Human knowledge expands constantly building on what has been passed on from earlier
generations. Today’s scientists, astronomers, physicists and mathematicians have greatly
benefited from discoveries and developments of the past. Future generations will build on
what we pass on to them
While growth in knowledge remains fairly steady over generations, at certain points in
history, some scientists come up with ideas that take humanity to a much higher level.
Such names as Isaac Newton and Albert Einstein immediately come to mind.
Muslim scientists, astronomers, geographers, mathematicians and physicians have also
made immense contribution to development in their respective fields. These included
such towering figures as al-Khwarizmi, al-Biruni, Ibn Hayyan, al-Haytham, Ibn al-Nafees
and Ibn Sina, among many others.
Presented in these pages are the contributions of some of these great figures from Islamic
history. Their contributions range from such diverse fields as Chemistry (al-Kimya),
Algebra (al-jabr), to Algorithm (from al-Khwarizmi) and great works of Medicine. Al-
Biruni measured the radius and circumference of the earth fairly accurately and also said
the earth rotates around its own axis and revolves around the sun. He established this
more than 1,000 years ago. Many Muslim scientists lived 1,000 – 1,200 years ago.
We hope this information will encourage readers—students and adults alike—to do their
own research and discover the rich heritage of Islamic history.
MUHAMMAD IBN MUSA AL-HAYTHAM
(965–1040 CE)
In his book, Kitab al-Manazir (The Book of Optics), Ibn al-Haytham was the first to disprove the ancient Greek idea propounded by Galen (200–124 BC) that light emits from the eye, bounces off objects, and comes back to the eye (extromission view). This theory held sway for more than 1200 years until Ibn al Haytham refuted it. He did not accept what he read or happen to be the conventional wisdom. He insisted on empirical evidence for scientific beliefs.
Galen (200–124 BC), however, had provided a very detailed description of the eye and the optic pathways. Particularly crucial for Ibn al-Haytham’s theory of vision was Galen’s view that the crystalline humor (our lens) was the sensitive or photoreceptive portion of the eye.
In his great work Kitab al-Manazir or Optics, Ibn al-Haytham carefully examined the extromission theories of his predecessors and systematically demolished each of them.
Against the extromission theory he writes:
“The act of vision is not accomplished by means of rays emitted from the visual organ”; rather, “vision is accomplished by rays coming from external objects and entering the visual organ.” Essentially Ibn al-Haytham took a new view of light, combined it with Ptolemaic optics, Galenic anatomy and the results of his own extensive experiments and produced a plausible intromission view that lasted until Kepler.
As he put it, “from each point of every coloured body, illumination by any light, issue light and colour along straight lines that can be drawn from that point.”
Following Galen, Ibn al-Haytham believed that the crystalline humor was the sensitive surface whose receipt of light was the first step of the visual processes. There were, however, two problems.
First, if from every point of every object, light traveled to the crystalline humor, then those light rays would intermix and total confusion would result. How could a point-to-point correspondence between the visual field and the crystalline humor, essential to Ibn al-Haytham’s theory of vision, be maintained?
He postulated that only light rays orthogonal to the surface of the crystalline humor passed through it. The others were refracted and refracted rays were weaker and not perceived. Thus, a topographically ordered point-to-point representation of the visual world entered the crystalline humor.
Second, how could an inverted image appear right side up? Ibn al-Haytham had used a camera obscura (see below) in his extensive optical experiments and compared it to the eye. Thus, he realized that if the light rays orthogonal to the curved surface of the crystalline lens continued, they would project an inverted image on the back of the eye.
So how does a correct image appear to the eye? Ibn al Haytham postulated precisely the appropriate\ refraction at the interface between the crystalline humor and the vitreous humor so that the rays leaving the latter would be parallel. Thus, they would provide a right-side-up topographic representation of the visual world to the back of the eye (retina) that he viewed as an extension of the optic nerves.
Beyond the receipt of light by a sensitive surface (the crystalline humor for him), Ibn al-Haytham realized that strictly optical considerations were no longer required. He did stress, and correctly so, that the point-to- point representation had to be maintained and conveyed to the ultimum sensus in the anterior part of the brain.
The pinhole camera
Ibn al Haytham was the first scientist to study the phenomenon of the pinhole camera. The concept of a pinhole camera is simple: a box with a tiny hole on one side is able to project an image of whatever is outside onto a side of the box on the inside. Those familiar with modern cameras will notice that that is how cameras work in general, but today with the addition of lenses. Ibn al-Haytham was able to build these pinhole cameras hundreds of years before the modern development of photography as we know it.
How a pinhole camera works
Study of Light
He also studied the way light is affected when moving through a medium such as water or gasses. From this, he was able to explain why the sky changes color at twilight (the sun’s rays hit the atmosphere at an angle, causing refraction). From this, he was able to calculate the depth of the earth’s atmosphere, 1000 years before it would be proven by spaceflight.
The translation of The Book of Optics had a huge impact on Europe. From it, later European scholars were able to build the same devices as he did, and understand the way light works. From this, such important things as eyeglasses, magnifying glasses, telescopes, and cameras were developed.
Beyond Light
As if revolutionizing the way humanity understands light and leading to the development of things we can’t live without in the 2000s wasn’t enough, Ibn al-Haytham was also a pioneer in other fields.
Astronomy
In 1020s and 1030s, he wrote numerous books on astronomy. He wrote about the mistakes of the Ptolemaic model of how the stars and planets move and provided a more realistic view of the way the universe works (although he knew the earth to be a sphere, he stuck to the ancient Greek idea that the earth was the center of the universe).
He had great influence on Isaac Newton, who was aware of Ibn al-Haytham’s works. He studied the basis of calculus, which would later lead to the engineering formulas and methods used today. He also wrote about the laws governing the movement of bodies (later known as Newton’s 3 laws of motion) and the attraction between two bodies – gravity. It was not apple falling from the tree that led Newton to gravity but the books of Ibn al-Haytham.
Since he was also trained in the traditional Islamic sciences, Ibn al Haytham wrote on how to use math to calculate the prayer direction towards Makkah. In a precursor to modern psychology, he researched the effect music therapy can have on humans and
animals.
Legacy
The list of accomplishments and contributions of Ibn al-Haytham goes on and on. The truly amazing thing is that he wrote over 200 books, but only around 50 have survived till today. What he discovered that we do not even know about probably far outshines even the amazing works that have made it to the present day.
