Chapter 1 of 7

All 7 chapters
  1. 1Sun, Earth and Moon, readunderstood
  2. 2Why we have day and night, readunderstood
  3. 3The Sun seems to move, readunderstood
  4. 4A year: going round the Sun, readunderstood
  5. 5The Moon goes round the Earth, readunderstood
  6. 6Phases of the Moon, readunderstood
  7. 7Eclipses, readunderstood

S2.9.1 Chapter 1

Sun, Earth and Moon

What are the Sun, the Earth and the Moon?

Your guess

Pick one before you read on. It is fine to be wrong.

Your guess

  • You picked A. Read on. At the end, the chapter comes back to your guess.

  • You picked B. Read on. At the end, the chapter comes back to your guess.

  • You picked C. Read on. At the end, the chapter comes back to your guess.

By the end you can

  • Explain the Sun is a star, and Earth and Moon are balls
  • Model the sizes of the Sun, Earth and Moon with round objects

Three big things shape our days and nights. They are the Sun, the Earth and the Moon. You live on the Earth.

The Sun is a star. A star is a huge ball of very hot, glowing gas. Gas is stuff like the air. You cannot hold it.

The Sun makes its own light and heat. It is the star nearest to us. The stars you see at night are like our Sun. They are far, far away.

On the left, a ball with rays, labelled Sun, with the words nearest star. On the right, eight small black dots, labelled other stars.Sunnearest starother stars
The Sun is a star. The other stars look like dots because they are so far away. Not to size.

The Earth is a ball of rock. It has water and air round it. The Earth is not a star. Its daylight comes from the Sun.

The Moon is a smaller ball of rock. It has no air. The Moon makes no light of its own. Sunlight lands on it and lights it up.

To reflect is to send light back. The Moon reflects sunlight. So does the Earth.

On the left, a ball with rays, labelled Sun, with the words makes light. Two arrows of light go from the Sun. One goes to a ball labelled Earth, with the words reflects light. The other goes to a smaller ball labelled Moon, with the words reflects light. At the bottom are the words not to size.Sunmakes lightEarthreflects lightMoonreflects lightnot to size
Only the Sun makes light. The Earth and the Moon send some of it back. Not to size.

Draw it first

Draw the Sun, Earth and Moon

  1. A big ball on the left, labelled Sun. A smaller ball in the middle, labelled Earth. A tiny ball at the top right, labelled Moon. One arrow of light goes from the Sun to the Earth, and one goes from the Sun to the Moon. At the bottom are the words not to size.Sun

    1 Draw a big ball on the left for the Sun. Write Sun.

  2. A big ball on the left, labelled Sun. A smaller ball in the middle, labelled Earth. A tiny ball at the top right, labelled Moon. One arrow of light goes from the Sun to the Earth, and one goes from the Sun to the Moon. At the bottom are the words not to size.SunEarthMoon

    2 Draw a smaller ball for the Earth. Draw a tiny one for the Moon. Write both names.

  3. A big ball on the left, labelled Sun. A smaller ball in the middle, labelled Earth. A tiny ball at the top right, labelled Moon. One arrow of light goes from the Sun to the Earth, and one goes from the Sun to the Moon. At the bottom are the words not to size.SunEarthMoonnot to size

    3 Draw an arrow from the Sun to the Earth. Draw one to the Moon. Write not to size.

This picture is not to size. The real Sun is much, much bigger.

The Sun is about 109 times as wide as the Earth. The Earth is about 4 times as wide as the Moon.

On the left, a big circle labelled Earth. An equals sign, =. On the right, a row of four small circles labelled 4 Moons. A line under each has the same length. At the bottom are the words about 4 to 1.=Earth4 Moonsabout 4 to 1
About four Moons side by side are as wide as the Earth.

You can show this with a model. A model is a small copy of something big.

