Geocentric model that both Venus and Mercury went around the Sun rather than the Earth, but this is no longer accepted. Martianus Capella definitely put Mercury and Venus in orbit around the Sun. Aristarchus of Samos was the most radical. He wrote a work, which has not survived, on heliocentrism, saying that the Sun was at the center of the universe, while the Earth and other planets revolved around it. His theory was not popular, and he had one named follower, Seleucus of Seleucia. In 1543, the geocentric system met its first serious challenge with the publication of Copernicus' "De revolutionibus orbium
Central place theory Central place theory Central place theory is a geographical theory that seeks to explain the number, size and location of human settlements in a residential system. The theory was created by the German geographer Walter Christaller, who asserted that settlements simply functioned as 'central places' providing services to surrounding areas. To develop the theory, Christaller made the following simplifying assumptions: All areas have: Therefore, the trade areas of these central places who provide a particular good or service must all be of equal size The theory then relied on two concepts: "threshold" and "range". The result of these consumer preferences