Alhazen
Alhazen (Abu Ali al-Hasan Ibn Al-Haitham), (965-1038) was an Arabian mathematician; he is sometimes called al-Basri, after his birthplace.He was born at Basra and died at Cairo. He is to be distinguished from another Alhazen who translated Ptolemy's Almagest in the 10th century.
Having boasted that he could construct a machine for regulating the flooding of the Nile, he was summoned to Egypt by the caliph Hakim; but, aware of the impracticability of his scheme, and fearing the caliph's anger, he feigned madness until Hakim's death in 1021.
Ibn al-Haitham was nevertheless a diligent and successful student, being the first great discoverer in optics after the time of Ptolemy. According to Giovanni Battista della Porta, he first explained the apparent increase of heavenly bodies near the horizon, although Bacon gives the credit of this discovery to Ptolemy. He taught, previous to the Polish physicist Witelo, that vision does not result from the emission of rays from the eye, and wrote also on the refraction of light, especially on atmospheric refraction, showing, e.g. the cause of morning and evening twilight. He solved the problem of finding the point in a convex mirror at which a ray coming from one given point shall be reflected to another given point.
His treatise on optics was translated into Latin by Witelo (1270), and afterwards published by F. Risner in 1572, with the title Oticae thesaurus Alhazeni libri VII., cum ejusdem libro de crepusculis et nubium ascensionibus. This work enjoyed a great reputation during the middle ages. Works on geometrical subjects were found in the Bibliothèque nationale in Paris in 1834 by E. A. Sedillot; other manuscripts are preserved in the Bodleian Library at Oxford and in the library of Leiden.
Ibn al-Haitham's "Optics" is possibly the earliest work to use the scientific method. He used the scientific method to distinguish between two theories of how the eye worked and determine which was correct. The "emission" theory of how the eye worked, had been supported by Euclid and Ptolemy - this theory postulated that sight worked through the eye emitting light. The other theory was the "intromission" theory, which had been supported by Aristotle - this theory postulated that sight worked by light entering the eye. Ibn al-Haitham applied the scientific method and performed experiments to determine that the "intromission" theory was the scientifically correct theory.
Ibn al-Haitham's scientific approach differed from that of the Ancient Greeks in that they saw that truth was determined by the logic and beauty of reasoning, and when experiment was used it was only as a demonstration. That's why Ptolemy, even though he did experiments, nevertheless supported the erroneous "emission" theory of vision. In contrast, Ibn al-Haitham saw experiments as being the essential factor which distinguished a true theory from a false one - through this insight he created the foundation for the "scientific method".
Initial text from 1911 encyclopedia -- Please update as needed