Ibn al-Haytham...

Ibn al-Haytham. (Image by Guérin nicolas, GFDL)

Post inspired by COSMOS episode this past Sunday (full episode at link).

al-Hasan ibn al-Haytham

The Arabian physicist, astronomer, and mathematician al-Hasan ibn al-Haytham (ca. 966-1039), or Alhazen, established the theory of vision that prevailed till the 17th century. He also defended a theory of the physical reality of Ptolemy's planetary models.

Al-Hasan was born at Basra in southern Iraq, where he must have received all his education. He gained sufficient fame for his knowledge of physics in his youth that he was called to Egypt by the Fatimid ruler al-Hakim to attempt to regulate the flow of the Nile. Failing in this effort, he was disgraced and established himself as a copyist of mathematical manuscripts; there still exists in Istanbul a manuscript of the Banu Musa's version of Apollonius's Conics copied by him in 1024. He continued to practice the scribal art in Cairo for the remainder of his life.

He did not cease to pursue his scientific studies, however, and published a large number of highly original works. He produced two catalogs of his own work, which are preserved by Ibn abi Usaybia. The first of these, compiled in 1027, comprises 25 books on mathematics and 44 on physics and metaphysics, including On the Structure of the World. The second, supplementary catalog was complied in 1028.

Al-Hasan's greatest scientific achievements were in the field of optics. In the discussion of the nature of vision at the beginning of Optics, he argues that light physically affects the eye, citing the pain experienced by looking directly at the Sun and the afterimage experienced by staring at fire and then looking into a weakly illuminated place. From this he argues that the assumption of emission of visual rays from the eye utilized by mathematical opticians, though convenient for their geometric analysis, must be physically wrong. Light rays rather proceed from the visible object to the eye and are always accompanied by color.

"al-Hasan ibn al-Haytham." Encyclopedia of World Biography. 2004. Encyclopedia.com. 9 Apr. 2014<http://www.encyclopedia.com>.
Islam Wikia: Ibn al-Haytham
Wikipedia: History of the Scientific Method/Ibin al-Haytham