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.
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 Newton’s first law of motion, described the attraction between masses and was aware of the magnitude of acceleration due to gravity, 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, 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 the microscope and the use of optical aids in Renaissance art.
Biography
Abu ‘Ali al-Hasan ibn al-Hasan ibn al-Haytham was born in the Arab city of Basra, Iraq (Mesopotamia), then part of the Shia Muslim Buyid dynasty of Persia, and he probably died in Cairo, Egypt. Known in the West as Alhacen or Alhazen, Ibn al-Haytham was born in 965 in Basra, and was educated there and in Baghdad. He was a supporter of the Ash’ari school of Islamic theology.
One account of his career has 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. During this time, 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 each of which he has left several outstanding books.
Legacy
Ibn al-Haytham was one of the most eminent physicists, whose development of optics and the scientific method are outstanding. Ibn al-Haytham’s work on optics is credited with contributing a new emphasis on experiment. His influence on physical sciences in general, and optics in particular, has been held in high esteem and, in fact, it ushered in a new era in optical research, both in theory and practice. The scientific method is considered to be so fundamental to modern science that some – especially philosophers of science and practicing scientists – consider earlier inquiries into nature to be pre-scientific. Due to its importance in the history of science, some have considered his development of the scientific method to be the most important scientific development of the second millenium.
Rosanna Gorini wrote the following on Ibn al-Haytham’s development of the scientific method:
“According to the majority of the historians al-Haytham was the pioneer of the modern scientific method. With his book he changed the meaning of the term optics and established experiments as the norm of proof in the field. His investigations are based not on abstract theories, but on experimental evidences and his experiments were systematic and repeatable.”
Roshdi Rashed wrote the following on Ibn al-Haytham:
“His work on optics, which includes a theory of vision and a theory of light, is considered by many to be his most important contribution, setting the scene for developments well into the 17th century. His contributions to geometry and number theory go well beyond the archimedean tradition. And by promoting the use of experiments in scientific research, al-Haytham played an important part in setting the scene for modern science.”
Nobel Prize winning physicist Abdus Salam wrote:
“Ibn-al-Haitham (Alhazen, 965-1039 CE) was one of the greatest physicists of all time. He made experimental contributions of the highest order in optics. He enunciated that a ray of light, in passing through a medium, takes the path which is the easier and ‘quicker’. In this he was anticipating Fermat’s Principle of Least Time by many centuries. He enunciated the law of inertia, later to become Newton’s first law of motion. Part V of Roger Bacon’s “Opus Majus” is practically an annotation to Ibn al Haitham’s Optics.”
George Sarton, the “father of the history of science”, wrote in the Introduction to the History of Science:
“[Ibn al-Haytham] was not only the greatest Muslim physicist, but by all means the greatest of mediaeval times.”
“Ibn Haytham’s writings reveal his fine development of the experimental faculty. His tables of corresponding angles of incidence and refraction of light passing from one medium to another show how closely he had approached discovering the law of constancy of ratio of sines, later attributed to Snell. He accounted correctly for twilight as due to atmospheric refraction, estimating the sun’s depression to be 19 degrees below the horizon, at the commencement of the phenomenon in the mornings or at its termination in the evenings.”
Robert S. Elliot wrote the following on the Book of Optics:
“Alhazen was one of the ablest students of optics of all times and published a seven-volume treatise on this subject which had great celebrity throughout the medieval period and strongly influenced Western thought, notably that of Roger Bacon and Kepler. This treatise discussed concave and convex mirrors in both cylindrical and spherical geometries, anticipated Fermat’s law of least time, and considered refraction and the magnifying power of lenses. It contained a remarkably lucid description of the optical system of the eye, which study led Alhazen to the belief that light consists of rays which originate in the object seen, and not in the eye, a view contrary to that of Euclid and Ptolemy.”
The Biographical Dictionary of Scientists wrote the following on Ibn al-Haytham::
“He was probably the greatest scientist of the Middle Ages and his work remained unsurpassed for nearly 600 years until the time of Johannes Kepler.”
The Latin translation of his main work, Kitab al-Manazir, exerted a great influence upon Western science e.g. on the work of Roger Bacon, who cites him by name, and Kepler. It brought about a great progress in experimental methods. His research in catoptrics centered on spherical and parabolic mirrors and spherical aberration. He made the important observation that the ratio between the angle of incidence and refraction does not remain constant and investigated the magnifying power of a lens. His work on catoptrics also contains the important problem known as Alhazen’s problem.
The list of his books runs to 200 or so, yet very few of the books have survived. Even his monumental treatise on optics survived only through its Latin translation. During the Middle Ages his books on cosmology were translated into Latin, Hebrew and other languages.
The Alhazen crater on the Moon was named in his honour. Ibn al-Haytham is also featured on the obverse of the Iraqi 10,000 dinars banknote issued in 2003. The asteroid “59239 Alhazen” was also named in his honour, while Iran’s largest laser research facility, located in the Atomic Energy Organization of Iran headquarters in Tehran, is named after him as well.
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