There are two hollow earth theories. According to the first one we live on the crust, but there is another world on the inside where lies - some say - the realm of Agartha, the home of the King of the World (see, for example, the fantasies of French philosopher René Guénon). The second theory has it that while we think we live on the outer crust, we actually live in the interior (on a convex surface instead of a concave one)[...]
It is widely rumoured on the internet that the hollow earth theory was taken seriously by top-ranking Nazis who believed in the occult sciences. In some circles of the German navy it was purportedly believed that the hollow earth theory would make it easier to pinpoint the exact position of British ships because, if infrared rays were used, the curvature of the Earth would not have obscured observation.
Hitler allegedly sent an expedition to the Baltic island of Rügen where a Dr Heinz Fischer trained a telescopic camera toward the sky in order to spot the British fleet sailing on the interior of the convex surface of the hollow earth. It is even said that some V1 missiles went astray because their trajectory was calculated on the basis of a hypothetical concave surface instead of a convex one.
I don't know. Maybe someone can explain it to me. Via PTDR.