Fludd's cosmic realms. Artwork showing the heliocentric (sun-centered) worldview described in the macrocosmic principles of the English physician, astrologer, and mystic Robert Fludd (1574-1637). During the 16th and 17th centuries, notions of macrocosm and microcosm were widely accepted. Many people believed that the same patterns found in the human body on a small scale (microcosm) are found in the natural universe as a whole (macrocosm). Fludd's philosophy is presented in Utriusque Cosmi, Maioris scilicet et Minoris, metaphysica, physica, atque technica Historia (The metaphysical, physical, and technical history of the two worlds, namely the greater and the lesser), published in Germany in 1617. Here, the sun is at center, surrounded by successive spheres of elemental materials.