Is there a magic cutoff period when offspring become accountable for their own actions? Is there a wonderful moment when parents can become spectators (旁观者) in the lives of their children and shrug, "It' s their life," and feel nothing?

    When I was in my twenties, I stood in a hospital corridor waiting for doctors to put a few stitches in my son's head. I was asked, "When do you stop worrying?" A nurse said, "When they get out of the accident stage." My mother just smiled faintly and said nothing.

    When I was in my thirties, I sat on a little chair in a classroom and heard how one of my children talked incessantly, disrupted (打断) the class, and was headed for a career making license plates. As if to read my mind, a teacher said, "Don't worry. They all go through this stage, and then you can sit back, relax, and enjoy them." My mother listened and said nothing.

    When I was in my forties, I spent a lifetime waiting for the phone to ring and the cars to come home, the front door to open.

    My friends said that when my kids got married I could stop worrying and lead my own life. I wanted to believe that, but I was haunted by my mother' s wan ( 淡淡的 ) smile and her occasional words, "You look pale. Are you all right? Call me the minute you get home."

    Can it be that parents are sentenced to a lifetime of worry? Is concern for one another handed down like a torch to blaze the trail of human frailties and the fears of the unknown? Is concern a curse? Or is it a virtue that elevates us to the highest form of life?

    One of my children became quite irritable recently, saying to me, "Where were you? I've been calling for three days, and no one answered. I was worried!!!"

    I smiled a wan smile.

    If you're wondering when you might get the flu, a new study indicates you should keep an eye on your local weather report.

    According to a research published in the Journal of Clinical Virology, if you keep your eye on the weather and watch for the first major dip in the temperature, you can essentially mark your calendar in prediction for an outbreak the flu.

    To figure out how the weather and flu outbreak may be connected, researchers analyzed statistics of 20,000 people in an area over three seasons. The number of people who caught the flu was then compared with local weather data.

    After each season, the team noticed one consistent finding: The first really cold period with low outdoor temperatures and low humidity (湿度) was always followed by a week of a mass influenza outbreak.

    The researchers say that aerosol particles (气溶胶粒子) containing virus and liquid are more able to spread in cold and dry weather. So, in theory, if you sneeze or cough and the surrounding air is very dry, the air will absorb the moisture and the particles containing the virus keep spreading through the air for a longer period of time.

    Luckily there are ways to keep off the illness regardless of the weather. Washing your hands, coughing into the crook (弯曲) of your arm and getting vaccine (疫苗) are the best ways to prevent the flu from spreading. People over the age of 65, pregnant women and young children are at the highest risk of developing complications (并发症) related to the virus, according to the CDC.

    The older we get, the more we learn, the better able we are to know what's right. Right? Not always. Sometimes the aging process can remove completely the natural aspects that keep us curious and give us strength to figure out what to do. As a matter of fact，children of all ages teach us lessons in our own lives.

    When a kid says“ That wasn't nice 'or' I don't like your shirt” or “I hate that kind of food!”, it's a natural reaction(反应)to shush the child not to do so, but what they say is true. When children see a wrong being done, they will interrupt to say it's not right. As adults, we usually sit nearby rather than hold a strong opinion or say something that might be unpopular.

    Kids cry, stamp( 跺) their feet or yell with excitement while it isn't socially acceptable for an adult. Letting emotions out and then moving on to deal with things, so jump and yell "yippee" when you are happy about something. Have a good cry when being upset. Stamp or throw a pillow when being alone and need to release. Most of life becomes a series of things once you reach a certain age. Finding pleasure and laughing seems out of place or silly when gaining knowledge or skills.

    “Why is the sky blue?” “ How much does an elephant weigh?” There are certain things that the Internet can tell you, but what about learning something in the first hand like the science experiment in the kitchen, digging up rocks in the backyard, how high the bicycle's wheels can fly over the gravel( 砂砾)? Don't stop exploring and find new learnings in the real world.

    Have you ever wondered what wild animals do when no one is watching? Scientists have been able to record the "private" moments of wildlife with leading-edge technology. Low-cost, dependable and small modern cameras are of big help.

    Cameras placed in hard-to-reach places have taken videos of everything from small desert cats to later snow loving felines (猫科) in the northern Rocky Mountains. These cameras are important tools to learn new information on wildlife.

