Ibn al-Haytham

Abū ‘Alī al-Haṣan ibn al-Haṣan ibn al-Haytham
Title	Ibn al-Haytham and Alhacen
Personal
Era	Islamic Golden Age
Region	Muslim scholar
Main interest(s)	Astronomy, Engineering, Mathematics, Optics, Physics, Science
Notable work(s)	Kitab al-Manazir (Book of Optics), Mizan al-Hikmah

Abū ‘Alī al-Haṣan ibn al-Haṣan ibn al-Haytham (965–1039) (Arabic: أبو علي الحسن بن الحسن بن الهيثم, Latinised: Alhacen or (deprecated) Alhazen), was a Muslim astronomer, engineer, mathematician, and physicist, who made significant contributions to the principles of optics, as well as motion, heliocentrism, analytical geometry, and integral calculus, and established the use of the experimental scientific method. He is sometimes called al-Basri (Arabic: البصري), after his birthplace Basra, Iraq, then part of the Buyid dynasty of Persia.[1] He is considered the "father of optics" for his empirical experiments on optics, including experiments with lenses, mirrors, refraction, and reflection, and for his proof of the intromission theory of light.

Ibn al-Haytham is also considered the pioneer of the modern scientific method. Rosanna Gorini writes:

"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."

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 tlie 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 also referred to Ibn al-Haytham as:

"The greatest Muslim physicist and student of optics of all times."

Among his other achievements, Ibn al-Haytham invented the camera obscura and pinhole camera, developed and proved the earliest general formula for integral calculus, laid the foundations for telescopic astronomy, and was the first Muslim astronomer to support a heliocentric model of the solar system.

The Alhazen crater on the Moon was named in his honour.

Life

He was born in Basra, Iraq, then part of the Buwayhid Shia Muslim dynasty of Persia,[2] and he probably died in Cairo, Egypt.[3]

Abū ‘Alī al-Hasan ibn al-Hasan ibn al-Haytham was one of the most eminent physicists, whose contributions to optics and the scientific method are outstanding. Known in the West as Alhacen or Alhazen, Ibn al-Haytham was born in 965 A. D. in Basrah, and was educated there and in Baghdad. 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 scores of important mathematical treatises. He later traveled to Spain and, during this period, he had ample time for his scientific pursuits, which included optics, mathematics, physics, medicine and development of scientific methods on each of which he has left several outstanding books.

He made a thorough examination of the passage of light through various media and discovered the laws of refraction. He also carried out the first experiments on the dispersion of light into its constituent colours. His book Kitab al-Manazir (Book of Optics) was translated into Latin in the Middle Ages, as also was his book dealing with the colours of sunset. He dealt at length with the theory of various physical phenomena such as shadows, eclipses, and the rainbow, and speculated on the physical nature of light. He is the first to describe accurately the various parts of the eye and give a scientific explanation of the process of vision. He also attempted to explain binocular vision and the apparent increase in size of the Sun and the Moon when near the horizon. He is known for the earliest use of the camera obscura. He contradicted Ptolemy's and Euclid's theory of vision that objects are seen by rays of light emanating from the eyes; according to him the rays originate in the object of vision and not in the eye. Through these extensive researches on optics, he has been considered as the father of modern optics.

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 catoptrics contain the important problem known as "Alhazen's problem". It comprises drawing lines from two points in the plane of a circle meeting at a point on the circumference and making equal angles with the normal at that point. This leads to an equation of the fourth degree.

In his book Mizan al-Hikmah, Ibn al-Haytham has discussed the density of the atmosphere and related it to altitude. He also studied atmospheric refraction. He discovered that the twilight only ceases or begins when the Sun is 19° below the horizon and attempted to measure the height of the atmosphere on that basis. He has also discussed the theories of attraction between masses, and it seems that he was aware of the magnitude of acceleration due to gravity.

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.

Ibn al-Haytham's work on optics is credited with contributing a new emphasis on experiment, drawing in part on the astronomical and optical work of Ptolemy. 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.

Alhacen is featured on the obverse of the Iraqi 10,000 dinars banknote issued in 2003. The asteroid 59239 Alhazen was also named in his honour. And Iran's largest laser research facility, located in the Atomic Energy Organization of Iran headquarters in Tehran is named after Alhacen as well.

Works

1572 C.E. Latin title page of Ibn al-Haytham's book

Alhacen was a pioneer in optics, engineering and astronomy. His contribution to mathematics and physics was also extensive. Alhacen taught that vision does not result from the emission of rays from the eye, and wrote on the refraction of light, especially on atmospheric refraction, for example, the cause of morning and evening twilight. He solved the problem of finding the point on a convex mirror at which a ray coming from one point is reflected to another point.

