Who suggested that the Earth is spherical on the basis that the sphere is a perfect shape, not from observations?

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

Answer: (A)

This question tests the idea that the belief in a spherical Earth can come from a philosophical sense that a sphere is the most perfect form, rather than from measurements or observations. Pythagoras and his followers argued that the sphere embodies harmony and perfection, and this view extended to the cosmos, with the Earth (and the heavens) being described as spherical because that shape was considered the ideal. That explains why the suggestion attributing a spherical Earth to the perfection of the sphere fits with Pythagorean thinking.

By contrast, later figures grounded their ideas in observation: Aristotle used observable phenomena like the way ships disappear hull-first over the horizon and lunar eclipses as evidence; Eratosthenes measured shadows at different places to estimate Earth's size; Newton offered a physical explanation in terms of gravity shaping bodies into round forms. So the reasoning tied to the sphere’s perfection points to Pythagoras as the source.