Earth is Big

Earth is Big — page 1 — Earth’s Inhabitants Are Young CONTENTS Introduction Earth Is Big Earth Is Small Earth Is Old Earth Is Cold Earth Is Hot Earth Is Wet Earth Is Dry Earth Is Fast Earth Is Slow 4 6 8 10 12 14 16 18 20 22 24 2

Earth is Big — page 2 — Earth Is Round Earth Is Jagged Earth Is Heavy Earth Is Light Earth Changes Quickly Earth Changes Slowly Is Earth Ours Earth Is Unique Glossary Index Source Notes 26 28 30 32 34 36 38 40 42 44 46

Earth is Big — page 3

Earth is Big — page 4 — Is the Earth heavy Well yes It has a mass of approximately 6.6 sextillion tons 6 septillion kilograms That’s a 6 with 21 zeros after it That seems like an awful lot doesn’t it But when you look at how dense the Earth is how much mass fits in each bit of space all of a sudden Earth starts to look pretty light There are a lot of metals that are denser than Earth including familiar ones like iron and silver and gold In this book we explore our planet and a lot of other things through measurement and comparison To do that we use what are known as standards of measurement units we have all agreed to such as feet pounds meters kilograms tons and degrees This agreement is key If we were to measure distance for example by the number of steps it takes to travel it then my measurement and yours would be different because we take different sized steps That’s why people invented standard units Throughout this book we’ll explore a lot of different standards Some will be very familiar to you Others might be totally new But all of them are fun because they give you the power to understand the world around us So welcome to big small heavy light cold hot wet dry fast slow round jagged planet Earth a fantastic home by any measure A note on the measurements in this book Across the globe there are lots of different systems for measuring things But wherever you are scientists use what’s called the metric system and many countries do too The metric system uses standard units such as meters and kilograms for their measurements In this book you'll see both United States customary units and metric units Information on converting metric to United States customary units such as inches and pounds can be found on page 43 of this book 5

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