See it three ways

As a picture

Three rows. In the first row is a ball with rays, labelled Sun, with the words hot gas, makes light. In the second row is a smaller ball, labelled Earth, with the words rock, water, air. In the third row is a tiny ball, labelled Moon, with the words rock, no air.Sunhot gas, makes lightEarthrock, water, airMoonrock, no air

In words

The Sun is a star. It makes its own light. The Earth and the Moon are balls of rock.

In symbols

Sun = 109 Earths wide. Earth = 4 Moons wide.

Say the Earth is a pea, 1 cm wide. Then the Moon is a seed, about 3 mm wide. Hold the seed 30 cm from the pea.

The Sun is then a ball about 1 m wide. It is more than 100 m away.

Try it

Make a model of the Sun, Earth and Moon

You need: a pea or a small bean, about 1 cm wide, a grain of rice or a tiny seed, a ruler or a sheet of writing paper, a string 50 cm long, a stick, flat ground outside.

Be safe: Never look at the Sun while you work outside. Look only at the ground. Never put the pea or the seed in your mouth.

  1. Put the pea on a flat place. It is the Earth.
  2. Measure 30 cm from the pea. A sheet of writing paper is about 30 cm long. Put the rice there. It is the Moon.
  3. Go outside. Tie the stick to one end of the string.
  4. Hold the other end on the ground. Pull the string tight.
  5. Walk the stick round and scratch a circle on the ground. It is 1 m wide. It is the Sun.
  6. Walk away from the circle. Count 200 steps. That is about 100 m. The real distance is a little more.

What you will see: The pea is tiny beside the Sun circle. The seed is even smaller, and close to the pea. The Sun is huge and very far away.

If you cannot try it, this is what happens.
A tiny pea on the left, labelled pea = Earth. A tiny seed on the right, labelled seed = Moon. A line between them, labelled 30 cm, shows how far apart they are. Below are the words Sun: a ball 1 m wide and more than 100 m away, and an arrow pointing far off to the right.pea = Earthseed = Moon30 cmSun: a ball 1 m widemore than 100 m away

A wrong idea many people have

The Sun and the Moon are the same size.

Why it feels right: In the sky, the Sun and the Moon look the same width.

The test that breaks it: Far things look small. Hold up your thumb at arm's length. Cover a house or a tree far away. The big thing looks smaller than your thumb. Look only at things on the ground, never at the Sun.

What is true: The Sun is about 400 times as wide as the Moon. It is also about 400 times as far away. So they look alike.

Key words

star
a huge ball of hot, glowing gas that makes its own light. The Sun is a star.
gas
stuff like the air. You cannot hold it.
model
a small copy of something big.
reflect
to send light back.

Back to your guess

The answer is B: All three are balls. Only the Sun makes its own light.

All three are balls. The Sun is a star and makes its own light. The Moon makes none.

Check yourself

Try each one before you look. A wrong answer tells you where to go next.

  1. What is the Sun?

    Tap your answer.

    1. Yes, that is right. The Sun is the star nearest to us. It makes its own light and heat.

    2. Not this one. The Earth and the Moon are balls of rock. The Sun is hot, glowing gas. Try another.

    3. Not this one. The Moon is a smaller ball of rock. It makes no light. The Sun is a star. Try another.

    See the answer

    A star: a huge ball of hot, glowing gas

    The Sun is the star nearest to us. It makes its own light and heat.

    • If you chose B: The Earth and the Moon are balls of rock. The Sun is hot, glowing gas.
    • If you chose C: The Moon is a smaller ball of rock. It makes no light. The Sun is a star.

  2. The Moon shines at night. Where does its light come from?

    Tap your answer.

    1. Not this one. The Moon is a ball of rock. It makes no light of its own. Try another.

    2. Not this one. The Earth is not a star. The light on the Moon comes from the Sun. Try another.

    3. Yes, that is right. Sunlight lands on the Moon and lights it up. The Moon makes none.

    See the answer

    The Sun lights the Moon

    Sunlight lands on the Moon and lights it up. The Moon makes none.

