Ad orientem
Ad orientem, meaning "to the east" in Ecclesiastical Latin, is a phrase used to describe the eastward orientation of Christian prayer and Christian worship, comprising the preposition ad (toward) and oriens (rising, sunrise, east), participle of orior (to rise). Ad orientem has been used to describe the eastward direction of prayer that the early Christians faced when praying, a practice that continues in the Eastern Orthodox Church, Oriental Orthodox churches, Mar Thoma Syrian Church, Assyrian Church of the East, as well as the Eastern Catholic and Eastern Lutheran churches. It was normative in the Roman Catholic Church until the 1960s, with the current exception of the Tridentine Mass; many Lutheran and Anglican churches continue to offer the Divine Service ad orientem. Although the Second Vatican Council never ordered any change from ad orientem to versus populum, in the aftermath of the Council, such a change was widespread in many places afterward and became the norm, though ad orientem was never forbidden, and indeed the Pauline Missal presumes the Mass is said ad orientem in its rubrics. In the celebration of the Mass, it indicates that the priestly celebrant faces the altar with his back to the congregants, so they all face the same direction, as opposed to versus populum, facing the people. Since the time of the early Church, the eastward direction of Christian prayer has carried a strong significance, attested by the writings of the Church Fathers. In the 2nd century, Syrian Christians hung a Christian cross on the eastern wall of their house, symbolizing "their souls facing God, talking with him, and sharing their spirituality with the Lord." Two centuries later, Saint Basil the Great declared that "facing the east to pray was among the oldest unwritten laws of the Church". Nearly all Christian apologetic tracts published in the 7th century in the Syriac and Arabic languages explicated the reason that Christians prayed facing the east is because "the Garden of Eden was planted in the east (Genesis 2:8) and that at the end of time, at the second coming, the Messiah would approach Jerusalem from the east." Parishes of the Coptic Church, a denomination of Oriental Orthodox Christianity, are designed to face east and efforts are made to remodel churches obtained from other Christian denominations that are not built in this fashion. (Wikipedia).
