Wednesday, April 16, 2008
"The Mother of Nuclear Fision"
We certainly wish that this will be the last instance of gender and ethnic intollerence for a truly sound realm of science should not judge the person doing the research and should be independent of political and racial beliefs. This is the story of Lise Meitner...dubbed "The Mother of Nuclear Fision" and co-discoverer of the element protactinium [No. 91] in 1918.
Lise Meitner (1878 - 1968)
Lise Meitner was born on November 7, 1878, in Vienna, Austria. The third of eight children of a Jewish family, she entered the University of Vienna in 1901, studying physics under Ludwig Boltzmann. After she obtained her doctorate degree in 1906, she went to Berlin in 1907 to study with Max Planck and the chemist Otto Hahn. She worked together with Hahn for 30 years, each of them leading a section in Berlin's Kaiser Wilhelm Institute for Chemistry. Hahn and Meitner collaborated closely, studying radioactivity, with her knowledge of physics and his knowledge of chemistry. In 1918, they discovered the element protactinium.
In 1923, Meitner discovered the radiationless transition known as the Auger effect, which is named for Pierre Victor Auger, a French scientist who discovered the effect two years later.
After Austria was annexed by Germany in 1938, Meitner was forced to flee Germany for Sweden. She continued her work at Manne Siegbahn's institute in Stockholm, but with little support, partially due to Siegbahn's prejudice against women in science. Hahn and Meitner met clandestinely in Copenhagen in November to plan a new round of experiments. The experiments that provided the evidence for nuclear fission were done at Hahn's laboratory in Berlin and published in January 1939. In February 1939, Meitner published the physical explanation for the observations and, with her nephew, physicist Otto Frisch, named the process nuclear fission. The discovery led other scientists to prompt Albert Einstein to write President Franklin D. Roosevelt a warning letter, which led to the Manhattan Project.
In 1944, Hahn was awarded the Nobel Prize for Physics for his research into fission, but Meitner was ignored, partly because Hahn downplayed her role ever since she left Germany. The Nobel mistake, never acknowledged, was partly rectified in 1966, when Hahn, Meitner, and Strassman were awarded the Enrico Fermi Award. On a visit to the U.S. in 1946, she was given total American press celebrity treatment, as someone who had "left Germany with the bomb in my purse."
Meitner retired to Cambridge, England, in 1968, where she died October 27. In 1992, element 109, the heaviest known element in the universe, was named Meitnerium (Mt) in her honor. Many consider Lise Meitner the "most significant woman scientist of the 20th Century."
Lise Meitner was born on November 7, 1878 in Vienna, Austria. Upon receiving a doctorate in physics from the University of Vienna in 1906, Meitner went to the University of Berlin. There, she began to work with a chemist, Otto Hahn, she doing the physics and he the chemistry of radioactive substances. The collaboration continued for 30 years, each heading a section in Berlin's Kaiser Wilhelm Institute for Chemistry.
In 1938 she was forced to leave Germany and went to Sweden. In her absence, Hahn and Fritz Strassmann continued experiments they had begun earlier with Meitner. Hahn wrote to Meitner, describing the results and while visiting her nephew Otto Frisch in Denmark, they proved that a splitting of the uranium atom was energetically feasible. This process was described in a landmark 1939 letter to the journal Nature with a term borrowed from biology: fission. Immediately, these results were confirmed around the world. In 1944, Hahn was awarded the Nobel Prize for Physics for his research into fission, but Meitner was ignored. The Nobel mistake, never acknowledged, was partly rectified in 1966, when Hahn, Meitner, and Strassmann were awarded the Enrico Fermi Award.
She retired to Cambridge, England where she died October 27, 1968. In 1997, it was announced that element 109 would be given the official name meitnerium (Mt) in her honor.
Excerpt from NOVA's Einstein's Big Idea:
NARRATOR: Max Planck encourages the world's most eminent physicists to take Einstein seriously. After four years of waiting he is appointed Professor of Physics at Zurich University. From there his career is meteoric. He is made Professor of Physics in Berlin, achieves world renown and becomes a household name. He is the undisputed father of modern physics.
