Abu Ja'far al-Khwarizmi Abu Ja'far al-Khwarizmi was an Arab mathematician who lived between AD 780 and 850. At a time when the spread of ideas was difficult, al-Khwarizmi wrote a book which contained many important mathematical concepts of the Middle East. This book changed all of European mathematics, introducing the decimal system and rules for doing algebra. 'Abd al-Rahman al-Sufi 'Abd al-Rahman al-Sufi was a Persian astronomer who lived during the 10th century. He was the first person to observe the Andromeda galaxy, our closest neighbor, and called it "little cloud". Al-Sufi's book on stars was translated into many languages and had a big influence on European astronomy. Leonardo Fibonacci Leonardo Fibonacci was an Italian mathematician who lived between 1170-1240. He travelled a lot on business with his father and was exposed to many different mathematical ideas. Fibonacci put all these ideas together, in books, so that anybody could learn them wit