By Jacob Koffler
July 23, 2015

[This article consists of 5 illustrations. Please see hardcopy of magazine or PDF.]

THE ARECIBO MESSAGE

On Nov. 16, 1974, a group of astronomers sent a coded message to globular star cluster M13, some 25,000 light-years away. It included a graphic figure of a human, the physical height of an average man, the human population of Earth and many other data points.

THE GOLDEN RECORDS

In 1977, Voyagers 1 and 2 launched from Cape Canaveral, each with a gold-plated copper disk containing sounds and images meant to represent life on Earth. Among them: greetings in 55 languages, music ranging from Mozart to Chuck Berry and a photo of the Great Wall of China.

CRAIGSLIST ADS

On March 11, 2005, Deep Space Communications Network transmitted over 100,000 Craigslist postings to a part of space with no known satellites, approximately 1 to 3 light-years away. Either there was no intelligent life there or they weren’t interested in “free kittens to a good home.”

‘ACROSS THE UNIVERSE’

On Feb. 4, 2008, NASA beamed the Beatles song in the direction of the star Polaris, 431 light-years away.

THE ‘WOW!’ SIGNAL

On Aug. 15, 2012, National Geographic, in conjunction with the Arecibo Observatory, broadcast 10,000 Twitter messages as well as videos from celebrities including Stephen Colbert into space. The three transmissions, to stars ranging from 41 to 150 light-years away, were in response to the famous “Wow!” signal, an electromagnetic spike picked up by Ohio State University’s Big Ear observatory in 1977 that was so strong, many believe it to have come from other intelligent life.

Contact us at editors@time.com.

This appears in the August 03, 2015 issue of TIME.

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