## Metadata - Author: [[Richard Rhodes]] - Full Title: Making of the Atomic Bomb - Category: #books ## Highlights - Niels Bohr once noted, “is itself the basis for civilization.” You cannot have the one without the other; the one depends upon the other. Nor can you have only benevolent knowledge; the scientific method doesn’t filter for benevolence. Knowledge has consequences, not always intended, not always comfortable, not always welcome. The earth revolves around the sun, not the sun around the earth. ([Location 118](https://readwise.io/to_kindle?action=open&asin=B008TRU7SQ&location=118)) - Bohr proposed once that the goal of science is not universal truth. Rather, he argued, the modest but relentless goal of science is “the gradual removal of prejudices.” The discovery that the earth revolves around the sun has gradually removed the prejudice that the earth is the center of the universe. The discovery of microbes is gradually removing the prejudice that disease is a punishment from God. The discovery of evolution is gradually removing the prejudice that Homo sapiens is a separate and special creation. ([Location 127](https://readwise.io/to_kindle?action=open&asin=B008TRU7SQ&location=127)) - The 1996 Canberra Commission on the Elimination of Nuclear Weapons identified a fundamental principle that it called the “axiom of proliferation.” In its most succinct form, the axiom of proliferation asserts that As long as any state has nuclear weapons, others will seek to acquire them. A member of the commission, the Australian ambassador-at-large for nuclear disarmament, Richard Butler, told me, “The basic reason for this assertion is that justice, which most human beings interpret essentially as fairness, is demonstrably a concept of the deepest importance to people all over the world. Relating this to the axiom of proliferation, it is manifestly the case that the attempts over the years of those who own nuclear weapons to assert that their security justifies having those nuclear weapons while the security of others does not, has been an abject failure.” Elaborating before an audience in Sydney in 2002, Butler said, “I have worked on the Nuclear Non-Proliferation Treaty all my adult life. . . . The problem of nuclear-weapon haves and have-nots is the central, perennial one.” From 1997 to 1999 Butler was the last chairman of UNSCOM, the United Nations commission monitoring the disarming of Iraq. “Amongst my toughest moments in Baghdad,” he said in Sydney, “were when the Iraqis demanded that I explain why they should be hounded for their weapons of mass destruction when, just down the road, Israel was not, even though it was known to possess some 200 nuclear weapons. I confess too,” Butler continued, “that I flinch when I hear American, British, and French fulminations against weapons of mass destruction, ignoring the fact that they are the proud owners of massive quantities of those weapons, unapologetically insisting that they are essential for their national security and will remain so.” “The principle I would derive from this,” Butler concluded, “is that manifest unfairness, double standards, no matter what power would appear at a given moment to support them, produces a situation that is deeply, inherently, unstable. This is because human beings will not swallow such unfairness. This principle is as certain as the basic laws of physics itself.” At a later time and place Butler spoke of the particular resistance of Americans to recognizing their double standard. “My attempts to have the Americans enter into discussions about double standards,” he said, “have been an abject failure—even with highly educated and engaged people. I sometimes felt I was speaking to them in Martian, so deep is their inability to understand. What Americans totally fail to understand is that their weapons of mass destruction are just as much a problem as are those of Iraq.” Or of Iran, North Korea—or of any other confirmed or would-be nuclear power. ([Location 181](https://readwise.io/to_kindle?action=open&asin=B008TRU7SQ&location=181)) - It is a profound and necessary truth that the deep things in science are not found because they are useful; they are found because it was possible to find them. Robert Oppenheimer It is still an unending source of surprise for me to see how a few scribbles on a blackboard or on a sheet of paper could change the course of human affairs. Stanislaw Ulam ([Location 225](https://readwise.io/to_kindle?action=open&asin=B008TRU7SQ&location=225)) - “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.” ([Location 522](https://readwise.io/to_kindle?action=open&asin=B008TRU7SQ&location=522)) - The American theoretical physicist Richard Feynman once spoke about his science with similar candor to a lecture hall crowded with undergraduates at the California Institute of Technology. “What do we mean by ‘understanding’ something?” Feynman asked innocently.100 His amused sense of human limitation informs his answer: We can imagine that this complicated array of moving things which constitutes “the world” is something like a great chess game being played by the gods, and we are observers of the game. We do not know what the rules of the game are; all we are allowed to do is to watch the playing. Of course, if we watch long enough, we may eventually catch on to a few of the rules. The rules of the game are what we mean by fundamental physics. Even if we know every rule, however . . . what we really can explain in terms of those rules is very limited, because almost all situations are so enormously complicated that we cannot follow the plays of the game using the rules, much less tell what is going to happen next. We must, therefore, limit ourselves to the more basic question of the rules of the game. If we know the rules, we consider that we “understand” the world. ([Location 666](https://readwise.io/to_kindle?action=open&asin=B008TRU7SQ&location=666)) - Science, Polanyi was hinting, worked like a giant brain of individual intelligences linked together. That was the source of its cumulative and seemingly inexorable power. But the price of that power, as both Polanyi and Feynman are careful to emphasize, is voluntary limitation. Science succeeds in the difficult task of sustaining a political network among men and women of differing backgrounds and differing values, and in the even more difficult task of discovering the rules of the chess game of the gods, by severely limiting its range of competence. “Physics,” as Eugene Wigner once reminded a group of his fellows, “does not even try to give us complete information about the events around us—it gives information about the correlations between those events.” ([Location 715](https://readwise.io/to_kindle?action=open&asin=B008TRU7SQ&location=715)) - Apprentices learned three broad criteria of scientific judgment.109 The first criterion was plausibility. That would eliminate crackpots and frauds. It might also (and sometimes did) eliminate ideas so original that the orthodox could not recognize them, but to work at all, science had to take that risk. The second criterion was scientific value, a composite consisting of equal parts accuracy, importance to the entire system of whatever branch of science the idea belonged to, and intrinsic interest. The third criterion was originality. Patent examiners assess an invention for originality according to the degree of surprise the invention produces in specialists familiar with the art. Scientists judged new theories and new discoveries similarly. Plausibility and scientific value measured an idea’s quality by the standards of orthodoxy; originality measured the quality of its dissent. ([Location 727](https://readwise.io/to_kindle?action=open&asin=B008TRU7SQ&location=727)) - But if Rutherford gave up commercial wealth for holy science, he won the atom in exchange. He found its constituent parts and named them. With string and sealing wax he made the atom real. ([Location 823](https://readwise.io/to_kindle?action=open&asin=B008TRU7SQ&location=823)) - Armed with the electron, and knowing from other experiments that what was left when electrons were stripped away from an atom was a much more massive remainder that was