The Making of the Atomic Bomb

Surgery that evening confirmed a partial strangulation, released the imprisoned portion of the small intestine and restored its circulation. Saturday Rutherford seemed to be recovering but he began vomiting again on Sunday and there were signs of infection, deadly in those days before antibiotics. Monday he was worse; his doctors consulted the surgeon, a Melbourne man, who advised against a second operation given the patient's age and symptoms. Rutherford was made comfortable with intravenous saline, six pints by Tuesday, and a stomach tube. Tuesday morning, October 19, he was slightly improved, but though his wife judged him “a wonderful patient [who] bears his discomforts splendidly” and believed she discovered “just a thread of hope,” he began that afternoon to weaken. A bequest he decided late in the day suggests he found gratitude in those last hours reviewing his life. “I want to leave a hundred pounds to Nelson College,” he told Mary Rutherford. “You can see to it.” And again loudly a little later: “Remember, a hundred to Nelson College.” He died that evening. “Heart and circulation failed” because of massive infection, his doctor wrote, “and the end came peacefully.”

An international gathering of physicists in Bologna that week celebrated the 200th anniversary of the birth of Luigi Galvani; Cambridge cabled the news of Rutherford's death on the morning of October 20. Bohr was on hand and accepted the grim duty of announcement. “When the meeting scheduled for that morning assembled,” writes Mark Oliphant, “Bohr went to the front, and with faltering voice and tears in his eyes informed the gathering of what had happened.” They were shocked at the abruptness of the loss. Bohr had visited Rutherford at Cambridge a few weeks earlier; the Cavendish men had seen their leader in fine fettle only days ago.

Bohr “spoke from the heart,” says Oliphant, recalling “the debt which science owed so great a man whom he was privileged to call both his master and his friend.” For Oliphant it was “one of the most moving experiences of my life.” Remembering Rutherford in a letter to Oppenheimer on December 20 Bohr balanced loss with hope, complementarily: “Life is poorer without him; but still every thought about him will be a lasting encouragement.” And in 1958, in a memorial lecture, Bohr said simply that “to me he had almost been as a second father.”

The sub-dean of Westminster immediately approved interment of Rutherford's ashes in the nave of Westminster Abbey, just west of Newton's tomb and in line with Kelvin's. Eulogizing Rutherford at a conference in Calcutta the following January, James Jeans identified his place in the history of science:

Voltaire said once that Newton was more fortunate than any other scientist could ever be, since it could fall to only one man to discover the laws which governed the universe. Had he lived in a later age, he might have said something similar of Rutherford and the realm of the infinitely small; for Rutherford was the Newton of atomic physics.

Ernest Rutherford unknowingly wrote his own more characteristic epitaph in a letter to A. S. Eve from his country cottage on the first day of that last October. He reported of his garden what he had also done for physics, vigorous and generous work: “I have made a still further clearance of the blackberry patch and the view is now quite attractive.”

In September 1934, in the wake of Fermi's June Nature article “Possible production of elements of atomic number higher than 92,” a curious paper appeared in a publication seldom read by physicists, the Zeitschrift fur Angewandte Chemie — the Journal of Applied Chemistry. Its author was a respected German chemist, Ida Noddack, co-discoverer with her husband (in 1925) of the hard, platinum-white metallic element rhenium, atomic number 75. The paper was titled simply “On element 93” and it severely criticized Fermi's work. His “method of proof was “not valid,” Noddack wrote bluntly. He had demonstrated that “his new beta emitter” was not protactinium and then distinguished it from several other elements descending down the periodic table to lead, but it was “not clear why he chose to stop at lead.” The old view that the radioactive elements form a continuous series beginning at uranium and ending at lead, wrote Noddack, was exactly what the Joliot-Curies' discovery of artificial radioactivity had disproved. “Fermi therefore ought to have compared his new radioelement with all known elements.”

The fact was, Noddack went on, any number of elements could be precipitated out of uranium nitrate with manganese. Instead of assuming the production of a new transuranic element, “one could assume equally well that when neutrons are used to produce nuclear disintegrations, some distinctly new nuclear reactions take place which have not been observed previously.” In the past, elements have transmuted only into their near neighbors. But “when heavy nuclei are bombarded by neutrons, it is conceivable that the nucleus breaks up into several large fragments, which would of course be isotopes of known elements but would not be neighbors.” They would be, rather, much lighter elements farther down the periodic table than lead.

Segre remembers reading the Noddack paper. He knows, because he asked them, that Hahn in Berlin and Joliot in Paris read it. It made very little sense to anyone. “I think whatever chemists read it,” Frisch reminisces, “probably thought that this was quite pointless, carping criticism, and the physicists possibly even more so if they read it, because they would say, ‘What's the use of criticizing unless you give some reason why that criticism would be valid?’ Nobody had ever found a nuclear disintegration creating far-removed elements.” Which was a point Noddack had carefully addressed, but was clearly one reason for the paper's neglect. The summary report for Nature on artificial radioactivity that Amaldi and Segre had delivered to Rutherford in midsummer 1934 makes the assumption explicit: “It is reasonable to assume that the atomic number of the active element should be close to the atomic number… of the bombarded element.”

But Fermi seldom left anything to assumption, however reasonable. He would certainly not have left to assumption this issue, about which he was already acutely sensitive because of Corbino's ill-timed speech (Noddack rubbed salt into that wound by referring to “the reports found in the newspapers”). He sat down and performed the necessary calculations. He later told at least Teller, Segre and his American protege Leona Woods that he had done so. Teller is quite sure he knows what those calculations were:

Fermi refused to believe [Noddack]… He knew how to calculate whether or not uranium could break in two… He performed the calculation Mrs. Noddack suggested, and found that the probability was extraordinarily low. He concluded that Mrs. Noddack's suggestion could not possibly be correct. So he forgot about it. His theory was right… but… it was based on the… wrong experimental information.

Here Teller indicts Aston's measurement of the mass of helium (the same that had misled Szilard to beryllium), which “introduced a systematic error into calculating the mass and energy of nuclei.”

Segre finds Teller's version of the story possible but not persuasive. The helium mass number problem would not necessarily have ruled out breaking up the uranium nucleus. “You know, occasionally Fermi would tell you things, then you asked him, ‘But really, how? Show me.’ And then he would say, ‘Oh, well, I know this on elf.' He spoke Italian. 'C.i.f.' meant 'con intuito formidable,' ‘with formidable intuition.’ So how he did it, I don't know. On the other hand, Fermi made a lot of calculations which he kept to himself.”

Leona Woods' version sheds light on Teller's:

Why was Dr. Noddack's suggestion ignored? The reason is that she was ahead of her time. Bohr's liquid- drop model of the nucleus had not yet been formulated, and so there was at hand no accepted way to calculate whether breaking up into several large fragments was energetically allowed.

If Noddack's physics was avant garde, her chemistry was sound. By 1938 her article was gathering dust on back shelves, but Bohr had promulgated the liquid-drop model of the nucleus and the confused chemistry of uranium increasingly preoccupied Lise Meitner and Otto Hahn.

9 An Extensive Burst

“I believe all young people think about how they would like their lives to develop,” Lise Meitner wrote in old age, looking back; “when I did so I always arrived at the conclusion that life need not be easy provided only that it was not empty. And this wish I have been granted.” Sixty years old in 1938, the Austrian physicist had earned wide