The vast majority of us spend our entire lives pulled down by gravity. Then there are astronauts.

This small population of space travelers has given researchers a rare look at what happens to the human body when it's able to spend large amounts of time outside the downward pull of the Earth. This week, a study on one of the largest groups of astronauts yet —34 participants—was published in The New England Journal of Medicine.

    In the new study, a team of international radiologists supported by NASA looked at MRIs of the brains of astronauts before and after their trips to space. The scientists found that upon returning to Earth, many of the astronauts' brains had become repositioned inside their skulls, floating higher than before. In addition, the space between certain brain areas appeared to have shrunk. The changes were more common in astronauts who took longer trips into space.

    The team characterized astronaut trips as short (an average of less than 14 days) or long (an average of about 165 days). Radiologists who didn't know each astronaut's duration（持续时间）in space compared MRIs from before and after their trips.

    Of the 34 total astronauts involved in the study, 18 took long trips to space—spending most of that time on the International Space Station —and of those, 17 returned to Earth with smaller areas between the frontal lobe（脑前额叶）and parietal lobe（顶叶）. The same area of the brain also shrank for three of the 16 astronauts who took shorter trips with the US Space Shuttle Program. The researchers also found that 12 of the ISS astronauts and six of the space-shuttle astronauts returned home with their brains sitting slightly higher in their skulls than before.

    It's not clear what, if anything, these brain changes mean for the health of space travelers. In general, it appears the human body tolerates space travel fairly well: the time astronauts have spent in zero-gravity environments so far doesn't seem to have had any strong or long-lasting effects.

    China has recently published its first artificial intelligence (AI) textbook for high school students, following a plan by central government last year to include AI courses in primary and secondary school.

    Under the joint efforts by the research center for MOOC at East Normal University and AI startup Sense Time Group, the nine-chapter textbook, named Fundamentals of Artificial Intelligence, was written by eminent scholars from well-known schools nationwide, Xinhua reported on Sunday.

    It includes the history of AI and how the technology can be applied in areas such as facial recognition, auto driving and public security.

    “The textbook focuses not only on basics of AI, also on practical use of AI in daily life,” said Chen Yukun, a professor at East China Normal University, who is also a contributor to the book. At present, about 40 high schools across the country have joined the first batch（批）of AI high education pilot program, by introducing the textbook in curriculum（全部课程）.

    “The AI sector is facing a talent shortage globally. The publication of the book is a breakthrough as it takes AI technology out of the 'ivory tower' and makes it part of high school learning,” said Lin Dahua, a professor at the Chinese University of Hong Kong.

    As early as 2016, the governments had estimated that demand for AI professionals may suddenly increase to 5 million in the coming years.

    “Many industries in the future will benefits from AI technology, so the aim of the related courses should be to let students learn the basic idea and methods of AI,” Lin said.

    China has made significant progress in technological research and development in recent years. According to a report released by US-based venture capital（风险资本）database CB Insights in March, China has for the first time surpassed the United States in equity funding（股权融资）to AI startups.

    If you get into the forest with your friends, stay with them always. If you don't, you may get lost. If you really get lost, this is what you should do. Sit down and stay where you are. Don't try to find your friends—let them find you by staying in one place.

    There is another way to help your friends or other nearby people to find you. Give them a signal (信号) by shouting or whistling (吹口哨) three times. Any signal given three times is a call for help.

    Keep up shouting or whistling always three times together. When people hear you, they will know that you are not just making noise for fun. They will let you know that they have heard your signal. They give you two shouts, two whistles, or two gun-shots (枪声). When someone gives you a signal, it is an answer to a call for help.

If you don't think that you will get help before night comes, try to make a little house—cover up to the holes with branches (树枝) with lots of leaves. Make yourself a soft bed with leaves and grass.

    What should you do if you get hungry or need drinking water? You would have to leave your little house to look for a river. Don't just walk away. Pick off small branches and drop them as you walk so that you can find your way back. The most important thing to do when you are lost is—stay in one place.

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    Blue Planet II's latest episode focuses on how plastic is having a disastrous effect on the ocean and slowly poisoning our sea creatures. Researchers recently also found that sea creatures living in the deepest place on Earth, the Mariana Trench, have plastic in their stomachs. Indeed, the oceans are drowning in plastic.

    Though it seems now that the world couldn't possibly function without plastics, consumer plastics are a remarkably recent invention. The first plastic bags were introduced in the 1950s; the same decade that plastic packaging began gaining in popularity in the United States. This growth has happened so fast that science is still catching up with the change. Plastics pollution research, for instance, is still a very early science.

    We put all these plastics into the environment and we still don't really know what the outcomes are going to be. What we do know, though, is disturbing. Ocean plastic is estimated to kill millions of marine animals every year. Nearly 700 species, including endangered ones, are known to have been affected by it. One in three leatherback turtles, which often mistake plastic bags for jellyfish, have been found with plastic in their bellies. Ninety percent of seabirds are now eating plastics on a regular basis. By 2050, that figure is expected to rise to 100 percent.

    And it's not just wildlife that is threatened by the plastics in our seas. Humans are consuming plastics through the seafood we eat. I could understand why some people see ocean plastic as a disaster, worth mentioning to the same degree as climate change. But ocean plastic is not as complicated as climate change. There are no ocean trash deniers (否认者), at least so far. To do something about it, we don't have to remake our planet energy system.

This is not a problem where we don't know what the solution is. We know how to pick up garbage. Anyone can do it. We know how to dispose (处理) of it. We know how to recycle. We can all start by thinking twice before we use single—use plastic products. Things that may seem ordinary, like using a reusable bottle or a reusable bag—when taken collectively, these choices really do make a difference.

Last September an American started a trip through Southwest China on a standard bike she had bought at a local shop. In three months, Jennifer Holstein cycled 2,500 kilometers through three provinces with just two small bags.

Living in Beijing, her life was already great. But Holstein felt the urge to travel the world and look for adventure. It was mid-August of 2021 that the idea came to her to travel China by bicycle. At that time, Holstein had never cycled for more than 20 kilometers around her local city of Beijing.

Holstein shared an experience from the beginning of her trip when she found herself stuck in a tunnel (隧道) with a flat tire (轮胎). It was dark and hot, and she was so scared because she had never changed a tire before. Suddenly, a group of cyclists old enough to be her grandparents came and rescued her.

In addition to receiving the kindness of people across China, Holstein also experienced several unique cultural experiences by attending three local weddings. She spoke about one wedding in detail, "I was in the middle of a small village in Sichuan province, and I was taken into a local Tibetan family's home and they invited me to take part in a wedding. They gave me a dress and even did my makeup. I never thought I would ever have the chance to take part in a Tibetan wedding."

According to Holstein, "Many people want to travel the world and take huge risks, but never do. Don't just live your life hoping your wildest dreams will become a reality someday. Try first and the rest will work itself out." In addition to biking for her own passion and curiosity, Holstein also linked her ride to raise 22,000 yuan for the United Foundation for China's Health.