Are We Alone? Calculate the Probability

What are the probabilities of intelligent life on other planets? Astronomer Frank Drake proposed an equation to estimate how many detectable civilizations might exist in the Milky Way galaxy alone. The Drake Equation involves seven factors: The rate of star formation per year in the galaxy (R), the percentage of stars that form planets (fp), the average number of planets for each star that has planets with conditions suitable for life (ne), the percentage of those planets on which life occurs (fl), the percentage of those planets where intelligence develops (fi), the percentage of species that produce interstellar communications (fc), and the average lifetime of a communicating civilization (L).

The BBC has provided an interactive model illustrating The Drake Equation. You can change the different factors yourself and see the results. Drake initially estimated that, given the uncertainties, there were probably between 1,000 and 100,000,000 civilizations in the Milky Way with the ability to communicate with us. According to the BBC, the “today’s skeptical estimate” is one communicating civilization in the Milky way and 78 billion in the entire universe.