The Arecibo message beamed humanity's hello to the stars
On this day · 16 November 1974
On a Puerto Rican afternoon in 1974, astronomers fired Earth's first deliberate interstellar postcard at a star cluster 25,000 light-years away.
On November 16, 1974, astronomers gathered at the Arecibo Observatory in Puerto Rico to rededicate its resurfaced 1,000-foot dish. To mark the moment, they pointed the telescope at the sky and broadcast a three-minute radio pulse toward M13, a dense globular cluster of several hundred thousand stars.
The message held 1,679 bits, a number that is the product of just two primes, 23 and 73. Arranged in that grid, the bits sketch a stick-figure human, the DNA double helix, our solar system, and the telescope itself. Astronomer Frank Drake designed it, with input from Carl Sagan and others, transmitting at 2,380 MHz.
It was less a phone call than a flare: M13 sits about 25,000 light-years away, so any reply lies fifty millennia off.
Nobody expected an answer. The point was the gesture, a demonstration that a species on a small planet could, for three minutes, make itself heard across the galaxy.
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