Next autumn when you see wild geese heading south for the winter flying in a V formation, you might think about what scientists have discovered as to why they fly that way.

    As each bird flaps its wings, it creates uplift(提升) for the bird immediately following. By flying in a V formation the whole group adds at least 71% greater flying range than if each bird flies on its own.

    People who share a common direction and sense of community can get where they are going more quickly and easily because they are traveling on the push of one another.

    When a wild goose falls out of the formation，it suddenly feels the drag and resistance of trying to go alone and quickly tries to get back into the formation to take advantage of the lifting power of the bird in front. When the head goose gets tired，it flies back into the formation and another goose flies to the front. It is wise to take turns doing difficult jobs whether it is people or wild geese flying south.

    Wild geese honk (发出雁叫声) from behind to inspire those up front to keep up their speed. What can we learn from this?

    When a wild goose gets sick or wounded by gunshots，and falls out of the formation，two other geese will fall out with that goose and follow it down to lend help and protection. They will stay with the fallen goose until it is able to fly or until it dies，and only then will they go on with their own or with another formation to catch up with their group.

    It was almost the worst birthday of Abraham Lincoln's life.

    On February 11, 1861 (the day before he turned fifty-two), Lincoln left for Washington to become the nation's sixteenth President. As he left home in Springfield, Illinois, Lincoln handed his son Robert a black oilskin(油布) bag, and told him to keep it carefully. He did not tell Robert what was inside.

    Unknown to his seventeen-year-old son, Lincoln had placed his newly written inaugural speech in the bag. It was to be the most important speech he ever made. And it was his only copy.

When the train arrived in Indianapolis—the first stop on the long journey—Lincoln rode off in a special carriage without his family. Robert walked from the station to the local hotel.

    When Robert arrived at the hotel, he learned that his family's rooms were not ready. So he asked that the bag should be held at the front desk. Then he went off to be with friends.

    On his return, Robert found his father waiting anxiously. Where was the bag? Robert explained that he had checked it at the desk.

An angry Lincoln sped to the hall and leaped over the front desk. He began searching through a huge pile of luggage.

    As puzzled guests looked on, Lincoln dragged from the pile a familiar-looking black bag and opened it, only to find someone else's dirty clothes. It was the wrong bag. Back he went to the pile.

    At last he found the valuable bag and the speech inside. Lincoln handed it to his son and said strictly, “Now you keep it!”

    It was the one and only time, Robert said, that his father had ever lost his temper at him. But with his speech fond and his birthday yet to be celebrated, Abraham Lincoln grew cheerful. As Robert proudly recalled, “Father did not scold(责骂).”

    Some people have the feeling that nothing can be done about their poor reading ability(能力）. They feel hopeless about it. Can you learn to read better or must you agree that nothing can be done about it?

    To be sure, people are different. You cannot to do everything as well as certain other people do. All the students in a class tried out for basketball, some would be very good players; others would be very poor; and many would be in between. But even the very poor players can become much better players if they are guided in the right way, and with plenty of practice. It is the same with reading. Some seem to enjoy reading and to read well without any special help. Others find reading a slow and tiring job. In between, there are all degrees of reading ability.

    Many experiments have shown that just about every poor reader can improve his reading ability. In these experiments, the poor readers were given tests of reading ability. After some of the causes of their poor reading were discovered, they were given special instruction and practice in reading. After a few months, another test of the same kind was given. In nearly all cases, these people had raised their reading scores.

    According to the Associated Press (AP), a Chinese scientist claims he successfully created the world's first genetically-edited babies.

    Chinese researcher He Jiankui, a research professor at China's Southern University of Science and Technology in Shenzhen, said he had edited DNA of twin girls born a few weeks ago. ①

    He's claims were immediately criticized by some scientists as unsafe and unethical. This kind of gene editing is forbidden in the United States and many other countries. ②Such changes to a person's DNA can pass to future generations and risk harming other genes.

    In interviews, He Jiankui defended his work. He said he had performed the gene editing to help protect the babies from future infection of HIV, the virus responsible for the disease AIDS. He said the process had “worked safely” and the twin girls were “as healthy as any other babies.” He told the AP he felt a strong responsibility “not just to make a first, but also to make an example” for future research. “Society will decide what to do next,” he said.

