Technology and Sustainable Development Edited by Roshdi Rashdi, Azzedineboudrioua and Vasudevan Lakshminarayanan (CRC Press, to Be Published April 2017)
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1 Chapter in Light-Based Science: Technology and Sustainable Development edited by Roshdi Rashdi, AzzedineBoudrioua and Vasudevan Lakshminarayanan (CRC Press, to be published April 2017) Ibn al-Haytham and His Influence on Post-Medieval Western Culture Charles M. Falco College of Optical Sciences University of Arizona, Tucson 85721 USA Abstract As described in this chapter, Ibn al-Haytham (Alhazen) made intellectual contributions that were subsequently incorporated throughout the core of post-Medieval Western culture. The noted science historian, David Lindberg, wrote that "Alhazen was undoubtedly the most significant figure in the history of optics between antiquity and the seventeenth century." Impressive and accurate as that characterization is, the examples in this chapter show that it significantly understates the impact that al-Haytham's work on optics had on areas as wide-ranging as the science, literature, art and even the theology of Europe. Introduction Ibn al-Haytham (Latinized as Alhazen or Alhacen) wrote nearly one hundred works on topics as diverse as astronomy, poetry and politics. Although today he is largely known for his writings on geometrical optics, astronomy, and mathematics, with his landmark seven-volume Kitāb al-Manāzir [Book of Optics], published sometime between 1028 and 1038, he made intellectual contributions that subsequently were incorporated throughout Western culture. The Kitāb al-Manāzir was translated into Latin as de Aspectibus sometime prior to 1230 where it profoundly influence on European intellectuals as diverse as the writer Geoffrey Chaucer, the theologian John Wyclif, and the scientific work on optics of Bacon, Pecham, and Witelo. The noted science historian, David Lindberg, wrote that "Alhazen was undoubtedly the most significant figure in the history of optics between antiquity and the seventeenth century." However, accurate as that characterization is, it significantly understates the impact that al-Haytham had on areas as wide-ranging as the art, science, theology, and literature of Europe. 2 Theories of Vision Translation of ancient writings on the science of optics during the first two centuries of the Islamic Golden Age provided contemporary intellectuals with the theories of vision of Euclid, Ptolemy, Galen and Aristotle. These translations of Greek texts contained disparate views on the way the organ of the eye reacts with light to aid in vision. Although Greek theories were largely appropriated by Islamic scholars until the first quarter of the 11th century, at that time a new method of inquiry was introduced by Ibn al- Haytham who combined experimental evidence with theoretical insights to develop a remarkably accurate theory of vision. His design and interpretation of experiments became the root source for Western understandings of optics up to the 17th century (Lindberg, 1967). Prior to al-Haytham's work theories of vision could be broadly classified into one of three categories: extramission, intromission, or a combination of the two. Extramission theories, well-known proponents of which are Euclid and Ptolemy, require some sort of illuminating particles be emitted by the eye (Linberg, 1981). Although there are obvious flaws with these theories, they do get the geometry correct and there is a one-to-one correspondence between points on the object and points on the eye. Intromission theories by philosophers including Aristotle postulated that objects continuously emitted microscopic replicas of themselves that travelled to the eye of the observer. Although intromission theories avoid some problems of extramission theories, such as near and far objects simultaneously being visible when the eye is opened, they, too, have obvious flaws. A third class of theories, proposed by Plato and Galen (and Aristotle, to a lesser degree), combined extromission and intromission theories and proposed that light emitted by the eye "activates" in some way the intervening air to allow replicas, or "species" to create the image (Lindberg, 1967, 1981). Ibn al-Haytham, recognizin problems with existing theories of vision, proposed a type of intromission theory of vision and validated his proposition by empirical understanding deduced from scientific experimentation. His methodology expanded understanding beyond the theoretical and resulted in him incorporating psychology as well as the behavior of light and the physiology of the eye to explain vision. 