Tuesday, December 15, 2009

532)Ibn al-Haytham(Alhazen) Revisited: He Criticised The Theories Of His Predecessors And Revolutionised Mathematical Optics In His Book 'Optics'

"....AND SHOULD'NT IB SCIENCE STUDENTS not learn about Ibn al-Haytham, the Muslim scholar who developed modern optics, as well as his predecessors Euclid and Ptolemy, whose ideas he challenged.....The legacy which I am describing actually goes back more than a thousand years, to the time when our forefathers, the Fatimid Imam-Caliphs of Egypt, founded Al-Azhar University and the Academy of Knowledge in Cairo. For many centuries, a commitment to learning was a central element in far-flung Islamic cultures. That commitment has continued in my own Imamat through the founding of the Aga Khan University and the University of Central Asia and through the recent establishment of a new Aga Khan Academies Program."(Aga Khan IV, "The Peterson Lecture" on the International Baccalaureate, Atlanta, Georgia, USA, 18 April 2008)

"The second great historical lesson to be learnt is that the Muslim world has always been wide open to every aspect of human existence. The sciences, society, art, the oceans, the environment and the cosmos have all contributed to the great moments in the history of Muslim civilisations. The Qur’an itself repeatedly recommends Muslims to become better educated in order better to understand God’s creation"(Closing Address by His Highness Aga Khan IV at the "Musée-Musées" Round Table Louvre Museum, Paris, France, October 17th 2007)

"The Holy Qu'ran's encouragement to study nature and the physical world around us gave the original impetus to scientific enquiry among Muslims. Exchanges of knowledge between institutions and nations and the widening of man's intellectual horizons are essentially Islamic concepts. The Faith urges freedom of intellectual enquiry and this freedom does not mean that knowledge will lose its spiritual dimension. That dimension is indeed itself a field for intellectual enquiry. I can not illustrate this interdependence of spiritual inspiration and learning better than by recounting a dialogue between Ibn Sina, the philosopher, and Abu Said Abu -Khyar, the Sufi mystic. Ibn Sina remarked, "Whatever I know, he sees". To which Abu Said replied," Whatever I see, he knows"."(Aga Khan IV, Aga Khan University Inauguration Speech, Karachi, Pakistan, November 11th 1985)


Dr Alnoor Dhanani from the Institute Of Ismaili Studies:

In the physical sciences, Muslim scientists were en­gaged in problems of natural philosophy, optics, and as­tronomy. The discussion of natural philosophy (focussed on the structure of matter, space, time, and motion) was largely between the religious philosophers and the Islamic Hellenistic philosophers. The former subscribed to atomism and the existence of the vacuum. In addition, they were proponents of an impetus theory of motion. Such views were in sharp op­position to Aristotelian natural philosophy. The two groups were therefore engaged in an examination and refutation of the ‘other’ system. Nevertheless, the religious philoso­phers’ theory of motion may have played a role in Ibn Sina’s formulation of his non-Aristotelian theory of “forced” and “natural” motion. Furthermore, Abu al­-Barakat al-Baghdadi (died after 1165 CE) rejected the Aristotelian theory of time and place and also believed that a vacuum was possible under certain circum­stances. Finally, as has been noted above, Ibn Bajja re­jected a key aspect of Aristotelian dynamics, that is, Aristotle’s formulation of the relationship between force, resistance, and velocity.

For the Hellenistic and early Islamic scientists, optics was a mathematical examination of light rays as they were transmitted through or reflected by various media, including lenses and mirrors of various shapes. This examination drew upon the works of Euclid and Ptolemy and advocated a theory of vision in which a cone of “visual rays” streamed from the eye to the visual object. A different account of vision was formulated by the Aristotelian natural philosophers (including Ibn Sina and Ibn Rushd) in their discussion of perception. For them, vi­sion is the reception of the “form” of the visual object by the eye. A third account of vision formulated by such medical writers as Galen and his followers (in­cluding the translator Hunayn ibn Ishaq) held that, as visual rays emerged from the eyes, the air was trans­formed into an instrument of vision. Therefore, the act of vision was the result of the contact of the “instru­ment” with the visual object. In the eleventh century CE, mathematician-scientist al-Hasan ibn al-Haytham (died 1040 CE) criticised the theories of his predecessors and revolutionised mathematical optics in his Optics. He maintained that optical inquiry “requires a combination of the natural and mathematical sciences”, thus anticipating one of the key methodological positions of the seventeenth century Scientific Revolution – the mathematisation of physics. Furthermore, Ibn al-Haytham recognized that any ac­count of optics must include an account of vision and must therefore discuss the psychology of visual per­ception.

