Lise Meitner and the Walk that Changed the World
It was December 1938, and a physicist, having recently fled Nazi Germany, and her nephew found themselves in the serene countryside of Kungälv, Sweden, taking a break from the desk. As snow crunched beneath their feet, they puzzled over a letter from physicist Otto Hahn, describing a mysterious experiment that produced barium from uranium. This experiment did not make sense until, right there in the woods, inspiration struck. They realized that the uranium nucleus had split in two, which was a revolutionary concept that would soon be known as nuclear fission. The physicist and the nephew? Lise Meitner and her nephew, Otto Frisch.
Hi, I’m Gabrielle Birchak. Welcome to Math! Science! History! Today, we are traveling back to one of the most pivotal moments in 20th-century science. Not to a lab. Not to a lecture hall. But to a snowy forest in Sweden. This is the story of that discovery and the remarkable woman who made it.
The Making of a Scientist
Lise Meitner was born in Vienna, Austria, in 1878. In an era when men barred women from higher education, she became only the second woman to earn a doctoral degree in physics from the University of Vienna in 1906.
Because of strict Austrian rules at the time, women weren’t allowed to attend college. But Meitner’s family believed in her education and could afford private schooling, which she finished in 1901. She then enrolled in graduate studies at the University of Vienna, where the great physicist Ludwig Boltzmann inspired her. His passion for science inspired her, and she chose to focus on physics, especially the new and exciting field of radioactivity. In 1905, she became only the second woman to earn a doctorate in physics from the University of Vienna, following Olga Steindler, who received her doctorate in physics in 1903.[1]
Upon receiving her degree in 1906, she began independent research to obtain results that Lord Rawleigh could not explain. She not only explained the results but then verified them experimentally. Her results were published in the paper “Some Conclusions Derived from the Fresnel Reflection Formula.” The research and the experiments were foundational to leading Ernest Rutherford to predict the nuclear atom.[2]
She then began attending Max Planck’s lectures at the Friedrich Wilhelm University in Berlin. Planck went on the record stating that he did not want women in the universities. However, Meitner was a brilliant exception to the extent that he even invited her to his home.[3] Still, these lectures were not engaging enough for her, and she had spare time. As a result, she approached Heinrich Rubens, who was the head of the Experimental Physics Institute. She wanted to do some research, and so Rubens introduced her to Otto Hahn. This is key because Hahn’s experience included deep research on radioactive substances. Hahn and Meitner were the same age and considered each other as peers.
Emil Fischer, who was the head of the chemistry institute, clearly wanted to work with both. As a result, he allocated a former woodworking shop in the basement to Hahn and Meitner for their laboratory, which they equipped with tools that enabled them to measure alpha and beta particles, as well as gamma rays. This would be foundational to their deep research. Meitner and Hahn were both unpaid, and many of the organic chemists at the institute regarded their work as irrelevant because they could neither see, measure, nor smell their radioactivity.[4]
The early part of her career was challenging, as she faced significant barriers as a woman in science. Because women were not allowed in the institute, she had to enter the basement laboratory through a separate door. Sadly, the inorganic chemistry department would only allow Hahn to visit two private laboratories in the upper levels. Meitner was not allowed to go upstairs. Additionally, she could not use the men’s restroom; as a result, she had to go down the street to a restaurant to use their restroom. However, a year later, women were allowed to study at Prussian universities. As a result, Fisher lifted restrictions and even had women’s toilets installed in the building. This did not go over well with many of the male chemists at the institute.
Nevertheless, she made friends, loyal friends who were there for her. These included Otto von Bayer, James Frank, Gustav Hertz, Robert Powell, Peter Pringsheim, and Wilhelm Westphal. These gentlemen would play a vital role in her life many years later.
Hahn and Meitner worked so well together that they published nine papers between 1908 and 1909. In their experiments, they applied radioactive recoil, which is the backward momentum that occurs when an atom or nucleus emits radiation or particles during radioactive decay. This was first recognized by Harriet Brooks, who was Canada’s first female nuclear physicist and one of the earliest pioneers in radioactivity. She had been working closely with Ernest Rutherford. She was one of the first to understand the behavior of radioactive elements. I promise to do a podcast on Harriet Brooks as well, because her brilliance needs to be recognized. The process of radioactive recoil involves a daughter nucleus being forcefully ejected as it recoils during the moment of decay.
