Los Alamos: The Fateful Mesa (1943–1946):
Smell of Piñones
Das Alte stürzt, es ändert sich die Zeit
Und neues Leben blüht aus den Ruinen.
The old is crumbling down—
The times are changing—
And from the ruins
Blooms a fairer life.
Schiller, Wilhelm Tell 4.2
My work had put me at the very center of the atomic bomb project. Although I was technically an enemy alien, so were many others who were vital to the enterprise, and I found myself in a relatively important position in the extraordinary adventure that was the Los Alamos laboratory.
I have already mentioned the creation of the Manhattan District and the choice of its chief in the person of Leslie R. Groves. Son of a Protestant clergyman and military chaplain from New England, Groves had studied at West Point and later had distinguished himself in the building of the Pentagon, reaching the peacetime rank of colonel. When he was assigned to the direction of the newly created Manhattan District, he knew nothing of things atomic. He thought at first that this assignment would be the end of his career, but dutifully accepted it.
To increase his prestige, he obtained the temporary rank of brigadier and plunged into his new duties with immense vigor, courage, decision, and even intelligence. What impressed me most was the speed with
which the general oriented himself in a new world totally foreign to him. He was able to deal successfully with such diverse groups as atomic scientists, unions, industrial managers, the British Mission, and assorted prima donnas. It is surprising to me how rapidly he managed to appreciate such persons as Oppenheimer, Fermi, or Wigner, so different from him in culture, outlook, language, and almost everything. Only Szilard remained beyond his grasp. Groves has written an autobiography, from which emerge not only his remarkable positive qualities but also his occasional narrow-mindedness, vanity, and prejudices.
In late 1942, the heads of the Manhattan District decided to build a laboratory devoted to the development of an atomic bomb. General Groves chose J. Robert Oppenheimer to be its director, and Oppenheimer, Groves, and a few others looked for a site for the laboratory in the high plateaus of New Mexico. Some members of the party inspected several localities on horseback, with negative results. The general later joined them, and together they proceeded by car to Los Alamos, where there was a private school for boys. The original buildings were two large wooden chalets, called Fuller Lodge and the Big House, which contained the mess hall, the boys' dormitory, and the classrooms. In addition, there were several wooden or stone buildings housing the staff and various activities, as well as a corral. This handful of buildings did not intrude on the landscape; rather, they harmoniously blended into it.
The mess hall in Fuller Lodge had a porch opening onto a lawn, and from it we had a spectacular view on the Sangre de Cristo Mountains, dominated by the Truchas Peak, across the Rio Grande valley. On the opposite side, behind the few other buildings of the school, there were extensive pine woods and smaller mountains that surrounded the invisible Valle Grande, where I was to spend many hours meditating and fishing. The view from Fuller Lodge could not fail to impress whoever saw it for the first time. I admired it with I. I. Rabi, and he says that my comment was that after ten years of looking at it, we would have had enough of the view. I do not know whether the story is true, but I report it because it shows what we then thought about the possible duration of our enterprise and of the war. My assessment of the war
situation was greatly mistaken, and later I was surprised in reading Churchill's memoirs to find that by then he was already sure the war was won. It certainly did not look that way to us simple mortals.
The view from Fuller Lodge became even more dramatic in late spring and summer at 4 P.M. , when every day a big thunderstorm started illuminating the horizon toward the Sangre de Cristo Mountains, with brilliant lightning criss-crossing the sky. The storm lasted a few hours and by 8 o'clock it was over, giving way to a serene night. The phenomenon was perfectly regular: at noon big cumulus clouds started forming in a sky that early in the morning had been perfectly clear; the clouds grew and rose in the sky, until they climaxed in the afternoon's thunderstorm. These summer storms cooled the days, which otherwise would have been hot, in spite of the altitude. Thus the climate was most pleasant, with moderately cold winters that permitted skiing. In the spring there was a profusion of wild flowers, and in the fall golden aspen thickets marked the fire scars in the pine forests, inviting hiking on solitary trails. These often went through small canyons with walls of volcanic rock on which Indians of bygone times had left mysterious pictographs.
Water was scarce and occasionally slightly muddy, and the inhabitants of Los Alamos made a big fuss about it. Later we had some periods of genuine water shortage, but they lasted only briefly and were significant mostly as topics of conversation. Checking statistics, I found that the amount of water daily available per person was large compared with that in many European cities.
At Los Alamos's altitude, 7,700 feet above sea level, the atmospheric pressure is only 22.4 inches of mercury, and water boils at 198° F, substantially lengthening cooking times. Several families bought pressure cookers as a remedy; we exercised patience. Typical complaints among the residents resembled a conversation I overheard between two women at the military PX, where we did most of our shopping, who grumbled about the sacrifices imposed by war; for instance, they could not find the exact cuts of meat they wanted.
I first went to Los Alamos in March 1943, and promptly found myself attending a conference devoted to informing the scientific personnel
of the future laboratory of the problems facing us and to making concrete plans for their solution. While waiting for the military to build the green wooden apartment houses that were to become our homes for the duration of the war, those attending the conference slept in the Big House in a sort of hall. There my gold Longines Chronograph, bought at the time of the League of Nations sanctions against Italy, was stolen from me during the night. The people sleeping in the dormitory were not of the kind likely to steal watches, and the Military Police maintained strict surveillance of the dormitory, where there were highly secret documents, schedules, and plans related to the atomic bomb. Nevertheless, my watch was stolen, and the MPs, whom I immediately informed, did not display much zeal in trying to track down the thief. The watch was never found, and the theft is still a mystery to me.
Oppenheimer had invited some thirty scientists to the gathering I was attending, including the future leaders of the project and consultants like Fermi and Rabi. In the conference's five sessions, Robert Serber systematically described all that was known concerning a possible bomb. E. U. Condon took notes on his lectures, which subsequently formed a report (now declassified) called "The Los Alamos Primer."
Serber's lectures were followed by discussion of what to do, as well as by animated debates on the laboratory's organization. The military would have liked to put everybody in uniform, but this unhappy idea found a strenuous opposition headed by R. F. Bacher, Rabi, and others who had experience with the MIT radar laboratories, and the military gave in.