Methodologically, Ibn al-Haytham’s work is signifi­cant for its clear concept and use of experiment to con­firm the specific properties of light by setting up a controlled situation where certain parameters may be varied. With regard to vision, he rejects the visual ray hypothesis (rays stream from the eye to the visual ob­ject) in favour of the natural philosophers intromission hypothesis (vision is the reception of the form of the vi­sual object in the eye). Ibn al-Haytham’s achievement was to reverse the direction of the visual rays of the mathematicians and hence mathematicise the “forms” of the natural philosophers. Surprisingly, the Optics does not seem to have made an impact in the Muslim world un­til the thirteenth century CE, and then only in the commen­tary on the Optics by Kamal al-din al-Farisi (died circa 1320 CE). In this work, al-Farisi formulated an explanation of the shape and colours of the primary and secondary rainbow on the basis of refraction and reflection in raindrops. Quite independently, a similar formulation was almost simultaneously arrived at in medieval Europe by Theoderic of Freiberg (died circa 1310 CE).

Ibn al-Haytham’s critical outlook also extended to astronomy where he was again critical of mathemati­cal models of planetary motion and their lack of cor­respondence with physics. Astronomy was a technical mathematical science based primarily on Ptolemy’s Almagest, although Sanskrit astronomical works had been translated into Arabic in the eighth century. The subsequent history of astronomy in classical and medieval Muslim civilisation consists of both theory and observations. Observations were made not only by individ­ual astronomers but were also conducted within the institution of the astronomical observatory – this insti­tution is one of the contributions of Muslim civilisa­tion to science. It was founded and established in Baghdad in the ninth century by the Caliph al-Mamun. The Baghdad observatory was staffed by several as­tronomers who were charged with revising Ptolemy’s astronomical tables on the basis of fresh observations. The result was compiled into the Tested Astronomical Tables. The Baghdad observatory is but one of several obser­vatories founded in classical and medieval Islam. Others include the famous Maragha observatory of the thirteenth century which was under the supervision of Nasir al-din al-Tusi and the fifteenth-century observatory of Ulugh Beg in Samarkand, both of which compiled their own as­tronomical tables. The precision reached by these ob­servatories was such that one modern author has exclaimed that the astronomer Tycho Brahe could have easily been a Turk! The influence of Arabic ob­servational astronomy survives in star names in use today, many of which are derived from Arabic, as are common astronomical terms such as “nadir,” “az­imuth,” and “zenith.”

Astronomical measurements required innovation in measuring instruments. Here, too, Muslim stronomers surpassed their predecessors by designing new instru­ments, revising older ones, and sometimes building ex­tremely large instruments to increase accuracy. The astrolabe is an example of an astronomical instrument that was derived from the Greeks but was improved by Islamic astronomers. Primarily used for determining the position of celestial bodies, it was combined with a number of movable plates and arcs to graphically solve complex trigonometrical functions and thereby deter­mine direction or time of prayer.

Theoretical innovation in astronomy was initiated by Ibn al-Haytham’s critical remarks about Ptolemy’s planetary models. According to the then prevalent Aristotelian natural philosophy, celestial bodies could only move in geocentric circles around the stationary earth. While Ptolemy had acknowledged this principle in his Almagest, he had to abandon it in his planetary models in order to account for observed positions of planets. Ibn al-Haytham objected to this practice in his Doubts against Ptolemy. This initiated a research project that culminated in the formulation of a new method of de­vising planetary models by Nasir al-din al-Tusi in the thirteenth century. Significantly, the same objections underlie Nicolaus Copernicus’ reformation of Ptolemaic astronomy. Moreover, Copernicus’ earlier work on the motion of the moon resembles the discussion of al-Tusi, raising speculation of a possible Muslim influence on the Polish as­tronomer who revolutionised astronomy with his helio­centric system.


Related Posts:

One mega-post, encompassing five regular posts, on the pioneering 9th century Muslim scientist Ibn al-Haytham or Alhazen(965CE to 1039CE).

'The Sciences' from the IIS's 'Muslim Philosophy And The Sciences' by Dr Alnoor Dhanani; Quotes of Aga Khan IV

A Collection of Posts on this Blog about Great Scientists; Quote of Aga Khan IV.

Easy Nash

The Qur'an itself repeatedly recommends Muslims to become better educated in order better to understand God's creation: Aga Khan IV(2007)
The Quran tells us that signs of Allah's Sovereignty are found in the contemplation of His Creation: Aga Khan IV(2007)
This notion of the capacity of the human intellect to understand and to admire the creation of Allah will bring you happiness in your everyday lives: Aga Khan IV(2007)
Islam, eminently logical, placing the greatest emphasis on knowledge, purports to understand God's creation: Aga Khan IV(2006)
The Holy Qu'ran's encouragement to study nature and the physical world around us gave the original impetus to scientific enquiry among Muslims: Aga Khan IV(1985)
The first and only thing created by God was the Intellect(Aql): Prophet Muhammad(circa 632CE)