Before daybreak on July 16th 1945 Enrico Fermi lay down in the open desert of New Mexico. At 05:30, the world’s first nuclear explosion took place ten miles (16km) away. He counted off the seconds after the flash, anticipating the arrival of the blast-wave. With preternatural calm, Fermi stood up and let some strips of paper flutter away as the wave passed. They flew about eight feet. The Trinity nuclear test, he pronounced after making some quick calculations, had released the equivalent of about 10 kilotonnes of TNT.
Fermi was, by that stage, already a celebrity among physicists. An obvious mathematics prodigy as a child in Italy, he had devoured texts written for adults. Throughout his life he kept few books, preferring to derive conclusions from first principles whenever he felt the need.
As he took up different posts in academic research in Italy and abroad, Fermi showed himself to be not only a theorist with unparalleled insight but also adept as an experimentalist (a rare combination) across every kind of physics. He had an uncanny knack for rough-and-ready calculations to obtain approximate answers for damnably difficult questions (the Trinity bomb, later analysis revealed, released 18 kilotonnes of TNT, which was surprisingly close to Fermi’s desert estimation).
He eschewed complexity, preferring to tackle only a problem’s essentials, discard any distracting elements and ruthlessly squeeze what remained. Such back-of-the-envelope calculations, which became known as “Fermi problems”, were such good examples of critical thinking that recruiters nowadays test applicants’ mettle by setting them as interview questions. Fermi’s solutions were so often right that his colleagues in Rome called him “the pope”. His boss recognised that he could help raise the reputation of Italian science.
Fermi’s discovery of how slow-moving neutrons helped to make some atoms radioactive won him the Nobel prize in 1938. He used the trip to Stockholm to abscond with his family from his increasingly fascist homeland. Once in America he became involved in the Manhattan Project, which led to the first nuclear bomb, bringing him renown well beyond the physics community.
Fermi was an inveterate showman. In Chicago, on the day he demonstrated the world’s first controlled nuclear chain reaction—a prerequisite for the uncontrolled kind in a nuclear weapon—he ran the show like a circus ringmaster, ramping up the tension by calling for lunch just as things literally heated up.
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