Making of the Atomic Bomb
Page 50
The Harvard president, who would be forty-seven late in March, was welcomed not only because of his university affiliation or his distinction as a member of the NDRC. He had been an outspoken opponent of American isolationism during the long months of the phony war and was therefore welcomed especially as a sign—with only the Prime Minister dissenting. Churchill was less than delighted at the prospect of lunching with the president of Harvard. “What shall I talk to him about?” he was heard to ask. “He thought you would be an old man with a white beard, exuding learning and academic formality,” Brendon Bracken, Churchill’s aide, told Conant afterward.1405 But braced by the American’s belligerently pro-British views and put at ease by the tweed suit he chose to wear, the Prime Minister eventually warmed over lunch in the bomb-shelter basement at 10 Downing Street, proffering a Churchillian monologue during which he repeated one of his choicer recent coinages: “Give us the tools, and we will finish the job.”
In 1920, at twenty-seven, when Conant was courting the woman he would marry—she was the only child of the Nobel laureate Harvard chemist T. W. Richards, a pioneer in measuring atomic weights—he had shared hopes for a grand future with her that coming from a less able man might have sounded absurd. “I said that I had three ambitions. The first was to become the leading organic chemist in the United States; after that I would like to be president of Harvard; and after that, a Cabinet member, perhaps Secretary of the Interior.”1406 Those may not seem conjoint ambitions, but Conant managed a version of each in turn. He was born of a Massachusetts family that had resided in the state since 1623. After Roxbury Latin and Harvard College he had taken a double Ph.D. under his future father-in-law in organic and physical chemistry. He emerged from the Great War with the rank of major for his work in poison-gas research at Edgewood. In his autobiography, written late in life, he justified his participation:
I did not see in 1917, and do not see in 1968, why tearing a man’s guts out by a high-explosive shell is to be preferred to maiming him by attacking his lungs or skin. All war is immoral. Logically, the 100 percent pacifist has the only impregnable position. Once that is abandoned, as it is when a nation becomes a belligerent, one can talk sensibly only in terms of the violation of agreements about the way war is conducted, or the consequences of a certain tactic or weapon.1407
Like Vannevar Bush, Conant was a patriot who believed in the application of advanced technology to war.
“Conant achieved an international reputation in both natural products chemistry and in physical-organic chemistry,” writes the Ukrainian-born Harvard chemist George B. Kistiakowsky.1408 Natural products include chlorophyll and hemoglobin and Conant contributed to the unraveling of both those vital molecules. His studies also helped generalize the concept of acids and bases, a concept now considered fundamental. If not the leading American organic chemist of his day, he ranked among the leaders. When Caltech tried to lure him away with a large research budget Harvard topped the offer and refused to let him go.
Number two on Conant’s youthful list, the presidency of his alma mater, he won in 1933. He told the members of the Harvard Corporation who approached him that he didn’t want the job, which was apparently a prerequisite, but would serve if elected. He was forty at the time of his election. He created the modern Harvard of eminent scholarship and publish-or-perish, up-or-out.
Conant’s third ambition achieved approximate fulfillment after the war in high, though less than cabinet-rank, appointment; his long span of voluntary government service began with the NDRC.
