Al-Farisi, Kamal al-Din Hasan ibn Ali ibn Hasan
Al-Farisi felt “perplexity” when he found several inconsistencies and errors in the classical works about optics . His teacher then managed to obtain a manuscript copy of the Kitab al-Manazir from Ibn al-Haytham, which was brought in “from a very distant land” (probably Egypt). Al-Farisi was greatly impressed by this work and decided to write a detailed commentary on it. He discussed it in great detail and completed it by adding appendices with other optical writings. Al-Farisi also included corrections to these texts, aptly calling the resulting work Tanqih al-Manazir (Revision of the [Kitab] al-Manazir) .
In one of al-Farisi’s comments in the Tanqih, he described how an object is seen in a certain color under sunlight, but in a different color under moonlight, and yet in another color in the light of fire. From this, al-Farisi concluded that colors are not really present in objects, but depend on illumination . The role of incident light had therefore been changed from being a mere catalyst for color vision as in the ancient Greek theories to being as prominent as in modern color theory .
Together with his teacher Qutb al-Din al-Shirazi, al-Farisi tried to find explanations why the famous experiment of Ptolemy, with a spinning top (or mill stone) having sectors painted in different colors, led to new colors .
Regarding the colors of the rainbow, Ibn al-Haytham had supported the Aristotelian idea that these were due to a mixture of light and darkness. Al-Farisi rejected this concept. He argued that if it was true, then the colors of the rainbow would be ordered from bright to dark. Also, the secondary rainbow would then have the same color order. Both are not supported by observation .
But al-Farisi would become most famous for his experimental study of the formation of rainbow colors. Inspired by Ibn Sina’s work and by Ibn al-Haytham’s Kitab al-Manazir and the latter’s treatise on the burning glass sphere, he filled a glass sphere with water and considered this as a model for a droplet of rain water in the atmosphere. He then studied the resulting reflection and refraction of light in a dark room (see Fig. 1). This led him to the first correct explanation of the colors of the rainbow, which he described in the Tanqih. Interestingly in Germany, at approximately the same time also Theodoric of Freiburg, equally inspired by the Kitab al-Manazir, carried out the same experiment and formulated the same conclusions.
It was recently discovered that in his Tanqih, al-Farisi included the text of al-Tusi on color ordering, in which five paths were proposed to go from white to black . In this way, this text would become available to many later generations. Al-Farisi also sought for an explanation of the different orderings of the colors in the primary and secondary rainbow. His dark room experiments let him conclude that the various colors of the rainbow were produced by a superposition of different images as projected after reflections and refraction in the sphere . Thereby, the colors became a function of the positions and luminous intensities of the composing images .
The Tanqih al-Manazir would become widely spread in the Muslim world, where it was used in academic classrooms, and would be commented upon until the sixteenth century. Therefore, in the Muslim world, this would be the main textbook on optics for more than three centuries. Since it would never be translated into any Western language, its influence on European science would remain marginal at best.
- 1.Kheirandesh, E.: Mathematical sciences through Persian sources: the Puzzles of Tusi’s optical works. In: Pourjavady, N., Vesel, Z. (eds.) Sciences, techniques et instruments dans le monde Iranien (Xe – XIXe siècle). Presses universitaires d’Iran and Institut Français de recherches en Iran, Téhéran (2004)Google Scholar
- 2.Kamal al-Din al-Farisi: Tanqih al-Manazir. Deccan, Hyderabad (1928). Two volumesGoogle Scholar
- 3.Gätje, H.: Zur Farbenlehre in der muslimischen Philosophie. Der Islam 43, 280–301 (1967)Google Scholar
- 5.Vernet, J.: Mathematics, astronomy, optics. In: Schacht, J., Bosworth, C.E. (eds.) The Legacy of Islam, p. 483. Clarendon, Oxford (1974)Google Scholar
- 6.van Campen, M.: De regenboog bij de Arabieren. University of Utrecht, Utrecht (1988). MSc Thesis, 95Google Scholar
- 7.Kirchner, E.: Origin and spreading of Tusi’s ideas on color ordering. Paper presented at the twelfth Congress of the International Colour Association (AIC), Newcastle, 8–12 July 2013. Conference proceedings, pp. 1197–1200Google Scholar
- 8.Rashed, R.: Kamal al Din. In: Gillespie, C.C. (ed.) Dictionary of Scientific Bibliography, pp. 212–219. Scribner’s sons, New York (1970)Google Scholar
- 9.Rashed, R.: Geometrical optics. In: Rashed, R. (ed.) Encyclopedia of the History of Arabic Science, vol. 2, pp. 643–671. Routledge, London (1996)Google Scholar