What is the first thing you want to do when you see someone yawn(打哈欠)? You want to yawn, too! Yawning is contagious.

    Scientists have found that all people yawn. Babies start to yawn even before they are born. The earliest yawn takes place when a baby is still inside its mother. When young children are about one year old, they start to yawn when they see others yawning. That's why scientists seem to think yawning is contagious.

    It's no secret that yawning is contagious, but why do we yawn? Well, scientists are not really sure.

    Some think we yawn because we feel bored. Recently scientists studied two groups of students between the ages of 17 and 19. One group watched music videos, and the other watched a boring color test. Scientists compared the numbers of their yawns and found that the color test group yawned more times than the video group.

    Another reason about yawning has to do with breathing. Some scientists believe that when we are bored or tired, we breathe more slowly. As our breathing slows down, we cannot get rid of(去除) enough carbon dioxide (CO₂) in our bodies. When there is too much carbon dioxide, our bodies will tell the brains (大脑) to breathe deeply. The result is a big yawn.                                                           

    In 2007, scientists suggested a new reason. They said that the reason people yawned was to cool down their brains. These scientists found that people who were warmer than others yawned more often.

    Scientists are still trying to find out why yawning happens and why it is so contagious. But they are only sure that when one person yawns, almost everyone else nearby wants to yawn, too.

    One of the hottest places on the earth is Death Valley. It's a desert valley in North America. The animals in Death Valley don't use technology to keep cool. They have special abilities that help them live there.

    The kangaroo rat is one animal that lives in Death Valley. During the day in Death Valley, it gets hotter than 100°F. The kangaroo rat rests all day in a hole in the ground. It covers the hole with grass to keep out the heat. The kangaroo rat comes out at night when it is cooler. This little rat is also very good at conserving (节约) water. It gets all the water it needs from the food it eats. Some kangaroo rats never take a drink of water in their whole lives!

    The sun makes the desert sand very hot. Animals, like snakes, get too hot if they lie on the hot sand too long. One snake, called the sidewinder, can solve this problem. When it travels, the sidewinder bends (使弯曲) its body into a“W”shape. Then it uses the bottom (底部的) parts of the“W”like legs and walks sideways (向一侧). That way it touches only a little of the sand at a time, so the hot sand doesn't burn the snake. This strange way of moving is how the sidewinder got its name.

    A lot of water in the desert is too salty for most animals to drink. All water has some salt in it. As the desert heat dries up pools of water, the salt is left behind. The remaining water in these pools can be much saltier than the ocean. One kind of fish, the desert pupfish, can live in these salty pools because it can drink the salt water.

It's not WASTE until it is WASTED

    With the World Environment Day coming, our school is now requiring every student to form a habit of sorting the waste.

    Here in our schoolyard we lay four different colors of rubbish bins for different kinds of rubbish. The red is for harmful waste; the blue is for waste that can be recycled(循环再用); the green is for kitchen waste; the yellow is for other waste.

    The following are some instructions for you

    Glass: Empty bottles without caps can be recycled to make new glass bottles.

    Warning: Mirrors and light bulbs(电灯泡) must not be included in the glass waste.

    Paper: Newspapers, magazines, boxes must be clean enough to be recycled.

    Warning: Paper tissues (餐纸) and wall paper are not recyclable as paper and should be kept separately.

    PMD waste: Packaging made of Plastic or Metal and Drink boxes are used to make new packaging.

    Warning: Plastic pots(e. g yoghurt pots ), plastic bags must not be included with the PMD waste.

    Harmful waste: out-of-date drugs, used batteries(电池)， paint and oil…

    Besides, if you don't need your old bikes at all, our school volunteers will collect them. We're going to fix them up and then give them away to kids who don't have enough money for a bike.

    To find out more about recycling, you can visit our school website.

    Some days, don't you think, "Wouldn't it be nice if the laundry would just do itself?” Self-cleaning clothes may sound crazy. But Australian researchers have found a way to make something like this possible!

    A team at RMIT University in Melbourne, Australia, found a way to put special nanostructures (纳米结构) into clothing, which can then clean the clothes. When sunlight hits the nanostructures, they break down the dirt and stains (污渍) that don't belong on your clothes.

    The nanostructures don't break down the actual clothing because cotton and the other clothing materials are too strong to be broken down. According to CNN, the researchers cover the clothing in a solution made of silver and copper (铜) nanostructures. All it takes is 40 minutes of sunlight and your clothes will look as good as new.

    So if you spill on yourself during lunch, you can step outside for a walk, and it will be clean by the time you go inside. It not only makes your life easier, but it can also be good for the environment.

    According to the US Department of Energy, the average load of laundry uses about 25 gallons (about 94 liters) of water. Water is a very important resource, so using less of it to wash clothesis better for the environment. But one of the scientists at RMIT University knows more needs to be done.

    “There's more work to do before we can start throwing out our washing machines,” said Dr Rajesh Ramanathan, “but this is a strong foundation .”

    So what's the next step? Ramanathan wants to either start selling the solution by itself or convincing clothing makers to treat the clothing with the solution while clothes are being made.

    As space science develops, man has learned more and more about space. Space is not only amazing but also dangerous. While working in space, spacemen are facing danger as well as success.

    Scientists have found out that the radiation(辐射) is the greatest danger to spacemen in space. When spacemen are working in space, they are in danger of the radiation from the sun and other stars, which is bad for their health. The harm of the radiation won't be found until their children even grandchildren are born. Some special medicine may work a little, but no really effective medicine has been found so far. Space rubbish is also thought to be a great danger to spacemen. It's reported that there were 9,000 man-made things flying in space. About 30% of these are satellites, 10% are spaceships, and the rest are space rubbish. An explosion(爆炸) in space in 1999 made a cloud of 300,000fragments, each at least 4mm in size. A small piece of these even knocked a spaceship window and caused some damage(损坏).

    Scientists are watching and reporting any possible danger all the time. They are working to deal with space rubbish. Although space is really dangerous, it interests many people on the earth. In the near future, it may become possible for people to spend a few days in a space hotel. People may even choose to leave the earth and live in space in a few years. So scientists are doing everything they can to help improve the space environment.