Words: Katie Cutforth
This article was first published in the Jan/Feb 2024 issue of IQ, the exclusive magazine for Mensa members, as part of our Abandoned Science series. Find out more about becoming a Mensa member here.
The question of what lies beneath our feet has been the subject of much speculation over the course of human history. Virtually every culture and religion worldwide has, at some point, entertained the idea of a subterranean world, often home to mysterious and powerful creatures.
The Greeks and Romans called it Hades. In Hindu mythology, the underworld is referred to as Patala. Early Christians were sure that Hell was a fiery pit deep in the centre of the Earth, with a similar idea found in Judaism’s Sheol. The idea appears in Buddhism, too, in the ancient city of Shamballa, which is supposedly located deep inside the Earth.
It’s safe to say that, when bright minds began to empirically investigate the mysterious interior of our Earth, they weren’t short of inspiration. One curious idea was surprisingly pervasive over the centuries and still pops up in conspiracy theories and folklore today: Hollow Earth Theory.
Put simply, Hollow Earth Theory proposes that planet Earth is a hollow shell. The usual estimate is that its walls are around 800 miles thick, with holes in the polar regions that stretch 1,400 miles across and curve smoothly inwards.
Belief in a hollow Earth dates back to at least the 17th century. The English astronomer and mathematician Edmond Halley suggested in 1692 that the planet was made up of two inner concentric shells and an innermost core, with atmospheres separating these shells. Halley envisaged the atmosphere inside as luminous (and possibly inhabited) and used the theory to explain earthly phenomena, like the Aurora Borealis.
Halley’s theory was disproven in the following century – first, tentatively, by Pierre Bouguer in 1740 and then definitively by Nevil Maskelyne and Charles Hutton around 1774 with the Schiehallion experiment. This study attempted to determine the mean density of the Earth, from which it was believed its mass and answers about its mysterious interior could be extrapolated.
By measuring the gravitational attraction of Schiehallion, a mountain in the Scottish Highlands, the researchers determined that the Earth is nearly twice as dense as the mountain on its surface – essentially debunking the Hollow Earth Theory. Remarkably, their findings about the Earth’s density were accurate within 20% of modern-day calculations.
Nonetheless, belief in a hollow Earth lived on into the 19th and 20th centuries – although by that time it was generally held to be pseudoscience. American army officer and lecturer Captain John Symmes claimed in 1818 that the Earth was formed by a series of concentric shells. Symmes believed that there was a wondrous and hidden world beneath our feet, lush with vegetation and animals, and devoted much of his later life to promoting this claim.
It’s not just scientific minds who have been drawn in by the notion of a hollow Earth. The idea has inspired many great fantasy and science-fiction writers including Edgar Allan Poe, Edgar Rice Burroughs and, perhaps most famously, Jules Verne, whose 1864 novel Journey to the Center of the Earth describes an expedition into the Earth’s interior via an Icelandic volcano.
Narratives of a hollow Earth and a subterranean world also appear in legends, such as the underground kingdom of Agartha, which to this day inspires artists, occultists and conspiracy theorists alike.
