Fermi's Paradox - The Last Challenge for Copernicanism?

TL;DR

This paper reviews Fermi's paradox, analyzing its implications for humanity's future and classifying existing solutions, highlighting how catastrophic hypotheses may support optimistic SETI prospects.

Contribution

It offers a new classification of solutions to Fermi's paradox and examines their methodological assumptions and implications for SETI.

Findings

Catastrophic hypotheses may justify guarded optimism for SETI.

Analysis of observation selection effects clarifies the paradox's resolution.

Classifying solutions helps guide future SETI strategies.

Abstract

We review Fermi's paradox (or the "Great Silence" problem), not only arguably the oldest and crucial problem for the Search for ExtraTerrestrial Intelligence (SETI), but also a conundrum of profound scientific, philosophical and cultural importance. By a simple analysis of observation selection effects, the correct resolution of Fermi's paradox is certain to tell us something about the future of humanity. Already a more than three quarters of a century old puzzle - and a quarter of century since the last major review paper in the field by G. David Brin - Fermi's paradox has generated many ingenious discussions and hypotheses. We analyze the often tacit methodological assumptions built into various answers to this puzzle and attempt a new classification of the numerous solutions proposed in an already huge literature on the subject. Finally, we consider the ramifications of various classes of hypotheses for the practical SETI projects. Somewhat paradoxically, it seems that the class of (neo)catastrophic hypotheses gives, on balance, the strongest justification for guarded optimism regarding our current and near-future SETI efforts.