Ibn al-Haytham (Alhazen)

965–1040 CE Basra / Cairo Optics & Physics

Key Contribution: Father of optics. First to explain how vision works correctly.

Preceded the West: Invented the scientific method centuries before Francis Bacon. Built the first camera obscura.

Abu Ali al-Hasan ibn al-Haytham, known in the West as Alhazen, is widely regarded as the father of modern optics. His seven-volume work Kitab al-Manazir (Book of Optics) fundamentally changed the understanding of light and vision. He disproved the ancient Greek "emission theory" (that eyes emit light rays) and correctly explained that vision occurs when light reflects off objects and enters the eye. He described the camera obscura, studied the properties of lenses and mirrors, and investigated the refraction and dispersion of light. Crucially, Ibn al-Haytham pioneered the scientific method — insisting on systematic experimentation, repeatable observations, and mathematical proof rather than philosophical speculation. Roger Bacon, Johannes Kepler, and René Descartes all built on his foundational work.