TheHollow Earth is a concept proposing that the planetEarth is entirely hollow or contains a substantial interior space. Notably suggested byEdmond Halley in the late 17th century, the notion was disproven, first tentatively byPierre Bouguer in 1740, then definitively byCharles Hutton in hisSchiehallion experiment around 1774.
It was still occasionally defended through the mid-19th century, notably byJohn Cleves Symmes Jr. andJ. N. Reynolds, but by this time it was part of popularpseudoscience and no longer a scientifically viable hypothesis.
The concept of a hollow Earth still recurs infolklore and as a premise forsubterranean fiction, a subgenre ofadventure fiction. Hollow Earth also recurs inconspiracy theories such as the underground kingdom ofAgartha and theCryptoterrestrial hypothesis and is often said to be inhabited by mythological figures or political leaders.
In ancient times, the concept of a subterranean land inside the Earth appeared inmythology,folklore andlegends. The idea of subterranean realms seemed arguable, and became intertwined with the concept of "places" of origin or afterlife, such as theGreek underworld, theNordicSvartálfaheimr, the ChristianHell, and the JewishSheol (with details describing inner Earth inKabalistic literature, such as theZohar andHesed L'Avraham). The idea of a subterranean realm is also mentioned inTibetan Buddhist belief.[1][2] According to one story from Tibetan Buddhist tradition, there is an ancient city calledShamballa which is located inside the Earth.[2]
According to theAncient Greeks,caverns under the surface led to theunderworld. Such were the caverns atTainaron inLakonia, atTroezen inArgolis, at Ephya inThesprotia, at Herakleia inPontos, and inErmioni.[3] InThracian andDacian legends, it is said that there arecaverns occupied by an ancient god calledZalmoxis.[4] InMesopotamian religion there is a story of a man who, after traveling through the darkness of a tunnel in the mountain of "Mashu", entered a subterranean garden.[5]
InCeltic mythology there is a legend of a cave called "Cruachan", also known as "Ireland's gate to Hell", a mythical and ancient cave from which strange creatures would emerge and be seen on the surface of the Earth.[6] There are also stories of medieval knights and saints who went on pilgrimages to a cave located inStation Island, County Donegal in Ireland, where they made journeys inside the Earth into a place ofpurgatory.[7] InCounty Down, Northern Ireland there is a myth which says tunnels lead to the land of the subterraneanTuatha Dé Danann, a group of people who are believed to have introducedDruidism to Ireland, and then went back underground.[8]
InHindu mythology, the underworld is referred to asPatala. In the Bengali version of the Hindu epicRamayana, it has been depicted howRama andLakshmana were taken by the king of the underworldAhiravan, brother of the demon kingRavana. Later on they were rescued byHanuman. TheAngami Naga tribes ofIndia claim that their ancestors emerged in ancient times from a subterranean land inside the Earth.[9] TheTaino from Cuba believe their ancestors emerged in ancient times from two caves in a mountain underground.[10]
Natives of theTrobriand Islands believe that their ancestors had come from a subterranean land through a cavern hole called "Obukula".[11] Mexican folklore also tells of a cave in a mountain five miles south ofOjinaga, and that Mexico is possessed by devilish creatures who came from inside the Earth.[12]
In theMiddle Ages, an ancient German myth held that some mountains located betweenEisenach andGotha hold a portal to the inner Earth. A Russian legend says theSamoyeds, an ancientSiberiantribe, traveled to a cavern city to live inside the Earth.[13] The Italian writerDante describes a hollow earth in his well-known 14th-century workInferno, in which the fall of Lucifer from heaven caused an enormous funnel to appear in previously solid and spherical earth, as well as an enormous mountain opposite it, "Purgatory".
