Szilard remained in the steamy city: “I was left alone in New York. I still had no position at Columbia; my three months [of laboratory privileges] were up, but there were no experiments going on anyway and all I had to do was to think.”1155
* * *
Szilard thought first about an alternative to water. The next common material up the periodic table that might work—that had a capture cross section considerably smaller than hydrogen’s, that was cheap, that would be thermally and chemically stable—was carbon. The mineral form of carbon, chemically identical to diamond but the product of a different structure of crystallization, is graphite, a black, greasy, opaque, lustrous material that is the essential component of pencil lead. Although carbon slows neutrons much less rapidly than hydrogen, even that difference might be put to advantage by careful design.
Lewis Strauss was leaving for Europe the week of July 2. Hoping that the financier might coax support for uranium research from Belgium’s Union Miniére, Szilard sent Strauss a last-minute letter arguing that a chain reaction in uranium “is an immediate possibility” but chose not to mention his new uranium-graphite conception.1156 Apparently he wanted to discuss it first with Fermi; the same day, July 3, he wrote the Italian laureate at length. “It seems to me now,” he reported, “that there is a good chance that carbon might be an excellent element to use in place of hydrogen, and there is a strong temptation to gamble on this chance.” He wanted to try “a large-scale experiment with a carbon-uranium-oxide mixture” as soon as they could acquire enough material. In the meantime he thought he would set up a small experiment to measure more accurately carbon’s capture cross section, only the upper limit of which was then known. If carbon should prove unsuitable their “next best guess might be heavy water,” rich in deuterium, though they would need “a few tons” of that scarce and expensive liquid. (Deuterium, H2, has a much smaller cross section for neutron capture than ordinary hydrogen.)
Across the one hundred sixty-third anniversary of the Declaration of Independence Szilard’s ideas evolved rapidly. On July 5 he visited the National Carbon Company of New York to look into purchasing graphite blocks of high purity (because impurities such as boron with large capture cross sections would soak up too many neutrons). He wrote Fermi his finding the same day: “It seems that it will be possible to get sufficiently pure carbon at a reasonable price.”1157 He also mentioned arranging the uranium and carbon in layers.
Fermi sat down in Ann Arbor at the end of the week to respond to Szilard’s first report. Independently he had arrived at a similar plan:
Thank you for your letter. I was also considering the possibility of using carbon for slowing down the neutrons. . . . According to my estimates a possible recipe might be about 39,000 kg of carbon mixed with 600 kg of uranium. If it were really so the amounts of materials would certainly not be too large.1158
Since however the amount of uranium that can be used, especially in a homogeneous mixture, is exceedingly small . . . perhaps the use of thick layers of carbon separated by layers of uranium might allow use of a somewhat larger percentage of uranium.
The idea of layering or in some other way separating the uranium from the graphite originated in calculations Fermi made in June for the manganese water-tank experiment. Fermi’s calculations led both men to consider partitioning the oxide from the graphite in the new design they were independently evolving. Partitioning would give the fast secondary neutrons room to slow down, bouncing around in the moderator, before they encountered any U238 nuclei. Szilard’s next letter, on July 8, mentions that “the carbon and the uranium oxide would not be mixed but built up in layers, or in any case used in some canned form.”1159 Both the July 5 and July 8 letters apparently crossed with Fermi’s letter in the mail.
