in and say, "You've got a call from Dan Goldin, NASA headquarters." He'd come back and say, "I gotta go. I gotta go to the airport." Then he'd come back several days later, and come right back in, and just pick up the pen right where it was [laughs]. No pleasantries or anything; we'd just get right to the science. But he was amazing, and an inspiration for a lot of us that came around Ed.

Robbie left our group kind of early on, actually. He became chairman of the Physics Department for several years. Then he was in charge of LIGO for several years. He was also provost at Caltech. During that time, he didn't try to keep that much engaged, with Voyager for example. But Ed did. When he did the same sort of thing—chairman of the Department and then director of JPL—came in, at nights and everything, signed travel orders, kept our group going. That wasn't the way it was supposed to be. It was supposed to be a new professor would come in and take his place. But that didn't happen, so he kept it going, during the nearly 10 years he was JPL director. Those two guys are amazing.

ZIERLER: Were you ever involved in LIGO?

CUMMINGS: No. I was involved in kibbitzing as a skeptic! [laughs]

ZIERLER: A skeptic!

CUMMINGS: Absolutely a skeptic.

ZIERLER: On what basis?

CUMMINGS: "How could they possibly do that? It's impossible." And they did it. That was amazing. One of the guys who was involved closely was Stan Whitcomb, and he got a lot of recognition for it all. Stan Whitcomb worked for me as an undergrad at Caltech in our group. He wrote an article about Voyager, our instruments, as an undergraduate. I think it was his undergraduate thesis project. Stan became a professor at Caltech for a while, but he has worked on LIGO I think mostly the whole time. I didn't get involved. No, I didn't think that was possible. What they were talking about, the dimensions of change, were so tiny, I didn't see how they could do that. So, they're amazing.

ZIERLER: Definitely one of the miracles of modern science.

CUMMINGS: Yes! [laughs]

Texas Roots

ZIERLER: Let's go all the way back to the beginning. Tell me first about your parents and where they're from.

CUMMINGS: I grew up in Texas. My father, as far as I can remember, he had been a teacher. He went to college and graduated from Texas Tech, and that was unusual, because he was born in 1909. My mother was born in 1909; she also went to Texas Tech and got a degree. They got out just about the time the Depression was on. They got teaching jobs, but the Depression was just terrible. They were having to give back part of their money, and only working nine months. My father was a math teacher, but he became a distributor for Tom Huston Peanut Company, in Wichita Falls, Texas. He ran a route to different grocery stores and various bars and everything. He had a brother who ran another route. Then there was another salesman. There were about three routes to cover a city of about 100,000. It's interesting, because my father's route, he took the route—we were segregated in Wichita Falls, completely, at that time. In fact, one of the stories was that—I went to this huge high school. It was one of the biggest around at the time. It was like over 3,000 students for three grades. It was not air conditioned, and it was hot in Texas. There was a Black high school across the tracks. Actually, they had railroad tracks, and they were on the other side. That's where our route was. They air conditioned Booker T. Washington High School so that they wouldn't want to come over to Wichita Falls High School. It was something! But then integration just—about the time I left, we had no Black students, but later, soon after, desegregation happened. Anyway, so my dad, he said, "When I die, I'll have more Black people at my funeral than white people," because he was dealing on that side of town. My mother didn't teach for very long, I don't recall, because she was never a teacher when I remember; she was just—she was doing some of the business part of the business, the books. I was, after school, often running over—I'd be taken over to where my father was and help him sell the candy.

I had two older brothers and an older sister. Still do. That was one inspiration. I was the youngest, and they had all done quite well in school. My brother was an anomaly because he was tall, like 6'3", and we don't know where he came from because my father was 5'6" and my mother was 4'11". But he sort of looked like us; we think it's legit. [laughs] Anyway, he won the state championship in football, for the team, and Wichita Falls was a highly rated team, because it was so big, and we were in the top division. My sister won the state tennis championship a year after she picked up a racket! Or two years, I guess. A year after she picked up a racket, she won a junior—she got to the finals, and the next year she won it. So, we were all athletes. I played tennis. My next older brother played tennis. We were also—well, I don't know about my oldest brother, about his grades, but the rest of us were top rated students. A "B" was not acceptable at all. [laughs] Although my parents really didn't put the pressure on. I think it was my sister and brother just older than me, their record was so good you just had to try to do that as well. I didn't really have a clear—I knew I was going to be mathematically oriented somewhere, whatever I did. I liked that. I didn't read too much, books or anything. I just worked on math problems. I remember there was a seminal moment when I was in the eighth grade, I think. I was taking algebra. Algebra was new to me, and the first six weeks, or whenever the test was, I made a 60, out of 100, and boy oh boy, that was a shock. I went up to the teacher and I said, "What do I have to do? I gotta have an A outta this thing! I can't just mess around here!" He said, "Well, you need to make 100 on the next five tests." Because I guess that was the first-six-weeks test, or weekly test or whatever it was. So, I did [laughs], and I maintained my perfect record. But that was a little early. It didn't really count at that point in eighth grade.

ZIERLER: What was the launch of Sputnik like? Did that register with you?

CUMMINGS: It did. I remember I was in front of Wichita Falls High School, in fact, when that announcement came out, and we were looking up at the sky. Of course you couldn't see anything. That was also fortunate, because that inspired a lot of stuff that happened. The Russians got ahead of us, quite ahead of us, and that inspired the Apollo program, which I think was tremendous what they did, to land someone on the Moon and bring him back, in the short time that they did that. That was astounding. I think Voyager was astounding in that it got conceived like in 1972 or something in terms of actually getting funding, and then launching two spacecraft, building another one, by 1977. I mean, the little things we were doing—with Solar Probe, our little box, our instrument, I think it took nearly ten years we were working on that thing. It's just ridiculous how quick it was with Voyager and Apollo. But yes, I wasn't sure what I was going to be interested in, and I didn't know even when I went—I went to Rice University. I actually had a tennis scholarship to University of Oklahoma, but my mother shot that down. "You're not going there." With a half-scholarship. Because we really couldn't afford anything.

Fortunately, Rice was free tuition at the time. That lasted until my junior year, but they grandfathered us all in, and so we never had to pay anything except room and board at Rice, which is very fortunate. My next oldest brother went to Rice, so he was there the first year that I was there. In fact, he went on to graduate school, so he was pretty much there the whole time I was there, which was helpful. He helped me a lot. He was a very organized person and became the executive director of USRA for about 30 years. He's still working part-time with that organization, I think. He was quite the Eagle Scout, Order of the Arrow, all this stuff. He was trying to get me to follow, and some of that stuff, I just wasn't interested in. But I remember thinking—he was three years older, so I have often said that I didn't have an original thought in my head until he left to go to college [laughs] when I was still in high school. He was quite directing me around. But in a good way. He was very smart and knew what I needed to do.

ZIERLER: Why was Rice free? I thought it was a private university. Did they have some special endowment?

CUMMINGS: Yes. They had a lot of endowment. There was a guy named William Marsh Rice, and I don't remember all the details about it, but he established it basically, with money. I think there was a lot of Texas oil money involved. The charter had to be modified later, because it was a period where—their charter said it was only for male, white students from Texas. And that didn't fly forever. [laughs] If you want federal money, you're not going to manage to do it that way. They did change it, and they admitted I think the first Black students there, and at Caltech too by the way, about the time I was in the same classes—sort of Caltech right after I got here, I think, and then at Rice, before that. I also went to Cambridge, England for a year. I won a scholarship called the Winston Churchill Foundation Fellowship. That was an amazing experience. I had never been anywhere, really, and to go to Europe—and then they had such liberal holiday periods over there. It was just ridiculous. They would have six weeks at Christmas, and several weeks at Easter or whatever. I managed to get a car over there. Somehow I guess I parlayed some of the funds [laughs] that they gave me into getting a car on the European delivery plan, which meant the steering wheel was on the wrong side, for there, for England. I had lots of fantastic experiences with that situation, nearly killed myself. The first friend I met there, I wanted it to be an English person but it ended up being an American. We got to be really close friends. We went all over Europe, everywhere. North Africa, Morocco, you name it, we were on the road every time there was a holiday. I remember when I picked up the car in London and I was supposed to drive it back to Cambridge, which I did, it had gotten to be nightfall by the time we left the dealer, and I drove, on the freeway, on the wrong side, and had to go down—because we saw a raft of headlights coming directly for us, so we scrambled down an on-ramp in the other direction, obviously. Then we finally got to safety and I can say I never made that mistake—I never made any kind of mistake after that!

