The Age of Radiance (12 page)

After decades as an academic backwater, Italian science was suddenly, all through Corbino’s efforts, now at the global forefront. The Italians were honored with overseas invitations to learn state-of-the-art experimental technique, with Amaldi off to Leipzig, Segrè to Hamburg, and Rasetti voyaging first to California and then to Berlin to work with the acclaimed Lise Meitner. The University of Michigan invited Fermi to teach summer school in 1930; he loved Ann Arbor so much he returned every few years. Segrè:
“Mechanical proficiency and practical gadgets in America counterbalanced to an extent the beauty of Italy. . . . We bought a car, the Flying Tortoise, which we drove back to New York, not without some mechanical difficulties along the way. These did not scare Fermi, who is a good mechanic. Once at a gas station he showed such expertise in repairing the automobile that the owner instantly offered him a job. And these were depression days.”

Ragazzi Corbino
—“Corbino’s boys”—became so close that they developed their own accent. College friends Fermi and Rasetti, imitating each other, jointly evolved a deep speaking voice and a slow, modulated cadence that was in turn adopted by all of their professional colleagues. One of them was riding the train and started chatting with a seatmate, who quickly asked if he was a Roman physicist. The stranger said he recognized “your way of speaking.”

Teaching quantum theory as Rome’s first atomic physicist, Enrico was nicknamed the Pope, since it took such profound faith to believe that matter was energy, energy was matter, and that both were sometimes particles and at other times waves. Rasetti was the cardinal, and Segrè, known for his temper (and for breaking furniture as a result of that temper), was the basilisk, a mythical creature whose eyes were alight with fire. The department was housed in an 1880 monastery on via Panisperna 89a, with ocher walls, tile roofs, and a cupola. Gabriel Maria Giannini: “Everything around us was moldy with its eight hundred years, and we were young—bound together by youth and by Fermi’s ageless thinking, which managed to find expression in
spite of the sound of the church bells pouring in torrents from a Romanic tower next door.” Emilio Segrè:
“The location of the building in a small park on a hill near the central part of Rome was convenient and beautiful at the same time. The garden, landscaped with palm trees and bamboo thickets, with its prevailing silence . . . made the Institute a most peaceful and attractive center of study. I believe that everybody who ever worked there kept an affectionate regard for the old place, and had poetic feelings about it.” One neighbor was G. C. Trabacchi, chief physicist of the Health Department, who shared his excellent collection of instruments and materials with untoward generosity, earning him the Fermi-engineered nickname Divine Providence. Trabacchi was especially providential when he loaned Fermi the radon-gas effluence of a gram of radium, which was at the time worth around $34,000. Hans Bethe (
Beta
), who won a Nobel for his fusion theory on the origin of starlight and who would become the chief of the Los Alamos theory group (inadvertently thrusting Edward Teller into a career combining Dr. Strangelove with Ronald Reagan), spent most of 1931 with the Fermi team:

Fermi worked in the Institute of Physics, which was on a small hill in the middle of Rome, surrounded by a sea of traffic but very quiet on that little hill. There were trees, ponds, a nice garden, a fountain—really quite an oasis in the hectic traffic of Rome. Fermi was twenty-nine years old when I got there. He was a full professor since he published Fermi’s Statistics at the age of twenty-five.

I had studied with [Arnold Sommerfeld, one of the cofounders of quantum mechanics], and Sommerfeld’s style was to solve problems exactly. You would sit down and write down the differential equation. And then you would solve it, and that would take quite a long time; and then you got an exact solution. And that was very appropriate for electrodynamics, which Sommerfeld was very good at, but it was not appropriate at all for nuclear physics, which very soon entered all of our lives.

Fermi did it very differently. . . . He would sit down and say, “Now, well, let us think about that question.” And then he would take the problem apart, and then he would use first principles of physics, and very soon by having analyzed the problems and understood the main features, very soon he would get the answer. It changed my scientific life. It would not have been the same without having been with Fermi; in fact I don’t know whether I would have learned this easy approach to physics which Fermi practiced if I hadn’t been there. . . .

