Early Arab perceptions of optics, eyesight and its errors
Regional, History, 10/5/1998

Ibn al-Haitham who died in 1039 BC had excelled especially in optics and became famous for his remarkable book Kitab al-Manazer. "The book of optics."

The book consists of seven detailed divisions in which Ibn al-Haitham accurately explained the mechanism of eyesight. He specified its features and the characteristics of light and shadow. He explained the perceptions of the eyesight and its errors. He marked out illusions that usually occurred to the vision in recognizing objects.

He was a scrupulous scientist. He doubted all people's convictions, believing that this right is common to all people. Differences arise from the various methods and styles in reaching right. He studied the philosophy of Aristotle and admired it.

His scientific tendencies were experimental. He doubts, so he observed and conducted experiments in order to reach a correct and accurate conclusion. His knowledge of mathematics and philosophy helped him organize and classify his treatises. He adopted names and terms in his researches which became, later on, scientific and technical terms in the field of optics.

The rules Ibn al-Haitham followed in handling optics have been called by modern scientists the technical methods. He had excelled, especially in this science. His theories in this field contribute to the high technology we enjoy today in the field of optics. His points of view and hypotheses in this science became acknowledged.

Ibn al-Haitham who defined light as the "heat that emanates from self luminous bodies like fire or the sun." Light, as he proclaimed, is two kinds. The first one comes out from self-luminous bodies. The second comes out from the bodies which reflect other light like the moon. Light, moreover, he added, is a physical material consisting of rays having definite lengths and widths. Ibn al-Haitham confirmed the now well-known principle about light. He said that it passes through transparent bodies while it does not through opaque ones.

The present adopted theory about light refraction was explained by Ibn al-Walid. Being a specialist in optics, Ibn al-Haitham described the eye as the main instrument of vision. His major contribution to optic science is the correct and accurate clarification of the mechanism of vision. He proved that vision realizes objects and the eye sees them by rays reflected from these objects to the eye and not the other way round. Ibn al-Walid, in fact, is one of the recognized scientists in the East and in the West. His influence and fame in the Islamic world, as a matter of fact, was not so wide.

The Islamic world was busy at the time with logical philosophy from al-Farabi to the days of al-Ghazali. Besides, Ibn al-Haitham had shunned people since his disappointment in controlling the flood of the Nile. Moreover, the fame of the scientist can not be compared to that of the philosopher of man of letters. A clear example of this fact is the reputation of Avicenna. It is not based, unfortunately, on his scientific or medical skills much as on his philosophical works and political career.

Ibn al-Haitham, nevertheless, had gained remarkable fame during his lifetime before he received the summons of the caliph. His books, especially "al-Manazer," have great value. The book had accounted for the development of science in general and of optics in particular.

Although Arab scientists did not avail themselves of Ibn al-Haitham, he nevertheless had a notable influence on the scientists of the West. His books on astronomy and physics were translated into foreign languages between the 13th and 18th centuries. These translations helped lead these sciences in the right direction.

The theories and attitudes of Ibn al-Haitham in optics and astronomy had outstanding prevalence in the Middle Ages. Though some of his theories about astronomy were wrong, they spread widely in the Islamic and Christian countries. His books, in fact, were translated into Latin, Hebrew and Spanish. Latin translations were very influential.

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