Drake Equation
A probabilistic argument used to estimate the number of active, communicative extraterrestrial civilizations in the Milky Way galaxy.
Origin
Astronomer Frank Drake wrote the equation on a chalkboard at the Green Bank Observatory in West Virginia on November 1, 1961, as an agenda for the first scientific meeting on the search for extraterrestrial intelligence. The small gathering included luminaries such as Carl Sagan and Melvin Calvin, who received word during the meeting that he had won the Nobel Prize.
Everyday Use
The Drake Equation is a good reminder of the importance of thinking in scales. We can have an idea about the way something works, or be entirely driven by one part of our day or some incessant task, but when take a step back and run the numbers on the absolute importance of x, y, or z, then perhaps we have a little more perspective on how to factor them into our lives.