a1 Joseph Fourier University, AGeing, Imagery and Modeling (AGIM) Laboratory, CNRS FRE3405, Faculty of Medicine of Grenoble, 38700 La Tronche, France
a2 European University of Brittany (UEB) – University of Brest, Complex Systems and Computer Science Laboratory (LISyC) – EA3883, 20 Avenue LeGorgeu, 29238 Brest Cedex, France
a3 Laboratoire de Physiologie Cellulaire Végétale. UMR 5168 CNRS-CEA-INRA-Université Joseph Fourier, CEA Grenoble, 17 rue des Martyrs, 38054, Grenoble Cedex 09, France
The number N of detectable (i.e. communicating) extraterrestrial civilizations in the Milky Way galaxy is usually calculated by using the Drake equation. This equation was established in 1961 by Frank Drake and was the first step to quantifying the Search for ExtraTerrestrial Intelligence (SETI) field. Practically, this equation is rather a simple algebraic expression and its simplistic nature leaves it open to frequent re-expression. An additional problem of the Drake equation is the time-independence of its terms, which for example excludes the effects of the physico-chemical history of the galaxy. Recently, it has been demonstrated that the main shortcoming of the Drake equation is its lack of temporal structure, i.e., it fails to take into account various evolutionary processes. In particular, the Drake equation does not provides any error estimation about the measured quantity. Here, we propose a first treatment of these evolutionary aspects by constructing a simple stochastic process that will be able to provide both a temporal structure to the Drake equation (i.e. introduce time in the Drake formula in order to obtain something like N(t)) and a first standard error measure.
(Received November 13 2011)
(Accepted December 06 2011)
(Online publication January 09 2012)