Olbers' paradox states that given the Universe is unbounded, governed by the standard laws of physics, and populated by light sources, the night sky should be ablaze with light. Obviously this is not so. However, the paradox does not lie in nature but in our understanding of physics. A Universe with a finite age, such as follows from big-bang theory, necessarily has galaxies of finite age. This means we can only see some of the galaxies in the Universe, which is the main reason why the night sky is dark. Just how dark can be calculated using the astrophysics of galaxies and stars and the dynamics of relativistic cosmology.
We know from the dynamics of individual galaxies and clusters of galaxies that the majority of matter that exerts gravitational forces is not detectable by conventional telescopes. This dark matter could have many forms, and candidates include various types of elementary particles as well as vacuum fluctuations, black holes, and others. Most of these candidates are unstable to decay and produce photons. So dark matter does not only affect the dynamics of the Universe, but the intensity of intergalactic radiation as well. Conversely, we can use observations of background radiation to constrain the nature and density of dark matter.
By comparing observational data with cosmological theory based on general relativity and particle physics, Dark Sky, Dark Matter reviews our present understanding of the universe and the astrophysics of the night sky and dark matter.
"Right after 'Why is the sky blue?,' 'Why is the sky dark?' is the next most commonly asked question kids, and non-kids, too, ask of parents, in particular, and science in general … the dilemma of the question actually became tougher to explain, resulting in what has become known as Olbers' paradox. Olbers, a Prussian astronomer, postulated in 1823, 'given that the Universe is unbounded, governed by the standard laws of physics, and populated by light sources of constant intensity, the simple cube law of volumes and numbers implies that the sky should be ablaze with light. Obviously, this is not so.' Dark Sky, Dark Matter takes this paradox and runs with it.
To the authors' credit, they begin the book with a remarkable history of Olbers and his paradox, explaining the variety of tactics people have used either to explain away the paradox or to support their own theories. The rest of the book delves into the astrophysical nature of the universe, structure of the stars and galaxies, radiation, and dark matter. The ancillary material includes three appendices that detail mathematical models and an adequate index.
This book utilizes advanced mathematics and physics appropriate for a graduate course in physics or astrophysics. Recommended for academic collections supporting physics (astrophysics) programs."
-Peggy Dominy, E-Streams
"The story of how all these exotic ingredients can be constrained by modern data is well told, and contains some interesting material. Overall, this book may well be consulted by graduate students seeking details of these topics."
-John Peacock, The Observatory, June 2003
The dark night sky
The modern resolution and energy
The modern resolution and spectra
The dark matter
Supersymmetric weakly interacting particles
Bolometric intensity integrals
Dynamics with a decaying vacuum
Absorption by galactic hydrogen