You may think that light pollution isn't something extraordinarily important. You may believe that every other type of pollution has a larger impact on the environment that light pollution does. But light pollution is serious.

    Light pollution, or “sky glow”, is the glow you can see at night above cities and towns. Light pollution is a problem that has been accompanying man ever since he started his first fire some 15,000 years ago. Light pollution is the light that comes from streetlights, buildings, parking lots and any other source of light that is reflected or directed into the atmosphere.

    Urban light pollution means that one-fifth of the world's population can no longer see the Milky Way(银河) with the naked eye(肉眼). Many city kids, even if they did look through the orange smog above their heads, would probably see only a handful of stars. We have lost our view of the stars, and we have mucked up our  night-time environment as well. Astronomers are calling for the dark places on Earth to be preserved as national parks.

    Lots of people find the ever-brightening night annoying, and animals that are programmed to prefer the dark may avoid a brightened habitat. Sea turtles can get lost searching for a beach to lay eggs, and their hatchlings(孵化的幼仔)may confuse over-lit beachfront resorts(度假胜地) for the ocean horizon, wasting precious energy needed to find the sea and escape predators(食肉动物). Because their necks aren't yet long enough to see things far away, baby turtles rely on the mirror image of the moon to guide them to the sea, to begin their new life. A car may even hit a particular turtle, which was thinking the light from a nearby city was moonlight reflecting off the ocean waves. Birds that live in and around cities can die because of sky glow, too. The bright lights can blind them, leading to countless collisions with buildings and other tall structures.

    On an individual level, people can help reduce much sky glow by using lighting only when necessary. The stars above us are priceless heritage— for not only for astronomers but for all humans. More of our children should be able to look up at night and see the Milk Way.

    Settled by the Celts, invaded by the Romans and the Normans, and ruled by the English, Wales' population has regularly changed over the ages. Wales, particularly South Wales, became a melting pot (熔炉) of European nationalities and cultures. At first workers from England, Ireland and the rural areas of Wales rushed into the coal mines of South Wales. By 1911, workers from Ireland, Italy and Spain had joined the industrial workforce (劳动大军) there. Many of these newcomers were prepared to work for less pay.

    But during this period, workers, dissatisfied with regular pay cuts, poor safety, returned to the land. In 1891, the rural population of Wales was about 616,000 and by 1911 just over 649,000 people lived and worked in these areas.

       The rural population continues to grow slowly even today. People from richer parts of the UK, particularly southern England, are buying holiday homes in Wales. In some areas this has led to a lack of housing for local people. This, combined with the lack of employment in rural Welsh communities, has started a new movement of people in search of jobs and homes into the towns and cities of Wales and to other parts of the UK and Europe.

    As so many Welsh people have moved to other countries over the last 200 years, it's really no surprise that many visitors come to see friends and relatives. These visitors strengthen their links to their land of origin and continue to support the Welsh's development. During the hot summer days, about 28% of the visitors visit the countryside and nearly 70% visit the seaside.

    April 23 marks the 400th anniversary of William Shakespeare's death. Organizations in Britain have planned numerous events to honor him.

    In Stratford-upon-Avon, his birthplace, the tourism organization has a great number of free events, including performances of Shakespeare's plays, and a dazzling fireworks display. And the BBC is broadcasting a live show from Stratfore-upon-Avon, celebrating Shakespeare's widespread influence on the world. In England's capital, the London Shakespeare Centre and King's College London are holding a series of public performances, exhibitions and activities. It isn't just England that honors the anniversary of the death of this extraordinary writer. In Washington, D. C., the Folger Shakespeare Library, which houses the world's largest collection of documents relating to William Shakespeare, is displaying a series of exhibitions.

    Shakespeare is probably the most famous author who ever lived and is considered a genius by most. He wrote around 37 plays and 154 sonnets(十四行诗), and his work has been translated into over one hundred languages! He penned beautiful metaphors(暗喻), serious dramas and amusing tales.

    Shakespeare also invented many new terms and phrases. If someone's behavior suggested they were not being honest and should not be trusted, Shakespeare called their actions suspicious. If someone was being silly and perhaps looking like a fool, Shakespeare found their actions laughable. And Shakespeare called people who offered their opinions on the quality of something critics. Today, for instance, food critics and film critics give audiences their opinions of food and film. The familiar phrase “break the ice” comes from Shakespeare's play The Taming of the Shrew. The “ice is broken” when a difficult conversation or meeting is calmed by some basic introduction, such as a simple game. More common words coined by Shakespeare include road, gossip, lonely, bump and hurry.

    Four hundred years after his death, Shakespeare surely lives on, in everyday speech, as the most famous writer of all time!

