The introductory chapter places radio astronomy in the context of the broader astronomical environment. The transformational discoveries made by radio astronomy and the circumstances surrounding these discoveries are summarized with an emphasis on the role of serendipity and its impact on science.

Karl Jansky’s illness led to his being assigned to a remote New Jersey Bell Telephone Labs site to investigate interference to transatlantic telephone circuits. In a series of personal letters written to his father, Jansky documented his two-year investigation leading to the discovery of radio emission from the center of the Milky Way. Pressure to work on defense-related projects and the growing tensions between Jansky and his supervisor Harold Friis led to a long-standing controversy about why Jansky did not continue his study of “star noise.” Although the astronomical community showed little interest in Jansky’s discovery, Grote Reber, a young engineer and avid radio amateur, built the world’s first radio telescope using his own private funds. After negative results because he was misled by the then prevailing theories of cosmic radio emission, Reber finally confirmed Jansky’s discovery and demonstrated that, unlike all previously known cosmic radiation, galactic radio emission was nonthermal. The work of Jansky and Reber set the stage for the later series of remarkable radio astronomy discoveries made possible by the wartime developments in radio and radar technology.