One of my favorite writers of all time is Jules Verne, as a kid I devoured his stories. The story I have the most fond memories of is the 1959 film “Journey to the center of the Earth”. It is a fictional story about a wondrous world in the center of our planet. History is filled with stories of underground worlds, think about Hades, Hell or the Norse Svartalfheim. Let me take you on a journey about the history of Hollow Earth.
Edmund Halley, the same guy that calculated the orbit of Halley’s Comet, came up with the hypothesis that the earth existed of an 800 kilometer (497 mile) thick peel, two internal peels and a core the size of the planets Venus, Mars and Mercury. These peels had their own atmosphere and magnetic poles. Halley used this hypothesis as explanation for strange compass readings.
De Camp and Ley stated in their Lands Beyond that Leonhard Euler also came up with a hollow earth theory. According to his theory the core was comprised of peels but it would be one peel and have its own little star. In the letters he send to princess of Anhalt-Dessau he speaks of a massive earth.
In 1818 John Cleves Symmes, Jr. also came with the suggestion that the earth existed of a hollow peel of 1300 kilometer (807 mile). He planned an expedition to the north pole where according to him a hole was found that gave access to these areas.
One of the proofs against the theory is gravity. If Earth was indeed hollow it would have had a lot less mass, and gravity on the surface would be much less than it is now. Also according to the laws of gravity, normal matter wouldn't be able to support these kind of cavities.
Other proof is delivered through seismologic research. The earth's core can be measured through vibrations delivered from earthquakes. With this research, geologist have gotten a pretty good understanding of the Earth’s crust, mantle, and core. A hollow Earth would have acted completely different seismologically than what they have observed thus far.
Visual perception of the Earth’s core currently limits itself to 12,3 kilometer (7,6 miles) depth. That is the depth of the SG-3 drillhole, the deepest scientist have ever gotten.
Admiral Richard E Byrd of the U.S.Navy was an early pioneer who set a record breaking flight over the North Pole and kept a diary. Written in this diary, there is a story of a warm climate with Mammoth-like creatures and an ancient human race that's been residing inside earth. His plane was forced to land by an ancient race who intercepted him with a saucer-shaped aircraft. He was greeted by the emissaries of the mythical land of Agartha. They expressed their concern about humanity’s use of the atomic bomb. The dates in the diary don't quite add up though.
And of course Nazi’s:
It’s a well documented fact that the Nazi’s explored the arctic regions to test weapons and set up bases. It is also well documented that Hitler was obsessed with the occult and esotericism. There is even speculation of an ancient enlightened society and that Hitler escaped to it. A letter from Karl Unger claims U-209 made it to Agartha and the earth is in fact hollow.
The lizard people:
There is another underworld in the Hindu Mahabharata known as Patala. Patala is said to be the seventh layer of the underworld and is ruled by the Nagas, half-human, half-reptilian, that is at war with the agarthans.
And let's not forget the story of the Italian plumber who goes down the sewer to discover a mushroom kingdom. There the princess is kidnapped over and over by the evil reptilian-like king.
Although science is still in its puberty, we have come a great length. The truth is that we don’t know what's down there, we can take measurements and make calculations, but we’re still limited to educated guesses. But sad as it may be to not find lizard people or dinosaurs, we still have a great deal to learn about our inner earth. Hollow earth is a 17th century theory and should be remembered as such. People like Edmund Halley, were the brilliant minds of their era and we should read their work and treat it with the respect it deserves, we should also be aware science was in its infancy and understand that this theory stands to earth's core research as leeches stands to open heart surgery.