In 1961, radio astronomer Frank Drake developed a pedagogy for analyzing the question of the frequency of extraterrestrial civilizations. Robert Zubrin shows a couple of significant mistaken assumptions by Drake. Robert Zubrin wrote this for Centauri Dreams.
Drake equation defines a “civilization” as a species possessing interstellar communication capability. This means radiotelescopes. By this definition, civilization did not appear on Earth until the 1930s. Although, Earth does not really have the means to usefully broadcast and had limited means to interpret interstellar radio communications. Also, we may need to look at laser or other forms of interstellar communication.
L is the average lifetime of a technological civilization.
N/L, is the rate at which such civilizations are disappearing from the galaxy.
R∗, the rate of star formation in our galaxy;
fp, the fraction of these stars that have planetary systems;
ne, is the mean number of planets in each system that have environments favorable to life;
fl the fraction of these that actually developed life;
fi the fraction of these that evolved intelligent species; and
fc the fraction of intelligent species that developed sufficient technology for interstellar communication
If we estimate L=50,000 years (ten times recorded history), R∗ = 10 stars per year, fp = 0.5, and each of the other four factors ne, fl, fi, and fc equal to 0.2, we calculate the total number of technological civilizations in our galaxy, N, equals 400.
Four-hundred civilizations in our galaxy may seem like a lot, but scattered among the Milky Way’s 400 billion stars, they would represent a very tiny fraction: just one in a billion to be precise. In our own region of the galaxy, (known) stars occur with a density of about one in every 320 cubic light years. If the calculation in the previous paragraph were correct, it would therefore indicate that the nearest extraterrestrial civilization is likely to be about 4,300 light years away.
The Drake equation is wrong. The equation assumes that life, intelligence, and civilization can only evolve in a given solar system once. This is manifestly untrue. Stars evolve on time scales of billions of years, species over millions of years, and civilizations take mere thousands of years.
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