Name: Aristarchus of Samos
Lived: c. 310–230 BC, Samos, Greece
Known for: Ancient Greek astronomer and mathematician
Famous for: First to propose a heliocentric model of the solar system (recorded by Archimedes); in his surviving work, On the Sizes and Distances of the Sun and Moon, he used geometry to estimate their relative sizes and distances.
Note: The diagram comes from On the Sizes and Distances of the Sun and Moon, written by Aristarchus in the 3rd century BC. It represents his geometric attempt to estimate the relative sizes and distances of the Sun, Earth, and Moon — a groundbreaking step toward understanding the scale of the cosmos.