positively charged, Thomson went on in the next decade to develop a model of the atom that came to be called the “plum pudding” model. The Thomson atom, “a number of negatively-electrified corpuscles enclosed in a sphere of uniform positive electrification” like raisins in a pudding, was a hybrid: particulate electrons and diffuse remainder.130 It served the useful purpose of demonstrating mathematically that electrons could be arranged in stable configurations within an atom and that the mathematically stable arrangements could account for the similarities and regularities among chemical elements that the periodic table of the elements displays. It was becoming clear that electrons were responsible for chemical affinities between elements, that chemistry was ultimately electrical. ([Location 844](https://readwise.io/to_kindle?action=open&asin=B008TRU7SQ&location=844)) - Between 1898, when Rutherford first turned his attention to the phenomenon Henri Becquerel found and which Marie Curie named radioactivity, and 1911, when he made the most important discovery of his life, the young New Zealand physicist systematically dissected the atom. ([Location 877](https://readwise.io/to_kindle?action=open&asin=B008TRU7SQ&location=877)) - The half-life measured the transmutation of half the atoms in an element into atoms of another element or of a physically variant form of the same element—an “isotope,” as Soddy later named it.143 Half-life became a way to detect the presence of amounts of transmuted substances—“decay products”—too small to detect chemically. The half-life of uranium proved to be 4.5 billion years, of radium 1,620 years, of one decay product of thorium 22 minutes, of another decay product of thorium 27 days. Some decay products appeared and transmuted themselves in minute fractions of a second—in the twinkle of an eye. It was work of immense importance to physics, opening up field after new field to excited view, and “for more than two years,” as Soddy remembered afterward, “life, scientific life, became hectic to a degree rare in the lifetime of an individual, rare perhaps in the lifetime of an institution.” ([Location 902](https://readwise.io/to_kindle?action=open&asin=B008TRU7SQ&location=902)) - Bohr was different in another regard as well; he was easily the most talented of all Rutherford’s many students—and Rutherford trained no fewer than eleven Nobel Prize winners during his life, an unsurpassed record. ([Location 1428](https://readwise.io/to_kindle?action=open&asin=B008TRU7SQ&location=1428)) - Bohr learned about radiochemistry from de Hevesy.268 He began to see connections with his electron-theory work. His sudden burst of intuitions then was spectacular. He realized in the space of a few weeks that radioactive properties originated in the atomic nucleus but chemical properties depended primarily on the number and distribution of electrons. He realized—the idea was wild but happened to be true—that since the electrons determined the chemistry and the total positive charge of the nucleus determined the number of electrons, an element’s position on the periodic table of the elements was exactly the nuclear charge (or “atomic number”): hydrogen first with a nuclear charge of 1, then helium with a nuclear charge of 2 and so on up to uranium at 92. ([Location 1442](https://readwise.io/to_kindle?action=open&asin=B008TRU7SQ&location=1442)) - since classical mechanics predicted that an atom like Rutherford’s, with a small, massive central nucleus surrounded by orbiting electrons, would be unstable, while in fact atoms are among the most stable of systems, classical mechanics was inadequate to describe such systems and would have to give way to a quantum approach. Planck had introduced quantum principles to save the laws of thermodynamics; Einstein had extended the quantum idea to light; Bohr now proposed to lodge quantum principles within the atom itself. ([Location 1519](https://readwise.io/to_kindle?action=open&asin=B008TRU7SQ&location=1519)) - “On the constitution of atoms and molecules” was seminally important to physics. Besides proposing a useful model of the atom, it demonstrated that events that take place on the atomic scale are quantized: that just as matter exists as atoms and particles in a state of essential graininess, so also does process. Process is discontinuous and the “granule” of process—of electron motions within the atom, for example—is Planck’s constant. ([Location 1584](https://readwise.io/to_kindle?action=open&asin=B008TRU7SQ&location=1584)) - Whether or not the will is free, for example, was a question that Bohr took seriously. To identify a kind of freedom of choice within the atom itself was a triumph for his carefully assembled structure of beliefs. The separate, distinct electron orbits that Bohr called stationary states recall Kierkegaard’s stages. They also recall Bohr’s attempt to redefine the problem of free will by invoking separate, distinct Riemann surfaces. And as Kierkegaard’s stages are discontinuous, negotiable only by leaps of faith, so do Bohr’s electrons leap discontinuously from orbit to orbit. Bohr insisted as one of the two “principal assumptions” of his paper that the electron’s whereabouts between orbits cannot be calculated or even visualized.284 Before and after are completely discontinuous. In that sense, each stationary state of the electron is complete and unique, and in that wholeness is stability. By contrast, the continuous process predicted by classical mechanics, which Bohr apparently associated with the licentiate’s endless ratiocination, tears the atom apart or spirals it into radiative collapse. ([Location 1609](https://readwise.io/to_kindle?action=open&asin=B008TRU7SQ&location=1609)) - 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 is”—which is the territory classical physics had claimed for itself. “Physics concerns what we can say about nature.” ([Location 1633](https://readwise.io/to_kindle?action=open&asin=B008TRU7SQ&location=1633)) - Harry Moseley’s crisp work gave experimental confirmation of the Bohr-Rutherford atom that was far more solidly acceptable than Marsden’s and Geiger’s alpha-scattering experiments. “Because you see,” Bohr said in his last interview, “actually the Rutherford work was not taken seriously. We cannot understand today, but it was not taken seriously at all. . . . The great change came from Moseley.” ([Location 1792](https://readwise.io/to_kindle?action=open&asin=B008TRU7SQ&location=1792)) - Germany’s chemical industry led the world and Bayer was the largest chemical company in Germany, with more than ten thousand employees. It manufactured some two thousand different dyestuffs, large tonnages of inorganic chemicals, a range of pharmaceuticals. The firm’s managing director, Carl Duisberg, a chemist who preferred industrial management along American lines, had invited the Oberpräsident of the Rhineland to attend the reception; he then invited Hahn to add a glow to the proceedings. Hahn lectured to the dignitaries on radioactivity. Near the beginning of the lecture he wrote Duisberg’s name on a sealed photographic plate with a small glass tube filled with strong mesothorium. Technicians developed the plate while he spoke; at the end Hahn projected the radiographic signature onto a screen to appreciative applause. ([Location 1798](https://readwise.io/to_kindle?action=open&asin=B008TRU7SQ&location=1798)) - “When our difficulties were solved through Dr. Weizmann’s genius,” continues Lloyd George, “I said to him: ‘You have rendered great service to the State, and I should like to ask the Prime Minister to recommend you to His Majesty for some honour.’ He said, ‘There is nothing I want for myself.’ ‘But is there nothing we can do as a recognition of your valuable assistance to the country?’ I asked. He replied: ‘Yes, I would like you to do something for my people.’ . . . That was the fount and origin of the famous declaration about the National Home for Jews in Palestine.”332 The “famous declaration” came to be called the Balfour Declaration, a commitment by the British government in the form of a letter from Arthur Balfour to Baron Edmond de Rothschild to “view with favour the establishment in Palestine of a national home for the Jewish people” and to “use their best endeavours to facilitate the achievement of this object.” ([Location 1898](https://readwise.io/to_kindle?action=open&asin=B008TRU7SQ&location=1898)) - She asked, argued, finally adamantly demanded that her husband abandon gas work. Haber told her what he had told Hahn, adding for good measure, patriot that he was, that a scientist belongs to the world in times of peace but to his country in times of war.352 Then he stormed out to supervise a gas attack on the Eastern Front. Dr. Clara Immerwahr Haber committed suicide the same night. ([Location 2017](https://readwise.io/to_kindle?action=open&asin=B008TRU7SQ&location=2017)) - The machine gun mechanized war. Artillery and gas mechanized war. They were the hardware of the war, the tools. But they were only proximately the mechanism of the slaughter. The ultimate mechanism was a method of organization—anachronistically speaking, a software package.376 “The basic lever,” the writer Gil Elliot comments, “was the conscription law, which made vast numbers of men available for military service.377 The civil machinery which ensured the carrying out of this law, and the military organization which turned numbers of men into battalions and divisions, were each founded on a bureaucracy. The production of resources, in particular guns and ammunition, was a matter for civil organization. The movement of men and resources to the front, and the trench system of defence, were military concerns.” Each interlocking system was logical in itself and each system could be rationalized by those who worked it and moved through it. Thus, Elliot demonstrates, “It is reasonable to obey the law, it is good to organize well, it is ingenious to devise guns of high technical capacity, it is sensible to shelter human beings against massive firepower by putting them in protective trenches.” ([Location 2165](https://readwise.io/to_kindle?action=open&asin=B008TRU7SQ&location=2165)) - The first subway on the European continent was dug not in Paris or Berlin but in Budapest. Two miles long, completed in 1896, it connected the thriving Hungarian capital with its northwestern suburbs. ([Location 2199](https://readwise.io/to_kindle?action=open&asin=B008TRU7SQ&location=2199)) - Out of the prospering but vulnerable Hungarian Jewish middle class came no fewer than seven of the twentieth century’s most exceptional scientists: in order of birth, Theodor von Kármán, George de Hevesy, Michael Polanyi, Leo Szilard, Eugene Wigner, John von Neumann and Edward Teller. All seven left Hungary as young men; all seven proved unusually versatile as well as talented and made major contributions to science and technology; two among them, de Hevesy and Wigner, eventually won Nobel Prizes. The mystery of such a concentration of ability from so remote and provincial a place has fascinated the community of science. Recalling that “galaxy of brilliant Hungarian expatriates,” Otto Frisch remembers that his friend Fritz Houtermans, a theoretical physicist, proposed the popular theory that “these people were really visitors from Mars; for them, he said, it was difficult to speak without an accent that would give them away and therefore they chose to pretend to be Hungarians whose inability to speak any language without accent is well known; except Hungarian, and [these] brilliant men all lived elsewhere.” ([Location 2244](https://readwise.io/to_kindle?action=open&asin=B008TRU7SQ&location=2244)) - That science can be a refuge from the world is a conviction common among men and women who turn to it. Abraham Pais remarks that Einstein “once commented that he had sold himself body and soul to science, being in flight from the ‘I∍ and the ‘we’ to the ‘it.’ ”426 But science as a means of escaping from the familiar world of birth and childhood and language when that world mounts an overwhelming threat—science as a way out, a portable culture, an international fellowship and the only abiding certitude—must become a more desperate and therefore a more total dependency. Chaim Weizmann gives some measure of that totality in the harsher world of the Russian Pale when he writes that “the acquisition of knowledge was not for us so much a normal process of education as the storing up of weapons in an arsenal by means of which we hoped later to be able to hold our own in a hostile world.”427 He remembers painfully that “every division of one’s life was a watershed.” ([Location 2404](https://readwise.io/to_kindle?action=open&asin=B008TRU7SQ&location=2404)) - Through the war years Bohr had struggled to follow, wherever it might lead, the “radical change” he had introduced into physics. It led to frustration. However stunning Bohr’s prewar results had been, too many older European scientists still thought his inconsistent hypotheses ad hoc and the idea of a quantized atom repugnant. The war itself stalled advance. Yet he persisted, groping his way forward in the darkness. “Only a rare and uncanny intuition,” writes the Italian physicist Emilio Segrè, “saved Bohr from getting lost in the maze.”430 He guided himself delicately by what he called the correspondence principle. As Robert Oppenheimer once explained it, “Bohr remembered that physics was physics and that Newton described a great part of it and Maxwell a great part of it.” So Bohr assumed that his quantum rules must approximate, “in situations where the actions involved were large compared to the quantum, to the classical rules of Newton and of Maxwell.”431 That correspondence between the reliable old and the unfamiliar new gave him an outer limit, a wall to feel his way along. ([Location 2419](https://readwise.io/to_kindle?action=open&asin=B008TRU7SQ&location=2419)) - In 1922, the year his Nobel Prize made him a Danish national hero, Bohr accomplished a second great theoretical triumph: an explanation of the atomic structure that underlies the regularities of the periodic table of the elements. It linked chemistry irrevocably to physics and is now standard in every basic chemistry text. Around the nucleus, Bohr proposed, atoms are built up of successive orbital shells of electrons—imagine a set of nested spheres—each shell capable of accommodating up to a certain number of electrons and no more. Elements that are similar chemically are similar because they have identical numbers of electrons in their outermost shells, available there for chemical combination. ([Location 2438](https://readwise.io/to_kindle?action=open&asin=B008TRU7SQ&location=2438)) - “That [the] insecure and contradictory foundation [of Bohr’s quantum hypotheses],” Einstein would say, “was sufficient to enable a man of Bohr’s unique instinct and perceptiveness to discover the major laws of spectral lines and of the electron shells of the atom as well as their significance for chemistry appeared to me like a miracle. . . . This is the highest form of musicality in the sphere of thought.” ([Location 2446](https://readwise.io/to_kindle?action=open&asin=B008TRU7SQ&location=2446)) - Bohr had learned to be alert for bright students who were not afraid to argue. “At the end of the discussion he came over to me and asked me to join him that afternoon on a walk over the Hain Mountain,” Heisenberg remembers. “My real scientific career only began that afternoon.”436 It is the memory of a conversion. ([Location 2467](https://readwise.io/to_kindle?action=open&asin=B008TRU7SQ&location=2467)) - Heisenberg seems to have begun with a distaste for visualizing unmeasurable events. As an undergraduate, for example, he had been shocked to read in Plato’s Timaeus that atoms had geometric forms: “It saddened me to find a philosopher of Plato’s critical acumen succumbing to such fancies.”441 The orbits of Bohr’s electrons were similarly fanciful, Heisenberg thought, and Max Born and Wolfgang Pauli, his colleagues at Göttingen, concurred. No one could see inside an atom. What was known and measurable was the light that came out of the atomic interior, the frequencies and amplitudes associated with spectral lines. Heisenberg decided to reject models entirely and look for regularities among the numbers alone. ([Location 2484](https://readwise.io/to_kindle?action=open&asin=B008TRU7SQ&location=2484)) - At