The oddness of life in space never quite goes away. Here are some examples.

    First consider something as simple as sleep. Its position presents its own challenges. The main question is whether you want your arms inside or outside the sleeping bag. If you leave your arms out, they float free in zero gravity, often giving a sleeping astronaut the look of a funny balled （芭蕾）dancer. “I'm an inside guy,” Mike Hopkins says, who returned from a six-month tour on the International Space Station. “I like to be wrapped up.”

    On the station, the ordinary becomes strange. The exercise bike for the American astronauts has no handlebars. It also has no seat. With no gravity, it's just as easy to pedal violently. You can watch a movie while you pedal by floating a microcomputer anywhere you want. But station residents have to be careful about staying in one place too long. Without gravity to help circulate air, the carbon dioxide you exhale (呼气) has a tendency to form an invisible （隐形的）cloud around you head. You can end up with what astronauts call a carbon-dioxide headache.

    Leroy Chiao, 54, an American retired astronaut after four flights, describes what happens even before you float out of your seat,”Your inner ear thinks your're falling . Meanwhile your eyes are telling you you're standing straight. That can be annoying—that's why some people feel sick.” Within a couple days —truly terrible days for some —astronauts' brains learn to ignore the panicky signals from the inner ear, and space sickness disappears.

    Space travel can be so delightful but at the same time invisibly dangerous. For instance, astronauts lose bone mass. That's why exercise is considered so vital that National Aeronautics and Space Administration (NASA) puts it right on the workday schedule. The focus on fitness is as much about science and the future as it is about keeping any individual astronauts return home, and, more importantly, how to maintain strength and fitness for the two and a half years or more that it would take to make a round-trip to Mars.

    “Don't get discouraged, Hallie,” Kathy said, comforting her with a hug. “It sounds as if you have a bit of a mystery to solve. Maybe you should do a little spying on Maya.”

    Feeling better, Hallie put on her scuba gear（潜水服）again and waited. Maya, the dolphin, had been swimming playfully, but suddenly she threw herself to the back of the tank where the filter box（过滤箱）was located. She stuck her nose down behind the box and then swam away.

    Hallie followed Maya. “What was she doing here?” she wondered. When she looked behind the box, her question was answered. She swam back and saw Maya was in front of Kathy with a comb in her mouth waiting for her treat.

    “Maya! Where did you get that?” demanded Kathy, taking the comb and throwing her a fish.

    “I know,” declared Hallie, handing Kathy a handful of items, “I followed her to the filter box and these are what I found.”

From the look on Kathy's face, Hallie knew everything was beginning to come to light.

    “Do you remember the other day you said that Maya really liked her treats?” asked Kathy.“Well, I think this was more than a training exercise for Maya. Every time you found something in the tank, that meant one less fish for Maya. She couldn't bring all the items to me at once, so she found a hiding place for them. That way you came up empty-handed, but Maya would always get her treat.”

    “Okay, Maya,” said Hallie facing the dolphin, “you win! The treats are all yours.”

    Maya dived down, and then jumped out of the water, turning herself over in midair. Shaking their heads in disbelief, Hallie and Kathy reached for the fish. Maya deserved the treat.

    It's never easy to explain exactly when a specific language began, and in the case of English we can hardly regard it as a separate language before the Anglo-Saxons came to Britain. Germanic invaders (入侵者) came and settled in Britain from the north-western coastline of continental Europe in the fifth centuries. The invaders all spoke a language that was Germanic (related to Dutch, Frisian, German and the Scandinavian languages), but we'll probably never know how different their speech was from that of their continental neighbors.

    The reason that we know so little about the language in this period is because we do not have much in the way of written records from any of the Germanic languages until several centuries later. When Old English writings began to appear in the seventh and eighth centuries there was a good deal of regional variation (变化), but not more than that found in later periods.

    The Celts already lived in Britain when the Anglo-Saxons arrived, but there are few obvious signs of their language in English today. Some scholars have suggested that the Celtic tongue might have had some influence on the grammatical development of English, particularly in some parts of the country, but this is highly speculative (猜测). The number of borrowed words that have entered Old English from this language is very small. Those that survive in modern English include “comb” (a type of valley), alongside some place names.

    Four of the World's Best Futurists(未来学家)

    Kevin Kelly

    Kevin Kelly is an author. His 1994 publication, Out of Control, discusses a future where machines and systems are so complex as to be indistinguished(难区分的) from living things.

    His latest book What Technology Wants suggests that technology is not just a mixture of wires and metals but a living thing that has its own need. The book looks out through the eyes of this global technological system to discover what it wants.

