Al-Haytham (c.965 - c.1040)

Born in Basra which is now in Iraq, Al-Haytham made his way to the great city of Cairo in Egypt. At the time it was ruled by the Abbasid dynasty who encouraged many scholars to the city and established a flourishing culture.

Al-Haytham ran into problems with the Caliph Al-Hakkim and had to pretend to be ill for a number of years. But when the Caliph died he seems to started work at the University of Al-Azhar. This institution, founded in 970, was the world’s first University.

He was extremely prolific in his studies writing 92 works of which 55 survive. Indeed this volume has led some people to wonder if there weren’t two people of the same name.

He wrote about a wide range of topics from philospophy and astronomy to geometry and number theory. But he is best remembered for his work on optics which was published in a book called Kitab al-Manazir.

This book is interesting for being among the first to concern itself with experimental and not just theoretical ideas. It correctly argues that all light is the same and gives the first explanation of human vision as the reflection from an object to the eye rather than the emanation of light rays from the eye.

The book also looks at what we call ‘Alhazen’s problem’. The name derives from the Latinization of his name and wonders at which point on a spherical mirror will light from a source be reflected to the eye of an observer? This problem later engaged the minds of mathematicians like Kepler and Descartes.