Contents. Part I The Big Bang and the Observable Universe

Transcription

1 Contents Part I The Big Bang and the Observable Universe 1 A Historical Overview The Big Cosmic Questions Origins of Scientific Cosmology Cosmology Today 7 2 Newton s Universe Newton s Laws of Motion Newtonian Gravity Acceleration of Free Fall Circular Motion and Planetary Orbits Energy Conservation and Escape Velocity Newtonian Cosmology Olbers Paradox 27 3 Special Relativity The Principle of Relativity The Speed of Light and Electromagnetism Einstein s Postulates Simultaneity Time Dilation Length Contraction Speeding Muons E = mc From Space and Time to Spacetime Causality in Spacetime 51 ix

2 x Contents 4 The Fabric of Space and Time The Astonishing Hypothesis The Geometry of Space Euclidean Geometry Non-Euclidean Geometry Curved Space The Curvature of Surfaces The Curvature of Three-Dimensional Space The General Theory of Relativity Predictions and Tests of General Relativity Light Deflection and Gravitational Lensing Gravitational Time Dilation Black Holes Gravitational Waves 78 5 An Expanding Universe Einstein s Static Universe Problems with a Static Universe Friedmann s Expanding Universe 89 6 Observational Cosmology Fingerprints of the Elements Measuring Velocities Measuring Distances The Birth of Extragalactic Astronomy Hubble s Law and the Expanding Universe An Expanding Universe A Beginning of the Universe? The Steady State Theory The Scale Factor Cosmological Redshift The Age of the Universe The Hubble Distance and the Cosmic Horizon Not Everything is Expanding The Fate of the Universe The Critical Density The Density Parameter 128

3 Contents xi 9 Dark Matter and Dark Energy The Average Mass Density of the Universe and Dark Matter Dark Energy The Fate of the Universe Again The Quantum World Quantum Discreteness Quantum Indeterminism The Wave Function Many Worlds Interpretation The Hot Big Bang Following the Expansion Backwards in Time Thermal Radiation The Hot Big Bang Model Discovering the Primeval Fireball Images of the Baby Universe CMB Today and at Earlier Epochs The Three Cosmic Eras Structure Formation Cosmic Structure Assembling Structure Watching Cosmic Structures Evolve Primordial Density Fluctuations Supermassive Black Holes and Active Galaxies Element Abundances Why Alchemists Did Not Succeed Big Bang Nucleosynthesis Stellar Nucleosynthesis Planetary System Formation Life in the Universe The Very Early Universe Particle Physics and the Big Bang The Standard Model of Particle Physics The Particles The Forces Symmetry Breaking The Early Universe Timeline 211

4 xii Contents 14.5 Physics Beyond the Standard Model Unifying the Fundamental Forces Vacuum Defects Domain Walls Cosmic Strings Magnetic Monopoles Baryogenesis 220 Part II Beyond the Big Bang 15 Problems with the Big Bang The Flatness Problem: Why is the Geometry of the Universe Flat? The Horizon Problem: Why is the Universe so Homogeneous? The Structure Problem: What is the Origin of Small Density Fluctuations? The Monopole Problem: Where Are They? The Theory of Cosmic Inflation Solving the Flatness and Horizon Problems Cosmic Inflation The False Vacuum Exponential Expansion Solving the Problems of the Big Bang The Flatness Problem The Horizon Problem The Structure Formation Problem The Monopole Problem The Expansion and High Temperature of the Universe Vacuum Decay Boiling of the Vacuum Graceful Exit Problem Slow Roll Inflation Origin of Small Density Fluctuations More About Inflation Communication in the Inflating Universe Energy Conservation 250

5 Contents xiii 17 Testing Inflation: Predictions and Observations Flatness Density Fluctuations Gravitational Waves Open Questions Eternal Inflation Volume Growth and Decay Random Walk of the Inflaton Field Eternal Inflation via Bubble Nucleation Bubble Spacetimes Cosmic Clones The Multiverse Testing the Multiverse Bubble Collisions Black Holes from the Multiverse String Theory and the Multiverse What Is String Theory? Extra Dimensions The Energy Landscape String Theory Multiverse The Fate of Our Universe Revisited Anthropic Selection The Fine Tuning of the Constants of Nature Neutron Mass Strength of the Weak Interaction Strength of Gravity The Magnitude of Density Perturbations The Cosmological Constant Problem The Dynamic Quantum Vacuum Fine-Tuned for Life? The Anthropic Principle Pros and Cons of Anthropic Explanations The Principle of Mediocrity The Bell Curve The Principle of Mediocrity Obtaining the Distribution by Counting Observers 315

6 xiv Contents 21.4 Predicting the Cosmological Constant Rough Estimate The Distribution The Measure Problem The Doomsday Argument and the Future of Our Civilization Large and Small Civilizations Beating the Odds Did the Universe Have a Beginning? A Universe that Always Existed? The BGV Theorem Where Does This Leave Us? A Proof of God? Creation of Universes from Nothing The Universe as a Quantum Fluctuation Quantum Tunneling from Nothing Euclidean Time The Multiverse of Quantum Cosmology The Meaning of Nothing The Big Picture The Observable Universe What Do We Know? Cosmic Inflation The Multiverse Bubble Universes Other Disconnected Spacetimes Levels of the Multiverse The Mathematical Multiverse and Ockham s Razor Answers to the Big Questions Our Place in the Universe 351 Appendix A 353 Further Reading 361 Index 365

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