Enrico Fermi famously asked, in his paradoxical analysis of the likely existence of extraterrestrial life, “Where is everybody?” If there are a certain (large) number of planets in the universe that are habitable, then a subset of these (also a large number) should be inhabited. Any civilization that formed, given enough time, could develop the means for interstellar communication or travel.
So yeah, “Where is everybody?”
Years later, Frank Drake developed a precise equation to calculate the likely number of inhabitable worlds within range of observation or communication from Earth. Well, it’s as precise as you define it, anyway, given that the variables that go in are just that - variable. Things like how long it would take a civilization to develop communication, how long said civilization would last, how many stars and planets are estimated to exist … just the basics.
It’s called the Drake Equation, and thanks to the stupendous folks over at BBC Future, you can go tweak the equation with an interactive tool! Click here to start defining your galaxial parameters and see how many civilizations you think should exist.
I’m getting some pretty big numbers . . !