Humanity's first interstellar postcard was a 1,679-bit binary shout into the void

Space · Published 17 October 2026 Swipe more like this →

In short: In 1974, humanity did not just listen to the cosmos; we spoke back. Using a massive radio telescope in Puerto Rico, scientists beamed a complex digital postcard toward a distant star cluster. This symbolic transmission represented our first intentional attempt to announce our existence to a potential alien audience.

In 1974, astronomers used the Arecibo Observatory in Puerto Rico to beam the first intentional interstellar transmission toward the Messier 13 star cluster, located approximately 25,000 light-years away.

Designed by Frank Drake with input from Carl Sagan and a team of Cornell and Arecibo scientists, the message was a demonstration of human technological achievement. A duration of roughly three minutes was used to transmit the signal on a 2380 megahertz frequency. The transmission contained 1,679 bits of data arranged in a 73x23 grid, using binary code to convey essentials like our counting system, the structure of DNA, a depiction of our solar system, and a drawing of the Arecibo telescope itself.

While the message was a milestone, it was not a serious attempt at a two-way conversation.

Because M13 is so distant, any potential reply would take about 50,000 years to reach Earth. Furthermore, the cluster's orbit means the message may not arrive at the exact center of the cluster by the time it gets there.

The project has faced retrospective criticism for its lack of diversity; about 90 percent of the message was created by a single 44-year-old white man. Today, scientists advocate for more inclusive, international protocols for such signals, weighing the desire for contact against the "Dark Forest" theory—the idea that broadcasting our location could attract hostile neighbors in a dangerous cosmic environment.

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