The Equation

The Drake Equation multiplies seven factors to estimate how many detectable civilizations exist. It spans star formation rates, habitable planets, the emergence of life and intelligence, and the lifespan of technological civilizations.

Early factors are now well-constrained: stars form at 1.5-3 per year in the Milky Way, most have planets, and many sit in habitable zones. The uncertainty explodes in biological and sociological factors — we have exactly one data point: Earth.