A theory that suggests that the moon is a large hollow sphere. Backed up by little evidence, but still regarded by some as a possibility, hollow moon theory originated during seismological tests on the moon following the Lunar landings.


This occured most notably in November 1969 after seismometers were set up on the moons surface by the astronauts of Apollo XII. When the Lunar module had taken off, heading back to earth the astronauts discarded the ascent stage of the lunar module, dropping it on the moons surface, smashing the craft and creating a tremor that was picked up by the seismometers and when the NASA scientists heard the data stream, they couldn’t believe what they were hearing. The moon was ringing like a bell and continued to do so for around an hour.


After they had had a chance to analyse the seismological information, NASA declared that the moon seemed to be a hollow sphere with a metallic layer around 34-40 metres deep. No other type of evidence has yet been found to back up the theory that the moon is hollow.