Fermi, Rossi, I, and perhaps some other Italian-speaking physicist, were lunching one day during this period at Fuller Lodge, and as usual, we slipped into Dante's language; as usual, talking loudly. General Groves was nearby, and he let us know that he did not like us speaking Hungarian (!) in public; he delicately hinted that if we wanted to speak foreign languages, we had better go into the woods.
Security originated disagreements between civilians and the military from the very beginning of the project. Military personnel were used
to obeying orders from above without question and without knowing the reasons. For civilians, and especially for scientists, this was very awkward. We understood the necessity of secrecy, but we also knew that one could not develop new ideas and a new technology while enforcing strict compartmentalization of the data. The importance of information on subjects seemingly remote from the main object was obvious to the scientists but incomprehensible to the military. Furthermore, the latter were concerned with legal requirements, while the scientists were committed to the technical success of the enterprise. In short the military wanted compartmentalization of information, which was deemed catastrophic by the scientists.
General Groves wiggled out of this impasse with good sense. He had soon realized that if he wanted to make the bomb as rapidly as possible, (and in so doing make his rank permanent, or even add a star to it), he needed first-class personnel, even if they had to be aliens, even if he had to rely on Axis citizens. Who could replace a Fermi? Thus when Groves saw that the usual security rules would preclude recruiting those he wanted, he invented new rules. Each of us was to guarantee some colleague he knew well. "Guarantee" sounded good, but how? Somebody proposed an oath on the Bible, but Groves objected: "Most of them are unbelievers." An Intelligence officer then proposed an oath on personal honor, but Groves replied: "They do not have any sense of honor." "Rather," he concluded, "let them swear on their scientific reputation. It seems to me it is the only thing they care for." I thus swore on my scientific reputation guaranteeing Fermi's and somebody else's loyalty, while Bethe and Bacher, I believe, guaranteed mine. The process continued in a circle.
Other problematic aspects of security involved the handling of personal mail. We were permitted to give our address to all our correspondents, even foreign ones, and the military authorities promised that they would not censor mail. The scientists remained justifiably skeptical, and simple tests demonstrated that the military were not keeping their promise. This gave rise to almost comical scenes and to serious resentment and protests, not so much because of the censorship as because its existence was falsely denied.
The Los Alamos site was surrounded by a tall wire fence, with gates, guarded by soldiers, at which one could enter and exit at will by signing a form and showing the proper identification papers. Nevertheless, the military never suceeded in correctly keeping track of the cars entering and exiting the site. This showed up when some cars stolen from the site were found outside of the fence, without there being any signature confirming that they had exited through a gate. Physicists joked about the divergence theorem for automobiles.
Once outside Los Alamos's fence, we had to remain within a certain large perimeter, which contained the city of Santa Fe and several tourist attractions. Exiting from this perimeter required special permission. These restrictions did not seem too inconvenient to Elfriede and me.
After the programming meeting, many of the attendees returned to their usual locations to prepare apparatus and to recruit the personnel required for the new lab. Most returned to Los Alamos after a few weeks with their helpers, to remain there until the end of the war or later. In the meantime, construction on the site proceeded at full speed, and by midsummer of 1943 the lab had started operating. A cyclotron brought in from Harvard University and accelerators from the universities of Wisconsin, Illinois, and Minnesota were the first substantial bits of apparatus available. Physicists, chemists, and metallurgists, as well as auxiliary personnel, arrived daily. As soon as possible, they activated the new laboratories and shops.
At the same time, water supply and sewers, sidewalks, electricity, and everything needed for the new city grew by leaps and bounds. The residential housing consisted of several four-family apartment houses, built of wood and painted green. Bachelors lived in dormitories. The hospital that was built was staffed above all with obstetricians and pediatricians, as required by the nature of the population and the remoteness of the site.
Soon the lab had a collection of nuclear physicists that was possibly more brilliant and active than any other in the world. On average, the members of this group were young, about thirty-two years old; some who were a little older had barely passed forty and were already quite famous. Several who would become famous later were about twenty
years old at the time. There were eight future Nobel prize winners (Alvarez, Bethe, Bloch, Chamberlain, Feynman, McMillan, Rabi, Segrè). Oppenheimer was thirty-nine. In these strange circumstances I again met many old friends, whose presence helped to inspire confidence in the ultimate success of the project.
During our first days at Los Alamos, Fermi and I investigated the living conditions we could expect. For instance, we washed our pants in a public launderette to see how good it was. At the Fuller Lodge cafeteria, Fermi sought to demonstrate the digestive powers of his Italian stomach by eating a clearly bad egg that had been served at breakfast. I tried to discourage him, but he insisted he could digest it without trouble. The result was that he became quite sick.
I returned to Berkeley to prepare the transfer of my group and collect the instruments needed for our assignments: measurements on spontaneous fission and on sundry nuclear data, including cross sections. We had already started most of these investigations at Berkeley.
For the proper working of a bomb, it was essential that the fissionable material be assembled in sufficient mass, and that neutrons be injected to initiate the chain reaction only after assembly. Neutrons introduced before the assembly was completed would reduce the efficiency of a bomb and make its working unpredictable. This untimely explosion was called predetonation. Now, especially in the case of plutonium, the high alpha activity could produce light-element impurities that even in very small amounts could predetonate the mass with unwanted neutrons. Extreme purification of the plutonium was the remedy. It was expected that with effort one might succeed. Unwanted neutrons could also come from spontaneous fission of the material. Nothing could be done about these neutrons. Hence the importance of assessing the presence of spontaneous fission.
This urgent job required especially clean and reliable techniques. The samples we expected were necessarily small in quantity, but at least those of plutonium would have substantial alpha activity. We observed the large ionization pulses produced by fission, and it was necessary that there should never be disturbances simulating such an event; no fluctuation in alpha emissions could be permitted to fool us. To
avoid external electrical disturbances from the mains, we found it was necessary to power everything with batteries in a place far away from other laboratories.
