It’s explained in the “A Tale of Two Phases” section. Life on Earth-like planets evolves through two major phases: a “Dinosaur Phase” focused on physical prowess and a “Human Phase” centered on intellectual capabilities. Transitions between these phases are considered to be rare and may require cataclysmic events like meteor impacts. Due to these constraints, intelligent life capable of technological communication is exceedingly rare in the galaxy.
The equation lays it all out rather succinctly, giving N=8.25 as the number of planets in our galaxy that have reached the “Human Phase”. Although the numbers used were extremely forgiving, with other estimates bringing the number down to only 2 or 3 planets.
What is the human-phase hypothesis? Your whole post doesn’t actually say!
It’s explained in the “A Tale of Two Phases” section. Life on Earth-like planets evolves through two major phases: a “Dinosaur Phase” focused on physical prowess and a “Human Phase” centered on intellectual capabilities. Transitions between these phases are considered to be rare and may require cataclysmic events like meteor impacts. Due to these constraints, intelligent life capable of technological communication is exceedingly rare in the galaxy.
The equation lays it all out rather succinctly, giving N=8.25 as the number of planets in our galaxy that have reached the “Human Phase”. Although the numbers used were extremely forgiving, with other estimates bringing the number down to only 2 or 3 planets.