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Unit 1
Unit 2
Unit 3
Unit 4
Unit 5
Unit 6

Kids' Big Questions
Big Questions, Complete Answers
The "why" questions kids actually ask, answered all the way down in short, clear lessons, each ending with the complete answer instead of a new question.
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Who it's for
Kids roughly 6 to 12, or a grown-up reading alongside them.
Animals
- 1 Why Don't Earthworms Get Crushed Underground? Start
- 2 Why Don't Fish Drown? Start
- 3 How Do Birds Fly? Start
- 4 Why Don't Spiders Stick to Their Own Webs? Start
- 5 How Do Cats Land on Their Feet? Start
- 6 Why Do Dogs Sniff Everything? Start
- 7 How Do Bees Make Honey? Start
- 8 Where Do Frogs Go in the Winter? Start
- 9 Why Do Geese Fly in a V? Start
- 10 How Do Flies Walk Upside Down on the Ceiling? Start
- 11 If People Came from Monkeys, Why Are There Still Monkeys? Start
- 12 How Do Bats Find Their Way in the Dark? Start
- 13 How Do Fireflies Light Up? Start
- 14 How Does a Caterpillar Turn into a Butterfly? Start
- 15 How Can Owls Turn Their Heads So Far? Start
- 16 How Do Squirrels Find Their Buried Nuts? Start
- 17 How Can Bears Sleep All Winter Without Eating? Start
- 18 How Do Spiders Make Silk? Start
- 19 Why Do Mosquitoes Bite? Start
- 20 Why Do Birds Sing? Start
- 21 Why Do Zebras Have Stripes? Start
- 22 Why Do Dogs Wag Their Tails? Start
- 23 How Do Ants Find Their Way? Start
- 24 Why Do Snakes Shed Their Skin? Start
- 25 How Do Chameleons Change Color? Start
- 26 How Do Penguins Stay Warm? Start
- 27 Why Do Cows Chew All Day? Start
- 28 How Do Beavers Build Dams? Start
- 29 Do Fish Sleep? Start
- 30 Why Do Cats Purr? Start
- 31 Why Don't Woodpeckers Get Headaches? Start
- 32 Why Do Cats' Eyes Glow in the Dark? Start
- 33 How Do Birds Know Where to Fly for the Winter? Start
- 34 Why Do Cats Have Whiskers? Start
- 35 How Do Snakes Move Without Legs? Start
Plants
- 1 Why Are Plants Green? Start
- 2 How Does a Tree Drink Water? Start
- 3 How Does a Seed Know Which Way Is Up? Start
- 4 Why Do Leaves Change Color in Fall? Start
- 5 Why Does Cutting an Onion Make You Cry? Start
- 6 If a Tree Is Alive, Why Doesn't It Scream When We Cut It? Start
- 7 Why Does a Cut Apple Turn Brown? Start
- 8 Why Do Some Trees Stay Green All Winter? Start
- 9 How Do Dandelion Seeds Fly? Start
- 10 Why Do Sunflowers Follow the Sun? Start
- 11 How Does a Venus Flytrap Catch Bugs? Start
- 12 Why Do Pine Cones Open and Close? Start
- 13 Why Do Mushrooms Pop Up After Rain? Start
- 14 Why Do Flowers Smell? Start
- 15 Why Do Trees Have Rings? Start
- 16 Where Does Maple Syrup Come From? Start
- 17 Why Does Corn Have Hair? Start
- 18 Why Does Grass Grow Back After You Mow It? Start
- 19 Why Don't Bananas Have Seeds? Start
Your Body
- 1 Why Do We Have to Breathe? Start
- 2 Why Does My Heart Go Thump-Thump? Start
- 3 Why Do I Have to Go to Sleep? Start
- 4 Why Do We Get Goosebumps? Start
- 5 Why Do Fingers Get Wrinkly in the Bath? Start
- 6 Why Do We Get Hiccups? Start
- 7 How Does My Cut Get Better? Start
- 8 Why Do My Baby Teeth Fall Out? Start
- 9 Why Do I Get Sick? Start
- 10 Where Does the Sound of My Own Voice Come From? Start
- 11 Why Doesn't the Water Spill Out of Our Eyes When We Bend Over? Start
- 12 What Keeps My Skin Attached to Me? Start
- 13 Why Do My Ears Pop in an Airplane or on a Big Hill? Start
- 14 Why Do We Have Belly Buttons? Start
- 15 Why Do We Have Two Eyes? Start
- 16 Why Do We Sneeze? Start
- 17 Why Do I Have to Brush My Teeth? Start
- 18 Why Does Spinning Make You Dizzy? Start
- 19 Why Does My Foot Fall Asleep? Start
- 20 Why Do We Get Brain Freeze? Start
- 21 Why Does My Stomach Growl? Start