InNative American mythology, it is said that the ancestors of theMandan people in ancient times emerged from a subterranean land through a cave on the north side of theMissouri River.[14] There is also a tale about a tunnel in theSan Carlos Apache Indian Reservation inArizona nearCedar Creek which is said to lead inside the Earth to a land inhabited by a mysterious tribe.[15] It is also the belief of thetribes of theIroquois that their ancient ancestors emerged from a subterranean world inside the Earth.[16] The elders of theHopi people believe that aSipapu entrance in theGrand Canyon exists which leads to theunderworld.[17][18]
Brazilian Indians, who live alongside theParima River in Brazil, claim that their forefathers emerged in ancient times from an underground land, and that many of their ancestors still remained inside the Earth. Ancestors of theInca supposedly came from caves which are located east ofCuzco, Peru.[19]
The notion was proposed byAthanasius Kircher's non-fictionMundus Subterraneus (1665), which speculated that there is an "intricate system of cavities and a channel of water connecting the poles".[20]: 137
Edmond Halley in 1692[21] started with Newton's (erroneous) estimate that the density of the Moon was almost double (9/5) the density of Earth.[22] Rather than assume a dense MoonHalley conjectured that the Earth might consist of a hollow shell about 800 km (500 mi) thick, two inner concentric shells and an innermost core. Atmospheres separate these shells, and each shell has its own magnetic poles. The spheres rotate at different speeds. Halley proposed this scheme in order to explain anomalous compass readings. He envisaged theatmosphere inside asluminous (and possibly inhabited) and speculated that escaping gas caused theAurora Borealis.[23]
Le Clerc Milfort in 1781 led a journey with hundreds ofMuscogee Peoples to a series ofcaverns near theRed River above its junction with theMississippi River. According to Milfort, the Muscogee Peoples believe their ancestors came out of the caverns under the surface of the Earth in ancient times. Milfort also claimed the caverns he saw "could easily contain 15,000 – 20,000 families".[24][25]
It is claimed that mathematicianLeonhard Euler proposed a single-shell hollow Earth with a small sun (1,000 kilometres across) at the center, providing light and warmth for an inner-Earth civilization, but that is not true. Instead, he did a thought experiment of an object dropped into a hole drilled through the center, unrelated to a hollow Earth.[26]
In 1818,John Cleves Symmes, Jr. suggested that the Earth consisted of a hollow shell about 1,300 km (810 mi) thick, with openings about 2,300 km (1,400 mi) across at bothpoles with 4 inner shells each open at the poles. Symmes became the most famous of the early Hollow Earth proponents, andHamilton, Ohio even has a monument to him and his ideas.[27] He proposed making an expedition to theNorth Pole hole,[28] thanks to efforts of one of his followers,James McBride.
J. N. Reynolds also delivered lectures on the "Hollow Earth" and argued for an expedition. Reynolds went on an expedition to Antarctica himself but missed joining theGreat U.S. Exploring Expedition of 1838–1842, even though that venture was a result of his agitation.
Though Symmes himself never wrote a book on the subject, several authors published works discussing his ideas. McBride wroteSymmes' Theory of Concentric Spheres in 1826. It appears that Reynolds has an article that appeared as a separate booklet in 1827:Remarks of Symmes' Theory Which Appeared in the American Quarterly Review. In 1868, professor W.F. Lyons publishedThe Hollow Globe which put forth a Symmes-like Hollow Earth hypothesis, but failed to mention Symmes himself. Symmes's son Americus then publishedThe Symmes' Theory of Concentric Spheres in 1878 to set the record straight.
Sir John Leslie proposed a hollow Earth in his 1829Elements of Natural Philosophy (pp. 449–53).
William Fairfield Warren, in his bookParadise Found – The Cradle of the Human Race at the North Pole (1885), presented his belief that humanity originated on a continent in the Arctic calledHyperborea. This influenced some early Hollow Earth proponents. According to Marshall Gardner, both theEskimo andMongolian peoples had come from the interior of the Earth through an entrance at theNorth Pole.[29]
NEQUA or The Problem of the Ages, first published in serialization in a Topeka, Kansas newspaper in 1900, is considered an earlyfeminist utopian novel. It mentions John Cleves Symmes' theory to explain its setting in a hollow Earth.
An early 20th-century proponent of hollow Earth,William Reed, wrotePhantom of the Poles in 1906. He supported the idea of a hollow Earth, but without interior shells or the inner sun.
