In the traffic lights,red means "stop",green means "go",and yellow means "hurry": Why those colors, though? Why not blue,purple,and brown?The following are transponded from others WeChat.

●Red is an inherited symbol from railroads

    Red symbolizes danger in many cultures,which makes sense,considering it has the longest wavelength of any color,meaning you can see it from a greater distance than other colors.Red has meant "stop" since long before cars existed,with railway signals use of red dating bake to the days when mechanical arms lifted and lowered to indicate whether the rail ahead was clear.So that one's simple.

●Green meant "caution" at first

    Green's role in lights has actually changed dramatically over time.Its wavelength is next to (and shorter than) yellow's,meaning it's still easier to see than any color other than red and yellow.Back in the early days of railway lights,green originally meant "caution",while the "all-clear" light was,well,clear or white.Trains,of,course,take an unlimitedly long time to stop,and legend has it that several disastrous collisions happened after an engineer mistook stars in the night horizon for an all-clear.Thus,green became "go",and for a long time,railways used only green and red to signal trains.

●Yellow means "caution" because it's almost as easy to see as red

    From the earliest days of motoring up until the mid-1900s,not all stop signs were red-many were yellow, because at night it was all but impossible to see a red stop sign in a poorly lit area.The yellow stop-sign craze began in Detroit in 1915,a city that five years later installed its first electric traffic signal,which happened to include the very first amber traffic light,at the corner of Michigan and Woodward Aves.

    Last night's meteor(流星) shower left many people in Emerald Valley dissatisfied. They gathered in the suburbs of the city with heavy telescopes，expecting to watch the brightly burning meteors passing through the sky. However, what they found was a sky so brightened by the city's lights that it darkened the light of the meteors passing overhead.

    “My family was so frustrated，” admitted town resident Duane Cosby, “We wanted to make this an unforgettable family outing，but it turned out to be a huge disappointment.”

    Astronomers—scientists who study stars and planets—have been complaining about this problem for many years. They say that light pollution prevents them from seeing objects in the sky that they could see quite easily in the past. They call on people and the government to take measures to fight against it.

    Besides professional and amateur(业余的) star observers, there is yet a population that suffers even more from light pollution. This population consists of birds，bats, frogs, and snakes etc. For example, outdoor lighting severely affects migrating(迁徙的)birds. According to the International Dark­Sky Association, “100 million birds a year throughout North America die in crashes with lighted buildings and towers. ”

    Countless animals injuries and deaths result from the use of artificial lighting. Clearly, people enjoy the benefits of lighting their evenings, but some scientists think it can be harmful to humans, too. They worry that exposure to light while sleeping can increase people's chances of getting cancer.

    Emerald Valley is only one community that is becoming aware of the negative effects of light pollution. For years, Flagstaff, Arizona has enforced lighting rules in its city in order to help astronomers with their observations. Similar efforts have been made worldwide, and a movement is underway to remind us to turn off lights when we are not using them, so that other creatures can share the night.

    Wetlands are ecosystems found in low, flat areas. Often they border ponds, rivers, lakes, and oceans. Wetlands include marshes, swamps, and bogs.

    No trees grow in a marsh, but there are lots of grassy plants. Ducks, turtles, and many different bugs (虫子) live there, too. Florida has the world's biggest freshwater marsh. The Everglades covers 4,000 square miles. The Everglades is not entirely fresh water, however. Near the sea the fresh water and salt water mix. Some plants and animals can live only in this brackish water.

    Saltwater marshes lie along the East Coast and the Gulf of Mexico. During high tide these marshes are under water. During low tide these marshes can be seen. The water rushes out, carrying bits of plants, dead animals, and minerals necessary for sea animals. Many plants and animals depend upon this ever-changing environment.

    Swamps are forested wetlands. Like marshes, they are often found near rivers or lakes and have mineral soil that drain very slowly. Unlike marshes, they have trees and bushes. Swamps have trees that grow with their roots underwater. But the trees will die if their roots stay underwater too long. Animals such as water snakes and frogs live in swamps.

    Bogs have damp, soft soil. So many dead plants have piled up that there is no longer any standing water. This rotting plant matter turns into peat (泥炭). In Ireland and Scotland peat is dried and burned to heat homes. Bog soil is useful for growing wild rice. Lots of insects live there.

    Most people do not find wetlands beautiful. But wetlands are important. Marshes and swamps store water, thus reducing the flooding a heavy rain can cause. About one-third of all of America's endangered plants and animals live in wetlands. Now laws protect some wetlands. More than a dozen wetlands in the US are refuges (保护区) and wildlife preserves.

Adult Education Courses

    On one of her trips to New York several years ago, Eudora Welty decided to take a couple of New York friends out to dinner. They settled in at a comfortable East Side cafe and within minutes, another customer was approaching their table.

    "Hey, aren't you from Mississippi?" the elegant, white-haired writer remembered being asked by a stranger. "I'm from Mississippi too."

    Without a second thought, the woman joined the Welty's table. When her dinner partner showed up, she also pulled up a chair.

    "They began telling me all the news of Mississippi," Welty said. "I didn't know what my New York friends were thinking."

    Taxis on a rainy New York night are rarer than sunshine. By the time the group got up to leave, it was pouring outside. Welty's new friends immediately sent a waiter to find a cab. Heading back downtown toward her hotel, her big-city friends were amazed at the turn of events that had changed their Big Apple dinner into a Mississippi.

    "My friends said: ‘Now we believe your stories,'" Welty added. "And I said: ‘Now you know. These are the people that make me write them.

    Beauticians, bartenders, piano players and people with purple hats, Welty's people come from afternoons spent visiting with old friends, from walks through the streets beside her house, from conversations overheard on a bus.

    It annoys Welty that, at 78, her left ear has now given out. However, she continues to walk into life and notes the vivid life. Sometimes, sitting on a bus or a train, she hears only a fragment(片段) of a particularly interesting story, yet she quickly takes out a notebook and write something fantastic under her point of pen.

    Do you know the term "tweenager"? It's a slang word being used in the UK to describe children 10-13 years old. They are between junior and the teenage years. Why are they suddenly referred to in this way?

    Tweenagers now have more money, freedom and influence upon their parents than they've ever had before. More and more companies are creating products and services for tweenagers. You can get everything from branded lunchboxes and mobile phone covers, to monthly fan magazines and clothing-it's all about sales.

    Most children in the UK today get more pocket money than kids did a decade ago. It is because parents are having fewer children on average than in the past. In addition, the divorce rate in the UK is continually rising and parents spend less time with their children than they used to. So, many parents try to compensate(补偿) by buying presents for them.

    And do tweenagers have more freedom? Well, UK children today are very familiar with media and computer. Many have a television, if not a computer, in their bedrooms. They have access to much more information about the world.

    They may have experienced a lot in life as well, since 24% of UK kids live in single-parent families. People now say that "Kids are getting older younger". With such sophistication (世故) at such a young age, they are much more fashion conscious and concerned about their image.

    In a world of TV programs that promise overnight success and fame at a young age, some people think it's extremely important to look fashionable. Surely none of the above is a good thing, is it? Can it really be healthy for us to encourage kids to be like adults at such a young age? Are we stealing childhoods in return for profit?

    The UK government is certainly concerned, and for that reason has strict laws preventing companies from marketing their products and services at children. So, is there a happy ending to this story?

    Companies have just worked out that the older tweenage audience is now looking for something darker and more rebellious. As a result, films such as Twilight are being produced for this older tweenage audience.