When you want to go somewhere, you can easily find your way by using a map app on your smartphone. Your smartphone “knows” where you are and can tell you where to go.

This is possible with the help of satellite navigation (satnav) systems. A satnav system uses groups of satellites (卫星) to find out where people are. It sends information to a receiver, such as a smartphone. 【小题1】

On June 23, the last satellite of China’s Beidou Navigation Satellite System was launched into space. 【小题2】 It is one of four global navigation systems, along with US’ GPS, Russia’s GLONASS and the European Union’s Galileo.

On July 31, Beidou started providing full-scale global services (全面的全球服务). 【小题3】

Since 2000, China has launched 59 Beidou satellites. Beidou can be used in areas that include farming, public services and business. 【小题4】 This summer, people along the Yangtze River used Beidou-based device to monitor (监测) floodwaters in real-time with an accuracy of just a few centimeters.

【小题5】 It allows people to send text messages up to 1,200 Chinese characters in length when mobile phone services are interrupted (中断) by natural disasters.

①What is it like to exercise in space? Simple things can be harder in microgravity (微重力), while difficult tasks might suddenly be a breeze. A video on Tuesday shows that Zhai Zhigang, one of the astronauts of Shenzhou XIII spaceship, is practicing tai chi with flowing (流畅的) movements.

②The three astronauts, Zhai Zhigang, Wang Yaping and Ye Guangfu have been in space for about two months since they began their six-month mission (任务) to build the space station on October 16th. Chinese people have long been wondering what really goes on inside the space station. While people were still surprised by Wang Yaping’s zero-gravity hairstyle, Zhai showed his “flying” skill and was clearly very good at it.

③ ※ The tradition of Chinese astronauts practicing tai chi started in 2012 when the country’s Shenzhou IX astronaut Liu Yang first did so in space and called the experience comfortable. Before returning from the Shenzhou XII mission in September, astronaut Nie Haisheng also practiced tai chi in the Tianhe core module during an Earth-space video call with Hong Kong youths.

④For space travelers, doing exercise is important. They must exercise to counter (抵消) the gravity-free conditions because the experience of “muscle and bone loss (肌肉和骨质流失)” in space will influence their health and ability to work in the long term.

⑤Besides doing tai chi, Chinese astronauts also play table tennis or ride a bike and run on a treadmill (踏步机) to help train their breathing.

Mark Twain once said that everyone talks about the weather, but no one ever does anything about it. This was true in his day. But it may not be the cave in today’s world. In fact, humans have found many different ways to control the weather.

Cloud seeding(云催化) is a kind of technology that can control rain. It is done by spreading chemicals like dry ice or silver iodide(碘化银) inside of clouds, either by rocket or airplane. This changes water content inside the cloud, which helps to control the rainfall, the time and even the place where it rains.

This technology has helped to solve natural disasters, such as droughts(干旱). It has also played a key role during important events. For example, China used cloud seeding in Beijing just before the 2008 Olympic Games in order to stop rain from falling during the event.

Cloud seeding has been put into use for some time, however, some scientists are still wondering whether this technology is safe. On one hand, it is believed that it might have side effects(副作用). For example, silver iodide may be bad for the environment. On the other hand, no two clouds are the same, so every new experiment introduces new conditions.

In addition to controlling rain, scientists have also tried to find ways to weaken storms and hurricanes. Scientists at the US National Hurricane Centre Headquarters think it might be possible to control hurricanes by using lasers(激光). Others believe that burning rock oil in a hurricane’s path could slow the storms down.