Geocentric model knew about Tusi's work or that of the Maragha school. Not all Greeks agreed with the geocentric model. The Pythagorean system has already been mentioned; some Pythagoreans believed the Earth to be one of several planets going around a central fire. Hicetas and Ecphantus, two Pythagoreans of the 5th century BC, and Heraclides Ponticus in the 4th century BC, believed that the Earth rotated on its axis but remained at the center of the universe. Such a system still qualifies as geocentric. It was revived in the Middle Ages by Jean Buridan. Heraclides Ponticus was once thought to have proposed
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