The earth is a planet and it 【小题1】 around the sun. Seven other planets also go around the sun.【小题2】of them has an environment like 【小题3】 of the earth, so scientists do not think they will find life on them. The sun and its planets are 【小题4】 the solar system, and our solar system is a small part of a 【小题5】larger group of stars and planets, called the Galaxy or the Milky Way. There are 【小题6】of stars in the Galaxy, and our sun is only one of them.

Scientists have also 【小题7】many other galaxies in the universe. They are very far and their light has to travel for many years to 【小题8】 us. So how 【小题9】 is the universe? It is 【小题10】to imagine.

Our earth gets its warmth and light 【小题1】. The sun is a huge blazing（酷热的）ball, a million times 【小题2】 the earth. And it is millions of miles away. The earth spins（旋转） round once every 24 hours. It turns to face the sun and spins away every 24 hours.

When our part of the earth looks on to the sun, we see sunlight and we 【小题3】. When our part turns away from the light, we have night.

When our part begins to turn 【小题4】 and we see the first sunlight, we call it morning.

When we are facing the sun most directly, it is noon. Then the sun is closest to begin straight（直接地）above us. When we begin to 【小题5】 from the sun, we have afternoon, evening and night.

The universe (宇宙) is so wide that we still don’t know much about it. It 【小题1】 the earth, the sun, the moon and the stars, and the space between them as well. Many of the stars can not be 【小题2】 because they are too far away. The moon travels around the earth. It’s our satellite. It’s the 【小题3】 to our earth. So far, humans have visited it already. And spaceships without people have reached other parts of the universe. Many countries have launched lots of man-made satellites into space. The satellites travel around the earth and help us 【小题4】 more about the earth, the weather and other things. They are used for 【小题5】 messages. With their help, TV and radio programs can be sent to countries all over the world. Satellites can also help us make telephone calls to foreign countries.

Our knowledge of the universe has been growing all the time. 【小题6】 space satellites (人造卫星), the world itself is becoming a much 【小题7】 place and people from different countries now understand each other better.