How Many Aliens Are There In Our Galaxy?

Today, we live in an age of exploration, where robots on Mars and planet-hunting telescopes are beginning to allow us to edge closer to an answer.

While we wait to establish contact, one technique we can use back on Earth is an equation that American astronomer Frank Drake formulated in the 1960s to calculate the number of detectable extraterrestrial civilizations that may exist in the Milky Way galaxy.

Brought to you by bbc.com.