 In either view, between the fall of the Western Roman Empire and the Renaissance, the West (or those regions that would later become the heartland of the culturally "western sphere") experienced a period of first, considerable decline, and then readaptation, reorientation and considerable renewed material, technological and political development.This whole period of roughly a millennium is known as the Middle Ages, its early part forming the "Dark Ages", designations that were created during the Renaissance and reflect the perspective on history, and the self-image, of the latter period.The knowledge of the ancient "Western world" was partly preserved during this period due to the survival of the Eastern Roman Empire and the introduction of the Catholic Church; it was also greatly expanded by the Arab importation of both the Ancient Greco-Roman and new technology through the Arabs from India and China to Europe.