Fifty years ago, the search for intelligent life in the universe began in earnest. That year, an astronomer at the National Radio Astronomy Observatory named Frank Drake began scanning the stars with a radio telescope, hoping to find evidence of a civilization we could communicate with. This was the first iteration of the famed SETI program, and it was the beginning of "the most ambitious, and potentially the most significant, research project in history," writes Paul Davies in The Eerie Silence: Renewing Our Search for Alien Intelligence. And thus far it's been spectacularly unsuccessful. Despite a half century of intensive effort, not a single extraterrestrial bacterium has been definitively identified, let alone an intelligent species.

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