Editing Big Bang (section)

=== As a named model ===
Ironically, it was Hoyle who coined the phrase that came to be applied to Lemaître's theory, referring to it as "this ''big bang'' idea" during a BBC Radio broadcast in March 1949.<ref name="Mitton2011_p129" /><ref name="Kragh2013" />{{refn|It is commonly reported that Hoyle intended this to be pejorative. However, Hoyle later denied that, saying that it was just a striking image meant to emphasize the difference between the two theories for radio listeners.<ref name="Croswell1995_chpt9" />|group="notes"}} For a while, support was split between these two theories. Eventually, the observational evidence, most notably from radio [[source counts]], began to favor Big Bang over steady state. The discovery and confirmation of the CMB in 1964 secured the Big Bang as the best theory of the origin and evolution of the universe.<ref name="penzias">{{cite journal |last1=Penzias |first1=Arno A. |author1-link=Arno Allan Penzias |last2=Wilson |first2=R. W. |author2-link=Robert Woodrow Wilson |date=July 1965 |title=A Measurement of Excess Antenna Temperature at 4080&nbsp;Mc/s |url=https://fermatslibrary.com/s/a-measurement-of-excess-antenna-temperature-at-4080-mc-s |url-status=live |journal=[[The Astrophysical Journal]] |volume=142 |pages=419–421 |bibcode=1965ApJ...142..419P |doi=10.1086/148307 |archive-url=https://web.archive.org/web/20191014185903/https://fermatslibrary.com/s/a-measurement-of-excess-antenna-temperature-at-4080-mc-s |archive-date=14 October 2019 |access-date=5 December 2019|doi-access=free }}</ref>

In 1968 and 1970, [[Roger Penrose]], [[Stephen Hawking]], and [[George F. R. Ellis]] published papers where they showed that [[Singularity (mathematics)|mathematical singularities]] were an inevitable initial condition of relativistic models of the Big Bang.<ref>{{cite journal |last1=Hawking |first1=Stephen W. |author1-link=Stephen Hawking |last2=Ellis |first2=George F. R. |author2-link=George F. R. Ellis |date=April 1968 |title=The Cosmic Black-Body Radiation and the Existence of Singularities in our Universe |journal=[[The Astrophysical Journal]] |volume=152 |page=25 |bibcode=1968ApJ...152...25H |doi=10.1086/149520}}</ref><ref>{{cite journal |last1=Hawking |first1=Stephen W. |author1-link=Stephen Hawking |last2=Penrose |first2=Roger |author2-link=Roger Penrose |date=27 January 1970 |title=The Singularities of Gravitational Collapse and Cosmology |volume=314 |issue=1519 |pages=529–548 |journal=[[Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences]] |bibcode=1970RSPSA.314..529H |doi=10.1098/rspa.1970.0021|s2cid=120208756 |doi-access= }}</ref> Then, from the 1970s to the 1990s, cosmologists worked on characterizing the features of the Big Bang universe and resolving outstanding problems. In 1981, [[Alan Guth]] made a breakthrough in theoretical work on resolving certain outstanding theoretical problems in the Big Bang models with the introduction of an epoch of rapid expansion in the early universe he called "inflation".<ref>{{cite journal |last=Guth |first=Alan |author-link=Alan Guth |date=15 January 1981 |title=Inflationary universe: A possible solution to the horizon and flatness problems |journal=[[Physical Review D]] |volume=23 |issue=2 |pages=347–356 |bibcode=1981PhRvD..23..347G |doi=10.1103/PhysRevD.23.347 |doi-access=free }}</ref> Meanwhile, during these decades, two questions in [[observational cosmology]] that generated much discussion and disagreement were over the precise values of the Hubble Constant<ref>{{cite journal |url=https://www.cfa.harvard.edu/~dfabricant/huchra/hubble/ |title=The Hubble Constant |last1=Huchra |first1=John P. |volume=256 |issue=5055 |pages=321–5 |author-link=John Huchra |year=2008 |journal=Science |archive-url=https://web.archive.org/web/20190930124013/https://www.cfa.harvard.edu/~dfabricant/huchra/hubble/ |archive-date=30 September 2019 |access-date=5 December 2019|pmid=17743107 |doi=10.1126/science.256.5055.321 |s2cid=206574821 }}</ref> and the matter-density of the universe (before the discovery of dark energy, thought to be the key predictor for the eventual [[Ultimate fate of the universe|fate of the universe]]).<ref>{{harvnb|Livio|2000|p=160}}</ref>

