Changes

Dark matter was first proposed by [[Jan Oort]] in 1932 as a reason for the spinning speeds of stars in the [[Milky Way]]. [[Fritz Zwicky]] in 1933 used dark matter to explain "missing mass" in the spinning speeds of [[galaxy|galaxies]] in [[galaxy cluster|clusters]]. Later, many other observations have suggested that there is dark matter in the universe. The spinning speeds of galaxies,<ref>[http://www.darkmatterphysics.com/Galactic-rotation-curves-of-spiral-galaxies.htm First observational evidence of dark matter]. Darkmatterphysics.com. Retrieved on 6 August 2013.</ref> [[gravitational lensing]] of background objects, the temperature distribution of hot gas in galaxies and clusters of galaxies: these are some of the examples that make scientists believe in dark matter.

Dark matter was first proposed by [[Jan Oort]] in 1932 as a reason for the spinning speeds of stars in the [[Milky Way]]. [[Fritz Zwicky]] in 1933 used dark matter to explain "missing mass" in the spinning speeds of [[galaxy|galaxies]] in [[galaxy cluster|clusters]]. Later, many other observations have suggested that there is dark matter in the universe. The spinning speeds of galaxies,<ref>[http://www.darkmatterphysics.com/Galactic-rotation-curves-of-spiral-galaxies.htm First observational evidence of dark matter]. Darkmatterphysics.com. Retrieved on 6 August 2013.</ref> [[gravitational lensing]] of background objects, the temperature distribution of hot gas in galaxies and clusters of galaxies: these are some of the examples that make scientists believe in dark matter.

According to the [[Planck (spacecraft)#2013 data release|Planck mission team]], and based on the [[standard model of cosmology]], the total [[Mass–energy equivalence|mass–energy]] of the [[observable universe|known universe]] contains 4.9% [[Baryon#Baryonic matter|ordinary matter]], 26.8% dark matter and 68.3% [[dark energy]].<ref name="planck_overview">{{cite journal |first1=P.A.R. |last1=Ade |first2=N. |last2=Aghanim |first3=C. |last3=Armitage-Caplan |last4=''et al''. (Planck Collaboration) |title=Planck 2013 results. I. Overview of products and scientific results&nbsp;– Table 9 |journal=Astronomy and Astrophysics |volume=1303 |pages=5062 |url=http://www.sciops.esa.int/index.php?project=PLANCK&page=Planck_Published_Papers |date=2013 |arxiv=1303.5062 |bibcode=2013arXiv1303.5062P |displayauthors=30 |access-date=2014-07-24 |archive-date=2016-08-13 |archive-url=https://web.archive.org/web/20160813220816/http://www.sciops.esa.int/index.php?project=PLANCK |url-status=dead }}</ref><ref name="wmap7parameters">{{cite web|title = First Planck results: the Universe is still weird and interesting|url =https://arstechnica.com/science/2013/03/first-planck-results-the-universe-is-still-weird-and-interesting/|author=Francis, Matthew |date= 2013|work=Arstechnica}}</ref> Thus, dark matter is estimated to make up 84.5% <!--26.8/(4.9 + 26.8)--> of the total matter in the universe, while dark energy plus dark matter make up 95.1% of the total "stuff" in the universe.<ref name=planckcam>{{cite web |url=http://www.cam.ac.uk/research/news/planck-captures-portrait-of-the-young-universe-revealing-earliest-light |title=Planck captures portrait of the young Universe, revealing earliest light |date= 2013 |publisher=University of Cambridge  |accessdate=22 March 2013}}</ref><ref>Ferris, Timothy. 2015. Dark Matter. ''National Geographic''. [http://ngm.nationalgeographic.com/2015/01/hidden-cosmos/ferris-text] {{Webarchive|url=https://web.archive.org/web/20141225013843/http://ngm.nationalgeographic.com/2015/01/hidden-cosmos/ferris-text |date=2014-12-25 }}</ref>

According to the [[Planck (spacecraft)#2013 data release|Planck mission team]], and based on the [[standard model of cosmology]], the total [[Mass–energy equivalence|mass–energy]] of the [[observable universe|known universe]] contains 4.9% [[Baryon#Baryonic matter|ordinary matter]], 26.8% dark matter and 68.3% [[dark energy]].<ref name="planck_overview">{{cite journal |first1=P.A.R. |last1=Ade |first2=N. |last2=Aghanim |first3=C. |last3=Armitage-Caplan |last4=''et al''. (Planck Collaboration) |title=Planck 2013 results. I. Overview of products and scientific results&nbsp;– Table 9 |journal=Astronomy and Astrophysics |volume=1303 |pages=5062 |url=http://www.sciops.esa.int/index.php?project=PLANCK&page=Planck_Published_Papers |date=2013 |arxiv=1303.5062 |bibcode=2013arXiv1303.5062P |displayauthors=30 |access-date=2014-07-24 |archive-date=2016-08-13 |archive-url=https://web.archive.org/web/20160813220816/http://www.sciops.esa.int/index.php?project=PLANCK |url-status=dead }}</ref><ref name="wmap7parameters">{{cite web|title = First Planck results: the Universe is still weird and interesting|url =https://arstechnica.com/science/2013/03/first-planck-results-the-universe-is-still-weird-and-interesting/|author=Francis, Matthew |date= 2013|work=Arstechnica}}</ref> So, dark matter is estimated to make up 84.5% <!--26.8/(4.9 + 26.8)--> of the total matter in the universe, while dark energy plus dark matter make up 95.1% of the total "stuff" in the universe.<ref name=planckcam>{{cite web |url=http://www.cam.ac.uk/research/news/planck-captures-portrait-of-the-young-universe-revealing-earliest-light |title=Planck captures portrait of the young Universe, revealing earliest light |date= 2013 |publisher=University of Cambridge  |accessdate=22 March 2013}}</ref><ref>Ferris, Timothy. 2015. Dark Matter. ''National Geographic''. [http://ngm.nationalgeographic.com/2015/01/hidden-cosmos/ferris-text] {{Webarchive|url=https://web.archive.org/web/20141225013843/http://ngm.nationalgeographic.com/2015/01/hidden-cosmos/ferris-text|date=2014-12-25}}</ref>

   

   

Because dark matter does not seem to give off or reflect [[light]], [[x-ray]]s, or any other [[electromagnetic radiation|radiation]], the instruments that are used to find normal matter (like hot gas, stars, planets, and us) can't find dark matter. It seems that dark matter is not made of the same thing as the matter we see every day on Earth. The only way we can tell if dark matter is there, is by how it affects things we can "see" by gravity.

Because dark matter does not seem to give off or reflect [[light]], [[x-ray]]s, or any other [[electromagnetic radiation|radiation]], the instruments that are used to find normal matter (like hot gas, stars, planets, and us) can't find dark matter. It seems that dark matter is not made of the same thing as the matter we see every day on Earth. The only way we can tell if dark matter is there, is by how it affects things we can "see" by gravity.