But Einstein's success was the downfall of his marriage. In 1919, he divorced Mileva and married his cousin. His fame led to numerous affairs.
E = mc2 became the Holy Grail of science. It held out the promise of vast reserves of energy locked deep inside the atom. Einstein suspected that it would take a hundred years of research to unlock it. But he hadn't banked on the Second World War and the genius of a Jewish woman in Hitler's Germany.
Twenty-eight year old Austrian Lise Meitner was painfully shy. Despite her anxiety, the young Doctor of Physics arrived in Berlin determined to pursue a career in the exciting, new field of radioactivity. Unfortunately, in 1907, German universities did not employ female graduates. Luckily, one man came to her aid.
OTTO HAHN: Fraulein Meitner?
LISE MEITNER: Yes?
OTTO HAHN: Otto Hahn. I'm a researcher in the Chemistry Institute. Professor Planck suggested I...
LISE MEITNER: Ah yes, Herr Hahn. I have read both your papers on Thorium and Mesothorium. Dr. Planck suggested that I...
OTTO HAHN: Yes, he suggested I speak to you. I need someone to collaborate with.
LISE MEITNER: I think I could really help with the physical analysis.
OTTO HAHN: And the mathematics?
LISE MEITNER: Yes, yes, and the mathematics.
OTTO HAHN: Studying radioactive atoms has become so much a collaboration between chemistry and physics these days.
LISE MEITNER: Yes, yes.
OTTO HAHN: I'll ask Fischer for a laboratory then.
LISE MEITNER: Excellent.
OTTO HAHN: I'll speak to you soon.
NARRATOR: Lise Meitner had just taken the first step on a journey that would irrevocably change world history. For her, it would be a road marked with success and renown, but also with terror and betrayal.
DAVID BODANIS: At this time, not a lot was known about the atom. At first people thought it was like a miniature cellular system, there's a solid nucleus of the center and electrons would spin around it, sort of like planets around our sun. A little later, some researchers proposed that the nucleus itself wasn't a solid chunk but was made up of separate particles, of protons and neutrons. But then, in what are called radioactive metals, things like radium and uranium, the nucleus itself seemed to be unstable, leaking out energy and particles. Perhaps this was an example of E = mc2, the mass of a nucleus turning into energy?
NARRATOR: Meitner and Hahn's collaboration to unlock the secrets of the atom, started out on an extremely unequal footing. He was given a laboratory. She was forced to work in a woodshop.
OTTO HAHN: I see you haven't set your hair on fire?
LISE MEITNER: Herr Hahn?
OTTO HAHN: The boss. He thinks that if he lets women into the Chemistry Institute they'll set their hair on fire.
LISE MEITNER: Ah, so his beard must be fireproof.
STAFF MEMBER (Dramatization): Good day, Herr Hahn.
OTTO HAHN: Good day.
LISE MEITNER: You see. I am nonexistent to this place. At least physicists recognize me for my abilities.
OTTO HAHN: Ah, yes, where would we chemists be without the steadying hand of the physicist?
RUTH LEWIN SIME (Meitner Biographer): It took years, but Lise lost her shyness eventually. In 1912, she and Hahn moved to the brand new Kaiser Wilhelm Institute for Chemistry where their status was really that of equals. Lise became the first woman in Germany to have the title of Professor.
OTTO HAHN: Lise, I have news. You remember the art student I told you of?
LISE MEITNER: Yes. Edith.
OTTO HAHN: Yes, well, I have asked her to marry me, and she has accepted.
LISE MEITNER: Ah. Doctor Hahn, congratulations.
OTTO HAHN: Yes, well, I wanted you to be the first to know.
LISE MEITNER: I'm very pleased for you, very pleased.
RUTH LEWIN SIME: Lise Meitner was warm hearted by nature, she had many friends, and she may have wanted to have a closer relationship with Otto. But it really does seem that physics was Lise's first love, maybe even her passion.
NARRATOR: The 1920s and '30s were the golden age of nuclear research. The largest known nucleus at the time was that of the Uranium atom containing 238 protons and neutrons. Meitner and Hahn were leading the race to see if even bigger nuclei could be created by adding more neutrons.
