Computer

    There are all kinds of machines. They are used in many different ways. One kind of machines is called computer. A computer can do many things. A computer can do maths problems. People can do maths problems,too. But they can't do it as fast as a computer. Computers remember things. Computers remember everything people tell them. People can not remember as many things as computers. Computers help to tell what the weather will be like. Computers help to fly rockets and spaceships.

    There are a lot of ways computers are used. They are used in thousands of ways. But they are not alwaysused in the same way. Some computers do just a few things. Some computers can do a lot of things. There are huge (巨大的) computers. There are small computers, too. There may be computers in your school. Do you know what they do?

    1970 was World Conservation(保护) Year. The United Nations wanted everyone to know that the world was in danger. They hoped something could be" done.

    Here is one example of the problem. At one time there were 1,300 kinds of plants, trees and flowers in Holland(荷兰), but now only 866 are left. The others have been destroyed (毁灭) by modern people and their science. We are polluting earth, air, water and everything around us. We can't live without these things. If things go on like this, we shall destroy ourselves.

    What will happen in the future? Perhaps it's more important to ask "What must we do?". More and more young people have known this. Many of them are helping to save our earth. For example, they plant trees. In a small town in the United States a large group of girls cleaned the banks of 11 kilometres of their river. Young people may hear about conservation through a song called "No one's going to change our world". It was made by Cliff Gichard and other singers. The money from it will help to conserve tigers, elephants and pandas on the earth.

    If your pen broke at school today, what would you do? You would go to a shop and buy a new one. What if you could simply print out a real, working pen with your 3-D printer without leaving your room?

    Ten years ago people could only see 3-D printing in science fiction movies. But now 3-D printing is here and it's bringing big changes.

    Unlike normal printing that can only copy a 2-D picture with ink. 3-D printing can build almost anything made from material. The printer layers(分层) the material in different shapes to create the object you want to be copied.

    The 3-D printer has been used to make many different things. People have made cups, cars and even an airplane with it. Doctors have been using 3-D printers for several years. People's nervous systems(系统) have been printed out in 3-D form in medical research. Some body parts have been printed and used in hospital. Several months ago, doctors used a 3-D printer to rebuild the face of a person who had a bad accident. In the future, it is expected that the printer will make human organs(器官)to save more lives.

    However there are drawbacks to the printer. At the moment, printing can be quite slow and it's still rather expensive. The average(平均的) price of a household printer is around $1,700, not including the cost of the materials.

    But as the technology develops, it shouldn't be long before disadvantages are improved. Only time will tell where this new technology will take us.

The Vine That Ate the South

    Kudzu is a fast-growing vine(蔓生植物) that covers a large area in the southern United States. It is so common that one might think it is a native plant, but it is not. Kudzu was brought to the United States from Japan in 1876. Many Americans thought it was beautiful, and they began to plant it. They didn't know it could grow up to a foot a day during the summer months. Nor did they know it would grow up and over anything in its path.

    In Japan, kudzu experienced cold winters and a short growing season. But in the United States, it has a very long growing season with warm and wet southern weather. It is fine weather for the vine to grow fast.

    In the 1920s, people used the vine to feed farm animals. Ten years later, the government supported to plant kudzu because it kept soil from washing away. However, by the 1950s, the government no longer wanted people to plant the vine. Twenty years after that, the government said it was a harmful plant.

    The vine grows up trees and buildings, making some beautiful shapes. However, trees die after kudzu covers them because they cannot get enough light. Scientists are looking for ways to kill the vine. They used poisons(毒药) to kill the vine. However, some of the poisons made it grow even better. Scientists also find it difficult to dig up Kudzu. The plant is really tough.

    Because kudzu is so hard to kill, some people are making the best of it. So they try to find different uses for the vine. They find the vine can be used to make paper and baskets, it can be used to feed the goats, and it can even be eaten by people. Scientists are studying it in the hope that the vine can be used as a medicine. At the very least, kudzu serves as an example of the unexpected results that can come from non-native plants.