the Drake equation

While working as a radio astronomer at the National Radio Astronomy Observatory in Green Bank, West Virginia, Dr. Frank Drake (currently on the Board of the SETI Institute) conceived an approach to bound the terms involved in estimating the number of technological civilizations that may exist in our galaxy. The Drake Equation, as it has become known, was first presented by Drake in 1961 and identifies specific factors thought to play a role in the development of such civilizations. Although there is no unique solution to this equation, it is a generally accepted tool used by the scientific community to examine these factors. [1]

In the BBC website under the "future" section, there is an excellent interactive infographic, that allows visitors to tamper and play with the factors of the equation, in order to yield different potential results, that help to quantify - if not to visualize - the question at hand. How many other civilizations are out there ?

It is not a rigorous equation, offering a wide range of possible answers. Instead it is more a tool used to help understand how many worlds might be out there and how those estimates change as missions like Kepler, a telescope that is currently searching for Earth-like planets, begin to discover more about our universe. Until ground-based observations, space telescopes and planet-roving robots uncover any tell-tale signs of life, what better way to speculate on how many intelligent alien civilizations may exist than to explore the universe with our interactive version of the equation. [2]

As many skeptics have pointed out, the Drake equation can give a very wide range of values, depending on the assumptions. It is essentially a very simple model that does not include potentially relevant parameters, and many changes and modifications to the equation have been proposed. [3]Criticism of the Drake equation follows mostly from the observation that several terms in the equation are largely or entirely based on conjecture. Star formation rates are on solid ground, and the incidence of planets has a sound experimental basis, but as we move from the left to right in the equation, estimating each succeeding factor becomes ever more speculative. The uncertainties revolve around our understanding of the evolution of life, intelligence, and civilization, not physics. No statistical estimates are possible for some of the parameters, where only one example is known. The net result is that equation cannot be used to draw firm conclusions of any kind, and the resulting margin of error is huge, far beyond what some consider acceptable or meaningful. [4]

[1] Ref. http://www.seti.org/drakeequation

[2] Ref. http://www.bbc.com/future/story/20120821-how-many-alien-worlds-exist

[3] Ref. https://en.wikipedia.org/wiki/Drake_equation

[4] Ref. http://www.sentientdevelopments.com/2007/05/drake-equation-is-obsolete.html