Editing Cosmic microwave background (section)

===Microwave background radiation predictions and measurements===
* 1941 – [[Andrew McKellar]] detected a "rotational" temperature of 2.3&nbsp;[[Kelvin|K]] for the interstellar medium by comparing the population of CN doublet lines measured by W. S. Adams in a B star.<ref name="dao7">
{{cite journal|last=McKellar|first=A.|title=Molecular Lines from the Lowest States of Diatomic Molecules Composed of Atoms Probably Present in Interstellar Space|journal=Publications of the Dominion Astrophysical Observatory|place=Vancouver, B.C., Canada| year=1941|volume=7|pages=251–272|issue=6|bibcode = 1941PDAO....7..251M }}</ref><ref>{{Cite book |last=Weinberg |first=Steven |author-link=Steven Weinberg |url=https://archive.org/details/gravitationcosmo00stev_0/page/514 |title=Gravitation and cosmology: principles and applications of the general theory of relativity |date=1972 |publisher=Wiley |isbn=978-0-471-92567-5 |location=New York |pages=[https://archive.org/details/gravitationcosmo00stev_0/page/514 514]}}</ref>
* 1948 – [[Ralph Alpher]] and [[Robert Herman]] estimate "the temperature in the universe" at 5&nbsp;K. Although they do not specifically mention microwave background radiation, it may be inferred.<ref>[[Helge Kragh]], Cosmology and Controversy: [https://archive.org/details/cosmologycontrov00helg/page/132 The Historical Development of Two Theories of the Universe] (1999) {{ISBN|0-691-00546-X}}. "Alpher and Herman first calculated the present temperature of the decoupled primordial radiation in 1948, when they reported a value of 5&nbsp;K. Although it was not mentioned either then or in later publications that the radiation is in the microwave region, this follows immediately from the temperature ... Alpher and Herman made it clear that what they had called "the temperature in the universe" the previous year referred to a blackbody distributed background radiation quite different from the starlight."</ref>
* 1953 – [[George Gamow]] estimates 7&nbsp;K based on a model that does not rely on a free parameter<ref name=Kragh /><ref>{{Cite journal |last1=Alpher |first1=Ralph A. |last2=Gamow |first2=George |last3=Herman |first3=Robert |date=December 1967 |title=Thermal Cosmic Radiation and the Formation of Protogalaxies |journal=Proceedings of the National Academy of Sciences |language=en |volume=58 |issue=6 |pages=2179–2186 |doi=10.1073/pnas.58.6.2179 |doi-access=free |issn=0027-8424 |pmc=223817 |pmid=16591578|bibcode=1967PNAS...58.2179A }}</ref>{{rp|2181}}
* 1955 – Émile Le Roux of the [[Nançay Radio Observatory]], in a sky survey at ''λ'' = 33&nbsp;cm, initially reported a near-isotropic background radiation of 3 kelvins, plus or minus 2; he did not recognize the cosmological significance<ref name=Kragh /> {{rp|343}}<ref name=PartridgeReview/>{{rp|location=8.3.1}} and later revised the error bars to 20K.<ref>Delannoy, J., Denisse, J. F., Le Roux, E., & Morlet, B. (1957). Mesures absolues de faibles densités de flux de rayonnement à 900 MHz. Annales d'Astrophysique, Vol. 20, p. 222, 20, 222.</ref><ref name=WrightUCLASite>{{Cite web |last=Wright |first=Edward |title=Cosmic Microwave Background |url=https://astro.ucla.edu/~wright/CMB.html |access-date=2024-05-28 |website=astro.ucla.edu}}</ref> 
