Victor F. Weisskopf (1908–2002) Reformulations of QED

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Obituary geniuses Richard Feynman and Julian Schwinger with their powerful, separate Victor F. Weisskopf (1908–2002) reformulations of QED. Weisskopf, who suffered from a lack of confidence in Victor Weisskopf, who died on 21 April at mathematics, did not publish, assuming the ripe age of 93, had, as he liked to put that he and French were wrong. They were it, “lived a happy life in a dreadful not — the other two had made the same century”. He knew what he was talking subtle mistake. FERMILAB/SPL about. He had been a major player in a The deep wounds inflicted on great voyage of discovery, and was always European science by the Nazis and the at the centre of a loving family and a vast nuclear arms race motivated many of circle of good friends. But he had also Weisskopf’s thoughts and actions after seen totalitarianism in Germany and the detonation of the atom bomb over Russia, and witnessed the first man-made Hiroshima. In 1946 he joined a small nuclear explosion. committee chaired by Einstein, the first of In 1928, Weisskopf left his native many platforms from which he spoke of Vienna to study physics at Göttingen, the danger posed by nuclear weapons. He Germany, where quantum mechanics had was a co-founder of the Federation of been born just three years before. It was American Scientists and the Union of already clear that the new mechanics Concerned Scientists. Starting with the could describe, at least in principle, any first Pugwash conference in 1956, he phenomenon involving particles moving pioneered relations with Soviet scientists with velocities that are small compared in pursuit of arms control. And it is no with the speed of light. Now the question coincidence that Pope John Paul II began was whether a successful marriage of to make forceful and widely publicized quantum mechanics with relativity could statements against the nuclear arms race be arranged. Paul Dirac had responded soon after Weisskopf’s election to the by inventing quantum electrodynamics Quantum theorist and Pontifical Academy. (QED), but it was soon realized that this inspiring leader Weisskopf never severed his strong ties theory faced potentially fatal problems. with Europe. He was delighted be to be It was to this fundamental issue that had been a misconception widely inferred named director-general of CERN (the Weisskopf repeatedly devoted himself. from Dirac’s theory. European laboratory for particle physics Today, QED and the theory of gravitation After Göttingen, Weisskopf had in Geneva, Switzerland) in 1961, are the most accurately tested theories of perhaps the most spectacular having answered questions about his physics — an outcome due in good part to postdoctoral career of modern physics, administrative experience with “none Weisskopf’s contributions. Willis Lamb, holding appointments with Werner whatever, my greatest strength”. He who did the most important experiment Heisenberg, Erwin Schrödinger, Pauli and proved to be an inspiring and effective in the history of the subject, wrote that Niels Bohr. In 1937, he left Europe for a leader, not only of CERN but of high- he based his analysis on “the 1927–34 position at the University of Rochester energy physics worldwide. Before long, formulation of QED due to Dirac, and began a long-term involvement with CERN and European high-energy physics Heisenberg, Pauli and Weisskopf”. nuclear physics. This culminated in the were on a par with competing research in Weisskopf’s first landmark result book Theoretical Nuclear Physics, written the United States, in good part thanks to concerned the spectral lines resulting with John Blatt and published in 1952, his controversial and ground-breaking from the radiation emitted by electrons in which for decades was the undisputed decision to build the world’s first the atom. The intrinsic width of spectral bible of the subject. But what had begun proton–proton collider. lines is due to the interaction of the as a harmless intellectual pursuit assumed A sketch of ‘Viki’ (as he was known atomic electrons with the radiation they a very different tone when he joined the everywhere) as a scientist does not begin emit. Working with Eugene Wigner, and atomic bomb project at Los Alamos. to give a picture of the man. He radiated at the age of just 22, Weisskopf devised the There he became deputy to Hans Bethe, emotional warmth combined with quantum theory of this effect. head of the theoretical-physics division. intellectual discipline and breadth — a The energy of a charge under the At the war’s end he joined the faculty rigorous romantic. He was an influence of its own field posed a much at Massachusetts Institute of Technology. accomplished pianist and loved music as deeper problem. In 1934, with some help Here, students and postdocs were exposed much as physics, playing excerpts from from Wendell Furry, Weisskopf to Weisskopf’s exceptional talent for the Haydn’s Creation when giving popular discovered that in QED this ‘self-energy’ intuitive argument, and also enjoyed the lectures on the early Universe. He called is far better behaved as the diameter of the warmth of the atmosphere he created. his popular exposition of science charge shrinks to zero than it is in New experimental techniques had Knowledge and Wonder. Viki exemplified classical physics. This behaviour is central emerged from the wartime radar project, the vitality and imagination that to today’s highly successful ‘standard and among the first consequences was produced one of history’s great model’ of elementary particles. Another Lamb’s discovery that the hydrogen intellectual revolutions, and gave it a vital contribution by the young Weisskopf spectrum was in stark conflict with human face. Kurt Gottfried was the demonstration, with Wolfgang existing theory. Weisskopf and his student Kurt Gottfried is in the Laboratory of Nuclear Pauli, that relativity and quantum Bruce French made the first complete Studies, Cornell University, Ithaca, New York mechanics do not require charged calculation, but it disagreed with the 14853, USA. particles to have spin — until then, this slightly later result found by the young e-mail: [email protected]