Making of the Atomic Bomb

  Just then, in 1932, Szilard found or took up for the first time that appealing orphan among H. G. Wells’ books that he had failed to discover before: The World Set Free.63 Despite its title, it was not a tract like The Open Conspiracy. It was a prophetic novel, published in 1914, before the beginning of the Great War. Thirty years later Szilard could still summarize The World Set Free in accurate detail. Wells describes, he says:

  . . . the liberation of atomic energy on a large scale for industrial purposes, the development of atomic bombs, and a world war which was apparently fought by an alliance of England, France, and perhaps including America, against Germany and Austria, the powers located in the central part of Europe. He places this war in the year 1956, and in this war the major cities of the world are all destroyed by atomic bombs.64

  More personal discoveries emerged from Wells’ visionary novel—ideas that anticipated or echoed Szilard’s utopian plans, responses that may have guided him in the years ahead. Wells writes that his scientist hero, for example, was “oppressed, he was indeed scared, by his sense of the immense consequences of his discovery. He had a vague idea that night that he ought not to publish his results, that they were premature, that some secret association of wise men should take care of his work and hand it on from generation to generation until the world was riper for its practical application.”65

  Yet The World Set Free influenced Szilard less than its subject matter might suggest. “This book made a very great impression on me, but I didn’t regard it as anything but fiction. It didn’t start me thinking of whether or not such things could in fact happen. I had not been working in nuclear physics up to that time.”66

  By his own account, a different and quieter dialogue changed the direction of Szilard’s work. The friend who had introduced him to H. G. Wells returned in 1932 to the Continent:

  I met him again in Berlin and there ensued a memorable conversation. Otto Mandl said that now he really thought he knew what it would take to save mankind from a series of ever-recurring wars that could destroy it. He said that Man has a heroic streak in himself. Man is not satisfied with a happy idyllic life: he has the need to fight and to encounter danger. And he concluded that what mankind must do to save itself is to launch an enterprise aimed at leaving the earth. On this task he thought the energies of mankind could be concentrated and the need for heroism could be satisfied.67 I remember very well my own reaction. I told him that this was somewhat new to me, and that I really didn’t know whether I would agree with him. The only thing I could say was this: that if I came to the conclusion that this was what mankind needed, if I wanted to contribute something to save mankind, then I would probably go into nuclear physics, because only through the liberation of atomic energy could we obtain the means which would enable man not only to leave the earth but to leave the solar system.

  Such must have been Szilard’s conclusion; that year he moved to the Harnack House of the Kaiser Wilhelm Institutes—a residence for visiting scientists sponsored by German industry, a faculty club of sorts—and approached Lise Meitner about the possibility of doing experimental work with her in nuclear physics. Thus to save mankind.68

  He always lived out of suitcases, in rented rooms. At the Harnack House he kept the keys to his two suitcases at hand and the suitcases packed. “All I had to do was turn the key and leave when things got too bad.” Things got bad enough to delay a decision about working with Meitner. An older Hungarian friend, Szilard remembers—Michael Polanyi, a chemist at the Kaiser Wilhelm Institutes with a family to consider—viewed the German political scene optimistically, like many others in Germany at the time.69, 70 “They all thought that civilized Germans would not stand for anything really rough happening.” Szilard held no such sanguine view, noting that the Germans themselves were paralyzed with cynicism, one of the uglier effects on morals of losing a major war.71

  Adolf Hitler was appointed Chancellor of Germany on January 30, 1933. On the night of February 27 a Nazi gang directed by the head of the Berlin SA, Hitler’s private army, set fire to the imposing chambers of the Reichstag. The building was totally destroyed. Hitler blamed the arson on the Communists and bullied a stunned Reichstag into awarding him emergency powers. Szilard found Polanyi still unconvinced after the fire. “He looked at me and said, ‘Do you really mean to say that you think that [Minister] of the Interior [Hermann Göring] had anything to do with this?’ and I said, ‘Yes, this is precisely what I mean.’ He just looked at me with incredulous eyes.” In late March, Jewish judges and lawyers in Prussia and Bavaria were dismissed from practice.72 On the weekend of April 1, Julius Streicher directed a national boycott of Jewish businesses and Jews were beaten in the streets. “I took a train from Berlin to Vienna on a certain date, close to the first of April, 1933,” Szilard writes. “The train was empty. The same train the next day was overcrowded, was stopped at the frontier, the people had to get out, and everybody was interrogated by the Nazis.73 This just goes to show that if you want to succeed in this world you don’t have to be much cleverer than other people, you just have to be one day earlier.”

  The Law for the Restoration of the Career Civil Service was promulgated throughout Germany on April 7 and thousands of Jewish scholars and scientists lost their positions in German universities. From England, where he landed in early May, Szilard went furiously to work to help them emigrate and to find jobs for them in England, the United States, Palestine, India, China and points between. If he couldn’t yet save all the world, he could at least save some part of it.