first, I was deeply alarmed. I had the feeling that, through the surface of atomic phenomena, I was looking at a strangely beautiful interior, and felt almost giddy at the thought that I now had to probe this wealth of mathematical structures nature had so generously spread out before me. I was far too excited to sleep, and so, as a new day dawned, I made for the southern tip of the island, where I had been longing to climb a rock jutting out into the sea. I now did so without too much trouble, and waited for the sun to rise. Back in Göttingen Max Born recognized Heisenberg’s strange mathematics as matrix algebra, a mathematical system for representing and manipulating arrays of numbers on matrices—grids—that had been devised in the 1850s and that Born’s teacher David Hilbert had extended in 1904. In three months of intensive work Born, Heisenberg and their colleague Pascual Jordan then developed what Heisenberg calls “a coherent mathematical framework, one that promised to embrace all the multifarious aspects of atomic physics.”443 Quantum mechanics, the new system was called. ([Location 2498](https://readwise.io/to_kindle?action=open&asin=B008TRU7SQ&location=2498)) - In 1516 a rich silver lode was discovered in Joachimsthal (St. Joachim’s dale), in the territory of the Count von Schlick, who immediately appropriated the mine. In 1519 coins were first struck from its silver at his command. Joachimsthaler, the name for the new coins, shortened to thaler, became “dollar” in English before 1600. Thereby the U.S. dollar descends from the silver of Joachimsthal. ([Location 2514](https://readwise.io/to_kindle?action=open&asin=B008TRU7SQ&location=2514)) - Tags: [[favorite]] - “Up to now,” he told that group in 1963, “and even more in the days of my almost infinitely prolonged adolescence, I hardly took an action, hardly did anything or failed to do anything, whether it was a paper in physics, or a lecture, or how I read a book, how I talked to a friend, how I loved, that did not arouse in me a very great sense of revulsion and of wrong.” ([Location 2601](https://readwise.io/to_kindle?action=open&asin=B008TRU7SQ&location=2601)) - He moved to Göttingen, the old medieval town in Lower Saxony in central Germany with the university established by George II of England, in the autumn of 1926, late Weimar years. Max Born headed the university physics department, newly installed in institute buildings on Bunsenstrasse funded by the Rockefeller Foundation. Eugene Wigner traveled to Göttingen to work with Born, as had Werner Heisenberg and Wolfgang Pauli and, less happily, the Italian Enrico Fermi, all future Nobel laureates. James Franck, having moved over from Haber’s institute at the KWI, a Nobelist as of 1925, supervised laboratory classes. The mathematicians Richard Courant, Herman Weyl and John von Neumann collaborated. Edward Teller would show up later on an assistantship. ([Location 2699](https://readwise.io/to_kindle?action=open&asin=B008TRU7SQ&location=2699)) - At the end of that summer of 1927 the Fascist government of Benito Mussolini convened an International Physical Congress at Como on the southwestern end of fjord-like Lake Como in the lake district of northern Italy. The congress commemorated the centennial of the death in 1827 of Alessandro Volta, the Como-born Italian physicist who invented the electric battery and after whom the standard unit of electrical potential, the volt, is named. Everyone went to Como except Einstein, who refused to lend his prestige to Fascism.483 Everyone went because quantum theory was beleaguered and Niels Bohr was scheduled to speak in its defense. At issue was an old problem that had emerged in a new and more challenging form. Einstein’s 1905 work on the photoelectric effect had demonstrated that light sometimes behaves as if it consists not of waves but of particles. Turning the tables, early in 1926 an articulate, cultured Viennese theoretical physicist named Erwin Schrödinger published a wave theory of matter demonstrating that matter at the atomic level behaves as if it consists of waves. Schrödinger’s theory was elegant, accessible and completely consistent. Its equations produced the quantized energy levels of the Bohr atom, but as harmonics of vibrating matter “waves” rather than as jumping electrons. Schrödinger soon thereafter proved that his “wave mechanics” was mathematically equivalent to quantum mechanics. “In other words,” says Heisenberg, “ . . . the two were but different mathematical formulations of the same structure.”484 That pleased the quantum mechanicists because it strengthened their case and because Schrödinger’s more straightforward mathematics simplified calculation. But Schrödinger, whose sympathies lay with the older classical physics, made more far-reaching claims for his wave mechanics. In effect, he claimed that it represented the reality of the interior of the atom, that not particles but standing matter waves resided there, that the atom was thereby recovered for the classical physics of continuous process and absolute determinism. In Bohr’s atom electrons navigated stationary states in quantum jumps that resulted in the emission of photons of light. Schrödinger offered, instead, multiple waves of matter that produced light by the process known as constructive interference, the waves adding their peaks of amplitude together. ([Location 2740](https://readwise.io/to_kindle?action=open&asin=B008TRU7SQ&location=2740)) - For though Bohr was an unusually considerate and obliging person, he was able in such a discussion, which concerned epistemological problems which he considered to be of vital importance, to insist fanatically and with almost terrifying relentlessness on complete clarity in all arguments. He would not give up, even after hours of struggling, [until] Schrödinger had admitted that [his] interpretation was insufficient, and could not even explain Planck’s law. Every attempt from Schrödinger’s side to get round this bitter result was slowly refuted point by point in infinitely laborious discussions.488 Schrödinger came down with a cold and took to his bed. Unfortunately he was staying at the Bohrs’. “While Mrs. Bohr nursed him and brought in tea and cake, Niels Bohr kept sitting on the edge of the bed talking at [him]: ‘But you must surely admit that . . .’ ”489 Schrödinger approached desperation. “If one has to go on with these damned quantum jumps,” he exploded, “then I’m sorry that I ever started to work on atomic theory.” Bohr, always glad for conflicts that sharpened understanding, calmed his exhausted guest with praise: “But the rest of us are so grateful that you did, for you have thus brought atomic physics a decisive step forward.” ([Location 2766](https://readwise.io/to_kindle?action=open&asin=B008TRU7SQ&location=2766)) - Working late one evening in his room under the eaves of Bohr’s institute Heisenberg remembered a paradox Einstein had thrown at him in a conversation about the value of theory in scientific work. “It is the theory which decides what we can observe,” Einstein had said.492 The memory made Heisenberg restless; he went downstairs and let himself out—it was after midnight—and walked past the great beech trees behind the institute into the open soccer fields of the Faelledpark. It was early March and it would have been cold, but Heisenberg was a vigorous walker who did his best thinking outdoors. “On this walk under the stars, the obvious idea occurred to me that one should postulate that nature allowed only experimental situations to occur which could be described within the framework of the [mathematical] formalism of quantum mechanics.”493 The bald statement sounds wondrously arbitrary; its test would be its consistent mathematical formulation and, ultimately, its predictive power for experiment. But it led Heisenberg immediately to a stunning conclusion: that on the extremely small scale of the atom, there must be inherent limits to how precisely events could be known. If you identified the position of a particle—by allowing it to impact on a zinc-sulfide screen, for example, as Rutherford did—you changed its velocity and so lost that information. If you measured its