Floods are second only to fire as the most common of all natural disasters.They occur almost everywhere in the world,resulting in widespread damage and even death.Consequently,scientists have long tried to perfect their ability to predict floods.So far,the best that scientists can do is to recognize the potential for flooding in certain conditions. There are a number of conditions,from deep snow on the ground to human error,which cause flooding.

    When deep snow melts it creates a large amount of water.Although deep snow alone rarely causes floods,when it occurs together with heavy rain and sudden warmer weather it can lead to serious flooding.If there is a fast snow melt on top of frozen or very wet ground,flooding is more likely to occur than when the ground is not frozen.Frozen ground or ground that is very wet cannot absorb the additional water created by the melting snow.Melting snow also contributes to high water levels in rivers and streams.

    Rivers that are covered in ice can also lead to flooding.When ice begins to melt,the surface of the ice cracks and breaks into large pieces.These pieces of ice move and float down the river,They can form a dam in the river,causing the water behind the dam to rise and flood the land upstream.If the dam breaks suddenly,then the large amount of water held behind the dam can flood the areas downstream too.

    Broken ice dams are not the only dam problems that can cause flooding.When a large human-made dam breaks or fails to hold the water collected behind it,the results can be devastating.Dams contain such huge amounts of water behind them that when sudden breaks occur,the great force of the water is like a great tidal wave.The dam waters can travel tens of kilometres,cover the ground in metres of mud and litter,and drown and crush every thing and creature in their path.

    Although scientists cannot always predict exactly when floods will occur,they do know a great deal about when floods are probably going to occur.Deep snow,ice-covered rivers,and weak dams are all strong conditions for potential flooding.

    People do not analyze every problem they meet. Sometimes they try to remember a solution from the last time they had a similar problem. They often accept the opinions or ideas of other people. Other times they begin to act without thinking. They try to find a solution by trial and error. However, when all these methods fail, the person with a problem has to start analyzing. There are six stages in analyzing a problem.

    First the person must recognize that there is a problem. For example, Sam's bicycle is broken, and he cannot read it to class as he usually does. Sam must see that there is a problem with his bicycle.

    Next the thinker must define the problem. Before Sam can repair his bicycle, he must find the reason why it does not work. For instance, he must determine if the problem is with the gears, the brakes, or the frame. He must make his problem more specific.

    Now the person must look for information that will make the problem clearer and lead to possible solutions. For instance, suppose Sam decided that his bike does not work because there is something wrong with the gear wheels. At this time, he can look in his bicycle repair book and read about gears. He can talk to his friends at the bike shop. He can look at his gears carefully.

    After studying the problem, the person should have several suggestions for a possible solution. Take Sam as an illustration. His suggestions might be: put oil on the gear wheels; buy new gear wheels and replace the old ones; tighten or loosen the gear wheels.

    Eventually one suggestion seems to be the solution to the problem. Sometimes the final idea comes very suddenly because the thinker suddenly sees something new or sees something in a new way. Sam, for example, suddenly sees that there is a piece of chewing gum between the gear wheels. He immediately realizes the solution to his problem: he must clean the gear wheels.

    Finally the solution is tested. Sam cleans the gear wheels and finds that afterwards his bicycle works perfectly. In short, he has solved the problem.

    Spring is a wonderful season to celebrate rebirth and new life. The long, cold winter is over. The weather is warmer and sunnier. The trees again have leaves and the flowers are blooming. The season represents hope, joy and beauty. At this time, many people think of this classical music piece—Spring, which shows happiness. Italian composer Antonio Vivaldi wrote it in the seventeen hundreds.

    However, not all songs about spring are happy. This song written and sung by K.D. Lang is about dreaming of spring in cold dark places. She recorded I Dream of Spring in 2008.

    Richard Rodgers and Oscar Hammerstein wrote It Might as Well Be Spring for the movie State Fair in 1945.Frank Sinatra sings it. It is a feeling of restlessness or excitement brought on by the coming of spring. Richard Rodgers also wrote Spring Is Here, this time with Lorenz Hart. Ella Fitzgerald sings this song about feeling lonely during this season.

    Frank Loesser wrote the sad song, Spring Will Be a Little Late This Year. Why has the season been delayed? Because the singer's lover has left her. Sarah Vaughn released(发行) her version of the song in 1953.

    By now you may be thinking, "Enough with the sad songs, already！"OK ,then how about a cowboy song? Gene Autry was one of the America's most famous singing cowboys. He recorded When It's Spring time in the Rockies in 1937.

    And finally, we'll leave you with a sunny song called Up Jumped Spring. Freddie Hubbard wrote this jazz song in 1977 and Billy Taylor Trio performs it.

