The Theoretical Physicist Who Worked With J. Robert Oppenheimer at the Dawn of the Nuclear Age

The Theoretical Physicist Who Worked With J. Robert Oppenheimer at the Dawn of the Nuclear Age

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Adam Falk: She knew who she was, and that she was going to be a physicist. I imagine that Oppenheimer was very happy to work with her but my understanding is that at that time, women were thought to be a… some kind of oddity.

Katie Hafner: This is Lost Women of Science. I'm Katie Hafner. Last summer, when the film Oppenheimer opened, we got curious–well, more curious than usual–about the conspicuous absence of female scientists in the movie. So we started looking into that, and it didn't take long before we came upon the name Melba Phillips. OK just to be clear Melba Phillips did not work on the Manhattan Project itself but she was a gifted physicist. She was one of Robert Oppenheimer's first graduate students at UC Berkeley in the early 1930s when he was just starting out and together they made an important discovery, now known as the Oppenheimer-Phillips Process.  

In this episode, we're going to explore Melba’s life and work– including the  Oppenheimer-Phillips Process and its enduring importance in nuclear physics. And just as important as the science itself is the story of a young woman who, nearly a hundred years ago, thought nothing of declaring herself a physicist, and the story of the famous man who just as notably, thought nothing of regarding her as one.

Melba Newell Phillips was born on February 1st, 1907 in–or we’re not exactly sure, maybe near–Hazleton, Indiana, a speck of a place in the southwestern corner of the state. Her family was rich with teachers and farmers. Melba, it turned out, had a natural aptitude for science, and she excelled so much in school that she skipped a couple of grades and graduated from high school at the age of 16. Some sources we’ve seen even say she was 15 when she graduated from high school. I think we can agree on this: young Melba was no slouch of a student.

Jill Weiss Simins: She definitely was naturally smart. She tried to follow in the family profession of becoming a teacher.

Katie Hafner: That's Jill Weiss Simins, a historian at the Indiana Historical Bureau. She’s done a lot of research on Melba’s life.

Jill Weiss Simins:  She actually passed the exam to become a teacher in Indiana, but she was too young.

Katie Hafner: And wasn't that lucky for the world, because...

Jill Weiss Simins: While she was waiting to be old enough, she pursued further education.

Katie Hafner: She decided to study physics at the school nearest to home, then known as Oakland City College in nearby Oakland City, Indiana. But when she arrived, she discovered that the school didn’t have a major in physics so she majored in mathematics. The physics she wanted was about 300 miles north in Michigan. She ended up getting her masters degree in physics from Battle Creek College and she stayed on to teach there. Then in the summer of 1929 she took a class in theoretical physics at the University of Michigan. That summer course became known for the high caliber of the teachers, including Edward Condon, who was a leading nuclear physicist, and the British physicist Paul Dirac. That class was an eyeopener for Melba and it became her ticket to work with Oppenheimer. 

Melba Phillips: I learned some things I’ve never forgotten, things about spectroscopy, atomic spectroscopy. The people in Michigan knew these things very well. That was extremely useful.

Katie Hafner:  And that is Melba herself, recorded in 1977, describing that class in an interview she did with the American Institute of Physics.

Melba Phillips: But I was so naive that I did the homework in Ed’s class, and at one point I was trying to check on some of the stuff he’d given us and I couldn’t get the same answer that he did.

Katie Hafner: Here's Randy Mills, a retired professor of social sciences at what is now Oakland city university. Randy knew the Phillips family in Indiana. 

Randy Mills: So everybody leaves but Melba, and she’s sitting there, and she’s all upset.

Melba Phillips: And I still remember that I couldn’t dream that I wasn’t making mistakes. Finally I went and asked the teacher.

Randy Mills: She says, Well, I'm working through this, and I went all the way through it, and I came up with a different answer. And so he kind of laughed. He said, well, there's no way you could have gotten that anyway during that time, but he said, let me look at your work.

Melba Phillips: It turned out that I was right. I think that maybe he looked at me twice at that point.

Randy Mills:  And he realizes that he'd made a mistake. Melba had gotten the right answer. And he very quickly contacted Oppenheimer there at Berkeley, and that's how she was sent there to do graduate work. 

Katie Hafner: So in 1930 the 23-year-old Phillips went to California to work with the 26-year-old J. Robert Oppenheimer, an assistant professor with a growing reputation for theoretical physics. It was common for Oppenheimer to leave the serious number crunching to graduate students, and Melba Phillips was very good at that. 

