Charles McGruder (BS '65), Astronomer, Astrophysicist, and Dark Matter Explorer

We know that dark matter exists, but we don't know what it is. Such is the state of play in physics. Advances in gravitational research can yield profound discoveries about the universe and the existence of this mysterious force, while at the same time, our best efforts in theory and experiment have so far yielded basically no insight after decades of effort worldwide.

Charles McGruder is working toward a breakthrough. As he explains in the discussions below, the capacity of dark matter to scatter light - without absorbing or emitting it - must be an important clue to identifying exactly what it is. McGruder is using some of the world's most advanced telescopes in pursuit of this question, and he speaks of his research with a sense of excitement that he is on the path to something big.

Reflecting on his family background, a key theme of McGruder's life is the positive influence of integration. Growing up, his family thrived as members of a diverse community, and this served McGruder well during his undergraduate years at Caltech, where he was one of the very few Black students on campus. Building on his background in theoretical physics, McGruder completed his graduate research in Germany, in part because of his desire to study in the country that birthed the twin pillars of modern physics; namely, general relativity and quantum mechanics. Insisting on an authentic research experience, the indefatigable McGruder wrote his thesis in German. Following his dissertation, McGruder embarked on a road trip through Africa, ultimately landing a lectureship at the University of Nigeria, where he might have stayed for the long term if not for a condition of marriage placed by his future father-in-law, who stipulated that McGruder would have to return to the United States with his daughter if they were to be married.

Comparing his brief appointment at Fisk and his long-term professorship at Western Kentucky, McGruder emphasizes that his childhood experiences ensured that Fisk, a historically Black institution of higher education, would be a short term proposition; it was at Western Kentucky that he has felt most at home. In the area of service, McGruder has been a leading figure in the National Society of Black Physicists, and its commitment to expanding opportunity for Black students in physics has been a mainstay of his career. In thinking broadly about the mysteries of dark matter, McGruder touches on an even more fundamental challenge in physics, and one that has persisted for nearly a century. Quantum mechanics and general relativity must be unified if physics is to provide us a complete picture of how the universe works. Progress toward that end happens incrementally, and McGruder sees his work as another brick in the wall, albeit, he hopes, a foundational brick.

DAVID ZIERLER: This is David Zierler, Director of the Caltech Heritage Project. It is Friday, December 3rd, 2021. It is my great pleasure to be here with Professor Charles McGruder. Charles, wonderful to be with you. Thank you so much for joining me today.

CHARLES MCGRUDER: It is my pleasure.

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

MCGRUDER: I am a Professor at Western Kentucky University, which is located in Bowling Green, Kentucky. That's in the Nashville Metropolitan Area.

ZIERLER: You are a named professor, if I'm not mistaken, the William McCormack Professor.

MCGRUDER: Correct. An endowed chair, it's called.

ZIERLER: Who is or was McCormack, and is there any relation to your work?

MCGRUDER: No, none at all. McCormack was a prominent doctor in Bowling Green. The president at the time, Gary Ransdell, was very interested in having endowed chairs. Before he came in as president of WKU, he was a fundraiser for another university, so he was very much interested in fundraising, and he wanted to have endowed chairs. He approached prominent people that he knew who would support an endowed chair. I'm the first person to get it, and I've had it for a number of years. It's actually a very good thing. As you well know, there's not a higher honor that a university can bestow on a professor, so I'm very pleased.

The Search for Dark Matter

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

MCGRUDER: Interesting question. You're not an astronomer?

ZIERLER: No.

MCGRUDER: Let me give you some background. It's an amazing thing, what I'm going to say. Human beings have been on this planet for—homo sapiens for at least 300,000 years. We've always been looking at the stars. We've been observing with telescopes since 1609. But what started to become clear starting in 1933, when a German who worked at Caltech—not at the time, though; he came to Caltech later—Fritz Zwicky—discovered that there's missing mass in the universe. There's mass we don't see, but it's there, because we see its gravitational effect. That was in 1933.

For decades, every once in a while, somebody would come up with something. It wasn't until Vera Rubin in the 1960s and a colleague—I don't remember the colleague's name—were able to prove that this unseen matter actually really truly exists. It's called dark matter. For four decades approximately, people have tried to detect dark matter in the laboratories. No success. Physics has a model of elementary particles called the Standard Model and dark matter is not included. It's a highly mysterious thing. Nobody has ever detected it in the lab. Nobody has ever detected it in astronomy, except through gravitation. People say, "Well, it doesn't emit light. It doesn't absorb light." But what I've been able to discover is that it actually scatters light. The fact that it scatters light gives us a way of seeing it at least in astronomical observations. That's exactly what I'm doing now.

ZIERLER: You're doing this observationally, or theoretically?

MCGRUDER: I'm using observations, but my deductions are all theoretical. It's based on observations, but there's a lot of theory in it.

ZIERLER: What are some of the telescopes that are most relevant for the observations that you're relying on?

MCGRUDER: I use two space telescopes, one called Gaia. The other is called WISE. Then I use a ground-based telescope called Sloan Digital Sky Survey. So I'm using three telescopes, two space- and one ground-based.

ZIERLER: Are you optimistic? Of course, discovering dark matter is one of the golden eggs in physics and astronomy. Do you think this is a really promising path toward truly understanding what dark matter is?

MCGRUDER: Yes. Well, you're the first person I've ever told! [laughs]

ZIERLER: Wow, I'm honored.

MCGRUDER: I've never told anybody this. Except I've submitted it, and I've gotten feedback, and I'm responding to the referee.

ZIERLER: When you say that it scatters light, what does that mean exactly?

MCGRUDER: Let me give you a good analogy. Leonardo da Vinci, around 1500, asked the question, "Why is the sky blue?" Nobody knew for almost 400 years until the end of the 19th century when Lord Rayleigh was able to show that the reason the sky is blue is because of how molecules scatter light. Scattering means that the direction of light is changed. You have the sunlight that comes in through the Earth's atmosphere, it hits the molecules in the Earth's atmosphere, and the molecules change the direction. It turns out that this scattering is inversely proportional to the fourth power of the wavelength. What that means is that blue light is scattered much more than red light. What happens is the blue light that comes in from the sun is scattered in all directions, and then it comes back, primarily from above, and you have the impression the sky is blue. But really it's due to the fact of how the molecules of the Earth's atmosphere scatter light. Am I making sense?

ZIERLER: Absolutely.

MCGRUDER: Good. What I'm saying is that dark matter particles do not absorb light, they don't emit light, but they scatter light.

ZIERLER: How can they scatter light if they don't absorb or emit light?

MCGRUDER: I don't really know the answer to that question. My suspicion is that the scattering may not be electromagnetic. It may be a different thing. But I'm not sure about that part yet. That's actually what I'm working on right now, trying to figure that out.

ZIERLER: That's exciting.

MCGRUDER: Oh, it's very exciting.

ZIERLER: Because you operate in this world, because you're a stakeholder in both ground-based and space-based astronomy, it's hot off the press—have you had a chance to look over the National Academy decadal report, and do you have any takeaways from it?

MCGRUDER: No, I have not looked at it, and I have no idea. I can't say anything to that.

The Positive Legacy of Integration

ZIERLER: Let's take it all the way back to the beginning. Let's start first with your parents. Tell me about them.

MCGRUDER: My father was a doctor. My mother studied I think sociology. They met at Howard University, which you may know is called the Black Harvard—it used to be called that—when my father was in medical school. My mother was born in Baltimore but raised in Philadelphia. My father, because of the segregation in the South, did not want to go back to the South, so he went to where my mother came from, Philadelphia. Basicall,y he worked there in Philadelphia at the Black hospital, and eventually moved into a suburb of Philadelphia called Bristol, Pennsylvania. I was born in Philadelphia in that Black hospital and raised in Bristol, Pennsylvania.

