Dark matter

Definition

Dark matter is a form of matter that does not emit, absorb, or reflect light, making it invisible to current detection methods. Its presence is inferred from its gravitational effects on visible matter and the structure of the universe.

5 Must Know Facts For Your Next Test

1. Dark matter constitutes approximately 27% of the universe's mass-energy content.
2. It was first proposed to explain discrepancies in the rotational speeds of galaxies.
3. Dark matter interacts primarily through gravity and possibly weakly via other forces.
4. Its existence is supported by observations such as gravitational lensing and cosmic microwave background radiation.
5. The exact nature and composition of dark matter remain unknown, with several candidate particles being proposed.

Review Questions

• What percentage of the universe's mass-energy content is made up of dark matter?
• How was dark matter initially hypothesized?
• What observational evidence supports the existence of dark matter?

Related terms

Gravitational Lensing:

The bending of light around massive objects, such as galaxies or clusters, due to their gravitational field. This effect provides evidence for dark matter.

$\Lambda$CDM Model: $\Lambda$CDM (Lambda Cold Dark Matter) is the standard model of cosmology that includes dark energy ($\Lambda$) and cold dark matter as major components influencing the evolution and structure of the universe.

Cosmic Microwave Background (CMB): Radiation left over from the early stages of the universe, providing a snapshot of its infancy. Variations in the CMB give clues about dark matter distribution.