If you see a group of people dancing and singing on the street or in the railway station,  you don't need to feel surprised．They are a flash mob （快闪族）, which is a group of people who come together suddenly in a public place, do something unusual for a brief period of time,  and then quickly break up．They are usually organized with the help of the Internet or other digital communication network．At a predetermined time, they gather and perform some  distractions（消遣） such as waving their hands and exchanging books, Then, they quickly break up before the police can arrive．Using mobile phones, the flash mob can change its location if the first one has been replaced for any reason．

    Bill Lasik, senior editor of Harper's Magazine, organized the first flash mob in Manhattan in May 2003 and the first successful flash mob came together on June 3, 2003 - after the first try was foiled at Macy's department store．Lasik claimed that the activity was designed to make fun of hipsters （起时髦的人）, and call attention to the cultural atmosphere．

    Flash mob gatherings can sometimes shock people．Such an activity might seem amusing and untrue, but it also might frighten people who are not aware of what is taking place．Undoubtedly, flash mobs can serve as good political tools in any direction．They also have great economic potential, such as using flash mobs to advertise a product．

    The flash mob is now becoming more and more popular．People use it to do many things．For example, in 2009, Michael Jackson's fans took part in a flash mob to remember him．Hundreds of his fans gathered singing and dancing Michael's famous song "Beat It" together．Flash mobs give people from all walks of life an opportunity to come together to create a memory．

    "How are you?" is a nice question. It's a friendly way that people in the United States greet each other. But "How are you?" is also a very unusual question. It's a question that often doesn't need an answer. The person who asks "How are you?" hopes to hear the answer "Fine", even if the person's friend isn't fine. The reason is that "How are you?" isn't really a question and "Fine" isn't really an answer. They are simply other ways of saying "Hello" or "Hi".

    Sometimes, people also don't say exactly what they mean. For example, when someone asks "Do you agree?" the other person might think, "No, I disagree. I think you're wrong…" But it isn't very polite to disagree so strongly, so the other person might say "I'm not sure." It's a nicer way to say that you don't agree with someone.

    People also don't say exactly what they are thinking when they finish talking with other people. For example, many talks over the phone finish when one person says "I have to go now." Often, the person who wants to hang up gives an excuse: "Someone's at the door." "Something is burning on the stove." The excuses might be real, or not. Perhaps the person who wants to hang up simply doesn't want to talk any more, but it isn't polite to say that. The excuse is more polite, and it doesn't hurt the other person.

    Whether they are greeting each other, talking about an idea, or finishing a talk, people don't say exactly what they are thinking. It's an important way that people try to be nice to each other, and it's part of the game of language.

    It is said that if you want to stay young, sit down and have a good think. This is the research finding of a team of Japanese doctors, who say that most of our brains are not getting enough exercise — and as a result, we are growing old unnecessarily soon.

    Professor Taiju Matsuzawa wanted to find out why otherwise healthy farmers in northern Japan appeared to be losing their ability to think and reason at a relatively early age, and how the process of aging could be slowed down. With a team of colleagues at Tokyo National University, he set about measuring brain volumes of a thousand people of different ages and varying occupations. Computer technology enabled the researchers to obtain precise measurements of the volume of the front and side parts of the brain, which controls functions like eating and breathing, does not contract with age, and one can continue living without intellectual on economical faculties. Contraction of front and side parts — as cells die off — was observed in some subjects in their thirties, but it was still not evident in some sixty-and seventy-year-olds. Matsuzawa concluded from his tests that there is a simple way to the contraction normally connected with age — using the head.

    The findings show in general terms that contraction of the brain begins sooner in people in the country than in the town. Those least at risk, says Matsuzawa, are lawyers, followed by university professors and doctors. White collar workers doing routine work in government offices are, however, as likely to have shrinking (萎缩) brains as the farm worker, bus driver and shop assistant.

    Matsuzawa's findings show that thinking can prevent the brain from shrinking. Blood must circulate properly in the head to supply the fresh oxygen the brain cells need. “The best way to maintain, good blood circulation is through using the brain.” he says. “Think hard and engage in conversation. Don't rely on pocket calculators.”

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    Two things changed my life: my mother and a white, plastic, daisy bike basket. I would be a different person if my mom hadn't turned a silly bicycle accessory(配件) into a life lesson I carry with me today.

