20. Ibn Al-Haitham
(354-430H/965-1038AD)

Ibn Al-Haitham is one of the most outstanding Arab scholars. He excelled in and contributed to the fields of optics, mathematics, natural science, medicine and philosophy.

His full name is Abu Ali Hasan ibn Al-Haitham, known by Europeans as ‘Alhazen’. He was born in Basrah, where he received his education. The Fatimid Caliph Al Hakim bi Amri Allah heard of Ibn Al-Haitham’s method to regulate the annual Nile flood. He invited him to Egypt and asked him to regulate the Nile’s water flow in order to prevent floods. Ibn Al-Haitham failed to do so and simulated foolishness and remained on this state until the caliph died, then  resumed work on copying the books of predecessors in the fields of mathematics and natural sciences. He also started writing his own books on different subjects.

Ibn Al-Haitham’s Contribution in Optics

European historians acknowledge Ibn Al-Haitham’s contribution in the development of optics. In ‘The Heritage of Islam’, Arnold says “the field of optics reached its peak with Ibn Al-Haitham"(120). Sarton says “Ibn Al-Haitham was the best scientist to have existed in the Islamic world in the Middle Ages in the field of natural science. He was one of the few most outstanding figures in optics in all times. He was also an astronomer, a mathematician and a doctor"(121). The Encyclopaedia Britannica considered him as the leading figure in optics after Ptolemy(122).

Ibn Al-Haitham was the first to conclude the magnifying property of a lens. He was also the first to describe accurately the various parts of the eye and gave them names that Western scientists adopted and translated into their languages. These terms are still accepted today. Among these terms are ‘Retina’, ‘Cornea’, ‘Humour Viteous’ and ‘Humour Aqueous’. His treatises on magnifying lens laid the ground for their use in the correction of eye dysfunctions(123).

Ibn Al-Haitham reached the conclusion that vision originates from rays sent by an object to the eye. These rays are reflected on the retina and transmitted to the brain through the optic nerve, constituting the image of the object. Through this conclusion, he contradicted Ptolemy’s and Euclid’s theory of vision that the eye sends out visual rays to the object of vision. Ibn Al-Haitham also did researches on light, colors, and the reflections of light in some experiments on the measurement of angles of incidence and refraction(124). Some researchers consider him as the father of optics.

Ibn Al-Haitham’s Contributions in Mathematics

Ibn Al-Haitham was a great mathematician. He used geometry, equations and algebra to solve astronomic questions. He also solved cubic equations and accurately calculated the rules of the surface of balls, pyramids, leaning discs, round sectors, and round pieces(125).

Ibn Al-Haitham’s Contributions in Astronomy

Ibn Al-Haitham was interested in astronomy and wrote several books in this field. He also made a number of observations. Among his important contributions was the design of a new method to determine the pole’s altitude. He elaborated a theory on the motion of planets, which continues bear influence up to now. A table that was made in Germany in 1428, showing the planets motion according to Ibn Al-Haitham’s theory, is still exposed in Austria. Ibn Al-Haitham discovered that all celestial bodies, including stationary stars, are self-luminous and radiate their light, except for the moon, which receives light from the sun(126).

Major works

Ibn Al-Haitham left a rich scientific heritage in various fields. Among his works :

-"Kitab al-Manadhir": a treatise on optics comprising research on light, the eye's anatomy and vision. This book created a revolution in optics and influenced Western scientists such as Bacon and Kepler. It remained a reference for several centuries. It was translated into Latin several times in the Middle Ages. The book contains seven essays, the first and third of which were revised and published in a book by Abdul Hamid Sabrah in 1983 in Kuwait. Dr. Rochdi Rashid annotated the seventh article in his book "Geometry and Optics in the 4th  century of the Hegira", published in Beirut in 1996. Complete handwritten copies of the book or of some of its articles still exist in several libraries, especially in Istanbul, Turkey.

- "Hal Shokouk Euclid’s";

- "Makalat al- Shokouk ala Batlimus";     

- "Kitab Sharh Oussoul Euclid’s fi al-Handass wa al-Adad";

- "Kitab al-Jamia fi Oussoul al-Hissab";

- "Kitab fi Tahlil al Massaïl Al-Handassia."

It is worth mentioning that Ibn Al-Haitham wrote 80 books and treatises in astronomy, dealing with the motion of planets, the moon, celestial bodies and their dimensions.

Ibn Al-Haitham’s works that were translated into Latin exerted a great influence on western scientists, such as Kepler and Francis Bacon. According to Mustapha Nadhif, Ibn Al-Haitham contributed in the development of the experimental methodology based on observation, experimentation and investigation(127) before Francis Bacon. In "The Influence of Arabs on Western Civilization", Abbas Mahmud Al-Akkad says that the translations of Ibn Al-Haitham’s books on optics were used as references by all the European scientists who came after him.