Chronology of Cosmic Microwave Background Astronomy

1934 Richard Tolman shows that blackbody radiation in an expanding universe cools but remains thermal.
1941 Andrew McKellar uses the excitation of CN doublet lines to measure that the "effective temperature of space'' is about 2.3 K.
1948 George Gamow, Ralph Alpher, and Robert Herman predict that a Big Bang universe will have a blackbody cosmic microwave background with temperature about 5 K.
1955 Tigran Shmaonov finds excess microwave emission with a temperature of roughly 3 K.
1964 A.G. Doroshkevich and Igor Novikov write an unnoticed paper suggesting microwave searches for the blackbody radiation predicted by Gamow, Alpher, and Herman.
1965 Arno Penzias, Robert Wilson, Bernie Burke, Robert Dicke, and James Peebles discover the cosmic microwave background radiation.
1966 Rainer Sachs and Arthur Wolfe theoretically predict microwave background fluctuation amplitudes created by gravitational potential variations between observers and the last scattering surface.
1968 Martin Rees and Dennis Sciama theoretically predict microwave background fluctuation amplitudes created by photons traversing time-dependent potential wells.
1969 R.A. Sunyaev and Yakov Zel'dovich study the inverse Compton scattering of microwave background photons by hot electrons.
1990 The COBE satellite shows that the microwave background has a nearly perfect blackbody spectrum and thereby strongly constrains the density of the intergalactic medium.
1992 The COBE satellite discovers anisotropy in the cosmic microwave background.