Why the ‘mother of the atomic bomb’ never won a Nobel – 10/08/2023 – Science

There’s a memorable scene in “Oppenheimer,” the hit movie about the building of the atomic bomb, in which Luis Alvarez, a physicist at the University of California, Berkeley, is reading a newspaper while getting a haircut. Suddenly, Alvarez jumps out of his chair and runs down the road to meet his colleague, theoretical physicist Robert Oppenheimer.

“Oppie! Oppie!” he screams. “They did it. Hahn and Strassmann in Germany. They split the uranium nucleus. They split the atom.”

The reference is to two German chemists, Otto Hahn and Fritz Strassmann, who in 1939 unknowingly reported a demonstration of nuclear fission, the fragmentation of an atom into lighter elements. The discovery was pivotal to the Manhattan Project, the top-secret American effort led by Oppenheimer to develop the first nuclear weapons.

The scene, however, is not entirely accurate, to the chagrin of some scientists. One important character is missing: Lise Meitner, a physicist who worked closely with Hahn and developed the theory of nuclear fission.

Meitner was a giant in her own right, a contemporary of Nobel laureates such as Albert Einstein, Niels Bohr and Max Planck. After the second atomic device was dropped in Nagasaki, Japan, the American press dubbed her the “mother of the atomic bomb”, an association she vehemently rejected.

Only Hahn won the Nobel Prize for nuclear fission. In speech, he referred to Meitner with a German term meaning assistant or employee, according to Marissa Moss, author of a recent book about Meitner. “Or at most a co-worker,” she said.

In 2022, Moss searched Meitner’s archive at Cambridge University. Since then, she has translated hundreds of letters between Meitner and Hahn, written in German, which she says offer a more detailed perspective on the end of their relationship. This view also challenges the common perception that Meitner accepted the Nobel Prize outcome without hard feelings.

According to Moss, the contempt went beyond gender. “It’s easy to say she didn’t get it because she was a woman,” Moss said. “A woman isn’t expected to make a fuss about things.” Moss also believes that Meitner’s heritage was at stake: “It’s because she was Jewish.”

In 1947, Meitner wrote to her nephew Otto Robert Frisch, a Jewish physicist who also contributed to the discovery of nuclear fission: “I know that his attitude contributed to the Nobel committee deciding against us,” she said of Hahn, in a letter translated by Moss. “But this is something purely private that we don’t want to make public.”

Nobel Week is a time when the scientific community celebrates its greatest achievements, but also, increasingly, examines omissions and injustices. Lise Meitner is one of many women in science who have not received due credit for their work, including, perhaps most notably, Rosalind Franklin, the chemist who contributed to the discovery of the double helix structure of DNA in 1953.

“There are hundreds, if not thousands, of women who achieve something great in science and simply go unrecognized in life,” said Katie Hafner, host of the “Lost Women of Science” podcast. Hafner recently completed a two-part episode about Meitner, the second half of which begins with the Oppenheimer scene. Unlike other figures on her podcast, Hafner said, “Lise Meitner is not lost.”

But, she added, “she is misunderstood.”

A radioactive pioneer

From the beginning, Meitner was breaking barriers. Born in 1878 in Vienna, she began studying physics privately, as women in Austria were not allowed to attend university until 1897. In 1901, she enrolled in graduate school at the University of Vienna; Five years later, she earned a doctorate in physics, only the second woman from her university to do so.

Meitner spent the rest of his career working among the greats. She moved to the University of Berlin and began attending classes taught by Max Planck, who won the Nobel Prize in Physics in 1918 — and who generally did not allow women to attend his lectures.

In 1938, Germany invaded Austria, leaving Meitner within the reach of the Nazi regime. She decided to run away. Bohr, a Nobel laureate in physics, arranged for her escape by train.

Meitner arrived in Sweden, devastated by having to leave her life’s work behind and worried about her family’s safety.

She continued to collaborate with Hahn via correspondence. He performed experiments, and she interpreted findings that he did not understand. One result perplexed them: when uranium atoms were bombarded with neutrons, the neutron was supposed to be absorbed and an electron released, creating a heavier element. Instead, Hahn found barium, a much lighter element. They were perplexed.

The discovery was outside Hahn’s expertise as a chemist. “Perhaps you can propose some fantastic explanation,” he wrote in a letter to Meitner translated by Ruth Lewin Sime, a chemist at Sacramento City College who published a biography of Meitner in 1996. “If there is something you can propose and publish, then it would still be, in a way, a job for the three of them!”

A theory is born

In Sweden, Meitner pondered the results with Frisch, her physicist nephew. On a cold day, Frisch recalled in a memory, they went for a walk, eventually stopping to sit on a tree trunk and write down calculations on pieces of paper.

They realized that uranium was extremely unstable and would likely fragment upon contact with, say, a neutron. These fragments would be violently exploded. If one of those pieces was barium, Meitner reflected, the other would have to be another light element called krypton. She calculated the energy driving the explosion using Einstein’s famous equation, E = mc^two.

Hahn and Strassmann had split the atom.

“We have read and carefully considered your paper,” Meitner wrote to Hahn in January 1939. “It may be energetically possible for such a heavy nucleus to disintegrate.” In a later letter, she expressed disappointment at being absent: “Even though I am here empty-handed, I am happy for these wonderful discoveries.”

Meitner and Frisch published their theoretical interpretation of Hahn and Strassmann’s results in the February 1939 issue of Nature. Frisch and Meitner designed experiments to test the hypothesis. In the following weeks, they published two more papers with the results, which became the first physical confirmation of what Frisch called “nuclear fission.”

Later that year, Germany invaded Poland. The Second World War had begun. And the race to build an atomic bomb was on.

Word spread about nuclear fission. Although a single split atom would not generate enough energy for potential use in a weapon, some speculated that a chain reaction could solve the problem. Bombarding uranium with neutrons not only produced lighter elements, it also created more neutrons. If these neutrons collided with more uranium, the reaction could sustain itself.

The American government set up the Manhattan Project to develop a weapon of this type. Many of Meitner’s colleagues, including Frisch and Bohr, became involved. Einstein did not do so, although he did write a letter to President Franklin D. Roosevelt urging him to secure uranium and fund chain reaction experiments.

Meitner, although invited, declined to participate. (“I don’t want anything to do with a bomb!” she famously said.) In 1945, after atomic bombs were dropped on Hiroshima and Nagasaki, leading to the end of the war, some newspaper reports claimed that Meitner had smuggled the recipe of Nazi Germany’s weapon in her bag. She rejected them. “You know much more in America about the atomic bomb than I do,” she told The New York Times in 1946.

In 1945, Hahn was nominated for the 1944 Nobel Prize in Chemistry, a year late, for the discovery of nuclear fission. Meitner and Frisch were also nominated for the physics prize that year. But only Hahn won.