It works like this: Imagine you’re in a batting cage. There’s a pitching machine, which, if you’ve been in a batting cage, you know is a solid, heavy device designed to stay in place. But when it fires a baseball, the machine gives a little jerk backward. We barely notice it, but it’s real. That tiny backward movement is caused by the force of the ball being launched forward. Now take that same idea and shrink it down to the atomic level.
Inside an atom, the nucleus is like that pitching machine: heavy and packed with particles. But sometimes it’s unstable. When it needs to become more stable, it emits a particle, such as an alpha particle or a neutron. And just like the pitching machine, the nucleus recoils in the opposite direction of the particle it emitted. This tiny jolt is called radioactive recoil, which happens because of one simple rule of physics: For every action, there’s an equal and opposite reaction.
So when the nucleus “throws” something out, it can’t help but move the other way. And this recoil is essential to the work that Meitner and Han were doing. The recoil is powerful enough on an atomic scale to knock atoms out of place in materials, break chemical bonds, or even damage cells if it happens inside the body. So in short, radioactive recoil is the atomic version of that barely-noticeable kickback your pitching machine feels when it fires a fastball. Small, fast, and, if you’re on the receiving end, potentially pretty impactful.
The reason I bring this up is that Meitner found that using radioactive recoil could help her detect radioactive substances. As a result, Meitner and Hahn were able to find two more new isotopes, including bismuth-211 and thallium-207.
In October 1912, the Kaiser Wilhelm Institute (KWI) for Chemistry opened in Berlin-Dahlem, and Meitner and Hahn moved their research to this new institute. The KWI, being privately funded, had no formal rule excluding women, a progressive step compared to the university.[5] However, Meitner’s status initially remained far from equal. Otto Hahn was appointed head of the new Radiochemistry Department with the title of “Professor” and a respectable salary. In contrast, Meitner was invited to join him only as an unpaid scientific guest. So, although the KWI had no formal exclusion of women, these rules highlight how women often entered such institutes through unofficial or junior roles.
By the end of 1912, Max Planck intervened to secure Meitner her first-ever paid position, hiring her as his assistant at the University’s Institute for Theoretical Physics (marking her as the first female scientific assistant in Prussia). Soon after, in 1913, Meitner was formally appointed as an associate of the KWI for Chemistry, equivalent in rank to Hahn’s position, which finally granted her a title and a modest salary. Notably, it was Emil Fischer who arranged for her new paid appointment at the KWI. This progression illustrates both the progress and remaining inequities that women continue to face in a male-dominated scientific world.
It took several years of excellent research and the gradual modernization of attitudes before she achieved official status and a corresponding salary. By 1926, Meitner would become the first woman to hold a professorship in physics in Germany.[6]
For over 30 years, Meitner and Hahn formed a close working partnership. She brought the theoretical physics expertise; he, the chemistry. Together, they explored the inner workings of the atomic nucleus, becoming pioneers in the newly emerging field of nuclear science.
Escaping Germany
But Meitner’s life and career would be upended by politics. In 1933, Adolf Hitler came to power. As a woman and, more importantly, a Jew, Meitner’s position in Germany became increasingly precarious. By 1938, it was no longer safe for her to stay. So, even though she was born an Austrian citizen in 1878, when Hitler came to power in Germany in 1933, Meitner, who had lived and worked in Berlin since 1907, retained her Austrian citizenship. However, in March 1938, Austria was annexed by Nazi Germany in the Anschluss. What this meant for all Austrians is that they were automatically considered German citizens under Nazi law. However, under the Nuremberg laws, Meitner was classified as Jewish even though she had converted to Lutheranism. This meant that she was now subject to the regime’s systemic racial persecution. Thus, she lost the protections of Austrian citizenship, and the Nazis forced her to resign from her position in Berlin. It was a horrible situation. She was a stateless person without a valid passport. As a result, like many individuals in the United States today, she faced arrest.
