If the Roman Catholic Church is the first and original Christian Church, when did the Eastern Orthodox Church begin?


It's not really accurate to say that the Roman Catholic church is older than the Orthodox church. It's more accurate to say that Western (Latin) and Eastern (Greek) theologians and church leaders had different opinions on a range of matters from at least the second century. There were differences of opinion within these two broad camps as well, but in general, Eastern fathers were more speculative while Western fathers were more practical.

Key early debates centered on Christology and whether Rome or Constantinople could claim supremacy in Christendom. We see the two "sides" lining up against each other at the Council of Nicea (325) and the Council of Chalcedon (451), as well as in other ways. (For more on this, see Mark Noll's excellent book Turning Points.)

Technically the East-West Schism occurred in 1054, when the pope and the Orthodox patriarch excommunicated each other. But the bodies that became the two churches had been drifting apart for a long time already. There were attempts at reconciliation until crusaders sacked Constantinople in 1204, which pretty much sealed the split.

To find out more about Eastern Orthodoxy, see CH issue 54.