November 16, 1974 -- A message was sent from
the Arecibo Observatory in Puerto Rico(the largest
radio telescope on Earth). The message, coded in binary,
is 1,679 bits long(1,679 is divisible by 2 prime numbers: 73 and 23, the
dimensions of the message). Each square on the image is represented by a
value of 1 in the signal. It was sent towards the M13 Global Cluster,
and should be arriving in only 25,000 years.
From the top down, the images are binary representations of the numbers 1- 10, atomic numbers of the five elements essential to terrestrial life, the chemical formula of the DNA molecule, numbers for the average human height and the world's human population, images of the human form, the solar system (with Earth displaced to indicate it is the planet from which the signal originated), and the transmitting radio telescope, with its diameter indicated.