During the ninth and tenth century learned men in the schools of Cordoba in Spain were corresponding with learned men in Cairo, Baghdad and Bukhara.
In Baghdad Al-Karismi developed the decimal system by using the Indian notion of Zero, and he invented the term 'algebra'. His works were instrumental in introducing the subjects of algebra and Hindu numerals into European mathematics.
Al-Hassan was a famous optician in Cairo who was the first to recognize the optical nerve in the human eye.
Ibn Sina (Avicenna) from Bukhara collected in over 100 books the entire scientific knowledege of his time and is called the 'Prince of Science'. His 'Canon of Medicine' is among the most famous books in the history of medicine.
Al-Biruni of Ghazni traveled in India and corresponded with Ibn Sina. Conversant in Turkish, Persian, Sanskrit, Hebrew and Arabic Al-Biruni became the most important interpreter of Indian science to Islam. In astronomical works he discussed the theory of the earth's rotation on its axis, and in geography he advanced the visionary view that the Indus valley had once been a sea basin.
Al-Battani of Harran carried out astronomical observations in Syria and wrote on mathematics, improving the calculation for sinus functions. His great astronomical work 'De motu stellarum' exercised a great influence on European astronomy. He determined the exact solar year to within a few seconds of today's estimates.
Abu Kasim was a physician in Cordoba, Spain. He was the most famous physician of his time and he treated patients from all over Europe. He employed vivisection of animals for his research, and wrote a standard text book on surgery.