The Arecibo message was broadcast into space on 16 November 1974. It was aimed at the globular star cluster M13 some 25,000 light years away because M13 was a large and close collection of stars that was available in the sky at the time. The message consisted of approximately 210 bytes, transmitted at a frequency of 2380 MHz with a power of 1000 kW. The total broadcast was less than three minutes.
The message consists of seven parts that encode the following:
Because it will take 25,000 years for the message to reach its intended destination of stars (and an additional 25,000 years for any reply), the Arecibo message was more a demonstration of human technological achievement than a real attempt to enter into a conversation with extraterrestrials. In fact, the stars of M13 that the message was aimed at will no longer be in that location when the message arrives.