A scientist from Damascus who excelled in mathematics, geometry,and astronomy. Abu al-Hassan Ala'-Din Ali Ibn Ibrahim Ibn Mohammedal-Ansari al-Muakit, known as Ibn ash-Shatir was born and died inDamascus. He was surnamed al-Mutaem because he used to inlay ivorywhen a child(1).

His father died when he was still a child and was taken in charge byhis grandfather, and then by the son of his father’s uncle and his aunt’shusband who taught him how to inlay ivory. He then accumulated animportant sum of money, which enabled him to visit numerous countriessuch as Egypt where he studied astronomy and mathematics in Cairo andAlexandria.

He spent the majority of his life in his position as timing officer andchief Muezzin in the Umayyad Mosque in Damascus(2).

Scientific Contributions

He had contributed in the invention of many instruments such as theastrolabe, his rectifications of sundials. He also came up with manyvaluable astronomical theories. His books on the astrolabe constituted areference for many centuries in ash-Sham and Egypt, and throughout theOthoman Empire and in other Islamic countries as they were essential indefining time in the Islamic world(3).

He also succeeded in accurately measuring the angle of deviation of the circle of constellations, as he estimated it at 23° 31 minutes. In this context, Sarton Says: “Ibn ash-Shatir was a scientist of a great genius. Hestudied the movement of celestial bodies in a very precise way, anddemonstrated that the angle of deviation of the circle of constellationswas 23° 31 min in 1365, whereas the exact value that has been calculatedby 20th century scientists by means of computers is 23° 31 minutes 19.8seconds(1).

Ibn as-Shatir proved also, thanks to his astronomical observations,the deficiency of Ptolemaic theory. He said that the earth evolves aroundthe sun, and the moon evolves around the earth, and this is whatCopernicus discovered many centuries later(2).

Major Works

Ash-Shatir has compiled many books, the majority of which are stilllost. Among his books, mentioned by Zarkali in his book “al aâlm”.

-“Zij al-Jadid” (The New Astronomical Table). This book waswritten at the request of the Othoman Caliph Murad I who reignedover ass-Sham between 1360 and 1398. It contains astronomicalmodels based on experiments, observation, and deduction(3).

-“Idah al-Moghib fi al-Amal bi ar-Robi al-Mojib” ;
-“Urjuza fi al-Kawakib” (Poem on Planets);
-“Rissala fi al-Ostorlab” (Treatise on Astrolabe);
-“Mukhtasar al amal bi al Usturlab” (Summary of AstrolabeUses);
-“An-Nafa al-Aam fi el-Amal bi ar-Robi’ at-Tam” ;
-“Rissalat Nuzhat as-Samis fi al-Amal bi ar-Rrobi al-Jamia” ;

-“Rissalat Kifayat al-Qunua fi al-Amal bi ar-Robi al-Maqtua.”