Al-Haitham is considered one of the founders of modern optics. Ptolemy and Aristotle theorised that light either shone from the eye to illuminate objects or that light emanated from objects themselves. But al-Haitham suggested that light travels to the eye in rays from different points on an object.
However, al-Haitham’s stellar career ended abruptly after he foolishly promised the ruler of Cairo that he could stop the Nile from flooding by building a dam at Aswan. He couldn’t, feigning insanity to avoid persecution. Ironically, his plans to build a dam were carried out hundreds of years later, on the same site he initially proposed, when human engineering abilities had caught up with his vision.