velocity—by scattering gamma rays from it, perhaps—your energetic gamma-ray photons battered it into a different path and you could not then locate precisely where it was. One measurement always made the other measurement uncertain. Heisenberg climbed back to his room and began formulating his idea mathematically: the product of the uncertainties in the measured values of the position and momentum cannot be smaller than Planck’s constant. So h appeared again at the heart of physics to define the basic, unresolvable granularity of the universe. What Heisenberg conceived that night came to be called the uncertainty principle, and it meant the end of strict determinism in physics: because if atomic events are inherently blurred, if it is impossible to assemble complete information about the location of individual particles in time and space, then predictions of their future behavior can only be statistical. ([Location 2784](https://readwise.io/to_kindle?action=open&asin=B008TRU7SQ&location=2784)) - The problem, Bohr said, was that quantum conditions ruled on the atomic scale but our instruments for measuring those conditions—our senses, ultimately—worked in classical ways. That inadequacy imposed necessary limitations on what we could know. An experiment that demonstrates that light travels in photons is valid within the limits of its terms. An experiment that demonstrates that light travels in waves is equally valid within its limits. The same is true of particles and waves of matter. The reason both could be accepted as valid is that “particles” and “waves” are words, are abstractions. What we know is not particles and waves but the equipment of our experiments and how that equipment changes in experimental use. The equipment is large, the interiors of atoms small, and between the two must be interposed a necessary and limiting translation. The solution, Bohr went on, is to accept the different and mutually exclusive results as equally valid and stand them side by side to build up a composite picture of the atomic domain. ([Location 2813](https://readwise.io/to_kindle?action=open&asin=B008TRU7SQ&location=2813)) - Carefully Bohr then examined the conflicts of classical and quantum physics one at a time and showed how complementarity clarified them. In conclusion he briefly pointed to complementarity’s connection to philosophy. The situation in physics, he said, “bears a deep-going analogy to the general difficulty in the formation of human ideas, inherent in the distinction between subject and object.”498 That reached back all the way to the licentiate’s dilemma in Adventures of a Danish Student, and resolved it: the I who thinks and the I who acts are different, mutually exclusive, but complementary abstractions of the self. ([Location 2833](https://readwise.io/to_kindle?action=open&asin=B008TRU7SQ&location=2833)) - And then he made his stunning announcement, couching it as always in the measured understatement of British science: “From the results so far obtained it is difficult to avoid the conclusion that the long-range atoms arising from collision of [alpha] particles with nitrogen are not nitrogen atoms but probably atoms of hydrogen. . . . If this be the case, we must conclude that the nitrogen atom is disintegrated.”510 Newspapers soon published the discovery in plainer words: Sir Ernest Rutherford, headlines blared in 1919, had split the atom. It was less a split than a transmutation, the first artificial transmutation ever achieved. When an alpha particle, atomic weight 4, collided with a nitrogen atom, atomic weight 14, knocking out a hydrogen nucleus (which Rutherford would shortly propose calling a proton), the net result was a new atom of oxygen in the form of the oxygen isotope 017: 4 plus 14 minus 1. There would hardly be enough 017 to breathe; only about one alpha particle in 300,000 crashed through the electrical barrier around the nitrogen nucleus to do its alchemical work.511 But the discovery offered a new way to study the nucleus. Physicists had been confined so far to bouncing radiation off its exterior or measuring the radiation that naturally came out of the nucleus during radioactive decay. Now they had a technique for probing its insides as well. Rutherford and Chadwick soon went after other light atoms to see if they also could be disintegrated, and as it turned out, many of them—boron, fluorine, sodium, aluminum, phosphorus—could. But farther along the periodic table a barricade loomed. The naturally radioactive sources Rutherford used emitted relatively slow-moving alpha particles that lacked the power to penetrate past the increasingly formidable electrical barriers of heavier nuclei. Chadwick and others at the Cavendish began to talk of finding ways to accelerate particles to higher velocities. Rutherford, who scorned complex equipment, resisted. Particle acceleration was in any case difficult to do. For a time the newborn science of nuclear physics stalled. ([Location 2922](https://readwise.io/to_kindle?action=open&asin=B008TRU7SQ&location=2922)) - The mass-spectrograph Francis Aston invented in 1919 could not release the binding energy of the atom. But with it he identified that binding energy and located the groups of elements which in their comparative instability might be most likely to release it if suitably addressed. He was awarded the Nobel Prize in Chemistry in 1922 for his work. After accepting the award alongside Niels Bohr—“Stockholm has been the city of our dreams ever since,” his sister, who regularly traveled with him, reminisces—he returned to the Cavendish to build larger and more accurate mass-spectrographs, operating them habitually at night because he “particularly detested,” his sister says, “various human noises,” including even conversations muffled through the walls of his rooms. ([Location 3004](https://readwise.io/to_kindle?action=open&asin=B008TRU7SQ&location=3004)) - In scientific work, creative thinking demands seeing things not seen previously, or in ways not previously imagined; and this necessitates jumping off from “normal” positions, and taking risks by departing from reality. The difference between the thinking of the paranoid patient and the scientist comes from the latter’s ability and willingness to test out his fantasies or grandiose conceptualizations through the systems of checks and balances science has established—and to give up those schemes that are shown not to be valid on the basis of these scientific checks. It is specifically because science provides such a framework of rules and regulations to control and set bounds to paranoid thinking that a scientist can feel comfortable about taking the paranoid leaps. Without this structuring, the threat of such unrealistic, illogical, and even bizarre thinking to overall thought and personality organization in general would be too great to permit the scientist the freedom of such fantasying. ([Location 3230](https://readwise.io/to_kindle?action=open&asin=B008TRU7SQ&location=3230)) - Most physicists had been content with the seemingly complete symmetry of two particles, the electron and the proton, one negative, one positive. Outside the atom—among the stripped, ionized matter beaming through a discharge tube, for example—two elementary atomic constituents might be enough. But Rutherford was concerned with how each element was assembled. “He had asked himself,” Chadwick continues, “and kept on asking himself, how the atoms were built up, how on earth were you going to get—the general idea being at that time that protons and electrons were the constituents of an atomic nucleus . . . how on earth were you going to build up a big nucleus with a large positive charge? And the answer was a neutral particle.” From the lightest elements in the periodic table beyond hydrogen to the heaviest, atomic number—the nucleus’ electrical charge and a count of its protons—differed from atomic weight. Helium’s atomic number was 2 but its atomic weight was 4; nitrogen’s atomic number was 7 but its atomic weight was 14; and the disparity increased farther along: silver, 47 but 107; barium, 56 but 137; radium, 88 but 226; uranium, 92 but 235 or 238. Theory at the time proposed that the difference was made