Randy Mills: She became his mathematician on a lot of his work because she was better at math than he was.

Katie Hafner: If you read what Phillips said about her early career you get a palpable sense of how excited and how happy she felt being part of this group of pioneering scientists during these heady days when quantum mechanics and nuclear physics were Oppenheimer’s greatest preoccupation. And from what we can tell, her gender was irrelevant to Oppenheimer. Here’s Jill Weiss Simins again:

Jill Weiss Simins: Oppenheimer becomes her faculty mentor and a great influence on her. He wasn't really, like, the all-knowing professor. He kind of treated his students as colleagues and really felt like they had a lot to contribute.

So pretty quickly, she moved from being Oppenheimer's student to his peer. 

Katie Hafner: Remember, this is the 1930s, and the number of women doing graduate work in physics in the United States could be counted on one hand. Well, maybe two. But you get the point.

Adam Falk: I'm Adam Falk and I'm the president of the Alfred P. Sloan Foundation. It's a foundation in New York City that makes grants to support research in science and economics and a number of issues surrounding science and economics, including the public understanding of those fields.

Katie Hafner: Adam Falk is also a physicist and he's the voice you heard at the beginning of the episode–by way of disclosure, the Sloan Foundation is one of the funders of Lost Women of Science. Adam pointed out just how rare it was for a woman in the 1930s to be pursuing a Ph.D. in theoretical physics. He also pointed out how thrilling it was to be a physicist in the 1930s. As Melba herself said years later in an interview with an Oppenheimer biographer, "Everything was happening in those years from the discovery of the neutron, the positron. All of this kind of thing was happening”

And a lot of it was happening at Berkeley.

Adam Falk: It was an extraordinarily exciting time. The first kind of particle collider was at Berkeley. It was called The Cyclotron. So this was a kind of rich experimental opportunity to start colliding nuclei and see, would they stick together? Would they bounce off each other? Would they transmute?

And so the people like Oppenheimer and Phillips who were theorists were in deep and immediate contact with the people doing experiments. And that's a very rich and exciting environment to be in.

Katie Hafner: After Phillips got her Ph.D., she remained part of a close-knit circle of scientists working with Oppenheimer. They used to meet for tea at 10 o'clock PM at the house where Phillips was renting a room. The discussions went long into the night. Here's Randy Mills again.

Randy Mills: We do know that they were — Oppenheimer and Melba were very close. Not only with class work, but also in their personal lives. They attended a lot of union organizing meetings during that time. The teachers were organizing during that time, but also other groups as well. They drove around a lot. He wasn't a very good driver, but she was because she'd driven tractors and everything else growing up in rural southwest Indiana.

Katie Hafner: In fact there are photographs from that period of Phillips with Oppenheimer and his car. 

Randy Mills: There's a beautiful picture. It's just almost breathtaking.

Katie Hafner: Yep, it’s quite some photo. Phillips is sitting in the driver’s seat of Oppenheimer’s Chrysler convertible coupe. All you can see of Oppenheimer is this thin shadow, kind of ghostly thing, cast over the front door of the car. She’s looking ahead and not at the camera. I’m assuming he took the photo. 

In any case there's only the slenderest of threads of evidence that the two dated. I mean, that thread is so slender it's almost non-existent but it made for a good story. Here's Randy Mills again.

Randy Mills: The most famous story about their relationship that you see in biographies is the one where they were up in the mountains there, by Berkeley and they had parked. And we don't know what that means, but they were certainly there in the evening. And she had fallen asleep in the back seat, so he put a cover, or his coat, on her and then he walked home,  but they didn't know that. So the police found her in the car, and of course, that back in those days, a woman in the back seat being by herself in a car, what's going on? And the concern quickly grew: Where's Oppenheimer? He's not here. So they're looking on the mountain sides and they've, they've — afraid he's fallen down a cliff or whatever.

Finally, they go to his apartment and they knock on the door and he's there. He comes to the door and the person, the officer that's there is, is saying, Why did you leave her there by herself? And he said, I guess I'm just eccentric. 

Katie Hafner:  The headline on the story in the San Francisco newspaper the next morning was this this: “Forgetful Prof. Parks Girl, Takes Self Home.”

He is referred to as Dr. Oppenheimer. She is Miss Phillips.

Jill Weiss Simins: She's already got her Ph.D. She should be called Dr. Melba Phillips like he’s Dr. Oppenheimer.

