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;
Central Illinois Regional Airport for the Central Illinois Air Derby. Billed at the time as the greatest such event in Illinois outside of Chicago, the show included four U.S. Army "ships" from Chanute Field in Rantoul, civilian aviators from places like Aurora, Champaign, Joliet and Kankakee, aerial "stunting" contests and races, parachutists and an air parade over downtown Bloomington. Despite the efforts of local aviation enthusiasts and the business community, attempts to establish long-term passenger service at the Normal field ended in failure. In the fall of 1931, Century Air Lines added Bloomington to its Chicago-to-St. Louis route, and the little grassy square (recently