I had the honor of being elected chief of my tribe(部落). With the title came great responsibility. It was my job to make peace with the Maori Tamaki tribe, whose village we visited. Their warriors leapt from a canoe and faced us down with fierce growls, bulging eyes and much swishing of sticks. They laid a palm frond on the ground and, as head honcho, I was compelled to accept this peace offering by picking it up, then touching noses with their chief. “Kia ora”, he said, welcoming us into the woodland home of his people.

    My “tribe” was my New Zealand tour group, who had forced me into being their leader. We'd been warned that the ceremony was a serious occasion and that to laugh or even smile would be considered rude to the Tamaki. After that it was non-stop fun as they showed their ancient customs and I received instruction in performing the haka, the war dance by the All Blacks rugby team.

    Then they pulled our dinner of lamb, beef and vegetables out of the ground. It had been slow-cooked in the heat that simmers just below the surface in the geothermal(地热的) area of North Island, a Maori tradition known as a hangi that goes back an extremely long period of time.

    Obviously, this form of it is put on for tourists but it was hugely enjoyable. The journey back to the hotel was alone worth the effort, our hilarious Maori elder driver being deserving of his own television show. “The wheels on the bus go round and round,” he got us singing, while he circuited(绕……环行) a roundabout three times.

    A couple of days from the end of my trip, there was still something missing, a New Zealand icon I yearned to see to make my grand tour complete. Riding over a hill, there it was – Aotearoa. The Maori name for New Zealand translates as “Land of the long white cloud”. Can I say “Kia ora, Aotearoa?” You bet I can.

    There are two main types of non­verbal communication. Body language is the first. Body language is body movements that depend on a person's attitude or feelings. Body language includes the way people walk，how they stand，and their facial features. In other words，any kind of meaning is shown by a person's attitude or body movements. For example，when a boy is sad he may drop his head and walk slowly. Or，if a girl is happy，she might run and jump or stand up straight and put her hands in the air. People don't have to say anything to show how they feel about things. The colour of people's skin may even show how they feel. For example，if people with light coloured skin get embarrassed，their skin may turn red，or if they are worried，they might get pale. Body language can be voluntary(主动的) or involuntary(无意识的)．An interesting fact is that blind children will smile when happy even though they have never seen a smile.

    The next main type of non­verbal communication is gestures. Gestures are communications like facial expressions，hand signals，eye gazing，and body postures. Examples include smiles，handshakes，waving，and raising certain fingers to say something. For instance，if you saw a friend at a noisy carnival，you might smile and wave at your friend. You might also point at the Ferris wheel if you wanted to meet your friend there. You could do all of these things without saying a word. Another great example is in baseball when the catcher signals to the pitcher the kind of pitch to use for the batter that is up.

    situation in which they had to observe two circles on a screen.

    At first glance,price-comparison websites are an example of capitalism at its best.But it has caused fierce competition on price and eviscerated profits.Towers Watson,a consultancy,said that "unnecessary" price competition following the rise of comparison sites in Britain had cost insurers ￡1 billion a year.

    Consumers should celebrate that;the firms' losses are their gains.But there is a catch.Comparison sites introduce a new layer of costs,including their own advertising campaigns.In theory,competition in the market for comparison sites ought to keep those costs down.But David Ronayne of Warwick University argues that consumers often lose out from comparison sites.They earn a commission for each shopper who uses them for consumption such as buying insurance.That referral（委托）cost is included in the price the consumer ends up paying.If the increased costs outweigh the saving the comparison enables,consumers end up worse off.

    These worries are not just theoretical.In 2014,Britain's competition regulator found that many comparison sites were using their contracts with retailers（零售商）to ban them from offering lower prices elsewhere.That weakened rivals' incentive（对手的动机）to cut fees,because prices on their site could not fall.By keeping prices similar,the contracts also reduced the incentive for consumers to search on multiple sites,thus helping sites retain their users.

    Weaker incentives to lower commissions mean weaker incentives to lower costs,too.That might explain why comparison websites advertise so heavily,and sometimes offer free gifts to those who use them.In a recent paper,Ben Edelman of Harvard Business School and Julian Wright of the National University of Singapore argue that when a site knows that the prices merchants provide through it will always be the lowest available,it increases investment in attracting customers,safe in the knowledge that the merchants and at last consumers will bear the cost.

    Is there any way to ensure the market for price comparison is competitive?Asking consumers to check multiple websites defeats the point of using them.One solution is to have only one site,but regulate it as a public utility（功用）. Alternatively,the governments could run the site itself.But creating good search and comparison sites may be too hard for them.It is much better to acknowledge that consumers will always have to do some comparison themselves to "keep the system honest".

