In 1966, Jordan published his 182-page work Die Expansion der Erde. Folgerungen aus der Diracschen Gravitationshypothese (The expansion of the Earth. Conclusions from the Dirac gravitation hypothesis)Die Wissenschaft, vol. 124. Friedrich Vieweg & Sohn, Braunschweig 1966 in which he developed his theory that, according to Paul Dirac's hypothesis of a steady weakening of gravitation throughout the history of the universe, the Earth may have swollen to its current size, from an initial ball of a diameter of only about . This theory could explain why the ductile lower sima layer of the Earth's crust is of a comparatively uniform thickness, while the brittle upper sial layer of the Earth's crust had broken apart into the main continental plates. The continents having to adapt to the ever flatter surface of the growing ball, the mountain ranges on the Earth's surface would, in the course of that, have come into being as constricted folds.Heinz Haber: Despite the energy Jordan invested in the expanding Earth theory, his geological work was never taken seriously by either physicists or geologists.
