In 1961 Frank Drake of Cornell University devised a formula to estimate the number of communicative civilizations in the Milky Way, which came to be called the Drake Equation. It consists of seven variables. If we can accurately estimate the values of these variables, such as the number of earthlike worlds per planetary system, we should have a fair idea of how many civilizations exist in the galaxy. Astronomers have a good idea for a couple of the values; some require an educated guess because astronomers, as yet, have only one civilization to work with — our own.
Use the Drake Equation to come up with your own estimate of how many civilizations might inhabit the Milky Way. Click on the image below and follow the steps, inputting your own guesses for each variable. We’ll do the math and show you what your estimates yield.