Since 2008, hunters have illegally killed more than 3000 rhinos in South Africa. The International Union for Conservation of Nature warns that rhinos may die out by 2026. People who hunt and kill illegally are called poachers. The most effective way to watch for and prevent illegal hunting is from the air. However, piloted flights are too costly. Fortunately, some Spanish college students have invented a drone (无人机) that can observe more places than a plane.

    Arnau Garcia is an aeronautical (航空学的) engineering student at the Polytechnic Institute of Catalonia, in Spain. He says observers from the air have trouble finding poachers when they hide under the trees. Mr. Garcia and other students have worked with the drone manufacturer HEMAV to help find the hidden poachers. They make it by using the thermal camera, which is especially sensitive to body heat. Even when the poachers keep still, it can also keep track of them.

    The drone can fly in the wind up to 55 kilometers per hour. It has an autopilot system, so it memorizes the flight path. The drone also has a microphone, a video camera and a GPS system. These permit it to report accurately where a picture is taken. After each flight, the drone can bring back detailed information about where rhinos are found, the conditions of water and plants in the area, and the positions of suspected poachers.

    Experts say the drone can fly as far as 70 kilometers from the base. It means that it could quickly observe large areas for poachers. However, the same search operation would take days for human observers. Thanks to the drone, many poachers have been caught and the number of rhinos is on the increase. In addition, HEMAV has received an increasing number of orders for the drone. Even South African national park officials attempt to fill the air with drones.

    The US will have a new president this fall. Voters will decide between the Democratic candidate (候选人), Hillary Clinton, and Donald Trump of the Republicans.

    But the voting is not a must for each person in the US. So quite a lot of people choose not to vote, especially the young generation. According to Fox News, one-in-five young voters between the ages of 18 and 35 said clearly that they wouldn't vote for either of the two candidates. Just 12 percent of voters aged 35-54, and only nine percent of voters aged 55 and older said the same thing.

    This is not only because young people don't like Clinton or Trump, according to the Fortune magazine. The truth is that they are traditionally less likely to vote than their parents.

    “Young people are not at an age in their life when they think politics or government has anything to do with them,” said Rodd Freitag, a political science professor at the University of Wisconsin-Eau Claire, US. “But for the older age groups, they have a home, they pay taxes (税), they care about schools and the community.”

    Many believe that the civic (公民的) education of an American youth is another reason why they don't vote.

    Students usually just do community services like cleaning the neighborhoods. This means they haven't learned how to link real life problems to politics through voting, according to Christopher Beem, a politics professor at the Pennsylvania State University.

    He said the country needs to help young people learn how to take part in politics and get them to see that they can make a difference.

    A Samoan airline says that it is the world's first carrier to charge passengers by their weight. Samoa Air, which opened in 2012, asks passengers to give their personal weight during booking, which is then charged according to the length of a flight. The customers will also be weighed just before they board the plane.

    "It is believed that all people throughout the world are the same size," Samoa Air CEO Chris Langton said. "Airplanes always run on weight, not seats."

    "There is no doubt in my mind that this is the concept of the future. This is the fairest way of your travelling with your family or yourself."

    Though the airline introduced the plan last November, it caught people's attention last week when the carrier began international flights to neighboring American Samoa.

    Almost at the same time, a Norwegian economist, Bharat Bhatta, published a report suggesting that airlines should charge obese passengers more.

    The Pacific Islands contain some of the world's most common countries for obesity, many ranking in the top 10, according to the World Health Organization (WHO). Samoa is ranked number four, with 59.6 percent of the population considered obese, said the most recent WHO report.

    According to Samoa Air's latest schedule, the airline charges up to $0.57 per kg for flights in Samoa and $1.03 per kg for its only international flight to American Samoa, around 250 miles.

    Children under 12 are charged 75 percent of the adult rate, with fares also based on weight. Any overweight baggage is calculated at the same rate as the passenger's personal weight.

    The plan could actually prove cheaper in some cases, such as for families travelling with small children, and Langton said customer reaction has mainly been "amazingly positive".

    The idea of charging passengers by weight has been hotly discussed before, and in the US some airlines require those who do not fit into a seat comfortably to buy a second seat.

    Play allows children to use their creativity while developing their imagination and physical, cognitive（认知的）, and emotional strength. Play is important to healthy brain development. Play allows children to create and explore a world they can master, conquering their fears while practicing adult roles. Undirected play allows children to learn how to work in groups, to share, to negotiate, and to resolve conflicts.