As the political climate in Nazi Germany grew increasingly dangerous, Meitner found herself in grave peril. Without a passport and under mounting pressure, she had to flee. Her escape was made possible thanks to the bravery of Dutch physicist Dirk Coster, who secretly traveled to Berlin under the guise of attending a conference. With the help of Adriaan Fokker, Coster arranged for Meitner to be smuggled across the German-Dutch border. From there, she made her way to Copenhagen, where she was quietly welcomed by Niels Bohr, a longtime colleague and supporter. Though he was not directly involved in her escape, Bohr’s influence and reputation helped ease her transition and provided a crucial scientific lifeline. With his backing and network, Meitner was able to continue on to Stockholm, Sweden, where she found refuge.[7] Their courage and support not only saved her life but also enabled Meitner to continue her groundbreaking research, which would soon lead to the discovery of nuclear fission.
Sadly, she was stateless for two years, which, as many individuals living in the United States are now realizing, is a dangerous thing. Unfortunately, in the United States, persecution is the new reality for so many people, and many worry that it will only get worse.
History, much like science and math, is a valuable tool that can be used to serve humanity. As I mentioned in previous podcasts, history shows us the red flags of danger. It is our responsibility to look for them so that we do not let history repeat itself.
Meitner settled in Stockholm, where she was given a research position at the Nobel Institute for Physics. In the early 1940s, Sweden granted her citizenship. But her lab lacked proper equipment. She was isolated, removed from the scientific community she had helped build. Still, she stayed in contact with Hahn, who continued their joint work in Berlin.
The Mystery Of Barium
Back in Germany, Hahn and his assistant Fritz Strassmann were conducting experiments with uranium. They were bombarding uranium atoms with neutrons to see what heavier elements they could create. According to the prevailing theory of the time, neutron bombardment should lead to the creation of heavier elements, which we now refer to as transuranic elements.[8]
But the results were strange. In December 1938, Hahn and Strassmann detected an unexpected element in their chemical residues: barium. But barium is much lighter than uranium.
Hahn didn’t understand what was happening. So he sent his experimental results in a letter to Meitner, hoping she could explain the physics behind the chemistry.[9] It arrived in the snowy Swedish countryside just before Christmas.
A Walk In The Woods
That Christmas, Meitner received a visit from her nephew, Otto Frisch, also a physicist. He had come to Sweden from Copenhagen to spend the holiday with her. Together, they went on long walks through the woods near Kungälv, outside Gothenburg.
On one of these walks, with snow crunching underfoot and fir trees towering above, they talked through Hahn’s letter. How could uranium atoms produce barium? They sat on a tree stump and started working it out on paper. Meitner proposed that the uranium nucleus had split into two. This theory was unprecedented. No one had ever suggested that a nucleus could break apart in this way. She applied Niels Bohr’s liquid drop model to the problem, suggesting that the nucleus could become elongated and unstable, eventually splitting into two smaller nuclei.[10]
To explain this further, the liquid drop model, developed by Niels Bohr and John Wheeler in the 1930s, describes the atomic nucleus as a drop of liquid made up of tightly packed protons and neutrons. This model was crucial in explaining nuclear fission, specifically when a nucleus becomes unstable and splits apart. So, imagine placing a glob of butter on a hot pan. At first, it holds together, but as heat builds, it begins to wobble, stretch, and flatten. Eventually, suppose you drop a tiny dab of butter on top of that glob. In that case, the butter can break apart into smaller blobs, releasing energy as it moves. So, in the same way, when a neutron strikes a heavy nucleus, it causes it to vibrate and deform. If the conditions are right, the nucleus splits in two, releasing a tremendous burst of energy. While the model doesn’t capture every detail of nuclear behavior, it laid the foundation for understanding how atoms split, and how that split powers everything from reactors to bombs.
