Drake Equation

A probabilistic argument used to estimate the number of active, communicative extraterrestrial civilizations in the Milky Way Galaxy.

Average Rate of Star Formation

R_∗

Current Estimate: 1.5 - 3

Fraction of stars with planets

f_p

Current Estimate: ~1

Average number of planets that can support life

n_e

Current Estimate: ~0.4

Fraction of Planets that Life Appears

f_l

Current Estimate: Unknown

Fraction of Planets that can Support Intelligent Life

f_i

Current Estimate: Unknown

Fraction of Planets that have Communicative Life

f_c

Current Estimate: Unknown

Average Lifetime of Communicative Civilizations

Current Estimate: Unknown

N = 1.8