* 1957 – Tigran Shmaonov reports that "the absolute effective temperature of the radioemission background ... is 4±3&nbsp;K".<ref>{{cite journal|last=Shmaonov|first=T. A.|date=1957|title=Commentary|language=ru|journal=[[Pribory I Tekhnika Experimenta]]|volume=1|pages=83|doi=10.1016/S0890-5096(06)60772-3}}</ref> with radiation intensity was independent of either time or direction of observation. Although Shamonov did not recognize it at the time, it is now clear that Shmaonov did observe the cosmic microwave background at a wavelength of 3.2&nbsp;cm<ref>{{cite book|last1=Naselsky|first1=P. D.|last2=Novikov|first2=D.I.|last3=Novikov|first3=I. D.|date=2006|title=The Physics of the Cosmic Microwave Background|publisher=Cambridge University Press |url=https://books.google.com/books?id=J2KCisZsWZ0C&pg=RA1-PA1|isbn=978-0-521-85550-1}}</ref>
* 1964 – [[A. G. Doroshkevich]] and [[Igor Dmitrievich Novikov]] publish a brief paper suggesting microwave searches for the black-body radiation predicted by Gamow, Alpher, and Herman, where they name the CMB radiation phenomenon as detectable.<ref>{{cite journal|last1=Doroshkevich|first1=A. G.|last2=Novikov|first2=I.D.|s2cid=96773397|date=1964|title=Mean Density of Radiation in the Metagalaxy and Certain Problems in Relativistic Cosmology|journal=[[Soviet Physics Doklady]]|volume=9|pages=4292–4298|doi=10.1021/es990537g|issue=23|bibcode = 1999EnST...33.4292W }}</ref>
* 1964–65 – [[Arno Penzias]] and [[Robert Woodrow Wilson]] measure the temperature to be approximately 3&nbsp;K. [[Robert Dicke]], [[Philip James Edwin Peebles|James Peebles]], P. G. Roll, and [[David Todd Wilkinson|D. T. Wilkinson]] interpret this radiation as a signature of the Big Bang.
* 1966 – [[Rainer K. Sachs]] and [[Arthur M. 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 wells of potential.
* 1969 – [[R. A. Sunyaev]] and [[Yakov Zel'dovich]] study the inverse [[Compton scattering]] of microwave background photons by hot electrons (see ''[[Sunyaev–Zel'dovich effect]]'').
* 1983 – Researchers from the [[Cavendish Astrophysics Group|Cambridge Radio Astronomy Group]] and the [[Owens Valley Radio Observatory]] first detect the [[Sunyaev–Zel'dovich effect]] from [[galaxy cluster|clusters of galaxies]].
* 1983 – [[RELIKT-1]] Soviet CMB anisotropy experiment was launched.
* 1990 – FIRAS on the [[Cosmic Background Explorer]] (COBE) satellite measures the black body form of the CMB spectrum with exquisite precision, and shows that the microwave background has a nearly perfect black-body spectrum with T = 2.73 K and thereby strongly constrains the density of the [[intergalactic medium]].
* January 1992 – Scientists that analysed data from the [[RELIKT-1]] report the discovery of [[anisotropy]] in the cosmic microwave background at the Moscow astrophysical seminar.<ref>''Nobel Prize In Physics: Russia's Missed Opportunities'', [[RIA Novosti]], Nov 21, 2006</ref>
* 1992 – Scientists that analysed data from [[Cosmic Background Explorer|COBE]] DMR report the discovery of [[anisotropy]] in the cosmic microwave background.<ref>
{{cite news|last=Sanders|first=R.|author2=Kahn, J.|date=13 October 2006|title=UC Berkeley, LBNL cosmologist George F. Smoot awarded 2006 Nobel Prize in Physics|url=http://www.berkeley.edu/news/media/releases/2006/10/03_nobelph.shtml|publisher=[[UC Berkeley|UC Berkeley News]]|access-date=2008-12-11}}</ref>
* 1995 – The [[Cosmic Anisotropy Telescope]] performs the first high resolution observations of the cosmic microwave background.
* 1999 – First measurements of acoustic oscillations in the CMB anisotropy angular power spectrum from the [[Mobile Anisotropy Telescope|MAT/TOCO]], BOOMERANG, and Maxima Experiments. The [[BOOMERanG experiment]] makes higher quality maps at intermediate resolution, and confirms that the universe is "flat".
