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.

   What do you usually do in your spare time? Chatting online is now a nationalpastime in China, especially among the post-90s and post-00s generation. To somepeople, however, online chats can seem like a kind of polite conversation. Yet hiddenrules and standards do exist, as long as you take the time to look for them.

   Get to the Point

   When sending a friend request, include your real name and any other identifyinginformation. Remember, everybody's time is precious. If there's something you want,cut right to the chase. Never send an "Are you there?" without any follow-upmessages. The quicker that you get to the point, the more likely the other personis to reply.

   Send the Right Things

   Please send texts, not voice messages. It might be easier for you to speakthan type, but what about the person on the other end? They may be unable to listento a 59-second message right now. Also, never send personal information by voicemessage—it is hard to note down. Emojis, GIFs and memes can save the daywhen you find yourself in an embarrassing conversation, or words fail you.

   Try to Understand

   You can always judge a person's mood by their text messages. If the personyou're talking to says "Good night" or "I'm going to take a shower."that's probably not what they're actually going to do, it is just an excuse to stoptalking to you. If someone hesitates for longer than three seconds before saying"Yes", they probably really mean "No". If you receive theseemojis from friends who are older, read them literally (照字面地) (as a smile, a waveor a laugh). For the post-90s and post-00s generation, however, they could be speechlessness.

Building a country is never easy. It takes hard work from generation (代人) to generation. But how about destroying it? A new report from The Guardian said longtime of climate change can do that, The report said Tuvalu will be the first country to be completely lost due to climate change. 

Tuvalu is a Pacific island nation with nine islands and 12, 000 people. It has long been at risk from rising sea levels, Now, 40 percent of the area in its capital is underwater at high tide (潮水). By the end of the century, it is believed that all the islands will be underwater, reported Reuters, So many people in Tuvalu have often moved around the country and even to other countries. 

To help with the problem, the country plans to build its country in the metaverse. The digital (数字化的) country will recreate the same landscape and keep its cultural and historical records, No matter where they live in the real world, the people in this country will have their new identity (身份) and " live " in its online communities. The government hopes to manage and serve them in cyberspace (网络空间). 

This news made many people in Tuvalu excited. But Li Zuxi, director of the metaverse lab of Qingbo Intelligent Technology, said it may not be the best solution. 

Though the digital nation belongs to Tuvalu, it's still built on a metaverse platform (平台), " said Li, "Now, the metaverse is not mature, which may bring some problems. " He gave us an example. If people from other countries enter the space of the digital country but just show their names, how do people know if they do or do not, truly belong to that country?Li added that instead of trying our best to build digital nations, it's better to pay attention to saving the real world now.