International Year of Light - 1000 Years of Arabic Optics (original) (raw)

The year 2015 marks the 1000th anniversary since the appearance of the remarkable seven volume treatise on optics Kitab al-Manazir written by the great Arabic scientist Ibn al-Haytham. Ibn al-Haytham's influence on experiment and theory in optics is truly remarkable, and he is considered the father of modern optics, ophthalmology, experimental physics and scientific methodology. This page will provide resources and links for you to learn about his contributions and the many other scientific contributions made during the Islamic Golden Age.

The year 2015 marks the 1000th anniversary of the appearance of a remarkable seven volume treatise on optics Kitab al-Manathir written by Ibn al-Haytham.

The Arab polymath Abu Ali al-Hassan ibn al-Haytham was born in Basra in southern Iraq in c. 965. Sometimes referred to by his Latinised name, Alhazen (from his first name, al-Hassan), he is generally known nowadays simply as Ibn al-Haytham.

Ibn al-Haytham is often referred to as the first real scientist, whose works were based on careful experimentation and rigorous recording of his results. His greatest work, the Book of Optics (Kitab al-Manathir)is a real science textbook, with detailed descriptions of experiments, including the apparatus and the way it was set up, the measurements taken and the results. These were then used to test his theories, which he developed using mathematical (geometrical) models.

Books 1 to 3 are devoted to the physiology of the eye and the theory of perception. Books 4 to 7 cover physical optics. The work debunks classical theories which maintained that light from the eye illuminated an object, and demonstrates that light is reflected from an object to the eye.

Ibn Al-Haythem also explained the “moon illusion” (the phenomenon where the moon appears larger near the horizon than when higher in the sky), understood the phenomenon of light travelling at different speeds in different media, introduced the concept of atmospheric refraction (the bending of light received on the surface of the earth from celestial bodies), carried out some of the first experiments on the dispersion of light into its constituent colours, studied shadows, rainbows and eclipses, and developed the mathematical equations to explain the reflection of light from curved mirrors.

He went on to write 25 works on astronomy, including treatises on cosmology, astronomical observation and calculation, and technical applications such as the determination of meridians, the direction of Mecca and the design of sundials.

Ibn al-Haytham's influence on experiment and theory in optics is truly remarkable, and he is considered the father of modern optics, ophthalmology, experimental physics and scientific methodology.

However, it was another scholar working in Baghdad some years earlier who discovered Snell’s law of refraction 650 years before Snell – an achievement which is often wrongly attributed to Ibn al-Haytham. Ibn Sahl wrote a treatise c. 984 called On the Burning Instruments (mirrors and lenses used to focus sunlight to create a hot spot), in which he derived Snell’s law geometrically as the ratio of the sides of triangles of light rays – exactly equivalent to the ratio of sines derived by Snell.

This above is summarised from Chapter 11, The Physicist, of Pathfinders by Professor Jim Al-Khalili.

To learn more about the Islamic Golden Age and other major Arabic contributions to optics, visit Wikipedia.