His Arabic name in full was Ghiyath al-Din Abu al-Fath Umar ibn Ibrahim al-Nisaburi al-Khayyam.
The Persian mathematician, astronomer, and poet was renowned in his own country and time for his scientific achievements but Khayyam is chiefly known to English-speaking readers through the translation of a collection of his robaiyat (“quatrains”) in “The Rubaiyat of Omar Khayyam” (1859) by the English writer Edward FitzGerald.
His name Khayyam (“Tentmaker”) may have been derived from his father's trade. He received a good education in the sciences and philosophy in his native Neishabur before traveling to Samarkand (now in Uzbekistan), where he completed the algebra treatise, “Risalah fi’l-Barahin ala Masail al-Jabr wa’l-Muqabalah” (“Treatise on Demonstration of Problems of Algebra”), on which his mathematical reputation principally rests. In this treatise he gave a systematic discussion of the solution of cubic equations by means of intersecting conic sections. Perhaps it was in the context of this work that he discovered how to extend Abu al-Wafa's results on the extraction of cube and fourth roots to the extraction of nth roots of numbers for arbitrary whole numbers “n”.
He made such a name for himself that the Seljuk sultan Malik-Shah invited him to Isfahan to undertake the astronomical observations necessary for the reform of the calendar. To accomplish this, an observatory was built there, and a new calendar was produced, known as the Jalali calendar. Based on making 8 of every 33 years leap years, it was more accurate than the present Gregorian calendar, and it was adopted in 1075 by Malik-Shah. In Isfahan he also produced fundamental critiques of Euclid's theory of parallels as well as his theory of proportion. In connection with the former his ideas eventually made their way to Europe, where they influenced the English mathematician John Wallis (1616–1703); in connection with the latter he argued for the important idea of enlarging the notion of number to include ratios of magnitudes (and hence irrational numbers).
His years in Isfahan were very productive ones, but after the death of his patron in 1092, the sultan's widow turned against him, and soon thereafter Omar went on a pilgrimage to Mecca. He then returned to Neishabur, where he taught and served the court as an astrologer. Philosophy, jurisprudence, history, mathematics, medicine, and astronomy are among the subjects mastered by this brilliant man.
Omar's poems had attracted comparatively little attention until they inspired FitzGerald to write his celebrated The Rubaiyat of Omar Khayyam, containing such now-famous phrases as “A Jug of Wine, a Loaf of Bread -- and Thou,” “Take the Cash, and let the Credit go,” and “The Flower that once has blown forever dies.” These quatrains have been translated into almost every major language and are largely responsible for coloring European ideas about Persian poetry. Some scholars have doubted that Omar wrote poetry. His contemporaries took no notice of his verse, and not until two centuries after his death did a few quatrains appear under his name. Even then, the verses were mostly used as quotations against particular views ostensibly held by Omar, leading some scholars to suspect that they may have been invented and attributed to Omar because of his scholarly reputation.
Each of Omar's quatrains forms a complete poem in itself. It was FitzGerald who conceived the idea of combining a series of these robaiyat into a continuous elegy that had an intellectual unity and consistency. FitzGerald's ingenious and felicitous paraphrasing gave his translations a memorable verve and succinctness. They are, however, extremely free translations, and more recently several more faithful renderings of the quatrains have been published.
The verses translated by FitzGerald and others reveal a man of deep thought, troubled by the questions of the nature of reality and the eternal, the impermanence and uncertainty of life, and man's relationship to God. The writer doubts the existence of divine providence and the afterlife, derides religious certainty, and feels keenly man's frailty and ignorance. Finding no acceptable answers to his perplexities, he chooses to put his faith instead in a joyful appreciation of the fleeting and sensuous beauties of the material world. The idyllic nature of the modest pleasures he celebrates, however, cannot dispel his honest and straightforward brooding over fundamental metaphysical questions.
(Encyclopaedia Britannica)