The sad tale of Einstein's blinkered polar partner

The title Einstein's German World , essays by the distinguished historian Fritz Stern, is a bit of a tease. Einstein was born in Germany but he spent less than half of his life there. The longest period was the two decades after his appointment in Berlin in 1913. But this collection includes items such as a critical review of Hitler's Willing Executioners , which has nothing to do with Einstein. Nonetheless, what makes this book essential reading for any student of Einstein is an essay of more than 100 pages titled "Together and apart: Fritz Haber and Albert Einstein". If I could have waved a magic wand I would have expanded this essay into a book.

Haber, who was born in Breslau in 1868 - making him a decade older than Einstein - won the Nobel prize for chemistry in 1918 for his synthesis of ammonia from nitrogen and hydrogen, making possible its practical use for explosives and fertilisers. He was born a Jew but had converted to help his career. In the first world war he was an enthusiastic soldier and one of the prime movers in the introduction of poison gas. In short, he and Einstein, who had always acknowledged his Jewishness and who was, until the rise of Hitler, a dedicated passivist, were antipodes. In 1911, Haber became the director of the Kaiser Wilhelm Institute for Physical Chemistry and Electrochemistry in Berlin, from where he played a key role in arranging Einstein's appointment in Berlin. Moreover, Haber helped to ease Einstein's transition from the informal academic life of Switzerland to the very formal academic life in Germany.

On a more personal level, both men had marital problems. Haber's first wife killed herself in 1915. Einstein's first wife had left Berlin for Switzerland with the couple's two sons, the marriage being at an end. In 1917, Haber took a second wife, who was 20 years younger, but the marriage ended in divorce in 19. Einstein's divorce took place in 1919 after an adulterous affair with his cousin, whom he then married. In the traumatic years before Einstein's marital situation stabilised, Haber did what he could to mediate between the parties. The two became very close.

Einstein had no illusions about what was happening in Germany. Haber did. Like many German Jews, especially those who had converted and had distinguished war records, he could not accept what was happening, at least until 1933. Even then, he might have been able to stay in Germany - though not in an academic or governmental position. Firms such as Siemens did hide some Jews, such as the Nobel physics laureate Gustav Hertz, but at 65 and in poor health, with no chance to start over, Hertz soon emigrated.

Hertz was, Stern notes, especially bitter that the industrial companies to whom he had been a valued consultant felt no remorse when he left. This was a common experience for Jewish scientists and others who were expelled. An exception was Max Planck, who was the most distinguished physicist in Berlin after Einstein left. Planck made an unsuccessful attempt to obtain exemptions for these scientists, including an interview with Hitler himself. He expressed regret to Haber, and after Haber died in Switzerland in 1934 Planck organised - an act of courage - a memorial commemoration in Berlin attended by some 500 people. It was perhaps the only time when the German scientific community made any public demonstration against Hitler. One can only wonder what might have happened if they had had the resolve to speak out earlier.

Stern provides a horrifying postscript to this story. While he was still in Germany, Haber's institute developed Zyklon B as a possible pesticide. Later, of course, after Haber had died, Zyklon B was the gas used by the Nazis in the gas chambers.

Jeremy Bernstein has written books on Einstein and German physics.