Ibn al-Haytham

Abū ʿAlī al-Ḥasan ibn al-Ḥasan ibn al-Haytham (Alhacen or Alhazen) (965 – 1039), was an Arab-Iranian Muslim polymath who made significant contributions to the principles of optics, as well as to anatomy, astronomy, engineering, mathematics, medicine, ophthalmology, philosophy, physics, psychology, theology, visual perception, and to science in general with his introduction of the scientific method. He is sometimes called al-Basri after his birthplace in the city of Basra in Iraq (Mesopotamia), then ruled by the Buyid dynasty of Persia.

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 studied 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 of 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.

Among his other achievements, Ibn al-Haytham described the pinhole camera and invented the camera obscura (a precursor to the modern camera), discovered Fermat's principle of least time and the law of inertia (known as Newton's first law of motion), discovered the concept of momentum (part of Newton's second law of motion), described the attraction between masses and was aware of the magnitude of acceleration due to gravity at a distance, discovered that the heavenly bodies were accountable to the laws of physics, presented the earliest critique and reform of the Ptolemaic model, first stated Wilson's theorem in number theory, pioneered analytic geometry and the first theorems on non-Euclidean geometry, formulated and solved Alhazen's problem geometrically, developed and proved the earliest general formula for infinitesimal and integral calculus using mathematical induction, and in his optical research laid the foundations for the later development of telescopic astronomy, as well as for the microscope and the use of optical aids in Renaissance art.

One account of his career had him summoned to Egypt by the mercurial caliph Hakim to regulate the flooding of the Nile. After his field work made him aware of the impracticality of this scheme, and fearing the caliph's anger, he feigned madness. He was kept under house arrest until Hakim's death in 1021. It was guring this time that he wrote his influential Book of Optics and scores of other important treatises on physics and mathematics. He later traveled to Spain and, during this period, he had ample time for his scientific pursuits, which included optics, mathematics, physics, medicine, and the development of scientific methods — on all of which he has left several outstanding books.

A reader of this Blog, who is the first author in the English language of this scholar, posted an entry. This is a link to that website.