For this reason, in June 1943, we got the use of the abandoned house of a forester in a canyon at Los Alamos called Pajarito (Little Bird). Seldom have I seen such a romantic and picturesque place. It was reached by jeep through trails flanked in season by great bushes of purple or yellow asters, where in full summer one could meet nice rattlesnakes. The tracks followed an open arroyo with steep, low walls, which here and there contained prehistoric Indian dwellings and glyphs with mysterious symbols. At the end of the canyon, we installed our apparatus. In one corner of our rustic laboratory, there was also a folding bed, in which one could sleep if need be.
I had commuted from Berkeley until we could obtain an apartment in Los Alamos. In June 1943, however, the whole family made the move to Los Alamos by car. Our daughter Amelia was then seven months old, and we placed her in a basket. Elfriede and I took turns driving, and Claudio, a very good boy, sat between us or in the back seat. Once in a while, the basket containing Amelia would fall to the floor from the back seat, but she did not seem very disturbed by this. We took the famous Route 66. At daybreak, when we started, the world seemed brand-new, and it was possible to believe we were its first inhabitants, but progressively the heat (without air conditioning in the car) prevailed and we slowly wilted. Troops were training for desert combat along the road, and nails from their boots gave us several flat tires.
From Santa Fe we reached Los Alamos by a dusty, winding road. First we crossed the Rio Grande by an old bridge near the pueblo of San Ildefonso, which was inhabited by Indians. From there, the road climbed to the mesa along a daring route punctuated by spectacular views. As the road climbed, the view on the Rio Grande Valley opened up until it culminated in a vast panorama, with the Sangre de Cristo Mountains as a backdrop.
At Los Alamos we were assigned an apartment on the upper floor of one of the newly built apartment houses. The other tenants included a man who used to play his trombone at night up to three o'clock.
Although we were reluctant to complain, this was too much, and we lodged a protest. It seems that trombone playing and drinking were consolations for marital problems. Our next-door neighbors, who were strict Mormons, had a son the same age as Claudio, and we started taking him with us on our Sunday jaunts, much to both boys' delight. Unfortunately, however, the Mormon parents discreetly asked us not to invite their son any more, because their religion frowned on Sunday outings.
Indian women from the pueblos of the Rio Grande valley were hired to help with the housework, and we visited the Ildefonso, Nambe, and other pueblos ourselves once in a while. During the great winter celebrations at San Ildefonso, we were invited to see the Indian ritual dances. There were no other spectators besides those from Los Alamos and some priests and nuns keeping an eye on their nominally Catholic flock.
One of the leaders of the ritual dances was Popovi, an excellent electrician working in the laboratory on our accelerators. When there were Indian religious ceremonies, he painted his face half yellow and half green and led the dance with utmost seriousness. He was the son of Maria Martinez, a celebrated ceramic artist. In 1943 one could buy Maria's black ceramics for a few tens of dollars; now they are worth at least a hundred times as much and many are in major American museums. A San Ildefonso vase even appears on a 1977 U.S. postage stamp celebrating Indian art. After the war, Popovi too became a famous artist, but lamentably, he died young, a victim of alcoholism.
From the very beginning, we found at Los Alamos old friends from California, such as R. B. Brode, H. H. Staub, Felix Bloch, Robert Serber, and Edwin McMillan; from other American states, such as John Manley, D. P. Mitchell, Donald Kerst, S. K. Allison, and Percival King; and from Europe, such as Bruno Rossi, Edward Teller, Victor Weisskopf, Hans Bethe, and others. Fermi came visiting frequently, as did John von Neumann, with whom I became friends. Joseph Kennedy, my close friend from Berkeley, had a leading position in chemistry.
Oppenheimer, in order better to direct the lab, needed the support and counsel of a certain number of trusted intimate collaborators. To
them he gave the most important administrative jobs. He organized the lab into divisions and then subdivided each division into groups. I was a group leader in the physics division. Initially, the division head was R. F. Bacher, who was soon promoted to associate director. Subsequent division leaders in physics included J. H. Williams from the University of Minnesota, not a great physicist, but a person with good common sense and unusual ability in dealing with practical problems, as well as with workers, mechanics, and unqualified personnel. He was followed by R. R. Wilson.
The division leaders had to put up with a certain spirit of independence and restlessness on the part of the group leaders. The division heads, often junior and scientifically inferior to their administrative subordinates, needed plenty of patience and tact to avoid awkward situations. The best they could do was to keep people happy and let them work. Goodwill, talent, and means were plentiful, and these ingredients easily produced results.
As a wise general policy, the administration gave directives and set goals, timetables, and priorities, but left ample freedom at the group level in technical choices and did not interfere in the execution of the work. For procurement, we had powerful priorities, allowing us to requisition anything we needed. D. P. Mitchell, a physics professor at Columbia University, was in charge. He knew where to find anything in the United States.
For the group leaders the problems were different. Once a goal was assigned, they had to find the way of reaching it in a limited time, and without errors that might have disastrous consequences. Furthermore there was always a problem lurking. The laboratory had one purpose only: to build a bomb as fast as possible. The physicists who worked on it often came across subjects that were scientifically most interesting, although irrelevant to the bomb; for the immediate purpose, these were a waste of time and effort. To keep balance in this predicament required a certain skill. On the one hand, discarding all irrelevant science, even if good, risked disgusting several of the best young people and might render them useless. On the other hand, it was inappropriate to devote too much time to pure science. All this produced tensions, especially
among the personnel coming from the universities and used to academic freedom of choice in their work. For those coming from industry, the situation was not new, and they were prepared for it.
My group comprised about fifteen people. I was the only established scientist. The other members were either promising graduate students or fresh Ph.D.s. In addition to Chamberlain, Wiegand, and Farwell, the physics students from Berkeley were G. A. Linenberger and John Jungerman. John Miskel, R. J. Prestwood, and Milton Kahn were chemistry graduate students. Several of them had lived in the same house at Berkeley. There were also Jack Aeby and Bill Nobles, students who had been recruited into the Army and put in a "Special Engineering Detachment" (SED). They were in uniform and subject to military discipline, but worked in the lab like everyone else. All these young men received a laboratory education equal or superior to what they could have got in a first-class university; furthermore, practice was supplemented by frequents talks or short courses on subjects connected with current problems.