    As our closest neighbor in space, the moon has been the subject of popular myths, songs and poems since ancient times. And it has no less fascinated scientists. But even after centuries of research many questions remain to be answered about Earth's only satellite. Perhaps the Chang'e-4 lunar probe will be able to reveal more of its secrets.

    On Dec 8, the probe lifted off from Xichang Satellite Launch Center in Sichuan Province. It is the first probe to the far side of moon.

    The Earth's gravity slows the moon's rotation, matching it to the speed of its orbit. Thus, the far side of the moon is always dark and has never been seen. It's this sense of the unknown that makes the far side of the moon such an interesting place for scientific and space exploration.

Long exposed to solar winds, the far side may have the special soil and minerals in its upper mantle(地幔).For this reason, Chang'e-4 will study the effect of solar winds on the lunar surface and any minerals found beneath the spacecraft.

    Chang'e-4 is also carrying flower seeds and potato and silkworm eggs to see whether life is possible on the moon. If it is, then the moon will become a more likely destination for space travel in the future. However, due to communication problems, exploration of the dark side will not be easy.

    As the far side is blocked off from us, radio noise coming off Earth is also blocked. This is why China launched the relay satellite Queqiao in May—so that communication between Earth and the probe could go ahead. Power supply will also be a challenge to the mission.

    Chang'e-4 gets energy from the sun through its solar panels. However, a lunar day has the length of 28 Earth days. This means that the probe will need to orbit the moon for over 20 days to be in a position to be able to land in moon daylight and so use its solar panels.

    According to Xinhua, if everything goes well, the satellite will land on the far side on Jan 2.

    The New York Times described the journey as “groundbreaking”, and wrote that it will “give clues to the history and development of the moon”.

    Unbelievable Stories of Animals Acting Just Like Humans

    Horses are picky eaters

    Horses have an even better sense of smell than humans do. When horses raise their noses and open their nostrils (鼻孔) , their nervous system allows them to sense smells we can't sense. This might explain why they refuse dirty water and carefully mover around meadows, eating only the tastiest grasses, experts say.

    Whale says thanks

    In 2011, a whale expert spotted a humpback whale trapped in a fishing net and spent an hour freeing it. Afterward, in an hour-long display of thanks, the whale swam near their boat and leaped into the air about 40 times.

    Pandas like to be naughty

    Is there anything more lovely than a baby panda, except maybe a human baby? In fact, baby pandas sometimes behave like human babies. They sleep in the same positions and value their thumbs. Pandas are shy by nature for its shy behaviors such as covering its face with a paw of ducking its head when confronted by a stranger.

    A cat honors its owner

    Paper towels, and a plastic cup are just a few of the gifts that Toldo, a devoted three-year-old gray-and-white cat, has placed on his former owner Iozzelli Renzo's grave every day since the man died in September 2011. Renzo adopted Toldo from a shelter when the cat was three months old, and the two formed an inseparable bond. After Renzo passed away. Toldo followed the coffin to the cemetery, and now “stands guard” at the grave for hours at a time.

    A few years back I worked in a university building that also housed a department full of psychologists, all of whom seemed to see us as perfect guinea pigs(豚鼠) for their latest theories. If an eager graduate student showed up in my office bearing desserts and asked me to pick one, I'd cast a careful glance and ask "Why?" before grabbing the apple pie.

    So one day, when someone from the Psychology Department posted instructions in the bathroom persuading all of us to "Think about five things for which you're grateful every day for a week!" my response was frankly doubtful. I did the math. Five things a day for seven days is a lot of brainpower to expend without so much as the promise of an apple pie.

    I wandered into the office of Heidi Zetzer, the director of our school's Psychological Services Clinic. "What's with the gratitude thing?" I asked. You don't ask an academic question－even a simple one unless you're prepared for a long answer. Heidi came alive, and I sat down. That's when I first heard the term "positive psychology". The gratitude thing, as I had called it, was but one small and simple element of the practice. "Kind of like training the brain to focus on joy," my friend Heidi explained. "It's only a week," she urged. "Try it." I did. And guess what? It worked.

    Every day for a week, I found five distinct things for which I was thankful. They had to be different every day. I couldn't get away with just being grateful for my wonderful husband. But I could, suggested Collie Conoley, another positive psychologist, express my gratitude for specific aspects of a certain person each day. He's a great cook. He always puts our family first.

    Life will never be perfect. I still see new stories that annoy me. The traffic in my city is maddening. I wish I could speed up my recovery. But with just one simple exercise, I'm rediscovering the peace of that old saying: accepting the things I can't change, working without complaint to change what I can, and being wise enough to know the difference.

    And all it took was a little gratitude.