The Arecibo message — humanity’s most famous deliberate radio message to another civilization — was aimed at a star cluster about 25,000 light-years away in 1974, meaning even an immediate reply would not reach Earth until around 52,000 CE

Imagine standing under a tent on a karst hillside in Puerto Rico, on an afternoon in November 1974, watching the dedication of a remodeled radio telescope.For just under three minutes it warbles at the sky. Then it stops. The audience around you has just heard humanity’s first deliberate radio message to another civilization broadcast over [...] The post The Arecibo message — humanity’s most famous deliberate radio message to another civilization — was aimed at a star cluster about 25,000 light-