6 Craziest Alternate History Theories That Will Break Your Brain

The Hollow Earth – The World Inside Our World

Before flat Earth, there was hollow Earth. The theory, suggested by the otherwise respectable astronomer Edmund Halley in the 17th century, claims that Earth consists of a hollow shell about 1,300 km thick, with openings at both poles and four inner shells. According to believers, there’s a sun inside, and a hidden civilisation called Agartha lives there. Some even claim there’s a forcefield at the poles that makes the entrances invisible. While it was thoroughly disproven by the late 18th century, the theory refuses to die.