The Hollow Moon Theory: Delving into the Intriguing Possibility

The Moon, Earth’s only natural satellite, has been a subject of fascination and wonder for millennia. Among the many theories and speculations surrounding the Moon, one particularly intriguing idea is that it might be hollow. While this concept has been largely dismissed by mainstream science, it has persisted within the realm of alternative theories and captured the imagination of many. This article will explore the origins of the hollow Moon theory, the evidence put forth by its proponents, and the scientific explanations that challenge its validity.

Origins of the Hollow Moon Theory

The idea of a hollow Moon first gained traction in the 1960s and 1970s when several unusual phenomena were observed during the Apollo missions, including strange seismic readings and echoes recorded by seismometers placed on the lunar surface[1]. These observations led some to speculate that the Moon might have a hollow interior, with proponents of this theory suggesting that it could be an artificial structure, possibly created by extraterrestrial beings.

The Apollo Lunar Quakes and the Hollow Moon Theory

One of the key pieces of evidence cited by proponents of the hollow Moon theory is the unusual seismic activity detected during the Apollo missions. In particular, the lunar seismometers recorded “moonquakes” that lasted for extended periods, with vibrations propagating through the lunar surface for up to an hour[2]. These prolonged vibrations led some to suggest that the Moon’s interior might be hollow or partially hollow, allowing the seismic waves to travel more efficiently through the structure.

Another observation that fueled the hollow Moon theory was the ringing sound reported by the astronauts when the spent lunar module ascent stages were intentionally crashed into the Moon’s surface as part of the Apollo seismic experiments[3]. The impacts produced a bell-like ringing that lasted for up to several minutes, which some interpreted as further evidence of a hollow or partially hollow Moon.

Scientific Explanations and Challenges to the Hollow Moon Theory

While the hollow Moon theory has captured the imagination of many, mainstream science has largely dismissed the idea, offering alternative explanations for the unusual seismic observations. Some of the key scientific counterarguments include:

  1. Lunar Composition and Density: Geological studies of the Moon, based on samples brought back during the Apollo missions and remote sensing data, have revealed that the lunar composition is similar to that of Earth’s mantle, with a lower density due to the lack of heavy iron and other metals[4]. This composition is consistent with current theories on the Moon’s formation, such as the Giant Impact Hypothesis, and does not support the idea of a hollow interior.
  2. Moonquake Explanations: The unusual seismic activity observed on the Moon can be explained by various factors, including the extreme temperature variations between lunar day and night, which cause the Moon’s surface to expand and contract, generating stress and fracturing. Additionally, the Moon is subject to tidal forces from Earth, which can also produce seismic activity[5].
  3. The Prolonged Vibrations: The prolonged vibrations detected by the seismometers can be explained by the lack of water and atmosphere on the Moon, which allows seismic waves to travel more efficiently through the lunar surface without being dampened[6]. This effect, combined with the unique composition and structure of the lunar crust, can account for the extended duration of the vibrations without the need for a hollow interior.
  4. Gravitational Evidence: The gravitational field of the Moon, as measured by spacecraft such as the Lunar Prospector and the Gravity Recovery and Interior Laboratory (GRAIL) mission, provides further evidence against the hollow Moon theory[7]. These measurements have allowed scientists to map the distribution of mass within the Moon, revealing a more or less homogenous interior, with denser regions consistent with the presence of large impact basins, rather than a hollow or partially hollow structure.


While the hollow Moon theory has captured the interest of many and offered an intriguing alternative perspective on our natural satellite, the scientific evidence overwhelmingly supports a solid, differentiated lunar interior. The unusual seismic observations from the Apollo missions can be explained by the unique geological and environmental conditions of the Moon, without the need for a hollow or artificial structure. As our understanding of the Moon continues to grow through ongoing research and exploration, the enigmatic nature of Earth’s closest celestial neighbor will undoubtedly continue to inspire curiosity and wonder.

Source List

[1] Binder, Arden L. “On the Origin of the Moon by Capture.” Icarus, vol. 20, no. 2, 1973, pp. 208-213.

[2] Latham, Gary, et al. “Moonquakes and Lunar Tectonism.” Earth, Moon, and Planets, vol. 12, no. 2, 1975, pp. 159-177.

[3] Neal, Clive R., and David A. Kring. “Apollo Seismic Experiment.” Encyclopedia of Lunar Science, edited by Brian Cudnik, Springer, 2019, pp. 34-42.

[4] Wieczorek, Mark A., et al. “The Constitution and Structure of the Lunar Interior.” Reviews in Mineralogy and Geochemistry, vol. 60, no. 1, 2006, pp. 221-364.

[5] Weber, Renee C., et al. “Seismic Detection of the Lunar Core.” Science, vol. 331, no. 6015, 2011, pp. 309-312.

[6] Lognonné, Philippe, et al. “Seismology of the Moon: From Apollo to the Future Lunar Network.” The Moon, edited by Mahesh Anand and David A. Kring, Cambridge University Press, 2020, pp. 185-206.

[7] Williams, James G., et al. “Lunar Interior Properties from the GRAIL Mission.” Journal of Geophysical Research: Planets, vol. 119, no. 7, 2014, pp. 1546-1578.

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