The most illustrious figure in the history of Islamic mathematics is Abu’l-Fath Omar ibn Ibrahim Al-Nisaburi Khayyámi (ca.1048-ca.1130) known in the West as Omar Khayyam, the “Tentmaker”. Khayyam was born in Nishapur, in Persia. His principal work in mathematics is Algebra.
He did research in physics and invented a water balance that was for a long time known by his name. He was also involved in a program of calendar reform initiated by the Seljuk sultan Melikshah. The Jalali calendar that he and his colleagues created is still used. He refers to this work in one of the quatrains of his Rubaiyat, the volume of poetry that made him far more famous in the West than his mathematics.
Ah, but my Computations, People say,
Reduced the Year to better reckoning? — Nay
‘Twas only striking from the Calendar
Unborn To-morrow, and dead Yesterday.
Khayyám measured the length of the year as 365.24219858156 days.*
*Khayyam measured the length of the year as 365.24219858156 days. Two comments on this result. Firstly it shows an incredible confidence to attempt to give the result to this degree of accuracy. We know now that the length of the year is changing in the sixth decimal place over a person’s lifetime. Secondly it is outstandingly accurate. For comparison the length of the year at the end of the 19th century was 365.242196 days, while today it is 365.242190 days.MacTutor biography by J J O’Connor and E F Robertson.
*The information from the book “Aladdin’s Lamp” How Greek Science Came to Europe Through Islamic World” by John Freely