    It was summer and, one day, my mother drove me to the bike shop to get a tire fixed — and there it was in the window. White, shiny, plastic and decorated with daisies, the basket seemed so appealing and I knew I had to have it.

    "Mom, please can I get it? I'll do extra chores for as long as you say. I'll do anything, but I need that basket. I love that basket. Please, Mom. Please?"

    "You know," she said, gently rubbing my back while we both stared at what I believed was the coolest thing ever, "If you save up, you could buy this yourself."

    "By the time I make enough it'll be gone!"

    "Maybe Roger here could hold it for you," she smiled at Roger, the bike guy.

    "For that long? He can't hold it for that long, Mom. Someone else will buy it. Please, Mom, please?"

    "There might be another choice," she said. My mother bought the beautiful basket and put it safely out of reach in some hiding place I couldn't find. Each week I eagerly counted my growing nest egg earned by extra work here and there (washing the car, helping my mother make dinner, delivering milk around the neighborhood). And then, weeks later maybe, I counted, re-counted and jumped for joy. Oh, I made it! I finally had the exact amount we'd agreed upon.

    Days later, the unthinkable happened. A neighborhood girl I'd played with appeared with the exact same basket fixed to her shiny, new bike. I rode my bike fast home to tell my mother about this disaster, this horrible turn of events.

    And then came the lesson I've taken with me through my life: "Honey, your basket is extra-special," Mom said, gently wiping away my hot tears. "Your basket is special because you paid for it yourself."

    Dr. John Wilkins was a natural philosopher who lived from 1614 until 1672. He was crazy about getting to the moon and meeting the people who surely lived there. Wilkins believed that anything as Earth-like as the moon must have been created by God for living beings, and he was determined to meet them — despite the fact that he was three centuries ahead of his time.

    In the 1600s, the scientific understanding of gravity and outer space was limited. Wilkins believed, like many 17th-century scientists, that there was no difference between the atmosphere of Earth and the conditions in space, and that Earth's pull was due to magnetism (磁力). It was only reasonable, then, that Wilkins believed a two-wheeled horse-drawn battle car with wings with enough speed could lift high enough off the ground to break free of Earth's magnetic pull and reach the moon.

    Then Wilkins moved on to more pressing issues with his remarkable ability to think of new ideas: How would travelers feed themselves during the journey? He theorized that the main cause of hunger was simply the act of working against gravity, so getting to the moon without being burdened by it would be able to be realized. There was some knowledge at that time about the fact that air gets thinner and colder the higher up you go, but he had a fix for that too, "moistened sponges (湿润的海绵) might help us against its thinness".

    By studying the way in which birds fly, which also happened to be part of the studies that led to planes and rockets centuries later, Wilkins put his theory to the test with the help of a colleague, Robert Hooke. Neither of the two ever recorded their attempts, but it's somewhat safe to say that it didn't work out. Hooke himself may have been the reason he gave up hope, in fact, since he was part of the team that discovered space was a place without oxygen.

What makes preschoolers eat their vegetables? Raise their hand? Wait their turn? "Because I say so" is a comment that parents often repeat. But when it comes to getting kids to behave, a recent study by Duke University researchers suggests that the voice of adult authority isn't the only thing that matters. Around age three, fitting in with the group starts to count big too.

To understand what cause preschoolers to fall    in    line, the researchers conducted a test in a lab, where they invited 3.5-year-olds to help set up for a pretend tea party. Each of the 104 children was given a blue sticker (贴纸) to wear at the start of the study, and told that the people with that color sticker were part of the same team. Next the researchers watched as the children decided among different kinds of teas, snacks, cups and plates for the tea party, first on their own and then after listening to the choices of other team members.

Sometimes the other team members considered their choice as a matter of personal preference ("For my tea party today, I feel like using this snack.") Other times they presented it as a need shared by the whole group. ("For our tea parties today, we always use this kind of snack.")

After listening to the choices of others, most of the time the children stuck with their first choice. In other words, children who had said they felt like using, say, the cookie finally picked the cookie no matter what the other person said they were using. But 23% of the time the children changed their choice to accept someone else's. And when they did, they were more likely to go along with the other person when a choice was presented as a group need rather than just a personal preference. The finding held up even when the other person was another child, not an adult.