| Introduction | 1 |
| 1 What Is the Shape of the Earth? | 2 |
| 2 What Is the Size of the Earth? | 6 |
| 3 If the Earth Is a Sphere, Why Don't We Slide Off? | 10 |
| 4 Does the Earth Move? | 11 |
| 5 When You Jump Up, Why Don't You Come Down in a Different Place? | 14 |
| 6 What Makes the Wind Blow? | 16 |
| 7 Why Is Summer Warmer than Winter? | 18 |
| 8 How Do We Measure Time? | 21 |
| 9 How Do We Measure Time Intervals Less than a Day Long? | 23 |
| 10 How Old Is the Earth? | 26 |
| 11 How Was the Age of the Earth Finally Determined? | 29 |
| 12 What Is Mass? | 31 |
| 13 What Is the Mass of the Earth? | 33 |
| 14 What Is Density? | 34 |
| 15 Is the Earth Hollow? | 35 |
| 16 What Is the Earth's Interior Really Like? | 37 |
| 17 Do the Continents Move? | 40 |
| 18 What Causes Earthquakes and Volcanoes? | 43 |
| 19 What Is Heat? | 48 |
| 20 What Is Temperature? | 48 |
| 21 How Do We Measure Temperature? | 50 |
| 22 What Is Energy? | 52 |
| 23 Is It Possible to Run Out of Energy? | 55 |
| 24 What Is the Internal Temperature of the Earth? | 56 |
| 25 Why Doesn't the Earth Cool Off? | 57 |
| 26 Does the Sky Turn in One Piece? | 59 |
| 27 Is the Earth the Center of the Universe? | 62 |
| 28 Once Again, Then, Is the Earth the Center of the Universe? | 64 |
| 29 Can Copernicus' View Be Improved? | 68 |
| 30 How Was the Earth Formed? | 70 |
| 31 Is the Earth a Magnet? | 74 |
| 32 Is the Earth a Perfect Sphere? | 76 |
| 33 Why Does the Moon Change Its Shape? | 79 |
| 34 Does the Earth Shine? | 81 |
| 35 Why Are There Eclipses of the Sun and the Moon? | 82 |
| 36 Does the Moon Turn? | 85 |
| 37 How Far Away Is the Moon? | 87 |
| 38 What Is the Mass of the Moon? | 89 |
| 39 What Are the Tides? | 92 |
| 40 How Do the Tides Affect the Earth? | 94 |
| 41 Is There Life on the Moon? | 95 |
| 42 What Caused the Craters on the Moon? | 98 |
| 43 How Was the Moon Formed? | 99 |
| 44 Can We Reach the Moon? | 103 |
| 45 What Are Meteorites? | 107 |
| 46 Might Meteorites Be Dangerous to Life and Property? | 109 |
| 47 What Are Asteroids? | 110 |
| 48 Are There Asteroids Only in the Asteroid Belt? | 112 |
| 49 What Are Comets? | 115 |
| 50 Why Do Comets Look Fuzzy? | 117 |
| 51 What Happens to Comets? | 119 |
| 52 Where Do Comets Come From? | 120 |
| 53 How Far Is the Sun? | 121 |
| 54 Is the Earth Large? | 123 |
| 55 Are There Planets the Ancients Didn't Know? | 125 |
| 56 In What Ways Are the Giant Planets Different? | 127 |
| 57 Is There Life on Venus? | 131 |
| 58 Is There Life on Mars? | 134 |
| 59 Is There Life in the Outer Solar System? | 137 |
| 60 What Does the Sun Look Like? | 141 |
| 61 What Is Sunlight? | 143 |
| 62 What Are Spectral Lines? | 145 |
| 63 What Is the Mass of the Sun? | 147 |
| 64 What Is the Sun Made Of? | 148 |
| 65 What Are the Planetary Bodies Made Of? | 149 |
| 66 How Hot Is the Sun? | 152 |
| 67 What Is the Solar Corona? | 154 |
| 68 What Are Solar Flares? | 156 |
| 69 Why Doesn't the Sun Cool Off? | 157 |
| 70 How Does Nuclear Energy Power the Sun? | 160 |
| 71 Are There Stars the Ancients Didn't Know? | 163 |
| 72 Are the Fixed Stars Really Fixed? | 164 |
| 73 Is There a Sphere of the Stars? | 166 |
| 74 What Are Stars? | 167 |
| 75 How Far Are the Stars, Actually? | 168 |
| 76 How Fast Does Light Travel? | 171 |
| 77 What Is a Light-Year? | 174 |
| 78 Is the Sun Moving? | 175 |
| 79 Are the Laws of Nature the Same Everywhere? | 176 |
| 80 What Are Variable Stars? | 179 |
| 81 How Do Stars Differ from One Another? | 180 |
| 82 What Happens When the Hydrogen Supply of a Star Runs Low? | 183 |
| 83 Will Our Sun Ever Become a Red Giant? | 185 |
| 84 Why Do Very Luminous Stars Still Exist? | 186 |
| 85 What Is a White Dwarf? | 187 |
| 86 What Is a Nova? | 191 |
| 87 What Is a Supernova? | 194 |
| 88 Is There Anything Useful About Supernovas? | 198 |
| 89 Is There Life on Planets Circling Other Stars? | 199 |
| 90 What Are Globular Clusters? | 203 |
| 91 What Are Nebulas? . | 204 |
| 92 What Is the Galaxy? | 205 |
| 93 Where Is the Center of the Galaxy? | 208 |
| 94 What Is the Doppler Effect? | 211 |
| 95 Is the Galaxy Rotating? | 214 |
| 96 Does Anything Reach Us from the Stars Besides Light? | 215 |
| 97 What Is the Electromagnetic Spectrum? | 219 |
| 98 How Did Radio Astronomy Develop? | 222 |
| 99 What Are Pulsars? | 224 |
| 100 What Are Black Holes? | 228 |
| 101 What Is in Interstellar Dust Clouds? | 230 |
| 102 What Is SETI? | 233 |
| 103 Is the Galaxy the Entire Universe? | 235 |
| 104 Are the Galaxies Moving? | 238 |
| 105 Is There a Center of the Universe? | 241 |
| 106 How Old Is the Universe? | 242 |
| 107 What Are Quasars? | 243 |
| 108 Can We See the Big Bang? | 246 |
| 109 How Did the Big Bang Arise? | 248 |
| 110 Will the Expansion of the Universe Continue Forever? | 249 |
| 111 Is There Matter in the Universe We Can't See? | 251 |
| Index | 253 |