Oppenheimer also assigned Martin Deutsch of the Massachusetts Institute of Technology and the Pole Joseph Rotblat to my group. Deutsch was an excellent physicist and had left experiments on angular correlations in gamma decay at MIT that made him deservedly famous. Rotblat had come to Los Alamos with the British Mission, after having fled Poland at the Nazi invasion and had been separated from his wife, of whom he had not had any further news (she had, in fact, been murdered by the Nazis). Understandably, he was too upset to do strenuous work and meet deadlines. I assigned him, along with Deutsch, to study gamma rays associated with fission, an interesting line of enquiry, but not of immediate vital significance.
Los Alamos was a closed society bearing some resemblance to a military garrison, but with a population not used to that type of life. Moreover, the pressure of work was immense and enhanced by the unavoidable deadlines and heavy responsibilities. No wonder the inhabitants became touchy and restless. Often they resented petty things to which they would never have paid attention under normal circumstances. Rank, housing assignments, the part of town in which one
lived, social invitations, administrative assignments, everything became important, occasionally in a childish way. The fact that one willy-nilly always saw the same people added to the difficulties.
The wives, displaced from their usual surroundings, added to the problems. Without the absorbing technical work of the husbands, and unavoidably in the dark about what was going on in the laboratories, they often became depressed, quarrelsome, and gossipy. The problem became so serious that Oppenheimer consulted a psychiatrist on how to cope with it. The doctor advised him to find work to keep the women busy and to pay them so that they would have a tangible proof of their usefulness. Following this advice, many became excellent secretaries, teachers, medical technicians, clerks, librarians, and so on. For a time, Elfriede worked as a secretary in my group; later she compiled a current isotope chart, or Segrè Chart, as it was called, with my help. It was a monumental work, and after the war, it was declassified and published. More than fifty thousand copies were sold without our getting any royalties.
With many children of school age, elementary schools were vital, and soon the project hired several of the best-qualified mothers to staff them, as well as a few professional teachers. They formed an excellent faculty. Other physicists' wives went to work soldering electronics apparatus, sometimes causing problems for the users, who started complaining about faulty contacts.
The magnificent surroundings of Los Alamos afforded easy and effective relaxation. Often we reached the end of the week completely exhausted and renewed our strength by going fishing on Sunday. Gasoline rationing limited our mobility, but by combining the gas coupons of several families, we could afford to go to the Valle Grande, the Jemez River, the Rio Frijoles, and several other good trout-fishing streams. For me one of the great pleasures was to wander in the cool of the morning along the meanders of the slow river that crossed the Valle Grande, looking for grasshoppers hiding under heaps of cow dung. With this bait I fished fat trout that made delicious meals. It was a prime way of recuperating from the week's hassles.
One Saturday evening I met Sir James Chadwick, the discoverer of
the neutron, at a dinner. We happened to talk about fishing, and he told me that the next day he planned to go fishing on the Jemez. Since I knew the river, I asked him what bait he planned to use. He answered rather dourly, "I use only dry flies." I hinted that experience suggested that on the Jemez fish took only grasshoppers. Next day late in the afternoon I was walking along the Jemez with my limit when I saw Sir James casting, perched on a rock. Foolishly, I asked him how he was doing. "Nothing doing," he answered unsmilingly, but he had not departed from his principles. I tried to teach Fermi to fish, and it seemed to me he liked it. However, he once returned from Chicago with a lake fishing rod and reel. I told him that it was not suitable for mountain streams, but to no avail. Fermi developed a theory on how trout should bite and on how to catch them. The theory was disproved by experiment, but this did not impress him in the least. Ultimately he abandoned fishing, but not his theory.
In addition to trout, we encountered beautiful porcupines, flocks of wild turkeys, and birds of all colors, which were sometimes truly spectacular. I once even saw what looked like a sort of small leopard, although I could not identify it. Marmots, badgers, and deer ventured even among the houses.
The flora too were splendid, with columbines of all colors in the spring and mushrooms in the fall. After a while I got to know the spots where animals and plants were to be found, so that I could, for example, go mushroom hunting by car, stopping where I knew I would find them. I picked a few mushroom species that were easily identifiable and abundant, and Elfriede would make them into delightful dishes. Once we invited Mici Teller, Edward Teller's wife, to dinner and served her a delicious dish of rice with mushrooms. Highly pleased by their flavor, she asked where I had bought them. When I told her I had picked them, her face changed color, and about fifteen minutes later she said she felt sick in her stomach. Such was the power of suggestion and fear. Needless to say, nobody else had the slightest trouble.
On the rare occasions when the pressure of the work allowed it, we took some longer outings in the Sangre de Cristo mountains and to
their lakes. There marmots completely ate the cork handle of my fishing rod; as an offset I caught spectacular trout, using as bait night moths that lodged in cracks between big stones. Trout took them only if they could not see the hook's leader. With that precaution, success was assured, otherwise it was a waste of time. Having discovered this trick, I challenged some of my friends and impressed them with my fishing skill.
Once, immediately after the end of the war, when Elfriede was expecting our second daughter, we went camping near a warm spring in a remote mountain spot. Next morning we explored the surroundings and found a beautiful hole of crystal clear warm water. We undressed and were enjoying the water, when some Indians who had invisibly followed us politely explained, in Spanish, that the spring was a holy place to them and invited us to decamp. On the same outing we met a newly wed young Navajo couple on horseback in their traditional attire. With the groom's permission we took pictures; the bride objected because she believed that the picture would take away her soul.
Autumn was a season of glorious yellow. The aspens and the beeches interspersed among the dark green of the conifers dropped their leaves, and their pleasant odor pervaded the usually bright, clear air along the trails. One evening I was balancing on a dead tree protruding from a small lake, fishing and admiring the colors of the fall sunset. The still, cool air announced the ending of the season and deep silence prevailed. Suddenly a loud report startled me so that I almost fell into the lake: a beaver had hit the water with his flat tail to frighten me off.
