Copernicus Publishes Heliocentric Model
Copernicus published his argument that the earth goes round the sun in 1543 and reportedly saw the printed book on the day he died. He was a Polish canon of Frombork cathedral with a doctorate in canon law from Ferrara, who practised medicine, advised on currency reform, and did astronomy in the time left over. The problem he was solving was aesthetic before it was empirical. The Ptolemaic system worked well enough for prediction and required each planet to move on a small circle whose centre moved on a large one, with an offset centre and an equant point about which the motion was uniform — a device Copernicus regarded as a violation of the principle that celestial motion must be uniform and circular. Putting the sun at the centre removed a great deal of that machinery and explained why Mercury and Venus never stray far from the sun and why the outer planets appear to move backwards. It did not make the predictions better, because he kept perfect circles and therefore needed epicycles of his own. He circulated a short summary around 1514 and delayed the full book for nearly thirty years, and it was published in Nuremberg by a Lutheran printer whose colleague added an unsigned preface calling the model a calculating device rather than a claim about reality. It was read by astronomers as a technical work for two generations. The Catholic church placed it on the Index in 1616, when Galileo made the claim about reality explicitly. Kepler replaced the circles with ellipses in 1609.
- Year: 1543 CE
- Category: Scientific
