other times we know we choose. In the real world it is meaningless to doubt existence; the doubt itself demonstrates the existence of the doubter. Much of the difficulty was language, that slippery medium in which Bohr saw us inextricably suspended. “It is wrong,” he told his colleagues repeatedly, “to think that the task of physics is to find out how nature
Later Bohr would develop far more elaborately the idea of mutual limitations as a guide to greater understanding. It would supply a deep philosophical basis for his statecraft as well as for his physics. In 1913 he first demonstrated its resolving power. “It was clear,” he remembered at the end of his life, “and that was
4
The Long Grave Already Dug
Otto Hahn cherished the day the Kaiser came to visit. The official dedication of the first two Kaiser Wilhelm Institutes, one for chemistry, one for physical chemistry, on October 23, 1912 — Bohr in Copenhagen was approaching his quantized atom — was a wet day in the suburb of Dahlem southwest of Berlin. The Kaiser, Wilhelm II, Victoria's eldest grandson, wore a raincloak to protect his uniform, the dark collar of his greatcoat turned out over the lighter shawl of the cloak. The officials who walked the requisite paces behind him, his scholarly friend Adolf von Harnack and the distinguished chemist Emil Fischer foremost among them, made do with dark coats and top hats; those farther back in the procession who carried umbrellas kept them furled. Schoolboys, caps in hand, lined the curbs of the shining street like soldiers on parade. They stood at childish attention, awe dazing their dreamy faces, as this corpulent middle-aged man with upturned dark mustaches who believed he ruled them by divine right passed in review. They were thirteen, perhaps fourteen years old. They would be soldiers soon enough.
Officials in the Ministry of Culture had encouraged His Imperial Majesty to support German science. He responded by donating land for a research center on what had been a royal farm. Industry and government then lavishly endowed a science foundation, the Kaiser Wilhelm Society, to operate the proposed institutes, of which there would be seven by 1914.
The society began its official life early in 1911 with von Harnack, a theologian who was the son of a chemist, as its first president. The imperial architect, Ernst von Ihne, went briskly to work. The Kaiser came to Dah-lem to dedicate the first two finished buildings, and the Institute for Chemistry especially must have pleased him. It was set back on a broad lawn at the corner of Thielallee and Faradayweg: three stories of cut stone filigreed with six- paned windows, a steep, gabled slate roof and at the roofline high above the entrance a classical pediment supported by four Doric columns. A wing angled off paralleling the cross street. Fitted between the main building and the wing like a hinge, a round tower rose up dramatically four stories high. Von Ihne had surmounted the tower with a dome. Apparently the dome was meant to flatter the Kaiser's taste. A sense of humor was not one of Wilhelm IPs strong points and no doubt it did. The dome took the form of a giant
Leaving Ernest Rutherford in Montreal in 1906 Hahn had moved to Berlin to work with Emil Fischer at the university. Fischer was an organic chemist who knew little about radioactivity, but he understood that the field was opening to importance and that Hahn was a first-rate man. He made room for Hahn in a wood shop in the basement of his laboratories and arranged Hahn's appointment as a
Hahn found the university's physicists more congenial than its chemists and regularly attended the physics colloquia. At one colloquium at the beginning of the autumn term in 1907 he met an Austrian woman, Lise Meitner, who had just arrived from Vienna. Meitner was twenty-nine, one year older than Hahn. She had earned her Ph.D. at the University of Vienna and had already published two papers on alpha and beta radiation. Max Planck's lectures in theoretical physics had drawn her to Berlin for postgraduate study.
Hahn was a gymnast, a skier and a mountain climber, boyishly good-looking, fond of beer and cigars, with a Rhineland drawl and a warm, self-deprecating sense of humor. He admired attractive women, went out of his way to cultivate them and stayed friends with a number of them throughout his happily married life. Meitner was petite, dark and pretty, if also morbidly shy. Hahn befriended her. When she found she had free time she decided to experiment. She needed a collaborator. So did Hahn. A physicist and a radiochemist, they would make a productive team.
They required a laboratory. Fischer agreed that Meitner could share the wood shop on condition that she never show her face in the laboratory upstairs where the students, all male, worked. For two years she observed the condition strictly; then, with the liberalization of the university, Fischer relented, allowed women into his classes and Meitner above the basement. Vienna had been only a little more enlightened. Meitner's father, an attorney — the Meitners were assimilated Austrian Jews, baptized all around — had insisted that she acquire a teacher's diploma in French before beginning to study physics so that she would always be able to support herself. Only then could she prepare for university work. With the diploma out of the way Meitner crammed eight years of
“There was no question,” says Hahn, “of any closer relationship between us outside the laboratory. Lise Meitner had had a strict, lady-Uke upbringing and was very reserved, even shy.” They never ate lunch together, never went for a walk, met only in colloquia and in the wood shop. “And yet we were really close friends.” She whistled Brahms and Schumann to him to pass the long hours taking timed readings of radioactivity to establish identifying half-lives, and when Rutherford came through Berlin in 1908 on his way back from the Nobel Prize ceremonies she selflessly accompanied Mary Rutherford shopping while the two men indulged themselves in long talks.
The close friends moved together to the new institute in 1912 and worked to prepare an exhibit for the Kaiser. In his first venture into radio-chemistry, in London before he went to Montreal, Hahn had spied out what he took to be a new element, radiothorium, that was one hundred thousand times as radioactive as its modest namesake. At McGill he found a third substance intermediate between the other two; he named it “mesothorium” and it was later identified as an isotope of radium. Me-sothorium compounds glow in the dark at a different level of faint illumination from radiothorium compounds. Hahn thought the difference might amuse his sovereign. On a velvet cushion in a little box he mounted an unshielded sample of mesothorium equivalent in radiation intensity to 300 milligrams of radium. He presented his potent offering to the Kaiser and asked him to compare it to “an emanating sample of radiothorium that produced in the dark very nice luminous moving shapes on [a] screen.” No one warned His Majesty of the radiation hazard because no safety standards for radiation exposure had yet been set. “If I did the same thing today,” Hahn said fifty years later, “I should find myself in prison.”
The mesothorium caused no obvious harm. The Kaiser passed on to the second institute, half a block up Faradayweg northwest beyond the angled wing. Two senior chemists managed the Chemistry Institute where Hahn and Meitner worked, but the Institute for Physical Chemistry and Electrochemistry, to give it its full name, was established specifically for the man who was its first director, a difficult, inventive German-Jewish chemist from Breslau named Fritz Haber. It was a reward of sorts. A German industrial foundation paid for it and endowed it because in 1909 Haber had succeeded in developing a practical method of extracting nitrogen from the air to make ammonia. The ammonia would serve for artificial fertilizer, replacing Germany's and the world's principal natural source, sodium nitrate dug from the bone-dry northern desert of Chile, an expensive and insecure supply. More strategically, the Haber process would be invaluable in time of war to produce nitrates for explosives; Germany had no nitrates of its own.