Fermi seemed to me at the time like the bright Italian sunshine. Clarity appeared wherever his mind took hold. . . . Depending on how we count, Fermi training led to ten, eleven, or twelve Nobel Prizes. I estimate the probability that an existing Nobel Prize winner in physics “gives birth” to another winner is less than 1/10. So if this is purely random, the probability of one winner giving birth to ten other winners would be one-tenth to the tenth power or one in 10 billion, which is essentially impossible.

Physics seemed to infuse Fermi’s every waking moment, as American physicist Phil Morrison remembered from his time with Enrico:
“I want to mention the ‘Fermi Questions.’ Fermi was the first physicist to my knowledge who enjoyed doing physics out loud walking through the hall. . . . As we walked, the sounds of our footsteps reflected off the high surface—wood, no acoustic treatment—and seemed to bounce throughout. And he said, ‘How far do you think our footsteps can be heard in this building?’ And then he began to tell me what the yield of sound would be from the impulse, how far that would go, how you have to worry about the wood conduction and the air passage. And pretty soon, by the end of the hall, he had [an answer]. It was a fast calculation. Sounded very reasonable. And when I tried to recalculate it, I got something like the same result—slowly and looking at the numbers over and over again. This was my idea of a Fermi Question: Turn every experience into a question. Can you analyze it? If not, you’ll learn something. If you can, you’ll also learn something.”

At that moment in the nuclear science of the 1930s, there was a whole series of astonishing new questions to answer. Inspired by Fred Joliot and Irène Curie’s revelations, those who’d taken an interest in radioelements began to focus on the atom’s nucleus as the source of uranic powers. This was a difficult proposition, as physicist Amir Aczel noted, since
“if an atom were the size of a bus, than the nucleus would be the dot on the letter
i
in a newspaper story read by a passenger on the bus.” Hitting that dot on the letter
i
would make Enrico Fermi a laureate. His efforts began in 1934, when he combined the Joliot-Curie method of artificial irradiation with Chadwick’s neutron discovery and his own theory of the weak force to imagine a tiny, uncharged particle that would not be waylaid on its path to crashing into an atom’s nucleus. Neutrons fired in the right way, Fermi believed, should be able to excite radiation and produce isotopes—subatomic variations of elements—on just about any member in good standing of the periodic table. Hans Bethe:
“Fermi organized a group to do this—of course, his
old collaborators and friends, but they added d’Agostino, who was a chemist, and most importantly, Trabacchi, who was a biophysicist in charge of the biophysics in the Department of Health of the City of Rome. He had a very precious possession, namely one gram of radium. And radium produces all the time radon, a gas, which can easily be separated because it escapes from the radium, and then you can expose any sample you want to the alpha rays from radon.” Emilio Segrè:
“Radon plus beryllium sources were prepared by filling a small glass bowl with beryllium powder, evacuating the air, and replacing the air with radon. Rasetti was vacationing in Morocco so Fermi, Amaldi, and Segrè got to work. Fermi did a good part of the measurements and calculations; Amaldi did the electronics; and I secured the substances to be irradiated, the sources, and the necessary equipment.”

It was a good thing these physicists were young and in shape, as this turned out to be a multistage investigation requiring a great deal of sprinting. Bombarding beryllium with radon produced neutrons, which Fermi and his team would in turn use to irradiate as many elements as they could get, to dramatically extend the Joliot-Curie findings of man-made radiance. Making neutrons from radon-charged beryllium, however, triggered their homemade version of Geiger counters that would be used to measure whether they’d succeeded in creating isotopes, making it look as though everything was already radioactive (Geigers weren’t yet commercially available, so every scientist working on radiation crafted his or her own). To keep this from affecting their results, Fermi and his grad students would bombard the test element with their neutrons in one room, then run the irradiated subject to the other end of the hall to measure it with the counters. Bethe:
“The experimenters had to run as fast as they could along the second-floor corridor from the exposure place to the counter. . . . I believe Fermi had the record of time of running from one place to another. There was a visit one time from a very dignified Spanish physicist, who wanted to see His Excellency Fermi, and he was shown a man in a very dirty lab coat, running like mad along the corridor.”

