From Academic Kids
The phrase hollow Earth refers to the esoteric idea that the planet Earth has a hollow interior, almost invariably including the idea that it has a habitable inner surface. Although at one time adventure literature made this idea popular and even commonplace, the notion now receives little support; substantial geodetic evidence has long controverted it and the scientific community dismisses it as pseudoscience.
Newton's law of gravity mathematically implies a gravitational force of zero everywhere inside a spherically symmetric hollow shell of matter, regardless of the shell thickness (ignoring other masses such as the Moon). Thus, contrary to popular belief, persons on the inside of a putative hollow earth would not experience an outward pull and could not stand on the inner surface; rather, they would experience weightlessness (with some slight residual gravity arising from the fact that the Earth does not have a perfectly symmetrical spherical shape). The centrifugal force from the Earth's rotation would pull a person outwards, but even at the equator this force is only 0.3% of ordinary Earth gravity.
Hollow Earth claims
Conventional Hollow Earths
Edmund Halley in 1692 (Philosophical Transactions of Royal Society of London) put forth the idea of Earth consisting of a hollow shell about 500 miles thick, two inner concentric shells and an innermost core, about the diameters of the planets Venus, Mars, and Mercury. 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 suggested that the atmosphere inside was luminous (and possibly inhabited) and that escaping gas caused the Aurora Borealis.
Some have claimed Leonard Euler also proposed a hollow earth idea, getting rid of mulitiple shells and postulating an interior sun to provide light to advanced inner-earth civilization. One site sees this as a misreading of a paper that simply involved a thought experiment.
In 1818, John Cleves Symmes, Jr. suggested that the Earth consisted of a hollow shell about 800 miles (1,300 km) thick, with openings about 1400 miles (2,300 km) across at both poles with 4 inner shells each open at the poles. Symmes became the most famous of the early Hollow Earth proponents. He actually proposed making an expedition to the North Pole hole, thanks to efforts of one of his followers, James McBride, but the new President of the United States, Andrew Jackson (in office 1829 - 1837), halted the attempt. Symmes died in 1829.
However, another follower, Jeremiah Reynolds, also delivered lectures on the "Hollow Earth" and also argued for an expedition. Eventually he would drop talk about a hollow Earth after the death of Symmes. Reynolds apparently went on an attempted expedition himself, but the outcome remains unclear. (Information on Reynolds remains sketchy and contradictory: we even lack an image of him. Some say he only had pecuniary interests, that his claimed 'expedition' consisted of an attempt to defraud and that he disappeared following it. Others say he did try to conduct his own expedition and failed, then missed out on joining the Great U.S. Exploring Expedition of 1838 - 1842, and later faded into obscurity).
Reynolds' agitation did result in an expedition: the Great U.S. Exploring Expedition of 1838 - 1842. This expedition also became known as the Wilkes Expedition. Reynolds did not participate because he had offended too many in his call for such a trip.
Symmes himself never wrote a book of his ideas but others did. McBride wrote Symmes' 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, a professor W.F. Lyons published The Hollow Globe which put forth a Symmmes-like Hollow Earth theory, but didn't mention Symmes. Symmes's son Americus then published The Symmes' Theory of Concentric Spheres to set the record straight.
The next proponent for the Hollow Earth, William Reed, wrote Phantom of the Poles in 1906. He propounded the idea of a hollow Earth, but without interior shells or inner suns.
Later came Marshall Gardner (distinct from science writer Martin Gardner) who wrote A Journey to the Earth's Interior in 1913 and then an expanded edition in 1920. He placed a interior sun in the hollow earth. He even built a working model of the hollow earth and patented it (#1096102). Gardner made no mention of Reed, but did take Symmes to task for his ideas.
Other writers have proposed that "ascended masters" of esoteric wisdom inhabit subterranean caverns or a hollow Earth. Antarctica, the North Pole, Tibet, Peru, and Mount Shasta in California, USA, have all had their advocates as the locations of entrances to these subterranean realms, with some advancing the theory that UFOs have their homeland in these places.
