History Today subscription

The Birth of Science in a Darkened Room

The father of modern optics could not have succeeded had he not feigned madness.

Pippo Carmona | Published 25 March 2019

Here’s looking at you: the anatomy of an eye, from Opticae Thesaurus (1572), German, woodcut.

While the annual flooding of the Nile is a blessing for Egyptian agriculture, it can also bring devastation to life and property. In the hopes of mitigating the yearly deluge, Fatimid Caliph Al-Hakim bi-Amr Allah (985-1021) invited scholars from all over the Muslim world to present to him ways to control the Nile. This was during the early phase of the Islamic Golden Age, which saw a revival of Hellenistic thinking and culture in the Muslim world, providing al-Hakim with an endless pool of talent and intellect from which to select. One of those who came answering the caliph’s call was Abu Ali al Hasan Ibn al-Haytham (965-1040). Much of what we know about him comes from the work of the 13th-century Muslim biographer and historian Ibn al-Qifti (1172-1248). According to al-Qifti, al-Haytham was already a well-known mathematician in Syria and in his hometown of Basra when he arrived at the caliph’s court in Egypt.

This was a key opportunity for al-Haytham to showcase his talents and win the caliph’s patronage. But it also came with a terrible risk. Caliph al-Hakim was known for his erratic and ruthless episodes. In one instance, the barking of a dog annoyed him so much that he ordered the slaughter of all the dogs in Egypt. One wrong move could easily spark the caliph’s wrath.

Al-Haytham managed to win the caliph over with an ambitious plan to build a dam in Aswan. To get a sense of just how difficult his proposal was, we only need to look at the present Aswan Low Dam, the first such construction on the Nile, completed after four years of construction in 1902. Standing 36 metres high and almost 2,000 metres in length, it was only achieved by using all the methods and equipment of modern technology. Eleventh-century engineering simply stood no chance against the destructive power of the Nile. When al-Haytham realised how impossible his task was, it was too late; the caliph was already expecting success. Fearing the fatal reprisal that came with disappointing the monarch, al-Haytham feigned madness, hoping the caliph would consider his untenable plans to have been the result of his illness. To his great luck, it worked. The caliph spared his life, insisting only that al-Haytham be held under strict house arrest in Cairo.

It was during his time in confinement that al-Haytham made perhaps his greatest contribution to science. Free from the distractions of the world, he revolutionised the field of optics by designing the first experiment with a camera obscura (‘darkened chamber’). The phenomenon of the camera obscura was known, but it was not fully understood. Problemata, a fourth-century BC text attributed to Aristotle, asks: ‘Why is it that when the sun passes through quadrilaterals, as for instance in wickerwork, it does not produce a figure rectangular in shape but circular?’ Al-Haytham experimented by making a pinhole, using the window shutters of a completely darkened room, for light to pass through and project onto the opposite wall. He discovered that scenes and images from outside the camera obscura were turned upside down by passing through the pinhole.

From his experiments, al-Haytham made two important conclusions, which he published along with his other findings, in his seven-volume treatise Kitab al-Manazir, or ‘The Book of Optics’. His first conclusion was that light travels in straight lines: ‘Vision perceives necessarily all the objects through supposed straight lines that spread themselves between the object and the central point of the sight.’ His second conclusion was that light comes from external sources.

This second finding was particularly important in debunking the prevailing theory of light at the time, which was proffered by towering intellectual figures, such as Ptolemy, Galen and Euclid. It was believed that the eyes emitted beams of light onto objects, rendering them visible. This idea came to be known as the ‘extramission theory’ of light. What al-Haytham proved with his camera obscura experiments was that light does not come from our eyes; rather, light comes from external sources that illuminate objects in our world: ‘Eyesight perceives the light and colour existing on the surface of the contemplated objects.’ As a result of these observations, along with the other findings in the Kitab, al-Haytham is today widely regarded as the father of modern optics.

After a decade of incarceration, al-Haytham was finally released following the caliph’s mysterious death in 1021. This renewed sense of freedom afforded al-Haytham the opportunity to further pursue his research. It is said that his total published output amounted to 200 books, 96 of which were scientific studies. Al-Haytham’s impressive contributions led the quantum physicist and popular science communicator Jim al-Khalili to view al-Haytham as more than just a pioneer in the science optics; for him, al-Haytham is also ‘the father of the modern scientific method’ for his insistence on the experimental scientific process. This he accomplished not just with his genius, but with the aid of luck and reckless daring. We do not just shed light on science metaphorically, but literally. After all, al-Haytham needed light, however small, while inside the darkened room to give birth to what we now call the scientific method.

Pippo Carmona is a biologist and historian of science.


Get Miscellanies, our free weekly long read, in your inbox every week