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Marissa Moss: Her crowning achievement as her colleagues mocked, was to win the Nobel Prize for the chemist she worked with, Otto Hahn, who did not discover nuclear fission, but did the experiments that led her to that incredible conclusion.
Katie Hafner: I'm Katie Hafner and this is Lost Women of Science. Over the past few weeks we’ve been bringing you a series of stories about women who worked on the Manhattan Project. But today, we're sharing the story of one who refused to have anything to do with it: physicist Lise Meitner, the scientist whose work was key to the discovery of nuclear fission.
We're diving into one particularly illuminating aspect of Meitner's story: her letters with her closest colleague, Otto Hahn.
Katie Hafner: Marissa, how many, what's your estimate on how many letters you translated?
Marissa Moss: Oh my gosh. Well, it's like 500 pages of letters and some pages have two or three letters on them. So definitely thousands.
Katie Hafner: Marissa Moss is an author and illustrator in the San Francisco Bay Area. Her most recent book is The Woman Who Split The Atom: the Life of Lise Meitner. While she was working on the Meitner book, Marissa went to the University of Cambridge, in England, where Meitner’s papers are archived. It was there that Marissa came upon a trove of thousands of letters.
Marissa Moss: She was a voluminous correspondent.
Katie Hafner: And throughout her life, Meitner wrote to Otto Hahn. Their relationship defined her work. It was also a source of frustration and disappointment. Time and again, the letters reveal Meitner’s struggle to communicate with a man alongside whom she had worked for nearly three decades, a man she had cherished as a friend. And they show two scientists striving to cement their legacy and contributions to their respective fields -- physics and chemistry.
As the Nazis rose to power in Germany, Hahn was able to preserve his position, while Meitner, a woman and Jewish, could not.
Lise Meitner was born in Vienna in November of 1878.
Marissa Moss: Okay, so she's born into a Jewish family in Austria and they live in the ghetto. And her father is a lawyer.
Katie Hafner: The Meitner children were all encouraged to pursue education. That included the girls. In 1897, the University of Vienna changed its policies to allow women to attend. Meitner enrolled there in 1901, when she was 23. Physics called to her. In 1905, she became the second woman in Vienna to earn a PhD in physics.
Marissa Moss: But Austria still was not very welcoming to women. And when she wanted to do advanced work, she was told: in physics, go to Berlin.
Katie Hafner: So that's what she did. Her focus was the new and exciting field of radioactivity. She'd already begun to establish her reputation as a physicist, working on alpha particle scattering.
Marissa Moss: And she was looking around for somebody to work with.
Katie Hafner: As the story goes, she was meeting with the head professor of the Experimental Physics Institute. He offered her a position as his unpaid assistant...
Marissa Moss: And as she's talking about it with him and thinking I can't work with him, Hahn walks into the office.
Katie Hafner: Otto Hahn, a chemist who was working on radioactivity himself. He'd heard about Meitner’s work. When they met, the two were both in their late 20s, only a year apart in age, and he’d been looking for a physicist to collaborate with.
Marissa Moss: So she's a peer and she feels like he's not intimidating. She feels like he's somebody she can ask questions and she could work with.
Katie Hafner: They began to work together at the chemistry institute where Hahn had his laboratory but…
Marissa Moss: She was basically not allowed to have a lab with the men. She couldn't go upstairs, even to where the men's labs were. She was given a basement room with a separate entrance and she had to go down the street to a hotel or a bar or a restaurant to use the bathroom.
Katie Hafner: For the next two years, Meitner worked in the basement laboratory.
It was a heady time for chemists and physicists alike. Meitner and Hahn were working at the very edges of scientific understanding.
As a chemist, Hahn wanted to identify new elements and their properties. For Meitner, the physicist, the more interesting part was radiation itself. Radiation is energy that well, radiates – heat, light, and electromagnetic waves are all examples. We call elements radioactive when they spontaneously release energy because of unstable nuclei.
