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 National Register of Historic Places listings in Central Chicago Currently there are 124 National Register of Historic Places listings in Central Chicago, out of 354 listings in the City of Chicago. Central Chicago includes 3 of the 77 well-defined community areas of Chicago: the historic business and cultural center of Chicago known as the Loop, as well as the Near North Side and the Near South Side. The combined area is bounded by Lake Michigan on the east, the Chicago River on the west, North Avenue (1600 N.) on the north, and 26th Street (2600 S.) on the south. This