Thespiritualist writerWalburga, Lady Paget in her bookColloquies with an unseen friend (1907) was an early writer to mention the hollow Earth hypothesis. She claimed that cities exist beneath a desert, which is where the people ofAtlantis moved. She said an entrance to the subterranean kingdom will be discovered in the 21st century.[30]
Marshall Gardner wroteA Journey to the Earth's Interior in 1913 and published an expanded edition in 1920. He placed an interior sun in the Earth and built a working model of the Hollow Earth which he patented (U.S. patent 1,096,102). Gardner made no mention of Reed, but did criticize Symmes for his ideas. Around the same time,Vladimir Obruchev wrote a novel titledPlutonia, in which the Hollow Earth possessed an inner Sun and was inhabited by prehistoric species. The interior was connected with the surface by an opening in theArctic.
The explorerFerdynand Ossendowski discussed a Hollow Earth in his 1922 book titledBeasts, Men and Gods. Ossendowski said he was told about a subterranean kingdom located inside the Earth.Buddhists knew it asAgharti.[31]
George Papashvily in hisAnything Can Happen (1940) claimed when he was in theCaucasus Mountains, he discovered a cavern containing human skeletons "with heads as big as bushel baskets" and an ancient tunnel leading to the center of the Earth. One man entered the tunnel and never returned.[32]
NovelistLobsang Rampa in his bookThe Cave of the Ancients said an underground chamber system exists beneath theHimalayas ofTibet, filled with ancient machinery, records and treasure.[33]Michael Grumley, acryptozoologist, has linkedBigfoot and otherhominidcryptids to ancient tunnel systems underground.[34]
According to theancient astronaut writerPeter Kolosimo a robot was seen entering a tunnel below amonastery in Mongolia. Kolosimo also claimed a light was seen from underground in Azerbaijan.[35] Kolosimo and other ancient astronaut writers such asRobert Charroux linked these activities toUFOs.
The 1964 bookThe Hollow Earth by "Dr.Raymond Bernard" presents the idea of UFOs coming from inside the Earth, states theRing Nebula proves the existence of hollow worlds, and speculates on the fate ofAtlantis and the origin of flying saucers.[36] An article byMartin Gardner revealed that Walter Siegmeister used the pseudonym "Bernard", but not until the 1989 publishing of Walter Kafton-Minkel'sSubterranean Worlds: 100,000 Years of Dragons, Dwarfs, the Dead, Lost Races & UFOs from Inside the Earth did the connection between Bernard and Siegmeister become known to the public.[37]
The science fictionpulp magazineAmazing Stories promoted one such idea from 1945 to 1949 as "The Shaver Mystery". The magazine's editor,Ray Palmer, ran a series of stories byRichard Sharpe Shaver, claiming that a superior prehistoric race had built ahoneycomb of caves in the Earth, and that their degenerate descendants, known as "Dero", live there still, using the fantastic machines abandoned by the ancient races to torment those of us living on the surface. As one characteristic of this torment, Shaver described "voices" that purportedly came from no explainable source. Thousands of readers wrote to affirm that they, too, had heard the fiendish voices from inside the Earth.Lost Continents and the Hollow Earth (1998) byDavid Hatcher Childress reprinted Palmer's stories and defended the Hollow Earth idea based on alleged tunnel systems beneath South America and Central Asia.[38]
Hollow Earth proponents have claimed a number of different locations for the entrances that lead inside the Earth. Other than the North and South poles, entrances in locations which have been cited include: Paris in France,[39]Staffordshire in England,[40]Montreal in Canada,[41]Hangzhou in China,[42] and theAmazon rainforest.[43]
InA Culture of Conspiracy, political scientistMichael Barkun draws a distinction between the termshollow earth andinner earth, to differentiate materials that conceive the majority of the interior of the planet to be hollow, from those that view it as solid buthoneycombed with interconnected spaces.[44][45][46]
Instead of saying that humans live on the exterior surface of a hollow planet, sometimes called a "convex" Hollow Earth hypothesis, it is hypothesized humans live on theinterior surface. This has been called the "concave" Hollow Earth hypothesis or skycentrism.
Cyrus Teed, a doctor from upstate New York, proposed such a concave Hollow Earth in 1869, calling his scheme "Cellular Cosmogony".[47] Teed founded a group called theKoreshan Unity based on this notion, which he calledKoreshanity. The main colony survives as a preserved Florida state historic site, atEstero, Florida, but all of Teed's followers have now died. Teed's followers claimed to have experimentally verified the concavity of the Earth's curvature, through surveys of the Florida coastline making use of "rectilineator" equipment.
