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.

    For many people around the world, a subway journey means speeding from one dull station to the next, surrounded by too many uncomfortable, impatient people. But on the Moscow Metro, taking the subway is like walking through a national heritage site. Depending on where you get off, you'll receive a brief course in architectural movements and face colorful glass windows, marble(大理石) columns, gilded(鎏金的) mosaics and painted scenes from Russian history.

    “These extraordinarily beautiful places are unlike any metro station I've ever seen, “says Vancouver-based photographer David Burdeny.

    When Burdeny, who himself has a master's degree in architecture, first found out about Moscow's metro stations, he was struck by the work of art. In all, he has photographed 20 of the most beautiful stations.

    Burdeny had originally planned to focus on Russian stations more generally, taking photos of examples in both St. Petersburg and Moscow.

    “But when I saw the stations in Moscow, they just completely blew away the St. Petersburg ones,” he says.

    Shooting in the subway sounds simple, but it is not without challenges. For one thing, Burdeny had to figure out a way to access them between 00:30 a.m. and 5:30 a.m., when the stations were closed.

    In the end, he settled on Arbatskaya Metro Station, whose vaulted(拱状的) arches he found the most beautiful. But it also represented a challenge he was not sure if he was able to overcome: conveying the hugeness of the spaces. The Arbatskaya platform, for example, stretches 820 feet.

    “Some of the arches are quite long,” he says. “When you enter them, they're just so completely grand.”

    The softshell turtle species is officially listed as endangered by the IUCN Red List. Scientists long thought softshell turtles were extinct in the Cambodian part of the Mekong River until they discovered some stragglers (掉队者) in the early 2000s.

    The species had quite a wide historical range across Asia, but much of that range is now completely gone. Much of the turtle's habitat in Southeast Asia have disappeared due to urban and industrial development along the Mekong River. The sand where turtles multiply is routinely carried away for use in construction projects, while fishing nets lift up hatchlings. People also take turtles and their eggs to sell for food.

    Initial surveys in 2003 and in 2007 found two small populations of the softshell turtles along a 30-mile stretch (水域) of the Mekong River. Since then, conservation groups have worked with local communities and officials to increase the wild population of these endangered turtles, including a program to hire former egg collectors to help search for and protect nests instead of harvesting the eggs.

    For the last decade, WCS, Conservation International, the Turtle Survival Alliance and local groups have worked to protect turtle nests. Their goal is to ensure eggs will multiply and hatch, and that baby turtles grow strong enough to eventually take care of themselves in the wild.

    A team recently released 150 hatchlings back into their natural habitat, bringing the total to more than 7,700 baby turtles in the past 10 years.

    Along the river banks of the Amazon and the Orinoco there lives a bird that swims before it can fly, flies like a fat chicken, eats green leaves, has the stomach of a cow and has claws(爪) on its wings when young. They build their homes about 4.6m above the river, an important feature(特征) for the safety of the young. It is called the hoatzin(麝雉).

    In appearance, the birds of both sexes look very much alike with brown on the back and cream and red on the underside. The head is small, with a large set of feathers on the top, bright red eyes, and blue skin. Its nearest relatives are the common birds, cuckoos. Its most striking feature, though, is only found in the young.

    Baby hoatzins have a claw on the leading edge of each wing and another at the end of each wing tip. Using these four claws, together with the beak(喙), they can climb about in the bushes, looking very much like primitive birds. When the young hoatzins have learned to fly, they lose their claws.

    During the drier months between December and March hoatzins fly about the forest in groups of 20 to 30 birds, but in April, when the rainy season begins, they collect together in smaller living units of two to seven birds for producing purposes.

    Ask any group of teenagers in the UK what they most like to eat, and foods like pizzas, curries, pasta, burgers and chips are bound to get mentioned and many young people would probably also list hanging out at the local fast food restaurant as one of their favorite pastimes (消遣).

    But what teenagers like to eat is not necessarily what they should be eating. According to the National and Nutrition Survey, far too many young people in the UK between the ages of 14 and 18 consume too much fat sugar and salt in their diet and take in too many calories. Meanwhile their intake of starchy carbohydrates (含大淀粉的碳水化合物), fibre, iron, vitamins and calcium is too low.

    For a growing body, eating foods containing plenty of calcium, such as milk, yoghurt and cheese, is particularly important as calcium is essential for the development of healthy, strong bones. Similarly, foods that are rich in iron are good for young, rapidly developing bodies, so red meat. bread, green vegetables, dried fruit and tonified(使增强体质的) breakfast cereals are also recommended.

    It is during our teenage years that habits of lifestyle can become entrenched (根深蒂固的),so it is crucial (全关重要的)that young people are educated about what foods arc good for them. In 2005, in an attempt 10 change eating habits and open teenagers' minds to new flavours and new tastes, celebrity chef Jamie Oliver launched a "Feed Me Better" campaign. As part of a television series Jamel School drivers, he worked with teachers and cooks in a number of schools across the UK to provide more healthy, nutritious school meal opt ions. Although there was initial resistance from sonic teenagers and parents. the campaign was generally hailed (把...... 誉为)as a huge success and helped to influence governmental policy on nutritional standards for school meals.

    No one expects to end the teenage love affair with fast and junk food but. hopefully, if projects "Feed Me Better" and the government's own "Change for Life" campaign continue to give out the right messages, more young people will understand the importance of balancing occasional treats with healthier food options.

Babies made from three people approved in UK

    Babies made from two women and one man have been approved by the UK's fertility regulator. The historic and controversial move is to prevent children from being born with deadly genetic diseases.

    Doctors in Newcastle — who developed the advanced form of In Vitro Fertilization or IVF (人工授精) — are expected to be the first to offer the procedure and have already appealed for donor eggs. The first such child could be born, at the earliest, by the end of 2017.

    Some families have lost multiple children to incurable mitochondrial (线粒体的) diseases, which can leave people with insufficient energy to keep their heart beating.

    The diseases are passed down from only the mother, so a technique using a donor egg as well as the mother's egg and father's sperm has been developed.

    The resulting child has a tiny amount of their DNA from the donor, but the procedure is legal and reviews say it is ethical (伦理的) and scientifically ready.

    "It is a decision of historic importance," said Sally Cheshire, chairwoman of the Human Fertilisation and Embryology Authority (HFEA). "I'm sure patients will be really pleased by what we've decided today."

    But some scientists have questioned the ethics of the technique, saying it could open the door to genetically-modified(转基因) 'designer' babies.

    The HFEA must approve every clinic and every patient before the procedure can take place. Three-person babies have been allowed only in cases where the risk of a child developing mitochondrial disease is very high.

    Prof Mary Herbert, from the Newcastle Fertility Centre, said, "It is enormously pleasing that our many years of research in this area can finally be applied to help families affected by these devastating diseases".

    "Now that we are moving forward towards clinical treatments, we will also need donors to donate eggs for use in treatment to prevent affected women transmitting disease to their children."

    Prof Sir Doug Turnbull, the director of the Welcome Centre for Mitochondrial Research at Newcastle University, said, "We are delighted by today's decision. We will also provide long-term follow up of any children born."

    NHS England has agreed to fund the treatment costs of the first trial of three-person IVF for those women who meet the HFEA criteria, as long as they agree to long-term follow up of their children after they are born.