up by additional protons in the nucleus closely associated with nuclear electrons that neutralized them. But the nucleus had a definite maximum size, well established by experiment, and as elements increased in atomic number and atomic weight there appeared to be less and less room in their nuclei for all the extra electrons. The problem worsened with the development in the 1920s of quantum theory, which made it clear that confining particles as light as electrons so closely would require enormous energies, energies that ought to show up when the nucleus was disturbed but never did. The only evidence for the presence of electrons in the nucleus was its occasional ejection of beta particles, energetic electrons. That was something to go on, but given the other difficulties with packing electrons into the nucleus it was not enough. “And so,” Chadwick concludes, “it was these conversations that convinced me that the neutron must exist. The only question was how the devil could one get evidence for it. . . . It was shortly after that I began to make experiments on the side when I could. ([Location 3291](https://readwise.io/to_kindle?action=open&asin=B008TRU7SQ&location=3291)) - Some of the experiments Chadwick conducted at the Cavendish in the 1920s to look for the neutron, he says, “were so desperate, so far-fetched as to belong to the days of alchemy.”571 He and Rutherford both thought of the neutron, as Rutherford had imagined it in his Bakerian Lecture, as a close union of proton and electron. They therefore conjured up various ways to torture hydrogen—blasting it with electrical discharges, searching out the effects on it of passing cosmic rays—in the hope that the H atom that had been stable since the early days of the universe would somehow agree to collapse into neutrality at their hands. The neutral particle resisted their blandishments and the nucleus resisted attack. ([Location 3347](https://readwise.io/to_kindle?action=open&asin=B008TRU7SQ&location=3347)) - Hans Geiger, among others, turned back to the electrical counter he had devised with Rutherford in 1908 and improved it. The result, the Geiger counter, was essentially an electrically charged wire strung inside a gas-filled tube with a thinly covered window that allowed charged particles to enter. Once inside the tube the charged particles ionized gas atoms; the electrons thus stripped from the gas atoms were drawn to the positively charged wire; that changed the current level in the wire; the change, in the form of an electrical pulse, could then be run through an amplifier and converted to a sound—typically a click—or shown as a jump in the sweep of a light beam on the television-like screen of an oscilloscope. The electrical counter could operate continuously and could count above and below the limits possible to fallible physicists peering at scintillation screens. ([Location 3375](https://readwise.io/to_kindle?action=open&asin=B008TRU7SQ&location=3375)) - “To [Chadwick’s] great credit,” writes Segré in tribute, “when the neutron was not present [in earlier experiments] he did not detect it, and when it ultimately was there he perceived it immediately, clearly and convincingly.598 These are the marks of a great experimental physicist.” ([Location 3516](https://readwise.io/to_kindle?action=open&asin=B008TRU7SQ&location=3516)) - As Kapitza had settled in at Cambridge he had noticed what he considered to be an excessive and unproductive deference of British physics students to their seniors. He therefore founded a club, the Kapitza Club, devoted to open and unhierarchical discussion. Membership was limited and coveted. Members met in college rooms and Kapitza frequently opened discussions with deliberate howlers so that even the youngest would speak up to correct him, loosening the grip of tradition on their necks. ([Location 3523](https://readwise.io/to_kindle?action=open&asin=B008TRU7SQ&location=3523)) - Oliphant says Chadwick spoke lucidly and with conviction, not failing to mention the contributions of Bothe, Becker, Webster and the Joliot-Curies, “a lesson to us all.”600 C. P. Snow, who was also present, remembers the performance as “one of the shortest accounts ever made about a major discovery.” When tall and birdlike Chadwick finished speaking he looked over the assembly and announced abruptly, “Now I want to be chloroformed and put to bed for a fortnight.”601 He deserved his rest. He had discovered a new elementary particle, the third basic constituent of matter. It was this neutral mass that compounded the weight of the elements without adding electrical charge. Two protons and 2 neutrons made a helium nucleus; 7 protons and 7 neutrons a nitrogen; 47 protons and 60 neutrons a silver; 56 protons and 81 neutrons a barium; 92 protons and 146 (or 143) neutrons a uranium. And because the neutron was as massive as a proton but carried no electrical charge, it was hardly affected by the shell of electrons around a nucleus; nor did the electrical barrier of the nucleus itself block its way. It would therefore serve as a new nuclear probe of surpassing power of penetration. “A beam of thermal neutrons,” writes the American theoretical physicist Philip Morrison, “moving at about the speed of sound, which corresponds to a kinetic energy of only about a fortieth of an electron volt, produces nuclear reactions in many materials much more easily than a beam of protons of millions of volts energy, traveling thousands of times faster.”602 Ernest Lawrence’s cyclotron, spiraling protons to million-volt energies for the first time the same month that Chadwick made his fateful discovery, fortunately proved to be adaptable to the production of neutrons. More than any other development, Chadwick’s neutron made practical the detailed examination of the nucleus. ([Location 3529](https://readwise.io/to_kindle?action=open&asin=B008TRU7SQ&location=3529)) - Hans Bethe once remarked that he considered everything before 1932 “the prehistory of nuclear physics, and from 1932 on the history of nuclear physics.”603 The difference, he said, was the discovery of the neutron. ([Location 3544](https://readwise.io/to_kindle?action=open&asin=B008TRU7SQ&location=3544)) - At four or five the “miracle” of a compass his father showed him excited him so much, he remembered, that he “trembled and grew cold.” It seemed to him then that “there had to be something behind objects that lay deeply hidden.”624 He would look for the something which objects hid, though his particular genius was to discover that there was nothing behind them to hide; that objects, as matter and as energy, were all; that even space and time were not the invisible matrices of the material world but its attributes. “If you will not take the answer too seriously,” he told a clamorous crowd of reporters in New York in 1921 who asked him for a short explanation of relativity, “and consider it only as a kind of joke, then I can explain it as follows. It was formerly believed that if all material things disappeared out of the universe, time and space would be left. According to the relativity theory, however, time and space disappear together with the things.” ([Location 3633](https://readwise.io/to_kindle?action=open&asin=B008TRU7SQ&location=3633)) - I sometimes ask myself how it came about that I was the one to develop the theory of relativity. The reason, I think, is that a normal adult never stops to think about problems of space and time. These are things which he has thought of as a child. But my intellectual development was retarded, as a result of which I began to wonder about space and time only when I had already grown up. ([Location 3660](https://readwise.io/to_kindle?action=open&asin=B008TRU7SQ&location=3660)) - He arrived in Berlin in April 1914. In the war years, separated from his first wife and living alone, he completed the general theory. To Max Born that “great work of art” was “the greatest feat of human thinking about nature, the most amazing combination of philosophical penetration, physical intuition, and mathematical skill” even though “its connections with experience were slender.” ([Location 3689](https://readwise.io/to_kindle?action=open&asin=B008TRU7SQ&location=3689)) - The