INTRODUCTION The Earth is our home the only place we humans have ever lived and for most of our history the only place we knew existed But once we began to study outer space we also started to discover that our planet is just one of many in the universe Since then we have ventured out into space and looked back at Earth from afar like a big blue ball in a sea of black The images from space have made us keenly aware of something as big as Earth seems to us here on the surface our planet is really tiny compared to the vastness of space Even so our home planet is quite different from the rest of the known worlds in our solar system Over billions of years different processes have shaped and molded it into a home like no other One of the best ways to get a better understanding of our home sweet home is to find out how Earth and the things that live on it compare to the rest of the universe That’s what this book is all about The best way to compare two things is to measure them We humans like to measure things There’s something powerful about knowing how big how heavy or how fast something is and being able to compare a tortoise to a cheetah to a race car to a comet Once you get started measuring and comparing you’ll notice we do it all the time We measure the temperature outside on a warm summer day the pressure of the air in a perfectly inflated soccer ball and our own ages so we can compare them to the ages of our friends and family Measuring and comparing also lets you see things from different angles Our planet orbits the Sun at an average distance of about 93 million miles 150 million kilometers Is that far Well it depends what you compare it to It’s a lot farther than a snail can walk in an hour or even a lifetime but it’s much closer than Pluto 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
EARTH IS BIG How big is the Earth The most common way of measuring the size of a planet is to use its diameter which is the distance from one edge to another running through the center at the equator Earth’s diameter is 7,926 miles 12,756 kilometers Let’s see how some smaller objects compare THE SOLAR SYSTEM Our solar system contains planets moons and lots of smaller objects Some including planets and dwarf planets orbit the Sun Moons orbit planets Many of these objects are smaller than Earth including Earth’s Moon our closest neighbor in space EARTH 7,926 miles 12,756 km Our planet VENUS 7,521 miles 12,104 km MERCURY 3,032 miles 4,879 km Smallest planet and closest planet to the Sun 66 EARTH’S MOON 2,159 miles 3,475 km fifth largest moon in the solar system When you compare the size of the Moon to the size of the Earth it is the largest moon compared to the size of the planet it orbits excluding dwarf planets CERES 592 miles 952 km Dwarf planet PLUTO 1,473 miles 2,370 km Dwarf planet When it was first discovered in 1930 Pluto was labelled as the ninth planet in the solar system But as scientists discovered more objects in space Pluto became one of the first of a new group of objects called dwarf planets instead CHARON 750 miles 1,207 km Largest of Pluto’s moons MARS 4,220 miles 6,792 km
kilometers HOW BIG IS BIG Miles and kilometers When people want to know how wide high or long something is they use units of length In the metric system the standard unit of length is the meter We measure large distances in miles or kilometers km 1 km equals 1,000 meters or 3,281 ft or 0.62 miles LONGEST NONSTOP COMMERCIAL FLIGHT 9,534 miles 15,343 km AMAZON RIVER 4,000 miles 6,437 km GREAT WALL OF CHINA 13,170 miles 21,196 km Coming up with a height for an average human is not easy because in some parts of the world people are naturally taller than in other places HUMAN 8 ft 11 in 2.72 m Tallest person ever BLUE WHALE 98 ft 30 m Largest animal GIRAFFE 18 ft 5.5 m Tallest land animal Feet inches and meters Feet inches and meters can be used for measuring everyday objects and creatures including the length or height of large animals such as humans CAPYBARA 4 ft 3 in 1.3 m Largest rodent LADYBUG 0.2 in 5 mm Inches and millimeters For small objects inches can be used or the meter can be divided into centimeters cm or millimeters mm One hundred centimeters make up a meter and one thousand millimeters make up a meter PINHEAD 0.03 in 1 mm Microns Even smaller objects can be measured in microns There are one million microns in a meter or 304,800 in a foot All of these objects are too small for the human eye to see without a microscope RED BLOOD CELL 6 8 microns Most common cell in the human body All living things from giant redwood trees to tiny bacteria swimming in pond water are made from different types of cells Scientists estimate that you have more than 30 trillion cells in your body BUMBLEBEE BAT 1.2 in 30 mm Smallest mammal The tiny bumblebee bat is found in Thailand and Myanmar meters millimeters microns nanometers Nanometers Extremely small objects are measured in nanometers There are one billion nanometers in a meter or 304,800,000 in a foot These objects require high tech equipment such as an electron microscope to see them CESIUM ATOM 0.26 nanometers Largest naturally ocurring atom Everything from the air you breathe to your body’s cells is made of tiny building blocks called atoms At the heart of an atom is the nucleus This is made up of smaller particles called protons and usually neutrons Whizzing around it are even smaller particles called electrons Different atoms contain different numbers of these particles WATER MOLECULE 0.27 nanometers Molecules are made up of two or more atoms Water molecules are made from one oxygen and two hydrogen atoms Nucleus Electron o h h HYDROGEN ATOM 0.05 nanometers Smallest atom 7 GIANT HUNTSMAN 12 in 300 mm Largest spider by leg span LACTOBACILLUS ACIDOPHILUS 2 9 microns Helpful bacteria found in the gut Bacteria are microscopic single celled organisms They live in every type of environment including our bodies Some cause diseases while others can be helpful CORONAVIRUS 0.12 microns Even smaller than bacteria many viruses attack cells and take them over causing you to become sick One type of coronavirus caused a global pandemic in 2020 and 2021
