Hitler thought the moon was made of ice. The idea came from an Austrian engineer named Hanns Hörbiger, who had suggested in 1913 that most objects in the solar system were icy, apparently because they’re shiny. No one took this seriously at the time, but German socialists began to support it during the ’20s, and eventually it became official Nazi policy, an alternative to “Jewish” science.

The idea was dismissed again after the war, but it had a strange holding power — as late as 1953 more than a million people in Germany, England and the United States still believed in Hörbiger’s theory.