Edward Purdy Ney (1920–1996)

Edward ('Eddie') Ney passed away on 9 July 1996 at age 75 in Minneapolis, Minnesota, after a 14-year battle with congestive heart failure. Ney was co-discoverer of heavy isotopes in the primary cosmic-rays, made pioneering contributions to the use of high altitude balloons for cosmic-ray and atmospheric research, and was one of the founders of infrared astronomy.

Ney loved to challenge conventional wisdom and took great pride in finding innovative solutions to difficult theoretical and technical problems. He loved to teach and several generations of students learned to think deeply about physics under his mentorship. Ed was elected to the National Academy of Sciences in 1971, the American Academy of Arts and Sciences in 1979 and won NASA's Exceptional Scientific Achievement Medal in 1975. A faculty member at the University of Minnesota since 1947, he was awarded the University's Outstanding Teaching Award in 1964. In 1974 he was appointed to a Regents' Professorship, and was recognized by an "Outstanding Achievement Award" in 1992.

Born 28 October 1920 in Minneapolis, Ney grew up in the small town of Waukon, Iowa. He loved meeting challenges head on and developed an intense interest in science as a student at Waukon High School. He recalls his high school principal declaring that "Nobody who ever graduated from this school has ever done anything in science, and neither will you." But Ed's response was "No one is going to tell me what I can't do!" In the fall of 1938, he entered the University of Minnesota. His physics career began in 1940 when Al Nier hired him as an undergraduate laboratory assistant to make mass spectrometric measurements of carbon dioxide samples enriched in¹³ C. In 1942, Ney entered graduate school at the University of Virginia. There he worked with Jesse Beams and Phil Abelson at the Naval Research Laboratory analyzing samples of enriched UF₆ and wrote a PhD thesis determining its self-diffusion constant. He joined the faculty at Virginia after his PhD in 1946.

With Beams and Leland Snoddy, Ney began to measure cosmic-ray showers with equipment they set up in Endless Caverns near New Market, Virginia. Before they got any substantial results, Ney wrote a short theoretical paper on the cascade component of cosmic rays that was read by Physical Review editor Jack Tate of the University of Minnesota. Tate was looking for someone to use Jean Piccard's balloons for cosmic-ray research and recruited Ney along with Frank Oppenheimer and Ed Lofgren. With their first graduate student, Phyllis Freier, they built and flew cloud chambers, counters and nuclear emulsions. Within a year, in collaboration with Bernard Peters and Helmut Bradt of the University of Rochester, they discovered that the primary cosmic-rays were positively charged nuclei. Sophie Alexa and Ed subsequently conducted a number of balloon flights to search for the cascade showers from high energy electrons that Minnesota colleague Charlie Critchfield had predicted would be required to balance the positive charge carried by the heavy nuclear cosmic-ray component. The actual discovery of these primary electrons was made by Jim Earl using improved cloud chambers at higher altitude. However, the flux Earl measured was the same as the upper limit established by the earlier Alexa and Ney experiments.

Following a number of failures with the new large plastic balloons then in use, Critchfield, Jack Winckler, and Ney established the Minnesota Balloon Project, jointly sponsored by the Air Force, Army, and Navy. Eventually, 693 experimental and scientific balloon flights were made to study and improve balloon design and to better understand the physics of balloon flight generally. The group developed the duct appendix, the natural shape balloon and the super pressure tetroon. Recently all 16 volumes of their work have been declassified.

When the Air Force and the Army withdrew their support in 1956, the Navy continued to support a basic program in balloon-born atmospheric and cosmic-ray physics research. Among Ney's students were Frank McDonald and John Naugle. Both became Chief Scientist of NASA. Another Ney student, Bob Danielson, went to Princeton University to work with Martin Schwarzschild to create the famous Stratoscope Program, using balloon-borne telescopes to observe the sun and other astronomical objects.

The search for cosmic-ray electrons eventually stimulated Ed's interest in solar physics and astronomy. He and Paul Kellogg proposed that synchrotron radiation from energetic electrons might account for much of the visible radiation from the corona, and they tested it quantitatively during the African Eclipse of 1959 using a network of small telescopes in the Sahara that mapped the coronal intensity and polarization. Their experiment proved that the coronal light was from Thomson scattering by free electrons. Ney enjoyed the logistical challenge posed by this expedition and from then on, he was an inveterate eclipse observer. He continued to measure the radial dependence of the scattering and polarization of the corona during eclipse expeditions to Cabo San Lucas and Tahiti. He also performed infrared imaging experiments during total eclipses at Bowbells, North Dakota and in India in an attempt to detect the zone where the sun's heat melts grains in the Zodiacal dust cloud.

The coronal experiments inspired Ed to observe other dim, diffuse sources of light in astrophysics. He and his students designed cameras and polarimeters that were flown on balloons, on Mercury and Gemini manned space flights, and on two Orbiting Solar Observatory (OSO) spacecraft. The experiments showed that the zodiacal light is highly polarized and is produced by scattering of sunlight from dust grains probably introduced by comets. A completely unexpected result was the observation of thousands of terrestrial lightning strokes by the OSO Zodiacal light detectors, which continued to draw Ney's attention to the physics of thunderstorms.

In 1962, Ed spent another sabbatical in Australia working with Hanbury Brown and Richard Twiss on their Intensity Interferometer. On his return to Minnesota, Ney, along with his former graduate students Fred Gillett and Wayne Stein, decided to enter the nascent field of infrared astronomy. At the time, only Frank Low at Arizona and Gerry Neugebauer at Caltech had the detectors and telescopes required, and Ney spent another sabbatical at Arizona learning the techniques from Low. In 1966 he began developing infrared cryostats and detectors at Minnesota, and built the O'Brien Observatory 30-inch infrared telescope in 1967. Later, he collaborated with Nick Woolf, Gillett, and Stein on the design of a 60-inch infrared telescope for the Mount Lemmon Observing Facility in Arizona. A fundamental result of the infrared astronomy program was Ney and Woolf's discovery that silicate and carbon grains, the building blocks of the terrestrial planets, form in circumstellar shells around aging stars. He and his colleagues also showed that comets contain the same materials. Ed spent another a sabbatical year in Wyoming collaborating with former students Bob Gehrz and John Hackwell on infrared studies of comets and novae.

In retirement Ney rekindled interests in atmospheric physics and thunderstorms, linking them to questions about natural radioactivity. He conducted campus roof-top experiments designed to measure the time variations in local radioactivity after the Three Mile Island nuclear accident. Intrigued by an obvious correlation between radiation levels and rainfall, Ed began to investigate the global problem of radon gas generated by natural uranium decay. He did this in his inimitable fashion by inventing elementary equipment for measuring the decay signature of radon and its active products in samples of rain water. Until the time of his death and despite poor health, Ney steadily explored his hypothesis that ionization produced by radon in the atmosphere plays a fundamental role in atmospheric precipitation of water.

Ney's personal papers have been donated to the University of Minnesota Archives. An oral history is deposited at the National Air and Space Museum. Ed is survived by his wife of fifty-four years June (nee Felsing), by their four children, John, Arthur, Judy, and William, and by eight grandchildren. They, along with his numerous students and colleagues have many fond memories of a most remarkable man.