Aristotle, unlike Plato, paid much attention to the results of observation and the experience of others. He proposed four observational proofs that the Earth is a sphere.
Ships disappear slowly over the horizon.
The shape of the Earth's shadow at lunar eclipse appears circular. Different stars are visible at northern and southern latitudes. His notion was that both are within a reasonable distance on a moderately sized sphere. Although he considered the possibility, he rejected the idea of an orbiting Earth because of the absence of detectable parallax . Parallax was not first proved until 1838 by Bessel.