Copernicus was one of the great polymaths of his age. He was a priest, mathematician, astronomer, astrologer, jurist, physician, classical scholar, governor, administrator, diplomat, economist, and soldier. During all these jobs, he treated astronomy as a hobby. However, his doctrine of heliocentrism that the sun, rather than the earth, is at the center of the solar system, is one of the most important scientific hypotheses in history. It was the beginning of modern astronomy.