“The duty of the man who investigates the writings of scientists, if learning the truth is his goal, is to make himself an enemy of all that he reads, and, attack it from every side. He should also suspect himself as he performs his critical examination of it, so that he may avoid falling into either prejudice or leniency.”- Al-Hazen
Alhazen was an accomplished Muslim scientist, mathematician, astronomer, philosopher and polymath from the “Golden Age” of Muslim civilization. Born in 965 in Basra, he became well-known as a physicist in medieval Europe. He is famously known as the “Father of experimental physics, modern optics and scientific methodology”. He is also well regarded as the first theoretical physicist. He was the first to realize that a hypothesis needs to be tested through verifiable experiments or mathematical proof, thus developing the scientific method 200 years before it was adopted by European scientists.
His ground breaking works in the field of optics has been penned-down in his 7-volume book entitled Kitab al-Manazir (Book of Optics), considered one of the greatest contributions to the field after Ptolemy’s Almagest. It was translated to Latin in 1270 and many renowned scientists based their work on this book. Alhazen was the first to describe accurately the structure of the eye and how it works. He contradicted Ptolemy’s and Euclid’s theory of vision which stated that eyes send out radiation to the object and maintained that the rays originated at the object. His focal point of research in the field of catoptrics was spherical mirrors, parabolic mirrors and spherical aberration. He observed that the ratio between the angle of incidence and the angle of refraction does not remain the same. He also studied the magnifying power of a lens. During his research on catoptrics, he came up with a problem now known as “Alhazen’s Problem” which led to the solution of the problem: “Given a light source, find the point on the mirror which would reflect the light to the eye of the observer”. The method he employed used equation of the fourth degree and he is often credited with developing the formula for expansion of the sum of any integral power.
In the field of mathematics, Alhazen reconciled algebra with geometry to form a new branch called analytic geometry. In number theory, his contributions involve solving problem of congruences using what is now known as the Wilson’s Theorem. He also made significant contribution to the field of astrophysics. In his book, Meezan Al-Hikmah (Balance of Wisdom), he discussed the density of atmosphere and its relationship to height. Using this theory, he also attempted to measure the height of homogenous atmosphere. He presented a detailed description of the structure of the earth and also made a model of the motion of the planets without the inherent contradictions that were present in Ptolemy’s model.
Alhazen wrote more than two hundred books, very few of which have survived. For his contribution to astronomy, a crater on the moon has been named Alhazen after him. His face is featured on 10,000 Iraqi dinar banknote. Aga Khan University, Pakistan named its Ophthalmology endowed chair after him to celebrate his work in optics.