For years, it hosted the largest single radio antenna on the planet, only surpassed in 2016 by a new telescope in China that is 1,600 feet in diameter.
One of its early feats, in 1967, was to discover that the planet Mercury rotates in 59 days, not 88 as astronomers had originally thought.
Over time, Arecibo became the flagship for the search for extraterrestrial intelligence, or SETI, the optimistic quest for radio signals from alien civilizations.
One of its directors was astronomer Frank Drake, then at Cornell, now retired from the University of California, Santa Cruz. He was famous for first pointing a radio telescope at another star for indications of friendly aliens, then for an equation, still in use today, that tries to predict how many of “them” are out there.
On Nov. 16, 1974, Dr. Drake beamed the equivalent of a 20-trillion-watt message toward M13, a cloud of about 300,000 stars some 25,000 light-years from Earth, as part of a celebration of an upgrade to the antenna.
The message consisted of 1,679 zeros and ones. Arranged in 73 rows and 23 columns, the bits formed pictures of a stick man, the radio telescope, a DNA helix, the solar system, the numbers 1 through 10 and more.
Before Dr. Drake sent it off, he tried out the message on his Cornell colleagues, including Carl Sagan, the author and proselytizer of the search for life in the cosmos. None of them could decode all of it. Maybe E.T. would be smarter when the signal finally reached somewhere, but the real point of such messages, Dr. Drake and Dr. Sagan always admitted, was to raise the consciousness of those of us back here on Earth and an awareness of our own status as cosmic travelers in an unknown and obviously weird universe.