2006-06-17-Lise Meitner-Otto Hahn

2006-06-17—Lise Meitner-Otto Hahn

Harrison Weblog

2006 blog

PBS documentary skillfully retells
the story of nuclear fission's discovery

jewishsightseeing.com, June 17, 2006

SAN DIEGO, Calif.—A well-done Public Broadcasting Service documentary, "Path to Nuclear Fission: The Story of Lise Meitner and Otto Hahn," retells the story of the double whammy that for many years prevented nuclear physicist Lise Meitner from being recognized as the person who first explained nuclear fission: she was both a woman and the daughter of Jews.

I watched the documentary earlier this month, but it continues to make the rounds of PBS stations around the United States, and no doubt will have its re-runs on such stations as KPBS here in San Diego that have already run it. If you didn't catch the program the first time around, it will be worth waiting for. In the meantime, however, here is a summary:

Meitner had converted from Judaism to Protestantism (Lutheranism) sometime before she received a doctorate in physics in 1906 from the University of Vienna. She next went to Berlin, to do post-doctoral work with the well-known German physicist Max Planck. Hahn, who was a Protestant by birth, had studied in his native Germany, and later in Montreal, Canada, under the internationally known organic chemist, Ernest Rutherford. After he returned to Germany, he and Meitner, who at the time were both 28, became part of a social group involving other important scientists including Albert Einstein.

There never was any romance between Meitner and Hahn, who were quite different in temperaments but who respected each other intellectually. Hahn was outgoing, Meitner was painfully shy. Hahn found work at the University of Berlin under Emil Fischer, an organic chemist. Meitner had no such luck. Women weren't even admitted as students at the University of Berlin, much less as faculty members. The bearded Fischer had a rule against women working in his laboratories, ironically explaining that they might set their hair on fire on the burners.

Faced with exclusion from science that was her life's passion, Meitner agreed to work quietly and without pay in a converted carpentry shop in the basement of Emil Fischer's Institute. Supporting herself with an allowance that she received from her parents, Meitner became Hahn's colleague in the study of beta emitters. Gradually, her brilliance as a scientist became known and Planck decided to make her his assistant in the physics department.

In 1912, Hahn was appointed as a research associate at the new Kaiser Wilhelm Institute by Fischer, who played a leading role there. The following year, Meitner also was appointed as a scientific associate at considerably lower pay.

After being interrupted by World War I, during which Hahn manufactured poison gas and Meitner worked as a nurse on the front, the colleagues resumed their research on radioactive elements, eventually identifying the "missing" element on the periodic table between thorium and uranium, then known as the elusive Element 91. As its discoverers in 1918, they named the element Protactinium.

The head of separate departments after the war, Meitner focused on radioactive decay and the behavior of the nucleus, while Hahn's special interest was radiochemistry. Both became acknowledged leaders in their fields. But then came January 30, 1933, the day that Nazi leader Adolf Hitler was sworn in as Germany's chancellor. One of the first acts of his regime was to ban Jews and persons of Jewish ancestry from civil service jobs. As the Kaiser Wilhelm Institute was private, not public, its Jews technically were not covered by the act. But Planck dismissed all Jews except a very select few, including Meitner.

For five years, the unmarried Meitner continued to work at the Kaiser Wilhelm Institute, until her situation was further eroded by the Anschluss between Germany and Austria, which by decree transformed all Austrians into Germans. That meant that Meitner no longer could claim to be a foreign national under the protection of her government. It was clear that her days at the Kaiser Wilhelm Institute were numbered. She applied for a
German passport, and was turned down; the Nazis saying they didn't want a Jew to go abroad and let her feelings about the regime become known. But Meitner escaped with the help of Dutch physicist Dirk Coster over the Dutch border, and from there went to Stockholm to work at the Nobel Institute for Experimental Physics. Her departure from Germany preceded Kristallnacht.

Instead of welcoming the renowned scientist, Manne Siegbahn, the head of the Nobel Institute, made her feel like an outsider—prejudice against women scientists once again working against Meitner. However, she continued to communicate with Hahn, who was pursuing his work in radiochemistry. Scientists at the time labored under a misconception, that if an element could be changed by irradiating it with neutrons, it would change only slightly. Hahn was bewildered by tests indicating that irradiating uranium with neutrons causes barium to be produced. Radium, the 88th element, which has similar properties to barium, is only four elements below uranium, the 92nd element on the periodic table. Barium, the 56th element, which has similar chemical properties to radium, has a much lighter atomic mass. Hahn had no idea what accounted for this and asked Meitner, during a secret meeting in Copenhagen, what could account for this?

Walking with her nephew, the physicist Otto Robert Frisch, Meitner pondered the problem. She decided that the phenomenon could be explained by use of physicist Nils Bohr's idea that, in the documentary's explanation, "the nucleus is like a liquid drop so that the drop might elongate and split in two."

The documentary quoted Frisch as recalling: "At this point we both sat down on a tree trunk and started to calculate on scraps of paper until we found that the uranium nucleus might indeed be a very wobbly unstable drop ready to divide itself at the slightest provocation such as the impact of a neutron. But there was another problem, when the smaller two drops separated they would be driven apart and would require a very large energy..."

The physicists realized that mass actually was converted into a tremendous amount of energy during this process—confirmation of Einstein's theory that energy equals mass times the speed of light squared. They called the word "fission" to describe the splitting of the atom.

Meitner told Hahn and his associate Fritz Strassman of their deductions, but when Hahn published a paper in January 1939 about atom splitting, he gave no credit whatsoever to Meitner—perhaps afraid that the Nazi government would penalize him for continuing to collaborate with a Jew. A paper by Meitner and Strassman explaining the physics of how this happened did not appear until a month later, making it appear that they were simply commenting on the Hahn-Strassman discovery rather than having been actual participants.

When the United States began assembling scientists from throughout the world for the Manhattan Project, in which her nephew Otto Robert Frisch was a participant, efforts were made to recruit Meitner. She refused with the memorable words: "I will have nothing to do with a bomb!"

At the conclusion of World War II, Hahn won the Nobel Prize in chemistry for the discovery of nuclear fission. Hahn denied that Meitner had anything to do with the discovery, saying instead that it resulted from test after test that he and Stassman had conducted. Perhaps, the documentary speculated, having claimed full credit throughout World War II for the discovery, he would have been humiliated after the war if he had admitted Meitner's role.

An effort by fellow physicists the following year to award a Nobel prize to Meitner was blocked by the jealous Siegbahn, according to the documentary.

For years, Meitner was denied recognition for the part she played in a discovery that changed the world, but, 16 years after her death, this was rectified in 1982 by German scientists who discovered Element 109 and named it meitnerium, partially in atonement for their country having driven away one of the world's greatest scientists.