Alhacen's optical writings influenced many Western intellectuals such as Roger Bacon, John Pecham, Witelo, and Johannes Kepler.

Optics

His seven volume treatise on optics Kitab al-Manazir (Book of Optics) (written from 1015 to 1021) drastically transformed the ancient Greek understanding of vision. Such ancient Greeks as Euclid and Ptolemy believed that sight worked by the eye emitting some kind of rays. The second or "intromission" theory, supported by Aristotle had light entering the eye. Alhacen argued on the basis of common observations (the eye is dazzled or even injured if we look at a very bright light) and logical arguments (how could a ray proceeding from the eyes reach the distant stars the instant after we open our eye?) to maintain that we cannot see by rays emitted from the eye. Alhacen developed a highly successful theory which explained the process of vision by rays proceeding to the eye from each point on the object.

Optics was translated into Latin by an unknown scholar at the end of the twelfth or the beginning of the thirteenth century. It was printed by Friedrich Risner in 1572, with the title Opticae thesaurus: Alhazeni Arabis libri septem, nuncprimum editi; Eiusdem liber De Crepusculis et nubium ascensionibus [4]. Risner is also the author of the name variant "Alhazen", before him he was known in the west as Alhacen, which is correct transcription of the Arabic name. This work enjoyed a great reputation during the Middle Ages. Works by Alhacen on geometrical subjects were discovered in the Bibliothèque nationale in Paris in 1834 by E. A. Sedillot. Other manuscripts are preserved in the Bodleian Library at Oxford and in the library of Leiden.

In his work on optics, Alhacen described sight as the inference of distinct properties of two similar and dissimilar objects. The eye perceives the size, shape, transparency (color and light), position, and motion from cognitive distinction which is entirely different from perceiving by mere sensation the characteristics of the object. The faculty of the mind, for Alhacen, includes perceiving through judgement and inference of distinct properties of similar objects outline and structure. Alhacen continues this body of work by concluding that the discrimination performed by the faculty of judgment and inference is in addition to sensing the objects visible form and not by pure sensation alone. We recognize visible objects that we frequently see. Recognition of an object is not pure sensation because we do not recognize everything we see. Ultimately, recognition does not take place without remembering. Recognition is due to the inference because of our mental capacity to conclude what objects are. Alhacen uses our ability to recognize species and likening their characteristics to that of similar individuals to support recognition associated and processed by inference. Alhacen further concludes that we are processing visual stimuli in very short intervals which allows us to recognize and associate objects through inference but we do not need syllogism to recognize it. These premises are stored infinitely in our souls. Alhacen is also credited to have invented the pinhole camera.

R. S. Elliot wrote:

"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."

Astronomy

According to Giambattista della Porta, Alhacen was the first to explain the apparent increase in the size of the Moon and Sun when near the horizon, although Roger Bacon gives the credit of this discovery to Ptolemy.

Ibn al-Haytham was also the first Muslim astonomer to support a heliocentric model of the solar system. He wrote a scathing critique of Ptolemy's geocentric model:

"Ptolemy assumed an arrangement that cannot exist, and the fact that this arrangement produces in his imagination the motions that belong to the planets does not free him from the error he committed in his assumed arrangement, for the existing motions of the planets cannot be the result of an arrangement that is impossible to exist."

The foundations of telescopic astronomy can also be traced back to Ibn al-Haytham. His work was influential in the development of the modern telescope.

Mathematics

In mathematics, Ibn al-Haytham developed analytical geometry by establishing linkage between algebra and geometry. Ibn al-Haytham discovered a formula for adding the first 100 natural numbers, which was later often attributed to Carl Friedrich Gauss. Ibn al-Haytham had used a geometric proof to prove the formula. His attempted proof of the parallel postulate was also similar to the Lambert quadrilateral and Playfair's axiom in the 18th century.

His work on catoptrics contains the important problem known as "Alhazen's problem". It comprises drawing lines from two points in the plane of a circle meeting at a point on the circumference and making equal angles with the normal at that point. This leads to an equation of the fourth degree. This led Ibn al-Haytham to derive the earliest formula for the sum of the fourth powers, and using an early proof by mathematical induction, he developed a method for determining the general formula for the sum of any integral powers, which was fundamental to the development of integral calculus.

Y. M. Faruqi writes:

"In seventeenth century Europe the problems formulated by Ibn al-Haytham (965-1041) became known as “Alhazen’s problem”."