ZIERLER: Did your father practice medicine when you were a kid?

MCGRUDER: Oh, yeah, he was a practicing physician. He practiced medicine until the very end of his life. He was like me! [laughs]

ZIERLER: What was his area of specialty?

MCGRUDER: No, specialties were not so common in those days, so he was what you would call a general practitioner. I guess today they call it a family doctor.

ZIERLER: Did your mom work outside of the home when you were growing up?

MCGRUDER: The first two years. The answer to your question is actually no, but she worked the first two years until I came along, and then she stopped working, which was typical in those days.

ZIERLER: Did your father ever talk about escaping segregation from the South but coming to the North, that doesn't necessarily mean escaping racial problems, of course. Did he ever reflect on the differences in his experiences?

MCGRUDER: In the North, it was much, much better than the South. Let me tell you one thing that he said. First of all, my father always went on vacation every year abroad, and he said that Blacks are only treated properly when they're abroad. He also insisted always on traveling first class. That was extremely important to him. So yes, he was aware of the problems here, very much so. But he was a prominent doctor, and how can I say it? Let me just say something that sounds very strange, but he claimed that 95% of his patients were white. My success is based on my father's success. My father's success is based on integration or lack of segregation or whatever you want to call it. I can't—how can I say this?—I can't in any way personally be negative when it comes to the racial thing. That comes from my father and my mother. Their best friends were white. That's the way I grew up! And that was true for me, actually, because I went to school with basically all whites. Not completely, but I was the only academic in my class who was Black. It was not a private school. That was one of the big decisions, by the way, my father made—whether to send me to a private school or not. Anyway, I'm 100% for integration, because that's what I am. I don't know how to say it.

ZIERLER: You grew up in Bristol your whole childhood?

MCGRUDER: No, Bristol Township. My father practiced in Bristol, but I grew up in Bristol Township. My first few years were in Bristol itself because above the office, he had an apartment, and that's where I was the first few years. I'm not sure, maybe the first three years.

ZIERLER: Were you scientifically inclined even as a kid?

MCGRUDER: That's an interesting story. I think the answer to your question as you posed it is no, but there's a history to this. Let me just start with the sixth grade. Actually, let me start earlier. I told you my father and my mother always traveled abroad for vacation. When I was maybe 12, maybe 11, we went to Mexico and spent a few weeks in Mexico. I remember going to Mexico City and we went to a bookstore. It was an English bookstore, and they had English books. My father said, "You can have any two books you want." I bought two books. One was called The Rocket Pioneers. The other was called Flying Saucers by Donald Menzel. So I obviously had a history of science that went back to that time.

Then when I got to sixth grade—I don't remember how old I was in sixth grade, so my stories may be a little bit confused—when I got to sixth grade, I had a teacher called Mr. Fricke. We didn't have enough science books for everybody, so what he did, he had a student called Robert Flanagin read from a science book. I thought it was horribly boring, just terrible, and so I was turned off from science. Now looking back I understand that my teacher didn't like science and because of the way he handled that situation, had turned me off. When I got into seventh grade, I fell in love with archeology. I just thought that was so interesting! I wanted to be an archeologist for about six months. Then after that time, I really understood, "Archeologists dig in the dirt!" [laughs] That's not what I wanted to do! [laughs] At all. So I joined the Astronomy Club and I've never looked back. [laughs]

ZIERLER: When John F. Kennedy announced that they were sending a man to the Moon, do you remember that? Was that exciting to you?

MCGRUDER: The answer is yes, very exciting. I always told myself, and this is really not fair what I'm going to say, but I told myself, "Well, if I can't be a scientist, I'm going to be an astronaut." [laughs] Not understanding how tough it is to be an astronaut! My son now wants to be an astronaut so [laughs] I now know firsthand how tough it is!

ZIERLER: In high school, did you really stand out in math and science?

MCGRUDER: Oh, absolutely. There's no question about it. I can remember, for example, my geometry teacher, Mr. Ackerman. I would go and ask him really deep questions about geometry. He thought I was stupid! [laughs] Then I was getting all these A's. He didn't understand that the questions were really deep, trying to understand what geometry was really all about on a very deep philosophical level. He didn't understand that. He wasn't on that level at all. But when I performed so well, he said, "Honestly, I didn't think you were bright, but you really are."

I can remember my trigonometry teacher, Mr. Thomas. He was the basketball coach. I felt, and the Blacks that played for him in basketball which were the majority of the team, we all felt the man was prejudiced. I think we had an advanced math class, I think it was called. One day, he put a problem on the board, and he said, "It's a very difficult problem." I just went up to the board and solved it. He said, "I can't stand smart people." That's what he said. I knew what he meant was, "I don't like Blacks who are smart." So yes, I was good in math.

The Path to Caltech

ZIERLER: Charles, when it was time to start thinking about colleges to apply to, who was it that told you that a place like Caltech was in range? Did you recognize it yourself? Was it a teacher, a guidance counselor, your parents? What made you think to apply?

MCGRUDER: I was in tenth grade. I had never heard of Caltech. I'll use the Caltech term—a troll. I don't know if you know that term?

ZIERLER: Yeah.

MCGRUDER: You do, okay. A troll by the name of Roger Kaplan was already in the tenth grade looking at colleges. He came to me, because he knew I was good in math and everything, and he said to me, "This is the best school in science in the country. Caltech." I told him, "I've never heard of it." He said, "Well, here's the freshman brochure." I looked through the freshman brochure and I saw a picture of the Caltech freshmen. I closed the book, gave it back to him, and said, "I don't want to go there. I want to play football!"

A year later, in the 11th grade, I started getting serious about college. I made the decision, "I don't want to play football. I just want to concentrate on being the best scientist I possibly can." I remembered, "Oh, Caltech is the best school." Then I started gathering info, and it was true, so it became my dream school. But there's a story behind it. I told you that when I was 11 or 12 or something like that, I bought these two books in Mexico. One was called Flying Saucers by Donald Menzel. So I fell in love with Harvard, and I wanted to go there, since that time. When it came time to apply to college, I lost interest. Caltech became the school I wanted to go to, but I didn't think I had a chance to get in.

I applied, and they said they would let us know in March. The letter came in March, and my parents got it. My father knew I was applying and everything. He gave me the letter. I said, "Thank you." I went to my room and I put the letter on my desk. My father said, "Aren't you going to open it?" I said, "No." I'm skipping back; that's when he gave me the letter. I said, "No, I'm not going to open it." I went and put it on my desk, I got back in order again, and I went downstairs. I was sitting downstairs in front of the TV. Because I knew it was a letter of rejection, and I had been dreaming about this so much, so intensely, about going to Caltech, I didn't want to let that dream die, so I wasn't going to open the letter. Why should I open the letter and get rejected and then the dream is gone? But I could still dream, as long as I didn't open the letter, so I didn't open the letter!

Then after 20 minutes, it suddenly hit me, "Wait a minute, that letter was thick! If it's a rejection, why are they sending me a thick letter?" [laughs] I ran up the stairs, I opened it as quickly as I could, and I was accepted! I couldn't believe it. I ran in to my parents and told them! My father said, "Would you please give me the letter?" I was baffled. Why did he want the letter? Later, my mother explained to me, "Well, it's a big thing for him, too, because he's going to pay for it, and it means a lot to him, and so he wants to have time after his office hours just to look at it by himself." And I understood.

ZIERLER: Was it always going to be physics and astronomy for you? Is that what you wanted to study from the beginning?

MCGRUDER: Yes, but not the astronomy so much. I wanted to be a theoretical physicist. I first started in physics, but I did not do well. I liked astronomy too, and so I was told that I could take astronomy, become an astronomy major, and take all the physics I wanted, but it didn't matter if I got poor grades, because all they cared about was astronomy. That's what I did. There were a couple instances like that in my life that led me to be an astronomer. That was one of them. I got my bachelor's degree in astronomy.

