The debate over how many Earth-like planets exist has a wide range — from one, if the Rare Earth hypothesis is right, to something approaching a hundred quintillion, if Milky Way rates hold across the universe’s roughly two trillion galaxies — and both answers are supported by serious researchers

Ask how many Earth-like planets there are, and the honest answer is that serious researchers give estimates spanning more than twenty orders of magnitude. At one end, essentially one, us, if the Rare Earth hypothesis is right. At the other, something approaching a hundred quintillion, if the rates we measure in the Milky Way hold [...] The post The debate over how many Earth-like planets exist has a wide range — from one, if the Rare Earth hypothesis is right, to something approaching a hundred