The Light/Dark Universe

by Overduin, James M.; Wesson, Paul S.

• ISBN13: 9789812834416
• ISBN10: 9812834419
• Format: Hardcover
• Copyright: 2008-08-20
• Publisher: World Scientific Pub Co Inc

Summary

To the eyes of the average person and the trained scientist, the night sky is dark, even though the universe is populated by myriads of bright galaxies. Why this happens is a question commonly called Olbers' Paradox, and dates from at least 1823. How dark is the night sky is a question which preoccupies astrophysicists at the present. The answer to both questions tells us about the origin of the universe and the nature of its contents - luminous galaxies like the Milky Way, plus the dark matter between them and the mysterious dark energy which appears to be pushing everything apart. In this book, the fascinating history of Olbers' Paradox is reviewed, and the intricate physics of the light/dark universe is examined in detail. The fact that the night sky is dark (a basic astronomical observation that anybody can make) turns out to be connected with the finite age of the universe, thereby confirming some event like the Big Bang. But the space between the galaxies is not perfectly black, and data on its murkiness at various wavelengths can be used to constrain and identify its unseen constituents.

Table of Contents

Preface	p. v
The Enigma of the Dark Night Sky	p. 1
Why is the sky dark at night?	p. 1
"By reason of distance"	p. 4
Island Universe	p. 5
Non-uniform sources	p. 6
Tired light	p. 9
Absorption	p. 10
Fractal Universe	p. 12
Finite age	p. 13
Dark stars	p. 16
Curvature	p. 17
Ether voids	p. 19
Insufficient energy	p. 20
Light-matter interconversion	p. 21
Cosmic expansion	p. 22
Olbers' paradox today	p. 25
The Intensity of Cosmic Background Light	p. 29
Bolometric intensity	p. 29
Time and redshift	p. 32
Matter, energy and expansion	p. 33
How important is expansion?	p. 37
Simple flat models	p. 39
Curved and multi-fluid models	p. 41
A bright sky at night?	p. 44
The Spectrum of Cosmic Background Light	p. 49
Spectral intensity	p. 49
Luminosity density	p. 52
The delta function	p. 54
The normal distribution	p. 58
The thermal spectrum	p. 59
The spectra of galaxies	p. 62
The light of the night sky	p. 65
R.I.P. Olbers' paradox	p. 69
Dark Cosmology	p. 73
The four dark elements	p. 73
Baryons	p. 76
Dark matter	p. 80
Neutrinos	p. 84
Dark energy	p. 86
Cosmological concordance	p. 88
The coincidental Universe	p. 94
The Radio and Microwave Backgrounds	p. 97
The cosmological "constant"	p. 97
The scalar field	p. 98
Decaying dark energy	p. 102
Energy density	p. 105
Source luminosity	p. 108
Bolometric intensity	p. 113
Spectral energy distribution	p. 114
Dark energy and the background light	p. 115
The Infrared and Visible Backgrounds	p. 119
Decaying axions	p. 119
Axion halos	p. 123
Bolometric intensity	p. 125
Axions and the background light	p. 127
The Ultraviolet Background	p. 133
Decaying neutrinos	p. 133
Neutrino halos	p. 135
Halo luminosity	p. 137
Free-streaming neutrinos	p. 140
Extinction by gas and dust	p. 141
Neutrinos and the background light	p. 145
The X-ray and Gamma-ray Backgrounds	p. 151
Weakly interacting massive particles	p. 151
Pair annihilation	p. 154
One-loop decay	p. 160
Tree-level decay	p. 162
Gravitinos	p. 166
WIMPs and the background light	p. 169
The High-Energy Gamma-ray Background	p. 175
Primordial black holes	p. 175
Evolution and density	p. 178
Spectral energy distribution	p. 181
Bolometric intensity	p. 184
Spectral intensity	p. 187
Higher dimensions	p. 191
The Universe Seen Darkly	p. 197
Bibliography	p. 203
Index	p. 217
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