ZIERLER: When did you arrive at Caltech? Was it 1961?

MCGRUDER: Yes.

ZIERLER: Were there any other Black students on campus at that point?

MCGRUDER: The answer was yes. There was a Black physics graduate student who was from Jamaica. He was the only Black that I ever saw on campus at that time. He stopped me somewhere along the line and offered to help me if I ever needed any help, but I never really hooked up with him.

ZIERLER: Now from your upbringing, how integrated it was, I assume you were not fazed by this when you got to Caltech? You were used to this environment?

MCGRUDER: Not at all fazed. My whole classroom experience was totally white up to then. When I got to Caltech, it was the same as I had experienced before. It didn't faze me at all.

ZIERLER: Who were some of the professors who really stand out in your memory, either who gave great lectures or who served as a mentor to you?

MCGRUDER: I'm going to expand what you just asked. The biggest mentor was Edwin Munger, who by the way was in history. I've always been drawn to history. I'm fascinated by it, and it still is one of the things I love. I read a lot of books on history, period. My cousin is a well-known historian and I've read most of her books and so many other books. History is something that absolutely fascinates me, but it's not something I would want to do for research. With his background, Munger, who was an expert in—I don't know if you've ever heard of him? Probably not.

ZIERLER: Sure.

MCGRUDER: Oh, you have! Okay, good. He was a very liberal-orientated person and took an interest in me. He was also interested in Africa, which I was interested in. We just gelled. If anybody was my mentor, that was him. Of course he's not a mentor in terms of science, but just in general. He really enriched my Caltech experience, very much.

Quasars Then and Now

ZIERLER: Scientifically, in physics and astronomy, what were some of the really exciting things that were happening on campus when you were there?

MCGRUDER: The discovery of quasars by Schmidt. I didn't really understand it, but even as an undergraduate, I heard about the discovery, the momentous discovery. Believe it or not, in the research work I'm doing right now, I'm using quasars!

ZIERLER: Wow, that's great.

MCGRUDER: It's all about quasars, and how quasar light is being scattered by dark matter. [laughs] But there's another thing I wanted to tell you. I knew who Fritz Zwicky was. I'm not sure if I knew about dark matter at that time, but I remember coming down the steps. He had his office in the basement of Robinson Hall. I remember coming down the steps, and his office door was right across from the steps. His door was open. I came down the steps, and he saw me, and I saw him. We stared at each other for some seconds. I think I was the one who broke it up, but then I just continued where I was going. Now that I'm working on dark matter, now that I believe I've made this discovery, I have remembered that incident. Here is the man who discovered dark matter, that it exists, and here I'm someone who may make a significant contribution to understanding what it is.

ZIERLER: Amazing.

MCGRUDER: So, wow! [laughs]

ZIERLER: Did you feel at Caltech that you were valued or that diversity was something that was important and it was great to have a Black student at Caltech interested in these things?

MCGRUDER: The answer is no, not at all. There was no affirmative action. There was no feeling that diversity is important. There was nothing like that. Which in many ways was very positive. It's positive because—take Clarence Thomas, the Supreme Court justice. He said he does not believe in affirmative action. I understand where he is coming from, although I am not of his opinion. Where he's coming from is, because affirmative action, what happens is the majority community often feels, "Oh, that Black is not as smart as we are. He's a token." Or she's a token, whatever. There was none of that for me at all. I was just as smart as everybody else, in terms of how my fellow students supported me or interacted with me.

ZIERLER: Because there was no affirmative action, everybody just assumed that you got there on your own merit like anybody else.

MCGRUDER: Exactly. That negative feeling that whites have towards Blacks, and that Blacks feel themselves that's internalized—taking special courses and all that other kind of stuff to bring them up to speed—I had none of that. In that sense, I was blessed.

ZIERLER: On the flip side of that, were you ever made to feel excluded, or did people assume that you were staff, or that you didn't look like you belonged at Caltech? Or did you not feel those things, also?

MCGRUDER: Let me start with a counterexample. I was in Ricketts House, and one of the people in Ricketts, a freshman by the name of Austin, he kept saying, "I don't belong here. I'm not smart. I'm not as smart as everybody else! I don't belong here." He kept saying that. After the first term, he left. He really truly felt that they made a mistake by admitting him. He just couldn't take it. He left. I never felt anything like that. The important thing is interacting with students, because they're your colleagues. You don't interact with professors very much.

The only thing I remember is we had something called a brake drum. You probably have never heard of it. What it is, it's a metal drum, and it's hidden somewhere, and when it's discovered—I think there's a limit where it can be; I don't remember all the details now. When it's discovered, then there's a fight between I think the freshman class and the sophomore class or something like that. I don't remember all the details. You go out on a field, and it's muddy and everything. It's part of the whole thing. Because I was very athletic, in my class, I was the mainstay. Nothing happened unless I was there. But yet when it came to the leadership of deciding where to hide the brake drum that the leadership was holding, I was excluded. I felt it then, and now looking back, I feel that was a part of racism. It was never out-spoken. It was never negative—"You don't belong" or anything like that. But I think that was the culture of the day that the students were following. "Blacks can't lead." Or shouldn't lead. That's the only thing, looking back, that I really feel—and maybe those who were there would interpret it differently, but that's kind of how I feel it was. Otherwise I don't remember any negativity from my fellow students.

ZIERLER: From a broader national perspective, in the early 1960s, as the Civil Rights Movement was ramping up, were you politically engaged at all? Were you following what was happening?

MCGRUDER: You could not not follow. It was on TV. It was everywhere. I can remember walking on campus and thinking, "Should I give up my studies and go and help?" I asked myself that question and the answer was, "No. Absolutely definitely no. I'm not going to do that. I'm going to try to be the best scientist I possibly can. That's what I need to be doing. That's going to be my contribution." And I haven't changed. I still feel the exact same way then as I do now!

The Fundamentals of Physics in Germany

ZIERLER: In terms of the science, in terms of your interests, you came in with an interest in theoretical physics, as you said. How did your interests evolve over your four years at Caltech?

MCGRUDER: It didn't change. That leads to another story, a second story about how I ended up being an astronomer. This is an amazing story. I decided to do my graduate work in Germany. Eventually I got to Heidelberg. How I got there is really not important. I didn't know anything. I didn't know where the Physics Department was. I wasn't even interested in astronomy. I wanted to be a theoretical physicist. I ran into an African in the cafeteria. I somehow asked him, "Where's the Physics building?" He said, "Oh, I know." He took me to the Physics Department. I went to the Department and I asked some secretary, "I'd like to become a physicist." She said, "Oh, you need to talk to Dr. Hauser." I went to him. He spoke English very well, as most Germans do. I told him what I wanted to do, and he listened and everything. We had a little conversation. Then he said to me, "Where did you go for your college?" I said, "Caltech." He said, "I know you!" I couldn't believe it. He said, "I know you!" He told me that he was at Caltech, and he knew me from the Feynman lectures. Because other people used to attend the Feynman lectures. I think you've heard of Feynman, right?

ZIERLER: Yeah. [laughs]

MCGRUDER: Okay, good. I guess he was there as a postdoc or something. I don't know. A lot of people used to go there who weren't in that class. Actually professors went there and also postdocs. Feynman teaching fundamental physics was a big thing. So he knew me. I was shocked out of my wits. I just couldn't believe it! [laughs] Oh my god, how could somebody know me? Then he really got serious about me studying in Heidelberg and everything. Somewhere along the conversation, he said to me, "What did you major in?" I said, "I majored in astronomy." Why did he ask the question, when I told him I wanted to be a physicist? He then said, "Oh, I know the director of Astronomy here in Heidelberg. He's looking for students. I'm going to call him up. Come back the next day."

