Hollow Moon

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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.

Contents

While Hollow Moon hypotheses usually propose the hollow space as the result of natural processes, the related Spaceship Moon hypothesis [1] [2] holds that the moon is an artifact created by an alien civilization; [1] [2] this belief usually coincides with beliefs in UFOs or ancient astronauts. [2] 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. [3] [4]

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 , [1] [5] which borrowed from earlier works set in a Hollow Earth, such as Ludvig Holberg's 1741 novel Niels Klim's Underground Travels. [6] [7]

Both the Hollow Moon and Hollow Earth theories are now universally considered to be fringe or conspiracy theories. [1]

Claims and rebuttals

Density

The fact that the Moon is less dense than the Earth is advanced by conspiracy theorists as support for claims of a hollow Moon. [8] The Moon's mean density is 3.3 g/cm3, whereas the Earth's is 5.5 g/cm3. [9] Mainstream science argues this difference is due to the fact that the Earth's upper mantle and crust are less dense than its heavy, iron core. [9] [5] [10]

The Moon rang like a bell

Between 1969 and 1977, seismometers installed on the Moon by the Apollo missions recorded moonquakes. The Moon was described as "ringing like a bell" during some of those quakes, specifically the shallow ones. [11] This phrase was brought to popular attention in March 1970 [1] in an article in Popular Science . [12]

On November 20, 1969, Apollo 12 deliberately crashed the Ascent Stage of its Lunar Module onto the Moon's surface; NASA reported that the Moon rang 'like a bell' for almost an hour, leading to arguments that it must be hollow like a bell. [1] Lunar seismology experiments since then have shown that the lunar body has shallow moonquakes that act differently from quakes on Earth, due to differences in texture, type and density of the planetary strata, but there is no evidence of any large empty space inside the body. [11]

Vasin-Shcherbakov "spaceship" conjecture

Speculative cutaway model of a Spaceship Moon Spaceship moon.jpg
Speculative cutaway model of a Spaceship Moon

In 1970, Michael Vasin and Alexander Shcherbakov, of the Soviet Academy of Sciences, advanced a hypothesis that the Moon is a spaceship created by unknown beings. [2] The article was entitled "Is the Moon the Creation of Alien Intelligence?" and was published in Sputnik , the Soviet equivalent of Reader's Digest . [1] [13] The Vasin-Shcerbakov hypothesis was reported in the West that same year. [14]

The authors reference earlier speculation by astrophysicist Iosif Shklovsky, who suggested that the Martian moon Phobos was an artificial satellite and hollow; this has since been shown not to be the case. [15] Skeptical author Jason Colavito points out that all of their evidence is circumstantial, and that, in the 1960s, the atheistic Soviet Union promoted the ancient astronaut concept in an attempt to undermine the West's faith in religion. [2]

"Perfect" solar eclipses

In 1965, author Isaac Asimov observed: "What makes a total eclipse so remarkable is the sheer astronomical accident that the Moon fits so snugly over the Sun. The Moon is just large enough to cover the Sun completely (at times) so that a temporary night falls and the stars spring out. [...] The Sun's greater distance makes up for its greater size and the result is that the Moon and the Sun appear to be equal in size. [...] There is no astronomical reason why Moon and Sun should fit so well. It is the sheerest of coincidence, and only the Earth among all the planets is blessed in this fashion." [16]

Since the 1970s, conspiracy theorists have cited Asimov's observations on solar eclipses as evidence of the Moon's artificiality. [17] [18] Mainstream astronomers reject this interpretation. They note that the angular diameters of Sun and Moon vary by several percent over time and do not actually "perfectly" match during eclipses. [19] Nor is Earth the only planet with such a satellite: Saturn's moon Prometheus has roughly the same angular diameter as the Sun when viewed from Saturn. [19]

Some scholars have claimed that "the conditions required for perfect solar eclipses are the same conditions generally acknowledged to be necessary for intelligent life to emerge"; If so, the Moon's size and orbit might be best explained by the weak anthropic principle. [19] [20] [21]

Scientific perspective

Multiple lines of evidence demonstrate that the Moon is a solid body which formed from an impact between Earth and a planetoid.

Origin of the Moon

Historically, it was theorized that the Moon originated when a rapidly-spinning Earth expelled a piece of its mass. [22] This was proposed by George Darwin (son of the famous biologist Charles Darwin) in 1879 [23] and retained some popularity until Apollo. [22] The Austrian geologist Otto Ampferer in 1925 also suggested the emerging of the Moon as cause for continental drift. [24] A second hypothesis argued the Earth and the Moon formed together as a double system from the primordial accretion disk of the Solar System. [25] [26] Finally, a third hypothesis suggested that the Moon may have been a planetoid captured by Earth's gravity. [22] [27] [28]

The modern explanation for the origin of the Moon is usually the giant-impact hypothesis, which argues a Mars-sized body struck the Earth, making a debris ring that eventually collected into a single natural satellite, the Moon. [29] [30] The giant-impact hypothesis is currently the favored scientific hypothesis for the formation of the Moon. [31]