ZIERLER: Would you say that the Space Race and John Kennedy's mission to the Moon, did that affect your course of study as an undergraduate? Did it change what you wanted to look at?

CUMMINGS: I greatly admired John Kennedy and also the Space Race. In fact I was at Rice Stadium—he made a famous speech there. You may be familiar with that. "We're going to the Moon." One of the ones they cite and they show in the video clips and everything was at Rice Stadium in like September of—my first year there, 1963 or 1962. It was so hot that day, and humid. Oh my gosh. And they were in suits. John Kennedy made mention of that. One of his famous lines was, "Why does Rice play Texas?" Because they were asking, "Why go to the Moon?" He says, "Well, why does Rice play Texas?" [Laughs] "Because it's there. It's gotta be done." Yeah, so I was inspired by that. I wanted to be an astronaut. I tried to be an astronaut. I wrote Alan Shepard from England, from Cambridge, and told him, "I want to be an astronaut. What do I need to do?" He said, "Well, you're not a pilot, so you're going to need to get in a different way." He suggested I get a PhD and try to get in through the science method. He actually wrote me back! This was snail mail of course, back then. But then I got really ill, actually in Cambridge, which I didn't know what it was at the time. I had my appendix out. That was quite the story.

I was playing tennis. I played tennis on a team there. I played tennis at Rice, too. I got a letter jacket. I was captain of the team for a couple of years. Even though I was by far not the best player, but we had a really good team. We won the Southwest Conference championship every year I was there. I thought I would play on the Cambridge varsity squad, but I got there, I had never played on grass, and I got one opportunity to see if I could make the team, and it was on grass, and the guy beat me. So, I went down to the junior squad, or their second level. We played against other teams. In the rain. I would say I felt like there was some dampness, moisture, misting, every single day I was at Cambridge. It was just [laughs] unbelievable. I wasn't there in the summer. I was just there from—I left in May.

That was something else, too. I had to deliver my car to Gothenburg, Sweden, and they would put it on a boat and send it to New York, and then I was going to go pick it up. So in May, I drove it over there and then took a ferry back to England, and then met up with the car in New York, sort of as planned, but then drove it to Texas, and then drove it to—I was working in the summer—I got to work that summer in Los Alamos. I had taken a job there—I spent two summers there. And that was interesting! Had a secret clearance. There was things going on I shouldn't—I didn't know about, and followed all the rules, so there wasn't a problem there. I got involved in a—it wasn't cosmic rays but it was close. It was the Vela program to detect nuclear explosions and stuff that the Russians might be doing. I worked in that group. I learned how to program there. They taught me Fortran. I met some people in the group that I've known ever since, because they were scientists more or less in the field that I'm in, just a little bit lower energy. But we have to know about the low energies, too, in the cosmic ray field, because they're important. I will say the one thing I remember about Rice—about my senior year, I took a course in space physics, and when I got to the cosmic ray part of that course, I said, "This is the most boring thing I can imagine. I'm not going into this." And of course it's exactly what I went into and what I've been doing ever since. When I got to Caltech—there was a student at Rice when I was a senior—we were both seniors—he went straight to Caltech, and I went to Cambridge, and I came a year later. By that time, he had a place to live and that sort of thing, so I moved in with him and another fellow. They all worked in this space radiation group, and so they hired—they just told me I had to go do it. That's where I wound up!

Working with Robbie Vogt

ZIERLER: As an undergraduate, had you heard of Caltech? Was there a professor at Rice who introduced you to Robbie Vogt?

CUMMINGS: No. I can tell you though that it goes back to high school, really, my desire to go to Caltech. There was someone from Caltech that came back to our high school and gave a lecture to the whole class, or maybe the math and physics—I'm not sure whether it was the whole school or not—but that guy just impressed me so much, I said, "I gotta go to Caltech." I was so enamored with it at that time. But we did have counselors and they told me that I could never get into Caltech,. I think they probably were right. But I proved them wrong in the end. I got there, somehow or another, but just a few years later [laughs], as a graduate student.

ZIERLER: Do you remember meeting Robbie for the first time?

CUMMINGS: Yes, I think I do! Because actually it could be a joke, but maybe it wasn't a joke, but Tom Garrard said that Robbie Vogt—Tom Garrard was my friend that had gone before me--said that Robbie Vogt was offering a bounty of $5 per graduate student that he could recruit into his group. I guess Tom got the $5! In today's dollars, that was actually something! Yeah, I remember going into his cramped little office. We were in the basement of East Bridge, or West Bridge, with the low ceilings and everything. That is where we worked for several years until we moved over to Downs Lab. Then, 12 years ago or something, we moved over to the crooked building, Cahill. We worked really hard. The whole graduate thing was—late at night, morning, you didn't stop. I had to take a bunch of classes the first year or two, because the draft was on. They wrote glowing letters about me—Robbie—to say that if I left, NASA would pretty much collapse, that sort of thing. [laughs] I couldn't be drafted. "Don't draft this man." I got drafted anyway. This is sort of getting back to my illness, which I didn't finish off on. In Cambridge I was playing tennis, and I remember my strings broke, and so I went back to my room and got really violently ill, and had to be taken to the hospital. They took my appendix out. A student did. I woke up. I said, "Who's my doctor?" They said this was just an exam room. "They had to pass a surgery exam and you were one of the guinea pigs [laughs]

ZIERLER: [laughs]

CUMMINGS: Anyway, they did a good job, but it wasn't my appendix after all. It was something else, which we didn't discover until I got to Caltech. In 1969, I got really ill, and was in the hospital, in the health center at Caltech for like three months. I missed a whole term. I missed going to Churchill that year. But somewhere along in there, I had to go take a physical with the draft squad—and a written exam—but anyway I took the physical and they rejected me because I had Crohn's disease. I've had Crohn's disease for all these years. I did have surgery in 1969 at Huntington Hospital, and it has been okay. I'm still on medication but I've really not had much suffering because of that. That has been fortunate.

ZIERLER: What was the main thrust of Robbie's research when you joined the lab?

CUMMINGS: It was cosmic rays. We were measuring—there was another experiment that went to Churchill every summer called pαe which measured protons, alphas, and electrons. Tom Garrard took over that experiment, my friend. I was just helping out with other experiments. There was an electron experiment that Marty Israel I think worked on, now at Wash U. Then E± —there was and E± already that Carl Rice, a graduate student ahead of me, was finishing up. He was going to be leaving, so they said, "You can take over that, and we're going to add a Cherenkov counter on top, which will help us with our measurements." I was sort of in charge of designing and building this Cherenkov counter that went on top of what was there already, which are these spark chambers and magnets. We were in this cosmic ray field. Where Ed and Robbie came from, the University of Chicago, was really big in this at the time. A man named Simpson, and a bunch of others, and Robbie and Ed came to Caltech from there, and they sort of established a cosmic ray group when they got to Caltech and continued what they were interested in.

ZIERLER: Tell me about developing your thesis topic. What did you work on?

CUMMINGS: I worked on E±—an experiment that I talked about, when we went to Churchill. Now, of course I had already written my thesis by 1973 when we lost the balloon. Building up to that, I can tell you an interesting story about, in 1972, the year before, I asked Robbie if I could go out on the recovery team. We'd get in a DC-3, and you go out there, and they land in some weird field or whatever they can find—a road or anything—nearby where it was, and then you pack it up and you bring it back. I had never gotten to do that. It wasn't just us up there. There were lots of institutions up there. University of Chicago was up there, University of Maryland, and various places. They all had experiments, and we were all on a schedule, trying to get time to get our balloon launched. A lot of other graduate students had been able to do this, but not from Caltech. Nobody from Caltech, it seemed to me, ever went out on a recovery. I convinced him that I'd like to go, and he said, "Okay, go ask Al Tomnitz over there"—the pilot—"when will they take off, and if it would be okay that you go." I went over and found Al Tomnitz out on the tarmac by his plane, the DC-3, which I had flown in before because he actually came to Pasadena and picked me up and took me back to the Raven headquarters in North Dakota—or, South Dakota; Sioux Falls. He was quite the character. Completely wild guy. I don't know what he was doing with this job.

