Ibn al-Haytham: the Father of Modern Optics
“The duty of the man who investigates the writings of scientists, if learning the truth is his goal, is to make himself an enemy of all that he reads, and attack it from every side. He should also suspect himself as he performs his critical examination of it, so that he may avoid falling into either prejudice or leniency.” Ibn Al-HaythamBy: Ahmed Abu Sultan/Arab America Contributing Writer Ḥasan Ibn al-Haytham was an Arab mathematician, astronomer, and physicist. Referred to as the father of modern optics, he made significant contributions to the principles of optics and visual perception in particular. His most influential work is titled “Book of Optics” during 1011–1021, which survived in a Latin edition. A polymath, he also wrote on philosophy, theology, and medicine. Ibn al-Haytham was the first to explain that vision occurs when light reflects from an object and then passes to one’s eyes. He was also the first to demonstrate that vision occurs in the brain, rather than in the eyes. He was an early pioneer in the scientific method five centuries before Renaissance scientists.
Journey
Ibn al-Haytham was born in 965 AD to an Arab family in Basra, Iraq, which was at the time part of the Buyid emirate. He held a position with the title vizier in his native Basra and made a name for himself for his knowledge of applied mathematics. As he claimed to be able to regulate the flooding of the Nile, he was invited to by Fatimid Caliph al-Hakim to realize a hydraulic project at Aswan. However, Ibn al-Haytham was forced to concede the impracticability of his project. Upon his return to Cairo, he was given an administrative post. After he proved unable to fulfill this task as well, he contracted the ire of the caliph Al-Hakim bi-Amr Allah and is said to have been forced into hiding until the caliph died in 1021, after which his confiscated possessions were returned to him. Legend has it that Alhazen feigned madness and was kept under house arrest during this period. During this time, he wrote his influential Book of Optics. Alhazen continued to live in Cairo, in the neighborhood of the famous University of al-Azhar and lived from the proceeds of his literary production until he died in 1040 AD.
Alhazen’s most famous work is his seven-volume treatise on optics. The Book of Optics was translated into Latin by an unknown scholar at the end of the 12th century or the beginning of the 13th century. It was printed by Friedrich Risner in 1572. This work enjoyed a great reputation during the Middle Ages. Works by Alhazen on geometric subjects were discovered in the Bibliothèque Nationale in Paris in 1834 by E.A. Sedillot. In all, A. Mark Smith has accounted for 18 full or near-complete manuscripts, and five fragments, which are preserved in 14 locations, including one in the Bodleian Library at Oxford, and one in the library of Bruges.
Alhazen’s most famous work is his seven-volume treatise on optics. The Book of Optics was translated into Latin by an unknown scholar at the end of the 12th century or the beginning of the 13th century. It was printed by Friedrich Risner in 1572. This work enjoyed a great reputation during the Middle Ages. Works by Alhazen on geometric subjects were discovered in the Bibliothèque Nationale in Paris in 1834 by E.A. Sedillot. In all, A. Mark Smith has accounted for 18 full or near-complete manuscripts, and five fragments, which are preserved in 14 locations, including one in the Bodleian Library at Oxford, and one in the library of Bruges.
“I constantly sought knowledge and truth, and it became my belief that for gaining access to the effulgence and closeness to God, there is no better way than that of searching for truth and knowledge.” Ibn Al-HaythamContributions to Science
Two major theories on vision prevailed in classical antiquity. The first theory, the emission theory, was supported by such thinkers as Euclid and Ptolemy, who believed that sight worked by the eye emitting rays of light. The second theory, the intromission theory supported by Aristotle and his followers, had physical forms entering the eye from an object. Previous Islamic writers had argued essentially on Euclidean, Galenist, or Aristotelian lines. The strongest influence on the Book of Optics was from Ptolemy’s Optics, while the description of the anatomy and physiology of the eye was based on Galen’s account. Ibn Al-Haytham’s achievement was to come up with a theory that successfully combined parts of the mathematical ray arguments of Euclid, the medical tradition of Galen, and the intromission theories of Aristotle. This however left him with the problem of explaining how a coherent image was formed from many independent sources of radiation; in particular, every point of an object would send rays to every point on the eye. What Ibn Al-Haytham needed was for each point on an object to correspond to one point only on the eye.
He attempted to resolve this by asserting that the eye would only perceive perpendicular rays from the object for any one point on the eye, only the ray that reached it directly, without being refracted by any other part of the eye, would be perceived. He argued, using a physical analogy, that perpendicular rays were stronger than oblique rays: in the same way that a ball thrown directly at a board might break the board, whereas a ball thrown obliquely at the board would glance off, perpendicular rays were stronger than refracted rays, and it was only perpendicular rays which were perceived by the eye. As there was only one perpendicular ray that would enter the eye at any one point, and all these rays would converge on the center of the eye in a cone, this allowed him to resolve the problem of each point on an object sending many rays to the eye; if only the perpendicular ray mattered, then he had a one-to-one correspondence and the confusion could be resolved.
“Whosoever seeks the truth will not proceed by studying the writings of his predecessors and by simply accepting his own good opinion of them. Whosoever studies works of science must, if he wants to find the truth, transform himself into a critic of everything he reads. He must examine tests and explanations with the greatest precision and question them from all angles and aspects.” Ibn Al-HaythamLegacy
Alhazen made significant contributions to optics, number theory, geometry, astronomy, and natural philosophy. Ibn Al-Haytham’s work on optics is credited with contributing a new emphasis on experiment. His main work, Book of Optics, was known in the Muslim world mainly, but not exclusively, through the thirteenth-century commentary. In al-Andalus, it was used by the eleventh-century prince of the Banu Hud dynasty of Zaragossa and author of an important mathematical text, al-Mu’taman ibn Hūd. A Latin translation of the Kitab al-Manazir was made probably in the late twelfth or early thirteenth century. This translation was read by and greatly influenced several scholars in Christian Europe including Roger Bacon, Robert Grosseteste, Witelo, Giambattista Della Porta, Leonardo Da Vinci, Galileo Galilei, Christiaan Huygens, René Descartes, and Johannes Kepler. His research in catoptrics centered on spherical and parabolic mirrors and spherical aberration.
He observed 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 problem known as Ibn Al-Haytham Meanwhile in the Islamic world. Alhazen wrote as many as 200 books, although only 55 have survived. Some of his treatises on optics survived only through Latin translation. During the Middle Ages, his books on cosmology were translated into Latin, Hebrew, and other languages.
The impact crater Ibn Al-Haytham on the Moon is named in his honor, as was the asteroid 59239 Alhazen. In honor of Ibn Al-Haytham, the Aga Khan University in Pakistan named its Ophthalmology endowed chair as “The Ibn-e-Haitham Associate Professor and Chief of Ophthalmology”. Ibn al-Haytham is featured on the obverse of the Iraqi 10,000-dinar banknote issued in 2003, and on 10-dinar notes from 1982.
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