Cosmic background radiation

This component is redshifted photons that have freely streamed from an epoch when the Universe became transparent for the first time to radiation.

Its discovery and detailed observations of its properties are considered one of the major confirmations of the Big Bang[1].

Fluctuations in cosmic background radiation across regimes create parameters for the amount of baryonic matter in the universe[5].

1896: Charles Édouard Guillaume estimates the "radiation of the stars" to be 5.6 K.[7] 1926: Sir Arthur Eddington estimates the non-thermal radiation of starlight in the galaxy has an effective temperature of 3.2 K. [1] 1930s: Erich Regener calculates that the non-thermal spectrum of cosmic rays in the galaxy has an effective temperature of 2.8 K.[7] 1931: The term microwave first appears 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."

1946: Robert Dicke predicts a microwave background radiation temperature of 20 K (ref: Helge Kragh) 1946: Robert Dicke predicts a microwave background radiation temperature of "less than 20 K" but later revised to 45 K (ref: Stephen G. Brush).