A book allegedly by a Dr Raymond Bernard which appeared in 1969, The Hollow Earth, exemplifies this idea. The book rehashes Reed and Gardner's ideas and totally ignores Symmes. Bernard also adds his own ideas: UFOs come from the interior, the Ring Nebula proves the existence of hollow worlds, etc. An article by Martin Gardner revealed that Walter Siegmeister used the pseudonym `Bernard', but only with Walter Kafton-Minkel's Subterranean Worlds: 100,000 years of dragons, dwarfs, the dead, lost races & UFOs from inside the earth in 1989 did the full story of Bernard/Siegmeister emerge.
The pages of the science fiction pulp magazine Amazing Stories promoted one such idea from 1945 to 1949 as "the Shaver Mystery". The magazine's editor, Ray Palmer, ran a series of stories by Richard Sharpe Shaver supposedly claimed as factual, though presented in the context of fiction. Shaver claimed that a superior pre-historic race had built a honeycomb 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.
Fantastic stories (supposedly believed as factual within fringe circles) have also circulated that Hitler and some of his followers escaped to hollow lands within the Earth after World War II via an entrance in Antarctica. (See also Hitler's supposed adherence to concave hollow-Earth ideas, below.)
In 2001 the Australian father-and-son team Kevin and Matthew Taylor (http://www.hyperogga.com/infoAboutMe.asp) self-published the book The Land of No Horizon (direct link (http://catalogue.nla.gov.au/cgi-bin/Pwebrecon.cgi?DB=local&Search_Arg=ISBN+%220646410571%22&SL=None&Search_Code=CMD&CNT=10) National Library of Australia ISBN 0646410571). Among other things it proposes (through reasoning) an expanding and hollow Earth (as well as other planetary bodies) which eventually reached equilibrium. The book also looks at a range of topics including but not limited to evolution, human physiology, impact craters and other geology in light of such a hollow earth.
Kevin & Matthew Taylor's view of a hollow planet envisages a hollow globe with a small (depending on planet size) central sun ignited by radiation from the inner surface. They use this view both to explain Earth's magnetic field (replacing the dynamo theory) and the origin and ignition of stars.
Concave hollow Earths
Instead of saying that we live on the outside surface of a hollow planet, sometimes called a "convex" hollow-Earth theory, some theorists have opined that our universe itself lies in the interior of a hollow world, calling this a "concave" hollow-Earth theory. This would resemble a Dyson sphere. Generally, scientists take neither type of speculation seriously.
Cyrus Teed, a self-described alchemist, proposed such a concave hollow earth in 1869, which he called "Cellular Cosmogony". Teed founded a cult called the Koreshan Unity based on this notion, called Koreshanity. Their main colony survives as a preserved Florida state historic site, but all of Teed's followers have now died.
Rumors suggest that Hitler, influenced by Teed's hollow-Earth ideas, actually sent an expedition in an unsuccessful attempt to spy on the British fleet by aiming cameras up into the sky. But the accuracy of such rumors remains questionable.
At least one proponent of a concave hollow Earth theory actually proposed new laws of physics to deal with the gravitation problem. Martin Gardner discusses the new model in one chapter of his book On the Wild Side. According to Gardner, this theory states 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, which corresponds to no point a finite distance away from Earth in the widely accepted scientific cosmology. 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 in the widely accepted scientific cosmology. Supposedly no experiment can distinguish between the two cosmologies. Martin Gardner does not accept the concave hollow Earth theory, and suggests that whoever proposed it may have had religious motives.
In a trivial sense, of course, one can always define a coordinate transformation such that the interior of the Earth becomes "exterior" and the exterior becomes "interior". (For example, in spherical coordinates, let radius r go to R²/r where R is the Earth's radius.) Since such transformations change the forms of physical laws, however, it does not follow that an observer could mistake the interior for the exterior in practice, and thus such arguments tend towards sophistry.
Hollow Earths in fiction
An early science-fiction work called Symzonia: A Voyage of Discovery by a "Captain Adam Seaborn" was published in 1823. It obviously reflected the ideas of John Cleves Symmes, Jr., and some have claimed Symmes as the real author. One recent reprint of the work gives Symmes as the author. Others disagree. Some researchers say it deliberately satirized Symmes ideas, and think they have identified the author as an early American author named Nathanial Ames who wrote other works, including one that might have served as the inspiration of Moby Dick (see Lang, Hans-Joachim and Benjamin Lease. "The Authorship of Symzonia: The Case for Nathanial Ames" New England Quarterly, June 1975, page 241-252.)