Significant progress in Big Bang cosmology has been made since the late 1990s as a result of advances in [[telescope]] technology as well as the analysis of data from satellites such as the [[Cosmic Background Explorer]] (COBE),<ref name=cobe>{{cite journal |last1=Boggess |first1=Nancy W. | last2=Mather | first2=John C. |author2-link=John C. Mather |author3-last=Weiss |author3-first=Rainer |author3-link=Rainer Weiss |last4=Bennett |first4=C. L. |last5=Cheng |first5=E. S. |last6=Dwek |first6=E. |last7=Gulkis |first7=S. |last8=Hauser |first8=M. G. |last9=Janssen |first9=M. A. |last10=Kelsall |first10=T. |last11=Meyer |first11=S. S. |last12=Moseley |first12=S. H. |last13=Murdock |first13=T. L. |last14=Shafer |first14=R. A. |last15=Silverberg |first15=R. F. |last16=Smoot |first16=G. F. |last17=Wilkinson |first17=D. T. |last18=Wright |first18=E. L. |display-authors=3 |date=1 October 1992 |title=The COBE Mission: Its Design and Performance Two Years after the launch |journal=[[The Astrophysical Journal]] |volume=397 |pages=420–429 |bibcode=1992ApJ...397..420B |doi=10.1086/171797|doi-access=free }}</ref> the [[Hubble Space Telescope]] and WMAP.<ref name="wmap1year">{{cite journal |last1=Spergel |first1=David N. |author1-link=David Spergel |last2=Bean |first2=Rachel |author2-link=Rachel Bean |last3=Doré |first3=Olivier |author-link3=Olivier Doré |display-authors=etal |date=June 2007 |title=Three-Year ''Wilkinson Microwave Anisotropy Probe (WMAP)'' Observations: Implications for Cosmology |journal=[[The Astrophysical Journal Supplement Series]] |volume=170 |issue=2 |pages=377–408 |arxiv=astro-ph/0603449 |bibcode=2007ApJS..170..377S |doi=10.1086/513700 |s2cid=1386346}}</ref> Cosmologists now have fairly precise and accurate measurements of many of the parameters of the Big Bang model, and have made the unexpected discovery that the expansion of the universe appears to be accelerating.<ref>{{cite journal |last1=Reiss |first1=Adam G. |last2=Filippenko |first2=Alexei V. |last3=Challis |first3=Peter |last4=Clocchiatti |first4=Alejandro |last5=Diercks |first5=Alan |last6=Garnavich |first6=Peter M. |last7=Gilliland |first7=Ron L. |last8=Hogan |first8=Craig J. |last9=Jha |first9=Saurabh |last10=Kirshner |first10=Robert P. |last11=Leibundgut |first11=B. |last12=Phillips |first12=M. M. |last13=Reiss |first13=David |last14=Schmidt |first14=Brian P. |last15=Schommer |first15=Robert A. |last16=Smith |first16=R. Chris |last17=Spyromilio |first17=J. |last18=Stubbs |first18=Christopher |last19=Suntzeff |first19=Nicholas B. |last20=Tonry |first20=John |title=Observational Evidence from Supernovae for an Accelerating Universe and a Cosmological Constant |date=1998 |journal=[[The Astronomical Journal]] |volume=116 |issue=3 |pages=1009–1038 |doi=10.1086/300499 |arxiv=astro-ph/9805201|bibcode=1998AJ....116.1009R |s2cid=15640044 }}</ref><ref>{{cite journal |last1=Perlmutter |first1=S. |last2=Aldering |first2=G. |last3=Goldhaber |first3=G. |last4=Knop |first4=R.A. |last5=Nugent |first5=P. |last6=Castro |first6=P.G. |last7=Deustua |first7=S. |last8=Fabbro |first8=S. |last9=Goobar |first9=A. |last10=Groom |first10=D.E. |last11=Hook |first11=I.M. |last12=Kim |first12=A.G. |last13=Kim |first13=M.Y. |last14=Lee |first14=J.C. |last15=Nunes |first15=N.J. |last16=Pain |first16=R. |last17=Pennypacker |first17=C.R. |last18=Quimby |first18=R. |last19=Lidman |first19=C. |last20=Ellis |first20=R.S. |last21=Irwin |first21=M. |last22=McMahon |first22=R.G.  |last23=Ruiz-Lapuente |first23=P.  |last24=Walton  |first24=N.  |last25=Schaefer  |first25=B. |last26=Boyle |first26=B.J. |last27=Filippenko |first27=A.V. |last28=Matheson |first28=T. |last29=Fruchter |first29=A.S. |last30=Panagia |first30=N. |last31=Newberg |first31=H.J.M. |last32=Couch |first32=W.J. |date=1999 |title=Measurements of Omega and Lambda from 42 High-Redshift Supernovae |volume=517 |issue=2 |journal=[[The Astrophysical Journal]] |pages=565–586 |arxiv=astro-ph/9812133 |doi=10.1086/307221|bibcode=1999ApJ...517..565P |s2cid=118910636 }}</ref>