The tallest building in the United States, the One World Trade Center, opened on November 3, 2014 in New York. The building is 1,776 feet tall, making it the 3rd tallest building in the world. It has 104 floors. The building stands in the area where the twin towers of the World Trade Center once stood. On September 11, 2001, a group of terrorists destroyed these twin towers and killed nearly 3,000 people. It took 8 years to build the new One World Trade Center. Does the height of the building in feet reminds you of something in history? The number is the year when the United States declared(宣布) its independence(独立) from Great Britain.

    One problem with such a tall building is how to clean the windows. Well, a platform(平台) hangs from ropes, and workers on the platform clean windows. On November 12, while two men were busy cleaning windows, a rope of the platform broke near the 68th floor. The two men were saved by cutting a hole in the glass window.

The two tallest buildings in the world are the BurjKhalifa in Dubai, UAE and the Makkah Royal Clock Tower in Mecca, Saudi Arabia.

    Sound travels very well through water-much better, in fact, than it does through air. So it shouldn't be surprising that many ocean animals make noise. They use sound to communicate and hunt. As biologist Brandon Southall says, “Their whole world is related to sound.”

    Dolphins whistle, organizing hunts. Lovesick whales sing so loudly they can be heard hundreds of miles away. But these days they aren't the only ones sounding off. They have more and more competition from human machines.

    Every day, thousands of huge container ships sail across the world's oceans. On top of the engine noise, the ships' propeller (螺旋桨) make a loud noise all the time. All that can make it hard for ocean animals trying to listen out for friends, or dinner. Animals swimming nearby a ship can be deafened or even killed.

    Underwater construction can also be dangerously loud. When construction machines called pile drivers were used during repairs to the San Francisco-Oakland Bay Bridge, dead fish appeared.

    Geologist (地质学家) pound on the seafloor too, trying to find oil wells and map Earth's surface. The results are useful lo science, but all that hammering probably gives ocean animal a headache.

    As people realize how important sound is to ocean animals, they are looking for ways to reduce human noise. Ships could get quieter just by slowing down. Engineers are also trying to find quieter propeller ships.

    Now some companies are using a simple invention called a bubble curtain, which makes sound waves passing through it lose energy and gel quieter. It seems to work - when bubble curtains were fixed on the San Francisco bridge project fish deaths dropped.

    We still have a lot to learn about sound in the oceans, but together we can help keep the sea a quieter place.

    More than 30,000 people went to the White House on Monday for the 136th Easter Egg Roll (复活节滚彩蛋). President Barack Obama and First Lady Michelle Obama held the event by inviting thousands of kids to color and look for eggs. The theme(主题) of the day was “Hop Into Healthy, Swing Into Shape.” It was part of the First Lady's “Let's Move!” program to reduce obesity rates (肥胖率) among American kids. Mrs. Obama spoke to young reporters about her goal(目标) to get children to eat right and keep moving.

    “We are working to make sure that kids born today grow up healthy, learn how to have balanced meals, and get more physical activity into their lives,” she said.

    Mrs. Obama said she wants children across the nation to understand that "exercise isn't just hard work, it's play. If you're running around with your dog, you're getting exercise. If you walk up the stairs, that's exercise, But if you're sitting in front of the TV or on a computer game, you're not exercising.”

    The First Lady said that for kids who have balanced meals most of the time, having a special snack, like chocolate, will not hurt." And if you are active, you can splurge (挥霍) a little more," she said. Mrs. Obama's favorite "splurge food" is French fries. But she balances her splurging by exercising almost every day. She loves to play tennis and she practices yoga.

    “A lot of kids look up to(敬仰) athletes, and I think it's important for athletes to share their good habits,” Mrs. Obama said. "Kids aren't just going to wake up and be LeBron James. He's practicing and eating right and working out and training. Our athletes can be really good messengers to kids who look up to them--they can say to kids, 'If you really want to be like me, then you really do need to eat your vegetables.'”

Help Hermit Crabs

    Hermit crabs are nature's recyclers. They eat waste and help keep oceans and shores clean. Unlike other crabs, the hermit crab has a thin outer shell over its soft tail. This makes the hermit crab easy prey for hungry predators(天敌).Hermit crabs stay safe by living in old seashells. A hermit crab is picky(狡猾); it tries on many shells until it finds one that fits just right. In recent years, however, many hermit crabs have had trouble finding their perfect homes. What is the problems. There are not enough shells to go around!