Several 20th-century German writers, includingPeter Bender, Johannes Lang, Karl Neupert, and Fritz Braut, published works advocating the Hollow Earth hypothesis, orHohlweltlehre. It has even been reported, although apparently without historical documentation, thatAdolf Hitler was influenced by concave Hollow Earth ideas and sent an expedition in an unsuccessful attempt to spy on the British fleet by pointing infrared cameras up at the sky.[48][49]
TheEgyptian mathematicianMostafa Abdelkader wrote several scholarly papers working out a detailed mapping of the Concave Earth model.[50][51] In his bookOn the Wild Side (1992),Martin Gardner discusses the Hollow Earth model articulated by Abdelkader. According to Gardner, this hypothesis posits that light rays travel in circular paths, and slow as they approach the center of the spherical star-filled cavern. No energy can reach the center of the cavern. A drill, Gardner says, would lengthen as it traveled away from the cavern and eventually pass through the "point at infinity" corresponding to the center of the Earth. Gardner notes that "most mathematicians believe that an inside-out universe, with properly adjusted physical laws, is empirically irrefutable". Gardner rejects the concave Hollow Earth hypothesis on the basis ofOccam's razor.[52]
Purportedly verifiable hypotheses of a Concave Hollow Earth need to be distinguished from a thought experiment which defines acoordinate transformation such that the interior of the Earth becomes "exterior" and the exterior becomes "interior". (For example, in spherical coordinates, let radiusr go toR2/r whereR is the Earth's radius; seeinversive geometry.) The transformation entails corresponding changes to the forms of physical laws. This is not a hypothesis but an illustration of the fact that any description of the physical world can be equivalently expressed in more than one way.[53]
In 1735,Pierre Bouguer andCharles Marie de La Condamine chartered an expedition from France to theChimborazo volcano in Ecuador. Arriving and climbing the volcano in 1738, they conducted avertical deflection experiment at two different altitudes to determine how local mass anomalies affected gravitational pull. In a paper written a little over ten years later, Bouguer commented that his results had at least falsified the Hollow Earth Theory. In 1772,Nevil Maskelyne proposed to repeat the same experiment to the Royal Society. Within the same year, the Committee of Attraction was formed and they sentCharles Mason to find the perfect candidate for the vertical deflection experiment. Mason found the Schiehallion mountain, where the experiment took place[54] and not only supported the earlier Chimborazo Experiment but yielded far greater results.
In 1798,Henry Cavendish published a measurement of the density of the Earth based on atorsion balance. These results were later repurposed into a measurement of thegravitational constant.[55]: 33
Based upon the size of the Earth and the force of gravity on its surface, the average density of the planet Earth is 5.515 g/cm3, and typical densities of surface rocks are only half that (about 2.75 g/cm3). If any significant portion of the Earth were hollow, the average density would be much lower than that of surface rocks. The only way for Earth to have the force of gravity that it does is for much more dense material to make up a large part of the interior. Nickel-iron alloy under the conditions expected in a non-hollow Earth would have densities ranging from about 10 to 13 g/cm3, which brings the average density of Earth to its observed value.[56]: 186
The picture of thestructure of the Earth that has been arrived at through the study ofseismic waves[57] is quite different from a fully hollow Earth. The time it takes for seismic waves to travel through and around the Earth directly contradicts a fully hollow sphere. The evidence indicates the Earth is mostly filled with solid rock (mantle and crust), liquid nickel-iron alloy (outer core), and solid nickel-iron (inner core).[58]
Another set of scientific arguments against a Hollow Earth or any hollow planet comes fromgravity. Massive objects tend to clump together gravitationally, creating non-hollow spherical objects such as stars and planets. The solid spheroid is the best way to minimize thegravitational potential energy of a rotating physical object; having hollowness is unfavorable in the energetic sense. In addition, ordinary matter is not strong enough to support a hollow shape of planetary size against the force of gravity; a planet-sized hollow shell with the known, observed thickness of the Earth's crust would not be able to achievehydrostatic equilibrium with its own mass and would collapse.[citation needed]
Drilling holes does not provide direct evidence against the hypothesis. The deepest hole drilled to date is theKola Superdeep Borehole,[59] with a true vertical drill-depth of around 12 km (7.5 mi). However, the distance to the center of the Earth is nearly 6,400 km (4,000 mi).[60]
The idea of a hollow Earth is a common element of fiction, appearing as early asLudvig Holberg's 1741 novelNicolai Klimii iter subterraneum («Niels Klim's Underground Travels»), in which Nicolai Klim falls through a cave while spelunking and spends several years living on both a smaller globe within and the inside of the outer shell.
