Ibn al-Haytham (Alhazen)
Arab scientist who founded optics as an experimental science and pioneered the scientific method.
Who or what
Abu Ali al-Hasan ibn al-Hasan ibn al-Haytham (965–1040), known in the West as Alhazen, was an Arab polymath.
His "Book of Optics" (Kitab al-Manazir) revolutionized understanding of light, vision, and scientific methodology.
Why it mattered
He was the first to prove that vision occurs when light enters the eye, not when rays emanate from it (refuting Euclid and Ptolemy).
He established that scientific theories must be proven through repeatable experiments — the birth of the experimental method.
Key works and moments
He used the camera obscura to prove that light travels in straight lines.
He explained rainbows, atmospheric refraction, and twilight through careful observation and experimentation.
Further detail
His method: observe a phenomenon, propose a hypothesis, design experiments to test it, analyze results mathematically, and draw conclusions.
He studied spherical and parabolic mirrors, lens aberration, and magnification — laying groundwork for telescopes and microscopes.
Legacy
His optics influenced Kepler, Descartes, Newton, and the entire European scientific revolution.
His experimental method prefigured the modern scientific method by 600 years.
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Assembled from the ReLU.chat curated knowledge base. These explanations are concise on purpose; check the sources for anything important.