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Dark Matter ○｜Definition｜1st｜20251119205401-00-⌔

Dark matter - Wikipedia

Dark matter

In astronomy and cosmology, dark matter is an invisible and hypothetical form of matter that does not interact with electromagnetic radiation, including light. Dark matter is implied by gravitational effects that cannot be explained by general relativity unless more matter is present than can be observed. Such effects occur in the context of formation and evolution of galaxies,1 gravitational lensing,2 the observable universe’s current structure, mass position in galactic collisions,3 the motion of galaxies within galaxy clusters, and cosmic microwave background anisotropies. Dark matter is thought to serve as gravitational scaffolding for cosmic structures.4 After the Big Bang, dark matter clumped into blobs along narrow filaments with superclusters of galaxies forming a cosmic web at scales on which entire galaxies appear like tiny particles.56

In the standard Lambda-CDM model of cosmology, the mass–energy content of the universe is 5% ordinary matter, 26.8% dark matter, and 68.2% a form of energy known as dark energy.78910 Thus, dark matter constitutes 85% of the total mass, while dark energy and dark matter constitute 95% of the total mass–energy content.11121314 While the density of dark matter is significant in the halo around a galaxy, its local density in the Solar System is much less than normal matter. The total of all the dark matter out to the orbit of Neptune would add up to about 10 kg, the same as a large asteroid.15 Dark matter is classified as “cold”, “warm”, or “hot” according to velocity (more precisely, its free streaming length). Recent models have favored a cold dark matter scenario, in which structures emerge by the gradual accumulation of particles.

Dark matter is not known to interact with ordinary baryonic matter and radiation except through gravity, making it difficult to detect in the laboratory. The most prevalent explanation is that dark matter is some as-yet-undiscovered subatomic particle, such as either weakly interacting massive particles (WIMPs) or axions.16 The other main possibility is that dark matter is composed of primordial black holes.171819

Although the astrophysics community generally accepts the existence of dark matter,20 a minority of astrophysicists, intrigued by specific observations that are not well explained by ordinary dark matter, argue for various modifications of the standard laws of general relativity. These include modified Newtonian dynamics (MOND), tensor–vector–scalar gravity, and entropic gravity. So far, none of the proposed modified gravity theories can describe every piece of observational evidence at the same time, suggesting that even if gravity has to be modified, some form of dark matter would still be required.21

Printed 2026-06-28.

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Footnotes

  1. Siegfried, T. (5 July 1999). “Hidden space dimensions may permit parallel universes, explain cosmic mysteries”. The Dallas Morning News. Archived from the original on 21 February 2015. Retrieved 24 October 2009. ↩

  2. Trimble, V. (1987). “Existence and nature of dark matter in the universe” (PDF). Annual Review of Astronomy and Astrophysics. 25: 425–472. Bibcode:1987ARA&A..25..425T. doi:10.1146/annurev.aa.25.090187.002233. ISSN 0066-4146. S2CID 123199266. Archived (PDF) from the original on 18 July 2018. ↩

  3. “A history of dark matter”. 2017. ↩

  4. “The Milky Way May Be Missing a Trillion Suns’ Worth of Mass”. Scientific American. 10 October 2023. Archived from the original on 27 April 2025. Retrieved 6 March 2025. ↩

  5. Schilling, Govert (23 May 2001). “Filaments of the Early Universe”. Science. ↩

  6. Stapelberg, Sebastian (5 December 2022). “The Cosmic Web of Galaxies, Dark Matter and How It Emerged”. Structures Blog. ↩

  7. “Planck Mission Brings Universe into Sharp Focus”. NASA Mission Pages. 21 March 2013. Archived from the original on 12 November 2020. Retrieved 1 May 2016. ↩

  8. “Dark Energy, Dark Matter”. NASA Science: Astrophysics. 5 June 2015. Archived from the original on 2 June 2013. Retrieved 12 July 2017. ↩

