The Making of the Atomic Bomb

cannot be less than 10⁸ [i.e., 100,000,000] gram-calories, and may be between 10⁹ and 10¹⁰ gram-calories… The union of hydrogen and oxygen liberates approximately 4 ? 10³ [i.e., 4,000] gram-calories per gram of water produced, and this reaction sets free more energy for a given weight than any other chemical change known. The energy of radioactive change must therefore be at least twenty-thousand times, and may be a million times, as great as the energy of any molecular change.

That was the formal scientific statement; informally Rutherford inclined to whimsical eschatology. A Cambridge associate writing an article on radioactivity that year, 1903, considered quoting Rutherford's “playful suggestion that, could a proper detonator be found, it was just conceivable that a wave of atomic disintegration might be started through matter, which would indeed make this old world vanish in smoke.” Rutherford liked to quip that “some fool in a laboratory might blow up the universe unawares.” If atomic energy would never be useful, it might still be dangerous.

Soddy, who returned to England that year, examined the theme more seriously. Lecturing on radium to the Corps of Royal Engineers in 1904, he speculated presciently on the uses to which atomic energy might be put:

It is probable that all heavy matter possesses — latent and bound up with the structure of the atom — a similar quantity of energy to that possessed by radium. If it could be tapped and controlled what an agent it would be in shaping the world's destiny! The man who put his hand on the lever by which a parsimonious nature regulates so jealously the output of this store of energy would possess a weapon by which he could destroy the earth if he chose.

Soddy did not think the possibility likely: “The fact that we exist is a proof that [massive energetic release] did not occur; that it has not occurred is the best possible assurance that it never will. We may trust Nature to guard her secret.”

H. G. Wells thought Nature less trustworthy when he read similar statements in Soddy's 1909 book Interpretation of Radium. “My idea is taken from Soddy,” he wrote of The World Set Free. “One of the good old scientific romances,” he called his novel; it was important enough to him that he interrupted a series of social novels to write it. Rutherford's and Soddy's discussions of radioactive change therefore inspired the science-fiction novel that eventually started Leo Szilard thinking about chain reactions and atomic bombs.

In the summer of 1903 the Rutherfords visited the Curies in Paris. Mme. Curie happened to be receiving her doctorate in science on the day of their arrival; mutual friends arranged a celebration. “After a very lively evening,” Rutherford recalled, “we retired about 11 o'clock in the garden, where Professor Curie brought out a tube coated in part with zinc sulphide and containing a large quantity of radium in solution. The luminosity was brilliant in the darkness and it was a splendid finale to an unforgettable day.” The zinc-sulfide coating fluoresced white, making the radium's ejection of energetic particles on its progess down the periodic table from uranium to lead visible in the darkness of the Paris evening. The light was bright enough to show Rutherford Pierre Curie's hands, “in a very inflamed and painful state due to exposure to radium rays.” Hands swollen with radiation burns was another object lesson in what the energy of matter could do.

A twenty-six-year-old German chemist from Frankfurt, Otto Hahn, came to Montreal in 1905 to work with Rutherford. Hahn had already discovered a new “element,” radiothorium, later understood to be one of thorium's twelve isotopes. He studied thorium radiation with Rutherford; together they determined that the alpha particles ejected from thorium had the same mass as the alpha particles ejected from radium and those from another radioactive element, actinium. The various particles were probably therefore identical — one conclusion along the way to Rutherford's proof in 1908 that the alpha particle was inevitably a charged helium atom. Hahn went back to Germany in 1906 to begin a distinguished career as a discoverer of isotopes and elements; Leo Szilard encountered him working with physicist Lise Meitner at the Kaiser Wilhelm Institute for Chemistry in the 1920s in Berlin.

