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.”

    At the end of every year, Time picks the best 25 inventions that are “making the world better and smarter”. Here we have picked three of this year's inventions that could be a part of your life in the near future.

The levitating(悬浮的) lightbulb

    This special lightbulb was invented by US artist and scientist Simon Morris. He got the idea of making a lightbulb float from hoverboards(悬浮滑板)，which he used to dream of having as a kid.

    But the floating is not the most amazing part. The rejection force between the opposite ends of the magnets(磁铁)，which were put in the bottom of the bulb and in the wooden base, does the job. What's new here is a technology called induction (电磁感应). It allows the lightbulb to get power from the base even they are not in contact.

Shoes that tie themselves

    They're not what you think-shoelaces that tie themselves in the way we tie them. Instead, the new shoes have small motors that control their laces. When you step in them, your feet will hit a sensor（传感器）in the shoes and the motor will automatically tighten the laces.

    But the shoes weren't just designed for lazy people's needs. They could actually give athletes an advantage during competition. They are also useful for people who cannot move their arms or fingers easily.

The no-touch thermometer

    Taking your body temperature usually means putting a thermometer (体温计) in your armpits (腋窝) and staying still for minutes. It may be easy for you, but it's an impossible task for little kids.

    Now, with the new thermometer, users can simply put it 2.5 centimeters from a patient's forechead and press the button, and it can get the reading in two seconds.

    She sat at the picnic table alone. Recess(休息) was in full swing. She remained awkward around her classmates. She seemed unsure of what to do or say, yet I could see her eyes longing for acceptance. Many students had already decided that her friendship would not be worth the energy required to overcome the awkwardness. Others teased her. Most ignored her — except for one.

    Brianna, the class clown, was making the other students laugh, as usual. “Brianna, do you see Molly down there? Would you mind walking down there and inviting her to come up here with the rest of us?”

    Brianna sighed. I could tell she didn't want to sacrifice precious minutes of her own recess to do what I was asking of her, but I also knew her heart. She often thought of others before herself — a rare character for anyone, much less a kid.

    Knowing this choice was hard for her, I pulled out a D-buck, our class currency. Though bribery(行贿) was not the ideal way to handle this situation, I needed her cooperation.

    “Here, I'll pay you for your time.”

    She offered an insincere smile, grasped the green paper, and headed down the hill.

    As the rest of the children screamed and laughed, my eyes locked on Brianna as she neared the picnic table. Molly could be difficult, and I wouldn't have been surprised if she sent Brianna back alone, refusing her invitation. When she encouraged herself to a standing position, I sighed with relief.

    A minute later, 1 felt tap on my shoulder. “Here, Mrs. D.” She handed me the D-buck.

    “ Why?” I asked.

    “I shouldn't keep this.” Her eyes fell to her feet, guilt radiating from her quiet voice. “I don't want Molly to think 1 only went to get her so I could earn a muck. She's my friend.”

    A moment later, they were all laughing again, and who should I see among them, laughing for the first time that week? Molly.

    Kung fu is one of the most popular topics of discussion among foreigners talking about China. As a discipline of kung fu with the largest number of practitioners in China, Tai Chi is gaining popularity worldwide. Tai Chi is sweeping the world thanks to its deep cultural roots and the health benefits coming from practicing it.

    The philosophy of Tai Chi features the concept of yin and yang, which is typical of Confucianism and Taoism. Tai Chi also takes in ideas from traditional Chinese medicine, including anatomy (解剖学) and physiology (生理学). It is a practice that couples hardness with softness, and it is a perfect example of traditional Chinese culture.

    Through lasting practice, learners begin to feel the positive impact (影响) of Tai Chi on their health. Unlike kung fu practices that focus on attacking and defending against enemies, Tai Chi focuses more on shaping good characters and keeping fit. By practicing Tai Chi, people will feel an improvement in their physical and psychological health by promoting a balance between yin and yang within their bodies. This is similar to Western medicine's improving people's self-healing ability and immune system.

    Tai Chi is playing an important role in presenting Chinese culture to the rest of the world, acting like a bridge between China and other countries. Recent years have seen a lot of international communication on Tai Chi. In provinces like Hebei, Henan, Shanxi and Shaanxi, where Tai Chi teaching and learning are particularly active, local governments and non-governmental institutions often organize activities and competitions for learners and fans to attend and participate in. Large sporting events hosted by China such as the Asian Games and Olympics have featured Tai Chi performances or contests. These activities have opened a window for the outside world to know more about Tai Chi, paving the way for its overseas wide spread.

    Today, Tai Chi not only belongs to China, but also to the whole world and to everyone who loves it.

    Can you imagine a world without music? Studies show that public schools across the country are cutting back on music classes to save money. Worse, some schools have never had music classes to begin with. But without them, students' academic growth and emotional health could suffer. In fact, music classes are necessary for all students in schools.

    Recent studies by Brown University have shown that students who received music education classes were better in math and reading skills than those without music classes. Another study by The College Board found that students taking music and art classes got higher points. Students' academic success seems to depend on their taking part in music education.

    Music programs in public schools also help to add to a student's sense of pride and self­confidence. Teens today have too many learning tasks. Besides, they have family problems, self­confidence problems, relationship troubles, and choices about drugs and alcohol. All of these can stop academic success, but music education can help. A study by The Texas Commission on Drug and Alcohol Abuse found that students who took part in school music programs were less likely to turn to drugs. Music programs encourage students to work together to produce an excellent performance.

    Music crosses language, class, cultural and political boundaries (界限). Music allows students from different countries to connect. For example, at a school talent show, a new Japanese student played a piano duet (二重奏) with an American classmate. Although they could not communicate verbally (口头上), they were able to read the music in order to play the duet. Two students from different cultures worked as a team with self­confidence and common purpose through music.

    The gift of music is priceless. We need to be sure to have necessary music classes for all students. The world is losing its music, and putting music into schools is the first step to get it back.

    Some insects, such as butterflies and ladybugs, are quite beautiful. But, did you know that many bugs are also edible and are filled with protein?

    Aletheia Price knows this—and a lot more—about bugs. She also thinks you should try eating some. If you visit the website www.eatbug.com, you will find all kinds of information about edible insects. Most of it was written by Aletheia Price when she was fifteen years old. Aletheia started eating bugs at the age of thirteen. Before long, she found that she really enjoyed some of them. She also became interested in finding out more about which kinds of bugs could be eaten and how to cook them.

    According to Aletheia, there are at least 1,462 kinds of edible insects. (Doesn't that make you wonder who tried all of them and decided they were edible?) Some of her favorite dishes include mealworm chocolate chip cookies, ant tacos(玉米卷), and chocolate-covered crickets(蟋蟀). On her website she has recipes for insect entrees(开胃菜) and some helpful tips. For example, when preparing crickets, it is best to remove their legs before cooking, for the legs tend to get stuck in your teeth. She also offers information for anyone who wants to raise bugs for food.

    Aletheia realizes that eating bugs is not for everyone. But, if you think about it, you have to admit that eating bugs might be a good idea. There are billions and billions of bugs in this world. If we could get used to eating them, we would have plenty of food for everyone.