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    Have you ever wondered why the roots of the plants always know which way to grow—into the soil but not above it? Some British scientists have recently solved this mystery.    

      It turns out that roots have special hairs that tie them into the soil and help them grow their way past obstacles, a team at the John Inners Center in Norwich reports in the February 29 issue of Journal Science.

    "The key is in the fuzzy(有绒毛的) coat of hairs on the roots of plants," says professor Liam Dolan. "We have found a growth control system that enables these hairs to find their way and to become longer when their path is clear."

    Root hairs explore the soil in much the same way a person would feel their way in the dark. If they come across an obstacle, they make their way around until they can continue growing in an opening. I the meantime, the plant is held in place as the hairs grip the soil.

    The hairs are guided by a clever chemical trick. A protein(蛋白质) at the tip of the root hairs called RHD2 helps them to take calcium(钙) from the soil. Calcium makes the hairs grow, and produce more RHD2, and take more calcium.

    But when an obstacle blocks the hair's path, or the hair reaches the surface of the soil, the cycle is broken and growth starts in another direction.

    This system gives plants the flexibility to explore a complex environment and to live in even the most unpromising soils, says Dolan.

    In poor soils such as in parts of Australia and Africa, native plants have adapted by producing enormous numbers of root hairs. A better understanding of this adaptation will allow scientists to develop hairy rooted crops that can grow in unfriendly environments.

    According to Dolan, "Research in the John Inners Center is taking a breeding approach(育种方法) to increase hair length in wheat but it will be some time before new cultivars(栽培变种) are developed."

    The Leaning Tower of Pisa was straight like a pole when the construction began in 1173. It started to shift direction soon after construction because of poor foundation in addition to the loose layer of subsoil(底土). At the beginning, it leaned to the southeast before the shaky foundation started to shift leaning towards the southwest. After the period of structural strengthening at the beginning of the 21^st century, now the Leaning Tower of Pisa leans at an angle of 3.97 degrees.

    In 1178, the shift in direction was observed for the first time when the construction had progressed further to the third floor. The tower was heavy for the three-meter foundation that was built on a weak area of land.

    For compensating(补偿) the leaning position, the builders started to construct the upper floors with one side higher than the other one. This caused the tower to lean in the other direction. This unusual structure led to the tower being actually curved. In spite of these efforts, the tower kept on leaning.

    The government of Italy started to plan prevention of the complete collapse of the tower in 1964. However, a request was put forward by the authorities to keep the leaning position because of the tourism industry of the region.

    After nearly two decades of careful planning by engineers, historians and mathematicians, the stabilization efforts for the Leaning Tower of Pisa started in 1990. The tower was closed for the general public and the people living nearby moved away. For reducing the total weight of the tower, its seven bells which represented the seven musical notes were removed. The tower was reopened for the general public on December 15, 2001.

    In May 2008, after removing another 70 metric tons of earth, the engineers announced that the tower had been finally stabilized and it would remain stable for at least 200 years.

    Contrary to popular belief, people who sleep six to seven hours a night live longer, and those who sleep eight hours or more die younger, according to the latest study ever conducted on the subject. The study, which has tracked the sleeping habits of 1.1 million Americans for six years, weakens the advice of many sleep doctors who have long recommended that people get eight or nine hours of sleep every night.

    “There's an old idea that people should sleep eight hours a night, which has no more scientific basis than the gold at the end of the rainbow,” said Daniel Kripke, professor of psychiatry（精神病学）at the University of California at San Diego who led the study published in a recent copy of JAMA Psychiatry.

    The study was not designed to answer why sleeping longer may be harmful or whether people could extend their lifespan by sleeping less.

    But Kripke said it was possible that people who slept longer tended to suffer from short-term absence of sleeping, a condition where weak breathing puts stress on the heart and brain. He also stressed that the need for sleep was similar to that for food, where getting less than people want may be better for them.

    The study quickly caused warnings and criticism（批评）, with some sleep experts saying that the main problem of America's sleep habits was deprivation（剥夺）, not sleeping too much.

