Nicolaus Copernicus (19 February 1473 – 24 May 1543) was a Polish astronomer. People know Copernicus for his ideas about the sun and the earth. His main idea was that our world is heliocentric (helios = sun). His theory was that the sun is in the middle of the solar system, and the planets go around it. This was published in his book, De revolutionibus orbium coelestium (On the Revolutions of the Heavenly Spheres) in the year that he died.
Copernicus was born in 1473 in the city of Thorn (Toruń) in Royal Prussia, a mainly German-speaking state that was ruled by the Polish king since 1466. He was the son of the merchant Niklas Koppernigk and his wife Barbara Koppernigk (born Barbara Watzenrode). His native language was German. He was taught first in Cracow and then in Italy, where he graduated as a lawyer of the church. He also studied medicine to serve his fellow clerics. Copernicus spent most of his life working and researching in Frauenburg (Frombork), Warmia, where he died in 1543.
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.