Hollow Earth

Notably suggested by Edmond Halley in the late 17th century, the notion was disproven, first tentatively by Pierre Bouguer in 1740, then definitively by Charles Hutton in his Schiehallion experiment around 1774.

It was still occasionally defended through the mid-19th century, notably by John Cleves Symmes Jr. and J. N. Reynolds, but by this time it was part of popular pseudoscience and no longer a scientifically viable hypothesis.

Hollow Earth also recurs in conspiracy theories such as the underground kingdom of Agartha and the Cryptoterrestrial hypothesis and is often said to be inhabited by mythological figures or political leaders.

The idea of subterranean realms seemed arguable, and became intertwined with the concept of "places" of origin or afterlife, such as the Greek underworld, the Nordic Svartálfaheimr, the Christian Hell, and the Jewish Sheol (with details describing inner Earth in Kabalistic literature, such as the Zohar and Hesed L'Avraham).

[6] There are also stories of medieval knights and saints who went on pilgrimages to a cave located in Station Island, County Donegal in Ireland, where they made journeys inside the Earth into a place of purgatory.

The Angami Naga tribes of India claim that their ancestors emerged in ancient times from a subterranean land inside the Earth.

[11] Mexican folklore also tells of a cave in a mountain five miles south of Ojinaga, and that Mexico is possessed by devilish creatures who came from inside the Earth.

[12] In the Middle Ages, an ancient German myth held that some mountains located between Eisenach and Gotha hold a portal to the inner Earth.

In Native American mythology, it is said that the ancestors of the Mandan people in ancient times emerged from a subterranean land through a cave on the north side of the Missouri River.

[14] There is also a tale about a tunnel in the San Carlos Apache Indian Reservation in Arizona near Cedar Creek which is said to lead inside the Earth to a land inhabited by a mysterious tribe.

[17][18] Brazilian Indians, who live alongside the Parima 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.

[19] The notion was proposed by Athanasius Kircher's non-fiction Mundus Subterraneus (1665), which speculated that there is an "intricate system of cavities and a channel of water connecting the poles".

[24][25] It is often claimed that mathematician Leonhard 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.

[30] NEQUA or The Problem of the Ages, first serialized in a newspaper printed in Topeka, Kansas in 1900 and considered an early feminist utopian novel, mentions John Cleves Symmes' theory to explain its setting in a hollow Earth.

Around the same time, Vladimir Obruchev wrote a novel titled Plutonia, in which the Hollow Earth possessed an inner Sun and was inhabited by prehistoric species.

[32] George Papashvily in his Anything Can Happen (1940) claimed the discovery in the Caucasus Mountains of a cavern containing human skeletons "with heads as big as bushel baskets" and an ancient tunnel leading to the center of the Earth.

Other than the North and South poles, entrances in locations which have been cited include: Paris in France,[40] Staffordshire in England,[41] Montreal in Canada,[42] Hangzhou in China,[43] and the Amazon rainforest.

Cyrus Teed, a doctor from upstate New York, proposed such a concave Hollow Earth in 1869, calling his scheme "Cellular Cosmogony".

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, including Peter Bender, Johannes Lang, Karl Neupert, and Fritz Braut, published works advocating the Hollow Earth hypothesis, or Hohlweltlehre.

It has even been reported, although apparently without historical documentation, that Adolf 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.

[49][50] The Egyptian mathematician Mostafa Abdelkader wrote several scholarly papers working out a detailed mapping of the Concave Earth model.

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.

[54] In 1735, Pierre Bouguer and Charles Marie de La Condamine chartered an expedition from France to the Chimborazo volcano in Ecuador.

Arriving and climbing the volcano in 1738, they conducted a vertical deflection experiment at two different altitudes to determine how local mass anomalies affected gravitational pull.

The solid spheroid is the best way to minimize the gravitational potential energy of a rotating physical object; having hollowness is unfavorable in the energetic sense.

Other notable early examples include Giacomo Casanova's 1788 Icosaméron, 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 novel The Narrative of Arthur Gordon Pym of Nantucket; Jules Verne's 1864 novel Journey to the Center of the Earth, which showed a subterranean world teeming with prehistoric life; George Sand's 1864 novel Laura, Voyage dans le Cristal where giant crystals could be found in the interior of the Earth; Sir Edward Bulwer-Lytton's novel Vril: The Power of the Coming Race, published anonymously in 1871; Etidorhpa, an 1895 science-fiction allegory with major subterranean themes; and The Smoky God, a 1908 novel that included the idea that the North Pole was the entrance to the hollow planet.

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 the MonsterVerse), television programs (Inside Job, Slugterra, and the third and fourth seasons of Sanctuary), role-playing games (e.g., the Hollow World Campaign Set for Dungeons & Dragons, Hollow Earth Expedition), and video games (Torin's Passage and Gears of War).

The Hollow Earth is a key location in Legendary Pictures's MonsterVerse franchise, being the point of origin of the Titans and the strange animals of Skull Island.

In 1975, Japanese artist Tadanori Yokoo used elements of the Agartha legend, along with other Eastern subterranean myths, to depict an advanced civilization in the cover art for jazz musician Miles Davis's album Agharta.