A British Mission, headed by Sir James Chadwick, joined us in 1944. It included among others my old friends Rudolf Peierls, Otto Frisch, and P. B. Moon. Later they were joined by William Penney (the future Lord Penney) and Sir Geoffrey Taylor, a first-class mathematical physicist endowed with an exceptional combination of intuition and analytical power, truly a giant when it came to problems of mechanics, hydrodynamics, and classical physics in general. Taylor had been a close friend of Rutherford's, a meteorologist, and an aviator in World War I. He came from a great scientific family, which counted among its members George Boole (1815–64), the inventor of Boolean
algebra, and the surveyor Sir George Everest (1790–1866), after whom the mountain is named. Many years later he came to Berkeley as a Hitchcock Lecturer.
The British mission unfortunately also included Klaus Fuchs, a German refugee who became a Russian spy. I had exchanged only a few words of introduction with him, but he passed under our window every day at noon, presumably going to lunch. Elfriede noted his sad aspect and, not knowing who he was, nicknamed him "il Poverino" (the poor soul). She was dismayed later in hearing that the "Poverino" was a spy.
We often saw the Brodes, the Tellers, and Rossi, because we were neighbors and had known each other a long time. The pianists Frisch, Weisskopf, Bloch, and Teller adorned the same neighborhood. All played well, but with differing proficiency, styles, and programs. Their music, according to Elfriede, who had a fine ear, revealed their personalities like an open book.
Common devotion to fishing and natural inclination tied me to the Swiss Hans Staub; his wife Erika and Elfriede were friends, and the Staub children were of the same age as ours. Staub came from Stanford, where he had worked with Bloch, and after the war returned to Zurich. In the evening we occasionally played poker at the Staubs' house. We played in a very amateurish unsophisticated way. Sometimes John von Neumann joined us. I do not remember that he won particularly often, but he knew the odds of every card combination and of every move.
In the fall of 1943, Niels Bohr and his son Aage arrived at Los Alamos. Shortly before, in Copenhagen, he had been warned that he was about to be arrested. He fled immediately, and after several adventures he had landed at Los Alamos. For security reasons he was given the false name Nicholas Baker and the Lab Direction ordered us to pretend that we did not recognize him, probably a useless precaution, because many knew his true identity. Bohr lived in a small house next to Fuller Lodge with his son, but traveled a lot.
Soon after Bohr's arrival, Oppenheimer convened a meeting at his own home, inviting European physicists already personally acquainted with Bohr, as well as a security officer, called in as a precaution against misunderstandings with the military authorities. Aage Bohr was also
present and helped materially because he spoke more distinctly than his father and on request repeated what his father had said. Bohr gave a detailed account of conditions in Denmark and of his personal adventures. He then expanded on what he knew about the rest of Europe. It was the first time we had had direct information from an eyewitness. The atmosphere was somber; almost all those present had relatives or friends in Europe, and the news was thus personally relevant.
After reporting on events in Denmark, Bohr concluded by saying that unfortunately one had to expect things to be much worse for other countries, because the Nazis considered the Danes Aryans, of Nordic race, and treated them as such; apparently they even hoped that by befriending them they might turn them into allies. At this point, Nora Rossi, Bruno's wife, asked: "But then why don't the Danes reciprocate and collaborate with the Reich?" I still remember the expression on Bruno's face, while Bohr patiently tried to explain the reasons why the Danes did not want to collaborate with the Nazis. Nora, a granddaughter of Cesare Lombroso's, as she often emphasized, was given to very self-assured utterances on Italy. Once Fermi started contradicting her with sensible, lowbrow arguments, as was his habit. Nora did not know how to reply and tried to shut him up by saying something along the lines of: "Don't think the Nobel Prize allows you to understand these things better than I do."
During Bohr's visits I had long and frequent physics conversations with him, mainly on nuclear fission. He used to come to my laboratory asking about experimental data and then started reasoning aloud, smoking a pipe that needed constant lighting. He mumbled so badly that Aage, who accompanied him, often repeated some phrase to make it intelligible. I made every effort to understand the words Bohr was uttering; their content was obviously important and instructive, but I had great difficulty. I asked Bohr as much as possible to repeat, but there were limits to how often I could do so and I felt embarrassed at abusing his courtesy. I often remained uncertain and frustrated.
At lunch time I listened to two rather silly radio soap operas: a sentimental story about a nurse, which was broadcast exactly at the time when "il Poverino" passed under our windows, and the biblical
story of Jezebel. For some reason, I don't recall why, I mentioned these programs one day to Bohr, who had just returned from a trip to Washington. He answered with great glee: "Then you will be able to give me the latest news; during my trip I lost track of Jezebel."
I was at Los Alamos on July 25, 1943, when Mussolini was toppled, and, naturally, I followed events in Italy in the newspapers. The combined ineptitude of the Italians and of the Allies, especially of the Americans, allowed the German occupation of Italy and the tragedies that followed. However, in Los Alamos, we did not know much of what was happening in the German-occupied zones. Only in June of 1944, after the Allies entered Rome, did I receive the news I coveted most. The first troups entering Rome had orders to look for Amaldi and other physicists to collect information on the German atomic project, and thus, through military intelligence, I obtained some news from home. Oppenheimer called me into his office and told me that my father was safe, but that my mother had been captured by the Nazis in one of their manhunts of October 1943. I was stunned, and Oppenheimer repeated the news to me several times, because he doubted whether I had understood. My father did not survive long; he died of natural causes in his home in Rome, at Corso Vittorio 229, on October 4, 1944, at eighty-five.
It took a long time before communications with Italy could be reestablished and I could obtain firsthand news. Only in 1947, on my first postwar visit to Italy did I learn the details, albeit even then only partially. The tragic and painful page of my parents' end is buried in the depths of my soul and must rest there.
The main and most important work of my group, the study of spontaneous fission, had been started in Berkeley by Kennedy, Seaborg, Wahl, and myself as early as 1941, but the minuscule amounts of material available and the still unsophisticated techniques used at that time allowed us to obtain only large upper limits to spontaneous fission rates, data of little practical interest. In the beginning, as we received increasingly enriched samples, we studied U235 with ever-increasing accuracy at Los Alamos; the alpha activity was moderate and the efficiency
for the detection of spontaneous fission could easily be calibrated using a known neutron source. Among other things, we found that the "spontaneous" fission at Los Alamos was greater than at Berkeley, which was not surprising because cosmic-ray neutrons, more abundant at a high altitude than at Berkeley, were obviously responsible for the effect. We had only to screen the chambers suitably to make it disappear.
