Cosmic background radiation#Features

{{Short description|Electromagnetic radiation from the Big Bang}}

{{distinguish|cosmic microwave background|cosmic infrared background}}

{{Physical cosmology}}

Image:Cobe-cosmic-background-radiation.gif data: uncorrected (top); corrected for the dipole term due to our peculiar velocity (middle); corrected additionally for contributions from our galaxy (bottom).]]

Cosmic background radiation is electromagnetic radiation that fills all space. The origin of this radiation depends on the region of the spectrum that is observed. One component is the cosmic microwave background. 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.{{Citation |last=Scott |first=Douglas |title=The standard cosmological model |journal=Canadian Journal of Physics |date=2005-10-26 |volume=84 |issue=6–7 |pages=419–435 |doi=10.1139/P06-066 |arxiv=astro-ph/0510731 |id=arXiv:astro-ph/0510731}} Background radiation is largely homogeneous and isotropic. A slight detectable anisotropy is present which correlates to galaxy filaments and voids.{{Cite journal |last1=Camacho-Ciurana |first1=G. |last2=Lee |first2=P. |last3=Arsenov |first3=N. |last4=Kovács |first4=A. |last5=Szapudi |first5=I. |last6=Csabai |first6=I. |date=2024-09-01 |title=The cosmic microwave background lensing imprint of cosmic voids detected in the WISE-Pan-STARRS luminous red galaxy catalog |url=https://www.aanda.org/articles/aa/full_html/2024/09/aa48970-23/aa48970-23.html |journal=Astronomy & Astrophysics |language=en |volume=689 |pages=A171 |doi=10.1051/0004-6361/202348970 |issn=0004-6361|arxiv=2312.08483 |bibcode=2024A&A...689A.171C }}{{Cite journal |last1=Hu |first1=Wayne |last2=Dodelson |first2=Scott |date=September 2002 |title=Cosmic Microwave Background Anisotropies |journal=Annual Review of Astronomy and Astrophysics |language=en |volume=40 |pages=171–216 |doi=10.1146/annurev.astro.40.060401.093926 |issn=0066-4146|arxiv=astro-ph/0110414 |bibcode=2002ARA&A..40..171H }} The discovery (by chance in 1965) of the cosmic background radiation suggests that the early universe was dominated by a radiation field, a field of extremely high temperature and pressure.{{cite news|url=http://whatisusa.info/the-first-minutes-of-the-big-bang/|title=First minutes of the Big Bang|publisher=What is USA News|date=12 March 2014|access-date=2013-11-19|archive-url=https://web.archive.org/web/20140312121214/http://whatisusa.info/the-first-minutes-of-the-big-bang/|archive-date=12 March 2014}}

There is background radiation observed across all wavelength regimes, peaking in microwave, but also notable in infrared and X-ray regimes. Fluctuations in cosmic background radiation across regimes create parameters for the amount of baryonic matter in the universe.{{Cite journal |last1=Kashlinsky |first1=A. |last2=Arendt |first2=R. G. |last3=Atrio-Barandela |first3=F. |last4=Cappelluti |first4=N. |last5=Ferrara |first5=A. |last6=Hasinger |first6=G. |date=2018-06-19 |title=Looking at cosmic near-infrared background radiation anisotropies |url=https://journals.aps.org/rmp/abstract/10.1103/RevModPhys.90.025006#s6 |journal=Reviews of Modern Physics |volume=90 |issue=2 |article-number=025006 |doi=10.1103/RevModPhys.90.025006|arxiv=1802.07774 |bibcode=2018RvMP...90b5006K }} See cosmic infrared background and X-ray background. See also cosmic neutrino background and extragalactic background light.

The Sunyaev–Zel'dovich effect shows the phenomena of radiant cosmic background radiation interacting with "electron" clouds distorting the spectrum of the radiation.{{Cite journal |last=Birkinshaw |first=Mark |date=1999-03-01 |title=The Sunyaev–Zel'dovich effect |url=https://www.sciencedirect.com/science/article/abs/pii/S0370157398000805 |journal=Physics Reports |volume=310 |issue=2 |pages=97–195 |doi=10.1016/S0370-1573(98)00080-5 |issn=0370-1573|arxiv=astro-ph/9808050 |bibcode=1999PhR...310...97B |hdl=1983/5d24f14a-26e0-44d3-8496-5843b108fec5 }}