Anyway, when I got over there that night, of course it was light really late, almost all night. We were near the Arctic Circle. Lots of parts everywhere. The engine was just sort of taken apart, and it was just laying out there on this tarp. I started asking the question if I could go. I said to him, "Well, you're obviously not going, so when do you think you might be going, and would it be okay?" And he said, "No, we're going. 6:00 in the morning." I said, "Really!" Then I had sort of second thoughts—"Should I get on this plane or not? The engine is apart right here in front of my face." Well, I got over there, and we took—he had a copilot. Every summer it was a different person that they hired.

I remember standing behind them when we took off. I don't remember there being any seatbelts, on anybody. Anyway, I was standing up, and pretty soon there was an antenna that stuck through the ceiling, through a little hole, and sparks began to fly all over the place inside there. Scared the hell out of me. I sat down, on a bench seat, and I sort of complained about it, and they said, "No, no, that's normal. Don't worry about that." We get up there, and we land, and as soon as we open the door, a horde of gigantic black flies or horseflies or whatever they were came right in the door. We had to close the door and put our mosquito net hats on. I mean, mosquitos were unbelievable there, but the black flies were more of a threat. I remember, for example [laughs]—not getting off course too much—but the mosquitos were so bad that when I opened the logbook years later, there would be a dead mosquito in it. So I would close the logbook; it just trapped a mosquito. Inside the building where we were working, we had mosquito netting around our faces and everything. It's just—not a pleasant place to be.

Anyway, we killed those black—took us about 30 minutes—we all had these little spray guns of Scotch 77 glue, and we sprayed them, and then their wings would—[laughs] they would fall down. Ugh! We finally get out there. We recover the balloon. We leave the balloon plastic out there for the farmers, who seemed to like it. That wasn't a problem. But we packed it up, and he takes off, and the copilot goes back to take a nap in the back, so I slid into the copilot seat. Al's telling me—well, I skipped one important thing. On the way out, I was standing behind him most of the time, looking out and looking, seeing what they were doing, and there was something called autopilot. I said, "Autopilot? This thing has an autopilot?" Al says, "Yeah, you want to see how it works?" I said, "Sure." So he turned to his copilot and said, "You're all trimmed up and ready to go?" and he said, "Yeah," and so he pulled this crank up that said autopilot on it, and the plane just flipped upside down and just completely—nothing was said, because I again was racking around inside that thing and I finally got my seat and sat there and I wouldn't say anything until we got back. I saw him in the cafeteria and I said, "Al, what about that autopilot?" He said, "Yeah, that damn thing never has worked." [laughs]

Anyway, so we're flying back with the payload, and I'm sitting in the copilot seat, and Al's flying. He's describing what you're supposed to do—"You do this, you do that, you make sure this little compass is right on that thing, and if it goes this way, you do this, and"—pretty soon I look over and he's sound asleep. So, I am flying the plane, for quite a while, while those guys slept. I was trying to do what he said to do, but apparently not so good. When he finally woke up, he looked down and he didn't recognize anything, and he got up and went and got his copilot, and they got some maps out on the floor of the DC-3, and they finally figured out where we were, which was pretty much back where we started because I had flown in this big circle. [laughs] Fortunately we had enough fuel to make it. Anyway, I lost my copilot seat at that point. They decided to take over. That was in 1972. What you asked me, though, was—so what did I do? Unfortunately a lot of what we were measuring turned out to be Jovian electrons, which we didn't realize at the time. They were sort of discovered—so you get those like every 13 months when the Jupiter is on the same magnetic field line as Earth—they come from Jupiter, so they weren't quite as interesting. But I had done a lot of work on the theoretical side, so they said, "You're going to write your thesis on all this theoretical stuff." Including about solar modulation, including about where the electrons come from. For the 1973 Denver ICRC, I had about four papers in there, on different aspects, that were included in my thesis, basically. So it was mostly theoretical. There was some observational stuff in there, but mostly theoretical.

ZIERLER: What was Robbie's style like as a mentor? Did you work closely with him?

CUMMINGS: Oh, yeah. Tough! He had a terrifically volatile temper. [laughs] And he would unload, and this would happen in the lab, too, back in Caltech. He also was over it immediately, which I didn't realize for quite some time. Because I would go home—I'm mad, I'm upset—but the next day, it's like it never happened. Nothing happened. He was just as fine as he could be. But, good for him! [laughs] He could get over it really quickly, but it took me longer. But we got along. Actually I have to say that when I was getting my degree, and was finishing, he helped me a lot. For goodness sake's, during my thesis oral exam, these professors started asking questions which he didn't think I would be expected to know. It was more or less about the Voyager mission, really. They were asking questions that—I hadn't even worked on this thing. So he got up to the board [laughs] and started answering their questions, and I sat down, for 20 minutes probably, in my thesis oral exam. But it was my qualifying exam, my candidacy exam, that was—tough. Robbie advised me to take it, because they had just changed the rule at Caltech. You could either take the oral exam, which is like three hours in front of these professors, and they could ask any questions about physics at all. It had nothing necessarily to do with your research. The thesis exam at least, it had to do with your research, so you knew something about it. He advised me, "Let's just get this thing over with. You could take the written. But there's like six different exams. They're really long." They wanted to change it because they were tired of the subjective nature of the PhD process. I think they didn't want to get blamed for flunking a person out or they just wanted the numbers to say, "Okay, you didn't pass the exams." So they were just switching over, and I had my choice of which way. Anyway, I did the oral thing, which was terrifying and stressful, to say the least. As soon as you started answering correctly that you knew something, they just said, "Okay, that's enough of that," and they would get on—they only wanted to know what you didn't know.

Anyway, after that was when I went into the hospital. Not long after that. I don't know if the stress triggered more of the symptoms or something, but that started a long illness, really. But as I say, he was—I had said to myself, "I'm not working for Robbie [laughs] when I get my real job." I did have an offer to go to Livermore, and so did Tom Garrard, but Robbie and Ed decided that they were ready for some permanency in the staff. They didn't like these graduate students just coming and going and taking whatever they knew with them, and then you've got to start all over training somebody else. They wanted a couple of staff scientists. So, they hired both of us, Tom and me. We both got our degree about the same time. So, I ended up taking the job. Later on, my wife was working over in the president's office, and Robbie became provost, and I said, "No way you're going to work for Robbie Vogt over there," and sure enough, she did. [laughs] She had a completely different experience, where he couldn't have been nicer, and she didn't understand what my problem was, that he was just a terrifically nice person. Though he was still in the habit of not losing an argument, I would say. [laughs]

Soft Money Longevity

ZIERLER: What was the title of your initial appointment? Were you a postdoc? A staff scientist?

CUMMINGS: No, I never did go through the postdoc thing. It was just the staff scientist, yeah. Then a few years, several years later, I got promoted to being a member of the professional staff, which had some benefits to it in terms of what the Institute contributed to your retirement or something, as I recall. Anyway, yeah, most people went the postdoc route and then were trying to become a professor somewhere. I wasn't really that interested—that is like running a business. It's like a dentist's office or something. You're looking out for everybody's salary in addition to trying to do your research. They're having to teach classes. My hat's off to these professors; they're something else, to be able to do all that.

ZIERLER: How much did your day to day change, going from graduate student to staff scientist?

CUMMINGS: Almost nothing. By that time I had done all my coursework so I was not taking any more courses. Well, it changed in the sense of what I worked on. As soon as I got hired, I went the fateful summer in Churchill and then when I started working on Voyager, that was a different experience. Yeah, that was pretty totally different. I had a lot of people to assist me—undergraduates, we even hired some people—to do all the testing of detectors and everything. We were designing our low-energy telescopes at the time. I was back and forth to Oak Ridge, Tennessee, where our company that made the detector, ORTEC, was located. I went back there to try to get the design of these detectors right and that sort of thing.