* 2002 – Polarization discovered by [[Degree Angular Scale Interferometer|DASI]].<ref>{{cite journal|last=Kovac|first=J.M.|year=2002|title=Detection of polarization in the cosmic microwave background using DASI|journal=[[Nature (journal)|Nature]]|pmid=12490941|volume=420|issue=6917|pages=772–787|doi=10.1038/nature01269|arxiv=astro-ph/0209478 |bibcode = 2002Natur.420..772K |s2cid=4359884|display-authors=etal|url=https://cds.cern.ch/record/582473|type=Submitted manuscript}}</ref>
* 2003 – E-mode polarization spectrum obtained by the CBI.<ref>{{cite journal|last=Readhead|first=A. C. S.|year=2004|title=Polarization Observations with the Cosmic Background Imager|journal=[[Science (journal)|Science]]|pmid=15472038|volume=306|issue=5697|pages=836–844|doi=10.1126/science.1105598|bibcode=2004Sci...306..836R|arxiv = astro-ph/0409569 |s2cid=9234000|display-authors=etal}}</ref> The [[Cosmic Background Imager|CBI]] and the [[Very Small Array]] produces yet higher quality maps at high resolution (covering small areas of the sky).
* 2003 – The [[Wilkinson Microwave Anisotropy Probe]] spacecraft produces an even higher quality map at low and intermediate resolution of the whole sky (WMAP provides {{em|no}} high-resolution data, but improves on the intermediate resolution maps from [[BOOMERanG experiment|BOOMERanG]]).
* 2004 – E-mode polarization spectrum obtained by the [[Cosmic Background Imager|CBI]].<ref>A. Readhead et al., "Polarization observations with the Cosmic Background Imager", Science 306, 836–844 (2004).</ref>
* 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'dovich Array]] begin the first surveys for very high redshift [[galaxy cluster|clusters of galaxies]] using the [[Sunyaev–Zel'dovich effect]].
* 2005 – [[Ralph A. Alpher]] is awarded the [[National Medal of Science]] for his groundbreaking work in nucleosynthesis and prediction that the universe expansion leaves behind background radiation, thus providing a model for the Big Bang theory.
* 2006 – The long-awaited three-year [[WMAP]] results are released, confirming previous analysis, correcting several points, and including [[Cosmic microwave background radiation#Polarization|polarization]] data.
* 2006 – Two of COBE's principal investigators, [[George F. Smoot|George Smoot]] and [[John C. Mather|John Mather]], received the [[Nobel Prize in Physics]] in 2006 for their work on precision measurement of the CMBR.
* 2006–2011 – Improved measurements from [[WMAP]], new supernova surveys ESSENCE and SNLS, and baryon acoustic oscillations from [[Sloan Digital Sky Survey|SDSS]] and [[Astronomical survey#List of sky surveys|WiggleZ]], continue to be consistent with the standard [[Lambda-CDM model]].
* 2010 – The first all-sky map from the [[Planck (spacecraft)|Planck telescope]] is released.
* 2013 – An improved all-sky map from the [[Planck (spacecraft)|Planck telescope]] is released, improving the measurements of WMAP and extending them to much smaller scales.
