The quantum revolution was made largely in German-speaking universities, in Berlin, Göttingen, Munich, Leipzig, Hamburg, Zurich and Vienna, with Copenhagen as its second home. In 1933 that world was broken apart. The story of what happened next shows how science depends on people, and on the freedom of those people to work wherever their talents take them.

The law of April 1933

Hitler became chancellor in January 1933. On April 7 his government passed the Law for the Restoration of the Professional Civil Service, which removed Jewish and politically unreliable civil servants, including professors, from their posts. Since German universities were state institutions, the law reached deep into science. Estimates vary, but roughly a quarter of the physicists in Germany lost their positions within a few years, among them many of the most gifted.

Einstein was visiting the United States when the Nazis took power. He resigned from the Prussian Academy of Sciences, never returned to Germany and settled at the Institute for Advanced Study in Princeton. Max Born was suspended at Göttingen and went first to Cambridge, then in 1936 to Edinburgh. James Franck resigned his Göttingen chair publicly in protest before he could be dismissed. Hans Bethe lost his post in Tübingen. Eugene Wigner, Edward Teller and Leo Szilard all left. Schrödinger's departure stood out: he was not targeted by the law, but he left Berlin in protest, going to Oxford. He later moved to Graz, fled again after Germany annexed Austria in 1938 and settled in Dublin.

Networks of rescue

Others organized help. In Britain the Academic Assistance Council was founded in 1933 to find posts and funds for displaced scholars, with Ernest Rutherford as its president. In the United States an Emergency Committee did similar work. Bohr's institute in Copenhagen served as a way station, offering refugees temporary positions while they sought permanent ones. Such networks saved careers and lives, though many scholars, especially younger and less famous ones, found no place.

"German physics"

Within Germany two Nobel laureates, Philipp Lenard and Johannes Stark, promoted what they called Deutsche Physik, German physics. It rejected relativity and quantum theory as "Jewish" abstraction, praising instead an intuitive, experimental science they called Aryan. In July 1937 Stark attacked Heisenberg in the SS weekly Das Schwarze Korps, calling him a "white Jew", a term for non-Jews who taught Jewish ideas. Heisenberg appealed through family connections to Heinrich Himmler and was eventually cleared, on terms that let him teach the new physics while keeping quiet about Einstein's name. The movement lost influence by the end of the decade, partly because the state needed physics that worked.

Staying and leaving

Those who stayed faced hard choices. Max Planck, in his seventies, tried to protect colleagues from inside the system; by his own later account he met Hitler in 1933 to plead for Jewish scientists and got nowhere. Planck's son Erwin was executed in 1945 for ties to the July 20 plot against Hitler. Heisenberg stayed and led part of Germany's wartime uranium research, and his motives remain debated.

The racial laws spread. Italy adopted its own in 1938, and Enrico Fermi, whose wife Laura was Jewish, saw what was coming. Awarded the Nobel Prize that year, he traveled to Stockholm to receive it and did not return, sailing on to New York with his family. In 1943, warned that Danish Jews were about to be deported, Bohr, whose mother was Jewish, escaped by boat across the sound to Sweden and later went on to Britain and the United States. Most of Denmark's Jews escaped to Sweden the same way that autumn, in one of the war's great rescues.

The flight of so many physicists shifted the center of science westward, above all to the United States, and many émigrés later worked on the bomb projects. The lesson many drew was plain: a state that expels people for their ancestry destroys its own science along with the lives it ruins.

Worked example: Lise Meitner's escape

Follow one life through these years. Lise Meitner, an Austrian of Jewish descent, worked in Berlin with the chemist Otto Hahn for three decades and was among the leading nuclear physicists in the world. Her Austrian citizenship protected her from the 1933 law until Germany annexed Austria in March 1938. She was now a German citizen with no protection and was barred from leaving legally. In July 1938, helped by the Dutch physicist Dirk Coster, she slipped across the border into the Netherlands with little more than a small suitcase, and went on to Stockholm.

That December, Hahn and Fritz Strassmann found barium in uranium bombarded with neutrons and wrote to Meitner, puzzled. Over Christmas, walking in the snow with her nephew Otto Frisch, she worked out that the uranium nucleus had split. The 1944 chemistry Nobel went to Hahn alone. Her story shows how exile could cost a scientist not only home and work but credit, and how much talent the persecutions scattered.