    Dr Michio Kaku

    Dr Michio Kaku is a professor of theoretical physics at the City of New York and author of The Future of the Mind and Physics of the Future.

    In The Future of the Mind , he explores the frontier of neuroscience. He predicts that one day we will be able to upload the human brain into a computer. In Physics of the Future, he predicts that glasses and contact lenses will be connected to the Internet and cars will become driverless with the power of the GPS system.

    David Brin

    Science fiction author and scientist, David Brin has received awards. In 1998, he won the Freedom of Speech Award for The Transparence Society. The book concerns threats to personal affairs and openness in the information age. In a world where the police monitor public places 24 hours a day with cameras and some credit companies can sell people's financial details to anyone willing to pay, Brin warns that surveillance(监控) technology will be used by too few people in the future. He argues that the tables should be turned and the public should have access to information like who is buying financial details from credit companies.

    Dr Ray Kurzweil

    Dr Ray Kurzweil is the main inventor of the first print-to-speech reading machine for the blind. He is the director of artificial intelligence development at Google.

    Over the past 25 years, a number of his predictions have come true. In 1990, he predicted a computer would defeat a human at chess by 1998.He predicts that by the 2020s, most diseases will go away and self-driving cars begin to take over the roads.

    It started during a yoga class. She felt a strange pull on her neck, a feeling completely foreign to her. Her friend suggested she rush to the emergency room. It turned out that she was having a heart attack.

    She didn't share similar symptoms with someone who was likely to have a heart attack. She exercised, watched her plate and did not smoke. But on reviewing her medical history, I found that her cholesterol (胆固醇) level was sky-high. She had been prescribed a cholesterol-lowering statin (他汀) medication, but she never picked up the prescription because of the scary things she had read about statins on the Internet. She was the victim of fake medical news.

    While misinformation has been the object of great attention in politics, medical misinformation might lead to an increase in deaths. As is true with fake news in general, medical lies tend to spread further than truths on the Internet—and they have very real bad consequences.

    False medical information can also lead to patients experiencing greater side effects through the "nocebo effect (反安慰剂效应) ". Sometimes patients benefit from an intervention (干预) simply because they believe they will—that's the placebo effect (安慰剂效应). The nocebo effect is the opposite. Patients can experience harmful effects because they anticipate them. This is very true of statins. In blinded trials, patients who get statins are no more likely to report feeling muscle aches than patients who get a placebo. Yet, in clinical practice, according to one study, almost a fifth of patients taking statins report side effects, leading many to discontinue the drugs.

    What else is on the fake news hit list? As always, vaccines (疫苗) . False concerns that the vaccine may cause side effects have greatly reduced coverage rates.

    Cancer is another big target for pushers of medical misinformation—many of whom refuse alternative therapies. "Though most people think cancer tumors are bad, they're actually the way your body attempts to contain the harmful cells," one fake news story reads. It warns that prescription medications lead to the uncontrolled cell mutations (变异) .

    Silicon Valley needs to face this problem. I am not a free-speech lawyer, but when human health is at risk, perhaps search engines, social media platforms and websites should be held responsible for promoting or hosting fake information. Meanwhile, journalists should do a better job of spreading accurate information.

    I first began experiencing depression (抑郁) at the age of 14 .At first depression would come and go, but later it became a continual part of my life.

    I was so strongly determined to find the way to overcome my depression that I tried everything from when I was in college, special teas, yoga (瑜伽), and advice given by doctors. However, I still felt I hadn't even come close to managing the problem.

    But one afternoon, I saw an article in a magazine that talked about how dogs were able to help people with depression. The next day, I decided to get a dog—a corgi (柯基犬).

    When I bought my little corgi, Buddy, home, I didn't realize how much he would change my life. One morning, I woke up with those familiar feelings again. I didn't want to get out of bed. I turned to pull the covers back over my head and give up. That's when I saw Buddy. He started jumping all over me, licking (舔) my face, letting me know that it was time to go outside. It was as if he were saying, "There's no time to be sad. The world is amazing!" And for the first time in my life, on a day when my depression were strong, I got out of bed. I put on my winter clothes and went for a walk in the snow with my new friend. I realized at that moment, walking down the street in winter, my life was changing. I really was a new person. This was my new beginning.

    It's been more than a year since that day, and I've never spent another morning unable to get out of bed. I've not cried myself to sleep or spent my days filled with fear and regret. Sure, I still have days when I feel sad or anxious. But with Buddy by my side, I've finally learned how to manage these feelings.