In England in the late winter of 1941 he met with the leaders of the British government, had an audience with the King, picked up an honorary degree at Cambridge and walked the Backs afterward to see the crocuses in bloom, made room for the NDRC mission among hostile U.S. military and naval attaches, lunched with Churchill again. His mission in Britain was diplomatic rather than technical. He discussed gas warfare and explosives manufacture but was unable to share in the intense exchange of information on radar because he knew very little about electronics. But although he was familiar with the work on uranium and it fell within his official NDRC responsibilities, secrecy and his “strong belief in the ‘need to know’ principle” kept Conant from learning what the British had learned about the possibility of a bomb.1409
He met a “French scientist” at Oxford, probably Hans von Halban, who complained of inaction on uranium-heavy water research. “Since his complaints were clearly ‘out of channels,’ I quickly terminated the conversation and forgot the incident.” That reaction was understandable: Conant could hardly know what security arrangements the British might have made with the Free French. But he also shied from Lindemann. They were lunching alone at a London club. “He introduced the subject of the study of the fission of uranium atoms. I reacted by repeating the doubts I had expressed and heard expressed at NDRC meetings.” Lindemann brushed them aside and pounced:
“You have left out of consideration,” said [Lindemann], “the possibility of the construction of a bomb of enormous power.” “How would that be possible?” I asked. “By first separating uranium 235,” he said, “and then arranging for the two portions of the element to be brought together suddenly so that the resulting mass would spontaneously undergo a self-sustaining reaction.”
Remarkably, the chairman of the chemistry and explosives division of the NDRC adds that, as late as March 1941, “this was the first I had heard about even the remote possibility of a bomb.” Nor did he pursue the matter. “I assumed, quite correctly, that if and when Bush wished to be in touch with the atomic energy work in England, he would do so through channels involving Briggs.” No wonder the Hungarian conspirers continued to tear their hair.
* * *
Then for the first time a ranking American physicist joined the debate whose voice could not be ignored. Even before Seaborg and Segré confirmed the fissibility of plutonium, Ernest Lawrence had measured the prevailing American skepticism and conservatism against the increasing enthusiasm of his British friends and responded with characteristic fervor. Ralph H. Fowler, Ernest Rutherford’s widower son-in-law, had visited Berkeley during the 1930s and attended picnics and weekend parties with the inventor of the cyclotron. Fowler was British scientific liaison officer in Washington now and from that close vantage he urged Lawrence to get involved. So did Mark Oliphant, whom Lawrence had met and liked on a visit to the Cavendish after the 1933 Solvay Conference.
Lawrence had encouraged the search for plutonium partly because he saw little hope for isotope separation by any of the methods so far discussed—by centrifuge, thermal diffusion or barrier diffusion. But around the beginning of the year he began thinking about separating isotopes electromagnetically, by the process that had already worked on a microscopic scale for Alfred Nier. It occurred to Lawrence that he could modify his superseded 37-inch cyclotron into a big mass spectrometer. The fact that Nier thought electromagnetic separation on an industrial scale impossible only spurred the Berkeley laureate on. Lawrence lived from machine to machine, as it were; conceiving a machine to do the job of liberating U235 from its confinement within U238 (while Fermi’s uranium-graphite reactor manufactured Berkeley-born plutonium) gave him something solid to fight for, a tangible program to push.
It assembled itself by stages. He was not yet ready emotionally to set aside his peacetime plans. Warren Weaver, the director of the division of natural sciences at the Rockefeller Foundation, visited Berkeley in February to see how construction was progressing on the 4,900-ton, 184-inch cyclotron for which the foundation had awarded a $1,150,000 grant less than twelve months earlier. Lawrence took time to complain about the Uranium Committee’s sloth—Weaver worked with another division of the NDRC—but then drove up behind the university to the cyclotron site on the hillside and first irritated and then enthralled the Rockefeller administrator with visions of a superior and much larger machine.
