Weather has a strong effect(影响) on people. It influences health, intelligence (智力) and feelings. In August, it is very hot and wet in the southern part of the United States. People there easily have heart trouble and other kinds of health problems during this month. In the Northeast and the Middle West, it is hot at some times and very cold at other times. People in those states will have heart trouble after the weather changes in February or March.
      The weather can also influence intelligence. For example, in a 1983 study by scientists, the IQ scores of some college students were very high during storm, but after the storm, their scores were low. Storms can increase intelligence. Very hot weather, on the other hand, can decrease(减少) it. Students in many schools of the United States often do badly in exams in the hot months of the year(July and August).
      Weather also has a strong effect on people's feeling. Winter may be a bad time for thin people. They usually feel cold during these months. They might feel depressed during cold weather. In hot summer weather, on the other hand, fat people may feel unhappy. At about 65F, people become stronger.
      Low air pressure(气压) makes people feel free, but it also increases forgetful- ness. People leave more bags and umbrellas on buses and in stores on low pressure days. There is a“perfect weather”for work and health. People feel best at a tempera- ture of about 64F with 65 percent humidity(湿度).
      Are you feeling sick, sad, tired, forgetful, or very intelligent today? The weather may be the reason.

    We have known for a long time that flowers of different plants open and close at different time of day. Yet no one really understands why flowers open and close like this at special times. It is not as simple as we might think, as new experiments(实验) have shown. In one experiment, flowers were kept in darkness. We might expect that the flowers, without any information about the time of the day, did not open as they usually do. In fact, they continued to open at their usual time. This shows that they have some mysterious (神秘的) way of knowing the time.

    Their sense of time does not depend on information from the outside world; it is, so to speak, inside them, a kind of “inner clock”. This discovery may not seem to be very important. However, it was later found that not just plants but also animals including man have this “inner clock”which controls(控制) working of their bodies and their activities.

    Human beings, then, are also controlled by this mysterious power. Whether we wish it or not, it affects such things in our life as our need for sleep, our need for food. And our ability to concentrate(集中).

Dear Edward,

    How are you doing? I just visited Machu Picchu in Peru today. I've never seen such a great place before. This place is so amazing that I want to share my feelings with you.

    When I first got to Machu Picchu, I felt like I was walking in the sky. Even the clouds were just under my feet. Do you know how high Machu Picchu is? I was surprised that it was at about 2,500m. How could people build a city on such a high mountain? It must have been very difficult to move stones there.

    Before the Europeans arrived, the Incas (印加人) were the last and the most modern society in the Andes (安第斯山). The Incas were afraid that the Spanish would find them, so they built Machu Picchu on an Andes plain (平地) as a secret city in the 14th or 15th century. As a result, the Spanish never found Machu Picchu.

    An American explorer discovered Machu Picchu in 1911. For a long time before that, nobody even knew Machu Picchu was there. After Machu Picchu was found, it was called “The Lost City of the Incas”. It is still a mystery why and how Machu Picchu was left and forgotten by everyone.

    I just had a wonderful day. Especially, I will never forget the “goodbye boy” who was a local boy dressed in traditional Inca clothes. When we went down the mountain by bus, the boy waved goodbye to us until we were out of sight (视线). He shouted some words at us too, and I guess, it meant, “Goodbye, come back again soon!” Why don't you visit Machu Picchu someday? I am sure you will love this place as much as I do.

Yours truly,

Lynn

    On April 2, we said goodbye to Tiangong I, China's first space lab. According to the China Manned Space Agency (中国载人航天), Tiangong I re-entered the Earth's atmosphere (大气层) and some of its debris (碎片) fell into the South Pacific Ocean.

    There are many spacecraft (宇宙飞船) that are still in orbit(轨道) above the Earth. After finishing their trips, they will all re-enter the Earth's atmosphere like Tiangong I.

    There are two types of re-entries: controlled re-entry and uncontrolled re-entry.

    Some satellites and manned spacecraft come back to the Earth in a controlled re-entry. Experts calculate (计算) the path of the falling spacecraft and its speed. Thy can guide the spacecraft to fall in a chosen area.

    Some spacecraft may have problems while in space after a certain amount of time. These spacecraft come back in an uncontrolled re-entry. It is hard to tell when and where these spacecraft will fall until the last few hours. The US space station Skylab came back partially uncontrolled in 1979. Parts of the station fell in western Australia, but no one was hurt.

    During re-entry, most of the spacecraft will burn up while passing through the Earth's atmosphere. Only a small amount of the debris will reach the ground. The debris typically ends up falling into the ocean, China Daily reported.

    How do you deal with plastic bags from the supermarket? Throw them away or recycle them? How about eating them?

    The bags are not harmful to the environment, Humans and animals can safely eat them. Indian company EnviGreen has made a bag with natural materials. It looks and feels just like plastic, but can break down(分解) easily.

    Ashwath Hedge who set up the EnviGreen Company spent four years doing experiments(实验) with 12 natural materials. They include potato, corn, vegetable oil and banana. He made the materials into liquid(液体) and used the liquid to make the bag.

    Although the EnviGreen bag is more expensive than a common plastic bag, it has many advantages. According to the Wall Street Journal, it takes 1,000 years for common plastic bags to break down. But an EnviGreen bag can naturally break down in less than 180 days. It also breaks down in less than a day in water, and in less than a minute in boiling water. Hedge was happy to show it in his interview, he put an EnviGreen bag in water and ate it with a smile.

    There are more than 15,000 tons of plastic waste in India every day. But only 9, 000 tons are processed. In China, 3 billion plastic bags are used every day. Maybe the EnviGreen bag could be a solution(解决方法) to the world problem of plastic pollution.

    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.