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In Feb．NASA sent the Beetles’ song “Across the Universe” to the North Star, which is 431 light-years away from the earth, hoping extraterrestrial beings(ET)－if there were－would receive it．
This move led to a heated argument between scientists．Some believed there was no ET while others were afraid that the earth would be discovered by the evil-intentioned ET．
But no response so far．
In the 1970s, the Pioneer and the Voyager, designed to travel through deep space, were fixed with a letter of the same content．This was a metal card, on which some important information about our planet was shown in the form of pictures, such as positions of the solar system and earth, the man’s and woman’s images and so on．Scientists hoped it would get received by some ET intelligence and led to its awareness of another intelligence’s existence．
Then, what content is the most important for the letter to ET?The first to come to scientists were the basics in nature：atomic structures or the matters a life needs．Thus, ET might treat us as a civilization armed with advanced science and technology and intend to get in touch with us．
But sociologists think all this is too simple．If ET is cleverer than us, they will think such low intelligence not worth responding to．So they have designed some more interesting topics：How are resources distributed in your civilization?What is the form of your democracy like?But theirs are for ever put on the shelf．
On Nov．16, 1974, a signal was sent in the direction of Hercules by a powerful radio telescope located in Puerto Rico, in which the numbers from 1 to 10, the solar system, the earth and DNA of mankind were described in the form of symbols．It has been flying at the speed of light to a star cluster 25000 light-years away．Even if an ET does make a reply, however, we’ll have to wait 50 thousand years, but what if the reply reads “We don’t quite understand you．Would you please repeat?”
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