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Innovation Blog

Drake Equation: The Biggest Question of All, or:

Is There Life in the Universe? (Is There Life on Earth?)

The Answer is 10

 By Shlomo Maital



Frank Drake

  In academic research, as in innovation, creative people dare to take huge gambles, by asking very hard, big humongous questions, questions whose very nature discredits their rationality.    Here is an example, featured on the wonderful Discovery program on BBC.

    Almost 50 years ago, a young astrophysicist named Frank Drake dared to ask the question, how many other civilizations exist in the Universe, apart from life on earth?  Until Drake, that question was regarded as whacko by astrophysicists, and those who researched it generally used methods that were, well, also quite whacko.  Drake endangered his career by tackling it. But he was driven by curiosity and passion.  So he tackled it anyway.  And then, the U.S. Science Foundation (which also thought it was a key question – these were Cold War days, what if Aliens contacted the Russians first instead of the Americans???) asked him to convene a conference on the subject, inviting the top experts.  So Drake called a conference to be held in Green Bank, West Virginia, attended by a dozen top astrophysicists, including the celebrity Carl Sagan. 

     Now, a conference has to have an agenda.  So Drake sat down, and built an equation that included the seven key factors that would determine how many civilizations there are in the universe that potentially could be contacted,  equal to “N”.

The Drake equation states that:

N = R^{\ast} \times f_p \times n_e \times f_{\ell} \times f_i \times f_c \times L \!

 where:  N = the number of civilizations in our galaxy with which communication might be possible;  and  R* = the average rate of star formation per year in our galaxy; fp = the fraction of those stars that have planets; ne = the average number of planets that can potentially support life per star that has planets;fℓ = the fraction of the above that actually go on to develop life at some point; fi = the fraction of the above that actually go on to develop intelligent life; fc = the fraction of civilizations that develop a technology that releases detectable signs of their existence into space; L = the length of time such civilizations release detectable signals into space

      Drake’s values give N = 10 × 0.5 × 2 × 1 × 0.01 × 0.01 × 10,000 = 10

      The universe is very large.  And very old. Our sun is 4.5 billion years old. Other suns are as much as 10 billion years old.  So these 10 civilizations are likely very very far away.  Millions of light years.  So messages sent from Earth by the SETI Study of Extra Terrestrial Intelligence are very unlikely to be answered in our lifetime.  But SETI’s listening program – if other civilizations have sent us messages, or simply use electro-magnetic radiation to communicate – might hear something interesting. 

       Imagine the scene. SETI radio telescopes get a message. It is from Civilization #9. 

       It says:   “We need to talk”. 


Blog entries written by Prof. Shlomo Maital

Shlomo Maital
September 2010
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