By the time he heard from Fermi, Szilard had seen still farther and realized that small spheres of uranium arranged within blocks of graphite would be “even more favorable from the point of view of a chain reaction than the system of plane uranium layers which was initially considered.”1160 The arrangement Szilard had in mind he called a “lattice.” (A geodesic dome would represent such a lattice arrangement schematically if it were a complete sphere and if all its interior volume were filled like its surface with evenly spaced points.) His calculations indicated somewhat larger volumes of material than had Fermi’s: “perhaps 50 tons of carbon and 5 tons of uranium.”1161 The entire experiment, he thought, would cost about $35,000.1162
If a chain reaction would work in graphite and uranium, Szilard assumed, then a bomb was probable. And if he had managed these conclusions, he further assumed, then so had his counterparts in Nazi Germany. He sought out Pegram in those early July days and tried to convince him of the urgent need for a large-scale experiment to settle the question. The dean resisted the assault: “He took the position that even though the matter appeared to be rather urgent, this being summer and Fermi being away there was really nothing that usefully could be done until the fall.”1163
For several weeks Szilard had been trying on his own to raise funds from the U.S. military. In late May he had asked Wigner to contact the Army’s Aberdeen Proving Ground, its weapons-development facility in Maryland. While he was thinking through the possibilities of a uraniumgraphite system he had talked to Ross Gunn about Navy support. Now Fermi’s letter of July 9 and a July 10 letter from Gunn arrived to discourage him. Fermi wrote of layering the carbon and uranium but calculated in terms of a homogeneous system—of graphite and uranium oxide crushed and mixed together. Szilard concluded he was being mocked: “I knew very well that Fermi . . . computed the homogeneous mixture only because it was the easiest to compute. This showed me that Fermi did not take this really seriously.”1164 Gunn in turn reported that “it seems almost impossible . . . to carry through any sort of an agreement [with the Navy] that would be really helpful to you. I regret this situation but see no escape.”1165
Despite his Olympian ego not even Leo Szilard felt capable of saving the world entirely alone. He called on his Hungarian compatriots now for moral support. Edward Teller had moved to Manhattan for the summer to teach physics at Columbia; Eugene Wigner came up from Princeton to conspire with them. In later years Szilard would recount several different versions of how their conversation went, but a letter he wrote on August 15, 1939, offers reliable contemporary testimony: “Dr. Wigner is taking the stand that it is our duty to enlist the cooperation of the [Roosevelt] Administration. A few weeks ago he came to New York in order to discuss this point with Dr. Teller and me.”1166 Szilard had shown Wigner his uraniumgraphite calculations. “He was impressed and he was concerned.”1167 Both Teller and Wigner, Szilard wrote in a background memorandum in 1941, “shared the opinion that no time must be lost in following up this line of development and in the discussion that followed, the opinion crystallized that an attempt ought to be made to enlist the support of the Government rather than that of private industry. Dr. Wigner, in particular, urged very strongly that the Government of the United States be advised.”1168
But the discussion slipped away from that project into “worry about what would happen if the Germans got hold of large quantities of the uranium which the Belgians were mining in the Congo.” Perhaps Szilard emphasized the futility of the government contacts that he and Fermi had already made. “So we began to think, through what channels could we approach the Belgian government and warn them against selling any uranium to Germany?”1169
It occurred to Szilard then that his old friend Albert Einstein knew the Queen of Belgium. Einstein had met Queen Elizabeth in 1929 on a trip to Antwerp to visit his uncle; thereafter the physicist and the sovereign maintained a regular correspondence, Einstein addressing her in plainspoken letters simply as “Queen.”
The Hungarians were aware that Einstein was summering on Long Island. Szilard proposed visiting Einstein and asking him to alert Elizabeth of Belgium. Since Szilard owned no car and had never learned to drive he enlisted Wigner to deliver him. They called Einstein�
��s office at the Institute for Advanced Study and learned he was staying at a summer house on Old Grove Pond on Nassau Point, the spit of land that divides Little from Great Peconic Bay on the northeastern arm of the island.
They called Einstein to arrange a day. At this time Szilard also furthered Wigner’s proposal to contact the United States government by seeking advice from a knowledgeable emigré economist, Gustav Stolper, a Berliner resettled in New York who had once been a member of the Reichstag.1170 Stolper offered to try to identify an influential messenger.
