Abū ʿAlī al-Ḥasan ibn al-Ḥasan ibn al-Haytham (Arabic: أبو علي، الحسن بن الحسن بن الهيثم; Persian: بوعلی محمد بن حسن بن هیثم c. 965 – c. 1040 CE), also known by the Latinization Alhazen or Alhacen, was an Arab Muslim scientist, mathematician, astronomer, and philosopher. Ibn al-Haytham made significant contributions to the principles of optics, astronomy, mathematics and visual perception. He was the first to explain that vision occurs when light bounces on an object and then is directed to one's eyes. He spent most of his life close to the court of the Fatimid Caliphate in Cairo and earned his living authoring various treatises and tutoring members of the nobilities.
Ibn al-Haytham is widely considered to be one of the first theoretical physicists, and an early proponent of the concept that a hypothesis must be proved by experiments based on confirmable procedures or mathematical evidence—hence understanding the scientific method 200 years before Renaissance scientists.
In medieval Europe, Ibn al-Haytham was honored as Ptolemaeus Secundus (the "Second Ptolemy") or simply called "The Physicist". He is also sometimes called al-Baṣrī after his birthplace Basra in Iraq, or al-Miṣrī ("of Egypt")....LESS