"We live in a changing universe, and few things are changing faster than our conception of it."
Timothy Ferris, The Whole Shebang
Bell Telephone Laboratories at Holmdel, New Jersey, was investigating the introduction of short-wave radio transatlantic telephone services, and was worried that static signals might interfere with voice transmission. In 1931 Bell physicist and engineer Karl Guthe Jansky (1905-1950) was instructed to find the source of the static. Using a high-quality 14.6 m (20.5 MHz) radio receiver and a quaint, wheel-mounted antenna system, he found three sources: nearby thunderstorms, distant thunderstorms, and a faint background hiss.
The intensity of the latter varied daily. After a few months' work, Jansky realized that the period was not the solar day of twenty-four hours but the twenty- three hours fifty-six minutes sidereal day. By 1932 he had pinpointed the source of the hiss as being the Sagittarius region of the Milky Way galaxy. His antenna thus became the first radio telescope.
Grote Reber, a ham radio operator and radio engineer from Wheaton, Illinois, subsequently built the first fully steerable radio telescope (that is, one that could move in both altitude and azimuth). His parabolic reflector turned out to be the prototype of several generations of radio telescopes. Reber started to map the radio sky, discovering the radio sources of Cassiopeia A and Cygnus A (in 1940) and the Andromeda Galaxy (in 1944). Radio emissions from the sun were discovered during World War II.
