Dark Matter
Definition
An unseen form of matter, detected only through its gravity, that outweighs ordinary matter roughly five to one.
Scientific overview
Dark matter does not emit or absorb light, but its gravity is required to explain the rotation of galaxies, the motions of galaxy clusters, gravitational lensing, and the pattern of the cosmic microwave background. It makes up about 27% of the Universe.
Evidence
- Flat galaxy rotation curves (Rubin)
- Cluster dynamics (Zwicky, 1933)
- Gravitational lensing, e.g. the Bullet Cluster
- The CMB power spectrum
Current measurements
| Fraction of the Universe | ≈ 27% | Planck Collaboration |
Open questions
- What is dark matter made of (WIMPs, axions, something else)?
- Why has no particle been detected directly?
- Could modified gravity explain the observations instead?
Rests on
Related discoveries & objects
Measured by
Related scientists
Related topics
Knowledge connections
- Required byStructure Formation
- Required byThe Present Universe
- Related toDark Matter Halo
- Part of modelThe Lambda-CDM Model
- Depends onGeneral Relativity
- Related toEvidence for Dark Matter
- Studied byVera Rubin
- Studied byFritz Zwicky
- Measured byPlanck
- Measured byEuclid
- Related toThe Standard Model (overview)
- Related toThe Lambda-CDM Model
- Related toModified Newtonian Dynamics (MOND)
- Related toPrimordial Black Hole
- Required byDark Matter Halo
- Associated withGravitational Lensing
- Associated withGalaxy Rotation Curves
- Associated withThe Coma Cluster
- Associated withMatter Density (Ωm)
- Associated withAmplitude of Fluctuations (σ8)
- Associated withGalactic Rotation
Sources & references
The primary and reference sources this topic draws on.
- NASANational Aeronautics and Space Administration
Mission data, planetary science, space telescopes, and public-domain imagery.
Most NASA-produced imagery is in the public domain; individual items are checked for usage terms before publication.
- Planck CollaborationESA Planck mission / Planck Collaboration
Cosmic microwave background maps and the cosmological parameters of the ΛCDM model.
- ESAEuropean Space Agency
European missions, observatories, and space science imagery.