What Is the Hollow Earth Theory?
At its simplest, the hollow earth theory holds that our planet is not solid all the way through. Instead it is a shell, sometimes with further shells nested inside, sometimes with a small sun glowing at the center, and often with openings at the North and South poles that lead to an interior world.
The idea has never been one fixed claim. It comes in several distinct flavors:
- The convex hollow Earth. We live on the outside of a shell. Inside lies open space, possibly lit and inhabited. This is the classic version from Halley and Symmes.
- The inner Earth. The planet is mostly solid but riddled with caverns and tunnels that hide lost races or ancient machinery. The political scientist Michael Barkun drew this distinction in his study of conspiracy culture, separating “hollow earth” material from “inner earth” material.
- The concave hollow Earth. We live on the inner surface of a sphere, and the sun, moon and stars are all inside with us. Its followers sometimes call it skycentrism.
Keeping these apart matters, because evidence that rules out one version is sometimes waved away by believers who quietly switch to another. A claim about tunnels under a mountain is not the same as a claim that the planet is an empty ball.
Underworlds Before Science: The Folklore Roots
Long before anyone measured the density of rock, people across the world told stories of places beneath the ground. The ancient Greeks spoke of caverns, at Tainaron in Lakonia and elsewhere, that led to the underworld. Norse tradition described Svartálfaheimr, a realm associated with the dark elves. Hebrew scripture names Sheol, Hindu tradition speaks of Patala, and medieval Christianity located Hell beneath the earth. Dante’s 14th-century Inferno imagined Lucifer’s fall from heaven punching a vast funnel into a once-solid globe.
Ireland has its own cluster of these tales. Cruachan was remembered as a gate to Hell from which strange creatures emerged, and pilgrims journeyed to a cave on Station Island in County Donegal believing it opened onto purgatory. That cave was sealed in October 1632.
Many Indigenous peoples hold emergence traditions, in which ancestors came up into this world from a land below. Hopi elders speak of a sipapu, an entrance to the underworld, associated with the Grand Canyon. Mandan, Iroquois, Taino, Inca, Angami Naga and Trobriand Islander traditions all include accounts of ancestors emerging from caves or a subterranean land. These are origin stories embedded in living cultures, carrying meaning about identity, place and belonging. They are not early versions of a geological model, and treating them as secret evidence for a hollow planet misreads what they mean to the people who tell them. You can explore more traditions like these in our folklore and legends section.
What the old stories share is an intuition the later theory would borrow: the ground beneath our feet might not be the bottom of the world.
Edmond Halley’s Hollow Earth Theory and the Compass Problem
The scientific hollow earth theory began with a practical headache. In the age of sail, navigators relied on magnetic compasses, and over the decades they noticed the needles did not point steadily north. The error varied from place to place and shifted over time, sending ships off course.
Edmond Halley, the astronomer remembered for his comet, gathered compass readings from many locations and years. He concluded that the magnetic poles were drifting in a slow, regular motion. Accounts date his first related papers to the Royal Society to the 1680s, with 1681 often cited. His full hollow Earth scheme appeared in 1692.
Halley also had a second reason to think the planet might be partly empty. Isaac Newton had estimated, wrongly as it turned out, that the Moon was nearly twice as dense as Earth. Rather than accept an unusually dense Moon, Halley suggested Earth might be less dense than it looked.
What Halley proposed
- An outer shell roughly 500 miles (800 km) thick.
- Two inner concentric shells and an innermost core, separated by atmospheres.
- Each layer carrying its own magnetic poles and rotating at a slightly different speed, which would explain the wandering compass.
- A luminous inner atmosphere, possibly home to life, with escaping glowing gas producing the aurora borealis.
It is worth giving Halley his due. He was working with real data and a real anomaly, and his model made a testable claim about the planet’s density. Modern geophysics explains the drifting magnetic field through motion in Earth’s liquid iron outer core, which is not so far from Halley’s picture of moving inner layers, minus the empty space.
One popular claim says the mathematician Leonhard Euler proposed a single hollow shell with a small sun at its center. That story is false. Euler worked through a thought experiment about an object dropped through a hole bored through the planet, which had nothing to do with a hollow world.
