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.”

    On Monday, the Centers for Disease Control and Prevention predicted that 42% of Americans could be overweight by 2030. Our expanding waistlines lead to not only a medical problem, but according to a recent article In The New York Times, it could also endanger personal safety in some situations—in an airplane crash, for example.

    The New York Times' Christen Negroni reports that engineers and scientists are questioning whether airplane seats are adequately constructed to protect overweight travelers. Government standards for airplane seat strength（强度）— first set moe than 60 years ago — require that the seats be made for a passenger weighing 170 pounds (77kg). Today, the average American man weighs nearly 194 pounds (88kg) and the average woman 165 pounds (75kg). Negroni reports:

    “If a heavier person completely fills seat, the seat is not likely to behave as intended during a crash,” said Robert Salazar, the leading scientist at the Center for Applied Biomechanics at the University of Virginia. “The energy absorption that is built into the aircraft seat is likely to be overpowered and the passengers will not be protected properly.”

    “Nor would the injury be limited to that passenger only,” Dr. Salzar said. “If a seat or a seat belt fails,” he said, “those people who are seated nearby could be endangered from ‘the uncontrolled movements of the passenger'.”

    Most complaints about airplane seats focus on their lack of comfort and high ticket price, and whether overweight passengers should be made to buy two seats. But The New York Times' article brings up another reason to feel anxious about flying. Investigators of the issue got in touch with the airplane seat and seat belt makers, but they refused to comment on the problem. Experts agreed that crash testing should be done with overweight dummies （人体模型）. Both airplane seats and seat belts should be tested, they said.

    Fortunately, however, according to Nora Marshall, a senior adviser at the National Transportation Safety Board, the board's investigators have never seen an accident involving a commercial plane in which the weight of a passenger was a problem.

    Tulou, the special residential architecture of Fujian Province was included on the UNESCO's World Heritage List during the 32nd session of the World Heritage Committee in Quebec, Canada.

    In the fourth century, Han Chinese living in the Central Plains area began to migrate south, gradually gathering in Fujian and forming the Hakka communities. As a defence against enemies, the Hakkas chose to live in compact (紧凑的) communities, and the tulou was their preferred houses. Tens of thousands of such earthen structures were constructed in Fujian Province.

    Most tulous are to be found in the valleys, surrounded by high mountains, and some are in the depths of the great mountains. Most are three to four storeys high, and look like circular blockhouses (堡垒). Rooms on the first floor are used as kitchens, rooms on the second floor are used as barns (谷仓), and rooms on the third and fourth floors are for bedrooms and living rooms. For defensive purposes, the rooms on the first floor have no windows.

    Raw materials for the tulou were obtained locally. Their main building material was a mixture of clay, sand, lime and water, and egg whites, brown sugar and rice water were added as adhesive agents (粘合剂). It was then mixed to form the walls. Once they dried, the walls were so hard that driving a nail into them would have been difficult. Fir branches, which are extremely strong and do not rot, were used to strengthen them, and many centuries later they have remained their original look.

    Tulous are located in a region where earthquakes happen frequently, and their circular construction helps them resist the regular shocks.

    The proven design even inspired one famous Peruvian architect, who paid several visits to Yongding, to build a tulou back home. Not long after, an earthquake struck only 10 kilometers away, and while all the houses around the earthen building fell down, his tulou remained.

    Millions of people all over the world use the word okay. In fact，some people say the word is used more often than any other word in the world.

    It may be common，but no one can seem to agree on how the “OK” came to be.

    Okay means “all right” or “acceptable”. It expresses agreement or approval. You might ask your brother，“Is it okay if I borrow your car?” Or if someone asks you to do something，you might say，“Okay ， I will.” Still，language experts do not agree about where the word came from.

    Some people say it came from the Native American Indian tribe known as the Choctaw. The Choctaw word “okeh” means the same as the American word okay. Experts say early explorers in the American West spoke the Choctaw language in the nineteenth century. The language spread across the country.

    But many people dispute(不同意)this.

    Language expert Allen Walker Read wrote about the word okay in reports published in the 1960s.He said the word began being used in the 1830s.It was a short way of writing a different spelling of the words “all correct.” Some foreign-born people wrote “all correct” as“o-l-l k-o-r-r-e-c-t.” and used the letters O.K.

    Other people say a railroad worker named Obadiah Kelly invented the word long ago. They said he put the first letters of his names—O and K—on each object people gave him to send on the train.

    Still others say a political organization invented the word. The organization supported Martin Van Buren for president in 1840.They called their group，the O.K. Club. The letters were taken from the name of the town where Martin Van Buren was born—Old Kinderhook，New York.

    Not everyone agrees with this explanation，either. But experts do agree that the word is purely American. And it has spread to almost every country on Earth.

    When my daughter Sara was in the fifth grade, she came to me with a problem." Marcy hates me！" she cried." Because Kathy is my friend, too. She wants me to be her friend and nobody else's. You talk to Marcy. You tell her that I want to be her friend, but I can have other friends, too！"

    Oh！I looked at her for a few moments，wondering how I got into this mess，when suddenly an idea came to me.

    Picking up two baskets from the living room, I explained, "When everyone is born, he or she has a little basket. This little one here is yours. The big one is mine. As you grow, so does the basket. You can see your little basket is inside mine because when you were born, there were too many things you couldn't do for yourself. I did everything you couldn't do on your own." She nodded.

    "Well, as you grew older and began to do some things on your own, I began placing a few more things in your basket. When you learned to tie your shoes, that went in your basket."

    She said softly, "I can tie my own shoes."

    "Right. As you grow older，there will be more and more things you must do on your own." As I spoke, I gradually took her basket out of mine and handed it to her." You will finally carry your own basket with things only you can do."

    She looked up at me and said," I understand. There are some things that I have to do for myself because they are in my basket."

    Better known by his stage name Kun, Cai Xukun is, without a doubt, one of the most popular stars in China.

    On July 26, the 21-year-old dropped his new single Young. Within just 20 seconds, it reached 1 million views and in only 3 days topped the music charts of Tencent's QQ music.

    Cai wrote the song by himself to share his understanding of modern-day youth. The singer has mixed R&B with electronic music to make his new beat cheerful. One reviewer wrote on QQ Music: "When you listen to the song, you just seem to go back to youth again."

    August 2 is Cai's birthday, and the song was a gift to himself. The singer hopes that he can always have the courage to follow his love of music, ignoring what anyone says. "My works are like my children and I have put my best effort into them. I want every piece of my work to have my own spirit in it. I feel more enjoyment when I am performing my own work." He told the Global Times.

    To find new inspiration, Kun attends different kinds of musical performances－from festivals to opera houses. "I just like to do everything, all for my music, all for my art," he told i-D.

    With talent and dedication(专注) to music, Cai is expected by many to make his mark in the competitive Chinese music industry.