2017-12-15:
Arecibo message

The Arecibo message was an interstellar radio message, sent in the direction of the star cluster M13 in the constellation of the Hercules in 1974. It was designed in the hopes an extraterrestrial intelligence would be able to decipher it, and learn some basic information about humanity and the planet Earth.

The message consisted of 1679 binary digits, a number chosen because it is the product of two prime numbers, allowing it to be assembled to a rectangle in only one way.

The parts of the message are as follows:

• the numbers 1 to 10 (white)
• the atomic numbers of the elements which make up the DNA (purple)
• the formulas for the sugars and bases in the DNA (green)
• the number of nucleotides in the DNA, along with a graphical representation of the DNA's helix structure (white and blue)
• a graphic of a human, as well as the average height, and the human population of Earth (red, blue, and white)
• a graphic of the Solar System, with a highlighted planet Earth (yellow)
• a graphic of the radio telescope which was used to send the message, along with its diameter (purple, white, and blue)

It will take approximately 25000 years for the message to arrive at its intended destination - and an additional 25000 years for any reply.