Victor Weisskopf 1908-2002
A colossus of modern physics, Victor Weisskopf died on 22 April at the age of 93. His career spanned and moulded the recent history of the subject. As well as increasing our understanding of the subnuclear world, he was also a key player in great dramas that unfolded during the 20th century.
Serving as director-general of CERN from 1961 until 1965, and taking on a number of responsibilities in the US, he was a true world citizen. In all of his roles, as both a scientist and a scientist-administrator, he left a mark. As Chairman of CERN's Scientific Policy Committee from 1964-66, the great French physicist Louis Leprince-Ringuet said of Weisskopf: "The spirit of CERN is his creation."
Born in Vienna in 1908, Weisskopf witnessed the development of quantum mechanics in the 1920s as a graduate student in Max Born's school in Göttingen, where Ehrenfest, Heisenberg, Jordan, Pauli and Wigner, among others under Born's guidance, were carving out the new theory. After Göttingen, Weisskopf worked with Schrödinger in Berlin, with Bohr at Copenhagen, then with Dirac and Peierls at Cambridge, before being invited by Pauli to be his assistant in Zurich. In 1937 he moved to the US, working at Rochester with Hans Bethe. During the 1930s, Weisskopf greatly influenced the development of quantum field theory.
The Second World War saw an abrupt change in career path when Weisskopf was appointed deputy to Bethe, the leader of the Theory Division at Los Alamos. The atmosphere at Los Alamos groomed him for further high responsibility and greatly influenced his characteristic style of management. Following this experience, his warnings of the dangers of nuclear weapons were highly influential.
Immediately after the war, he moved to MIT, which was his US base for the rest of his life. Returning to quantum field theory, in 1947 he was one of the discussion leaders at the historic conference on Shelter Island, New York, where the modern theory of quantum electrodynamics first emerged. In 1950 he was appointed "professeur étranger" at the Sorbonne in Paris, France. He continued to work on fundamental physics problems, and his 1971 paper with Julius Kuti helped pave the way for the modern theory of quantum chromodynamics. His contributions to basic physics therefore spanned almost half a century. He was also quick to spot new talent - in 1948 he invited the 18-year-old Murray Gell-Mann to come to MIT as a research student.
In 1960, while serving as president of the American Physical Society, he was appointed to the CERN directorate. He became director-general the following year, succeeding John Adams who had taken on the responsibility following the death of the incumbent director-general, Cornelis Bakker, in an air accident.
It was during Weisskopf's historic mandate as CERN director-general that the infant laboratory's role in life was charted, and major new investments made. Weisskopf elevated the organization from an experiment in international collaboration to a mission, and endowed it with the necessary stature. Under his guidance, the future of CERN was shaped.
The Intersecting Storage Rings, the world's first proton collider, was identified as a major goal. A parallel but more distant aim was a larger proton synchrotron - the 300 GeV project - which eventually led to the SPS. This foresight opened the way for the SPS proton-antiproton collider, the LEP electron-positron collider and finally the Large Hadron Collider. Weisskopf also ensured that the PS synchrotron became equipped with the right infrastructure to become the hub of all CERN's particle beam requirements. Later he described his five years at CERN as "among the most wonderful of my life".
His other lasting creations include the European Committee for Future Accelerators and the US High Energy Physics Advisory Panel, both of which continue to influence and guide the evolution of high-energy physics on their respective sides of the Atlantic.
His great contemporary, Hans Bethe, lists three major contributions Weisskopf made to basic physics: calculating the width of energy levels and their fundamental relation with lifetime; the mathematical divergence of the electron's self-energy; and, with Herman Feshbach, elucidating ideas on nuclear scattering. Others would list more. With Fermi and Teller, he showed that the cosmic ray "mesotron" interacted far too weakly to be the carrier of the Yukawa nuclear force. His book Theoretical Nuclear Physics with John Blatt is still classic reading. In later years, he was continually in demand as a lecturer and author. As well as numerous scientific monographs and memorial volumes, his books include Physics in the 20th century, Knowledge and Wonder, The Joy of Insight and The Privilege of being a Physicist.
After leaving CERN in 1965, he maintained a nearby house in the Pays de Gex, France, to which he returned every summer until 1998, when travel became difficult for him. For many years, his lectures to summer students were a highlight at CERN. Delivered with minimal notes, these delightful talks were full of anecdotes and insight. With Kurt Gottfried as co-author, this material was published as The Concepts of Particle Physics. With wide interests in music and the arts as well as in science, it was fitting that from 1975 until 1978 he was president of the American Academy of Arts and Sciences.
Weisskopf was showered with honours and received almost every distinction imaginable. (And some not so imaginable, including honorary "sapeur-pompier", or fireman, in the French village of Vesancy, a distinction of which he was especially proud.) Only the Nobel prize was to elude him.
But it is at CERN, which he was fond of describing as the "United Scientific States of Europe", where his influence is most greatly felt. In his final progress report to CERN Council as director-general in 1965, he confidently predicted that "the real golden age of CERN is ahead of us".
Ralph Shutt 1913-2001
Born in Switzerland, Ralph Shutt first worked with cloud chambers in Berlin before emigrating to the US in 1939. After the Second World War he played a leading role in track chamber physics with the new high-energy synchrotrons. Using an innovative "diffusion cloud chamber" at the Brookhaven Cosmotron in 1953, he and his colleagues saw that highly unstable particles are produced in pairs - "associated production". This discovery soon led to the idea of strangeness as a quantum number. At the Brookhaven Alternating Gradient Synchrotron, Shutt led the effort to develop and exploit the newly invented bubble chamber. This led to the discovery of many new resonances and particles, culminating with the 1964 discovery of the omega-minus, which confirmed the SU3 classification of particle states. He subsequently transferred his attention to the development of superconducting magnets, work that eventually bore fruit for the RHIC heavy-ion collider.