Aristarchus of Samos was an ancient Greek astronomer and mathematician, born around 310 BC. He is best known for proposing a heliocentric model of the solar system, suggesting that the Earth and other planets revolve around the Sun. This idea was revolutionary for its time, as most people believed in a geocentric model, where everything revolved around the Earth. In addition to his heliocentric theory, Aristarchus also estimated the relative sizes and distances of the Sun and Moon. His work laid the groundwork for future astronomers, including Copernicus and Galileo, who further developed the understanding of our solar system.