I'd planned to spend my weekend in the sun, potting flowers outdoors. But that was before the pair of crows (乌鸦). Out of nowhere, they had set up their base camp in our backyard.

    We first discovered our feathered enemies on Friday morning. It was early, and the sound the birds made traveled through our neighborhood. I figured they'd go away soon. But, no. They were getting louder and probably annoying my neighbors nearly as much as us with the noise. I admit I got a little desperate.

    Then, on Sunday afternoon, I looked out the kitchen window to see our dog Quatchi staring at something on the ground. I went to explore and found a small coal-black bird in the grass. Its eyes were milky, and it stayed perfectly still as my dog inched towards it. Only when Quatchi touched his nose to its head did it walk away. I took hold of the dog and locked him inside and came back with my camera.

    It never occurred to me that the young would be hanging out on the ground, growing and gaining strength as its parents guarded it from above. The second I saw this little creature I forgave the crows.

    To be honest, I've never been much of a bird person. I also have a healthy respect for birds, and by healthy I mean slightly fear-based. They're basically living dinosaurs.

    I wish they'd chosen another backyard. There are only so many sunny days in Seattle, and I still can't do any gardening out there. But I'm also grateful that I got to see this little bit of nature unfold up close. It's pretty amazing.

    The experience has also strengthened my desire to create a beautiful backyard garden that attracts lots of bees, butterflies, and yes, birds. They are welcome here.

    Last year I ruined (毁) my summer vacation by bringing along a modem convenience that was too convenient for my own good: the iPad. Instead of looking at nature, I checked my email. Instead of paddling a small boat, I followed my Twitter feed (推特简讯). Instead of reading great novels, I stuck to reading four newspapers each morning. I was behaving as if I were still in the office. My body was on vacation but my head wasn't.

    So this year I made up my mind to try something different: withdrawal (退出) from the Internet. I knew it wouldn't be easy, since Fm bad at self-control. But I was determined. I started by giving the iPad to my wife.

    The cellphone signal (信号) at our house was worse than in the past, making my attempts at cheating an experience in frustration (沮丧). I was trapped, forced to go through with my plan. Largely cut off from email, Twitter and my favorite newspaper websites, I had few ways to connect to the world except for radio and how much radio can one listen to, really? I had to do what I had planned to all along: read books.

    This experience has had a happy ending. With determination and the strong support of my wife, I won in my vacation struggle against the Internet, realizing finally that it was I, not the iPad, that was the problem. I knew I had won when we passed a Starbucks and my wife asked if I wanted to stop to use the Wi-Fi. “I don't need it,” I said.

    However, as we return to post-vacation life, a harder test begins: Can I continue when Fm back at work? There are times when the need to know what's being said right now is great. And I have no intention (愿望) of giving up my convenience completely. But I hope to resist (抵抗) the temptation (诱惑) to check my email every five minutes, which leads to checking my Twitter feed and a website or two.

    I think a vacation is supposed to help you reset your brain to become more productive. Here I hope this one worked.

    When Nancy Flexer opened the door to her classroom near the end of her final school year, all 41 years of her career as a beloved first-grade teacher came to life right in front of her.

    Cole Elementary School in Tennessee surprised Flexer with a memorable and emotional retirement party featuring former students of all ages, dating back to the first class she taught in the 1973-74 school year. A video of the event shows an overwhelmed Flexer being moved to tears as she hears former students who are now adults tell her how much she affected their lives.

    "I'm one of the luckiest people in this world," Flexer said. "I remember I opened the door to the classroom thinking no one was in there, and it was wall-to-wall people and banners and everything. It was the coolest thing that could've ever happened in my life. How many times do we really realize the lives we've touched, the manner in which we've touched them, and that these are memories that stay with them for life?"

    Despite being young when they were taught by Flexer, students easily recalled the heartwarming notes she wrote them on report cards, the ways she helped them overcome shyness and awkwardness, and how she inspired them to future academic success to earn scholarships and advanced degrees.

Even though Flexer hadn't seen some of the former students for decades, she instantly remembered the names of every single one there.

    A scrapbook(剪贴簿) of her career was presented to her as one student after another recalled the effect Flexer had on his or her life.

    “I've had many opportunities to move to a school closer to my home, but I said 'Cole gave me so much in my life that when I retire, I will retire from Cole school and give back what's been given to me.” Flexer said. “My career could've taken me nowhere that would have made me happier. I think of it as a blessing.”

    Since the sex of a sea turtle(海龟)is determined by the heat of sand hatching the eggs, scientists had suspected they might see slightly more females. Climate change, after all, has driven sea temperatures higher, which, in these creatures, favors female children. They found female sea turtles from Raine Island, the Pacific Ocean's largest and most important green sea turtle living area, now outnumber males by at least 116 to 1. "This is extreme," says turtle scientist Camryn Allen.

    Biologist Michael Jensen wanted to know if climate change had already changed turtles' sexes. By using genetic(基因的) tests, he'd figured out that he could follow turtles of all ages. Still, his research data would lack an important detail: sex. Only after a turtle matures is it possible to tell its sex from the outside -- mature males have slightly longer tails. By then turtles can be decades old, so scientists often use Iaparoscopy(腹腔镜检查)，sending a thin tube into each animal, but that's not so practical if you're hoping to examine hundreds of creatures. Fortunately, at a turtle conference, he met Allen, and all she needed was a little blood.

    They compared their results with temperature data for nesting beaches. What worries them is that Raine Island has been producing almost female turtles for at least 20 years. This is no small thing. More than 200,000 turtles come to nest there. During high season, 18,000 turtles may settle in at once. "But what happens in 20 years when there are no more males coming up as adults? Are there enough to maintain the population?" says Allen. They also found cooler beaches in the south are still producing males, but that in the north, it's almost entirely females hatching. These findings clearly point to the fact that climate change is changing many aspects of wildlife biology.