Wigner picked up Szilard on the morning of Sunday, July 16, and drove out Long Island to Peconic.1171 They reached the area in early afternoon but had no luck soliciting directions to the house until Szilard thought to ask for it in Einstein’s name. “We were on the point of giving up and going back to New York”—two world-class Hungarians lost among country lanes in summer heat—“when I saw a boy aged maybe seven or eight standing on the curb. I leaned out of the window and I said, ‘Say, do you by any chance know where Professor Einstein lives?’ The boy knew that and he offered to take us there.”1172
C. P. Snow had visited Einstein at the same summer retreat two years before, also losing his way, and makes the scene familiar:
He came into the sitting room a minute or two after we arrived. There was no furniture apart from some garden chairs and a small table. The window looked out on to the water, but the shutters were half closed to keep out the heat. The humidity was very high.1173
At close quarters, Einstein’s head was as I had imagined it: magnificent, with a humanizing touch of the comic. Great furrowed forehead; aureole of white hair; enormous bulging chocolate eyes. I can’t guess what I should have expected from such a face if I hadn’t known. A shrewd Swiss once said it had the brightness of a good artisan’s countenance, that he looked like a reliable old-fashioned watchmaker in a small town who perhaps collected butterflies on a Sunday.
What did surprise me was his physique. He had come in from sailing and was wearing nothing but a pair of shorts. It was a massive body, very heavily muscled: he was running to fat round the midriff and in the upper arms, rather like a footballer in middle-age, but he was still an unusually strong man. He was cordial, simple, utterly unshy. The large eyes looked at me, as though he was thinking: what had I come for, what did I want to talk about?
. . . The hours went on. I have a hazy memory that several people drifted in and out of the room, but I do not remember who they were. Stifling heat. There appeared to be no set time for meals. He was already, I think, eating very little, but he was still smoking his pipe. Trays of open sandwiches—various kinds of wurst, cheese, cucumber—came in every now and then. It was all casual and Central European. We drank nothing but soda water.
Similarly settled, 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.”1175
Einstein hesitated to write Queen Elizabeth but was willing to contact an acquaintance who was a member of the Belgian cabinet. Wigner spoke up to insist again that the United States government should be alerted, pointing out, Szilard goes on, “that we should not approach a foreign government without giving the State Department an opportunity to object.” Wigner suggested that they send the Belgian letter with a cover letter through State. All three men thought that made sense.
Einstein dictated a letter to the Belgian ambassador, a more formal contact appropriate to their State Department plan, and Wigner took it down in longhand in German.1176 At the same time Szilard drafted a cover letter. Einstein’s was the first of several such compositions—they served in succession as drafts—and the origin of most of the statements that ultimately found their way into the letter he actually sent.
Wigner carried the first Einstein draft back to Princeton, translated it into English and on Monday gave it to his secretary to type. When it was ready he mailed it to Szilard. Then he left Princeton to drive to California on vacation.
A message from Gustav Stolper awaited Szilard at the King’s Crown. “He reported to me,” Szilard wrote Einstein on July 19, “that he had discussed our problems with Dr. Alexander Sachs, a vice-president of the Lehman Corporation, biologist and national economist, and that Dr. Sachs wanted to talk to me about this matter.”1177, 1178 Eagerly Szilard arranged an appointment.
Alexander Sachs, born in Russia, was then forty-six years old. He had come to the United States when he was eleven, graduated from Columbia in biology at nineteen, worked as a clerk on Wall Street, returned to Columbia to study philosophy and then went on to Harvard with several prestigious fellowships to pursue philosophy, jurisprudence and sociology. He contributed economics text to Franklin Roosevelt’s campaign speeches in 1932; beginning in 1933 he worked for three years for the National Recovery Administration, joining the Lehman Corporation in 1936. He had thick curls and a receding chin and looked and sounded like the comedian Ed Wynn. His associates at the NRA used to point him out to visiting firemen under that nom de guerre as ultimate proof, if the NRA itself was not sufficient, of Roosevelt’s gift for radical innovation. Sachs communicated in dense, florid prose (he had been thinking that spring of writing a book entitled The Inter- War Retreat from Reason as Exemplified in the Mis-history of the Recent Past and in the Contemporaneous Conduct of International Political and Economic Affairs by the United States and Great Britain) but could coruscate in committee.
