Sahaana Vijay
Abstract
As of October 2021, there are 441 operational nuclear reactors in roughly 30 nations.[1] These nuclear reactors generate power through nuclear fission, which earned Otto Hahn, a German chemist, the Nobel Prize in chemistry in 1944.[2] While the prize was unshared, Hahn did not discover nuclear fission alone; he and his long-term colleagues, physicist Lise Meitner and his assistant Fritz Strassmann, undertook a four-year study in their Berlin laboratory that resulted in the discovery of fission. This article, however, will throw light on the contributions of the Austrian-Swedish physicist, Lise Meitner, who first coined the term nuclear fission in a research paper.
Figure 1: Sculpture of Lise Meitner in Humboldt University of Berlin.
Early Years & Discovery
It was in 1938 that Nazi Germany, under the leadership of Adolf Hitler, annexed Austria to the Third Reich, which led to many Jews fleeing the country to escape persecution, and Lise Meitner was one of them.[3] In December the very same year, Meitner, along with Hahn and Strassmann, discovered fission. Lise Meitner was a prolific woman in physics, who as a nuclear physicist, never lost her humanity.
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Lise Meitner was born in Vienna, Austria, on November 7, 1878. In 1901, she entered the University of Vienna, where she studied physics under the physicist Ludwig Boltzmann, a well-known theoretical physicist and a liberal who advocated for women’s education; he often advised her to envision physics as a battle for ultimate truth. She earned her doctorate in 1906, the second woman in Vienna to do so.[4] In 1907, Meitner moved to Berlin, where she met the chemist Otto Hahn and studied radioactivity with him. Their collaboration culminated in the discovery of protactinium, a very heavy radioactive element, in 1918. In fact, they were nominated for the Nobel Prize for ten consecutive years for their work. While Hahn continued to study radiochemical methods, Meitner went on to pursue nuclear physics.[4]
In the 1930s, the Italian physicist Enrico Fermi had found out that when a nuclear reaction occurs, the incoming neutron causes the target neutron to emit a photon or an alpha particle. In heavier elements, the nucleus would receive an extra neutron, and if the element is radioactive, it will decay by producing beta radiation. When Fermi bombarded Uranium, which was the heaviest known element at that time, he had discovered new elements that did not have the properties of Uranium or any other element. At that time, Lise Meitner was already one of the top nuclear physicists and was studying the transuranic elements discovered by Fermi. She reached out to Hahn and his assistant, Strassmann, to study them in detail. Hahn and Strassmann carried out the analysis, whereas Meitner explained the processes theoretically. The discovery of the neutron by James Chadwick in 1932 gave a boost to their research on radioactivity and transuranic elements.
In 1938, she escaped Germany to the Netherlands and then Denmark, where she stayed with her friend, another prominent physicist, Niels Bohr. Meitner finally settled in Sweden, where she worked at the Nobel Institute for Physics.[5] In December, Hahn and Strassmann found out that when the Uranium nuclei were bombarded with neutrons, lighter elements such as Barium and Krypton were produced. They reported the findings to Meitner, who confirmed, after her meticulous calculations, that nuclear fission had taken place and is a real phenomenon. She also found out that this phenomenon can produce tremendous amounts of energy. News of this discovery quickly spread to the world, after which the United States prepared themselves to build the first atomic bomb under the Manhattan Project.
Aftermath
After this discovery, it was Otto Hahn alone who received the Nobel Prize, as mentioned earlier. Her contributions were largely forgotten, though she deserved the prize. Why was she marginalised?
Strassmann probably did not receive the Nobel Prize due to the fact that he was a junior investigator and the Nobel committee often preferred the seniors; however, Meitner and Hahn had equal professional status.
Albeit a great scientist, Otto Hahn often downplayed Meitner’s contributions, stating that the discovery of nuclear fission was exclusively based on the experiments conducted by him while Meitner had fled Germany and that she had nothing to do with it, except for delaying it. He also disagreed that physics had something to do with nuclear fission. Hahn further published the results without including her name, though he could not explain clearly how the Barium neutrons suddenly popped. This was due to the fact that he could not include a non-Aryan’s name in the publication. He was afraid for his position and himself as they lived in Nazi Germany where Jews were discriminated against.[4]
The Nobel committee could not acknowledge that this was an interdisciplinary field and that Meitner contributed equally, and therefore, conferred the prize solely on Hahn. Even though Meitner wrote to the journal Nature explaining what Hahn had allegedly discovered on his own, her contributions were overlooked. Strassmann, on the other hand, begged to differ. He asserted that Meitner had a pivotal role in the discovery and that she had been their ‘intellectual leader’.[4]
This was a blatant example of racism and sexism displayed by the Nobel committee, as she was a Jewish woman.
Legacy
Later, in 1943, she was asked to join the Manhattan Project, but she declined the offer as she ‘did not want anything to with a bomb’. Ergo, her nephew, who also worked with her to first articulate the science of nuclear fission to the world, wrote the epitaph on her gravestone as follows – ‘Lise Meitner: a physicist who never lost her humanity.’ She continued her research work in Sweden and later England and died in the year 1968.
Even though she was not awarded the Nobel Prize, her work was honoured by naming the element with atomic number 109 as Meitnerium. As a tribute to her, a statue of her was installed in the Humboldt University of Berlin. Furthermore, Meitner and Hahn were awarded the Enrico Fermi Award by the U.S. Department of Energy. The story of nuclear fission could not be told without the mention of the physicist Lise Meitner, and she would always be remembered as, the mother of nuclear energy.[5]
“Science makes people reach for truth and objectivity; it teaches people to accept reality, with wonder and admiration, not to mention the deep awe and joy that the natural order of things brings to the true scientist.” ― Lise Meitner
Figure 2: Physicists & Chemists in Berlin. Lise Meitner is to the extreme left. Can you spot Einstein? [Wikimedia Commons]
References
[1] “Nuclear Power Plants by Country 2021.” Statista, 1 Dec. 2021, https://www.statista.com/statistics/267158/number-of-nuclear-reactors-in-operation-by-country/.
[2] Otto Hahn – Facts. NobelPrize.org. Nobel Prize Outreach AB 2022. Thu. 24 Feb 2022. https://www.nobelprize.org/prizes/chemistry/1944/hahn/facts/
[3] Sime, Ruth Lewin. “Lise Meitner: A 20th Century Life in Physics – ResearchGate.” ResearchGate, Endeavour, 2002, https://www.researchgate.net/publication/240921896_Lise_Meitner_a_20th_century_life_in_physics.
[4] Sime, Ruth Lewin. “Lise Meitner and the Discovery of Nuclear Fission.” Academia.edu, Scientific American , Jan. 1998, https://www.academia.edu/4280348/Lise_Meitner_and_the_Discovery_of_Nuclear_Fission.
[5] Pershing, Bob. “Lise Meitner, the Mother of Nuclear Energy.” LinkedIn, LinkedIn, 3 Dec. 2016, https://www.linkedin.com/pulse/lise-meitner-mother-nuclear-energy-bob-pershing.