The phrase Hollow Earth expresses the esoteric idea that the planet Earth is hollow, almost invariably including the idea that it has a habitable inner surface. Although at one time this idea was popular with some and even commonplace in adventure literature, it is now ridiculed and has long been contradicted by substantial evidence and dismissed as pseudoscience by the scientific community.

Newton's Law of Gravity mathematically implies that the gravitational force is zero everywhere inside a spherically symmetric hollow shell of matter, regardless of the shell thickness (ignoring other masses such as the Moon). Thus, even if the Earth were hollow, someone on the inside would not be pulled outwards or be able to stand on the inner surface, as is popularly supposed; rather, they would be weightless (with some slight residual gravity arising from the fact that the Earth is not a perfectly symmetric sphere). 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.

In ancient times the idea of subterranean realms seemed arguable, and intertwined with the concept of places such as the Greek Hades, the Jewish Sheol, and the Christian Hell.

In 1818, John Cleves Symmes, Jr. suggested that the Earth comprised a hollow shell about 800 miles (1,300 km) thick, with openings about 1400 miles (2,300 km) across at both poles. He proposed calling the "inner lands" Symzonia.

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 suggesting advocates as the locations of entrances to these subterranean realms, with some advancing the theory that UFOs have their actual homeland in these places.

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 series of stories by Richard Sharpe Shaver, claiming they were factual, though presented as 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. One characteristic of this torment was "voices" that came from no explainable source. Thousands of readers wrote to affirm that they, too, had heard the fiendish voices from inside the earth.

Contents

1 Concave Hollow Earths 2 Hollow Earth in fiction 3 See also 4 External links

Concave Hollow Earths

Instead of saying that we live on the outside surface of a hollow planet, sometimes called a "convex" hollow-Earth theory, a few others have opined that our universe is itself on the interior of a hollow world, calling this a "concave" hollow-Earth theory. Neither type of speculation is generally taken seriously by scientists.

One such proponent in 1869 was Cyrus Teed, a self-described alchemist who founded a cult called the Koreshians based on the notion.

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 the man who 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 the forms of physical laws are changed by such transformations, however, it does not follow that the interior could be mistaken for the exterior in practice, and thus such arguments tend towards sophistry.

Hollow Earth in fiction

Edgar Allan Poe used the idea in his 1838 The Narrative of Arthur Gordon Pym.

Jules Verne, who normally did not stray far from the bounds of scientific plausibility in his works, used the idea of a hollow Earth in his 1864 novel, A Journey to the Center of the Earth.

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). Burroughs's Pellucidar is notable for the fact that, although the inner surface of the Earth is of absolutely smaller area than the outer, those areas which are oceans on the outer surface are continents on the inner and vice-versa, so that Pellucidar actually has a greater land area than the "outer" continents combined. It is also inhabited by primitive humans and by an exciting mix of all those large and dangerous creatures which have unfortunately become extinct on the outer surface, and to which Burroughs did not hesitate to add such improvements as the Mahars, creatures vaguely resembling large intelligent pterodactyls with dangerous psychic powers. Pellucidar is lit by a central miniature sun which never sets, so that the 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 is convinced that it resides inside a hollow earth. As a result, they cannot accept his interplanetary origin.

The fantasy series The Death Gate Cycle, by Margaret Weis and Tracy Hickman, also features a concave hollow earth, beginning in Elven Star, the second book in the series. This world, called Pryan the World of Fire, is a classic hollow earth, and the constant light from the 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.

See also

• Dyson sphere

External links

• At the Earth's Core http://www.literature.org/authors/burroughs-edgar-rice/at-the-earths-core/ , by Edgar Rice Burroughs
• 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