How Hollow is our Earth?: Halley’s Amazing Theory (Erpel’s Visions Book 4)

Once again, Karl-Heinz Erpel brought up a seemingly crazy theory of a celebrated scientist in order to verify its validity. Was it an act of tomfoolery when Edmond Halley cooked up his theory of a hollow earth? At least our modern scientists tend to believe this. With the experienced eye of a visionary, Erpel investigates the true backdrop of this subterranean story. And again, extraterrestrial visitors seem to be the answer to all unanswerable questions!