Timeline of cosmic microwave background astronomy

• 1896 - Charles Edouard Guillaume estimates the "radiation of the stars" to be 5.6K.Guillaume, C.-E., 1896, La Nature 24, series 2, p. 234, cited in "History of the 2.7 K Temperature Prior to Penzias and Wilson" (PDF)
• 1926 - Sir Arthur Eddington estimates the non-thermal radiation of starlight in the galaxy ".. by the formula E = σT⁴ the effective temperature corresponding to this density is 3.18º absolute .. black body"Eddington, A., The Internal Constitution of the Stars, cited in "History of the 2.7 K Temperature Prior to Penzias and Wilson" (PDF)
• 1930s - Cosmologist Erich Regener calculates that the non-thermal spectrum of cosmic rays in the galaxy has an effective temperature of 2.8K
• 1931 - Term microwave first used in print: "When trials with wavelengths as low as 18 cm. were made known, there was undisguised surprise+that the problem of the micro-wave had been solved so soon." Telegraph & Telephone Journal XVII. 179/1
• 1934 - Richard Tolman shows that black-body radiation in an expanding universe cools but remains thermal
• 1938 - Nobel Prize winner (1920) Walther Nernst reestimates the cosmic ray temperature as 0.75K
• 1941 - Andrew McKellar uses the excitation of CN doublet lines to measure that the "effective temperature of space" is about 2.3 K
• 1946 - Term microwave first used in an astronomy article, "Microwave Radiation from the Sun and Moon" by Robert Dicke and Robert Beringer.
• 1946 - Robert Dicke predicts a microwave background radiation temperature of 20K (ref: Helge Kragh)
• 1946 - Robert Dicke predicts a microwave background radiation temperature of "less that 20K" but later revised to 45K (ref: Stephen G. Brush)
• 1946 - George Gamow estimates a temperature of 50K
• 1948 - George Gamow, Ralph Alpher, and Robert Herman predict that a Big Bang universe will have a black-body cosmic microwave background with temperature about 5 K
• 1949 - Ralph Alpher and Robert Herman re-re-estimate Gamow's estimate at 28K.
• 1955 - Tigran Shmaonov finds excess microwave emission with a temperature of roughly 3K
• 1960s - Robert Dicke re-estimates a microwave background radiation temperature of 40K (ref: Helge Kragh)
• 1964 - A. G. Doroshkevich and Igor Dmitrievich Novikov write an unnoticed paper suggesting microwave searches for the black-body 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, eventually confirmed at approximately 2.7K
• 1966 - Rainer Sachs and Arthur Wolfe theoretically predict microwave background fluctuation amplitudes created by gravitational potential variations between observers and the last scattering surface (see Sachs-Wolfe effect)
• 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 (see Sunyaev-Zeldovich effect)
• 1983 - Researchers from the Cambridge Radio Astronomy Group and the Owens Valley Radio Observatory first detect the Sunyaev-Zeldovich effect from clusters of galaxies
• 1990 - The Cosmic Background Explorer (COBE) satellite shows that the microwave background has a nearly perfect black-body spectrum and thereby strongly constrains the density of the intergalactic medium.
• 1992 - The COBE satellite discovers anisotropy in the cosmic microwave background.
• 1995 - The Cosmic Anisotropy Telescope performs the first high resolution observations of the cosmic microwave background.
• 1999 - The BOOMERanG experiment makes higher quality maps at intermediate resolution, and confirms that the Universe is "flat".
• 2003 - The Very Small Array produces yet higher quality maps at high resolution (covering small areas of the sky).
• 2003 - The WMAP satellite produces an even higher quality map at low and intermediate resolution of the whole sky (WMAP provides no high-resolution data, but improves on the intermediate resolution maps from BOOMERanG).
• 2004 - The Arcminute Cosmology Bolometer Array Receiver produces a higher quality map of the high resolution structure not mapped by WMAP.
• 2005 - The Arcminute Microkelvin Imager and the Sunyaev-Zel'dovic Array begin the first surveys for very high redshift clusters of galaxies using the Sunyaev-Zel'dovich effect.

Future

• 2008 The Clover Project will give an improved precision intermediate and high resolution map, and measure the B-mode polarization
• 2009 The Planck (satellite) will give improved precision at all resolutions

Notes

Astronomy timelines