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The life of Enrico Fermi: phase four

Fermi’s arrival in the United States of America coincided with news of the discovery of nuclear fission by a small group of German physicists. Fermi realized that he and the Boys of Via Panisperna had split the nucleus of uranium into two large pieces during their experiments, even though they hadn’t known it at the time. It was evident that the enormous amount of energy predicted by Einstein could be released by the process of fission of uranium.

The beginning of WWII and the dangerous advance of nazi-fascism put great pressure on research into the use of nuclear energy for military purposes. The news came out of Germany that the greatest German physicist at the time was working on a nuclear fission weapon. All the physicists who had escaped to the US, Fermi included, were alarmed. Albert Einstein wrote a letter to President Roosevelt, warning him of the danger that would be created by the probable construction of a German nuclear weapon, giving Hitler the possibility of conquering the world.

So President Roosevelt gave direction of the Manhattan Project to the military to build a fission bomb. The entire community of US physicists was involved.  Fermi had a major role in this project. At first he worked in the labs at Columbia University in New York on producing nuclear chain reactions. Then, in 1942, his group’s activity was transferred to the University of Chicago. Built in the gym underneath the stadium, the nuclear pile Chicago Pile One began operating under Fermi’s precise and omnipresent direction in December of 1942, remaining active for 28 minutes. This was the world’s first experiment in self-sustaining nuclear fission. In a cryptic phone call, the Nobel prizewinner, Arthur Compton, announces the success of the experiment to James Conant, president of the National Defense Research Committee:

(second male voice) “The Italian navigator just landed in the New World.”

The story was told many times by Fermi’s wife, Laura.

(first female voice) “One of the physicists gave Enrico a flask of Chianti: the gift was a sign of special appreciation for the homeland of he who received it. All those present drank in silence, with no toasts, then everyone put their signatures on the straw wrapping of the flask.”

July 11, 1944. Fermi receives American citizenship and in September moves to the desert of Los Alamos where he’ll give important contributions to the building of the atomic bomb and where he’ll remain under military secrecy until the end of the war. “The Last Man Who Knew Everything”, as his biography is titled, will dominate every aspect of the project whether experimental, technological or theoretical and it’s to him that anyone with a problem would turn to find a solution.

Laura speaks again:

(first female voice) “I learned not to ask questions. No more “What are you doing today or How did work go or Who are you working with?”

At war’s end it was time for future projects. Fermi founds a new school, The Chicago School, and many of his coworkers and students will go on to become successful physicists and Nobel prizewinners. They’ll continue to develop many different avenues of research, always approached with a method that preached “don’t do anything with more than the barest minimum of precision”; this unique approach allowed him to offer various key suggestions to future Nobel winners.

He becomes a consultant to the US government even though he was not in favor of using nuclear energy for military purposes. He took up regular correspondence with Italy again, contributing to relaunching research in our country. His famous conferences held at the school of Varenna in 1954 are memorable. November 28 of that same year he died of cancer. He was only 53 years old. His friend Emilio Segrè would say of him:

(second male voice) “Nobody except Fermi knew how to dominate those highest peaks.”

The Manhattan project

War and science

In October of 1939, Albert Einstein signed a famous letter, written together with Leo Szilàrd and addressed to the then-US president, Franklin Delano Roosevelt, warning him of the probable construction by the Germans of a nuclear weapon that could allow Hitler’s Germany to conquer the world. Szilàrd, a Hungarian physicist, had the intuition of the possibility of chain reactions and began to work with Enrico Fermi as soon as Fermi stepped off the boat in New York to try and create it.

President Roosevelt decided that the letter required action and authorized the creation of an Advisory Committee on Uranium whose first result was to demonstrate the greater capacity for fission of the uranium isotope U-235 over the better known U-238. U-235 is present in nature in only tiny amounts, around 0,7%, while U-238 is far more abundant. The interest in U-235 lies in the fact that it’s the only naturally occurring fissionable isotope; in other words, it has a strong tendency to split if bombarded with thermal neutrons and its fission is accompanied by the emission of a sufficient number of neutrons to start a chain reaction.

The National Defense Research Committee was then created and following that, the Office of Scientific Research and Development.

Work proceeded very slowly until that dawn of December 7, 1941, when Japan dragged the US into WWII with its famous attack on Pearl Harbour.