ZIERLER: How did you first get involved with Voyager? Were you interacting with Ed Stone at that point?

CUMMINGS: Yeah, I was interacting with both of them. Ed Stone, he was supporting other graduate students, not me. But he would come around at night. I would be in the office. He'd say, "What are you working on?" We'd discuss it a while, and he'd say, "No, you gotta wrap this up. You can't just keep coming up with different things to work on, because everything kind of leads to something else, and you don't know this and—" I was just going off in all different directions. I guess about four different directions ended up in my thesis, but I was heading—I was already in the sixth year, so I needed to get out. He helped me focus on just what I had already done, and don't take up anything new right now until you get this written up.

ZIERLER: What year did you start to get involved really with Voyager?

CUMMINGS: It was 1973. It was November 11 or 12, as I recall.

ZIERLER: What was the status of the mission at that point? Gary Flandro and the gravity assist, was that all worked out by that point?

CUMMINGS: Yeah, that all had worked out.

ZIERLER: What was Voyager doing? Were they in building mode?

CUMMINGS: Yes, design and build. Our instrument was called CRS, Cosmic Ray Subsystem, and it was a collaboration between several groups, but mostly Goddard Space Flight Center was doing the electronics and the HETs—high-energy telescopes—and we were doing the low-energy telescopes and the electron telescope. A lot of interactions between Goddard and us, really, trying to get this thing developed. We had an electrical engineer named Bill Althouse, who was in charge of our—we had to do a ground support equipment, GSE, thing. So, I was very busy, right until launch really.

ZIERLER: Tell me about the instrument. What were its science objectives? What were some of the engineering challenges?

CUMMINGS: We were trying to get to low energies, so we needed really thin detectors, and we didn't quite reach—we originally thought we were going to do 20-micron detectors, and it wound up being 35-micron detectors because they're delicate. That was a challenge. The engineers were involved in this as well. Also you need to keep everything in kind of a small—everything has to weigh almost nothing. You can't waste mass. We didn't really have much in the way of mechanical engineering experience at Caltech in our group, so we hired that outside. The electrical, and how the signals get routed and everything, the engineer took over that. I was mostly involved in the—there were just hundreds and hundreds of detectors. There was not only Voyager 1 and Voyager 2, but there was a Voyager Proof Test Model, identical in every way. So, building three of everything. Then you had a spare set of everything. So, we had lots of detectors, and a lot of testing, and a lot of thermal vacuum testing to make sure it's going to work in vacuum, over a temperature range. Of course we never imagined going to -65 C, which is where we are now.

ZIERLER: Because Voyager was only envisioned for the outer planets?

CUMMINGS: It was envisioned—really, Robbie takes credit for making sure the hydrazine tanks were full on Voyager before launch. He told me that, not too long ago. Because we did envision cruising on past the planets and getting to interstellar space. We thought that was a possibility, even early on. Now it didn't get sold that way. It was only going to Jupiter and Saturn, and five years, and that was it. They sold it going to Uranus and Neptune when we accomplished our goals at Jupiter and Saturn in such a way that Voyager 2 could be left in the ecliptic plane. If Voyager 1 had messed up at Saturn and not done a good job on Titan, then Voyager 2 would have had to repeat that, and that would have put it out of the ecliptic plane, and we wouldn't have gotten to Uranus and Neptune. So they sold that, during the mission, and then they sold the VIM—Voyager Interstellar Mission—once we got past the last planet.

ZIERLER: During this time, are you mostly working at JPL, or this is all done out of campus?

CUMMINGS: It's all done out of campus. Some of it goes over to JPL. There's testing that goes on over there as well. But most of the time it was Caltech.

ZIERLER: What's the structure? Is there a PI of the instrument? Are you leading this?

CUMMINGS: Robbie Vogt was the PI of the instrument. Ed Stone became the PI later, when Robbie went over to administrative duties and stuff like that.

ZIERLER: Just to give a sense where it fit in overall, how many other instruments are there on the spacecraft?

CUMMINGS: There's now five working, but there were more when we were launched, because there were all the camera experiments. There were something like 10 or 11 total. In the particles and field department, which we were part of, there was our instrument, CRS. There was a low-energy charged particle experiment called LECP that was run out of Johns Hopkins University, Applied Physics Lab. Then there was a magnetometer to measure the magnetic field. There was a solar wind instrument. Then there was a plasma wave instrument. Those are the five that are still going now. On one of them—Voyager 1 no longer has a working solar wind instrument. It failed just after the last planet. But we do have it on Voyager 2, so that's good.

ZIERLER: Tell me about launch day. What was that like for you?

CUMMINGS: That was disappointing. I was not senior enough to warrant being there for the launch. So I didn't get to—I was the last person to touch the spacecraft, but that was quite a few days before launch. I would go down there for both launches and do the inspection—well, there was a lot of stuff; I had to stay there quite a while, actually, because we had to get our instrument ready, put it on the spacecraft, make sure it's working. In one case eventually we had to take one off, a telescope off and send it back to Goddard for them to figure out why it was counting so noisy and send it back. So there was a lot of stuff going on down there. We also worried about contamination. I noticed when I was down there on one occasion that they were repaving asphalt on the route that the big trailer tractor thing that was going to take the spacecraft over to where it gets launched. I raised the attention on that, and they actually did something about that. They did worry about that, too. Because normally we flush our instruments with dry nitrogen to keep contamination—our detectors could be contaminated by fumes and stuff. So, it was busy down there. The last thing that I was supposed to do was go up in there and make sure our little windows were okay on our telescopes, the low-energy telescopes. I just have gone through my notebooks from that period and found that I must have touched them [laughs] because it says there that I was twisting them and one of them was a little bit loose, so I twisted it 30 degrees. That's how I know I touched it. Otherwise I might have just gone up there and looked at it. But they screwed on, the little windows. It was weird, because I'm thinking now, man, what about the radiation from the RTGs? I remember when they put the RTGs on, everybody had to clear the building. Those things were radioactive. [laughs] So, I don't know, I wasn't up there too long anyway but—they opened up a hatch, and they put the hatch back on.

ZIERLER: When did Voyager start sending back data that was useful for you? How long did that take?

CUMMINGS: It was pretty quick. There was not a long delay. Once we got turned on, we were collecting our data, we had to figure out if there's any command changes we need to make, or configuration changes. Some of that went on. It was very complicated at the encounters with the planets, because we had lots of different modes on our instrument that we could be in, and so they devised a system where we could rotate through those modes as we were getting real close to the planet where things were changing really rapidly. But it was fascinating, with the encounters. We actually, and another instrument, LECP, discovered—or found—sulfur and oxygen atoms being accelerated to high energies, and we were seeing them, in great abundance, right near Jupiter. It turns out that there were things coming out of the volcanoes of Io that got accelerated up to high enough energy that we could measure them. I was never much of a magnetospheric physics guy, but there were big magnetospheres, so there was a lot of data taken around the planets.

ZIERLER: What was it like, the planetary encounters? Was it suspenseful? Was it exciting? How long did it last?

CUMMINGS: It was exciting. I actually went over a lot of times—they would have meetings every morning where the press was there, and they would talk about the discoveries the previous day. The evening before that, all the scientists got together with Ed Stone and they roughed out, "Okay, which part of it is the story going to be for the press?" I got to go over and sit in on those, and that was fascinating. These people were discovering one thing after another with the cameras and everything, so they dominated mostly the press conferences.

Voyager Beyond the Planets

ZIERLER: When did you realize that the Voyager mission would go beyond the Solar System?

CUMMINGS: Well, that wasn't clear if it was ever going to make it or not. There was a lot of jokes being made, because we would keep predicting when we were going to get first to the termination shock. That was our first goal. It seemed to be hanging out there every time—we'd make a prediction, and then some new data, and they were joking, "Well, it's always 10 AU out beyond where you are." [laughs] But actually I look back, and we had a paper I think just a couple years before Voyager 1 crossed, which predicted, right at that point, 94 AU, right where we crossed. So, we were homing in on it. Now, the question is, we didn't know how far it was to the heliopause, at all. It turned out to be closer than what the theorists thought it was going to be, which is a good thing. They're still trying to figure out, why is it as close as it is, based on their MHD modeling. It could have been so far out we didn't make it before Voyager expired, but we've had a good run in there. 2012, for Voyager 1, so, we've been quite a few years in the interstellar medium.