Katie Hafner: That's historian Jill Weiss Simins again.

Jill Weiss Simins: But she’s called either Miss Phillips or I think even at one point, Little Melba, and they call her his assistant.

Katie Hafner:  Little Melba? I don’t think so! Around the time of the abandoned-in-the-car incident, Phillips and Oppenheimer were working together on what has become known as the Oppenheimer-Phillips Process. And she was by no means his assistant; definitely not in the sense of being his secretary. It was a scientific collaboration in every sense of that phrase.

This was a time when theoretical physicists in Berkeley, like Oppenheimer and Phillips, could just stroll down the corridor to their colleagues running the cyclotron and see what kind of experiments they were doing with atomic particles.

The atom hadn't yet been split– that happened in 1938–but people were beginning to think that it might be possible. At Berkeley they were throwing atoms together inside the cyclotron to see what would happen next. And what Oppenheimer and Phillips discovered was an important stepping stone on the path to nuclear fission. All about that after the break.

Katie Hafner: So just what is this Oppenheimer-Phillips Process I was telling you about before the break? I’m going to start in a kind of roundabout way. At Lost Women of Science, we share the Sloan Foundation's mission to promote the public understanding of science. And we spend a lot of time looking for ways to explain the science we're talking about. But this Oppenheimer-Phillips thing? For a non-physicist, it's complicated. Being a non-physicist, I confessed to Adam Falk that I had turned to ChatGPT for an explanation. My prompt into the AI engine was: use an analogy to Describe the Oppenheimer-Phillips Process in language a nonscientist can understand. Which it did, in a couple of seconds. The analogy It came up with? Marbles.

I asked Adam to read the explanation.

Adam Falk: Imagine you're playing with marbles. You have a big marble, representing a nucleus of a heavy atom, and a small marble, representing a deuteron, which is just a kind of small atomic particle. You roll the small marble towards the big one, but instead of hitting it head on, the small marble brushes lightly against the side of the big marble. That part really isn't... relevant or quite right.

Katie Hafner: Our first red flag.

Adam Falk: ….When this happens a part of the small marble sticks to the big one the rest of the small marble bounces away. That's true.

Katie Hafner: But as Adam went on to explain, ChatGPT actually misses the point of the experiment. But let's get back to Oppenheimer and Phillips for a minute and why they might want to bounce atomic particles against each other. It was to see what kind of energy was released.

Oppenheimer and Phillips were trying to explain some curious results produced by the physicists down the hall at the cyclotron, where they would fire a deuteron at an atomic nucleus. The puzzling thing was that it took less energy than expected to get the two particles to interact, rather than just bounce off each other. And when they did interact, sometimes more energy would be released than the deuteron came in with. A deuteron contains one proton and one neutron. The proton is positively charged, as is the nucleus of the heavier atom it is approaching.

The solution has to do with understanding the interaction of two positively charged particles, when they are in close enough proximity for one to distort the other.

Adam Falk: What's interesting about the process is that it's difficult for two nuclei to interact because they both have positive charge. What Oppenheimer and Phillips realized is you don't have to shoot them as fast as you would think. And the reason is that when the deuteron gets near the carbon nucleus, as it’s coming in, it rearranges itself.

Katie Hafner: Alone by itself, a deuteron is round. But as it gets near the other nucleus, it stretches out. There’s a proton end and a neutron end, and the proton end–the positive charge which would be repelled by the positive charge in the atom it is approaching–is farther away from the other nucleus than the neutron end.

Adam Falk: And if they can really collide, this process can happen where the bigger one takes the neutron out of the deuteron and then the proton flies away. So the deuteron in that sense donates its neutron to the nucleus and the proton flies away. Which means that it's actually an easier process to have happen than you would have thought if you didn't have that analysis. And that's the thing that they realized. And that's what was so important. And, that's the part ChatGPT doesn't know anything about.

Katie Hafner: In effect, the experiment showed that you needed less energy to get a nuclear reaction when atomic particles collided. So, AI is pretty good, but it gets one thing wrong and then misses the most important part.

Adam Falk: I mean, I'm actually astonished at how well it did, right? That is, it did as well as you might expect a student who had just read up on this process but wasn't a physicist to do, if they had kind of just gone and read a little bit and tried to explain it. And I'm pretty impressed that a large language model can do that well.