Symmes’ Holes and the Road to Antarctica
John Cleves Symmes Jr. turned the hollow earth theory from a scientific conjecture into a popular cause. In his version the Earth was a series of concentric shells, open at the poles. Accounts of the details vary: one description gives a shell around 810 miles (1,300 km) thick with polar openings some 1,400 miles (2,300 km) across, while others describe five nested layers lit by an inner sun. Symmes believed the auroras were reflections of that sun and that Arctic animals such as reindeer and bears migrated into the warm interior each winter.
After his 1818 declaration fell flat, Symmes spent about a decade on the lecture circuit. Congress voted twice on a petition for a federally funded polar expedition; the second time it gathered 25 votes in favor, not nearly enough. In 1820 a novel called Symzonia, credited to a “Captain Adam Seaborn,” described a voyage down one of the holes, and many scholars suspect Symmes wrote it himself. His follower James McBride published Symmes’s Theory of Concentric Spheres in 1826. Hamilton, Ohio, still has a monument to Symmes and his ideas.
The convert who changed course
The strangest twist belongs to Jeremiah N. Reynolds, a newspaper editor who quit his job to lecture alongside Symmes. Over time Reynolds dropped the inner suns and lost civilizations and began pushing instead for a genuine scientific voyage to the far south. President John Quincy Adams noted in his diary that Reynolds had abandoned the much-ridiculed theory, and by late 1828 plans for a South Pole expedition were taking shape. Then Adams lost the election to Andrew Jackson, and the plan collapsed.
Reynolds tried a privately funded voyage in 1829 that reached the Antarctic Peninsula region before turning back, followed by a mutiny in Chile that left him stranded for two years. In 1836 he addressed the House of Representatives again, and that year Congress approved funding. Adams, by then a congressman, voted for it. The resulting U.S. Exploring Expedition of 1838 to 1842 charted wide stretches of southern ocean. Reynolds was not aboard.
So a theory about polar holes helped set in motion a real voyage of discovery. The idea lingered for decades afterward: an 1882 magazine piece described a proposal by a Mr. Howgate to station men at ever-higher latitudes and follow migrating animals into “Symmes’ Hole.”
Agartha, Inner Suns and UFOs: The 20th-Century Revival
By the late 19th century, the hollow earth theory had left serious science behind and found a second life in fiction and fringe writing. William Bradshaw’s 1892 novel The Goddess of Atvatabar mapped an interior world, the utopian novel Nequa (1900) borrowed Symmes’ theory for its setting, and the Russian geologist Vladimir Obruchev wrote Plutonia, where prehistoric creatures survive under an inner sun.
Nonfiction proponents kept going too. William Reed’s Phantom of the Poles (1906) argued for a hollow planet without inner shells or a central sun. Marshall Gardner’s A Journey to the Earth’s Interior (1913, expanded 1920) restored the inner sun, and Gardner even patented a working model of his hollow globe.
Where Agartha comes from
The name most often attached to an inner-earth civilization is Agartha, or Agharti. A story attributed to Tibetan Buddhist tradition tells of an ancient city called Shamballa inside the Earth, though how closely that version matches the tradition itself is debated. The explorer Ferdynand Ossendowski brought Agharti to a wide Western audience in his 1922 book Beasts, Men and Gods, writing that he had been told of a subterranean kingdom known to Buddhists by that name. Later writers merged it into hollow Earth lore as a hidden capital of an advanced underground people.
Saucers from inside the planet
After World War II the theory fused with the flying saucer era. From 1945 to 1949, the pulp magazine Amazing Stories, under editor Ray Palmer, ran what it called “The Shaver Mystery”: stories by Richard Sharpe Shaver claiming a prehistoric race had carved a honeycomb of caves, and that their degenerate descendants, the “Dero,” used abandoned machines to torment surface dwellers, including by projecting voices. According to accounts of the period, thousands of readers wrote in saying they had heard such voices too.
