“Hello, Earth! Can you hear me?” That's voice more than 400,000 people received recently. It was from Philae, a space vehicle that landed on a comet(彗星)in 2014. However, its transmissions (传输信号)back home went silent since then.

It took a long time for Philae to make its way across the solar system (太阳系)and reach comet 67P/C-G. The pace vehicle got there aboard the Rosetta probe (探测器), which has been circling around the comet since Philae separated from it in November, 2014．

Philae's job was to collect materials to study the comet's composition. And for about two and a half days after landing, it did just that, sending the information back to scientists on Earth. But Philae's landing on the comet's icy surface had not been smooth. While touching down, it jumped up and ended up in the shadow of something like a huge rock. Philae runs on solar power, but there was no light in the place where it landed. In the end, it failed to work.

However，as comet 67P/C-G moved closer to the sun, more sunlight reached the space vehicle, allowing it to power up and come back online. Philae then sent something to Rosetta, which passed on the information back to Earth.

“We only received the information for about 85 seconds, but that's enough to let us know it is alive and well,”says Stephan Ulamec, who works for the European Space Agency.“We hope to work out where it landed exactly on the 4-kilometer-wide comet. Now we plan to change how Rosetta moves so that Philae can keep on communicating and receiving instructions.”

    Dolphins (海豚) live in a dark underwater world. It's often impossible to see each other or anything else around them, so sound plays an important role in their survival. To communicate with each other, dolphins produce all kinds of sounds.

    Only other dolphins understand what the sounds mean. Scientists haven't uncovered their secret communication, except for one kind of whistle. It might last less than a second, but this whistle is a big deal. Why? Because these whistles are actually names of dolphins — and every dolphin has one. Scientists call these sounds a “signature whistle.” When other dolphins hear the whistle, they know which dolphin is calling.

    Dolphins often hunt by themselves but still need to stay connected to the group. Since they can't always see each other, dolphins use their signature whistles to check in with other dolphins hundreds of yards away. “In coastal areas, dolphins exchange whistles even when they're a third of a mile apart,” says Greg Campbell, who studies animals. That means dolphins shout out to group members that might be nearly five football fields away.

    What's amazing is who names the baby dolphin. Not the mother. Not an auntie dolphin or another group member. Scientists believe the baby dolphin itself comes up with the signature whistle. Like human babies, a baby dolphin plays with sounds throughout its first year. While testing its sound skills, a baby dolphin is doing something amazing. It's creating or figuring out its signature whistle. How or why it chooses its signature whistle is not clear. Studies show that most of the time the signature whistle is nothing like its mother's or group members' whistles.

    When the baby dolphin is about a year old, its signature whistle is set. It repeats it often so the other dolphins learn to recognize it.

    Deciphering(破译) dolphin names is just the beginning of figuring out what dolphins communicate about. Do they chat about sharks? Discuss the tides? Maybe they even have a name for people. Someday scientists are to decipher the rest of dolphins' communication.

    Hidden from the noise of Washington, D.C., Hillwood Museum is a special treasure. It contains (包含) one of the finest personal collections (收藏) of Russian and French art in the world.

    Hillwood Museum was once the home of Marjorie Merriweather Post. She was a rich businesswoman. She owned one of the largest food companies in the United States. She was also very interested in collecting beautiful French art and furniture.

    She moved to Russia in the 1930s as her third husband, Joseph Davies, became the American ambassador (大使) in Moscow. Marjorie Merriweather Post had a love for Russian art as well. She bought the house in Washington in 1955 and she wanted to make it into a museum after her death. Many art experts helped Mrs. Post create its fine collection.

    Hillwood has many rooms which are filled with her treasures. Visitors can see beautiful music boxes from the eighteenth century and colorful paintings of European princesses (公主). Experts say the ancient wood and gold furniture from France is some of the finest ever made. Visitors can even look at Mrs. Post's jewels and clothes.

    The museum also has several beautiful gardens. One is designed like the gardens in Japan. It has a bridge and visitors can watch flowers floating in the water. Flowers are also grown all the year in a special glass building or greenhouse. These flowers are placed in the house throughout the year.

After a walk, visitors can rest at a nearby eating place. They can also buy objects to remember this special museum.

