In today's world, almost everyone knows that air pollution and water pollution are harmful to people's health. However, not all the people know that noise is also a kind of pollution, and that is harmful to human health, too.

    People who work and live under noisy conditions usually become deaf. Today, scientists believe that 10% of the workers in Britain are becoming deaf because of the noise where they work. Many of the workers who print newspapers and who weave cloth (织布) become deaf. Plenty of people living near airports also become deaf. Recently it was discovered that many teenagers in America could hear no better than 65-year-old persons, because these young people like to listen to pop music and most of pop music is a kind of noise. Besides, noise which is produced by jet planes or machines will make people's life difficult and unpleasant. It can make people ill or even drive them mad.

    It is said that a continuous noise of more than 85 decibels (分贝) can cause deafness. Now the governments in many countries have made laws to control noise and make it less than 85 decibels.

    In China, the government is trying to solve not only air and water pollution problems but also noise pollution problems.

    A long time ago, people thought that the Sun went round the Earth. In some countries people even said that the Sun was a god (神). They thought the god drove across the sky each day on a golden horse. Now we know the Earth goes round the Sun. It takes the Earth a year to go all way round the Sun. Today men even know how far it is for the Earth to go round the Sun. They tell us that the Earth travels over a thousand miles a minute on its journey round the Sun.

    The Sun is really a star. It is much bigger than the Earth and it is very hot. Some people have been to the Moon but we know that no one can ever go to the Sun. It is far too hot for people to live anywhere near it. The Sun is about three hundred thousand times heavier than the Earth and more than a million times larger.