Rutherford's research at McGill unraveling the complex transmutations of the radioactive elements earned him, in 1908, a Nobel Prize — not in physics but in chemistry. He had wanted that prize, writing his wife when she returned to New Zealand to visit her family in late 1904, “I may have a chance if I keep going,” and again early in 1905, “They are all following on my trail, and if I am to have a chance for a Nobel Prize in the next few years I must keep my work moving.” The award for chemistry rather than for physics at least amused him. “It remained to the end a good joke against him,” says his son-in-law, “which he thoroughly appreciated, that he was thereby branded for all time as a chemist and no true physicist.”

An eyewitness to the ceremonies said Rutherford looked ridiculously young — he was thirty-seven — and made the speech of the evening. He announced his recent confirmation, only briefly reported the month before, that the alpha particle was in fact helium. The confirming experiment was typically elegant. Rutherford had a glassblower make him a tube with extremely thin walls. He evacuated the tube and filled it with radon gas, a fertile source of alpha particles. The tube was gastight, but its thin walls allowed alpha particles to escape. Rutherford surrounded the radon tube with another glass tube, pumped out the air between the two tubes and sealed off the space. “After some days,” he told his Stockholm audience triumphantly, “a bright spectrum of helium was observed in the outer vessel.” Rutherford's experiments still stun with their simplicity. “In this Rutherford was an artist,” says a former student. “All his experiments had style.”

In the spring of 1907 Rutherford had left Montreal with his family — by then including a six-year-old daughter, his only child — and moved back to England. He had accepted appointment as professor of physics at Manchester, in the city where John Dalton had first revived the atomic theory almost exactly a century earlier. Rutherford bought a house and went immediately to work. He inherited an experienced German physicist named Hans Geiger who had been his predecessor's assistant. Years later Geiger fondly recalled the Manchester days, Rutherford settled in among his gear:

I see his quiet research room at the top of the physics building, under the roof, where his radium was kept and in which so much well-known work on the emanation was carried out. But I also see the gloomy cellar in which he had fitted up his delicate apparatus for the study of the alpha rays. Rutherford loved this room. One went down two steps and then heard from the darkness Rutherford's voice reminding one that a hot-pipe crossed the room at head-level, and to step over two water-pipes. Then finally, in the feeble light one saw the great man himself seated at his apparatus.

The Rutherford house was cheerier; another Manchester protdgd liked to recall that “supper in the white- painted dining room on Saturdays and Sundays preceded pow-wows till all hours in the study on the first floor; tea on Sundays in the drawing room often followed a spin on the Cheshire roads in the motor.” There was no liquor in the house because Mary Rutherford did not approve of drinking. Smoking she reluctantly allowed because her husband smoked heavily, pipe and cigarettes both.

Now in early middle age he was famously loud, a “tribal chief,” as a student said, fond of banter and slang. He would march around the lab singing “Onward Christian Soldiers” off key. He took up room in the world now; you knew he was coming. He was ruddy-faced with twinkling blue eyes and he was beginning to develop a substantial belly. The diffidence was well hidden: his handshake was brief, limp and boneless; “he gave the impression,” says another former student, “that he was shy of physical contact.” He could still be mortified by condescension, blushing bright red and turning aside dumbstruck. With his students he was quieter, gentler, solid gold. “He was a man,” pronounces one in high praise, “who never did dirty tricks.”

Chaim Weizmann, the Russian-Jewish biochemist who was later elected the first president of Israel, was working at Manchester on fermentation products in those days. He and Rutherford became good friends. “Youthful, energetic, boisterous,” Weizmann recalled, “he suggested anything but the scientist. He talked readily and vigorously on every subject under the sun, often without knowing anything about it. Going down to the refectory for lunch I would hear the loud, friendly voice rolling up the corridor.” Rutherford had no political knowledge at all, Weizmann thought, but excused him on the grounds that his important scientific work took all his time. “He was a kindly person, but he did not suffer fools gladly.”

In September 1907, his first term at Manchester, Rutherford made up a list of possible subjects for research. Number seven on the list was “Scattering of alpha rays.” Working over the years to establish the alpha particle's identity, he had come to appreciate its great value as an atomic probe; because it was massive compared to the