> Ancient Mesopotamian astronomy, for instance, used a flat earth model. More astonishingly, Chinese astronomers used a flat earth model until the 16th century.

> Ancient Mesopotamian astronomy, for instance, used a flat earth model. More astonishingly, Chinese astronomers used a flat earth model until the 16th century. This is hardly a proof these astronomers did believe their model pictured the shape of the Earth correctly. In fact, a kind of flat Earth model and a (horizontal coordinate system)[https://en.wikipedia.org/wiki/Horizontal_coordinate_system https://en.wikipedia.org/wiki/Horizontal_coordinate_system) is used to this day in astronomy to demonstrate how the sky and the celestial bodies appear to an observer on the ground. This was exactly the purpose of earlier astronomers because from this knowledge they could deduce predictions about the seasons and eclipses (and, ok, lucky and unlucky days and so on). If you're ready to deal with a modicum of epicycles and are only interested in purely local ephemerides, the model is actually not so bad as a framework for calculations and the real improvement only comes with a heliocentric model with elliptical orbits, not so much from a spherical Earth.