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;
Trading Places He explains that this axiom asserts its importance not in the fact that "our time" sees an increased expectation of new operas being developed but, rather, in the fact that there is an increased expectation of "new productions of operas." Cavell draws a comparison of themes between "Trading Places" and the opera "The Marriage of Figaro", stating that "what "Trading Places" wants from its reference to "Figaro" is mostly the idea of resourceful and sociable young and poor overcoming with various disguises the conniving of the unsociable old and rich but with no sense that the old may be redeemed