Book contents
- Frontmatter
- Contents
- Preface
- 1 Overview: Galaxies and Cosmology
- 2 Galactic Structure and Dynamics
- 3 Friedmann Model of the Universe
- 4 Thermal History of the Universe
- 5 Structure Formation
- 6 Cosmic Microwave Background Radiation
- 7 Formation of Baryonic Structures
- 8 Active Galactic Nuclei
- 9 Intergalactic Medium and Absorption Systems
- 10 Cosmological Observations
- Notes and References
- Index
1 - Overview: Galaxies and Cosmology
Published online by Cambridge University Press: 05 June 2012
- Frontmatter
- Contents
- Preface
- 1 Overview: Galaxies and Cosmology
- 2 Galactic Structure and Dynamics
- 3 Friedmann Model of the Universe
- 4 Thermal History of the Universe
- 5 Structure Formation
- 6 Cosmic Microwave Background Radiation
- 7 Formation of Baryonic Structures
- 8 Active Galactic Nuclei
- 9 Intergalactic Medium and Absorption Systems
- 10 Cosmological Observations
- Notes and References
- Index
Summary
Introduction
Attempts to understand extragalactic objects and the universe by using the laws of physics lead to difficulties that have no parallel in the application of the laws of physics to systems of a more moderate scale. The key difficulty arises from the fact that our universe exhibits temporal evolution and is not in steady state. Thus different epochs in the past evolutionary history of the universe are unique (and have occurred only once), and the current state of the universe is a direct consequence of the conditions that were prevalent in the past. For example, most of the galaxies in the universe have formed sometime in the past during a particular phase in the evolution of the universe. This is in contrast to star formation within a galaxy that we can observe directly and study by using standard statistical methods.
In principle, we should be able to see the events that took place in the universe in the past because of the finite light travel time. By observing sufficiently far-away regions of the universe, we will be able to observe the universe as it was in the past. Although technological innovation will eventually allow us to directly observe and understand all the past events in the history of the universe (especially when neutrino astronomy and gravitational wave astronomy start complementing photon-based observations), we are far from such a satisfactory state of affairs at present.
- Type
- Chapter
- Information
- Theoretical Astrophysics , pp. 1 - 84Publisher: Cambridge University PressPrint publication year: 2002