* 2014 – On March 17, 2014, astrophysicists of the [[BICEP and Keck Array|BICEP2]] collaboration announced the detection of inflationary [[gravitational waves]] in the [[B-modes|B-mode]] [[power spectrum]], which if confirmed, would provide clear experimental evidence for the [[Inflation (cosmology)|theory of inflation]].<ref name="BICEP2-2014"/><ref name="NASA-20140317">{{cite web |last=Clavin |first=Whitney |title=NASA Technology Views Birth of the Universe |url=http://www.jpl.nasa.gov/news/news.php?release=2014-082 |date=March 17, 2014 |website=[[NASA]] |access-date=March 17, 2014 }}</ref><ref name="NYT-20140317">{{cite news |last=Overbye |first=Dennis |author-link=Dennis Overbye |date=March 17, 2014 |title=Space Ripples Reveal Big Bang's Smoking Gun |work=[[The New York Times]] |url=https://www.nytimes.com/2014/03/18/science/space/detection-of-waves-in-space-buttresses-landmark-theory-of-big-bang.html |url-access=registration |access-date=March 17, 2014}}</ref><ref name="NYT-20140324">{{cite news |last=Overbye |first=Dennis |author-link=Dennis Overbye |title=Ripples From the Big Bang |url=https://www.nytimes.com/2014/03/25/science/space/ripples-from-the-big-bang.html |archive-url=https://ghostarchive.org/archive/20220101/https://www.nytimes.com/2014/03/25/science/space/ripples-from-the-big-bang.html |archive-date=2022-01-01 |url-access=limited |date=March 24, 2014 |work=[[The New York Times]] |access-date=March 24, 2014 }}{{cbignore}}</ref><ref name="PRL-20140619">
{{cite journal |author=Ade, P.A.R. (BICEP2 Collaboration) |title=Detection of B-Mode Polarization at Degree Angular Scales by BICEP2 |year=2014 |journal=[[Physical Review Letters]] |volume=112 |issue=24 |page=241101 |doi=10.1103/PhysRevLett.112.241101 |pmid=24996078|arxiv = 1403.3985 |bibcode = 2014PhRvL.112x1101B |s2cid=22780831 }}</ref><ref>{{cite web | url=http://www.math.columbia.edu/~woit/wordpress/?p=6865 | title=BICEP2 News {{pipe}} Not Even Wrong}}</ref> However, on 19 June 2014, lowered confidence in confirming the [[cosmic inflation]] findings was reported.<ref name="PRL-20140619" /><ref name="NYT-20140619">{{cite news |last=Overbye |first=Dennis |author-link=Dennis Overbye |title=Astronomers Hedge on Big Bang Detection Claim |url=https://www.nytimes.com/2014/06/20/science/space/scientists-debate-gravity-wave-detection-claim.html |archive-url=https://ghostarchive.org/archive/20220101/https://www.nytimes.com/2014/06/20/science/space/scientists-debate-gravity-wave-detection-claim.html |archive-date=2022-01-01 |url-access=limited |date=June 19, 2014 |work=[[The New York Times]] |access-date=June 20, 2014 }}{{cbignore}}</ref><ref name="BBC-20140619">{{cite news |last=Amos |first=Jonathan |title=Cosmic inflation: Confidence lowered for Big Bang signal |url=https://www.bbc.com/news/science-environment-27935479 |date=June 19, 2014 |work=[[BBC News]] |access-date=June 20, 2014 }}</ref>
* 2015 – On January 30, 2015, the same team of astronomers from BICEP2 withdrew the claim made on the previous year. Based on the combined data of BICEP2 and Planck, the [[European Space Agency]] announced that the signal can be entirely attributed to [[Cosmic dust|dust]] in the Milky Way.<ref name="nature-20150130">{{cite journal|title=Gravitational waves discovery now officially dead|last=Cowen|first=Ron|date=2015-01-30|journal=Nature|doi=10.1038/nature.2015.16830|s2cid=124938210}}<!--|access-date=2015-10-26--></ref>
* 2018 – The final data and maps from the [[Planck (spacecraft)|Planck telescope]] is released, with improved measurements of the polarization on large scales.<ref>{{Cite journal |author1=Planck Collaboration |display-authors=etal |title=Planck 2018 results. I. Overview and the cosmological legacy of Planck |journal=Astronomy and Astrophysics |year=2020 |volume=641 |pages=A1 |doi=10.1051/0004-6361/201833880 |arxiv=1807.06205 |bibcode = 2020A&A...641A...1P|s2cid=119185252 }}</ref>
* 2019 – [[Planck (spacecraft)|Planck telescope]] analyses of their final 2018 data continue to be released.<ref>{{Cite journal |author1=Planck Collaboration |display-authors=etal |title=Planck 2018 results. V. CMB power spectra and likelihoods |journal=Astronomy and Astrophysics |year=2020 |volume=641 |pages=A5 |doi=10.1051/0004-6361/201936386 |arxiv=1907.12875 |bibcode=2020A&A...641A...5P |s2cid=198985935 }}</ref>