    Ideally, much of play involves adults, but when play is controlled by adults, children acquiesce（顺从）to adult rules and concerns and lose some of the benefits play offers them, particularly in developing creativity, leadership, and group skills. In contrast to passive entertainment, play builds active, healthy bodies. In fact, it has been suggested that encouraging unstructured play may be an exceptional way to increase physical activity levels in children, which is one important strategy in the resolution of the obesity problem.

    Children's development is critically influenced by appropriate, affective relationships with loving and consistent caregivers as they relate to children through play. When parents observe their children in play or join with them in child-driven play, they are given a unique opportunity to see the world from their children's vantage point as the child navigates a world perfectly created just to fit his or her needs. The interactions that occur through play tell children that parents are fully paying attention to them and help to build enduring relationships. Parents who have the opportunity to look at their children's world learn to communicate more effectively with their children aid are given another setting to offer guidance. Less verbal children may be able to express their views, giving their parents an opportunity to gain a fuller understanding of their perspective. Quite simply, play offers parents a wonderful opportunity to engage fully with their children.

    Play is essential to the academic environment. It ensures that the school setting attends to the social and emotional development of children as well as their cognitive development. It has been shown to help children adjust to the school setting and even to strengthen children's learning willingness. Social-emotional learning is best integrated（融合）with academic learning; it is concerning if some of the forces that enhance children's ability to learn are improved at the expense of others. Play and unscheduled time that allow for peer interactions are important components of social-emotional learning.

    Once when I was facing a decision that involved high risk, I went to a friend. He looked at me for a moment, and then wrote a sentence containing the best advice I've ever had: Be bold and brave and mighty (强大的) forces will come to your help.

    Those words made me see clearly that when I had fallen short in the past, it was seldom because I had tried and failed. It was usually because I had let fear of failure stop me from trying at all. On the other hand, whenever I had jumped into deep water, forced by courage or circumstance (环境), I had always been able to swim until I got my feet on the ground again.

    Boldness means a decision to bite (咬) off more than you can eat. And there is nothing mysterious about the mighty forces. They are inner powers we have: energy, skill, sound judgment, creative ideas––even physical strength greater than most of us realize.

    Admittedly, those mighty forces are spiritual ones. But they are more important than physical ones. A college classmate of mine, Tim, was an excellent football player, even though he weighed much less than the average player. “In one game I suddenly found myself facing a huge player, who had nothing but me between him and our goal line,” said Tim. “I was so frightened that I closed my eyes and crazily threw myself at that guy like a bullet (子弹) ––and stopped him cold.”

Boldness—a willingness to get yourself to the extreme—is not one that can be gained overnight. But it can be taught to children and developed in adults. Confidence builds up. Surely, there will be setbacks (挫折) and disappointments in life; boldness in itself is no guarantee (保证) of success. But the person who tries to do something and fails is a lot better off than the person who tries to do nothing and succeeds.

    So, always try to live a little bit beyond your abilities — and you'll find your abilities are greater than you ever dreamed.

    If we want to find out what kind of technology people used in the past, we normally have to rely on archaeologists to find ruined buildings and parts of tools or instruments or machines. Archaeologists then try to reconstruct, sometimes with the help of computer technology, what these ancient buildings and objects must have looked like, and how they might have been made. Sometimes historians are lucky and find an ancient document with a written description of these ancient buildings and objects.

    We can understand, then, why Chinese historians were so excited when they found cave paintings which show ancient science. They found these paintings in the world-renowned Mogao Grottoes of Dunhuang City, in Northwest China's Gansu Province. There are 500 man-made caves and they have survived for at least 1,600 years. Almost all of these caves have paintings on their ceilings or walls and they date from the 4th to 14th centuries. Wang Jinyu is an expert on these cave paintings (also called frescoes) and he says: "We discovered frescoes containing scientific and technological content in almost all of the caves which have frescoes." What is remarkable about these cave paintings according to the Xinhua News Agency is that they provide evidence of "scientific and technological inventions by ancient Chinese in maths, physics, chemistry, astronomy, geography, agronomy, architecture, textiles, traffic and transportation, arms and military equipment and medical sciences".

    Among the discoveries experts have made are cave paintings showing ancient techniques of pottery making and wine production and paintings showing ancient weaving machines and then toothbrushes! The paintings also give some evidence of the lifestyle at the time with, for example, pictures of people boiling milk over 1,000 years ago. Experts believe that there is more evidence to be found, but even now the caves are a wonderful natural museum. If the walls and ceilings of the caves were all put together they would form a tapestry 20 kilometers long and 2 meters high!

    It won't be possible to travel back in time-that only happens in films-but visiting these caves would be the nearest experience you could get to travelling back in time.