Dark matter

Definition

Dark matter is a form of matter that does not emit, absorb, or reflect light, making it invisible to current instruments. It exerts gravitational forces and is thought to constitute approximately 27% of the universe's mass-energy content.

5 Must Know Facts For Your Next Test

1. Dark matter was first hypothesized by Fritz Zwicky in the 1930s while studying galaxy clusters.
2. It is essential for explaining the rotation curves of galaxies, which show that outer regions rotate faster than can be accounted for by visible mass alone.
3. Gravitational lensing provides indirect evidence for dark matter through its effect on light from distant objects.
4. The Cosmic Microwave Background (CMB) data supports the existence of dark matter as part of the universe's composition.
5. Unlike normal baryonic matter, dark matter does not interact with electromagnetic forces, making it difficult to detect directly.

Review Questions

• Who first proposed the existence of dark matter?
• How does dark matter influence the rotation curves of galaxies?
• What evidence from gravitational lensing supports the existence of dark matter?

Related terms

Baryonic Matter:

Ordinary matter consisting of protons, neutrons, and electrons that makes up stars, planets, and living organisms.

Gravitational Lensing:

The bending of light from a distant source caused by the gravitational field of an intervening massive object.

Cosmic Microwave Background (CMB): The thermal radiation left over from the Big Bang, providing evidence about the early universe and its composition.