Ibn al-Haytham and the Book of Optics: how the experimental method took shape

Ibn al-Haytham is remembered not only for what he concluded about light, but for how he reached his conclusions.

Life and work

Al-Ḥasan ibn al-Haytham lived between the late tenth and early eleventh centuries CE. Born in Basra, he spent years in Cairo, where he wrote his most famous work, the Book of Optics (Kitāb al-Manāẓir).

A new account of vision

He rejected the ancient idea that the eye sends out rays toward objects. Instead he argued that we see when light reflected from objects enters the eye, and he supported this with geometry and observation.

Method over conclusion

Just as important was his approach: systematic experiments, measurement and verification. He studied the dark chamber (camera obscura), reflection and refraction, and designed set-ups that others could repeat.

Influence

The Book of Optics was translated into Latin and shaped the study of optics in Europe for centuries. That is why he is often cited as a pioneer of the experimental scientific method, and as a reminder that the method grew across many civilisations.

Build a camera obscura

Make a small hole in one end of a cardboard box and tape tracing paper over the other end. Cover your head and the box with a dark cloth and point the hole at a bright window: an upside-down image appears on the paper. Change one thing at a time, such as hole size or distance, and record what happens, just as Ibn al-Haytham did.

Original Vemetto explainer in English, adapted from our Arabic page. Last reviewed: 9 November 2026.