Even if trees cannot walk, they are still on the move.

    In parts of the Arctic, entire forests are moving northward. Across the Arctic, temperatures are rising faster than anywhere else in the world. As that happens, the tree line that marks where forests stop and the treeless tundra(冻土地带) starts has been shifting northward. Trees growing along the tree line must protect themselves from the cold wind. To do this, plants tend to grow horizontal(水平的) branches low to the ground. The energy it takes for trees to grow this way means they don't have enough energy to make seeds.

    But as Earth's climate has been warming, trees no longer have to just grow horizontally. Many can instead grow up toward the sky. This takes less energy. And with all the leftover energy. these trees have started producing more seeds. This happens especially in places where the white spruce(白云杉) grows.

    White spruce, which is a North American tree, is quite able to produce a lot of seeds, which can move long distances in the wind. When wind-blown seeds end up on the tundra beyond the tree line, they eventually can sprout(发芽) new trees. This explains how a forest can move. Of course, the process would work only if the tundra were warm enough. But in recent years, the whole planet has been warming.

    New trees will provide shelters for some snow, keeping the sun's rays from making the white surface disappear. Instead, the trees absorb the sun's heat. This warms the surrounding air. The extra warmth encourages even more trees to produce seeds. That further boosts a forest's ability to expand. In addition, more trees will trap more snow, preventing much of it from being blown away. Snow can trap heat in the soil below, which encourages trees to grow. The recent rise of temperature has helped more trees grow. The recent rise of temperatures has helped more trees grow past the tree line. People worry about impacts on the animals that depend on frozen conditions for food and shelter.

    How can we reduce the risk?

    There are four general approaches to dealing with volcanic dangers. We can try to keep the danger from occurring—often an impossible task. We can try to change its path or reduce its impact on existing development. We can take steps to protect future development. We can also do our best to have disaster response plans in place before they are needed.

    Removing the Threat

    Clearly, there is no way to stop an eruption. We can, however, attempt to reduce the eruption's effects by strengthening structures, for example, building protective works such as walls to make lava (熔岩) flow away from developed areas. Such efforts can be and have been successful, but are of limited use in a large-scale eruption.

    Planning for the Future

    Protecting future development from volcanic dangers is a simple task. Before building houses, we should judge the risk. If the risk seems too great, a safer location should be found. This type of planning is very effective, but all too often, people are drawn to the lush(葱郁的)，rolling land of a quiet volcano.

     Disaster Preparedness (预案)

    When a volcano comes to life, a few weeks may not be enough time to avoid a tragedy. Planning is the key to saving lives. Well before the warning signs occur, people must be educated about volcanic dangers. Escape plans must be in place. Communication between scientists, officials, the media, and the general public should be practiced. Emergency measures must be thought out and agreed upon.

    If you doubt the importance of these efforts, take another look at past volcanic tragedies, such as the eruption of Nevado del Ruiz. Communication failures left the town of Armero unprepared for escape. When a deadly mudflow came down the slope (斜坡), 21,000 people—90 percent of the town's people—died.

    When pups are between 2 and 3months old, their mothers will abandon them for any number of reasons. With no mother to watch out for them, infant (婴儿) mortality of pups under one year skyrockets (飞涨) to around 90%. So, only about 10% of motherless, homeless pups survive.

    Without mothers, how are these abandoned pups supposed to survive? For the study, researchers Clive Wynne at Arizona State, Nadine Chersini at Utecht University, and Nathan Hal at Texas Tech University brought in 51 college students and asked them to rate the attractiveness of headshots (头部特写) of puppies at different ages.

    The pups peaked at different ages, but they were all ranked likable between six to eight weeks, since newly abandoned pups are competing with each other for human heartstrings (怜悯), evolution says they should be most likable around 6 and 11 weeks. This is around the time they are weaned (断奶) and let go of by their mothers.

    There are a few characteristics that humans find particularly adorable across species: big, forward-facing eyes, floppy and unstable limbs (肢), and a soft, rounded body shape. We're also keen to scream when animals have large heads in comparison to their bodies, and this reaction goes back to evolution.

    Called kinderschema (婴儿萌), these qualities are also apparent in human babies and necessary for their survival. The characteristics activate the decision-making part of the brain to encourage you to protect and nurture the baby. At the same time, the brain's pleasure center releases dopamine (多巴胺). With these two reactions, your brain makes you want to protect the baby and rewards you for doing so. With your protection, the baby can survive.

Preparing Cities for Robot Cars

    The possibility of self-driving robot cars has often seemed like a futurist's dream, years away from materializing in the real world. Well, the future is apparently now. The California Department of Motor Vehicles began giving permits in April for companies to test truly self-driving cars on public roads. The state also cleared the way for companies to sell or rent out self-driving cars, and for companies to operate driverless taxi services. California, it should be noted, isn't leading the way here. Companies have been testing their vehicles in cities across the country. It's hard to predict when driverless cars will be everywhere on our roads. But however long it takes, the technology has the potential to change our transportation systems and our cities, for better or for worse, depending on how the transformation is regulated.

