When asked to point out one or two things that are most important to themselves, many put friends ahead of homes, jobs, clothes and cars.

    A true friendship carries a long history of experience that determines who we are and keeps us connected. It is a treasure we should protect. Unfortunately, the better friends you are, the more probably you'll have disagreements. And the result can be what you don't want—an end to the relationship.

    The good news is that most troubled friendships can be mended. First, don't let your pride get in your way. Most of us can forgive each other when differences are brought out in the open. Second, apologize when you're wrong — even if you've been wronged. Over the course of a friendship, even the best people make mistakes. Sometimes, it may be best if the wronged person takes the lead and apologizes. When you apologize, give your friend a chance to admit(承认) that he has been wrong. Third, see things from your friend's point of view. And finally, accept that friendships change as our needs and lifestyle change. Making friends can sometimes seem easy. The hard part is keeping the connections strong during the natural ups and downs that have an effect on all relationships. My suggestion: consider friendship as an honor and a gift, and worth the effort to treasure and nurture(培养).

Industrial emissions (排放) of carbon dioxide and other planet-warming greenhouse gases have raised the global average temperature by about 0.8℃ since the beginning of the Industrial Revolution. But studies have disagreed about what impact the rise is having on the world's species, says Mark Urban, an ecologist at the University of Connecticut, Storrs. Some have estimated that as many as 54% of species could eventually become extinct as a result of the climate change, but others have suggested no significant impact.①

    Such disparate result might originate from the limited nature of some individual studies, possibly because they focused only on a few species or a relatively small geographical region, says Urban.② To address these limits, Urban used statistical methods to help blend the results of previous studies into an apples-to-apples comparison that estimates the risk of extinction of species worldwide.

    ③He chose to analyze only the results of studies that had assessed extinction risks of more than one species. Then he researched into the details, such as the regions in which species considered, whether those species were limited to one small region or were widely spread, and whether the species were free to move as climate changed or were blocked by barriers such as mountain ranges or urban development.④

    Effects of climate change aren't always immediate, Urban says, and the risks of extinction he's estimated are the long-term results of species not being able to find a suitable habitat. Maybe the habitat will merely shrink to a size that can't support the species, or maybe it will disappear entirely. In some cases, he notes, a species might not be able to outpace the shift in its range, dying out before it can reach a new homeland. For over the generations that rapid warming might kill them off before they can spread to a suitable new habitat.

    A five-year-old dog named Kelsey has been praised as a hero for helping to save the life of her owner who slipped in the snow and broke his neck.

    The man, Bob, was alone when he left his Michigan farmhouse on New Year's Eve to collect firewood. Expecting a journey of only several meters, Bob was wearing just long johns (衬裤), a shirt and slippers when he went outside, although the temperature was around -4℃.

    After the accident, he was unable to move in the snow. Fortunately, Kelsey came to his assistance.

    "I was shouting for help, but my nearest neighbor is about 400 meters away, and it was 10:30 pm, Bob explained." But my Kelsey came. By the next morning, my voice was gone and I couldn't yell for help, but Kelsey didn't stop barking."

    Kelsey's companion kept him warm by lying on top of him. She licked his face and hands to keep him awake." Kelsey kept barking but never left my side," Bob recalled. "She kept me warm. I knew I couldn't give up and that it was my choice to stay alive."

    Bob spent 20 hours in the freezing cold. When he finally lost consciousness, his dog kept barking. Finally, hearing the barking, Bob's neighbor discovered him at 6:30 pm on New Year's Day and called the emergency services at once. When Bob arrived in hospital, his body temperature was below 21℃. However, doctors were surprised to find that he didn't have any frostbite (冻疮). They believed it was because of Kelsey's determination to keep him warm, Dr. Chaim Colen, the doctor who treated Bob, said, "Animals can help and his dog really saved him... He was very fortunate.”

    Bob said he was "enormously" grateful to both Dr. Colen and his Kelsey, "They saved my life. They are truly heroes!"

    A few weeks ago, I called an Uber to take me to the Boston airport for a flight home for the holidays. As I slid into the back seat of the car, the warm intonations(语调) of the driver's accent washed over me in a familiar way.

    I learned that he was a recent West African immigrant with a few young children, working hard to provide for his family. I could relate: I am the daughter of two Ethiopian immigrants who made their share of sacrifices to ensure my success. I told him I was on a college break and headed home to visit my parents. That's how he found out I go to Harvard. An approving eye glinted at me in the rearview window, and quickly, we crossed the boundaries of rider and driver. I became his daughter, all grown up — the product of his sacrifice.

