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.

Protect Children from Cyber-bullying

    When you think about bullying, you might think of a child being bullied by another in the schoolyard. As more young people have access to computers and cell phones, traditional bullying has gone digital, which has not yet gained awareness in Chinese parents.

    Cyber-bullying, first invented by Canadian educator Bill Belsey, is the use of the Internet and related technologies to harm other people, in an intentional, repeated, and unfriendly manner. It involves threatening text messages, the spread of online rumors on social networking sites, and intentionally keeping someone out of an online group. Cyber-bullying is at an all-time high in the US. According to a study from the US Department of Justice, more than 43% of teenagers report being victims（受害者）of cyber-bullying.

    Compared to face-to-face bullying, cyber-bullying is considered to have a worse emotional effect on the victims, and kids could feel more desperate and depressed. Severe, long-term or frequent cyber-bullying can leave victims at greater risk for anxiety, depression, and other disorders. Research says that cyber-bullying victims were almost twice as likely to have attempted suicide compared to youths who had not experienced it.

In traditional schoolyard bullying, at least home is a safe place for the victims. But cyber-bullying is endless—it could happen anytime. Moreover, in the digital world, bullying is much easier, as a bully can pick on people with a much lower risk of being caught.

    Actually, cyber-bullying has become a worldwide issue. In the US, as several teens committed suicide because of cyber-bullying, some schools set rules to punish cyberbullies. Laws to punish cyber-bullying have been introduced in some states. In China, cyber-bullying is still considered by many parents and educators as a problem that involves physical contact. However, as cell phones and laptops are becoming common equipment for teenagers, social interactions have increasingly moved from personal contact to virtual contact. Cyber-bullying is spreading faster than expected.

    For schools and parents, safety rules should be set in the virtual world for kids, such as telling them not to let out anything to a stranger. Active steps should be taken to make the public aware of the seriousness of this problem, because it would be too late to take measures after tragedy strikes.

    BEIJING, China —Pollution in China remains very serious as the country's rapid economic growth brings new environmental problems, a minister said Saturday.

    Vice Environment Minister Zhang Lijun said China has made progress on environmental protection, but admitted that its rapid economic growth over the past decade has had a negative effect on the environment.

    "Our rapid economic development has continuously brought our country new environmental problems, particularly dangerous chemicals, electronic waste and so on. These environmental pollutants (污染物) bring new problems and affect human health," Zhang told a news conference.

    He said that emissions(排放)of traditional pollutants remain high and some areas have failed to meet government standards.

China has pledged to continue reducing emissions this year of three key air pollutants— ammonia nitrogen, sulfur dioxide and nitrogen oxide. The government has also promised to bring down demand for chemical oxygen—a measure of water pollution by l.5 percent from the 2010 levels.

    In the last five years, there were 912 "environmental emergencies" involving heavy metal pollution, including several well-publicized instances of mass contamination, Zhang said. Thousands of children were affected by lead poisoning in several provinces in 2009 and 2010 because they lived near metal smelters or battery factories.

    The minister noted that rapid development in the next five years would increase the need for China to improve environmental protection and shift to a more sustainable(可持续的) model of economic development from its dependence on industries which consume huge quantities of energy.

    China is focusing on clean energy, including solar, wind and nuclear power, as one way to reduce its dependence on coal, which generates three-quarters of its electricity and is also used for winter heating in northern cities. China also hopes the strategy will reduce its demand for oil and gas and increase economic growth and jobs.

    Zhang told reporters there was no plan to adjust China's overall strategy for nuclear development but he said Beijing will learn lessons from Japan after a violent earthquake resulted in a radioactive leak(放射能泄露).

    "Some lessons we learn from Japan will be considered in the making of China's nuclear power plans," he said. "But China will not change its determination and plan for developing nuclear power."

    A man walked into a small Irish pub and ordered three beers. Bartender was surprised, but he served that man three beers. One hour later the man ordered three beers again. The very next day that man ordered three beers again and drank quietly at a table. This repeated several times and shortly after the people of the town were whispering about the man, who was ordering three beers at once.

