The Hollow Earth theory was a scientific theory popular in the 18th and 19th centuries that proposed the earth was not a solid sphere but rather had a hollow interior with entrances at both of the poles. There was also said to be an ancient, undiscovered race of humans residing within the interior. Though it had been soundly disproved by scientists, the theory was nevertheless very influential among some scientists and literary figures during this time; Edgar Allan Poe's Narrative of Arthur Gordon Pym of Nantucket (1838) and Jules Verne's Journey to the Center of the Earth (1864) were influenced by this idea. It still figures in some contemporary science fiction.
The British astronomer Edmund Halley believed that the Earth consisted of four concentric spheres and that there was life within the interior of the planet. He believed the aurora borealis was produced by the escape of luminous gas from the thin crusts at the poles. He posited that the existence of earthquakes, springs, geysers, wells, volcanoes, caverns, and caves all suggested that there were subterranean expanses that may have indeed been far deeper than scientists accepted.
One of the most famous promoters of this theory was the American Army captain John Cleves Symmes. He espoused Halley's view of interior concentric spheres and took up vigorous lobbying of Congress for an expedition to the North Pole to find the entrance; nothing came of this. Nonetheless, his theory was widely accepted and he became a minor celebrity for his speeches and lectures on the subject. It is his name that is most widely associated with the theory. Some researchers believe he wrote the novel Symzonia; Voyage of Discovery, which was attributed to a "Captain Adam Seaborn". There is no proof that he did write the text, nor is there proof that he unequivocally did not. It may have been a satire of his ideas rather than an articulation of them. One of his most famous followers was the explorer Jeremiah Reynolds, a great influence on Poe's Narrative of Arthur Gordon Pym.
In the 19th century, Cyrus Reed Teed, an alchemist and herbalist, experienced a vision of a woman who told him the denizens of Earth are actually living inside of the hollow earth. Teed promoted this idea for decades, even founding a cult called the Koreshans. In 1905 William Reed published The Phantom of the Poles claiming that there were no poles at all; rather, the "poles" are entrances to the hollow Earth. Marshall B. Gardner claimed in 1913 that there were no concentric spheres but that there was a massive sun within the Earth. Other pseudo-scientists throughout the 20th century continued to promote this theory, explaining away the proof that it is false by claiming government conspiracy hushes up the truth.