Long before Copernicus, the Greek astronomer and mathematician Aristarchus (c. 310–c. 230 BC) theorized that the earth revolves around the sun. But his findings were rejected by most other Greeks and then largely forgotten until his vindication almost 2,000 years later.
Aristarchus was born on Samos, a Greek isle near the coast of modern-day Turkey that was also the birthplace of the mathematician and religious leader Pythagoras (c. 580–c. 500 BC). Some of Aristarchus’s ideas are thought to have been influenced by related beliefs of the Pythagoreans, who were still influential in the Greek world for centuries after their founder’s death.
After leaving Samos, Aristarchus settled in Alexandria. He became a student of Strato of Lampsacus (c. 335–c. 269 BC), who had been one of Aristotle’s disciples in Athens. Aristotle, along with most other Greeks of the time, believed that the earth was the unmoving center of the universe, a view that Aristarchus was almost certainly taught.
The only surviving work by Aristarchus is On the Sizes and Distances of the Sun and Moon. In the treatise, Aristarchus tried to calculate the sizes of the two celestial bodies and their distances from the earth. Although his estimates were way off, he correctly realized that the sun was far larger than the earth.
That discovery apparently led him to question whether the comparatively tiny earth could really be the center of the universe. Unfortunately, all of Aristarchus’s later writings are lost, but the Greek engineer Archimedes (c. 287–c. 212 BC) recorded that Aristarchus eventually proposed a new model of the universe that put the sun at the center. Aristarchus also surmised—correctly—that the stars were celestial objects like the sun and were located at far greater distances from the earth than most ancients assumed. He also theorized that the movement of the stars in the sky was actually caused by Earth’s spinning on its axis, another view that proved correct.
The heliocentric model, however, was ignored or ridiculed by most Greeks—including Archimedes. Nearly four centuries later, the astronomer Ptolemy (c. 100–170) published the geocentric Almagest, which would be the dominant astronomy text in the Western world through the Middle Ages. Not until Nicolaus Copernicus (1473– 1543) published De revolutionibus orbium coelestium libri VI in 1543 would another scientist finally confirm Aristarchus’s bold conclusion.
ADDITIONAL FACTS
- One of the most prominent craters on the moon was named in the Greek astronomer’s honor. The Aristarchus crater is relatively young—the impact that created it occurred about 450 million years ago—and is often visible to the naked eye from Earth.
- According to the ancient historian Plutarch (c. 46–c. 120), a critic of Aristarchus’s named Cleanthes (c. 330–c. 230 BC) suggested bringing charges of impiety against the astronomer because his heliocentric model removed the earth from the central role.
- Aristarchus performed all of his observations without a telescope, resulting in many errors.
