Al-Tusi, Nasir al-Din
Muhammad ibn Muhammad ibn Hasan al-Tusi, usually known as Nasir al-Din al-Tusi, was born in Tus (Iran) and later worked in Maragha (Azerbaijani) and Baghdad (Iraq). His influence reaches into many fields . His work on reforming Ptolemaic theoretical astronomy would be crucial for later astronomers, including Copernicus. In mathematics he published landmark editions of the works of Euclid and Archimedes and developed trigonometry as a discipline separated from astronomy. He wrote several works on optics . For Shiite theology, al-Tusi wrote an important work on ethics, and he also authored the first systematic treatment of rationalist theology in 12 imam Shiism, a work still central in Shiite theological education.
Al-Tusi was born in a Twelver Shi’a family. Under patrons at Ismaili courts, he became a famous mathematician. When in 1256 under Mongol rule, Hulagu destroyed the Abbasid Empire, al-Tusi had taken refuge at the last Ismaili stronghold located on the mount of Alamut. After the Mongols destroyed this mountain fortress, Hulagu personally saved al-Tusi’s life since the ruler’s interest in astrology made him respect al-Tusi’s astronomical knowledge. Al-Tusi persuaded Hulagu to support building the first full-scale astronomical observatory in the world at Maragha. With al-Tusi as director, it would collect a mass of observation data during about 50 years, and it would inspire later observatories in Samarkand and India and possibly even Tycho Brahe’s observatory in Denmark.
Regarding the production of colors from black and white there are numerous paths, from which one gradually walks from white to black. The path through yellow belongs there: First by the mixing of dense and fire, both in small amount, the straw-yellow is produced, then the lemon-yellow, then the saffron-yellow, then the orange-yellow, then the grenade-yellow, then in it the tendency towards black increases, according to the increase in the number of dense particles and the decrease of fire, until it becomes black.
Another path goes through red. First it becomes rosy, then like evening-red, then blood-colored, then purple, then violet, violet-colored. […]
This all occurs according to the differences of particles in transparency, opacity (density), light and darkness. Now and then one sees a color together with another, and a different color is produced, such as green from yellow and blue, verdigris from green and white. There are infinitely many of such arrangements, and some are often found in small particles of plants and animals. Anyone who observes them is surprised by their number. [3, 4]
Thus, while Ibn Sina had specified three paths from white to black, al-Tusi described five of such paths. They go via yellow, red, green, blue, and gray, as illustrated in the Figure above. Remarkably Forsius in 1611 also described five different tint/shade scales from white to black. This may all be compared to the German monk Theophilus (ca. 1120), who described how to produce up to 12 grades in a tint/shade scale. The text of al-Tusi shows that he must have considered color space to be two dimensional. Interestingly, at approximately the same time in Latin Europe, Grosseteste had argued on theoretical grounds that color space is three dimensional [5, 6].
Also in his work on minerals and gem stones, the Tansukhname-yi Ilkhani (the book on precious stones for the Ilkhan [i.e., for Mongol ruler Hulagu]), al-Tusi describes a color theory [3, 7]. Written primarily by Nishaburi, and largely copied by al-Tusi and Kashani, these texts are the first to describe a limited hue scale. It describes that by mixing blue and yellow in different proportions, colors are produced that change gradually from blue, via green, to yellow. This description represents a great step forward from the Aristotelian point of view that stated that green is one of the colors painters cannot produce. Although several scholars before Nishaburi and al-Tusi had mentioned that green can be produced by mixing blue and yellow, no earlier scholar had described that depending on the mixing ratios, different hues of green are produced .
The common opinion among scholars since Aristotle had been that by mixing black and white all colors can be produced. But following Nishaburi, Tusi wrote that “if white color and black color are mixed with each other, an incense-grey color will result.” This had been stated only twice before in history and in much less clear wordings. Clearly this statement, which was a starting point for Newton’s optical work, was not made for the first time by Scaliger in 1557, as is generally thought .
- 1.Nasr, S.H.: al-Tusi. In: Gillespie, C.C. (ed.) Dictionary of Scientific Bibliography, vol. 13, pp. 508–514. Scribner’s sons, New York (1970)Google Scholar
- 2.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
- 4.Persian edition in Nourani, A.: Ajvebat al-Masā’el al-Nasīrīyah. Institute for Humanities and Cultural Studies, Tehran (2005). German translation in: Wiedemann, E.: Über die Entstehung der Farben nach Nasir al Din al Tusi. Jahrbuch der Photographie 22, 86–91 (1908). Reprinted in Wiedemann, E.: Aufsätze zur arabischen Wissenschaftsgeschichte, pp. 256–261. Georg Olms, Hildesheim (1970)Google Scholar
- 6.Kirchner, E.: Color theory and color order in medieval Islam: a review. Col. Res. 40 (2015) 5–16.Google Scholar
- 7.Razavi, M.: Tansukhname-ye Ilkhany. Miras-i Maktub, Tehran (1969)Google Scholar