Today there are many fires than in the past. Over 100,000 wildfires burn each year in America. Russia has 20,000 to 35,000 wildfires every year. Australia has on average 60,000 each year. These fires destroy（损害）huge areas of forests and burn hundreds of homes.

Many experts believe there are several reasons for this sudden increase in fires. The first reason is climate（气候）change. Recent weather has been warmer and drier. This leads to dangerous fire conditions. When lightening strikes（发生雷电），dry grass easily catches fire. Hot winds add to the problem. The wind spreads a fire quickly. In 2010, Russia had the hottest and driest summer in a century. In just one month, 500 fires destroyed over 2,000 homes. Some people lost their lives.

Traditional fire-fighting practices are another reason for the increase in fires. In America, firefighters used to quickly put out every fire. They didn't allow the grass and trees to burn. As a result, today many forests have thicker vegetation（植被）.Thicker vegetation means more fuel（燃料）for fires. Also, without fires from time to time, forests become overcrowded and unhealthy. Some trees are dead. The dead wood then easily catches fire. So surprisingly, America has many more fires today partly because of its past fire-fighting practices.

Scientists now understand that a fire can be a natural part of a healthy forest. As a result, countries like Australia allow more fires to burn naturally. Sometimes, fire fighters even start fires to get rid of（去除）dead wood. Of course, they carefully control the fires. The fire thins out old trees. This allows sunlight to reach the ground. As a result, fires help new trees to grow. Therefore, if a fire is not a serious threat（威胁）to people, firefighters may let it burn naturally.

What is your favorite color? Ask famous persons like Cate Blanchett, Scarlett Johnson, and Bono (singer for the band U2), and maybe they will say “green.” That's not because these artists like the color green best. Instead, they are interested in green fashion.

       Green fashion is about making (and wearing) clothes that are good for humans, animals, and the Earth. In the past, green fashion made people think of ugly clothes. But today, green fashion is different. It is about looking good and caring about the Earth and other people. You can have interesting clothes and be green.

Around the world, green fashion is becoming popular. For example, the U.K. company People Tree sells men's and women's clothing and accessories(配搭物). They are made from natural fabrics(织物) like cotton and wool. Workers who make the clothes are from countries like Kenya(肯尼亚), and Bangladesh(孟加拉国). People Tree pays the men and women good money for the clothes they make.

Singer Bono and his wife also started a clothing company called EDUN. When the clothes are sold, EDUN uses most of the money to help people around the world.

    Nearly all our food comes from the soil. Some of us eat meat, of course, but animals live on plants. If there were no plants, we would have no animals and no meat. So the soil is very necessary for life. The top of the ground is usually covered with grass or other plants. There may be dead leaves and dead plants on the grass. The waste matter(粪) from animals also falls on it.

    All soil needs food. If we do not give it any, the plants will be weak. Farmers found that animals' waste is the best food for the soil, but chemical fertilizers(化肥) are also very useful. The same crop（庄稼）should not be grown in the same place every year; it 's better to have a different crop. A change of crop and the use of a good fertilizer will keep the land good.

    How much sleep do we need? We are all different. Some people need only three hours of sleep a night. Others need ten hours of sleep a night. Most Americans sleep an average(平均) of seven to eight hours a night. After the age of fifty, the average sleeping time goes down to 6.5 hours a night.

    Most people have a bad night when they cannot fall asleep(睡着). The name of this problem is called insomnia.

    This isn't a new problem .Many famous people in history had insomnia .Some of these people had special ideas to make them sleep .Benjamin Franklin, the famous inventor had four beds. He moved from one to another to fall asleep .King Louis XIV(国王路易十四)of France had four hundred and thirteen beds and hoped to fall asleep in one of them .Mark Twain, the famous American writer, had a different way. He lay on his side across the end of his bed.

    Albert Einstein is right once again! He thought of the idea about gravitational waves years ago with his Theory of Relativity, but scientists are finally discovering that it really exists now. But what are gravitational waves, and why are they important?

    Well, gravitational waves are made by black holes and can change time in space. Black holes aren't holes but are lots of matter put together into a very small area. They are created when a star, much like our sun, explodes and leaves behind this dense* material. It doesn't shine like a star any more, and it becomes black.

    The black holes that made these waves are special. About 1.3 billion years ago, there were two black holes that kept moving closer and closer together. Finally, they hit each other and formed one big black hole. The energy is given off and created the ripples* in space. These ripples are gravitational waves. For example, imagine you throw a stone into a pool. It creates ripples that change the shape of the water. Well, that's kind of what the influence of one black hole hitting the other has in space.

    Gravitational waves are hard to explore. But thanks to the efforts of scientists, the ripples were discovered on Feb. 11th, which is the first time in human history. Einstein was excellent to know this 100 years ago before we have the technology. It can give us a new view of the universe we live in. The discovery of gravitational waves, unlike stars, galaxies and other bright objects, black holes don't produce light, so we can't see them by tools. Gravitational waves allow scientists to look at the universe not only with light, but also with gravity. "Everything else in astronomy like the eye," A scientist told The New York Times. "Finally, astronomy grew ears. We had never ears before."

    Now, we will be able to find black holes and things that are much further away from Earth, which means much more space exploration in the future. And who knows, this discovery could even lead to time travel!