Geocentric model the coordinate system in order to predict the motions of planetary bodies, though doing so may make calculations easier to perform or interpret. A geocentric coordinate system can be more convenient when dealing only with bodies mostly influenced by the gravity of the Earth (such as artificial satellites and the Moon), or when calculating what the sky will look like when viewed from Earth (as opposed to an imaginary observer looking down on the entire solar system, where a different coordinate system might be more convenient). The Ptolemaic model of the solar system held sway into the early modern age;
National Register of Historic Places listings in Central Chicago Chicago architecture. Architect Louis Sullivan's work is represented by the Carson, Pirie, Scott and Company Building, and Auditorium Building. Though Frank Lloyd Wright worked downtown early in his career as an assistant to Sullivan - including work on the James Charnley House - his own work in the central city is represented only by a renovation of the lobby of Daniel Burnham's and John Wellborn Root's Rookery Building. At least three sites relate to the city's role in nationwide retailing. Included also are several religious buildings, six hotels, and four theaters. National Register of Historic Places listings in Central Chicago