Fermi paradox
Rare Earth hypothesis
Human extinction
NEO Earth Close Approaches
The 'Great Silence': the Controversy Concerning Extraterrestrial Intelligent Life (PDF)
Why I Hope the Search for Extraterrestrial Life Finds Nothing (PDF)
The Fermi Paradox: An Approach Based on Percolation Theory
Existential Risk Prevention as Global Priority (PDF)
Extraterrestrial intelligent beings do not exist (PDF)
The Intelligent Apes