The difficult, but important, part of the work came with the study of Pu239 . Once we had milligram samples, we soon recognized that Pu239 had a rate of spontaneous fission high enough to interfere seriously with the proposed methods of bomb assembly through predetonation. These findings, starting in April 1943 with a few counts, became firmer with better samples and longer observation times. We also checked the number of neutrons emitted per spontaneous fission. By July 1944, our results brought the Los Alamos lab to a real crisis, although the relevant information was based on a few counts only. Spontaneous fission in plutonium was so frequent that the plutonium alternative for making a bomb was excluded unless one could invent and develop a totally different assembly method. The predicament was grave indeed; it meant that about half of the total work of the project might be useless for war purposes. The statistical accuracy of our measurements was low, but I was sure that what we had seen was real and not a freak owing to malfunctioning of the apparatus. Even if we had seen only three or four events, I was prepared to guarantee that they were fissions and nothing else.
Soon we noticed another important effect. Plutonium coming from stronger neutron irradiations gave more spontaneous fissions. In the beginning we were perplexed by this finding, but soon we realized that spontaneous fission came from the isotope Pu240 and not from Pu239 . The first was produced in the pile by neutron irradiation of the second. It was thus proportional to the square of the total neutron flux used. However, high fluxes were necessary for producing enough plutonium. It was possible to envisage separating the main product, Pu239 , from Pu240 , but the prospect of separating plutonium isotopes was not alluring. We confirmed that Pu240 was the isotope with high spontaneous
fission by irradiating Pu239 with neutrons and observing that the formation of Pu240 increased the spontaneous fission of the sample.
As a consequence of this discovery, the Los Alamos project took a sharp turn. Fortunately, the implosion method invented and suggested by Seth Neddermeyer, a former pupil of C. D. Anderson's, avoided the predetonation problems connected with the slowness of the gun assembly of the bomb. Neddermeyer's invention had at first been discarded, but now it was given the highest priority and was transformed into a technically viable proposition. Von Neumann, Geoffrey Taylor, and Fermi contributed materially to its theoretical analysis. For the practical part, a new division under George B. Kistiakowsky was charged with preparing explosive lenses and assembling them. Rossi and Staub had an important part in showing that the implosion was really compressing the material and working according to plan. Through Staub I was able to follow the development of this technique.
When we irradiated Pu239 with neutrons to form Pu240 , we also formed a sizeable amount of element 95, americium. I tried to persuade Kennedy and Wahl to investigate it at Los Alamos, but they were deeply absorbed in urgent war work and did not want to subtract part of their effort from the main purpose of the lab. Seaborg, though not allowed into Los Alamos, obtained the plutonium that had been reirradiated for us and extracted americium from it. I would have liked to have been less patriotic and conscientious than Kennedy and to have pursued that investigation at Los Alamos.
In addition to regular group assignments, I once in a while received requests from Oppenheimer to look into special problems that arose suddenly and unexpectedly. For instance, once he told me to go immediately to Oak Ridge in Tennessee, to the big isotope separation plants. One of these consisted of many huge mass spectrographs, called calutrons, built under the guidance of Lawrence and the Berkeley physicists. The enriched uranium was chemically purified and converted to suitable compounds for further work. Nobody, however, had checked whether the process might somewhere accumulate enough material to
start a nuclear reaction. It was no joke. With bad luck there might have been a real catastrophe. Because of compartmentalization, the local chemists had not considered that danger. Richard Dodson and I rushed to Oak Ridge to study the situation and urge instant adoption of appropriate precautions if necessary. At the same time we were under orders not to reveal secret information. Certainly, however, it was better to stretch secrecy rules than to incur a nuclear disaster. We carefully inspected the plant and found several spots that were outright dangerous, which we duly corrected. When I returned to Los Alamos I had a strange surprise. I found in my suitcase, which I had jealously guarded because it contained secret documents, an alarm clock in a nicely wrapped box. How it got into my suitcase is still a mystery.
Another time Oppenheimer asked Rossi and me to figure out the effects of a nuclear explosion of a certain power and to write him a report on the subject. We were even told to consider the psychological effects on an enemy. We locked ourselves in a room and started figuring temperatures, pressures, radiation density, and so on. We had been at work for some time when we heard Fermi's voice, coming from a nearby corridor. I proposed consulting him. It turned out that he had already done a good part of the calculations and estimates on his own. We agreed well as far as we had gone. With his help we were able to finish the job in a short time; it was later pretty well substantiated by fact. As to the psychological part of the assignment, however, although we discussed it at some length, we could not reach any solid conclusion and we refused to make predictions.
Strange things happened in wartime Los Alamos. One day Oppenheimer called me and asked me to make a rather senseless experiment, which consisted in exploding a charge near a uranium salt. The outcome was easily predictable, but Oppenheimer nonetheless insisted that I perform the experiment, and I complied, obtaining the expected result. I then asked Oppenheimer why he had wasted my time in this way. Oppenheimer answered that he had known the outcome in advance too, but that President Roosevelt had personally asked that the experiment be done and that he had felt bound to comply. Possibly the president received a number of claims to inventions through irregular
channels and occasionally skipped regular appraisals. To Roosevelt's credit, however, he had had a good enough nose to recognize the importance of atomic energy when it was proposed to him irregularly.
In the spring of 1945 the atomic bomb project was reaching the home stretch. The way of making the bomb had been found and the design had been fixed. Fissionable material was arriving in appreciable amounts. The purpose of the lab was changing from research and technical invention to production and testing. We thus prepared experiments that would help reveal the performance of the bomb.
A nuclear explosion is a very complex event, with mechanical, thermal, optical, chemical, and nuclear aspects. There was obviously plenty to measure; the energy released was the overall central parameter, which could be inferred in many different, independent ways. Each measurement had its particular difficulties, but one was common to all of them: the experiment could not be repeated. If something failed, there was no second chance. This was a most unusual condition for physicists and worried everybody. A second problem was that we did not know even the order of magnitude of several of the quantities to be measured; we thus required instruments or families of instruments able to cover a vast range.
