The Making of the Atomic Bomb

The idea of atoms, tiny objects that make up the matter of the universe, goes back to the ancient Greeks. Many signs point to some elemental property at the bottom of physical things. By the 19th century, most British scientists believe atoms must exist, but scientists on the Continent are more skeptical. A friend of Szilard’s, Michael Polanyi, is a philosopher of science who sees scientists as free members of an informal republic. They work to find answers to questions about the nature of things, but those answers tend to be provisional, and the methods of finding them out vary with each question.

Science, then, is an art, and it must be taught by masters, yet there is no final authority on what is true and what subjects should be worked on, except the decisions of individual scientists as they speak freely to one another and choose projects best suited to their skills and preferences. There is no orthodoxy in science, but scientists need a way to winnow good, new ideas from bad. A new concept is a rebellion of sorts against the consensus; to gain acceptance, it must be plausible, add value and accuracy to its field, and be compellingly original.

Rutherford grows up on a farm in 1870s New Zealand, where he learns toughness leavened by a willingness to be astonished. He studies science, graduates from the University of New Zealand, makes skillful discoveries about radio waves that break the consensus, and wins a scholarship to Cambridge University in England. There, he develops one of the first radio receivers and works in the new field of X-rays. Chastised for his eagerness to make money off of his discoveries, Rutherford becomes a budget-conscious pursuer of pure science. His mentor, JJ Thomson, works with cathode ray tubes and makes the first discovery of a subatomic particle, the electron, whose existence proves that something larger, the much-sought-after atom, really exists.

Shortly thereafter, radioactive elements are discovered. Rutherford discovers alpha and beta particles, the first observed products of radioactive decay. In 1899 he receives an appointment to teach physics at Canada’s McGill University. Rutherford and an associate, Frederick Soddy, discover that thorium disintegrates into argon; this is the first observation of radioactive decay. Their tests on other radioactive elements, including uranium, reveal that the radiation has a characteristic half-life, or time in which the radiation is reduced by half, of anywhere from fractions of a second to billions of years. Radioactivity also releases energy; Rutherford jokes that “some fool in a laboratory might blow up the universe unawares” (44).

In 1907, by now with wife and daughter, Rutherford returns to England to teach and do research at the University of Manchester. Rutherford’s work on radioactivity earns him the 1908 Nobel Prize in chemistry. In his acceptance speech, Rutherford announces his discovery that a common radioactive decay product, which he has named the “alpha” particle, is in fact a charged helium atom. He works hard at studying how various materials affect alpha particles but wants to keep account of them, so he and Hans Geiger develop a gauge—an early form of the famous Geiger counter—that clicks at each particle’s arrival at a screen. His team also uses a microscope to observe the tiny glow emitted by alpha particles as they strike a zinc-sulfide plate. Rutherford’s observations prove that every atom has a positively charged nucleus surrounded by negatively charged electrons. Electrons orbiting like planets should crash into the nucleus, yet atoms are highly stable. This presents a new mystery to solve. 

Bohr is a study in contrasts. Tall and muscular, a nationally ranked Danish soccer player, Bohr is shy and quiet in speech. He holds strong beliefs but sometimes feels crippled with doubt. A hardheaded realist who loves working with his hands, Bohr becomes a theoretical physicist second only to Einstein. As children, Bohr and his younger brother Harald—with whom Niels is close—sit at the feet of their father, Christian, a physiologist, as he hobnobs with fellow scientists and philosophers. Bohr has trouble writing, so his mother becomes his secretary; for the rest of his life, Bohr has someone take his dictations.

In college, Bohr studies math and the philosopher Kierkegaard; Bohr worries over the problem of identity and how it can split into two, or “tvi,” specifically how the self can think about itself in an infinite regress. Bohr’s favorite book is an 1824 novel by Poul Moller, The Adventures of a Danish Student, that includes extended dialogs between two college undergrads, one of whom describes a compelling doubt about his own consciousness: “ […] on many occasions man divides himself into two persons, one of whom tries to fool the other, while a third one, who is in fact the same as the other two, is filled with wonder at this confusion” (59). When not tormented by these doubts, Bohr also does lab work on the surface tension of liquids and wins a gold medal from the Danish science academy.

Bohr earns his PhD; his father arranges a fellowship to Cambridge for 1911. At first Bohr enjoys Cambridge, but he annoys the director, JJ Thomson, by pointing out errors in his work on the electron; Thomson assigns him a dead-end project. Bohr soon meets Rutherford and in 1912 transfers to Manchester to work with him. There, Bohr quickly produces “spectacular” work, figuring out that radioactivity comes from the atomic nucleus, and that the size of the nucleus’ positive electric charge—its “atomic number”—determines an element’s place on the periodic table.