  He came up for air in September. By then he was living at the Imperial Hotel in Russell Square, having transferred £1,595 from Zurich to his bank in London.74 More than half the money, £854, he held in trust for his brother Béla; the rest would see him through the year.75 Szilard’s funds came from his patent licenses, refrigeration consulting and Privatdozent fees. He was busy finding jobs for others and couldn’t be bothered to seek one himself. He had few expenses in any case; a week’s lodging and three meals a day at a good London hotel cost about £5.5; he was a bachelor most of his life and his needs were simple.

  “I was no longer thinking about this conversation [with Otto Mandl about space travel], or about H. G. Wells’ book either, until I found myself in London about the time of the British Association [meeting].”76 Szilard’s syntax slips here: the crucial word is until. He had been too distracted by events and by rescue work to think creatively about nuclear physics. He had even been considering going into biology, a radical change of field but one that a number of able physicists have managed, in prewar days and since. Such a change is highly significant psychologically and Szilard was to make it in 1946. But in September 1933, a meeting of the British Association for the Advancement of Science, an annual assembly, intervened.

  If on Friday, September 1, lounging in the lobby of the Imperial Hotel, Szilard read The Times’ review of The Shape of Things to Come, then he noticed the anonymous critic’s opinion that Wells had “attempted something of the sort on earlier occasions—that rather haphazard work, The World Set Free,’ comes particularly to mind—but never with anything like the same continuous abundance and solidity of detail, or indeed, the power to persuade as to the terrifying probability of some of the more immediate and disastrous developments.” And may have thought again of the atomic bombs of Wells’ earlier work, of Wells’ Open Conspiracy and his own, of Nazi Germany and its able physicists, of ruined cities and general war.77

  Without question Szilard read The Times of September 12, with its provocative sequence of headlines:

  THE BRITISH ASSOCIATION

  BREAKING DOWN

  THE ATOM

  TRANSFORMATION OF

  ELEMENTS

  Ernest Rutherford, The Times reported, had recited a history of “the discoveries of the last quarter of a century in atomic transmutation,” including:

  THE NEUTRON

  NOVEL TRANSFORMATIONS

  All of which made Szilard restive. The leading s
cientists in Great Britain were meeting and he wasn’t there. He was safe, he had money in the bank, but he was only another anonymous Jewish refugee down and out in London, lingering over morning coffee in a hotel lobby, unemployed and unknown.

  Then, midway along the second column of The Times’ summary of Rutherford’s speech, he found:

  HOPE OF TRANSFORMING ANY ATOM

  What, Lord Rutherford asked in conclusion, were the prospects 20 or 30 years ahead?78

  High voltages of the order of millions of volts would probably be unnecessary as a means of accelerating the bombarding particles. Transformations might be effected with 30,000 or 70,000 volts. . . . He believed that we should be able to transform all the elements ultimately.

  We might in these processes obtain very much more energy than the proton supplied, but on the average we could not expect to obtain energy in this way. It was a very poor and inefficient way of producing energy, and anyone who looked for a source of power in the transformation of the atoms was talking moonshine.

  Did Szilard know what “moonshine” meant—“foolish or visionary talk”? Did he have to ask the doorman as he threw down the newspaper and stormed out into the street? “Lord Rutherford was reported to have said that whoever talks about the liberation of atomic energy on an industrial scale is talking moonshine. Pronouncements of experts to the effect that something cannot be done have always irritated me.”

  “This sort of set me pondering as I was walking in the streets of London, and I remember that I stopped for a red light at the intersection of Southampton Row. . . .79 I was pondering whether Lord Rutherford might not prove to be wrong.”80

  “It occurred to me that neutrons, in contrast to alpha particles, do not ionize [i.e., interact electrically with] the substance through which they pass.81

  “Consequently, neutrons need not stop until they hit a nucleus with which they may react.”

  Szilard was not the first to realize that the neutron might slip past the positive electrical barrier of the nucleus; that realization had come to other physicists as well. But he was the first to imagine a mechanism whereby more energy might be released in the neutron’s bombardment of the nucleus than the neutron itself supplied.

  There was an analogous process in chemistry. Polanyi had studied it.82 A comparatively small number of active particles—oxygen atoms, for example—admitted into a chemically unstable system, worked like leaven to elicit a chemical reaction at temperatures much lower than the temperature that the reaction normally required. Chain reaction, the process was called. One center of chemical reaction produces thousands of product molecules. One center occasionally has an especially favorable encounter with a reactant and instead of forming only one new center, it forms two or more, each of which is capable in turn of propagating a reaction chain.

  Chemical chain reactions are self-limiting. Were they not, they would run away in geometric progression: 1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024, 2048, 4096, 8192, 16384, 32768, 65536, 131072, 262144, 524288, 1048576, 2097152, 4194304, 8388608, 16777216, 33554432, 67108868, 134217736 . . .

  “As the light changed to green and I crossed the street,” Szilard recalls, “it . . . suddenly occurred to me that if we could find an element which is split by neutrons and which would emit two neutrons when it absorbs one neutron, such an element, if assembled in sufficiently large mass, could sustain a nuclear chain reaction.83, 84

  “I didn’t see at the moment just how one would go about finding such an element, or what experiments would be needed, but the idea never left me. In certain circumstances it might be possible to set up a nuclear chain reaction, liberate energy on an industrial scale, and construct atomic bombs.”

