The Drake Equation: Daydreaming of the History of other Civilizations

The Drake equation is a probabilistic argument used to estimate the number of active, communicative extraterrestrial civilizations in the Milky Way galaxy. The equation was written in 1961 by Frank Drake not for purposes of quantifying the number of civilizations,[1] but intended as a way to stimulate scientific dialogue at the world's first search for extraterrestrial intelligence (SETI) meeting, in Green Bank, West Virginia. The equation summarizes the main concepts which scientists must contemplate when considering the question of other radio-communicative life.[1] The Drake equation has proved controversial since several of its factors are currently unknown, and estimates of their values span a very wide range. This has led critics to label the equation a guesstimate, or even meaningless.

http://www.noeticscience.co.uk/the-drake-equation-versus-the-fermi-paradox-is-there-intelligent-life-out-there/

http://cargocollective.com/olagus/The-Drake-Equation-for-Kids

The Fermi paradox videos by kurzgesagt on YouTube provide an excellent insight into this the complex philosophy associated with understanding if there is life in the universe.