If you live in one of the Arab states of the Middle East, then you will likely have been greeted by an interesting new Google doodle today for the anniversary of one of the most celebrated Muslim medeival scientists.

Ibn al-Haytham, known in the West by his Latinized name Alhazen, was born 1 July, 956 AD, in Basra in present-day Iraq but lived most of his life in Egypt. A polymath, Alhazen has contributed to the sciences of optics, astronomy, mathematics and philosophy. He is one of the earliest, if not the first, theoretical physicists in the world, using mathematics to prove his theories of optics.

Alhazen is best known for his work to prove experimentally how we see objects. He disproved the emission theory, which was popular at that time and stated that the eyes shine light on objects that we see, and countered that we see objects because light from them falls on our eyes instead. He was also the first to prove that light moved in straight lines through experimentation on mirrors and lenses and studying refraction and reflection.

This led to the discovery he is best known for, the camera obscura, or pinhole camera. His books had the first clear description of it and an analysis of how it worked.

Most of this research was done when he was under house arrest, after feigning madness when he had promised the caliph of Egypt, Al-Hakim bi-Amr Allah, he would be able to control the flow of the Nile but it proved too daunting a task for him. His arrest was lifted following the death of the caliph and he continued his research and made money copying books.

The most important contribution of Alhazen to science must be his “Book of Optics”, a seven-volume study of optics and other related disciplines. The book was quite influential in Europe when it was translated in the 12th century. The experimental approaches and mathematical verification that Alhazen took when writing the book were essential for laying the foundation of the scientific method. It was considered the most important book on optics in Europe until Kepler’s work.

In addition to his work on optics, Alhazen is thought to have published 200 books of science in total, with at least 96 being currently known. Most of his work has been lost, but nearly 50 books have survived and are still being studied.