Many objects in the universe are invisible, but they send radio waves. The radio telescope* thus appeared, and it is considered one of the greatest inventions in the twentieth century. Reber built the world's first radio telescope in 1937. Ryle and Hewish developed radio telescope systems for the location of weak radio sources, and they shared the Nobel Prize for Physics in 1974.

    A radio telescope is usually made up of:

    One or more antennas to collect the radio waves. Most antennas are made in the shape of a dish to collect and reflect, the radio waves to the sub—reflector, in the same way as a curved mirror focuses visible light to one point.

    A receiver and amplifier to receive the radio waves from the sub—reflector, and make these weak radio waves strong enough to be recorded and turned into electronic signals. To make an amplifier sensitive enough, it is usually cooled to, very low temperatures (e. g. as low as —270℃）.

    A recorder to keep a record of the electronic signals. Most radio telescopes today keep the signals to the computer's memory disk for astronomers to analyze later.

    Radio wavelengths are much longer than those of visible light, and the radio waves from deep space are always weak. To catch Radio wavelengths are much longer than those of visible light, and the radio waves from deep space are always weak. To catch these waves, radio telescopes usually have huge antennas. The sizes of most antennas in use today are around 50 to 300 metres in diameter. The antenna of FAST in Guizhou, China, the latest and largest radio telescope in the world, is 500 metres in diameter, as large as the size of 30 football fields.

    To avoid interferences, and keep the telescopes sensitive, radio telescopes are built in places where there are no human radio waves or electronic signals. For example, FAST is 5 kilometres away from the closest village and 25 kilometres away from the nearest town.

    Radio telescopes create pictures of the sky, not in visible light, but in radio waves. This is extremely useful, because there are objects that can't be seen, objects that we wouldn't even know without radio telescopes.

With devices (设备) that can be conveniently (便利地) controlled from anywhere, a smart home offers convenience to its owners. These devices can be connected with each other through the Internet, allowing the user to control functions, such as security access (安全访问), lighting and temperature. 

"Haitangxiaozhen", an Internet user from Xuzhou, Jiangsu, shared his experience of setting up a smart home. He first bought the service of "intelligent networking". It can be extended (延伸) to every room. He then can use an app to control various smart home devices. 

He said that he usually got off work late, ____. But now, cooked rice waits for him at home because he can turn on the rice cooker with his phone in advance. During summer, he usually turns on the air conditioner 30 minutes before getting home. He can also check the security camera at the door anytime through his phone in case he forgets whether he has locked the door or not. It's very convenient for him. 

During winter and summer holidays, when his child was alone at home, he used to worry about safety problems. For this reason, he specially installed a smart camera. With it, he can check if his child is OK at any time. His home also has a kitchen safety set, including smoke sensors (传感器), gas sensors and water sensors. 

And these devices are really smart. They come with self-learning skills so they can learn the home owner's timetables and make changes as needed. 

All these conveniences are making smart homes more and more popular both in China and around the world. 

"Smart homes are not yet perfect. They also bring problems. Every device has its own app, leading to a large number of apps for me to deal with." another user said. 

I live in Guangzhou. {#blank#}1{#/blank#}

Everything is alive. The trees have a lot of green leaves, and they can help keep me cool on sunny days. {#blank#}2{#/blank#} They smell really nice.

The best thing about summer is the summer holiday!{#blank#}3{#/blank#}I enjoy going swimming with my friends. I also love going running in the park with my best friend. {#blank#}4{#/blank#} and it is nice to eat ice cream on a hot day. Sometimes I go to the beach with my family. I like to build sandcastles with my little sister.

{#blank#}5{#/blank#}

①Are you a shy person? Do you expect to become outgoing? Being outgoing can help a lot in your life. In fact, being outgoing is not as hard as you think. Here is some advice on how to become outgoing. 

②You can start to try becoming outgoing when you stay with your friends. But the real challenge(挑战) comes when you meet strangers or new friends. Smile at them, and usually they will smile at you, too. You may find it easy to start talking in this way. 

③Start a talk positively (积极地). Try to speak first. Simple greetings such as"Hello!""How is it going?" and"It's a little cloudy today, isn't it?" are a good start. After that, you can talk more. For example, you can talk about the latest news. But you'd better read some news in newspapers and have your own ideas first. Or you may find that you won't have much to say. 

④The best way to become outgoing is to go out. It is also a very important step. Usually those who like to do the same things can get to know each other better. 

If you like playing sports, go to a sports club. You may make many new friends there if you get over your shyness. 

Reading is really important. Hopefully, we can get  {#blank#}1{#/blank#}（知识；学问）through reading, which not only broadens our horizons, but also makes us  {#blank#}2{#/blank#}（有判断力的；明智的）and happier. Moreover, our school studies can be greatly {#blank#}3{#/blank#}（影响）if we keep reading, and our future will become brighter. 

However, some students spend too much time  {#blank#}4{#/blank#} (使用) their mobile phones to listen to music, watch movies or play online games. So I would like to suggest that everyone should do more reading of good books, {#blank#}5{#/blank#}（尤其；特别）Chinese classic novels every day. In this way, we can  {#blank#}6{#/blank#}(传播；展开）our Chinese traditional culture. Meanwhile, we can enrich our minds quite a lot by reading regularly and it is also good for us to get fully developed and it can help improve our writing  {#blank#}7{#/blank#}（能力）. Surely, we can read books  {#blank#}8{#/blank#}（独自；单独）, or with our friends. 

All in all, doing reading does us much good if we do it from now on, and it is strongly suggested that we should make reading a  {#blank#}9{#/blank#}（习惯）of our life. To carry a book with you wherever you go is old and good  {#blank#}10{#/blank#}（建议）. John Adams asked his son to carry a book. "You will never be lonely, " he said, "with a writer in your pocket. "