OTD in Space - Nov. 16: Arecibo Observatory Broadcasts Interstellar Message

On November 16, 1974, humans sent their first message to the stars in an attempt to contact extraterrestrials. They did this using what was then the largest radio telescope in the world, located at the Arecibo Observatory in Puerto Rico. A group of scientists led by Frank Drake and Carl Sagan sent their message to the M13 star cluster. The message was written in binary code and contained information about human DNA. It also included figures of a human, the solar system and the Arecibo telescope. The idea was that if any aliens were to receive the signal and figure out how to decode it, they would know where it came from. Because M13 is 25,000 light-years away, it will take 25,000 years for any M13 aliens to hear our message — if they are even out there. The Arecibo message is only one of several messages intended for extraterrestrials. We have also included messages on several spacecraft, such as Pioneer and Voyager.