    David Lindenmayer of the Australian National University College of Science in Canberra says that older trees play important roles in maintaining landscapes and ecosystems.

    David studies conservation, landscape, ecology and biodiversity at the Australian National University College of Science in Canberra. “Lots of people recognize that as humans get older they tend to have less and less children while trees do it the other way around. What really happens is that the older some of these really big old trees get, the more seeds they produce and the more germinant（萌芽的）they're likely to be. So it's actually the polar opposite of what we see with humans and most other animals, so really quite extraordinary. “On January 26th he spoke to Scientific American Editor in Chief Mariette DiChristina when they were both at the World Economic Forum in Davos.

    In actually it's quite a worrying situation, because in plenty of forests and woodland and other ecosystems around the world, populations of large old trees are declining very quickly. And this matters because a lot of biodiversity, a lot of carbon, a lot of key ecosystem processes are associated with those really big, old trees.

    We can make sure we grow more forests, that we protect the big trees we have now, and that we don't do things that really put a lot of pressure on those trees. We should not be cutting down really big old trees anymore.

Seeds on Ice

    Close to the North Pole, remote and rocky Plateau Mountain in the Norwegian archipelago of Svalbard seems an unlikely spot for any global effort to safeguard agriculture. In this cold and deserted environment, no grains, no gardens, no trees can grow. Yet at the end of a 130-meter-long tunnel cut out of solid stone is a room filled with humanity's most precious treasure, the largest and most diverse seed collection—more than a half-billion seeds.

    A quiet rescue mission is under way. With growing evidence that unchecked climate change-will seriously affect food production and threaten the diversity （多样性） of crops around the world, the Svalbard Global Seed Vault （地窖） represents a major step towards ensuring the preservation （贮藏） of hundreds of thousands of crop varieties. This is a seed collection, but more importantly, it is a collection of the traits found within the seeds: the genes that give one variety resistance to a particular pest and another variety tolerance for hot, dry weather.

    Few people will ever see or come into contact with the contents of this vault. In sealed boxes, behind multiple locked doors, monitored by electronic security systems, enveloped in below—zero temperatures, and surrounded by tons of rock, hundreds of millions of seeds are protected in their mountain fortress. Frozen in such conditions inside the mountain, seeds of most major crops will remain viable for hundreds of years, or longer. Seeds of some are capable of retaining （保留） their ability to grow for thousands of years.

    Everyone can look back now and say that the Seed Vault was a good and obvious idea, and that of course the Norwegian government should have approved and funded it. But back in 2004, when the Seed Vault was proposed, it was viewed as a crazy, impractical, and expensive idea.

    We knew that nothing would provide a definite guarantee. But we were tired, fed up, and frankly scared of the steady, greater losses of crop diversity. The Seed Vault was built by optimists who wanted to do something to preserve options so that humanity and its crops might be better prepared for change. If it simply resupplied seed gene banks with samples those gene banks had lost, this would repay our efforts.

    The Seed Vault is about hope and commitment-about what can be done if countries come together and work cooperatively to accomplish something significant, long-lasting, and worthy of who we are and wish to be.

    A butterfly's wings can have many jobs besides keeping the insect in the air. They may be called on to attract mates, to warn potential enemies to stay away, to do other animals or even to provide disguise(伪装).

    All of these roles, though, depend on their colouration-which is unchanging. This plays into the idea that butterfly wings are dead tissue, like a bird's feathers or a mammal's hair. In fact, that is not true. For example, in some species males' wings harbour special cells that release chemicals which attract females.

    Nanfang Yu, a physicist at Columbia University, in New York, has been looking into the matter. One of his interests is the optical (光学的) properties of biological materials. That has led him to study butterfly wings in more detail. And, in cooperation with Naomi Pierce, a butterfly specialist at Harvard University, he has now shown, in a paper published this week in Nature Communications, that butterfly wings are, indeed, very much alive.

    Initially, Dr Yu and Dr Pierce wanted to know how the insects keep their body temperatures up without their wings overheating. Unlike birds and mammals, butterflies do not produce enough internal heat to metabolize(新陈代谢). Instead, they rely on outside heat sources-usually the sun-to bring their bodies up to speed. But their wings, being thin protein membranes (膜), have a limited thermal capacity. Those wings can therefore overheat quickly if the insects are exposed to the sunlight too long, or, oppositely, can cool down too rapidly if they are flying through cold air.

In their experiments, the two researchers used a laser (激光) to heat up spots on the wings of dozens of butterfly species. When the temperature of the area under the laser reached 40℃ or so, the insects responded within seconds by doing things that stopped their wings heating up further. These actions included a butterfly turning around to minimize its exposure to the laser, beating its wings or simply walking away.