In his article titled “Recollections of the Discovery of Nuclear Fission,” Frisch wrote, “We had found the solution. We were the first to understand that the uranium nucleus had split in two. It was a moment of great elation. We could hardly believe it ourselves.”[11]
Thus, that day as Meitner and Frisch walked through the quiet forest, the snow muffled every sound. The bare trees stretched skyward like skeletal fingers, their limbs stark against the pale winter sky. The air was still, save for the crunch of their boots and the occasional chirp of a bird flitting overhead; nature was serene and undisturbed. In that silent, frozen landscape, they discussed the impossible: the splitting of the atom. It was a moment of quiet revelation, born in beauty and isolation. Meitner and Hahn likely had no idea what their discovery could create. The energy released by nuclear fission could be massive. If controlled and placed in the hands of the humane, it could produce power. If uncontrolled and given free rein by unethical individuals, it could create a monstrous bomb.
The idea they unearthed there would lead to horrors far removed from the calm of the woods. Instead of birdsong, the world would later hear screams. Instead of fresh snow, there would be scorched earth, fire, ash, and blood. In that peaceful walk, they had touched the edge of something powerful enough to light cities, or to level them.
The Aftermath
So, after Meitner and Frisch reached their conclusion, Frisch performed the calculations and confirmed it. The mass difference between uranium and the resulting elements accounted for a massive release of energy, as per Einstein’s equation, E = mc². This release of energy was the result of nuclear fission. Meanwhile, before Frisch returned to Copenhagen, Hahn had already submitted his findings to a German journal, but did not credit Meitner or Frisch in his publication. This action was a betrayal that would echo for decades.
Regardless, with Niels Bohr’s encouragement, Frisch quickly published his and Meitner’s paper in Nature, titled “Disintegration of Uranium by Neutrons: A New Type of Nuclear Reaction.” When Hahn and Fritz Strassmann chemically identified barium as a product of bombarding uranium with neutrons, this outcome made no sense within the framework of known nuclear physics. The uranium nucleus hadn’t merely rearranged, it had split. Meitner and Frisch’s paper helped explain the process of nuclear fission, and their work would change the course of history.
But, referring back to the liquid drop model, Meitner and Frisch showed that such a fission process would release an enormous amount of energy, more than anyone had previously imagined, thanks to Einstein’s equation, E = mc². Their concise article introduced the term “a new type of nuclear reaction,” but the implications were anything but modest. It was the first correct theoretical explanation of nuclear fission, opening the door to both nuclear power and the devastating weaponry that would soon reshape the modern world.[12]
Despite this, when the Nobel committee awarded the 1944 Prize in Chemistry, it went solely to Hahn. They did not even mention Meitner’s name. Historians and physicists alike have since called this omission one of the most glaring oversights in Nobel history.
The Philosopher Of Science
Lise Meitner never returned to Germany. She continued her work in Sweden and later moved to Cambridge, England, after the war.
Though her name was known among physicists in the United States, Lise Meitner was never officially asked to join the Manhattan Project. The closest she came was through informal channels. In 1943, Niels Bohr, who had fled occupied Denmark and was consulting on the bomb effort in America, suggested Meitner’s name as someone who might be helpful. But by then, she had already made up her mind. Living in neutral Sweden, Meitner had watched the world descend into war and saw what unchecked scientific ambition could lead to. When she learned of the Manhattan Project, she firmly declined to participate. While newspapers later dubbed her “the mother of the atomic bomb,” she rejected the title with sorrow and conviction. She was horrified by how the men at the Manhattan Project had used her discovery to create nuclear weapons. She had helped explain how to split the atom, but she wanted no part in splitting humanity with it.[13] Meitner remained adamant: science should serve humanity, not destroy it.
Beyond her groundbreaking role in the discovery of nuclear fission, Lise Meitner made several other significant contributions to physics. Early in her career, she and Hahn discovered the element protactinium, which was a considerable achievement in the field of radiochemistry. She also conducted extensive research on beta decay, contributing to our understanding of how atoms release energy. Another lesser-known fact is that she was one of the first to theorize about the Auger effect, which describes how atoms release energy through electron transitions. Her work laid the groundwork for many areas of nuclear and atomic physics, and her legacy is truly expansive.
