During the early 9th century, al-Khwarizmi attended the House of Wisdom where he studied Greek and Indian scientific treatises. In 820, he described the use of the astrolabe, an instrument used to observe the position of stars. Although not the first to produce a work on the astrolabe, al-Khwarizmi's contribution was significant, especially in the Islamic world, where the astrolabe could be used to calculate the time of daily prayers.
One of Al-Khwarizmi's major achievements was a treatise on mathematics entitled The Compendious Book on Calculation by Completion and Balancing, published around 830. It contained a description of the branch of mathematics now known as algebra.