Light/dark Universe, The: Light From Galaxies, Dark Matter And Dark Energy

by Paul S Wesson, James M Overduin

Overview

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.

Product Details

ISBN-13:	9789812834416
Publisher:	World Scientific Publishing Company, Incorporated
Publication date:	08/21/2008
Pages:	236
Product dimensions:	6.20(w) x 9.10(h) x 0.90(d)

Table of Contents

Preface v

1 The Enigma of the Dark Night Sky 1

1.1 Why is the sky dark at night? 1

1.2 "By reason of distance" 4

1.3 Island Universe 5

1.4 Non-uniform sources 6

1.5 Tired light 9

1.6 Absorption 10

1.7 Fractal Universe 12

1.8 Finite age 13

1.9 Dark stars 16

1.10 Curvature 17

1.11 Ether voids 19

1.12 Insufficient energy 20

1.13 Light-matter interconversion 21

1.14 Cosmic expansion 22

1.15 Olbers' paradox today 25

2 The Intensity of Cosmic Background Light 29

2.1 Bolometric intensity 29

2.2 Time and redshift 32

2.3 Matter, energy and expansion 33

2.4 How important is expansion? 37

2.5 Simple flat models 39

2.6 Curved and multi-fluid models 41

2.7 A bright sky at night? 44

3 The Spectrum of Cosmic Background Light 49

3.1 Spectral intensity 49

3.2 Luminosity density 52

3.3 The delta function 54

3.4 The normal distribution 58

3.5 The thermal spectrum 59

3.6 The spectra of galaxies 62

3.7 The light of the night sky 65

3.8 R.I.P. Olbers' paradox 69

4 Dark Cosmology 73

4.1 The four dark elements 73

4.2 Baryons 76

4.3 Dark matter 80

4.4 Neutrinos 84

4.5 Dark energy 86

4.6 Cosmological concordance 88

4.7 The coincidental Universe 94

5 The Radio and Microwave Backgrounds 97

5.1 The cosmological "constant" 97

5.2 The scalar field 98

5.3 Decaying dark energy 102

5.4 Energy density 105

5.5 Source luminosity 108

5.6 Bolometric intensity 113

5.7 Spectral energy distribution 114

5.8 Dark energy and the background light 115

6 The Infrared and Visible Backgrounds 119

6.1 Decaying axions 119

6.2 Axion halos 123

6.3 Bolometric intensity 125

6.4 Axions and the background light 127

7 The UltravioletBackground 133

7.1 Decaying neutrinos 133

7.2 Neutrino halos 135

7.3 Halo luminosity 137

7.4 Free-streaming neutrinos 140

7.5 Extinction by gas and dust 141

7.6 Neutrinos and the background light 145

8 The X-ray and Gamma-ray Backgrounds 151

8.1 Weakly interacting massive particles 151

8.2 Pair annihilation 154

8.3 One-loop decay 160

8.4 Tree-level decay 162

8.5 Gravitinos 166

8.6 WIMPs and the background light 169

9 The High-Energy Gamma-ray Background 175

9.1 Primordial black holes 175

9.2 Evolution and density 178

9.3 Spectral energy distribution 181

9.4 Bolometric intensity 184

9.5 Spectral intensity 187

9.6 Higher dimensions 191

10 The Universe Seen Darkly 197

Bibliography 203

Index 217