Do you know the whales in the sea? There are many relatives(亲属) in the whale family and they always live together with whales.

    Few people know dolphins(海豚) are part of the whale family. Dolphins are not fish. They are mammals(哺乳动物). They breathe air, and they have babies and feed them with milk. Dolphins are famous for their wonderful shows. They can jump high out of the water and show turns in the air. These jumps give the dolphins time to breathe.

    Porpoises(鼠海豚) are also in the whale family and are quite like dolphins. But they are different in the size and shape of the mouth. The dolphin's mouth is long and thin, but the porpoise's is short and thick. Dolphins are also more talkative than porpoises. Dolphins make sounds to talk with each other under water. But porpoises do not do this. Both of them are smart and friendly to humans.

    Not all the members of the whale family are friendly. Big whales are much easier to be angry than smaller dolphins or porpoises. An angry whale can be dangerous. Perhaps this helped to create the story of Moby Dick that sank (使下沉) a ship and made all the people on it die in the sea.

    Researchers have developed paper that can be printed with UV light (紫外线), free from the need for ink (油墨). People can clear the information away on the light-printable paper by heating it to 120℃and it can be reused more than 80 times.

    The research was carried out in order to reduce the effects of paper production on deforestation (滥砍滥伐). The researchers, from Shandong University in China and the University of California, Riverside, said that the secret behind the technology is a color-changing chemical. A thin coating of the chemical can be used on usual paper and turn it into a reusable, light-printable one. Heating the paper for 10 minutes can help clear the information away more quickly.

    Professor Yadong Yin, a chemistry professor at the University of California and a co-author of the study, said, "The greatest importance of our work is the development of a new technology to produce an ink-free rewritable paper that has the same feel and appearance as usual paper. Our work is believed to have great economic and environmental influences on the modem society." Paper production has a bad influence on the environment. It's the main cause of industrial pollution and paper thrown away by people makes up about 40% of landfills where waste is buried under the ground.

    It is predicted that light-printable paper will be inexpensive in the future. The printing process is also more cost-effective than the usual one as no ink is needed. Most importantly, it can be reused many times, which greatly reduces the cost.

The Giraffe

    The giraffe is the tallest modern land animal. It can be over 5. 5 meters tall. Its neck bone may be 1. 9 meters long. Yet the giraffe has only seven bones in its neck, the same number as in the human. Even a small bird has many more bones in its neck than in a tall giraffe. Each bone in a giraffe's neck is very long, while the bones in a human's neck are small. That makes the difference. A female giraffe gives birth to one baby at a time. The baby, called a calf, is about 1. 9 meters tall at birth. By the age of eight it is full-grown. The giraffe can live for 30 years; the giraffe is good at running; it can run 30 kilometers per hour. The giraffe likes to live together, usually 7~10 a group. The giraffe eats mostly leaves. Because it has a long neck, it can reach the leaves high up on the trees.

    Imagine one day, the water taps (水龙头) in your house stop running. You have to buy water from shops. And still there isn't enough for everyone. Your mother has to save the family's shower water to do other things. Would you be able to stand that kind of life?

    Probably not. But that's what kids in Yemen are experiencing. Experts said Yemen is going to be the first country in the world to run out of water. According to a report, the capital, Sana, will run out of drinking water as early as 2025.

    Because of the shortage, the government often cuts the water supply(供应). Hannan, an 18-year-old from Lahej, told Times, "In a good week we'll have a water supply all week. But then the following week there will be water only for a day or two."

    Hannan said only rich people have enough water to use. They can buy water from the shops or from the water trucks. Private companies own the trucks. They travel around the city every day to sell water—at very high prices. "A lot of people can't afford it," she said.

    The average(平均) person in Yemen uses 100 to 200 cubic(立方) meters of water per year. That is far below the international water poverty(贫困) line of 1,000 cubic meters.

    The government is thinking of making use of seawater. But it will cost a lot and it may not happen soon enough to help the people of Yemen.

The Vine That Ate the South

    Kudzu is a fast-growing vine(蔓生植物) that covers a large area in the southern United States. It is so common that one might think it is a native plant, but it is not. Kudzu was brought to the United States from Japan in 1876. Many Americans thought it was beautiful, and they began to plant it. They didn't know it could grow up to a foot a day during the summer months. Nor did they know it would grow up and over anything in its path.

    In Japan, kudzu experienced cold winters and a short growing season. But in the United States, it has a very long growing season with warm and wet southern weather. It is fine weather for the vine to grow fast.

    In the 1920s, people used the vine to feed farm animals. Ten years later, the government supported to plant kudzu because it kept soil from washing away. However, by the 1950s, the government no longer wanted people to plant the vine. Twenty years after that, the government said it was a harmful plant.

    The vine grows up trees and buildings, making some beautiful shapes. However, trees die after kudzu covers them because they cannot get enough light. Scientists are looking for ways to kill the vine. They used poisons(毒药) to kill the vine. However, some of the poisons made it grow even better. Scientists also find it difficult to dig up Kudzu. The plant is really tough.

    Because kudzu is so hard to kill, some people are making the best of it. So they try to find different uses for the vine. They find the vine can be used to make paper and baskets, it can be used to feed the goats, and it can even be eaten by people. Scientists are studying it in the hope that the vine can be used as a medicine. At the very least, kudzu serves as an example of the unexpected results that can come from non-native plants.