Copernicus comes across as a quiet, modest man. He was happy to live a placid life in his native Poland, working for the church and studying the stars. But he came up with an idea that was to utterly change the way we think about the world.
His interest in astronomy was awakened while studying in Bologna where he assisted the Professor of astronomy. On returning to Poland he entered the church working for his uncle but he continued his astronomical studies and his reputation began to grow. In 1514 a hand written book appeared called Little Commentaries which he distributed to his friends. He began work on the great De revolutionibus the next year. But publication of this was fraught as Frauenberg, where he lived, was plunged into war for a number of years.
We might never have learnt of Copernicus were it not for Rheticus, a protestant who went to the Catholic stronghold of Frauenberg to learn from Copernicus. He encouraged him in writing and wrote an introduction to his book. He left Frauenberg, taking De revolutionibus with him for publication. This was published at the end of Copernicus’ life - he apparently received a copy on his deathbed. But the printer made some changes, adding a preface claiming the book was not intended as the truth but as a means of making simpler astronomical calculations. While this outraged some, others feel this addition was the only reason the book was read and not condemned outright.
De revoluitionibus came up with what is now known as the heliocentric model of the galaxy. This argues that the sun is the fixed point around which the planets orbit and the earth is a planet which orbits the sun and rotates on its own axis. The idea had a profound effect, overturning the ideas of Ptolemy. Kepler and Galileo went on to defend the idea, while Newton 150 years later was to provide the theoretical evidence supporting Copernicus’ theory.