Sachs heard Szilard out. Then, as Szilard wrote Einstein, he “took the position, and completely convinced me, that these were matters which first and foremost concerned the White House and that the best thing to do, also from the practical point of view, was to inform Roosevelt. He said that if we gave him a statement he would make sure it reached Roosevelt in person.”1179 Among those who valued Sachs’ opinions and called him from time to time for talks, it seems, was the President of the United States.
Szilard was stunned. The very boldness of the proposal won his heart after all the months when he had confronted caution and skepticism: “Although I have seen Dr. Sachs once,” he told Einstein, “and really was not able to form any judgment about him, I nevertheless think that it could not do any harm to try this way and I also think that in this regard he is in a position to fulfill his promise.”1180
Szilard met Sachs shortly after returning from Peconic—between Sunday and Wednesday. Unable at midweek to reach Wigner en route to California, he tracked down Teller, who thought Sachs’ proposal preferable to the plan they had previously worked out.1181 Drawing on the first Einstein draft, Szilard now prepared a draft letter to Roosevelt. He wrote it in German because Einstein’s English was insecure, added a cover letter and mailed it to Long Island. “Perhaps you will be able to tell me over the telephone whether you would like to return the draft with your marginal comments by mail,” he proposed in the cover letter, “or whether I should come out to discuss the whole thing once more with you.” If he visited Peconic again, Szilard wrote, he would ask Teller to drive him, “not only because I believe his advice is valuable but also because I think you might enjoy getting to know him.1182 He is particularly nice.”
Einstein preferred to review a letter to the President in person. Teller therefore delivered Szilard to Peconic, probably on Sunday, July 30, in his sturdy 1935 Plymouth.1183 “I entered history as Szilard’s chauffeur,” Teller aphorizes the e
xperience.1184 They found the Princeton laureate in old clothes and slippers. Elsa Einstein served tea. Szilard and Einstein composed a third text together, which Teller wrote down.1185 “Yes, yes,” Teller remembers Einstein commenting, “this would be the first time that man releases nuclear energy in a direct form rather than indirectly.”1186 Directly from fission, he meant, rather than indirectly from the sun, where a different nuclear reaction produces the copious radiation that reaches the earth as sunlight.
Einstein apparently questioned if Sachs was the best man to carry the news to Roosevelt. On August 2 Szilard wrote Einstein hoping “at long last” for a decision “upon whom we should try to get as middle man.”1187 He had seen Sachs in the interim; the economist, who certainly coveted the assignment of representing Albert Einstein to the President, had generously listed the financier Bernard Baruch or Karl T. Compton, the president of MIT, as possible alternates. On the other hand, he had strongly endorsed Charles Lindbergh, though he must have known that Roosevelt despised the famous aviator for his outspoken pro-German isolationism. Szilard wrote that he and Sachs had discussed “a somewhat longer and more extensive version” of the letter Einstein had written with Szilard at their second Peconic meeting; he now enclosed both the longer and shorter versions and asked Einstein to return his favorite along with a letter of introduction to Lindbergh.
Einstein opted for the longer version, which incorporated the shorter statement that had originated with him but carried additional paragraphs contributed by Szilard in consultation with Sachs. He signed both letters and returned them to Szilard in less than a week with a note hoping “that you will finally overcome your inner resistance; it’s always questionable to try to do something too cleverly.”1188 That is, be bold and get moving. “We will try to follow your advice,” Szilard rejoined on August 9, “and as far as possible overcome our inner resistances which, admittedly, exist. Incidentally, we are surely not trying to be too clever and will be quite satisfied if only we don’t look too stupid.”1189
Making of the Atomic Bomb Page 42