From the Book - Second edition.
The physicist Enrico Fermi
3. They are (or were) here
They are here and they call themselves Hungarians
They are here and they call themselves Politicians
They are throwing stones at Radivoje Lajic
They are watching us from UFOs
They were here and left evidence of their presence
They exist and they are us : we are all aliens!
The planetarium hypothesis
4. They exist, but we have yet to see or hear from them
They have not had time to reach us
A percolator theory approach
Bracewell-von Neumann probes
They are signaling but we don't know how to listen
They are signaling but we don't know at which frequency to listen
They are signaling but we don't know where to look
The signal is already there in the data
We haven't listened long enough
They are signaling but we aren't receiving
Everyone is listening, no one is transmitting
They have no desire to communicate
They develop a different mathematics
They are calling but we don't recognize the signal
They are distance learners
They are somewhere but the universe is stranger than we imagine
Intelligence isn't permanent
We live in postbiological universe
They are hanging out around black holes
The transcension hypothesis
Infinitely many civilizations exist but only one within our particle horizon : us
The universe is here for us
Life can have emerged only recently
Planetary systems are rare
Continuously habitable zones are narrow
Earth has an optimal "pump of evolution"
The galaxy is a dangerous place
A planetary system is a dangerous place
Earth's system of plate tectonics is unique
Life's genesis is rare (revisited)
Goldilocks twins are rare
The prokaryote-eukaryote transition is rare
Toolmaking species are rare
High technology is not inevitable
Intelligence at the human level is rare
Language is unique to humans
Science is not inevitable
Consciousness is not inevitable
Conclusion : the Fermi Paradox resolved.