    Websites that compare the comparison sites can help,although it is easy to see how they could fall prey to the same problems.Any firm with captive users（被动用户）,be it a comparison site a search engine,or a social-media platform,can charge a high price for access to the eyes of its customers.For all their innovation,Internet middlemen are not unlike supermarkets.Shoppers would never imagine that a single store had the lowest price for all the items they need.

    "IF ALIENS are so likely, why have we never seen any？" That is the Fermi Paradox（悖论） named after Enrico Fermi, a physicist who posed it in 1950.

    Fermi's argument ran as follows. The laws of nature supported the appearance of intelligent life on Earth. Those laws are the same throughout the universe. The universe contains zillions of stars and planets. So, even if life is unlikely to arise on any particular astronomical body, the sheer abundance of creation suggests the night sky should be full of alien civilizations. Fermi wondered why aliens had never visited the earth. Today, the paradox is more usually cast in light of the inability of radio﹣telescope searches to detect the equivalent（相等的） of the radio waves that leak from Earth into the universe, and have done for the past century.

    Thinking up answers to this apparent contradiction has become something of a scientific parlour（客厅）game. Perhaps life is really very unlikely. Perhaps the priests are right: human beings were put on Earth by some creator God for His own unknown purposes, and the rest of the universe is merely background scenery. Perhaps there are plenty of aliens, but they have decided that discretion is a safer bet than gathering together. Or perhaps galactic（银河的） society avoids communicating with Earth specifically. One frightening idea is that technological civilizations destroy themselves before they can make their presence known. They might blow themselves up after inventing nuclear weapons （an invention that, on Earth, Fermi had been part of）, or cook themselves to death by over﹣burning fossil fuels.

    In a paper published last month on arXiv, an online repository（文献库） , a group of three astronomers at Pennsylvania State University have analyzed the history of alien hunting and come to a different conclusion. In effect, they reject one of the paradox's main theory. Astronomers have seen no sign of aliens, argue Jason Wright and his colleagues, because they have not been looking hard enough.

    A telescope, called Gaia, is being designed by astronomers in Europe, and it couldn't be more different from Pan-STARRS, which is another telescope being designed. While Pan-STARRS will be looking for asteroids (小行星) and comets headed for Earth, Gaia will be looking at our entire galaxy (银河系).

    Gaia is designed to draw a map of the Milky Way, our home galaxy. Just as a map of your town gives you a picture of where things are located, Gaia's map of the galaxy will tell astronomers where the stars are. Over five years, Gaia will observe (观察) about a billion stars and other objects in our galaxy. Each object will be observed about 70 times.

    Gaia will be sent into space connected to a rocket. It contains two telescopes, each focused at a different angle (角度). These two telescopes act like Gaia's “eyes”. The reason why humans can see things in 3D is that we have two eyes focused on the same object, at slightly different angles. By using two telescopes like eyes, Gaia can produce the first 3D map of the positions of the stars it views.

    Gaia, which is to be sent into space, will be a powerful telescope. If you were to use it on Earth, for example, you could stand 600 miles away from your best friends and still get a clear picture of their hair.

    Gaia is one of more than a dozen telescopes being designed by scientists right now. The next generation of telescopes will reveal new parts of our universe that will seem surprising. The universe, with all its planets, stars and other strange objects, is a puzzle with pieces that we can see by using powerful telescopes.

In 1835, William Talbot finally succeeded in producing a photograph of his country house. He declared that his was the first house ever known to have drawn its own picture. The drawing was formed "by the action of light upon sensitive paper." Photography offered nature a "pencil" to paint herself through optical （光学的） and chemical means alone.

By the mid-nineteenth century, people no longer needed to hire a draftsman to draw detailed images because the process could be completed instantly with a camera. Advocates for the technology stated that not only was it more precise than the human hand-it was faster and cheaper.

The removal of human fallibility in the creating process was one of photography's biggest selling points, but this also started debates about the new medium's implications for visual culture. Could images made largely by a machine be considered art? If so, where did human creativity, fit in this process?

As the twenty-first century becomes increasingly automated （自动化的）, more and more people attempt to identify where human agency exists in the technologically driven world. Images generated with artificial intelligence by companies like OpenAI are stimulating questions like those that emerged with the coming of the photograph. By typing a sentence, users can generate "new" images composed from images collected across the internet. The result has been a flood of Al-generated images in places that are previously unique to human authors. Painting competitions, commercial graphic design and the fashion of portraiture（肖像） have all since collided with the technology in troubling ways.

The fine arts were thought to be a final hold-out of human creativity, but the surprisingly high quality of Al-generated images is producing deeper questions about the nature of originality. If the history of photography tells us anything, it's that the debate won't be settled quickly; straightforwardly or by the institutions we typically associate with cultural gate-keeping.