Sometimes, you just can't help it. Maybe you're watching a sad movie, or thinking about the friend who moved away. Next thing you know, your eyes are watering, and you havetears running down your cheeks. Why do peoplecry when they are emotional? What are tears? Scientists are working hard to find the answers to these questions.

    Ad Vingerhoets is a professor of psychology at Tilburg University, in the Netherlands. He is one ofthe few scientists in the world who have studied crying. According to Vingerhoets, there are three types of tears. Basal tearsare the first type. Theylubricate(润滑) the eyes andact as a protective barrier between the eye and the rest of the World. Next arereflex tears. They wash youreyes clean when something gets in them. Finally, there are emotional tears. “These are released in response to emotional states, ”explains Vingerhoets. “Especially when we feel helpless.”

    Scientists believe that crying has something to do with how humans developed and learned to depend on each other.“Humans are very complex social creatures,”says Lauren Bylsma, a professor at the University of Pittsburgh, in Pennsylvania.“It seems that tears serve to arouse help and support from others," She says. “Another reason we weep is that humans have the longest developmental period of almost any animal. It takes along time to grow up. ”

    Vingerhoets agrees. “I think that the reason why humans shed tears(流眼泪) has somethingto do with our childhood,”he says. “That's the time when we are stir dependent on adults for love and protection and care. The major advantage of emotional tears is that you can target them at a specific person.”Vingerhoets says this ability to target someone could have come in hand in prehistorictimes, when humans were living among dangerous animals. Crying couldattract predators(捕食者). Tears were asafer way to get attention. In this case, it is better to use a silent signal to ask for help,”he says.

    Vingerhoets and Bylsma do frequent studies to better understand why humans cry. According to Byhma, there is still much more to discover. “It's surprising,”she says,“how much we still don't know.”

    Frequently, we speak about people being “color-blind” but very few of us are. Even those who describe themselves as color-blind are normally just color lack. A strongly, color-blind person will still be able to tell 20 different colors, compared to the 100 or so that normal-sighted people see.

    Pingelap, a tiny island in the Pacific, is a beautiful spot but one that has a genetic trouble. It is known as Color-blind Island because so many people who live on this remote island can only see black and white.

    Not being able to see colors is bad enough. But one islander, Herrol, who's a fisherman, also struggles in full sunlight because all he sees is a painful burnt-out image. “I find it difficult to go outside in the sun,” he says, “because when it's sunny I cannot see to do my work.”

    But if being truly color-blind is rare, why is it that around 10% of the population of Pingelap live in a totally black and white world?

    Well, we know that in 1780 the population of Pingelap was all but wiped out by a tsunami (海啸). As few as 20 people survived, one of whom was the king. It's believed he had a genetic fault that causes colour-blindness and he passed this fault on to his many generations.

    There is one advantage. Herrol can see well, really well, in the dark. So when it gets dark, Herrol and his friends get in their boats and hunt flying fish. They hang up flaming torches and the fish are attracted to the flames. “This type of fishing is fun,” Herrol says, “especially if we catch plenty. So even though it's hard work we enjoy it.”

    Millions of Americans are living in areas at high-risk of river flooding, many of whom are completely unaware of the danger.

    While the risk of coastal flooding from extreme storms and rising seas rightly attracts plenty of attention, Americans are being urged to look inland for a similar threat receiving far less recognition: river flooding. New research conducted by the University of Bristol has shown that as many as 41 million Americans are highly at risk from river floods – more than three times the number previously estimated – with real estate (住宅区) in areas such as Louisiana, Florida, Arizona and West Virginia found to be especially at threat.

    For the first time, it has been possible to produce super quality flood risk maps that cover the whole United States, while previous Federal Emergency Management Agency (FEMA) flood maps cover no more than 60 per cent of the country. The fine details provided by these new maps also makes it possible to predict the powerful effects of flooding on many smaller streams than before, thus raising concerns about the increasing number of people potentially threatened.

    "We were all surprised by how many Americans we find are exposed to flooding from rivers," says Oliver Wing, from the University of Bristol's School of Geographical Sciences. "It's particularly worrisome considering that most of these people aren't even aware of the risk they face."

    Additionally, there is the possibility that this lack of awareness means construction in high-risk river flooding areas will continue to rise, despite the threats. Estimates (估量) suggest that projected population growth, continued urbanization trends (城市化趋势), and the unpredictable threats caused by climate change will leave over 60 million Americans vulnerable (易受攻击的) to a 100-year flood by the middle of the century. 'All of this highlights the urgent need for large areas of floodplain and flood risk management planning,' adds Wing.