ZIERLER: Because the instrument, the whole mission was not conceptualized for interstellar space, once everybody realized that it was approved that Voyager could keep going, what kind of real-time adjustments were necessary in order to keep everything scientifically useful?

CUMMINGS: I wouldn't say there was any particular thing that had to be changed. We did realize some important measurements could be made if we made a command change, and we did that. We needed to see even lower energies than we were normally seeing, and we adjusted some command states so that we could make some important measurements, which we did. But now that we're in interstellar space, that particular command had to be reversed, because it wasn't helpful, it wasn't useful. It was only useful between the termination shock and the heliopause. So we didn't make too many changes. We rarely command the spacecraft. . We just did send a command to our instrument on Voyager 2 that took effect two days ago. Which is pretty rare. But we did have something come up—a detector started counting high, at high rate, which was interfering with the overall measurements of the telescope, so I devised a way to turn it off, and it will not affect our real science value, actually. Fortunately, we have four of these telescopes, and it was a minor problem. Hopefully it works. A technician that works with me had just sent me an email this morning saying he's working on seeing if it worked. [laughs] We're going to find that out later today.

ZIERLER: To clarify, Voyager 1 and Voyager 2 are identical. Does that mean that the instruments, that your instruments, were identical also?

CUMMINGS: Nearly. Essentially identical. We have four LET telescopes that are essentially identical. Each individual detector has its own thickness, slightly. It's not going to be 35 on the nose, that sort of thing. Just minor little differences like that. But those are mounted the same way and everything. But on Voyager 1 and 2, on the HETs, the high-energy telescopes, they're actually mounted back to back. There's actually four independent ones of those, too, because there's two of them, and detections from both ends can be made. They were oriented slightly different on the two spacecraft such that they would in space kind of make an orthogonal set for measuring anisotropies, different particles in different directions. It was a little bit of a pie in the sky thing. That's the only difference, really.

ZIERLER: Given that Voyager 1 and 2 were on different trajectories, that they encountered different planets at different times, that they entered interstellar space at different times, what was the value of that for your research, having those two different tracks?

CUMMINGS: That is very good, at least measuring two different points for the modelers. A lot of this has to be filled in by modeling, because we're only measuring in two trajectories. When we cross these boundaries like the heliopause or something, we're getting two samples. You cross the termination shock at two different places. That's very valuable information. If we had more, the merrier, but at least we have two.

ZIERLER: It was Voyager 2 that entered interstellar space first, correct?

CUMMINGS: No, Voyager 1.

Heliopause Debates and Discoveries

ZIERLER: Ahh, right. When that happened, I wonder if you could narrate some of the scientific debate? When did the heliopause become known? What were some of the debates and how was that finalized?

CUMMINGS: It wasn't obvious at first, at all. We thought from our data it looked like we had crossed, the way our detectors responded. The main problem was that the magnetometer experiment didn't record a change in direction of the magnetic field as it went across the heliopause. Now, we're talking about the magnetic field of the Sun being lined up with the magnetic field of the galaxy, in that case. That didn't seem to make sense. We agreed, but we thought a lot of other indications were that we had crossed. I can tell you, this debate is still going on, actually. There are at least two people that still think we haven't crossed. [laughs] This debate went on for about a year. We had many calls. I remember Ed and I went up to JPL and they recorded the debates that we were having. There's some history there, that they knew it was going to be historic, so they did that. We were arguing pretty vociferously—some were arguing against it. Some were with it.

Finally, the PWS experiment in most of our minds solved the case, for interstellar space. That's because they measure—we were getting occasionally some sort of evidence that the Sun is still affecting us out there. We're in a very local interstellar medium and we're defining that now is where the Sun still has an influence. It sends out waves, and they go through the heliopause, and they continue on, and they affect an environment around the spacecraft to some extent. Not so much for galactic cosmic rays. We all agree that galactic cosmic rays—well, there is an effect on this; it's a different kind of effect. I'll get to that in a minute. Anyway, the Sun sends something out, and the PWS experiment picked up these electron ion oscillations, electron proton oscillations I guess they're called, EPO events. They measure the frequency of some oscillation going on with low energy thermal particles. That frequency is directly related to the density of the electrons, for example, in the space around it. If you know that frequency, you know what the density is. From the solar wind instrument, we knew what the density had been doing—and the density decreases as you go out, from the Sun. The density was very low from the solar wind instrument—before we crossed the heliopause—of course the solar wind instrument is a lot trickier to get a good result from in interstellar space. So we knew it was a very low density but the plasma oscillations indicated a much higher density, the density in fact that was expected in interstellar space, expected to be much more dense; it was about 80 times denser. That in most of our minds sealed the deal; we had crossed into interstellar space. We've got to find out why the magnetic field direction didn't change. It didn't change either in Voyager 1 or Voyager 2. That's an active area of research, a mystery to be solved. Modelers are coming to grips with it, and they think it will eventually—that it's a boundary layer kind of a thing, that the interaction between the heliosphere and the interstellar medium just is more complicated and it occurs over a longer time than we thought. Then we will eventually get to the direction of the galactic magnetic field.

ZIERLER: When Voyager 2 crossed over to interstellar space, what value did this bring to these debates?

CUMMINGS: It had the same problem, actually, but that came much later, where we had already decided what the heliopause boundary would look like. In terms of solar wind—I mentioned these anomalous cosmic rays before—anomalous cosmic rays are thought to be in the heliosheath. We don't know exactly where they're accelerated or by what mechanism. We think it's diffusive shock acceleration. I think it's diffusive shock acceleration at the termination shock, but just not at the place where the Voyagers crossed. There are theories that claim it's back down the tail or the flank of the Sun's comet-shaped heliosphere, because there's an interstellar wind, and it's blowing, and we're moving through it, so it kind of swept back like a wind blows a—there's lots of modeling going on about that, too, because different people think different things. Those particles are what we would term heliosheath particles. We wouldn't expect to see them in the interstellar medium. And guess what? They disappeared as soon as we crossed this boundary. They're gone. Galactic cosmic rays, on the other hand, we expect to be as intense or more intense when you get into interstellar space, and they jumped up, right at this boundary. So, from the particle standpoint, it was some similarities, some differences in detail, but you've still got the issue with the magnetic field direction. I'll be interested to see how that works out.

ZIERLER: Because there are these debates that are ongoing, on the flip side of that, thinking back 100 years of cosmic ray research, what did crossing into the interstellar space resolve? What mysteries are now really understood as settled?

CUMMINGS: We understand what the energy spectrum is. That leads to a good feeling about the maximum radiation that an astronaut could ever meet. The heliosphere could shrink down to inside the Earth, probably if we ran into an interstellar cloud that's very dense or something. They think this has happened in the past. It could be a thousand years or something, but it may happen again. But also the energy density of cosmic rays compared to star light and other things, magnetic field, is settled. We measured that. I'll tell you one thing that was interesting to me, and I had no knowledge that this was going to happen, but as soon as we published this paper in 2016, there were lots of papers on dark matter, saying that we put a constraint on what the models of dark matter are, because the electron spectrum is what it is. The electrum spectrum particularly, we had no knowledge at all. I had that in my thesis, of what the thing was in interstellar space—I had a huge variation. Now we know what that is, and that helped them with their modeling.

ZIERLER: Where do you fit in on these debates, given that there are these ongoing mysteries? What points of view do you represent?

CUMMINGS: I represent the point that we definitely crossed the heliopause when we said we crossed. There are only a couple of people—they're prominent people [laughs]; I will say that—that think we'll still cross it, and that we are just in some region of compressed solar wind. They've got their little models. That would explain the magnetic field not changing, that we're still sampling the interplanetary magnetic field, not the galactic magnetic field. And somehow that we got into a region where the solar wind itself is what we're measuring, and it's very dense. I'm not a big fan of that, and I think they'll work out—we're tracking the magnetic field to see if it is changing, gradually. It's not changing much! It will be interesting to see, if Voyager can still remain on—and we need to keep it on as long as possible, especially for the magnetic field measurements.