Scientists at the time had found ways to observe and measure radiation and they were aware of different types of radiation. They’d identified alpha, beta and gamma rays. But the nature of these rays and the internal structure of the atom itself was still a mystery.
Meitner followed every new discovery and presented her own findings at conferences. It was at one of these conferences that she met Albert Einstein. In his lecture, he theorized that matter and energy were forms of the same thing and presented an equation for the conversion. And yes, it's the one you all know: E = mc2
Scientists saw the potential: if it were possible to break apart an atom, a tremendous amount of energy could be released. But at the time, that seemed like an impossibility.
Meitner and Einstein became friends and lifelong correspondents.
In Berlin, Meitner was finally building a scientific community. Hahn remained her closest colleague. But although they spent their working lives together, in his memoir, Hahn wrote that,
Marissa Moss: He didn't quote-unquote consider her a friend because she was very formal and careful and they didn't even eat lunch together.
Katie Hafner: Meitner was by nature a shy and reserved person.
Marissa Moss: And people asked her later in her life, why didn't you ever get married? It just never occurred to her. She was so focused on doing science and she didn't want anything to distract her.
Katie Hafner: She once wrote this in a letter to a friend…
SPEAKER: Herzlich liebe ich die Physik – I love physics with all my heart.
Es ist so eine Art persönliche Liebe – It is a kind of personal love as one has for a person to whom one is grateful for many things
wie gegen einen Menschen, dem man sehr viel verdankt.
Katie Hafner: In 1912, Meitner and Hahn moved to the new Kaiser-Wilhelm Institut fur Chemie where her work earned her a modern lab, a step up from the basement.
And finally, Meitner was given a title – scientific associate – and a salary, albeit a tiny one.
In 1914, World War I broke out. Hahn was drafted and he soon began working with a special team to help Germany develop chemical weapons.
Marissa Moss: Which by the way, in a later newspaper interview, he justifies saying, well, if we hadn't done it, they would've done it. So we just had to do it first.
Katie Hafner: Meitner volunteered as an x-ray nurse.
Marissa Moss: She basically shows them how to use it. And because it's a new technology and she's an expert in it, she's actually given quite a bit of status. She's treated like a doctor.
Katie Hafner: It was during the First World War that Meitner and Hahn began what would turn into years of writing letters to each other. And you can see from those first letters that she already considered him a confidant. She addressed him with the familiar “Du” instead of the formal “Sie,” which back then especially was unusual for professional colleagues. She wrote,
SPEAKER: Du kannst dir mein jetziges Leben kaum vorstellen.
You can hardly imagine my way of life that I once worked in physics and one day will again, seems as far away to me now as if it had never happened, nor will again.
Diese Physik, in der ich einmal gearbeitet habe und eines Tages wieder arbeiten werde, kommt mir jetzt so weit weg vor, als hätte es sie nie gegeben und wird auch nicht wieder.
Katie Hafner: But in 1917, Meitner returned to her lab in Berlin. Hahn was still on active duty in the war.
Marissa Moss: And when she goes back, he writes her letters of instruction and basically tells her what to do, and they basically do science by mail.
Katie Hafner: They continued their work this way until the end of the war. When Hahn returned to Berlin, they were able to pick up right where they left off. In the decade that followed, Meitner and Hahn did some of their most exciting research.
They isolated and identified new elements. In 1924, they earned their first joint Nobel Prize nomination for their work with the new element protactinium. They were nominated another six times in the next 10 years.
But throughout these years, the Nazis were gaining momentum in Germany. In 1933, the same year Hitler became chancellor, Meitner lost her university position. Jewish academics throughout Germany were being forced out of their jobs. By the middle of the 1930s, most of Meitner's Jewish colleagues had left Berlin, but Meitner stayed.
Marissa Moss: And she doesn't leave because she is terrified of not doing science. She thinks not doing science will be worse than death, and she doesn't see the possibility to do science elsewhere because unlike all the Jewish men who are being invited to work in America and England she had no invitations.
