Dark matter

⑂ Comparison. The views on this question, side by side under the same headings. The table is not a score: the number of pieces of evidence says nothing about their strength or truth. Details and sources are on each view’s own page.

Views shownModified Newtonian dynamics (MOND)Cold dark matter (the ΛCDM model)

	Idea / theory / claim · 1983Modified Newtonian dynamics (MOND)	Idea / theory / claim · 1984Cold dark matter (the ΛCDM model)
For everyone	In 1983 Mordehai Milgrom proposed that the rotation speeds of galaxies could be explained not by invisible matter but by a law of gravity that works differently at very weak accelerations. MOND predicts galaxy rotation curves from the visible matter alone with striking success. By contrast it struggles with galaxy clusters and the cosmic microwave background. Recent tests with wide binary stars have given opposing results.	On this view about four-fifths of the matter in the universe consists of slow-moving ("cold") particles that do not interact with light. Together with dark energy (Λ) it forms the standard model of cosmology (ΛCDM). The model successfully explains the cosmic microwave background, the large-scale distribution of galaxies and observations such as the Bullet Cluster. Despite decades of searching, however, dark matter particles have not been detected directly in the laboratory.
Claims	Because gravity departs from Newton's law at very weak accelerations, galaxies rotate fast without any need for invisible matter.	Most matter consists of cold, invisible particles that interact only through gravity.
Supporting	Observation In 153 galaxies the observed acceleration was found to follow a single, tight relation with the acceleration computed from visible matter alone, of the form MOND predicts. Observation An analysis of wide binary stars with Gaia data reported orbital speeds higher than Newton predicts at very low accelerations.	Observation In the Bullet Cluster the mass centres found by gravitational lensing are clearly offset from the X-ray-emitting hot gas, showing that most of the mass is not in the visible gas. Measurement The heights of the peaks in the power spectrum of the cosmic microwave background agree with high precision with a dark matter component separate from baryons.
Challenging	Observation A detailed statistical analysis of 8,611 wide binaries in Gaia data preferred Newtonian dynamics over MOND with very high confidence. Observation In the Bullet Cluster the mass lies apart from the visible gas, which is hard to explain by changing the law of gravity alone.	Experiment LZ, one of the world's most sensitive direct-detection experiments, found no signal from WIMP-type dark matter particles and set strict upper limits on possible interactions.
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