    While much of the debate so far has been focused on the safety of driverless cars (and rightfully so), policymakers also should be talking about how self-driving vehicles can help reduce traffic jams, cut emissions (排放) and offer more convenient, affordable mobility options. The arrival of driverless vehicles is a chance to make sure that those vehicles are environmentally friendly and more shared.

    Do we want to copy—or even worsen—the traffic of today with driverless cars? Imagine a future where most adults own individual self-driving vehicles. They tolerate long, slow journeys to and from work on packed highways because they can work, entertain themselves or sleep on the ride, which encourages urban spread. They take their driverless car to an appointment and set the empty vehicle to circle the building to avoid paying for parking. Instead of walking a few blocks to pick up a child or the dry cleaning, they send the self-driving minibus. The convenience even leads fewer people to take public transport—an unwelcome side effect researchers have already found in ride-hailing (叫车) services.

    A study from the University of California at Davis suggested that replacing petrol-powered private cars worldwide with electric, self-driving and shared systems could reduce carbon emissions from transportation 80% and cut the cost of transportation infrastructure (基础设施) and operations 40% by 2050. Fewer emissions and cheaper travel sound pretty appealing. The first commercially available driverless cars will almost certainly be fielded by ride-hailing services, considering the cost of self-driving technology as well as liability and maintenance issues (责任与维护问题). But driverless car ownership could increase as the prices drop and more people become comfortable with the technology.

    Policymakers should start thinking now about how to make sure the appearance of driverless vehicles doesn't extend the worst aspects of the car-controlled transportation system we have today. The coming technological advancement presents a chance for cities and states to develop transportation systems designed to move more people, and more affordably. The car of the future is coming. We just have to plan for it.

How Much Can We Afford to Forget?

    In 2018, Science magazine asked some young scientists what schools should teach students. Most said students should spend less time memorizing facts and have more space for creative activities. As the Internet grows more powerful, students can access(获得)knowledge easily. Why should they be required to carry so much of it around in their heads?

    Civilizations(文明)develop through forgetting life skills that were once necessary. In the Agricultural(农业的)Age, a farmer could afford to forget hunting skills. When societies industrialized, the knowledge of farming could be safe to forget. Nowadays, smart machines give us access to most human knowledge. It seems that we no longer need to remember most things. Does it matter?

    Researchers have recognized several problems that may happen. For one, human beings have biases (偏见), and smart machines are likely to increase our biases. Many people believe smart machines are necessarily correct and objective, but machines are trained through a repeated testing and scoring process. In the process, human beings still decide on the correct answers.

    Another problem relates to the case of accessing information. When there were no computers, efforts were required to get knowledge from other people, or go to the library. We know what knowledge lies in other brains or books, and what lies in our heads. But today, the Internet gives us the information we need quickly. This can lead to the mistaken belief — the knowledge we found was part of what we knew all along.

    In a new civilization rich in machine intelligence, we have easy access to smart memory networks where information is stored. But dependency on a network suggests possibilities of being harmed easily. The collapse of any of the networks of relations our well-being(健康)depends upon, such as food and energy, would produce terrible results. Without food we get hungry; without energy we feel cold. And it is through widespread loss of memory that civilizations are at risk of falling into a dark age.

    We forget old ways to free up time and space for new skills. As long as the older forms of knowledge are stored somewhere in our networks, and can be found when we need them, perhaps they're not really forgotten. Still, as time goes on, we gradually but unquestionably become strangers to future people.

Singapore researchers say they have developed a form of electronic skin that can create a sense of touch. They hope their invention will give people with prosthetic hands (假肢手) the ability to identify different objects.

The skin device measures 1 square centimeter. The system contains 100 small sensors that attempt to recreate things like texture (质地), temperature and even pain. The researchers call the device Asynchronous Coded Electronic Skin, or ACES, which can process information faster than humans' nervous system. Machine learning methods trained the device to recognize 20 to 30 different textures. It can even correctly read Braille letters most of the time, the researchers say.

The system does not require the users' movement to work. Humans need to slide to feel texture. But in this case the skin, with just a single touch, is able to detect textures of different roughness.

A demonstration showed that the device could identify the difference between a soft ball and a solid plastic one. "When you lose your sense of touch, you essentially become numb and prosthetic users face that problem, " said Benjamin Tee, leader of the research team. "So by recreating an artificial version of the skin, for their prosthetic devices, they can hold a hand and feel the warmth and feel that it is soft."

Tee said his idea for the device came from the movie Star Wars, when character Luke Skywalker loses his right hand and it is replaced with a robotic one. In the film, the new hand is able to experience touch sensations just like the real one.

The artificial skin technology is still going through experiments and development. But Tee said there had already been a lot of interest in the system, especially from the medical community. Tee said similar inventions that his team has developed include see-through skin that can repair itself when torn and a material for wearable electronic devices that gives off light.