Visit www.sciencea-z.com

Earth, Moon, Sun, and Stars

A Science A–Z Earth Series

Word Count: 755

www.sciencea-z.com

Written by Alyse Sweeney

Earth, Moon, Sun,

and Stars

www.sciencea-z.com

Key elementS USed in thiS BooKthe Big idea: Earth is part of a system of fast-moving objects in space. Earth rotates on its axis, Earth revolves around the Sun, and the Moon revolves around Earth. These movements affect important aspects of our daily lives, including night and day, our calendars, the availability of light and heat, and the appearance of the Moon and the Sun in the sky. Humans have an ever-growing understanding of how the Earth, Moon, and Sun move and interact. This understanding helps us make sense of what we see in the sky, both by day and by night. An understanding of our nearby space neighborhood can also inspire future exploration deeper into space, which may someday even include the discovery of life on distant planets.Key words: air, atmosphere, calendar, circle, crescent, dark, day, Earth, energy, full moon, gas, heat, light, month, Moon, neighbor, new moon, night, orbit, phases, planet, reflect, revolve, rock, rotate, sky, space, spin, star, Sun, water, year

Key comprehension skill: Cause and effectOther suitable comprehension skills: Compare and contrast; classify information; main idea and details; identify facts; elements of a genre; interpret graphs, charts, and diagrams

Key reading strategy: VisualizeOther suitable reading strategies: Ask and answer questions; summarize; connect to prior knowledge; using a table of contents and headings; using a glossary and bold terms

Earth, Moon, Sun, and Stars © Learning A–Z Written by Alyse Sweeney

All rights reserved.

www.sciencea-z.com

Written by Alyse Sweeney

Earth, Moon, Sun, and Stars

Photo Credits:Front cover: © Paul Paladin/Dreamstime.com; back cover, pages 7 (bottom), 11 (Earth): © iStockphoto.com/Andrey Prokhorov; title page: © iStockphoto.com/David de Groot; page 4: © Sean White/Design Pics/Corbis; page 5: © iStockphoto.com/Fanelli Photography; page 6: © iStockphoto.com/Ewa Wysocka-Galka; page 7 (top): © iStockphoto.com/Eric Hood; pages 9 (Sun), 11 (Sun), 13 (Earth, Sun): © iStockphoto.com/George Argyropoulos; pages 9 (Earth, stars), 14 (Earth), 16 (Earth, stars), 11 (stars), 13 (stars): courtesy of NASA/GSFC; page 9 (car): © Jupiterimages Corporation; page 11 (inset): © iStockphoto.com/Jill Chen; page 12: © Cathy Yeulet/123RF; pages 14 (Moon), 16 (Moon): © iStockphoto.com/Dra Schwartz; page 15 (top): © Paul Paladin/ 123RF; page 15 (bottom left): © iStockphoto.com/Andrey Stenkin; page 15 (bottom right): © iStockphoto.com/Kativ; page 17: © iStockphoto.com/Manley620

illustration Credit:page 8: Cende Hill/© Learning A–Z

3

introduction

When we look up into the sky, we are looking into outer space. We can see the Sun, the Moon, and stars. They all seem to move very slowly across the sky.

We live on a giant ball of rock and water called earth. We don’t see it because we live on it! It is also moving through space. It moves in a giant circle around the Sun.

4

table of Contents

Introduction ............................ p. 4

Earth ..................................... p. 6

The Sun ................................. p. 8

Day and Night ...................... p. 11

A Year ................................. p. 13

Our Moon ............................ p. 14

Changing Shapes of the Moon ......................... p. 16

Conclusion ........................... p. 17

Glossary .............................. p. 18

If you stare at the sky for an hour, you might see the stars move slowly.

The moon is also a ball of rock but smaller than Earth. The Moon moves in a giant circle around Earth. As Earth moves around the Sun, the Moon moves around Earth.

Let’s learn more about Earth, the Sun and stars, and the Moon. Let’s learn about how they move through space.

5 6

earth

Earth is where we live. It is one of eight planets that go around the Sun.

Earth is the third planet from the Sun. Being this far away keeps Earth from getting too hot or too cold. Planets closer to the Sun are so hot that steel would melt. Planets farther away are way too cold. Earth has the right amount of heat and light for plants and animals to live here.

