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'[[Image:Cobe-cosmic-background-radiation.gif|thumb|256px|Cosmic background radiation spectrum as determined with the COBE satellite, (top) uncorrected, (middle) corrected for the dipole term due to our peculiar velocity, (bottom) corrected for contributions from the dipole term and from our galaxy.]] '''Cosmic background radiation''' is [[electromagnetic radiation]] from the sky with no discernable source. It comes from the effects of interplanetary dust, and [[interstellar matter]]. The origin of this radiation depends on the region of the [[electromagnetic spectrum|spectrum]] that we are observing. One component is the [[cosmic microwave background radiation]]. This component is [[redshifted]] [[photons]] that have freely streamed from an [[Timeline of the Big Bang|epoch]] when the [[universe]] became transparent for the first time to radiation. Its discovery and detail observations of its properties are considered one of the major confirmations of the [[Big Bang]]. The [[Sunyaev Zel'dovich effect]] shows the phenomena of radiant cosmic background radiation interacting with "electron" clouds distorting the spectrum of the radiation. There is also background radiation in the [[infrared]], [[x-ray]]s, etc., with different causes, and they can sometimes be resolved into individual source. See [[cosmic infrared background]] and [[X-ray background]]. See also [[cosmic neutrino background]] and [[extragalactic background light]]. ==History of significant events== 1896: [[Charles Edouard Guillaume]] estimates the "radiation of the stars" to be 5.6[[Kelvin|K]].[http://redshift.vif.com/JournalFiles/Pre2001/V02NO3PDF/V02N3ASS.PDF Ref (PDF)] 1926: Sir [[Arthur Eddington]] estimates the non-thermal radiation of [[starlight]] in the galaxy has an effective temperature of 3.2[[Kelvin|K]]. [http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1927Sci....66...81E&db_key=AST&data_type=HTML&format=&high=42ca922c9c22437] 1930s: [[Cosmologist]] [[Ernst Regener]] calculates that the non-thermal spectrum of cosmic rays in the galaxy has an effective temperature of 2.8K 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." ''Telegraph & Telephone Journal'' XVII. 179/1" 1938: [[Nobel Prize]] winner (1920) [[Walther Nernst]] reestimates the cosmic ray temperature as 0.75K 1946: The term "[[microwave]]" is first used in print in an astronomical context in an 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: [[Ralph Alpher]] and [[Robert Herman]] re-estimate Gamow's estimate at 5K. 1949: Ralph Alpher and Robert Herman re-re-estimate Gamow's estimate at 28K. 1960s: Robert Dicke re-estimates a MBR (microwave background radiation) temperature of 40K (ref: Helge Kragh) 1960s: [[Arno Penzias]] and [[Robert Woodrow Wilson]] measure the temperature to be approximately 3 K. Robert Dicke, [[P. J. E. Peebles]], P. G. Roll and [[David Todd Wilkinson|D. T. Wilkinson]] interpret this radiation as a signature of the big bang. ==See also== '''Main''': [[Timeline of cosmic microwave background astronomy]], [[Cosmic microwave background radiation]], [[Galaxy formation and evolution]], [[Orders of magnitude (length)|Magnitude]], [[Universe]] '''[[Cosmology]]''': [[Big Bang]] '''[[Physics]]''': [[Dark matter]], [[Dirac sea]], [[Hot dark matter]], [[Irradiation]], [[Sunyaev Zeldovic Effect]] '''Other''': [[List of astronomical topics]] * [[Cosmic neutrino background]] * [[Cosmic background]] ==External links== *[http://heasarc.nasa.gov/docs/objects/background/background.html The Diffuse X-ray and Gamma-ray Background & Deep Fields] [[Category:Observational astronomy]] [[Category:Physical cosmology]] [[Category:Cosmic background radiation]] [[ca:Fons cosmològic]] [[de:Hintergrundstrahlung]] [[it:Radiazione cosmica di fondo]] [[nl:Kosmische achtergrondstraling]] [[ja:宇宙背景放射]] [[fi:Kosminen taustasäteily]]'