With the death of Philip Morrison on 22 April 2005, the physics community and the world of ideas lost a unique personality. Phil was a true polymath; his knowledge was encyclopedic and his contributions span several branches of theoretical physics as well as elementary and secondary science education, the interface of science with the public, and arms control and public policy.

Born in Somerville, New Jersey, on 7 November 1915, Phil grew up in Pittsburgh. He was stricken with polio at age four and did not enter school until the third grade. He spent his last years confined to a wheelchair, but that did not slow him down in the slightest.

Phil graduated from the Carnegie Institute of Technology in 1936 and went on to the University of California, Berkeley, to study under J. Robert Oppenheimer. After receiving his PhD in theoretical physics in 1940, he taught briefly at San Francisco State College.

Phil’s experience with the atomic bomb was literally hands-on. After a stint at the Metallurgical Laboratory in Chicago, in 1944 he was transferred to Los Alamos, where he was a group leader and a member of the team that was responsible for assembling the plutonium bomb. He carried the plutonium core on his lap to Alamogordo, New Mexico, for the test explosion, helped assemble the Nagasaki bomb on Tinian Island, flew over the target cities shortly after the atomic explosions, and was one of the first Americans to inspect the Hiroshima bomb site and report on the devastation that had been wreaked. The experience left an indelible mark on him; for the rest of his life he pursued with passion the cause of “no third bomb.”

At the end of World War II, Phil co-founded the Association of Los Alamos Scientists, which subsequently became the Federation of American Scientists, dedicated to establishing civilian control over nuclear weapons and promoting a sensible nuclear policy. From 1947 until 1949, he served as the federation’s first president.

In 1946 Phil joined the faculty of Cornell University and resumed his career as a physicist. His book Elementary Nuclear Theory (Wiley, 1947), written with Hans Bethe, was one of the first on that subject. His influential paper with Giuseppe Cocconi in 1959 initiated SETI, the search for extraterrestrial intelligence. They proposed that radio telescopes be used in the search and suggested the 21-cm hyperfine-transition line of hydrogen as a plausible carrier for transmissions from other civilizations. No transmission has been received to date, but the search continues.

Phil’s major research interest at Cornell was the origin of cosmic rays; an important 1954 paper with Stan Olbert and Bruno Rossi dealt with that subject. A 1958 publication by Phil initiated the study of gamma-ray astronomy. Another important paper, written in 1960 with his student Hong-Yee Chiu, dealt with cosmic neutrinos. And in 1963, with his student James Felten, Phil identified the inverse Compton effect, in which a low-energy photon collides with an energetic electron, as a source of high-energy cosmic photons.

Phil’s political views were definitely left-wing. In 1936 he joined the Communist Party, as did many other idealists concerned about social justice during the dark days of the Depression; he left the party in 1942. At Cornell he continued his political activism, working on behalf of several organizations that were accused of being communist fronts. As a result he came under attack from professional anticommunists; during the heyday of McCarthyism, any organization with the word “peace” in its name was suspect, and Phil was part of the American Peace Crusade. As an example of Phil’s “subversive” activities, at a Carnegie Hall meeting of the National Council of the Arts, Sciences, and Professions in 1953 he introduced a resolution asking the US and USSR to adopt “a spirit of understanding and conciliation in order to solve the problem of international regulation of atomic weapons.” W. E. B. DuBois and Pete Seeger shared the stage with him on that occasion. In the same year he was grilled by Senator William Jenner’s Internal Security Subcommittee. Under intense pressure from hard-line trustees and alumni, the Cornell administration contemplated taking action to dismiss Phil, but he survived, aided by strong support from Bethe, Robert Wilson, and Dale Corson. He did, however, agree to curtail his political activities. The story is vividly recounted in Silvan S. Schweber’s book In the Shadow of the Bomb (Princeton U. Press, 2000), which contrasts Bethe’s steadfast defense of Phil with Oppenheimer’s shabby treatment of Bernard Peters.

In 1964 Phil moved to MIT, where he spent the remainder of his career. In 1973 he was named Institute Professor, MIT’s highest academic rank. His research there dealt with supernovae; radio astronomy; x-ray astronomy; and the properties of quasars, pulsars, and other energetic astrophysical phenomena. One of us (Sartori) had the exhilarating experience of collaborating with Phil in research in those areas during the late 1960s and early 1970s.

Phil’s contributions to science education began with the Physical Science Study Committee project, organized by Jerrold Zacharias in 1956, which strongly influenced the teaching of high-school physics. Subsequently he was involved in numerous aspects of elementary science education, both in the US and in the third world, particularly in Africa. He was recognized as an outstanding teacher.

His desire to make science more accessible to and appreciated by the public resulted in several influential television programs and books, including the six-part PBS series The Ring of Truth and its companion book (Random House, 1987), written in collaboration with his wife, Phylis; the 1982 book Powers of Ten (Scientific American Library), also with Phylis, which accompanies the film by Charles and Ray Eames and guides the viewer through 41 orders of magnitude in size from the proton to the galaxies; several BBC productions; and his book Nothing Is Too Wonderful to Be True (AIP Press, 1995). In 2000 he received the National Science Board’s Public Service Award for communicating science and enhancing the public understanding of it, and for educating, encouraging, and influencing a new generation of scientists.

Phil was probably best known to the public through his nearly 1500 book reviews in Scientific American. Started in 1965, the reviews spanned a broad spectrum of topics; there was scarcely a field of science in which he did not have an interest—and, it seemed, expert knowledge. Anyone who ever visited the Morrisons’ apartment in Cambridge, Massachusetts, will recall the sight of books piled haphazardly everywhere. The annual Christmastime review of children’s books, which he wrote jointly with Phylis, was always eagerly awaited. Phil also contributed many articles, each a model of clarity and elegance, to Scientific American and other popular publications.

Phil was a passionate advocate of nuclear arms control and a critic of many aspects of US military policy throughout the cold war and afterward. He was the quintessential “outsider.” His views found expression in numerous op-ed pieces and articles and in several books: The Price of Defense (Times Books, 1979), with other members of the Boston Science Group; The Nuclear Almanac (Addison-Wesley, 1984), with fellow MIT faculty members; and, with one of us (Tsipis), Reason Enough to Hope (MIT Press, 1988).

A memorial service last September packed MIT’s Kresge Auditorium. In attendance were colleagues, students, and friends representing each of Phil’s many fields of endeavor. There were many moving tributes to an exceptional intellect.

Physics Today is changing the way it publishes obituaries. Some will continue to appear in print, but most will be available only online (see Physics Today, October 2005, page 10). Subscribers can visit http://www.physicstoday.org/obits to notify the community about a colleague’s death and submit obituaries up to 750 words, comments, or reminiscences. Each month, recently posted material will be summarized here, in print. Select online obituaries will later appear in print.

Philip Morrison