You are sitting on the desk. A teacher is writing on the blackboard. Kids are yelling in the playground outside. A book falls off the desk next to you. Suddenly, the teacher hands you a pop quiz.

Don't panic! {#blank#}1{#/blank#} You're in a “virtual（虚拟的）classroom”. Everything you see and hear is coming to you through a computer-operated display that you're wearing on your head like a pair of very big glasses. Wearing this kind of virtual-reality equipment, you can find yourself sitting in a classroom, touring a famous museum, wandering across a strange landscape, flying into space, or playing with a cartoon character. {#blank#}2{#/blank#} Virtual-reality equipment that delivers images and sounds directly to your eyes and ears makes these fake worlds seem lifelike.

Unlike the classroom, the technology is real. It's a type of technology that uses computer programs to imitate real world situation.{#blank#}3{#/blank#} Movie directors and video game producers have been using computers for years to create ever more realistic special effects. Some companies are now building three-dimensional（三维）fantasy worlds in which players, linked by computer networks, appear to meet and go on explorations together.

    {#blank#}4{#/blank#} They see virtual reality technology as a useful tool for learning more about why people act as they do. It could help psychologists deter identify and come up with solutions for behaviors problems, for example.

“We've spent the last 100 years looking for certain laws in how people interact with the real world,” says psychologist Albert. “ {#blank#}5{#/blank#} This is psychologist's dream.”

    I have never forgotten the firm belief I had in the arrival through the chimney (烟囱) of the little Santa Claus (圣诞老人), the kind, white-bearded old man who at midnight left in my tiny shoe a present I found the next morning.

    Midnight! It's the perfect hour children don't know. What great efforts I made not to go to sleep before the little old man appeared!

    I had both a great desire and great fear of seeing him, but could never stay awake until then, and the next day my first look was for my shoe. He never failed to carefully wrap (包装) every present for me. I would run barefoot to get my treasure. It never was a very expensive present, for we were not rich. It was a cookie, an orange, or very simply a fine red apple. But it felt so precious that I barely dared to eat it. What a great role imagination plays in a child's life!

    I do not at all agree with the idea that the lies about Santa Claus should be stopped. Doubts and truth come all too soon on their own. I very well remember the first year, when I was five or six, I doubted that it was not Santa Claus who put the cookie in my shoe. Since then, it has never tasted as good as the first few years of my life.

    I noted that my son believed in him longer; boys are more naïve (天真的) than little girls. Like me, he made great efforts to stay awake until midnight. Like me, he loved the cookie baked in Heaven's kitchens. And like me, the first year of his doubts was the last year of the visit of the good old man.

    Plastic waste has polluted the Arctic. Two new studies have spied bags, fishing rope and tinier bits of rubbish in the Barents Sea. This sea sits north of Norway, Sweden, Finland and Russia. It mixes with the Arctic Ocean, which is even farther north.

    Plastic waste in the Arctic could harm wildlife and may hint that large volumes of human rubbish are collecting there, says Melanie Bergmann. She is one of the scientists who spotted the waste. She studies Earth's oceans at the Alfred Wegener Institute in Bremerhaven, Germany. She first started counting bits of plastics in the Barents Sea because she kept spotting signs of the stuff there in images taken with deep-sea cameras.

    Bergmann and her colleagues counted pieces of plastic from an icebreaker, a boat designed to break through large blocks of ice in very cold waters. They also tracked plastic pieces they saw during helicopter rides over Arctic waters. The team found 31 pieces of plastic. “That doesn't seem like much, but it shows us that we've really got a problem, one that extends even to this remote area, far from civilization,” Bergmann says. She and her colleagues described their findings October 21 in Polar Biology.

    Another team has also been counting plastics in the area. Those scientists took water from the Barents Sea and counted the number of smaller bits of plastics, called microplastics.

    Plastic in the ocean is dangerous to animals. Some may get caught in rope or bags. And wildlife may swallow bags and other plastic bits. That makes them feel full. But some may eventually starve because they are not getting the nutrients they need to live. Sometimes plastics also may break down in an animal's body and release poisonous chemicals. If another animal later eats the one that swallowed plastic, it too can end up with poisonous chemicals in its body. This, in turn, can travel up the food web, endangering predators (肉食动物) — even people.

    The number of snow geese arriving in the Arctic each spring to breed has risen over the past few decades. At first, wildlife biologists saw this as an environmental crisis, pointing to marshes（湿地） where plants were eaten by the hungry birds. In response, the federal government loosened restrictions on snow goose hunting.

