“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.”

    Modern graffiti began in big cities in the United States in the 1970s. In New York, young people wrote their names, or 'tags', in pen on walls around the city.

    One of the first 'taggers' was a teenager called Demetrius. His tag was TAKI 183. He wrote his tag on walls and in stations in New York. He did it just for fun and he had never imagined his behavior would have launched an amazing art campaign. Other teenagers saw Demetrius's tag and started writing their tags too. Soon, there were tags on walls, buses and trains all over New York.

    Then, some teenagers started writing their tags with aerosol paint. Their tags were bigger and more colourful. Aerosol paint graffiti became very popular in the 1970s and 1980s. It appeared on trains, buses and walls around the world.

    In the 1990s and 2000s, a lot of graffiti artists started painting pictures. Some artists' pictures were about politics. Other artists wanted to make cities beautiful and painted big, colorful pictures on city walls.

    In some countries, writing or painting on walls is a crime. Sometimes, graffiti artists have problems with the police. In other countries, artists can draw and paint in certain places. For example, in Taiwan, there are 'graffiti zones' where artists can paint on walls. In São Paulo in Brazil, street artists can paint pictures on walls and houses. Their pictures are colorful and beautiful. Some tourists visit São Paulo just to see the street art!

    In Bristol in the UK, there is a street art festival in August every year. Artists paint all the buildings in a street. Lots of people come to watch the artists and take photos. You can see exhibitions of street art in some galleries too. There have been exhibitions of street art in galleries in Paris, London and Los Angeles.

Venom(毒液）from a local scorpion(蝎子）in Cuba is being used by Cuban scientists as an effective weapon to fight cancer. The venom, with stopping pain, anti-inflammatory (炎症） and anti-cancer properties, is the active ingredient in the medicine “Vidatox 30 CH“ which can be used to treat liver, brain, lung and other cancers. The treatment has been successfully used for more than four years in humans after being first tested in biological models. Labiofam, a Cuban laboratory, has breeding(繁殖)centers for both the Red Scorpion and Blue Scorpion. Each month, some 30,000 scorpions in Las Minas town, 270 km east of Havana are made to give the venom. After two years, the scorpions are released back into their natural habitat.

Denyer Sanchez, a biologist from Labiofam, explained that the conditions are adjusted for reproduction, proved by the high number of breeding female scorpions. He said when the offspring(后代）becomes able to live in the environment, we release them because they do not have the necessary size yet to remove their venom, said Sanchez. Sanchez also said that there is still much to research on the exploitation process of scorpions, such as female death rate or the ability to survive of the released scorpions.

Cuban research on the scorpion's venom began at the end of 1980s in Guantanamo province, the island's eastern tip, where a group of biologists and doctors became interested in the stories told by the peasants about the venom's benefits. However，the first discovery was made by Cuban biologist Misael Bordier. In 2001, Bordier visited Mexico's National Autonomous University (UNAM) and presented the research progress in a professional journal. Bordier died in 2005, one year before Cuba's Industrial Property Office gave Labiofam the rights to exploit the patent related to the venom.

    Sue Hendrickson is a self-taught fossil（化石）hunter. As a kid, Sue Hendrickson often walked with her head down. “People said, 'Look up. Smile!” she says. “Now, I realize I was born to look for things and just didn't know it.”

    Sue Hendrickson does more than look—she finds valuable things: Shipwrecks（沉船）with treasure, ancient sunken cities, and in 1990, she found Sue, the world's largest, most complete Tyrannosaurus rex（霸王龙）. Is Hendrickson lucky? Well, maybe. But she also knows how to look.

    “I limit the area where I'm going to look,” she says. No one knew the location of the sunken ship San Diego in the Philippines. For a year, Hendrickson and other researchers searched papers and sailors' diaries. “The descriptions of the ship's sailors led us to the wreck,” she says. The team also used a tool that can respond to metal. This tool found the San Diego. All the work paid off. The 400-year-old ship was complete, with valuable gold and silver coins.

    To find the dinosaur she calls “the biggest animal that ever walked on earth,” Hendrickson started with maps made to search for oil. What Hendrickson found was the largest and most complete T-rex found to date. The T-rex is 42 feet long with 200 bones! Because it is so complete, scientists were able to infer that Sue walked at about 6 miles per hour and did not run faster than 15 miles an hour. Before Sue was discovered, they thought T-rex was much faster. To learn more about T-rex Sue, go to the Field Museum in Chicago.

    There's plenty left to be found, Hendrickson says, including answers to mysterious such as how T-rex lived. “I tell kids that they need to grow up and work them out because all of us old persons haven't yet!”

    On a recent trip to London, I decided to visit some exciting new restaurants that are using technology to change the way people dine out. My first stop was at an Italian restaurant in the city center. When I walked into the restaurant, I was given a tray (托盘)and a special card, but I had no idea what to do next! The manager came up to me and explained that I could swipe (刷) my card at any of the food and drink stations in the restaurant, and that the card would record my order. No waiters necessary! I made my selection and then handed my card to the cashier. Once I'd paid for my meal, I collected it and made my way to the dining area on the second floor. The food was very delicious, but, I must admit, I didn't enjoy having to carry my food up two flights of stairs.

    On the next night, a friend of mine suggested that we visit his favorite high-tech restaurant. When we arrived, I was surprised to discover that there were no paper menus; instead, the menus appeared on the touch screen surface of the table. All we had to do was touch our choices with our fingers and wait for the waiters to bring us our meal. The touch screen tabletop also allowed us to change different tablecloths and even play games. We had so much fun playing games that we hardly touched our food when it arrived--we really should have told the waiter to give us takeaways instead.

    On my last day in London, I decided to get some tapas from a Spanish takeaway near my hotel. I had heard that the owners had placed a webcam (网络摄像机) at the restaurant to allow their customers to watch the long lunchtime queue (队列) online. This came in very handy for me. While I packed my baggage, I kept an eye on the queue and then raced to the restaurant when the lunchtime rush was over. Without that wonderful webcam, I could have missed my plane.

    Tiny microbes(微生物)are at the heart of a new agricultural technique to manage harmful greenhouse gas. Scientists have discovered how microbes can be used to turn carbon dioxide into soil-enriching limestone(石灰石), with the help of a type of tree that grows in tropical areas, such as West Africa.

    Researchers have found that when the Iroko tree is grown in dry, acidic soil and treated with a combination of natural fungi(霉菌)and other bacteria, not only does the tree grow well, it also produces the mineral limestone in the soil around its root.

    The Iroko tree makes a mineral by combining Ca from the earth with CO2 from the atmosphere. The bacteria then create the conditions under which this mineral turns into limestone. The discovery offers a new way to lock carbon into the soil, keeping it out of the atmosphere. In addition to storing carbon in the trees, leaves and in the form of limestone, the mineral in the soil makes it more suitable for agriculture.

    The discovery could lead to reforestation(重新造林)projects in tropical countries, and help reduce carbon dioxide in the atmosphere in the developing world. It has already been used in West Africa and is being tested in Bolivia, Haiti and India.

    The findings were made in a three-year project involving researchers from the Universities of Edinburgh, Granada, Lausanne and Delft University of Technology. The project examined several microbiological methods of locking CO2 as limestone, and the Iroko-bacteria way showed best results. Work was funded by the European Commission under the Future Emerging Technologies (FET) scheme.

    Dr Bryne Ngwenya of the University of Edinburgh's School of GeoSciences, who led the research, said: "By taking advantage of this natural limestone-producing process, we have a low-tech, safe, readily employed and easily operating way to lock carbon out of the atmosphere, while improving farming conditions in tropical countries?