In the seventeenth and eighteenth centuries the idea of a hollow Earth was explored by European scientists. In 1692 Edmond Halley famously proposed a series of smaller concentric earths nesting inside our outer crust like matryoshka dolls. In the nineteenth century the openings to the Earth’s interior were generally thought to be at the north and south poles, and indeed this idea helped the push for exploration expeditions. Alas, the scientific consensus is now clear that Earth is not hollow after all, but let’s ignore that for now and look at some of the ways a hollow Earth could work.
Then there’s the possibility that inside our Earth is nested another sphere, and creatures live on the surface of that. In this scenario their “sky” is the interior of our crust. If the interior sphere is small enough there could be room for a small “sun” orbiting around it in the space between it and our outer crust. Halley’s version is a further twist on this with four layers of Earth altogether: our surface, two more hollow shells, and a solid sphere at the center. This makes Earth the high-rise apartment building of planets, with a much vaster population possible. Halley suggested that the spaces between these layers were luminous and it was this luminous gas escaping at the poles that caused the auroras.
In 1741 L. Holberg imagined a planetoid orbiting the luminous core of Earth just like Earth around the sun, and it was on this planetoid’s surface that life could be found. For more about his version, including his underground sentient tree people, see my previous post here. Holberg’s version requires Earth to be almost entirely empty on the inside. Other versions, like J. Verne’s, make Earth perhaps more like a giant Swiss cheese than an actual hollow: Earth’s interior life inhabits caves much vaster and deeper than generally known, but nevertheless mere caves in a solid matrix. Or what if the interior of Earth were filled with liquid and the life in there was aquatic? Or can you think of others ways the geometry could work?
Atlantians. In 1964 W. Siegmeister (under the pseudonym Bernard) added that the hollow Earth Atlantians sometimes emerge in flying saucers and other such UFOS. In 1975 M. Grumley said it was inhabited by Bigfoots and their cryptoid ilk.
There are so many different concepts of how the hollow Earth might work that, as you can imagine, there is no single name for the interior realm. Hades is the Greek underworld, Patala the Indian underworld. According to F. Ossendowski in 1922, the Buddhists called the interior world Agharti (or Agartha, Agartta, etc. But I don’t know of any evidence that the Buddhists did any such thing!) In 1952 De Camp and Ley suggested two interior suns called Pluto and Proserpine. (They attributed this idea to John Leslie in 1829, but that seems to be false, too.) An anonymous 1820 author wrote of Symzonia, in 1879 E. Bulwer-Lytton wrote of the Vril-ya, in 1892 W. Bradshaw wrote of Atvatabar, and in 1914 E.R. Burroughs wrote of Pellucidar. There are many others, of course, as this is one of those speculative themes whose appeal is particularly broad and enduring.
[Pictures: The Inferno, wood block print from Sito, et Forma Dell’ Inferno by Dante Alighieri, 1915 Gregoriis edition (Image from JF Ptak Science Books);
Geographical Apparatus, patent application by M.B. Gardner, 1914 (Image from google patent files);
Map of the Interior World, from The Goddess of Atvatabar by William Richard Bradshaw, 1892 (Image from Wikimedia Commons).]