    But how widespread is this phenomenon -- and what is the consequence?

    The sun was shining and Clare felt like doing something active. She'd had enough of the moment of living in the past. What she really wanted was some skiing if she could get herself organized. She walked into the ski school office and within ten minutes had arranged a private class for the whole afternoon. One of the ski teacher would meet her at the ski lift station at the end of the village at midday. The ski hire shop next door rented her some skis and boots and she carried them back to the hotel. There she changed into some more or less suitable clothes and took the hotel's electric taxi down to the lift station. She was a bit early and had time to look around, and get nervous. She hadn't skied for about ten years, though she'd been quite good at that time. Everyone said it was liking riding a bike-you didn't forget how to do it. She stood there looking up at the mountains, trying to remember what to do.

    Madam Newton?" Yes," she said. And there was her ski teacher, looking exactly like all the other ski teachers she remembered sun-tanned, handsome and totally self-confident. Half an hour later all thoughts of the unhappy days had disappeared as she skied behind Bruno and concentrated on staying on her feet.

    "Upper body still, make your legs do the work, Madame", shouted Bruno over his shoulder. "Call me Clare, please" she said. "OK. Lean forward a bit more, Clare. That's it. Good. You are remembering now, en?" "Yeah, I am ... slowly. It's great. I'd forgotten what an amazing buzz skiing gives you".

    They skied down some different runs with Bruno being wonderfully encouraging, and she really did begin to feel confident on the skis. Going up in the lifts, Clare and Bruno chatted — just the usual "where are you from, what do you do" sort of chat, but it was pleasantly relaxing. In the middle of the afternoon, they stopped at an old farmhouse for coffee and apple cake. There were lots of other skiers doing the same. Clare felt as if she belonged - something about being part of a group, all with a shared interest, she supposed. It was a feeling she'd not had for a long time.

    Bruno said hello to a few people, and went over to talk to one of the waiters. Clare took the opportunity to study him a bit. Up until now, she'd just been skiing behind a man in a red ski suit, so it was interesting to see that he was quite tall, with curly brown hair and eyes to match. From the colour of his face he looked as if he'd spent his whole life in the open air. She guessed he was about forty.

    "Are you in Zermatt for long, Clare?" asked Bruno, after he'd been sitting with her a few minutes, "No, only a few days probably. Just a short break to get away from everything at home", replied Clare. She didn't feel like explaining the real reason. People looked at her differently when they knew. "But I'd like to do some more skiing. Would you be able to do anything tomorrow?"

    "I think so. But you'll have to book it through the ski school office. I can't arrange anything with you directly", said Bruno, putting on his gloves and standing up. "Come on. Let's do a bit more now." "Great," replied Clare. After another hour, Clare said, "Time to stop, I think," Bruno agreed. "You should have a sauna tonight. It'll help your body relax. Not so stiff (僵硬的）tomorrow, you know." Clare didn't care about stiff she was going to be tomorrow. She hadn't felt quite as good as this for months — full of fresh air, physically tired but in her mind — alive. Happy! Yes, that was how she felt.

Round and Round They Go

Space is becoming more crowded. On December 3, a Falcon 9 rocket made by SpaceX thundered into the sky. On board were 64 small satellites, more than any American company had launched before in one go. They have a variety of uses, from space-based- radar to the monitoring of radio-frequency- emissions.

These objects are part of the latest breed of low-Earth-orbit (LEO) satellites. This launch is just taste of what is planned. SpaceX and OneWeb, a communications firm, plan to launch satellites in their thousands, not hundreds. The pair are set to double the total number of satellites in orbit by 2027.

That promises to change things dramatically on Earth. LEO satellites can bring internet connectivity to places where it is still unavailable or unaffordable. This will also be a lasting source of new demand for the space economy. Morgan Stanley, a bank, projects that the space industry will grow from $350 billion in 2016 to more than $1. I trillion by 2040. New internet satellites will account for a half this increase.

For that to happen, however, three worries must be overcome. Debris(碎片)is the most familiar concern. As long ago as 1978, Donald Kessler, a scientist at NASA, proposed situation in which, when enough satellites were packed into low-Earth orbits, any collision could cause a chain reaction which would eventually destroy all space craft in its orbital plane(平面). The syndrome which bears Mr. Kessler's name weighs heavily on the minds of executives at the new satellite firms. Debris could cause entire tracts(广阔的一片) of space to be unusable for decades.

Solutions exist. One is to grab malfunction satellites and pull them down into Earth's atmosphere. Another is to monitor space more intensively for debris; a US Air Force programme called Space Fence is due to start in 2019. But technology is only part of the answer. Rules are needed to govern the safe disposal(清除) of old satellites from low-Earth orbit. The United States' Federal Communications Commission is revising its regulations with this in mind. Other countries should follow suit.

Cyber-security is a second, long-standing worry. Hackers could take control of a satellite and seal intellectual property, redirect data flows or cause a collision. The satellite industry has been slow to respond to such concerns. But as more of the world's population comes to rely on the infrastructure of space for access to the internet, the need for action intensifies.

The third issue follows from the first two. If a simple mistake or a cyber-attack can cause a chain reaction which wipes out hundreds of billions of dollars of investment, who is liable? Underwriters(保险商) are studying the plans of firms that wish to operate large numbers of satellites. But there is a long way to go before the risks are well understood, let alone priced.

As space becomes more commercialized mind-bending prospects open up: packages moved across the planet in minutes by rocket rather than by plane, equipment sent to other small planets, passengers launched into orbit and beyond. All that and more may come, one day. But such activities would raise the same questions as LEO satellites do. They must be answered before the space economy can truly develop.