Women's Heritage Month part II

Continuing with the story of Lisa Meitner….

When the Great War began in 1914 Lisa served the first part as a nurse handling X-ray equipment a job in those days fraught with danger. In 1916 she was called back to Berlin , but not without inner struggle. She felt in a way ashamed of continuing her research efforts others were enduring so much pain and suffering.

In 1917 Lisa was given her own physics section at the Kaiser Wilhelm Institute for Chemistry and in 1923, she discovered the cause, for the emission from surfaces of electrons with 'signature' energies. Typically for the time the effect was named after Pierre Victor Auger, a French scientist who independently discovered the effect two years later in 1925. This wasn’t to be the only time in her life that the credit for Lisa’s work would go to a man.

With the discovery of the neutron in the early 1930s, speculation arose in the scientific community that it might be possible to create elements heavier than uranium then the heaviest known element (atomic number 92 which means it has 92 protons) in the laboratory. A scientific race began across Europe, all concerned believed that this was abstract research into the nature of the atom. No-one had any inkling where this would lead.

Basically what scientists were doing back then is exactly what people do today. If they can’t understand how something works they take it to bits. If this isn’t easy they start knocking bits off until it stops working and then try and discover why. With the discovery of the sub-atomic particle the neutron scientists found a way of shooting beams of them into the element uranium hoping eventually they might hit the nucleus of a uranium atom. No easy task when we remember that 99.99% of an atom is empty space, with the nucleus a tiny core in the centre. Remember our analogy of the pea and the football pitch?

When Hitler came to power in 1933, Meitner was acting director of the Institute for Chemistry. Although she was protected by her Austrian citizenship, other Jewish scientists were dismissed or forced to resign from their posts. Most of them emigrated from Germany. Her response was to say nothing and bury herself in her work (although she later acknowledged, in 1946, that It was not only stupid but also very wrong that I did not leave at once).

After the annexation or Anschluss of Austria, her situation became desperate. Her protection as a foreigner in Germany vanished overnight, her Austrian passport was revoked and now as a member of the greater Reich as a Jew she wasn’t entitled to a passport. However in July 1938, Meitner, with help of Dutch physicists escaped to the Netherlands. She reached safety, but had to leave all her possessions behind and had only 10 marks in her purse.

Meitner was lucky to escape, as she had already been informed on by one of her colleagues. Eventually she made for Stockholm, where she took up a post at Manne Siegbahn's laboratory, despite the difficulty caused by Siegbahn's prejudice against women in science. Here she established a working relationship with Niels Bohr the famous Danish scientist. While here she continued to correspond with her German colleagues and Hahn and Meitner met clandestinely in Copenhagen in November to plan a new round of experiments.

Back in Berlin Hahn continued with the experiments they had planned. Soon the results began to baffle him, after bombarding uranium with neutrons Hahn began to discover traces of barium another element. The point here is the barium atom was a considerably smaller atom than uranium. Baffled Hahn wrote to Meitner. Meitner who was on a skiing holiday with her nephew Otto Frisch, literally sat down on a pile of logs and began to scribble calculations on a piece of paper, and came to a remarkable conclusion - the Uranium atom had been split in two. Meitner and Frisch excitedly began to articulate a theory of how the nucleus of uranium had been split into the smaller atoms barium and krypton, this they concluded could only take place if the process were accompanied by the ejection of several more neutrons This is shown in the diagram where the nucleus of an uranium atom is seen rather like a liquid drop. When struck my a neutron it at first wobbles and then splits into two.



That wasn’t all however, adding up all of the mass (weight) of the bits left over from the break-up of the uranium atom it turned out that a tiny amount of mass was missing. The only explanation was it had been converted into energy. Perhaps because Hahn was working on a tiny scale he hadn’t noticed this energy, but relatively speaking the amount of energy was huge. When mass is converted into energy it is governed by Einstein’s famous equation.



Here E is energy m is mass and c is the speed of light. When you consider that the speed of light is approximately 300,000,000 metres per sec, and that c2 = 300,000,000 x 300,000,000 you immediately get an idea of the huge amount of energy that can be released from even a tiny amount of mass. This was energy on a hitherto undreamt of scale.

Immediately on finishing their holiday Otto Frisch, confirmed Lisa’s predictions experimentally in his lab.

This however is not the end of this remarkable story. We have seen that when a uranium atom is hit by a neutron it breaks up with the release of a huge amount of energy. However this break up is accompanied by the release of another three neutrons, each which can go on to split three more uranium atoms, releasing even more energy. Clearly this process can cascade until the release of energy reaches explosive proportions.



Meitner immediately recognized the possibility for a so-called chain reaction of enormous explosive potential. Her work had an electrifying effect on the scientific community. Because it was 1939 and it was now clear that war was imminent, scientists kept this information to themselves. No-one could contemplate alerting Hitler to the potential of an atomic bomb. Unfortunately, there is always someone who will set aside all scruple just to get his name in print and a French scientist did just that. The cat was truly out of the bag. Scientists immediately persuaded Albert Einstein to use his reputation, to write to President Franklin D. Roosevelt to warn him, this led eventually to the establishment of the Manhattan Project. Meitner however refused an offer to work on the project at Los Alamos, declaring "I will have nothing to do with a bomb!" Meanwhile in Germany scientists too began working on a bomb. The race for Armageddon was on.

In 1944, with the war still raging the Swedes made the politically charged decision to award Hahn the Nobel Prize for Chemistry for the discovery of nuclear fission. The same man who was working to put the bomb in Hitler’s hands. Many scientists felt that the discovery nuclear fission belonged to Meitner or at least should be jointly recognised with Hahn. Hahn to his ultimate discredit didn’t demur and accepted the award on his own.

As the years went by scientists became increasingly rankled by the injustice of Lisa Meitner not receiving a Nobel prize and in 1966 Meitner was awarded the prestigious Enrico Fermi Award. On a visit to the USA in 1946 she received the honour of the "Woman of the Year" by the National Press Club dinner with President Harry Truman and others at the National Women's Press Club, as well as many honorary doctorates and lectured at Princeton, Harvard and other universities. Lise received the Max Planck Medal of the German Physics Society in 1949. An even rarer honour was given to her in 1997 when element 109 was named meitnerium in her honour.

Later years after the war, Meitner, while acknowledging her own moral failing in staying in Germany from 1933 to 1938, was bitterly critical of Hahn and other German scientists who had collaborated with the Nazis . Referring to the leading German scientist Werner Heisenberg, she said: "Heisenberg and many millions with him should be forced to see these camps and the martyred people." She wrote to her old colleague Hahn:

"You all worked for Nazi Germany. And you tried to offer only a passive resistance. Certainly, to buy off your conscience you helped here and there a persecuted person, but millions of innocent human beings were allowed to be murdered without any kind of protest being uttered ... [it is said that] first you betrayed your friends, then your children in that you let them stake their lives on a criminal war – and finally that you betrayed Germany itself, because when the war was already quite hopeless, you did not once arm yourselves against the senseless destruction of Germany."

Meitner moved to Britain in 1960 and died in Cambridge in 1968, shortly before her 90th birthday. As was her wish, she was buried in the village of Bramley in Hampshire, at St. James parish church, close to her younger brother Walter, who had died in 1964. Her nephew Otto Robert Frisch composed the inscription on her headstone. It reads "Lise Meitner: a physicist who never lost her humanity."

Thus the story of a quiet unassuming woman of enormous talent, who was serially cheated out of her due recognition by men, but whose example lives on to inspire the lives of other women. I for one owe a great deal to Lisa Meitner.