    One reason for the seashell shortage is that ocean water is not as clean as it once was. This has caused chemical changes to sea water. Some sea animals, like snails, are affected by these changes.  Now there are fewer snails making shells. People visiting the beach often take shells home as souvenirs(纪念品).This is another problem. Other people even take shells for their own pet hermit crabs! They do not realize that hermit crabs in the wild need those shells too.

    Now people are working to solve this hermit crab housing shortage. They are teaching beach-Boers to leave seashells where they belong--at the seashore! Some people even make fake seashells that they hope the hermit crabs will like. For example, a group called Project Shelter invited people who visited their website to create different designs for hermit crab shells.

    These designers had a lot to consider. What kind of material should be used to build a seashells. The material must be light enough for the hermit crab to carry, but strong enough to protect the crab from predators. The man-made shells could not contain glue or any other substance(物质)that might harm a hermit crab. Another challenge with building a hermit crab home was the opening to the shell. Too big would mean the crab would not feel safe. Too small would be uncomfortable, and the crab would not want to move in.

    The Project Shelter shells are placed in the wild for hermit crabs to find. Lucky hermit crabs can move into these new dream homes.

    Smile! It makes everyone in the room feel better because they, consciously or unconsciously, are smiling with you. Growing evidence shows that an instinct for facial mimicry(模仿) allows us to empathize with and even experience other people's feelings. If we can't mirror another person's face, it limits our ability to read and properly react to their expressions. A review of this emotional mirroring appears on February 11 in Trends in Cognitive Sciences.

    In their paper, Paula Niedenthal and Adrienne Wood, social psychologists at the University of Wisconsin, describe how people in social situations copy others' facial expressions to create emotional responses in themselves. For example, if you're with a friend who looks sad, you might "try on" that sad face yourself without realizing you're doing so. In "trying on" your friend's expression, it helps you to recognize what they're feeling by associating it with times in the past when you made that expression. Humans get this emotional meaning from facial expressions in a matter of only a few hundred milliseconds.

    "You reflect on your emotional feelings and then you generate some sort of recognition judgment, and the most important thing that results in is that you take the appropriate action—you approach the person or you avoid the person," Niedenthal says. "Your own emotional reaction to the face changes your perception of how you see the face in such a way that provides you with more information about what it means."

    A person's ability to recognize and "share" others' emotions can be prevented when they can't mimic faces. This is a common complaint for people with motor diseases, like facial paralysis(瘫痪) from a stroke, or even due to nerve damage from plastic surgery. Niedenthal notes that the same would not be true for people who suffer from paralysis from birth, because if you've never had the ability to mimic facial expressions, you will have developed compensatory ways of interpreting emotions.

    People with social disorders associated with mimicry or emotion-recognition damage, like autism(自闭症), can experience similar challenges. "There are some symptoms in autism where lack of facial mimicry may in part be due to limitation of eye contact," Niedenthal says.

    Niedenthal next wants to explore what part in the brain is functioning to help with facial expression recognition. A better understanding of that part, she says, will give us a better idea of how to treat related disorders.

    The idea behind Facebook is to make us feel connected all the time. But in my research, I've found that the truth is quiet different.

    Technology, it turns out, has made being alone seem like a problem that needs soling. When young people are alone, even for a minute or two, they feel the need to connect to get on Facebook or some other social networks and chat. But in connecting, they often end up feeling more isolated. Why? Because by being in constant (不断的) connection, they lose the ability to feel satisfied with their own company (独处).

    Facebook can help us keep in touch with our friends, but we too often use it instead of spending face to face time with them. And since we feel the need to keep up with them online, we don't have moments of loneliness where we can collect our thoughts and learn how to be comfortable being alone.

——Sherry Turkle, Profescer

    Facebook connects more of us to more of our friends and family in more places than we have ever been connected before. Yes. Facebook is a huge time sink -maybe the biggest ever. Many people post useless stuff. And seeing too much of your friends lives can make you jealous (嫉妒的), but it won't make you lonely.

    Jane, a former student of mine, who is back in New York after living abroad for ten years told me that Facebook helps her a lot. The first time she moved back to New York from abroad, she felt disconnected from her family and friends. now because of lots of photos and information updates (更新), she knows what is happening with her friends all the time.

    In fact, if you are lonely in real life, you will be lonely online as well.

——Sree Steniveasan, Chief Digital office