Thursday, 28 June 2012

CASE 409 - Drake equation

There supposidly a way to estimate the number of technologically advanced civilizations that might exist in our Galaxy. While working at the National Radio Astronomy Observatory in Green Bank, West Virginia, Dr frank Drake conceived a means to mathematically estimate the number of worlds that might harbor beings with technology sufficient to communicate across the vast gulfs of interstellar space. The Drake Equation, as it came to be known, was formulated in 1961 and is generally accepted by the scientific community.

N = R* fp ne fl fi fc L

where, • N = The number of communicative civilizations • R* = The rate of formation of suitable stars (stars such as our Sun) • fp = The fraction of those stars with planets. (Current evidence indicates that planetary systems may be common for stars like the Sun.) • ne = The number of Earth-like worlds per planetary system • fl = The fraction of those Earth-like planets where life actually develops • fi = The fraction of life sites where intelligence develops • fc = The fraction of communicative planets (those on which electromagnetic communications technology develops) • L = The "lifetime" of communicating civilizations Frank Drake's own current solution to the Drake Equation estimates 10,000 communicative civilizations in the Milky Way. Dr. Drake, who serves on the SETI League's advisory board, has personally endorsed SETI's planned all-sky survey.


Criticism of the Drake equation follows mostly from the observation that several terms in the equation are largely or entirely based on conjecture. Thus the equation cannot be used to draw firm conclusions of any kind. As Michael Crichton, a science fiction author, stated in a 2003 lecture at Caltech: The problem, of course, is that none of the terms can be known, and most cannot even be estimated. The only way to work the equation is to fill in with guesses. [...] As a result, the Drake equation can have any value from "billions and billions" to zero. An expression that can mean anything means nothing. Speaking precisely, the Drake equation is literally meaningless... Another objection is that the very form of the Drake equation assumes that civilizations arise and then die out within their original solar systems. If interstellar colonization is possible, then this assumption is invalid, and the equations of population dynamics would apply instead. One reply to such criticisms is that even though the Drake equation currently involves speculation about unmeasured parameters, it was not meant to be science, but intended as a way to stimulate dialogue on these topics. Then the focus becomes how to proceed experimentally. Indeed, Drake originally formulated the equation merely as an agenda for discussion at the Green Bank conference.

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