    • If you chose A: The Moon is a ball of rock. It makes no light of its own.
    • If you chose B: The Earth is not a star. The light on the Moon comes from the Sun.

  3. The Earth is a pea 1 cm wide. The Sun is 109 times as wide as the Earth. How wide is the Sun model?

    See the answer

    109 cm, a little more than 1 m

    109 times 1 cm is 109 cm. That is a little more than 1 m.

  4. The Earth is about 4 times as wide as the Moon. A bead for the Earth is 12 mm wide. How wide is the bead for the Moon?

    See the answer

    3 mm

    The Moon is a quarter as wide. 12 mm shared into 4 equal parts is 3 mm.

  5. Mei says the Sun and the Moon are the same size. They look alike in the sky. Is she right?

    Tap your answer.

    1. Not this one. Far things look small. Your thumb can cover a far-off house. Try another.

    2. Yes, that is right. The Sun is about 400 times as wide as the Moon. It is also about 400 times as far away.

    3. Not this one. The Moon is the smaller one. The Sun is about 400 times as wide. Try another.

    See the answer

    No. The Sun is much bigger, but much farther away.

    The Sun is about 400 times as wide as the Moon. It is also about 400 times as far away.

    • If you chose A: Far things look small. Your thumb can cover a far-off house.
    • If you chose C: The Moon is the smaller one. The Sun is about 400 times as wide.

  6. Draw the Sun, the Earth and the Moon, from biggest to smallest. Write which one makes light.

    See the answer

    A big Sun, a smaller Earth, a tiny Moon. The Sun makes light.

    The Sun is the biggest and it is a star. The Earth is smaller. The Moon is the smallest.

  7. Which sentence about the Sun, the Earth and the Moon is true?

    Tap your answer.

    1. Not this one. The Moon shines only because sunlight lands on it. It is a ball of rock, not a star. Try another.

    2. Not this one. The Earth is not a star. Its daylight comes from the Sun. Try another.

    3. Not this one. The Sun is not rock. It is a huge ball of hot, glowing gas. Try another.

    4. Yes, that is right. The Sun is a star and makes its own light. The Earth and the Moon are balls of rock.

    See the answer

    Only the Sun is a star. The Earth and the Moon are balls of rock.

    The Sun is a star and makes its own light. The Earth and the Moon are balls of rock.

    • If you chose A: The Moon shines only because sunlight lands on it. It is a ball of rock, not a star.
    • If you chose B: The Earth is not a star. Its daylight comes from the Sun.
    • If you chose C: The Sun is not rock. It is a huge ball of hot, glowing gas.

  8. Kofi makes a model. The pea is the Earth, 1 cm wide. The seed is the Moon. How far from the pea does Kofi put the seed?

    Tap your answer.

    1. Not this one. That is where the Sun goes in the model. The Moon is much nearer than the Sun. Try another.

    2. Not this one. Drawings often put the Moon close to save room. The Moon is far away. Try another.

    3. Not this one. That is only 10 Earths away. The Moon is about 30 Earths away. Try another.

    4. Yes, that is right. The Moon is about 30 Earths away from us. With a pea 1 cm wide, that is 30 cm.

    See the answer

    30 cm from the pea

    The Moon is about 30 Earths away from us. With a pea 1 cm wide, that is 30 cm.

    • If you chose A: That is where the Sun goes in the model. The Moon is much nearer than the Sun.
    • If you chose B: Drawings often put the Moon close to save room. The Moon is far away.
    • If you chose C: That is only 10 Earths away. The Moon is about 30 Earths away.

Keep it

Copy this into your exercise book.

The Sun is a star, a huge ball of hot glowing gas. It makes its own light. The Earth and the Moon are balls of rock. The Sun is 109 Earths wide. The Earth is 4 Moons wide.

Draw: Draw a big ball, a small ball and a tiny ball. Write Sun, Earth and Moon.

Reading with a child? A short page for the adult: what this chapter teaches and three questions to ask.

No internet tomorrow? Save the whole book as one file (717 KB). It opens on any phone.