That's what he did. He called him up. I came back the next day. He told me where to go, and I went there, and the professor was expecting me. We talked, and he said he had to see what I could do. He said he wanted me to work on different research areas to see what I liked, but he said I had to give a class, because he had to see—I may be getting the sequence wrong. Maybe he said I had to give a lecture. It was typical in Germany that a student takes a research topic and gives a lecture on it. I think that's what happened first. I said, "Yeah, I'll give a talk."

It was an astronomy series. I had a number of subjects to choose from. I chose cosmic rays. So I gave a talk. I can't remember how long it was after our discussion, maybe a month or so, something like that. I gave the talk. After that, this professor stood up, turned to the audience and said—I gave the talk in German—he said, "McGruder has only been in Germany for one year." I felt so bad, I thought I did really badly, everything else. Turned out everybody was totally impressed! [laughs] Totally impressed with my knowledge of Germany, with my knowledge of cosmic rays. He said to me, "When do you want to start your PhD? What I want you to do is to go to certain areas to see what you really like." So it opened a door to me. Caltech opened the first door, with this guy who hooked me up, but he hooked me up with astronomy. I wanted to be a physicist! It's amazing.

ZIERLER: By the time you graduated from Caltech, did you specifically know you wanted to study abroad for graduate school?

MCGRUDER: Yes. It was in my sophomore year, third term, I was walking down campus and walking up the steps to Dabney. Dabney was on the right. It hit me—go to Germany, get your PhD, then go on and spend the rest of your life in Africa. That's what I wanted to do. My basic philosophy is, "Life is there to follow your dreams." That's exactly what I did.

ZIERLER: Why was that your dream, ultimately, to live and work in Africa?

MCGRUDER: I didn't like the racial tensions in the United States. It made me feel—I wasn't fully accepted, I wasn't fully respected, I wasn't—socially, more than anything else. I just did not want to live in that environment anymore. It was just time to go. So it was very important to me to get out of the country. Remember what I told you that my father said—"A Black man is only respected when he's abroad." So that was—I had to go. I didn't even apply to any graduate schools in the country. I was not interested in staying in the country. I was going to get out. I was going to do what I did.

ZIERLER: Was it Germany specifically, or graduate school in Europe?

MCGRUDER: No. Germany. Modern physics is based on only two theories, the theory of relativity and quantum mechanics. Both of these theories were developed in Germany. All the original articles were in German. That goes back to something else. You talked about a mentor. Now, before I started at Caltech, after getting admitted, my father and I flew out to California. We went to Caltech. Then we flew to San Francisco because my father's sister lived in Oakland. Now, my father's sister had a daughter. I just mentioned her a few minutes ago. I said she's a well-known historian. Because you said you're in history; that's why it came up. She was a student at the University of California Berkeley, and she threw a party for me. At that party, there was a Black graduate student by the name of Irvin. That was his first name, and I remember it because my cousin's last name was Irvin, so I couldn't forget it. He was at the party. My cousin was a historian so most of her friends were that kind of type. There wasn't anybody in science, but he was a math major, a graduate student in math. We talked. He said to me, "The way to learn science or math is to read the original articles."

I knew nothing about all this stuff. He was living in the same building as my cousin. My cousin had an apartment there, and he had an apartment, too. He went up to his apartment, brought down a math journal and showed me. That stuck. "The way to learn is to read the original articles in journals." That was the background of why it was important for me to go to Germany, because that's where modern science originated. That's where both relativity and quantum mechanics came from. I needed to learn German and read this stuff in the original language.

ZIERLER: Where did you first arrive when you got to Germany?

MCGRUDER: Berlin. Lufthansa had a program by which Americans could go over and work in Germany. They facilitated that. I got a job as a construction worker in Berlin for the whole summer. It was very nice! [laughs]

ZIERLER: Was the draft something that you needed to deal with, or did you get a deferment?

MCGRUDER: That's another interesting story. My local draft board issued me a—was it called 1A, used to be, where they would draft you. I protested and they rejected it. Then they said that I had interrupted my studies because I spent my first semester in Germany learning German, and not in my studies. Which is another story in itself. But they said I interrupted my studies which I was not allowed to do. They rejected it, and I was going to be drafted. But then I appealed to the state selective board, or whatever they called it in those days, and they understood that you can't study in Germany without learning German. They didn't consider the interruption of my studies, and so I was not drafted. There was a term for it. I don't even remember what it's called anymore. So no, I didn't have to go into Vietnam. It would have been a horrible experience if I did. But no, I was deferred for the whole time.

ZIERLER: Once you got your bearings in Germany, were your experiences in accord with your father, who said that Blacks were treated better abroad than they were at home?

MCGRUDER: I think the answer is yes. I had a very good life in Germany. I enjoyed it immensely. After a year or two, I had a German girlfriend, and we stayed together for many years. I was really very comfortable. I loved Germany. I knew I couldn't stay. I didn't want to stay. It was never planned for me to stay. So I moved on, and went to Africa, as I told you I planned to do. But yeah, I enjoyed my Germany experience. Even today, it means a lot to me. I did a lot of reading in Germany. All the books I read were in German. I got up to 40-some books a year I was reading, everything in German. Even today, I will read one book in German and one book in English. What this means is since I read so many books in Germany when I was there, I have read more books in German than I ever have in English. My scientific notes, they're all in German, because that's where I learned to research, in Germany. I'm obviously not German, but in a sense I'm a German scholar, because I'm imbued with the language.

ZIERLER: Tell me about developing your dissertation at the University of Heidelberg. How did that play out?

MCGRUDER: First of all, the professor, Professor Elsässer, wanted to talk to me about it. He said, "Oh, I guess you're going to write your thesis in English." Somebody from Finland had just done that, gotten permission to do it. I said, "No, I want to write in German." And I did. That was the culmination of my German experience. It was very important to me to write that in German. He smiled. He was very surprised, but he smiled. He was happy that I wanted to do that. For me, the writing of my thesis in German was really an important part of my accomplishment, so to speak. I don't know if I'm answering your question.

ZIERLER: Yeah. Was the theoretical physics background an asset in working in astronomy as a graduate student?

MCGRUDER: The answer is no. However, it was very important when it came to the examination. Now, in Germany there is no undergraduate degree in astronomy. There's no master's degree in astronomy. The only degree is a PhD. It makes sense because you can't be an astronomer without being a physicist. Modern astronomy is astrophysics. But it turned out that many of the PhD students had done very poorly in the examination. The way that works is they don't have like the American system where you constantly take exams. What they do, they have an oral exam at the end. The oral exam consisted of astronomy, math, and physics. There was a problem, because the astronomy students were not doing well in physics and math. I was told, "Look, this is a challenge. It's a problem for them. It means that basically the astronomy professors have to beg the other professors to let them pass." And all this and that. It was a pretty uncomfortable experience for the professors, so I was worried about this.

When I took the tests, particularly in physics, the physicists would ask questions, and I'd answer the questions, and then he started going on stuff that was beyond. I answered a couple of them, and he was impressed, so he started asking even more difficult questions. There was one question, I knew the answer, but I had no idea where the answer was coming from, so I said, "No, I don't know." Then he said, "Oh, it's this" and I knew it. Afterwards, both he and the math professor said that I did extremely well, and they complimented by astronomy professor, so he had no problems. Unfortunately, I did badly in astronomy, but [laughs] that's another story. But they had already recommended I get my PhD, so they couldn't change anything! [laughs]

ZIERLER: What were some of the exciting things happening in astronomy when you were a graduate student, and how did you see your research slotting into those bigger questions?