From that moment on everything changed and nuclear projects sped forward because they suddenly assumed a strategic military importance for the United States of America. The Uranium Commitee was substituted by the Executive Commitee, approved by President Roosevelt, contingent upon the construction of the first atomic bomb. The responsibility of its development and implementation from an engineering and industrial standpoint was given to the military. The Manhattan Project began modestly in 1939 but grew to employ more than 130,000 people at a cost of almost 2 billion dollars (equivalent to around 23 billion dollars today).

The Manhattan Engineer District, which had the job of building the bomb, was created under the command of general Leslie Groves. The uncertainty of the size of the project, the scientific and technological diffculties and the underestimation of its costs were truly enormous: the scientists were working in unexplored terrain that had previously existed only science fiction books. After Fermi’s first chain reaction in Chicago in 1943, the town of Oak Ridge in Tennessee was chosen to build the facilities that would have the objective of separating the isotope U-235 from U-238 to be utilized in the development of nuclear arms.

Because it was so easily fissionable, the element plutonium, a fundamental component of modern nuclear weapons, was also put into production.

In short order, Oak Ridge grew into a city of more than 50,000 inhabitants complete with stores, schools, and dance halls. The path chosen by the US included collaboration with public and private organizations, research centers, businesses, military personnel, scientists, technicians, and entrepreneurs. With great concentration and effort, the men and women of that time were coming into a new awareness of the atom that would change human history forever.

Los Alamos

The atomic bomb

 

In 1943 the US War Department expropriates every remaining farm in an area of the New Mexico desert known today as Los Alamos. That fairly isolated area would be used for the super secret Manhattan Project. Structures for research and development were quickly built and scientists and engineers from all over the world were assigned to the project but all information on the city and its project were held under tight secrecy. The Los Alamos laboratory director was American physicist Robert Oppenheimer who, with the help of the greatest American and European physicists, designed the actual bombs. Among the ex-Boys of Via Panisperna besides Enrico Fermi, Emilio Segrè participated in the endeavor; Franco Rasetti did not take and Bruno Pontecorvo, looked upon with suspicion by the military for his communist sympathies, wasn’t invited.

The Manhattan Project was anything but a one-man show. Hundreds of scientists in Los Alamos, Chicago, and Oak Ridge not to mention thousands of technicians, construction workers, human “calculators”, secretaries and low-level military personnel all contributed their efforts. Many of these thousands of people only learned the real reason for their work in August of 1945 when President Truman announced that the bombs had been dropped on Japanese cities. It’s difficult to imagine how the Manhattan Project could have been completed without the other scientists essential to its realization: Bethe, von Neumann, Alvarez, Segrè, Serber, Bainbridge, Feynman, Neddermeyer, just to cite a few of the hundreds of brilliant physicists that came to that high plateau of Los Alamos to build the bomb. Fermi’s work was fundamental to their success. Historians maintain that without Fermi the Manhattan Project would have progressed much more slowly and certainly in different ways. Fermi was in fact one of the key physicists of the whole project: he didn’t invent the bomb but he and Szilárd certainly did invent the nuclear reactor. 

The choices regarding the use of the bomb after Germany’s capitulation were made at the highest levels with only superficial attention paid to the opinions of scientists. The new US president, Harry Truman, coming into power after Roosevelt’s death a few months prior, knew that he alone had the responsibility for the decision to use these weapons against enemy cities or not. For better or worse, Fermi and the other scientists involved in the project had changed the future of humanity: they had to assume, however, an enormous responsability, particularly because of the dramatic context in which they had worked.

Oppenheimer, commenting on the bombing of Hiroshima and Nagasaki, said:

“In a certain basic sense that no vulgarity, humorism or exaggeration can dissolve, these physicists have known sin; this is a knowledge that cannot be lost.”

David Schwartz, writing in his biography “The Last Man Who Knew Everything”

“As Fermi understood from a young age, one of the main points of the revolution in physics of the 20th century was the enormous energy hidden within matter, energy that would have blown to bits the first physicist to release it. He never imagined that destiny would have given him the role of that first physicist. If every great gift has a price to pay, this was certainly one of the greatest: the field that he loved and pursued with such passion his whole life revealed one of Nature’s secrets that gave man the ability to destroy the world.”