Willis Emerson wrote another science fiction novel worthy of mention: The Smoky God 1908. The novel claims to recount the true adventures of one Olaf Jansen who traveled into the interior, found an advanced civilization, and then left it. Some people regard The Smoky God as non-fiction.
Edgar Rice Burroughs, more concerned with entertainment than plausibility, also wrote tales of adventure in the inner world of Pellucidar (including, at one point, a visit from his character Tarzan). Note that, although the inner surface of the Earth has an absolutely smaller area than the outer, Burroughs's Pellucidar has oceans on the outer surface corresponding to continents on the inner surface and vice-versa, so that Pellucidar actually has a greater land area than the "outer" continents combined. Primitive humans and an exciting mix of all those large and dangerous creatures which have unfortunately become extinct on the outer surface inhabit Pellucidar, and Burroughs did not hesitate to add such improvements as the Mahars, creatures vaguely resembling large intelligent pterodactyls with dangerous psychic powers. For light Pellucidar has a central miniature sun which never sets, so that its human inhabitants have never developed the notion of time.
In the science-fiction novel The Inhabited Isle, written by the Russian authors Boris and Arkady Strugatsky, an Earthling space traveller lands on a planet where, due to extremely high atmospheric refraction, the native population believes that it resides inside a hollow earth. As a result, they cannot accept the Earthling's interplanetary origin.
The fantasy series The Death Gate Cycle, by Margaret Weis and Tracy Hickman, also features a concave hollow world, beginning in Elven Star, the second book in the series. This world, called 'Pryan the World of Fire', presents a classic hollow world, in which the constant light from its central sun has caused the plant life to grow to such size that all of the people on Pryan live atop the highest trees on a nearly rock-solid network of branches and leaves.
Rudy Rucker's novel The Hollow Earth appeared in 1990, and features Poe and his ideas.
The novel Indiana Jones and the Hollow Earth by Max McCoy (1997) expands on the legend of Hitler's supposed escape to the Earth's interior.
- At the Earth's Core (http://www.literature.org/authors/burroughs-edgar-rice/at-the-earths-core/), by Edgar Rice Burroughs
- The Cellular Cosmogony (http://www.sacred-texts.com/earth/cc/index.htm), by Koresh: full text of Cyrus Teed's book about the inside-out earth at sacred-texts.com
- The Phantom of the Poles (http://www.sacred-texts.com/earth/potp/index.htm), by William Reed: full text at sacred-texts.com.
- Crank.net - Hollow Earth (http://www.crank.net/hollow.html): people who believe
- Hollow Earths (http://www.crystalinks.com/hollowearth.html): a historical list of hollow-Earth proposals
- Hollow Earths (http://unmuseum.mus.pa.us/hollow.htm): page illustrating several hollow-earth proposals with diagrams
- Stephen Wagner, Nazis and the Hollow Earth (http://paranormal.about.com/library/weekly/aa011199.htm), Paranormal.About.com (Jan. 11, 1999): (thinly sourced) discussion of rumors about the Nazis and hollow Earth ideas.
- Koreshan State Historic Site (http://www.floridastateparks.org/koreshan/default.asp), official web page.
- Unofficial Koreshan State Historic Site (http://koreshan.mwweb.org/), unofficial web page.
- American Communal Utopias and The Koreshan Unity: A Bibliography (http://faculty.mansfield.edu/skaspere/Restricted/koreshan.html) Brief overview and great bibliography of works, if slightly dated.
- Turning the Universe Inside-Out: Ulysses Grant Morrow's Naples Experiment (http://www.lhup.edu/~dsimanek/hollow/morrow.htm) Examination of the Naples Experiment, and why it failed, but also covers the major hollow earth theories and Koreshan beliefs.
- The Smoky God (http://www.gutenberg.org/etext/3007), by Willis George Emerson. Complete novel
- Voyage to our Hollow Earth (http://www.voyagehollowearth.com/), Journey to the North Pole & Beyond - 24 day Trip, June 26, 2006 - July 19, 2006. Expedition aboard the IceBreaker YAMALde:Theorie der hohlen Erde