liocentric theory which ultimately became the accepted basic model for the practice of modern astronomy. Another major figure associated with the era is classicist poet Jan Kochanowski.
Polish–Lithuanian Commonwealth
The 1569 Union of Lublin established the Polish–Lithuanian Commonwealth, a more closely unified federal state with an elective monarchy, but which was governed largely by the nobility, through a system of local assemblies with a central parliament. The establishment of the Commonwealth coincided with a period of great stability and prosperity in Poland, with the union soon thereafter becoming a great European power and a major cultural entity, occupying approximately one million square kilometres of central Europe, as well as an agent for the of the 'Western culture' through Polonization in modern-day Ukraine, Belarus and Western Russia. Poland-Lithuania suffered from a number of dynastic crises during the reigns of the Vasa kings Sigismund III and Władysław IV and found itself engaged in a major conflicts with Russia, Sweden and the Ottoman Empire, as well as a series of minor Cossack uprisings.
From the middle of the 17th century, the nobles' democracy, suffering from internal disorder, gradually declined, thus leaving the once powerful Commonwealth extremely vulnerable to foreign intervention. From 1648, the Cossack Khmelnytsky Uprising engulfed the south and east eventually leaving Ukraine divided, with the eastern part, lost by the Commonwealth, becoming a dependency of the Tsardom of Russia. This was soon followed by the 'Deluge', a Swedish invasion, which raged through the Polish heartlands and caused unprecedented damage to Poland's population, culture and infrastructure. Famines and epidemics followed hostilities, and the population dropped from roughly 11 to 7 million. However, under John III Sobieski the Commonwealth's military prowess was re-established, and in 1683 Polish forces played a major part in