3 Ibn al-Haytham's experiments included using flat and curved mirrors to control and manipulate light as well as involved observing the effect of light passing through apertures of various sizes into darkened spaces (i.e. camera obscura) (Smith, 2001a, 2001b). Significantly, his experiments provided al- Haytham with the theoretical construct of light rays that he used as a means for describing and interpreting the visual system, and linked sight and vision with the properties of light throughout his studies. One important aspect of vision that al-Haytham did get wrong is the fact that an image projected by a lens is upside down and has its right-to-left parity reversed. Although his experiments with eyeballs should have given him the correct answer, apparently this was more than he could accept in a theory of vision even though it is contained within his optical formalism. Leonardo da Vinci also failed to accept this as an explanation for vision when he approached the problem much later (Kemp, 1977), and ultimately it would be Kepler five hundred years later who would follow Ibn al-Haytham's formalism to its logical conclusion when he developed the theory of the retinal image. Significantly, Kepler titled his work "Amendments to Witelo," incorrectly crediting the 13th century priest who had plagiarized al- Haytham's work. Appropriation of Ibn-al Haytham's Work into European Culture There is little doubt that Ibn al-Haytham’s Kitāb al-Manāzir, translated into Latin as De Aspectibus in the early to mid-13th century, is largely responsible for the widespread appropriation of its contents by Western European intellectuals (Lindberg, 1967). Although it is important to note there are variations in organizational structure and interpretation of specific terms between the Latin version and the Arabic original (Smith, 2001), the influence of al-Haytham's writing on European culture was profound, as will be described in the rest of this chapter. Optics 4 The earliest known reference to the Latin translation of the Kitāb al-Manāzir, De Aspectibus, is in De proprietatibus rerum, [On the Property of Things] c1220-1230 by Bartolomeo Anglicus (Smith, 2001), an early encyclopedia covering a wide variety of subjects. The text refers several times to the study of optics and to Ibn al-Haytham. This encyclopedia was required reading at the University of Paris in 1296, available in the university library of the Sorbonne by 1306, and widely used as reference material at Oxford, Cambridge, Canterbury and Merton College by the mid-fourteenth century (Holbrook, 1998). However, specific proposals contained within De Aspectibus are most significantly referred to in the optics manuscripts Perspectiva by Roger Bacon (c1268), Perspectiva by Erazmus Witelo (c1278), and Perspectiva communis by John Pecham (c1280) (Lindberg, 1967). Although today we think of these scholars as optical scientists, they were theologians who approached their work as such which influenced their interpretation of medieval optical theories. Bacon, for example, was a Franciscan friar, who secretly transmitted his scientific manuscripts to the Papal court (Smith, 2005). Pecham and Witelo also were priests and relied on Ibn al-Haytham in constructing their own evolving optical theories, although taking liberties with their interpretations and infusing their writings with spiritual undertones. The collective work of these scholars had enormous influence on the progression of optical understanding in Europe in the centuries that followed. Literature European literature published during the period after al-Haytham's work had been translated into Latin illustrates not only how widespread interest and understanding of optics had become, but how influential this Arab scholar was. Ibn al-Haytham is referred to several times in the epic poem Roman de la Rose [Romance of the Rose] by Guillaume de Lorris and Jean de Meun, one of the most widely read works in the French language for 300 years after its publication in c1275 (Ilardi, 2007). In the text the authors describe the properties of mirrors, with the text exhibiting a non-trivial understanding of optics. One short passage from these four pages makes its debt to Ibn al-Haytham (Alhacen) quite clear: 5 There [in Alhacen’s Observations] he will be able to discover the causes and the strengths of the mirrors that have such marvelous powers that all things that are very small – then letters, very narrow writing, and tiny grains of sand – are seen as so great and large and are put so close to the observers – for everyone can distinguish among them – that one can read them and count them from so far off that anyone who seen the phenomenon and wanted to tell about it could be believed by a man who had not seen it or did not know its causes. This would not be a case of belief, since he would have the knowledge of the phenomenon (Ilardi, 2007, p. 44). A century later Geoffrey Chaucer refers to Ibn al-Haytham in Canterbury Tales, the first major piece of literature in the vernacular English language. Chaucer, too, was influenced by his understanding of the content of Ibn al-Haytham's works on vision and optics as is clear from the following passage: They spoke of Alhazen and Vitello and Aristotle, who wrote of curious mirrors and of perspective glasses, as they know who have heard their books. (NeCastro, 2007, p. 3) Interestingly, although Ibn al-Haytham contributions were disseminated in Europe through the texts of Bacon, Pecham and Witelo where they influenced a period of scientific discovery in optics, they also informed advancement of visual literacy. The science of optics in turn provided the syntax upon which new spatial understandings were constructed.