    In 1996, someone found some very old clothes in an old mine in Nevada, USA; they included a pair of dirty old jeans. Today, those jeans are very valuable, and they are now in the Levi Strauss Archival Collection in San Francisco. The jeans, which are over 120 years old, are the oldest pair of Levi's 501 jeans in the world.

    They are almost the same as a modern pair of 501's; there are just some small differences in the detail. For instance, today's 501's have two back pockets, while the old pair just has one.

    In 1853, a young tailor from Germany, called Levi Strauss, began working in San Francisco; Levi sold thick canvas(帆布) to miners; the miners used the canvas to make tents.

    One day, a miner told Levi that he could not find trousers that were strong enough for work in the gold mines. Levi decided to make some trousers out of canvas. Very soon, he sold all the canvas trousers he had made! They were just what miners wanted.

    However, the canvas was rather heavy and stiff(坚硬的). Levi therefore began to look for a different textile(织物). Soon he found a heavy textile from France; it was denim(斜纹粗棉布). Denim was a bit lighter than canvas, but it was very strong. It was ideal for miners.

    However, original denim was almost white, and miners did not like the color! Their denim trousers got dirty as soon as they began working! Levi Strauss therefore decided to use colored denim, and he chose dark blue. In 1873, he began to make denim trousers with metal rivets(铆钉) to make them stronger. “Blue jeans” arrived!

Levi's jeans were so popular that his company got bigger and bigger. Soon, other firms were making blue jeans too. Miners liked them, but so did cowboys and other working men. Blue jeans became classic American working trousers. After the Second World War, jeans became popular all over the world. Today, blue jeans are made all over the world.

    One family, which moved from Japan and settled at the turn of the century near San Francisco, had built a business in which they grew roses and trucked them into San Francisco three mornings a week.

    The other family also marketed roses. For almost four decades the two families were neighbors, and the sons took over the farms, but then on December 7, 1941, Japan attacked Pearl Harbor. Although the rest of the family members were American, the father of the Japanese family had never been naturalized. As they planned to leave the country, his neighbor made it clear that, if necessary, he would look after his friend's nursery (花圃). It was something each family had learned in church-Love the neighbor as themselves. "You would do the same for us," he told his Japanese friend.

    It was not long before the Japanese family was transported to a poor landscape in Canada. A full year went by. Then two. Then three. While the Japanese neighbors were in Canada, their friends worked in the greenhouses. Sometimes the father's work could stretch to 16 and 17 hours. And then one day, when the war in Europe had ended, the Japanese family packed up and boarded a train. They were going home.

    What would they find? The family was met at the train station by their neighbors, and when they got to their home, the whole Japanese family were shocked. There was the nursery, complete, clean and shining in the sunlight, neat, prosperous and healthy. And the house was just as clean and welcoming as the nursery. And there on the dining room ground was one perfect red (玫瑰花蕾), just waiting to unfold-the gift of one neighbor to another.

    Race walking shares many fitness benefits with running, research shows, while most likely contributing to fewer injuries. It does, however, have its own problem.

    Race walkers are conditioned athletes. The longest track and field event at the Summer Olympics is the 50-kilometer race walk, which is about five miles longer than the marathon. But the sport's rules require that a race walker's knees stay straight through most of the leg swing and one foot remain in contact (接触) with the ground at all times. It's this strange form that makes race walking such an attractive activity, however, says Jaclyn Norberg, an assistant professor of exercise science at Salem State University in Salem, Mass.

    Like running, race walking is physically demanding, she says, According to most calculations, race walkers moving at a pace of six miles per hour would burn about 800 calories(卡路里) per hour, which is approximately twice as many as they would burn walking, although fewer than running, which would probably burn about 1,000 or more calories per hour.

    However, race walking does not pound the body as much as running does, Dr. Norberg says. According to her research, runners hit the ground with as much as four times their body weight per step, while race walkers, who do not leave the ground, create only about 1.4 times their body weight with each step.

    As a result, she says, some of the injuries associated with running, such as runner's knee, are uncommon among race walkers. But the sport's strange form does place considerable stress on the ankles and hips, so people with a history of such injuries might want to be cautious in adopting the sport. In fact, anyone wishing to try race walking should probably first consult a coach or experienced racer to learn proper technique, she says. It takes some practice.