Abu ʿAli al-Ḥasan ibn al-Ḥasan ibn al-Haytham (Arabic: أبو علي الحسن بن الحسن بن الهيثم, Latinized: Alhacen or (deprecated) Alhazen) (965 – 1039), was a Muslim polymath who made significant contributions to the principles of optics, as well as anatomy, astronomy, engineering, mathematics, medicine, ophthalmology, philosophy, physics, psychology, visual perception, and science in general with his pioneering development of the scientific method. He is sometimes called al-Basri (Arabic: البصري), after his birthplace in the city of Basra in Iraq (Mesopotamia), then ruled by the Buyid dynasty of Persia. His ethnic background is unclear; some scholars consider him Arab, and some consider him Persian. He was a supporter of the Ash’ari school of Islamic theology.
Ibn al-Haytham is regarded as the father of optics, for his influential Book of Optics, which correctly explained and proved the modern intromission theory of vision, and for his experiments on optics, including experiments on lenses, mirrors, refraction, reflection, and the dispersion of light into its constituent colours. He also explained binocular vision and the moon illusion, speculated on the finite speed, rectilinear propagation and electromagnetic aspects of light, and argued that rays of light are streams of energy particles travelling in straight lines. Due to his quantitative, empirical and experimental approach to physics and science, he is considered the pioneer of the modern scientific method and experimental physics, and some have described him as the “first scientist” for this reason. He is also considered by some to be the founder of psychophysics and experimental psychology, for his experimental approach to the psychology of visual perception, and a pioneer of the philosophical field of phenomenology. His Book of Optics has been ranked alongside Isaac Newton’s Philosophiae Naturalis Principia Mathematica as one of the most influential books ever written in the history of physics.
