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.

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    For many years, scientists have said that the earth is getting warmer. Now they have found something new—hot cities! In the southern US, they have found that cities become very hot in summer. For example, the city of Atlanta in Georgia has roof(屋顶) temperature of up to 50^oC while it is 27℃ in the streets! At night, the outside of buildings stays so hot that the heat of the city causes storms over the city!

    China also has the same kind of problems. Every year more farmland is used for factories or offices. More housing is needed, too. As people become richer, they buy more cars. New roads are needed and new car parks are built in the city centers. This all makes cities hotter.

    It isn't easy to change the situation. City planners say that we should plant more trees in the middle of cities. Every new street should have trees on both sides, they say. Trees make the temperature lower, so we should have more trees in our parks and squares. We should also paint our roofs white. If we do this, they do not become so hot. Every roof in a hot and sunny country should have solar(太阳的) roof panels. The electricity from these can be used to run the air conditioners (空调)in the buildings.

    People continue to cut down forests around the cities. This makes the problem worse. Cities are growing faster and faster. By the year 2025, four fifths(五分之四) of the population will be living in cities. If we go on like this, there will not be enough farmland to feed everyone in the world.

    No Car Day first started by 34 cities in France on September 22, 1998. People started it to protect the environment. By now, more than 1,000 cities around the world have a No Car Day.

    The first No Car Day in China was in Chengdu in 2001. Other cities, including Taipei, Shanghai and Wuhan, also support(支持) the day.

    In Beijing, more and more people are joining in the program. It asks drivers to leave their cars at home for one day each month and walk or ride a bike to work. It also calls on Beijingers not to use cars on June 5(World Environment Day). The slogan(口号) for the day is, "If we drive for one less day, we can have one more nice day."

    So far, more than 200,000 drivers Show their support. "We can't decide the weather, but we can choose not to drive," said Wu Zhonghua, a car dub manager. Beijing is trying to have 238 blue sky days this year. In the first quarter of 2017, Beijing only had 52 blue sky days. This was 11 days less than the number for the same period the year before.

    We must do more for No Car Day.

    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.

    China isn't well known for its science fiction films, but recently a new film called The Wandering Earth has become a great success. It has earned over $697 million worldwide. It tells an amazing story of the Earth in danger, along with exciting scenes of spaceships and outer space.

    The Wandering Earth is based on a story by Liu Cixin. In the story, the sun was dying out, people all around the world worked together to move Earth out of the solar system and sail Earth to a new star system. The film began with the early life of a young boy who was born just after the project started. The engineers pushed Earth away and built underground cities that were vast enough for all the other humans to live in. Yet the 2500 years' journey came with all kinds of dangers. In order to save the humans, a group of young people came out and fought hard for the planet.

    China is playing an increasingly important part in the film industry. Its growing middle class has seen the rise of film market across the country, and Chinese viewers have become an important part of film industry. Hollywood Projects like Iron Man 3 specifically filmed more scenes in China for its market. Chinese film industry is keeping growing. Just as Americans want to get into the Chinese market, Chinese filmmakers are looking for the way to the international market.

    According to The Hollywood Reporter, The Wandering Earth is China's "first space" film. Chinese science fiction writer, Anna Wu, says science fiction "is a new challenge for the Chinese film industry." Some Chinese filmmakers have achieved a great success at this kind of film, but most of them still have a long way to go.

    Still, Wu notes that within China, "Not all the science fiction films have had success. It still takes time to accept science fictions, and that with the development of our country, people are getting busier, wealthier and more stressed," which creates a perfect environment for this new kind of film and television. The Wandering Earth, she says, is a good example. "I also care about the money it earns, which will affect the future of Chinese science fiction films."