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.

    The famous director of a big and expensive movie planned to film a beautiful sunset over the ocean, so that the audiences could see his hero and heroine in front of it at the end of the film as they said goodbye to each other forever. He sent his camera crew out one evening to film the sunset for him.

    The next morning he said to the men, “Have you provided me with that sunset?”

    “No, sir,” the men answered.

    The director was angry. “Why not?”  he asked.

    “Well, sir,” one of the men answered, “we're on the east coast here, and the sun sets in the west. We can get you a sunrise over the sea, if necessary, but not a sunset.”

    “But I want a sunset!” the director shouted. “Go to the airport, take the next flight to the west coast, and get one.”

    But then a young secretary had an idea. “Why don't you photograph a sunrise,” she suggested, “and then play it backwards? Then it'll look like a sunset.”

    “That's a very good idea!” the director said. Then he turned to the camera crew and said, “Tomorrow morning I want you to get me a beautiful sunrise over the sea.”

    The camera crew went out early the next morning and filmed a bright sunrise over the beach in the middle of a beautiful bay. Then at nine o'clock they took it to the director. “Here it is, sir,” they said, and gave it to him. He was very pleased.

    They all went into the studio. “All right,” the director explained, “now our hero and heroine are going to say goodbye. Run the film backwards so that we can see the ‘sunset' behind them.”

    The “sunset” began, but after a quarter of a minute, the director suddenly put his face in his hands and shouted to the camera crew to stop.

    The birds in the film were flying backwards, and the waves on the sea were going away from the beach.

    Emily and Zach are confused! Their parents told them they could choose between Massachusetts and Arizona for their vacation this summer.

    Emily has always wanted to visit Boston, the capital of Massachusetts. Zach and she both agree that walking along the Freedom Trail would enable them to see Boston's most famous places of historic interest, like the site of the school Ben Franklin attended and the Old State House. If Emily and Zach went to Massachusetts, they could spend a few days at the beaches on Cape Cod. Emily loves body boarding, and Zach is great at body surfing. They both enjoy building sandcastles .

    Zach finds learning about Native Americans wonderful and has always wanted to travel along the Apache Trail in Arizona. This mountain highway passes Native American ruins in Tonto National Forest. Emily is not as interested in traveling along this trail as Zach, but they both would like to visit Phoenix, the capital, and then travel to Grand Canyon National Park and Meteor Crater (陨石坑). Zach learned in science class that Meteor Crater is a hole over 4,000 feet wide and 520 feet deep that was created when a huge object from space fell to Earth. The object went so deep that it has never been found. Zach would really like to try to discover it. But Emily thinks if experienced scientists and researchers cannot find it, Zach might as well not even bother (费工夫) to try.

    The only drawback for Zach and Emily if they choose Arizona would be the heat. It is very hot and dry in this southwestern state. Massachusetts, on the other hand, is in the northeastern United States. Here Zach and Emily and their parents could enjoy mild (温和的) temperatures. Their parents love hot weather, but Zach and Emily do not really like to sweat.

    How will they ever decide to which state they should travel? If only they could take two trips!

    Work started this week on next season's flu vaccine (疫苗), with experts working off forecasts about which types of the flu virus will be making the rounds. But don't expect any improvements. Flu experts are already admitting that most vaccines will give at best basic protection, because they're based on old-fashioned technology. It's not a new problem, but one that the slow-moving world of drug and vaccine production seems helpless to improve upon.

    Every flu vaccine is a cocktail, aimed at either three or four of the most common flu types. Flu vaccines must be recreated every year because flu viruses develop constantly in a process called antigenic drift. In February, global flu experts gather to trade notes on what viruses are circulating in different countries and to come to an agreement on which types the next vaccines should be made to target.

    In recent years, flu vaccines have been based on H1N1, H3N2 and either one or two types of influenza B virus. Each of these has a "reference" type, which is used to make seed virus. Producers add the seed types to eggs and incubate (孵) them as the virus grows. Then they purify the virus, and either weaken it or kill it to make a vaccine.

