The Making of the Atomic Bomb

respect by hard and careful work. When Wolfgang PauU had wished to propose an elusive, almost massless neutral particle to explain the energy that seemed to disappear in beta decay — it came to be called the neutrino — he had made his proposal in a letter to Lise Meitner and Hans Geiger. James Chadwick was “quite convinced that she would have discovered the neutron if it had been firmly in her mind, if she had had the advantage of, say, living in the Cavendish for years, as I had done.” “Slight in figure and shy by nature,” as her nephew Otto Frisch describes her, she was nevertheless formidable.

During the Great War she had volunteered as an X-ray technician with the Austrian Army; “there,” says Frisch, “she had to cope with streams of injured Polish soldiers, not understanding their language, and with her medical bosses who interfered with her work, not understanding X-rays.” She arranged her leaves from duty to coincide with Otto Hahn's and hurried to the Kaiser Wilhelm Institute for Chemistry in Dahlem to work with him; that was when they identified the element next down from uranium that they named protactinium. After the war she did physics separately until 1934, when, challenged by Fermi's work, she “persuaded Otto Hahn to renew our direct collaboration” to explore the consequences of bombarding uranium with neutrons. Meitner headed the physics department at the institute then, of which Hahn had become the director. She had attained by middle age, Hahn remarks fondly, “not only the dignity of a German professor, but also one of his proverbial attributes, absent- mindedness.” At a scientific gathering “a male colleague greeted her by saying, ‘We met on an earlier occasion.’ Not remembering that earlier occasion, she replied in all seriousness, ‘You probably mistake me for Professor Hahn.’” Hahn supposed she was thinking of the many papers they had published together.

If she hid her shyness behind formidable reserve, among friends, Frisch says, “she could be lively and cheerful, and an excellent storyteller.” Her nephew thought her “totally lacking in vanity.” She wore her thick dark hair, now graying, pulled back and coiled in a bun and her youthful beauty had muted to bright but darkly circled eyes, a thin mouth, a prominent nose. She ate lightly but drank quantities of strong coffee. Music moved her; she followed it as other people follow trends and fashions in art (a family cultivation — her sister, Frisch's mother, was a concert pianist). She made a duet at the piano on visits with her musical nephew, “though hardly anybody else knew that she could play.” She lived in an apartment at the KWI and when there was time she took long walks, ten miles or more a day: “It keeps me young and alert.” Her most holy commitment, Frisch thought, “the vision she never lost” that filled her life, was “of physics as a battle for final truth.”

The truth she battled for through the later 1930s was hidden somewhere in the complexities of uranium. She and Hahn, and beginning in 1935 a young German chemist named Fritz Strassmann, worked to sort out all the substances into which the heaviest of natural elements transmuted under neutron bombardment. By early 1938 they had identified no fewer than ten different half-life activities, many more than Fermi had demonstrated in his first pioneering survey. They assumed the substances must be either isotopes of uranium or transuranics. “For Hahn,” says Frisch, “it was like the old days when new elements fell like apples when you shook the tree; [but] Lise Meitner found [the energetic reactions necessary to produce such new elements] unexpected and increasingly hard to explain.”

Meanwhile Irdne Curie had begun looking into uranium with a visiting Yugoslav, Pavel Savitch. They described a 3.5-hour activity the Germans had not reported and suggested it might be thorium, element 90, with which Curie had years of experience. If true, the Curie-Savitch suggestion would mean that a slow neutron somehow acquired the energy to knock an energetic alpha particle out of the uranium nucleus. The KWI trio scoffed, looked for the 3.5-hour activity, failed to find it and wrote the Radium Institute suggesting a public retraction. The French team identified the activity again and discovered they could separate it from their uranium by carrier chemistry using lanthanum (element 57, a rare earth). They proposed therefore that it must be either actinium, element 89, chemically similar to lanthanum but even harder than thorium to explain, or else a new and mysterious element.

