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Abū ʿAlī al-Ḥasan ibn al-Ḥasan ibn al-Haytham

Abū ʿAlī al-Ḥasan ibn al-Ḥasan ibn al-Haytham frequently referred to as Ibn al-Haytham and sometimes as al-Basri was an Arab scientist, polymath, mathematician, astronomer and philosopher who made significant contributions to the principles of optics, astronomy, mathematics, meteorology, visual perception and the scientific method from the ‘Golden Age’ of Muslim civilization. He was also nicknamed Ptolemaeus Secundus (“Ptolemy the Second”) or “The Physicist” in medieval Europe. Ibn al-Haytham also wrote insightful commentaries on works by Aristotle, Ptolemy, and the Greek mathematician Euclid. He has been described as the father of modern optics, ophthalmology, experimental physics and scientific methodology. Ibn al-Haytham was born in 965 in Basra, to an Arab family. he lived mainly in Cairo, Egypt, and died there at age 74.

Ibn al-Haytham was educated in Basra which during the Islamic Golden Age, Basra was a “key beginning of learning” and in Baghdad. Ibn al-Haytham’s most important work is Kitāb al-manāẓir (“Optics”). Although it shows some influence from Ptolemy’s 2nd century AD Optics, it contains the correct model of vision: the passive reception by the eyes of light rays reflected from objects, not an active emanation of light rays from the eyes. It combines experiment with mathematical reasoning, even if it is generally used for validation rather than discovery. The work contains a complete formulation of the laws of reflection and a detailed investigation of refraction, including experiments involving angles of incidence and deviation. In his Ḥall shukūk fī Kitāb Uqlīdis (“Solution of the Difficulties of Euclid’s Elements”) Ibn al-Haytham investigated particular cases of Euclid’s theorems, offered alternative constructions, and replaced some indirect proofs with direct proofs. He made an extended study of parallel lines in Sharḥ muṣādarāt Kitāb Uqlīdis (“Commentary on the Premises of Euclid’s Elements”) and based his treatment of parallels on equidistant lines rather than Euclid’s definition of lines that never meet.