1 . If someone asks you, “    1    ” I think you will answer “Blue”. I’m afraid that you will be wrong.     2     It looks blue because we are looking at the blue sunlight. The sunlight is shining on little bits of dust (灰尘) in the air.

    3     I’m sure that you have asked this question, too. We know that there is air all around the world, but we couldn’t fly very high because as we go high, the air gets thinner. If we go far enough away from the Earth, we find there is no air.

Maybe we can answer some questions now. What is the sky? Where is it? It is all around the world.     4     In space, there is nothing, but only the Sun, the Moon, the Earth and all the other stars.

2 . If someone asks you, “What colour is the sky?” I think you will answer “blue”. I’m afraid that you are wrong. The sky has no colour. It looks blue because we are looking at the blue sunlight. It is shining on little bits of dust (灰尘) in the air.

Is the sky full of air? I’m sure that you have asked this question, too. We know there is air all around the world. But we couldn’t fly very high because as we go high, the air gets thinner (更稀薄的). If we go far enough (足够的) away from the earth, we find there is no air.

Maybe we can answer some questions now. What is the sky? Where is it? The sky is space. It’s all round the world. In space there is nothing, but only the Sun, the Moon, the Earth and all the stars.

4 . Many people believe that the Moon was once part of the Earth and broke away millions of years ago. Other people say that it came from another part of space.

There are high mountains, deep valleys and wide flat spaces on the Moon. Animals and plants can’t live on the Moon because it has no air or water. There are no clouds, no rain and no snow, either.

Sound needs air to travel. There is no air on the Moon. So there can be no sound there. The Moon is a silent place.

The Moon has no light of its own. It looks bright because the Sun’s light shines on it. During the day, the rocks become hotter than boiling (沸腾的) water. This is because the Moon is closer to the Sun than the Earth.

The Moon is about 383 thousand kilometres away from the Earth. It takes a spaceship about three days to reach the Moon. But it would take a car nearly six months to travel this way.

5 . We live on Earth. It’s our home. But how much do you know about it? Let me tell you something about our Earth.

The Earth is not flat as we see but it is like a huge sphere in the space. Like the other seven planets (行星), the Earth is running around the Sun. It’s the third nearest one to the Sun. It takes the Earth about 365 days to run around the Sun.

At the same time, the Earth is going around itself. If you are in space, you can see lots of white clouds over the surface (表面) of the Earth. Through the clouds, you can see the blue colour of the oceans, and the brown colour of the land. About 70% of the Earth is covered with water. Why do we have day and night? When the half of the Earth is facing the Sun, it’s daytime. As the Earth turns, and this half is away from the Sun, night is coming. And it’s daytime for the other half.

In the universe (宇宙) , as we all know, there is the Sun, the Moon, the Earth and a large number of stars. Through our Geography lessons, we know that the Sun is a star, the Earth is a planet and the Moon is a satellite (卫星) . We also know the Earth goes around the Sun and the Moon goes around the Earth. We have day and night because the Earth keeps turning all the time When our part of the Earth turns to the Sun, it is day. When our part of the Earth turns away from the Sun, it is night.

Just because the Moon is closer to the Earth than the Sun, it looks much bigger than the Sun. Big things will look smaller when they are farther and small things also look bigger when they are nearer.

The Sun is big enough to give out strong light. The Moon can’t give out any light at all, but it looks quite bright, too. Why? In fact, the light from the Moon comes from the Sun. The Moon looks much bigger and brighter than the stars, but in fact the stars are much bigger and brighter than the Moon. They look smaller than the Moon also because they are farther away from the Earth.

There are many other facts about the universe and we should study hard to know more.

Do you know anything about the Moon? How much do you know about it?

    1    ? Scientists tell us so much about the Moon. So it’s easy for us to have the idea of going to the Moon. But what would it be like to really go there?

The Moon is not a friendly place. There is no air or water. There are only lots of dust (灰尘) and mountains around on it.     2    . The temperature (温度) of the Moon is different from day to night.     3    . But it’s very cold at night.

    4     As we know, sound can only travel in the air but there is no air on the Moon.

But from the Moon, you can see our beautiful Earth. It is shining more brightly than the other stars in the dark.     5     The photos would be wonderful.

The universe (宇宙) is everything out in space. Nobody ______ how large the universe is. When we talk about the universe, we mean the Earth, the Sun, the Moon and all the ______ , and the space between them.

Now let me tell you something about the ______ . It is like a large ball. It ______ around the Sun. And ______ and land cover it. If you are in a spaceship and ______ the Earth from space, you will find that there are some blue parts. They are the seas.

We live on the outside part of the Earth. Around us is the air. It takes the Earth 24 ______ to turn in a full circle (整圈). When you see the Sun shining ______ , it’s the day for you. But when the Earth turns you away from the Sun, everything around you ______ dark(黑暗的).

Can you tell me something else about the universe? I think it is ______ and I want to learn more about it.