Billion and Billions =)

2. The Pioneer Plaques (1972, 1973)

Mounted to Pioneer spacecraft before they made their merry way into the inhospitable reaches of space outside the solar system, the Pioneer Plaque was the first-but not the last!-interstellar communiqué in which Carl Sagan had a say. Attached to both Pioneers and positioned to minimize the corrosive effects of solar dust, the plaque might well be the first thing an alien culture knows about us. (Well, the plaque, and also the fact that we hurl things into space and aim them right at you.)

Message Content: The Pioneer plaque forewent an auditory component and instead tried to include the maximum information about Pioneer’s source; thanks to Sagan, Linda Salzman Sagan, and Franke Drake, every inch is packed with data: A diagram of a hydrogen atom; a pulsar map with the sun at the centre, showing the relative distances of 14 pulsars and the binary code of their periods, which can help date the launch era; figures of a nude man and woman set in front of a to scale silhouette of Pioneer; a sketch of our solar system with a long arrow indicating the Earth as the planet that launched the little guy.

Message Assumptions: Alien life form can see in two dimensions, has a concept of arrows.

Likely Impression: Earth is filled with humanoids who haven’t had the brains to develop clothes, possibly because they’re too busy fighting off the absolutely enormous serpent reaching out from the third planet and launching space probes willy-nilly.

awkward history of space transmittance . com