Short answers, pulled from the story.
The earliest recorded use of the term "Western world" in English dates to 1586, found in the writings of William Warner, according to the Oxford English Dictionary. The idea of a distinct Western civilization began to crystallize with the rise of Christianity during the Late Roman Empire, and the geopolitical concept took further shape when Constantine the Great divided the Roman Empire in the 4th century CE.
The Great Schism, also called the East-West Schism, occurred in 1054 CE, three months after the death of Pope Leo IX in April of that year. The church in Rome excommunicated the patriarch of Byzantium, formalizing the split between the Western Catholic Church and the Eastern Orthodox Church.
During the Cold War from 1947 to 1991, the Western world was redefined as the First World, composed of NATO members and countries aligned with the United States. This stood in contrast to the Soviet-aligned Second World and the unaligned Third World, a tripartite framework that dissolved after Mikhail Gorbachev's rise in the 1980s and the subsequent dissolution of the Soviet Union.
Australia is included in modern definitions of the Western world because of its significant cultural ties to Britain through colonization and European immigration, not because of its geographic location. Countries are grouped into the West based on shared cultural, political, and historical inheritance rather than their position on a map.
By 1913, the British Empire held sway over 412 million people, and by 1920 it covered 35,500,000 square kilometers of the Earth's total land area. Before it abolished its slave trade in 1807, the British Empire was responsible for transporting 3.5 million African slaves to the Americas, a third of all those transported across the Atlantic.
Approximately 70% of Western populations are Christians. A 2011 Pew Research Center survey found that 76.2% of Europeans, 73.3% of people in Oceania, and about 86% of people in the Americas described themselves as Christians, though church attendance has declined in many European Union countries in recent decades.