Katie Hafner: All of which could boil down to the lesson being this: Ask GPT-4 or Gemini, or any AI. being, to explain something scientific that’s super complicated in terms you can understand, and it's ... okay. Not perfect. But back to the science itself. I asked Adam why it's important that the Deuteron can in fact collide with the atom and that the atom can grab its nucleus.

Adam Falk: So at this time people were starting to explore this whole question of how nuclei interact with each other, right? And they were doing experiments at the cyclotron. Of course, this became very important within the decade as they started to understand nuclear chain reactions that led to the atomic bomb in the end. Because these are exactly the kinds of interactions that happen in chain reactions. You have nuclei that decay and emit particles and then they interact with other nuclei that are in the substance.

So this is one of the stepping stones that's really important for understanding the kind of physics that you need in order to have a bomb or a nuclear reactor or something like that. And this was early on.

Katie Hafner: So it was very foundational.

Adam Falk: Very foundational, very important work.

Katie Hafner: In fact, Adam said he found a paper written a few years later by none other than Hans Bethe, one of the truly great physicists of the 20th century. 

Adam Falk: And he writes a paper in Physical Review called The Oppenheimer-Phillips Process. He clearly thinks it's very, very important.

Katie Hafner: I asked Adam how he thought Oppenheimer and Phillips had divided the work.

Adam Falk: It was probably very, very collaborative. If I had to guess, this wouldn't have happened without him, but that once the idea came up, they were full partners in working it out.

Katie Hafner: And this got me thinking about something. I brought it up with Adam. I said one thing we're really careful about at Lost Women of Science, and  it's something I'm constantly aware of, is this question of are we focusing on this woman for the right reasons. How important was her scientific contribution? And are we in high dudgeon about the fact that she didn't get the recognition she deserved because she was a woman? And are we losing sight of the actual science that she did? What I asked Adam was, Is it kind of a chicken and egg? Did Melba Phillips not have the chance to do the science she could have done?

Adam Falk: I think it would be, you know, fair to assume that she was very good at the physics that she did, that, that she wasn't kind of along for the ride on her advisor's project and, you know, really someone who was lucky to be in the place where a good idea came along and she was on the paper.

I think there's plenty of evidence — and that happens to both men and women. I think there's plenty of evidence that that is not the way to understand her, that this was published two years after she got her degree. She went on to a prestigious postdoc. I think the evidence is that she was a very good graduate student who did very good work with her advisor, Oppenheimer, and that a significant element in her not going on as a physicist had to do with the roles that women were confined to in the society of the time.

Katie Hafner: So there you have it. Melba Phillips was a promising young physicist who worked at an exciting place doing some of the most exciting theoretical work of the century in nuclear physics. However, in 1933, Oppenheimer himself recommended Phillips for a teaching position at Berkeley. He described her as quote "an extraordinarily able woman. The only woman I have ever known who had a genuine vocation for mathematics and theoretical physics, and an outstanding talent for it."

 But she wasn't hired. Phillips later downplayed the rebuff. She chalked it up to a lack of funding at the school due to the Great Depression.

Then in 1935, the year the Oppenheimer-Phillips process article was published, she left Berkeley. She spent the next several years campus hopping, with short-term teaching gigs at Bryn Mawr College, then Princeton, Connecticut College for Women, then Brooklyn College. All of which sounds... exhausting.

Then came World War II. Melba Phillips went to the Harvard Radio Research Laboratory, where for several months she worked on technology for disrupting enemy radar. Her career after the war, though, bears an uncanny resemblance with that of her mentor. Both she and Oppenheimer became targets of an anti-communist witch hunt.

In December of 1951, Phillips received a letter from the New York Joint Committee Against Communism calling her to account for her support of eleven groups that the Committee suspected were affiliated with Communist organizations. Phillips’ response to the letter was brazen. She went out of her way to point out an additional group that she believed the committee had left out. 

Then, in 1952, Phillips was back teaching at Brooklyn College when trouble showed up at her door. The McCarran Subcommittee, whose goals were similar to those of Joseph McCarthy's House Committee On Un-American Activities, summoned her to explain her affiliation with a number of labor groups. Phillips refused to answer, invoking the Fifth Amendment.

Here's Jill Weiss Simins again:

Jill Weiss Simins: Pleading the Fifth was part of her sticking to her moral convictions. And she did make clear that this was not an admission of guilt of any communist affiliation, but simply adhering to her principles.

