Question

What does the Drake equation mean? Is it really proved and fool proof?

No, the Drake Equation is not "fool-proof." Many people falsely believe that The Drake Equation "proves" the existence of intelligent life elsewhere in the universe. On the contrary, the Drake Equation simply expresses how many civilized worlds there would be in our galaxy given certain assumptions and known mathematical relationships. The equation is expressed as follows:

N = R * Fp * Ne * Fl * Fi * Fc * L

Where N = The number of communicative civilizations in the Milky Way, and where:

R = The rate of formation of suitable stars in the galaxy

Fp = The fraction of those stars with planets

Ne = The number of "earths" per planetary system

Fl = The fraction of those planets where life develops

Fi = The fraction of life sites where intelligence develops

Fc = The fraction of planets where technology develops

L = The "lifetime" of such civilizations releasing detectable signals into space

While the first three factors (R*, Fp, and Ne) can be estimated by scientists to some degree of certainty, the latter factors can only be reasonably guessed. For example, many scientists believe that where life can evolve (Ne) it will (Fl = 100%), while others believe that the development of life is far more rare (Fl < 10% or even < .01%). Changes in each of the latter four factors of the Drake Equation can cause the solution, N, to equal anything from zero to the hundreds of thousands! Clearly, the Drake Equation is only a theoretical tool at this point; it has no unique solution. For more details on the factors in the equation as well as a great equation "demo" you can play with yourself, check out the following sites:

http://www.activemind.com/Mysterious/Topics/SETI/drake_equation.html

www.seti.org/science/drake-bg.html Anna Lee Strachan, NASA Astrobiology Institute
January 28, 2002