Katie Hafner: Lise Meitner had been working with Otto Hahn for nearly three decades by this point. She didn't want to lose that. But then, in 1938, Germany invaded Austria. Annexation meant that Meitner was suddenly stateless, her Austrian passport meaningless. She realized she had to leave.
Marissa Moss: She's hoping, hoping, hoping desperately she can get something in Denmark with Niels Bohr because he's a big champion of her, but there's a big problem because she waits so long to leave she can't get an exit visa.
Katie Hafner: Meitner had no way of getting an exit visa -- and besides, no valid passport to stamp it in. But Niels Bohr, the renowned Danish physicist, and some of her other colleagues were determined to find a way.
Marissa Moss: Basically, her friends put a plan in place and just hand it to her and say, we're getting you out of there.
Katie Hafner: They kept the plan secret from everyone at the Institute, even Hahn. Two Dutch physicists, one in Berlin and the other working in the Netherlands, would get her out. They waited to tell Hahn until the day before Meitner was due to leave. It would give Hahn and Meitner a chance to say goodbye to each other. Hahn invited her to have dinner at his home.
Marissa Moss: He surprises her, when he says goodbye. He gives her a ring. He gives her a ring of his mother's and says, you might need this because maybe she can sell it. Get some money. He knows how poor she is and it's the one genuine gesture that he gives her. And she just is stunned by it and very moved.
Katie Hafner: Meitner kept the ring for the rest of her life.
At the institute, Hahn marked his calendar with an entry reading "Meitner goes to Vienna". He told everyone she'd be seeing family, hoping that would explain her absence and discourage any questions.
She left the city on a small local train, headed for the Netherlands, riding with one of her Dutch physicist friends.
When they reached the border, Dutch and German officials got on the train.
Marissa Moss: She's terrified of what happens if they ask for documents, cause she doesn't have any.
Katie Hafner: The German police asked her Dutch friend for his identification.
Marissa Moss: And he shows his papers and his visas and he's Dutch and he's going back to the Netherlands, and Meitner is just absolutely frozen. And they glance at her and they walk on by, because she's a woman. She's his wife who cares.
Katie Hafner: And that's how they made it across the border. From the Netherlands, she took a boat to Copenhagen and spent some time with Niels Bohr before heading to Stockholm, where she'd be working at a new Physics Institute.
By August of 1938, Meitner was settled in Stockholm and Hahn announced to the Kaiser Wilhelm Institute that she had retired. In truth, they continued writing to one another and working together, and it would be through their correspondence that they'd make their biggest discovery yet. That's after the break.
Marissa Moss: She lands in Stockholm and she's utterly miserable.
Katie Hafner: In August 1938, Lise Meitner was safely out of Germany. But the Physics Institute in Sweden where she'd been offered a one year position had little interest in her experimental work.
Marissa Moss: She has no workroom. She has no colleagues. She feels completely isolated. And she writes these just incredibly depressing letters to her friends saying, my life equals zero.
Katie Hafner: And of course, she wrote to Otto Hahn.
SPEAKER: Sechste September 1938. Lieber Otto. Dear Otto, the problems with the Institute depress me. It sounds like I've left my duty in the lurch. There is so little left from my life. I can't also lose the trust of the few people I worked with for so many years, during the best times of my life.
(die ganze Instituts Sache drückt mich sehr. Wenn Pflüger fragt, ob ich die Nerven verloren habe, so spricht doch daraus die Besorgnis, dass ich meine Pflicht im Stich gelassen habe.)
Katie Hafner: Meitner worried that her colleagues back in Berlin would feel that she'd abandoned them -- and their work.
SPEAKER: They must think that I ran away without concern for them, when you could clearly tell them that it was no longer possible for me to stay.
(Sie müssen doch glauben, dass ich Pflichtvergessen davongelaufen bin, wenn du ihnen nicht mit deutlichen Worten sagst, dass mein Bleiben nicht möglich war.)