    A couple of weeks later, the bartender decided to clear this out and inquired: “I do not want to pry, but could you explain, why do you order three beers all the time?” The man replied: “It seems strange, isn't it? You see, my two brothers live abroad at the moment, one – in France and another – in Italy. We have made an agreement, that every time we go to pub each of us will order extra two beers and it will help keeping up the family bond”.

    Soon all the town have heard about the man's answer and liked it a lot. The man became a local celebrity. Residents of the town were telling this story to newcomers or tourists and even invited them to that pub to look at Three Beer Man.

    However, one day the man came to pub and ordered only two beers, not three as usual. The bartender served him with bad feeling. All that evening the man ordered and drank only two beers. The very next day all the town was talking about this news, some people pray for the soul of one of the brothers, others quietly grieved.

    When the man came to pub the next time and ordered two beers again, the bartender asked him: “I would like to offer condolences to you, due to the death of your dear brother”. The man considered this for a moment and then replied: “Oh, you are probably surprised that I order only two beers now? Well, my two brothers are alive and well. It's just because of my decision. I promised myself to give up drinking.”

    No one is sure how the ancient Egyptians built the pyramids near Cairo. But a new study suggests they used a little rock 'n' roll. Long-ago builders could have attached wooden poles to the stones and rolled them across the sand, the scientists say.

    "Technically, I think what they're proposing is possible," physicist Daniel Bonn said.

    People have long puzzled over how the Egyptians moved such huge rocks. And there's no obvious answer. On average, each of the two million big stones weighed about as much as a large pickup truck. The Egyptians somehow moved the stone blocks to the pyramid site from about one kilometer away.

    The most popular view is that Egyptian workers slid the blocks along smooth paths. Many scientists suspect workers first would have put the blocks on sleds(滑板). Then they would have dragged them along paths. To make the work easier, workers may have lubricated the paths either with wet clay or with the fat from cattle. Bonn has now tested this idea by building small sleds and dragging heavy objects over sand.

    Evidence from the sand supports this idea. Researchers found small amounts of fat, as well as a large amount of stone and the remains of paths.

    However, physicist Joseph West thinks there might have been a simpler way, who led the new study. West said, "I was inspired while watching a television program showing how sleds might have helped with pyramid construction. I thought, 'Why don't they just try rolling the things?' "A square could be turned into a rough sort of wheel by attaching wooden poles to its sides, he realized. That, he notes, should make a block of stone "a lot easier to roll than a square".

    So he tried it.

    He and his students tied some poles to each of four sides of a 30-kilogram stone block. That action turned the block into somewhat a wheel. Then they placed the block on the ground.

    They wrapped one end of a rope around the block and pulled. The researchers found they could easily roll the block along different kinds of paths. They calculated that rolling the block required about as much force as moving it along a slippery(滑的)path.

    West hasn't tested his idea on larger blocks, but he thinks rolling has clear advantages over sliding. At least, workers wouldn't have needed to carry cattle fat or water to smooth the paths.

Best Way to Save Money

    Although the best way to save money can vary from person to person, depending on age, family size and other characteristics, there are still some easy things that all shoppers can do to keep more money in their bank accounts.

    Avoid Impulse (冲动的) Purchases

    When you shop, a best way to save money is to have a plan in mind to help you avoid impulse purchases. For instance, you might leave your credit cards at home and only carry the exact amount of cash that you will need for your planned purchase. Some shoppers agree to discuss any purchases over a certain dollar amount with their spouses (配偶) first.

    Know When to Pay for Quality

    Sometimes the best way to save money in the long term is to spend a little more money right now. A good piece of furniture can stay in the family for decades. A high-quality pair of shoes will last longer than a bargain pair and prevent foot pain. Leaner cuts of meat and organic produce provide health benefits for your family.

    Buy Secondhand

    Check classified ads, thrift stores and garage sales for used clothing, toys, furniture, and much more available at a part of their original cost. For the most secondhand savings, check out groups like Freecycle where members offer unwanted items for free to anyone willing to pick them up.

    Borrow Instead of Buy

    If you're only going to use something once, try to borrow it instead of spending your money on it. Borrow a tool from your neighbor. Swap books with a friend. Check out the resources at your local library. You'll also be reducing disorder in your home.