“Community” is not a concept that is easy to define (定义) . In this essay I will examine what turns individuals into a community, and discuss some different types. I will also look at what all communities have in common, the benefits they offer and draw conclusions about their increasing importance.

    The word “community” may make you think of traditional communities in the developing world, where large families live together. We may also imagine the neighbours as people who are happy to help out whenever it is needed. The stereotpical(老套的) view is that of a village, where people have little but can feel very rich because everyone takes responsibility for the welfare of the others.

    On the other hand, there are other types of communities: ultramodern(超现代的) ones, where the community members are unlikely to have actually met each other. These are online communities, where people blog or chat about particular issues that are important to them. They come across others on websites and may develop a relationship there with like-minded people, discussing the same topics. The view is often that these are artificial connections between people who are, in effect, still isolated(孤立的) strangers.

    In reality, the connections are real. Moreover, there are many types of communities in between these extremes: people who join clubs, who sign up with voluntary, political or other organizations, or who take part in group discussions in their local area. They may be campaigning about issues or simply getting together for companionship and support.

    Human beings are social by nature, so it should not be a surprise that we organize ourselves in groups. However, there is more going on: these groups provide something that we cannot achieve on our own. The main benefit of being part of a larger group is strength in numbers. For example, we can access and share more information, we can take part in team sports, we can complain and campaign more effectively and even if we are just having a chat, online or in person, we can feel supported in whatever we do.

    Whatever forms communities take, what defines them is the sense of identity and safety that they provide for their members: the knowledge that there are people who we have something in common with and who can be relied on when we need each other.

    It was a dark and stormy night. I was about to go to bed when I heard a tapping sound on my window.

"Who's there?" I shouted. Suddenly there was a flash of lightning; I saw a face at the window. It looked like an alien（外星人）— an alien that I had seen on the television show, "the X files".

    I felt very scared. I ran to my bed and pulled my blanket over my head. I started to shout for my parents but there was no reply. Then I remembered that they were at a fancy dress party.

    I looked out of my blanket but it was too dark to see anything. Then I heard footsteps. They were getting louder and louder. I ran to my drawer to take out my camera and started to take pictures in the direction of the window. Soon the footsteps died off.

The grandfather clock struck. It was 12 midnight. I went back to my bed and tried to sleep. But I could not sleep. I felt too frightened. I sat up, and my mind was full of thoughts. Time passed — finally, I fell asleep.

    I woke up only after eight and decided to find out what it had been. I found some footprints outside my bedroom window. I measured them with a ruler and found them to be exactly the same size as my father's shoes. I then went to town to get the film developed. I didn't realize that I did not use the flash until I saw the black photos.

    When I reached home, I told my father the whole incident and he started to laugh. I started laughing too when he told me that he had dressed up as an alien for the party. Today, I am still amused to think I was so afraid of my own father.

    The United States Congress is responsible for making and approving federal laws—rules that everyone in the country must follow. But exactly how do those laws get made? The process is not easy, and it takes a long time.

    A law begins when someone puts forward an idea. The idea can come from anyone, but it has to get to a U. S. lawmaker who wants it to become legislation. In time, the idea is further developed into a written proposal, called a bill.

    Then, a member of Congress officially proposes the bill. After the bill is introduced, it is sent to a small group of lawmakers, called a "committee". Sometimes committee members seek more information about the proposal by holding hearings. Sometimes the committee changes the bill. Sometimes it decides not to take any action. In that case, we say lawmakers "table" the bill, or let it "die in committee".

    But now and then, the bill is offered to lawmakers not on the committee. Those lawmakers debate the bill further. They might change the bill again. Finally, the full House or Senate votes on the bill. If it does not earn the majority of votes, the bill does not advance.

    Finally, the agreed-upon bill is sent to the president. If the president signs it, the bill becomes a law. If the president does nothing and Congress is officially meeting, the bill becomes a law. But if the president does nothing and Congress is not in session, the bill does not pass. Or the president can officially reject the bill. If that happens, the bill is not stopped. Instead, it is returned to both the Senate and the House. If two-thirds of the senators and two-thirds of the House members approve the bill once again, even with the president objecting, they turn the bill into a law.

    A group of scientists is gathering today in the U. K. to discuss a thick piece of ice that's cracking in Antarctica, which is of the size of Delaware.

    The ice shelf is called Larsen C, and it now has a 90-mile crack running through it. The big rift (裂缝) is slicing the ice shelf from top to bottom. But this is not just another sad climate change story. It's more complicated. "A lot of things are going on deep inside the ice," says Adrian Luckman, a glaciologist.

    Luckman says climate change is certainly influencing this region. Larsen C used to have two neighbors to the north, Larsen A and Larsen B. As the air and water warmed, those ice shelves started melting and then disappeared in 1995 and 2002. But the crack in Larsen C seems to have happened on its own, for different reasons.

    Larsen C has many cracks. All ice shelves do. This particular crack has been around since at least the 1960s. The unusual part is that in 2014, this crack — and only this crack — started growing quickly. Why?

    "Well, that is a little bit of a mystery and that's why it drew itself to our attention," says Luckman. One puzzling aspect is how it managed to cut through areas of softer ice that bind (连接) the ice from neighboring glaciers into one giant sheet. Starting in 2014, that soft ice did very little to slow down this rift.

    Scientists are split on how important this crack is for the stability of the whole ice shelf. Some say if this giant section breaks off, it won't make a difference. Others disagree.

    "Ice shelves are the gates of Antarctica in a way, and the gatekeepers of Antarctica. The ice shelves are already floating, so if they fall apart it does not immediately affect sea levels. It's what they hold back -water from all the inland glaciers — that could be problematic. If all the water packed in those glaciers made their way to the sea, it could significantly raise global sea levels," says Ala Khazendar, a geophysicist.

    We talk continuously about how to make children more "resilient (有恢复力的)"，but whatever we're doing, it's not working. Rates of anxiety disorders and depression are rising rapidly among teenagers. What are we doing wrong?

    Nassim Taleb invented the word "antifragile" and used it to describe a small but very important class of systems that gain from shocks, challenges, and disorder. The immune (免疫的) system is one of them: it requires exposure to certain kinds of bacteria and potential allergens (过敏原) in childhood in order to develop to its full ability.

    Children's social and emotional abilities are as antifragile as their immune systems. If we overprotect kids and keep them "safe" from unpleasant social situations and negative emotions, we deprive (剥夺) them of the challenges and opportunities for self-building they need to grow strong. Such children are likely to suffer more when exposed later to other unpleasant but ordinary life events, such as teasing and social rejection.

    It's not the kids' fault. In the UK, as in the US, parents became much more fearful in the1980s and 1990s as cable TV and later the Internet exposed everyone, more and more, to those rare occurrences of crimes and accidents that now occur less and less. Outdoor play and independent mobility went down; screen time and adult-monitored activities went up.

    Yet free play in which kids work out their own rules of engagement, take small risks, and learn to master small dangers turns out to be vital for the development of adult social and even physical competence. Depriving them of free play prevents their social-emotional growth. Norwegian play researchers Ellen Sandseter and Leif Kennair warned: "We may observe an increased anxiety or mental disorders in society if children are forbidden from participating in age adequate risky play."

    They wrote those words in 2011. Over the following few years, their prediction came true. Kids born after 1994 are suffering from much higher rates of anxiety disorders and depression than did the previous generation. Besides, there is also a rise in the rate at which teenage girls are admitted to hospital for deliberately harming themselves.

    What can we do to change these trends? How can we raise kids strong enough to handle the ordinary and extraordinary challenges of life? We can't guarantee that giving primary school children more independence today will bring down the rate of teenage suicide tomorrow. The links between childhood overprotection and teenage mental illness are suggestive but not clear-cut. Yet there are good reasons to suspect that by depriving our naturally antifragile kids of the wide range of experiences they need to become strong, we are systematically preventing their growth. We should let go­and let them grow.

    Nowadays six Amazon Scout delivery robots rolled out in a pilot program in Snohomish County, Wash. The robots carry meals, groceries and packages to homes and offices in this region just north of Seattle. They have appeared on the sidewalks of London, Beijing and other cities and communities worldwide. These machines must overcome pedestrian legs, naughty dogs and broken pavement, which raises some questions.

    These services are gaining attraction as a growing number of city residents expect immediate or scheduled delivery for just about everything. Between 2017 and 2018 online retail sales in the U.S. increased by 16 percent. On the final step of all these deliveries, called the last mile, humans on bicycles, motorized scooters (电动车) or large delivery trucks typically deliver packages. All the vehicles compete for space on busy urban streets. "Deliveries are trending upwards in all crowded city centers, and if city and state leaders don't start thinking about creative solutions like robot deliveries, we can expect even worse traffic jams," says Paul Mackie, director of a transportation policy research center in Arlington.

    A study by this center found 73 percent of delivery vehicles in Arlington were parked outside of authorized areas, often blocking bike lanes and crosswalks. By moving the last step of deliveries from the road to the sidewalk, cities could reduce traffic jams and solve the parking problem entirely, Mackie says.

    Companies such as Amazon are not developing this delivery technology simply to clear up urban traffic. Self-driving vehicles and sidewalk robots could cut down last-mile delivery costs in cities by as much as 40 percent, according to a 2018 report by a consultancy firm. A delivery robot can cost thousands of dollars to manufacture, and most currently require human management and conservation. But in the long run companies that use autonomous delivery vehicles in the next several years could end up saving billions of dollars, the report stated.