The Crater vs. The Snowflake: Johannes Kepler on Signs of Intelligent Life

Johannes Kepler discussed the possibility of extraterrestrial life multiple times throughout his published work in the early 1600s. While Kepler’s ideas about extraterrestrial life were tied to his theological understanding of the universe, he also took the circular lunar features (now known to be impact craters) seen through the telescope as possible evidence of such life, bringing his speculations into the realm of science. His analysis of the lunar craters provided one of the first scientifically-grounded and evidence-based arguments for the existence of extraterrestrial intelligence. However, Kepler’s discussion raises the question of how he saw the lunar “circles” as different from other phenomena, such as the six-sided snowflake, that he believed reflected a divine intelligence expressed in the fundamental order of nature. We’ll consider what this early historical example reveals about the challenges of interpreting possible signals of extraterrestrial intelligence and the underlying assumptions embedded in such analyses.