Nicolaus Copernicus was an early astronomer who is best known for proposing the heliocentric model of the solar system, in which the sun is at the center rather than the earth. Copernicus was born in Poland and lived from 1473-1543. He entered the University of Cracow in 1493 and studied painting and mathematics. After graduating he became a priest, which gave him time to pursue the study of astronomy.
The common belief at this time was celestial bodies moved in fixed orbits around the earth, as suggested by Aristotle. Copernicus developed a detailed heliocentric model that included a formula for calculating the positions of planets throughout the year. This model began to take shape around 1508, and was advanced by Copernicus’ construction of his own planetarium in 1513 that allowed him to view the planets.
In 1541 Copernicus completed a manuscript of his work which caused the Catholic Church to regard him as a heretic. The Church’s ban on Copernicus’ book was lifted in the 17th century. By that time Johannes Keppler had expanded upon the heliocentric model and had correctly shown that the planets’ orbits are elliptical, not circular as Copernicus predicted. The heliocentric theory was finally advanced with the help of later observations and calculations by Keppler, Isaac Newton, and Tyge Brahe.