Cosmic and Galactic Rays

ZIERLER: I wonder if you could give a sense of scale. Of course Voyager 1 and 2 are now in interstellar space, but how close are they to our Sun relative to how far away they are to the next closest star? Would there be a subsequent mission that might further enhance our understanding of what cosmic rays might look like from another star, coming from the spacecraft?

CUMMINGS: If we're outside of their heliosphere, then I think the expectation is that the measurements will look very much the same as we're measuring now.

ZIERLER: It's just nothing. There's just no cosmic rays, anywhere close.

CUMMINGS: No, no, there will be cosmic rays there, just as they are here. It would be the same. It probably would be more or less the same. Exactly where the source of the cosmic rays is coming from, that spectrum would be different. But in an average sense, we're measuring something sort of an average, and that other star would be pretty far away from the sources too, so it would probably look pretty much the same. We think there might be some variation—because of our measurements and comparing it to other kinds of measurements—over the galaxy. There could be some variation in the cosmic ray intensity. But this is such a short distance to the next star that that particular zone probably wouldn't be that much affected. I will say that I believe it's in 40,000 years, the Voyagers will be closer to a different star than our own star. That's going to be a mission beyond [laughs] hope, I think.

ZIERLER: We've always heard that our Sun is a regular star. Is that to say then that cosmic rays that come from our Sun are more or less like cosmic rays that would come from other stars?

CUMMINGS: First of all, Voyagers right now in interstellar space are really not measuring cosmic rays from the Sun. The Sun, the instruments inside the heliosphere, are doing that. I would suspect—Voyager, we're dominated by galactic cosmic rays now. The Sun does have a phenomenon—it used to be called solar cosmic rays, but they changed the name, because we don't think that's really appropriate; they're called solar energetic particles now—they get emitted when you have a burst from the Sun, a flare, or you have a coronal mass ejection, which drives a shock, which accelerates particles. Similar instruments are on these—in fact, we have some very similar instruments of all our missions, on 1 AU, the ones that are at 1 AU, like ACE or Solar Probe, which is of course going in really close. So, we're measuring particles that are energized, and they are variable, when the Sun is involved. You get these flares that erupt; they're big, some of them are small. Compositions vary. Another star might have some differences in that department. I don't know.

ZIERLER: To clarify, we're still much closer to our Sun than to any other stars, and yet you said Voyager 1 and 2 are now measuring cosmic rays that are galactic in origin. How is that possible, given that we're so much closer to our Sun than to other stars?

CUMMINGS: Other stars are not the source of the galactic cosmic rays. The galactic cosmic rays are actually coming from probably way far away, quite far away, on average. There are these supernova explosions that occur and they're dotted around the galaxy, so we're seeing an output from those things, traveling all this way. During that time, they do lose energy and the spectrum does change, but the Sun's output is quite a bit smaller in terms of getting out to where we are, and it has to traverse—it's pretty far for solar energetic particles to—I can't remember the last time we would say we saw something directly from the Sun. Early on in the mission, yes, they were abundant, but they disperse, one over r squared, sort of, too. But there's multiple sources of galactic cosmic rays dotted all over the galaxy.

ZIERLER: That's a very important point: cosmic rays don't just come from the Sun or from other stars.

CUMMINGS: No. They come from stars that explode. There's also a realization that they may come from other kinds of sources, like neutron star mergers may produce some galactic cosmic rays that we measure, because some of the isotopic composition matches up better with that theory than with the supernovae explosions. That's one of the things we measure the composition—I didn't mention that—but how abundant is oxygen, compared to iron, these things like that, and how do they differ from the Sun. There are some differences that lead us to believe—in fact, we think there are certain kinds of stars, OB stars, that have high winds that are called Wolf-Rayet winds, that would explain our neon-22 versus neon-20 abundance, for example. That's an isotopic thing. We are sort of with our measurements able to comment on where in the galaxy these—or what kinds of places in the galaxy the cosmic rays really are coming from.

For the Love of Bird Watching

ZIERLER: Moving on to a very different topic, not so much on the science, tell me about your interest in bird watching and how this has developed into a tradition at Caltech.

CUMMINGS: Okay! It does have a Voyager connection, actually. Ernie Franzgrote was our liaison for our CRS instrument to JPL. You have to have some go-between help us out with their project management and everything. Ernie was interested in birds, and he was interested in having a bird walk. We knew each other quite well. He came to me and suggested we start walking around, doing a bird walk. I was reluctant a bit, because I have been a bird watcher a long time. It came out of our family. My oldest brother was in the hospital once and got a bird book and that started it in our family in about the early 1960s.. Then there became a competition in the family to get to a certain number of species observed. I didn't join in that so much, but my two brothers did, and they were in it to get to 700 species observed, which is a big number. It's not all of them, but it's a lot of them. It takes a lot of work to get to 700 species observed, in North America. Then my sister came on late, and being the competitor she is, she was the first one to get to 700 [laughs].

ZIERLER: [laughs]

CUMMINGS: Do not count out my sister Carol on anything! We're involved in a Wordle competition right now, by the way, too. We're a competitive family, by far. Anyway, my brother Kermit spread the word about the birds; we all started looking at birds. By the time Ernie came to me, that had been 20 years after I had already been looking at birds. I accumulated quite a list myself, by international travels. The cosmic ray bunch, it's an international group. They study cosmic rays everywhere. When I'd go to these conferences—there was an international cosmic ray conference every other year in some weird foreign place—not weird; great places—and then there was COSPAR every other year, interspersed. So, about once a year, I was racking up birds left and right. I would get 100 birds in Australia, 100 birds in South Africa, and, you know. So I've got a lot more birds than they have, but they don't count those because they're not North American. So, Ernie comes over, and our first walk was in October of 1986 and it wasn't really much of a walk. We took our lunch over to Tournament Park and we sat there and watched what we could see. We saw about four birds, I think. But one of them was a new one on my life list, a Townsend's warbler, which I had not seen. I said, "My god! There's some value to this thing!" Then we got a little more organized and decided that we would walk around campus for like an hour, over lunch, one day a week. That's what happened. We were only two of us for quite a while, and we didn't go exactly every week, because there were things that intervened. But the last many years, I've made it where it's once a week. Not more than that, and not less than that, because my software that does all the plotting and everything, it really works better if there's just one walk per week [laughs]. I treat the data just like I do the cosmic ray data; I plot it up every which way, and it's on the website!

ZIERLER: Are there any particular rare or elusive species that have been especially exciting for you to witness?

CUMMINGS: Actually something just recently happened a couple months ago. In Tournament Park, we have a tree—we call it the sapsucker tree, because we see occasionally—not frequently but occasionally, we'll see either a red-breasted sapsucker or a red-naped sapsucker. But someone recently pointed out to me that, "Hey, somebody said they saw a yellow-bellied sapsucker in Tournament Park." I said, "You gotta be kidding!" Yellow bellied sapsuckers I thought were East Coast birds, or east of the Mississippi. In fact, that was the first bird I put on my life list, it was a yellow-bellied sapsucker in Texas. I was quite intrigued by that, and we did observe the yellow-bellied sapsucker on more than one occasion, recently. That was pretty astounding. There was actually—there have been some news articles. There's a link on my web page to news or something like that. I remember one time I was featured in a Los Angeles Times editorial—editorial!—on the great blue heron that visited Caltech. That guy must have had nothing to write about. I don't know why [laughs] he was writing about that on an editorial page. Yeah, so we got pretty regular. Ernie Franzgrote was really an expert on hummingbirds, and that was his big interest. He wrote a book on them and went to Colombia and South America. There's a wonderful DVD he made with all the different ones, which is just astounding—hummingbirds—really professional job. Unfortunately—I don't know how long it has been now—he died—but he was really the one. We were the cofounders but it was his inspiration that got us started in the first place.

ZIERLER: Has your embrace of binocular technology really advanced over the years? Are you able to see further and further away as the tech has gotten better?