dispersion of the Jewish people from Palestine—the Diaspora—began in the sixth century B.C. when Babylon conquered the southern Palestinian kingdom of Judah, destroyed Solomon’s temple and carried a large body of Jews into captivity. ([Location 3782](https://readwise.io/to_kindle?action=open&asin=B008TRU7SQ&location=3782)) - As if to mark in some distant inhuman ledger the end of one age and the beginning of another, Marie Sklodowska Curie, born in Warsaw, Poland, on November 7, 1867, died that day of Szilard’s filing, July 4, 1934, in Savoy. Einstein’s was the best eulogy: “Marie Curie is,” he said, “of all celebrated beings, the only one whom fame has not corrupted.” ([Location 4619](https://readwise.io/to_kindle?action=open&asin=B008TRU7SQ&location=4619)) - Thus by the mid-1930s the three most original living physicists had each spoken to the question of harnessing nuclear energy. Rutherford had dismissed it as moonshine; Einstein had compared it to shooting in the dark at scarce birds; Bohr thought it remote in direct proportion to understanding. If they seem less perceptive in their skepticism than Szilard, they also had a better grasp of the odds. The essential future is always unforeseen. They were experienced enough not to long for it. ([Location 4912](https://readwise.io/to_kindle?action=open&asin=B008TRU7SQ&location=4912)) - (Carrier chemicals made it possible to separate from the parent solution the few thousand atoms of daughter substances produced by neutron bombardment. A chemically similar daughter substance, traceable by its unique half-life, would lodge in the spaces of the carrier’s crystals as those regular solids formed from solution by chemical precipitation and would thus be carried away. Which carrier accomplished the carrying gave a clue to the part of the periodic table to which the unknown daughter substance belonged. Then it became a matter of further separating the daughter substance from the carrier by fractional crystallization, following it as before by tracing its characteristic radioactivity.) ([Location 5344](https://readwise.io/to_kindle?action=open&asin=B008TRU7SQ&location=5344)) - In “a state of slight confusion” Frisch spent the next day repeating the experiment for anyone who cared to see.1014 One who came down in the morning to the basement laboratory was a black-haired, blue-eyed American biologist of Irish heritage named William A. Arnold who was studying on a Rockefeller Fellowship with George de Hevesy.1015 Arnold was thirtyfour, Frisch’s age, on leave from the Hopkins Marine Station at Pacific Grove, California. He had made his way to Europe from San Francisco the previous September by freighter with his wife and young daughter. He could have gone to Berkeley to pick up radioisotope technique, but would have missed living in Copenhagen, learning from de Hevesy—would have missed contributing a coinage to the gamble that is history. Frisch showed the American the experiment and pointed out the pulses on the oscilloscope. “From the size of the spikes,” Arnold recalls, “it was clear that they must represent 100–200 MeV, very much larger than the spikes from [uranium’s natural background of] alpha particles.” Later that day Frisch looked me up and said, “You work in a microbiology lab. What do you call the process in which one bacterium divides into two?” And I answered, “binary fission.” He wanted to know if you could call it “fission” alone, and I said you could. Frisch the sketch artist, good at visualizing as his aunt was not, had metamorphosed his liquid drop into a dividing living cell.1016 Thereby the name for a multiplication of life became the name for a violent process of destruction. ([Location 5697](https://readwise.io/to_kindle?action=open&asin=B008TRU7SQ&location=5697)) - America first heard the news of the splitting of uranium—the term “fission” had not yet crossed the Atlantic—at the Princeton physics department journal club on the chill Monday evening of January 16, 1939. ([Location 5745](https://readwise.io/to_kindle?action=open&asin=B008TRU7SQ&location=5745)) - The Manhattan District bore no relation to the industrial or social life of our country; it was a separate state, with its own airplanes and its own factories and its thousands of secrets. It had a peculiar sovereignty, one that could bring about the end, peacefully or violently, of all other sovereignties. Herbert S. Marks We must be curious to learn how such a set of objects—hundreds of power plants, thousands of bombs, tens of thousands of people massed in national establishments—can be traced back to a few people sitting at laboratory benches discussing the peculiar behavior of one type of atom. Spencer R. Weart ([Location 5984](https://readwise.io/to_kindle?action=open&asin=B008TRU7SQ&location=5984)) - Thorium was lighter than U235, U238 heavier, but the middle isotope differed more significantly in another important regard. When Th232 absorbed a neutron it became a nucleus of odd mass number, Th233. When U238 absorbed a neutron it also became a nucleus of odd mass number, U239. But when U235 absorbed a neutron it became a nucleus of even mass number, U236. And the vicissitudes of nuclear rearrangement are such, as Fermi would explain one day in a lecture, that “changing from an odd number of neutrons to an even number of neutrons released one or two MeV.”1093 Which meant that U235 had an inherent energetic advantage over its two competitors: it accrued energy toward fission simply by virtue of its change of mass; they did not. ([Location 6130](https://readwise.io/to_kindle?action=open&asin=B008TRU7SQ&location=6130)) - Natural uranium masked U235’s continuous fissibility; the more abundant U238 captured most of the neutrons. Only by slowing the neutrons with paraffin below the U238 capture resonance at 25 eV had experimenters like Hahn, Strassmann and Frisch been able to coax the highly fissionable U235 out of hiding. In a burst of insight Bohr had answered Placzek’s objections and replenished his liquid drop. ([Location 6145](https://readwise.io/to_kindle?action=open&asin=B008TRU7SQ&location=6145)) - The slow-neutron fission of U235 occupied the foreground of his discussion because it explained the puzzling difference between uranium and thorium. But Bohr also considered U235’s behavior under fast-neutron bombardment. “For fast neutrons,” he wrote near the end of the paper, “ . . . because of the scarcity of the isotope concerned, the fission yields will be much smaller than those obtained from neutron impacts on the abundant isotope.”1098 The statement implies but does not ask a pregnant question: what would the yields be for fast neutrons if U235 could be separated from U238? ([Location 6161](https://readwise.io/to_kindle?action=open&asin=B008TRU7SQ&location=6161)) - More crucial for Bohr was the issue of secrecy. He had worked for decades to shape physics into an international community, a model within its limited franchise of what a peaceful, politically united world might be. Openness was its fragile, essential charter, an operational necessity, as freedom of speech is an operational necessity to a democracy. Complete openness enforced absolute honesty: the scientist reported all his results, favorable and unfavorable, where all could read them, making possible the ongoing correction of error. Secrecy would revoke that charter and subordinate science as a political system—Polanyi’s “republic”—to the anarchic competition of the nation-states. ([Location 6306](https://readwise.io/to_kindle?action=open&asin=B008TRU7SQ&location=6306)) - As Fermi’s team had discovered in Rome in 1934, hydrogen was more efficient than any other element at slowing down neutrons, and slow neutrons avoided the parasitic capture resonance of U238. But hydrogen itself also absorbed some slow neutrons, reducing further the number available for fission. And it was already clear that every possible secondary neutron would have to be husbanded carefully if a chain reaction was to be initiated in natural uranium. George Placzek came down from Cornell, where he had found a new home, for a visit, looked over the arrangement and insightfully foreclosed its future. As Szilard tells it: We were inclined to conclude that . . . the water-uranium system would sustain a chain reaction. . . . Placzek said that our conclusion was wrong because in order to make a chain reaction go, we would have to eliminate the absorption of [neutrons by the] water; that is, we would have to reduce the amount of water in the system, and if we reduced the water in the system, we would increase the parasitic absorption of [neutrons by] uranium [because with less water fewer neutrons would be slowed]. He recommended that we abandon the water-uranium system and use helium for slowing down the neutrons. ([Location 6430](https://readwise.io/to_kindle?action=open&asin=B008TRU7SQ&location=6430)) - Szilard told Einstein about the Columbia secondaryneutron experiments and his calculations toward a chain reaction in uranium and graphite. Long afterward he would recall his surprise that Einstein had not yet heard of the possibility of a chain reaction. When he mentioned it Einstein interjected, “Daran habe ich gar nicht gedacht!”