In 1964 a book titled The Hollow Earth, by “Dr. Raymond Bernard,” argued that flying saucers came from inside the planet through polar openings. Its version described a shell about 800 miles thick with polar holes about 1,400 miles across, curving so gently that a traveler could sail over the lip without noticing. Pilots never saw the holes, Bernard said, because compasses fooled them into circling the rim. As proof he leaned on a quoted remark attributed to Admiral Richard Byrd about the “land beyond the Pole.” “Bernard” was later revealed to be a pen name of Walter Siegmeister.
Believers have since placed entrances at the poles, under Paris, in Staffordshire, Montreal, Hangzhou and the Amazon. A group of believers once told staff at a geophysics institute in Alaska that an opening in the Alaska Range served as a saucer port. The cryptozoologist Michael Grumley went further, linking Bigfoot and other hominid cryptids to ancient tunnel systems, a thread that ties into the wider record of Bigfoot sightings and hoaxes. For more on the saucer side of the story, see our UFOs and UAP coverage, where UAP means unidentified anomalous phenomena, the term officials now prefer.
Living on the Inside: Concave Earth and Inner Suns
One branch of the hollow earth theory turns the whole picture inside out. In 1869 Cyrus Teed, a doctor from upstate New York, proposed “Cellular Cosmogony”: humans live on the inner surface of a sphere, with the sun and the heavens at its center. Teed founded a religious community, the Koreshan Unity, around the idea. Its members claimed to have confirmed the upward curve of the Earth by surveying the Florida coast with a device they called a rectilineator. The main colony at Estero, Florida, is now preserved as a state historic site, though no followers remain.
German writers later promoted their own concave model, the Hohlweltlehre, and some members of the Nazi naval staff were reportedly influenced by it, sending an unsuccessful mission to spot the British fleet by aiming infrared cameras at the sky. The Egyptian mathematician Mostafa Abdelkader worked out a detailed mathematical mapping of the concave model. The science writer Martin Gardner observed that such an inside-out universe, with physical laws suitably adjusted, could be impossible to refute by experiment, and rejected it anyway on the grounds of Occam’s razor: it adds complexity without explaining anything better.
So how would a hollow world be lit?
Every version needed an answer, and they disagreed:
- Halley: a glowing inner atmosphere.
- Symmes and Marshall Gardner: a small central sun.
- Concave models: light bending along curved paths inside a star-filled cavern.
- Reed: no inner sun at all.
None of these mechanisms has observational support. The light question is a symptom of a deeper issue: the theory has to invent new physics at each step to keep the interior habitable.
What Disproved the Hollow Earth Theory?
The hollow earth theory was falsified in the 18th century, which is exactly what makes Halley’s version good science: it was testable, and it failed the test.
Weighing the planet
In the late 1730s, the French scientists Pierre Bouguer and Charles Marie de La Condamine measured how the Chimborazo volcano in Ecuador tugged on a plumb line. Bouguer later remarked that the results at least ruled out a hollow Earth. In 1774 the Astronomer Royal Nevil Maskelyne repeated the idea at Schiehallion in Scotland, a mountain scouted by Charles Mason for its symmetrical shape, with much stronger results. Charles Hutton’s calculations from that survey showed Earth’s average density far exceeded the mountain’s. In 1798 Henry Cavendish measured Earth’s density directly with a torsion balance.
The numbers are decisive. Earth’s average density is about 5.5 grams per cubic centimeter, while typical surface rock is about 2.75. If much of the interior were empty, the average would fall below that of the crust, not rise to double it. The only way to match the measured gravity is a heavy interior, consistent with nickel-iron at roughly 10 to 13 grams per cubic centimeter under deep pressure.
Listening to earthquakes
Seismic waves from earthquakes travel through and around the planet, and their timing reveals what they pass through. The pattern points to a solid crust and mantle, a liquid nickel-iron outer core and a solid inner core. A hollow sphere would produce entirely different travel times.
