It was the Muslims from Arabia, nomads and settled people alike, whose invasions in the 6th and 7th cent. widely diffused both the Arabic language and Islam. They founded a vast empire, which at its height stretched from the Atlantic Ocean on the west, across North Africa and the Middle East, to central Asia on the east. The Arabs became the rulers of many different peoples, and gradually a great Arab civilization was built up. Although many of its cultural leaders were not ethnically Arabs (some were not even Muslims, but Christians and Jews), the civilization reflected Arab values, tastes, and traditions. Education flourished in the Islamic lands, and literature, philosophy, medicine, mathematics, and science were particularly developed by the Arabs. At the same time in all the provinces of the huge empire, except in Persia, Arabic became the chief spoken language. The waves of Arab conquest across the East and into Europe widened the scope of their civilization and contributed greatly to world development. In Europe they were particularly important in Sicily, which they held from the 9th to the late 11th cent., and the civilization of the Moors in Spain was part of the great Arabic pattern. Christian scholars in those two lands gained much from Islamic knowledge, and scholasticism and the beginnings of modern Western science were derived in part from the Arabs. The Arabs also introduced Europe to the Greek philosophers, whose writings they had already translated into Arabic. The emergence of the Seljuk Turks in the 11th cent. and of the Ottoman Turks in the 13th cent. ended the specifically Arab dominance in Islam, though Muslim culture still remained on the old Arab foundations.