Al-Biruni found accurately the specific gravity of eighteen...
Al-Biruni found accurately the specific gravity of eighteen different precious substances and metals. He realized that the velocity of light was enormously greater than that of sound. Al-Biruni developed the mathematical part of geography, improved mensuration, and determined quite accurately the latitude and longitude of a number of places; he devised easy methods of stereographic projection.
He showed how water flows in natural springs and how it comes out in artificial wells, and explained these facts in accordance with the laws of hydrostatics. His observations led him to the conclusion that the Indus Valley was at one time a part of the sea which became solid by the deposit of alluvial soil. The most illustrious name in Arabic medical annals after al-Razi is that of ibn Sina (Latin Avicenna) (370-428/980-1037).
Al-Razi was more of a physician than ibn Sina, but ibn Sina was more of a philosopher. In this physician, philosopher, philologist, and poet, medieval Arab science culminates and is, one might say, incarnated. Ibn Sina wrote on the theory of numbers. For accurate measurement of distances he invented an apparatus involving the same principle as our modern Vernier. He made a masterly study of a number of physical subjects like motion, contact, force, vacuum, infinity, light, and heat.
Ibn Sina expressed his views on all the information that could be gathered in physics philosophically. He showed that however great the velocity of light may be, it must be limited. He did valuable research in music also, but his principal subject was medicine for which he earned the title of Shaikh al-Ra'is. Jalal al-Din Malik Shah patronized astronomical studies.
He established in 467/1074 at Rayyan observatory where there was introduced into the civil calendar an important reform based on an accurate determination of the length of the tropical year. To this task of reforming the Persian calendar he called to his new observatory the celebrated 'Umar al-khayyam. Umar al-Khayyam was born between 430/1038 and 440/1048 at Nishapur where he died in 517/1123. He is known to the world primarily as a Persian poet.
Very few people realize that he was a first-class mathematician and astronomer as well. The researches of al-Khayyam and his collaborators resulted in the production of the calendar named, after his patron, al-Tarikh al-Jalali, which is even more accurate than the Gregorian calendar.