How one man’s imprisonment led to discovery of how we see the world today!

Legacy: Camera Obscura

Location: Cairo, Egypt

Era: 11th century

Key Figure: Ibn al-Haytham

How does vision works? Some scholars argued that rays departed from our eyes while others stated something entered to constitute it as an object. Arguments remained a subject of dialogue for a long time among the Greek scholars until Ibn al-Haytham absolutely changed the perception of light and vision.

Born in Basra, Iraq, he was invited by the ruling Caliph of Cairo to limit the impact of the Nile flood.

Confident about his abilities, he boasted his capabilities to tame the Nile flood by constructing dams and reservoirs. Whilst he noticed its mass and scale, he realized the scenario is out of his competencies.

Fearing wrath from Caliph, he decided to act lunatic, for which, Caliph positioned him under house arrest for his protection. It was while imprisonment he made the discovery for which he is remembered today.

One day, he saw the light entering his darkened room from pinhole projecting the view of the outside world on the opposite wall.

Illustration of the camera obscura principle

At that time, people believed, vision is captured by sending invisible rays through eyes. However, he realized that sight was enabled due to visible rays entering our eyes from the object.

By experimenting with darkroom “Camera Obscura” he revealed to the world that light enters our eyes in the form of a geometric cone of vision.

A diagram depicting Al-Haytam's observations of light's behaviour through a pinhole

He studied and experimented with lens and mirrors: flat, spherical, concave, convex, parabolic and cylindrical. He also treated the eye as a dioptrics system by applying the geometry of refraction. Furthermore, he brilliantly calculated the height of the atmosphere to be 16 kilometers using atmospheric refraction. This compares aptly with the modern measurement of the troposphere to be 11 kilometers. He was first to use experimental evidence to cite the theories which were unusual for that time as physics was much like philosophy. Like many other people since then and now, Ibn al-Haytham wondered too, why the moon appears so big when in low sky. People argued it was due to the atmosphere, but he was first to state that it was an optical illusion- and scientists are still not sure why it happens.

Many of his works including the huge book of Optics were translated into Latin which inspired many like, Roger Bacon, Leonardo da Vinci, and Johannes Kepler.

Today, most of the inventions are based on his accurate understanding of light and vision which laid its foundation more than a thousand years ago.


1001 Inventions (ISBN: 978-1-4262-0934-5)


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