Katie Hafner:  New York was like a lot of other states in the McCarthy era. It had a law that required — I repeat, required — the firing of any public employee who refused to answer questions about communist affiliations. 

Our producer, Deborah Unger found that audio you heard earlier of Melba Phillips herself talking during the interview with the American Institute of physics in 1977.  

It isn't the greatest audio quality. So I'll tell you that what you're going to hear is Melba Phillip's going on the record about her dismissal from Brooklyn College in 1952.

Melba Phillips:  I was dismissed from Brooklyn College in October 19–end of October, 1952–and I was essentially unemployed until around 1957…. not that I wasn’t busy.

Katie Hafner:  She goes on to say that she was essentially unemployed until 1957. And then she says: “not that I wasn't busy.” 

And yeah. She was busy. She wasn't destitute. She still received money from the farm she still owned in Indiana. But after those interrogations –we don't have the proof of this –but my guess is that she couldn't find a job teaching. So to make ends meet, she edited a couple of physics textbooks. In 1957, when McCarthyism finally faded, her teaching dry spell ended. And she got a job teaching physics at Washington University in St. Louis where she ran a program to help high school teachers improve their physics classes. And in 1962 she got her first, her very first permanent academic appointment at the University of Chicago. She stayed there for ten years until she retired.

Here's Jill Weiss Simins again:

Jill Weiss Simins: Who she was was somebody that is working in this climate and not even pausing for a second to feel like she shouldn't be there. So I think she was ahead of her time in not just blazing a trail through the physics citadel that other women could follow, but doing it in this unselfish way where it wasn't really about her, it was about the work.

Katie Hafner: Watch the film Oppenheimer and you'll get the impression that Oppenheimer's life was over after he was targeted by the anti-Communists. Yes, his security clearance was revoked, but he kept his position as director of the Institute for Advanced Study in Princeton, one of the most prestigious, if not the most prestigious job you can get in physics. 

If Melba Phillips had stayed in Oppenheimer’s orbit, would she have gone on to make more contributions to theoretical physics? I asked Adam Falk what he thought.

Adam Falk: There's no question there was an enormous waste of the talent of women who would have been terrific academicians, terrific physicists. And the assumptions about the roles of women in society meant they were never given a chance.

And that sounds like that could well have been the case, you know, with her. Speaking more specifically, it's honestly hard to know. I think there were many men who would have written a really good paper with their advisor and then not gone on to have academic careers, would have gone on to teaching.

But there's no doubt that, you know, she had been given nothing like the kinds of opportunities that a man in a similar situation would have been given at that time.

Katie Hafner: In 1987, Brooklyn College issued a formal apology to Melba Phillips for firing her during the McCarthyism period 35 years earlier. And if you happen to find yourself on the campus of Oakland City University in Oakland City, Indiana, you can visit a plaque honoring her. 

Here's Jill Weiss Simins, reading from that plaque:

Jill Weiss Simins: Innovative physicist and educator Melba Phillips worked closely with J. Robert Oppenheimer. In 1935, they proposed the Oppenheimer-Phillips Process, a staple of nuclear physics with continued application. During World War II and after the U.S. dropped atomic bombs on Japan, Phillips advocated for peaceful use of atomic energy.

Like many academics, during the McCarthy era, she faced charges of communist affiliation and lost teaching positions. Nonetheless, she became an influential physics educator and a leader within the field.

Katie Hafner: Melba Phillips never married and she had no children. At the end of her life, she returned to Indiana and lived with her niece near her hometown. She died in a nursing home in 2004, barely 15 miles from the farm where she was raised. She was 97 years old. On her death certificate, her occupation is listed as teacher in the field of education. Not physics. Education. But we know and now you know that Melba Phillips was so much more.

This has been Lost Women of Science. Deborah Unger and Joe Armstrong produced the episode and Sophie McNulty scored and edited it. Hansdale Hsu was our sound engineer. Lizzy Younan composes our music. Keren Mevorach designs our art, and Alexandra Atiya was our fact checker. Thanks to Amy Scharf, Julie Chow, Jeff DelViscio, Jill Weiss Simins, Randy Mills, and Adam Falk. Also many thanks to the folks at the American Institute of Physics for their help. Lost Women of Science is funded in part by the Alfred P. Sloan Foundation and the Anne Wojcicki Foundation. We’re distributed by PRX and published in partnership with Scientific American. Please visit us at lostwomenofscience.org, and don’t forget to click on that all-important donate button. I’m Katie Hafner. See you next time.