—“I never thought of that!” He was nevertheless, says Szilard, “very quick to see the implications and perfectly willing to do anything that needed to be done.1174 He was willing to assume responsibility for sounding the alarm even though it was quite possible that the alarm might prove to be a false alarm. The one thing most scientists are really afraid of is to make fools of themselves. Einstein was free from such a fear and this above all is what made his position unique on this occasion.” ([Location 6542](https://readwise.io/to_kindle?action=open&asin=B008TRU7SQ&location=6542)) - Revulsion against the bombing of cities had grown in the United States since at least the Japanese bombing of Shanghai in 1937.1198 When Spanish Fascists bombed Barcelona in March 1938, Secretary of State Cordell Hull had condemned the atrocity publicly: “No theory of war can justify such conduct,” he told reporters. “ . . . I feel that I am speaking for the whole American people.”1199 In June the Senate passed a resolution condemning the “inhuman bombing of civilian populations.”1200 As war approached, revulsion began to give way to impulses of revenge; in the summer of 1939 Herbert Hoover could urge an international ban on the bombing of cities and still argue that “one of the impelling reasons for the unceasing building of bombing planes is to prepare reprisals.”1201 Bombing was bad because it was enemy bombing. Scientific American saw through to a darker truth: “Although . . . aerial bombing remains an unknown, indeterminate quantity, the world may be sure that the unwholesome atrocities which are happening today are but curtain raisers on insane dramas to come.”1202 So although Roosevelt had asked Congress for increased funds for long-range bombers nine months before, in appealing to the belligerents on September 1, 1939, he could still articulate the moral indignation of millions of Americans: The ruthless bombing from the air of civilians in unfortified centers of population during the course of the hostilities which have raged in various quarters of the earth during the past few years, which has resulted in the maiming and in the death of thousands of defenseless men, women and children, has sickened the hearts of every civilized man and woman, and has profoundly shocked the conscience of humanity.1203 If resort is had to this form of inhuman barbarism during the period of the tragic conflagration with which the world is now confronted, hundreds of thousands of innocent human beings who have no responsibility for, and who are not even remotely participating in, the hostilities which have now broken out, will lose their lives. I am therefore addressing this urgent appeal to every Government which may be engaged in hostilities publicly to affirm its determination that its armed forces shall in no event, and under no circumstances, undertake the bombardment from the air of civilian populations or of unfortified cities, upon the understanding that these same rules of warfare will be scrupulously observed by all of their opponents. ([Location 6653](https://readwise.io/to_kindle?action=open&asin=B008TRU7SQ&location=6653)) - Whatever scientists of one warring nation could conceive, the scientists of another warring nation might also conceive—and keep secret. That early in 1939 and early 1940, the nuclear arms race began. Responsible men who properly and understandably feared a dangerous enemy saw their own ideas reflected back to them malevolently distorted. Ideas that appeared defensive in friendly hands seen the other way around appeared aggressive. But they were the same ideas. ([Location 7014](https://readwise.io/to_kindle?action=open&asin=B008TRU7SQ&location=7014)) - Nuclear research in the Soviet Union during this period was limited to skillful laboratory work. Two associates of Soviet physicist Igor Kurchatov reported to the Physical Review in June 1940 that they had observed rare spontaneous fissioning in uranium. “The complete lack of any American response to the publication of the discovery,” writes the American physicist Herbert F. York, “was one of the factors which convinced the Russians that there must be a big secret project under way in the United States.”1284 It was not yet big, but by then it had begun to be secret. ([Location 7050](https://readwise.io/to_kindle?action=open&asin=B008TRU7SQ&location=7050)) - By the spring of 1940 experiments at Columbia and the DTM had thus ruled out both slow- and significant fast-neutron fission in U238 and ruled in slow-neutron fission in U235. The asymmetry might have been a clue. No one picked it up. ([Location 7224](https://readwise.io/to_kindle?action=open&asin=B008TRU7SQ&location=7224)) - cachexia, ([Location 7282](https://readwise.io/to_kindle?action=open&asin=B008TRU7SQ&location=7282)) - curtaining the bombers in dark asylum. ([Location 7390](https://readwise.io/to_kindle?action=open&asin=B008TRU7SQ&location=7390)) - At Oxford in December 1940, Franz Simon, now officially working for the MAUD Committee, produced a report nearly as crucial to the future of uranium-bomb development as the original Frisch-Peierls memoranda had been.1355 It was titled “Estimate of the size of an actual separation plant.” Its aim, Simon wrote, was “to provide data for the size and costs of a plant which separates 1 kg per day of 235U from the natural product.”1356 He estimated such a plant would cost about £5,000,000 and outlined its necessities in careful detail. ([Location 7407](https://readwise.io/to_kindle?action=open&asin=B008TRU7SQ&location=7407)) - Germany had access to the world’s only heavy-water factory and to thousands of tons of uranium ore in Belgium and the Belgian Congo. It had chemical plants second to none and competent physicists, chemists and engineers . It lacked only a cyclotron for measuring nuclear constants. The Fall of France—Paris was occupied June 14, an armistice signed June 22—filled that need. Kurt Diebner, the War Office’s resident nuclear physics expert, rushed to Paris. ([Location 7424](https://readwise.io/to_kindle?action=open&asin=B008TRU7SQ&location=7424)) - Chadwick had also made further cross-section measurements. He was already a sober man; when he saw the new numbers a more intense sobriety seized him. He described the change in 1969 in an interview: I remember the spring of 1941 to this day. I realized then that a nuclear bomb was not only possible—it was inevitable. Sooner or later these ideas could not be peculiar to us. Everybody would think about them before long, and some country would put them into action. And I had nobody to talk to. You see, the chief people in the laboratory were Frisch and [Polish experimental physicist Joseph] Rotblat. However high my opinion of them was, they were not citizens of this country, and the others were quite young boys. And there was nobody to talk to about it. I had many sleepless nights. But I did realize how very very serious it could be. And I had then to start taking sleeping pills. It was the only remedy. I’ve never stopped since then. It’s 28 years, and I don’t think I’ve missed a single night in all those 28 years.1402 ([Location 7696](https://readwise.io/to_kindle?action=open&asin=B008TRU7SQ&location=7696))