MCGRUDER: Big things were happening in Germany at that time. The way German physics works is they have these Max Planck Institutes. I don't know if you've ever heard of them. They're very prestigious and well-funded. There was nothing in astronomy! The Germans did not have a reasonable telescope anywhere. My professor got permission to form a Max Planck Institute of Astronomy. People called him then the Optical Pope [laughs] because he was the leader of German optical astronomy. Germany then bought a whole mountain in Namibia, which used to be a German colony, where they planned to put a telescope. The Max Planck Institute was formed.

There was already a Max Planck Institute of Nuclear Physics in Germany, and so I did my PhD work there. Since we were becoming, Max Planck Institute of Astronomy, they gave us a whole section or a whole room or something. I can't remember exactly which. I used their computer. So I was there at a time when astronomy in Germany was really building up. That was so exciting. My research work was not particularly associated with that, but it was in optical astronomy. It was something that my professor wanted, so in that sense, it was, but only in a broader sense. But I was lucky to be in Germany at a very exciting time, when they were building up in astronomy.

Road Trip Through Africa

ZIERLER: When you successfully defended, of course Africa is a very big place. How did you narrow down where you wanted to go?

MCGRUDER: That's another interesting story. My brother and I always had a dream of traveling through Africa. After my PhD, we traveled to England, and we went to the factory in Solihull, which is right outside of Birmingham, and purchased a brand-new Land Rover, which is a British Jeep. We got it cheaply because they were trying to sell cars and there were no import taxes, all this stuff. We spent two years traveling through Africa. I went back to Germany, and I worked on my publication. I got three publications out of my PhD. The first had already gone, and I was working on the latter two. My brother fixed up the Land Rover for a safari, Jerry Cans and all that other stuff. When I finished, we traveled through Europe, then traveled across the Mediterranean to Morocco, and traveled through the coast to Algiers, went down through the Sahara Desert into Africa. Then we eventually got to West Africa and we traveled through Central Africa to East Africa. After two years of that, I went back to Germany and did my own postdoctoral work.

ZIERLER: By own, what does that mean? You were independent? You were not affiliated?

MCGRUDER: I was independent. Nobody was supporting me. What happened was we sold the Land Rover for one and a half times what we paid for it. We split the money in half, and that money survived to support me for over a year in Germany. It was very fortunate.

ZIERLER: What did you focus on for your postdoc? Was it an expansion or a refining of your thesis, or it was new research?

MCGRUDER: No, I wanted to be a theoretical physicist, so I taught myself general relativity and got out a paper in Nature on the principle of equivalence. I just followed through on my dreams. I mean, that's what life is for! [laughs]

ZIERLER: At that point, was there a fork in the road, whether to return to Africa, stay in Germany, or go back to the States? What were you deciding?

MCGRUDER: No, no. Remember, when I was a sophomore at Caltech and I was going up the steps at Dabney, I said I was going to go to Germany to get my PhD and spend the rest of my life in Africa. "Let's follow through on that." I had applied for a position at the University of Nigeria, and I was waiting for a visa that whole time that I was doing my postdoctoral work. There were ups and downs but I eventually got it and went back. I taught at the University of Nigeria for like 15 years or something. I can't remember. Let's see, I went there in 1978 and I left in 1989. That was over a decade, anyway.

ZIERLER: Tell me about the University of Nigeria.

MCGRUDER: Yeah, okay! [laughs] One of the purposes of the Africa trip, another primary purpose, was to look for a place for me to work. I didn't know anything about Africa and certainly not anything about astronomy in Africa. In every country we went to, in English-speaking countries, I would go to the university and try to find out if there's any astronomy, if I could teach there, starting in Liberia, because we eventually went up the coast of Liberia. I just kept going to universities. I kept hearing the name, "Oh, astronomy is in the University of Nigeria. Professor Okoye." I kept hearing that name.

When we got to Nigeria and we went to this university, which is called the University of Nigeria—I can remember my brother and I driving in our Land Rover, and we went up high into the mountains, or hills. I don't know what you call them. Then we got on campus, and my brother said to me, "This is for you." He said, "It's nice and cool, because it's high. And look at all these beautiful girls." [laughs] Igbo girls are very pretty! [laughs] It turned out that Professor Okoye, who was the name I had been hearing, he couldn't believe it. Here's this American astrophysicist coming out of the desert! [laughs] And he had nobody to work with! He was so happy to have me, of course, to have me come. But there was a problem with all the visa stuff and everything else, so I couldn't start then and there. I wanted to continue my trip anyway. I think it took over a year for me to eventually get it. One time, they even retracted my visa. Oh, it was a whole bunch of stuff. But I came back and I stayed there for quite a few years.

Professorship in Nigeria

ZIERLER: Charles, being on the faculty at the University of Nigeria, how well-connected did you feel, or not, to the broader world of physics and astronomy?

MCGRUDER: I was totally disconnected. We had no current journals. There was no internet, of course. What I would do to do my research work is—part of the contract is either every year or every two years, I'd get a trip back home, which they paid for. I don't remember which, now, but I ended up going every year anyway. I would go back to the U.S., stay at home, and go to Princeton, and work in Princeton Library all summer long. That's how I kept up with things. But I was very comfortable in Nigeria, in the sense that being a lecturer was a high position. It wasn't financially plush, but I had a vehicle, I had an apartment that was paid for by the university. I was comfortable.

ZIERLER: What was the research that you were doing back at Princeton and what you were able to bring back with you to Nigeria?

MCGRUDER: The answer is I taught myself general relativity, Einstein's theory of general relativity. I continued that research work at the University of Nigeria and got out another publication. That Princeton thing was really important to me, because I was able to at least every summer to keep up with things. I continued with my studies. I did not publish a lot, but that didn't mean I wasn't thinking about things, and wasn't really involved. Research-wise, I eventually went off on a tangent that didn't work. But I think I was okay. Somehow, psychologically, it was really very comfortable.

ZIERLER: Of course, general relativity, there's a hotbed of activity at Princeton during these years. Did you interact with anybody, or that was just a convenient place for you to do your research?

MCGRUDER: Nobody. Absolutely totally nobody. I was happy one day, since I was there all the time in the library, when one of the librarians invited me to lunch. To me that was the biggest thing that I had at Princeton. I did not interact with anybody.

ZIERLER: People like Bob Dicke, John Wheeler, did you try, or you weren't interested? I eventually did meet Bob Dicke, but it was through German friends and I spent about 20 minutes in his office and we did not talk about science. Clearly, he was uncomfortable.

MCGRUDER: I didn't know them. They didn't know me. Because of my background, I have got to the point I can't work with anybody. My son now, who is a graduate student at Harvard in my field, astronomy, we were talking about this recently. I told him, "I can't work with anybody." I've been alone all these years. I'm just incapable of doing anything with anybody! I'm exaggerating, because if you look at my publications, you'll see there are publications with other people. But that's very different than my core work. My core work is always alone.

That's true even today. Like I just told you, this paper I'm working on now, you're the first person I've ever talked to about it. I've told my son about it. I did forget that. I did tell my son about it. But apart from that, nobody else knows anything except the journal and the referee. That's the way it is with me. If I'm doing other stuff, something on the telescope or something like that, of course you publish with your colleagues. My real stuff that I'm interested in is always by myself.

ZIERLER: Going back to this idea of being an undergraduate at Caltech and having a dream to live in Africa without having a very clear sense of where you might be or what that might look like, to the extent that there was some racial utopianism or dreaminess to your vision of living in Africa, as you said, you were comfortable living in Nigeria. How closely did your experiences accord with what undergraduate Charles was dreaming of when you first had this idea?

MCGRUDER: Professionally, it was in many ways a very positive experience, because I was totally free to do exactly what I wanted. I was very valued in the department, both as a teacher and as a research person. In particular, the astronomer who hired me, Professor Okoye, eventually built up and had graduate students and really built up a major center. I was well respected.

