Out from the Cold

books & arts Out from the cold Half-Life: The in Italy, this environment was the catalyst for MI5 started to take a keener interest in his Divided Life of shaping his communist beliefs. Pontecorvo political leanings. After concluding that it was Bruno Pontecorvo, also met his future wife, Marianne Nordblom. “difficult to regard a man with Pontecorvo’s Physicist or Spy War broke out soon after they had their first international outlook and family history child, and following the Nazi occupation of as reliable” for sensitive nuclear projects, a By Frank Close Paris they fled to the USA in 1940. face-saving solution was engineered, in the form of a professorship at the University of BASIC BOOKS: 2015. Liverpool. But Pontecorvo never took this 400 PP. £20 appointment: in that fateful summer of 1950, midway through a family holiday in Italy, he abruptly headed to Stockholm and onwards through Finland to the Soviet Union, only to runo Pontecorvo’s defection to the resurface publicly five years later. Soviet Union in 1950 is one of the more / ALAMY © RIA NOVOSTI What triggered Pontecorvo’s sudden flight? Bsingular events in the history of Cold War There is no smoking gun to prove that he ever science. A talented physicist who had been passed secrets to the Soviet Union. But Close involved in wartime nuclear research, his concludes that the kaleidoscopic body of abrupt decision to flee behind the Iron Curtain facts surrounding his defection only falls into with his family is shrouded in mystery. Was place once one accepts the hypothesis that Pontecorvo a Soviet spy or an idealist looking he had been a spy prior to 1950 — any other to escape anti-communist hysteria in the interpretation requires an unwieldy number of West, consciously choosing to live in Russia? additional explanations, akin to the epicycles In Half-Life, Frank Close, a professor of invoked by medieval astronomers looking to physics at the University of Oxford, sets In the USA, Pontecorvo developed the keep the geocentric model of the Solar System out to answer this question. He does so by first industrial application of neutrons consistent with observation. Moreover, Close painstakingly bringing together evidence from for geophysical prospecting, by looking has also uncovered a letter from the British archives, letters and interviews with surviving at how they interact with different rock embassy in Washington to the Director family members and scientific colleagues. As formations and working out when there General of MI5 in London, raising concerns one might expect for an unsolved Cold War was oil underground. Soon after, in 1943, about Pontecorvo’s political views stretching mystery — especially one involving secrets he was co-opted into the Anglo-Canadian back to his days in the USA. Close contends about the nuclear bomb — others have already arm of the Manhattan Project by an old that this would have gone through Kim Philby, investigated and written about Pontecorvo’s Parisian contact, and moved to Chalk River the double agent who was stationed in defection, most notably Simone Turchetti in Laboratories to work on the ‘pile physics’ Washington at the time, who would have The Pontecorvo Affair (Univ. Chicago Press, of nuclear reactors. During this time he tipped off Moscow; in turn, the Soviets 2012) and Miriam Mafai in Il Lungo Freddo had access to classified information that would have warned Pontecorvo that his cover (BUR, 2012). What sets Close’s work apart would have been of interest to the Soviets, had been compromised and facilitated his is that, in addition to bringing to light new and Close presents a body of circumstantial defection. Thus began the second half of his archival material obtained from the UK evidence suggesting that he might indeed life, as a research scientist in Dubna. intelligence agency MI5, it also describes have been leaking this information. Whereas the book will inevitably attract in detail the context and significance of After the war ended in 1945, Pontecorvo readers interested in a good story about Pontecorvo’s research over the course of his remained in Canada and devoted himself to espionage, Half-Life is also a masterful career. The result is, if not quite the solution pure science: it is during this period that he reappraisal of Pontecorvo’s scientific to the mystery of Pontecorvo’s sudden proposed, with input from his colleagues at achievements. Although his most famous disappearance, certainly an exhaustive analysis Chalk River, the chlorine–argon method for work is on neutrinos — their co-existence with of the factors that would have precipitated it. detecting neutrinos, and suggested that the muons and oscillating nature are two of the Pontecorvo was born into a wealthy Jewish Sun would be a considerable source of these more famous insights he made during his time family near Pisa, Italy, in 1913. After studying ghostly particles. He also made pioneering in Dubna — what is most striking is the sheer with Enrico Fermi in Rome, where he insights, at least on a qualitative level, breadth of Pontecorvo’s work over the course participated in pioneering experiments with regarding the existence of the weak force. of his entire life. In Ugo Amaldi’s words: “How slow neutrons, he won a scholarship in 1936 Close describes these discoveries in detail, many have made great contributions in both to work in Paris with Irène and Frédéric Joliot- and is almost forensic in breaking down theory and experiment? Fermi, Rutherford, Curie, who had just received the Nobel Prize precisely which aspects can be credited to Pontecorvo — not many at Nobel level.” That in Chemistry for their work on radioactive whom, but his admiration for Pontecorvo he was never awarded the prize may have elements. Pontecorvo’s time in Paris was the physicist is clear. been the price for his flight to the USSR, eventful. In addition to working on nuclear After his stint in Canada, Pontecorvo suggests Close. He leaves us in no doubt that isomerism, he came into contact with a vibrant moved to the UK in 1949, to work for the he would have been a worthy recipient. ❐ and cosmopolitan political scene. Having Atomic Energy Research Establishment already embraced the antifascism movement in Harwell. And it is at this point that REVIEWED BY ANDREA TARONI NATURE PHYSICS | VOL 11 | MARCH 2015 | www.nature.com/naturephysics 207 © 2015 Macmillan Publishers Limited. All rights reserved.

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