    They hide in trees, hang from helicopters, even follow people down on motorcycles—all so that they can snap a shot of a celebrity. They are paparazzi—photographers who make a living by taking pictures of the rich and famous.

    This September, California, a state with plenty of celebrities, passed a law aimed at taking action against paparazzi. The law forbids photographers from entering private property to take pictures, from using high-tech devices to take pictures of people on private property, and from "persistently following in order to take a picture." Violators can be fined or spend time in prison. The United State Congress is considering passing a similar law.

    Supporters of the California law say it will protect the privacy of celebrities, whom paparazzi have been bothering for years. Opponents (反对者) say the law restricts photojournalists from doing their job.

    Most celebrities seem to like having their pictures taken when they are in public at award shows or other events. After all, it's free publicity. But when they're not in public, they say, photographers should leave them alone. Yet paparazzi have been known to secretly look in windows and worse. Actor Michael J. Fox said that paparazzi have even "tried to pretend to be medical personnel at the hospital where my wife was giving birth to our son."

    Celebrities have as much right to their privacy as anyone else, supporters of the law state. Supporters further argue that the California law is a fair way to keep the press at bay, because the law still allows photographers to do their job. It only punishes them, supporters say, when they violate celebrities' privacy.

    Opponents of the law say it violates the First Amendment to the United States Constitution (美国宪法第一修正案), which guarantees that no laws will be made to limit "the freedom of speech, or of the press." Although some people might not consider paparazzi a part of the legal press, the California law does not single out paparazzi. It applies to photographers working for any publication.

    Opponents of the law are also concerned about its wording. "Does 'persistently' mean following someone for six minutes, six seconds, or six days?" asked lawyer Douglas Mirell. The wording of the law is too vague, critics complain, and could be used to punish almost any news photographer.

    The United States needs a free press to keep the public informed about important news, paparazzi law opponents say. Limiting the press in any way, they argue, limits the freedom of all.

    It is common to see many different kinds of insects while spending time outside in the summer. Some of them do not trouble people and can even add beauty to the natural environment. Other insects can harm the environment or humans. The population of these insects seems to stay large and healthy.

    But scientists say this does not appear to be true for some flying insects that serve an important purpose. There is growing evidence that these insects are decreasing across the world.

    One researcher looking into the present insect population is Doug Tallamy, a professor at the University of Delaware. He remembers walking through Washington D. C., in the past when it was "alive with insects, especially butterflies". Now, he said, "The flying insects are actually gone." Wilson said this point seemed to be proved during a drive he made last year from Boston to Vermont. He was surprised that, during his trip, he counted only one insect that had hit the car's front window. Several other scientists have carried out similar tests by checking how many insects hit their cars while traveling.

    While researchers admit this method is not scientific, they say it can still help them understand the changing flying insect population. There have not been many studies done on the flying insect populations covering large areas. However, some international research suggests a downward turn. In 2006, a group of studies showed that there had been a 14-percent drop in ladybugs(瓢虫) in the United States and Canada from 1987 to 2006. In Germany, a 2017 study found an 82-percent drop in the number of flying insects compared to levels recorded in 1990.

    After the German study, other countries also started looking into the problem. David Wagner of the University of Connecticut says other evidence leads him to believe the findings of the 2017 study are "clearly not a German thing".

The Palace Museum's clock collection, more than 1,500 in number, is arguably one of the most breathtaking clock preservations worldwide. {#blank#}1{#/blank#} (make) between the 18th century and the 20th century, some were crafted in Britain, France and Switzerland, some were from the Clock Worship of the Qing Palace, the others were {#blank#}2{#/blank#} mixture of both the East and the West.

The {#blank#}3{#/blank#} (major) of British clocks feature bronze cases inlaid with splendidly colorful jewels. They are diverse {#blank#}4{#/blank#} form, recreating all kinds of architecture and natural sights, and often include automatic {#blank#}5{#/blank#} (decorate) such as fountains, moving figures, boats and birds. These clocks represent the highest level of craftsmanship in Britain.

Most of the French clocks here are the products of the early 20th century. Whether in terms of theme {#blank#}6{#/blank#} decorative style, the French clocks in the collection have a style of {#blank#}7{#/blank#} (they) own, and deserve their place in history.

The Swiss timepieces {#blank#}8{#/blank#} (most) comprise small, unconventionally shaped desk clocks and delicate pocket watches. They were specially made {#blank#}9{#/blank#} (suit) the tastes of Chinese customers.

Clocks may turn back in time, but humans may never dream of doing so. Today, the Palace Museum {#blank#}10{#/blank#} (aim) to carry on this touching tale of "time" as guardians of this traditional craftsmanship.