John Simpson, pioneering physicist, dies at age 83

“With instruments almost continuously in space for the last 40 years, John Simpson was always probing the frontiers of the solar system for new knowledge,” said Edward Stone, director of NASA’s Jet Propulsion Laboratory.

“With several generations of graduate students, he pioneered new areas of research ranging from outbursts of solar particle radiation to the origin and lifetime of cosmic-ray particles from nearby regions of the Milky Way,” said Stone.

“His contributions, however, extended beyond deep space and included broader national and local contributions that reflected his dedication to the importance of the role of science and the university in society.”

Simpson came to Chicago in 1943 to work on the Manhattan Project. On Aug. 7, 1945, the day after the United States dropped the atomic bomb on Hiroshima, Simpson and his colleagues organized the Atomic Scientists of Chicago to campaign for the peaceful use of nuclear power under international control. Simpson served as the group’s first chairman. In December 1945, Simpson co-founded the Bulletin of the Atomic Scientists.

In late 1945, Simpson also became an unofficial adviser to U.S. Sen. Brien McMahon of Connecticut, who chaired the Senate Special Committee on the Control of Atomic Energy. Together they and others worked successfully to promote and develop the McMahon Act of 1946, which provided for the civilian control of atomic energy.

Simpson soon turned his attention to cosmic rays, subatomic particles that constantly bombard Earth from all directions at nearly the speed of light. In 1948, Simpson invented the cosmic ray neutron intensity monitor. By 1951 he had set up five monitoring stations from the city of Chicago to the magnetic equator in Peru.

“When the sun is active, we get fewer cosmic rays here,” said Eugene Parker, the S. Chandrasekhar Distinguished Service Professor Emeritus in Physics. “John pointed out that this was probably due to magnetic fields varying in space. They had the effect of somehow eliminating the lower-energy cosmic rays here on Earth.”

During a spectacular solar flare in 1956, Simpson’s neutron monitors collected the first evidence pointing to the existence of the heliosphere, a region influenced by the sun’s magnetic field that extends far beyond the planets. During the International Geophysical Year from 1957 to 1958, the neutron monitor became the standard for conducting cosmic-ray research.

Simpson also used outer space as his laboratory to study the composition of cosmic rays and how the sun’s magnetic and galactic fields accelerate them. He established Chicago’s space research program in 1958 with Peter Meyer, Professor Emeritus in Physics, and a $5,000 allocation from the University. Starting with the Pioneer 2 satellite, which was launched in 1958, Simpson has served as the lead researcher for 34 instruments flown in Earth orbit and throughout the solar system.

He and his team built the first cosmic-ray detector to visit Mars in 1965, the first to Jupiter in 1973, to Mercury in 1974 and to Saturn in 1979. Simpson’s instruments aboard the Pioneer 10 and Pioneer 11 spacecraft discovered the radiation belts of Jupiter and Saturn.

Cosmic-ray observations are still being collected by Simpson’s Cosmic Ray Experiment on the Eighth Interplanetary Monitoring Platform in Earth orbit and the Cosmic Ray and Solar Particle Experiment aboard the Ulysses spacecraft, which orbits the sun. Ulysses was the first spacecraft to leave the narrow orbital plane of the planets to make observations near the sun’s north and south poles.

“John was extremely enterprising,” Parker said. “More than any other person, I think, he developed new schemes for making cosmic-ray measurements.”

Simpson’s creativity extended to the invention of a new way of detecting microscopic dust particles in space in the early 1980s. Flying on the Soviet Union’s 1986 Vega 1 and Vega 2 missions to Halley’s Comet, Simpson’s detectors were the only U.S. instruments to encounter the comet.

Simpson’s dust instruments continue to collect data on a variety of space missions: the Stardust mission, which is headed toward a 2004 rendezvous with Comet Wild-2; the Cassini mission to Saturn; and the Air Force’s Advanced Research and Global Observation Satellite. Anthony Tuzzolino and Bruce McKibben, both Senior Scientists with the Enrico Fermi Institute, continue Simpson’s work with the dust instruments.

After completing his work in the Manhattan Project in 1946, Simpson became an Instructor in Physics at the University. Working his way up the ranks, he became the Edward L. Ryerson Distinguished Service Professor in 1968, and Arthur H. Compton Distinguished Service Professor in 1974. He received Emeritus status in 1987. He also served as Director of the Enrico Fermi Institute from 1973 to 1978.

He received many awards, including this year’s William Bowie Medal, the highest award of the American Geophysical Union. He was elected to the National Academy of Sciences in 1959.

Survivors include his wife, Elizabeth Simpson of Chicago; two children from his first marriage, Mary Ann Smith of Bangor, Mich., and John A. Simpson of Nahant, Mass.; three grandchildren, Ryan and Christopher Smith of Bangor and John A. Simpson of Nahant. Simpson was divorced from his first wife, Elizabeth Hiltz Simpson, in 1977. She died in 1990.