    But how do the Inuit, in whose backyard this is taking place, view the situation? A recent plan is giving Inuit wildlife experts the opportunity to lend their knowledge to managing the species. The snow goose study, which is supported in part by Polar Knowledge Canada and led by the Kivalliq Wildlife Board (an Inuit organization that manages hunting, trapping and fishing in central Nunavut), asked the experts to share their generations of knowledge about snow geese and their views on what should be done.

    “The community had concerns about controlling the population,” says Ron, a community officer of the Kivalliq Inuit Association, “and Inuit snow goose knowledge had never been recorded. People wanted to pass on what they knew.” Inuit experts disagreed with that, considering it wasteful and unnecessary. They felt hunting more snow geese in an organized way, such as paying local hunters a minimal amount of money and distributing the birds to disadvantaged families or operating a limited commercial hunt by employing local people, would be appropriate.

    Inuit wildlife experts will plan to call on scientists this fall. They say they hope to search for a common way forward and that while there may be too many snow geese in some areas, it's not a crisis. Biologists now generally agree that there seem to be plenty of undamaged marshes available and newer research shows that some damaged areas can recover.

    “Now that we have recorded and documented Inuit knowledge of snow geese,” says Ron, “when facing the crisis other people will be able to use the information to help manage the species, which is fundamental to dealing with it effectively.”

    There are two types of people in the world. Although they have equal degree of health and wealth and other comforts of life, one becomes happy, the other becomes unhappy. This arises from the different ways in which they consider things, persons, events and the resulting effects upon their minds.

    People who are to be happy fix their attention on the convenience of things. The pleasant parts of conversation, the well prepared dishes, the goodness of the wine, the fine weather. They enjoy all the cheerful things. Those who are to be unhappy think and speak only of the opposite things. Therefore, they are continually dissatisfied. By their remarks, they sour the pleasure of society, offend (hurt) many people, and make themselves disagreeable everywhere. If this turn of mind was founded in nature, such unhappy persons would be the more to be pitied. The intention of criticizing and being disliked is perhaps taken up by imitation. It grows into a habit, unknown to its possessors. The habit may be strong, but it may be cured when those who have it realize its bad effects on their interests and tastes. I hope this little warning may be of service to them, and help them change this habit.

    Although in fact it is chiefly an act of the imagination, it has serious results in life since it brings on deep sorrow and bad luck. Those people offend many others; nobody loves them, and no one treats them with more than the most common politeness and respect. This frequently puts them in bad temper and draws them into arguments. If they aim at getting some advantages in social position or fortune, nobody wishes them success. Nor will anyone start a step or speak a word to favor their hopes. If they bring on themselves public objections, no one will defend or excuse them, and many will join to criticize their wrongdoings. They should change this bad habit and be pleased with what is pleasing, without worrying needlessly about themselves and others. If they do not, it will be good for others to avoid any contact with them. Otherwise, it can be disagreeable and sometimes very inconvenient, especially when one becomes mixed up in their quarrels.

    When it comes to medical care, many patients and doctors believe "more is better." But what they do not realize is that overtreatment—too many scans, too many blood tests, too many procedures—may bring harm. Sometimes a test leads you down a path to more and more testing, some of which may be invasive, or to treatment for things that should be left alone.

    Terrence Power, for example, complained that after his wife learned she had Wegener's disease, an uncommon disorder of the immune system, they found it difficult to refuse testing recommended by her doctor. The doctor insisted on office visits every three weeks, even when she was feeling well. He frequently ordered blood tests and X－rays, and repeatedly referred her to specialists for even minor complaints. Even when tests came back negative, more were ordered, and she was hospitalized as prevention when she developed a cold. She had as many as 25 doctor visits during one six－month period. The couple was spending about $30,000 a year for her care.

    After several years of physical suffering and near financial ruin from the medical costs, the couple began questioning the treatment after discussing with other patients in online support groups. "It's a really hard thing to determine when they've crossed the line," Mr. Power said. "You think she's getting the best care in the world, but after a while you start to wonder: What is the purpose?" Mr. Power then spoke with his own primary care doctor, who advised him to find a new specialist to oversee Mrs. Power's care. Under the new doctor's care, the regular testing stopped and Mrs. Power's condition stabilized. Now she sees the doctor only four or five times a year.