But there's something more to life than that, and that is social. To the average Nigerian, I was a foreigner and a white man. Now, I need to explain that. I'll tell some stories. The first story is when there's a new professor there, or lecturer, they call them, people will come and always want to sell you stuff. So this one person came, and he wanted to sell me insurance. He was describing the insurance, and he said to me, "Other white men buy this insurance." I said, "Am I white?" He said, "Yeah." I was shocked out of my wits! [laughs] I said to him—I took a picture from my self—it wasn't on my desk; it was on my bookcase or something. I showed him the picture. I said, "Is this man white or Black?" "Oh, he's Black." I said, "That's my grandfather!" I took another picture, and I said, "Is this man white or Black?" "He's Black." I said, "That's my father!" [laughs] He didn't know what to say.

I was totally confused by this. I went to a physicist in the department who got his PhD in physics at the University of Nigeria. I knew he hadn't traveled abroad. I went to him, and I said—his name was Pius Okeke. I said, "Pius, am I white or Black?" He said to me, "That's the question." [laughs] I couldn't believe my ears. I said, "Well, why do you think I'm white?" He said, "Well, it's the way you talk. You talk like a white man." He may have gone into other things, but he said he didn't know. He went abroad. He came back. I came to him, after he came back. I think he was abroad for a year or two or whatever. I came back to him and I said, "Pius, am I white or Black?" You know how he answered the question? He said to me, "I think you should settle down and marry a Nigerian girl and stay here." He understood. [laughs] After being in Britain for a couple years, or whatever it is, he understood who I was. But the average Nigerian thought I was a white man! That was an extremely interesting experience to go to Africa and be a white man! [laughs] I never expected that!

Now the other part is African society is conservative. I knew—and it was my plan—to marry in Africa and settle. I understood that you can't live in Africa without being married, because that's African culture. You marry and have kids. But it took me a decade to find a wife. Why? Because they only marry—and I'm exaggerating somewhat—from their village. They don't marry people from other tribes. They don't marry people from a hundred miles away! [laughs]

ZIERLER: Let alone a white guy from Caltech! [laughs]

MCGRUDER: Exactly. Well [laughs]—yeah. So it took me a decade to find a wife. It was clear that there were some difficult things that were associated with my experience there. I couldn't just be a part of things. Also, I understood that I couldn't have any administrative positions. I couldn't become head of the department. I couldn't become president and dean and all that stuff. I didn't want to be anyway, so it wasn't an issue, but I did understand that as a foreigner, I was out of that kind of stuff. So there were circumstances that didn't make me feel 100% comfortable.

ZIERLER: As a lecturer, in your interactions with students, what did you learn about Nigeria and education and socioeconomics?

MCGRUDER: A university education in Nigeria is something that's very prestigious. It's very important. I would think it is more important than in the United States. People value it a lot. It's only accessible to people with means, because it costs money, but it's more valued than here. But what I saw in Nigeria—and I was talking with a Nigerian recently, just at Thanksgiving dinner. I had Thanksgiving dinner with the international students at my university. We were talking about this very thing. When I went to Nigeria, I thought I could help to build up a powerhouse in astronomy and help make a great intellectual center, at least in my field, in Africa. That was my dream. And it fell apart. It fell apart because Nigeria fell apart. Nigeria started out being a country with a heck of a lot of potential, because they had well-educated people. It had oil, so it had money. We thought Nigeria was going to take off. There was a civil war, but the Igbos didn't break off. They lost, just like the South lost our Civil War in this country. But we still felt that it could take off. It didn't. It deteriorated. I was there when all that deterioration took place. When I went to Nigeria, the naira—that's their currency—was worth more than both the dollar and the German D-mark. When I left, it was the exact opposite. It really seriously deteriorated.

Marital Terms and Return to the States

ZIERLER: This is to say that if Nigeria was in better shape, you would have stayed?

MCGRUDER: No. It's another interesting story how I ended up leaving Africa. I knew to stay, I needed a wife. After a decade, the world opened, or the spirits opened, or the Gods opened or whatever, and they gave me a wife. But what happened was her father insisted that if I wanted to marry his daughter, I had to take her back to live in America. He said there were two reasons why he insisted that I could only marry her under those conditions. One was he was a high government official, and his daughter was raised in basically a rich environment—chauffeurs, and chauffeur-driven cars, and big government houses, and all the money she needed, and all that kind of stuff. He felt I could not support his daughter as a lecturer at a university on that level. First point.

Second point, as a true African, he felt the woman belonged in the husband's place. To him, my place was America. I had to take her back. [laughs] So I wanted to marry to stay, and I ended up marrying to leave! [laughs] I was in love with the girl, so I had to go! [laughs] I was talking to an African the other day, at a conference, in South Africa. He was asking me about how I left Africa. I said I got kicked out of Africa by my father-in-law. [laughs]

ZIERLER: Charles, as you're thinking about needing to make a move in the United States, how did you go about that? What opportunities were available to you circa 1989?

MCGRUDER: When my father-in-law made this condition on marriage, I started applying, from Africa. The first position that I got was a visiting professorship at Western Kentucky University. I accepted it. After that, a tenure track position from Lincoln University came through, but I thought that was improper to accept it once I had accepted the one at Western Kentucky University. It turned out to be the best thing, because I was a visiting professor for a year. The people in the department—admittedly, I made an effort. People in the department got to like me. After that time, I went to Fisk University for three years, but the headship at WKU became open. There was one professor there who remembered me very well and suggested that I would be a good candidate. The dean came down. I applied. The faculty accepted me. There was a big fight because the president didn't want me, as a Black person. He was from the Deep South. But that was overcome, and I became department head there for nine years.

ZIERLER: Didn't you tell the president that you were white, as you learned in Africa?

MCGRUDER: [laughs] I must have been—besides, I didn't know it at the time. They told me a couple years later after it actually happened, of how they had to work to get me in. [laughs]

ZIERLER: Tell me about your experience at Fisk.

MCGRUDER: I didn't flourish at Fisk. I didn't flourish at Fisk I think because of my own making. What I'm really interested in is research. That's my bottom line. I enjoy teaching. But I can't stand other stuff. I don't like meetings. I don't like all this other stuff that's associated with being a university professor. So I never attended meetings. I was bad. I was naughty. When it came time for tenure and stuff like that, people didn't even know me. [laughs] It didn't work out. I was already leaving anyway.

ZIERLER: With this being an HBCU, was that not particularly meaningful to you?

MCGRUDER: I think the answer to the question is no. It's something I've never strived for. It's not my world. My background is integration all the way, so a totally Black environment is not necessarily something that I've ever aspired to. Not at all. So I think the answer to your question is no, it did not have a particular meaning for me.

Appointment and Leadership at Western Kentucky

ZIERLER: By the time you joined the faculty at Western Kentucky University, to go back to this idea that you had to come to the States during your time in Nigeria just to stay current with the literature to stay up on your research, just being in the United States regularly, how did your research interests change?

MCGRUDER: Initially, they did not. Well, let me be careful. One of the reasons I didn't want to return to the United States was the idea that I have to chase money, get grants and stuff like that. I didn't like that at all. It's something that really turns me off. I don't want to spend my time doing that. I want to spend my time doing my research work, not in all this grant-seeking and all that kind of stuff. That's one of the things that turned me off that I didn't want to come. Now, once I got back, I had to do that. But there, America had changed in the intervening years. There was affirmative action. There was an effort to get minorities involved in things. It was a whole different country than when I left. Very different. I felt wanted! [laughs] And appreciated. I was helped in getting my first grant. Somebody from NASA, Phil Sakomoto showed me what I needed to do.

