Nikos Prantzos

The issue for extraterrestrial intelligent life is one of the most hotly debated topics since ancient times. In the past 60 years or so, the debate was largely shaped by the ‘Drake equation’ and the ‘Fermi paradox’. The former was proposed by Frank Drake in 1961 and became ever since the key quantitative tool to evaluate the number of extraterrestrial civilizations in the Galaxy today. The latter was formulated a decade earlier by Enrico Fermi, but it remained virtually unknown until 1975, when it was independently re-discovered twice (Hart 1975, Viewing 1975). In a concise form (‘where are they?’), it opposes a healthy skepticism to the optimistic views on ETI: if there are many of them, why do not we see any evidence of their presence on Earth or in the solar system?

I will present an overview of the history of the debate on extraterrestrial intelligence, as well as some developments on the quantitative implications of the Drake formula, adopting recent results of the tatistics of extra-solar planets. I will also present a recent original analysis of the Fermi paradox, formulated for the first time in terms of that formula.