"In fibris corporis planetae": Johannes Kepler and the Fabric of the Earth

The ‘invention’ of strata lapidea seems to have been the result of a process of recognition, within the body of the earth, of naturally generated and orderly structures that could be read geometrically. During the early seventeenth century an important and still largely unacknowledged contribution to this process was made by Johannes Kepler. Notably, in some crucial chapters of his Astronomia nova (1609) and in the Epitome astronomiae Copernicanae (1618–1621), Kepler speculated on the existence of filaments, fibres and shells in the body of the sun and the planets and described their possible structures and arrangements in a series of illustrations. He also extensively discussed their functions as structures endowed with a motive virtus that played a central role in his dynamic physical astronomy.