"Al-Haytham’s contributions to geometry and number theory went well beyond the Archimedean tradition. Al-Haytham also worked on analytical geometry and the beginnings of the link between algebra and geometry. Subsequently, this work led in pure mathematics to the harmonious fusion of algebra and geometry that was epitomised by Descartes in geometric analysis and by Newton in the calculus. Al-Haytham was a scientist who made major contributions to the fields of mathematics, physics and astronomy during the latter half of the tenth century."

Motion

Ibn al-Haytham studied the mechanics of motion of a body and maintained that a body moves perpetually unless an external force stops it or changes its direction of motion. This is the law of inertia later stated by Galileo Galilei and now known as Newton's first law of motion.

See also

• Hockney-Falco thesis
• Optics
• Scientific method

References

• Lindberg, David C. Theories of Vision from al-Kindi to Kepler. Chicago: Univ. of Chicago Press, 1976. ISBN 0-226-48234-0
• Sabra, A. I., "The astronomical origin of Ibn al-Haytham’s concept of experiment," pp. 133-136 in Actes du XIIe congrès international d’histoire des sciences, vol. 3. Paris: Albert Blanchard, 1971; reprinted in A. I. Sabra, Optics, Astronomy and Logic: Studies in Arabic Science and Philosophy. Collected Studies Series, 444. Aldershot: Variorum, 1994 ISBN 0-86078-435-5
• Omar, Saleh Beshara. Ibn al-Haytham's Optics: A Study of the Origins of Experimental Science. Minneapolis: Bibliotheca Islamica, 1977. ISBN 0-88297-015-1

Further reading

Primary Sources

• Langermann, Y. Tzvi, ed. and trans. Ibn al-Haytham's On the Configuration of the World, Harvard Dissertations in the History of Science. New York: Garland, 1990. ISBN 0824000412

• Sabra, A. I., ed. The Optics of Ibn al-Haytham, Books I-II-III: On Direct Vision. The Arabic text, edited and with Introduction, Arabic-Latin Glossaries and Concordance Tables. Kuwait: National Council for Culture, Arts and Letters, 1983.

• Sabra, A. I., ed. The Optics of Ibn al-Haytham. Edition of the Arabic Text of Books IV-V: On Reflection and Images Seen by Reflection. 2 vols., Kuwait: The National Council for Culture, Arts and Letters, 2002.

• Sabra, A. I., trans. The Optics of Ibn al-Haytham. Books I-II-III: On Direct Vision. English Translation and Commentary. 2 vols. Studies of the Warburg Institute, vol. 40. London: The Warburg Institute, University of London, 1989. ISBN 0-85481-072-2

• Smith, A. Mark, ed. and trans. Alhacen's Theory of Visual Perception: A Critical Edition, with English Translation and Commentary, of the First Three Books of Alhacen's De aspectibus, the Medieval Latin Version of Ibn al-Haytham's Kitāb al-Manāzir, 2 vols. Transactions of the American Philosophical Society, 91.4-5, Philadelphia, 2001. ISBN 0-87169-914-1

• Smith, A. Mark, ed. and trans. Alhacen on the Principles of Reflection: A Critical Edition, with English Translation and Commentary, of Books 4 and 5 of Alhacen's De Aspectibus, the Medieval Latin version of Ibn-al-Haytham's Kitāb al-Manāzir, 2 vols. Transactions of the American Philosophical Society, 96.2-3, Philadelphia, 2006. ISBN 0-87169-962-1

Secondary Literature

• Falco, Charles M. "Ibn al-Haytham and the Origins of Modern Image Analysis" presented at a plenary session at the International Conference on Information Sciences, Signal Processing and its Applications, 12–15 February 2007. Sharjah, United Arab Emirates (U.A.E.).[5] In this lecture, Falco speculates that Ibn al-Haytham may have influenced the use of optical aids in Renaissance art. (See Hockney-Falco thesis.}

• Omar, Saleh Beshara. Ibn al-Haytham and Greek optics: a comparative study in scientific methodology. PhD Dissertation, Univ. of Chicago, Dept. of Near Eastern Languages and Civilizations, June 1975.

External links

• O'Connor, John J.; Robertson, Edmund F., "Abu Ali al-Hasan ibn al-Haytham", MacTutor History of Mathematics Archive, University of St Andrews
• Weisstein, Eric Wolfgang (ed.). "Alhazen (ca. 965-1039)". ScienceWorld.
• Ibn al-Haitham on two Iraqi banknotes
• http://www.daviddarling.info/encyclopedia/A/Alhazen.html
• Alhazen Master of Optics
• The Miracle of Light - a UNESCO article on Ibn Haitham
• Roshdi Rashed. "A Polymath in the 10th Century", Science, 297 (2002): 773

See also

• List of Arab scientists
• List of Iranian scientists
• List of Iraqis