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.

【推荐2】Do you hope to move to another city or a foreign country? It may be interesting. But how about moving to ______ planet? A US company now has a plan: sending people to Mars ______ 20 years.

To begin with, the company plans to send ______ people to go to Mars first. It will ______ them several months to get there. When they arrive, they will build a ______ first.

But Mars is not an easy place to ______. It's rocky, cold and has lots of sandstorms(沙尘暴). Also, there is ______ air for breath. So people would have to live in a special house. They would have to ______ special clothes if they go out.

People will have to find ______ resources(资源), iron, water and so on. All these could help people live there...

Sounds interesting? You might want to go to Mars now. ______ will things go well like the company hopes? We'll wait and see.