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.

Humans have always wondered about the Earth they live on and about the sky above them.

When early humans looked at the night sky, they _____ themselves a lot of questions. They looked at the Moon and _____ what this strange bright object in the sky was. They did not understand _____ it changed its shape from night to night. They _____ the stars and planets. They also wanted to know why some of them changed their positions, _____ others did not. They also thought about the _____ of the Earth. All the early people believed the Earth was flat.

In different parts of the world, there were _____ ideas about the universe (宇宙). The ancient Greeks were the first people to _____ the universe more scientifically. In the sixth century BC Pythagoras put forward the _____ that the Earth was round. ______, he could not explain why people at the bottom of the Earth did not ______.

It was not until the sixteenth and seventeenth centuries that scientists found the answers ______ some important questions. Galileo’s telescope made ______ possible for people to see the sky more ______ and find the positions of the stars and planets. Finally in 1665, Isaac Newton ______ to the world what gravity was and people understood why they did not fall off the Earth.

In 1997, Americans launched two space probes (探测器). They were ________ Voyager I and Voyager Ⅱ. They sent ________ photos and facts about the more distant planets. Now they are traveling out in the galaxy (星系). Here are some facts about the Voyager spacecraft.

The total cost of the Voyager mission (任务) is 865 million dollars at that time. This ________ very expensive. But it is only twenty cents for each American each year.

The television cameras of the Voyager are ________ powerful that they could read a newspaper headline (报纸标题) at a distance of one kilometer. But in fact there aren’t any newspapers in ________!

Scientists have put a message on the Voyager spacecraft. We hope that someone will find it one day. But it will ________ the Voyager 40,000 years to reach another solar system like ours, with planets. The ________ is on a special disc (盘), a bit like a CD. The disc has sounds and pictures on it. There are thirty-nine sounds of the earth. Some of them are ________ sounds, such as the sea, wind, and thunder (雷声). Some are animal sounds, such as birds, dogs, and humans. Some are man-made sounds, like machines, buses, and trains. They also put on music from many different countries in the world. ________ there are spoken greetings from earth-people in fifty-five languages. There is a message in English from the president of America. There are also 116 pictures of the ________ and its people.