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Copyright © 2023 by Nomad Press. All rights reserved.

No part of this book may be reproduced in any form without permission in writing from the publisher, except by a reviewer who may quote brief passages in a review or for limited educational use. The trademark Nomad Press and the Nomad Press logo are trademarks of Nomad Communications, Inc.

ISBN Softcover: 978-1-64741-010-0

ISBN Hardcover: 978-1-64741-007-0

Educational Consultant, Marla Conn

Questions regarding the ordering of this book should be addressed to

Nomad Press

PO Box 1036, Norwich, VT 05055

www.nomadpress.net

Printed in the United States.

CONTENTS

Timeline

Gravity in Nature

Introduction

Which Way Is Down?

Chapter 1

Getting to Know Gravity

Chapter 2

Gravity Basics: Matter and Mass

Chapter 3

Discovering Gravity

Chapter 4

Gravity in Space

Chapter 5

Putting Gravity to Work—And Play!

Glossary • Metric Conversions

Resources • Essential Questions

Index

Interested in Primary Sources? Look for this icon.

Some of the QR codes in this book link to primary sources that offer firsthand information about the topic. Many photos are considered primary sources as well because a photograph takes a picture at the moment something happens. Use a smartphone or tablet app to scan the QR code and explore more! You can find a list of the URLs on the Resources page. You can also use the suggested keywords to find other helpful sources.

gravity

TIMELINE

GRAVITY IN NATURE

Gravity is a natural force, and you can find it everywhere in nature! In fact, our natural world wouldn’t exist if gravity hadn’t pulled billions of particles together to make our planet. What else can we thank gravity for?

WATERFALLS

LEAVES FALLING

TIDES

AVALANCHES

SNOW AND RAIN

THE MOON ORBITING THE EARTH

APPLES FALLING FROM TREES

Introduction

WHICH WAY IS

DOWN?

Think about a cup falling off the counter. Does the cup fall up or down? Why? This may seem like a silly question, but the answer involves a very important concept in the universe—gravity!

On Earth, the invisible force of gravity pulls everything toward Earth’s center. This is something we learn as we’re first beginning to walk. It’s not easy! And gravity continues to be a huge part of our lives, and the world around us, for as long as we live. You can’t turn it on or off. It pulls you down whether you want it to or not. Without it, you would float away!

How does gravity keep you safe? What forces can you use to work against gravity and why do we need to do this sometimes? Why does the position of your belly button matter? How do astronauts work in zero gravity? Can gravity make life easier? You’ll learn the answer to these questions and more in this book!

ESSENTIAL QUESTION

What force keeps us on the earth?

WORDS TO KNOW

IT’S ALL A MATTER OF MATTER

Gravity works on all matter. Matter is anything that takes up space and can be measured. Chocolate cake is matter. It takes up space. You can stick a fork in it and describe how it looks and tastes. You can measure how much it weighs, how large it is, and if it is hot or cold.

A feather is matter. So are dogs and cats, a car, this book, your body, and even a speck of dust. What about air and other gases? Are those matter? Can invisible things