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{{cite journal|last=Narlikar|first=J. V.|last2=Wickramasinghe|first2=N. C.|year=1967|title=Microwave Background in a Steady State Universe|journal=[[Nature (journal)|Nature]]|volume=216|pages=43–44|doi=10.1038/216043a0|bibcode=1967Natur.216...43N}}</ref>. Utilizzando questo modello, e sulla base dello studio delle caratteristiche delle linee di assorbimento negli spettri delle stelle, l'astronomo [[Andrea McKellar]] ha scritto nel 1941: "Si può calcolare che la temperatura rotazionale dello spazio interstellare è di 2 K.<ref name="dao7" /><ref>Nell'originale: ''It can be calculated that the rotational temperature of interstellar space is 2 K.''</ref>. Tuttavia, durante gli [[anni 1970]] venne stabilito che la radiazione cosmica di fondo è un residuo del Big Bang. Questo perché nuove misurazioni a una gamma di frequenze dello spettro hanno mostrato che era uno spettro di [[corpo nero]] termico, un risultato che il modello dello stato stazionario non riusciva a riprodurre<ref>

{{cite journal|last=Peebles|first=P. J. E.|coauthors=''et al.''|year=1991|title=The case for the relativistic hot big bang cosmology|journal=[[Nature (journal)|Nature]]|volume=352|pages=769–776|doi=10.1038/352769a0|bibcode=1991Natur.352..769P}}</ref>.

[[Image:Horn Antenna-in Holmdel, New Jersey.jpeg|thumb|left|L'antenna Holmdel con la quale Penzias e Wilson scoprirono la radiazione cosmica di fondo.]]

Harrison, Peebles, Yu ande Zel'dovich realizedsi thatresero theconto earlyche universe wouldl'universo haveprimordiale toavrebbe havedovuto inhomogeneitiesavere atdisomogeneità thea levellivello ofdi 10⁻⁴ oro 10⁻⁵.<ref>

{{cite journal|last=Harrison|first=E. R.|year=1970|title=Fluctuations at the threshold of classical cosmology|journal=[[Physical Review D]]|volume=1|pages=2726–2730|doi=10.1103/PhysRevD.1.2726}}</ref><ref>{{cite journal|last=Peebles|first=P. J. E.|last2=Yu|first2=J. T.|year=1970|title=Primeval Adiabatic Perturbation in an Expanding Universe|journal=[[Astrophysical Journal]]|volume=162|pages=815–836|doi=10.1086/150713}}</ref><ref>

{{cite journal|last=Zeldovich|first=Y. B.|year=1972|title=A hypothesis, unifying the structure and the entropy of the Universe|journal=[[Monthly Notices of the Royal Astronomical Society]]|volume=160|pages=1P–4P|doi=|bibcode=1972MNRAS.160P...1Z}}</ref>. [[Rashid Sunyaev]] laterpoi calculatedcalcolò thel'impronta observableosservabile imprintche thattali thesedisomogeneità inhomogeneitiesavrebbero wouldsulla haveradiazione oncosmica thedi cosmic microwave background.fondo<ref>

{{cite conference|last=Doroshkevich|first=A. G.|last2=Zel'Dovich|first2=Y. B.|last3=Syunyaev|first3=R. A.|date=12–16 September 1977|title=Fluctuations of the microwave background radiation in the adiabatic and entropic theories of galaxy formation|editors=Longair, M. S. and Einasto, J. |booktitle=The large scale structure of the universe; Proceedings of the Symposium|publisher=Dordrecht, D. Reidel Publishing Co.|pages=393–404|___location=Tallinn, Estonian SSR|bibcode=1978IAUS...79..393S|accessdate=2008-12-12}} While this is the first paper to discuss the detailed observational imprint of density inhomogeneities as anisotropies in the cosmic microwave background, some of the groundwork was laid in Peebles and Yu, above.</ref>. IncreasinglyLimiti stringentsempre limitspiù onstretti thesull'anisotropia anisotropydella ofradiazione thecosmica cosmicdi microwavefondo backgroundsono werestati setstabiliti byda groundesperimenti basedda experimentsterra terra, butanche these anisotropyl'anisotropia wasè firststata detectedinnanzitutto viarilevata analysisattraverso ofl'analisi dei dati del [[RELIKT-1]] data <ref>{{cite news|last=Zaitsev|first=Y.|date=21 November 2006|title=Nobel Prize In Physics: Russia's Missed Opportunities|url=http://www.bilkent.edu.tr/~crs/russianmissedopport.htm|publisher=[[RIA Novosti]]|accessdate=2008-12-11}}</ref><ref>{{cite article|last=Skulachev|first=Dmitry|title=History of relict radiation study: Soviet "RELIKT" and American "COBE"|url=http://www.inauka.ru/phisic/article93112/print.html|publisher=Izvestia Nauki (Science News)|accessdate=2010-05-28}}</ref>, whatciò wasche reportedè instato Januaryriportato 1992.nel Becausegennaio ofdel multimonth[[1992]]. delayA incausa formaldel publicationritardo byplurimensile magazines,nella whichpubblicazione nonethelessformale printedda actualparte datedelle ofriviste submissionspecializzate, ofil thepremio article, [[Nobel Prize]]per inla physicsfisica forper il 2006 wentvenne toassegnato al team behinddel [[COBE]], whichche rilevò detectedle theanisotropie anisotropytramite viaun Differentialradiometro Microwavedifferenziale Radiometera instrumentmicroonde fewpochi monthsmesi laterdopo<ref>

{{cite journal|last=Smooth|first=G. F.|coauthors=''et al.''|year=1992|title=Structure in the COBE differential microwave radiometer first-year maps|journal=[[Astrophysical Journal Letters]]|volume=396|issue=1|pages=L1–L5|doi=10.1086/186504}}</ref><ref>

{{cite journal|last=Bennett|first=C.L.|coauthors=''et al.''|year=1996|title=Four-Year COBE DMR Cosmic Microwave Background Observations: Maps and Basic Results|journal=[[Astrophysical Journal Letters]]|volume=464|pages=L1–L4|doi=10.1086/310075}}</ref>.

Inspired by the RELIKT-1/COBE results, a series of ground and balloon-based experiments measured cosmic microwave background anisotropies on smaller angular scales over the next decade. The primary goal of these experiments was to measure the scale of the first acoustic peak, which COBE did not have sufficient resolution to resolve. This peak corresponds to large scale density variations in the early universe that are created by gravitational instabilities, resulting in acoustical oscillations in the plasma.<ref>