^Matt Williams. Beyond "Fermi's Paradox" IV: What is the Rare Earth Hypothesis?(PDF). Universe Today. 29 July 2020 [6 June 2021]. (原始内容存档(PDF)于2020-11-28). Origins: The term “Rare Earth” takes its name from the book Rare Earth: Why Complex Life Is Uncommon in the Universe (2000), by Peter Ward and Donald E. Brownlee ... As the authors describe it, the Rare Earth argument comes down to two central hypotheses ... making Earth a very special place