    And then came the fateful question: "What do you study?" I answered "history and literature" and the pride in his voice faded, as I knew it might. I didn't even get to add "and African-American studies" before he cut in, his voice thick with disappointment, "All that work to get into Harvard, and you study history?"

    Here I was, his daughter, squandering the biggest opportunity of her life. He went on to deliver the age-old lecture that all immigrant kids know. We are to become doctors (or lawyers, if our parents are being generous) — to make money and send money back home. The unspoken demand, made across generations, which my Uber driver laid out plainly, is simple: Fulfill your role in the narrative(故事) of upward mobility so your children can do the same.

    I used to feel anxious and backed into a corner by the questioning, but now as a junior in college, I'm grateful for their support more than anything. This holiday season, I've promised myself I won't huff and get annoyed at their inquiries. I won't defensively respond with "but I plan to go to law school!" when I get unrequested advice. I'll just smile and nod, and enjoy the warmth of the occasion.

Scientists have discovered a bit of hand-made string (线绳) that's around 50,000 years old in Neanderthal remains. The first Neanderthal remains were found in the Neander Valley in Germany, which is where the name comes from. Neanderthals may have lived mainly in caves and made stone tools, but recent discoveries have given hints that Neanderthals developed some advanced skills that people used to think impossible. For example, Neanderthals knew how to make glue from the bark (树皮) of a tree.

Now, scientists report they've found a piece of string on a stone tool made by Neanderthals. Before this, the oldest known piece of string was one made by humans about 19,000 years ago. The string is about a quarter of an inch long. Almost all things made from plants during that time have broken down and disappeared, so it's very special to find this bit of string.

The scientists don't know whether the string was attached to the tool. But that doesn't interest them as much as the fact that Neanderthals knew how to make string. Bruce Hardy, the lead scientist on the project, says that knowing how to make string was meaningful for humans. "We wouldn't really be here today without that technology," he says.

Making string is a very arduous process. This string was made from the inside bark of an evergreen tree. To make string that is strong enough, the string must be made of several smaller fibers twisted (缠绕) together in a special way. For the Neanderthal string, several fibers needed to be twisted together into something like yarn. Then three pieces of yam needed to be twisted together in the opposite direction to make the final string.

The scientists aren't sure what the string was used for, but they say that string like. the bit that was found could be used to make bags, baskets, traps, or other things. The researchers also suggest that because Neanderthals needed to make pairs and count fibers to make the string, the bit of string may also tell us something about the kinds of math that Neanderthals could do.

It's 1:30 am in Kenya's populated north, and 50 people are lying on their backs on the shore of a dried-up river, staring up at the night sky. These stargazers have travelled 250 miles to Samburu to witness the Perseid meteor shower(英仙座流星雨). They are not disappointed: Every few minutes, arrows of light shoot across the sky like silent fireworks.

The Star Safari is organised by a Kenyan astronomer, Susan Murabana, who has brought a 50 kg,170 cm-long telescope to allow the group to view Mars and deep-sky objects. But here in Samburu, where light pollution is minimal, the Perseid meteors—visible with the naked eye (裸眼)—steal the show.

Every two months, Murabana and her husband load their telescope on to the roof of their 4×4 and set off to rural communities, where they give up to 300 children a chance to view the planets and learn about constellations (星座) and the basics of astrophysics. They primarily targets schools in remote areas because of her mission to give girls an opportunity that she wishes had been available to her.

"When I started this work, I didn't see people who looked like me. I was a lone ranger and I wanted to change that." says Murabana.

"There is a common misconception in Kenya that astronomy in general is hard, boring, and only for boys," she adds. "I'd like to teach young girls that astronomy is neither of these things and that they, too, can become astronomers," says Murabana.

Murabana's passion for astronomy began in her early 20s when her uncle invited her to join a similar outreach session organized by the Cosmos Education. "That was a gamechanger. If an outreach group had come to me when I was a young teenager, my attitude towards a career in astronomy would have been positive. I ended up studying sociology and economics, but maybe I would have desired to be an astronomer," she says.

Inspired by the Cosmos Education, Murabana completed an online master's degree in astronomy with the James Cook University in 201l and set up her own outreach programme. She looked to Dr Mae Jemison, the first black woman in space, as a role model. "I hope that one day, through this work, I will spark a chain reaction that leads to the first African woman in space."