Definition: Radio Astronomy: Radio Astronomy is a subfield of astronomy that studies electromagnetic radiation from objects outside the earth's atmosphere. Radio Astronomy uses telescopes which collect invisible rays given off or reflected by stars & other space objects.
James Clerk Maxwell (6/13/1831 11/5/1879) was a Scottish mathematician & theoretical physicist. In the 1860s, his equations showed that electromagnetic radiation from stellar sources could exist with any wavelength, not just optical. It wasn't until 1931 that Karl Jansky (10/22/1905 02/14/1950), an American physicist and radio engineer with Bell Telephone Laboratories, confirmed the theory. While investigating static that interfered with short wave transatlantic voice transmissions, Jansky used a large directional antenna to track the interference. He noticed that his analog pen/paper recording system kept recording a repeating signal of unknown origin.
Since the signal peaked once a day, Jansky first thought the signal was originating from the sun. However, continued analysis demonstrated that the signal was repeating on a cycle of 23 hrs and 56 mins, which is typical of an astronomical source. Comparing his observations with astronomical maps, he concluded the radiation was strongest in the direction of Sagittarius. Though he announced his discovery in 1933 and asked to continue his research, Bell Labs re-assigned Jansky to another project.
Grote Reber (12/22/1911 12/20/2002) was a ham radio operator who studied radio engineering, and worked for various radio manufacturers in Chicago from 1933 to 1947. When he heard of Jansky's discoveries in 1933, he wanted to follow up this discovery and learn more about cosmic radio waves. In 1937, he built a large (9m) parabolic "dish" radio telescope. Later, he went on to conduct the first sky survey in the radio frequencies.