CONTENTS
1
PLAYING THE GAME 1
1.1 The Purpose of the Book 1
1.2 The Assumptions I Make 3
1.3 Organization 4
1.4 The Mathematics and Physics You Need 5
1.5 Energy and Power 6
I
POTTER PHYSICS 11
2
HARRY POTTER AND THE GREAT CONSERVATION LAWS 13
2.1 The Taxonomy of Fantasy 13
2.2 Transfiguration and the Conservation of Mass 14
2.3 Disapparition and the Conservation of Momentum 16
2.4 Reparo and the Second Law of Thermodynamics 21
3
WHY HOGWARTS IS SO DARK 27
3.1 Magic versus Technology 27
3.2 Illumination 28
4
FANTASTIC BEASTS AND HOW TO DISPROVE THEM 38
4.1 Hic sunt Dracones 38
4.2 How to Build a Giant 39
4.3 Kleiber’s Law, Part 1: Mermaids 45
4.4 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) 59
5.1 The Future of Transportation 59
5.2 The Reality of Space Travel 61
5.3 The Energetics of Computation 63
5.4 The Energetics of the Regular and the Flying Car 64
5.5 Suborbital Flights 68
6
VACATIONS IN SPACE 71
6.1 The Future in Science Fiction: Cheap, Easy Space Travel? 71
6.2 Orbital Mechanics 74
6.3 Halfway to Anywhere: The Energetics of Spaceflight 74
6.4 Financing Space Travel 82
7
SPACE COLONIES 86
7.1 Habitats in Space 86
7.2 O’Neill Colonies 87
7.3 Matters of Gravity 89
7.4 Artificial “Gravity” on a Space Station 93
7.5 The Lagrange Points 103
7.6 Off-Earth Ecology and Energy Issues 106
7.7 The Sticker Price 112
8
THE SPACE ELEVATOR 115
8.1 Ascending into Orbit 115
8.2 The Physics of Geosynchronous Orbits 116
8.3 What Is a Space Elevator, and Why Would We Want One? 118
8.4 Why Buildings Stand Up—or Fall Down 119
8.5 Stresses and Strains: Carbon Nanotubes 122
8.6 Energy, “Climbers,” Lasers, and Propulsion 123
8.7 How Likely Is It? 125
8.8 The Unapproximated Elevator 127
9
MANNED INTERPLANETARY TRAVEL 130
9.1 It’s Not an Ocean Voyage or a Plane Ride 130
9.2 Kepler’s Three Laws 131
9.3 The Hohmann Transfer Orbit 134
9.4 Delta v and All That 136
9.5 Getting Back 137
9.6 Gravitational Slingshots and Chaotic Orbits 138
9.7 Costs 142
10
ADVANCED PROPULSION SYSTEMS 145
10.1 Getting There Quickly 145
10.2 Why Chemical Propulsion Won’t Work 146
10.3 The Most Famous Formula in Physics 147
10.4 Advanced Propulsion Ideas 148
10.5 Old “Bang-Bang”: The Orion Drive 153
10.6 Prospects for Interplanetary Travel 155
11
SPECULATIVE PROPULSION SYSTEMS 157
11.1 More Speculative Propulsion Systems 157
11.2 Mass Ratios for Matter-Antimatter Propulsion Systems 168
11.3 Radiation Problems 173
12
INTERSTELLAR TRAVEL AND RELATIVITY 176
12.1 Time Enough for Anything 176
12.2 Was Einstein Right? 178
12.3 Some Subtleties 182
12.4 Constant Acceleration in Relativity 184
13
FASTER-THAN-LIGHT TRAVEL AND TIME TRAVEL 188
13.1 The Realistic Answer 188
13.2 The Unrealistic Answer 188
13.3 Why FTL Means Time Travel 190
13.4 The General Theory 193
13.5 Gravitational Time Dilation and Black Holes 195
13.6 Wormholes and Exotic Matter 198
13.7 The Grandfather Paradox and Other Oddities 205
III
WORLDS AND ALIENS 215
14
DESIGNING A HABITABLE PLANET 217
14.1 Adler’s Mantra 218
14.2 Type of Star 221
14.3 Planetary Distance from Its Star 226
14.4 The Greenhouse Effect 229
14.5 Orbital Eccentricity 232
14.6 Planetary Size and Atmospheric Retention 233
14.7 The Anna Karenina Principle and Habitable Planets 237
14.8 Imponderables 239
15
THE SCIENTIFIC SEARCH FOR SPOCK 242
15.1 Exoplanets and Exoplants 242
15.2 Doppler Technique 246
15.3 Transits and the Kepler Mission 249
15.4 The Spectral Signatures of Life 250
15.5 Alien Photosynthesis 251
16
THE MATHEMATICS OF TALKING WITH ALIENS 255
16.1 Three Views of Alien Intelligences 255
16.2 Motivation for Alien Contact 259
16.3 Drake-Equation Models and the Mathematics of Alien Contact 267
IV
YEAR GOOGOL 273
17
THE SHORT-TERM SURVIVAL OF HUMANITY 275
17.1 This Is the Way the World Will End 275
17.2 The Short-Term: Man-Made Catastrophes 275
18
WORLD-BUILDING 292
18.1 Terraforming 292
18.2 Characteristics of Mars 294
18.3 Temperature and the Martian Atmosphere 295
18.4 Atmospheric Oxygen 299
18.5 Economics 301
19
DYSON SPHERES AND RINGWORLDS 303
19.1 Dyson’s Sphere 303
19.2 The Dyson Net 305
19.3 Niven’s Ringworld 311
19.4 The Ringworld, GPS, and Ehrenfest’s Paradox 318
19.5 The Ringworld Is Unstable! 320
19.6 Getting There from Here—and Do We Need To? 324
20
ADVANCED CIVILIZATIONS AND THE KARDASHEV SCALE 326
20.1 The Kardashev Scale 326
20.2 Our Type 0.7 Civilization 327
20.3 Type I Civilizations 329
20.4 Moving Upward 331
20.5 Type II Civilizations 332
20.6 Type III Civilizations 334
21
A GOOGOL YEARS 336
21.1 The Future of the Future 336
21.2 The “Short Term”: Up to 500 Million Years or so 336
21.3 The “Medium Term”: Up to about 1013 Years 338
21.4 The “Long Term”: Up to a Googol Years 341
21.5 Black Hole–Powered Civilizations 344
21.6 Protons Decay—or Do They? 346
21.7 A Googol Years—All the Black Holes Evaporate 346
21.8 Our Last Bow 349
Acknowledgments 351
Appendix: Newton’s Three Laws of Motion 353
Bibliography 359
Index 371
