Within the uncertainties of involved astronomical and biological parameters, the Drake equation typically predicts that there should be many exoplanets (< 100 to millions) in our Milky Way Galaxy hosting active, communicative civilizations. These optimistic calculations are however not supported by evidence, which is often referred to as the Fermi paradox. University of Texas at Dallas Professor Robert Stern and ETH-Zurich’s Professor Taras Gerya elaborate on this long-standing enigma by showing the importance of long-term plate tectonics as well as oceans and continents for the evolution of active, communicative civilizations.
In 1961, the American astrophysicist and astrobiologist Dr. Frank Drake devised an equation in which several factors are multiplied together to estimate the number of intelligent civilizations in our Galaxy capable of making their presence known to humans:
N = R * fp * ne * fl * fi * fc * L
N: the number of civilizations in the Milky Way Galaxy whose electromagnetic emissions (radio waves, etc.) are detectable;
R: the number of stars formed annually;
fp: the fraction of those stars with planetary systems;
ne: the number of planets per solar system with an environment suitable for life;
fl: the fraction of suitable planets on which life actually appears;
fi: the fraction of life-bearing planets on which intelligent life emerges;
fc: the fraction of civilizations that develop a technology that produces detectable signs of their existence;
L: the average length of time (years) such civilizations produce such signs.
Assigning values to the seven variables has been an educated guessing game, leading to predictions that such civilizations should be widespread. But if that is true, why is there no conclusive evidence of their existence?
This contradiction is known as the Fermi paradox, named for the Italian and later naturalized American nuclear physicist and Nobelist Dr. Enrico Fermi, who informally posed the question to colleagues.
“Life…
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