Geocentric model and planets were holes in invisible wheels surrounding Earth; through the holes, humans could see concealed fire. About the same time, Pythagoras thought that the Earth was a sphere (in accordance with observations of eclipses), but not at the center; they believed that it was in motion around an unseen fire. Later these views were combined, so most educated Greeks from the 4th century BC on thought that the Earth was a sphere at the center of the universe. In the 4th century BC, two influential Greek philosophers, Plato and his student Aristotle, wrote works based on the geocentric model.
Truce term credibility". "Pax" was no longer a group word as reported by the Opies. Other terms reported included "pips", "force field" and "quits". The authors concluded that either the Opies had grossly oversimplified the picture or things had radically changed in 30 years (some seven to eight generations of primary school children). They also noted that although some schools reported a marked preference for a particular term, all schools reported at least some children using different terms. The Concise Scots Language Dictionary published in 1999, records the use of "keys" as a truce term in Fife, south west and west central