When astronomer Frank Drake organized the first SETI (search for extraterrestrial intelligence) conference back in 1961 in Green Bank, West Virginia, only a dozen people attended.

“I invited everyone in the world I knew about who was interested in the subject or who had written something about it—so all 12,” Drake remembers fondly. “All [were] very enthusiastic, because they’d all been in a situation I’d been in—that they were very interested in this subject, but it was taboo. They really couldn’t pursue or even talk about it, so it was just a joy to be with other people who were as eager as they were.”

It was at this meeting that Drake introduced what became known as the Drake equation, a formula intended to estimate the number of intelligent and communicative civilizations in the Milky Way. Drake claims he had “no idea” how much of an impact it would have on people’s conceptions of the possibility of intelligent life beyond Earth.