The hollow Earth stories share common ground with theosophist beliefs. Also stories about Thule and Hyperborea. If the hollow Earth thing is true, then perhaps an expedition to the Northwestern passage and Baffin Bay is worth looking too. Nunavut, Greenland, and the surrounding ocean floor look remarkably close to Mercator’s Hyperborea.
Proponents of a Hollow Earth make much of certain satellite photographs of the planet which were released by NASA. These appear to show a crater-like dark aperture in the centre of the Earth. However, critics insist that the photographs referred to are composites, created by layering multiple photographs together, and that the dark area in the centre is nothing more than an area which happened not to be illuminated by daylight at the time the images were taken. Someone on the inside of a hollow Earth would not experience an outward pull and could not stand on the inner surface; rather, the theory of gravity implies that a person on the inside would be nearly weightless. This was first shown by Newton, whose shell theorem mathematically predicts a gravitational force (from the shell) of zero everywhere inside a spherically symmetric hollow shell of matter, regardless of the shell’s thickness. The best scientific argument against that of a hollow Earth (or in fact any hollow planet) is gravity. Massive objects tend to clump together gravitationally, creating non-hollow spherical objects we call stars and planets. The solid sphere is the best way in which to minimize the gravitational potential energy of a physical object; having hollowness is therefore unfavorable in the energetic sense. In addition, ordinary matter is not strong enough to support a hollow shape of planetary size against the force of gravity. A book by “Dr. Raymond Bernard” appeared in 1964, The Hollow Earth. According to Mr. Bernard our world is hollow, with the crust of the earth being 800 miles thick. There exists two openings at the North and South Pole, each hole having a circumference of 1400 miles wide. At the center of the earth is not a molten core but an inner sun which is six hundred miles wide and is 2900 miles from the Inner Surfaces. The diameter of the lip at the opening at the poles is 1200 miles long, thus a person can not see the other side of the opening.
Richard E. Byrd’s most famous polar expeditions were first drawn into the hollow Earth controversy when a great many articles and books – notably Worlds Beyond the Poles by Amadeo Giannini and The Hollow Earth by Dr Raymond Bernard – claimed that Byrd had actually flown, not across the North and South Poles, but down into the great hollows that led into the Earth’s interior. Ray Palmer, quoting extensively from Giannini’s book (as did Dr Bernard), introduced this theory in the December 1959 issue of Flying Saucers, and thereafter ran a voluminous correspondence on the subject.