    Using eggs is a tricky (=difficult) and unpredictable process. Sometimes the virus doesn't grow well in eggs, which can mean less vaccine than expected. The result is a flu vaccine that doesn't offer much protection. "As long as we have eggs we are going to have this problem," said Scott Hensley, a flu virus expert, "The only solution is not to depend on eggs."

    Flu is a major killer. The 2017-2018 season has been a severe one, hitting the entire U. S. with widespread influenza infection (感染) at once for weeks on end, and killing 97 children so far. Against this threat, even a less satisfying flu vaccine will definitely help. "Even when you have these mismatches it will not prevent infection but likely prevent disease severity," said Hensley.

    The end of the school year is in sight — Christmas cards, candy canes and of course, end of year reports.

    While most parents welcome an assessment of their kids' performance, they do not expect their own input to be evaluated. But a school in the UK is changing that. As well as assessing their students, they are dishing out grades to mums and dads. Parents that are really involved in their kid's education are rewarded with an A, and parents that haven't done their bit get a disappointing D.

    The school, Greasley Beauvale Primary in Nottinghamshire, uses criteria such as whether mums and dads have attended school events such as plays and parent-teacher conferences to decide on the grade. The school's principal, Donna Chambers, said that the scheme (方案)had been well received.

    “There were some critics, but my response was 'well, it can't do any harm'. Between 15 percent and 20 percent of parents started out in the lower categories but now that has been reduced to just two percent,” she explained.

    Chambers hopes that the scheme will help motivate parental involvement. “The system is important because you have got to get the parents on board from day one. That one hour initial conversation saying they could improve will pay dividends for the rest of that child's academic life”, she said.

    But while the scheme may be well-intentioned, it is likely to be connected with parent shaming. There are lots of reasons why some mums and dads might not be involved in school activities such as work commitments, looking after younger children or caring for elderly relatives.

    And of course, being involved in your kid's education doesn't begin and end at school. There is a lot that goes on behind the scenes from helping with homework to keeping uniforms freshly laundered. And what about all the parents who stayed up sewing special costumes at the last minute? Surely that earns a gold star instead of a grade!

    Siblings refer to one's brothers and sisters. We're attached to siblings as adults far longer than we are as children. Our sibling relationships, in fact, are the longest-lasting family ties we have.

    “Paul, my younger brother, and I, kind of annoyed each other when we were kids,” said Anna, an interviewee, “But as adults, we've always had each other's back, especially when dealing with our mother's health crisis. Paul is the first person I want to talk to when something worries me.”

    There's probably a biological explanation for the close bond of the sibling relationship. Siblings share half their genes, which biologists say should be motivation enough for each other's devotion.

    One thing that can weaken closeness in adulthood is a parent who played favorites in childhood; this sense of hatred can last a lifetime. The simple concept of parental favoritism was enough to shake their relationship.

    “What Paul and I are pretty sure is our parents treated us the same when we were growing up. Yet we're very different people,” Anna said,“ Paul is outgoing while I'm shy. Paul is an amateur pianist while I can't read music or carry a tune. In families with more than one child, every sibling seems to get a label in contrast to every other sibling.”

    The very presence of siblings in the household can be an education. When a new baby is born, the older sibling gains social skills by interacting with the younger, and the younger gains cognitively（认知角度地）by imitating the older. They learn from the friction between them, too, as they fight for their parents' attention. Mild conflict between brothers and sisters teaches them how to interact with friends and co-workers for the rest of their lives.

    It's so sad when things between siblings fall apart, which happens when aging parents need care or die — old feelings of contradiction and jealousy erupt all over again. Many families get through their parents' illnesses just fine, establishing networks where the workload is divided pretty much equally. But about 40 percent of the time there is a single primary caregiver who feels like she is not getting any help from her brothers and sisters, which can lead to serious conflicts.

    Throughout adulthood, the sibling relationship “is powerful and unchanged,” said Jane Mersky Leder, author of the new e-book The Sibling Connection. Whether we are close to our siblings or distant, she writes, they remain our brothers and sisters — for better or for worse.

    So remember the immortal（永恒的）words of folksinger Loudon Wainwright Ⅲ, in a song called Thanksgiving.“ On this brilliant occasion, this special family dinner, if I argue with a loved one, please make me…”