Dark matter
Dark matter is an invisible, hypothetical form of matter that does not interact with electromagnetic radiation. Dark matter is implied by gravitational effects that cannot be explained by Einstein's general relativity unless more matter is present than can be astronomically observed. According to the Lambda-CDM model of cosmology, the mass–energy content of the universe is approximately 5% ordinary matter, 27% dark matter, and 68% a form of energy known as dark energy.
Quotes
[edit]- Even if one were to entertain the (incorrect) concept that there were dark matter, then one would even so need to use MOND as an effective and highly efficient theoretical framework to describe the observed stellar-dynamical systems.
- Pavel Kroupa, (March 30, 2026) "114. How Much of a Galaxy Is Really a Galaxy?". The Dark Matter Crisis, astro.uni-bonn.de.
- Three Lines of Evidence for Dark Matter
Three independent observations imply that matter cannot account for the gravity we observe in the universe.
• Galaxy rotation: Outer stars orbit too fast to be held by visible mass alone.
• Cluster dynamics: Galaxy clusters move too quickly to stay bound without unseen mass.
• Gravitational lensing: Background light bends more than visible foreground mass can explain.- Don Lincoln, (May 29, 2026) "Biggest Mysteries in Physics: Antimatter, Dark Energy & ToE - Don Lincoln | Lex Fridman Podcast #497". Lex Fridman, YouTube. (quote at 2:28:31 of 2:53:42 in video)
- … tidal dwarfs … are born in gas tails produced in the aftermath of high-speed galaxy collisions. These dwarfs are formed in one, relatively clean, process, whereby previous history is erased. CDM predicts robustly that practically no DM finds its way into these dwarfs, contrary to what is claimed to be observed … MOND does predict correctly the observed mass discrepancies in such systems.
- Mordehai Milgrom, (2011) . "MD or DM? Modified dynamics at low accelerations vs dark matter". arXiv preprint arXiv:1101.5122.
- The evidence for the dark matter of the hot big bang cosmology is about as good as it gets in natural science. The exploration of its nature is now led by direct and indirect detection experiments, to be complemented by advances in the full range of cosmological tests, including judicious consideration of the rich phenomenology of galaxies. The results may confirm ideas about DM already under discussion. If we are lucky we also will be surprised once again.
The case for the hypothetical nonbaryonic dark matter (DM) of the relativistic hot big bang Lambda cold dark matter (ΛCDM) cosmology and its companion in the dark sector, Einstein’s cosmological constant Λ [or the near equivalent, dark energy (DE)], rests, in part, on precision measurements, notably of the thermal cosmic microwave background (CMB) radiation. However, equally important are the less precise measurements that look at the universe from many different sides and test for systematic errors in the measurements and inadequacies of the theory used to interpret the measurements.- P. J. E. Peebles, (2013) . "Dark Matter". arXiv:1305.6859 [astro-ph.CO]. DOI:10.48550/arXiv.1305.6859. (Essay for the Dark Matter Sackler Colloquium, October 2012, Irvine, California; also published in: (May 2, 2014) "Dark Matter". Proceedings of the National Academy of Sciences (40): 12246–12248.)
- I don’t know if we have dark matter or need a change in gravity or need something else; we know so little about our universe. It is a strange and mysterious universe. But that’s fun.
- Vera Rubin, as quoted by Neta Bahcall in: (2021) . "Biographical Memoir of Vera C. Rubin (1928–2016)". Biographical Memoirs of the National Academy of Sciences: 1–13. (quote from page 7)
