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
Summer term Summer term Summer term is the summer academic term at many British schools and universities and elsewhere in the world. In the UK, 'Summer term' runs from the Easter holiday until the end of the academic year in June or July, and thus corresponds to the Easter term at Cambridge University, and Trinity term at Oxford, Dublin and some other places. 'Summer term' is defined in some UK statutory instruments, such as the Education (Assessment Regulations) (Foundation to Key Stage 3) Order (Northern Ireland) 2007, which says: "summer term" means the period commencing immediately after the Easter holiday and ending