How did Eratosthenes estimate Earth's circumference?
By comparing sunlight angles at different locations✓Bonne réponse
By sailing once around the entire globe
By assuming Earth was a flat disk
By timing a steam-powered vessel
Explication
Eratosthenes compared the angles made by sunlight at different places and used geometry to infer the size of Earth. Sailing around the globe was unnecessary, and a flat-Earth assumption would undermine the calculation.