They began at the beginning, with the periodic table’s slot number one—hydrogen—and proceeded up the grid: oxygen, lithium, beryllium, boron, carbon. Nothing worked. Even with Trabacchi’s precious seed as a source, they could find no induced radiance. Element after element failed, then failed again, then again and again . . . until they got to fluorine. From then on, the success rate was incredible: out of sixty elements tested, forty could be alchemized into radioactive isotopes. Joliot-Curie’s quirk of happenstance had been turned by the Fermi team into a scientific procedure.

When Fermi’s team bombarded uranium, their chemical tests showed its nucleus capturing the neutrons, spitting out photons of gamma radiation, and becoming heavier, turning into an isotope with an atomic number (in protons) of 93 and an atomic weight (in protons and neutrons) of 239—an element that had not yet been discovered. Would this be as epochal as the Curies’ discovery of radium? The Nobel committee thought so, as did the Fascists. But Fermi wasn’t absolutely sure since the chemistry needed for proof was inconsistent. Even so, on October 22, 1934, a professional’s intuition would trigger the discovery of a fundamental ingredient in the birth of nuclear power.
“One day, as I came to the laboratory, it occurred to me that I should examine the effect of placing a piece of lead before the incident neutrons,” Fermi remembered. “Instead of my usual custom, I took great pains to have the piece of lead precisely machined. I was clearly dissatisfied with something: I tried every excuse to postpone putting the piece of lead in its place. When finally with some reluctance I was going to put it in its place, I said to myself: ‘No, I do not want this piece of lead here; what I want is a piece of paraffin.’ It was just like that with no advance warning, no conscious prior reasoning. I immediately took some odd piece of paraffin and placed it where the piece of lead was supposed to have been. About noon everyone was summoned to watch the miraculous effects of the filtration by paraffin. At first I thought the counter had gone wrong because such strong activities had not appeared before.”

Hans Bethe:
“Neutron research led to many surprises. It turned out that if you (as I remember it from the tales, since I wasn’t there) put the sample on top of a wooden table, the radioactivity was stronger than if you put it on top of a marble table. Of course, everything in Rome was of marble, if it wasn’t of wood. And so, I guess they got the idea that maybe different surroundings might make a difference, and so instead of using a lead box around the sample, they decided to use a paraffin box. And the paraffin box was tremendously effective. The radioactive count increased about 100-fold with most of the elements. That was a great surprise, of course. And Fermi, having discovered that in the morning, went to lunch, and over lunch he decided what was the reason for it. . . . The hydrogen, which was in paraffin and in wood, would slow down the neutrons.” The slowing down made neutrons more likely to collide with neighboring nuclei, and more likely to sustain a chain reaction. Laura Fermi:
“Physics was comprehensible, as long as atoms were small planetary systems and discoveries could be made in goldfish ponds . . . like the discovery of slow neutrons. . . . Back in the laboratory after their siesta, the group decided to test Fermi’s theory using the most
abundant hydrogenated substance at hand; and so they plunged neutron source and target in the goldfish pond at the back of the old physics building. Lo and behold! Fermi was right. Water too increased the radioactivity in the target by many times.”

After the Fermi team announced that bombarding uranium produced short-lived transuranics—an array of isotopic variants that, to the inexperienced radiochemists of the time, appeared to be innumerable—the University of Rome experiments were taken up by the Joliot-Curie team in Paris, and by Lise Meitner and Otto Hahn in Berlin. Racing to uncover uranium’s secrets, the three labs appeared to generate more and more transuranes, with ever more half-life decays. The method used by modern science, especially within a focused group such as this—sending details of experiments and results to each other, publishing findings as soon as possible, colluding and at the same time rapaciously competing to be first with a groundbreaking discovery—would in the web argot of the next century be called hive mind, a collective effort of human brainpower that would create far more than any one person or team could achieve alone. Scientists have been hive-minding, it turns out, since the Royal Academy began publishing during the Enlightenment.

By the end of 1935, however, the
ragazzi
Corbino
were undone, with Rasetti at Columbia, Segrè at Palermo, Pontecorvo in France, and the atmosphere in Italy relentlessly gloomy as the country prepared for war in Ethiopia and the limitations brought by globally imposed sanctions. Only Amaldi and Fermi remained in the department of physics’ garden monastery.