1 . Slowing down was the last thing on Elaine Schaefer's mind when she turned 70 last year. She'd enjoyed an ambitious travel schedule for the previous decade. She didn't feel too old to travel.

Yet many people are asking that slightly embarrassing question: Can you be too old to travel? The travel industry has already responded. Try renting a car in Europe, for example. In Croatia, Schaefer wouldn't be able to this year, because the maximum age is 70. Insurance companies require higher rates; tour operators limit certain activities. That feels like a " no" for many travelers.

Definitely some folks should think twice before traveling, but not only based on their age. It's their level of fitness, says Kirsten Veldman, a former tour guide who now edits a retirement blog. She recalls a 93-year-old who was disabled and traveling alone on a Caribbean tour. "You can't expect to ask a tour leader to be there for you 24/7 for medical care. " she says. "Tour guides don't have the time, skills, and knowledge for it. So, in this case, my advice is: he shouldn't have traveled with us in this situation. "

But some tour operators serve older travelers. For example, Grand Circle Travel started in 1958 to serve senior members. “We have travelers into their 80s and even 90s. Some travel as a couple and some alone,” says company spokeswoman Ann Shannon. “We have no age limit.”

If you ask travel experts, they'll tell you that age is just a number. It's a question of physical, and to a certain extent, mental ability. "Many of our travelers are retired, focused on keeping their good health, and are experienced travelers who have a good idea of what to expect, "says Sara Baer-Sinnott, president of Oldways, a food and nutrition nonprofit that operates tours. "Someone in their 40's may struggle more than someone in their 80s. "

2 . Happiness is not a warm phone, according to a new study exploring the link between young life satisfaction and screen time. The study was led by professor of psychology Jean M. Twenge at San Diego State University (SDSU).

To research this link, Twenge, along with colleagues Gabrielle Martin at SDSU and W. Keith Campbell at the University of Georgia, dealt with data from the Monitoring the Future (MtF) study, a nationally representative survey of more than a million U. S. 8th-, 10th-, and 12th-graders. The survey asked students questions about how often they spent time on their Phones, tablets and computers, as well as questions about their face-to-face social interactions and their overall happiness.

On average found that teens who spent more time in front of screen devices — playing computer games, using social media, texting and video chatting — were less happy than those who invested more time in non-screen activities like sports, reading newspapers and magazines, and face-to-face social interactions.

"The key to digital media use and happiness is limited use," Twenge said. "Aim to spend no more than two hours a day on digital media, and try to increase the amount of time you spend seeing friends face-to-face and exercising — two activities reliably linked to greater happiness."

Looking at historical trends from the same age groups since the 1990s, it's easy to find that the increase of screen devices over time happened at the same time as a general drop-off in reported happiness in U. S. teens. Specifically, young peopled life satisfaction and happiness declined sharply after 2012. That's the year when the percentage of Americans who owned a smartphone rose above 50 percent. By far the largest change in teens' lives between 2012 and 2016 was the increase in the amount of time they spent on digital media, and the following decline in in-person social activities and sleep.

3 . Here on Earth where most of us live, we spend about a third of everyday lying down sleeping and two-thirds standing or sitting in an upright position.

That's not really how it goes in space when people are weightless and the zero gravity environment causes more liquid to shift to the head. Faces get swollen, legs lose volume and appear to be smaller. Many astronauts have complained of eye and back problems after coming back down to Earth and its gravity.

And now scientists say they have discovered some new risks with long-term space flight. A study published recently in JAMA Network Open, a medical journal, examined 11 healthy astronauts who had been on the International Space Station for six months. Eight of them had unusual characteristics observed in their blood. For instance, six of the astronauts had reverse （反向的）blood flow from their heads.

The lead author of the study says he doesn't know if that's actually harmful. The blood is still leaving the head from other pathways, so flowing backwards through a jugular vein（颈静脉） may not be dangerous. But he says it does show a change in how blood moves through the body while in space.

Another issue the study found was blood clots （凝块）. One astronaut had one. Another showed signs of a partial blood clot. That is potentially harmful as the clots can block the flow of blood to the lungs. The astronaut who had one was treated for the rest of the spaceflight and made it home safely.

What does all this mean? Well, one researcher says these issues have probably been oc- curring since humans first went into space and that they would likely resolve themselves when astronauts came back down to Earth. Knowing about them now gives doctors something else to monitor when people leave our atmosphere.

4 . When I was young, I had a wrong understanding of being great. I believed I was special and different and should be rich and famous because of my talent. I was going to live my dream rather than being a “normal” person. But as time passed, reality set in and my perspective changed.

I am a teacher, married to a salesman with a baby and a mortgage（按揭贷款）. Could my life be more normal? Yet, I am okay with this.

Were I to have a conversation with my twenty-year-old self, she wouldn't understand why I'm not going to NYC to get an audition （试演）. In four years my coworkers have never heard me sing. If I'd bought a house, it should have been in an interesting neighborhood with coffee houses at every corner. She would laugh at the corner house in the neighborhood I now call home.

But I know things she didn't know. Life is so much more complicated, wonderful and terrible. I know what it means to work for love, not just sitting back and letting it happen the way it can when you're young. I know about bringing life into the world, and the complexity of emotions.

