The Moon is hollow or artificial
Seismic data from Apollo mission instruments and subsequent lunar research confirm the Moon has a solid, differentiated interior with a crust, mantle, and small dense core. The 'rings like a bell' description was a scientific metaphor for long-duration moonquakes, not evidence of a hollow interior.
What we know
The hollow moon theory originated from a misinterpretation of Apollo seismic data. During the Apollo 12 mission in 1969, astronauts deliberately crashed the lunar module onto the surface and seismometers recorded vibrations that lasted approximately one hour. Scientists described the Moon as 'ringing like a bell' - a metaphor comparing the long-duration vibrations to the resonance of a struck bell. Conspiracy theorists interpreted this literally as evidence the Moon is hollow.
The scientific explanation is that the Moon's lack of water (which dampens vibrations on Earth) and its cold, rigid rock structure allow seismic waves to propagate for much longer than on Earth. Water absorbs seismic energy rapidly; the dry, crystalline lunar rock does not. The long-lasting vibrations are evidence of the Moon's dry, rigid composition, not of a hollow interior.
Multiple independent lines of evidence confirm the Moon is not hollow. Moment of inertia measurements (how mass is distributed relative to the center) require a dense small core and consistent density throughout, incompatible with a hollow shell. Seismic tomography from Apollo instruments has mapped the Moon's structure, confirming a crust of approximately 45 km thickness, an extensive mantle, and a core of approximately 330 km radius. The Wikipedia article on the Hollow Moon hypothesis notes: '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.'
Common claims
- The Moon rang like a bell, proving it is hollowFalse. The long-duration vibrations are explained by the Moon's lack of water damping; seismic data confirms a solid interior.
- The Moon's perfect size for solar eclipses proves it is artificialNot supported. The apparent size match is a coincidence of the current epoch; the Moon is slowly moving away from Earth.
- Scientists cannot explain the Moon's origin, suggesting it was placed thereMisleading. The giant impact hypothesis is the leading origin theory with substantial supporting evidence, though some details remain studied.