Plato’s student Aristotle offered further “evidence of the senses” to support his own conclusion that the Earth “must necessarily be spherical.” First, there was the evidence of lunar eclipses. When the Moon passes through the shadow of the Earth, that shadow is always the circular shadow of a sphere. Also, Aristotle argued, “our observations of the stars” make it clear “not only that the earth is circular, but also that it is a circle of no great size.” He pointed out that “quite a small change of position to south or north” significantly changes “the stars which are overhead, and the stars seen are different, as one moves northward or southward.” Just as ships can be hidden from view by the curvature of the horizon, so too can the stars.