Internal structure

Schematic cross-section of the internal structure of the Moon Main lunar core en.jpg
Schematic cross-section of the internal structure of the Moon

Multiple lines of evidence disprove that the Moon is hollow. [1] [32] One involves moment of inertia parameters; the other involves seismic observations. [1] [32] The moment of inertia parameters indicate that the core of the Moon is both dense and small, with the rest of the Moon consisting of material with nearly-constant density. Seismic observations have been made, constraining the thickness of the Moon's crust, mantle and core, demonstrating it could not be hollow. [33]

Mainstream scientific opinion on the internal structure of the Moon overwhelmingly supports a solid internal structure with a thin crust, an extensive mantle and a small denser core. [34] [35]

Moment of inertia factor

BodyMoment
of inertia
factor
Hollow Sphere0.67
Uniform Sphere0.4
Denser at Core< 0.4
Moon0.39
Earth0.33
All Mass at Core0.0

The moment of inertia factor is a number, ranging from 0 to .67, that represents the distribution of mass in a spherical body. A moment of inertia factor of 0 represents a body with all its mass concentrated at its central core, while a factor of .67 represents a perfectly hollow sphere. [36] A moment of inertia factor of 0.4 corresponds to a sphere of uniform density, while factors less than 0.4 represent bodies with cores that are more dense than their surfaces. [37] The Earth, with its dense inner core, has a moment of inertia factor of 0.3307 [37]

In 1965, astronomer Wallace John Eckert attempted to calculate the lunar moment of inertia factor using a novel analysis of the Moon's perigee and node. [38] His calculations suggested the Moon might be hollow, a result Eckert rejected as absurd. [39] Subsequent analysis revealed Eckert had failed to account for nonuniformity of Earth's rotation in the orbital theory of the Moon. [40] By 1968, other methods had allowed the Moon's moment of inertia factor to be accurately calculated at its accepted value. [41]

From 1969 to 1973, five retroreflectors were installed on the Moon during the Apollo program (11, 14, and 15) and Lunokhod 1 and 2 missions. [42] These reflectors made it possible to measure the distance between the surfaces of the Earth and the Moon using extremely precise laser ranging. True (physical) libration of the Moon measured via Lunar laser ranging constrains the moment of inertia factor to 0.394 ± 0.002. [43] This is very close to the value for a solid object with radially constant density, which would be 0.4. [43]

Seismic activity

From 1969 through 1972, Apollo astronauts installed several seismographic measuring systems on the Moon and their data made available to scientists (such as those from the Apollo Lunar Surface Experiments Package). The Apollo 11 instrument functioned through August of the landing year. The instruments placed by the Apollo 12, 14, 15, and 16 missions were functional until they were switched off in 1977. [44] [45]

The existence of moonquakes was an unexpected discovery from seismometers. Analysis of lunar seismic data has helped constrain the thickness of the crust (~45 km) [35] [46] and mantle, as well as the core radius (~330 km). [34]

Doppler Gravity Experiment

A visualization of the lunar gravity field based on Lunar Prospector data. LPgravityfield.png
A visualization of the lunar gravity field based on Lunar Prospector data.

In 1998, the United States launched the Lunar Prospector, which hosted the Doppler Gravity Experiment (DGE) -- the first polar, low-altitude mapping of the lunar gravity field. The Prospector DGE obtained data constituted the "first truly operational gravity map of the Moon". [47] The purpose of the Lunar Prospector DGE was to learn about the surface and internal mass distribution of the Moon. [47] This was accomplished by measuring the Doppler shift in the S-band tracking signal as it reaches Earth, which can be converted to spacecraft accelerations. [47] The accelerations can be processed to provide estimates of the lunar gravity field. Estimates of the surface and internal mass distribution give information on the crust, lithosphere, and internal structure of the Moon. [47]

Fiction

Conspiracy theory

Related Research Articles

<span class="mw-page-title-main">Moon</span> Natural satellite orbiting Earth

The Moon is Earth's only natural satellite. It orbits at an average distance of 384,400 km (238,900 mi), about 30 times the diameter of Earth. Over time Earth's gravity has caused tidal locking, causing the same side of the Moon to always face Earth. Because of this, the lunar day and the lunar month are the same length, at 29.5 Earth days. The Moon's gravitational pull – and to a lesser extent, the Sun's – are the main drivers of Earth's tides.

<span class="mw-page-title-main">Giant-impact hypothesis</span> Hypothesis of the formation of the Moon

The giant-impact hypothesis, sometimes called the Theia Impact, is an astrogeology hypothesis for the formation of the Moon first proposed in 1946 by Canadian geologist Reginald Daly. The hypothesis suggests that the Early Earth collided with a Mars-sized protoplanet of the same orbit approximately 4.5 billion years ago in the early Hadean eon, and the ejecta of the impact event later accreted to form the Moon. The impactor planet is sometimes called Theia, named after the mythical Greek Titan who was the mother of Selene, the goddess of the Moon.

