Ibn al-Haytham (Alhazen)

Author of the Book of Optics in seven volumes: he showed that light enters the eye and not the reverse (refuting Aristotle and Euclid), explained reflection and refraction, used the camera obscura in his experiments, and solved Alhazen's problem which had no known solution. After Kaml's 1572 Latin translation, Kepler, Descartes and Newton built on it, and historians count him the first to separate the experimental-mathematical method, founding the modern scientific method.