In order to have at least an idea of the working conditions we could expect, we decided to set off a pile of ordinary explosive at the site of the future test and to make on it the same type of measurements we would later make on the atomic bomb. Although normal explosives could simulate only part of the effects—because, for instance, they do not emit neutrons or gamma rays—this was nevertheless better than nothing.
We were preparing this preliminary experiment when, on April 12, 1945 the laboratory's loudspeakers announced the sudden death of President Roosevelt. Everybody rushed into the corridors of the buildings; some seemed stunned, others were haggard or could not speak, and several had tears in their eyes.
The preliminary experiment was performed on May 7, 1945. While we were in the desert setting up the experiment, we received news of Hitler's suicide, of the surrender of Germany and of the end of the
war in Europe. One of my reactions was: "We have been too late." For me Hitler was the personification of evil and the primary justification for the atomic bomb work. I am sure that this feeling was shared by many of my colleagues, especially the Europeans. Now that the bomb could not be used against the Nazis, doubts arose. Those doubts, even if they do not appear in official reports, were discussed in many private conversations.
The efforts to complete the bomb, however, continued unabated. The nuclear explosives, plutonium and U235 , were by now arriving regularly from Hanford, Washington, and Oak Ridge, Tennessee, respectively. The Los Alamos personnel converted them into metal, shaped them, and prepared the ordinary explosive lenses for the implosion, the initiators, the fuses, and everything else required for the bomb, finally delivering a complete, working weapon to the military. The military were in charge of target selection, transportation, and delivery. Of course, political and strategic decisions on the use of the bomb could, under the U.S. Constitution, be made only by the president of the United States as commander in chief.
In July many of the scientists participating in the test moved to the desert. Our group was charged with measuring prompt gamma rays emitted at the instant of the explosion (as distinguished from those due to fission products) and the total gamma radiation at several distances, as well as sundry neutron intensities. We planned and built the instruments in the lab and then tested and calibrated them in the desert, readying them for the real test.
The New Mexico desert where we were working is not completely arid; on the contrary there is appreciable precipitation, but the rain is concentrated in very few violent storms, which in a few minutes can transform a dry arroyo into a turbulent stream carrying huge amounts of water. It is not rare for somebody to lose his car or even drown in crossing an arroyo that only a few minutes earlier was dry. I could not believe it, until once Elfriede and I had a narrow escape in such a stream in our car. The desert vegetation, often curiously adapted to the dry climate, is primarily shrubs and cactus, with some grass and no trees. Animals escape the sun by going underground. Many are nocturnal.
Rattlesnakes and other reptiles, such as gila monsters, as well as spiders, scorpions, and other unusual creatures are plentiful.
The final test received the code name "Trinity," and its appointed director was Kenneth Bainbridge, who seemed to me rather disorganized. He often changed schedules, and he posted his all-important daily orders in various places, so that we did not know where to find them. He ended by placing them in the lavatories, saying that everybody would see them there. Fortunately, Oppenheimer must have sensed the problem and gave Bainbridge as second in command J. H. Williams, who was excellently suited to handle a situation requiring the laying of many miles of cables, building roads and shelters and other civil engineering jobs. Bainbridge and Williams had to coordinate a very complicated operation subject to a tight schedule, involving laborers, military personnel, contractors, truck drivers, and prima donna physicists.
We physicists lived in separate barracks, identical to those of the military personnel, and we also enjoyed their excellent food. We started working intensely at daybreak. The early morning hours were the best; as the sun rose higher in the sky, the heat became oppressive, the light blinding, and we wilted. In the evening, we fell exhausted on our cots, only to start again the next sunrise. In this way we spent several days measuring the scattering by air and ground of gamma radiations emitted by a strong radioactive source simulating a bomb. Just as I had done many years earlier at the Officers' Training School in Spoleto, I took with me a French novel by Gide; it transported me into a world totally different from the one surrounding me.
On July 14, 1945, everything was finally ready for the test. In the evening a tremendous thunderstorm broke. I had gone to sleep, but soon I was awaked by a deafening noise, whose origin I could not grasp. I got up and found that Sam Allison too had arisen. We took a powerful flashlight and went out to see what was happening. We found that a hole near our barracks had filled with water, and in it thousands of frogs were celebrating a love feast. We returned to sleep still uncertain whether the weather Would allow the test, but shortly the announcement that the test would proceed at daybreak woke us up.
Oppenheimer, General Groves, and many other authorities went to
previously assigned observation places. I was with Fermi, in the open, at about ten miles from the explosion. As a precaution we were lying down on the ground, and we had very dark glasses to protect our eyes. Suddenly the whole landscape was inundated by an extremely bright light, incomparably brighter than that of the normal explosive we had tested in May, and that looked, and was, much brighter than sunlight at noon. In fact, in a very small fraction of a second, that light, at our distance from the explosion, could give a worse sunburn than exposure for a whole day on a sunny seashore. At the moment of the explosion, for an instant, the thought passed my mind that maybe the atmosphere was catching fire, causing the end of the world, although I knew that that possibility had been carefully considered and ruled out.
Immediately after the explosion, Fermi stood up and dropped some small pieces of paper, which instead of falling straight down were shifted when the shock wave reached us. Fermi measured the shift and pulled out a sheet of paper on which he had a calculated table of the shift as a function of the energy released. He thus obtained an instant estimate, albeit crude, of the explosion's energy.
For the rest of the day, we collected the data registered by the different instruments and prepared to return to our base at Los Alamos. This work lasted until late in the evening, when, dog tired, we departed for our mesa. After several hours of driving, we arrived at Los Alamos's guarded gate, where a sentinel stopped us. After some discussion the post commander decided to let the civilians in, although it was past midnight, the official time at which the gate was closed, but he was adamant in refusing entry to the military because they had no regular pass. I had with me a pair of young members of the SED (Special Engineering Detachment) and found it preposterous, after such a day, to prevent them from sleeping in their regular barracks. I started arguing and at the same time initiated a surreptitious march toward an emergency telephone I had spotted and that I knew connected directly to the top military commander at Los Alamos. When I came within reach, I deftly grabbed it and instantly had the commanding colonel on the line. He sounded sleepy, and I fear I had awakened him. In a few words I explained the predicament. He then summoned the commander of
the guard to the phone and ordered him to let my men in. The commander of the guard, although obviously annoyed, had to obey. Next day, however, the colonel's adjutant telephoned me wanting to know the names of the SED men who had been with me the previous night. I suspected somebody wanted revenge on such small fry for the disturbance of the colonel's slumbers. I acted surprised and insisted I could not remember the incident. That closed the episode.
