“Dad, did you ever imagine that your formula would become so famous?” I ask the kind-eyed, 91-year-old person next to me on the patio.

My dad, Frank Drake, is quiet for a moment. Perhaps he’s thinking back to the November day 60 years ago when he unceremoniously drafted a formula that went on to shape humankind’s hunt for extraterrestrial civilisations. Or maybe he’s listening to the shrieking scrub jays and chattering woodpeckers in the yard, confirmation that noisy lifeforms are thriving in at least one part of the cosmos.

“No,” Dad says after the pause. “I never imagined that it would become of such widespread interest. I also expected that there might be alterations made to it, and that has not happened.”

Now known as the Drake Equation, Dad’s formula provides a framework for scientists looking for intelligent life beyond Earth. By considering a series of variables, the equation allows scientists to estimate the number of detectable alien civilisations that might be scattered across the Milky Way.

The formula has since become one of the most recognisable equations in science. It’s a common tattoo. It’s a beer. It’s written on the side of U-Haul trucks. Its logic has been borrowed and parodied in cartoons about finding a date or calculating the number of credible-seeming alien sightings.

Scores of scientists are still guided by the equation today, and the latest discoveries about other planets both within and beyond our solar system are helping researchers to fill in the variables. It’s a remarkable legacy considering he only wrote the thing down in 1961 when he was strapped for time and needed to organise a meeting.

To read more, click here.