Lawrence rehearsed his complaint again in March when Conant, back from London, traveled out
to deliver an address. “Light a fire under the Briggs committee,” the energetic Californian badgered the president of Harvard. “What if German scientists succeed in making a nuclear bomb before we even investigate possibilities?” That prepared Lawrence for a full assault.1410 He launched it on March 17 when he met with Karl Compton and Alfred Loomis at MIT.1411
Loomis had turned to physics after a lucrative career in the law and investment banking. Compton was a physicist of distinction who had taught for fifteen years at Princeton, where he took his Ph.D., before becoming president of MIT in 1930. Both men understood the politics of organizations. Yet they were sufficiently seized with Lawrence’s fervor that Compton telephoned Vannevar Bush almost as soon as Lawrence left the room and dictated a follow-up letter the same day. Briggs was “by nature slow, conservative, methodical and accustomed to operate at peacetime government bureau tempo,” Compton wrote, conveying Lawrence’s blunt complaints, and had been “following a policy consistent with these qualities and still further inhibited by the requirement of secrecy.” The British were ahead even though America had “the most in number and the best in quality of the nuclear physicists of the world.” The Germans were “very active.” Briggs had invited only a very few U.S. nuclear physicists into the work. There were other possibilities in fission research besides the pursuit of a slow-neutron chain reaction for power, possibilities “capable, if successful, of far more important military usage.”1412
Though they felt free thus to lecture Bush, both Loomis and Compton stood in awe of Lawrence—Loomis had recently contributed $30,000 to a private fund simply to make it easier for Lawrence to travel around the country—and thought Bush could do no better than to turn him loose: “I hasten to say that the idea of Ernest himself taking an active part in any reorganization was in no sense suggested by him or even in his mind, but I do believe that it would be an ideal solution.”
Bush’s ego was commensurate with his responsibilities, as Loomis and Compton ought to have known. It might have been politic to welcome Lawrence’s campaign, especially since Loomis was a first cousin and close friend of Henry L. Stimson, the respected and influential Secretary of War; but Bush decided instead to take it as a challenge to his authority, the first the physics community had mounted since he invented the NDRC, welcoming a fight he knew he could win. He met Lawrence in New York two days after the MIT meeting and let fly:
I told him flatly that I was running the show, that we had established a procedure for handling it, that he could either conform to that as a member of the NDRC and put in his kicks through the internal mechanism, or he could be utterly on the outside and act as an individual in any way that he saw fit. He got into line and I arranged for him to have with Briggs a series of excellent conferences. However, I made it very clear to Lawrence that I proposed to make available to Briggs the best advice and consultation possible, but that in the last analysis I proposed to back up Briggs and his committee in their decision unless there was some decidedly strong case for entering into it personally. I think this matter was thoroughly straightened out, therefore, but it left its trail behind.1413
By threatening to push Ernest Lawrence out into the cold with the emigrès Bush managed temporarily to confine the uranium problem. Confinement lasted less than a month.
In 1940 Lawrence had recruited a Harvard experimentalist named Kenneth Bainbridge, by trade a nuclear physicist—Bainbridge built the Harvard cyclotron—to work on radar at MIT. When Conant went to London to open the new NDRC office there, Bainbridge and others had followed, to work with the British each in his own field of competence. But since Bainbridge knew nuclear physics as well as radar and had even looked into isotope separation, the British allowed him also to attend a full-dress meeting of the MAUD Committee. To Bainbridge’s surprise, the committee had “a very good idea of the critical mass and [bomb] assembly [mechanism], and urged the exchange of personnel. . . . Their estimate was that a minimum of three years would be required to solve all the problems involved in producing an atomic weapon.”1414 Bainbridge immediately contacted Briggs and suggested he send someone over to represent the United States in uranium matters.1415
Beneath Bush’s organizational bristle lay genuine perplexity. “I am no atomic scientist,” he writes candidly; “most of this was over my head.”1416 As he saw the situation that April, “it would be possible to spend a very large amount of money indeed, and yet there is certainly no clear-cut path to defense results of great importance lying open before us at the present time.”1417 But he felt the increasing pressure—Lawrence’s prodding, Bainbridge’s confirmation of British progress—and reached out now for help.
“It was Bush’s strategy,” writes the American experimental physicist Arthur Compton, Karl’s younger brother, “as co-ordinator of the nation’s war research, to use the National Academy [of Sciences] as the court of final appeal for important scientific problems.”1418 On a Tuesday in mid-April, after meeting with Briggs, Bush wrote Frank B. Jewett, the senior Bell Telephone engineer who was president of the National Academy. Briggs had heard from Bainbridge and alerted Bush; Bush and Briggs, “disturbed,” had conferred. “The British are apparently doing fully as much as we are, if not more, and yet it seems as though, if the problem were of really great importance, we ought to be carrying most of the burden in this country.” Bush wanted “an energetic but dispassionate review of the entire situation by a highly competent group of physicists.”1419 The men chosen ought to have “sufficient knowledge to understand and sufficient detachment to cold bloodedly evaluate.”
