Hollow Moon

The Hollow Moon and the closely related Spaceship Moon are pseudoscientific hypotheses that propose that Earth's Moon is either wholly hollow or otherwise contains a substantial interior space. No scientific evidence exists to support the idea; seismic observations and other data collected since spacecraft began to orbit or land on the Moon indicate that it has a solid, differentiated interior, with a thin crust, extensive mantle, and a dense core which is significantly smaller (in relative terms) than Earth's. While Hollow Moon hypotheses usually propose the hollow space as the result of natural processes, the related Spaceship Moon hypothesis holds that the Moon is an artifact created by an alien civilization; this belief usually coincides with beliefs in UFOs or ancient astronauts. This idea dates from 1970, when two Soviet authors published a short piece in the popular press speculating that the Moon might be "the creation of alien intelligence"; since then, it has occasionally been endorsed by conspiracy theorists like Jim Marrs and David Icke. An at least partially hollow Moon has made many appearances in science fiction, the earliest being H. G. Wells' 1901 novel The First Men in the Moon, which borrowed from earlier works set in a Hollow Earth, such as Ludvig Holberg's 1741 novel Niels Klim's Underground Travels. Both the Hollow Moon and Hollow Earth theories are now universally considered to be fringe or conspiracy theories.