SPACE.com -- The Drake Equation to estimate intelligent extraterrestrial life


	The Drake Equation to estimate intelligent extraterrestrial life posted: 03:55 pm ET 03 October 2000

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The Drake equation is an attempt to estimate the number of technological civilizations that might exist in our galaxy.

SpaceTV explains the Drake equation.

It was developed by Dr. Frank Drake while working as a radio astronomer at the National Radio Astronomy Observatory in Green Bank, West Virginia. Drake is now chairman of the board of trustees of the SETI Institute.

The Drake equation, as it has come to be known, was first presented by Drake in 1961. It 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.

N = R_* × f_p × n_e × f_l × f_i × f_c × L

Where,

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Drake equation Calculator

N = The number of communicative civilizations
The number of civilizations in the Milky Way Galaxy whose radio emissions are detectable.

R_* = The rate of formation of suitable stars
The rate of formation of stars with a large enough "habitable zone" and long enough lifetime to be suitable for the development of intelligent life.

f_p = The fraction of those stars with planets
The fraction of sun-like stars with planets is currently unknown, but evidence indicates that planetary systems may be common for stars like the sun.

n_e = The number of "Earths" per planetary system
All stars have a habitable zone where a planet would be able to maintain a temperature that would allow liquid water. A planet in the habitable zone could have the basic conditions for life as we know it.

f_l = The fraction of those planets where life develops
Although a planet orbits in the habitable zone of a suitable star, other factors are necessary for life to arise. Thus, only a fraction of suitable planets will actually develop life.

f_i = The fraction life sites where intelligence develops
Life on Earth began over 3.5 billion years ago. Intelligence took a long time to develop. On other life-bearing planets it may happen faster, it may take longer, or it may not develop at all. For more information, please visit Dr. William Calvin's "The Drake Equation's fi".

f_c = The fraction of planets where technology develops
The fraction of planets with intelligent life that develop technological civilizations, i.e., technology that releases detectable signs of their existence into space.

L = The "Lifetime" of communicating civilizations
The length of time such civilizations release detectable signals into space.

Related links:
Drake Equation Calculator
SETI Science

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