Returning to Copenhagen that summer to get married and teach at the university, Bohr continues to struggle with his new theory of electron orbits. He builds on research by Planck, who discovers that heated objects give off energy in discrete amounts called quanta, and by Einstein, who shows that quanta of light are carried by photons to and from electrons. (Each of these men win Nobel Prizes for those discoveries.) Add to these the unique lines of color emitted by heated materials when their light is passed through a prism, and Bohr has his theory: Electrons occupy orbital shells around the nucleus, and when photons add discrete quanta of energy to them, the electrons jump to higher-energy shells, then reemit photons and jump back down to lower-energy shells.

When these quanta will be absorbed and released is impossible to determine; subatomic particles therefore exhibit a sort of individual freedom that appeals deeply to Bohr. The electron jumps resonate with Kierkegaard’s notion of “leaps of faith” (76) that resolve dilemmas; the uncertainties about exactly when these jumps occur suggest a randomness in nature that allows for free will. By early 1913 the work is done; it will earn Bohr a Nobel Prize. 

Chemist Otto Hahn, who worked with Rutherford in Canada, in 1912 begins doing research with physicist Lise Meitner—the second woman ever to receive a PhD from the University of Vienna—at the new Kaiser Wilhelm Institute for Chemistry in Berlin. They study radioactive elements and the clues they provide in the new field of nuclear physics. At Manchester, Harry Moseley works with X-ray crystallography, another new field in which X-rays are fired through various materials and then through a crystal that diffracts the rays into distinct energy lines. Using the precise, stairstep shifts in the X-ray spectral lines, Moseley is soon able to put the elements into their correct order on the periodic table. This provides strong proof that Bohr and Rutherford’s theory of the atom is correct.

War breaks out in Europe in August 1914. Moseley volunteers as a lieutenant in the Royal Engineers; Bohr and his wife move from Denmark to Manchester to work again with Rutherford. Rutherford’s colleague Chaim Weizmann, a biochemist and “passionate Zionist,” has discovered how to make bacteria generate acetone from starch, and the British government badly needs acetone to make cordite, the explosive used to propel artillery shells. In 1915, the government gives Weizmann carte blanche to scale up acetone production to industrial levels. Weizmann’s work is a resounding success, and he uses his new influence to campaign for British support for a Jewish national home in Palestine. The Balfour Declaration, a letter proclaiming such support, comes later in the war.

The war bogs down into lines of trenches. On the German side, Hahn works with Fritz Haber—inventor of synthetic fertilizer and synthetic nitrates for explosives—to develop poison gas as a breakthrough war weapon. Their chlorine gas is used against British forces at Ypres in April 1915; 5,000 die and 10,000 are wounded. Though both sides have lobbed tear gas during recent battles, the chlorine attack violates international agreements and is the first major use of asphyxiating gas during wartime. Though Germany is way ahead of England and France in industrial chemistry, both sides quickly develop and use more advanced forms of poison gas, especially phosgene, chloropicrin—“vomiting gas”—and mustard gas, which melts gas masks. Haber’s wife, Clara, herself a chemistry PhD, despises the poison-gas industry as barbaric; she pleads with Haber to halt his research. Haber refuses, and Clara commits suicide.

In 1915, the British try to take Gallipoli, a peninsula that guards the straits between Europe and Asia; the Turks fight back, and in one encounter Moseley is killed. American physicist Robert Millikan eulogizes Moseley by declaring that his loss makes the war “one of the most hideous and most irreparable crimes in history” (97). Large German biplanes drop bombs on a small harbor town in southeast England in May 1917, the first strategic bombing of civilians. More bombing raids follow, about two a month, especially against London, and soon the raids include incendiaries. Strategists wonder whether future wars will focus more on bombing raids than battlefield action.

The war is highly mechanized. The US builds a massive factory to produce poison gas; the British fire 170 million artillery shells; machine guns can slaughter tens of thousands of soldiers in a single day, turning volunteers and conscripts alike from heroes into victims, their trenches a “long grave already dug” (103). Mutinies break out; finally, the introduction of tanks, a blockade that chokes off German supplies, and the arrival of American soldiers break the stalemate. Nine million die. Aerial bombing opens up the possibility that civilian casualties will come to dominate the next war.