1: Earth Science.
2: How Do We Know the Earth is 4.54 Billion Years Old?.
3: Why Did We End Up with a 24-Hour Day?.
4: Why Doesn’t the Earth Have More Craters?.
5: How Did Earth Get an Oxygen-Rich Atmosphere?.
6: Why is Earth the Only Planet with a Liquid Ocean?.
7: Is Carbon Dioxide the Most Dangerous Greenhouse Gas?.
8: Why are Scientists So Worried about Frozen Methane in the Earth’s Crust?.
9: Why is the Chemistry of the Ocean So Important?.
10: Could an Earthquake Ever Sink a Whole Country?.
11: Should I be Scared of Supervolcanoes?.
12: Why are There So Many Different Types of Minerals?.
13: Are Gold and Diamonds Good for Anything Besides Jewelry?.
14: What Would Happen If We Desalinated the Entire Ocean?.
15: What Would Happen If the Ice Caps Completely Melted?.
16: Why Does a Hurricane Have an Eye, and Why is It So Calm?.
17: Could We Ever Use Up All the Oxygen in the Atmosphere?.
18: Could We Ever Control the Weather?.
19: Has Anyone Ever Drilled All the Way Through Earth’s Crust?.
20: Could We One Day Travel to the Center of the Earth?.
21: Why Does a Compass Work?.
22: Could the North and South Poles Really Switch?.
23: If the Poles Switch, what Would Happen to Our Compasses?.
24: Does a Single Large Volcanic Eruption Pollute the Atmosphere Much More Than All Human Industry Ever Has?.
25: If We Reverse Climate Change, Could the Sea Level Drop Dramatically?.
26: Could the Ocean Ever Freeze Completely Solid?.
27: How Can We be Sure There Wasn’t a Technological Civilization Living on Earth Millions of Years Ago?.
28: Life Science.
29: What is the Earliest Evidence We Have of Life on Earth?.
30: Why Does Every Living Thing Need Water to Survive?.
31: Why Isn’t DNA Perfect? Why are There Mutations?.
32: If We Could Control DNA, Could We Bring Back Any Extinct Animal We Wanted?.
33: Why Do Viruses Make Us Sick … But Only Some Viruses?.
34: Why Do Living Things Age and Die?.
35: Do All Living Things Die? Are There Any Immortal Species?.
36: Is There Any Evidence Humans are Still Evolving?.
37: Why are There So Few Kinds of Large Mammals?.
38: Why Aren’t There Any Half-Evolved Animals?.
39: Why are Some Animals Poisoned by Foods that are Harmless to Humans?.
40: Why Can’t Birds Taste Chili Peppers?.
41: What Makes Spider Silk So Amazingly Strong and Light?.
42: Why Can’t Animals Make Energy from Sunlight Like Plants?.
43: Doesn’t Higher Co2 in the Atmosphere Make Plants Healthier?.
44: Cheetahs are the Fastest, Elephants are the Biggest … what’s a Human’s “Animal Superpower”?.
45: How Can Plants Grow and Regrow from One Tiny Patch of Dirt for Years?.
46: Is It True that Most of the Cells in My Body Aren’t Human?.
47: Are Some Birds as Smart as Primates?.
48: Why Do Some Animals Lay Eggs?.
49: Why Do All Large Animals Have Four Limbs?.
50: How Do Insects and Spiders Breathe, and Why Can’t I See Them Breathing?.
51: Did Dinosaurs Have Warm or Cold Blood, and how Would We Tell Anyway?.
52: How Do We Heat Our Blood, and Why is It a Particular Temperature?.
53: Why Can I Heal a Deep Gash in My Arm, But Can’t Regrow a Lost Tooth or FIngertip?.
54: Why Can’t I Breathe Water Even Though a Fish Can (Sort of) Breathe Air?.
56: How Many Elements are There Really?.
57: Why are Some Elements Radioactive?.
58: Why Does Lead Protect Me from Radiation?.
59: What Keeps Molecules Stuck Together?.
60: What Exactly is a Flame?.
61: Why Do Gasoline Engines Pollute, While Hydrogen Fuel Cells Don’t?.
62: What’s the Advantage of Cooking Our Food?.
63: Why Do Some Chemicals Explode when You Mix Them Together?.
64: What Makes Gasoline Such a Good Fuel?.
65: Why is Smell Our Weakest Sense?.