    “None of this says sleep kills people,” said Daniel Buysse, a psychiatrist at the university of Pittsburgh Medical Center.

    “You should sleep as much as you need to feel awake, alert and attentive the next day,” Buysse added. “I'm much more concerned about people short-changing themselves on sleep than people sleeping too long.”

    “Sleeplessness produces a variety of health consequences that were not measured in the study,” critics said.

    Suppose you are a visitor in the land of Mongolia, some friends ask you to eat with them. What kind of manners do they want you to have? They want you to give a loud burp after you finish eating. Burping would show that you like your food. In some countries, if you give a big burp, you are told to say “Excuse me, please”.

    In many places people like to eat together. But in some parts of Polynesia it is bad manners to be seen eating at all. People show their good manners by turning their backs on others while they eat.

    What are manners like in an East African town? The people try not to see you. They are being polite. You may see a friend. He may not see you at all. If you are polite, you will sit down beside him. You will wait until he finishes what he is doing. Then he will talk to you. Manners are different all over the world. But it is good to know that all manners begin in the same way. People need ways to show that they want to be friends.

    As computers become all the more popular in China, Chinese people are increasingly relying on computer keyboards to input Chinese characters. But if they use the computer too much, they may end up forgetting the exact strokes （笔画）of each Chinese character when writing on paper. Experts suggest people, especially students, write by hand more.

    Do you write by hand more or type more? In Beijing, students start using a computer as early as primary school. And computer dependence is more wide-spread among university students. Almost all their writings are typed on a computer.

    All the students interviewed say they usually use a computer.

    It's faster and easier to correct if using a computer. And that's why computers are being used more and more often to modern education. But when people are taking stock in computers increasingly, problems appear. "When I'm writing with a pen, I find I often can't remember how to write a character, though I feel I'm familiar with it."

    "I'm not in the mood to write when faced with a pen and paper."

    Many students don't feel this is something to worry about. Now that it's more convenient and efficient to write on a computer, why bother to handwrite?

    Many educators think differently. Shi Liwei, the headmaster of a famous primary school in the capital said "Chinese characters enjoy both practical and aesthetic(审美的) value. But those characters typed with computer keyboards only maintain their practical value. All the artistic beauty of the characters is lost. And handwriting contains the writer's emotion. Through one's handwriting, people can get to know one's thinking and personality.

    Beautiful writing will give people a better first impression of them."

    To encourage students to handwrite more, many primary schools in Beijing have made writing classes compulsory(必修的)and in universities, some professors are asking students to turn in their homework and essays written by hand.

Quantum mechanics (量子力学) is a branch of science that studies the smallest particles (粒子) in the universe, like atoms (原子) and even smaller things. It might sound super complex, but let's break it down in simple language.

Imagine you have a small particle, like an atom. In the world of quantum mechanics, these particles don't behave like the things we see in our everyday lives, like balls or cars. Instead, they act kind of like waves and particles at the same time, which is really strange!

One of the most famous ideas in quantum mechanics is the "Uncertainty Principle", raised by physicist Wemer Heisenberg. This principle says that we can't precisely know both the position and the speed of particle at the same time. It's not because our measuring tools are bad; it's because the particles themselves are naturally uncertain.

Another weird thing about quantum mechanics is something called "Entanglement". Imagine you have two particles that are connected in a special way. If you change one of them, the other instantly changes, no matter how far apart they are. It's like they're talking to each other faster than the speed of light, which goes against what we know from everyday experiences.

Quantum mechanics also deals with probabilities. Instead of saying, "This particle will be here at this exact time," scientists say, "There's a certain chance it'll be here, and a certain chance it won't." It's like predicting the weather, but on a super small scale.

In a nutshell, quantum mechanics is a strange and fascinating world where particles act both like waves and particles, where you can't know everything about a particle at once, and where particles can be mysteriously connected no matter how far apart they are. It's a mind-boggling field that challenges our understanding of how the universe works, and even though it's tough to grasp, it's an essential part of modern physics.