    Some videos help scientists see the effects of climate change. For example, the desert animal javelin and the tree-loving coatimundi have been caught on cameras north of their normal home. This could mean global warming is enlarging their living area northward.

    Researchers use cameras along with global positioning systems, or GPS. They attach GPS devices (设备) to mule deer and antelope in and around Yellowstone National Park. Then they can record their movements, or migrations (迁移) . These cameras can be left in very rural (荒野的) areas for days, weeks or even month. They can provide information on how many animals are moving over a given period of time.

    Rural video can show details about animal behavior, such as the calls made by migrating. Also some cameras record animal life and show everything from bison in Saskatchewan, Canada, to the underwater weed forest off California's Channel Islands.

    However, rural cameras have their problems too. Animals such as wolverines and bears sometimes attack them. Scientists do not know if the attacks are the result of anger or interest. Also, the devices have become popular tools to help hunters look for animals. Some people argue that it is unfair to use the cameras that way. Even with such problems, rural cameras are clearly an important scientific tool in researching wild animals.

    My name is Kobus Vermeulen. On February 16, 2015, I was one of five South Africans among the 100 people selected by Mars One to begin training to live on the Red Planet. The Dutch not-for-profit's aim is simple: build a human colony (殖民地) on Mars. Since I have begun this journey, the one question that people ask me most is why I want to leave a good planet for wasteland. Here is why.

    I have been interested in Mars since I was a child, and I always thought that if I had the opportunity to leave the planet, I would take it. So the why begins with a child's dream.

    However, as I grew, so did the why. In my eyes, since the 1970s the public has stopped trying to learn more about space. We've put our dream aside. We're satisfied with getting our dose (一份) of the future from sci-fi movies and comic books. And so the first part of my motivation (动机) is to get people thinking about space travel and the colonization (殖民化) of other planets in real terms again instead of just as sci-fi visions of the future.

    If we want that future, the truth is that we have to build it, and anything worth doing comes with risks. Somebody has to take the risks, and I, along with thousands of other people, am willing to take them.

    But it goes deeper than that. If the task of Mars One is even partially (部分地) successful, it will encourage a new generation of scientists and engineers that will build us an even better future.

    Without a dream, there is no reason to build those things. The public that does not try to understand science and technology does not choose good leaders. Leaders who don't care for science and technology do not make budgets (预算) for it. Besides, without the money, the dream dies. Projects like Mars One are like a focusing lens (聚焦透镜) for dreams. It is an opportunity to change hearts and minds at the grassroots level.

    Earlier this month, two rock climbers achieved what many thought impossible: They climbed up the 3,000-foot-high Dawn Wall in Yosemite National Park without specialized equipment. Climbing without this equipment is called "free-climbing." Until now, no one had free-climbed to the top of the rock face, which is a part of the mountain EI Capitan.

    EI Capitan, which means "the captain" or "the chief" in Spanish, has always presented a challenge to climbers. But the Dawn Wall, on the mountain^'s southeast face, is a particularly difficult route to the summit (顶峰). It is a rock formation that is both steep and relatively smooth. This makes free-climbing the rock face seem almost impossible.

    About seven years ago, professional climber Tommy Caldwell spotted a possible route up the wall. It took years of planning and preparation, but this month, Caldwell, 36, and his friend Kevin Jorgeson, 30, finally make the climb.

    Free climbers do use ropes and other basic safety equipment to catch them if they fall — and Caldwell and Jorgeson fell often. Before starting their climb, they broke down their route into 32 sections. Each section was based on a rope length called a "pitch." The rope was secured into the rock face to catch the climbers if they fell.

    Caldwell and Jorgeson's goal was to climb the Dawn Wall without returning to the ground. If they fell, they had to start that pitch all over again. The two men started climbing on December 27. They slept in hanging tents, and a team of friends brought them food each day.

    The men had spent years rehearsing (排练) the movements it would take to get through each pitch. They made it through the first half of the climb relatively easily. But halfway up, Jorgeson ran into trouble. In one difficult spot, he fell each time he attempted to climb. After 10 days of trying, Jorgeson finally made it to the next pitch.

    Getting through that troublesome pitch gave both climbers renewed energy. They finished the rest of the climb five days later, on January 14.