That first grant is what got me that position at Western Kentucky University, because it had two stipulations. You needed to be a full professor, and you needed to have an active research grant. That's all, and I had both of those. I got back in the system, and eventually I think I ended up with a total of $3 million of grants by the time I stepped down as department head. So I actually flourished at WKU. We acquired a telescope in Kitt Peak National Observatory and got a major grant to start off things. We did quite well. I think I adjusted to the system better than I thought I could.

But in terms of my own research, what happened was before I entered campus at Western Kentucky University and came back as the department head, there were only three astronomers. By the time I left after nine years there, there were 11. I really built up the department! [laughs] I got resistance from people there, but I really built it up. We were clearly the powerhouses in astronomy in Kentucky. There was no question about it, in observational astronomy. We were doing very well. But in terms of my own research, what happened was, I was still interested in the things that I loved. What I had discovered in general relativity was this concept of gravitational repulsion. I had gotten a couple of papers out. The first one was in Nature that I told you about. I got another one out in Physical Review. I was really interested in this stuff. I wasn't really interested in astronomy even though I was hiring all of these astronomers and got a telescope and everything. But that was part of what the system demanded.

I was still working on this gravitational repulsion, and I had gotten some data. Interestingly, somebody at Stanford University had performed an experiment looking at the gravitational force experienced by electrons. His name was—it starts with Fred Witterborn. I can't remember it now, but it's not important. His result was that electrons don't fall at all. I felt, "Wait a minute. I just discovered this thing about gravitational repulsion. Maybe that's what they're experiencing. Maybe he didn't do it quite right or something." From Nigeria, I wrote him and said, "I'd like to get the data." He was very open and said sure, but he didn't know about the visa. Then I told him, "It's no problem. I'm American."

Then I spent a day with him at Stanford. I think at the time, he was at this Astrobiology Center. I think that's where he was. NASA Astrobiology Center. I can't remember what it's called. He was showing me the data and everything, so then we got talking. He said that he went to Caltech. I put out my hand and I said, "I'm a Ricketts man." He couldn't believe it! [laughs] This guy from Africa who you think is a Nigerian turns out to be [laughs] that we're both Caltech grads! [laughs] Obviously the whole atmosphere changed. [laughs] Anyway, he gave me all the data, and I went to somebody who followed him up on the experiment and got some more data from him. I spent years trying to figure out what was going on here, and I never got it. I never got anything else except that they got. Basically, I wasted a couple years. Eventually, I said, "Wait a minute. I've hired all these astronomers. I'm not doing astronomy. I should do some astronomy." So I did some astronomy, did some interesting binary stuff and other stuff.

Then I hooked up with a guy who wanted to do eclipsing binaries. I wanted to do exoplanets, but it's the same thing, the same concepts involved. We agreed that I would do some eclipsing binary work and we would then apply for a grant to NSF and then move forward. But after some time, maybe two years or something—I don't remember the timeframes, at all—he wrote me and said, "You can't get money from NSF anymore on eclipsing binaries. They're just not funding it." He had another area, which I can't remember what it was. Maybe in artificial intelligence or something? He said he wasn't going to be doing eclipsing binaries anymore. I said, "Okay." My whole motivation was to work with him, to get started. I can remember, right here outside this office where I am now—and I'm at home now—I sat on the chair, and I thought about it. I reread my previous works on gravitational repulsion and theoretical physics. They were both theoretical physics. I said to myself, "Can I do this stuff?" It has been years now since I've done it, but maybe I can still do it." That's when I started off on my own, again. In between I got another paper on gravitational repulsion. Now I'm working on what I just told you now.

Service to Physics Societies

ZIERLER: Charles, when did you get involved with the National Society of Black Physicists?

MCGRUDER: Oh, wow. That's a very interesting story, because that Society means a lot to me. What happened was when I was in Africa—oh, there's another interesting story, actually. I had never met a Black scientist my whole life. After graduate school, I was traveling through Africa, and I heard about this Black physicist. I had never met one! As you know, I was traveling by Land Rover. I went to Ghana, and in Ghana, I heard about this Black physicist who was at the University of Kumasi. I met him, and it was the first Black physicist I ever met, in Africa. From him, I heard about another Black physicist who was American. He had been in West Africa but he had traveled to East Africa. When I got to East Africa, I met him, the first Black American physicist I ever met, and here I was in my mid-thirties! [laughs] He told me about a Black physicist organization, the National Society of Black Physicists, but I didn't have a connection to it, I didn't know it, but at least I knew it existed.

After my first year back in the United States as a visiting professor at Western Kentucky University, I started applying for positions. I applied to I think Lawrence Livermore, something like that. One of the government labs, anyway. I don't think I went through in the application. I think I got a letter saying, "You don't have the area that we're interested in" or something. But the president of NSBP was there, and he responded to me saying, "There's this organization, National Society of Black Physicists. Why don't you come to our next meeting?" He kept me informed. That next meeting was in Baton Rouge, Louisiana, and I fell in love with the Society. That was 1990. I have never missed a meeting since then.

ZIERLER: Oh, wow.

MCGRUDER: And I never will, as long as I'm healthy.

ZIERLER: Who was the president of NSBP at that point?

MCGRUDER: Kennedy Reed, at that time. As you probably know, I became president at one time. We held our annual meeting at Stanford University one of the years I was president. I don't know what else to say, but that's how I hooked up with the Society.

ZIERLER: How would you compare, just from a service perspective, your work with NSBP and with the APS, where you were a member of the Committee of Minorities?

MCGRUDER: I don't know how to answer that question, to be honest.

ZIERLER: Are they working toward the same purposes? Different goals? Cross-purposes?

MCGRUDER: Sometimes it's cross-purposes, because the APS has had a general desire to consume us, to consume NSBP and make us just a part of them. We've resisted that for many years. But as you know, APS is really opening up. Jim Gates is now the president. He used to be president of NSBP. He's a friend. I enjoyed my time at APS, very much. I think I contributed significantly to it. But it cannot compare to NSBP. There's just no comparison. It's like they may have the same goals but it's like having family goals, and you and a friend having similar goals. There's a whole difference between family and friends. Family is family. It's really basic. Friends, no matter what, there's some superficial level. That's the best way I can compare it.

ZIERLER: What are those goals of NSBP, and how have they changed over the years?

MCGRUDER: NSBP started out as a group of Black physicists coming together. Basically they had the lectures. Each would talk about their research. But it was a coming together of colleagues. I changed it. I said, "What NSBP needs to do is to create the next generation. That needs to be our primary objective." Before I came on, there was a separate student organization, and they would meet differently. It wasn't NSBP Students; they had even a different name. They would meet separately from the professionals. I didn't want that at all. I said, "Here's what we need to do. I always want the students to be with us. That's our primary objective, to bring along the next generation. I want us to go for grants from NSF to achieve that." That's when our society started having much larger meetings, much larger people. The students were always there. I think that was my contribution as president, to shift the emphasis of NSBP from a group of professionals getting together, that kind of stuff, to a group that is focused on creating the next generation.

ZIERLER: Because a student today, a Black student today, by definition would have such a very different experience and possibly perspective that you did when you were an undergraduate, where there wasn't affirmative action, there weren't things like offices of diversity and inclusivity, given that today's student has such a different experience, how can the NSBP respond to that, in fostering that next generation of physicists?

MCGRUDER: I think the biggest thing is mentoring and role modeling. If you remember, it wasn't until my mid-thirties when I first met a Black physicist. For most people, that's not acceptable. It's not comfortable. I've always been completely on my own. That's part of my personality. I was able to take that. But for most young people, that's just not acceptable. They feel uncomfortable if they're the only ones. They feel uncomfortable if there's nobody there that looks like them. So I think that our primary goal, just by having the students come to our meetings and seeing us successful professionals that are doing everything we can to help them, makes a very big difference.

