english: He noticed that every time you saw the Earth's shadow on the Moon, it was circular, and the only shape that constantly creates a circular shadow is a sphere, Q.E.D. the Earth is round.
non_english: je vždy okrúhly a jediný tvar, ktorý stále vytvára okrúhly tieň, je guľa. Dôkaz - Zem je guľa.