Editing Physical cosmology (section)

===Equations of motion===
{{main|Friedmann–Lemaître–Robertson–Walker metric}}

Within the [[standard cosmological model]], the [[equations of motion]] governing the universe as a whole are derived from general relativity with a small, positive cosmological constant.<ref>
{{cite journal |author=Ojeda |first1=P. |last2=Rosu |first2=H. |date=June 2006 |title=Supersymmetry of FRW barotropic cosmologies |journal=Int. J. Theor. Phys. |volume=45 |issue=6 |pages=1191–1196 |arxiv=gr-qc/0510004 |bibcode=2006IJTP...45.1152R |doi=10.1007/s10773-006-9123-2 |s2cid=119496918}}
</ref> The solution is an expanding universe; due to this expansion, the radiation and matter in the universe cool and become diluted. At first, the expansion is slowed down by [[gravitation]] attracting the radiation and matter in the universe. However, as these become diluted, the cosmological constant becomes more dominant and the expansion of the universe starts to accelerate rather than decelerate. In our universe this happened billions of years ago.<ref name=Springel2006>{{cite journal | title=The large-scale structure of the Universe | last1=Springel | first1=Volker | last2=Frenk | first2=Carlos S. | last3=White | first3=Simon D.M. | journal=Nature | volume=440 | issue=7088 | pages=1137–1144 | year=2006 | doi=10.1038/nature04805 | pmid=16641985 | bibcode=2006Natur.440.1137S | arxiv=astro-ph/0604561 | citeseerx=10.1.1.255.8877 | s2cid=8900982 }}</ref>