  Leo Szilard stepped up onto the sidewalk. Behind him the light changed to red.

  2

  Atoms and Void

  Atomic energy requires an atom. No such beast was born legitimately into physics until the beginning of the twentieth century. The atom as an idea—as an invisible layer of eternal, elemental substance below the world of appearances where things combine, teem, dissolve and rot—is ancient. Leucippus, a Greek philosopher of the fifth century B.C. whose name survives on the strength of an allusion in Aristotle, proposed the concept; Democritus, a wealthy Thracian of the same era and wider repute, developed it. “ ‘For by convention color exists,’ ” the Greek physician Galen quotes from one of Democritus’ seventy-two lost books, “ ‘by convention bitter, by convention sweet, but in reality atoms and void.’ ” From the seventeenth century onward, physicists postulated atomic models of the world whenever developments in physical theory seemed to require them.85 But whether or not atoms really existed was a matter for continuing debate.

  Gradually the debate shifted to the question of what kind of atom was necessary and possible. Isaac Newton imagined something like a miniature billiard ball to serve the purposes of his mechanical universe of masses in motion: “It seems probable to me,” he wrote in 1704, “that God in the beginning formed matter in solid, massy, hard, impenetrable, movable particles, of such sizes and figures, and with such other properties, and in such proportion to space, as most conduced to the end to which he formed them.”86 The Scottish physicist James Clerk Maxwell, who organized the founding of the Cavendish Laboratory, published a seminal Treatise on Electricity and Magnetism in 1873 that modified Newton’s purely mechanical universe of particles colliding in a void by introducing into it the idea of an electromagnetic field. The field permeated the void; electric and magnetic energy propagated through it at the speed of light; light itself, Clerk Maxwell demonstrated, is a form of electromagnetic radiation. But despite his modifications, Clerk Maxwell was as devoted as Newton to a hard, mechanical atom:

  Though in the course of ages catastrophes have occurred and may yet occur in the heavens, though ancient systems may be dissolved and new systems evolved out of their ruins, the [atoms] out of which [the sun and the planets] are built—the foundation stones of the material universe—remain unbroken and unworn. They continue this day as they were created—perfect in number and measure and weight.87

  Max Planck thought otherwise. He doubted that atoms existed at all, as did many of his colleagues—the particulate theory of matter was an English invention more than a Continental, and its faintly Britannic odor made it repulsive to the xenophobic German nose—but if atoms did exist he was sure they could not be mechanical. “It is of paramount importance,” he confessed in his Scientific Autobiography, “that the outside world is something independent from man, something absolute, and the quest for laws which apply to this absolute appeared to me as the most sublime scientific pursuit in life.” Of all the laws of physics, Planck believed that the thermodynamic laws applied most basically to the independent “outside world” that his need for an absolute required.88 He saw early that purely mechanical atoms violated the second law of thermodynamics. His choice was clear.

  The second law specifies that heat will not pass spontaneously from a colder to a hotter body without some change in the system. Or, as Planck himself generalized it in his Ph.D. dissertation at the University of Munich in 1879, that “the process of heat conduction cannot be completely reversed by any means.” Besides forbidding the construction of perpetual-motion machines, the second law defines what Planck’s predecessor Rudolf Clausius named entropy: because energy dissipates as heat whenever work is done—heat that cannot be collected back into useful, organized form—the universe must slowly run down to randomness.89 This vision of increasing disorder means that the universe is one-way and not reversible; the second law is the expression in physical form of what we call time. But the equations of mechanical physics—of what is now called classical physics—theoretically allowed the universe to run equally well forward or backward. “Thus,” an important German chemist complained, “in a purely mechanical world, the tree could become a shoot and a seed again, the butterfly turn back into a caterpillar, and the old man into a child. No explanation is given by the mechanistic do
ctrine for the fact that this does not happen. . . . The actual irreversibility of natural phenomena thus proves the existence of phenomena that cannot be described by mechanical equations; and with this the verdict on scientific materialism is settled.”90 Planck, writing a few years earlier, was characteristically more succinct: “The consistent implementation of the second law . . . is incompatible with the assumption of finite atoms.”91

  A major part of the problem was that atoms were not then directly accessible to experiment. They were a useful concept in chemistry, where they were invoked to explain why certain substances—elements—combine to make other substances but cannot themselves be chemically broken down. Atoms seemed to be the reason gases behaved as they did, expanding to fill whatever container they were let into and pushing equally on all the container’s walls. They were invoked again to explain the surprising discovery that every element, heated in a laboratory flame or vaporized in an electric arc, colors the resulting light and that such light, spread out into its rainbow spectrum by a prism or a diffraction grating, invariably is divided into bands by characteristic bright lines. But as late as 1894, when Robert Cecil, the third Marquis of Salisbury, chancellor of Oxford and former Prime Minister of England, catalogued the unfinished business of science in his presidential address to the British Association, whether atoms were real or only convenient and what structure they hid were still undecided issues: