Houses fall down. Trees fall over. Large holes form in the ground. Could Alaska be sinking? That's what some villagers in Alaska have been asking themselves recently and scientists think they know why. Warmer temperatures may be causing Alaska's frozen ground to thaw (解冻).

    About 85 percent of Alaska's land surface has permafrost (永久冻结带). Permafrost supports the ground above it—including trees, houses, and roads. But why is the permafrost thawing?

    Some scientists say that human-caused pollution is leading to global warming. And most scientists agree that Alaska has been getting warmer. They say that the warmer temperature is causing permafrost to thaw in some areas. The thawing permafrost can cause problems for people, plants, and animals.

    The collapsing (倒塌) is a problem in the villages in Alaska which are built on permafrost, and some of them may have to move to safer ground, where there is no permafrost.

    The Alaskan town of Glennallen saw its old post office collapse. And, according to James Walters, a permafrost expert at the University of Northern Iowa, house-moving companies have been very busy.

    “Melting permafrost can also destroy trees and forests,” Walters said. “When holes in the ground form, trees fall into them and die. This could turn a forest into a swamp (沼泽), and animals which need the forests will have to move elsewhere.”

    “The melting could cause severe problems.” Walters says, “This could take hundreds of years, but in the end Alaska will look quite different from what it looks like now.”

    One day, at night, a thief tried crawling (爬行) into a farmer couple's house. In the house lived many mice. The woman in the moonlight saw a mouse crawl into the house. “Look! In comes one.” She said to the man in the house. The thief was so frightened that he hurriedly crawled out of the house and said to the one waiting outside, “She found me when I was just in.” But the thief outside didn't believe him, so he said, “Let us two try to crawl into the house together.” At that time two mice happened to crawl into the house, too. The woman saw the mice and shouted, “In come two, catch them!” The two thieves were terribly frightened. The man in the house said, “You saw them come in but where are they? I will catch them tonight” The two thieves started running away at once.

    The two thieves wanted to make it clear whether they had been found or not the night before. The next day they acted as men selling sweet potatoes and came before the house. The man and the woman were working in their fields. The rein (缰绳) broke and the woman came home for a new one. She saw two men selling sweet potatoes and wanted to buy some. She picked out two which looked like mice. At the time the man couldn't wait for her any longer in the fields and he ran back from the fields to hurry her up. The woman showed the sweet potatoes to the man and said, “How they look like the two of last night!” The man said, “I asked you to fetch a rein, why don't you hurry for it?” The two thieves ran away quickly without their sweet potatoes.

    A young woman sits alone in café sipping tea and reading a book. She pauses briefly to write in a nearby notepad before showing her words to a passing café waiter: “Where are the toilets please?” This is a familiar scene in Tokyo's so-called “silent cafes”, where customers are not allowed to speak, and only communicate by writing in notepads.

    The concept rises by a desire to be alone among young Japanese, a situation brought by economic uncertainly, a shift in traditional family support structures and the growing social isolation. The phenomenon is not limited to coffee shops but covers everything from silent discos, where participants dance alone wearing wireless headphones connected to the DJ, to products such as small desk tents designed for conversation-free privacy in the office. One Kyoto company even offers single women the opportunity to have a “one woman wedding” – a full bridal affair, complete with white dress and ceremony, and the only thing missing is the groom. The trend has its own media expression – “botchi-zoku”, referring to individuals who consciously choose to do things completely on their own.

    One recent weekday afternoon, Chihiro Higashikokubaru, a 23-year-old nurse, travelled 90 minutes from her home, to Tokyo on her day off in order to enjoy some solo time. Speaking quietly at the entrance of the café, Miss Higashikokubaru said: “I heard about this place via Twitter and I like the idea of coming here. I work as a nurse and it's always very busy. There are very few quiet places in Tokyo, and it's a big busy city. I just want to come and sit somewhere quietly on my own. I'm going to drink a cup of tea and maybe do some drawings. I like the idea of a quiet, calm atmosphere.”

    The desire to be isolated is not a new concept in Japan, home to an estimated 3.6 million “hikikomori” – a more extreme example of social recluses（隐士）who withdraw completely from society.

    No student of a foreign language needs to be told that grammar is complex. By changing the order of the words and by adding a range of auxiliary verbs (助动词) and suffixes (后缀), we can turn a statement into a question, state whether an action has taken place or is soon to take place, and perform many other word tricks to convey different meanings. However, the question which many language experts can't understand and explain is—who created grammar?

