Hollow earth

From The Book of THoTH (Leaves of Wisdom)

A "hollow Earth" theory posits that the planet Earth has a hollow interior and probably a habitable inner surface. Although at one time adventure literature made this idea popular, the notion now receives little support; substantial geodetic evidence has long controverted it and the scientific community dismisses it as pseudoscience.

Contrary to popular belief, someone on the inside of a putative 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 of zero everywhere inside a spherically symmetric hollow shell of matter, regardless of the shell's thickness. A tiny gravitational force would arise from the fact that the Earth does not have a perfectly symmetrical spherical shape, and also from tidal forces due to masses such as the Moon which do not form part of the spherical shell. The centrifugal force from the Earth's rotation would also pull a person outwards, but even at the equator this is only 1/300 of ordinary Earth gravity.

In ancient times, the idea of subterranean realms seemed arguable, and became intertwined with the concept of "places" such as the Greek Hades, the Nordic svartalfheim, the Jewish Sheol, and the Christian Hell.

Edmund Halley in 1692 (Philosophical Transactions of Royal Society of London) put forth the idea of Earth consisting of a hollow shell about 500 miles thick, two inner concentric shells and an innermost core, about the diameters of the planets Venus, Mars, and Mercury. Atmospheres separate these shells, and each shell has its own magnetic poles. The spheres rotate at different speeds. Halley proposed this scheme in order to explain anomalous compass readings. He envisaged the atmosphere inside as luminous (and possibly inhabited) and speculated that escaping gas caused the Aurora Borealis.