LISE MEITNER: So, the atom-pretty familiar, nucleus in the center, electrons orbiting around. The nucleus is our focus: the nucleus, made up of protons and neutrons. Now, the largest nucleus we know is that of the Uranium atom. Its nucleus is a tightly packed structure of 238 protons and neutrons. The thrust of our work is to try to fire neutrons into this huge structure, and if we can get a neutron to stick in here, it will be a breakthrough.
NARRATOR: Meitner may have been on the brink of a major discovery, but Germany in the 1930s was a dangerous place to be, even for a world-class scientist.
KURT HESS: The Jewess endangers our Institute.
RUTH LEWIN SIME: When the Nazis came to power, one of the first things they did was to drive out Jewish academics from the universities. Einstein was very prominent, and for that reason he was one of the first to go. He was hounded out of Germany in 1933. Lise was not dismissed at that time. She was able to stay because she was Austrian. But in March 1938, Austria was annexed into Germany, and at that point her situation became untenable.
OTTO HAHN: What is it?
LISE MEITNER: Frightening news.
FRITZ STRASSMAN (Dramatization): What's happened?
LISE MEITNER: Kurt Hess is going around saying that I should be got rid of.
OTTO HAHN: I, I actually knew. I heard today. I was going to speak to the treasurer of the Institute before I told you. We'll speak to him tomorrow. Come on, let's get you home. It's late. We'll finish up.
NARRATOR: The pressure on Meitner was unbearable. Hahn, who was known for his anti-Nazi views, did his best to protect her, at least initially.
OTTO HAHN: I need to talk to you about Lise.
HEINRICH HORLEIN (Dramatization): Not now, I'm too busy.
OTTO HAHN: We have to protect her.
HEINRICH HORLEIN: How? What can we do? The situation is the way it is. Who knows what could happen next? She can't stay. It's just not tenable.
OTTO HAHN: But she hasn't got a visa or even a valid passport, and she may soon be forbidden to leave Germany.
HEINRICH HORLEIN: We can't harbor a Jew. If she stays the regime will shut us all down.
OTTO HAHN: Lise, Horlein demands that you leave.
FRITZ STRASSMAN: You can't throw her out.
OTTO HAHN: Horlein says you should not come into the Institute any more.
LISE MEITNER: Well, I have to write up the thorium irradiation tomorrow, so I have to come in.
FRITZ STRASSMAN: You've given up.
NARRATOR: When it became clear that Meitner would be dismissed and probably arrested, physicists all around Europe wrote letters inviting her to conferences, giving her an excuse to leave Germany. The Nazis refused to let her go. In July of 1938, a Dutch colleague traveled to Berlin and illegally took Lise back with him on a train to Holland. The trip was so frightening that at one point she begged to go back. Despite the great danger, she got through.
RUTH LEWIN SIME: She had lost everything: her home, her position, her books, her salary, her pension, even her native language. She had been cut off from her work just at the time when she was leading the field and was on the brink of a major scientific discovery.
NARRATOR: No matter what privations she suffered, Lise was still thinking of physics. Amazingly she and Hahn were able to collaborate by letter.
LISE MEITNER: I hope, my dear Otto, that after 30 years of work together and friendship in the institute, that at least the possibility remains that you tell me as much as you can about what is happening back there.
RUTH LEWIN SIME: Lise was invited by an old student friend to spend Christmas on the west coast of Sweden. Her nephew, Otto Robert Frisch, who was also a physicist, came to join her there.
OTTO ROBERT FRISCH: Aunt? Aunt? Aunt Lise? How are you, my dear? Merry Christmas? Aunt?
LISE MEITNER: I need your help, come on let's go out.
OTTO ROBERT FRISCH: But, I was hoping you'd help me.
NARRATOR: Back in Berlin, Hahn was getting strange results. He found no evidence to suggest that bombarding the uranium nucleus with neutrons had caused it to increase in size. In fact, his experiments seemed to be contaminated with radium, a smaller atom. He desperately needed Meitner's expert analysis. From afar, she was starting to suspect that something very different was happening in their experiment.
LISE MEITNER: Hahn and Strassman are getting some strange results with the uranium work.