But understand Hähnchen, what it is to me. My future is cut off. Should the past be taken away from me as well? It's clear that neither Phillips nor Fluger understood what was going on, and that the answer you gave him could only confirm that I had acted very selfishly.
(Aber versteh doch hähnchen, um was es sich für mich handelt meine Zukunft ist abgeschnitten soll mir auch noch die vergangenheit weggenommen werden. Es ist doch klar, dass weder Philipps noch Flüge verstanden haben, was alles vorlag und dass die Antwort, die du ihm gegeben hast sie ja nur darin bestärken konnte ich hätte sehr egoistisch gehandelt.)
Katie Hafner: She calls Hahn “Hähnchen.” It's the diminutive, a term of endearment. There's both a sweetness and a desperation in her words. In the same letter, Meitner asks Hahn to send her the materials and books she had to leave behind.
Marissa Moss: It takes, I think it's nine months before she finally gets her things. And when they arrive, they've all been shattered and destroyed
Katie Hafner: Shattered and destroyed, that is, by the Nazis. Things were getting worse in Germany and Nazi-occupied territories. In November of 1938, Meitner got the news that her sister's husband had been arrested and sent to Dachau, one of the first concentration camps.
Alone and anxious about her family, Meitner tried to build a life in Stockholm. She hoped to continue the work that she'd been doing with Hahn in Berlin.
Marissa Moss: The big work that Meitner and Hahn had been working on for the past the decade, up to that, was transuranics, which is they were bombarding uranium with neutrons and seeing what—they thought things were chipping off. And that was what was chipping off was elements that were heavier than uranium, that—hence they were called transuranics.
Katie Hafner: Uranium is the last of the naturally occurring elements on the periodic table, with an atomic number of 92. Anything beyond that is “transuranic.” These radioactive elements are short-lived and generally produced artificially in laboratory settings. Meitner and Hahn had published multiple papers on transuranics. But Hahn's recent experiments were producing perplexing results. He expected that bombarding uranium with slow moving neutrons would produce more transuranics.
Marissa Moss: But it's very odd because what he ends up finding is not elements that are heavier instead he's finding lighter elements
Katie Hafner: Hahn shared his results with Meitner by mail.
Marissa Moss: And he's very befuddled and confused and he thinks something has contaminated his work. He doesn't understand. He’s done this experiment over and over again, and he's still getting these strange, strange results, and he’s pleading with her, begging with her to explain it to him.
Katie Hafner: He told Meitner that where he'd expected to see radium, a heavy metal, he was instead finding barium, a much lighter element. He wrote to Meitner, “perhaps you can suggest some fantastic explanation.”
But the results seemed important enough to merit swift publication, even without Meitner's interpretation. So in December of 1938, Hahn and his colleague, Fritz Strassmann, at the Kaiser Wilhelm Institute submitted a paper to Die Naturwissenschaften, a prominent science journal in Germany.
In the meantime, Meitner was determined to puzzle out those results.
Marissa Moss: So this was Christmas of 38. Otto Robert Frisch, who's Meitner's nephew, who is also a physicist and has been working with Niels Bohr in his lab in Copenhagen, he comes to visit his aunt.
Katie Hafner: Otto Robert Frisch's father was still imprisoned at Dachau, and his mother was still in Vienna, so the holiday was quiet: just Meitner and Frisch visiting one of Meitner’s friends on the western coast of Sweden. Meitner told her nephew about Hahn's results.
Marissa Moss: And she says, what's going on? Can you help me think this out. And he gets on some skis to go cross-country skiing. She's walking beside him in the snow.
Katie Hafner: Frisch tells her that Hahn probably just needs to repeat the experiments.
Marissa Moss: and she says, no, no, no, no. He is too careful a chemist for that. I know that. And he's redone these experiments several times and he gets the same results. And that's when she has this sudden epiphany.
Katie Hafner: Meitner thinks back to what she knows about the structure of the atom and the nature of mass and energy. And she realizes...
Marissa Moss: wait a second, all along, we thought we were seeing transuranics, we weren't. We were seeing the uranium nucleus split. We were seeing nuclear fission.
