The "pioneers" of radio astronomy are Karl Jansky and Grote
Reber. Jansky, working at Bell Labs, wanted to investigate the sources of
static that might interfere with radio voice transmissions for
transatlantic radio telephone service. He built a rotating antenna
designed to receive radio waves at a wavelength about 14.5
meters, and identified a faint steady hiss of unknown origin. He eventually
figured out that the radiation was coming from the Milky Way galaxy.
Reber, fascinated by Jansky's discovery, constructed his own telescope in
1937 in his back yard in Illinois. A receiver on his
telescope at 1.9 meters wavelength was successful in detecting radio
emission from the Milky Way, in 1938, confirming Jansky's discovery.
On March 25, 1951, Harold Ewen and Edward Purcell used a horn antenna in
the first detection of the 21 cm emission from neutral hydrogen in the
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