OTTO ROBERT FRISCH: Really?
LISE MEITNER: A couple of months ago Hahn told me that they were finding radium amongst the uranium products. We are looking for a much bigger element, and here we are finding something much smaller. I urged Hahn to check again, it couldn't be radium. And now he writes to me and tells me that it's not radium, it's barium.
OTTO ROBERT FRISCH: But that's even smaller.
LISE MEITNER: Exactly. Hahn is sure that it's another error, but I don't know any more. It is at least possible that barium is being produced.
OTTO ROBERT FRISCH: So Hahn still needs you to interpret the data.
LISE MEITNER: It is my work too, you know.
OTTO ROBERT FRISCH: Exactly.
LISE MEITNER: Well, I can't be there, can I? Come on, let's walk.
OTTO ROBERT FRISCH: Surely, he's made a mistake, hasn't he? He hasn't done what you told him to.
LISE MEITNER: My darling, Robert, he may not be a brilliant theorist, but he's too good a chemist to get this wrong.
RUTH LEWIN SIME: If you imagine a drop of water, a big drop, it's unstable, on the verge of breaking apart. It turns out that a big nucleus like uranium is just like that. Now for four years Meitner and Hahn and all other physicists had thought that if you pump more neutrons into this nucleus, it'll just get bigger and heavier. But suddenly Meitner and Frisch, out in the midday snow, realized that this nucleus might just get so big that it would split in two.
LISE MEITNER: If the nucleus is so big that it has trouble staying together, then couldn't just a little tiny jog from a neutron and...
OTTO ROBERT FRISCH: Yes, but if the nucleus did split, the two halves would fly apart with a huge amount of energy. Where's that energy going to come from?
LISE MEITNER: How much energy?
OTTO ROBERT FRISCH: Well, we worked out that the mutual repulsion between two nuclei would generate about 200 million electron volts. But something has to supply that energy.
LISE MEITNER: Wait, let me do a packing fraction calculation. The two nuclei are lighter than the original uranium nucleus by about one-fifth of a proton in mass.
OTTO ROBERT FRISCH: What? So some mass has been lost? Einstein's E = mc2?
LISE MEITNER: If we multiply the lost mass by the speed of light squared we get...200 million electron volts. He's split the atom.
OTTO ROBERT FRISCH: No, no, no. You've split the atom.
RUTH LEWIN SIME: It was an amazing discovery. Of course in the laboratory we are talking about tiny amounts of uranium and correspondingly tiny amounts of energy. But the point is that the amount of energy released was relatively large and that came from the mass of the uranium itself. The energy released was entirely consistent with Einstein's equation, E=mc2.
NARRATOR: Meitner and Frisch published the discovery of what they called nuclear fission to great acclaim. But betrayal awaited them. Otto Hahn was under pressure from the Nazi regime to write his Jewish colleague out of the story. He alone was awarded the 1944 Nobel Prize for the discovery. In his speech he barely mentioned the leading role of Meitner. Bizarrely even after the war, Hahn maintained it was he and not Meitner who had discovered nuclear fission.
LISE MEITNER: Now I want to write something personal, which disturbs me and which I ask you to read with more than 40-year friendship in mind, and with the desire to understand me. I am [now] referred to as "Hahn's long time co-worker." How would you feel if you were only characterized as the longtime co-worker of me? After the last 15 years, which I wouldn't wish on any good friend, shall my scientific past also be taken from me? Is that fair? And why is it happening?
DAVID BODANIS: Lise Meitner had been working on this for 30 years. She'd only broken apart a handful of atoms, but that was enough, once she had broken even one, the genie was out of the bottle.
What Meitner had started...after that physicists around the world began to realize they could take it a lot further.
NARRATOR: In 1942, an intense effort to build an atom bomb was begun. All over America, secret installations sprang up under the code name "The Manhattan Project."
DAVID BODANIS: Meitner was asked to join the Manhattan project, and she refused. She refused to have anything to do with the atomic bomb. But Robert Frisch was different. He was an important member of the team, because he was convinced of the need to beat the Nazis in a nuclear arms race.
Lise Meitner: A Life in Physics
Ruth Lewin Sime