Ibn al-Haytham

(354- 430 /965 - 1039)

 

Abu `Ali al-Hasan b. al-Hasan (or Husayn) b. al-Haytham al-Basri al-Misri,

known in mediaeval Latin texts as Alhazen, Avennathan and Avenetan. He was the best physicist and mathematician of his time. Most of his works (more than one hundred titles) are devoted to mathematics and physics, but he also wrote on medicine and philosophy.

Ibn al-Haytham was born in Basra in 354. He went to Egypt during the time of al-Hakim, who reigned 386-411, and al-Haytham undertook to control the flow of the Nile River. Regulating the water was not possible, and he quit the task and left. He returned to Cairo after the caliph died and earned his living by copying scientific and mathematical manuscripts. He was highly knowledgeable about Greek writers and he edited and criticized Ptolomy. He died in 430.

 

Ibn al-Haytham is remembered for his mathematical genius, and is known today for his resolution of Alhazen’s problem: two points, A and B, are fixed on the plane of a circle with centre O and radius R. Find in the circle the point M where the ray of light emitted by A must be reflected in order that it may pass through B. Ibn al-Haytham resolved the problem by making an intersection of an equilateral hyperole with the circle. He demonstrated that of two regular polygons inscribed in the same circle, the one with the greater number of sides also has the larger surface and the larger perimeter. 

 

Ibn al-Haytham explained the use of the camera obscura in observing solar eclipses. He established the theorem of the cotangent in determining the direction of the qibla. Ibn al-Haytham established that the astronomic twilight began or finished when the negative height of the sun reached 19 degrees and proceeding from there, he fixed the height of the atmosphere at 52,000 paces. He correctly explained the atmospheric refraction and the augmentation of the apparent diameter of the sun and moon when they are near the horizon. He established that rays of light start from the object to travel towards the eye, and not the reverse. He discovered spherical aberration. He determined that because the Milky Way had no parallax, it was very remote from the earth and did not belong to the atmosphere. 

 

 

His works:

1)       Makala fi ‘stkhradj samt al-kibla

2)       Makala fi hay’at al- `alam

3)       Kaia fe ‘l-manazir

4)       makal fi daw’ al-kamar, the ideas on light colors and the celestial movements

5)       Fi’l-Maraya ‘l-mukrika bi’l-dawa’er

6)       Fi ‘l-maraya ‘l-mukrika bi ‘l-kutu`