Niels Bohr's Wartime Humanitarian Record Reexamined in Philip Ball's New Biography

In 1998, Michael Frayn's play Copenhagen opened in London to wide acclaim. It dramatized a conversation between the Danish physicist Niels Bohr and the German Werner Heisenberg in the autumn of 1941. Whether the play captured what actually happened in that room is still unresolved, and a new biography by Philip Ball, The Man Who Broke Reality, returns to the question while drawing a broader portrait of Bohr as a humanitarian.

The meeting took place while Nazi Germany occupied Denmark, a country the Nazis regarded as a model for Aryan states. The Danes, with few resources, did not resist the takeover, but their social democratic government refused German pressure to act against Danish Jews. The reviewer in The Jerusalem Post notes that most Danes ostracized Heisenberg during his visit, at a time when hints of mass murder of Jews were beginning to filter through.

Ball's account stresses what Bohr did for colleagues fleeing Nazism, especially after the race laws were introduced. Many refugees found shelter in Copenhagen before moving on. Bohr kept a list of them and carried it abroad on his travels, trying to find them posts. Among those who made their way to his institute were Stefan Rozenthal, Otto Frisch, Max Born and Leo Szilard, often with funding from the Rockefeller Foundation. A cyclotron began operating there in 1938, and the institute became a central site for the developing knowledge of nuclear fission in occupied Europe. The review suggests this was probably why Heisenberg came.

Bohr was not Jewish by religion, though his mother, Ellen, came from the Adler family, a liberal banking family descended from David Baruch Adler and Jenny Raphael, settled in Copenhagen since 1850. The family was highly assimilated and Bohr was raised Lutheran. He broke with Christianity after hearing a clergyman call the sinking of the Titanic "God's will." Nazi scientists nonetheless called him a "white Jew," accusing him of collusion in "Jewish physics."

Heisenberg's motives remain disputed. After the war he argued that he had worked within Nazi oppression to keep control of the nuclear project and keep it from Hitler. In a letter he never sent, written in 1958, Bohr called that explanation little more than an apologia for German nationalism. Lise Meitner and other Jewish scientists believed Heisenberg had then regarded a German victory as inevitable. The review asks whether he was an apolitical goodwill ambassador or was pursuing an atomic weapon, and leaves the question open.

The book also traces Bohr's scientific path: study under J. J. Thomson at the Cavendish Laboratory, then work with Ernest Rutherford at Manchester, where Chaim Weizmann had been a researcher. Bohr replaced the plum-pudding model of the atom with electrons orbiting a nucleus, each in a specific energy level, emitting a photon when jumping between "quantized" orbits. This explained the structure of the periodic table and helped predict where undiscovered elements would fit. Hafnium was named from the Latin name for Copenhagen. He and Einstein stayed friends despite disagreeing over chance in quantum processes, which Einstein resisted as a "dice-throwing God."

In early 1943, the British sent word through the Danish resistance that Bohr risked deportation to Germany. That summer, strikes and sabotage led Hitler to end the lenient treatment of Denmark, which was to be made Judenrein. The German diplomat Georg Ferdinand Duckwitz alerted the Danes, and the great majority of Denmark's Jews were ferried across the straits to Sweden. Bohr was taken there too, then flown to Britain on Churchill's orders and lodged at London's Savoy Hotel. He later went to Los Alamos under the name "Nicholas Baker" to advise younger scientists.

Neither Bohr nor Einstein helped build the bomb, though both laid its theoretical groundwork, and both tried after the war to prevent proliferation and an arms race with the Soviet Union. Bohr had also tried to help Soviet colleagues, pressing the Kremlin, without success, to let Pyotr Kapitza leave, and seeking aid for the imprisoned Lev Landau. In his last decade he was a central figure in founding CERN in Switzerland, a project of cooperation across nationalities in the wake of the Holocaust, Hiroshima and Nagasaki. The reviewer calls Ball's book perceptive and accessible, and credits it with recovering many half-forgotten scientists who faced moral dilemmas under dictators.