Either way, their findings called the KWI work into doubt. Hahn met Joliot in May at a chemistry congress in Rome and told the Frenchman cordially but frankly that he was skeptical of Curie's discovery and intended to repeat her experiment and expose her error. By then, as Joliot undoubtedly knew, his wife had already raised the stakes, had tried to separate the “actinium” from its lanthanum carrier and had found it would not separate. No one imagined the substance could actually be lanthanum: how could a slow neutron transmute uranium into a much lighter rare earth thirty-four places down the periodic table? “It seems,” Curie and Sa-vitch reported that May in the Comptes Rendus, “that this substance cannot be anything except a transuranic element, possessing very different properties from those of other known transuranics, a hypothesis which raises great difficulties for its interpretation.”

In the course of this exotic debate Meitner's status changed. Adolf Hitler bullied the young chancellor of Austria to a meeting at the German dictator's Berchtesgaden retreat in Bavaria in mid-February. “Who knows,” Hitler threatened him, “perhaps I shall be suddenly overnight in Vienna: like a spring storm.” On March 14 he was, triumphantly parading; the day before, with the raw new German Wehrmacht occupying its capital, Austria had proclaimed itself a province of the Third Reich and its most notorious native son had wept for joy. The Anschluss — the annexation — made Meitner a German citizen to whom all the ugly anti-Semitic laws applied that the Nazi state had been accumulating since 1933. “The years of the Hitler regime… were naturally very depressing,” she wrote near the end of her life. “But work was a good friend, and I have often thought and said how wonderful it is that by work one may be granted a long respite of forgetfulness from oppressive political conditions.” After the spring storm of the Anschluss her grant was abruptly withdrawn.

Max von Laue sought her out then. He had heard that Heinrich Himmler, head of the Nazi SS and chief of German police, had issued an order forbidding the emigration of any more academics. Meitner feared she might be expelled from the KWI and left unemployed and exposed. She made contact with Dutch colleagues including Dirk Coster, the physicist who had worked in Copenhagen with George de Hevesy in 1922 to discover hafnium. The Dutchmen persuaded their government to admit Meitner to Holland without a visa on a passport that was nothing more now than a sad souvenir.

Coster traveled to Berlin on Friday, July 16, arriving in the evening, and went straight to Dahlem to the KWI. The editor of Naturwissenschaf-ten, Paul Rosbaud, an old friend, showed up as well, and together with Hahn the men spent the night helping Meitner pack. “I gave her a beautiful diamond ring,” Hahn remembers, “that I had inherited from my mother and which I had never worn myself but always treasured; I wanted her to be provided for in an emergency.”

Meitner left with Coster by train on Saturday morning. Nine years later she remembered the grim passage as if she had traveled alone:

I took a train for Holland on the pretext that I wanted to spend a week's vacation. At the Dutch border, I got the scare of my life when a Nazi military patrol of five men going through the coaches picked up my Austrian passport, which had expired long ago. I got so frightened, my heart almost stopped beating. I knew that the Nazis had just declared open season on Jews, that the hunt was on. For ten minutes I sat there and waited, ten minutes that seemed like so many hours. Then one of the Nazi officials returned and handed me back the passport without a word. Two minutes later I descended on Dutch territory, where I was met by some of my Holland colleagues.

She was safe then. She moved on to Copenhagen for the emotional renewal of rest at the Carlsberg House of Honor with the Bohrs. Bohr had found a place for her in Sweden at the Physical Institute of the Academy of Sciences on the outskirts of Stockholm, a thriving laboratory directed by Karl Manne Georg Siegbahn, the 1924 Physics Nobel laureate for work in X-ray spectroscopy. The Nobel Foundation provided a grant. She traveled to that far northern exile, to a country where she had neither the language nor many friends, as if to prison.

Leo Szilard was looking for a patron. Frederick Lindemann had arranged an ICI fellowship for him at Oxford beginning in 1935, and for a while Szilard worked there, but the possibility of war in Europe made him restless. From Oxford in late March 1936 he had written Gertrud Weiss in Vienna that she should consider emigrating to America; he appears to have applied his reasoning to his own case as well. Szilard had met Weiss in his Berlin years and subsequently advised and quietly courted her. Now she had graduated from medical school. At his invitation she came to Oxford to see him. They walked in the country; she photographed him standing at roadside before a weathered log barrier, rounding at thirty-eight but not yet rotund, with a budding young tree filigreed behind him. “He told me he would be surprised if one could work in Vienna in two years. He said Hitler would be there. And he was” — the Anschluss — “almost to the day.”