Which philosopher offered arguments supporting that the Earth is spherical, citing changing horizons in different directions, the round shadow of the Earth during lunar eclipses, and the appearance of ships at sea as they approach?

• A. Eratosthenes
• B. Pythagoras
• C. Aristotle
• D. Newton

Answer: (C)

Observing how the Earth shapes what we see in the sky and at sea leads to the conclusion that Earth is a sphere. The round shadow Earth casts on the Moon during a lunar eclipse is a telltale sign: a sphere always casts a round shadow, regardless of orientation, whereas a flat Earth would produce a different, inconsistent shadow. When ships sail away toward the horizon, they disappear hull-first, which happens because the surface curves away—this gradual concealment of the lower parts reflects curvature rather than a flat plane. And the way horizons and star patterns change with direction and latitude fits a curved surface: moving north or south or looking toward different parts of the sky brings different views, exactly what a spherical body would produce. Aristotle used these observations to argue for a spherical Earth, tying together multiple lines of evidence into a coherent picture. Other thinkers, such as Pythagoras and later Eratosthenes, also contributed to the idea that Earth is round, but the specific combination of a circular lunar shadow, hull-first disappearance of ships, and direction-dependent horizons is classically associated with Aristotle.