The bomb test had succeeded beyond expectation and the energy released was near the maximum anticipated. Although what had happened at Alamogordo was a secret, several persons had seen the light of the explosion from a great distance, and among the people who had stayed at Los Alamos at the time of the test, there was the feeling that something extraordinary had happened. At the test site it was strictly forbidden to take pictures of the event, but somebody had smuggled in cameras, and a young SED man in my group took color pictures of the explosion. On his return to Los Alamos, he developed them and they were ready before the official ones. He showed them to me, and to avoid trouble we went to Oppenheimer and gave him a copy. I believe it was immediately dispatched to President Truman. The young photographer, however, was not permitted to profit in any way.
About the time of the Trinity test, there was intensive political activity in several laboratories connected with the bomb. The Chicago scientists especially, goaded by Szilard, tried to influence the use of the bomb. Fermi was involved in high-level committees on the subject, and I gave him my own opinions, but I was not aware of what was going on behind the scenes in Washington and elsewhere. Fermi spoke to me admiringly of General George Marshall, of his speed in comprehending difficult and new problems and of his sureness of judgment in very complicated situations. Considering the times and circumstances, I can hardly see how President Truman could have acted very differently from the way he did.
We celebrated Japan's surrender by taking the day off. Elfriede, Fermi, and I drove to the Valle Grande, where we took some pictures that have been reproduced many times. In the same period, Fermi told me that he expected to become a celebrity and asked me to take pictures
of him for the public. Thus we took a whole roll of thirty-six Leica pictures in my office at Los Alamos.
I have been asked innumerable times my thoughts immediately after the bomb's explosion and in the following days. I did not jot them down at the time and recollections would probably be distorted. I certainly rejoiced in the success that crowned years of heavy work, and I was relieved by the ending of the war.
I cannot remember my long-range thoughts; during the war I was mostly concerned with its progress, and with personal plans for the immediate future. More general ideas evolved with time and should always be dated in reporting them. There was optimism for the future in the sense that one trusted mankind's rationality more than was warranted. The confidence in and expectations of the League of Nations after the first world war and the United Nations after the second show how optimistic mankind can be and also how ready to bank on utopian dreams.
Many scientists, like everybody else, nurtured illusions about the farsightedness, intelligence, and reasonableness of their fellow men. Some politicians too were simpleminded, others cynically believed they could preserve technical advantages that were by nature transient. The technical people knew that the bomb could not remain an American monopoly, and I, like many others, gave the authorities that questioned me a correct estimate of the time required before other countries would have the same weapon.
With over forty years of hindsight, it seems to me that most developments were unpredictable and often depended on accidents. Politicians do not come out well as far as intelligence and farsightedness are concerned, and they often acted on erroneous information. Be this as it may the Bomb possibly had the beneficial effect of preventing major wars between the superpowers, by inspiring mutual terror.
During our stay at Los Alamos, we became U.S. citizens. We had applied for citizenship in 1939, and after the statutory period an examiner came to question us. He could not enter Los Alamos, so the examination took place in a guard post at the gate. The examiner started
with Elfriede, McMillan acting as witness. The examiner asked her: "Do you believe in polygamy?" Elfriede: "No"; the examiner then turned to McMillan, who confirmed: "To the best of my knowledge, no." After several questions to Elfriede on American government and the Constitution, the examiner turned to me. By then it was about noon, and the examiner wanted to quit. He said: "I am sure that a person like you, before coming to the United States, has studied its Constitution and has informed himself in detail about it." I assented to this flattering surmise, and this ended my examination. A few weeks later we were sworn in at the superior court in Albuquerque, and the judge proclaimed us citizens of the United States. After the ceremony we returned home by a splendid detour along the Jemez. A few days later, however, a very apologetic and embarrassed judge telephoned me to say that he had to set aside the citizenship decree because he had overlooked the fact that the law prohibited naturalization decrees for a certain period before a presidential election. He begged me to take the nullification in my stride and not to raise a fuss, promising to remake me a citizen immediately after the election. Naturally, I agreed, and thus we became citizens twice. However, during the period when I believed I was a citizen thanks to the invalid decree, I had signed some patent affidavits swearing that I was a citizen. I asked the patent lawyer what to do. He told me to sit tight, and that if and when a problem arose, "We shall ask the Supreme Court."
With the end of the war, we started thinking and talking seriously about our immediate futures and long-range plans. I decided to continue my university career rather than stay permanently at Los Alamos, as I could easily have done. However, I did not have a university base, a fact that produced much uncertainty, as the next chapter will show.
Fermi was leaning toward moving permanently to Chicago, but, as usual, what interested him most were scientific projects. He sensed that the future was with particle physics and with a sardonic smile quoted the Duce's motto "Either renew yourself or perish." I had less
futuristic thoughts. One expected great progress in neutron physics from the use of nuclear reactors; above all I would have liked to return to work on transuranic elements.
In the next chapter I shall tell the reasons and the events that made me return to Berkeley.
Our family was increased on November 7, 1945, by the birth of a second daughter. We named her Fausta to welcome her, and as a second name we called her Irene, as a wish for peace. My five years of Latin and Greek study finally served for something. . . .
We left Los Alamos in the middle of January 1946. Elfriede, Amelia, and Fausta flew. I went by car with Claudio, who was then about nine. On the trip I let Claudio drive for long stretches of the Arizona highways. He did very well, and I could even slumber while he drove. We briefly visited the Grand Canyon, and along the way I was amazed by the huge number of military airplanes parked in the desert wingtip to wingtip, visible proof of America's colossal industrial power.
Some of the members of my group remained at Los Alamos. Others went to St. Louis. Wiegand came with me to Berkeley to finish his studies; Deutsch returned to MIT; Chamberlain and Farwell went to Chicago to work for their doctorates under Fermi, who had accepted them on my recommendation.