Why do not the aliens send back earth contact signal (Photos).

Keywords: aliens earth contact signal <P> </ P> <CENTER> </ CENTER> <P> </ P> <P align=center> Earth scientists had alien card issued </ P> <P .> <CENTER> </ CENTER> <P> </ P> <P align=center> extraterrestrial intelligent life in the end why it is so silent </ P> <P> World Scientific reports [tech. /]: Beatles .the classic song "through the sky," February 4, 2008 by NASA (NASA) sent to the Polaris 431 light years away, scientists hope the aliens there - if there is one - to hear. .</ P> <P> This led Arizona State University who was meeting some scientists argue. .Zhefan debate in the United States, "Search for Extraterrestrial Intelligence" (SETI) project at the "Sound of Silence," an episode in the seminar. .SETI project can be traced back 50 years ago, it has been tried by radio in contact with extraterrestrial intelligent life, but 50 years later, people get only the features of the radio without any noise. .</ P> <P> then, extraterrestrial intelligent life in the end Why is it so silent? </ P> <P> 1984, the United States Indiana University, a pioneer of modern semiotics 托马斯西比奥 g wrote an article entitled " .years of communication methods to communicate, "the papers. .U.S. Department of Energy paper for a thousand years to alert the humans to do the research. .Today, many people will be nuclear waste buried in the ground, to prevent future generations and then accidentally dig them up, the U.S. Department of Energy wants to design a one thousand years of human can understand the warning signs. .</ P> <P> Xibiaoke examined in detail a variety of ideas and programs, come to a depressing conclusion: all natural languages, all human communication system, will change over time, .After a thousand years human beings can not understand the warning we left. .</ P> <P> in the history of attempts to communicate with aliens, people initially thought that aliens might be on the moon or other planets of the solar system. .So the famous mathematician Gauss in the 19th century's communication approach is to use the forest or the Sahara desert on Earth to try to spell out a giant pattern to the alien on the moon visible from the moon. .It now appears that this idea is somewhat funny. .</ P> <P> </ p>.