Known chiefly in the West for his 'Rubáiyát,' Ghiyāth al-Dīn Abu al-Fath 'Umar ibn al- Nīshāpūrī al-Khayyām (Omar Khayyam these days) was a Persian mathematician and astronomer of renown throughout the Islamic world. He was born in May 1048 in the town of Nishapur, the Seljuk capital in Khorasan. At some point in his early life, Omar went to Balkh (now in Afghanistan) to study under the Sheik Mansuri, and then later under the famed Imam Mowaffaq Nishapuri. As his studies ended, he began his scientific career writing treatises on various subjects, notably one on geometry and the theory of proportions. Other influential works from this period include one on algebra, a book on music, and the textbook 'Problems in Arithmetic' … all before he was 25 years old.
In 1070, Omar Khayyam moved to Samarkand, there supported by a prominent jurist, which allowed the polymath to work on a complete classification of cubic equations, his most famous book: 'Treatise on Demonstration of Problems of Algebra.' Then his 'Explanations of the Difficulties in the Postulates in Euclid’s Elements,' in which he devoted several sections to the fifth (parallel) postulate, revolutionized geometry; in the process, he laid the initial brick in the edifice of non-Euclidean geometry.
Omar made such a name for himself that the Seljuk sultan Malik-Shah invited him to undertake observations and calculations to reform the calendar. To accomplish this, Khayyam oversaw the construction of a state-of-the-art (for the time) observatory, and soon produced the Jalali calendar. Based on making eight of every 33 years “leap years,” it was more accurate than the Julian calendar in use in Europe, and in 1079 it became the official calendar throughout the expanding empire. After the sultan’s death he served as court astrologer until his death in 1131.