Definition: A cosmologist is a physicist who specializes in the study of the formation and evolution of the universe. Their interests revolve around the formation of massive structures within the universe, such as galaxies or galaxy clusters, rather than the behavior of individual stars. The current major issues in cosmology include (but are certainly not limited to):
- Understanding the specific nature of the big bang, including whether the predictions of inflation theory hold up
- Determining the matter density of the universe
- Determining the rate of expansion of the universe
- Determining the topology of the universe (this is a particular subfield known as cosmic topology, presented in detail in Jean-Pierre Luminet's The Wraparound Universe)
- Exploration of the ekpyrotic universe hypothesis (as presented by Turok & Steinhard in their book Endless Universe: Beyond the Big Bang)
- Understanding quantum gravity concepts, such as string theory, and applying them to the early universe.