Earth

From Earth, the Moon and the Sun are the biggest objects we can see in the sky.

From the Sun, the planets are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.

Mercury

Venus

Mars

SaturnJupiter

UranusNeptune

7

the Sun

The Sun is just one of billions of stars in space. Like most stars, it is a giant ball of very, very hot gas.

The Sun sends light to Earth. Light from the Sun hits Earth. It lets us see during the day. The light changes to heat when it hits Earth. The heat rises and warms Earth’s atmosphere. Without the Sun, Earth would be dark, cold, and lifeless.

8

Most of Earth is covered by water. Water is also below ground and in the air. That’s why Earth is called the water planet.

Living things need water to live. They also need air. Earth has a blanket of air around it. This blanket of air is called the atmosphere.

The atmosphere is made of water, oxygen, and other gases. It helps keep in heat.

Light turns to heat.

The Sun sends light to Earth.

9 10

Most stars are much bigger than our Sun. The Sun looks bigger than other stars because it is much closer to Earth. But even though it is our closest star, it is still very, very far away.

The Sun is much, much bigger than Earth. If Earth were the size of a marble, the Sun would be as big as a ball over five feet tall. The Sun is so big that one million Earths would fit inside it!

The Sun is so big that 109 Earths would fit across it.

If you could drive to the Sun at the speed of a car on the highway, it would take about 177 years to get there!

109 Earths

146 million kilometers(93 million miles)

Our Sun is small compared to the next-closest stars: Sirius, Pollux, and Arcturus.

Sirius

Pollux

The Sun

Arcturus

11 12

day and night

Earth is always spinning like a top, or rotating. This rotating causes day and night. When the side of Earth we are on faces the Sun, we see the Sun’s light. It is day. As we stand on a spinning Earth, the Sun looks as if it is moving across the sky.

Night comes when the side of Earth we are on rotates away from the Sun. The side facing away from the Sun is dark at night. When it is daytime on our side of Earth, it is nighttime on the other side of Earth.

It takes 24 hours for Earth to rotate once. That’s one day.

Day

Night

A year

The Earth also moves, or revolves, around the Sun in a path called an orbit. It takes 365¼ days for Earth to make a complete trip around the Sun. That’s one year!

13 14

our moon

The Moon is Earth’s closest neighbor in space. It is much smaller than Earth. About 50 Moons would fit inside Earth, or four Moons across it.

The Moon is much closer to Earth than the Sun. If you could drive a car to the Moon at the same speed as driving down a highway, it would take 150 days to get there.Earth takes 365 ¼ days, or a year, to circle the Sun.

Four Moons would fit across Earth. Fifty Moons would fit inside Earth’s ball.

15 16

The Moon does not make its own light. The Moon shines because it reflects the Sun’s light. We see the Moon at night and sometimes during the day. Moonlight is really sunlight bouncing off the Moon.

Changing Shapes of the moon

The Moon revolves around Earth just as Earth revolves around the Sun. It takes 28 days for the Moon to travel once around Earth.

The Moon seems to change shape as it moves. It really does not change shape. We just see different amounts of the sunlit side as the Moon goes around Earth.

The Moon takes 28 days to orbit Earth.Earth

Moon

New Moon

CrescentMoon

1st Quarter

3rd Quarter

Full Moon

17 18

Conclusion

Think about a calendar. A month is a little longer than the time it takes the Moon to go around Earth. A year is made of 12 months. In the time it takes Earth to go all the way around the Sun, the Moon goes around Earth 13 times. A year usually has 365 days. In the time Earth makes one trip around the Sun, Earth spins 365 times. Are you dizzy yet?

Glossary

atmosphere the blanket of air surrounding a planet, star, or moon (p. 7)

earth the planet we live on (p. 4)

moon Earth’s only natural satellite(p. 5)

orbit the path taken by one object in space circling around another larger object (p. 13)

planets very large objects that travel in orbit around a star (p. 6)

reflects bounces off something like a ball bouncing off a wall (p. 15)

revolves moves in a circle around something (p. 13)

rotating spinning around (p. 11)

stars large, faraway objects in space that make their own light (p. 8)

Sun the star that Earth goes around (p. 8)