Timeline of other background radiation fields 1912 - Victor Hess[?] discovers that the ionization of air increases with altitude indicating the existence of cosmic radiation 1949 - Herbert Friedman[?] detects evidence for extrasolar X-rays 1962 - Riccardo Giacconi, Herbert Gursky[?], F. Paolini[?], and Bruno Rossi[?] formally discover the X-ray background