Stop reading for a minute and think about what you see when you look up at the sky on a clear night. You probably see many stars (星星). Long long ago, farmers watch some stars to know when to plant their crops. Travelers did so to find their way in the dark. Today stars are still important to some people.

    Scientists find that most stars are very big. In fact some stars are so far away that it would take millions of years to get to them even by spaceship.

    Another thing we know today about stars is that some are made up of(由…组成) hot gases. The gases are so hot that they send out light. If you watch a star carefully, you may notice that it twinkles(闪烁)sometimes. As you may understand, light from a star must shine through the air before you can see the star. Air is always moving, it makes light from the star move back and forth. When the light moves, it makes the star twinkle. Stars also have different colors. The colors of a star depend on how hot it is. To our surprise, the cool stars are red and the hottest stars are white.

    Taking away a city's rubbish is a big job. Every day tracks come into a city to collect it. Most rubbish is made up of things we can't eat or use. If we kept these things we would soon have a mountain of rubbish.

    In some cities the rubbish is collected and taken outside of city to a dump. Often the city dump is placed where the ground is low or there is a big hole. The kitchen rubbish is broken into small pieces and sent into the sewage system. The sewage system takes away the used water from toilets, bathtubs and other places.

    To keep mice and flies away, some earth is used to cover the newly dumped rubbish. Later, grass may be planted on the rubbish-filled land. Finally, a house or a school may be built there, and then you'd never know that this had once been an old rubbish dump.

    In other cities the rubbish is burnt in special places. The fire burns everything but the metal. Sometimes the metal can be used again in factories where things are made of metal. The food parts of rubbish are put in special piles where they slowly change into something called humus, which looks like black earth. It is rich with the kinds of things that feed plants and help make them grow.

    Over 80G of the ancient forests have already been destroyed. Thousand-year-old trees are cut down just to make everyday goods. More and more wild animals are in danger now. Wild animals are our friends, and we cannot live without them. If we take no action, more and more wild animals will disappear in the future. It is time for us to save and protect endangered animals. Then what can we do? Here are some steps.

    Step one: Find out what animals are living near your place. Spend some time learning about the animals.

    Step two: Help to build more nature reserves and other wilderness areas. Protecting the living areas of wild animals is one of the best ways to help protect endangered animals. You can raise money for them or spend some time helping build nature reserves.

    Step three: Buy foods and goods that are made from materials which do not harm endangered animals or their living areas.

    Step tour: Join a local Wild Animals Club. You can take action to protect wild animals. There are many global groups that try to call on people to protect the environment by changing people's ideas and behaviours. Children, teenagers, teachers and schools from all over the world can help to save the animals. Everyone can do a little to help them, and every little bit of help is important!

    Animals are natural resources that people have wasted all through our history. Animals have been killed for their fur and feathers, for food, for sports, and simply because they were in the way. Thousands of kinds of animals have disappeared from the Earth forever. Hundreds of animals are on the danger list today. About 170 kinds in the United States alone are considered in danger. Why should people care? Because we need animals, and because once they are gone, there will never be any more. Animals are more than just beautiful or interesting. They are more than just a source of food. Every animal has its place in the balance of nature. Destroying one kind of animal can create many problems. For example, when farmers killed large numbers of hawks, the farmers' stores of corn and grain were destroyed by rats and mice. Why? Because hawks eat rats and mice, with no hawks to keep down their numbers, the rats and mice multiplied quickly.

    Luckily, some people are working to help save the animals. Some groups raise money to let people know about the problem. And they try to get the governments to pass laws protecting animals in danger. Quite a few countries have passed laws. These laws forbid the killing of any animal or plant on the danger list. Slowly, the number of some animals in danger is growing.

    Gardening is popular in many parts of the world. It brings us sweet smelling flowers, fresh fruit and vegetables. But you can get more from your garden.

    Gardening helps to keep healthy. Today's people sit indoors for too long and don't get much exercise. When you garden, you have to move around. It's a good chance for you to exercise your body by watering flowers or doing some digging. Besides, when you are in your garden, you can feel the warm sunshine. This means you are getting Vitamin D. It helps your bodies use calcium (钙), which is necessary to keep your bones (骨骼) strong.

    It gets them off computers, televisions and phones. Gardening can be a great teacher to teach children about nature and healthy eating. It can also help them to understand the meaning of "No pains, no gains."

Gardening is a great way to meet people and build relationships. When you are gardening, you are outdoors. So it is a perfect time to communicate with your neighbors. Most people love to talk about their hobbies, and so do gardeners. They usually enjoy showing people what they are growing. And most enjoy sharing advice and stories about their gardens.