  9. Ade, P. A. R.; Aghanim, N.; Armitage-Caplan, C.; et al. (Planck Collaboration) (22 March 2013). “Planck 2013 results. I. Overview of products and scientific results – Table 9”. Astronomy and Astrophysics. 1303: 5062. arXiv:1303.5062. Bibcode:2014A&A…571A…1P. doi:10.1051/0004-6361/201321529. S2CID 218716838. Archived from the original on 9 June 2016. Retrieved 5 May 2016. ↩

  10. Francis, Matthew (22 March 2013). “First Planck results: the Universe is still weird and interesting”. Ars Technica. Archived from the original on 2 May 2019. Retrieved 14 June 2017. ↩

  11. “Planck captures portrait of the young Universe, revealing earliest light”. University of Cambridge. 21 March 2013. Archived from the original on 17 April 2019. Retrieved 21 March 2013. ↩

  12. Carroll, Sean (2007). Dark Matter, Dark Energy: The dark side of the universe. The Teaching Company. Guidebook Part 2 p. 46… dark matter: An invisible, essentially collisionless component of matter that makes up about 25 percent of the energy density of the universe… it’s a different kind of particle… something not yet observed in the laboratory… ↩

  13. Ferris, Timothy (January 2015). “Dark matter”. Hidden cosmos. National Geographic Magazine. Archived from the original on 25 December 2014. Retrieved 10 June 2015. ↩

  14. Jarosik, N.; et al. (2011). “Seven-year Wilson microwave anisotropy probe (WMAP) observations: Sky maps, systematic errors, and basic results”. Astrophysical Journal Supplement. 192 (2): 14. arXiv:1001.4744. Bibcode:2011ApJS..192…14J. doi:10.1088/0067-0049/192/2/14. S2CID 46171526. ↩

  15. Siegel, Ethan (3 July 2018). “This Is How Much Dark Matter Passes Through Your Body Every Second”. Forbes. Archived from the original on 20 December 2024. Retrieved 6 March 2025. ↩

  16. Timmer, John (21 April 2023). “No WIMPS! Heavy particles don’t explain gravitational lensing oddities”. Ars Technica. Retrieved 21 June 2023. ↩

  17. Carr, B. J.; Clesse, S.; García-Bellido, J.; Hawkins, M. R. S.; Kühnel, F. (26 February 2024). “Observational evidence for primordial black holes: A positivist perspective”. Physics Reports. 1054: 1–68. arXiv:2306.03903. Bibcode:2024PhR..1054…1C. doi:10.1016/j.physrep.2023.11.005. See Figure 39. ↩

  18. Bird, Simeon; Albert, Andrea; Dawson, Will; Ali-Haïmoud, Yacine; Coogan, Adam; Drlica-Wagner, Alex; Feng, Qi; Inman, Derek; Inomata, Keisuke; Kovetz, Ely; Kusenko, Alexander; Lehmann, Benjamin V.; Muñoz, Julian B.; Singh, Rajeev; Takhistov, Volodymyr; Tsai, Yu-Dai (1 August 2023). “Primordial black hole dark matter”. Physics of the Dark Universe. 41 101231. arXiv:2203.08967. Bibcode:2023PDU…4101231B. doi:10.1016/j.dark.2023.101231. ISSN 2212-6864. S2CID 247518939. ↩

  19. Carr, Bernard; Kühnel, Florian (2 May 2022). “Primordial black holes as dark matter candidates”. SciPost Physics Lecture Notes 48. arXiv:2110.02821. doi:10.21468/SciPostPhysLectNotes.48. S2CID 238407875. Archived from the original on 7 March 2023. Retrieved 13 February 2023. (See also the accompanying slide presentation. Archived 13 February 2023 at the Wayback Machine ↩

  20. McGaugh, Stacy S.; Hossenfelder, Sabine (April 2019). “Is Dark Matter Real?”. Scientific American. 28 (2s): 36–43. Bibcode:2018SciAm.319b..36H. doi:10.1038/scientificamerican0818-36. PMID 30020902. Right now a few dozens of scientists are studying modified gravity, whereas several thousand are looking for particle dark matter. ↩

  21. Carroll, Sean (9 May 2012). “Dark matter vs. modified gravity: A trialogue”. Archived from the original on 14 February 2017. Retrieved 14 February 2017. ↩

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