<span class="mw-page-title-main">Lunar Laser Ranging experiments</span> Measuring the distance between the Earth and the Moon with laser light

Lunar Laser Ranging (LLR) is the practice of measuring the distance between the surfaces of the Earth and the Moon using laser ranging. The distance can be calculated from the round-trip time of laser light pulses travelling at the speed of light, which are reflected back to Earth by the Moon's surface or by one of several retroreflectors installed on the Moon. Three were placed by the United States' Apollo program, two by the Soviet Lunokhod 1 and 2 missions, and one by India's Chandrayaan-3 mission.

<span class="mw-page-title-main">Mass concentration (astronomy)</span> Region of a planet or moons crust that contains a large positive gravitational anomaly

In astronomy, astrophysics and geophysics, a mass concentration is a region of a planet's or moon's crust that contains a large positive gravity anomaly. In general, the word "mascon" can be used as a noun to refer to an excess distribution of mass on or beneath the surface of an astronomical body, such as is found around Hawaii on Earth. However, this term is most often used to describe a geologic structure that has a positive gravitational anomaly associated with a feature that might otherwise have been expected to have a negative anomaly, such as the "mascon basins" on the Moon.

<span class="mw-page-title-main">Lunar mare</span> Large, dark, basaltic plains on Earths Moon

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<span class="mw-page-title-main">Apache Point Observatory Lunar Laser-ranging Operation</span>

The Apache Point Observatory Lunar Laser-ranging Operation, or APOLLO, is a project at the Apache Point Observatory in New Mexico. It is an extension and advancement of previous Lunar Laser Ranging experiments, which use retroreflectors on the Moon to track changes in lunar orbital distance and motion.

<span class="mw-page-title-main">Planetary core</span> Innermost layer(s) of a planet

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<span class="mw-page-title-main">Genesis Rock</span> Rock retrieved from the Moon in 1971

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<span class="mw-page-title-main">Geology of the Moon</span> Structure and composition of the Moon

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<span class="mw-page-title-main">Near side of the Moon</span> Hemisphere of the Moon facing the Earth

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<span class="mw-page-title-main">Lunar magma ocean</span> Theorized historical geological layer on the Moon

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A quake is the result when the surface of a planet, moon or star begins to shake, usually as the consequence of a sudden release of energy transmitted as seismic waves, and potentially with great violence. The types of quakes include earthquake, moonquake, marsquake, venusquake, sunquake, starquake, and mercuryquake.

<span class="mw-page-title-main">Internal structure of the Moon</span>

Having a mean density of 3,346.4 kg/m3, the Moon is a differentiated body, being composed of a geochemically distinct crust, mantle, and planetary core. This structure is believed to have resulted from the fractional crystallization of a magma ocean shortly after its formation about 4.5 billion years ago. The energy required to melt the outer portion of the Moon is commonly attributed to a giant impact event that is postulated to have formed the Earth-Moon system, and the subsequent reaccretion of material in Earth orbit. Crystallization of this magma ocean would have given rise to a mafic mantle and a plagioclase-rich crust.

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<span class="mw-page-title-main">GRAIL</span> 2011–12 NASA mission to study the Moon

The Gravity Recovery and Interior Laboratory (GRAIL) was an American lunar science mission in NASA's Discovery Program which used high-quality gravitational field mapping of the Moon to determine its interior structure. The two small spacecraft GRAIL A (Ebb) and GRAIL B (Flow) were launched on 10 September 2011 aboard a single launch vehicle: the most-powerful configuration of a Delta II, the 7920H-10. GRAIL A separated from the rocket about nine minutes after launch, GRAIL B followed about eight minutes later. They arrived at their orbits around the Moon 25 hours apart. The first probe entered orbit on 31 December 2011 and the second followed on 1 January 2012. The two spacecraft impacted the Lunar surface on December 17, 2012.

<span class="mw-page-title-main">Lunar seismology</span> Study of ground motions of the Moon

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<span class="mw-page-title-main">Origin of the Moon</span> Theories explaining the formation of Earths Moon

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<span class="mw-page-title-main">Theia (planet)</span> Planet hypothesized to have impacted Earth and created the Moon

Theia is a hypothesized ancient planet in the early Solar System which, according to the giant-impact hypothesis, collided with the early Earth around 4.5 billion years ago, with some of the resulting ejected debris coalescing to form the Moon. Collision simulations support the idea that the large low-shear-velocity provinces in the lower mantle may be remnants of Theia. Theia is hypothesized to have been about the size of Mars, and may have formed in the outer Solar System and provided much of Earth's water, though this is debated.

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<span class="mw-page-title-main">Seismic velocity structure</span> Seismic wave velocity variation

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  58. ↑ "Peer review: Who Built the Moon?". The Guardian . 1 September 2005.
  59. ↑ David G. Robertson (2016). UFOs, Conspiracy Theories and the New Age: Millennial Conspiracism. Bloomsbury Academic. p. 148. ISBN   978-1-4742-5322-2.
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