    When He's claims became public, the university made a statement saying his work had “seriously went against academic ethics and standards.” University officials said they had no knowledge of his research and had looked into the case. ③

    China's National Health Commission was “highly concerned” about the claims and ordered local health officials “to immediately look into” He's activity. “We have to be responsible for the people's health and will act on this according to the law,” the commission said.

    Scientists discovered in recent years a new way to edit genes that make up a person's DNA throughout the body. The tool, called CRISPR-cas9, makes it possible to change DNA to supply a needed gene or take one away that is causing problems. So far the tool has only been used on adults to treat deadly diseases, and the changes only affected that person.

    ④Kiran Musunuru, a scientist from University of Pennsylvania, told the AP that if such an experiment had been carried out on human beings, it could not be “morally or ethically reasonable.” Julian Savulescu, a medical ethics expert at Britain's University of Oxford, agreed. “If true, this experiment may cause disasters,” he told Reuters.

    However, one well-known geneticist, Harvard University's George Church, defended the attempt to edit genes to prevent infections of HIV. He told the AP that since HIV is “a major and growing public health threat” he finds such experiments “valuable.”

    A Chinese scientist's attempt to produce the world's first gene-edited babies who are immune to HIV has caused floods concern.

    In an online video posted on Monday, He Jiankui, a biological researcher, announced that a pair of twin baby girls, Lulu and Nana, was born healthy a few weeks ago with genetic editing technology that can prevent them from being infected with HIV.

    He, who was believed to be in Hong Kong on Monday to attend the Second International Summit on Human Genome Editing, could not be reached for comment. But his announcement sparked a heated argument concarning medical ethics（伦理）and effectiveness.

    The Shenzhen Health and Family Planning Commission said on Monday evening that it had not received any ethical assessment application for the study, which is required as a prior condition for such experiments.

    More than 120 scholars from universities and institutes with high status from China and abroad,such as Tsinghua University and the Massachusetts Institute of Technology (MIT),strongly condemned the research in a signed statement, saying the “research” lacks effective ethics inspection, and it amounts to human experimentation,which is “crazy”.

    In the statement, published on Sina Weibo, the scientists said any attempt to make changes to human embryos with genetic editing and give birth to such babies involves high risk as an inevitable part, due to inaccuracies in existing genetic editing technologies.

    “Scientists all over the world dare not make such attempts due to the huge risks and more importantly, ethics. The government must make quick legal moves to strictly supervise（监督）such research. The Pandora's Box has been opened, and we may still have a chance of closing it before it is too late,”the statement said.

    Tsui Lap-chee, president of the Academy of Sciences of Hong Kong, said a lot of issues may occur in gene editing. If one gene is edited, it will affect others that interact with it. And the whole genome, a collection of genes, may also be affected.

    In 1800, only three percent of the world's population lived in cities. Only one city — Beijing — had a population of over a million. Most people lived in rural areas, and never saw a city in their lives. In 1900, just a hundred years later, roughly 150 million people lived in cities, and the world's ten largest cities all had populations exceeding one million. By 2000, the number of city dwellers exceeded three billion; and in 2008, the world's population crossed a tipping point — more than half of the people on Earth lived in cities. By 2050, that could increase to over two-thirds. Clearly, humans have become an urban species.

    In the 19th and early 20th centuries, many people viewed cities negatively — crowded, dirty environments full of disease and crime. They feared that as cities got bigger, living conditions would worsen. In recent decades, however, attitudes have changed. Many experts now think urbanization (城市化) is good news, offering solutions to the problems of Earth's growing population.

    Harvard economist Edward Glaeser, author of The Victory of the Cir, is one such person. Glaeser argues that cities are very productive because "the absence of space between people" reduces the cost of transporting goods, people, and ideas. While the flow of goods has always been important to cities, what is most important today is the flow of ideas. Successful cities enable people to learn from each other easily, and attract and reward smart people with higher wages.

    Another urbanization supporter is environmentalist Stewart Brand. Brand believes cities help the environment because they allow haft of the world's population to live on about four percent of the land. This leaves more space for open country, such as farmland. City dwellers also have less impact per person on the environment than people in the countryside. Their roads, sewers, and power lines need fewer resources to build and operate. City apartments require less energy to heat, cool, and light. Most importantly, people in cities drive less so they produce fewer greenhouse gases per person.

    So it's a mistake to see urbanization as evil; it's a natural part of development  The challenge is how to manage the growth.