Puzzle No. 115: When?

The Arab polymath Ibn al-Haytham (Latinised as Alhazen, c. 965 to c. 1040) composed his seven-volume Kitab al-Manazir (Book of Optics) in Cairo between roughly 1011 and 1021, traditionally during a period of house arrest under the Fatimid caliph al-Hakim. The treatise overturned the prevailing extramission theory of vision, establishing instead the intromission model in which sight results from light entering the eye, and it laid out systematic accounts of reflection, refraction, the camera obscura, and the anatomy of perception. Crucially, Ibn al-Haytham insisted that hypotheses be tested against controlled, repeatable experiments and mathematical demonstration rather than accepted on the authority of ancient writers, an approach widely regarded as an early articulation of the experimental scientific method. Translated into Latin around the turn of the thirteenth century, the work profoundly shaped European optics and natural philosophy, influencing figures from Roger Bacon and Witelo to Kepler. It remains a landmark in the history of science and earned its author the epithet 'father of modern optics.'

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