The Drake Equation


The Drake equation, also known as the Green Bank equation, is used to yield the number of technically advanced civilizations in the Milky Way Galaxy. The equation uses astronomical, biological, and psychological factors to determine this number. The formula was first discussed in 1961 at a conference on the “search of extraterrestrial intelligence”, formulated largely in part by astrophysicist Frank Drake.

The formula states: N = R*fpneflfifcL.

R* is the mean rate of star formation in the galaxy; fp is the fraction of stars with planetary systems.; ne represents the number of planets in such systems that are ecologically suitable for the origin of life; fl is the fraction of such planets on which life in fact develops; fi shows the fraction of such planets on which life evolves to an intelligent form; fc is the fraction of such worlds in which the intelligent life form invents high technology capable at least of interstellar radio communication; and L, shows the average lifetime of such advanced civilizations.

The correct number for each factor is poorly known, and the uncertainty of each variable only grows across the equation. However, the most widely quoted values for each factor are R* = 10/yr, fp = 0.5, ne = 2, fl = 1, fi fc = 0.01. According to these numbers, N should equal 10. Following this, if civilizations destroy themselves within the decade of achieving radio astronomy, then there are no other intelligent life forms in the galaxy with whom we can communicate.

2 thoughts on “The Drake Equation

  1. I think it’s really interesting that despite all the calculations that show a high possibility for extraterrestrial intelligence, we still have no evidence of galactic civilizations. With the potential solutions from the Fermi’s paradox, I do think that we could potential reach a turning point as explorations continue and that hopefully, human civilization can survive long enough to find out!


  2. I used to work at the Green Bank Observatory as a tour guide. It is where I developed my love for astronomy. Frank Drake performed the first search for aliens at Green Bank in 1960 (Project Ozma). In 2010, when I was working there, the observatory had a month-long celebration commemorating the search. This included a talk by Dr. Drake himself. I got to meet him. He mentioned during his talk that if other civilizations developed satellite technology that would also pose a problem in detecting them because satellites beam the info back down to the planet. Early radio and television signals were just sent out so it is possible that our first detection would just be “accidental leakage” of their entertainment system if it uses radio waves.

    Also, the room where the Drake Equation was developed has a small plaque stating that the equation was developed there. I do believe the decorations in that lounge hasn’t changed since the 1960s either. It is very retro in there.


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