The Last Man Who Knew Everything: The Life and Times of Enrico Fermi, Father of the Nuclear Age. By David Schwartz. Basic Books; 451 pages; $35 and £27.99.

JUST 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.

David Schwartz, the author of “The Last Man Who Knew Everything”, is the son of another Nobel-winning physicist. His father left some intriguing correspondence on Fermi, which inspired Mr Schwartz to learn more. He interviewed many of Fermi’s students and colleagues, shedding light also on Fermi the educator (his lectures were so renowned that even notes taken by his assistants were a bestseller).

Mr Schwartz deftly conveys the aesthetic beauty of Fermi’s insights without getting mired in their minutiae. His book includes only enough scientific detail to explain each discovery as it happened. Fermi is depicted as a natural leader—in the laboratory, on hiking trails near his workplaces in Rome and New Mexico, and in the square-dances he came to love in America. Yet for all his gregariousness Fermi tended to reveal little of his emotions in conversations or correspondence, even as he worked on the team to develop humanity’s most terrible weapons. Laura, his wife, did not know until after the bombs fell just what her husband had really been up to in his laboratory.

As a result, Mr Schwartz tussles with many of the same questions that have dogged previous Fermi biographers. Did he stay so long in Italy, joining Benito Mussolini’s vaunted Accademia d’Italia, just for the funds and freedom to pursue his precious research? Did he participate in the Manhattan Project out of patriotism for his adopted country, or was he dragged along because of his expertise in nuclear physics? Or was he just insatiably curious about whether the bomb could indeed be made?

It would be easy to depict Fermi as a standard reticent genius who solved every problem as if he had, as one student put it, “an inside track to God”. But Mr Schwartz’s sleuthing also reveals how science works in its proper context: how each finding builds on the last; how identical ideas can occur to more than one person when the intellectual conditions are right; how an insight into nature arises not from a vacuum but from hard-won experience and, usually, some clever calculating.

Fermi was once described by a student as the last man who knew everything. He went on to make important discoveries in particle physics, geophysics and even the science of the stars. And he never stopped calculating. Even on his deathbed, he used a stopwatch to determine exactly how much fluid he was receiving from his intravenous drip. It was a simple problem, really, if you focused on the essentials.