How many alien civilizations are capable of contacting us?
Source : www.msnbc.com/modules/drake/ (via Ndunlks)
In 1961, radio astronomer Frank Drake presented an equation designed to
estimate that number on the basis of seven assumptions. For now, the Drake
Equation tells you more about your own views on life in the universe than
about scientific fact. But the scientific community continues to use it as a
yardstick for the SETI search. Plug in your estimates for the following seven
factors and come up with your own answer.
1. How many stars with suitable conditions for creating habitable planets
are formed annually in our galaxy? (The typical estimates for this number
range from five to 20.)
2. In percentage terms, how many of those stars actually have planets? (The
recent discovery of extrasolar planets has led astronomers to raise their
estimates of this number. The typical range is 3 percent to 50 percent.)%
3. In those planetary systems, what is the average number of worlds in the
"habitable zone," where water exists in liquid form? (Please enter zero or a
positive number.)
4. On what percentage of those habitable worlds does life actually arise?
(In light of recent studies of Mars and Europa, a moon of Jupiter, some
astronomers argue that this number is close to 100 percent.)%
5. In percentage terms, how many of those life-bearing worlds give rise to
intelligent life?%
6. In percentage terms, how many of those worlds with intelligent life
develop technologies that release detectable signs of their existence into
space?%
7. On average, for how many years do such civilizations release detectable
signals into space? (This ranks as one of the most controversial numbers in
the calculation. In recent years, some astronomers have grown more optimistic
that the only such civilization we know about — our own — will be able to
avoid blowing itself into oblivion anytime soon. Please enter zero or a
positive number.)
http://www.msnbc.com/modules/drake/default.asp - The Drake equation
Calculating the Possibility of Extra Terrestrial Life
Source : UASR Mailing list
In the early 1960’s Frank Drake sought a way to calculate the
probability of finding other intelligent races. He came up with
an equation to calculate the possibility of extra terrestrial
civilizations; which became known as the ‘Drake Equation’. Using
this equation Mr. Drake determined that there was the possibility
of 100,000 to 1,000,000 extra terrestrial civilizations in our Milky
Way Galaxy!
Here is the equation:
N=R*FpNpFlFiFcL
N = the number of technological civilizations in our galaxy
R* = The rate of formation of suitable stars
F(p) = the fraction of stars having planets.
N(e) = the number of suitable planets per planetary system.
F(l) = the fraction of planets on which life develops
F(i) = the fraction of life that evolves to intelligence beings.
F(c) = the fraction of intelligent species to develop the means of communication.
L = The length of time such civilizations release detectable signals into space.
Drake and other early extraterrestrial-life enthusiasts, including Carl Sagan,
arrived at a value for N between 100,000 and 1,000,000--still only about
one technological civilization per million stars in the Milky Way, which
astronomers believe contains some 200 billion stars.
SOURCE: http://www.abductee.net/five/drake.html
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