(b) is counterfactual today. Nobody can calculate how many nearby star systems should have given birth to star faring civilizations—since nobody knows p(origin of life). We can’t even make life from plausible inorganic materials yet. We are clueless—and thus highly uncertain.
(b) is counterfactual today. Nobody can calculate how many nearby star systems should have given birth to star faring civilizations—since nobody knows p(origin of life). We can’t even make life from plausible inorganic materials yet. We are clueless—and thus highly uncertain.