In 1947 the explorer Richard Byrd flew to the South Pole, and when he returned, he is believed to have described finding an entrance to the center of the Earth. From there, people have speculated that people or creatures inhabit this space, flying out whenever they like, but having very little to do with those of us on the surface.

These inner-Earth creatures are supposed to be demons, or super-creatures, or perhaps gnomes or trolls or elves. Imagination paints them as enormous or tiny, reptilian or human-like, scientifically advanced or barely civilized. None of these speculations is provable, but to date no one has a convincing argument backed by scientific evidence just what is at the center of the Earth, so the speculation Byrd initiated goes on.