Mathematics

Omar Khayyam

1048 to 1131, Nishapur, Persia (present-day Iran)

The astronomer who cut cones to solve cubic equations and reformed the calendar, now remembered in the West for quatrains whose authorship is genuinely uncertain.

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Lessons

Solving the Cubic by Cutting Cones

Omar Khayyam’s Treatise on the Proofs of Problems of Algebra (c. 1070): the first systematic classification of cubic equations and a geometric solution for every type, found by intersecting conic sections - togeth…

The Jalali Calendar: Measuring the Year

In 1079 Khayyam led the astronomers of the Isfahan observatory in reforming the Persian calendar for Sultan Malik-Shah. The resulting Jalali calendar, built on precise solar observation, was by many reckonings more accu…

The Fifth Postulate and the Seed of a New Geometry

In his Commentary on the Difficulties in the Postulates of Euclid (1077), Khayyam tried to prove Euclid’s troublesome fifth postulate. Studying a special quadrilateral - now called the Khayyam-Saccheri quadrilater…

What Is a Number? Ratios and the Reality of the Irrational

In the second part of his Euclid commentary, Khayyam reexamined the theory of ratios in Book V of the Elements and pressed a revolutionary idea: that a ratio - even between incommensurable magnitudes - is itself a kind…

The Rubaiyat: The Skeptic Behind the Astronomer

The quatrains traditionally attributed to Khayyam - made famous in the West by Edward FitzGerald’s free 1859 adaptation - voice a philosophy of carpe diem, doubt, and the limits of knowledge. They reveal a tension…

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