Ibn al-Haytham
Arab scholar of optics and mathematics, known in Latin as Alhazen
Scholar born in Basra who worked in Cairo and wrote the seven-volume Book of Optics. It explained vision as light reaching the eye from objects and rejected the older idea that rays leave the eye.
Why this person matters
His Book of Optics was the next major work in optics after Ptolemy and was later translated into Latin. It treats seeing as a process to be explained with experiments. Modern historians differ on how closely his methods match later experimental science.
Main contributions
A theory of vision from light entering the eye
In the Book of Optics he rejected the extramission theory of Euclid and Ptolemy, in which visual rays leave the eye. In his account each point on a visible object sends rays to the eye.
Visual cognition and binocular vision
The seven books cover eye anatomy (Book 1), visual cognition (Book 2), and binocular vision and visual errors (Book 3), followed by reflection and refraction. His eye anatomy is largely based on Galen.
Experiments in optics
He used dark chambers, pinhole cameras and sighting tubes to show that light travels in straight lines, and he cited eye pain from bright light and afterimages against visual rays. The historian A. I. Sabra saw in this a distinct concept of experiment.
Context and limits
Titles such as father of modern optics are characterisations, and some historians urge caution, especially when he is read apart from Ptolemy. G. J. Toomer doubted that a claim of systematic experimental variation could be assessed without more translation. Readings of colour constancy and unconscious inference in his text are interpretations. Sources disagree on his death (1039, 1040 or 1041) and on the dates of the Optics.
In your introductory course
Sensation and perception.Mentioned in sensation and perception chapters as an early account of how the eye produces vision. He is also an example of non-European science that fed later European work.
Related course reading: Psychology 2e, section 5.1. This is course context rather than a biographical source.
Years of active work
- 1011
Under the usual dating, he began writing the Book of Optics around this year (one citation instead places its composition in 1028 to 1038).
- 1021
Under the usual dating, the seven volumes were complete by about this year, the year in which the caliph al-Hakim died.
Sources
- MacTutor, Abu Ali al-Hasan ibn al-HaythamUniversity. Institutional biography inspected.
- EBSCO Research Starters, AlhazenReference work. Reference article inspected.
- Wikipedia, Ibn al-HaythamReference work. Reference article inspected.
- Linda Hall Library, Ibn al-Haytham (Scientist of the Day)Reference work. Institutional biography inspected.