The Arecibo Interstellar Message Anniversary marks November 16, 1974, when humanity transmitted its first deliberate, high-powered radio broadcast into deep space from the 305-meter Arecibo telescope in Puerto Rico, carrying fundamental mathematical, chemical, and biological data of human civilization.
On November 16, 1974, to celebrate a major upgrade of the 1,000-foot (305-meter) spherical reflector dish at the Arecibo Observatory in Puerto Rico, a team led by Cornell astronomer Frank Drake and astronomer Carl Sagan beamed an interstellar radio transmission toward the globular cluster Messier 13 (M13), located 25,000 light-years away in the constellation Hercules. The broadcast consisted of 1,679 binary digits (a semiprime number, the product of 73 rows and 23 columns). When arranged into a two-dimensional grid, the pictorial message depicted: the numbers one through ten in binary, the atomic numbers of hydrogen, carbon, nitrogen, oxygen, and phosphorus (the elemental building blocks of DNA), the molecular formulas of nucleotides, the double helix structure of DNA, a graphic stick figure of a human being with human population statistics, a map of the Solar System showing Earth elevated toward space, and a diagram of the Arecibo radio telescope. The broadcast remains a crowning milestone in SETI (Search for Extraterrestrial Intelligence) history and an enduring symbol of humanity's cosmic curiosity.
