Arecibo message
It will take 25,000 years for the message to reach the stars, and at least another 25,000 years to get any reply. This means the Arecibo message was a show of human technological achievement, not a real attempt to talk to extraterrestrial life.  The stars of M13 that the message was aimed at will no longer be in that location when the message arrives. Cornell University said on November 12, 1999, the real purpose of the message was not to make contact, but to show the power of the new equipment. (Cornell University had built and operated the radio telescope for the United States National Science Foundation.)