In 1946, she was named “Woman of the Year” by the National Press Club in Washington, D.C., celebrated alongside Eleanor Roosevelt for her contributions to science and peace. That same year, she received honorary doctorates from several U.S. institutions, including Harvard University and Smith College. In Europe, honors continued to accumulate: in 1955, she was awarded both the prestigious Max Planck Medal by the German Physical Society and the Otto Hahn Prize for Chemistry and Physics, the latter shared with Hahn and Strassmann. In 1957, Meitner received the Pour le Mérite for Sciences and Arts, one of Germany’s highest civilian honors. She was also elected a Foreign Member of the Royal Society in the United Kingdom in 1955, making her only the third woman ever to receive that distinction. These awards reflect the scientific community’s growing acknowledgment of her vital role in the discovery of nuclear fission and her principled refusal to participate in its weaponization. In 1997, long after her death, the element Meitnerium-109 was named in her honor.
The Nobel That Never Came
Meitner was nominated for a Nobel Prize 48 times. Forty. Eight. Times. And yet, she never received one.
At first glance, this seems unbelievable. How could the woman who helped explain nuclear fission, the very discovery that ushered in the atomic age, be left out? But the answer lies at the tangled intersection of science, gender, politics, and timing.
To begin with, Meitner faced an uphill battle simply because she was a woman. In the early twentieth century, physics and chemistry were extensively male-dominated fields. Despite her achievements, she was often referred to not as a scientist, but as Hahn’s assistant. Behind closed doors, she was sometimes referred to as “Miss Meitner,” even after earning her doctorate and publishing independently. Gender bias ran deep, and the Nobel Committees were no exception. At the time, only two women, Marie Curie and Irène Joliot-Curie, had ever won Nobel Prizes in the physical sciences.
Then there’s the issue of what kind of science gets rewarded. The 1944 Nobel Prize in Chemistry went to Hahn, recognizing his experimental detection of barium in neutron-bombarded uranium. But the theoretical interpretation, the breakthrough realization that this meant the nucleus had split, came from Meitner and her nephew, Frisch. The Nobel Committee favored experimental chemistry over theoretical physics, even though the interpretation is what made the discovery historically and scientifically meaningful. Meitner’s role wasn’t just support; she connected the pieces that defined the phenomenon as fission.
Wartime politics didn’t help. When the Nobel Prize was awarded, Meitner was a Jewish refugee living in Sweden, having fled Nazi Germany in 1938. Hahn, by contrast, had remained in Germany. The Nobel Committee may have feared the optics of awarding a prize to someone in exile, or of highlighting a Jewish woman’s critical contribution while the world was still reeling from Nazi atrocities. It’s no coincidence that the Nobel committee did not announce Hahn as the recipient until after the war had ended.
There’s also a more mundane, but no less tragic reason: Meitner lacked a strong advocate on the Nobel Committee. Many laureates have behind-the-scenes champions pushing their case year after year. Meitner didn’t. Her nominations were scattered, often switching between physics and chemistry categories, and they came too late to override the 1944 decision.
Later in life, she was honored with numerous awards, honorary doctorates, the Max Planck Medal, and even the naming of element 109, meitnerium. But the Nobel? That remained forever just out of reach.
Today, scientists and historians widely recognize that Lise Meitner’s exclusion was one of the greatest injustices in the history of science. Not because she wasn’t nominated, but because the system simply wasn’t ready to see her. These groups of men weren’t blind to her brilliance; they chose to look away.
She was not just a brilliant physicist. Even in exile, even with very little, she changed the world. Not with force. Not with power. But with quiet brilliance and the courage to speak truth, even when others did not. No doubt, she was also a deeply ethical scientist, someone who stood by her principles in the face of immense pressure.
Lise Meitner once said:
“Science makes people reach selflessly for truth and objectivity; it teaches people to accept reality, with wonder and admiration… not to mention the deep awe one feels in discovering the order of the universe.”[14]
Thus, her life reminds us that sometimes the most profound discoveries don’t happen in labs; they occur in conversations, on long walks, during stolen moments of peace in a world at war.