Katie Hafner: The process would release energy -- an amount that could be calculated using Einstein's equation: Energy = mass times the speed of light (that’s the C – the constant – in the equation) squared.
Marissa Moss: She's slogging the snow in boots and she stops, does the math, a scrap of paper in her pocket and says, that's it. The numbers all add up. And Otto Robert is like, oh my goodness.
Katie Hafner: These days, most students learn about nuclear fission in high school. We accept it and balance our nuclear equations and it can all seem rote and obvious.
But imagine for a moment what it was like for Meitner and her nephew. Back then, the notion of the atom as indivisible, as the smallest possible building block of the universe, was fundamental to how they made sense of the world.
Marissa Moss: But Meitner realizes there's something holding together the nucleus, like what holds together a drop of water. And if it's shocked enough, it gets pulled apart. Just as a drop of water can be pulled apart, the surface tension can pull it apart.
Katie Hafner: Meitner's realization drew upon recent work that Niels Bohr and other scientists had been doing on the structure of the atom. They proposed a liquid-drop model of the nucleus, where subatomic particles were held together by strong nuclear forces. Meitner realized that the nucleus was not indivisible after all. She seemed open to this insight in a way that other scientists weren't-- even Bohr himself.
Marissa Moss: Science means you have to have an open mind and not look for what you expect. Hahn is looking for what he expects. Bohr was looking for what he expected. Meitner is looking at what's there and trying to explain what is this, and that's how she comes up with this discovery.
Katie Hafner: Together, Meitner and her nephew, Otto Robert Frisch, wrote and submitted a paper to the journal Nature. That paper was the first to use the term fission for the splitting apart of the nucleus. They titled it: "Disintegration of Uranium by Neutrons: A New Type of Nuclear Reaction."
All of this happened in just a few weeks -- Hahn's original paper came out January 6th. Meitner and Frisch submitted theirs only ten days later. And throughout, Hahn and Meitner were furiously sending letters back and forth to each other.
Voice Actor: (7 Februar. Liebe Lise) Dear Lise, Earlier, I got your letter from February 5th and I'll answer right away. I don't think you're aware of how much I pushed on your behalf, and how happy I was to help you. I've tired myself out to do small things, whatever I could. On the large scale, I can't do anything.
Voice Actor: Dear Hähnchen, today, I got your letter from the eighth, which made me pretty unhappy. I must have expressed myself very badly since you misunderstood every word.
( Liebes Hähnchen Heute bekam ich deinen Brief vom Achten, der mich ziemlich unglücklich macht. Ich muss mich wohl sehr ungeschickt ausgedrückt haben, denn du hast tatsächlich fast jedes Wort missverstanden. )
Katie Hafner: As Marissa Moss sees it, these letters show not only the breakdown in Hahn and Meitner's relationship -- they reveal that Hahn was increasingly concerned about his reputation and standing as a scientist.
Marissa Moss: And part of it is he’s getting pushback, major pushback from the physicists in Berlin at the Kaiser Wilhelm Institute where he is, because now they see, wait a second, you're, you've been working with a Jew. How have you been sharing good German science with a Jew?
Katie Hafner: Hahn wrote to Meitner about it.
Voice Actor: I don't give these things much weight, of course, but didn't want to confess to the gentleman that you were the only one who found out everything immediately.
Katie Hafner: Still, over time, what he was hearing from his colleagues began to trouble him. Was she trying to take credit for his work? Would he lose standing at the Kaiser Wilhelm Institute because he’d been working with her?
Meitner's discovery was rapidly causing waves worldwide. At a big international conference of theoretical physicists in Washington, DC, Bohr presented her findings. Hahn was worried about what it would mean for him in Berlin.
Marissa Moss: He writes to her about the pressure he’s facing and that she, he keeps using the term loyal. She should be loyal to the Kaiser Wilhelm Institute, because surely she understands his position there and how tenuous it was because he helped her and worked with her.