    Some recent languages evolved due to the Atlantic slave trade. Since the slaves didn't know each other's languages, they developed a make-shift language called a pidgin. Pidgins are strings of words copied from the language of the landowners. They have little in the way of grammar, and speakers need to use too many words to make their meaning understood. Interestingly, however, all it takes for a pidgin to become a complex language is for a group of children to be exposed to it at the time when they learn their mother tongue. Slave children didn't simply copy the strings of words used by their elders. They adapted their words to create an expressive language. In this way complex grammar systems which come from pidgins were invented.

    Further evidence can be seen in studying sign languages for the deaf. Sign languages are not simply a group of gestures; they use the same grammatical machinery that is found in spoken languages. The creation of one such language was documented quite recently in Nicaragua. Previously, although deaf children were taught speech and lip reading in the classrooms, in the playgrounds they began to invent their own sign system, using the gestures they used at home. It was basically a pidgin and there was no consistent grammar. However, a new system was born when children who joined the school later developed a quite different sign language. It was based on the signs of the older children, but it was shorter and easier to understand, and it had a large range of special use of grammar to clarify the meaning. What's more, they all used the signs in the same way. So the original pidgin was greatly improved.

    Most experts believe that many of the languages were pidgins at first. They were initially used in different groups of people without standardization and gradually evolved into a widely accepted system. The English past tense—“ed” ending— may have evolved from the verb “do”. “It ended” may once have been “It end-did”. It seems that children have grammatical machinery in their brains. Their minds can serve to create logical and complex structures, even when there is no grammar present for them to copy.

    When people see machines that respond like humans, or computers that perform amazing feats of strategy, they sometimes joke about a future in which humanity will need to accept robot overlords. But buried in the joke is a seed of unease. Science fiction writing and popular movies have shown us about artificial intelligence (AI) that exceeds the expectations of its creators and escapes their control, eventually outcompeting and enslaving humans or targeting them for extinction(灭绝).

    Even in the real word, not everyone is ready to welcome AI with open arms. In recent years, as computer scientists have pushed the boundaries of what AI can accomplish, leading figures in technology and science have warmed about the frightening dangers that artificial intelligence may pose to humanity, even suggesting that AI capabilities could destroy the human race.

    But why are people so frightened about the idea of AI?

    Elon Musk is one of the famous voices that have raised red flags about AI, In July 2017. Musk told attendees at a meeting of the National Governors Association, I have exposured to the very cutting-edge Al, and I think people should be really concerned about it. I keep sounding the alarm bell. But until people see robots going down the street killing people, they don't know how to react, because it seems so impossible."

    Earlier, in 2014, Musk had labeled AI "our biggest existential threat," and in August 2017, he declared that humanity faced a greater risk from AI than the terrorists. Physicist Stephen Hawking, who died on March14, also expressed concerns about AI, telling the BBC in 2014 that "the development of full artificial intelligence could spell the end of the human race.

    Feeding birds is a popular way to watch wildlife. But experts say it might put wild birds at risk.

    Feeding birds is not necessary for their survival except in extreme weather conditions. Feeders(喂食器)can definitely help birds get through that kind of weather. But most birds eat insects and show little interest in bird feeders. For those birds, we can grow native plants in a natural environment. Birds which are fond of eating seeds will be more likely to come to feeders if there is some cover nearby. This lets them feed and then fly to protective areas, such as in trees.

    The most common mistake people make with their bird feeders is that they put feeders in places where birds are easily frightened by passers-by, risk being hurt by cats, or risk flying into windows.

    So set up a bird feeder at least one meter away from a window. That way, if a bird gets frightened, it won't get killed when it hits the glass. Owners of cats should keep them inside home so they can't hurt the birds.

    Some birds are more aggressive at feeders. They eat a lot and do not leave much food for other birds. A solution is to put the food in more than one place by using different kinds of seeds or fruits. This can also increase the number and diversity of birds in your neighborhood. But don't feed wild birds anything salty, like potato chips, or food that could choke them, like bread.

    Pay attention to food quality and freshness. Unprotected food left too long in feeders will turn moldy(发霉), which can kill wildlife.

    Another word of advice: Always provide a supply of clean water for birds, but use care when looking for the right birdbath. If the birdbaths are too deep for birds, putting a few large stones in the water can give the birds a place to sit.