66: How Does Light “Charge Up” Glow-in-the-Dark Stickers and Toys?.
67: How Does Our Sense of Taste Work?.
68: Would it be Possible to Freeze the Air Solid?.
69: How Does Oxygen Actually Give Me Energy to Survive?.
70: Why is Carbon Monoxide in Car Exhaust So Dangerous?.
71: How is it Possible for Food Companies to Make Artificial Flavors?.
72: Why Does Unhealthy Food Make Me Fat?.
73: What Makes Some Things Brittle, Instead of Just Hard or Soft?.
74: Why Do Soap and Hot Water Make it Easier to Clean Things?.
75: Why doesn’t Stainless Steel Get Rusty?.
76: What Gives Gemstones Their Amazing Colors?.
77: Why is Frozen Carbon Dioxide Called “Dry Ice”?.
78: What’s So Special about Carbon, Anyway?.
79: How Does a Nonstick Frying Pan Surface Stick to the Pan?.
80: Why is Life on Earth Carbon-Based?.
81: What Exactly is an “Organic Compound”?.
83: Why is the Night Sky Dark?.
84: Is There Anything in the Universe Bigger Than a Galaxy?.
85: How Do We Know how Old the Universe is?.
86: Why can’t We See the Bright Center of Our Galaxy?.
87: Is Saturn the Only Planet with Rings?.
88: Why Do the Gas Giant Planets have so Many Moons?.
89: Why is the Moon so Large?.
90: How Do Astronomers Discover New Planets?.
91: How Much of the Universe Can I See with the Naked Eye?.
92: Why Do We Use “Light Year” as a Measure of Distance?.
93: What Makes the Stars Twinkle?.
94: Why Does the Milky Way Glow?.
95: How Do Astronomers Figure Out how Far Away a Star is?.
96: Why Doesn’t the North Star Move in the Night Sky?.
97: Why Does the Moon Always Show the Same Face to the Earth?.
98: Are the Amazing Colors in Astronomical Photos Real?.
99: Is the Universe Really Infinite?.
100: Is There Any Actual Evidence the Big Bang Really Happened?.
101: When and how will the Sun Die?.
102: What will Happen to the Solar System (and Earth) After the Sun Dies?.
103: Will the Universe Ever End?.
104: If There Really Were Aliens on Other Planets, Wouldn’t We Have Met Them by Now?.
105: Why Isn’t Pluto Considered a Planet Anymore?.
106: Is the Andromeda Galaxy Really Going to Crash Into the Milky Way?.
107: How Many Earth-Like Planets Could There be?.
108: Why are Pulsars So Important to Astronomers?.
110: Why Can’t a Spaceship Travel Faster Than Light?.
111: Is the Speed of Light the Same Everywhere?.
112: Why Did We Invent Quantum Physics?.
113: Is Time Travel Possible?.
114: What’s the Big Deal with the “Uncertainty Principle”?.
115: How can a 10,000-ton Boat Float, While a 10-ton Truck Sinks?.
116: Every Time We Launch a Rocket Into Space, Does it Affect the Spin of the Earth?.
117: Why Do Atomic Clocks that Go Up to the International Space Station Appear to Run Slower in Space?.
118: Could the Egyptians Really have Built the Pyramids All by Themselves?.
119: When Did People Stop Believing the Earth was Flat?.
120: How Can I be Sure the Earth Orbits the Sun?.
121: Why are Tornadoes Only Common in Some Areas?.
122: Why Don’t the Filaments in Cheap Light Bulbs Last Forever?.
123: How Do We See Colors?.
124: Why Do Magnets Stick Together?.
125: What Would Happen If the Sun Collapsed Into a Black Hole?.
126: Why is a Powerful Electrical Current So Lethal?.
127: Why Do So Many People Survive Being Struck by Lightning?.
128: Is Wireless Electrical Power Really Possible?.
129: Why Can’t I Survive a 200-Foot Fall Into Water?.
130: Why is a Metal Spoon Colder Than a Plastic Spoon?.
131: Why Do Tsunamis Only Become So Destructive Close to Land?.
132: Why Do I See the Lightning Flash Long Before I Hear the Thunderclap?.
133: Why Do I Float More Easily in the Ocean?.
134: Everyone Knows Hot Air Rises … But Why Does it?.
135: How Does Gravity Work?.
About the Author.