Harold Irving Ewen
American scientist From Wikipedia, the free encyclopedia
American scientist From Wikipedia, the free encyclopedia
Harold Irving "Doc" Ewen (March 5, 1922 – October 8, 2015) was an American physicist, radio astronomer, and business executive. He served in the United States Navy in World War II as a second lieutenant. As a graduate student under Edward M. Purcell, he was the first to detect the galactic 21-cm hydrogen line.
Harold Irving Ewen | |
|---|---|
| Born | March 5, 1922 |
| Died | October 8, 2015 (aged 93) |
| Education | Ph.D. (1951) |
| Alma mater | Harvard University |
| Known for | Detection of 21-cm hydrogen line |
| Spouse | Mary Ann Whitney[1] |
| Children | Donald, Bruce, Mark, Deborah, David, Daniel, and Rebecca[1] |
| Parents | |
| Awards | IEEE Morris E. Leeds Award (1970) Beatrice M. Tinsley Prize (1988) |
| Scientific career | |
| Thesis | Radiation from Galactic Hydrogen at 1420 Megacycles per Second (1951) |
| Doctoral advisor | Edward M. Purcell |
Ewen was born on March 5, 1922, in Chicopee, Massachusetts,[3] son of S. Arthur Ewen and Ruth F. Fay. After an education at the Technical High School in Springfield, Massachusetts,[2] he matriculated at Amherst College, studying undergraduate mathematics and astronomy,[1] and was awarded a B.A. in 1943.[3] With World War II underway, he joined the Navy.[1] Initially, he taught celestial navigation at Amherst as part of a pilot training program. Ewen received training in electronics and radar technology at Princeton University and MIT,[4] then joined Navy airborne squadron 112, based in England, as a radar officer with the rank of Second Lieutenant.[5][6][7]
Following the war, Ewen began graduate studies at Harvard on the G.I. Bill,[7] pursuing a degree in physics. He participated in the development of the 95-inch Harvard Cyclotron.[4] Edward M. Purcell suggested that Ewen study prior work on the hyperfine line of neutral hydrogen. As a naval reserve officer, Ewen was able to obtain a translation of a 1945 paper by the Dutch astronomer H. C. van de Hulst on the subject. Van de Hulst expressed pessimism that such a signal would be detectable. Nonetheless, Ewen and Purcell agreed that his thesis topic should be to construct a microwave spectrometer to find a lower limit on the detectability of the 21-cm hydrogen line.[6]
With a $500 grant from the AAA&S, Ewen was able to purchase components to construct a pyramidal horn antenna and a 21-cm receiver. With the instrument assembled, a galactic 21-cm signal was successfully detected on March 25, 1951.[6] This unexpected result was soon confirmed by Dutch and Australian astronomers.[8] Ewen was able to defend his thesis in May of that year, and he was awarded a Ph.D. from Harvard. He joined the Harvard Business School to pursue an MBA.[6]
In the fall of 1951, Ewen was called up to serve in the Korean War.[5] He remained for a month before negotiating his return to civilian life.[6] He joined with Bart Bok as directors of the newly founded Harvard radio astronomy program during 1952–1958,[9] creating the nation's first Ph.D. program in this new field. During the 1950s, Ewen was involved in the planning for a national radio astronomy facility, and the site search for what would eventually become the Green Bank Telescope observatory.[4]
Ewen joined with his friend Geoff Knight to launch the Ewen Knight Corporation in 1952, which was established to construct a hydrogen line receiver for Harvard at the Agassiz Station. This company became a major supplier of equipment for radio observatories, including the NRAO.[6] In 1956 he was married to Mary Ann Whitney;[10] the couple would have seven children.[1] Ewen was elected to the American Academy of Arts and Sciences in 1957.[11] He founded the Ewen Dae Corporation in 1958,[3] whose name was a play on [k]night and day and also became the initials of the couple's first child.[6][10]
Ewen devised a sextant-like radio direction finder that was used on submarines to find the position before firing missiles.[6] During 1989-1992 he was executive vice president at the Millitech Corporation, becoming vice president for special projects, 1993–2000. He served as president of E.K. Associates starting in 1992.[4] In 2001, he became a research professor at the University of Massachusetts. Following his retirement, on November 12, 2002, Ewen gave the inaugural Gordon Lecture at the Arecibo Observatory.[9] He was the technical operations director of Special Projects LLC in 2004.[4]
In 1970, Ewen was given the IEEE Morris E. Leeds Award "for contributions to the design of sensitive radiometric systems, and for the codiscovery of the 21-cm spectral line of interstellar hydrogen".[12] Ewen and Purcell were awarded the Beatrice M. Tinsley Prize in 1988 for the "first detection of 21-cm hyperfine transition radiation of neutral hydrogen".[13] The horn antenna used to detect the galaxy's 21-cm line from Harvard is now a historical marker.[14]
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