Hollow Earth is a theory in which it is believed that the earth is hollow inside and that there are inhabitants in it. This was however dismissed as pseudoscience yet it has remained in the realms of fantasy and fiction.

Proponents of this theory even believe that Adolf Hitler and his followers thought of escaping to the hollow lands through the holes in the Antarctic. Several writers wrote that mega structures existed in the inner surface.

But the only depth that humans have reached is that of the Kola Superdeep Borehole's, which extends up to 7.6 miles or 12.3 kilometers. That is the knowledge regarding the depth of the earth's inner surface.

History

In 1692, Edmund Halley proposed that the earth is made up of three concentric spheres, each rotating in different speeds and that each have their own magnetic poles. That made him claim the existence of anomalies in compass readings.

In their book Lands Beyond, De Camp and Ley said that Leonhard Euler claimed a hollow earth idea as well. But instead of concentric spheres, it has a 600 mile-wide sun in its inner core, which gives lights to its inner inhabitants.

In the 19th century, John Cleve Symmes, Jr. proposed an expedition to the hole of North Pole with the help of James McBride, but the attempt was halted by Andrew Jackson. In 1826, McBride released a book entitled, Symmes' Theory of Concentric Spheres.

Jeremiah Reynolds lectured about the Hollow Earth but was not included in the Great US Exploring Expedition of 1838-1842 and proposed that an expedition be made.

In his book, A Journey To the Earth's Interior which was later expanded in 1920, Marshall Gardner included a sun in the Earth's interior and included Symmes in his idea. He even made and patented a model of his own Hollow Earth.

There was also other literature written about it. One of them is the story of Richard Sharpe Shaver in Amazing Stories' which began in 1945-1949. It was said that a race called Dero lived there and used to torture those who are living in the surface.

A so-called Dr, Bernard wrote The Hollow Earth in 1969 and claimed that UFOs come in the inner surface of the Earth. Dr. Walter Siegmeister was claimed by Martin Gardner to have used Bernard as a pen name and was made well known by Walter Kafton-Minkel in his 1989 book Subterranean Worlds: 100,000 years of dragons, dwarfs, the dead, lost races and UFOs from inside the Earth.

The Concave Hollow Earth

There also existed notions of a concave hollow Earth theory in which it was described that the Earth's surface was similar to the Dyson sphere in terms of structure. Moreover, it was said that the universe is found within our world, but scientists never took this seriously. The same is for Martin Gardner who rejected the whole idea of the concave hollow earth theory using Occam's razor.

One of the believers is the founder of Koreshan Unity, Cyrus Teed, called his belief of a concave hollow Earth Cellular Cosmogeny. He based his ideas on this theory and termed it Koreshanity.

Meanwhile, Mostafa Abdelkader, an Egyptian mathematician, wrote scholarly papers on the concave hollow earth theory just as he had written in A Geocomsos: Mapping Outer Space Into A Hollow Earth. German writers Peter Bender, Johanns Lang, Karl Neupert and Frtiz Braun advocated hollow earth theories or Hohlweltlehre in their works. This influenced Hitler to send out an expedition but failed.

Relation of Newton's Law of Gravity to the Hollow Earth Theory

Regarding his Law of Gravity, on the other hand, Isaac Newton proposed that anyone standing inside the hole of a hollow earth will feel weightless, because of the centrifugal force which will throw the person away from the Earth. The planet's mass does not make the hollow earth theory feasible, because a supposedly hollow inside would lower its gravitational pull.