And I can attest, I have been there. In my early college years, I would often sit alone in my apartment, in the dark because I had forgotten to turn on the lights, with a tiny desk lamp, entirely consumed by my studies, taking in insight and inspiration. There is no greater feeling than an epiphany. And I don’t know who needs to hear this, but for those of you who have your head in a book, consuming mathematics, physics, chemistry, and even history, I genuinely hope that you feel the intensity of a revelation and that inspires you to keep moving forward in your research and your discoveries. Your enlightenment can change the world, and that’s really what we need right now. We need a future where science illuminates, not annihilates.
Thank you for listening to Math! Science! History! And until next time, carpe diem!
ADDITIONAL SOURCES:
Lanouette, William, and Bela Silard. Genius in the Shadows: A Biography of Leo Szilard, the Man Behind the Bomb. Chicago: University of Chicago Press, 1992.
Mehra, Jagdish, and Helmut Rechenberg. The Historical Development of Quantum Theory, Vol. 6. New York: Springer, 2001.
Walker, Mark. German National Socialism and the Quest for Nuclear Power, 1939–1949. Cambridge: Cambridge University Press, 1992.
Hattersley, “The Women Behind the Science: Lise Meitner.” https://www.ppd.stfc.ac.uk/Pages/Lise-Meitner.aspx
[1] Alina Bradford. “Lise Meitner: Life, Findings and Legacy.” Live Science, March 29, 2018. https://www.livescience.com/62162-lise-meitner-biography.html.
[2] Physics Journal. Leipzig : S. Hirzel, 1899. http://archive.org/details/physikalischeze00unkngoog.
[3] Lewin Sime, Ruth. “From Exceptional Prominence to Prominent Exception.” Der Nervenarzt 73, no. 11 (November 1, 2002): 1107-11. https://doi.org/10.1007/s00115-002‑1426‑9.
[4] Hahn, Otto. Otto Hahn: A Scientific Autobiography. New York, C. Scribner’s Sons, 1966, 52. http://archive.org/details/ottohahnscientif0000hahn_y3a1.
[5] Lewin Sime, Ruth. “From Exceptional Prominence to Prominent Exception.” Der Nervenarzt 73, no. 11 (November 1, 2002): 1107-11. https://doi.org/10.1007/s00115-002‑1426‑9.
[6] Dumancic, Mirta, and Shirin A. Enger. “Pioneering Women in Nuclear and Radiation Sciences.” Radiotherapy and Oncology 197 (August 2024): 110374. https://doi.org/10.1016/j.radonc.2024.110374.
[7] Sime, Ruth Lewin. Lise Meitner : A Life in Physics. Berkeley : University of California Press, 1996, 32–39. http://archive.org/details/lisemeitnerlifei00sime.
[8] Hahn, Otto, and Strassmann, Fritz. “Über die Entstehung von Bariumisotopen aus Uran durch Bestrahlung mit Neutronen.” Die Naturwissenschaften, vol. 27, no. 1, 1939, pp. 11–15.
[9] Frisch, Otto. “Recollections of the Discovery of Nuclear Fission.” Physics Today, vol. 31, no. 11 (1978), pp. 43–48.
[10] Bohr, Niels, and J.A. Wheeler. “The Mechanism of Nuclear Fission.” Physical Review 56, no. 5 (1939): 426–450. https://doi.org/10.1103/PhysRev.56.426
[11] Frisch, Otto R. “Recollections of the Discovery of Nuclear Fission.” Nature 213, no. 5078 (1967): 355–358.
[12] Frisch, Otto R., and Lise Meitner. “Disintegration of Uranium by Neutrons: A New Type of Nuclear Reaction.” Nature 143, no. 3615 (1939): 239–240.
[13] Rhodes, Richard. The Making of the Atomic Bomb. New York: Simon & Schuster, 1986.
[14] Sime, Ruth Lewin. Lise Meitner : A Life in Physics. Berkeley : University of California Press, 1996, 32–39. http://archive.org/details/lisemeitnerlifei00sime.