Gravity and collapse
Massive bodies pull themselves into solid spheres because that arrangement minimizes gravitational energy. A shell of ordinary rock the size of a planet could not hold its own weight and would collapse. And under Newton’s shell theorem, a uniform hollow shell exerts no net pull on anything inside, so the shell itself would not hold inner inhabitants against its surface.
| Claim | Status |
|---|---|
| Halley proposed nested shells in 1692 to explain compass drift | Documented history |
| Symmes petitioned Congress for a polar expedition | Documented history |
| Reynolds’ lobbying fed into the U.S. Exploring Expedition | Documented history |
| Earth is hollow with openings at the poles | Contradicted by density, seismic and satellite evidence |
| An inner civilization called Agartha exists | Claim; no physical evidence |
| UFOs fly out of polar or mountain openings | Claim; no physical evidence |
| Byrd’s remarks reveal a land beyond the Pole | Interpretation of a quoted remark, not evidence of an opening |
Why the Hollow Earth Theory Endures
If the science was settled by 1800, why does the hollow earth theory still circulate? Part of the answer is that it scratches several itches at once. It promises unexplored territory on a fully mapped planet. It offers a home for lost races, Atlantis survivors and flying saucers. And it carries the thrill of secret knowledge: if the holes are real, someone must be hiding them, which is how it slides into the broader world of conspiracy theories alongside stories like the Philadelphia Experiment.
It also thrives in fiction, where subterranean adventure became its own genre. A story does not need to be true to be a good stage, and a hollow world makes a superb one.
Common mistakes when weighing the claims
- Mixing up versions. Real caves and tunnels exist, but they do not make the planet hollow. Inner earth and hollow Earth are different claims.
- Treating emergence myths as evidence. Indigenous origin traditions have their own meanings and should not be drafted into a geology argument.
- Leaning on quotes out of context. A vague remark about the “unknown” beyond a pole is not a description of a hole.
- Repeating attributions without checking. The Euler inner-sun story is the clearest example of a myth that spread because it sounded plausible.
- Ignoring that Halley’s idea was tested. Its failure is a success story for science, not a cover-up.
What remains genuinely open is not whether the planet is hollow, but why the dream of a world beneath our feet has held on for so many centuries and so many cultures. That question belongs to history, psychology and storytelling as much as geology. For long-form conversations about the unexplained, the Troubled Minds Vault collects the radio show’s archive, and the full journal has more strange corners of the map to wander.
Questions and answers
Who first proposed the hollow earth theory?
Underground realms appear in myths worldwide, but the first serious scientific version came from astronomer Edmond Halley. After years of studying compass variation, he published a model in 1692 in which Earth was an outer shell about 500 miles thick surrounding two inner shells and a core, each with its own magnetic poles. Some accounts date his first related papers to the Royal Society to 1681. The idea was then a legitimate attempt to explain real data.
Who invented the Agartha theory?
No single person can be credited. Stories of a hidden kingdom beneath the Earth were attached to Asian traditions, including a tale of an underground city called Shamballa attributed to Tibetan Buddhism. The explorer Ferdynand Ossendowski brought the name Agharti to a wide Western audience in his 1922 book Beasts, Men and Gods, saying he had been told of the subterranean realm during his travels. Later hollow earth writers folded it into their theories.
How does a hollow Earth get light?
Each version answers differently. Halley imagined the inner atmosphere itself was luminous and suggested escaping gas caused the northern lights. Symmes and later writers such as Marshall Gardner placed a small inner sun at the center. Believers in a concave Earth, where we live on the inside, argued that light travels in curved paths. None of these mechanisms has any observational support, and the planet's measured density rules out the space they require.
Is there any proof of a hollow Earth?
No. Gravity experiments beginning in the 1730s showed Earth is far denser than its surface rocks, which would be impossible if large parts were empty. Its average density is about 5.5 grams per cubic centimeter, roughly double that of typical crustal rock. Seismic waves from earthquakes travel through the planet in ways that reveal a solid mantle, a liquid outer core and a solid inner core. Satellite imagery shows no polar openings.
What would happen if the hollow Earth were real?
Physics makes the scenario strange. Under Newton's shell theorem, a uniform hollow sphere exerts no net gravitational pull on anything inside it, so inner-world inhabitants would not be pressed against the inner surface by the shell itself. A planet-sized shell of ordinary rock also could not support its own weight and would collapse. The theory's lush interior lands are therefore a literary image rather than a workable world.
Stay curious. Keep the question open.
Follow the evidence wherever it leads.
