One of the most famous formulas in astronomy was not born in a laboratory. It was scribbled by Frank Drake in 1961 because he had invited ten leading scientists to Green Bank, West Virginia, and realized days beforehand that he had no agenda for the meeting. This episode traces the origins of the Drake Equation, starting with the 1959 Cocconi and Morrison paper that pointed radio astronomers to the 1,420 MHz hydrogen line, through Drake's Project Ozma listening to Tau Ceti and Epsilon Eridani, and on to the conference where Carl Sagan, Philip Morrison, Melvin Calvin, and dolphin researcher John C. Lilly nicknamed themselves the Order of the Dolphin.

We work through each variable of the equation as a roadmap rather than a calculator: the rate of star formation and fraction of stars with planets, now vastly better understood thanks to the Kep ...