CUMMINGS: No, I think they're all the same technology that has been around for a long time. Usually something like 8x42 is what birdwatchers use. There are a lot of factors that come into what's a good birdwatching binocular. If it's too heavy, if it's 10x50 or something, it is often hard to hold steady. You need a wide field of view to be able to find a bird when you're looking up in a tree. So, there are definitely birdwatching binoculars that are called out. If they're too small, then they're not bright enough, and if you're sort of in the semi dark, then you won't be able to see much. The price varies a lot. [laughs] You can spend $3,000 on a birdwatching binocular if you want to. I haven't done that.

In fact, I have had, in our group, in our Caltech— birdwatching people in the past, there are some astounding birdwatchers that have gone through our little walk. One fellow, he got his degree over in Chemistry or something from a Nobel Prize winner. He gave all that up to go professionally into birdwatching, and leading tours around the world. He also has a job as the guy that, if you're doing a big project and you're going to impact the environment on a big property or something, then they hire him to go out and survey the birds and make sure you're not going to have a problem with rare species or something. That guy was one of the most astounding ones that could identify by sound. I remember the first time he came with us, he called out a MacGillivray's Warbler. He had heard it. He just said he heard it. I said, "MacGillivray's Warbler? What in the heck? We've never seen one of those." I challenged him on it. At that time, he thought maybe I knew something. But it turned out pretty quick that he was the expert [laughs]. We looked up, and we found it! In the tree. I said, "Man, okay, you're my superhero now." There are guys like that, that have come through. This fellow right now in our building, at Cahill—he did quite a few walks, but he doesn't walk on these walks anymore—but he's astounding with the hearing, too. The hearing is really important, and it takes a special talent, because I don't think I have it. I can identify quite a few of the more regular birds that we see, but those guys, they're just clicking them off—"There, there, and there. There's one here, there's one there." It's amazing!

ZIERLER: Because you've been birdwatching for so long, have you detected changes in bird… either migratory developments or bird numbers of particular species, due to climate change?

CUMMINGS: Yes. There have been lots of changes. There's one particular thing, and it applies to yellow-rumped warblers, for example—they are here, they arrive at week 40, and they leave at week 16 the next year, reliably, 100%, within a week or two, plus or minus one, I would say. You could set your calendar by those guys. Then when they're here, they're 100% here. You see them every week. That's the most popular or most frequent bird you'll see during that time. Then there have been long-term trends where we no longer see birds that we used to see. If you go on my website, there are plots that show these trends. We lost the spotted dove a long time ago. It used to be 100% reliable and it went completely away. The black phoebe came on about the same time, went from zero to being almost 100% probable now. I don't know if it has anything to do with climate change or not, but there are definitely long-term trends. Some of it is due to West Nile virus. We lost a lot of sightings of jays and crows and ravens there for a while. They more or less have recovered, but not the scrub jay, for example; it's still down in numbers. Yeah, that is interesting, and it's sort of one of the reasons I can't quit. [laughs] I keep the data going. You just feel like you've got all this inertia built up, and you just—it's not for everybody. I understand that, totally. We see mostly the same birds. We rarely see a new bird. We're up to 128 different species, and typically we see 20 to 30 of those each week. And it's seasonal, much fewer in the summer than in the winter. When they turn off Voyager, maybe I'll turn off the bird walk. [laughs]

Communicating Astrophysical Discovery

ZIERLER: Tell me about presenting for the prestigious von Kármán Lecture Series. What was that like? What were some of the big points that you wanted to convey to the audience?

CUMMINGS: I wanted them to be entertained. I actually have always been thought of as a comedian, throughout my whole life. I was always the silly one when I was the young kid. Always trying to make people laugh. In the von Kármán thing, I wanted to mix some humor with the science, and I felt like I did that. [laughs] The diameter of the antenna on Voyager, for example, I figured out was two Ed Stones and a head, so I called it "two stones and a pebble." That's how [laughs]—that, you know, is about 12 feet, not 12 meters. I think that's sort of semi-valuable information, when you do it that way. Anyway it was a good experience. I'm always very nervous doing these things, but they came across really well, I felt like. I have now done it three times. I changed it up, and one time I did that—the von Kármán is a two-day presentation. You do it once at JPL and then we go over to PCC the next evening and do it. PCC is no longer in it anymore, but I think they come to Caltech, and do it on the second day, repeat. But I had done the one that featured a lot of armadillos in the 2007 one, and people had come to that. Then they came back for the second one where I omitted the armadillos and went in a different track. And they complained! They said, "Wait a minute, I was here for the armadillos!" I figured, well, you already heard about the armadillos; how about something else?" Anyway, in 2007 we had just crossed the termination shock on Voyager 1 so that was new news. The planets are always there. They're always—the old news, but they're still fascinating. All those moons, they're so different. Then the science kept changing. We'd get further out, and now we've crossed the heliopause, so that was a good opportunity to talk about those results in the von Kármán as well.

ZIERLER: Being on campus for more than 50 years, have you had any opportunities either to teach or to mentor students?

CUMMINGS: Well, not teaching. The most opportunities I had mentoring students was during the balloon campaigns that we did. We had undergrads go with us up to Fort Churchill, Canada, spend the summer. I've had undergrads work for me in the lab, particularly on Voyager. There were a lot of those. There was some mentoring there. It has been quite a while, though, since I've actually—I was doing hardware myself, and those things, so I was closer to it. Lately I've been more the project manager type, so other people in the lab are working with students, perhaps, and that sort of thing.

ZIERLER: Moving our conversation closer to the present, when COVID hit, what did that mean for you in terms of working from home? How have you found that to be a workable, long-lasting solution?

CUMMINGS: In March-something, 2020, Caltech dismissed everybody to go work at home. So, we all went to work at home. Now it's after 2023, and so—at first, it was a bit of a challenge, but the IT people in our group—we have a whole IT group that services essentially everybody in Cahill—got me through it and got me working pretty efficiently. Now, it would be inefficient if I would go back, which I very well may, but one of the problems with working part-time there and part-time at home is that I've got a lot of research materials that I need to refer to. I've got a few hundred pounds of documents over here in the corner of my den, and I don't want to have to take those back and forth every day, or something like that. So I've got to figure it out. It's mostly either here 100% or there 100%. I can see possibly going back at—my whole computer system setup is going to be different, unless I just keep with my laptop, which is probably what I'm going to do. I have a whole computer thing that's there. It's totally different. And one of the things I found out is I had all these reminders—it was a Solaris machine, which they're trying to get rid of, because they're no longer supported by Sun, and all the Voyager data analysis on the Solaris machine that I do and some of the other people in my group also rely on the Suns, but we're all trying to be moved off, back to Linux machines or something. I've made some progress along those lines. But I have a Sun Solaris machine right under my desk, which they decided not to turn off, thank goodness [laughs] just because I complained. We're going to keep that going as long as possible, but at some point I'll probably be doing the analysis in a different way. So, it's a question of—I will lose some efficiency I'm sure when I go back, but I may need to. My group is there as well. The people I interact with on cosmic rays, they're next door, and next door down the hall from that.

The Holy Grail of Space Physics

ZIERLER: Now that we've worked right up to the present, for the last part of our talk I'd like to ask a few retrospective questions about your career and then we'll end looking to the future. First, on the science, what do you think has been the most profound discovery that you have both contributed to and you've witnessed to in your career? What stands out in your memory?

CUMMINGS: What stands out is measuring the composition and the energy spectra of galactic cosmic rays in interstellar space. That was actually the holy grail of cosmic ray physics, really, in a lot of ways, especially for the low-energy physics. I mean, the high-energy particles could get in, really high-energy particles, and they're a big part of cosmic ray physics around the world, as well. But as far as our particular energy range we could cover with our instrument, that was the totally new thing that nobody knew what it was going to be like. And so that was the biggest thing.

ZIERLER: Being around Caltech for so long, how has the Institute changed over the years, and what feels the same?

