Al-Hazen: Arab mathematician

Book of Optics or Kitab al-Manazir, was written by Abū ‘Alī al-Ḥasan ibn al-Ḥasan ibn al-Haytham (965–1039 AD).

Abū ‘Alī al-Ḥasan ibn al-Ḥasan ibn al-Haytham or Ibn al-Haytham in brief, commonly known as Alhazen (also spelled Alhacen) in the Western literature, was an Arab Islamic polymath, physician, astronomer, mathematician, physicist and philosopher.

Ibn al-Haytham was born in Basra of Old Persia (now southern Iraq) in about 965 AD. His birthplace also resulted in him being known as al-Basri. Ibn alHaytham spent his primary education in his native city and continued his education in Baghdad (currently the capital city of Iraq). Ibn al-Haytham became a government minister (vizier) in Basra and spent his spare time working on mathematics, writing a treatise on the ancient (and impossible) problem of squaring the circle.

His work in optics irrefutably proved that vision is a function of external light rays entering the human eye; his rigorous and quantitative approach formed the basis of the modern experimental method in science.

Ibn al-Haytham was the first person to firmly reject the extramission theory of vision. In contrast to the popular theories of his predecessors, including those of Galen (130–200 AD), Ptolemy (died 178 AD) and Euclid (330– 260 BC), Ibn al-Haytham believed that objects are seen by light rays emanating from the objects and not from the eyes.

Ibn al‐Haytham's mathematical research was particularly in the field of geometry and not of algebra. The contributions of Ibn al‐Haytham in geometry can be divided into several groups, the most important of which are in infinitesimal mathematics and the theory of conic sections and their applications. He composed 12 treatises on infinitesimal mathematics and then on conic theory.

Ibn al-Haytham was a prolific author. Ibn Abi Usaibi’a attributed more than 200 works to Ibn al-Haytham, covering a wide variety of philosophical and scientific matters including medicine, mathematics, astronomy, physics, optics and vision, cosmology, meteorology and metaphysics.

One of Ibn al-Haytham 's most significant creations was a seven-volume work on optics titled Kitab al-Manazir (later translated to Latin as Opticae Thesaurus Alhazeni – Alhazen's Book of Optics). Al-
Hazen: Arab mathematician 

Jean-Paul Marat of French Revolution

Before the Revolution, Jean-Paul Marat (24 May 1743 – 13 July 1793) had been a doctor and a writer and he had fancied himself an important scientist.

He was born in Switzerland and became a French Revolutionary.

In September 1789, he launched the newspaper that brought him fame: L’Ami du people (The Friend of the People).

His journalism was renowned for its fiery character and uncompromising stance toward ‘enemies of the revolution’ and basic reforms for the poorest members of society.

His newspaper was little more than an extended editorial page filled with intemperate calls for violence against traitors and for an elected dictator to serve for a limited time to save the Revolution.

His reputation as a blood thirsty writer who called for the executions of counter-revolutionaries made many suspects that he was behind the September Massacres. In 1792, Marat was elected to the National Convention.

Marat suffered from the chronic skin condition psoriasis and spent much time in his bath with a vinegar soaked bandage.

This was where Charlotte Corday found him. As soon as they were alone together she stabbed him, cutting his carotid artery.
Jean-Paul Marat of French Revolution