1.1 The Purpose of the Book The Assumptions I Make Organization The Mathematics and Physics You Need Energy and Power 6

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1 CONTENTS 1 PLAYING THE GAME The Purpose of the Book The Assumptions I Make Organization The Mathematics and Physics You Need Energy and Power 6 I POTTER PHYSICS 11 2 HARRY POTTER AND THE GREAT CONSERVATION LAWS The Taxonomy of Fantasy Transfiguration and the Conservation of Mass Disapparition and the Conservation of Momentum Reparo and the Second Law of Thermodynamics 21 3 WHY HOGWARTS IS SO DARK Magic versus Technology Illumination 28 4 FANTASTIC BEASTS AND HOW TO DISPROVE THEM Hic sunt Dracones How to Build a Giant 39

2 VIII CONTENTS 4.3 Kleiber s Law, Part 1: Mermaids Kleiber s Law, Part 2: Owls, Dragons, Hippogriffs, and Other Flying Beasts 49 II SPACE TRAVEL 57 5 WHY COMPUTERS GET BETTER AND CARS CAN T (MUCH) The Future of Transportation The Reality of Space Travel The Energetics of Computation The Energetics of the Regular and the Flying Car Suborbital Flights 68 6 VACATIONS IN SPACE The Future in Science Fiction: Cheap, Easy Space Travel? Orbital Mechanics Halfway to Anywhere: The Energetics of Spaceflight Financing Space Travel 82 7 SPACE COLONIES Habitats in Space O Neill Colonies Matters of Gravity Artificial Gravity on a Space Station The Lagrange Points Off-Earth Ecology and Energy Issues The Sticker Price THE SPACE ELEVATOR Ascending into Orbit The Physics of Geosynchronous Orbits What Is a Space Elevator, and Why Would We Want One? Why Buildings Stand Up or Fall Down Stresses and Strains: Carbon Nanotubes Energy, Climbers, Lasers, and Propulsion 123

3 CONTENTS IX 8.7 How Likely Is It? The Unapproximated Elevator MANNED INTERPLANETARY TRAVEL It s Not an Ocean Voyage or a Plane Ride Kepler s Three Laws The Hohmann Transfer Orbit Delta v and All That Getting Back Gravitational Slingshots and Chaotic Orbits Costs ADVANCED PROPULSION SYSTEMS Getting There Quickly Why Chemical Propulsion Won t Work The Most Famous Formula in Physics Advanced Propulsion Ideas Old Bang-Bang : The Orion Drive Prospects for Interplanetary Travel SPECULATIVE PROPULSION SYSTEMS More Speculative Propulsion Systems Mass Ratios for Matter-Antimatter Propulsion Systems Radiation Problems INTERSTELLAR TRAVEL AND RELATIVITY Time Enough for Anything Was Einstein Right? Some Subtleties Constant Acceleration in Relativity FASTER-THAN-LIGHT TRAVEL AND TIME TRAVEL The Realistic Answer The Unrealistic Answer Why FTL Means Time Travel The General Theory 193

4 X CONTENTS 13.5 Gravitational Time Dilation and Black Holes Wormholes and Exotic Matter The Grandfather Paradox and Other Oddities 205 III WORLDS AND ALIENS DESIGNING A HABITABLE PLANET Adler s Mantra Type of Star Planetary Distance from Its Star The Greenhouse Effect Orbital Eccentricity Planetary Size and Atmospheric Retention TheAnna Karenina Principle and Habitable Planets Imponderables THE SCIENTIFIC SEARCH FOR SPOCK Exoplanets and Exoplants Doppler Technique Transits and the Kepler Mission The Spectral Signatures of Life Alien Photosynthesis THE MATHEMATICS OF TALKING WITH ALIENS Three Views of Alien Intelligences Motivation for Alien Contact Drake-Equation Models and the Mathematics of Alien Contact 267 IV YEAR GOOGOL THE SHORT-TERM SURVIVAL OF HUMANITY This Is the Way the World Will End The Short-Term: Man-Made Catastrophes 275

5 CONTENTS XI 18 WORLD-BUILDING Terraforming Characteristics of Mars Temperature and the Martian Atmosphere Atmospheric Oxygen Economics DYSON SPHERES AND RINGWORLDS Dyson s Sphere The Dyson Net Niven s Ringworld The Ringworld, GPS, and Ehrenfest s Paradox The Ringworld Is Unstable! Getting There from Here and Do We Need To? ADVANCED CIVILIZATIONS AND THE KARDASHEV SCALE The Kardashev Scale Our Type 0.7 Civilization Type I Civilizations Moving Upward Type II Civilizations Type III Civilizations A GOOGOL YEARS The Future of the Future The Short Term : Up to 500 Million Years or so The Medium Term : Up to about Years The Long Term : Up to a Googol Years Black Hole Powered Civilizations Protons Decay or Do They? A Googol Years All the Black Holes Evaporate Our Last Bow 349 Acknowledgments 351 Appendix: Newton s Three Laws of Motion 353 Bibliography 359 Index 371

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