Hollow Earth. It is considered for now as a theory because the mainstream science is still trying to explore or discover whether the idea is real or not. Though some people believe in the existence of such place inside our planet.

In fact, some movies portrayed the existence of the Inner Earth civilizations mostly based on the novel of Jules Vernes in 1864 titled “A Journey to the Center of the Earth.”

The idea about the Hollow Earth appeared as early as 1741 in the fiction novel by Ludvig Holberg titled “Nicolai Klimii Iter Subterraneum (Niel 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 pre-20th century 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 dwarfs; 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; and George Sand’s 1884 novel Laura, Voyage dans le Cristal where unseen and giant crystals could be found in the interior of the Earth.

Earlier during Ancient times, the idea of subterranean realms seemed arguable, and became intertwined with the concept of “places” such as the Greek Hades, the Nordic svartalfheim, the Christian Hell, and the Jewish Sheol (with details describing inner Earth in Kabalistic literature, such as the Zohar and Hesed L’Avraham).

Edmond Halley in 1692 put forth the idea of Earth consisting of a hollow shell about 800 km (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 envisaged the atmosphere inside as luminous (and possibly inhabited) and speculated that escaping gas caused the Aurora Borealis.

De Camp and Ley have claimed (in their Lands Beyond) that Leonhard Euler also proposed a hollow-Earth idea, getting rid of multiple shells and postulating an interior sun 1000 km (600 miles) across to provide light to advanced inner-Earth civilization but they provide no references; indeed, it seems that if Euler did propose a hollow-Earth then it was as a thought experiment.

De Camp and Ley also claim that Sir John Leslie expanded on Euler’s idea, suggesting two central suns named Pluto and Proserpine (this was unrelated to the dwarf planet Pluto, which was discovered and named some time later). Leslie did propose a hollow Earth in his 1829 Elements of Natural Philosophy (pp. 449–453), but does not mention interior suns.

In 1818, John Cleves Symmes, Jr. suggested that the Earth consisted of a hollow shell about 1300 km (800 miles) thick, with openings about 2300 km (1400 miles) 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 proposed making an expedition to the North Pole hole, thanks to efforts of one of his followers, James McBride. United States president John Quincy Adams indicated he would approve of this but he left office before this could occur.

The new President of the United States, Andrew Jackson, halted the attempt. It is possible this is the source of the (untrue) legend that Jackson believed in a Flat Earth, and was consequently the only United States president to do so.

Jeremiah Reynolds also delivered lectures on the “Hollow Earth” and argued for an expedition. Reynolds went on an expedition to Antarctica himself but missed joining the Great U.S. Exploring Expedition of 1838–1842, even though that venture was a result of his agitation.

Though Symmes himself never wrote a book about his ideas, several authors published works discussing his ideas. 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 Symmes-like Hollow Earth hypothesis, but failed to mention Symmes himself. Symmes’s son Americus then published The Symmes’ Theory of Concentric Spheres in 1878 to set the record straight.

In the 20th Century, the Nazi era Thule Society reported much about Tibetan myths of openings into the Earth. There is even a theory that Hitler ordered a research journey for such an opening in Antarctica, based on a speech of Admiral Dönitz in front of a German submarine in 1944, when he claimed “The German submarine fleet is proud of having built an invisible fortification for the Führer, anywhere in the world.” During the Nuremberg Trials, Dönitz spoke of “an invisible fortification, in midst of the eternal ice.”

An early twentieth-century proponent of hollow Earth, William Reed, wrote Phantom of the Poles in 1906. He supported the idea of a hollow Earth, but without interior shells or inner sun.

Marshall Gardner (distinct from Martin Gardner, mentioned below) wrote A Journey to the Earth’s Interior in 1913 and an expanded edition in 1920. He placed an interior sun in the hollow Earth. He even built a working model of the hollow Earth and patented it (U.S. Patent 1,096,102).

Gardner made no mention of Reed, but did take Symmes to task for his ideas. In the same time Vladimir Obruchev wrote a fiction novel Plutonia, where the hollow Earth’s interior possessed one inner (central) sun and was inhabited by prehistoric species. The interior was connected with the surface by a hole in the Arctic.

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 a subterranean realm referred to as Agartha, with some even advancing the hypothesis that UFOs have their homeland in these places.

Now in the 21st Century, Year 2011, Horatio Valens and Paul Veneti presented a two-hour “Lazeria Map Collection” video on centuries-old maps of the Arctic region and the North Pole, making a case for a 100-mile wide canyon in the center of the physical North Pole, into which north-flowing rivers drain into a hollow Earth. The maps were collected by Harry Hubbard.

What do you think about the idea of Hollow Earth? It seems people are now very eager to know more about this. And people want to know the Truth about this.