Our sun is a star, and nine worlds (天体) move round it. Worlds like these are planets. But here are other stars, other suns, not only thousands of them, but millions of them. Do different stars have planets? We can see the planets round our own sun. But we haven't been anymore. The stars are too far away from us. Stars give out light, but the planets don't have any light of their own. So we can't see them. They are too far, and too dark. Still, we can tell that some stars have planets. While a big planet goes round, it pulls its star to one side. And sometimes we can see this. Then we know that the star has a planet. For example, Barnard's Star is a small red star. And it is the quickest star in the universe. But sometimes it moves slower, and then quicker again. We have known Bernard''s Star for many years, and now we are sure it has a planet.

    You can be proud of yourselves, even if you can only make one or two of these green changes. The goal here is to limit carbon dioxide and other greenhouse gases, which are closely connected to the big problem of global-warming (全球变暖).

    WAY 1: Bring your own cup to Starbucks. You'll get a 10-cent discount, and it's one less paper cup to end up in a dustbin. The store won't create more waste when they throw away a cup.

    WAY 2: Turn off your computer. When in standby mode, your PC is still using energy. Turning off a monitor (显示器) for 40 hours a week may only save $ 5 a month, but it reduces CO₂ by 750 pounds.

    WAY 3: Reuse plastic bags. Instead of throwing away 100 billion plastic bags a year, try and get a second, third, or tenth use out of them. Better yet, next time you shop, try a reusable bag. The amount of oil it would take to make just 14 plastic bags would run your car for one mile.

    WAY 4: Use recycled paper in the bathroom. Most of the toilet paper we use is made from trees found in forests. If every family replaced(替换)one roll of toilet paper with a recycled one, 424,000 trees would still be standing.

    WAY 5: Plant a tree. Adding green to your garden is beautiful and earth-pleasing. Just one tree will help make cleaner air and save the environment from 5, 000 pounds of hot carbon dioxide each year.

C

    Rivers are one of our most important natural resources(资源). Many of the world's great cities are located on rivers, and almost every country has at least one river through it that plays an important part in the lives of its people.

    Since the beginning of history, people have used rivers for transportation. The longest one in the United States is the Mississippi. The lifeline of Egypt is the Nile. To the people of India, the Ganges is great, but it is also important for transportation. Ships can travel along it for a thousand miles. Other great rivers are the Congo in Africa and the Mekong in southeastern Asia. The greatest of all for navigation(航海), however, is the Amazon in Brazil. It is so wide and so deep that large ships can go about two thousand miles up it.

    Besides transportation, rivers give food, water to drink, water for crops, and chances for fun and recreation for the people who live along their banks. In order to increase the supply of water for crops, engineers sometimes build a dam(坝) across a river and let a lake form behind the dam. Then people can use the water not only to irrigate(灌溉) their fields but also to make electricity for their homes and industries.

    However, large cities and industries that are located on rivers often cause problems. As the cities grow in size and industries increase, the water in the rivers becomes polluted with chemicals and other materials. People are learning the importance, however, of doing more to keep their rivers clean if they want to enjoy the benefits of them.

    China Science and Technology Museum was opened to the public in September 1988. But the second project was completed in May, 2000. Its main task is to spread knowledge of science and technology among the public.

    The activities of China Science and Technology Museum include popular science exhibitions, Astro­vision film shows, training education programmes and experiment exhibition programmes. The museum has an area of 40，000 square metres, of which 16, 000 square metres is for exhibition halls.

    The Astro­vision Theatre is one of the museum's major attractions and also one of the largest Astro­vision theatres in the world. It makes visitors feel they are in actual events rather than see a film. Many great science activities are often held at the museum, and the museum wants to be an important window to the world.

    What might the future be like? Here are some predictions(预测): things to come, things to go.

    The Spring Festival has caused headaches for millions of Chinese. More than 2 billion people travel at the same time and the journey is difficult. But in 28 years, Spring Festival travel may not be a problem at all. China plans to build more than 120,000 kilometers of railway and a fast transportation network that will serve 90% of the population by 2020. And because most of China will be cities, people will not have to go to other places to find a job, so it will no longer be a problem.

    Newspaper will come to an end in 2043. In the future, digital(数字的) newspapers will be sent to personal web tools through Internet. Readers can discuss topics with journalists and editors. Information will move faster.

    Oil is running out faster than expected. But scientists have found something else for oil as fuel(燃料). Coal, natural gas, nuclear power(核能) and even water can take the place of oil as sources of energy(能源).

    Schools will go electronic(电子化). Computers will be important and popular among the students. Everything will be in the computer and students will not need to bring books to school. They will find information on the Internet. A computer will be the students' library, schoolbag and connection to the outside world. There will be robot teachers, they will check homework on computers and communicate with the students' parents through e-mail. And school buses will be comfortable and safe.