So she should show some loyalty to him and to the Kaiser Wilhelm Institute.
Katie Hafner: She responded with her characteristic steady, quiet insistence.
Voice Actor: 1st Marz, 1939, I ask you sincerely write to me, quite frankly, which people were offended and in which places. Once I know what was taken amiss, then maybe I can clarify things.
(Ich bitte dich aber jetzt herzlich, schreibe mir ganz aufrichtig, welche Herren eingeschnappt waren und wegen welcher Stellen. Wenn ich aufrichtig weiß, was verübelt worden ist, kann ich es vielleicht aufklären.)
Katie Hafner: Meitner, too, had cause for concern. Since they were no longer publishing papers together, she counted on Hahn to reference her work in his writing. Otherwise, it would seem like the discovery of fission was entirely Hahn's achievement.
Voice Actor: 15th Juli. Now, as for my remark about the theoretical interpretation of the fission process, you didn't refer to our work. I've only mentioned it because I think you can be misunderstood.
(Was nun meine Bemerkung darüber betrifft, dass ihr bei der theoretischen Deutung des Fischen Prozesses euch nicht auf unsere Arbeit bezogen habt, so habe ich sie nur angeführt, weil mir scheint, dass ihr missverstanden werden könnt.)
Katie Hafner: Meanwhile, the political situation got worse. As a Jew, Meitner could not access her pension – the assets had been seized. As for her academic publications, co-written with Hahn...
Marissa Moss: With the Nazi regime, her name is stripped off of every publication they ever submitted, ever published. It's taken off. So he stands alone as the writer.
Katie Hafner: But Meitner did succeed in getting her siblings out of Austria. By the summer of 1939, one sister had joined her in Sweden and another made it to England. Meitner herself considered accepting a position at Cambridge, but that September, Germany invaded Poland and war was declared.
Archival: Germany's air arm, better known as the Luftwaffe blazes the trail for the opening attacks on Holland, Belgium and tiny undefended Luxembourg.
The attacks come at dawn without warning.
Hitler's combat engineers have given evidence that the impregnable fort of yesterday is today just another target for superior offensive weapons.
Katie Hafner: The start of the war kicked off an arms race -- and both Allied and Axis powers considered the possibility of an atomic bomb. That's next time on Lost Women of Science.
Ashraya Gupta: This has been Lost Women of Science. This episode was produced by me, Ashraya Gupta. Lizzy Younan composes our music. Paula Mangin creates our art. Alex Sugiura is our audio engineer and Danya AbdelHameid is our fact-checker.
Katie Hafner: Thanks to Amy Scharf, Jeff DelViscio, Jeannie Stivers, Eowyn Burtner, Nora Mathison, Deborah Unger, Hilda Gitchell, and Lauren Croop.
Thanks also to Barbara von Bechtolsheim and Peter Wehmeier for reading the Meitner-Hahn letters. And special thanks to Marissa Moss for all her input.
Ashraya Gupta: Lost Women of Science is funded in part by the Alfred P. Sloan Foundation and Schmidt Futures. We’re distributed by PRX and produced in partnership with Scientific American.
Katie Hafner: You can find a lot more – including the all-important donate button – at lostwomenofscience.org. Thanks so much for listening. I’m Katie Hafner.
The Woman Who Split the Atom: The Life of Lise Meitner, Marissa Moss, Abrams Books for Young Readers, 2022
Lise Meitner: A Life in Physics, Ruth Lewin Sime, University of California Press, 1997
Disintegration of Uranium by Neutrons: a New Type of Nuclear Reaction, L. Meitner & O.R. Frisch, Nature, 11 February, 1939
Lise Meitner Looks Back, Bulletin of the Atomic Scientists 20, no. 9 (November 1964), p.2-7
Operation Epsilon: The Farm Hall Transcripts, Sir Charles Frank, Berkeley, University of California Press, 1993
Lise Meitner, Atomic Pioneer, Deborah Crawford, New York, Crown, 1969
[Image credit: Paula Mangin]