Astronomy › Section U · Evolution and distribution of galaxies › Topic U.4
The challenge of dark matter
Galaxies and clusters move as if they contain far more mass than we can see. Several independent methods agree that this dark matter outweighs ordinary matter about five to one, yet what it is made of remains one of the biggest open questions in science.
In this topic
- Weighing what we cannot see
- Not much close to home
- Dark halos around galaxies
- Worked example: Zwicky's argument for a cluster
- Dark matter in clusters
- The mass-to-light ratio
- Worked example: a cluster's mass-to-light ratio
- The Bullet Cluster
- What could dark matter be?
- Known and unknown
- Common mistakes to avoid
- Key takeaways
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