Peter Meyer, a distinguished cosmic-ray physicist, died in Chicago on 7 March 2002 from a stroke, following a long illness.
Peter was born in Berlin, Germany, on 6 January 1920 and grew up in the liberal environment of an educated, music-loving physician-family, attending an all-French–speaking high school. He studied physics at the Technical University in Berlin, with Hans Geiger as one of his teachers, and earned a degree as Diplom-Ingenieur in 1942. His partially Jewish origin put Peter in severe danger in Nazi Germany and excluded him from completing his doctoral studies.
After the war, Peter attended the University of Göttingen and received his PhD in physics in 1948 under the guidance of Wolfgang Paul. His thesis was on a precision measurement of the deuteron’s binding energy.
Peter continued nuclear physics research at the University of Cambridge as a member of the university’s staff and as a postdoctoral fellow. From 1950 to 1953, he worked as a staff scientist at the Max Planck Institute for Physics in Göttingen.
In 1953, Peter accepted an invitation from John Simpson to become a research associate at the University of Chicago’s Institute for Nuclear Studies (now the Enrico Fermi Institute). With Simpson, he used detectors on military airplanes and high-altitude balloons to study global and time variations of cosmic rays. This work was essential to differentiating between galactic, solar, and terrestrial effects on the observed cosmic-ray intensities. From observations of a giant solar flare in February 1956, Simpson, Peter, and Eugene Parker concluded that interplanetary space contains a magnetic field embedded in a plasma; that idea later led to the concept of the solar wind.
Peter became an assistant professor in the physics department at Chicago and in the Institute for Nuclear Studies in 1956. He advanced to full professorship by 1965, served as the director of the Enrico Fermi Institute from 1978 to 1985, and was chair of the physics department from 1986 to 1989. He became a professor emeritus in 1990.
Peter collaborated with Simpson on some of the earliest cosmic-ray detectors flown in space. Simultaneously, he started an independent research program that would make use of increasingly sophisticated instrumentation on giant stratospheric balloons. Using purely electronic detectors, he succeeded in 1961, with his graduate student Rochus Vogt, in identifying the electron component in the cosmic rays, independently of the cloud chamber observations of James Earl at the University of Minnesota, made at the same time. A key question, whether these electrons were secondary debris from cosmic-ray collisions in interstellar space, or were mostly accelerated in primary cosmic ray sources, could be decided by measuring the proportions of negative electrons and positrons. Together with one of us (Hildebrand) and graduate students Jack Fanselow and Robert Hartman, Peter designed the first balloon-borne magnet spectrometer for this measurement. They showed in 1964 that, indeed, the majority of the electron component is negative and, hence, must come from primary sources.
Further extensive studies on the electron component, including studies of electrons from the Sun and from Jupiter, were undertaken by Peter and his group (including Dietrich Hovestadt, Jacques L’Heureux, and Paul Evenson) for the next 20 years, using instruments on balloons and on space missions.
In another series of balloon experiments, Peter studied the elemental composition of cosmic rays at highly relativistic energies. Jointly with one of us (Müller) and graduate student Einar Juliusson, and at about the same time as observations of Luis Alvarez’s group in Berkeley, Peter discovered in the early 1970s that the relative intensity of the secondary nuclei from spallation in interstellar space decreases continuously with increasing energy, as if the primary cosmic rays traversed a smaller and smaller galactic path length at higher energies. Therefore, the energy spectrum of cosmic rays at their sources must be different from that locally observed and must be quite hard—exactly as models of acceleration in strong supernova shocks would later predict. Those studies continued, and eventually led to a very large instrument, dubbed the “Chicago Egg,” that was flown on the space shuttle Challenger in 1985. In that experiment, Peter and Müller, who were joined by L’Heureux and Simon Swordy, used transition radiation detectors for the first time to measure the energy of cosmic-ray nuclei in the TeV region.
There was a common thread to all of Peter’s projects: He loved the challenge of applying new techniques to one-of-a-kind instrumentation flown above the atmosphere. To him, scientific discovery and experimental finesse belonged together, and he was extremely conservative in assessing the outcome of his work. Nothing irritated him more than far-fetched claims based on shaky data.
Peter was a devoted teacher. He became a foreign member of and frequent visitor to the Max Planck Institute for Extraterrestrial Physics in Garching, Germany. In 1984, he received the Alexander von Humboldt Award for Senior US Scientists, and in 1989, he was elected to the National Academy of Sciences. Many of his colleagues gratefully remember the open-mindedness and fair judgment he displayed as a member of numerous advisory boards and science policy committees.
Music was a serious passion in Peter’s life; he was an accomplished cellist. Together with his first wife, nuclear physicist Louise Meyer-Schützmeister, who played the piano, he arranged for regular chamber-music evenings at his home. Those concerts, fondly remembered by all who had the privilege to listen, continued for nearly two decades after Meyer-Schützmeister’s death in 1981. Peter married microbiologist Patricia Spear in 1983.
Peter was a Prussian of the old school: punctual, reliable, tolerant, and honest. He could be gregarious and had a wonderful sense of humor, traits that probably prevented him from talking with bitterness about his experiences during World War II. He was an outdoors enthusiast, and devoted to his family: Family vacations in the mountains, at his cottage on Lake Michigan, or in the Canadian wilderness, and regular ski trips were essentials in the yearly rhythm of his life.
Through firm guidance and unselfish advice, warm hospitality, or camaraderie at balloon-flight expeditions, Peter touched the lives and careers of the engineers and technicians who worked for him, professional colleagues, generations of college students, postdocs, and most of all, 17 graduate students who received their PhDs under his direction. To all of them, Peter’s departure leaves fond and enduring memories.