My life is simple. It is small, and may seem interchangeable with so many other lives there. I may never make an impact outside my house. But I've learned it is important to be relative. To my little girl, I am irreplaceable. When she cries, she calls for “Mama”. When she reaches out, it's for me alone. So, is it a small life? It's perfectly fine to me. In fact, I think it's what I've wanted all along.

6 . Rap, a style of hip-hop music, was created in the 1980s in the United States. It first became popular among young black people in New York City. By the beginning of the 21st century, it had become a presence around the world. Its performers, called rappers, have their own fashion style. They often wear a baseball cap, large jewelry, brightly colored clothes and oversized jeans. And it’s evident that rap is no stranger to negative stereotypes (刻板印象), but this entertainment medium, is actually a means of human expression. You can find a lot of evidence.

Rapper Chen Jinnan performed her hit song Malice From the World on the reality show Rap for Youth. Chen said that she wrote the song last year after receiving a message from a fan who was battling severe depression and had been ignored by her parents and schoolmates. “I shared my own story with her in the hope of offering her encouragement,” Chen told China Daily. Another rapper who appeared on the show is a well-known rapper TangoZ, who expresses his love for his hometown of Hangzhou — his “heaven on Earth”— and raps in the dialect. “Wu dialect is disappearing at an alarming rate, so I struggle to make the situation a bit better.” he told independent media platform RADII China.

Just as Li Yuchun, a mentor (导师) on the reality show, pointed out that rapping is not defined by anger. “A lot of people think that Diss–or disrespect–is the only definition of rap. But on this show, I’m touched and proud of the fact that you can express gratitude and kindness through music writing and rapping,” she said.

Actually, rapping, for most performers, is a way to express opinions and let their voices be heard. If you dive deep into it, you’ll find that it’s charming. Just as Hannah George wrote on the website Soundigest. “It’s a diary ... someone’s life on display for the world to enjoy, grieve (悲伤) with or be inspired by.”

7 . When our Scottish puppy, Annie, reached adolescence, she suddenly stopped following my commands. Previously, if I called “come”, she would fly across our yard to my arms. Now, the 8-month-old gave me a look and ran the other way. Our dog trainer advised us to stop worrying. “She's a teenager,” she said. “She'll grow out of it.”

Now, a new study is backing that up: Dogs experience a period that makes them act out, just like human teenagers. Puppies bond with humans much as children do. “But owners often feel like they're failing when their puppies reach adolescence,” said Lucy Asher, lead author of the new study.

Asher and her team monitored 70 female dogs being raised as guide dogs. They asked caregivers to score them on their attention-seeking behaviors like sitting close to their owners and separation-related behaviors like trembling when left behind. Both types of behaviors show general anxiety and fearfulness. Dogs with high scores entered adolescence earlier — at about 5 months, compared with 8 months for those with lower scores. Further, adolescent dogs that were stressed by separation from their caregivers were also increasingly disobedient to that person, but not others.

To test obedience, the scientists assessed a separate group of 69 guide dogs, first at 5 months and later at 8 months. They asked the dog's caregiver and a stranger to give the command to “sit”. All of the preadolescent puppies quickly sat for both people, but when the same puppies reached adolescence, they refused to follow the order from their caregivers. However, they readily obeyed the stranger. Dogs that weren't securely attached to their caregivers were even more willing to follow the stranger's commands.

Because of the similarity between adolescent puppies and humans, dogs could serve as a model species for studying adolescence in humans. And on a more practical note, the temporary nature of dog disobedience might make us worry less when our puppies suddenly get minds of their own. Just ask Annie — she's now happy to come, sit, and stay a while.

8 . I stood behind the curtain, my hands shaking. As I listened to the crowd laugh at the host's jokes, I thought about why I believed I could do that. Two months earlier, I had signed up for improv（即兴表演）classes at a local theater, along with four other graduate students.

When I first heard about the improv classes, I was torn. I feared getting on stage and performing in front of strangers. However, I knew I wanted to work as a science communicator after finishing my Ph.D., so it seemed like a perfect opportunity to improve my communication ability and gain confidence thinking on my feet.

During our first class, we learned the key concept of improv: “yes, and”. If someone says that rhinos are librarians, for example, then rhinos are librarians. We don't question the logic; we say “yes” and continue with the scene as if nothing is wrong. To do this effectively, we have to avoid second-guessing ourselves. Sometimes scenes go in unexpected directions. The best improv happens when performers stay open to different possibilities. Over time, I started to enjoy our classes. I also became better at listening and communicating clearly in the moment.

That training came in handy 6 months ago, when I was giving a seminar about my science research. An audience member surprised me with a question that didn't grow out of the information I had presented. Instead of getting perplexed, I used that approach, and it helped me find an appropriate answer.

Last year, I used that approach when dealing with confusing data. Instead of getting discouraged, I kept exploring the data and ended up identifying a new type of cell — one that wasn't behaving as expected. If I hadn't stayed open to the possibility that the results were real, I would have missed out on the most exciting finding of my Ph.D. program so far.