CUMMINGS: The computing has changed over the years tremendously. When I first got here, there was a building on campus with the computers in it, and we had sheets of paper where we put our program together, took it over there, and there were people that punched what we wrote down onto punch cards and then the cards were fed into the computer and we would come back in a few hours and get the results. Nowadays, totally different, of course. [laughs] We don't have to walk across campus at all. I can tell you, if you ever find the movie The Cloning of George Appleby —because I was coming back from the computing center when I was a graduate student—and the campus was mostly a dust bowl at that time. That's one of the big changes is the beautification of campus that has gone on, over the years. I was coming back across, and they were filming a movie, and it turned out to be The Cloning of George Appleby , and they asked me if I wanted to be in the movie, asked me and another guy. We were both coming back from dropping off our cards in the computer. We said, "Okay." So, we were in this movie—we thought [laughs]. They told us what to do, and we did it. But maybe I looked in the camera or something, because I did see the movie later, and I was not in it. [laughs]

ZIERLER: [laughs]

CUMMINGS: I got cut! But that was reminding me—but if you look at that movie, you'll see how desolate the campus looked. It was a mess. There was a fellow that was rich and famous—Stephen Bechtel, I think it was—donated the money, I don't remember how many years ago, but it was for landscaping for Caltech, and they turned it into really one of the more beautiful campuses around. It has grown. It has expanded. That's another thing that has happened over the years. So many new buildings. It seems like there's a new building going up every year, for as long as I can remember. It seems like when a new president comes in, that's his legacy, is getting [laughs] new buildings or something, getting some people to donate for new buildings.

My particular building, I really don't like the outside of it, at all. That was kind of an interesting story itself. We all had to contribute to the design of the new building. I was responsible for making inputs on the labs. We needed to know what kind of electricals we needed, we needed to know the benches, and all this kind of stuff. So, I was interacting with people from the firm that was designing the building. I had seen designs and little models, and "Man, what are they thinking?" But they had interviewed us to get ideas about the building, and apparently the reason it is so crooked—part of it is due to cosmic rays! Part of it is due to an interview they had with me, or others, and they said those lines that are coming down at angles represent particles going through our detectors. And I said, "No. I don't want that." But anyway, I had no choice in it. I did meet the guy that designed the building. He would have meetings every once in a while to give us a progress report, a status update. I remember one famous thing—he thought—I got over there first to the meeting. He came right up to me and he started talking to me like he knew me. I had never seen him before in my life. But he just wanted someone to talk to. We talked a little bit. he was telling me, "Oh, we're 95% there. We're just about done." About that time, some other people showed up, so I moved to the back of the room, waited for the report. He got up and started talking, and at some point, people from the audience could say something, and there was somebody, a professor stood up and made some comment, and finally I just stood up and I said, "I think it's a really ugly building." And, boy, did he take exception to that. He gave me a lecture for about ten minutes in front of everybody about the design, and what did I think about the—there's a museum in Paris that's weird—anyway, there was one there. I said, "Yeah, I've been there. This is just as ugly. It was ugly, too." [laughs]

So I really let him have it, and he let me have it. I don't think it changed anything, because the only thing that this other lady wanted done was change the smokestacks that were on top of the building get rid of them. It made it look like a ship. There were going to be three gigantic smokestack-looking things in the middle. But the genesis of all this cracked, crooked thing, he claimed was the result of different kinds of physical forces fighting each other, and that's why it's all crooked and looked like the earthquake has already struck. That's the part I didn't—in fact, when it was being built, and we would go over there and visit and take a look inside, and it's so crooked inside that we were all getting woozy. We would get dizzy! Because the hallways are leaning, the walls are leaning, you can't even put a picture up vertically. It's pretty strange. But I got over that. The inside's not so bad. It's the outside that really still bothers me. The guy won the Pritzker Prize, for crying out loud, after that. Not from this particular work, I don't think, but he was a famous designer, architect.

ZIERLER: Looking at all of the data you have, all of the work that remains to be done, I wonder if you can convey a sense of just why there's so much data to sift through right now, and what your motivations are, what you hope to accomplish for however long you want to stay involved in the data.

CUMMINGS: There are specific topics that I'm interested in that are not finished yet. There are several papers I've written, a couple papers I've written and haven't submitted yet, because we're trying to work out some other issue that came up. [laughs] I remember just when the COVID 19 happened, and I'm working from home, and I was working with some collaborators on a paper, and it involved something that uses something called the Compton-Getting effect. During the research for that, we realized that something could be wrong with the Compton-Getting effect. We need that effect to be understood, and we need to understand, in order to conclude what we were going to conclude. It had to do with where these anomalous cosmic rays are coming from. We were on the verge—and we still think it's true, but I put that one on hold, and ended up writing—going off and writing a paper about this problem and why it may negate some results of some other papers that have been accepted, but we threw a monkey wrench in that, and we called it No stagnation region at the nose of the heliosphere or something like that. So, we were refuting even our Voyager colleagues who had written papers. The modelers need to know what the flow of the plasma is like in the heliosheath, and we thought they had it wrong. We're still—I could submit that paper tomorrow if I knew exactly how this Compton-Getting effect worked, if it really works the way we think it does. So there's that.

I've got a couple papers in the works right now. One is on the isotopes of galactic cosmic rays in the interstellar medium. We think we have a discovery there. There's a lot more deuterium than the modelers predict, so that should be interesting. I'm working right now on a paper about the observational aspects of cosmic rays in the heliosheath—from where you begin the heliosheath from the termination shock to the heliopause, we're looking at intensity versus time profiles for Voyager 1 and Voyager 2, and they're totally different, and we're trying to understand why they are different. There are different theories about that. That was what I was working on today. It's interesting, because it's something new all the time, and some exciting plots or something, something has an impact on the result.

ZIERLER: There's still discovery to be made is what you're saying.

CUMMINGS: Exactly! We were very surprised to find in some of the first observations of interstellar space—and it was a topic that Ed Stone's last graduate student, Jamie Rankin, took up for her thesis experiment—but it has been found, and not only us but LECP actually were the first people to point this out—was that depending on which direction you look when you're in interstellar space compared to where the magnetic field direction is, you will see a different level of intensity of galactic cosmic rays. Not a big effect. We thought it would all be uniform and everything would be isotropic; it would be the same no matter where you looked. But no, that didn't turn out to be the case. Turns out if you look perpendicular to the magnetic field, you see a lower intensity of galactic cosmic ray at least for ions—not electrons, which is another thing—than if you look in parallel with the field. By like a few percent, 10% or something. We all had the feeling—I did anyway—that once we got past the heliopause, it's going to get boring. There's just going to be the same thing every day. You're just going to collect more statistics. It would be good for the rare cosmic rays—that'll be good—but it wouldn't be anything like what we were seeing in the heliosheath. We're still seeing shocks out there from the Sun that propagate through the heliopause. I would be anxious to get away from that, personally, to go out where it's boring, but I don't think we're probably going to make it. It'll be interesting to see how far a distance the Sun makes an effect into the local interstellar medium.

ZIERLER: Last question looking to the future—if Voyager makes it to 50, when Voyager makes it to 50, what will that mean for you, what will that mean for Caltech and JPL, and what will that mean for space physics?

CUMMINGS: One thing I've felt is that the Voyagers are very popular with the public. I don't hear anyone disparaging the Voyagers mission. It would be good for the public. The von Kármáns I gave were the most packed ones that they had. Over at PCC, they were packed. That was one of the most gratifying things, actually, that happened after one of those von Kármáns at PCC—I don't know how long it was after that, but my car didn't start [laughs] and so, I called up the mechanic that we use over at Accurate Auto, near PCC, right across the street, and he told me what to do and bring it in. I brought it in, and he said, "Are you Alan Cummings? Are you the Alan Cummings that gave that lecture?" I said, "Yeah." He said, "Guess what? I went to it, and I took my daughter"—who was in junior high or something—"and she was not doing well in her grades." And he claimed that I changed her life, and that she came out of that thing saying, "I want to be him. I want to be just like him." She ended up, he claimed, turning D's into A's. I said, "Wow. I made an influence on maybe just one person," but that did make me feel good.

ZIERLER: That's great. [laughs] This has been a great conversation. I want to thank you so much for spending the time. I really appreciate it.

CUMMINGS: Thank you, David.