Editing Physical cosmology (section)

===Dark matter===
{{Main|Dark matter}}
Evidence from [[Big Bang nucleosynthesis]], the [[cosmic microwave background]], structure formation, and [[galaxy rotation curve]]s suggests that about 23% of the mass of the universe consists of non-baryonic dark matter, whereas only 4% consists of visible, [[baryonic matter]]. The gravitational effects of dark matter are well understood, as it behaves like a cold, [[Radioactive decay|non-radiative]] fluid that forms [[galactic halo|haloes]] around galaxies. Dark matter has never been detected in the laboratory, and the particle physics nature of dark matter remains completely unknown. Without observational constraints, there are a number of candidates, such as a stable [[supersymmetry|supersymmetric]] particle, a [[weakly interacting massive particle]], a gravitationally-interacting massive particle, an [[axion]], and a [[massive compact halo object]]. Alternatives to the dark matter hypothesis include a modification of gravity at small accelerations ([[MOND]]) or an effect from brane cosmology. [[TeVeS]] is a version of MOND that can explain gravitational lensing.<ref name=Klasen2015>{{cite journal | title=Indirect and direct search for dark matter | last1=Klasen | first1=M. | last2=Pohl | first2=M. | last3=Sigl | first3=G. | journal=Progress in Particle and Nuclear Physics | volume=85 | pages=1–32 | date=November 2015 | doi=10.1016/j.ppnp.2015.07.001 | arxiv=1507.03800 | bibcode=2015PrPNP..85....1K | s2cid=118359390 }}</ref>