At a regular Washington meeting of the National Academy the following Friday Jewett, Bush and Briggs recruited their review group. They put Lawrence on the committee and the recently retired director of the research laboratory at General Electric, a physical chemist named William D. Coolidge. Then they sought out Arthur Compton, a Nobel laureate and professor of physics at the University of Chicago, and proposed he head the review. Compton humbly questioned his “fitness for the task” and jumped at the chance.1420
Arthur Holly Compton was the son of a Presbyterian minister and professor of philosophy at the College of Wooster in Wooster, Ohio. Compton’s Mennonite mother was dedicated to missionary causes and had been the 1939 American Mother of the Year. He followed his older brother Karl into science and surpassed him in achievement but preserved the family piety as well. “Arthur Compton and God were daily companions,” notes Leona Woods, Enrico Fermi’s young protégé at the University of Chicago. She judged Compton nevertheless “a fine scientist and a fine man. . . . He was remarkably handsome all his life and athletically spare and strong.”1421 Fermi had concluded, writes Woods, that “tallness and handsomeness usually were inversely proportional to intelligence,” but “he excepted Arthur Compton . . . whose intelligence he respected enormously.”1422
Compton’s physics was first-rate, as Fermi’s respect implies. He graduated from the College of Wooster and took his Ph.D. at Princeton. In 1919, the first year of the program, he was appointed a National Research Council fellow and used the appointment to study under Rutherford at the Cavendish. The difficult work he began there—examining the scattering and absorption of gamma rays—led directly to the discovery of what came to be called the Compton effect, for which he won the Nobel Prize.
In 1920, Compton writes, he accepted a professorship at Washington University in St. Louis, “a small kind of place,” to get out of the mainstream of physics so that he could concentrate on his scattering studies, which he was then extending from gamma rays to X rays.1423 He scattered X rays with a graphite block and caught them and measured their wavelengths Moseley-style with a calcite-crystal X-ray spectrograph. He found that the X rays scattered by the graphite came out with wavelengths longer than their wavelengths going in: as if a shout bounced off a distant wall came back bizarrely deepened to a lower pitch. If X rays—light—were only a motion of waves, then their wavelengths would not have changed; Compton had in fact demonstrated in 1923 what
Einstein had postulated in 1905 in his theory of the photoelectric effect: that light was wave but also simultaneously particle, photon. An X-ray photon had collided elastically with an electron, as billiard balls collide, had bounced off and thereby given up some of its energy. The calcite crystal revealed the energy loss as a longer wavelength of X-ray light. Arnold Sommerfeld hailed the Compton effect—elastic scattering of a photon by an electron—as “probably the most important discovery which could have been made in the current state of physics” because it proved that photons exist, which hardly anyone in 1923 yet believed, and demonstrated clearly the dual nature of light as both particle and wave.1424
The subtle experimenter lost his subtlety when he shifted from doing science to proselytizing for God. Rigor slipped to Chautauqua logic and he perpetrated such howlers as the notion that Heisenberg’s uncertainty principle somehow extends beyond the dimensions of the atom into the human world and confirms free will. Bohr heard Compton’s Free Will lecture when he visited the United States in the early 1930s and scoffed. “Bohr spoke highly of Compton as a physicist and a man,” a friend of the Danish laureate remembers, “but he felt that Compton’s philosopohy was too primitive: ‘Compton would like to say that for God there is no uncertainty principle. That is nonsense. In physics we do not talk about God but about what we can know. If we are to speak of God we must do so in an entirely different manner.’ ”1425