Some  representative  examples  will be presented  to  give an idea  about  the treasures  of the Arabric  heritage  in various  fields  of physical  sciences  including  optics,  mechanics,  materials  science, (physical metallurg), geophysics, astrophysics...

Science and Technology Islamic Heritage:
After the fatll of the Western Roman Empire (475 A.D), which righly marks the start of the Dark Ages, little or no scientific progress was made in Eutopre for a great while.

In 642 A.D. Alexandria fell to the Muslims, and by the end of the Seventh century the lands of Islam extended from Persia across the Southern Coast of the Mediterranean to Spain. The center of Scholarship shifted to Islam world, where, in Brifault's words:
“... the patient ways of investigation, the accumulation of positive knowledge, the minute methods of science, detailed and prolonged observation and experimental inquirry were altogether” the basis of the Islamic culture. The achievements of the Middle Ages and creation of the experi-mental spirit were primarily due to the Muslims down to the 12th century. Barely a hundred years after the Prophet's death. The Muslims hand made it their task to master the then-known sciences.

With  feverish haste, but systematically, they translated the entire corpus of the then-known knowledge in their religious language, Arabic. Founding institutes of advances study (Bait-ul- Hikma), they acquired, an absolute ascendancy in the sciences that lasted fot the next 350 years.

A semi-quantitative measure of this is given by George Sarton in his monumental “History of Science”. Sarton divides his story of the highest achievemet in science into Ages, each Age lasting 50 years. With each, he associates one central figure: thus 500-450 BC is the Age of Plato, followed by the Ages of Aristotle, Euclid, Archimedes and so on.

From 750 to 1100 CE, however, it is an unbroken succession of the Ages of Jabir, Khwarizmi, Razi, Masudi, Abu'l-Wafa, Biruni and Omar Khayam.

In those 350 years, Arabs, Turks, Afghan and Persians- chemists, algebraists, clinicians, geograpers, and mathematicians, physicists and astronomers of the commonwealth of Islam-held the world stage of sciences.

Only after 1100 CE, in Sarton's scheme, do the first Western names begin to apear; however for another 250 years, they share the honours with men of Islam like Ibn Rushd, Nasir-ud-din Tusi and Ibn Nafis.

An important reason for the success of the scientific enterprise in Islam was its international character. The Islamic commonwealth itself cut across nations and colour; and early Muslim society was tolerant of men from outside it, and of their ideas.

In the following, these thoughts will be eluciclated for some branches of science and technology.

1- Optics:

a) Theory of Vision:

Islamic achievements in optics were solidly based on the foundation laid by the ancient Greeks. Greek optics was primarily a theory of vision, and it was a subject of varied discussions initiated by  Euclid, Ptolemy, Aristotle, Galen and others. The manner in which the eyes function was a point of great misconception until al-Hasan Ibn-al- Haytham alias Alhazen (965- 1039) formulated a theory of vision quite distinct from any other that had existed earlier. Ibn-al-Haytham derived the idea that vision occurs when a “form” emanating from the object enters the eye. To achieve this theory, Ibn-al-Haytham followed, for the first time, an inductive menthod based on observation, experiment, casuality and uniformity of nature.

He used the methods of agreement and concomitant variation to elaborate the casue and effect.

He realised that the old theory of vision based on an impression produced in the eye or brain is incomplete without an explanation of how the impression comes to be perceived as an object located at a certain distance, having a certain size and shape, and so forth.

This, in turn, led him to construct a highly original theory of the psychology of visual perception and to give a detailed description of the structure of the eye on the basis of contemporary anatomical works. The name “iris” dates back to Alhazen who described the eye as partitioned into three regions which were watery, crystalline and glassy, respectively.

Development of the theory of vision had to wait several centuries after Ibn-al-haytham until the German Jesuit Christoph Scheiner (1575- 1650) performed a classic and irrefutable experiment. He removed the coating on the back of an anumal's eye, and peering through its transparent retina form behind, was able to perceive a small inverted image of the scene beyond the eye. At just about the same time Descartes performed similar experiments.

b) Rectilinear propagation of light:

The prototype of the modern Photographic camera was a device known as the “camera obscura”, the earliest form of which was simply described by Ibn-al-Haytham who utilized it to examine solar eclipses indirectly. He explained the formation of inverted images of shining objects inside a “dark chamber” that allows the light to go through a small hole in one of its walls. In discusing this problem, Ibn-al-Haytham ascertained that light propagates from shining objects to their images, passing through the hold of the “dark room”, in straight lines.

In Europe, the notebooks of Leonardo da Vinci contains several descriptions of the obscura but the first detailed treatment appears in Magia Naturalis (Natural Magic) by Giovanni della Porta. He recommended it as a drawin aid a function to which it was soon quite propularly put. Johannes Kepler had a portable tent version which he used while surveying in Austria. By the latter part of the Sixteenth Hundreds, a small-held “camera obscura” were commonplace.

On the other hand, in the Book of Optics (Kitab al-Manazir) in which Ibn-al-Haytham experssed the results of his investigations, the attention was called to the fact that light propagation from sources to objects must be in a time, even undetectable, varrying from medium to another, The denser the medium the lower is the “velocity” of light.

Moreover, he enunciated that a ray of light, in passing through a medium, takes the path which is the easier and “quicker”. In this he was anticipatin Descartes and Fermat by many centuries.

( c ) Laws of reflection and refraction:

lbn-al-Haytham explained the laws of reflection and refraction of light, puttingt the angles of incidence and reflerctionl or refraction in the same plane normal to the interfacc. He used suitable models to descripe these propertise in mechanical terms and considered the light as consisting of small spheres or "particles" moving at the surface of reflection or refraction in accorclance with the rectangularl law of forces. In this he introduced an experimentally etablished approach later elaborated by Newton.

Illn-al-Haythatn's Optics is a large and comprehensive work that includes many valuable thoughts. The so-called Alhazen problems of reflection from plane, spherical and parabollic mirrors are still of scientific interest.

Part V of Roger Bacon's “Opus Majus” is particularly a copy of Ibn Al Haytham's Optics. No  wonder Bacon “never” wearied of clearing that a knowledge of Arabic  Science was the only way of true knowledge.

End of PART I-

By: Prof. Ahmad Fouad Basha
Professor of Physics - Facultyo f Science- Cairo- University

Posted on: March 5, 2012