Have you ever lost your direction? Then you might find satellite navigation(satnav) systems(卫星定位系统) helpful.

    A satnav system uses groups of satellites. They send information to a receiver(接收器), such as your smartphone. Then they can find where you are.

The earliest satnav system is the Global Positioning System(GPS) of the United States. The US has put 24 satellites into space to make sure GPS can locate(定位) a person correctly and globally. Likewise, Russia's GLONASS and European Union's Galileo can also work globally.

    But China is catching up, building its own BeiDou Navigation Satellite System. BeiDou is China's homegrown satnav system, reported Xinhua. It was set up in 2000, when China sent BeiDou's first navigation experiment satellite into space. With it, China became the third country to build a satnav system after the US and Russia.

    BeiDou can find you wherever you are. It helps you go faster by finding shortcuts(捷径) and using correct directions. When you are in trouble and call the police, they will know exactly where you are if you have a cellphone that uses BeiDou.

    Today, there are more than 20 BeiDou satellites above our heads. And the system is able to offer open services to the Asia-Pacific region(亚太地区).

    In November, China plans to send more BeiDou-3 satellites into space. BeiDou-3's position accuracy(准确度) is less than five meters, Ran Chengqi, a senior designer of the satellite navigation system, told China Daily.

    By 2020, BeiDou is planned to have 35 satellites and begin serving globally, reported Xinhua.

    Psychology tells us that many people hate to take risks. But it is good for us to take risks, especially when the risk is to achieve a desired result. In that way, we become stronger and braver.

    Our human nature should be to take risks, but some people just sit and wish they didn't have the fear to move on. This is because they failed a few times in their lives. Please step out and don't let the past hold you back from living life to the fullest. Move forward and move on! In studying the psychology of taking risks, we find that human provides us with the desire to experiment and take chances.

    Risk taking is a great advantage that allowed our ancestors to become stronger and stronger day by day. By taking risks they fought off enemies and discovered new territories. This attitude has become a part of our modern culture. Riding a roller coaster is a common risk taking activity. Even each person seems to enjoy the risk although they have the understanding that it is dangerous. This psychological and biological connection creates an interesting connection between what is unsafe and what humans enjoy.

    Getting in a car each day is a risk. Getting out of bed is a risk, too. We need to take risks so that we can complete many things. Astronauts take risks when they get inside a rocket; however, the things they achieve are great. Businessmen take a risk when they buy parts of a company, however, without doing that, they could not make more money.

    We need to take risks so that we can gain something. It is impossible to move forward in life, earn money, enjoy a relationship, play a sport, or doing anything else without taking a risk. It is all part of the game. It's one of the most important parts of life.

    Maria Sibylla Merian

    Today, children can happily explain how a caterpillar (毛毛虫) turns into a butterfly, thanks to Maria Sibylla Merian. Born in Germany in 1647, Merian was fond of insects, and she began collecting, studying and drawing them when she was as young as 13. It was through her study of caterpillar that she discovered the truth about their life cycles, and she went on to publish two volumes of naturalist research about the life cycles of insects.

    Ada Lovelace

    Ada Lovelace, born in 1815, was the daughter of famous British poet Lord Byron, but she wasn't a poet herself. She was the world's first computer programmer. Lovelace wrote some suggestions as to how to program “computing machines” to calculate a specific sequence of numbers. Besides this, she predicted them to do everything that could possibly be represented by a series of numbers, from producing images to composing music.

    Hedy Lamarr

    She was born in 1914 in Austria and moved to the United States in the hope of going after a film career. In 1942, in the midst of her Hollywood success, she and composer George Antheil received a patent for a device that could change radio signal frequencies. The purpose of the technology was to keep military enemies—especially, the Nazis --from decoding (解码) messages. But it did more than that--it paved the way for much of the wireless technology we use today.

    Today show's Kathie Lee Gifford is hoping to bring the story of David to a new generation with her latest musical project, The Little Giant.

    The 13-song album tells the story of the shepherd (牧羊人) boy who defeated a giant with five stones and a slingshot and became a king. The idea of the record came after Gifford and her husband Frank went on a life-changing trip to the Holy Land in 2012.

    Gifford hoped to shine light on David's story to help a new generation find their own purpose; it's why she decided to compose this album that invites kids to hear the tale of the shepherd in a fun and educational way. Gifford based the record's opening track "What is Your Stone" on bravery and faith. She hopes the songs can help children find confidence in themselves.

    Though the album is aimed towards families and children, Gifford found recording the story of David to be an exercise in healing after the death of her beloved husband Frank who passed away two years ago.

    "I catch myself saying that I lost him sometimes," Gifford says, "No, he hasn't been gone. The trip took root in my husband's life, because he truly came to understand exactly what David did. "

    Gifford says the trip and the teachings stayed with her husband until his death. 66For the next three years, when people came to visit us, they'd always see Frank's trophy (奖杯) room because it's like a museum," Gifford explained. "He would take them over. Instead of all of his trophies, he would point to the stones we brought back from the travelling destination and talk a out them. "

    Gifford expects her own journey, her new album and her commitment to bringing a bit of joy to people through her show can help inspire children to discover their own faith and purpose.

    On April 2, we said goodbye to Tiangong I, China's first space lab. According to the China Manned Space Agency（中国载人航天）, Tiangong I re-entered the Earth's atmosphere （大气层）and fell into the South Pacific Ocean.

    There are many spacecraft that are still in orbit above the Earth. They are flying at heights ranging from 300 to 1,000 kilometers. After finishing their trips, they will all re-enter the Earth's atmosphere like Tiangong I.

    There are two types of re-entries：controlled（受控的）re-entry and uncontrolled re-entry.

    Some satellites（卫星）and manned spacecraft come back to the Earth in a controlled re-entry. Scientists calculate（计算）the path of the falling spacecraft and its speed. They can guide the spacecraft to fall in a chosen area. In 2017,Tianzhou I, China's first cargo（货运）spacecraft, was directed to fall in the South Pacific Ocean.

    Some spacecraft may have problems while in space, or are simply no longer usable after a certain amount of time.  These craft come back in an uncontrolled re-entry.  It is hard to tell when and where these spacecraft will fall until the last few hours. The US space station Skylab came back partially uncontrolled in 1979. Parts of the station fell in western Australia, but no one was injured.

    During re-entry, most of the spacecraft will burn up while passing through the Earth's atmosphere. Only a small amount of the debris（碎片）will reach the ground.

    The debris typically ends up falling into the ocean, China Daily reported. Tiangong I weighs about 8.5tons. The amount of debris that falls to the Earth might be about 1 to 1.5 tons, the Beijing News reported.  That is about the same weight as a car.

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