Aristarchus

Aristarchus of Samos (circa 310–230 BCE) was an ancient Greek astronomer and mathematician from the island of Samos. He is best known for proposing one of the earliest known heliocentric models, in which the Sun sits near the center of the known cosmos and the Earth and other planets move around it. His ideas represented a radical departure from the prevailing geocentric view of his era.

In his astronomical work, Aristarchus attempted to determine the sizes and distances of the Sun and Moon using geometric reasoning applied to lunar phases and eclipses. He argued that the Sun is much larger than the Earth and that its distance is correspondingly greater, which led him to conclude that the Sun, not the Earth, should occupy the central position in the cosmos. He is generally credited with the notion that the Moon orbits the Earth and that the planets, including Earth, orbit the Sun.

Only fragments of Aristarchus’s writings survive, and much of what is known about his methods comes from later authors such as Archimedes. His heliocentric model did not gain traction in antiquity, and the geocentric framework persisted for many centuries. Nevertheless, Aristarchus’s ideas are recognized today as a pioneering step in the history of astronomy, foreshadowing the revolutionary shift brought about by Copernicus and subsequent scientists. His work illustrates an early use of geometric reasoning to explore celestial distances and motions.