- 22 Why Do Grown-Ups Get Gray Hair? Start
- 23 Why Do We Blink? Start
- 24 Why Do We Get Thirsty? Start
- 25 Why Do We Burp? Start
- 26 Why Do We Shiver? Start
- 27 Why Do I Yawn When Someone Else Yawns? Start
- 28 Why Do My Veins Look Blue If My Blood Is Red? Start
- 29 Why Do We Have Fingerprints? Start
- 30 Why Does My Nose Run When It's Cold? Start
Earth & Weather
- 1 Why Is the Sky Blue? Start
- 2 Why Is the Ocean Salty? Start
- 3 Where Does Wind Come From? Start
- 4 What Makes Thunder and Lightning? Start
- 5 How Do Snowflakes Get Their Six Points? Start
- 6 Where Do Rainbows Come From? Start
- 7 Why Does Ice Float? Start
- 8 Why Is It Cold in Winter and Hot in Summer? Start
- 9 If Rain Comes from Clouds, Why Doesn't the Whole Cloud Fall at Once? Start
- 10 Where Does the White Go When Snow Melts? Start
- 11 Why Do Volcanoes Blow Up? Start
- 12 Why Is the Grass Wet in the Morning? Start
- 13 How Does Wind Make Waves? Start
- 14 Where Does Fog Come From? Start
- 15 Why Does the Ground Shake in an Earthquake? Start
- 16 How Do Icicles Get So Long and Pointy? Start
- 17 Who Dug Out the Caves? Start
- 18 Where Does Beach Sand Come From? Start
- 19 Why Does a Hot Road Look Wet? Start
- 20 Why Do Balls of Ice Fall from the Sky? Start
- 21 Why Are There So Many Lakes Around Here? Start
- 22 Why Can I Smell Rain Before It Comes? Start
- 23 What Makes a Tornado? Start
Space
- 1 Why Don't We Fall Off the Earth? Start
- 2 Where Does the Sun Go at Night? Start
- 3 Why Does the Moon Change Shape? Start
- 4 Why Can You See the Moon in the Daytime? Start
- 5 Why Is the Sun So Hot? Start
- 6 Why Do Stars Twinkle? Start
- 7 Why Does the Moon Follow the Car? Start
- 8 Where Do the Stars Go in the Daytime? Start
- 9 What Makes the Northern Lights? Start
- 10 Why Is Mars Red? Start
- 11 Why Are Sunsets Red and Orange? Start
- 12 Why Does the Moon Have So Many Craters? Start
- 13 What Are Shooting Stars? Start
- 14 Why Do Astronauts Float? Start
- 15 Why Does Saturn Have Rings? Start
- 16 What Is the Milky Way? Start
- 17 Why Do We Always See the Same Side of the Moon? Start
- 18 Why Does the Moon Look So Big When It's Rising? Start
- 19 What Is a Black Hole? Start
- 20 If the Sun Is So Bright, Why Is Space Dark? Start
How Things Work
- 1 How Does Soap Get My Hands Clean? Start
- 2 How Does a Giant Airplane Stay Up in the Sky? Start
- 3 How Do Magnets Stick to Things? Start
- 4 Why Does a Rubbed Balloon Stick to the Wall? Start
- 5 Why Does a Spoon Look Bent in Water? Start
- 6 Why Does My Voice Bounce Back When I Yell? Start
- 7 Why Don't Birds Get Shocked When They Sit on Power Lines? Start
- 8 Why Doesn't Glue Stick to the Inside of the Bottle? Start
- 9 Why Does My Reflection in a Spoon Flip Upside Down? Start
- 10 How Can a Heavy Steel Boat Float When a Tiny Pebble Sinks? Start
- 11 Why Does Popcorn Pop? Start
- 12 Why Does a Compass Point North? Start
- 13 How Does a Fridge Keep Food Cold? Start
- 14 Why Do Bubbles Have Colors? Start
- 15 Why Does a Helium Balloon Float? Start
- 16 Why Do They Put Salt on Icy Roads? Start
- 17 Why Does Bread Rise? Start
- 18 How Do Glow-in-the-Dark Toys Work? Start
- 19 How Does a Microwave Heat Food? Start
- 20 How Does a Battery Make My Toys Go? Start
- 21 How Does a Screen Make All Those Colors? Start
- 22 How Does a Straw Pull My Drink Up? Start
- 23 How Does a Touchscreen Know Where You Touch? Start
- 24 How Does a Zipper Work? Start
- 25 How Do Glasses Help People See Better? Start
- 26 How Does a Thermos Keep Soup Hot? Start
- 27 What Is Fire Made Of? Start
- 28 How Does a Bike Stay Up When It's Moving? Start
- 29 How Does a Toilet Flush? Start
- 30 How Does a Light Bulb Light Up? Start