Other notable early examples includeGiacomo Casanova's 1788Icosaméron, a 5-volume, 1,800-page story of a brother and sister who fall into the Earth and discover the subterranean utopia of the Mégamicres, a race of multicolored, hermaphroditic dwarves;Symzonia: A Voyage of Discovery by a "Captain Adam Seaborn" (1820) which reflected the ideas of John Cleves Symmes, Jr.;Edgar Allan Poe's 1838 novelThe Narrative of Arthur Gordon Pym of Nantucket; Jules Verne's 1864 novelJourney to the Center of the Earth, which showed a subterranean world teeming with prehistoric life;George Sand's 1864 novelLaura, Voyage dans le Cristal where giantcrystals could be found in the interior of the Earth;Sir Edward Bulwer-Lytton's novelVril: The Power of the Coming Race, published anonymously in 1871;Etidorhpa, an 1895 science-fiction allegory with major subterranean themes; andThe Smoky God, a 1908 novel that included the idea that the North Pole was the entrance to the hollow planet.
InWilliam Henry Hudson's1887 romance,A Crystal Age,[61] the protagonist falls down a hill into aUtopian paradise; since he falls into this world, it is sometimes classified as a hollow Earth story; although the hero himself thinks he may havetraveled forward in time by millennia.
The idea was used byEdgar Rice Burroughs in the seven-novel "Pellucidar" series, beginning withAt the Earth's Core (1914). Using a mechanical drill, called the Iron Mole, his heroesDavid Innes and ProfessorAbner Perry discover a prehistoric world called Pellucidar, 500 miles below the surface, that is lit by a constant noonday inner sun. They find prehistoric people, dinosaurs, prehistoric mammals and theMahar, who evolved from pterosaurs. The series ran for six more books, ending withSavage Pellucidar (1963).[62] The 1915 novelPlutoniabyVladimir Obruchev uses the concept of the Hollow Earth to take the reader through various geological epochs.
In recent decades, the idea has become a staple of the science fiction and adventure genres across films (Children Who Chase Lost Voices,Ice Age: Dawn of the Dinosaurs,Aquaman and theMonsterVerse), television programs (Inside Job,Slugterra, and the third and fourth seasons ofSanctuary),role-playing games (e.g., theHollow World Campaign Set forDungeons & Dragons,Hollow Earth Expedition), and video games (Torin's Passage andGears of War). The idea is also partially used in theMarvel Comics universe, where there exists a subterranean realm beneath the Earth known asSubterranea. TheSuper Nintendo Entertainment System (SNES) video gameTerranigma features this concept in the opening and closing acts of the game.
The Hollow Earth is a key location inLegendary Pictures'sMonsterVerse franchise, being the point of origin of theTitans and thestrange animals ofSkull Island. Initially being teased inKong: Skull Island andGodzilla: King of the Monsters, a full expedition into the Hollow Earth is a primary focus ofGodzilla vs. Kong, its sequelGodzilla x Kong: The New Empire, and theMonarch: Legacy of MonstersTV series.
Owen Egerton's bookHollow: A Novel[63] uses the Hollow Earth concept and includes a trip to find an entrance to the hollow Earth lead by con artist but the title also works as a recurring metaphor in a story of grief and despair.[64][65]
In 1975, Japanese artistTadanori Yokoo used elements of theAgartha legend, along with otherEastern subterranean myths, to depict an advanced civilization in the cover art for jazz musicianMiles Davis's albumAgharta.[66] Tadanori said he was partly inspired by his reading ofRaymond W. Bernard's 1969 bookThe Hollow Earth.[67]
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