Vision, Light and Optics: Discovered by Muslims.
Before Al Haytham, a ninth-century Muslim polymath, known as Al-Kindi was the first person to question the Greek theories of vision. The Greeks believed that rays came out of our eyes (a little like laser technology) and this allowed us to see. However, Al Kindi stated that our visual cone is not made up of discrete rays but rather it is a volume of continuous radiations in three dimensions.
Al Kindi
He was “one of the twelve giant minds of history”1, as stated by the 16th century Italian physician and mathematician Geronimo Cardno. Al Kindi examined vision with and without a mirror. He spoke of how light rays came in a straight line, the effect of distance and angle on sight and about optical illusions.
He wrote two disquisitions on physiological and geometrical optics which were used by other scholars including German physicist Witelo and English scholar Roger Bacon. Al Kindi’s work was so profound that various English scholars and others in the field repeatedly referred to his work.
Ibn Al Haytham
The questioning of how our vision works was continued by Al-Hasan Ibn al-Haytham, who built on Al-Kindi’s work. Ibn al-Haytham, was a Muslim scientist who revolutionised vision, optics and light. In the tenth century, Ibn al-Haytham eventually found that vision was possible due to the refraction of light rays.
He was born in Basra, Iraq, in 965. The story of how he reformed the understanding of light and vision began when he was summoned by the ruling caliph in Cairo to control the Nile’s unpredictable flood. Upon arriving and assessing the situation, Ibn al-Haytham found that this challenge he had agreed to complete was in fact impossible. The Caliph at the time was brutal and out of fear of the wrath that would occur due to his failure, Ibn al-Haytham pretended he was mad! For his own protection, the Caliph placed him under house arrest and this 10-year imprisonment led to the world-renowned discoveries that modern science still follows.
In his darkened room, Ibn al-Haytham saw light projecting through a pinhole and this helped him realise that light rays that are emitted from objects enter our eyes.
Next, he began experimenting within the room and “camera obscura” and showed how light enters eyes in the shape of a geometric cone of vision. He further experimented with lenses and mirrors.
This illustration shows how light shines through a small hole in the darkened room, projecting an inverted image on the opposite sheet. He called this “Qamara”, the world’s first Camera Obscura.
Book of Optics
These developments were published in the acclaimed Book of Optics which he wrote between 1011 and 1021. This book was translated in many languages, including Latin, influencing the works of Leonardo Da Vinci, Roger Bacon and Johannes Kepler. Contemporary society relies on this accurate understanding of light and vision, which was founded by the Muslim scientist Ibn al-Haytham, over a thousand years ago.
Contribution to the Scientific Method
Ibn al-Haytham also realised that his senses were prone to error and thus he began scientific methods of variation, testing, verification and experimentation to ensure that his findings were all accurate. This was unusual at the time as physics was without experiment, much like philosophy. His methods of investigation later became known as the crucial modern scientific method of research.
“He, Ibn al-Haytham, was the greatest Muslim physicist and student of optics of all times. Whether it be in England or far away Persia, all drank from the same fountain. He exerted a great influence on European thought from Bacon to Kepler.”
George Sarton in his History of Science.
Kamal al Din al Farisi, a Muslim persian mathematician built on Ibn al-Haytham’s work. Al Farisi experimented with a glass sphere filled with water, to try to understand and explain the colours of the rainbow. He used this sphere as a model of a raindrop and showed that sunlight bent twice through the droplet.
Ibn al-Haytham’s dark chamber which he named “camera obscura” formed the basis of optical devices such as cameras. His distinguished research paved the path for experimental science and the rational perspectives of later scholars.
His Legacy
Unfortunately, Al Haytham’s contributions were disregarded since his death. When his books were translated to Latin, he was not referred to by his real name but rather “Alhazen”. Changing the names of Muslim scholars to one that is more European sounding often occurred during the European Renaissance, with aims of discrediting Muslims and their contributions within the wider world.
A crater on the moon is named Alhazen in honor of Hasan Ibn Al Haytham’s vast contributions on vision and camera developments.
Nevertheless, the brilliant minds of these Muslim scholars inspired many generations and continues to be a source of motivation for others. Indisputably, without their research, especially Ibn Haytham’s discoveries, the modern world of science as we know it today, would not exist.