ZIERLER: What successes do we see in terms of representation at the faculty level? What are the trends?

MCGRUDER: I don't know. I've not kept up with it in recent years. The last time I was associated with this was when on the APS Committee. At that time, the trends among students, that is the pipeline, was negative. That's one of the suggestions that I made to APS, that we need to have a meeting with people from HBCUs and other institutions that are interested in this, and try to see what we need to do to rectify the situation. I don't know what's happening since I left APS. I have honestly not kept up with it, so I really can't answer your question.

ZIERLER: Do you see WKU as a leader? Is it a place where Black students can come and feel comfortable and be accepted in physics and astronomy?

MCGRUDER: I think the answer to that question is no. When I became department head, there were no Black students in Physics at WKU. During my tenure, I managed to achieve that a quarter of the students were Black. Not only that, the president and vice president and I think treasurer of the SPS, the student thing, they were all Black. It was a complete takeover. How is that possible? Because I was there as the boss. I was department head, so Black students felt comfortable. Nothing was going to happen, because I was going to stop it if there was any problems, and they knew it. Plus, I did recruiting. I hired a recruiter. I gave the students money. I was able to attract students and achieve what people would probably think impossible. We went from zero to 25% in just a few years. That's a pretty significant accomplishment.

The Quest to Merge Relativity and Quantum Mechanics

ZIERLER: For the last part of our talk, given that we've gotten all the way up to the present, let's focus back on the science. I'll come back to something very interesting you said about your recognition that the two big theories, relativity and quantum mechanics, came from Germany. This of course remains the big puzzle in physics, how to merge them, how to have a theory that includes quantum mechanics and relativity. From your work on gravitation, all of the recent advances, what are the prospects? Where do you see things headed?

MCGRUDER: First of all, I understand something about general relativity because I've published a few papers on it, but I've never published anything in quantum mechanics. I don't have a feel for it. Of course, I'm aware of the fact that the two theories are separate and somehow, they need to be combined, but I have no ideas on that at all.

ZIERLER: Therein lies the problem, right? That the study is geared in a way where these issues are treated separately. Is your understanding in a broader sense that at some point in the future, there's a research agenda that would break down those barriers?

MCGRUDER: That has been the history of physics. But I think we need to be open for surprises. One of the surprises may be this dark matter, what it is.

ZIERLER: Dark energy, too. While we're at it, we should figure that out, also. [laughs]

MCGRUDER: Right. That's another thing I am working on, but that comes later. I've got to finish this dark matter, first. Physics has presented with a lot of surprises. A lot. I don't really have any preconceived notions that we're going to have some unified theory of general relativity and quantum mechanics. It's something I would never work on, and it's something I'm not necessarily feeling that it's going to come about. I'm, if anything, skeptical.

ZIERLER: Is that to say that you see your research as a brick in the wall toward building that greater understanding?

MCGRUDER: Definitely. I think dark matter, because it does not appear to fit in with the matter that we know, it may be some key to something else that we also don't know about. I just don't know. But this mystery of dark matter is—to me, when I teach my students—I teach what is called "Astronomy for Poets" at many institutions. I teach non-majors. I love that. Because I want my students to understand the basics of my field, I tell them, "We don't understand what this dark matter is. It may shatter some of our basic beliefs about what matter is." I'm actually expecting that. I have a very open mind when it comes to this combination of these two theories, quantum mechanics and general relativity, because there may be things that come about that don't even fit into either theory.

ZIERLER: Best-case scenario with your research on scattering, what will we know as a result that we don't currently understand?

MCGRUDER: That's a very good question. First of all, the fact that it scatters light, assuming that it is confirmed. That's only my—I wouldn't say speculation because it's based on evidence, but that's my conclusion. That will open the door to actually determining some of the properties of dark matter. What I'm exactly doing right now is using the information I have now about how it is scattered to see if I can get some information about some of the properties of dark matter. So far, I have not done that, but I'm trying my best. My paper is in limbo. The referee is—first sentence, he loves it, and then he had some comments about especially making crystal-clear that what I'm saying is not dust. I think I've done that part, but in the process of doing it, I realized I may be able to derive some of the properties of dark matter. It's tough, because now I have to do quantum mechanics, which I know nothing about, and other stuff. The publisher has been on my case—"When are you going to resubmit?" and all this business. But I really want to see if I can at least come up with some possibilities for dark matter.

ZIERLER: Some retrospective questions. Given your commitment to that pipeline issue, to increasing diversity in the field, what are some concrete achievements that give you special satisfaction in all of your service work, in all of your efforts, that this is ultimately where the field is headed or can head?

MCGRUDER: Clearly, as the president of the National Society of Black Physicists, what I just told you about, in changing the direction of NSBP. That has kept, and the students are always there now, so what I started has really taken off, and I'm extremely proud of that. That is clearly my greatest achievement. The other thing is looking back on my career—it's a long story, and I won't bore you with the details, but basically I had the idea of bringing an academy to Western Kentucky University, whereby we bring high school students, brilliant high school students from Kentucky, to WKU. They're high school students, but they take all college courses, so they graduate with 60 college credits. I think that's one of the greatest achievements I've done with my life, bringing that idea to campus and seeing it fulfilled. Actually, that Academy was considered the best public high school in the country, a year or two ago. I was the one who brought it to campus! [laughs] That's clearly one of my greatest achievements. If nothing happens to the research, if this paper I'm writing gets rejected and everything, at least I've done something.

A Sense of Adventure is Good for the Science

ZIERLER: In all of the twists and turns and surprises that your life has taken, your openness to new adventures, to new cultures, how has that benefited the science, your approach to the science, to the big mysteries out there?

MCGRUDER: I'm not sure I'm answering your question, but let me give you a little insight. I was interviewed recently by a German who studied in England. He is a historian, like you. He was studying the history of diversity in astronomy, so he interviewed me. He asked me to compare my German education with my American education. It's something I had never thought of. I thought about it, and I said, you know something? I'm an extremely lucky person. Because I had the best education in physics you could get, because I had Feynman to teach me physics for two years. Number one. Number two, I went to Germany, and the Germans are noted for creating these geniuses. That's something that this guy who knew me from Caltech, the German, the story I told you about, he mentioned that in our initial conversation. I had the opportunity because of circumstances, namely the constellation I was observing can only be seen from the southern hemisphere, and because of apartheid I couldn't go to South Africa at the time. So I had a lot of time on my own, and I spent that time learning science on my own. I think that has put me in the position of being a successful scientist, having the best of these two worlds. So I consider myself extremely fortunate. I didn't realize that until he asked the question. I've had the best of two worlds. It is really important to me that what I'm doing now is successful, and this thing on dark energy that I told you about, to be successful, because that would culminate my research career.

ZIERLER: Charles, on that note, last question, looking to the future. We've already talked about best-case scenario for dark matter. You have your sights set on dark energy. What's the research? What might you do in that field?

MCGRUDER: There has been a surprise that has happened in astronomy, and that is—you've heard of something called the Hubble constant?

ZIERLER: Of course.

MCGRUDER: Good. Well, it turns out that the Hubble constant, when you measure it using one method, that is supernovae or a few other optical objects, you get a different value than when you measure it using measures from the early universe. The two values are different, and they differ more than the errors in the measurements. That's a really big mystery that nobody really understands. I've got some ideas of how that may be rectified, and I suspect that my ideas on rectifying it will mean we're going to have to think very different about cosmology.

ZIERLER: That's exciting. I want to wish you a lot of luck in getting there.

MCGRUDER: Thank you! [laughs]

ZIERLER: Charles, this has been so fun. I'm so glad we connected. Thank you so much for spending this time with me.

MCGRUDER: It has been my pleasure. I've enjoyed it.

[END]